Diabetes drug may reduce risk of developing Parkinson's disease

A new study in humans appears to confirm what has been shown in animal studies - that a class of drug used to treat diabetes may reduce the risk of developing Parkinson's disease.

Study finds diabetes patients taking glitazone pills were less likely to develop Parkinson's disease than patients receiving other diabetes treatments.

Published in PLOS Medicine, the study shows diabetes patients taking glitazone prescription drugs were almost a third less likely to develop Parkinson's disease than patients who were on other diabetes treatments and who had never taken that class of drug.

Estimates suggest around 1 in 500 people are affected by Parkinson's disease. To date, there are no effective treatments that directly tackle the disease, which kills nerve cells that produce dopamine - a brain chemical that is essential for conveying messages to muscles that control movement.

Lab and animal studies have shown that glitazones may prevent loss of nerve cells.

The new study - led by the London School of Hygiene & Tropical Medicine in the UK - is the first to investigate glitazone use and incidence of Parkinson's disease in humans.

First author Dr. Ruth Brauer, who worked on the study while at the School and is now at King's College London, says:

"Although our study only looked at people with diabetes, we believe it's likely that the protective effect of glitazones may also be seen in people without diabetes."

The study suggests the reduced risk of developing Parkinson's only lasts while patients keep taking glitazones - the results showed no lasting benefit for patients who used to take them and then switched to other drugs.

Glitazones treat diabetes by activating a receptor to reduce insulin resistance. The receptor is called peroxisome proliferation-activated gamma (PPARɣ). However, the receptor also has other functions, many of which have not been studied extensively in humans. A receptor is a protein embedded in the cell wall that acts as a gatekeeper allowing only certain signals to enter.

28% lower incidence of Parkinson's disease in patients taking glitazones

For the study, the researchers examined the electronic health records of over 160,000 diabetes patients in the UK to match 44,597 glitazone users with 120,373 people using other antidiabetic drugs. Each glitazone user was matched to five users of other diabetic treatments of the same age, gender, attending the same clinic, and at the same diabetes treatment stage.

The data spanned from 1999 - when glitazones were first prescribed for the treatment of diabetes - to 2013. From the records covering this period, the researchers could see how many of the participants were diagnosed with Parkinson's disease.

The researchers found a 28% lower incidence of Parkinson's disease in the patients taking glitazones compared with counterparts taking other treatments for diabetes. The finding did not change when they took into account other factors that might affect Parkinson's disease risk - including smoking and head injury.

The authors note the study was not designed to look at whether the drug might slow the progress of Parkinson's once patients have been diagnosed with it - and so cannot say whether it does.

They also point out that glitazones have been linked with some serious side effects, including bladder cancer and cardiovascular problems.

The team hopes the unique findings will spur further studies, as Dr. Brauer concludes:

"Our results suggest that treatments which activate the PPARɣ receptor in the same way as glitazones could be promising targets in future drug research."

The Michael J. Fox Foundation for Parkinson's Research funded the study.

The findings follow another recent Medical News Today report of a study that suggests two existing antimalaria drugs may slow Parkinson's disease, while reducing some of the side effects seen with current treatments.

Written by Catharine Paddock PhD

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