Effect of two different diets on liver gene expression associated with glucose metabolism in dairy cows

Ruminant animals depend mainly on hepatic gluconeogenesis pathway to maintain glucose homeostasis. Effects of diets with different ingredients on gene expression profile related to bovine hepatic glucose metabolism are unknown. Objective of this study was to examine gene expression coding for rate-limiting enzymes in hepatic glucose metabolism in response to two different diets. In this study, two kinds of isoenergetic and isonitrogenous diets were designed. Group I diets consisted mainly of corn straw (37.1%), corn (33.5%) and soybean meal (23.6%). Group II diets consisted mainly of alfalfa hay (28.4%), corn silage (26.5%) and corn (22.8%). After 30-day experimental period, biopsy section of liver and blood samples were obtained before feeding. Expression of 28 genes coding for rate-limiting enzymes in hepatic gluconeogenesis pathway, pentose phosphate pathway, glycogen synthesis pathway, glycogen decomposition pathway, glycolysis pathway, glucose aerobic oxidation pathway, and glucose transporters was detected with reverse transcription quantitative PCR (RT-qPCR). Results showed that Group II led to marked up-regulation of phosphoenolpyruvate carboxykinase (PEPCK) and marked up-regulation tendency of glucose-6-phosphatase (G6P), both involved in hepatic gluconeogenesis pathway (P<0.05). No significant differences were observed in mRNA expression of genes involved in other glucose metabolism pathways. Higher relative percentage mRNA abundance of G6P (22.6%), representing the important gluconeogenic enzyme and also catalyzing the last step in glycogenolysis, underscored its importance for ruminant hepatic glucose metabolism. It was concluded that different dietary ingredients could change gene expression of hepatic gluconeogenesis pathway, especially PEPCK and G6P. Dietary ingredients had little effect on other bovine hepatic glucose metabolism pathways and glucose transporter protein. Results indicate that in order to respond to different diet ingredients, genes involved in gluconeogenesis pathway play an important role.