How the timing of dinner and genetics affect individuals' blood sugar
control
Connections among food intake, melatonin levels and genetics may be
important for diabetes risk

Date:
January 25, 2022
Source:
Massachusetts General Hospital
Summary:
Eating dinner close to bedtime, when melatonin levels are high,
disturbs blood sugar control, especially in individuals with a
genetic variant in the melatonin receptor MTNR1B, which has been
linked to an elevated risk of type 2 diabetes. The high melatonin
levels and food intake associated with late eating impairs blood
sugar control in carriers of the MTNR1B genetic risk variant
through a defect in insulin secretion.



FULL STORY ========================================================================== Blood sugar control, which is impaired in individuals with diabetes, is affected by various factors -- including the timing of meals relative
to sleep as well as levels of melatonin, a hormone primarily released
at night that helps control sleep-wake cycles. In research published
in Diabetes Care, a team led by investigators at Massachusetts General
Hospital (MGH), Brigham and Women's Hospital (BWH) and the University
of Murcia in Spain conducted a clinical trial to look for connections
between these two factors.


==========================================================================
"We decided to test if late eating that usually occurs with elevated
melatonin levels results in disturbed blood sugar control," says senior
author Richa Saxena, PhD, a principal investigator at the Center for
Genomic Medicine at MGH.

For the randomized crossover study that included 845 adults from Spain,
each participant fasted for eight hours and then for the next two evenings
had first an early meal and then a late meal relative to their typical
bedtime. The investigators also analyzed each participant's genetic code
within the melatonin receptor-1b gene (MTNR1B) because previous research
has linked a variant (called the G-allele) in MTNR1B with an elevated
risk of type 2 diabetes.

"In natural late eaters, we simulated early and late dinner timing by administering a glucose drink and compared effects on blood sugar control
over two hours," explains Saxena. "We also examined differences between individuals who were carriers or not carriers of the genetic variant
in the melatonin receptor." The team found that melatonin levels in participants' blood were 3.5-fold higher after the late dinner. The late
dinner timing also resulted in lower insulin levels and higher blood sugar levels. (This connection makes sense because insulin acts to decrease
blood sugar levels.) In the late dinner timing, participants with the
MTNR1B G-allele had higher blood sugar levels than those without this
genetic variant.

"We found that late eating disturbed blood sugar control in the whole
group.

Furthermore, this impaired glucose control was predominantly seen in
genetic risk variant carriers, representing about half of the cohort,"
says lead author Marta Garaulet, PhD, a professor of physiology and
nutrition in the Department of Physiology at the University of Murcia.

Experiments revealed that the high melatonin levels and carbohydrate
intake associated with late eating impairs blood sugar control through
a defect in insulin secretion.

"Our study results may be important in the effort towards prevention of
type 2 diabetes," says co-senior author Frank A.J.L. Scheer, PhD, MSc,
director of the Medical Chronobiology Program at BWH. "Our findings are applicable to about a third of the population in the industrialized world
who consume food close to bedtime, as well as other populations who eat
at night, including shift workers, or those experiencing jetlag or night
eating disorders, as well as those who routinely use melatonin supplements close to food intake." The authors note that for the general population,
it may be advisable to abstain from eating for at least a couple of hours before bedtime. "Genotype information for the melatonin receptor variant
may further aid in developing personalized behavioral recommendations,"
says Saxena. "Notably, our study does not include patients with diabetes,
so additional studies are needed to examine the impact of food timing and
its link with melatonin and receptor variation in patients with diabetes." Funding for the study was provided by the National Institutes of Health,
the Spanish Government of Investigation and the Seneca Foundation.

========================================================================== Story Source: Materials provided by Massachusetts_General_Hospital. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Marta Garaulet, Jesus Lopez-Minguez, Hassan S. Dashti, Ce'line
Vetter,
Antonio Miguel Herna'ndez-Marti'nez, Milla'n Pe'rez-Ayala, Juan
Carlos Baraza, Wei Wang, Jose C. Florez, Frank A.J.L. Scheer,
Richa Saxena.

Interplay of Dinner Timing and MTNR1B Type 2 Diabetes Risk Variant
on Glucose Tolerance and Insulin Secretion: A Randomized Crossover
Trial.

Diabetes Care, 2022; DOI: 10.2337/dc21-1314 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220125124032.htm

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