Amylase intrapancreatic infusion delays insulin release during an intravenous glucose tolerance test,proof of acini–islet–acinar interactions

BACKGROUND The possible existence of an acini–islet–acinar(AIA)reflex,involving mutual amylase and insulin interactions,was investigated in the current acute experiment on pigs.AIM To confirm the existence of an AIA reflex and justify the placement of the exocrine and endocrine pancreatic components within the same organ.METHODS The study was performed on six pigs under general anesthesia.An intravenous glucose tolerance test was performed,with a bolus infusion of 50%glucose to the jugular vein,while amylase(5000 U/kg)or vehicle intrapancreatic infusions were administered via the pancreaticoduodenalis cranialis artery during 30 min with a 1 mL/min flow rate.RESULTS The amylase infusion to pancreatic arterial circulation inhibited and delayed the insulin release peak which is usually associated with the highest value of blood glucose and is typically observed at 15 min after glucose infusion,for>1 h.The intrapancreatic infusion of the vehicle(saline)did not have any effect on the time frame of insulin release.Infusion of 1%bovine serum albumin changed the insulin release curve dramatically and prolonged the high range of insulin secretion,far beyond the glucose peak.CONCLUSION Intrapancreatic arterial infusion of amylase interrupted the integrated glucose–insulin interactions.This confirms an AIA reflex and justifies placement of the exocrine and endocrine pancreatic components within the same organ.

Hypothesis that alpha-amylase evokes regulatory mechanisms originating in the pancreas,gut and circulation,which govern glucose/insulin homeostasis

The anti-incretin theory involving the abolishment of diabetes type(DT)II by some of methods used in bariatric surgery,first appeared during the early years of the XXI century and considers the existence of anti-incretin substances.However,to date no exogenous or endogenous anti-incretins have been found.Our concept of the acini-islet-acinar axis assumes that insulin intra-pancreatically stimulates alpha-amylase synthesis(“halo phenomenon”)and in turn,alphaamylase reciprocally inhibits insulin production,thus making alpha-amylase a candidate for being an anti-incretin.Additionally,gut as well as plasma alphaamylase,of pancreatic and other origins,inhibits the appearance of dietary glucose in the blood,lowering the glucose peak after iv or oral glucose loading.This effect of alpha-amylase can be interpreted as an insulin down regulatory mechanism,possibly limiting the depletion of pancreatic beta cells and preventing their failure.Clinical observations agree with the above statements,where patients with high blood alpha-amylase concentrations are seldom obese and seldom develop DT2.Obese-DT2,as well as DT1 patients,usually develop exocrine pancreatic insufficiency(EPI)and vice versa.Ultimately,DT2 patients develop DT1,when the pancreatic beta cells are exhausted and insulin production ceases.Studies on biliopancreatic diversion(BPD)and on BPD with duodenal switch,a type of bariatric surgery,as well as studies on EPI pigs,allow us to observe and investigate the above-mentioned phenomena of intra-pancreatic interactions.