Direct effects of testosterone, 17 beta-estradiol, and progesterone on adrenergic regulation in cultured brown adipocytes: potential mechanism for gender-dependent thermogenesis.

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 beta-estradiol, progesterone, and norepinephrine (NE) on adrenergic receptor (AR) gene expression (alpha 2A-, beta 1-, -, and beta 3-AR) and lipolytic activity was investigated in differentiated brown adipocytes in culture. We report that the expression of each AR subtype gene was distinctively regulated by NE and sex hormones in brown adipocytes. Testosterone-treated cells had lower lipolytic activity and increased expression of antilipolytic receptors alpha 2A-AR. Both 17 beta-estradiol and progesterone decreased alpha 2A-AR expression and alpha 2A/beta 3-AR protein ratio, but progesterone had higher potency than 17 beta-estradiol, increasing beta-AR levels, mainly beta 3-AR expression, and enhancing lipolysis stimulated by NE. 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 AR balance and lipolytic activity, and they might play a role in the gender dimorphism for the recruitment process in BAT.