Stephen William Hawking, one of the most prominent physicists, must be known to everyone, as well as the "ice bucket challenge" that once swept the Internet, they are all related to a rare disease, that is, ALS.
Media publicity has made ALS one of the more "well-known" rare diseases, and in 2000, the International Patient Congress held in Denmark officially designated June 21 as "World ALS Day". But most of us don't know enough about the disease.
ALS is a popular term for "amyotrophic lateral sclerosis (ALS)", which generally progresses from the limbs to the center, and the limb muscles gradually disappear, and the function is gradually lost until the respiratory muscles disappear, and the respiratory function is lost, and the patient often dies of respiratory failure.
ALS generally does not impair a person's intellectual reasoning, sight, hearing, or senses of taste, smell, and touch, which means that the person is aware that his or her condition is deteriorating step by step while he or she remains awake, and feels that his or her abilities are deteriorating little by little.
ALS is a rare and serious neurodegenerative disease that affects upper and lower motor neurons, resulting in diffuse muscle paralysis with fewer treatment options. Etiology and pathogenesis remain largely unclear, but some environmental, genetic, and molecular factors are thought to be involved in the disease process.
Risk factors include exposure to toxic substances, lifestyle, dietary Xi, occupation, weight, etc. Studies have shown that some foods and nutrients, including red meat, sodium, glutamate, and more, may be risk factors for ALS. We know that dietary Xi, lifestyle and other factors are closely related to the status of the intestinal flora.
New research has identified an association between gut dysbiosis and neurodegenerative diseases (e.g., Parkinson's disease, Alzheimer's disease, ALS).
In these diseases, neuroinflammation is increasingly recognized as a driver of disease onset and progression. Gut bacteria play a vital role in maintaining and regulating the immune system, and changes in gut microbial composition can affect neurological function by affecting neuroimmune interactions, synaptic plasticity, myelination, and skeletal muscle function.
This article takes you to understand this "special disease" from the symptoms, risk factors, causes of ALS, gastrointestinal and metabolic dysfunctions, association and mechanism of action with intestinal microbiota, possible clinical relevance, and diagnosis (different from some other neurodegenerative diseases). The article concludes with a list of some of the existing studies on ALS interventions.
01
What is ALS?
ALS
肌萎缩侧索硬化症 (ALS)
▪ Deadly neurodegenerative diseases
▪ Motor neurons degenerate and stop sending messages to muscles
▪ The muscles gradually weaken, begin to twitch and atrophy
▪ Eventually, the brain loses the ability to initiate and control movement
▪ Symptoms can get worse over time
▪ In the late stage, it will be burdened with huge psychological pressure and financial burden
morbidity
Different countries have different frequencies of ALS. Although the world average incidence of this disease is about 1.9 cases per 100,000 people per year. The literature reports high rates of ALS in some Western countries, such as Sweden and Scotland, with 3.8 cases per 100,000 people per year, and conversely, Eastern countries, such as China, with 0.8 cases per 100,000 person-years.
•The incidence of ALS in China is relatively low
The prevalence and incidence of ALS in China are lower than those in developed countries, and maintain a relatively stable trend.
A total of 727,718 urban and rural community residents were surveyed in seven provinces, of which 65.74% were urban residents and 34.26% were rural residents.
Nine patients with amyotrophic lateral sclerosis were screened out, and the overall prevalence of amyotrophic lateral sclerosis in seven provinces of China was 1.24/100,000.
• There are direct differences in regional occupations
Prevalence varies widely from province to province:
- The highest prevalence in Zhejiang Province was 9.43/100,000
- The prevalence in Jiangsu, Gansu, Sichuan, and Shandong provinces is extremely low
By region:
- The prevalence in the eastern region (Shandong, Jiangsu, and Zhejiang) was 3.75 per 100,000
- The prevalence in the central region (Henan and Jiangxi) was 0.21 per 100,000
- The prevalence in the western region (Gansu and Sichuan) is 0
By urban and rural areas:
- The prevalence of amyotrophic lateral sclerosis in rural residents was 2.01 per 100,000
- 0.84 per 100,000 urban residents
From the perspective of occupational distribution:
7 people are farmers, accounting for 77.78%.
Most of the patients developed the disease after middle age, and the average duration of the disease in the 9 patients was 50.33±13.90 years.
•Gender ratio of ALS patients in hospitals: more males
Among the 169 amyotrophic lateral sclerosis patients surveyed in the hospital, 117 were males and 52 were females, with a male-to-female sex ratio of 2.25:1, and in the occupational distribution, 50.3% were farmers, of which male farmers accounted for the highest proportion of patients, with a total of 63 patients, accounting for 37.28% of all patients surveyed in the hospital.
The peak age of the disease was 60~69 years old, the average age of men was 61.43±12.66 years, and the average age of women was 59.98±12.76 years, which was 1~2 years later than that of women. 51.48% of the patients in the hospital survey had no history of chronic disease.
conclusion
(1) In the population sampling survey of 7 provinces in China, the overall prevalence of amyotrophic lateral sclerosis was slightly lower than that of other countries and regions in the world, the prevalence rate in rural areas was higher than that in urban areas, the onset time was slightly earlier than that reported internationally, and the survival time was slightly lower than that reported internationally. Patients with familial amyotrophic lateral sclerosis have an earlier onset and longer survival time than sporadic lateral sclerosis.
(2) The population survey and hospital survey unanimously found that the proportion of male patients with amyotrophic lateral sclerosis screened was higher than that of women, and the proportion of rural patients was the highest, and most of the patients did not have other chronic diseases.
symptoms
Early onset
There are three main types of disease: one is from the upper limbs, the second is from the legs, and the third is from the oral muscles
About 80% of ALS cases typically present with persistent weakness or spasms in the arms or legs.
✦ Upper extremities are the most common
The upper limb is the most common and accounts for the highest proportion, and the pathogenesis is as follows:
- First of all, it is difficult for the hand to complete fine movements, such as when using the key to open the door, the rotation is weak, and it will be difficult to unlock the lock;
- Gradually, it is difficult to hold chopsticks and pick up vegetables, especially peanuts, which require fine movements;
- After two or three months, the small muscles of the hand are atrophied and the muscles of the tiger's mouth are sunken;
- Then it begins to spread to difficulty lifting the arm, progressing from one limb to the other, which is a gradual process.
✦ Lower extremity disease
Onset from the lower limbs, patients may show that one limb is walking on one side, the instep is drooping, the road surface is unbalanced and easy to trip, but there is no numbness and pain, only the walking is becoming more and more difficult, and the clinical onset of the lower limbs is relatively rare.
✦ Oral muscle onset is very rare
The third is that the patient has difficulty speaking, which is the least common clinical practice. The disease begins with poor speech and a large tongue, which is easily confused with stroke, but there is a difference. In stroke patients, the difficulty of speaking is sudden, and ALS is a gradual process, followed by dysphagia.
The early onset is characterized by the following features:
- difficulty walking or performing normal daily activities;
- tripping and falling;
- weakness in the legs, feet, or ankles;
- weakness or clumsiness of the hands;
- slurred speech or difficulty swallowing;
- fleshy jumps of muscles in the arms, shoulders and legs;
- Inappropriate crying, laughing, or yawning.
Note: Flesh jumping may be one of the more obvious features in the early stage of ALS.
What is Meat Hop?
Uncontrollable muscle tremor is what we usually call "flesh jump", which is actually caused by the irregular and involuntary contraction of a group of muscle cells, which is medically called fasciculations (fasciculations).
Flesh jumping can also be divided into two conditions, one is benign and the other may be caused by ALS.
Common causes of benign "flesh beating": exercise, acute viral infection, hyperthyroidism, tetany, drug use, anxiety, etc., among which long-term exercise is the main reason.
The above-mentioned benign "flesh beating", of course, is not "ALS", but if the muscle beating is accompanied by muscle weakness and atrophy, it should be highly vigilant, and possible diseases include: motor neuron disease (ALS), peripheral neuropathy and a small number of muscle diseases, patients should go to the neuromuscular disease subspecialty of the Department of Neurology as soon as possible!
Common onset
All three conditions have one thing in common, that is, they feel that there is no particularly significant numbness and pain.
Note: The onset of upper limb disease is easily confused with cervical spondylosis, the onset of lower limb disease is easily suspected of lumbar disc herniation, and the onset of speech or swallowing difficulties is easily blurred with stroke.
metaphase
Amyotrophic lateral sclerosis is a gradual progression of the disease, and the disease manifests differently and develops at different rates for each person, generally taking at least 1 year and usually no more than 5 years.
As the disease progresses to the middle stage, symptoms such as motor weakness and difficulty breathing may occur.
• Difficulty swallowing
In patients with intermediate stage amyotrophic lateral sclerosis, the nervous system in the body is damaged, and the nerves around the throat are also damaged. In severe cases, this condition can compress the patient's trachea, causing the patient to experience difficulty swallowing.
• Muscle weakness
It is also a common symptom in patients with mid-stage amyotrophic lateral sclerosis, which is caused by damage to the nerves of the patient, resulting in a large area of muscle and muscle tone loss. In severe cases, the muscles become weak, but as the disease progresses, the symptoms become more pronounced, and in severe cases, the patient loses the ability to take care of himself.
• Obstructed breathing
When patients in the middle stages of amyotrophic lateral sclerosis are severely ill, they cause damage to the patient's brainstem neurons. Once the brainstem neuronal system is destroyed, the patient will be obstructed from breathing, and in severe cases, he may lose the ability to speak, and can only rely on a respirator to maintain life.
A small percentage of patients may present with extramotor manifestations such as dementia, paresthesias, and bladder and rectal dysfunction, and a small percentage may present with extraocular muscle dysfunction.
Advanced
In the later stage of the disease, in addition to eye movements, all motor systems of the whole body are involved, involving respiratory muscles, dyspnea, respiratory failure, etc. The late symptoms of ALS include muscle atrophy and stiffness of the limbs, as follows:
• Muscle atrophy
Obvious muscle atrophy, muscle weakness, muscle contracture, limb weakness, inability to move, some patients have tongue muscle atrophy, muscle spasm, positive pathological reflex, tendon hyperreflexia, dysphagia, choking on drinking water, and need ventilator assisted treatment;
• Stiffness of the limbs
Stiffness of the limbs: immobility, expressed by facial eye movements, called atresia, requiring gastric tube support for symptomatic treatment and maintenance of vital signs;
• Disturbances in physical signs
Signs of disorders: Disturbances in breathing, heartbeat, and blood pressure, as well as systemic electrolyte disorders and internal environmental imbalances.
ALS can also lead to some serious complications such as malnutrition, infections, pressure ulcers (bedsores), depression, anxiety, and more.
Patients with amyotrophic lateral sclerosis (ALS) may develop malnutrition and dehydration due to damage to the muscles that control swallowing. They are also at a higher risk of inhaling food, liquids or saliva into their lungs, which can cause pneumonia.
caution
Amyotrophic lateral sclerosis usually doesn't affect the brain or cause cognitive (thinking) problems. However, a lack of adequate nutrition can lead to cognitive impairment, and the devastating effects of the disease on the body can lead to depression.
Some people with amyotrophic lateral sclerosis will have problems with memory and decision-making, while others will eventually be diagnosed with frontotemporal dementia.
It is worth noting that:
Some patients with ALS have gastrointestinal discomfort that precedes neurological symptoms.
02
Risk factors for ALS
Physiological condition
Age
Although the disease can occur at any age, symptoms most often appear between the ages of 55 and 75.
Note: There are also data suggesting that the risk of the disease increases with age, most commonly around the age of 40-65 years.
There are also isolated cases of ALS in children.
Sex
Men are more likely than women to develop amyotrophic lateral sclerosis. However, with age, after the age of 70, the difference between men and women disappears.
Physiological indicators
➤ Metabolic diseases
Diabetes:
The actual clinical and pathophysiological correlation between diabetes mellitus and ALS is unclear and is currently being studied as follows:
- Diabetes mellitus has a protective effect against the development of ALS in older adults, while the opposite is true for younger subjects.
- Pre-existing insulin-dependent diabetes was associated with a higher risk of ALS (odds ratio 5.38, 95% CI 1.87-15.51)
➤ Inflammation
There is several lines of evidence that inflammation is a major component of ALS. Normally, immune cells are not present in large numbers in the central nervous system. However, immune cells are present in the nervous system of patients with amyotrophic lateral sclerosis, which cause neuroinflammation (inflammation of the central nervous system, including the brain).
Others, including oxidative stress, mitochondrial dysfunction, and glutamate toxicity, have been implicated in causing amyotrophic lateral sclerosis or promoting its progression.
This is explained in more detail in a later section.
Lifestyle: Smoking
Smoking and tobacco smoke exposure may increase the odds of ALS through inflammation, oxidative stress, and neurotoxicity caused by heavy metals or other chemicals present in cigarette smoke.
A large prospective study in the United States (414493 male and 572736 female participants; 617 male ALS deaths and 539 female ALS deaths) reported an increased risk of ALS from formaldehyde exposure, a component of cigarette smoke.
Physical trauma
Head trauma or electrical burns may be associated with ALS.
One study recruited n=188 patients with ALS and conducted a 2:1 control from the general population in the same region.
Head trauma was associated with an increased risk of ALS (adjusted odds ratio [OR] 1.60 95% confidence interval [CI] 1.04 to 2.45) and had a greater effect on injuries occurring 10 years or more prior to symptom onset (P = .037).
Patients who reported severe electrical burns had an increased risk of ALS (adjusted odds ratio 2.86, 95% CI 1.37-6.03), had the highest odds ratio for burns after age 30 years (odds ratio 3.14), and had odds ratios for burns 10 years or more before symptom onset (odds ratio 3.09).
Heavy labor
An earlier study found heavy labor as a risk factor, and a case-control study of New England construction workers (109 vs. 253 controls) found increased rates of disease (OR = 2.9, 1.2–7.2).
Note: The evidence specifically regarding the role of physical activity in the etiology of ALS remains inconclusive.
Race
Caucasians and non-Hispanics are most likely to develop the disease.
environmental factors
Researchers are studying the effects of environmental factors such as exposure to toxic or infectious substances, viruses, diet, smoking, occupational factors.
Habitation factors and chemicals
ALS has been linked to exposure to many chemicals, with most of the supporting evidence relating to agricultural chemicals such as pesticides, fertilizers, herbicides, and insecticides.
Australia reported similar findings for 179 pairs of case-controls. Regular gardening (non-occupational exposure) was significantly associated with ALS (OR = 6.64, 95% CI = 1.61–27.4). Stratification by sex showed a significant correlation only in males (OR = 4.90, 95% confidence interval = 1.11–21.7).
For people under 60 years of age, the link between a home close to industry and a sewage treatment plant or farm has also been demonstrated. Living near these places can expose you to a variety of air, water, and soil contaminants.
Recently, a study of 66 age, ethnicity, and sex-matched cases and controls found a significant association between occupational exposure to pesticides and ALS (OR = 6.50, 95% confidence interval = 1.78–23.77).
heavy metal
Heavy metals (lead, mercury, cadmium, etc.), especially lead, may play a variety of roles in the pathogenesis and progression of ALS.
Places or occupations where exposure to lead or other substances is likely:
Working in machinery, painting, or construction is associated with ALS, and other occupations including agriculture, fishing, logging, and hunting may also be associated with ALS.
In many case-control studies, lead exposure has been associated with ALS. In New England (109 vs. 256 controls), elevated blood and bone lead levels were associated with an increased incidence of ALS (OR = 1.9, 95% confidence interval = 1.4–2.6).
In Boston (95 and 106 controls), self-reported lead exposure was associated with ALS (p = 0.02).
In addition, other metals, particularly mercury and cadmium, have been studied, but the results have been inconsistent. Composite measurements of heavy metal exposure (lead and mercury) were significantly associated with an increased risk of ALS (OR = 3.65). Although lead exposure has been associated with ALS, an association and causal mechanism for mercury, cadmium, or other metals has not been shown.
In a small Japanese study (21 patients, 36 controls), patients with ALS had significantly lower levels of mercury and selenium in their plasma and blood cells than the control group, due to their disability, including consumption of a liquid diet.
A very small study (9 patients) conducted in Italy showed that the blood cadmium levels of the patients were significantly higher than those of the control group (excluding patients with advanced stages of the most functional impairment).
Note: Grouping exposures of different metals together may result in misclassification of exposures and reduced ability to detect associations, which is a limitation of current and earlier studies.
Dust/fibers/fumes
Several studies have indirectly suggested occupational exposure to particulate matter in ALS. Airborne dust, smoke, and fibers found in certain occupational environments can be significant exposures to airborne particulate matter. Particulate matter exposure has been examined with neurological outcomes in many studies and has been associated with ALS in several occupational settings.
Note: The occupational environment under investigation (veterinarian, hairdresser, grader and sorter) may increase co-exposure to solvents, metals, and possibly other media. No studies directly assessed the relationship between exposure to particulate matter in the environment and ALS.
Radiation/electromagnetic fields
Radiation has been recognized as a potential risk factor for ALS, as radiculopathy manifestations may be caused by electrical injury with a long latency period.
Three previous studies have reported associations between radiation or electromagnetic field exposure;
Electrical-related occupations (OR = 1.3, 95% CI = 1.1–1.6), and exposure to electromagnetic fields (OR = 2.3, 95% confidence interval = 1.29–4.09) were associated with ALS.
In a cohort mortality study of 139905 males at five large electric utilities in the United States, mortality from ALS was related to the duration of exposure to electromagnetic fields (RR = 2.0, 95% confidence interval = 1.0–9.8).
<向上滑动阅览>
caution
Due to the small sample size of some of these experiments and the possibility of interference from other factors, the correlation should be made with caution.
Genetic factors
Most cases of ALS are thought to be episodic. This means that the disease appears to occur randomly, with no clearly associated risk factors, and no family history of the disease. Although family members of people with sporadic ALS are at increased risk of developing the disease, the overall risk is low, and most people do not develop ALS.
Familial (hereditary) ALS
About 5 to 10 percent of ALS cases are familial, meaning a person inherits the disease from their parents. Familial forms of ALS usually require only one parent to carry the disease-causing gene. Mutations in more than a dozen genes have been found to cause familial ALS, such as genes such as C9ORF72, SOD1, SPTLC1, FUS, TARDBP, TDP-43, OPTN, TBK1, and others.
The mechanism of action of gene mutations will be explained in detail in the next section.
03
Pathogenesis of ALS
The pathophysiological process of ALS is multifactorial, reflecting a complex interplay between genetic and environmental factors.
This section elaborates on the pathogenesis of ALS from the following aspects:
- Genetic mutations
- Neuroinflammation
- Crosstalk from the peripheral immune system to the central nervous system
Genetic abruptness
To date, there are dozens of genes associated with amyotrophic lateral sclerosis, and mutations in these genes account for about two-thirds of all familial cases.
Genetic profile of ALS between 1993 and 2016
doi:10.1016/S1474-4422(17)30401-5
Familial amyotrophic lateral sclerosis cases account for approximately 10% of all amyotrophic lateral sclerosis cases. Of this 10%, about 70% can be explained by genetics.
SOD1: involves motor neurons, glial cells, and skeletal muscle cells
ALS family cases are associated with mutations in Cu/Zn superoxide dismutase (SOD1), a key antioxidant enzyme that protects cells from the harmful effects of superoxide radicals, suggesting that alterations in SOD1 function and/or aberrant SOD1 aggregation have a strong impact on promoting the pathogenesis of ALS.
Alterations in SOD1 metabolism affect many cellular functions involving different cell types (i.e., motor neurons, glial cells, and skeletal muscle cells) that may interact to produce pathological phenotypes.
doi.org/10.3390/antiox11040614
The copper/zinc superoxide dismutase-1 (SOD1) gene has been found in both familial amyotrophic lateral sclerosis (FALS) and sporadic amyotrophic lateral sclerosis (SALS), but it has been less studied in Chinese amyotrophic lateral sclerosis patients, and few studies have been conducted in large samples.
In 499 patients with ALS (487 SALS and 12 FALS) in the Department of Neurology, West China Hospital, Sichuan University, the frequency of SOD1 mutations was 1.03% (5/487) in SALS and 25% (3/12) in FALS from Southwest China.
OPDN: ALS caused by loss-of-function mutations
OPDN is the only gene known to cause classical ALS through loss-of-function mutations.
OPTN typically inhibits NF-κB activity, a key component of the innate immune response, and in its absent or mutated form, NF-κB translocates to the nucleus and promotes the expression of a large number of pro-inflammatory genes, thereby enhancing microglia-mediated neuroinflammation.
Note: Whether OPTN directly affects NF-κB is a controversial topic, however, most studies agree that mutant OPTN is associated with dysregulation of the NF-κB pathway, thereby promoting a pro-inflammatory response.
TBK1: Involved in a variety of ALS-related pathways like autophagy and neuroinflammation
Mutations in TBK1 are associated with amyotrophic lateral sclerosis. The TBK1 protein binds to and phosphorylates many proteins, including OPTN and sequestosome-1/p62, and regulates innate immunity and autophagy.
TBK1 belongs to the IKK kinase family involved in innate immune signaling pathways, specifically, TBK1 is an inducer of type 1 interferon. TBK1 also plays an important role in autophagy and mitophagy.
Mutations in TBK1 may lead to impaired autophagy, which may lead to the accumulation of protein aggregates, autophagosomes, and damaged mitochondria in motor neurons. Neuronal damage may trigger an innate response in cells surrounding the neuron, leading to neuroinflammation that triggers ALS.
TBK1 mutations have been identified in approximately 1% of patients with familial ALS and in approximately 1% of patients with sporadic ALS.
TNIP1: a key inhibitor of inflammatory signaling
According to a large genome-wide association study in populations in China, Europe, and Australia, mutations in TNIP1 were associated with amyotrophic lateral sclerosis.
TNIP1 is functionally associated with OPTN and inhibits NF-κB activation and tumor necrosis factor (TNF)-induced NF-κB-dependent gene expression. Dysfunction or deficiency of TNIP1 may predispose healthy cells to an inflammatory response to exposure to other harmless TLR ligands. TNIP1 has also been implicated in several immune diseases, including lupus and psoriasis.
SQSTM1: impairs aggregate protein degradation and autophagy to cause ALS
Several new SQSTM1 mutations have been identified in patients with ALS.
The SQSTM1 gene encodes p62, a major pathological protein that regulates autophagy and oxidative stress (bottom).
Interaction of autophagy and inflammasome pathways in amyotrophic lateral sclerosis
doi.org/10.1016/S1474-4422(18)30394-6
Mutations in SQSTM1 alter the function of p62 and promote the pathophysiology of ALS by impairing aggregate protein degradation and autophagy.
VCP: VCP mutations affect muscles, bones, and the brain
Mutations in the VCP gene are associated with familial and sporadic amyotrophic lateral sclerosis.
VCP is an important component of the autophagy and ubiquitination-proteasome pathway, another cellular mechanism that degrades and processes damaged, misfolded, and excess proteins. Mutations in VCP impair overall protein degradation and lead to TDP-43 deposition, which can lead to inclusion body myopathy, Paget's disease, frontotemporal dementia, or ALS. VCP mutations are responsible for 1% to 2% of familial ALS cases.
CX3CR1: mutations impair the neuroprotective response of microglia
CX3CR1 is a specific receptor on microglia that binds to fractalkine, a protein released from motor neurons, thereby promoting a neuroprotective response. Mutations in the receptor CX3CR1 impair fractalkine binding and lead to shorter survival in patients with ALS, but do not increase the risk.
The CX3CL1/CX3CR1 communication system has anti-inflammatory and neuroprotective effects and plays an important role in maintaining autophagic activity.
However, CX3CR1 is an ALS disease-modifying gene, and polymorphisms in CX3CR1 impair the neuroprotective response of innate immune microglia, providing evidence for its role in neuroinflammation in the pathogenesis of ALS disease.
These mutated genes provide direct evidence that immune system-induced inflammatory mechanisms are involved in the pathogenesis of ALS. In addition, these mutant genes suggest that autophagy inhibits the activation of the NLRP3 inflammasome, and mutations in these immune-related genes prevent physiological inhibition of inflammasome-mediated activation, thus activating inflammatory pathways (IL-1β and IL-18) and contributing to ALS pathogenesis.
TARDBP: Mutations cause damage to cells
Mutations in ARDBP have been associated with familial cases of ALS and frontotemporal dementia.
The TARDBP gene provides instructions for building a protein called TDP-43, which is normally located in the nucleus and is involved in various steps of protein production. Mutations in the TARDBP gene cause the TDP-43 protein to form aggregates (clumps) outside the nucleus, causing damage to the cell.
TDP-43 aggregates have been found in approximately 97% of ALS patients, including those without mutations in the TARDBP gene.
C9orf72: Associated with neurodegeneration, inflammation, immune interactions
Several studies have explored the pathogenic mechanism of C9orf72-mediated disease. C9ORF72 is associated with neurodegeneration, inflammation, and the regulation of our immune interactions with the environment.
One of the reasons why the C9orf72 mutation is difficult to detect is that the mutation is located in an intron of the C9orf72 gene.
A significant increase in microglial inflammatory activity was recorded in C9orf72 in ALS patients and was associated with faster disease progression.
NOTE: Activated microglia are a prevalent feature of ALS/FTD pathology, and C9orf72 has an important role in myeloid cells.
There are three main disease mechanisms: loss of function of the C9orf72 protein and increased functional toxicity of the C9orf73 repeat RNA or dipeptide repeat protein produced by repeat-associated non-ATG translation.
Note: NEK1 and C21orf2 interact and are involved in microtubule assembly, DNA damage response and repair, and mitochondrial function.
MATR3: mutations are associated with neuromuscular function deterioration
MATR3 is an RNA and DNA-binding protein that interacts with TDP-43, a disease protein associated with ALS and frontotemporal dementia.
In ALS patients with MATR3 mutations, upper and lower motor neurons are affected, with a survival of 2-12 years.
Hind limb paralysis and muscle atrophy occurred in transgenic mice overexpressing the MATR3 protein, suggesting that neuromuscular function is sensitive to MATR3 levels.
In 2014, four mutations in MATR3 (p. S85C, p.F115C, p.P154S, and p.T622A) were identified by exome sequencing in four families of European ancestry with ALS alone or with both ALS and dementia. Since 2014, 11 other variants have been described, occurring predominantly in patients with sporadic ALS.
CCNF: Mutations cause abnormal protein stagnation
CCNF is a substrate recognition component of the Skp1-cullin-F-box E3 ubiquitin ligase complex, which is responsible for labeling proteins with ubiquitin and their degradation by the ubiquitin protease system.
Mutations in CCNF may lead to abnormal protein arrest, which may be exacerbated by TDP43 proteinopathies. Therefore, therapies that improve protein clearance or reduce ubiquitination may be viable treatments.
Other relatively rare mutations include:
CCHHD10、TUBA4A等。
Interactions between genes associated with amyotrophic lateral sclerosis
10.1016/S1474-4422(17)30401-5
The outer circle is a karyotype ideogram that shows 24 chromosomes (22 autosomes, X chromosomes, Y chromosomes) and the inner circle shows the position of each gene. Connections between genes represent interactions at the protein or gene level. Interaction data was obtained from a bio-generic repository of interaction datasets. The black line indicates the cytogenetic band pattern. Biological processes related to genes or interactions are indicated by color.
Neuritis
There is growing evidence of abnormalities in the immune system throughout ALS. Immune cells are activated and contribute to the chronic pro-inflammatory microenvironment around ALS and in the central nervous system.
The pro-inflammatory nature of ALS is systemic, with crosstalk between the peripheral immune system (PIS) and the central immune system (CIS). To date, crosstalk is not well defined.
With a deeper understanding of ALS, researchers have realized the importance of the two systems interacting and communicating continuously. CNS-resident immune cells and peripheral immune cells interact through immune molecules.
The dysfunctional central nervous system barriers, including the blood-brain barrier and the blood-spinal cord barrier (BSCB), open the door to "crosstalk" and are also regulated by the inflammatory environment. Thus, chronic systemic inflammation leads to MN death, damage to motor neuron axons, and neuromuscular junction dysfunction.
Schematic diagram of immune crosstalk between PNS and CNS
doi: 10.3389/fnagi.2022.890958
The double-headed arrows indicate the communication of the two cells. A blue single arrow indicates that the cell releases inflammatory mediators and affects its target. The orange, green, and purple arrows indicate peripheral cell infiltration into the central nervous system, respectively.
In the central nervous system, resident immune cells microglia are activated and mediate neuroinflammation by releasing pro- or anti-inflammatory substances (e.g., cytokines) and interacting with infiltrating peripheral immune cells; astrocytes control microglia activation, migration, and proliferation.
In the PNS, resident immune cells, including T lymphocytes, mast cells, and monocytes, are activated and infiltrate along peripheral motor nerves and neuromuscular junctions. At the same time, they infiltrate the central nervous system, triggered by microglia-derived inflammatory mediators.
In addition, CNS barrier dysfunction, including the blood-brain barrier and blood-spinal cord barrier (BSCB), contributes to peripheral immune cell infiltration and accelerates harmful interactions. Thus, an inflammatory response that straddles both systems leads to motor neuron (MN) death, MN axon damage, and neuromuscular junction dysfunction.
Inflammation of the central nervous system is prevalent in ALS
Glial cells, including microglia and astrocytes, trigger a neuroinflammatory response that interacts with infiltrating peripheral immune cells and ultimately induces or accelerates neuronal death in the central nervous system of ALS.
Microglia are resident innate immune cells of the central nervous system that mediate neuroinflammation by releasing immune molecules, including cytokines and chemokines. Microglial activation is heterogeneous and depends on the nature of the pathological injury.
A growing body of research has demonstrated that microglia exhibit an anti-inflammatory phenotype and protect motor neurons at the onset of disease, while end-stage microglia transform into a pro-inflammatory phenotype and exacerbate neurodegeneration of motor neurons in ALS.
Activated microglia promote cytotoxicity by secreting reactive oxygen species and pro-inflammatory cytokines, including IL-1β, IL-6, and TNFα.
Astrocytes are the most common glial cells in the brain and maintain the central nervous system barrier, secrete neurotrophic and neuroprotective factors, regulate neurotransmitter uptake and circulation, and promote neurogenesis. Studies have identified the role of astrocytes as immunomodulators, as they can control microglia activation, migration, and proliferation.
- In the early stages of the disease, astrocytes provide neuroprotective functions.
- As the disease progresses, activated astrocytes (activated by microglial processes or independently by motor neuron release compounds) join the activated microglia and release pro-inflammatory cytokines, promoting a neurotoxic environment that leads to motor neuron death.
Thus, inflammatory cytokines released by astrocytes and microglia may promote glutamate excitotoxicity, thereby linking neuroinflammation and excitotoxic cell death.
When a critical threshold is reached, reactive astrocytes and microglia may initiate an irreversible pathological process that subsequently leads to non-cellular autonomous death of motor neurons in patients with ALS.
In the brain and other nervous tissues, cytokines communicate between neurons, astrocytes, and microglia.
Schematic diagram of major pathophysiological events in ALS
Dysregulation of the inflammatory pathway is present not only in 10% of patients with ALS with a positive family history, but also in 90% of patients with sporadic ALS.
Patients with sporadic ALS also have increased inflammation of CNS-responsive microglia and astrocytes and activate peripheral monocytes and lymphocytes infiltrating the CNS. The cause of this immune dysregulation in patients with sporadic ALS is unknown. The inflammatory cytokine IL-6 is secreted by activated macrophages and microglia in transgenic mSOD1 mice and ALS patients.
Immune activation in the periphery of ALS
Presence of peripheral immune abnormalities in ALS. In general, the chronic peripheral immune response is pro-inflammatory in ALS. Lymphocytes, monocytes (including macrophages), neutrophils, natural killer (NK) cells, and mast cells (MCs) are peripheral resident immune cells. The total white blood cell count in the blood of patients with ALS was found to be elevated.
In peripheral blood, most studies have shown a decrease in neuroprotective CD4 T lymphocyte levels, whereas CD4 T lymphocyte subsets, regulatory T cells (Tregs) are reduced and dysfunctional in patients with ALS. In ALS, the number of cytotoxic CD8 T lymphocytes in peripheral blood is controversial. NK T lymphocytes are thought to be detrimental to ALS and are increased in the peripheral blood of patients with ALS.
B lymphocytes have been discussed only in ALS, and studies have shown that they play a complementary role in the pathogenesis of ALS. Changes in monocyte proportions have been reported, with circulating monocytes preferentially differentiating into a pro-inflammatory phenotype in patients with ALS. The number of neutrophils in peripheral blood is increased and has been shown to be significantly associated with disease progression.
NK cells are innate immune cells and mediate cytotoxicity. Patients with ALS have elevated levels of NK cells in the blood and may be pathogenic.
An increased number of circulating mast cells was shown in ALS mice, whereas evidence was lacking in ALS patients.
Distal axonal lesions are a recognized pathologic feature of ALS. Recruited by activated mast cells, macrophages, and neutrophils along degenerated motor axons in sciatic nerve and skeletal muscle was observed in ALS.
Peripheral immune cells can also infiltrate the central nervous system and have an impact on motor neurons and glial cells, which are discussed below. There is growing discussion about the role of peripheral immune cells in their prognosis. In this regard, as technology and understanding have evolved, researchers have shifted to exploring specific populations or individual bone marrow subsets to classify or monitor patients.
Alterations of the central nervous system barrier in ALS
The CNS barrier is formed by a layer of endothelial cells and is connected by endothelial tight junctions (TJs), adhesion proteins, and cytoplasm. The basement membrane called the basal lamina (BL) is encased by pericytes and astrocyte ends, supporting endothelial cells and associated pericytes.
They constitute the physical barrier of the CNS, whereas the biochemical barrier of the CNS is conferred by various transport systems.
Alterations in the brain barrier were observed early in ALS patients and mice, suggesting that damage may contribute to pathogenesis.
These changes are summarized below:
- Breach of the integrity of the physical barrier
- Functional regulation of biochemical barriers
- In the immune response, barrier cells secrete neuroimmune-related substances
CNS disorders are the central point of humoral based communication between the central and peripheral immune systems. A better understanding of how the integrity or function of the CNS barrier is altered may provide a way to terminate harmful crosstalk in ALS.
★ Blood-brain barrier and blood-spinal cord barrier: maintaining CNS homeostasis
The blood-brain barrier and blood-spinal cord barrier (BSCB) are capillary-based barriers that separate brain and spinal cord tissue from peripheral blood circulation, respectively. These two barriers are morphologically similar in that they are both located within nonporous capillary endothelial cells, which are sealed together by tight junctions and adhesion molecules.
While BSCBs have higher connective permeability than the blood-brain barrier, these two barriers tightly regulate the paracellular and transcellular exchange of nutrients, endogenous chemicals, metabolites, and xenobiotics in and out of the central nervous system (CNS). As such, they play an important role in maintaining homeostasis in the CNS microenvironment, which is essential for normal neuronal function.
In addition, both barriers are highly expressive of various exogenous efflux transport pumps that are members of the ATP-binding cassette (ABC) transporter superfamily.
★ Changes in the expression levels of transporters at both barriers, altering drug concentrations in brain and spinal cord tissues
Lumen capillary expression of multiple exogenous transporters, such as P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance-associated protein 2 (MRP2), is a major obstacle to drug delivery to the brain and spinal umbilical cord due to their concentrated efflux activity that pumps drugs back into the bloodstream from the barrier endocortical plasma membrane or cytosol compartment for subsequent clearance.
Note: P-gp: P-glycoprotein is a relatively common molecular pump that protects cells from the invasion of foreign harmful molecules, which is located on the cell membrane and constantly "searches" for foreign hydrophobic molecules, just like a "security" to protect the cell.
Changes in the expression levels of these transporters at both barriers can alter drug concentrations in brain and spinal cord tissues. Therefore, understanding the transporter activity of the blood-brain barrier and BSCB is critical for more accurate prediction of drug pharmacokinetics and pharmacodynamics in the CNS.
★ The full therapeutic efficacy of riluzole in the CNS is limited by these transporters
Induction of P-gp at the CNS barrier in some patients with ALS is possible and may explain the difficulty of determining effective pharmacological treatment for ALS. In addition, riluzole, the only drug currently approved by the FDA for ALS administration, is recommended as a substrate for P-gp and BCRP.
Since riluzole is a substrate for the two ABC heterologous efflux transporters P-gp and BCRP, the full therapeutic efficacy of riluzole in the CNS may be limited by these efflux transporters on the blood-brain barrier and BSCB.
Recent studies using mouse models of ALS in vivo have shown that P-gp and BCRP transport activity and expression are induced in the CNS barrier at an advanced stage of disease progression. These inductions may further limit the therapeutic efficacy of riluzole in the central nervous system.
ALS-induced upregulation of P-gp can further limit the permeability of riluzole across the CNS barrier and reduce its concentration at neuronal target sites, thereby reducing its therapeutic efficacy. In this case, the appropriate adjustment of the dose or treatment window of CNS drug therapy as a substrate for P-gp should be studied throughout the course of ALS progression in patients who are expected to induce P-gp at the CNS barrier.
In conclusion, pharmacological interventions to prevent P-gp-induced or substrate interactions can be used to improve therapeutic efficacy in CNS diseases (e.g., ALS) that show P-gp-induced at the CNS barrier.
★ Disruption of the integrity of the physical barrier of ALS
Several studies have found alterations in the ultrastructure of the CNS barrier in patients with ALS, including microvascular endothelial cell swelling and cytoplasmic vacuolation, decreased pericyte coverage, and isolation of astrocytes terminal foot processes from endothelial cells in the spinal cord of ALS patients.
Ultrastructural alterations were also observed in the brainstem, cervical spine, and lumbar spinal cord, but not in the motor cortex of ALS mice. These changes have been noted to occur in the early stages of the disease and worsen as the disease progresses.
TJ is formed by a variety of proteins, such as zonula occludens-1 (ZO-1) and occludin, and blocks the paracellular movement of solutes. Significant reductions in the expression of TJ and adhesion proteins such as ZO-1 and occludin were observed in the spinal cord of ALS patients and mice. Despite changes in adhesion proteins, the morphological structure of TJ in the postmortem spinal cord of ALS patients was found to be intact under electron microscopy. Although the morphological structure of TJ was preserved, detection of endogenous proteins in the CNS showed increased paracellular permeability and leakage of the CNS barrier.
Basal laminar (BL) thickening was observed in both ALS patients and mice:
Detachment of endothelial cells exposes BL to plasma proteins, fibrin, and collagen IV within BL, which then accumulates, resulting in thickening of BL. Since BL abnormalities were detected in the early stages of ALS mice, these findings suggest that it may occur as a compensatory mechanism or repair process.
Based on these findings, ultrastructural abnormalities and reduced TJs adhesion protein expression may lead to impaired junctional integrity and increased paracellular permeability, allowing peripheral material and cells to enter the central nervous system. As a result, it promotes communication between the peripheral immune system and the central immune system and accelerates the systemic inflammatory response.
★ Functional regulation of the biochemical central nervous system barrier
The biochemical central nervous system barrier is conferred by various transport systems, such as ATP-binding cassette (ABC) proteins. They can effectively eliminate various endogenous and exogenous toxins from endothelial cells to maintain cellular homeostasis. The most studied ABC protein, P-glycoprotein (P-gp), is the major efflux transporter of fat-soluble small molecules expressed at the CNS barrier.
The expression and activity of P-gp were upregulated in both ALS patients and mice. Tumor necrosis factor α (TNF-α) and growth factor-β 1 (TGF-β1) have been shown to upregulate the expression and activity of P-gp in mice and rats. They are associated with overexpression of P-gp due to elevated levels of TNF-α and TGF-β1 in ALS patients and mice.
In addition, astrocytes have also been suspected to be responsible for the increased expression of P-gp in ALS genotype-dependent ALS. For example, co-cultured ALS-associated mutant SOD1 astrocytes affect P-gp in nearby endothelial cells by secreting soluble factors such as TNF-α, chemokines, and reactive oxygen species (ROS).
At the same time, the ALS-associated mutant C9orf72 astrocytes have been shown to have no effect on endothelial P-gp expression. In addition, the expression of another efflux transporter, breast cancer resistance protein (BRCP), was upregulated in ALS patients and mice.
In general, the increase in the abundance and activity of P-gp and BRCP in the CNS barrier indicates the regulation of biochemical CNS barrier interface function, which may ultimately influence the development of ALS.
Barrier cells secrete neuroimmune-related substances
Barrier cells, including endothelial, pericyte, and astrocytes, secrete neuroimmune-related substances in response to immune stimulation by peripheral or central immune cells. Brain endothelial cells (BECs) can constitutively secrete interleukin-6 (IL-6), prostaglandins, and nitric oxide in response to different stimuli.
Due to the reduced number of pericytes in ALS, its inflammatory-mediated role may also contribute to ALS pathology. Pericytes are the most sensitive to TNF-α compared to other barrier cells and can release IL-6 and macrophage inflammatory protein-1α (MIP-1α, also known as CCL3) in response.
Inflammatory reactive pericytes support neutrophil migration by releasing IL-8 and matrix metalloproteinase 9, which leads to the subsequent development of neuroinflammation.
Astrocytes are activated in the immune response to ALS.
On the one hand, astrocytes control the activation, migration, and proliferation of microglia through a variety of inflammatory cytokines, and secrete proteins such as MCP-1 that mediate monocyte migration, thereby amplifying neuroinflammation in the CNS.
On the other hand, biochemicals such as nitric oxide, vascular endothelial growth factor (VEGF), glial cell-derived neurotrophic factor (GDNF), and MM-9 released by reactive astrocytes on the barrier regulate the expression of TJ protein and proliferate endothelial cells, thereby affecting the integrity and permeability of the CNS barrier.
Thus, barrier cells can not only relay information from one side to the other (as in the peripheral immune system to the central nervous system), but are also involved in mediating the inflammatory microenvironment.
Crosstalk contributes to the systemic inflammatory environment
In ALS, damaged motor neurons interact with glial cells, which release levels of cytokines and chemokines, and subsequently recruit innate and adaptive immune cells to infiltrate the CNS to promote inflammation.
Pro-inflammatory signals travel from the central immune system to the peripheral immune system, and from the peripheral immune system to the central immune system, thus contributing to the systemic inflammatory environment of ALS.
Cytokines and chemokines in ALS
Many cytokines and chemokines, such as IL-1, IL-6, TNF, and CC chemokine ligand 2 (CCL2), have been shown to cross the central nervous system barrier, and these barriers mediate their trafficking, penetration, and uptake.
On the one hand, the levels of cytokines and chemokines in ALS change significantly due to the activation of immune cells (see table)
On the other hand, elevated levels of pro-inflammatory mediators increase the permeability of the CNS barrier, acting directly on their receptors to alter the function of resident cells, induce immune cell trafficking, and exacerbate barrier disruption and neuroinflammation.
The main role of cytokines and chemokines in ALS
doi: 10.3389/fnagi.2022.890958
Central nervous system infiltration of peripheral immune cells
Accumulating evidence suggests that many peripheral blood leukocytes are first activated in the peripheral immune system and then migrate to the central immune system in ALS.
The regulation of leukocyte transport to the central nervous system is multifaceted and depends on the activation status of leukocytes, the TJ complex at the endothelial interface, and the inflammatory microenvironment in the central nervous system and PNS.
Targeting peripheral leukocytes in ALS therapy may be feasible because peripheral leukocytes can be easily monitored and intrathecal or intraventricular are associated with multiple risks. Therefore, there is a need for a better understanding of how peripheral immune cells infiltrate the central nervous system.
★ T lymphocytes
The infiltration of T lymphocytes in ALS is well known. Chemokines and chemokine receptors are essential for parenchymal infiltration. The chronic inflammatory environment induces upregulation of leukocyte adhesion on the surface of endothelial cells, which bind to CD6 expressed on T lymphocytes to allow it to enter the brain parenchyma. In addition, T-lymphocyte-derived TNF-α and IL-17 induce the secretion of MM-9 by immune cells and motor neurons, promoting T-lymphocyte infiltration into the CNS.
A large body of evidence highlights the differences between T cell subsets and the specific mechanisms by which they enter the CNS in ALS. For example, endothelial cells secrete chemokines such as CXCL9, CXCL10, CXCL11, CCL19, CCL21, and MCP-1 to recruit CD4+ T cells through the CNS barrier. Treg cells with inhibitory effects on neuroinflammation are activated and recruited to the CNS via CCL5/CCR5 and CCL6/CCR6 mechanisms to inhibit microglial activation in the early stages of the disease.
CD8+ T cells show strong infiltration and induce motor neuron death through MHC-I expressed in activated microglia and damaged motor neurons.
★ Mast cells
Results from previous studies have shown that mast cells play a role in the early degeneration of PNS and have a knock-on effect on neuronal damage. Later studies confirmed the infiltration of mast cells in the spinal cord of patients with ALS. Expression of receptors on MC is influenced by IL-6, CCL5, and TNF-α released by activated microglia, which regulates mast cell activation and CNS recruitment.
In addition, mast cells can release proteases to TJs and extracellular matrix components, thereby affecting the permeability and integrity of the blood-brain barrier, leading to mast cell invasion of the CNS.
★ Monocyte.
Peripheral monocytes can be easily sampled. Accommodating evidence suggests that infiltrating monocyte-derived macrophages are homologs of central nervous system microglia and enter the central nervous system through the compromised blood-brain barrier in ALS. Human blood mononuclear cells are readily available in vitro and easily differentiate into macrophages.
A limited number of activated peripheral monocytes infiltrate the central nervous system and affect neuroinflammation in ALS. Previous studies have shown a change in the proportion of monocytes in ALS. In patients with rapidly progressive ALS, monocytes in the peripheral circulation are usually in a pro-inflammatory state. Recently, peripheral monocytes have been shown to infiltrate the CNS, which is associated with improved motor neuron survival in ALS, but infiltration may be limited.
In addition, monocyte-derived macrophages are activated in ALS. Activated macrophages exert neuroprotective functions by misfolding protein clearance during disease. Macrophages also show limited infiltration of the central nervous system.
The accumulation of monocytes in the central nervous system is due to the proliferation of infiltrating cells, not the infiltration of accumulated circulating monocytes.
★ Treg cells
Treg is an immune-tolerant cellular mediator with the ability to inhibit various types of immune responses. Active inhibition of Tregs plays a key role in the control of autoantigen-reactive T lymphocytes and the induction of in vivo and peripheral tolerance.
Tregs prevent the activation and effector functions of activated Tresps.
In blood leukocytes isolated from patients with rapidly progressive ALS, both the number of Tregs and their FOXP3 protein expression were reduced, and these levels were inversely correlated with the rate of disease progression.
mRNA levels of FOXP3, TGF-β, IL-4, and GATA-3 (a Th2 transcription factor) are reduced in patients with rapid progression and are inversely correlated with the rate of progression, and both are accurate indicators of progression rates.
No differences in IL-10, TBX21 (Th1 transcription factor), or IFN-γ expression were found between patients with slow and rapid progression.
Epigenetically, the percentage of methylation in the Treg-specific demethylated region is higher in ALS Treg. After in vitro expansion, ALS Tregs regained their ability to suppress control Tregs levels, suggesting that autologous passive transfer of amplified Tregs may provide a novel cell therapy to slow disease progression.
★ Other immune cells: neutrophils, natural killer cells
Few studies have discussed the role of neutrophils and NK cells in neuroimmune crosstalk. However, given the significant correlation between the increased number of neutrophils and NK cells in peripheral blood and disease progression, as well as their role in the innate immune response, it is thought to affect neuroinflammation of the central nervous system in a complex manner.
For example, mice with end-stage ALS show high NK cell frequencies in the spinal cord.
NK cell-derived IFN-γ induces microglia to develop an inflammatory phenotype, regulates the release of CCL2, a chemokine that regulates CNS infiltration from motor neurons, and impairs Treg cell migration.
Summary
Crosstalk involving central and peripheral immune cells, the central nervous system barrier, cytokines, and chemokines has been fully discussed above. Dysfunction of all these elements leads to non-fibrinous death of motor neurons. These exchanges play an important role in the systemic inflammatory environment of ALS.
The central nervous system barrier plays a vital role in crosstalk. It is important to note that the effects of neuroinflammation are twofold, as it exerts a neurotoxic or neuroprotective effect during the disease.
Normalizing immune crosstalk and homeostasis, rather than suppressing inflammation, may provide potential therapeutic targets and directions for future research.
04
Changes in the intestinal microbiota of ALS patients
Patients with amyotrophic lateral sclerosis (ALS) have a changed gut microbiome that includes an imbalance of potentially protective flora and other pro-inflammatory microbiota compared to healthy people.
The studies initially conducted were characterized by small and select patient cohorts, even less than 10 individuals, providing relatively consistent data to support dysbiosis in ALS.
Phylogenetic distribution of microbiota involved in amyotrophic lateral sclerosis
doi.org/10.3390/ijms232213665
The above data are from six studies of ALS involving a total of 159 patients with ALS and 165 healthy controls. Orange indicates inconsistent results, blue indicates a decrease in relative abundance, and red indicates an increase in relative abundance.
According to some studies, the main changes in the gut microbiota of ALS patients are as follows:
Letizia Mazzin et al., Amyotrophic Lateral Sclerosis.2021 Jul 25
A prospective longitudinal study on the composition of the ALS microbiota was published in 2020, showing that the gut microbiota of ALS patients differed compared to the control group, regardless of the degree of disability. In addition, they observed an increase in cyanobacteria (cyanobacteria are known for their neurotoxic effects). The members of the phylum Cyanobacteria were significantly higher in the patients than in the control group, supporting the hypothesis that cyanobacteria play a fundamental role in the pathogenesis of ALS.
Some studies have found that in ALS patients, glutamate-metabolizing bacteria are more abundant, and the main butyrate-producing bacteria are lower, which is consistent with the results of the analysis of the microbiota of ALS.
The existing gut microbiota studies on ALS are summarized as follows:
doi: 10.3389/fcimb.2022.839526
In these studies, the cause of pro-inflammatory dysbiosis is related to microbial imbalances that may damage the intestinal epithelial barrier and promote immune/inflammatory responses, leading to alterations and playing a role in the pathogenesis of ALS.
Differences in gut microbiota between ALS patients and mate controls
In one study, researchers explored differences in the composition of the microbiome associated with ALS.
ALS patients (n = 10) were compared with their spouses (n = 10). Patients with ALS were found to have a higher gut microbiota diversity and a deficiency of Prevonella species compared with their spouses. Healthy couples did not exhibit these differences.
Fecal and plasma inflammatory markers are similar in patients with ALS and their spouses. Predictive analysis of microbial enzymes showed reduced activity in ALS patients in several metabolic pathways, including carbon metabolism, butyrate metabolism, and systems involving histidine kinases and response modulators.
★
★ ★ ★
★
There were differences in the gut microbiota of ALS patients compared to the spouse control group. Alterations to the gut microbiota, such as by ameliorating Prevonella deficiency and/or altering butyrate metabolism, may have translational value for ALS treatment.
A case of intestinal microbiota detection of grain he-ALS
A total of 109 ALS patients were used, and a total of 442 patients were matched
Gender ratio:
- Female: 38 cases
- Male: 71 cases
By age:
- 7 cases under 30 years old
- 11 cases aged 30-40 years
- 20 cases aged 40-50 years
- 50-60 years old 46 cases
- 60 or more, 13 cases
In terms of diversity, the ALS population was slightly lower than that of the control population, but the difference was not significant.
There are some differences in the characteristics of the microbiota:
Let's look at the differences:
The Bacteroides in ALS was significantly higher than that in the control.
Faecalibacterium was lower than that of the control population;
In addition, the population of Sutterella ALS was significantly higher than that of the control population.
Bacteroides, an important genus of keystone bacteria, are found in the human gut and have a symbiotic relationship with humans. They help break down food and produce the nutrients and energy that the body needs. However, when bacteroides enter parts of the body other than the gastrointestinal area, they can cause or exacerbate infections such as abscesses, as detailed in:
Bacteroides, an important keystone bacteria in the gut
Faecalibacterium is one of the important producers of butyric acid, has an anti-inflammatory effect, maintains the activity of bacterial enzymes, protects the digestive system from intestinal pathogens. For more information about Faecalibacterium, please see:
Intestinal core bacteria - F. plasusus (F. plasus) Prausnitzii), a next-generation probiotic that prevents inflammation
Sutterella, one of the most abundant bacteria in the phylum Proteobacteria, is an anaerobic or microaerophilic, bile-tolerant bacterium with mild pro-inflammatory abilities in the human gastrointestinal tract, as described in:
Intestinal core bacteria - Sutterella
In addition to the abundant bacteria, Bifidobacteria and Butycoccus spp., ALS were also lower than the controls:
Based on the test results of cereals, the abundance of harmful bacteria in ALS patients was significantly higher than that in the control population, and the probiotics and digestion efficiency were lower than those in the control population.
In addition, vitamin B1, vitamin B12 and vitamin C were significantly lower than those of the control population, and the relative vitamin D levels were higher than those of the control population.
(Source: Corn Flora Database)
05
The gut microbiota may influence the pathogenesis of ALS
The microbiota can affect central nervous system and neuronal health in direct or indirect ways:
■ Directly through the production of neuroactive metabolites and toxins
■ Indirectly by regulating immune responses, dietary compounds, or drug metabolism
Metabolites
Gut microbes and their metabolites can directly stimulate enterochromaffin cells to produce several neuropeptides (eg, peptide YY, neuropeptide Y, cholecystokininin) or neurotransmitters (eg, serotonin), which can diffuse into the bloodstream, reach the brain, and affect central nervous system function.
The intestinal epithelium regulates the translocation of specific bacterial products, such as short-chain fatty acids, vitamins, or neurotransmitters, into the bloodstream and then through the circulatory system to the central nervous system. In this way, circulating microbiota-derived metabolites, neuropeptides, and neurotransmitters can enter the central nervous system and directly affect its neurobiology.
Regulation of microbial metabolites in ALS
Letizia Mazzin et al., Amyotrophic Lateral Sclerosis.2021 Jul 25
A) Toxins and neuroactive metabolites produced by impaired IEBs or intestinal bacteria can cross the blood-brain barrier, spread to the systemic circulation, and affect the pathogenesis of ALS, or microbial metabolic end products may indirectly affect the central nervous system through immune system regulation.
B) Bacteria-derived metabolites can alter energy homeostasis, promote oxidative stress, and induce mitochondrial dysfunction and neuroinflammation. In particular, peripheral immune T lymphocytes regulate the fate of microglia, thereby regulating neuronal degeneration or survival.
Th1, Th17, and GM-CSF-producing CD4+ T lymphocytes favored the microglial M1-like neurotoxic phenotype;
Th2, Treg, and certain CD8+ T cell types may help promote a neurosupportive M2-like phenotype.
A. muciniphila administration can ameliorate disease progression in mice, and they applied untargeted serum metabolomic analysis to identify possible mediators. Interestingly, A. muciniphila-treated mice showed elevated serum levels of NAM, and its direct administration showed beneficial effects, possibly by modulating mitochondrial function and oxidative stress pathways.
Note: NAM is a precursor to coenzymes required for energy transduction, signaling pathways, and antioxidant mechanisms and may be impaired in ALS-associated neurodegeneration.
Patients with ALS have lower concentrations of NAM in serum and cerebrospinal fluid, as well as lower expression of NAM-synthesizing bacterial genes in feces compared to healthy subjects, supporting the fact that the gut microbiota can produce compounds that are able to penetrate the blood-brain barrier and affect neuronal function.
Gut microbiota metabolites affect neuronal health
Intestinal microbial metabolites can directly or indirectly affect neuronal health through inflammation of the central nervous system.
doi: 10.1186/s12916-020-01885-3
a) Metabolites released by the gut microbiota can enter the systemic circulation, where they can enter the central nervous system, and in the case of nicotinamide released by Akkermansia muciniphila, this may alter energy homeostasis and oxidative stress.
NOTE: Nicotinamide is a precursor to NAD and NADP, which are coenzymes required for the proper functioning of energy transduction and antioxidant pathways, as well as other cell signaling mechanisms, many of which have been implicated in neurodegeneration associated with ALS.
B–D exist by a number of proposed mechanisms through which microbial metabolites can influence the immune response and have an impact on the inflammatory state of the central nervous system:
b) Short-chain fatty acids reduce inflammation by inhibiting HDAC within microglia, leading to downregulation of pro-inflammatory factors (IL-1β, IL-6, and TNF-α) and upregulation of anti-inflammatory markers (TGF-β and IL-4).
- Short-chain fatty acid-mediated HDAC inhibition can also affect Tregs to increase their activity through upregulation of FOXP3.
- Short-chain fatty acids also affect astrocytes, reducing their inflammatory effects by downregulating IL-1β, IL-6, and TNF-α.
- Finally, short-chain fatty acids exert anti-inflammatory effects on different peripheral blood mononuclear cells: they inhibit NF-kB, leading to reduced production of pro-inflammatory cytokines, immune cell recruitment and activation.
c) Aryl hydrocarbon receptor (AHR) ligands regulate astrocyte activity and produce anti-inflammatory properties.
d) Polyamines induce FOXP3 expression in Treg cells and promote their differentiation and activation. These molecules also inhibit inflammatory macrophages (M1), thereby preventing macrophage-induced inflammation.
A case of intestinal microbiota detection of grain he-ALS
In terms of neurotransmitters:
The levels of GABA (lack of anxiety, insomnia, etc.), nitric oxide (depression, anxiety, etc.), acetic acid, and propionic acid (short-chain fatty acids, lack of which leads to inflammation) in ALS patients were lower than those in the control population.
p-cresol (toxic metabolite, causing constipation, etc.) was higher than in the control population. This may also be related to gastrointestinal symptoms such as constipation that may occur in patients with ALS.
(Source: Corn Flora Database)
toxin
The gut microbiota converts dietary and environmental compounds into neurotoxins
β-Methylamino-1-alanine (BMAA) is a well-known neurotoxic amino acid found in the brains of patients with amyotrophic lateral sclerosis/PDC in Guam and is thought to be produced by standard dietary compounds in the gut. For example, cyanobacteria and other bacteria with anaerobic methylation functions can biosynthesize BMAA by methylation of L-serine and L-alanine.
Gut microbes can also convert amino acids such as L-tryptophan into bioactive molecules such as indole, which, once sulfonated, can trigger neuroinflammation and neuronal damage. The gut microbiota can metabolize choline and L-carnitine to trimethylamine (TMA), which is then demethylated to dimethylamine (DMA) and formaldehyde.
According to in vitro and in vivo studies, formaldehyde can cause mitochondrial membrane damage, the production of dangerous free radicals, and the misfolding and accumulation of neuronal Tau proteins, which can lead to the onset of ALS.
Environmental pollutants can also have a negative impact through the action of the microbiota.
Exposure to polycyclic aromatic hydrocarbons (PAHs) is a risk factor for ALS, and gut microbes can reverse the endogenous detoxification process of PAHs, regenerating them into benzo[a]pyrene (BaP), whose neurotoxic effects have been demonstrated in zebrafish.
In addition, dysbiosis of the gut microbiota may be responsible for the metabolic alterations observed in ALS. Interestingly, a decrease in intestinal dysbiosis, particularly Firmicutes, is associated with higher REE, which may be responsible for the increased energy expenditure in ALS patients.
immunoreaction
The role of microbiota-induced inflammation in the pathogenesis of ALS
▸ The gut microbiota affects the innate and adaptive immune systems
An established key point in the pathogenesis of ALS is neuroinflammation, which is associated with complex dysregulation of resident and peripheral immune cells (e.g., microglia and astrocyte activation, T cell infiltration, and increased pro-inflammatory mediators).
The gut microbiota communicates with the gut immune system, helps maintain immune tolerance, and forms an immune response during inflammation. Once a pathogen invades or the gut microbes leak, microbial-related molecular patterns can stimulate innate cells to produce pro-inflammatory cytokines, which in turn activate adaptive immune cells, thereby promoting the disruption of immune homeostasis.
In addition to innate immune cells, gut microbes can directly affect the development and differentiation of CD4+ and CD8+ T cells, the main components of the adaptive immune system.
▸ Dysbiosis of the gut microbiosis affects several brain biological processes
Germ-free mice and antibiotic-treated mouse models show a wide range of immune abnormalities, including altered microglial density, morphology, and maturation, suggesting that gut microbiota can influence the development and function of immune cells in the central nervous system.
▸Short-chain fatty acids affect Tregs and thus ALS
Short-chain fatty acids are the final metabolic microbial products of dietary fiber, mainly produced by Bacteroides and Firmicutes. They are known to mediate regulatory T cell (Tregs) induction through histone deacetylase inhibition.
ALS is characterized by simultaneous activation of different lymphocyte subsets Th1 and Th17 and a reduction in Tregs, which have a protective effect in both mice and humans, and more Tregs are associated with slow disease progression.
Tregs have been shown to directly differentiate macrophages from the M1 state to the M2 state, with M2 microglia associated with stable disease stages, while Th1 and M1 microglia predominate in the rapidly progressive phase, indicating a shift from protective to toxic.
▸Intestinal microbiota changes affect the occurrence and progression of ALS symptoms
One study found that changes in the gut microbiota precede the expansion and activation of the circulatory and CNS immune systems, as well as the onset and progression of symptoms.
Gut microbiota-driven pro-inflammatory signaling may be essential for glial physiological function and the maintenance of neuronal health. In fact, the gut microbiota regulates astrocyte activity through aryl hydrocarbon receptor (AHR)-mediated mechanisms involving type I interferon signaling.
Drug metabolism
Effect of gut microbiota on the efficacy of ALS drugs
The intestinal microbiota can also influence the disease through the metabolism of intestinal drugs.
In 2019, a study evaluated the ability of a group of gut bacteria to metabolize a range of commonly prescribed drugs, including riluzole, the only drug shown to have a survival benefit in patients with ALS.
The 40 species of bacteria screened were significantly metabolized by riluzole, many of which had varying prevalence in the population.
Plasma concentrations of riluzole have been reported to show lower intra-patient variability compared to relatively high inter-patient variability, which cannot be explained by metabolic differences following intestinal absorption. Correction of riluzole bioavailability by gut microbiota can explain the variation in plasma levels between patients.
Other symptoms of ALS
Effect of gut microbiota on non-motor amyotrophic lateral sclerosis symptoms
The gut microbiota has been linked to other symptoms that affect people with ALS, such as depression, anxiety, and constipation. The gut microbiota can produce various peptides and neurotransmitters that can directly affect mood, while the brain influences the gut through a variety of mechanisms, including stress responses. Unraveling the role of the gut microbiota in regulating brain function associated with neuropsychiatric disorders is only just beginning, but it has the potential to be a means of improving the quality of life of ALS patients.
With regard to constipation, another symptom often reported by patients with ALS, the role of the microbiome in the luminal fluid (metabolism of bile acids, production of short-chain fatty acids and production of methane) and the role of the mucosal layer of the colon in regulating the absorption of fluid into the bloodstream have been proposed. Improving the management of these symptoms will improve quality of life, regardless of disease progression.
Above we can know that the gut microbiota can affect ALS through hypermetabolism and gastrointestinal abnormalities, leading to a deeper understanding of the complex network of microbiome-host interactions behind ALS.
06
Diagnosis of ALS
Some people who don't know much about ALS tend to confuse ALS with other neurodegenerative diseases. The four common neurodegenerative diseases are amyotrophic lateral sclerosis (ALS), Huntington's disease, Alzheimer's disease (Alzheimer's disease), and Parkinson's disease.
▸ Alzheimer's disease
Alzheimer's disease (AD) is a progressive degenerative disease of the nervous system with insidious onset. Clinically, it is characterized by generalized dementia such as memory impairment, aphasia, apraxia, agnosia, impairment of visuospatial skills, executive dysfunction, and personality and behavior changes, and the etiology is still unknown.
The onset of the disease is slow or insidious, and patients and their families often cannot tell when the disease began. It is more common in people over 70 years of age, and in a small number of patients, symptoms become clear quickly after physical illness, fracture, or mental irritation. There are more females than males (3:1 female:male).
✦ Difference with ALS
ALS is also called motor neuropathy. The lesions mainly involve upper and lower motor neurons, and the main manifestations are limb weakness, muscle atrophy, fasciculation, and may be accompanied by choking on drinking water, dysphagia and other manifestations.
Alzheimer's disease mainly affects the patient's mental and behavioral ability, executive ability, thinking response, and life ability. Symptoms of atrophy and weakness in the limbs are generally not present.
▸ Parkinson's disease
Parkinson's disease, also known as parkinson's disease, is a chronic disease of the central nervous system that affects the patient's mobility, and mostly occurs in middle-aged and elderly people.
• Manifest symptoms
The main manifestations in the early stages of the disease include resting tremor, muscle rigidity, slowness, difficulty initiating movements, and postural abnormalities. A resting tremor is an uncontrollable shaking of a person's hand or arm that occurs at rest or worsens during emotional stress.
Later, it was discovered that in addition to tremors, there were other symptoms such as panicked gait (small broken steps when walking and walking faster and faster), lowercase syndrome (writing smaller and smaller), and no back and forth swinging of the upper limbs when walking.
✦ Difference with ALS
•The cause of the disease is different
Parkinson's disease is a disease caused by damage to the striatum of the brain that leads to a disorder of dopamine secretion, and its cause is related to brain trauma, aging and other factors.
In most cases, the cause of ALS is unknown, and a few are caused by genetic factors, and motor neuron damage often occurs.
•Clinical manifestations differ
Clinical manifestations: Patients with Parkinson's disease will have abnormal symptoms such as trembling and inflexibility of limbs, and generally do not have muscle atrophy. However, ALS often occurs after muscle atrophy, which causes patients to gradually lose their normal motor function.
• Hazards are different
Parkinson's disease is a neuropathic disorder characterized by tremors, bradykinesia, and abnormal gait.
ALS is a motor neuron disease characterized by gradual muscle atrophy and weakness, and more severe conditions such as dysphagia, speech and respiratory failure may occur.
▸ Huntington's disease
Also known as chorea or Huntington's disease. An autosomal dominant neurodegenerative disease caused by a mutation in a patient's gene on chromosome 4, which produces a mutated protein that gradually clumps together in cells to form large molecular clusters that accumulate in the brain and affect the function of nerve cells.
• Manifest symptoms
In general, patients develop the disease in middle age, which is characterized by chorea-like movements, and gradually loses the ability to speak, move, think, and swallow as the disease progresses, and the disease continues to progress for about 10 to 20 years, and eventually leads to death.
✦ Difference with ALS
• Athletic aspects
Huntington's disease is characterized by throbbing or twitching of the limbs, but ALS is a muscle atrophy that causes inability to move, and tics are different from the "flesh jumping" of the early days of ALS, which is a large movement similar to "dance".
• Cognitive aspects
People with ALS are conscious and do not develop cognitive impairment.
However, Huntington's disease can manifest as progressive dementia. Memory and numeracy are reduced in daily life and work, and the patient's ability to remember new information is only mildly impaired, but recall is markedly impaired.
Affective disorders are the most common psychiatric symptoms of Huntington's disease and include anxiety, nervousness, irritability, or apathy, or loss of interest.
People with Huntington's disease may also have personality changes, antisocial behaviour, schizophrenia, paranoia and hallucinations.
Diagnosis of ALS
In terms of diagnosis, because the cause and mechanism of ALS are still unclear, specific diagnostic markers have not been screened for this disease.
In addition, the early symptoms of ALS mentioned earlier are not typical and must be distinguished from other neurodegenerative diseases, so early patients will spend a lot of manpower, material resources and time to make differential diagnosis to rule out.
✦ Manifestation diagnosis
(1) The examination should assess the strength of the muscles of chewing and swallowing, including the mouth, tongue and throat muscles.
and (2) lower motor neuron (LMN) function, such as muscle atrophy, muscle strength, or muscle beating (called fasciculations).
and (3) upper motor neuron (UMN) function, such as tendon hyperreflexia and muscle spasms (degree of muscle tension and rigidity).
(4) Loss of control of emotional reactions, such as emotional changes such as crying or laughing. Changes in thinking, such as loss of judgment or loss of basic social skills. The examiner will also assess the patient's speech fluency and ability to recognize words. These symptoms are uncommon and not easily taken seriously.
Note: The neurologist will also ask questions such as pain, sensory loss, or extrapyramidal problems.
✦ Detection and diagnosis
Electromyography (EMG): Needle-like electrodes are inserted through the skin into various muscles. This test assesses muscle contraction and electrical activity at rest. Muscle abnormalities seen on an electromyography can help doctors diagnose or rule out ALS.
Nerve conduction study: This study measures the ability of nerves to send impulses to muscles in different areas of the body. This test can determine if there is nerve damage or certain muscle or nerve disorders.
MRI: MRI can produce detailed images of the brain and spinal cord. Shows spinal cord tumors, cervical disc herniation, or other conditions that may be causing symptoms.
Blood and urine tests: Analysis of your blood and urine samples in a laboratory may help with the differential diagnosis.
Spinal tap (lumbar puncture): Cerebrospinal fluid is obtained to complete the examination and to help diagnose and rule out ALS.
Muscle biopsy: If your doctor thinks you have a muscle disorder and not ALS, this test will take your muscle tissue under local anesthesia for analysis.
Grain grass - prediction by microbiota characteristics
Microbiota characteristics were used to predict ALS and control populations
After metabolic and other indicators: Combined accuracy: 0.88
It can be understood that based on the characteristics of the microbiota, 84% of ALS patients can be distinguished.
(Source: Corn Flora Database)
07
Treatment and improvement of ALS
While there is currently no complete cure for ALS, there are treatments that can slow the loss of bodily function and improve the quality of life for patients.
01
Medication improvement
Nervous system-based drugs
Riluzole (Rilutek，利鲁唑)
is an oral medication that is FDA-proven for the disease-modifying treatment of ALS.
It has been reported to reduce damage to motor neurons by lowering levels of glutamate, which transmits messages between nerve cells and motor neurons. Clinical trials in patients with amyotrophic lateral sclerosis have shown that riluzole prolongs survival by several months, particularly in bulbar disease.
Note: People with dysphagia may prefer a thickened liquid form (Tiglutik) or tablet (Exservan) that dissolves on the tongue.
依达拉奉(Radicava)
Administered by intravenous infusion, it has been shown to slow the decline in clinical assessment of daily functioning in patients with ALS.
Researchers believe that edaravone works by scavenging free radicals, thereby reducing damage to the nervous system and slowing disease progression.
Sodium phenylbutyrate-taurine diol (Relyvrio)
The efficacy of Relyvrio in the treatment of ALS was demonstrated in a 24-week multicenter, randomized, double-blind, placebo-controlled, parallel-group study.
Sodium phenylbutyrate-taurine diol is used in patients with ALS. Based on the ALSFRS-R score over 24 weeks, sodium phenylbutyrate-tauroursodiol has been reported to result in a slower rate of functional decline than placebo.
Relyvrio can be taken orally by mixing one packet with 8 ounces of room temperature water. It can also be administered through a feeding tube. The recommended dose for the first three weeks is one sachet per day (3 g sodium phenylbutyrate and 1 g tauroursodiol). After three weeks, the dose was increased to one sachet twice a day. The medication can be taken before a snack or meal.
Caution:
The most common adverse effects of Relyvrio were diarrhea, abdominal pain, nausea, and upper respiratory tract infection. Relyvrio contains tauroursodiol, a bile acid that may cause worsening diarrhea in patients with conditions that interfere with bile acid circulation. These patients should consider consulting a specialist before taking Relyvrio.
巴氯芬(Baclofen)
Baclofen helps relieve muscle spasms by relaxing the body's muscles.
Studies have shown that baclofen is particularly effective in relieving muscle spasms when used with assisted or unassisted range-of-motion physical therapy.
Note: The dose of baclofen must be monitored closely to avoid limb and trunk weakness when the patient takes a high dose (e.g., 40 to 80 mg) too early.
Digestive system-based medications
Glycopyrrolate
A variety of medications can reduce saliva production. As swallowing becomes more difficult, it usually accumulates in the mouth. One of the most common drugs is glycopyrrolate (Robinul).
Atropine sulfate
Atropine sulfate helps relieve excess saliva. Atropine: 0.4 mg tablet
Trihexylbenzene
Trihexylbenzoyl also helps control excess saliva.
Your doctor may prescribe medications for other digestive disorders to help relieve other symptoms of ALS, such as constipation.
Drugs based on other systems of the human body
替扎尼定(Tizanidine)
Tizanidine helps relieve muscle spasms by relaxing muscles.
Tizanidine works by blocking nerve signals sent from the brain to the muscles.
The dosage of tizzanib is administered in a range of 2-10 mg per day.
Note: Side effects, while uncommon, may occasionally include weakness, constipation, dizziness, and other problems.
Methylcobalamin
Methylcobalamin, or methyl B12, is a daily injection of medication used to boost energy and build muscle strength. Prescription required for these ingredients: 25 mg/1mL (pH 2.7-3.0)
glutathione
Glutathione is often effective for limb strength. It is given intravenously. A butterfly syringe is required. These ingredients require a prescription: Compound Glutathione 200mg/ml.
Quinine sulfate
Quinine sulfate reduces cramping.
Muscle cramps should be stopped or significantly reduced the night before bedtime. Prescription requiring 324 mg capsules, without fillers/preservatives.
Typically, quinine sulfate is used when patients with ALS have not been successfully treated with tizanidine and/or baclofen.
Note: Side effects of medications may include allergic reactions, thrombosis (the formation of blood clots in blood vessels), or kidney problems.
Nuedexta
Nuedexta can improve chewing and swallowing, in addition to relieving the effects of pseudobulbar – excessive laughter and/or crying. Even if these are not current problems, Nuedexta often acts as a preventative agent and may delay the onset of bulbar problems. Universal formula: dextromotsafine 25 mg / quinidine 10 mg
美西律Mexilitine
Taking 300 mg of mexiletine daily can relieve muscle cramps. This medication can be prescribed by a neurologist or doctor. 200 mg capsules (regular)
NeuRx diaphragm pacing system
The NeuRx diaphragm pacemaker uses a minimally invasive approach that is scientifically and clinically proven to maintain the strength of the diaphragm muscle and the resulting lung capacity.
Others, such as pain relievers such as diazepam (Diastat, Valium) or muscle relaxants, can help relieve spasticity.
Nonsteroidal anti-inflammatory drugs (NSAIDs)
Because inflammation promotes the development of ALS, researchers speculate that NSAIDs (anti-inflammatory drugs) may have a protective effect. However, some clinical trials have not found any beneficial effect on overall survival in patients with ALS.
Nonsteroidal anti-inflammatory drugs, such as ibuprofen or naproxen, may help relieve pain and discomfort throughout the body.
Note: Due to potential gastrointestinal and cardiovascular side effects, NSAIDs should only be taken as directed.
加巴喷丁 (Gabapentin)
Gabapentin is an antiepileptic drug, but it can also be used for ALS.
Animal studies have shown that gabapentin can improve survival in people with ALS, and clinical trials have shown that it can reduce muscle cramps and tics in people with ALS.
Gabapentin works by regulating glutamate levels, similar to riluzole.
Note: Side effects of gabapentin include fatigue, weight gain, indigestion, drowsiness, dizziness, ataxia, and tremor.
三环类抗抑郁药（Tricyclic antidepressants）
These drugs are widely used in the treatment of ALS and have a variety of effects. In particular, depression and anxiety are common in ALS, and appropriate doses of tricyclic drugs can alleviate depression.
Note: Side effects, such as dry mouth and weight gain, may also help with other symptoms of ALS, such as excess oral saliva and weight loss.
吗啡（Morphine）
Morphine is an opioid that can be used to treat pain. Morphine can help relieve the feeling of hypopnea in people with advanced ALS.
In cases of emotional instability, selective serotonin reuptake inhibitors, amitriptyline, benzodiazepines, and dextromethorphan/quinidine hydrobromide can be used, among others.
02
Microbiota-based interventions
Drink
Nutrition has a direct impact on the gut microbiota, which influences the local gut immune response and thus the autoimmune response.
The presence of compounds with antioxidant potential, such as vitamins, curcumin, coenzyme Q10, etc., in the diet, can be used as a therapeutic strategy.
Foods that should be excluded or restricted
▸ Avoid seafood
The literature has reported that the high incidence of ALS in the Kii Peninsula of Japan may be related to β-methylamino-L-alanine (BMAA). BMAA is a naturally occurring, neurotoxic, non-protein amino acid produced by symbiotic cyanobacteria in the roots of cycad seeds, which are particularly common in the region. It is hypothesized that ALS patients in this region are unable to stop BMAA accumulation.
Dietary sources of BMAA may be seafood, such as fish, mussels, crabs, and oysters. A high incidence of ALS has also been reported in Guam, where the population uses potential cycad-derived products. Another possible source of BMAA contamination could be fruit bats or flying foxes, as they consume cycad seeds, which are an integral part of the diet of local residents.
Although more research is needed, researchers have recently demonstrated the relationship between BMAA and microcystin leucine and arginine (other cyanide toxins) using a zebrafish larval model. In addition, neonatal rats exposed to BMAA were affected by motor deficits, suggesting that exposure during neurodevelopment may contribute to ALS. Previous studies have investigated the mechanism of action of BMAA on neurodegeneration: BMAA kills NADPH yellow transmitterase-positive motor neurons and exerts a toxic effect on glial cells that affect motor neuron damage.
▸ Avoid high-fat diets (controversial)
Excessive intake of fatty foods, especially saturated fat foods, and loss of ROS defense mechanisms, such as mutations in the SOD1 gene, are the main aspects of ALS patients. Therefore, it is reasonable to link the high consumption of fatty foods in some countries to a greater likelihood of detecting ALS cases.
This may partly explain why the incidence of ALS is so high in states such as Sweden and Scotland, where the diet is known to focus particularly on fatty food intake.
However, the role of fat intake in ALS is controversial, as different studies have shown opposite results. Nelson et al. demonstrated that high fat intake was associated with the onset of ALS. Another study showed the opposite result: subjects with higher fat intake had a reduced risk of ALS.
▸ Avoid glutamate diets
Adverse effects of glutamate have been reported in ALS. It is the main excitatory neurotransmitter in the brain, and high levels of glutamate present in mushrooms, milk, and protein-rich foods can lead to increased intracellular calcium levels, which promotes neuronal death.
▸ Avoid heavy metal diets
Exposure to metals is thought to be a possible risk factor for ALS, but the results are inconclusive. Studies have shown that cadmium and lead may be associated with an increased risk of ALS and zinc, while their risk is reduced based on the level of metals in the blood before the disease, with lead having the strongest a priori link.
Mercury is suspected to be part of the pathogenesis of ALS, but the results are inconclusive, particularly in the diet of mercury exposure, especially seafood consumption. Mercury is produced by several industries and stored in aquatic predators such as sharks, swordfish, mackerel, and tuna.
Mercury can produce oxygen radicals, promote excitotoxicity, and reduce DNA, RNA, and protein synthesis, all of which are associated with ALS. However, some studies have reported that patients with ALS are exposed to the same amount of mercury as those with non-ALS. The difference may be that patients with ALS are more susceptible to mercury due to genetic/epigenetic predispositions.
caution
The differences between different studies may be due to the fact that a single metal analysis may not adequately assess the correlation of health risks, suggesting the potential for toxic exposure to interact with additives or synergistic effects.
Can be introduced into the diet
Early research suggests that polyphenols (e.g., resveratrol, curcumin, epigallocatechin gallate, quercetin, and phenolic acids) present in fruits, vegetables, coffee, tea, and whole grains may have favorable neuroprotective effects on ALS.
Observed in vivo and in vitro, these bioactive compounds may have the potential to regulate mitochondrial biogenesis, improve energy metabolism, reduce toxic protein aggregation, reduce microglia and astrocyte inflammation, and improve motor function and survival.
Nutritional care for patients with ALS should include a high intake of fruits, vegetables, high-fiber grains, and lean protein sources such as fish and chicken.
—Nieves, associate professor of clinical epidemiology and nutrition at Columbia University
Eat more fruits and vegetables
In a study that included more than 302 patients with ALS, fruits, vegetables, antioxidants, and β-carotene were shown to be associated with enhanced ALS function.
In a small study of 77 South Koreans, increased intake was associated with a reduced risk of sporadic amyotrophic lateral sclerosis when the benefits of fruit and β-carotene were specifically studied.
Follow the Mediterranean diet
One known high-phenol diet is the Mediterranean diet, which has also been shown to reduce neurodegeneration through high olive oil content. SOD1G93A mice exposed to a diet of high virgin olive oil had longer lifespans and improved exercise capacity.
A second supportive study showed that extra virgin olive oil extract acts as a neuroprotective agent in cultures obtained from SOD1G93A mouse models. The extract reduces neurodegeneration by downregulating the amount of nitric oxide released by activated glial cells stimulated by SOD1 mutations. In addition, the TLR4 signaling pathway, a known pathogenic pathway in ALS, was inhibited by olive oil extract.
Another group focused on anthocyanin-rich extracts from strawberries, a compound known for its antioxidant, anti-inflammatory, and anti-apoptotic properties. Anthocyanins belong to the flavane group and are plant phenols. They found that hSODG93A mice supplemented with the extract exhibited delayed onset and prolonged survival.
Eating Xi habits
One of the main factors in the pathogenesis of ALS appears to be a lipid-based diet, which plays a crucial role in neurodegeneration due to the high release of ROS.
25–68% of patients with ALS exhibit an hypermetabolic phenotype of increased energy expenditure, especially at rest.
Patients with advanced ALS may require a high-fat diet to compensate for caloric intake
Recent studies have shown that patients with presymptomatic ALS may have an increased total daily energy expenditure compared to healthy individuals.
In ALS, weight loss is an independent prognostic factor, with a 1-point drop in body mass index (BMI) associated with a 30% increase in mortality.
High-calorie food supplements with high fat content can stabilize weight loss in patients with advanced ALS. This can be explained by the metabolic changes reported in the studies of presymptomatic mice.
Inadequate food intake and weight loss due to dysphagia and loss of appetite in patients with ALS may reflect hypermetabolism and increased catabolic requirements (figure below). This may lead to ALS patients increasing their caloric intake by eating fatty foods as a compensatory measure.
Metabolic differences between healthy individuals and patients with amyotrophic lateral sclerosis
(A) In healthy individuals, energy intake is used to meet energy requirements during normal energy requirements, but when excess energy is present, energy is stored in adipose tissue and liver. The inability to maintain energy supply leads to a negative energy balance, in which energy reserves in adipose tissue and liver are used to meet energy needs.
(B) Patients with amyotrophic lateral sclerosis have hypermetabolism, i.e., increased energy requirements. In fact, in ALS, reduced energy intake leads to a decrease in energy storage in adipose tissue and liver, and increases dependence on stored energy use. Thus, the decrease in body mass index in ALS patients is a consequence of negative energy balance and high metabolism.
Probiotics
A detailed study published in the journal Nature showed that intestinal supplementation with Akkermansia muciniphila, an intestinal microbiome that plays an important role in the degradation of intestinal mucin, could improve ALS symptoms in genetically SOD1G93A mice.
At the metabolite level, the beneficial effects of intestinal supplementation of Akkermansia muciniphila were shown to be dependent on an increase in nicotinamide levels in the central nervous system of SOD1G93A mice, while also demonstrating a down-regulation of nicotinamide levels in ALS patients. However, in ALS models and patients, mucin degradation produces short-chain fatty acids, and some SCFA-producing bacteria are negatively affected.
For more information about AKK bacteria, please refer to:
AKK bacteria – the next generation of beneficial bacteria
In ALS patients treated with probiotics daily for 6 months, the abundance of Rikenellaceae was significantly increased.
The probiotic formula is a blend of five lactic acid bacteria: Streptococcus thermophilus ST10–DSM 25246, Lactobacillus fermentum LF10–DSM 19187, Lactobacillus delbrueckieckie LDD01–DSM 22106, Lactobacillus plantarum LP01–LMG P-21021, and Lactobacillus salivarius LS03–DSM 22776. There were no adverse events due to probiotic supplementation. Bacterial diversity was moderated in ALS patients compared to the control group, with significant increases in cyanobacteria at the phylum, family, and genus levels in ALS patients, and a decrease in cyanobacterial abundance over time in both the probiotic and placebo groups, although the difference was not significant.
Prebiotics
A study published in 2013 reported the beneficial effects of the most commonly used prebiotic in GM SOD1G93A mice, including the administration of galacto-oligosaccharides in this animal model, which delayed the onset of disease, extended the lifespan of mice, significantly reduced motor neuron loss and muscle wasting, and improved the inflammatory response of the central nervous system in SOD1G93A mice.
Other widely used prebiotic compounds are polyunsaturated acids. In particular, in a longitudinal study that included a prospective cohort of five ALS patients in the United States, it was shown that ingestion of Omega-3 polyunsaturated acids could delay the onset of the disease.
However, supplementation with eicosapentaenoic acid in the diet of transgenic SOD1G93A mice during the presymptomatic phase accelerated disease progression and shortened the lifespan of mice, suggesting that the toxic aldehyde oxidation products of this polyunsaturated acid increased in the spinal cord of animals, increasing reactive microglia.
Postbiotics
Postbiotic formulations are the latest addition to the biological family and include bioactive compounds produced by food-grade microorganisms during fermentation, such as short-chain fatty acids, microbial components, functional proteins, secreted polysaccharides, extracellular polysaccharides (EPS), cell lysates, phosphophophosphoric acids, peptides derived from pepticomannan and columnar structures.
The administration of butyrate increases the level of Treg lymphocytes in the blood, favors the reduction of the level of the inflammatory cytokine IL-17, and slows the disease progression in SOD1G93A transgenic mice.
Michy transplantation
A female patient with ALS underwent a transendoscopic enteral tube to undergo a flushed microbiota transplantation (WMT), a modified fecal microbiota transplantation (FMT), at a 12-month follow-up.
This case report is the first to demonstrate direct clinical evidence for the use of WMT in the treatment of ALS, suggesting that WMT may be a new treatment strategy to control this so-called incurable disease.
It is important to note that the accidental scalp trauma that the patient later suffered was treated with prescription antibiotics, which led to a worsening of ALS. Subsequent salvage WMT succeeded in halting the progression of the disease and rapidly improved.
Other supplements
★ Creatine.
Creatine is a dietary supplement that is noteworthy due to its beneficial effects. It is an endogenous compound synthesized from arginine, glycine, and methionine. Since most creatine is stored in skeletal muscle, athletes are Xi to incorporate it into their diet to improve muscle tone.
Recent studies have described novel uses of creatine in preventing or delaying the onset of neurodegenerative diseases. In particular, long-term creatine supplementation has been shown to improve survival and motor coordination. They measured the neuroprotective effects of creatine and studied transgenic mice with altered versions of the SOD1 gene. The results showed that creatine administration protected neurons from oxidative damage. Athletes who supplemented with creatine had no adverse side effects.
However, two clinical trials completed in 2003 and 2004 tested oral creatine supplementation, which provided little significant improvement in longevity and muscle strength in ALS patients alone. Therefore, more research is needed to understand the actual amount of creatine at work, and as a result, the Northeast Amyotrophic Lateral Sclerosis Consortium (NEALS) is currently analyzing the long-term effects of creatine supplementation.
★ Coenzyme Q10
Coenzyme Q10 (CoQ10), or ubiquinone, an endogenously produced lipid, is present in our diet and functions as a cofactor in the mitochondrial respiratory system.
Ubiquitinol is a reduced form of coenzyme Q10 and has antioxidant and anti-inflammatory effects. It avoids the formation of free radicals, changes in proteins, lipids and DNA, and reduces the concentration of lipid peroxidation.
In addition, there is an association between an increase in ROS and a deficiency of coenzyme Q10 in many diseases, including neurological disorders.
Some studies have reported the beneficial effects of CoQ10 in different diseases such as hypertension, fibromyalgia, and male infertility. Coenzyme Q10 is also used in several neurodegenerative diseases, such as ALS and Parkinson's disease. A balanced diet can provide adequate amounts of CoQ10, but vulnerable subjects may need supplementation. Although coenzyme Q10 was well tolerated, studies were limited to pregnant women and children.
Note: Coenzyme Q10 may cause side effects such as diarrhea, vomiting, and rashes. In addition, coenzyme Q10 may reduce the therapeutic effectiveness of several medications, such as warfarin.
★ L-serine supplements
Dietary supplements of the amino acid L-serine also act as a neuroprotective agent.
L-serine supplementation was identified as a cytoprotective agent against BMAA toxicity and led to L-serine supplementation as a potential treatment. A phase 1 clinical trial published in 2018 reported a 34% reduction in the slope of progression.
★ Vitamin.
Vitamins are involved in the development of the nervous system and can be used as a prognostic factor. Due to their cellular antioxidant properties, they can also be used in the treatment of ALS. They are generally well tolerated and do not cause significant adverse effects. However, their use as a supplement remains controversial.
- Vitamin E
The effects of vitamin E supplementation on cognitive function and neurological disorders are controversial. Several studies have shown no effect in people with cognitive deficits or Alzheimer's disease. Other studies have found that vitamin E can lower OS markers after 3 months of vitamin E and riluzole in patients with ALS, which is a beneficial effect. However, vitamin E does not affect the survival of patients.
Recent studies have shown that vitamin E also has regulatory functions, including signal transduction, inhibition of protein kinase C activity, inflammatory response, and regulation of gene expression. High intake of vitamin E (associated with polyunsaturated fatty acids such as Omega-3s, which are present in fish and algal oil) is associated with a 50-60% lower risk of ALS. Although vitamin E supplementation has a protective effect against neurodegenerative diseases, its efficacy remains to be demonstrated.
- Vitamin C
Another vitamin with a potential role in ALS is vitamin C. Limited studies have been conducted and a small number of samples have been used. Prior to ALS, vitamin C supplementation in animal models did not affect the onset of ALS, but reduced the progression of disease-induced paralysis.
It was also found in the Guhe database that the vitamin C in the intestinal microbiota test results of ALS patients was significantly lower than that of the control group.
- Vitamin A
Low levels of vitamin A have been reported in neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. However, there are conflicting results regarding the role of vitamin A in patients with ALS. Fitzgerald et al reported that a high intake of vitamin A contained in carotenoids was associated with a low risk of developing ALS. Other studies have found no significant association between vitamin A and ALS.
★ Phytochemicals
The low incidence of neurodegenerative diseases in China may be due to the widespread consumption of fruits and vegetables, which is associated with the abundance of phytochemicals.
Previous studies have shown that plant-derived bioactive compounds, known as phytochemicals, have neuroprotective effects in neurodegenerative diseases. In fact, a growing body of research confirms their antioxidant properties. Phytochemicals are found in vegetables, grains, and fruits and are often described in the literature as "nutritious foods."
Phytochemicals include a wide range of compounds such as carotenoids, phenolic compounds, and terpenoids.
carotenoid
Carotenoids are a plant pigment that is widely found in many fruits, with typical red, yellow, and orange colors. They target peroxy groups. They are also precursors to vitamin A, another antioxidant.
The literature reports the synergistic effect of β-carotene with vitamins E and C in scavenging reactive nitrogen species. Previous studies have shown that carotenoid intake is inversely associated with ALS risk.
Polyphenols
Polyphenols are a class of compounds that are made up of a variety of molecules. It is characterized by the presence of at least one phenolic ring, hydroxyl, methyl, or acetyl group substituted for hydrogen that is important for antioxidant and antitumor activity.
Several studies conducted in animal models of ALS have shown that polyphenols have neuroprotective effects. Flavonoids are the main components of phenolic compounds. They belong to a large group of plant pigments, and their chemical structure is derived from flavonoids. They are made up of the following subclasses: anthocyanins, flavanones, flavano-3-ols, flavonoids, flavonols, and isoflavones.
Flavonoids play a role in neuroinflammation, inhibiting microglial activation and interacting with neuronal receptors. Human neuronal SH-SY5Y neuronal cells are a neurodegenerative disease model that is treated with several flavonoids, namely quercetin, isoquercetin, and afzeline. The treatment showed beneficial effects of downregulating cyclooxygenase-2 expression and the apoptotic pathway.
Resveratrol is an antioxidant compound found in grapes that has been extensively studied for its neuroprotective properties. It regulates Sirtuin 1 (SIRT1), a major member of the Sirtuin deacetylated protein, which regulates gene expression through epigenetic gene silencing. One study showed that resveratrol increased the expression of SIRT1 in the cortex and hippocampus, reducing cognitive impairment.
Resveratrol reduces in vitro neurotoxicity in cerebrospinal fluid (CSF) in patients with ALS, prevents neuronal loss, and improves Ca2+ homeostasis, which appears to be related to the antioxidant capacity of resveratrol. Curiously, use in conjunction with riluzole inhibits this protective effect.
In fact, Ca2+ instability is associated with impaired autophagy mechanisms and toxic protein aggregation in neurodegenerative diseases, including amyotrophic lateral sclerosis. Therapeutic interventions aimed at modulating the autophagy pathway appear to be an interesting way to reduce protein aggregation, mainly in the early stages of ALS.
Extended reading:
Effects of the interaction between gut microbiota and dietary polyphenols on human health
Curcumin
Curcumin, which is extracted from the rhizomes of turmeric in the ginger family, may have beneficial effects on neurodegeneration due to its anti-inflammatory and antioxidant properties, as demonstrated by experimental animal models. However, the clinical efficacy of curcumin remains controversial. Given curcumin's potent activity as an antioxidant, it may play a key role in neuronal degeneration.
In fact, increased levels of reactive oxygen species (ROS) stimulate transcription of pro-inflammatory genes and the release of cytokines such as TNF-α, IL-1, IL-6, and chemokines that contribute to neuroinflammatory processes. Thus, the chronicity of neuroinflammation can be considered the cause of neuronal degeneration.
Several studies in mouse models have shown that curcumin can reduce oxidative stress conditions and increase levels of antioxidants such as glutathione and superoxide dismutase. In particular, the literature has reported the presence of an overexpressed and mutant version of TAR DNA-binding protein 43 (TDP-43) in familial ALS. The result is its aggregation and localization errors in neuritis or cytoplasm.
The researchers analyzed the potential role of curcumin as a therapeutic agent using a cellular ALS-like model produced by mutant human TDP-43. They demonstrated that the dimethoxycurcumin present in curcumin has a protective effect on mitochondrial membrane potential, reducing the level of uncoupling protein 2.
A clinical study showed that treatment with nano-curcumin and riluzole for 1 year improved the survival rate of ALS patients. Curcumin has no adverse toxicological effects on rats or humans. However, in dose-response studies, some patients exhibited episodes of diarrhea and nausea, possibly side effects.
Extended reading:
How to regulate the intestinal flora?Introduction to common natural substances, probiotics, and prebiotics
Terpenoids
Terpenoids are a very large family of plant secondary metabolites. In vitro studies have shown that diterpenes, monoterpenes, and sesquiterpenes extracted from aromatic plants have significant antioxidant activity, suggesting that they are anti-neurodegenerative compounds.
Omega-3 + Vitamin E
Not all natural compounds that show significant health benefits also have neuroprotective effects in neurological disorders. For example, Omega-3 supplementation in a mouse model of ALS has reported an increase in cellular damage that may increase disease progression. Similar results were obtained in a recent study of a mouse model of familial ALS. However, the combination of Omega-3 and vitamin E can reduce the risk of ALS.
Other therapies
Physical therapy and special equipment can enhance an individual's independence and safety throughout the course of ALS.
Hyperthermia or whirlpool therapy to relieve muscle spasms.
Moderate exercise is recommended, but may help maintain muscle strength and function. Gentle, low-impact aerobic exercise, such as walking, swimming, and cycling, strengthens unaffected muscles, and range of motion and stretching can help prevent muscle spasms and contractures.
Physical therapists can recommend exercises that provide these benefits without over-exercising the muscles.
Occupational therapists can recommend the use of devices such as splints, ramps, orthotic braces, walkers, handrails, extensors, wheelchairs, etc., to help individuals conserve energy and stay active.
Speech therapy and communication training to maintain verbal communication skills as much as possible.
Special equipment such as wheelchairs, electric beds, or mattresses to maximize functional independence.
Mindfulness for stress reduction
According to the results of a study published in the European Journal of Neurology, mindfulness-based programs may help improve anxiety and depression in people with ALS.
An open-label, randomized clinical trial was conducted to evaluate whether mindfulness Xi improved depression and anxiety at 18 months after diagnosis in 100 patients with ALS. Patients are assigned to receive either usual care or an eight-week mindfulness-based stress reduction (MBSR) program.
Annotation:
Mindfulness can be thought of as a non-judgmental way that shifts attention to the process of experiencing the moment by noticing how the present moment is novel.
The goal of the MBSR program is to shift attention to the present moment ("What I'm doing now; how I'm feeling right now") and to accept feelings, perceptions, and emotions without judgment.
Studies have shown that the intervention group using ALS-specific MBSR reported better quality of life and lower levels of depression compared to patients who received usual care.
Note: At all stages of the disease, the patient's individual wishes should be taken into account and advance care planning should be started as early as possible.
Conclusion
Patients with ALS exhibit varying disease severity, and although some risk factors have been identified, these are insufficient to adequately account for this heterogeneity. The gut microbiome may be critical in addressing these discrepancies, as it may directly or indirectly affect ALS.
Further research is essential to identify relevant microbial actors in ALS so that they can be targeted in future treatments to alter the gut microbiota, modulate disease progression, and improve quality of life. This intervention is likely to be personalized for patients in different settings and genotypes.
Overall, there is hope for better classification of cases according to the pathogenic mechanism in order to carry out targeted therapies with beneficial effects, and ALS will become a treatable disease in the future.
Care for people with ALS
At present, although ALS is difficult to completely cure, researchers have never given up exploring various treatments for ALS. In the field of intestinal flora, Guhe will also help explore the microbiota characteristics of ALS patients, detect disease risks as early as possible and intervene in time, and also hope to help patients with rare diseases like ALS find suitable intervention methods based on their own microbiota through more data and cases.
Note: This article may not be reproduced without the author's authorization.
The content of this account is for communication reference only, and is not used as a diagnosis and medical basis.
Featured References
Stopińska K, Radziwoń-Zaleska M, Domitrz I. The Microbiota-Gut-Brain Axis as a Key to Neuropsychiatric Disorders: A Mini Review. J Clin Med. 2021 Oct 10; 10(20):4640. doi: 10.3390/jcm10204640. PMID: 34682763; PMCID: PMC8539144.
Zhang Y, Ogbu D, Garrett S, Xia Y, Sun J. Aberrant enteric neuromuscular system and dysbiosis in amyotrophic lateral sclerosis. Gut Microbes. 2021 Jan-Dec; 13(1):1996848. doi: 10.1080/19490976.2021.1996848. PMID: 34812107; PMCID: PMC8632307.
D'Antona S, Caramenti M, Porro D, Castiglioni I, Cava C. Amyotrophic Lateral Sclerosis: A Diet Review. Foods. 2021 Dec 17; 10(12):3128. doi: 10.3390/foods10123128. PMID: 34945679; PMCID: PMC8702143.
Yu W, He J, Cai X, Yu Z, Zou Z, Fan D. Neuroimmune Crosstalk Between the Peripheral and the Central Immune System in Amyotrophic Lateral Sclerosis. Front Aging Neurosci. 2022 May 3;14:890958. doi: 10.3389/fnagi.2022.890958. PMID: 35592701; PMCID: PMC9110796.
Beers DR, Appel SH. Immune dysregulation in amyotrophic lateral sclerosis: mechanisms and emerging therapies. Lancet Neurol. 2019 Feb; 18(2):211-220. doi: 10.1016/S1474-4422(18)30394-6. PMID: 30663610.
Chan GN, Evans RA, Banks DB, Mesev EV, Miller DS, Cannon RE. Selective induction of P-glycoprotein at the CNS barriers during symptomatic stage of an ALS animal model. Neurosci Lett. 2017 Feb 3;639:103-113. doi: 10.1016/j.neulet.2016.12.049. Epub 2016 Dec 21. PMID: 28011392; PMCID: PMC5278641.
Chen L, Liu X, Tang L, Zhang N, Fan D. Long-Term Use of Riluzole Could Improve the Prognosis of Sporadic Amyotrophic Lateral Sclerosis Patients: A Real-World Cohort Study in China. Front Aging Neurosci. 2016 Oct 24;8:246. doi: 10.3389/fnagi.2016.00246. PMID: 27822184; PMCID: PMC5075535.
Chiu IM, Phatnani H, Kuligowski M, Tapia JC, Carrasco MA, Zhang M, Maniatis T, Carroll MC. Activation of innate and humoral immunity in the peripheral nervous system of ALS transgenic mice. Proc Natl Acad Sci U S A. 2009 Dec 8; 106(49):20960-5. doi: 10.1073/pnas.0911405106. Epub 2009 Nov 20. PMID: 19933335; PMCID: PMC2791631.
Cragnolini AB, Lampitella G, Virtuoso A, Viscovo I, Panetsos F, Papa M, Cirillo G. Regional brain susceptibility to neurodegeneration: what is the role of glial cells? Neural Regen Res. 2020 May; 15(5):838-842. doi: 10.4103/1673-5374.268897. PMID: 31719244; PMCID: PMC6990768.
Erickson MA, Banks WA. Neuroimmune Axes of the Blood-Brain Barriers and Blood-Brain Interfaces: Bases for Physiological Regulation, Disease States, and Pharmacological Interventions. Pharmacol Rev. 2018 Apr; 70(2):278-314. doi: 10.1124/pr.117.014647. PMID: 29496890; PMCID: PMC5833009
Chua JP, De Calbiac H, Kabashi E, Barmada SJ. Autophagy and ALS: mechanistic insights and therapeutic implications. Autophagy. 2022 Feb; 18(2):254-282. doi: 10.1080/15548627.2021.1926656. Epub 2021 May 31. PMID: 34057020; PMCID: PMC8942428.
Oakes JA, Davies MC, Collins MO. TBK1: a new player in ALS linking autophagy and neuroinflammation. Mol Brain. 2017 Feb 2; 10(1):5. doi: 10.1186/s13041-017-0287-x. PMID: 28148298; PMCID: PMC5288885.
Peggion C, Scalcon V, Massimino ML, Nies K, Lopreiato R, Rigobello MP, Bertoli A. SOD1 in ALS: Taking Stock in Pathogenic Mechanisms and the Role of Glial and Muscle Cells. Antioxidants (Basel). 2022 Mar 23; 11(4):614. doi: 10.3390/antiox11040614. PMID: 35453299; PMCID: PMC9032988.
Calvo AC, Valledor-Martín I, Moreno-Martínez L, Toivonen JM, Osta R. Lessons to Learn from the Gut Microbiota: A Focus on Amyotrophic Lateral Sclerosis. Genes (Basel). 2022 May 12; 13(5):865. doi: 10.3390/genes13050865. PMID: 35627250; PMCID: PMC9140531.
Lu G, Wen Q, Cui B, Li Q, Zhang F. Washed microbiota transplantation stopped the deterioration of amyotrophic lateral sclerosis: the first case report and narrative review. J Biomed Res. 2022 Jun 28:1-8. doi: 10.7555/JBR.36.20220088. Epub ahead of print. PMID: 35821195.
Cox LM, Calcagno N, Gauthier C, Madore C, Butovsky O, Weiner HL. The microbiota restrains neurodegenerative microglia in a model of amyotrophic lateral sclerosis. Microbiome. 2022 Mar 11; 10(1):47. doi: 10.1186/s40168-022-01232-z. PMID: 35272713; PMCID: PMC8915543.
Zeng, Q., Shen, J., Chen, K. et al. The alteration of gut microbiome and metabolism in amyotrophic lateral sclerosis patients. Sci Rep 10, 12998 (2020).
Alonso R, Pisa D, Carrasco L. Searching for Bacteria in Neural Tissue From Amyotrophic Lateral Sclerosis. Front Neurosci. 2019 Feb 26;13:171. doi: 10.3389/fnins.2019.00171. PMID: 30863279; PMCID: PMC6399391.
Boddy SL, Giovannelli I, Sassani M, Cooper-Knock J, Snyder MP, Segal E, Elinav E, Barker LA, Shaw PJ, McDermott CJ. The gut microbiome: a key player in the complexity of amyotrophic lateral sclerosis (ALS). BMC Med. 2021 Jan 20; 19(1):13. doi: 10.1186/s12916-020-01885-3. PMID: 33468103; PMCID: PMC7816375.
Sun J, Huang T, Debelius JW, Fang F. Gut microbiome and amyotrophic lateral sclerosis: A systematic review of current evidence. J Intern Med. 2021 Oct; 290(4):758-788. doi: 10.1111/joim.13336. Epub 2021 Jul 8. PMID: 34080741.
Martin S, Battistini C, Sun J. A Gut Feeling in Amyotrophic Lateral Sclerosis: Microbiome of Mice and Men. Front Cell Infect Microbiol. 2022 Mar 11;12:839526. doi: 10.3389/fcimb.2022.839526. PMID: 35360111; PMCID: PMC8963415.
Nicholson K, Bjornevik K, Abu-Ali G, Chan J, Cortese M, Dedi B, Jeon M, Xavier R, Huttenhower C, Ascherio A, Berry JD. The human gut microbiota in people with amyotrophic lateral sclerosis. Amyotroph Lateral Scler Frontotemporal Degener. 2021 May; 22(3-4):186-194. doi: 10.1080/21678421.2020.1828475. Epub 2020 Nov 2. PMID: 33135936.
Garofalo S, Cocozza G, Porzia A, Inghilleri M, Raspa M, Scavizzi F, Aronica E, Bernardini G, Peng L, Ransohoff RM, Santoni A, Limatola C. Natural killer cells modulate motor neuron-immune cell cross talk in models of Amyotrophic Lateral Sclerosis. Nat Commun. 2020 Apr 14; 11(1):1773. doi: 10.1038/s41467-020-15644-8. PMID: 32286313; PMCID: PMC7156729.
Hertzberg VS, Singh H, Fournier CN, Moustafa A, Polak M, Kuelbs CA, Torralba MG, Tansey MG, Nelson KE, Glass JD. Gut microbiome differences between amyotrophic lateral sclerosis patients and spouse controls. Amyotroph Lateral Scler Frontotemporal Degener. 2022 Feb; 23(1-2):91-99. doi: 10.1080/21678421.2021.1904994. Epub 2021 Apr 5. PMID: 33818222.
Andrew AS, Bradley WG, Peipert D, Butt T, Amoako K, Pioro EP, Tandan R, Novak J, Quick A, Pugar KD, Sawlani K, Katirji B, Hayes TA, Cazzolli P, Gui J, Mehta P, Horton DK, Stommel EW. Risk factors for amyotrophic lateral sclerosis: A regional United States case-control study. Muscle Nerve. 2021 Jan; 63(1):52-59. doi: 10.1002/mus.27085. Epub 2020 Oct 18. PMID: 33006184; PMCID: PMC7821307.
Masrori P, Van Damme P. Amyotrophic lateral sclerosis: a clinical review. Eur J Neurol. 2020 Oct; 27(10):1918-1929. doi: 10.1111/ene.14393. Epub 2020 Jul 7. PMID: 32526057; PMCID: PMC7540334.