Effect of emeriamine on exocrine and endocrine pancreatic function in normal and diabetic rats

Towards Chemoenzymatic Syntheses of Both Enantiomers of Phosphoemeriamine

An enzyme-promoted addition of nitromethane to the appropriate phosphorylated imine (aza-Henry reaction) intended to be used in the synthesis of the title phosphoemeriamine, a phospha-analog of emeriamine (aminocarnitine), failed due to the tautomerization of the imine to the corresponding enamine. Nevertheless, both enantiomers of phosphoemeriamine were synthesized in high yield and enantiomeric purity using another chemoenzymatic approach, starting with a crucial step involving a CAL-B-mediated acetylation of the appropriate racemic precursor-diethyl 2-amino-3-dimethylaminopropylphosphonate-under kinetic resolution conditions. The enzymatic reaction was very efficient and provided each enantiomeric product in acceptable yield and with enantiomeric excess of 91 and 92%. The following appropriate chemical transformations led to the desired enantiomers of phosphoemeriamine in the form of phosphoemeriamine sesquichloride with enantiomeric excess up to 90%.

Mechanism of Exocrine Pancreatic Insufficiency in Streptozotocin-Induced Type 1 Diabetes Mellitus

Diabetes mellitus (DM) is a major health problem at present affecting about 180 million people worldwide. DM is associated with many metabolic abnormalities in the body including the indigestion of carbohydrates leading to malnutrition and weight loss. In this article we investigate the cellular and molecular mechanisms of exocrine pancreatic insufficiency in streptozotocin (STZ, 60 mg kg(-1), i.p.)-induced DM in male rats compared to healthy age-matched controls. Either electrical field stimulation (EFS) or cholecystokinin octapeptide (CCK-8, 10(-8) M) can elicit large and significant (P < 0.05) increases in amylase output from pancreatic segments compared to basal secretion. Insulin (10(-6) M) alone has no significant effect on amylase output compared to basal but it enhanced the secretory responses to either EFS or CCK-8. When rats were rendered diabetic with STZ, either EFS or CCK-8-evoked amylase output was significantly (P < 0.01) decreased compared to the responses obtained with either EFS or CCK-8 alone in healthy age-matched control pancreas. In addition, CCK-8 can elicit large dose-dependent release of amylase in age-matched control and diabetic acinar cells with significantly (P < 0.05) reduced responses in diabetic acinar cells. CCK-8 evoked a large rapid increase in peak cytosolic free calcium concentration ([Ca2+]c) followed by a decrease to a plateau phase in age-matched control fura-2-loaded pancreatic acinar cells. These responses were significantly (P < 0.05) decreased in STZ-induced diabetic acinar cells. In the presence of 10(-6) M insulin, CCK-8 evoked a much larger increase in the Ca2+ transient compared to the response obtained with CCK-8 alone. These effects were significantly (P < 0.01) inhibited in STZ-induced diabetic acinar cells. Similarly, in zero extracellular Ca2+ [Ca2+]ĉ, the CCK-8-evoked [Ca2+]c was significantly (P < 0.05) reduced in both diabetic and age-matched control acinar cells, but with more pronounced reduction in diabetic acinar cells. CCK(A) receptor mRNA levels remained unchanged in diabetic rat acinar cells compared to age-matched healthy control. In contrast, amylase mRNA was significantly (P < 0.05) reduced in diabetic acinar cells compared to control. The results indicate that reduced amylase secretion in response to either EFS or CCK-8 in the diabetic pancreas may be due to reduced [Ca2+]c and gene expression for amylase and not to the gene expression of CCK(A) receptor in pancreatic acinar cells.

Mechanism of exocrine pancreatic insufficiency in streptozotocin-induced diabetes mellitus in rat: effect of cholecystokinin-octapeptide

This study investigated the effects of cholecystokinin-octapeptide (CCK-8) on pancreatic juice flow and its contents, and on cytosolic calcium (Ca2+) and magnesium (Mg2+) levels in streptozotocin (STZ)-induced diabetic rats compared to healthy age-matched controls. Animals were rendered diabetic by a single injection of STZ (60 mg kg(-1), I.P.). Age-matched control rats obtained an equivalent volume of citrate buffer. Seven weeks later, animals were either anaesthetised (1 g kg(-1) urethane; IP) for the measurement of pancreatic juice flow or humanely killed and the pancreas isolated for the measurements of cytosolic Ca2+ and Mg2+ levels. Non-fasting blood glucose levels in control and diabetic rats were 92.40 +/- 2.42 mg dl(-1) (n = 44) and >500 mg dl(-1) (n = 27), respectively. Resting (basal) pancreatic juice flow in control and diabetic anaesthetised rats was 0.56 +/- 0.05 ul min(-1) (n = 10) and 1.28 +/- 0.16 ul min(-1) (n = 8). CCK-8 infusion resulted in a significant (p < 0.05) increase in pancreatic juice flow in control animals compared to a much larger increase in diabetic rats. In contrast, CCK-8 evoked significant (p < 0.05) increases in protein output and amylase secretion in control rats compared to much reduced responses in diabetic animals. Basal [Ca2+]i in control and diabetic fura-2-loaded acinar cells was 109.40 +/- 15.41 nM (n = 15) and 130.62 +/- 17.66 nM (n = 8), respectively. CCK-8 (10(-8)M) induced a peak response of 436.55 +/- 36.54 nM (n = 15) and 409.31 +/- 34.64 nM (n = 8) in control and diabetic cells, respectively. Basal [Mg2+]i in control and diabetic magfura-2-loaded acinar cells was 0.96 +/- 0.06 nM (n = 18) and 0.86 +/- 0.04 nM (n = 10). In the presence of CCK-8 (10(-8)) [Mg2+]i in control and diabetic cells was 0.80 +/- 0.05 nM (n = 18) and 0.60 +/- 0.02 nM (n = 10), respectively. The results indicate that diabetes-induced pancreatic insufficiency may be associated with derangements in cellular Ca2+ and Mg2+ homeostasis.

Effect of L-aminocarnitine, an inhibitor of mitochondrial fatty acid oxidation, on the exocrine pancreas and liver in fasted rats

Fasting induces pancreatic secretory lipase, possibly through an increased utilization of fatty acids and/or ketone bodies by the acinar cells. To test this hypothesis, the effects of L-aminocarnitine (ACA), an inhibitor of mitochondrial beta-oxidation and ketone body formation, on the pancreatic enzyme composition were studied in rats. The characteristics and reversibility of the hepatic steatosis produced by ACA in fasted animals were also investigated. In fasted rats, ACA decreased the plasma levels of beta-hydroxybutyrate, glucose and insulin, but increased that of glucagon. Fasting for 3 days increased the pancreatic lipase content by 80%. Administration of ACA (3, 10 or 30 mg kg(-1) daily) for 3 days to fasted rats led to dose-related decreases in pancreatic lipase content, the fasting-induced increase was prevented even by the lowest dose. Nevertheless, ACA in the fasted rats likewise decreased the pancreatic contents of protein, amylase and trypsinogen to varying degrees, suggesting a general defect of protein synthesis. The 3-day treatment with ACA during fasting led to dose-related, marked increases in hepatic weight and triglyceride content. Light and electron microscopy revealed lipid vesicles of varying sizes in the hepatocytes; the fat deposition was predominant in the periportal zones of the hepatic lobules. By means of electron microscopy, lipid vacuoles were observed in the centroacinar cells, but not in the acinar cells of the pancreas. In rats treated with 30 mg kg(-1) of ACA daily for 3 days while they were fasted, cessation of ACA treatment and refeeding with normal chow led to normalization of the pancreatic enzyme contents within 6 days, and gradual and complete disappearance of the hepatic steatosis within 24 days. Microscopy also demonstrated complete recovery in both the liver and the pancreas. The results indicate that pancreatic secretory lipase induction during the adaptive phase of starvation is dependent on an unhindered mitochondrial beta-oxidation of fatty acids and ketogenesis. The dose-related degree of hepatic triglyceride accumulation which can be produced readily by administration of ACA during short-term starvation in the rat may serve as a new, convenient experimental model for studies of fatty liver.