Integrative role of orexigenic peptides in neuroprotection and neurodegenerative disease modulation.

The neuroprotective properties of several anorexigenic peptides, including leptin and glucagon-like peptide-1, are well established across models of neurodegenerative diseases. However, less is known about the role of orexigenic neuropeptides-including neuropeptide Y, agouti-related peptide, melanin-concentrating hormone, orexins, galanin, and peripherally released hormone ghrelin-that are best known for their role in energy balance and stimulation of food intake. Growing evidence highlights their broader neuroprotective properties across preclinical models of Alzheimer's disease (AD) and Parkinson's disease (PD). In AD, these peptides reduce hallmark pathologies such as amyloid burden, tau phosphorylation, oxidative stress, and neuroinflammation, while enhancing synaptogenesis, neurogenesis, and cognitive function. In PD models, ghrelin protects nigrostriatal dopaminergic neurons by restoring autophagic flux, suppressing endoplasmic reticulum stress-mediated apoptosis, and reducing microglial activation, whereas orexin A and B preserve tyrosine hydroxylase expression, promote neuronal excitability, and improve motor and cognitive outcomes. Taken together, these findings position orexigenic peptides as promising modulators of neurodegeneration and highlight their potential as therapeutic targets in AD and PD.