The Role of Glucagon-like Peptide-1 Receptor Agonists in Alzheimer's and Parkinson's Disease: A Literature Review of Clinical Trials.

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are widely used in the treatment of type 2 diabetes and obesity due to their metabolic effects. Emerging evidence suggests they may also have neuroprotective effects, indicating their potential as disease-modifying therapies in neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). Preclinical studies in animal models have demonstrated that GLP-1RAs can reduce neuroinflammation, oxidative stress, neuronal apoptosis, and pathological protein aggregation, while enhancing glucose metabolism and mitochondrial function. This narrative review analyzed results from human clinical trials evaluating GLP-1RAs in AD and PD, based on a search of four databases (Web of Science, Medline, Embase, and Clinical Trials). The analysis included eleven studies. In AD, clinical trials suggest that GLP-1RAs such as liraglutide and semaglutide may enhance brain glucose metabolism, facilitate glucose transport across the blood-brain barrier, and benefit neuronal networks. However, most studies did not demonstrate improvements in cognitive functions or radiological markers. Short-term clinical trials of GLP-1RAs, including exenatide and lixisenatide, demonstrated promising effects on motor and selected non-motor symptoms in patients with PD, but their disease-modifying effects remain unproven. GLP-1RAs showed a favorable safety profile. Despite promising findings, small study populations, heterogeneous protocols, and short observation periods limit definitive conclusions. Further larger, long-term studies are needed, particularly to clarify the risk-benefit balance, weight control, and long-term outcomes.