Regulation of adiponectin secretion and expression by insulin and β-agonists in rat

The adipocytokines, including adiponectin, are important factors in the regulation of insulin sensitivity and carbohydrate and lipid metabolism. It is proved that concentrations of adiponectin are decreased in obesity, an insulin resistant state. The current study is to address potential mechanisms regulating adiponectin secretion and expression in vivo. To observe the regulation of adiponectin by fasting-refeeding and β-agonists, male Wistar rats were fasted for 18 h and allowed to refeed with/without a β3-adrenergic receptor agonist infused into refeeding rats. We also investigated the effects of insulin clamp on adiponectin secretion and expression, including euglycemic–hyperinsulinemic clamp and hyperglycemic–hyperinsulinemic clamp. Plasma adiponectin levels were determined by radioimmunoassay. Using real-time PCR assays, we analyzed the expression of adiponectin genes in rat primary adipocytes. Refeeding of 18-h fasted rats increased plasma adiponectin concentration (∼2-fold) and adipose tissue adiponectin expression (∼3-fold), and these effects were mimicked by hyperinsulinemia in the absence of refeeding and completely blocked by administration of β-agonists during refeeding. We conclude that (i) adiponectin secretion and expression are acutely regulated in vivo by nutritional status; (ii) in vivo, insulin and β-agonists act directly at the adipocyte to regulate adiponectin secretion and expression.