Imbalanced triacyglycerol metabolism in fat cells from estrogen-treated rats

Lipoprotein lipase in rat heart--III. Effects of sex steroid hormones on tri-, di- and monoacylglycerol lipase activities in post-heparin effluents

The in vivo administration of ethinylestradiol to female rats causes dose-dependent decreases in tri-, di- and monoacylglycerol lipase activities in post-heparin heart effluents; monoacylglycerol lipase is less sensitive to estrogen than the other two.

Nutritional dependence of the effect of estrogen on fat cell lipoprotein lipase

We investigated the effects of ethynylestradiol (EE) at low dose (1.2 micrograms/day) injected s.c. for 10 days on lipoprotein lipase (LPL) in fat cells of female rats fed a standard diet (5% lipid, 49.5% glucid, 23.5% protein) as a function of the nutritional state. EE caused a 150% increase in LPL activity in the fed state, and a 65% decrease in the fasting state, resulting in a large increment in the physiological feeding-fasting difference. Feeding the rats a diet supplemented with 20% lard reversed the estrogen-dependent LPL increase in the fed state. Under all experimental conditions, EE caused a depletion of fat stores and an increase in plasma levels of triacyglycerol.

Ethynylestradiol alters lipid composition and phosphatidylethanolamine metabolism in red blood cells

Treatment of female rats with ethinylestradiol at a dose of 60 micrograms/rat, daily for 21 days, produced marked changes in red blood cell lipids. Cholesterol was decreased by 22% and total phospholipids were increased by 13%, resulting in a 31% decrease in the cholesterol to phospholipid ratio. The mass distribution of phosphatidylcholine and phosphatidylethanolamine relative to total phospholipids was unchanged. Whereas control red cells incorporated preferentially fatty acids in phosphatidylcholine, ethinylestradiol stimulated their incorporation specifically in phosphatidylethanolamine, where increases occurred with palmitic acid (+75%), oleic acid (+68%) and arachidonic acid (+31%). Incorporation in phosphatidylcholine was unaffected with any of the 3 fatty acids. The stimulation of fatty acid incorporation in phosphatidylethanolamine is likely to reflect an estrogen-dependent increase in turnover rate of fatty acids in this phospholipid. Such alterations in lipid composition and fatty acid incorporation in red cell phospholipids may have significant effects on membrane function.

Effects of 2-fluoroestradiol on lipid metabolism in the ovariectomized rat

Biological activities of estrogen molecules are altered by fluorination of ring A, and the resulting impairment to form catechols. 2-fluoroestradiol (2-F-E2) has been found to be devoid of carcinogenic action despite its high estrogenic potency; its metabolic effects are so far unknown. This study was designed to investigate the effects of 2-F-E2 on lipid metabolism, as compared to those of estradiol-17 beta(E2). Ovariectomized rats received E2 or 2-F-E2 by s.c. injection at a dose of 60 micrograms for three consecutive days. Parameters measured were weights of parametrial fat depots, fat cell volumes, levels of triacylglycerol and acylcholesterol in plasma, and enzymatic responses to the estrogens in isolated parametrial fat cells as evaluated in terms of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) activities. 2-F-E2 and E2 were found to produce comparable decreases in fat depots, cell volumes and plasma levels of acylcholesterol whereas plasma triacylglycerol was unchanged. Both estrogens decreased LPL, and increased HSL activities to the same extent. Thus, 2-F-E and E2 exhibited comparable effects on lipid metabolism. These effects appeared to depend mainly on the estrogenic potency of these molecules, and to be distinct from their carcinogenic action. Despite its high estrogenic potency, 2-F-E2 was found to be slightly less estrogenic than E2.