Rapid desensitization of lipolysis in the visceral and subcutaneous adipocytes of rats

In adipocytes, short and long term stimulation of beta adrenergic receptors (beta AR) induces the desensitization to catecholamines, leading to a decrease in the intracellular accumulation of cAMP, but the roles played by this in lipolysis is not clear. In this study, we assessed the catecholamine-induced desensitization of lipolysis and compared this in adipocytes isolated from visceral and subcutaneous fat tissues of rats. When adipocytes were pretreated with isoproterenol (ISO), the norepinephrine (NE)-induced lipolysis was significantly reduced dose- and time-dependently. A similar reduction of the lipolytic response was also found in NE-, dobutamine-, terbutaline- or BRL37344-induced lipolysis. The ISO- and each beta AR agonist-induced lipolysis in the visceral fat was not only higher than in the subcutaneous fat, but also markedly reduced by ISO- or NE-pretreatment. These results showed that short-term treatment of three subtypes of beta AR by each agonist induces a rapid reduction in the lipolytic response to beta AR stimulation. This suggests some common mechanism for the rapid desensitization of beta AR-agonist-induced lipolysis, in contrast with previous reports on the characteristics of beta AR subtypes. In addition, the regional difference of adipose tissue not only in inducing lipolysis but also in rapid desensitization was also apparent.