Molecular mechanisms underlying regional variations of catecholamine-induced lipolysis in rat adipocytes

The mechanisms underlying catecholamine control of lipolysis were studied in rat white adipocytes from epididymal, retroperitoneal, and subcutaneous fat depots. Sensitivity of subcutaneous adipocytes to selective beta 3-adrenoceptor agonists was lower than that of internal adipocytes. beta 3-Adrenoceptor mRNA levels were lower in subcutaneous adipocytes. A decreased beta 1/beta 2-adrenoceptor-mediated lipolysis was also observed in these adipocytes, and the number of beta 1/beta 2-adrenoceptors was lower than in the internal adipocytes. The number of alpha 2-adrenoceptors was higher in subcutaneous adipocytes without a marked difference in alpha 2-adrenoceptor-mediated antilipolysis between the depots. Subcutaneous adipocytes were also characterized by a lower maximal lipolytic response to drugs acting at different levels of the lipolytic cascade, suggesting differences at the postreceptor level. Lower hormone-sensitive lipase activity and mRNA levels in subcutaneous adipocytes were in agreement with the lipolysis data. These results suggest that the pattern of expression of the genes of the lipolytic pathway varies with the anatomic location of the fat depot.