Fasting and postprandial Ghrelin levels in Parkinson's disease: a systematic review and meta-analysis

Parkinson's disease (PD) is a progressive movement disorder with motor and non-motor symptoms, including gastrointestinal and olfactory dysfunctions. These symptoms may be associated with plasma concentrations of the hormone ghrelin. Lower fasting and postprandial plasma levels of total and active ghrelin were reported in PD, despite heterogeneous findings. In this meta-analysis, we assessed the magnitude of ghrelin dysregulation in PD and explored associated factors. We included quasi-experimental and observational studies assessing fasting and postprandial plasma concentrations of total and/or active ghrelin in individuals with PD and controls (eight studies; 985 subjects). Compared to controls, fasting individuals with PD exhibited a significant reduction in total and active ghrelin concentrations. PD also showed significantly reduced postprandial concentrations of total and active ghrelin. This meta-analysis suggests that ghrelin may be crucially involved in the dysfunctions often observed in PD. Further studies should explore factors such as sex, drug therapy, and disease stages.