Genetic Dysfunction in Melatonin Receptor Gene May Be Responsible for Diabetes
Melatonin is a hormone that is strongly tied to control of sleep-wake cycles. Chronic disruption to sleep is linked to many health effects, including a stronger risk for Type 2 diabetes. Researchers with the Imperial College London delved deeper into this process and discovered a gene that when mutated cause an increased risk for altered blood sugar. The findings could lead to new, personalized treatments for the disease.
The MT2 protein is a receptor for melatonin, encoded by a gene known as melatonin receptor 1B or MTNR1B. Mutations in this gene disrupt the proper functioning of melatonin, which in part regulates the release of insulin that controls blood sugar levels. In 2008, researchers at Imperial College London discovered some common variations in this genetic process which slightly increased the risk of Type 2 diabetes. However, in this new study, the team drilled down to four rare mutations which increases the risk of the disease by almost six times.
Professor Philippe Froguel, from the School of Public Health, examined the MT2 gene in over 7,600 people at several institutions in the UK and France. Overall, the found 40 variants associated with Type 2 diabetes. Four of these were rare, but rendered the melatonin receptor completely incapable of responding to melatonin, suggesting a direct link between the gene mutation and diabetes.
The scientists then confirmed the link with these four variants in an additional sample of almost 12,000 people.
Dr. Froguel said, "Blood sugar control is one of the many processes regulated by the body's biological clock. This study adds to our understanding of how the gene that carries the blueprint for a key component in the clock can influence people's risk of diabetes. Although each mutation is rare, they are common in the sense that everyone has a lot of very rare mutations in their DNA. Cataloguing these mutations will enable us to much more accurately assess a person's risk of disease based on their genetics."
In addition to the control of insulin release, melatonin is also involved in energy metabolism and body weight control to some extent. Researchers studying small animals note that improving melatonin production could have a positive effect on the basal metabolic rate leading to a potential treatment for obesity. Obesity and Type 2 diabetes are linked as excess body weight can increase insulin resistance leading to elevated blood sugar levels.
Although dietary supplementation with melatonin appears safe for short-term use, the inclusion of some healthy foods may also supply the hormone. These include mustard, Goji berries, almonds, sunflower seeds, cardamom, fennel, coriander, and cherries.
A. Bonnefond et al. 'Rare MTNR1B variants impairing melatonin receptor 1B function contribute to type 2 diabetes' Nature Genetics, published online 29 January 2012.
University of Granada, “Melatonin might help in controlling weight gain and preventing heart diseases associated to obesity” April 27, 2011.
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