Published on 24 May 2016

The sleep hormone melatonin that helps us sleep at night has been linked to type 2 diabetes by researchers in Sweden.

A study by researchers at Lund University in Sweden, recently published in the journal Cell Metabolism, found that the sleep hormone melatonin could stop insulin production in people with a common gene variant.

In people with type 2 diabetes the body does not produce enough insulin, or the body’s cells do not react to insulin. This is known as insulin resistance.

The sleep hormone melatonin could be linked to people developing type 2 diabetes

Melatonin is a naturally occurring hormone that helps maintain our circadian rhythm, or patterns of body function and activity over 24 hours.

The amount of melatonin produced can vary throughout the course of the day, and is affected by light. When it is dark, the level of melatonin increases, peaking at night. It is often referred to as “the hormone of darkness”, and used as a sleeping drug or to prevent jet lag, among other things.

Professor Hindrik Mulder of Lund University (previously funded by DRWF in Sweden - Diabetes Research Network Sverige) and study author said: “This could explain why the risk of type 2 diabetes is greater among, for instance, overnight workers or people with sleeping disorders.

“A third of all people carry this specific gene variant. Our results show that the effect of melatonin is stronger in them. We believe that this explains their increased risk of developing type 2 diabetes.”

The findings, which are published in the scientific journal Cell Metabolism, are the result of many years of work.

The research for the study dates back to 2009, when the researchers presented an extensive gene mapping study that showed that the gene variant of the melatonin receptor 1B, which is common in the population, was found to increase the risk of people developing type 2 diabetes. The gene variant causes the level of the melatonin receptor on the insulin cell surface to increase, which makes the cells become more sensitive to melatonin and weakens their ability to secrete insulin.

A person sleeping near an alarm clock.

The researchers are now studying the processes in mice and human beta cells, as well as completed a study of how the effects of drugs are influenced by genetic factors – one of the first of its kind within type 2 diabetes, where participants have been recruited based on their genetic make-up.

The study included 23 healthy people and carriers of the gene variant in question and 22 non-carriers. All participants were roughly of the same age and with the same body mass index (BMI). There was also no difference in terms of their family history of diabetes.

They were given four milligrams of melatonin before bedtime over the course of three months.

Researchers found that insulin secretion was significantly lower among those who carried the risk gene than those in the control group. They also reported that the amount of glucose (sugar) in the blood was higher among all participants after being treated with melatonin for three months. However, it was especially evident in carriers of the risk gene who were unable to increase their insulin secretion.

It has been previously known that people who work overnight shifts suffer from metabolic diseases such as type 2 diabetes to a greater extent.

Professor Mulder said: “It is perhaps therefore less suitable for carriers of the risk gene to work overnight shifts, as the level of melatonin will probably increase at the same time as the effects of the increase are enhanced. There is still no scientific support for this theory, but it ought to be studied in the future, on the basis of our new findings.”

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