Prior research has identified a connection between a genetic mutation and an increased risk of type 2 diabetes, but a new study is the first to link this genetic variation to glucose tolerance with melatonin supplementation. It is believed that as many as 50% of individuals of European ancestry carry this genetic variation.

Published in the journal Metabolism, the team recruited 17 normoglycemic women from a female rugby team at the University of Murcia and identified 11 as carriers of the MTNR1B genetic variant rs10830963 that is associated with an increased risk of type 2 diabetes. The women received either melatonin 5mg or placebo in the morning and evening, followed by glucose tolerance assessment via an oral glucose tolerance test (75g). Blood samples were collected at baseline and at 30-minute intervals after receiving the glucose doses for the next two hours.

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The effect of melatonin on glucose tolerance was six times worse in those with the genetic variant compared to non-carriers; the genetic mutation was implicated in 26% of the inter-individual differences in the effect of melatonin on glucose area under the curve (AUC). No differences were seen in the evening regarding the effect of melatonin on glucose AUC between carriers and non-carriers. The absence of the effect in the evening may have been due to a limited sample size.

“Our results suggest that it may be important to take genetics into account when thinking about timing of food consumption and melatonin administration,” noted Frank Scheer, PhD, associate professor of medicine at Harvard Medical School and the Director of the Medical Chronobiology at Brigham and Women’s Hospital. More studies are needed to confirm these study results, with larger patient populations, he added.

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