Nutritional regulation of pyruvate kinase and phosphoenolpyruvate carboxykinase at the enzymatic and molecular levels in cobia Rachycentron canadum

Fish Physiology and Biochemistry
Ruixin LiLiqiao Chen


Despite being a carnivorous fish species, cobia (Rachycentron canadum) can utilize high levels of dietary carbohydrate (up to 360 g kg-1). By contrast, rainbow trout (also carnivorous) cannot, due to the absence of molecular induction of glycolytic enzyme and inhibition of gluconeogenic enzyme gene expressions such as pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK). We hypothesized that this phenomenon is species-specific and will not be observed in cobia. Our results show that, at the molecular level, the mRNA abundance of the important glycolytic (PK) and gluconeogenic (PEPCK) enzymes in cobia liver are regulated by dietary carbohydrate-to-lipid (CHO:L) ratios and nutritional status (fed, unfed, and refed). Significantly upregulated hepatic PK and depressed PEPCK gene expressions were observed when the fish were fed with an increasing CHO/L-ratio diet or were refed. However, in contrast to gene expression, there was no significant effect of dietary CHO/L ratios on PK enzyme activity. The decrease in PEPCK activity was significantly found between low CHO/L ratio and high CHO/L ratio diets, whereas the moderate CHO/L ratio group showed intermediate values. But PEPCK activity appeared to be independent of nutr...Continue Reading


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Related Concepts

Dietary Carbohydrates
Gene Expression
Pyruvate Kinase
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GCR2 protein, S cerevisiae
Glucose Tolerance

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