More and more people - including those with type 2 diabetes and sleeping problems - are using synthetic melatonin as a sleeping aid. This may not be such a good idea: at least, new research suggests that it may reduce insulin sensitivity. ‘And since reduced insulin sensitivity happens to be key to the development of type 2 diabetes, people should perhaps be a little careful about taking melatonin if they are predisposed to developing type 2 diabetes, until more is known about the potential link’, says the researcher behind the finding, Ulla Kampmann, MD, PhD, an associate professor at the Steno Diabetes Center in Aarhus.

Poor sleep is a risk factor for type 2 diabetes
She and her colleagues took an interest in melatonin partly because poor sleep quality and insufficient sleep increase the risk of a large number of diseases, and of type 2 diabetes in particular. ‘In fact, poor sleep is as big a risk factor for the disease as being genetically predisposed through having family members with type 2 diabetes’, she says.

Melatonin is the natural sleep hormone and is produced by the pineal gland in the brain during sleep. In Denmark, melatonin is prescription-only and is increasingly being prescribed by doctors to children or to adults over the age of 55, but in the USA, for example, it is sold over the counter and is popular because it is considered to be harmless by many people. However, genetic studies have shown that some genetic variants that predispose to type 2 diabetes are located in the genes that have to do with the body’s melatonin receptors, while other clinical studies have shown that insulin secretion is reduced in healthy women when performing an oral glucose tolerance test after taking melatonin. So, there are a number of indications that melatonin may affect glucose metabolism.

High-dose melatonin given to 20 healthy young men
About four years ago, Ulla Kampmann was awarded postdoc funding by the DDA to study the effects of melatonin on glucose metabolism, and she has just published some of the results of that research in the high-impact journal, Journal of Pineal Research. Together with her research colleagues, Ulla Kampmann gave 20 healthy young men high doses of melatonin - 40 mg altogether - on one day, and a placebo on another day. Their lipid oxidation (fat burning) insulin sensitivity, insulin secretion etc., were examined in the laboratory. The results showed that consumption of melatonin and a consequent high concentration of melatonin in the body reduced blood pressure and increased lipid oxidation (fat burning), but had no effect on the production of various endocrine hormones, including insulin. On the other hand, melatonin reduced insulin sensitivity by 10%, and it is this finding that makes Ulla Kampmann say that people should perhaps be a little careful about taking melatonin if they are predisposed to developing type 2 diabetes, until more is known about the potential link.

Further research in progress
To ascertain whether a small (10 mg) dose of melatonin taken just before bedtime every day for three months can improve sleep and hence possibly improve insulin sensitivity, Ulla Kampmann and her colleagues are now studying patients with type 2 diabetes in the laboratory. They are again studying substrate metabolism, lipid oxidation, blood pressure levels, endocrine hormone levels and the effect on insulin sensitivity and insulin secretion, but are accordingly looking at the long-term effect of a small dose of melatonin in patients with type 2 diabetes.

In addition, Ulla Kampmann and her colleagues are just about to publish another study in which they investigated the effect of high-dose melatonin on the incretin effect, i.e. the insulin secretion observed after glucose is taken orally, which is mediated by the incretin hormones GLP-1 and GIP. This effect is significantly reduced in patients with type 2 diabetes, making it interesting to investigate whether melatonin might influence insulin secretion via the incretin effect.

Findings important for frequent users
Together, the melatonin studies yield important new information about the hormone melatonin and its effect on the body’s glucose metabolism. This information is important to the many people who use melatonin frequently as an apparently harmless sleeping aid and who are, for other reasons, at risk of getting type 2 diabetes.

The projects represent the first important steps on the way to investigating the effects of melatonin on glucose metabolism and thus ascertaining whether melatonin is harmful or beneficial to people who have type 2 diabetes or are at risk of developing it.

CONTACT
Ulla Kampmann, MD, PhD, Associate Professor
Clinician and Clinical Researcher
Steno Diabetes Center Aarhus, Aarhus University Hospital
ullaopst@rm.dk
Phone: +45 2237 0857

READ THE ARTICLE HERE
Journal of Pineal Research: https://doi.org/10.1111/jpi.12706
Acute metabolic effects of melatonin - A randomized crossover study in healthy young men
Ulla Kampmann, Esben S. Lauritzen, Niels Grarup, Niels Jessen, Torben Hansen, Niels Møller, Julie Støy
Published: 21 November 2020