Diabetes linked to behavioural disorder

Anyone can go nuts over managing diabetes, but people with the disease are more prone to anxiety and depression than those with other chronic diseases that require similar levels of management, says a study.

Insulin resistance that can lead to Type 2 diabetes is linked to behavioural disorder, the findings showed.

"This is one of the first studies that directly shows that insulin resistance in the brain actually can produce a behavioural change," said senior author C. Ronald Kahn, professor at the Harvard Medical School.

Insulin resistance is linked to lower levels of the key neurotransmitter dopamine in areas of the brain associated with anxiety and depression, the findings showed.

For the study, the researchers genetically modified mice to make their brains resistant to insulin.

The scientists first found that the animals exhibited behaviours that suggest anxiety and depression, and then pinpointed a mechanism that lowers levels of the key neurotransmitter dopamine in areas of the brain associated with those conditions.

The researchers assessed the genetically modified mice in multiple tests that place mice under stress.

Young mice behaved much like normal mice, but mice tested at 17 months of age (which is starting late middle-age for mice) displayed significant behavioural disorders.

It is not clear why the changes in behaviour might increase with age, Kahn said, but the effect is common among mouse models of neurological disorders, and is seen in the same human neurological diseases.

The study appeared in the journal Proceedings of the National Academy of Sciences (PNAS).