Binge drinking directly causes insulin resistance, which in turn leads to type 2 diabetes. This was the finding of a new study on rats, that the researchers say is the first to show binge drinking alone, separate from other factors like overeating, increases risk for type 2 diabetes.

People with a history of binge drinking have a higher risk of developing metabolic syndrome and type 2 diabetes. But until this study it was not clear how the link worked, and whether binge drinking alone raised the risk.

Researchers at the Diabetes Obesity and Metabolism Institute at the Icahn School of Medicine at Mount Sinai, in New York, write about their findings in the 30 January issue of the journal Science Translational Medicine.

They also found that alcohol appears to disrupt insulin-receptor signaling by causing inflammation in the hypothalamus, an area of the brain that among other things, is important for metabolic processes.

The main role of the insulin receptor is to control the uptake of glucose. Decrease in signaling of this receptor means the cells can’t take up glucose, and the result is hyperglycemia (too much glucose in the blood), and other consequences of type 2 diabetes.

Insulin resistance is where insulin does not bind properly to the receptor, thus hampering its ability to send the right signals to cells so they can use glucose for energy. This can happen even when the pancreas is producing enough insulin to keep glucose levels under control.

A symptom of insulin resistance is high levels of insulin in the bloodstream. This is a major component of metabolic syndrome, a group of risk factors that together increase the risk for type 2 diabetes, coronary artery disease, and stroke.

Senior author Christoph Buettner, an Associate Professor of Medicine, Endocrinology, Diabetes and Bone Disease, at the Icahn School of Medicine, says in a statement:

“Insulin resistance has emerged as a key metabolic defect leading to type 2 diabetes and coronary artery disease (CAD).”

“Someone who regularly binge drinks even once a week, over many years, may remain in an insulin resistant state for an extended period of time, potentially years,” he adds.

For their study, the researchers simulated human binge drinking by giving rats alcohol for three days. Another group of rats acted as controls: they had the same calorie intake as the binge drinking rats, but without consuming alcohol.

The researchers then ran a series of tests to check glucose metabolism.

They found even when there was no trace of alcohol left in their bloodstream, the binge drinking rats had higher levels of circulating insulin than the control rats, suggesting insulin resistance, induced by the alcohol, was the cause.

First author Claudia Lindtner, an Associate Researcher of Medicine, Endocrinology, Diabetes and Bone Disease at the Icahn School of Medicine, says:

“Previously it was unclear whether binge drinking was associated with an increased risk for diabetes, since a person who binge drinks may also tend to binge eat, or at least eat too much.”

“Our data show for the first time that binge drinking induces insulin resistance directly and can occur independent of differences in caloric intake,” she adds.

A study released in November 2012 from the US Centers for Disease Control and Prevention shows there has been a dramatic rise in rates of diagnosed diabetes in the US in the last decade and a half. It suggests while one reason is that people with diabetes are living longer, the other reason is an increase in cases of the disease.

Written by Catharine Paddock PhD