Sexual dimorphism in the adrenergic control of rat brown adipose tissue response to overfeeding

Gender-related differences in the brown adipose tissue (BAT) response to overfeeding rats on a cafeteria diet were studied by assessing the balance between the expression of beta -adrenoceptors (beta (1)-, beta (2)-, beta (3)-AR) and alpha (2A)-AR and their relation to the expression of uncoupling proteins (UCP1, UCP2, UCP3). Cafeteria diet feeding for 15 days, which involved a similar degree of hyperphagia in both sexes, led to a greater body weight excess in females than in males and a lower activation of thermogenesis. Gender-related differences were found for different adrenoceptor expression and protein levels, which might explain, in part, sex differences in the thermogenic parameters. The lower expression of alpha (2A)-AR in females than in males could be responsible for the higher expression of UCP1 and thermogenic capacity under non-hyperphagic conditions. However, in a situation of high adrenergic stimulation - as occurs with overfeeding - as there is a preferential recruitment of the beta (3)-AR by noradrenaline compared with other adrenergic receptors, the higher levels of beta (3)-AR in males rats than in females could be responsible for the greater thermogenic capacity and the lesser weight gain in males. Thus, the alpha (2)/beta (3) balance in BAT could be a key in the thermogenic control.