CENEXA   05419
CENTRO DE ENDOCRINOLOGIA EXPERIMENTAL Y APLICADA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Regulation of liver glucokinase activity in intact normal rats and in rats with dietary-induced insulin resistance
Autor/es:
MASSA ML; GAGLIARDINO JJ; FRANCINI F
Lugar:
Roma, Italia
Reunión:
Congreso; 44th EASD Annual Meeting; 2008
Institución organizadora:
European Association for the Study of Diabetes
Resumen:
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, and triglyceridemia. GK activity in the cytosolic fraction (CF) of FRD animals was also higher than in the control group (360 ± 9.9 vs. 100 ± 3.8 %; P < 0.001). GK protein level in CF was higher, though not significantly, in FRD animals (116 vs. 100%). On the other hand, GK activity was higher in the digitonin nuclear fraction (DNF) of C rats [69 ± 3.4 vs. 31 ± 1.2 % of total activity (DNF+CF); P < 0.001]. Opposite results were obtained in FRD animals, i.e., GK activity was lower in DNF than in CF [14 ± 1.1 vs. 82 ± 2.3% of total activity (DNF+CF); P < 0.001]. 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 (70% decrease). Conclusions: The regulatory effect of GK compartmentalization and PFK2 role upon liver GK activity reported in vitro fully operate in normal intact animals. According to the results of the immunological blockade of PFK2, in this model this enzyme would be the main responsible for the increase in GK activity. Thus, these two mechanisms (cellular translocation and PFK2 interaction) would 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.