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Summary
The effects of 8-days treatment with 17α-estradiol (33.3 µg/kg) and progesterone (1.7 mg/kg) on plasma lipids and fatty acid composition of plasma phospholipids were examined in intact (INT) and bilaterally common carotid arteries occluded (BCO) male Wistar rats. Significant decrease of triglyceride level was found in BCO rats after the estradiol treatment. Both hormones elevated proportion of 18:1n-7 fatty acid in INT, but they failed to have such an effect in BCO. Estradiol increased 22:5n-3 and total n-3 polyunsaturated fatty acids (PUFA) in intact, and decreased 18:2n-6 in BCO rats. Significantly lower level of total n-3 was found in progesterone-treated than in estradiol-treated BCO rats. Given that n-3 PUFA have many beneficial effects on cell and tissue function, while n-6 PUFA have mostly the opposite effects, estradiol, rather than progesterone, was seen to improve plasma lipids and phospholipids FA profiles in INT and BCO animals. Estradiol significantly elevated the estimated activity of Δ9-desaturases and progesterone of Δ5-desaturase in BCO group, with no effects in INT rats.
Key words
Estradiol * Progesterone * Male rats * Plasma lipids * Fatty acids
Introduction
Sex hormones are well known to influence lipid metabolism and fatty acid (FA) content in different mammal's tissue such as liver, muscle, pancreas, arterial wall, adipose tissue and brain (D'Eon and Braun 2002, Oztekin et al. 2007, Irwin et al. 2008). Estrogen increases the activity of hormone sensitive lipase, leading to the rise in circulating FA (D'Eon and Braun 2002). On the other hand, progesterone counteracts this stimulatory effect of estrogen and reduces plasma free FA, mostly acting via phosphodiesterase IV and cAMP (Saleh et al. 1999, Campbell and Febbraio 2001). In rats, estradiol decreases circulating total cholesterol and low density lipoproteins (LDL) level, and prevents LDL binding to the artery wall, while no cholesterol-lowering effect of progesterone was found (Lundeen et al. 1997, Walsh et al. 2000). Plasma triglycerides (TG) are also affected by estradiol. Brooks-Asplund et al. (2002) detected an estradiol-induced increase of plasma TG level in male lean and obese Zucker rats, the same effect was detected in ovariectomized female rats (Liu et al. 2004). In humans, estrogen therapy is associated with improved plasma lipoprotein profiles (McCrohon et al. 1999).
There is plenty of evidence about beneficial role...