Utility of the plasma pancreatic polypeptide response to modified sham feeding in diabetic gastroenteropathy and non-ulcer dyspepsia

Background: The relationship between cardiovascular and gastrointestinal (ie, plasma pancreatic polypeptide [PP] response to modified sham feeding [MSF]) indices of vagal function is unclear. Hyperglycemia inhibits PP secretion via vagally mediated mechanisms. Our aims were to (a) compare the PP response, (b) its relationship with glycemia, and (c) the relationship between PP response to MSF, gastric emptying (GE) of solids, and symptoms during GE study in healthy controls, patients with diabetic gastroenteropathy (DM), and non-ulcer dyspepsia (NUD). Methods: In 24 healthy controls, 40 DM, and 40 NUD patients, we measured plasma PP concentrations during MSF, cardiovagal functions, GE, and symptoms during a GE study. Key Results: Baseline PP concentrations were higher in DM than in controls and NUD (P =.01), and in type 2 than in type 1 DM patients (P <.01). The PP increment during MSF was normal (≥20 pg/mL) in 70% of controls, 54% of DM, and 47% of NUD patients. Overall, the PP response and cardiovagal tests were concordant (P =.01). Among patients with a reduced PP increment with MSF, 7/10 of T1DM and 1/7 of T2DM patients had moderate or severe cardiovagal dysfunctions (P <.05). The PP response to MSF was not associated with GE. Conclusions & Inferences: Up to 30% of healthy controls have a reduced PP increment during MSF, limiting the utility of this test to detect vagal injury. The PP response is more useful when it is normal than abnormal. A reduced PP response is more likely to be associated with cardiovagal dysfunctions in T1DM than in T2DM.