Common insecticides may pose type 2 diabetes risks through effect on circadian rhythm

Camille Bienvenu
Tue, 24 Jan 2017
Common insecticides may pose type 2 diabetes risks through effect on circadian rhythm
Chemicals found in commonly used insecticides have been shown to interfere with our biological clocks, disrupting insulin secretion and upping risks for type 2 diabetes.

The findings were part of a large investigation by the National Institute of Environmental Health Sciences into environmental chemicals encountered in household products.

These chemicals were analysed by researchers from the University at Buffalo, in New York, using methods such as predictive computational modeling and laboratory experiments.

They have found that carbamates, the active ingredient in insecticides and other garden products, are able to bind to receptors governing circadian rhythms that have to do with blood sugar regulation.

These receptors are no other than those of the hormone melatonin, a master regulator of some of these biological clocks. Melatonin–mediated circadian regulation physiologically serves to inhibit nocturnal insulin release.

For this purpose, melatonin levels are naturally high during the overnight fasting and sleeping period. But, if changes to this melatonin synchronisation occur, it can upset circadian insulin secretion.

This is what seems to happen with carbaryil, a carbamate studied by the researchers.

Carbaryl, which is found in the third most widely used insecticide overseas, appears to have the ability to bind to the melatonin MT2 receptors. By doing so, carbaryl essentially puts the melatonin system into overdrive.

Studies have previously showed that disruptions to the MT2-receptor could be linked with an elevated risk of developing type 2 diabetes. Here, researchers suggest that increased melatonin signalling through the MT2 receptor could be what increases risk.

Another carbamate insecticide on the researchers' radar is carbofuran, which they found shared the same affinity for the melatonin MT2 receptors. It is however less used than carbaryl because of its ban from food crops in 2009.

According to researchers, the consequences of circadian disruption by exposure to carbaryl are not to be taken lightly, as it can have a profound influence on blood sugars and insulin levels.

Enhanced melatonin signalling in the pancreatic islets, where the MT2 receptors are, can significantly reduce insulin secretion, which can lead to hyperglycemia and a greater risk of type 2 diabetes.

The scientists also do not rule out the possibility that the negative effects of carbamates extend beyond impaired insulin secretion, since melatonin synchronises many other important functions of the pancreas and liver.

While the negative effects of carboxyl represent a tangible health risk, researchers believe that it would take a prolonged exposure to the product for circadian insulin secretion to become significantly out of balance.
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