Stimulating lipolysis in subcutaneous adipose tissues by chronic dexamethasone administration in goats

The objective of this study was to investigate the effects of chronic stress induced by a low dosage of dexamethasone (Dex) on the lipolytic response in adipose tissue of goats. Ten male goats were randomly assigned to two groups; one group was injected subcutaneously with 0.2 mg/kg Dex, and the other group was injected subcutaneously with the same volume of saline as a control (Con) for 21 days. The result revealed that plasma triglycerides (TG) (P < 0.05) concentrations decreased in response to Dex administration. Plasma glycerol, mainly derived from degradation of TG, increased during the Dex treatment (P < 0.05). Expression of genes involved in lipolysis-including G protein β subunit (Gnb1) (P < 0.01), hormone-sensitive lipase (Lipe) (P < 0.05), and perilipin-3 (Plin3) (P < 0.05) - were up-regulated in adipose tissue by Dex. Paralleling the increase in gene expression, the pLIPE/LIPE ratio also increased in response to Dex, which reflected higher LIPE activity, in adipose tissue (P < 0.05). However, the expression of genes involved in fatty acids synthesis-such as acetyl CoA carboxylase (Acc), fatty acid synthase (Fas), and stearoyl-CoA desaturase (Scd)-were not changed by Dex, while the abundance of diglyceride acyltransferase 1 and 2 (Dgat1 and Dgat2) mRNA, which catalyze the formation of TGs from diacylglycerol and Acyl-CoA, increased (P < 0.05) in adipose tissue of Dex-treated goats compared with Con goats. Moreover, plasma leptin concentration decreased in response to Dex; however, Leptin mRNA expression tended to increase in adipose tissue, indicating a negative feedback regulatory mechanism. Adiponectin gene expression was also up-regulated in adipose tissue by Dex (P < 0.05). Taken together, our findings demonstrate that chronic glucocorticoid administration induces an imbalance in TG metabolism, resulting in a lower level of leptin and a higher level of glycerol in blood by promoting lipolysis and Gnb1 and Plin3 expression in adipose tissue, as well as increasing the pLIPE: LIPE ratio.