Effects of glucose on target gene expression in primary cultures of hepatocytes == The results of western blot and enzyme activity analysis for H6PDH and 11-HSD1 in primary hepatocytes treated with different concentrations of glucose (530 mM) are shown inFig. expression. Also, glucose-6-phosphate (G6P) experienced a positive regulation on H6PDH and 11-HSD1 in hepatocytes. In addition, main hepatocytes treated with different doses of insulin in high glucose induced alteration of H6PDH and 11-HSD1 while in low glucose there was no significant effect. These findings suggest that glucose instead of insulin directly regulates H6PDH and 11-HSD1 and suppression of the two enzymes could be considered as an effective target for the treatment of type 2 diabetes. Keywords:Hexose-6-phosphate dehydrogenase, 11-Hydroxysteroid dehydrogenase type 1, Glucose, Type 2 diabetes == 1. Introduction == It has long been exhibited that glucocorticoids contribute to the pathophysiology of metabolic disorder syndrome, including hypertension, obesity, and type 2 diabetes mellitus. Glucocorticoids EMD638683 work antagonistically to the action performed by insulin characterized by increased hepatic gluconeogenesis and decreased ability of insulin to inhibit glucose production. Increased glucocorticoid production EMD638683 induces glucose intolerance and insulin resistance in genetically obese db/db and ob/ob mice and Zucker (fa/fa) rats EMD638683 (Freedman et al., 1986;Schwartz et al., 1992). Pharmacological blockade of EMD638683 glucocorticoid receptor reduces glucocorticoid-related hyperglycemia and insulin resistance in these animal models. However, glucocorticoid actions were regulated by 11-hydroxysteroid dehydrogenase type 1 (11-HSD1). 11-HSD1 is usually a NADPH-dependent enzyme that resides within the ER lumen and expresses highly in liver, adipose tissue, and skeletal muscle mass. This isozyme is usually a bidirectional enzyme which functions predominantly as a reductase in vivo, catalyzing the interconversion of the active hormone cortisol (human) or corticosterone (rat) and inert EMD638683 cortisone (human) or 11-dehydrocorticosterone (rat). The physiological role of the enzyme is supposed to regulate local glucocorticoid levels in the target tissues, and then influence the key hepatic gluconeogenic enzymes including phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) (Banhegyi et al., 2004). Activation of 11-HSD1 results in the production of excess tissue glucocorticoids and induction of local glucocorticoid-mediated alterations of insulin action, adiposity, and glucose homeostasis, all of which are associated with visceral obesity and type 2 diabetes. In contrast, reduction of 11-HSD1 expression prevents regeneration of active glucocorticoids, attenuates hepatic and adipose tissue glucocorticoid action (Nammi et al., 2007). The role of 11-HSD1 in the development of obesity and type 2 diabetes is due to its reductase activity, which requires NADPH as the cofactor. NADPH is usually regenerated by hexose-6-phosphate dehydrogenase (H6PDH) (Atanasov et al., 2004;Banhegyi et al., 2004), a microsomal enzyme FGF-18 located in the lumen of the endoplasmic reticulum (ER) and principally expressed in hepatocytes and adipocytes (Hewitt et al., 2005;McCormick et al., 2006;Liu et al., 2008). H6PDH catalyzes the initial step (conversion of glucose-6-phosphate to 6-phosphogluconolactone) of the pentose phosphate pathway within the lumen of the endoplasmic reticulum (Clarke and Mason, 2003), but this enzyme is usually distinguished biochemically from glucose-6-phosphate dehydrogenase (G6PDH), which catalyzes the same reactions in the cytosol by having much broader substrate specificity (White et al., 2007). Furthermore, hepatic 11-HSD1 reductase activity was impaired in H6PDH knockout mice through inactivation of local NADPH regeneration and these mutant mice exhibited fasting hypoglycemia (Lavery et al., 2006). Subsequently, a series of in vitro studies have exhibited close cooperativity between 11-HSD1 and H6PDH in preparations of rat liver microsomes with manipulation of H6PDH expression directly altering the set point of 11-HSD1 activity (Atanasov et al., 2004;Banhegyi et al., 2004). Although some investigations about the effect of insulin or glucose on 11-HSD1 have been reported (Voice et al., 1996;Whorwood et al., 2001), there is no statement about the effect of insulin or glucose on H6PDH. Moreover, it was not known whether the effect of insulin or glucose on H6PDH and 11-HSD1 was direct or indirect. In the present study, we first investigated the difference between fasting and non-fasting says.