Ghrelin-based interventions in preclinical models of Parkinson's disease: a systematic review

Ghrelin plays a crucial role in metabolism and gastrointestinal function. In the central nervous system, ghrelin modulates both hedonic and homeostatic control of eating behavior. Ghrelin promotes neuron survival by reducing apoptosis, inflammation, and oxidative stress, making it a potential therapeutic agent for neurodegenerative diseases. Parkinson's Disease (PD) is a neurodegenerative disease characterized by motor and non-motor symptoms. The motor impairments result primarily from the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta. Individuals with PD exhibit reduced levels of fasting and postprandial plasma ghrelin, and its receptors (GHSR) are expressed in the substantia nigra. Thus, this review aimed to evaluate the effects of ghrelin or GHSR agonists administration in experimental models of PD. A systematic search was conducted across PubMed, Scopus, Web of Science, and Embase. The 12 included studies involved PD models induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 6-hydroxydopamine (6-OHDA), as well as A53T transgenic mice. Interventions were performed with acylated and/or des-acylated ghrelin, in addition to the GHSR agonist HM01. Intervention with ghrelin was able to reduce dopaminergic neurodegeneration and improve motor function, while also positively impacting metabolic and gastrointestinal functions, expanding its relevance to non-motor consequences of PD. Considering that most results were obtained using acute toxin-induced models and only male animals, further studies using progressive PD models and evaluating sex differences are needed. Thus, although preclinical evidence supports ghrelin or GHSR agonists as promising agents for treatment, future studies will be essential to inform clinical translation and optimize therapeutic strategies for individuals with PD.