Unimpaired postprandial pancreatic polypeptide secretion in Parkinson's disease and REM sleep behavior disorder

Background: Pancreatic polypeptide is released immediately after food ingestion. The release is operated by vagal‐abdominal projections and has therefore been suggested as a test for vagal nerve integrity. Pathoanatomical and clinical studies indicate vagal dysfunction in early Parkinson's disease (PD). Methods: We assessed the postprandial secretion of pancreatic polypeptide and motilin in healthy controls (n = 18) and patients with idiopathic rapid‐eye‐movement sleep behavior disorder (iRBD, n = 10), a potential premotor stage of PD, as well as in drug‐naive (n = 19) and treated (n = 19) PD patients. Results: The postprandial pancreatic polypeptide secretion showed a physiological pattern in all groups and even an enhanced response in drug‐naive PD and iRBD. Motilin concentrations correlated with pancreatic polypeptide concentrations. Conclusions: Postprandial pancreatic polypeptide secretion is not a suitable test for vagal nerve integrity in PD. The unimpaired pancreatic polypeptide response in iRBD and PD might be explained by partially intact vagal‐abdominal projections or compensatory mechanisms substituting a defective neuronal brain–gut axis. © 2012 Movement Disorder Society