PT320, a Sustained-Release GLP-1 Receptor Agonist, Ameliorates L-DOPA-Induced Dyskinesia in a Mouse Model of Parkinson's Disease

GLP-1 Receptor Agonists: A New Treatment in Parkinson's Disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. Recent data highlight similarities between neurodegenerative diseases, including PD and type 2 diabetes mellitus (T2DM), suggesting a crucial interplay between the gut-brain axis. Glucagon-like peptide-1 receptor (GLP-1R) agonists, known for their use in T2DM treatment, are currently extensively studied as novel PD modifying agents. For this narrative review article, we searched PubMed and Scopus databases for peer-reviewed research, review articles and clinical trials regarding GLP-1R agonists and PD published in the English language with no time restrictions. We also screened the references of the selected articles for possible additional articles in order to include most of the key recent evidence. Many data on animal models and preclinical studies show that GLP1-R agonists can restore dopamine levels, inhibit dopaminergic loss, attenuate neuronal degeneration and alleviate motor and non-motor features of PD. Evidence from clinical studies is also very promising, enhancing the possibility of adding GLP1-R agonists to the current armamentarium of drugs available for PD treatment.

Sitagliptin elevates plasma and CSF incretin levels following oral administration to nonhuman primates: relevance for neurodegenerative disorders

The endogenous incretins glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) possess neurotrophic, neuroprotective, and anti-neuroinflammatory actions. The dipeptidyl peptidase 4 (DPP-4) inhibitor sitagliptin reduces degradation of endogenous GLP-1 and GIP, and, thereby, extends the circulation of these protective peptides. The current nonhuman primate (NHP) study evaluates whether human translational sitagliptin doses can elevate systemic and central nervous system (CNS) levels of GLP-1/GIP in naive, non-lesioned NHPs, in line with our prior rodent studies that demonstrated sitagliptin efficacy in preclinical models of Parkinson's disease (PD). PD is an age-associated neurodegenerative disorder whose current treatment is inadequate. Repositioning of the well-tolerated and efficacious diabetes drug sitagliptin provides a rapid approach to add to the therapeutic armamentarium for PD. The pharmacokinetics and pharmacodynamics of 3 oral sitagliptin doses (5, 20, and 100 mg/kg), equivalent to the routine clinical dose, a tolerated higher clinical dose and a maximal dose in monkey, were evaluated. Peak plasma sitagliptin levels were aligned both with prior reports in humans administered equivalent doses and with those in rodents demonstrating reduction of PD associated neurodegeneration. Although CNS uptake of sitagliptin was low (cerebrospinal fluid (CSF)/plasma ratio 0.01), both plasma and CSF concentrations of GLP-1/GIP were elevated in line with efficacy in prior rodent PD studies. Additional cellular studies evaluating human SH-SY5Y and primary rat ventral mesencephalic cultures challenged with 6-hydroxydopamine, established cellular models of PD, demonstrated that joint treatment with GLP-1 + GIP mitigated cell death, particularly when combined with DPP-4 inhibition to maintain incretin levels. In conclusion, this study provides a supportive translational step towards the clinical evaluation of sitagliptin in PD and other neurodegenerative disorders for which aging, similarly, is the greatest risk factor.

Exendin-4: A potential therapeutic strategy for Alzheimer's disease and Parkinson's disease

Neurodegenerative disorders, which affect millions worldwide, are marked by a steady decline of neurons that are selectively susceptible. Due to the complex pathological processes underlying neurodegeneration, at present, there is no viable therapy available for neurodegenerative disorders. Consequently, the establishment of a novel therapeutic approach for such conditions is a clinical void that remains. The potential significance of various peptides as neuroprotective interventions for neurodegenerative disorders is gaining increasing attention. In the past few years, there has been growing scientific interest in glucagon-like peptide-1 receptor agonists due to their claimed neuroprotective effects. Exendin-4 is a glucagon-like peptide-1 receptor agonist that is known to possess anti-diabetic effects and does not degrade for hours, making it a superior candidate for such disorders. Moreover, exendin-4's neuroprotective effects have been reported in several preclinical studies. Exendin-4's diverse therapeutic targets suggest its potential therapeutic uses in neurodegenerative ailments like Alzheimer's disease and Parkinson's disease and have garnered an increasing amount of attention. Given the substantial body of evidence supporting the neuroprotective potential of exendin-4 in various research models, this article is dedicated to exploring the promising role of exendin-4 as a therapeutic agent for the treatment and management of Alzheimer's disease and Parkinson's disease. This review draws insights from the findings of numerous preclinical and clinical studies to highlight the collective neuroprotective advantages of exendin-4 and the potential mechanisms that underlie its neuroprotective effects.