Growth hormone regulates leptin gene expression in bovine adipose tissue: correlation with adipose IGF-1 expression

Leptin, the product of the ob gene, is secreted front white adipocytes and regulates food intake and whole-body energy metabolism. In rodents and huma ns, leptin gene expression is under complex endocrine and metabolic control , and is strongly influenced by energy balance. Growth hormone (GH) has myr iad effects on adipose tissue metabolism. The primary aim of this study was to determine the ability of GH to regulate leptin mRNA expression in bovin e adipose tissue in vitro and in vivo. Incubation of subcutaneous adipose t issue explants for 24 h with GH alone had no effect on bovine leptin gene e xpression, whereas high concentrations of insulin or dexamethasone (DEX) po tently stimulated bovine leptin mRNA abundance. GH, ill combination with hi gh concentrations of insulin, DEX, or both, attenuated the ability of insul in or DEX to stimulate leptin expression in vitro. These data indicate that GH can indirectly regulate leptin expression in vitro by altering the adip ose tissue response to insulin or DEX. We extended these: studies to examin e the ability of GH to regulate leptin expression in vivo, using young cast rate male cattle treated with no hormone (control) or GH (200 mu g/kg body weight per day) for 3 days. GH increased plasma GH and insulin concentratio ns, but not those of cortisol or non-esterified fatty acid (NEFA) concentra tions. GH treatment increased adipose tissue leptin and IGF-1 mRNA concentr ations (n=9, P>0.001). In addition, leptin abundance was highly correlated with adipose tissue IGF-1 mRNA in GH-treated animals (P>0.001). The timing of GH-induced changes in leptin gene expression preceded measurable GH effe cts on adiposity.