People who have sleep disorders and those who often work overnight are known to be at increased risk for type 2 diabetes.

Now, a new study conducted by researchers in Sweden sheds light on the link between melatonin and the disease, which could explain why type 2 diabetes tends to be more prevalent in people who lack sleep at night.

Melatonin plays a key role in regulating circadian rhythm. The amount of this naturally occurring hormone is influenced by light.

When it is dark, melatonin level increases which is why it peaks at night earning it the moniker "hormone of darkness." It is also for this reason that it is used as a drug for sleeping.

In the new study published in the journal Cell Metabolism on May 12, researchers found a genetic variation that causes beta cells that produce insulin to be more sensitive to melatonin.

Insulin is a hormone produced in the pancreas that regulates the amount of glucose in the blood. The lack of insulin or an inability to respond to insulin may lead to the development of diabetes.

With increased sensitivity to melatonin, the body's ability to secrete insulin is impaired which throws off control of the blood sugar.

Study researchers Hindrik Mulder, from Lund University, said that a third of all people carry the gene variant in the melatonin receptor 1 b gene (MTNR1B), which increases the level of melatonin receptors in beta cells causing them to become more sensitive to melatonin, which prevents them from secreting insulin.

Mulder and colleagues treated 23 healthy individuals who carry the gene variant and 22 people who do not have the variant with melatonin at night for a period of three months and found the secretion of insulin was lower among those with the genetic variation.

"Our data support a model where enhanced melatonin signaling in islets reduces insulin secretion, leading to hyperglycemia and greater future risk of T2D," the researchers wrote in their study.

Blood glucose levels were also observed to be higher among the all the participants following treatment of melatonin albeit this effect was most significant in those who have the genetic variation.

"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," Mulder said.

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