Sex steroids and lipoprotein metabolism

Sex Modifies the Impact of Type 2 Diabetes Mellitus on the Murine Whole Brain Metabolome

Type 2 diabetes mellitus (T2DM) leads to the development of cardiovascular diseases, cognitive impairment, and dementia. There are sex differences in the presentation of T2DM and its associated complications. We sought to determine the impact of sex and T2DM on the brain metabolome to gain insights into the underlying mechanisms of T2DM-associated cognitive complications. Untargeted metabolomic analysis was performed, using liquid chromatography-mass spectrometry, on whole brain tissue from adult male and female db/db mice (a T2DM model) compared to wild-type (WT) C57Bl6/J mice. Regardless of sex, T2DM increased free fatty acids and decreased acylcarnitines in the brain. Sex impacted the number (103 versus 65 in males and females, respectively), and types of metabolites shifted by T2DM. Many choline-containing phospholipids were decreased by T2DM in males. Female-specific T2DM effects included changes in neuromodulatory metabolites (γ-aminobutyric acid, 2-linoleoyl glycerol, N-methylaspartic acid, and taurine). Further, there were more significantly different metabolites between sexes in the T2DM condition as compared to the WT controls (54 vs. 15 in T2DM and WT, respectively). T2DM alters the murine brain metabolome in both sex-independent and sex-dependent manners. This work extends our understanding of brain metabolic sex differences in T2DM, cognitive implications, and potential sex-specific metabolic therapeutic targets.

Prognostic and immune implications of a novel 7-methylguanosine-related microRNA signature in breast invasive carcinoma: from exploration to validation

OBJECTIVES

This study aims to develop and validate a prognostic signature based on 7-methylguanosine-related (M7G-related) miRNAs for predicting prognosis and immune implications in breast invasive carcinoma (BRCA).

MATERIALS AND METHODS

M7G-related miRNA data of BRCA were obtained from The Cancer Genome Atlas (TCGA). Least absolute shrinkage and selection operator (LASSO)-penalized, univariate, and multivariate Cox regression analyses were used to construct the prognostic signature. Furthermore, the predictive validity was verified using Kaplan-Meier (KM) survival risk and receiver operating characteristic (ROC) plots. Internal random sampling verification was used to simplify and validate the signature. RT-qPCR was used to quantify the expression level of transcriptional profiles. The independent prognostic role of the risk score was validated using univariate and multivariate regression. Single-sample Gene Set Enrichment Analysis (ssGSEA) was used for functional and immune enrichment analysis.

RESULTS

A total of 18 M7G-related miRNAs were identified to construct the prognostic signature in BRCA. The low-risk group exhibited significantly higher overall survival than the high-risk group in the KM survival plot (P < 0.001). The area under the curve (AUC) for 1-, 3-, and 5-year survivals in the ROC curve were 0.737, 0.724, and 0.702, respectively. The survival significance in the training and testing cohorts was confirmed by random sampling verification. The most prominent miRNAs in the signature were the miR-7, miR-139, miR-10b, and miR-4728. Furthermore, immune scores for B, mast, and Th1 cells varied between risk groups. Our research demonstrated that CD52 was the most positively correlated gene with immune cells and functions in BRCA.

CONCLUSION

Our study presents a comprehensive and systematic analysis of M7G-related miRNAs to construct a prognostic signature in BRCA. The signature demonstrated excellent prognostic validity, with the risk score as an independent prognostic factor. These results provide critical evidence for further investigation of M7G miRNAs and offer new insights for BRCA patients in the context of effective immunotherapy.

The effect of hormone therapy on bone mineral density and cardiovascular factors among Iranian female athletes with amenorrhea/oligomenorrhea: A randomized clinical trial

Background: Functional hypothalamic menstrual disorder (FHMD) has a destructive effect on the athlete's bone mineral density and cardiovascular system. Utilizing hormone replacement therapy to treat FHMD in athletes is controversial. This study was conducted to examine the effect of hormone therapy on bone density and the cardiovascular system of professional female athletes with FHMD. Methods: In this study, 18 female athletes with at least a 2- year history of FHMD were recruited in a 9-month single blind randomized clinical intervention (RCT) and randomly classified into 2 groups: the oral contraceptive pills (OCP) group, who received a lowdose combined oral contraceptive (OC) containing 30 µg ethinyl estradiol and 150 µg levonorgestrel (n= 10), and the control group (n= 8). Bone mineral densitometry (BMD) and certain cardiovascular risk factors were measured before and after the 9-month trial. The Chi square test was used to compare the quantitative and qualitative results. Results: Bone mineral density did not change significantly in either group. Very low density lipoprotein (VLDL) (p= 0.035) and Apolipoprotein B (Apo B) (p= 0.04) reduced significantly in the OCP group. An increase was observed in the serum levels of Apolipoprotein A (Apo A) (p= 0.01) in the control group. Changes in the Apo B to Apo A ratio was significant in both groups (OCP group: p= 0.018, control group: p= 0.040). No significant changes were observed in the other measured factors. Conclusion: Although the administration of estrogen did not significantly increase bone mineral density, it had positive effects on the cardiovascular system and lipid profile.

Lipid metabolism of orchiectomised rats was affected by fructose ingestion and the amount of ingested fructose

We examined whether lipid metabolism in orchiectomised (ORX) rats was affected by fructose ingestion and the amount of ingested fructose. Sucrose was used as a fructose source. Sham-operated and ORX rats were fed one of the following three diets for 28 d: a maize starch-based diet without sucrose (SU0), a diet by which half or all of maize starch was replaced by sucrose (SU50 or SU100). Body-weight gain and food intake were increased by sucrose ingestion, but decreased by ORX. Plasma total cholesterol concentration was increased by ORX and dose-dependently by sucrose ingestion. Plasma TAG concentration was decreased by ORX, but was increased dose-dependently by sucrose ingestion. Plasma insulin concentration was decreased by ORX, but was not affected by sucrose ingestion. Liver TAG was increased by sucrose ingestion and ORX; however, liver cholesterol concentration was not affected by sucrose ingestion and ORX. The hepatic activity of cholesterol 7α-hydroxylase 1 was not affected by sucrose ingestion and ORX; however, faecal excretion of bile acids was decreased. The mRNA level of microsomal TAG transfer protein, which is the gene related to hepatic VLDL production, was increased by ORX and sucrose ingestion. The mRNA level of uncoupling protein-1 was decreased by ORX, but not by sucrose ingestion. Plasma insulin concentration tended to correlate with the level of sterol-regulatory element-binding protein-1c mRNA (r 0·747, P = 0·088). These results show that lipid metabolism in ORX rats would be affected by the consumption of fructose-rich sweeteners such as sucrose and high-fructose syrup.

Hypocholesterolaemic effect of water-insoluble fish protein from Alaska pollock in ovariectomised rats is not abolished by methionine addition

The present study investigated whether the hypocholesterolaemic effect of water-insoluble fish protein (IFP) from Alaska pollock in ovariectomised (OVX) rats was affected by methionine (Met) addition. OVX rats (6 months old) were fed a cholesterol-free diet containing casein, IFP or IFP+Met as a protein source for 28 d. The ratio of Met:glycine was lower in the IFP and IFP+Met diets compared with the casein diet. Body-weight gain, food intake and liver lipids were not affected by the diet. Plasma total cholesterol concentration was lower in OVX rats fed the IFP diet compared with those fed the casein diet. The hypocholesterolaemic effect of the IFP diet was not abolished by Met addition. Amount of bile acids in the small-intestinal content and faecal excretion of bile acids were higher in OVX rats fed the IFP and IFP+Met diets compared with those fed the casein diet. Ileal bile acid transporter (IBAT) mRNA level and faecal excretion of bile acids were significantly lower and higher, respectively, in OVX rats fed the IFP diet compared with those fed the casein diet, but not in those fed the IFP+Met diet. Thus, the hypocholesterolaemic effect of the IFP diet seems to be mediated by increased faecal excretion of bile acids coupled with decreased reabsorption of bile acids from the ileum through a decrease in IBAT and the change in cholesterol metabolism linked to the amino acid profile.

Effects of hormone replacement therapy on serum lipids and phospholipids in postmenopausal women

Hormone replacement therapy (HRT) has been shown to reduce the risk of cardiovascular disease and the beneficial effects may be mediated in part by favourable changes in plasma lipid levels. Evidence exists concerning the effect of combined oestrogen and progestogen on lipids, nevertheless no such evidence can be found on the phospholipid profile, which is important the lipid metabolic pathways. In the present study, involving the serum lipids and lipoproteins, we observed an increase in the concentration of total cholesterol (P < 0.001), HDL-C (P < 0.001), HDL-C (P < 0.001), 2 HDL-C (P < 0.001) and a decrease in the ratio LDL-C/ 3 HDL-C (P < 0.001) in the subjects of Group B (oestrogen plus progestogens) compared with controls (baseline). Also, we found an increased in triglycerides (P < 0.01) and ApoA-1 (P < 0.01) concentrations in the subjects of Group A (oestrogen alone) compared with controls (baseline). With regard to the phospholipids, the main changes observed in their concentrations were: an increase in phosphatidyl choline (P < 0.001) and a decrease in phosphatidyl serine (P < 0.01) for both groups compared with controls. Also, a decrease in phosphatidylinositol (P < 0.01) in Group B compared with controls (baseline). The significance of these results are discussed.

Comparative analysis of oestrogen and raloxifene effects on the phospholipid composition of high density lipoproteins in healthy postmenopausal women

The beneficial effect of selective oestrogen receptor modulators such as raloxifene in cardiovascular disease may be mediated partly by favourable changes in the phospholipid composition of high density lipoprotein (HDL) subclasses. In Group A (oestrogen alone) HDL2 phosphatidylcholine increased (P<0.001), while there was a decrease in HDL2 phosphatidylinositol (P<0.05) and HDL2 phosphatidylethanolamine (P<0.05) compared to controls (baseline). In the same group, HDL3 phosphatidylcholine increased (P<0.001) and HDL3 phosphatidylethanolamine decreased (P<0.01). In Group B (raloxifene) HDL2 phosphatidylcholine increased (P<0.001) as well as HDL2 diphosphatidylglycerol (P<0.01) while there were decreases in HDL2 sphingomyelin (P<0.01) and HDL2 phosphatidylethanolamine (P<0.05). In the same group, an increase in HDL3 phosphatidylcholine (P<0.001) and a reduction in HDL3 phosphatidylinositol (P<0.05) were observed as well as a decrease in HDL3 phosphatidylethanolamine (P<0.01) and HDL3 diphosphatidylglycerol (P<0.05). The significance of these results is discussed.

The mechanism of the cholesterol-lowering effect of water-insoluble fish protein in ovariectomised rats

The purpose of the present study was to investigate whether water-insoluble fish protein (IFP) from Alaska pollock (Theragra chalcogramma) prevents hypercholesterolaemia induced by ovarian hormone deficiency. Wistar female rats, aged 6 months, were subjected to sham-operation or ovariectomy, and fed a cholesterol-free diet containing casein or IPF as a protein source for 28 d. Body-weight gain and food intake increased in the ovariectomised rats as compared with the sham-operated rats. Plasma total cholesterol concentration was decreased and faecal bile acid excretion was increased by IFP in the ovariectomised rats, but not in the sham-operated rats. Plasma homocysteine concentration was decreased by IFP in the ovariectomised rats, but not in the sham-operated rats. Liver lipids and liver cholesterol concentrations were increased and cholesterol 7alpha-hydroxylase (CYP7A1) activity was decreased by ovariectomy, but not by diet. Bile acid content and the ratio of cholic acid groups to chenodeoxycholic acid groups in bile were increased by ovariectomy, but decreased by IFP. Bile acid content in the small intestine was increased by IFP in the ovariectomised rats, but not in the sham-operated rats. 3-Hydroxy-3-methylglutaryl-CoA reductase and microsomal TAG transfer protein mRNA levels were decreased by ovariectomy and IFP, whereas LDL-receptor mRNA level was decreased by ovariectomy but unaffected by diet. Thus, the preventive effect of IFP on the ovarian hormone deficiency-associated increase in plasma cholesterol concentration seems to be mediated by accelerated faecal excretion of bile acids, coupled with an increase in the intestinal pool of bile acids.

Hypolipidaemic effect of maize starch with different amylose content in ovariectomized rats depends on intake amount of resistant starch

The effect of amylose content on digestibility of starch in the small intestine and on the concentration of plasma lipid were studied in ileorectostomized rats and in ovariectomized rats, respectively. Seven kinds of starch with different amylose content (0, 27, 54, 62, 76, 79, 86 %) were used as test starch, which contained 0·4, 5·6, 37·1, 40·2, 45·6, 36·9 and 36·1 % resistant starch (RS), respectively. Rats were fed one of test diets containing 30 % test starch with different amylose content for 14 d in ileorectostomized and for 21 d in ovariectomized rats. Food intake was not significantly different among the groups. In ileorectostomized rats, the small intestinal starch digestibility decreased with increasing intakes of amylose and RS. In ovariectomized rats, body weight gain was lower on the higher amylose maize starch diets. The concentrations of plasma TAG and cholesterol decreased with increasing intake of RS. The concentrations of liver total lipids and TAG decreased with increasing intake of RS, but that of liver cholesterol did not. There was significant positive correlation between the level of sterol regulatory element-binding protein-1c mRNA and concentration of liver TAG. Total SCFA amount in the caecum increased logarithmically with increasing dry weight of caecal contents. The amount of bile acids in the small intestinal content and the excretions of bile acids and neutral steroids in faeces increased with increasing RS intake. These results show that starch rich in RS is more effective in preventing ovarian hormone deficiency-induced hyperlipidaemia.

Sex steroids and plasma lipoprotein levels in healthy women: The importance of androgens in the estrogen-deficient state

The role of endogenous estrogens and androgens and their potential interaction in atherosclerosis is not well understood. Therefore, we investigated the effects of natural menopause and endogenous sex steroids on triglycerides (TG), a major risk factor for cardiovascular disease in women. Fasting lipid and lipoprotein concentrations, postheparin lipase activities, kinetic indicators of triglyceride lipolysis, and various hormone levels, including dehydroepiandrostenedione-sulfate (DHEA-S), (bioavailable) testosterone, and androstenedione, were determined in 18 premenopausal and 18 postmenopausal women, matched for age and body composition. Fasting plasma TG were 0.69 +/- 0.29 mmol/L in postmenopausal women and 0.73 +/- 0.33 mmol/L in premenopausal women (difference not significant [NS]). Approximately 30% of all plasma TG were present in the very-low-density lipoproteins (VLDLs) in both groups. No differences were found between groups in plasma lipolytic potential of TG-rich lipoproteins. Univariate analysis revealed that VLDL-TG concentrations were strongly related to insulin (r = 0.84, P =.0001) and androstenedione (r = 0.65, P =.004) in postmenopausal women. Multivariate analysis of potential determinants of VLDL-TG showed that insulin, androstenedione, and bioavailable testosterone were independent variables, explaining 87% of the variability (r = 0.93, P =.0001) in postmenopausal women. In contrast, in premenopausal women, the only identified predictor of fasting VLDL-TG in univariate and multivariate analysis was insulin (r = 0.72, P =.001). Our results show that the association of androgens with TG varied depending on androgen concentrations, the relative androgenic potential, and most importantly on hormonal milieu. Endogenous androgens were only related to plasma VLDL-TG in the estrogen-deficient state.

Female rats are protected against oxidative stress during copper deficiency

BACKGROUND

Copper deficiency induces a dramatic decrease of superoxide dismutase activity and leads to alteration of antioxidant defense systems.

METHODS

and

OBJECTIVE

Experiments were conducted in weanling male, intact and ovariectomized female rats, fed either a copper-adequate or copper-deficient diet for seven weeks, in order to determine whether endogenous estrogen could modulate oxidative stress and the severity of copper-deficiency.

RESULTS

Feeding male rats a copper-deficient diet induced typical signs of copper deficiency, such as decreased hepatic copper, growth retardation, anemia, heart hypertrophy, pancreas atrophy and hypercholesterolemia. Furthermore, copper deficiency increased the amount of lipid peroxidation products in the heart, liver and pancreas following in vitro iron induction. Although levels of hepatic copper in copper-deficient females were similar to those of their male counterparts, the females were partially protected from the adverse effects of the deficiency (no growth retardation, less severe anemia, lesser extent of lipid peroxidation). Thus, female rats are provided with a greater degree of protection against oxidative damage than males. However, females did not appear to be protected against pancreas atrophy, heart enlargement and hypercholesterolemia induced by copper deficiency. This observed partial protection of females was lost after ovariectomy as shown by decreased body weight and hematocrit, heart enlargement and higher tissue peroxidation in ovariectomized females compared to intact females.

CONCLUSIONS

The results suggest that the partial protection of copper deficient females is related to the antioxidant properties of estrogens. The protective action of estrogen against oxidative stress is of particular importance when antioxidant defenses are decreased as shown in this experimental model.

Effects of postmenopausal hormone replacement therapy on HbA(1c) levels

OBJECTIVE

Estrogen seems to contribute to glucose homeostasis in women. The objective of this study was to examine the effects of hormone replacement therapy (HRT) on HbA(1c) levels in Japanese postmenopausal women and to determine whether the effects varied with age.

RESEARCH DESIGN AND METHODS

We studied 99 postmenopausal women taking HRT (mean +/- SD age 56.5 +/- 6.9 years, BMI 21.5 +/- 2.3 kg/m(2)) and 101 postmenopausal women not on HRT (51.4 +/- 6.1 years, 21.3 +/- 2.4 kg/m(2)). HRT consisted of continuous conjugated equine estrogen (CEE; 0.625 mg/day) and medroxyprogesterone acetate (MPA; 2.5 mg/day) for >2 years.

RESULTS

HbA(1c) levels are positively associated with age and BMI in women who use HRT as well as in those who do not use HRT. After adjusting for age and BMI, HRT showed no effects on HbA(1c) levels. However, HbA(1c) levels were significantly lower in postmenopausal women aged 40-49 years who were taking HRT than in women of similar age who were not taking HRT (mean +/- SE 4.776 +/- 0.092 vs. 5.096 +/- 0.078%, P < 0.05). No differences in HbA(1c) levels between women who did and did not use HRT were observed in those older than 50 years.

CONCLUSIONS

Oral HRT involving CEE combined with MPA may decrease HbA(1c) levels in women aged 40-49 years and is likely to have no adverse effects on HbA(1c) levels in women older than 50 years.

Metabolic syndrome in the rat: females are protected against the pro-oxidant effect of a high sucrose diet

Metabolic syndrome is more prevalent in men than in women. In an experimental dietary model of metabolic syndrome, the high-fructose-fed rat, oxidative stress has been observed in males. Given that estradiol has been documented to exert an antioxidant effect, we investigated whether female rats were better protected than males against the adverse effects of a high-sucrose diet, and we studied the influence of hormonal status in female rats. Males and females were first fed a sucrose-based or starch-based diet for 2 weeks. In the males, the plasma triglyceride (TG)-raising effect of sucrose was accompanied by significantly lowered plasma alpha-tocopherol and a significantly lowered alpha-tocopherol/TG ratio (30%), suggesting that vitamin E depletion may predispose lipoproteins to subsequent oxidative stress. In males, after exposure of heart tissue homogenate to iron-induced lipid peroxidation, thiobarbituric reactive substances were significantly higher in the sucrose-fed than in the starch-fed rats. In contrast, in sucrose-fed females, neither a decrease in vitamin E/TG ratio nor an increased susceptibility of heart tissue to peroxidation was observed, despite both a significantly decreased heart superoxide dismutase activity (14%) and a significant 3-fold increase in plasma nitric oxide concentration compared with starch-fed females. The influence of hormonal status in female rats was then assessed using intact, ovariectomized, or estradiol-supplemented ovariectomized female rats fed the sucrose or starch diet for 2 weeks. After exposure of heart tissue to iron-induced lipid peroxidation, higher susceptibility to peroxidation was found only in ovariectomized females fed the sucrose diet compared with the starch group and not in intact females or ovariectomized females supplemented with estradiol. Thus, estrogens, by their effects on antioxidant capacity, might explain the sexual difference in the pro-oxidant effect of sucrose diet resulting in metabolic syndrome in rats.

Early increase of oxidative stress and reduced antioxidant defenses in patients with uncomplicated type 1 diabetes: a case for gender difference

OBJECTIVE

Diabetes increases the risk of coronary heart disease (CHD) to a greater extent in women than in men. We investigated whether type 1 diabetic patients with short duration of disease and without complications have an altered oxidative status and whether there are differences between men and women.

RESEARCH DESIGN AND METHODS

We investigated oxidative status in 29 control subjects and 37 patients with uncomplicated type 1 diabetes with duration of 6 +/- 3 years.

RESULTS

Compared with control subjects, type 1 diabetic patients had lower total plasma antioxidant capacity (TRAP) (720.3 +/- 111.2 vs. 972.5 +/- 97.7 micromol/l in men, P < 0.001; 579.8 +/- 95.4 vs. 930.1 +/- 84.2 in women, P < 0.001), higher lipid hydroperoxide (ROOH) levels (6.4 +/- 2.2 vs. 2.0 +/- 0.7 micromol/l in men, P < 0.001; 8.1 +/- 1.9 vs. 2.2 +/- 0.6 in women, P < 0.001), higher total conjugated diene (CD) levels (0.037 +/- 0.003 vs. 0.033 +/- 0.002 A.U. in men, P < 0.001), lower 246-nm CD levels (0.0032. +/- 0.0010 vs. 0.0070 +/- 0.0012 A.U. in men, P < 0.001; 0.0022 +/- 0.0011 vs. 0.0072 +/- 0.0014 A.U. in women, P < 0.001), and higher 232-nm CD levels (0.0348 +/- 0.0041 vs. 0.0257 +/- 0.0022 A.U. in men, P < 0.001; 0.0346 +/- 0.0031 vs. 0.0246 +/- 0.0074 A.U. in women, P < 0.001). Compared with diabetic men, diabetic women had lower TRAP (P < 0.01), higher ROOH levels (P < 0.01), and lower 246-nm CD levels (P < 0.05). Plasma concentration of uric acid was significantly lower in patients with type 1 diabetes than in control subjects (3.3 +/- 0.3 vs. 4.3 +/- 0.2 mg/dl; P = 0.009) with a significant difference between women and men with type 1 diabetes (2.6 +/- 0.3 vs. 3.9 +/- 0.3, respectively; P = 0.009).

CONCLUSIONS

Our findings suggest that reduced antioxidant activity and increased oxidative stress occur early after the diagnosis of type 1 diabetes, especially in women, and this might explain, at least in part, the increased susceptibility of diabetic women to cardiovascular complications.

The effect of tibolone on the lipoprotein profile of postmenopausal women with type III hyperlipoproteinemia

OBJECTIVE

To investigate the short-term effect of treatment with tibolone on plasma lipid and lipoprotein levels in postmenopausal women with type III hyperlipoproteinemia (HLP).

DESIGN AND INTERVENTION

Patients were randomized to receive, in a double-blind cross-over fashion, a fixed dose of tibolone, 2.5 mg once daily or placebo for 8 weeks. The two treatment periods were separated by a wash-out period of 6 weeks. At each visit body weight and blood pressure were determined. Before and after each treatment period, fasting venous blood samples were obtained from the patients for biochemical measurements.

SETTING

The Leiden University Medical Center.

SUBJECTS

Postmenopausal women with type III HLP (aged < or = 65 years) were recruited from the Lipid Clinics of the Leiden University Medical Center, the Amsterdam Medical Center, the Utrecht Medical Center and the University Hospital Rotterdam. Five out of 25 women with type III HLP were eligible to be included in the study. Four of the five included patients completed the study according to the protocol. One patient was excluded from blinded therapy because total cholesterol levels increased above 20 mmol L(-1).

MAIN OUTCOME MEASURES

A significant reduction of plasma triglyceride, total cholesterol, VLDL cholesterol and VLDL triglyceride levels.

RESULTS

Plasma triglyceride and total cholesterol levels decreased from 6.82 +/- 3.58 to 2.45 +/- 1.36 mmol L(-1) and from 13.53 +/- 3.64 to 6.61 +/- 2.03 mmol L(-1), respectively (both P < 0.05). The body mass index remained unchanged. The glycated haemoglobin percentage decreased significantly from 5.8 to 5.3%. Treatment with tibolone resulted in a profound reduction in plasma apolipoprotein E, VLDL cholesterol and VLDL triglyceride levels (mean reductions of 66, 77 and 70%, respectively, P < 0.05).

CONCLUSIONS

Tibolone is a valuable adjuvant to current therapy in postmenopausal women with type III HLP.

Estrogen receptors and the activity of nitric oxide synthase in the artery of female rats receiving hormone replacement therapy

OBJECTIVE

To observe the expression of estrogen receptor and the activity of NOS in the arteries of female rats receiving estrogen replacement therapy.

METHODS

Seventy-two female rats were randomly divided into four groups: group A: sham-ovariectomy; group B: ovariectomy; group C: ovariectomy with estrogen replacement therapy (benzoate estradiol, 5 microg i.m. once in 2 days); group D: ovariectomy with estrogen and progesterone replacement therapy (benzoate estradiol, 5 microg i.m. once in 2 days and progesterone, 1 mg i.m. once in 2 days). The rats were killed after 2 months. The receptor-binding assay was adopted to measure the estrogen receptors in the arteries of the rats, and the activity of NOS in the arteries was assessed by the hemoglobin reductase method.

RESULTS

The ER number and NOS activity in the arteries of the ovariectomized group are less than those in sham-ovariectomy group (p<0.05). The ER number and NOS activity in the arteries of groups C and D are larger and higher than those in the ovariectomized group (p<0.05). No significant differences in the ER number and NOS activity were observed between groups C and D.

CONCLUSION

The ER number and NOS activity in the rat artery significantly decrease after ovariectomy, while hormone replacement therapy can significantly increase the artery NOS activity and retain the ER number in the artery of the ovariectomized rats to normal level. The result may contribute to explaining the beneficial effect of estrogen in the prevention of coronary artery diseases in postmenopausal women.

The metabolic consequences of treating postmenopausal women with non-oral hormone replacement therapy

OBJECTIVE

To define the metabolic profile of postmenopausal hormone replacement therapies when delivered through gels, patches, implants or other non-oral routes. Such information may be useful in the absence of reliable clinical data on the effects of these therapies on the risk of cardiovascular disease.

DESIGN AND METHODS

Selective literature review.

PATIENTS

Postmenopausal women.

RESULTS

Non-oral oestrogen therapies fail to invoke the hepatic response associated with oral therapy. Changes in hepatic protein synthesis are minimal and so plasma levels of binding globulins and other proteins tend to be normal. Many of the perturbations of the haemostatic system seen with oral therapy are avoided. In the absence of hepatic over-synthesis of apolipoproteins, plasma lipoprotein levels are unchanged or reduced. The direct effects of oestrogen on vascular function are apparent when the hormone is administered non-orally.

CONCLUSIONS

The net effect of non-oral estrogen therapies on the risk of cardiovascular disease is difficult to predict on the basis of current data. Some changes in plasma lipoprotein levels, such as the reduced fasting levels of triglycerides, would be considered desirable, but the cardioprotective increase in levels of high-density lipoproteins is absent. The differential effect on haemostasis markers is promising, but preliminary data relating to transdermal patches fail to support the idea that non-oral therapies will avoid the increased risk of venous thromboembolism associated with oral therapy. The ability of non-oral therapies to improve vascular function implies that they will offer postmenopausal women at least some of the cardiovascular protection seen with oral therapy.

Interaction of corticosterone and gonadal steroids on lipid deposition in the female rat

The present study was designed to evaluate the interaction of corticosterone (CORT) and female gonadal steroids on energy balance and lipid metabolism. To this end, a 2 x 4 factorial experiment was carried out in which two cohorts of rats differing in their ovary status [OV status: intact (INT) and ovariectomy (OVX)] were each divided into four groups defined by their CORT status [CORT status: nonadrenalectomized (non-ADX), ADX without CORT replacement (placebo subcutaneous pellet), ADX with low-dose CORT replacement, and ADX with high-dose CORT replacement]. After 3 wk of treatment and a 12-h fast, rats were killed and their carcasses analyzed for energy (lipid and protein) content. In addition, indexes of endogenous triglyceride (TRIG) production (liver TRIG content), transport into plasma (triglyceridemia), and incorporation into fat stores [lipoprotein lipase (LPL) activity in adipose tissue (AT)] were assessed. OV and CORT status interacted on body weight gain, total energy, and fat gains. The interactions arose from the fact that the twofold increase in these variables brought on by OVX was abolished by ADX and restored by CORT replacement. Although in ADX groups there was a dose-related restoration of total energy and fat gain by CORT replacement in both INT and OVX cohorts, the impact thereupon of OVX observed in the non-ADX group reappeared only in ADX animals receiving the high dose of CORT. Protein gain was increased by OVX solely in non-ADX rats, whereas the high dose of CORT prevented any net protein gain independently of the OV status. Consistent with treatment effects on total body fat gain, OVX resulted in an increase in liver TRIG content, AT weight, AT LPL activity, and plasma insulin. All these effects of OVX were abolished by ADX and restored by the high dose of CORT. Plasma TRIG were unaffected by OV status but were highly responsive to CORT status. All treatment effects were highly correlated with cumulative food intake. This study shows that the presence of CORT is required for OVX to exert its action on global energy balance and the concomitant, closely integrated adaptations of lipid metabolism.

Association of estrogens with human plasma lipoproteins: studies using estradiol-17beta and its hydrophobic derivative

Estrogen replacement therapy is widely used to combat symptoms of menopause, but factors influencing the transport of estrogen in plasma and its cellular uptake have been explored only to a limited extent. In this study, labeled estradiol-17beta (E2) was compared with its hydrophobic derivative (estradiol-3,17-diacetate, E2AA) in terms of (1) distribution within various lipoproteins and lipoprotein-free fractions of human plasma by ultracentrifugation and (2) uptake by human endothelial cells. Although added E2 was predominantly bound to HDL and lipoprotein-free fractions, E2AA was associated to some degree with VLDL and LDL but was still present in significant amounts in HDL and lipoprotein-free fractions. Significant associations of E2 with lipoproteins were also confirmed by polyacrylamide gel electrophoretic separation of E2-labeled plasma. In normal plasma, however, <10% of E2 was associated with lipoproteins when measured by radioimmunoassay. Incubation of E2AA and E2 with human dermal capillary endothelial cells showed similar uptake by 24 hours. A significant portion of E2AA was hydrolyzed to estradiol-17-monoacetate both in plasma and in cells. The addition of HDL and LDL to medium containing lipoprotein-deficient serum significantly reduced labeled E2 and E2AA uptake, respectively, by endothelial cells. These studies suggest that (1) although the association of E2 with HDL under normal conditions may be small, it increases significantly with higher estrogen concentrations of E2; (2) the hydrophobic ester of E2 shows increased binding to VLDL and LDL; and (3) this approach may be useful in manipulating the delivery of selected E2 derivatives to cells.

Lifestyle, fibrinolysis and lipids

Lifestyle including eating habits, physical training, smoking, drinking alcoholic beverages etc. can to a certain extent maintain or spoil our health. The physiological mechanisms of haemostasis and of lipoprotein metabolism play a role in acute cardiovascular diseases but also in a great number of chronic diseases in which vascular pathology is prominent. Imparied fibrinolysis and increased lipid levels are often incriminated in vascular disease. Lifestyle can modify fibrinolysis as well as lipid levels. Physical training, moderate eating habits, no smoking, moderate alcohol intake will be a beneficial influence on both fibrinolysis and lipid levels. The possibility that long-term pharmacological intervention may adversely affect fibrinolysis and lipid levels should always be considered.

Lipoprotein profiles and glucose tolerance in lean and obese chimpanzees

We compared serum lipid profiles and glucose tolerance of obese and lean chimpanzees maintained on a 10.9% fat diet. Seven of 14 obese and 6 of 17 lean chimpanzees were hypercholesterolemic (low density lipoprotein cholesterol > 160 mg/dl), three obese and three lean animals had total cholesterol/high density lipoprotein cholesterol ratios of 5.9-10.7, and two obese and one lean chimpanzee had abnormal glucose tolerance. Useful numbers of captive chimpanzees thus exhibit metabolic abnormalities without recourse to high fat diets and could serve as surrogates in studies of human metabolic diseases.

The effect of medrogestone on plasma lipids and lipoproteins in postmenopausal women using conjugated estrogens: an open randomized comparative study

OBJECTIVE

To test the hypothesis that the progestogen medrogestone has no effect on changes in lipoprotein metabolism evoked by continuous estrogen replacement therapy, paying special attention to high-density lipoproteins (HDL).

DESIGN

Open multicenter randomized comparative trial.

PATIENTS

Postmenopausal hysterectomized women aged 49 to 64 years.

INTERVENTION

Continuous oral treatment with 0.625 mg daily of conjugated estrogens (CE) alone (n = 55) or CE plus 5 mg of the progestogen medrogestone orally during the last 12 days of each 28-day cycle (n = 59).

MAIN OUTCOME MEASURES

At baseline and at cycles 3, 6, and 13 we measured the plasma levels of apolipoprotein (Apo) A1, cholesterol in total HDL and in its subfractions HDL2 and HDL3, using density gradient ultracentrifugation.

RESULTS

High-density lipoprotein cholesterol increased from baseline at all assessments in both treatment groups, being significantly greater in the CE group (+15% at cycle 13) than in the CE and medrogestone group (+8%). However, HDL2-cholesterol increased in both treatment groups, but with no significant difference between the two groups. High-density lipoprotein 3 cholesterol increased only in the CE group (+7% at cycle 13); there was no significant change in HDL3-cholesterol in the CE and medrogestone group. Low-density lipoprotein (LDL) cholesterol decreased from baseline at all assessments in both treatment groups (-6% and -9%, respectively, at cycle 13). The change in very low-density (VLDL) lipoprotein cholesterol was not significant in either of the two groups. Medrogestone had no significant effects on the estrogen-induced increases in apo A-1 and triglycerides nor on the decreases in ApoB and LDL-cholesterol. Neither hormone significantly affected VLDL-cholesterol or Lp(a) levels.

CONCLUSION

Medrogestone did not eliminate the increase in plasma HDL levels evoked by CE.

New targets for lipid lowering and atherosclerosis prevention

The effectiveness of plasma lipid lowering in the clinic is well supported by a growing number of contributions, indicating the significant improvement in cardiovascular risk in primary and particularly in secondary prevention. While these studies have clearly indicated that the more potent agents for cholesterol reduction can provide a very effective help, other pathways of lipid metabolism have gained interest. These should be evaluated, in the hope of providing a more complete answer to the question of regulating lipid absorption, distribution, and tissue deposition. In addition to newer more potent systemic lipid-lowering drugs (in particular hydroxymethylglutaryl coenzyme A reductase inhibitors), nonsystemic agents, including cholesterol sequestrants, are receiving attention. Some of these are effective at low concentrations, thus providing a potentially powerful tool for plasma cholesterol regulation. Another area of development is that of acyl coenzyme A cholesterol acyltransferase inhibitors, i.e., drugs interfering with cholesterol esterification in tissues, particularly in the arterial wall; the major problem with these seems to be that of poor tolerability and of lack of definitive proof of plasma cholesterol reduction in humans. At present, drugs for the treatment of elevated lipoprotein(a) levels are not available, with few exceptions; in this case, a better understanding of the regulation of lipoprotein(a) metabolism and of the potential benefit of treatment seems necessary. Elevation of congenitally low high density lipoprotein cholesterol levels may also be an important target: microsomal enzyme inducers have been tested, but have not provided a clinically significant response; drugs with a mixed endocrine-hypolipidemic activity possibly may prove effective. Other targets, e.g., the correction of the lipoprotein pattern characterized by "small low density lipoprotein," and the development of drugs specifically acting on the cholesteryl ester transfer protein and lipoprotein lipase systems, are being explored. Finally, new areas of development are in recombinant apolipoproteins (apo's) and in gene therapy. One case, i.e., that of apo A-I/HDL, is entering the clinical field; the mutant apo A-IMilano might provide help because of a combined cholesterol removing/fibrinolytic activity. In the case of gene therapy, at present, data on low density lipoprotein receptor replacement are encouraging. Further options, such as gene transfer in the arterial wall to induce vascular protection/disobliteration of occlusions, are also being tested.