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

Abstract

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

References

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Datasets Mentioned

BETA
CAA39849.1
AAB93666.1
AAH45421.1
AJD07313.1
EU266539
FJ645270
KM262818

Methods Mentioned

BETA
electrophoresis
PCR

Related Concepts

Diet
Dietary Carbohydrates
Gene Expression
Lipids
Liver
Pyruvate Kinase
RNA, Messenger
Zebrafish
GCR2 protein, S cerevisiae
Glucose Tolerance

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