Prostaglandin E 2 action and binding in human adipocytes: Effects of sex, age, and obesity

Abstract

The antilipolytic effect of prostaglandin E 2 (PGE 2) was studied in subcutaneous human adipocytes. The influence of sex, age, and obesity on the PGE 2 effect was investigated. The antilipolytic effects of PGE 2 were related to the PGE 2 binding data obtained in the same adipocytes. The maximal antilipolytic action of PGE 2 was slightly reduced in adipocytes in males compared with females (maximal inhibition 86% v 97%, P > .05). The PGE 2 binding was similar in adipocytes in females and males. The antilipolytic effect of PGE 2 and the PGE 2 binding was similar when young females were compared with older females. However, the antilipolytic effect of PGE 2 was significantly reduced in obese compared with nonobese subjects. If lipolysis was only stimulated by adenosine deaminase, the sensitivity of PGE 2 was reduced in obesity (IC 50, 1.45 nmol/L v 0.47 nmol/L, P < .01), but the maximal antilipolytic effect of PGE 2 in the two groups was similar, with an inhibitory effect of 95% to 98%. If lipolysis was stimulated by both adenosine deaminase and theophylline (2 mmol/L), it was especially the maximal antilipolytic effect of PGE 2 that was impaired in adipocytes from obese subjects (lipolysis was maximally inhibited by 61% v 92%, P < .01). When the PGE 2 binding was expressed in relation to adipocyte surface area, the total binding capacity (B max) was reduced in adipocytes in obese subjects from 26.5 to 17.9 fmol 100 cm 2 ( P < .05). In contrast to PGE 2, the antilipolytic effect of the α 2-adrenergic agonist clonidine was similar between the two groups, and in accordance with that finding, the α 2-receptor binding to adipocytes was also similar in the two groups. Thus, the reduced antilipolytic effect of PGE 2 does not seem to involve a more general impairment of the antilipolytic pathways in adipocytes from obese subjects.