Modulation of key metabolic enzyme of Labeo rohita (Hamilton) juvenile: effect of dietary starch type, protein level and exogenous alpha-amylase in the diet.
ABSTRACT A 60-day feeding trial was conducted to delineate the effect of both gelatinized (G) and non-gelatinized (NG) corn with or without supplementation of exogenous alpha-amylase, either at optimum (35%) or sub-optimum (27%) protein levels, on blood glucose, and the key metabolic enzymes of glycolysis (hexokinase, HK), gluconeogenesis (glucose-6 phosphatase, G6Pase and fructose-1,6 bisphosphatase, FBPase), lipogenesis (glucose-6 phosphate dehydrogenase, G6PD) and amino acid metabolism (alanine amino transferase, ALT and aspartate amino transferase, AST) in Labeo rohita. Three hundred and sixty juveniles (average weight 10 +/- 0.15 g) were randomly distributed into 12 treatment groups with each of two replicates. Twelve semi-purified diets containing either 35 or 27% crude protein were prepared by including G or NG corn as carbohydrate source with different levels of microbial alpha-amylase (0, 50, 100 and 150 mg kg(-1)). The G corn fed groups showed significantly higher (P < 0.05) blood glucose and G6PD activity, whereas G6Pase, FBPase, ALT and AST activity in liver was higher in the NG corn fed group. Dietary corn type, alpha-amylase level in diet or their interaction had no significant effect (P > 0.05) on liver HK activity, but the optimum crude protein (35%) fed group showed higher HK activity than their low protein counterparts. The sub-optimum crude protein (27%) fed group showed significantly higher (P < 0.05) G6PD activity than the optimum protein fed group, whereas the reverse trend was observed for HK, G6Pase, FBPase, ALT and AST activity. Addition of 50 mg alpha-amylase kg(-1) feed showed increased blood glucose and G6PD activity of the NG corn fed group, whereas the reverse trend was found for G6Pase, FBPase, ALT and AST activity in liver, which was similar to that of the G or NG corn supplemented with 100/150 mg alpha-amylase kg(-1) feed. Data on enzyme activities suggest that NG corn in the diet significantly induced more gluconeogenic and amino acid metabolic enzyme activity, whereas G corn induced increased lipogenic enzyme activity. Increased amino acid catabolic enzyme (ALT and AST) activity was observed either at optimum protein (35%) irrespective of corn type or NG corn without supplementation of alpha-amylase irrespective of protein level in the diet.
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ABSTRACT: The glucokinase (GK) enzyme (EC 220.127.116.11.) is essential for the use of dietary glucose because it is the first enzyme to phosphorylate glucose in excess in different key tissues such as the pancreas and liver. The objective of the present review is not to fully describe the biochemical characteristics and the genetics of this enzyme but to detail its nutritional regulation in different vertebrates from fish to human. Indeed, the present review will describe the existence of the GK enzyme in different animal species that have naturally different levels of carbohydrate in their diets. Thus, some studies have been performed to analyse the nutritional regulation of the GK enzyme in humans and rodents (having high levels of dietary carbohydrates in their diets), in the chicken (moderate level of carbohydrates in its diet) and rainbow trout (no carbohydrate intake in its diet). All these data illustrate the nutritional importance of the GK enzyme irrespective of feeding habits, even in animals known to poorly use dietary carbohydrates (carnivorous species).Nutrition Research Reviews 06/2014; · 3.86 Impact Factor
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ABSTRACT: A current priority in the aquaculture industry is the replacement of fishmeal with alternative feedstuffs, including plant-based protein ingredients, to ensure its sustainability. However, most plant-based feedstuffs have a wide variety of anti-nutritional factors, which may impair nutrient utilization, interfering with fish performance and health. The use of exogenous enzymes as feed additives to improve nutrient digestibility of plant-based feedstuffs has been researched extensively in poultry and swine. In aquaculture, the use of phytase to improve phosphorus utilization has emerged quite readily. However, the use of carbohydrase enzymes has not been as nearly as common in aquatic species, despite their promising effects in improving nutrient digestibility by hydrolyzing non-starch polysaccharides present in plant feedstuffs. Based on the information gathered in this review, supple-mentation of exogenous carbohydrases to plant-based fish diets should improve nutrient digestibility and reduce nutrient excretion. On the other hand, the effects of exogenous carbohydrases on fish performance are still unclear due to the difficulty in cross-study comparisons. Overall, based on the information gathered in this review, it is clear that research on exogenous carbohydrase supplementation in aquaculture nutrition is not extensive. According to promising results and opportunities found in other non-ruminant animals, and favorable effects found in aquaculture species studied to date, it may be significant to increase research on this subject because it could be a useful tool to improve and sustain commercial aquaculture.Aquaculture 01/2015; 435:286-292. · 1.83 Impact Factor
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ABSTRACT: Six hundred Labeo rohita (average weight 6.78 g) were distributed in 24 tanks (25 fish/tank), which were allotted to eight experimental groups in triplicates. Half of the experimental groups were maintained at ambient water temperature of 26°C, whereas other half were exposed to 32°C for one week then later maintained in 26°C for four weeks. Fish reared under different temperature regime were fed either one of the four diets containing 20, 30, 40 or 45% protein. Growth, feed efficiency and protein retention were higher at 32°C and continue for next two weeks after decreasing temperature. The dietary protein level and water temperature interactions are more effective in modulating the response of hepatic glucokinase than that of hexokinase and pyruvate kinase. In contrast, hepatic gluconeogenesis was not affected by rearing temperature. Hepatic aspartate amino transferase and alanine amino transferase activity was found higher (p<0.05) at low temperature and at high protein level. It is suggested that the metabolic activities of fish are triggered by short term exposure to higher temperature and the increased metabolic activity extended for duration of three weeks during which 40% dietary protein level found to support the growth of fish.Aquaculture Nutrition 04/2013; 19(2). · 1.69 Impact Factor