Glucose homeostasis dependency on acini-islet-acinar (AIA) axis communication: a new possible pathophysiological hypothesis regarding diabetes mellitus.

Studies have highlighted the existence of two intra-pancreatic axes of communication: one involved in the regulation of enzyme production by insulin-the insular-acinar axis; and another involved in the regulation of insulin release by pancreatic enzymes-the acini-insular axis. Previous studies by our laboratory show that pancreatic enzymes can affect blood glucose homeostasis and insulin secretion independently of their digestive functions, both from the gut lumen and probably from the blood. As a result we would like to introduce here the concept of acini-islet-acinar (AIA) axis communication (feedback), which could play an important role in the development of obesity and diabetes type 2. The AIA feedback links the endocrine and exocrine parts of the pancreas and emphasizes the essential role that the pancreas plays, as a single organ, in the regulation of glucose homeostasis by amylase most probably in gut epithelium and by insulin and glucagon in peripheral blood.

Experiments suggesting extra-digestive effects of enteral pancreatic amylase and its peptides on glucose homeostasis in a pig model.

The studies presented were designed to highlight the impact of pancreatic enzymes on glycemic control and insulin response. Blood glucose and plasma insulin levels were monitored after intravenous, oral or direct gut glucose tolerance tests (GTT) in 6 pigs with an intact gastrointestinal tract and in 12 pigs following duodenal-jejunal bypass (DJB) surgery. In the intact pigs, pancreatic enzymes (Creon®) given orally 1 h prior to the GTT, lowered the blood glucose levels during the oral and meal GTT and reduced the plasma insulin response during the intravenous and meal GTT. In DJB pigs, blood glucose and plasma insulin levels were higher following glucose loading into the by-passed biliopancreatic limb as compared to that following glucose loading orally or into the common intestinal limb. Infusion of amylase or amylase peptides together with glucose into the biliopancreatic limb lowered blood glucose levels in DJB pigs. These preliminary data suggest new, extra-digestive, actions of enteral pancreatic enzymes - probably amylase or its peptides - on glucose homeostasis, with an reduction in net glucose absorption into the blood and in insulin response. This ability of digestive enzymes (amylase) to reduce post-prandial hyperglycaemia in an insulin-independent manner could aid in preventing the development of obesity and diabetes.

Specificity of the 3H-triolein assay for pancreatic lipase in blood plasma.

The aim of this study was to investigate the specificity of the 3H-triolein assay and to investigate the recovery of highly purified pancreatic lipase and pancreatic lipase in the form of pure non-activated pig pancreatic juice. Blood plasma from pigs was analysed for pancreatic lipase activity using the 3H-triolein substrate assay, with a method specific for lipoprotein lipase and with a method specific for hepatic lipase. The recovery of pancreatic lipase from pancreatic juice was approximately 100%, while the recovery of highly purified pancreatic lipase in plasma or whole blood was found to be approximately 1%. Preparations of highly concentrated, purified lipoprotein lipase showed activity in the 3H-triolein assay designed for pancreatic lipase, but the activity did not exceed 1% of the activity of this enzyme measured in an assay specific for lipoprotein lipase (samples containing physiological levels of lipoprotein lipase did not show any activity in the assay). Hepatic lipase was not measurable under the conditions of the 3H-triolein assay. In conclusion, the 3H-triolein assay showed pronounced specificity for pancreatic lipase compared with lipoprotein lipase or hepatic lipase.

Does the pancreas really produce much more lipase than required for fat digestion?

Thirty years ago, it was reported that a linear relationship does not exist between the amounts of human pancreatic lipase secreted in chronic pancreatitis and the degree of steatorrhea, which was considered to appear only after more than 90% of the pancreatic secretory capacity had been lost. From these observations, it was generally thought that the lipolytic potential of the pancreas is much higher than required. In recent years, however, it has been noted that: 1) the level of inhibition of digestive lipases and gastrointestinal lipolysis by the lipase inhibitor orlistat were almost linearly correlated with the amount of excreted fat; 2) in minipigs with experimentally-induced pancreatic exocrine insufficiency, the amounts of enteric-coated pancreatic extracts needed for restoring fat digestion to normal levels were estimated to be much higher than those usually administered; 3) human pancreatic lipase specific activity on meal triglycerides is 3 orders of magnitude lower than the very high specific activity usually measured under experimental in vitro conditions which are far from physiological conditions; 4) in patients with reduced human pancreatic lipase secretion, gastric lipase plays a significant role in fat digestion. This last observation might explain the absence of a linear relationship between human pancreatic lipase secretion in chronic pancreatitis and steatorrhea. From the low specific activity displayed by human pancreatic lipase on meal triglycerides, one can better understand why more lipase than expected is needed, why fat digestion lasts for more than a few minutes and, finally, why there is not such an excess secretory capacity for lipase as had been previously thought.

Influence of intravenous drug abuse on vascular access placement and survival in HIV-seropositive patients.

BACKGROUND: The influence of intravenous drug abuse (IVDA) on hemodialysis access placement practices and access survival in HIV-infected patients is unknown. METHODS: We conducted a retrospective study of 60, HIV seropositive, maintenance hemodialysis patients. Type of access and assisted access survival (measured from date of placement) were compared in those with (77%) and without (23%) a history of IVDA. RESULTS: Mean age was 37.8 years, mean baseline serum albumin was 2.9 g/dl and median CD4 count was 222 cells/mm3. Fifteen patients, all IVDA, were dialyzed using only tunneled catheters (median number of catheters per person (range): 2.5 (1-11)). There were longer delays in creation of a permanent access (p = 0.08), but no difference in the type of permanent access placed in IVDA versus the non-IVDA group. Over 1,051 cumulative months of access follow-up, 134 tunneled catheters, 28 grafts and 19 fistulae were placed, with observed failure rates of 1 per 4.7 access-months, 1 per 19.7 access-months, 1 per 38.2 access-months, respectively. The adjusted relative hazard of access failure for grafts versus catheters was 0.41 (95% CI: 0.23, 0.72; p = 0.002) and for fistulae versus catheters was 0.21 (95% CI: 0.08, 0.52; p = 0.001). Thirty-two percent of accesses were removed due to infection, an infection removal rate for catheters of 1 per 7.8 access-months and for grafts of 1 per 62.5 access-months; all graft infections occurred in the IVDA group. No fistula was removed due to infection. CONCLUSION: Fistulae are the first line of choice for hemodialysis access in HIV-seropositive patients regardless of IVDA history; if not feasible, graft placement in non-IVDA or abstinent IVDA patients is recommended. In those with active IVDA, the optimal method of renal replacement therapy and type of hemodialysis access remain uncertain.

The enzyme levels in blood are not affected by oral administration of a pancreatic enzyme preparation (Creon 10,000) in pancreas-insufficient pigs.

After oral intake, small amounts of intact protein may be absorbed into the blood circulation. The current study investigated whether orally administered pancreatic enzymes were absorbed from the intestine. The study included 28 pigs; 3 control pigs with intact pancreatic function and 25 pigs that were made exocrine pancreas insufficient by duct ligation (20 pigs) or total pancreatectomy (5 pigs). The pigs received a pancreatic enzyme preparation (0, 2, 4, or 8 g of Creon 10,000) together with the feed. The blood plasma was analyzed for pancreatic lipase activity with a [3H]-triolein substrate assay, while (pro)colipase and cationic trypsin(ogen) levels were measured with enzyme-linked immunosorbent assay (ELISA). Administration of Creon (0-8 g) caused no significant changes in plasma (pro)colipase or cationic trypsin(ogen) levels. Lipase activity peaks in plasma samples were found, but they did not correspond to the administration of Creon. The potential source of these plasma lipase activity peaks is discussed. The results showed no absorption into blood of pancreatic enzymes after oral administration (0, 2, 4, or 8 g of Creon mixed with 100 g of feed) to pancreas-insufficient pigs.