Narrative Review "Dual Frontiers in Neurodegeneration: Pharmacological Synergies and Divergences in Parkinson's Disease and Type 2 Diabetes Mellitus".

Diabetes mellitus (DM) and Parkinson’s disease (PD) are both chronic diseases that have a bidirectional relationship, wherein DM increases the risk of developing PD. Both diseases are related through overlapping pathways, insulin resistance, oxidative stress, and chronic inflammation, which can potentially lead to neurodegeneration. Insulin resistance and impaired insulin signalling present in DM may exacerbate neurodegeneration in PD. Current treatments for PD and DM can interact, such that dopaminergic drugs used to manage PD may increase the risk of altering glucose uptake, leading to exacerbated insulin resistance. Conversely, anti-diabetic drugs like GLP-1 receptor agonists and metformin may even be neuroprotective. However, not all anti-diabetic drugs provide utility in managing PD symptoms; some merely provide general metabolic change. The interplay between PD and DM remains largely uncharacterized, and due to the overlapping nature of these conditions, expanding the scope of research into novel and/or personalized causes of their combined effects may improve treatment efficacy.