Internal Body Clock May Increase Risk of Type 2

An international team of researchers reports that a mutation in a gene that controls a person’s body clock can cause higher blood sugar levels, leading to a 20 percent increased risk of acquiring type 2 diabetes.

Researchers from England, Canada, France, and Denmark found that a mutation near a gene called MTNR1B affects how the body uses melatonin, a hormone that regulates the body’s circadian rhythm, or internal body clock. If melatonin is not working correctly, it can alter a person’s sleep patterns by interfering with the normal circadian rhythms that govern drowsiness and alertness. As a result, people affected by the mutation tend to sleep less and gain weight-factors that have been clearly associated with the onset of diabetes.

Scientists think that melatonin is a key player in regulating the body’s insulin levels. The mutation is suspect because it may cause MTNR1B to direct melatonin to manage insulin levels incorrectly. Improper insulin levels can lead to high blood sugar and inflammation.

The researchers, who published their findings in Nature Genetics, studied the genetic makeup of 2,151 French children and adults (1,329 lean and 822 obese) and found that the mutation, called rs1387153, was associated with higher blood sugar levels.

They also found that the more genetic mutations associated with high blood sugar that a person has, the higher his or her blood sugar levels will be. For example, people with just one mutation had an average fasting blood glucose level of 5.12 mmol/l while those with five mutations had an average of 5.4 mmol/l.

Of the study subjects who had six or more mutations, 43 percent had fasting blood glucose levels of 5.6 mmol/l  a figure that would be considered admirable by most people with type 2, but one that the American Diabetes Association calls “impaired,” meaning that it signals a high risk for diabetes.

Aside from genetic testing that could alert people to the potential risks they run for acquiring diabetes, the study opens the possibility that sleep therapy could help stave off the onset of type 2 by thwarting or circumventing an abnormal circadian rhythm. Perhaps more restful sleep patterns could lower blood sugar levels and help prevent weight gain.

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