Previous studies suggest that sex hormones could be responsible, at least in part, for the gender-dependent thermogenesis found in the adrenergic control of brown adipose tissue (BAT) under control conditions and in response to diet and cold. Catecholamines as well as several hormones, including sex hormones, may alter the function or expression of different adrenoceptor subtypes in brown adipocytes in vivo, and a confirmation could be provided by in vitro experiments. Therefore, the effect of testosterone, 17-estradiol, progesterone and norepinephrine on adrenergic receptor gene expression (_2A-, ₁-_, 2- and ₃-AR) and lipolytic activity was investigated in differentiated brown adipocytes in culture.

We report that the expression of each adrenergic receptor subtype gene was distinctively regulated by norepinephrine and sex hormones in brown adipocytes. Testosterone-treated cells had lower lipolytic activity and increased expression of antilipolytic receptors _2A-AR. Both 17-estradiol and progesterone decreased _2A-AR expression and _2A/₃-AR protein ratio, but progesterone had higher potency than 17-estradiol increasing -adrenergic receptor levels, mainly ₃-AR expression, and enhancing lipolysis stimulated by norepinephrine.

In conclusion, our results support the idea that male and female sex hormones, as a part of the hormonal environment of BAT, have direct and opposite effects on the adrenergic receptor balance and lipolytic activity, and they might play a role in the gender dimorphism for the recruitment process in BAT.