October 07, 2015
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Melatonin at mealtimes may increase type 2 diabetes risk in people with gene variant

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Taking melatonin close to mealtimes may put people with the genetic variant MTNR1B at a greater risk for developing type 2 diabetes, according to recent study findings published in Metabolism.

“Our work is the first to show that a person’s genetic profile could impact their ability to tolerate glucose when they take melatonin,” Frank Scheer, PhD, associate professor of medicine at Harvard Medical school and director of the medical chronobiology at Brigham and Women’s Hospital, said in a press release.

Scheer and colleagues evaluated 17 normoglycemic women to determine whether the genetic variant MTNR1B influenced the effect of melatonin (5 mg) on glucose tolerance at different times of the day compared with placebo. Eleven of the participants were carriers.

All participants received melatonin or placebo in the morning and evening, followed by an oral glucose tolerance test. Participants had blood samples taken before and at 30-minute intervals after taking glucose doses for the next 2 hours.

The effect of melatonin on glucose area under the curve (AUC) was different between carriers and noncarriers in the morning (P = .036); glucose tolerance was six times worse in the carrier group.

“Our results suggest that we may need to exert caution when taking melatonin close to meal times, especially in carriers of the risk variant,” Marta Garaulet, PhD, professor of physiology at the University of Murcia in Spain, said in the release.

A difference also was found with the effect of melatonin on glucose concentration 2 hours after the OGTT between carriers and noncarriers (P = .04) and after adjustment for age and BMI (P = .017).

No significant differences were found between carriers and noncarriers for the effect of melatonin on glucose AUC and insulin measures in the evening.

“Our data suggest that when subjects take melatonin, the genetic risk variant in MTNR1B causes a much greater change in glucose tolerance in carriers compared to noncarriers, even in people who are not obese and not diabetic,” Scheer said. “Our results suggest that it may be important to take genetics into account when thinking about timing of food consumption and melatonin administration.” – by Amber Cox

Disclosure: The researchers report no relevant financial disclosures.