Diabetes doubles risk of Parkinson's disease; metformin protects brain

Diabetes more than doubles the risk of developing Parkinson's disease while metformin therapy protects against that risk, according to research published in the publication Parkinsonism and Related Disorders.

Parkinson's disease is a disorder of the brain that leads to tremors and difficulty with walking, movement and coordination. It most often develops in people age 50 or older and is one of the most common nervous system disorders of the elderly, according to the National Institutes of Health. There is no known cure.

The major 12-year study in Taiwan found that while diabetes increases the risk of Parkinson's 2.2 fold, including metformin in the therapy negates that risk.

“An exciting aspect of the finding is that metformin seems to be working to protect the brain against neurodegeneration which contributes to Parkinsonism. This means it may also be considered a relevant therapy for the prevention of dementia as well,” said Mark Wahlqvist, professor at the National Health Research Institutes in Taiwan and lead author of the study.

Metformin is the first-line medication for patients with type 2 diabetes. This affordable and commonly prescribed oral drug lowers blood glucose levels by decreasing the amount of glucose produced by the liver and enhancing insulin action. It's a type of biguanide drug used since the 1950s with a relatively safe record.

Researchers also found that use of sulfonylurea drugs, a common treatment for diabetes, further increases the risk by about 57 percent.

Sylfonylureas are a category of oral medications that stimulate the beta cells of the pancreas to release more insulin, according to the American Diabetes Association. Sylfonylurea drugs have been in use since the 1950s and include glipizide, glyburide, glimepiride and chlorpropamide.

Researchers theorize that metformin may re-set the regulation of energy metabolism in the brain cells. They suspect that exercise and diet may have the same energy regulating effect.

The study does not examine the mechanism behind metformin's protective effect on the brain. Researchers say that additional research is needed in this area.

Past research has shown that metformin reduces cardiovascular mortality and several cancers, including those of the large bowel, liver and pancreas.

Sources: Parkinsonism and Related Disorders, American Diabetes Association, National Institutes of Health