Breed-specific patterns of hepatic gluconeogenesis and glucocorticoid action in pigs
In the present study, Erhualian and Pietrain pigs were employed to investigate the breed-specific patterns of hepatic gluconeogenesis by detecting the related enzyme mRNA expression, and to analyse the relationship with the hepatic glucocorticoid receptors and 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) expression. Furthermore, hepatic DNA methyltransferase 1 (DNMT1) expression was determined to detect DNA methyltransferase state difference between the two breeds. The results demonstrated that the Erhualian pigs exhibited significantly lower plasma lactate acid concentration, but higher liver lactate acid content than the Pietrain pigs. A significantly higher expression of pyruvate carboxylase (PC), fructose-1, 6-bisphosphatase (FBP) and the mitochondria phosphoenolpyruvate carboxykinase (PCK2) mRNA were observed in Erhualian pigs. The Erhualian pigs demonstrated a significantly higher expression of glucocorticoid receptor and 11β-HSD1 mRNA than the Pietrain pigs, though there was no difference in the hepatic cortisol content between the two breeds. The hepatic DNMT1 mRNA expression in the Erhualian pigs was significantly lower, and the DNMT1 protein content in Erhualian pigs tended to be decreased compared with Pietrain pigs ( P=0.066). The results suggest that the Erhualian pigs demonstrated higher hepatic gluconeogenesis capacity in comparison to the Pietrain pigs. The up-regulation of hepatic glucocorticoid receptor and 11β-HSD1 expression may be involved in the enhanced hepatic gluconeogenesis in Erhualian pigs. Moreover, the down-regulation of DNMT1 in Erhualian pigs implies possible involvement of DNA methylation in a breed-specific pattern of hepatic gluconeogenesis.