Regulation of pancreatic amylase by dietary carbohydrate in chronic alcoholic rats

Overexpression of hydroxymethylglutaryl CoA synthase 2 and 2,4-dienoyl-CoA reductase in rat pancreas following chronic alcohol consumption

OBJECTIVES

The mechanism of alcohol-induced pancreatic damage is unclear. The aim of this study was to clarify the effects of chronic alcohol intake on the pancreatic proteome.

METHODS

Rats were fed an alcohol-containing Lieber-DeCarli liquid diet, and the pancreatic proteome was compared with that of pair-fed control rats using agarose 2-dimensional gel electrophoresis followed by liquid chromatography-tandem mass spectrometry.

RESULTS

The expression of 3 proteins was consistently altered in alcohol-fed rats: 1 protein was down-regulated, and 2 proteins were up-regulated. The 2 up-regulated proteins were identified as 2,4-dienoyl-CoA reductase and hydroxymethylglutaryl-CoA synthase (HMGCS2). The combined concentration of malondialdehyde and 4-hydroxyalkenals was significantly greater in alcohol-fed rats. It is noteworthy that the reactivity of anti-4-hydroxy-2-nonenal antibody was significantly higher toward HMGCS2 isolated from alcohol-fed rats. The activity of HMGCS2 was higher in alcohol-fed rats, but the relative increase in enzyme activity in alcohol-fed rats was less than the relative increase in HMGCS2 expression.

CONCLUSIONS

Chronic alcohol consumption results in distinct alterations in the expression of 3 pancreatic proteins. The reactivity of 4-hydroxy-2-nonenal toward one of the up-regulated proteins, HMGCS2, increased markedly following chronic alcohol intake, suggesting that up-regulation of HMGCS2 is connected with alterations of lipid peroxidation induced by alcohol.

Inhibition of bone repair in a rat model for chronic and excessive alcohol consumption

Alcohol abuse is associated with increases in both the incidence of fractures and complications in fracture healing. The purpose of this study was to determine the dose-dependent effects of ethanol on bone repair in a rat model. Three-month-old male Wistar rats were continuously fed liquid diets containing ethanol as either 36% or 26% of total calories or control diets for 6 weeks. Then, a bone repair model was created in all rats. Bone healing and liver metabolism were evaluated 7 weeks after bone injury. For each dose, there were three ethanol-feeding groups receiving (1) ethanol for 13 weeks, (2) control diet for 13 weeks (pair-fed), and (3) ethanol before bone injury and control diet (pair-fed) after injury. Another group was fed ethanol (36%) before injury and given control diet ad libitum after injury. There were also two nutritional controls consuming control diet and standard rat chow ad libitum for 13 weeks. Abnormal liver metabolism was evident at the higher ethanol dose - increases in cytochrome P4502E1 specific activity (5-fold; P < .01), triglyceride content (4-fold; P < .02), and liver weight (25%; P = .05) - compared with pair-fed controls. The higher dose of ethanol resulted in deficient bone repair when compared with rats receiving ethanol-free control diet by pair-feeding: 26% less (P = .02) rigidity of the repaired bone, 41% less (P = .02) intrinsic stiffness, 24% less intrinsic strength (P = .05), and 14% less (P = .001) ash density of the repair tissue. The reduced food consumption of ethanol-fed rats compared with that in the nutritional controls did not contribute to this deficiency. Furthermore, removal of ethanol (as 36% of calories) from the diet after bone injury completely restored normal bone healing and nearly normalized the liver metabolism. The lower ethanol dose (26% of calories) had a minimal effect on liver metabolism and bone repair. We conclude that ethanol (as 36% of calories) in the rat diet, especially during the postinjury period, was solely responsible for the observed inhibition of bone repair.

Protective effect of long term high fiber diet consumption on rat exocrine pancreatic function after chronic ethanol intake

The effects of ethanol administration on exocrine pancreas have been widely studied, but little is known about the effect of dietary fiber in combination with chronic ethanol on exocrine pancreatic function. The aim of this work was to examine the chronic effects of a high fiber diet, ethanol ingestion, and a combination of both on the function of the rat exocrine pancreas. Four groups of rats were fed for six months the following diets: 1.- NW: standard laboratory diet; 2.- FW: high fiber diet (15% cellulose); 3.- NE: standard laboratory diet and 20% ethanol in the drinking water; and 4.- FE: high fiber diet and 20% ethanol. Cholecystokinin (CCK) and acetylcholine (Ach) effects on amylase release and intracellular calcium mobilization in pancreatic acini were studied. In rats fed a 20% ethanol (NE), both the basal amylase release and the basal [Ca(2+)](i) were significantly increased; nonetheless, CCK and Ach-induced amylase release were significantly reduced compared with control rats. Ach- but not CCK-stimulated [Ca(2+)](i) increase in NE rats was significantly decreased compared with NW. In rats fed a combination of ethanol and a high fiber diet (FE) all the parameters under study were not significantly affected compared to control rats (NW). In conclusion, high fiber consumption does not alter the function of the exocrine pancreas. However, it ameliorates the deleterious effect of chronic ethanol consumption on pancreatic amylase secretion and, at least partially, reverses the ethanol-induced alterations on [Ca(2+)](i) in the rat exocrine pancreas.

Nutritional factors required for alcoholic liver disease in rats

Decades ago it was suggested that nutritional factors are important in the development of alcoholic liver disease (ALD). However, several models of experimental alcoholism considered that the diets fed to animals were nutritionally adequate, complete and balanced. Therefore, a concept prevailed that the effects observed were due to alcohol per se and that they occurred despite a nutritionally adequate status in the animal. Examination of various models revealed that animals were malnourished because they ingested reduced levels of macro- and micronutrients. Furthermore, they consumed only small amounts of carbohydrate and a high level of unsaturated fat for long periods during the development of ALD. Alcoholic rats show many effects of inadequate nutritional status, such as a slow growth, depressed levels of liver glycogen and pancreatic amylase, enhanced protein degradation and circulating levels of branched-chain amino acids, and increased levels of enzymes involved in gluconeogenesis and alterations in the activities of enzymes related to the metabolism of carbohydrate as compared with controls. Chronic consumption of alcohol did not result in fatty liver, high blood alcohol concentration (BAC) or other observed effects when intake of energy, carbohydrate and other nutrients was increased. Furthermore, pre-existing effects of alcohol consumption, such as fatty liver, BAC and delayed gastric emptying, were reversed in rats receiving increased energy and carbohydrate intakes while continuing alcohol ingestion. Thus, nutritional status of the animal determines the production or prevention of ALD or other effects that were considered to be due to alcohol alone.

Action of intraduodenal ethanol on exocrine pancreatic secretion in chronic alcoholic rats fed with different diets

The effects of diet composition (equilibrated and fat- and protein-rich) in combination with chronic ethanol ingestion on pancreatic exocrine secretion were studied in rats after a 7-month treatment period, also analyzing under these experimental conditions the acute effects of intraduodenal administration of 20% ethanol. Chronic consumption of ethanol affected pancreatic flow but its acute administration stimulated the secretion of fluid, especially in control rats. Total protein secretion is depressed in all rats receiving ethanol as fluid, but this was increased when rats drank water. Amylase activity depends on carbohydrate levels, decreased with fat and protein-rich diet but not with ethanol ingestion. Diet composition by itself did not affect specific trypsin activity but this increased significantly when a fat- and protein-rich diet was administered together with ethanol. Trypsin activity remained unchanged when ethanol was perfused into the duodenum in animals receiving ethanol chronically.