Melatonin is commonly used in Finland for the treatment of insomnia. Melatonin is also a sleep hormone that is produced by the body that affects through the melatonin receptors. It has been shown that a relatively common variant in the melatonin receptor gene (MTNR1B) has a link to reduced insulin production and increased risk of type 2 diabetes.
Study participants: 44 subjects from the PPP Botnia study were recruited to study. Half of these were individuals with the risk genotype (GG) and half without the risk genotype (CC). None of the participants had been diagnosed with diabetes.
The participants were treated with melatonin (Circadin® 4 mg) for the period of 3 months. The participants were invited for a study visit before and 3 months after the melatonin treatment. On both study visits, the participants filled out a questionnaire to monitor sleep rhythm and sleep problems within two weeks period before the first study visit.
The participants underwent an oral glucose tolerance test (75g OGTT) at the beginning of the study and 3 months after. Blood samples were drawn before the tolerance test and every 30 minutes after drinking the glucose liquid until 2 hours. The blood samples were tested for melatonin concentration, blood glucose level, blood lipid values, as well as insulin- and C-peptide values that reflect the insulin secretion from the pancreas. In addition, four spare tubes were drawn for other hormone- and fatty acid measurements. We also monitored the effect of melatonin on sleep quality and energy consumption during one week using Actigraph –meter.
The study showed that melatonin treatment reduced insulin secretion and raised blood glucose levels in all study participants but more extensively in risk genotype carriers.