Effect of acute hyperglycaemia on basal and fat-induced exocrine pancreatic secretion in humans

1. We have investigated the effect of acute hyperglycaemia on pancreatico-biliary secretion in healthy subjects. Duodenal outputs of trypsin, lipase, amylase, bicarbonate and bilirubin were measured for 90 min under basal conditions and for 90 min in response to intrajejunal fat administration (1 g/h) on 2 separate days: during normoglycaemia (blood glucose 5 mmol/l) and during acute hyperglycaemia aimed at 15 mmol/l. Plasma cholecystokinin levels, as the major hormonal stimulus of pancreatic and biliary secretion, and plasma pancreatic polypeptide levels, as an indirect measure of vagal-cholinergic tone, were determined at regular intervals. 2. In the basal period pancreatico-biliary secretion was significantly (P < 0.05) reduced during hyperglycaemia compared with normoglycaemia. During normoglycaemia and hyperglycaemia intrajejunal fat significantly (P < 0.05) stimulated pancreaticobiliary secretion. However, during hyperglycaemia, fat-stimulated 90 min pancreatico-biliary secretion was significantly (P < 0.05) reduced compared with normoglycaemia: trypsin (23 +/- 7 units versus 66 +/- 20 units), lipase (36 +/- 8 k-units versus 74 +/- 18 k-units), amylase (8 +/- 2 k-units versus 18 +/- 5 k-units) and bilirubin (32 +/- 8 mumol versus 71 +/- 14 mumol). Plasma cholecystokinin levels increased significantly (P < 0.05) during fat administration and were not different between the two experiments. Plasma pancreatic polypeptide levels were significantly (P < 0.05) reduced during hyperglycaemia both in the basal period and during intrajejunal fat administration. 3. It is concluded that basal and fat-stimulated pancreatico-biliary secretion are significantly reduced during acute hyperglycaemia. Acute hyperglycaemia does not affect intrajejunal fat-stimulated cholecystokinin secretion. Acute hyperglycaemia inhibits basal and stimulated pancreatic polypeptide secretion suggesting vagal-cholinergic inhibition of pancreatico-biliary secretion during hyperglycaemia.