Progesterone stimulation of HMG-CoA reductase activity in cultured cells

Comprehensive meta-analysis of the effects of oral medroxyprogesterone acetate plus conjugated equine oestrogens on the lipid profile in women: Insights from randomized controlled trials

BACKGROUND

Menopause is associated with elevated cardiovascular risk due to the loss of the cardioprotective effect of oestrogens. Postmenopausal women are often prescribed hormone replacement therapy (HRT) in order to control menopause symptoms and correct hormone imbalances; however, HRT can impact serum lipids' concentrations. At present, data on the effect of the administration of medroxyprogesterone acetate plus conjugated equine oestrogens (MPACEE) on the lipid profile in females are uncertain, as the investigations conducted so far have produced conflicting results. Thus, we aimed to clarify the impact of MPACEE prescription on the serum lipids' values in women by means of a systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

We employed a random-effects model based on the DerSimonian and Laird method to determine the combined estimates of the intervention's impact on the lipid profile. The computation of the weighted mean difference (WMD) and its corresponding 95% confidence interval (CI) relied on the mean and standard deviation values from both the MPACEE and control group, respectively.

RESULTS

A total of 53 RCTs were included in the meta-analysis with 68 RCT arms on total cholesterol (TC), 70 RCT arms on low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG), and 69 RCT arms on high-density lipoprotein cholesterol (HDL-C). Administration of MPACEE resulted in a significant reduction of TC (WMD = -11.93 mg/dL; 95% CI: -13.42, -10.44; p < .001) and LDL-C (WMD = -16.61 mg/dL; 95% CI: -17.97, -15.26; p < .001) levels, and a notable increase in HDL-C (WMD = 3.40 mg/dL; 95% CI: 2.93, 3.86; p < .001) and TG (WMD = 10.28 mg/dL; 95% CI: 7.92, 12.64; p < .001) concentrations. Subgroup analysis revealed that changes in the lipid profile were influenced by several factors: body mass index (for TC, HDL-C, TG), MPACEE dosages (for TC, LDL-C, HDL-C, TG), age (for TC, LDL-C, HDL-C, TG), durations of the intervention (for TC, LDL-C, HDL-C, TG), continuous/sequential administration of MPACEE (continuous for TC; sequential for LDL-C, TG) administration of MPACEE and serum lipids' concentrations before enrolment in the RCT (for TC, LDL-C, HDL-C, TG).

CONCLUSIONS

MPACEE administration can influence serum lipids' concentrations in females by raising HDL-C and TG levels and reducing LDL-C and TC values. Therefore, postmenopausal women who suffer from hypercholesterolaemia might benefit from this type of HRT.

Cholelithiasis induced in the Syrian hamster: evidence for an intramucinous nucleating process and down regulation of cholesterol 7 alpha-hydroxylase (CYP7) gene by medroxyprogesterone

This report reviews previously published studies from our laboratory and shows some recent morphological data obtained with scanning and transmission electron microscopy regarding gallstone formation and alteration of the gallbladder epithelium in the Syrian hamster model. Both male and female hamsters were treated with female sex steroids (estradiol alone, estradiol and medroxyprogesterone, medroxyprogesterone alone) during one month. The results show that the Syrian hamster is a good model to study bile changes, gallbladder structure changes, including gallstone formation, and the regulation of cholesterol metabolism at the molecular level. Arguments in favor of this animal model are presented and, during gallstone formation, epithelial cell changes, anionic mucus secretion, and formation of gallbladder luminal deposits can be demonstrated. Recent molecular biology observations related to the effect of female sex steroids on liver cholesterol 7 alpha-hydroxylase (CYP7) gene suggest that progestin alone or primed by estrogen down regulates CYP7 transcription and activity. In addition, progesterone in cell culture systems has been shown to enhance intracellular accumulation of free cholesterol by increasing its uptake and synthesis and by decreasing its esterification by inhibiting the activity of acylcoenzyme A: cholesterol acyltransferase. Non-esterified cholesterol is free to migrate to the extracellular spaces and may contribute to nucleation within the bile. It is suggested that these effects of progesterone on cholesterol metabolism combined with the CYP7 gene down regulation, physical changes in the mucus and the hypomotility of the gallbladder and biliary ducts result in hypersaturation of cholesterol in the bile which favors gallstone formation.

Review of progress in sterol oxidations: 1987-1995

Material dealing with the chemistry, biochemistry, and biological activities of oxysterols is reviewed for the period 1987-1995. Particular attention is paid to the presence of oxysterols in tissues and foods and to their physiological relevance.