Chronic glucokinase activator treatment activates liver Carbohydrate response element binding protein and improves hepatocyteATPhomeostasis during substrate challenge

Aim To test the hypothesis that glucokinase activators (GKAs) induce hepatic adaptations that alter intra-hepatocyte metabolite homeostasis. Methods C57BL/6 mice on a standard rodent diet were treated with a GKA (AZD1656) acutely or chronically. Hepatocytes were isolated from the mice after 4 or 8 weeks of treatment for analysis of cellular metabolites and gene expression in response to substrate challenge. Results Acute exposure of mice to AZD1656 or a liver-selective GKA (PF-04991532), before a glucose tolerance test, or challenge of mouse hepatocytes with GKAsex vivoinduced various Carbohydrate response element binding protein (ChREBP) target genes, including Carbohydrate response element binding protein beta isoform (ChREBP-beta),GckrandG6pc. Both glucokinase activation and ChREBP target gene induction by PF-04991532 were dependent on the chirality of the molecule, confirming a mechanism linked to glucokinase activation. Hepatocytes from mice treated with AZD1656 for 4 or 8 weeks had lower basal glucose 6-phosphate levels and improved ATP homeostasis during high substrate challenge. They also had raised basal ChREBP-beta mRNA and AMPK-alpha mRNA (Prkaa1, Prkaa2) and progressively attenuated substrate induction of some ChREBP target genes andPrkaa1 and Prkaa2. Conclusions Chronic GKA treatment of C57BL/6 mice for 8 weeks activates liver ChREBP and improves the resilience of hepatocytes to compromised ATP homeostasis during high-substrate challenge. These changes are associated with raised mRNA levels of ChREBP-beta and both catalytic subunits of AMP-activated protein kinase.