Recently discovered gene variant mediates insulin secretion through the release of melatonin.

An international research team has identified a new variant of the MTNR1B gene associated with both elevated fasting glucose levels and a high risk for type 2 diabetes. The MTNR1B gene indirectly mediates insulin secretion through the release of melatonin—indicating a previously unknown relationship between sleep-wake cycles and fasting glucose levels.

The international MAGIC (Meta-Analyses of Glucose and Insulin-related traits Consortium) Consortium combined data from 13 case-control studies including more than 18,000 diabetic and 64,000 nondiabetic study participants.

The MTNR1B gene is expressed in insulin-producing islet cells and encodes one of the two known melatonin receptors. It is assumed that this receptor inhibits the release of insulin through melatonin. The fact that the melatonin level in the body is higher at night and declines during the day, and the insulin level is higher during the day and lower during the night, implicates an association between sleep-wake rhythm and fasting glucose levels.

The study is published in the January issue of Nature Genetics.