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 ov erfeeding rats on a cafeteria diet were studied by assessing the balance be tween the expression of beta -adrenoceptors (beta (1)-, beta (2)-, beta (3) -AR) and alpha (2A)-AR and their relation to the expression of uncoupling p roteins (UCP1, UCP2, UCP3). Cafeteria diet feeding for 15 days, which invol ved a similar degree of hyperphagia in both sexes, led to a greater body we ight excess in females than in males and a lower activation of thermogenesi s. Gender-related differences were found for different adrenoceptor express ion and protein levels, which might explain, in part, sex differences in th e thermogenic parameters. The lower expression of alpha (2A)-AR in females than in males could be responsible for the higher expression of UCP1 and th ermogenic capacity under non-hyperphagic conditions. However, in a situatio n of high adrenergic stimulation - as occurs with overfeeding - as there is a preferential recruitment of the beta (3)-AR by noradrenaline compared wi th other adrenergic receptors, the higher levels of beta (3)-AR in males ra ts than in females could be responsible for the greater thermogenic capacit y and the lesser weight gain in males. Thus, the alpha (2)/beta (3) balance in BAT could be a key in the thermogenic control.