ABSTRACT
Objective To explore the potential mechanisms of regulating adiponectin secretion and expression in vivo in rats.Methods To observe the regulation of adiponectin by fasing-refeeding and β-adrenergic agonists, male Wistar rats were fasted for 18 h and allowed to refeed or a β3-adrenergic receptor agonist was infused into refeeding rats.The effects of insulin clamp on adiponectin secretion and expression, including euglycemichyperinsulinemic clamp and hyperglycemic-hyperinsulinemic clamp, were also investigated.Plasma adiponectin level was determined by radioimmunoassay.Adiponectin mRNA expression in adipose tissue of rats was detected by realtime PCR.Results (1) Refeeding 18 h fasted rats increased plasma adiponectin concentration (about 2-fold) and adipose tissue adiponectin expression (about 3-fold), which were completely blocked by administration of β-adrenergic agonist.(2) Hyperinsulinemic clamp increased plasma adiponectin concentration and adiponectin gene expression in adipose tissue.Conclusions Adiponectin secretion and expression are acutely regulated in vivo by nutritional status.Insulin and β-adrenergic agonists regulate adiponectin secretion and expression in adipose tissue.
ABSTRACT
Objective To investigate the effects of tumor necrosis factor-alpha (TNF-α) on insulin sensitivity and glucose-lipid metabolism in TNF-α-induced IR mice. Methods Male C57BL/6J mice were given an intraperitoneal injection of TNF-α (H group,6μg/kg; M group,3μg/kg; L group,1μg/kg;twice daily) and saline (NC group) for 7 days. The plasma glucose and insulin were assayed during intravenous glucose tolerance test (IVGTT) and hyperinsulinemic-euglycemic clamp combined with 3-[3H] glucose as a tracer was carried out. Results After TNF-α treatment,fasting blood glucose (FBG),plasma insulin and free fatty acids (FFA) were significantly elevated in H group compared with NC,L and M groups (P<0.01 and P<0.05,respectively). There was a lower glucose tolerance in H group versus other three groups during IVGTT. The insulin release by glucose stimulation was higher in H group versus NC and L groups (P<0.01 and P<0.05). Basal glucose disappearance rate (GDR) and hepatic glucose production (HGP) were significantly increased in H group compared with NC group (P<0.01). During the steady-state of clamp,plasma insulin levels were significantly increased in H group versus NC group (341.7±17.7 vs 84.7±5.5mU/L,P<0.01). The suppressive effect of insulin on FFA was significantly blunted in H group compared with NC group (0.82±0.03 vs 0.43±0.07mmol/L,P<0.01). Steady-state glucose infusion rate (GIR) was significantly decreased in H group compared with NC group (39.1±2.3 vs 54.2±2.2 mg·kg-1·min-1,P<0.01). Although GDR was increased in both group,but it was still lower in H group than in control group(47.9±0.8 vs 53.9±2.0 mg.kg-1.min-1,P<0.01).As compared with baseline,HGP in the controls was almost completely suppressed during steady state of clamp,but in H group suppressed by approximately 41%. Conclusions High-dose TNF-α treatment induces the abnormality of glucose-lipid metabolism and the insulin resistance of hepatic and peripheral tissue in mice
ABSTRACT
Objective To investigate the effects of tumor necrosis factor-alpha (TNF-?) on insulin sensitivity and glucose-lipid metabolism in TNF-?-induced IR mice. Methods Male C57BL/6J mice were given an intraperitoneal injection of TNF-? (H group,6?g/kg; M group,3?g/kg; L group,1?g/kg;twice daily) and saline (NC group) for 7 days. The plasma glucose and insulin were assayed during intravenous glucose tolerance test (IVGTT) and hyperinsulinemic-euglycemic clamp combined with 3-[3H] glucose as a tracer was carried out. Results After TNF-? treatment,fasting blood glucose (FBG),plasma insulin and free fatty acids (FFA) were significantly elevated in H group compared with NC,L and M groups (P