▎ WuXi AppTec content team editor
During the physical examination, many people pay attention to the level of cholesterol in the blood. Among them, low-density lipoprotein (LDL, also known as "bad" cholesterol) is higher than the standard, or high-density lipoprotein (HDL, also known as "good" cholesterol) is below the standard, often reminding us of the risk of cardiovascular disease.
Now, a new scientific study points out that "good" cholesterol is also an important indicator of brain health. Researchers at the University of Southern California (USC) Keck Medical Center found that the amount of HDL in cerebrospinal fluid is related to cognitive abilities in older adults and may have a protective effect on Alzheimer's disease.
The study was published in the academic journal Alzheimer's & Dementia
The researchers recruited 180 seniors over the age of 60 to analyze their blood and cerebrospinal fluid samples. HDL is the smallest of the particles in plasma lipoproteins, and in cerebrospinal fluid, the particles of HDL are smaller than most HDL particles in the blood. Using a newly developed "ion mobility" technique, the researchers measured and counted the size and number of HDL particles in the sample.
At the same time, the researchers conducted cognitive tests on a subset of participants. The results of the analysis showed that older adults with higher hdl content of small particles in cerebrospinal fluid performed better on cognitive tests. And, regardless of the sex, age, education, and carrying the late-onset Alzheimer's disease-risk gene APOE4, this association was shown.
Image credit: 123RF
The researchers observed that the higher the content of HDL particles in the cerebrospinal fluid and the stronger the cognitive association, was more pronounced among those participants who did not have cognitive decline. This may suggest that hdL lipoprotein granules can be a key entry point long before the brain's cognitive decline, when early intervention in Alzheimer's disease can be made.
Professor Hussein Yassine, who led the study, said: "We found that these small particles were lubricating the system and keeping it healthy before cognitive impairment appeared. At this time, you also have the opportunity to intervene through exercise, medication or any other means to protect the health of brain cells. ”
In addition, the researchers also found that the small particles of HDL in the cerebrospinal fluid are more numerous, related to another key indicator: higher levels of amyloid beta 42 in the cerebrospinal fluid. This peptide misfolds and accumulates on neurons to form plaques, which is an important pathological feature of Alzheimer's disease; conversely, higher concentrations in circulating cerebrospinal fluid are associated with a lower risk of Alzheimer's disease.
"These small particles of HDL may be involved in clearing and excreting this polypeptide so that they do not form the amyloid plaque seen in Alzheimer's disease, which we speculate may be helpful in preventing Alzheimer's disease." Professor Yassine said.
Image credit: 123RF
Why HDL particles in cerebrospinal fluid can play a role in protecting brain health, the researchers also made a preliminary explanation in the paper. They propose that these small particles, through their ability to quickly exchange cholesterol, affect the composition of cell membranes of brain neurons, playing a role in neuronal growth and repair. In addition, they may also protect cognitive abilities by affecting the function of blood vessels and preventing the blood-brain barrier from being affected by inflammation.
These hypotheses are subject to subsequent studies, including further study of the structure and function of HDL in the brain to determine whether specific components are exchanged through blood, brain, and cerebrospinal fluid. They also plan to identify the association of small particles of HDL with cognitive abilities in larger cohorts in the future, to find new biomarkers for the prevention of Alzheimer's disease, and to provide potential targets for the treatment of Alzheimer's disease.
Resources:
[1] Ashley E. Martinez et al., (2022) The small HDL particle hypothesis of Alzheimer's disease. Alzheimer's & Dementia. Doi: https://doi.org/10.1002/alz.12649
[2] Small ‘good cholesterol’ particles may have a role in Alzheimer’s prevention. Retrieved Apr. 18, 2022 from https://www.eurekalert.org/news-releases/949458
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