EFFECTS OF ESTROGEN ON FREE FATTY-ACID METABOLISM IN HUMANS

To determine whether estrogen directly affects effective adipose lipolysis, palmitate rate of appearances ([C-14]palmitate) was measured in 15 postmenopausal women. Each volunteer was studied after greater than or equal to 12 mo of estrogen treatment and again after greater than or equal to 2 mo of estrogen deficiency. Plasma hormone concentrations were controlled and identical on the 2 study days with use of the pancreatic clamp technique, and the Lipolytic response to epinephrine and epinephrine + phentolamine was assessed. Results showed that overall palmitate flux was greater (10-20%, P < 0.05) during the estrogen-deficient than during the estrogen-replete study. Adrenergic stimulation of lipolysis was not specifically influenced by estrogen treatment, and control of plasma hormone concentrations did not eliminate the difference in palmitate flux between the estrogen-deficient and estrogen-replete study days. We conclude that estrogen deficiency is associated with increased plasma free fatty acid availability and that estrogen likely has direct, albeit small, effects on adipose tissue lipolysis.