GLP‐1 receptor agonists for Parkinson’s disease?
Insulin has a role in brain neuronal metabolism and repair and promoting synaptic function. One of the many changes associated with Parkinson’s disease is desensitisation to the effects of insulin signalling – which is why there is interest in the potential of GLP-1 agonists, a group of peptides that stimulate insulin secretion. They are currently licensed for the treatment of type 2 diabetes and, less widely, obesity.
A Cochrane systematic review has now examined the evidence for this potential indication. Of 99 relevant publications, only two randomised trials were identified – both with exenatide, the first GLP-1 agonist to be marketed – involving a total of 107 participants. One double-blind study included follow-up for 5 years; the other was single-blind, with follow up for 12 months then at 2 and 12 months after withdrawal of treatment.
There was some evidence from the double blind trial that exenatide improved motor function compared with placebo but there was no change in quality of life; weight was not affected. Both findings were ‘low certainty’. The treatment-withdrawal study also suggested an effect on motor function and possibly quality of life, but with a similar level of doubt about adverse effects and weight loss.
Studies on GLP-1 agonists in the treatment of Parkinson’s disease are ongoing but the evidence so far suggests their impact on motor function may persist after discontinuing exenatide, raising the possibility of a disease‐modifying effect. However, an effect on quality of life, activities of daily living and psychological outcomes is ‘unclear’.