Dear Doctors: A few years ago, you mentioned a study on the idea that GLP-1 drugs might have a protective effect for people with early-stage Parkinson's disease. I assume that the study is finished now. Is it possible to summarize the outcomes of that trial?
Dear Reader: The term GLP-1 is short for glucagon-like peptide-1. This type of hormone is released after eating. The hormone is produced by the intestines to tell the pancreas to make more insulin. This helps control blood sugar, slows the movement of food through the digestive tract and acts on appetite pathways in the brain. This all helps people feel full so they eat less and often lose weight.
GLP-1 drugs have been used since 2005 to manage Type 2 diabetes. But their off-label use for weight loss pushed them into the headlines. By the time the Food and Drug Administration approved GLP-1s to combat obesity in 2021, their use had grown exponentially. The drugs' popularity gave researchers a large pool of medical data. This included hints of unexpected health benefits associated with GLP-1 use. The benefits were in areas as diverse as cardiac health, kidney function, sleep apnea, blood lipid levels and liver disease. The study you are asking about found a possible link between GLP-1s and benefits in early-stage Parkinson's disease.
The study was published in the New England Journal of Medicine. It looked at disease progression in 156 adults who were in the earlier stages of Parkinson's disease. This is a progressive neurological disorder. In this disorder, changes to certain tissues in the brain interfere with movement. Symptoms include muscle rigidity, slowed movement, impaired balance, changes to speech and tremor. Half of the study participants received a GLP-1 drug. The other half received a placebo. Everyone kept taking their usual Parkinson’s medications. After a year, the symptoms of participants in the GLP-1 group seemed to not progress as rapidly as in the placebo group. This suggested a neuroprotective effect.
At this time, follow-up results of that study have not yet been reported. Also, findings from related studies have been mixed. A two-year clinical trial looked at a different GLP-1 drug. This study didn’t find a statistically significant difference in progression between the groups. Although this study was similar in size to the research you are asking about, it was twice the length. The duration and the use of a different GLP-1 drug, which may reach different brain targets, may have led to that different outcome. It could also involve something known as a "false signal." This refers to a data pattern in research. It’s when results suggest an if-then relationship, but it does not carry through in repeated experiments.
The results of the most recent study are disappointing. But the researchers have proposed more studies to explore similar drugs that may reach other targets in the brain. The potential for GLP-1 drugs to ease Parkinson's progression remains uncertain. The good news is research into this approach continues.
(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
