Effects of catechin-rich green tea on gene expression of gluconeogenic enzymes in rat hepatoma H4IIE cells

Rat hepatoma H4IIE cells were stimulated with dexamethasone and dibutyryl cAMP to increase gene expressions of gluconeogenic enzymes, glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK). Inclusion of catechin-rich green tea beverage (GTB) in the culture medium reduced the up-regulation of these genes as well as that of hepatocyte nuclear factor 4 alpha (HNF4 alpha) gene. GTB was fractionated into chloroform-soluble (Fraction I), ethyl acetate-soluble (Fraction II), methanol-soluble (Fraction III) and residual (Fraction IV) fractions. Fractions II and HI containing catechins caused an attenuation of the up-regulated expression of these genes as well as the down-regulation of HNF4 alpha gene expression. Fraction IV had a synergistic effect on the up-regulation by dexamethasone/dibutyryl cAMP of the PEPCK gene expression and up-regulated HNF4 alpha gene expression. These results suggest that GTB down-regulated the expression of the HNF4 alpha gene to cause the down-regulated gene expression of gluconeogenic enzymes. One reason why GTB did not down-regulate hepatic PEPCK gene expression in previous animal experiments may be that the component(s) acting to up-regulate PEPCK gene expression was more effective in vivo than in cultured cells.