GDNF and Parkinson disease: Aerobic exercise has been associated with neuroprotective effects in the nigrostriatal dopaminergic system, so as to improve many motor and non-motor Parkinson’s symptoms, and the proposed mechanisms that link physical activity to neuroprotective effect are an increase in serum urate, an increased release of neurotrophic factors [e.g., brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF)], upregulation of the transcriptional regulator peroxisome proliferator-activated receptor gamma (PPARγ) coactivator 1α (PGC1α), and regulation of dopamine turnover74.