Pancreatic polypeptide response to a protein-rich meal in diabetic patients with and without neuropathy

A protein-rich meal and insulin-induced hypoglycemia (ITT) are two of the most important stimuli on pancreatic polypeptide (PP) secretion in diabetic patients. Previous studies have shown a reduced PP response to ITT in diabetic patients with autonomic neuropathy (AN). Twelve patients without AN (mean age 44 +/- 10.8 yr, mean duration of diabetes 11 +/- 5.6 yr), 9 with AN (51.4 +/- 6 yr, 15.8 +/- 6.9 yr) and 9 controls (N) were studied. AN was assessed by the evaluation of the beat-to-beat variation of the heart rate during deep breathing. PP secretion was stimulated by a protein-rich meal (200 g meat, 150 g milk). All insulin-dependent diabetic (IDD) patients lacked circulating PP antibodies. All diabetic patients showed a significant reduction in the early vagal phase compared to controls. This behavior was more evident in diabetic patients with AN and the secondary phase of these two groups overlapped with the response of controls. These data may be explained by the initial alterations of vagal functions not detectable by current methods.