▎ WuXi AppTec content team editor
Studies have shown that changes in meal timing appear to affect metabolic changes, as well as elevated blood sugar after a meal. For diabetics, melatonin levels are also a factor in addition to meal times.
Melatonin is a hormone that is secreted in large quantities at night or when light is low, and its main function is to regulate the sleep-wake cycle. So, how do melatonin receptor genes and dinner time affect an individual's blood sugar control? Is there an association with the risk of developing type 2 diabetes?
Recently, led by scholars from Massachusetts General Hospital (MGH) and Brigham and Women's Hospital (BWH) at Harvard Medical School, a collaborative research team from the United States and Spain explored this and published the results in Diabetes Care, an authoritative journal in the field of diabetes. The results showed that: 1) 1 hour before bedtime (when endogenous melatonin levels are high), eating dinner leads to too little insulin secretion and decreased glucose tolerance, which increases the risk of type 2 diabetes. 2) This risk is higher especially in individuals with variants of the melatonin receptor MTNR1B gene.
Screenshot source: Diabetes Care
There have been many previous studies that have found that the melatonin receptor 1B gene (MTNR1B) increases the risk of developing type 2 diabetes and gestational diabetes, which has been considered a genetic bridge between circadian rhythms and glucose metabolism.
The study was designed to explore whether re-eating can lead to blood sugar control disorders in the setting of elevated endogenous melatonin levels (e.g., near bedtime), particularly in carriers of the type 2 diabetes-related G allele in the MTNR1B gene. The randomized crossover study included 845 Spanish adults aged 18 to 70 years who had no history of diabetes and no history of drug use.
The study set up two meal times: the "early dinner group," which ate dinner 4 hours before regular sleep time, and the "late dinner group," which ate dinner 1 hour before regular sleep time. All subjects were randomly grouped into one group and then switched to another group on another night and repeatedly tested the relevant indicators.
Image credit: 123RF
Eating dinner is simulated by an oral glucose tolerance test. Each subject took 75 grams of glucose drink orally for the next two evenings after fasting for 8 h to simulate early and late time eating, and recorded glucose tolerance (blood glucose and insulin response) within 2 hours (every 30 minutes) of both groups of subjects, as well as differences between MTNR1B G allele carriers and non-carriers.
Eat too late for dinner and have poor blood sugar control
The research team found that
Subjects in the late dinner group had 3.5 times higher levels of melatonin in their blood compared to the early dinner group.
Late dinner time also led to a 6.7% decrease in the area under the insulin curve (AUC, which is an indicator of β cell function in the islets) and an 8.3% increase in glucose AUC, i.e., the later the dinner time, the lower the insulin level and the higher the blood sugar level. The researchers say the association is justified because insulin works to lower blood sugar levels.
In the case of late dinner intake, subjects with the MTNR1B G allele had higher blood glucose levels than subjects without this genetic variant. Genotype differences in glucose tolerance are attributed to reduced β cell function in the MTNR1B G allele population.
The findings suggest that carbohydrate intake (typical of late eating) accompanied by elevated endogenous melatonin levels, particularly in carriers of the MTNR1B G allele, impairs glycemic control, which can be attributed to defects in insulin secretion.
Therefore, too late for dinner increases the risk of diabetes.
Provide evidence for the prevention of type 2 diabetes
"Our findings may be important for strategies to prevent type 2 diabetes." Study co-senior author Dr Frank A.J.L. Scheer, director of the BWH Medical Chronobiology Program, said.
He further noted that "the findings of this study apply to about one-third of the population in the industrialized world, including those who eat near bedtime, others who eat at night (including night shift workers, or those with jet lag and eating disorders), and those who use melatonin supplements in large quantities." ”
The researchers note that for the general population, fasting is wise for at least four hours before bedtime.
Future Exploration and Prospects
Lead researcher and senior author Dr. Richard Saxena of the MGH Center for Genomic Medicine said, "Genotype information on melatonin receptor variants may help develop individualized behavioral recommendations. ”
She also stressed, "It's important to note that our study didn't include people with diabetes, so more research is needed in people with diabetes to examine the effects of eating time and its relationship to melatonin and genetic variants." ”