A novel concept to preserve the beneficial effects of hormone replacement therapy in bilaterally female ovariectomized rats: Role of lovastatin therapy

Estrogen replacement therapy (ERT) is claimed to reduce cardiovascular mortality by about 50\% in postmenopausal women. This improvement is caused by favorable changes in lipid and lipoproteins metabolism, however., it also increases the incidence of the endometrial hyperplasia. Addition of progestin to ERT, referred to as hormone replacement therapy (HRT), has been shown to successively reduce this risk to the endometrium. Unfortunately, it has an adverse effect on high-density lipoprotein cholesterol (HDLC) concentration, thus compromising the benefits of ERT. Therefore the issue here whether HRT given alone and/or concomitantly with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (lovastatin) could exert any significant additional favorable effect on the lipid profile in bilaterally ovariectomized female rats. Sixty female Wistar rats were ovariectomized and treated with ERT (0.625 mg kg(-1) estradiol, E-2, IM every 2 weeks), HRT (estradiol plus progesterone, E-2 + P, 0.625 mg kg(-1) estradiol and 5 mg progesterone kg(-1) respectively, IM every 2 weeks), and lovastatin (20 mg kg(-1) day(-1) orally) plus HRT (L + HRT) for 6 weeks. Blood aliquots were collected for serum and plasma separation. Serum vitamin E and plasma levels of C-reactive protein (CRP), nitric oxide (NO), lipid profile, and the susceptibility of non-HDLC to oxidation were determined. Moreover., thoracic aortas were dissected and directed for measurement of its lipid peroxide and NO contents. Treatment of ovariectomized rats with HRT showed a significant decrease (P < 0.0001) in HDLC concentration compared to the group treated alone with ERT and increase (P < 0.0001) in CRP levels compared to ovariectomized rats. HDLC and CRP are two powerful and significant predictors for increased cardiovascular risk in postmenopausal women. Addition of lovastatin as a complementary therapy to HRT revealed a significant 27\% increment in HDLC and 48\% decrement in CRP concentrations. Moreover, it significantly increased vitamin E, each of plasma and tissue content of NO and decreased atherogenic indexes (TC/HDLC, LDLC/HDLC), aortic lipid peroxide and susceptibility of non-HDLC to oxidation. In conclusion, this current study demonstrated that lovastatin together with continuous combined HRT seems to be more effective in the secondary prevention of coronary heart disease not only due to lipid lowering properties but also related to several other additive effects such as modification of endothelial function and inflammatory responses. (C) 2002 Elsevier Science Ltd.