Medication used to treat diabetes could reduce the risk of developing Parkinson's disease, according to new research, opening up a range of potential options for treating and managing the degenerative brain disorder.

Looking at patient records for 100,288 individuals with type 2 diabetes, scientists found that while these individuals had a higher than normal risk of developing Parkinson's, commonly prescribed diabetes drugs also seemed to lower that risk.

Those who were taking two particular types of diabetes drugs – GLP-1 receptor agonists and DPP4 inhibitors – were less likely to be diagnosed with Parkinson's later in life than those on other treatments. In the case of GLP-1 receptor agonists, the likelihood dropped by 60 percent.

"Our study has strengthened evidence that there is a link between type 2 diabetes and Parkinson's disease, although it remains clear that most people with diabetes will not go on to develop Parkinson's," says neuroscientist Tom Foltynie, from University College London in the UK.

The research follows up a 2018 study that covered some 2 million individuals with type 2 diabetes, showing that while the chances of developing Parkinson's remained low, having diabetes increased that chance by around a third – though as yet it's not clear exactly why.

Scientists are particularly keen on exploring the potential of the medication exenatide, which is a GLP-1 receptor agonist: small studies have already suggested that exenatide can limit some of the degenerative effects of Parkinson's disease.

In this new study, patient records were collated for an average of just over three years, with 329 of the 100,288 individuals developing Parkinson's within that time. That's not a huge number, but it was enough to reveal a smaller fraction of people taking DPP4 inhibitors and GLP-1 receptor agonists went on to develop Parkinson's than those using a third antidiabetic drug, or those not using antidiabetic drugs at all.

"It may be helpful for doctors to consider other risk factors for Parkinson's disease when prescribing medications for type 2 diabetes, but further research will be needed to confirm clinical implications," says pharmacoepidemiologist Li Wei, from University College London.

GLP-1 receptor agonists are designed to bind onto and activate receptor proteins found on pancreas and neuron cells that stimulate insulin secretion, which lowers blood glucose levels. Animal studies have suggested this might also trigger some way of protecting neurons from harm; the new research backs that up.

This is all very promising, but there's a long way to go – the team behind the new study is about to recruit volunteers for a phase 3 clinical trial that will look more closely at the potential effects of exenatide on brain disorders.

With the number of people with Parkinson's worldwide now in the millions, and the number expected to keep on rising, new ways of at least managing this condition and other diseases of the brain are urgently required. Exenatide could be one way forward.

"We have added to evidence that exenatide may help to prevent or treat Parkinson's disease, hopefully by affecting the course of the disease and not merely reducing symptoms, but we need to progress with our clinical trial before making any recommendations," says Foltynie.

The research has been published in Brain.