Hyperfunction of the entero-PP axis in non-insulin dependent diabetes mellitus

In a previous study we have found that the plasma pancreatic polypeptide (PP) response to oral glucose loading is exaggerated in diabetic patients compared with normal subjects. We have investigated, therefore, the effects of a protein-rich meal or meat extract ingestion on plasma PP secretion and examined also the effects of intravenous arginine administration on PP levels in normal subjects and in patients with noninsulin-dependent diabetes mellitus (NIDDM). Following a 600 Kcal meal ingestion, plasma PP levels increased immediately and showed biphasic secretion in normal subjects and in NIDDM, but the response was exaggerated in NIDDM. A 50 g meat extract administration also produced an exaggerated PP response in NIDDM compared with normal subjects. In NIDDM and normal subjects, plasma PP levels did not change significantly during an arginine infusion (30 g for 45 min) but after the end of the infusion PP levels increased significantly compared with basal levels. In normal subjects, plasma PP rose abruptly after a bolus arginine injection (4 g for 2 min) and then remained at significantly high levels even 30 min after the injection. In NIDDM, however, plasma PP levels tended to increase, but not significantly, after the bolus arginine injection. Since in NIDDM the protein-rich meal and meat extract ingestion produced an exaggerated rise in plasma PP while the PP responses to the intravenous arginine administration were rather impaired compared with normal subjects, we suggest that the entero-PP axis is overactive in NIDDM.