Regulation of liver glucokinase activity in intact normal rats and in rats with dietary-induced insulin resistance

MASSA L; GAGLIARDINO JJ; FRANCINI F

Roma

Congreso; 44th Annual Meeting of the European Association for the Study of Diabetes; 2008

EASD

Background and Aims: To study the regulation of liver glucokinase activity by its gene transcription, protein expression, cellular translocation and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase [PFK2], in rats with insulin resistance induced by a fructose-rich diet (FRD). Materials and Methods: Glycemia (GOD-PAP), triglyceridemia (enzymatic assay), insulinemia (RIA), GK activity (spectrophotometry), GK and PFK2 protein and gene expression (Western blot and real- time PCR] were measured in liver of control and FRD rats. Results: FRD rats had significantly higher values of glycemia, insulinemia, triglyceridemia and GK activity in whole crude liver homogenates (176 vs. 100%) and in the cytosolic fraction (CF) (86 vs. 33%). GK protein level in CF was higher, though not significantly, in FRD animals (116 vs. 100%). GK transcription level was similar in both groups while PFK2 gene expression was 4-fold higher in FRD animals. PFK2 protein expression in CF was 5-fold higher in FRD and its immunological blockage decreased significantly GK activity. Conclusions: The regulatory effect of GK compartmentalization and PFK2 upon liver GK activity reported in vitro fully operates in normal intact animals. They also participate in the adaptative response of liver metabolism to insulin resistance to maintain normal glucose homeostasis. These results provide a new potential site for therapeutic interventions in type 2 diabetes.