Nutritional and hormonal regulation of uncoupling protein gene expression in rat adipocytes

Nutritional and hormonal regulation of the expression of uncoupling protein (UCP)-1, -2, and -3 mRNA and protein was investigated in primary cultured adipocytes of rats. The UCP-1, -2, -3 mRNA and protein induction in the adipocytes reached maximal levels at 4 h in the presence of glucose with or without insulin. Moreover, the UCP induction was accelerated by triiodothyronine (T3) or epinephrine, and reached a maximum at 2 h. It appeared that the induction of UCP mRNA and protein was rapid. UCP-1 mRNA expression was stimulated by the presence of T3 or epinephrine in the culture medium. UCP-2 mRNA expression was more markedly increased by glucose, unsaturated fatty acids, insulin and T3 than UCP-1 or -3 mRNA expression. UCP-3 expression was more markedly increased by epinephrine than by T3. The protein expression of the UCPs was induced by glucose and the hormones nearly parallel to the UCP mRNA expression. Thus, UCP-2 expression appears to be stimulated by energy sources such as glucose and fat, and by regulators of thermogenesis and basal metabolic rate such as T3 and insulin, in contrast to UCP-1 and -3 expression.