Insulin resistance increases circulating malondialdehyde-modified LDL and impairs endothelial function in healthy young men

BACKGROUND: Endothelial dysfunction is regarded as an early feature of atherosclerosis. Both LDL oxidation and insulin resistance play important roles in the pathogenesis of atherosclerosis. Recent studies have demonstrated a significant association between oxidized LDL and insulin resistance. METHODS: We investigated relationships between insulin resistance, circulating malondialdehyde-modified (MDA)-LDL, and endothelial function in 36 healthy young men. Insulin sensitivity was estimated according to homeostasis model assessment of insulin resistance (HOMA-IR); we defined subjects with values of at least 2.5 as an insulin resistant (n=12) and those with values below 2.5 as insulin sensitive (n=24). We evaluated endothelial function by flow-mediated vasodilation (FMD) of brachial artery during reactive hyperemia, using high-resolution ultrasound. We also measured serum MDA-LDL by a sandwich enzyme-linked immunosorbent assay. RESULTS: MDA-LDL was significantly higher (146+/-46 vs. 101+/-32 IU/l, P=0.002) and FMD was significantly lower (3.94+/-1.53 vs. 5.59+/-1.62 %, P=0.002) in the insulin-resistant group than in the insulin-sensitive group. The resistant group showed a significant inverse correlation between MDA-LDL and FMD (r=-0.675, P=0.016), while the sensitive group did not (r=0.163, NS). By multivariate regression analysis, MDA-LDL and age were determinants of FMD (R2=0.766) in the insulin-resistant group, while no variable determined FMD in the sensitive group. Nitroglycerin-induced endotheliumindependent dilation was similar in both groups. CONCLUSIONS: These results suggest that the production of circulating MDA-LDL may be accelerated by insulin resistance, thus impairing endothelial function even in healthy young men.     

A comparison of low-dose and standard-dose oral estrogen on forearm endothelial function in early postmenopausal women

We investigated the effects of low-dose estrogen plus progestin on endothelial function. Postmenopausal women received daily doses of conjugated equine estrogen (CEE, 0.625 mg) plus medroxyprogesterone acetate (MPA, 2.5 mg) (standard-dose group, n = 18), CEE (0.3 mg) plus MPA (2.5 mg) (low-dose group, n = 18), or no treatment (control group, n = 15) for 3 months. Serum concentrations of lipids and malondialdehyde (MDA)-modified low-density lipoprotein (LDL) were measured. Forearm blood flow (FBF) during reactive hyperemia and after sublingual nitroglycerin administration was measured by strain-gauge plethysmography. Decreases in serum concentrations of LDL cholesterol and MDA-modified LDL and increases in high-density lipoprotein cholesterol and nitrite/nitrate were observed in both treatment groups. After 3 months of treatment, similar increases in the maximal FBF response during reactive hyperemia were observed in both treatment groups (standard-dose group, from 35.8 +/- 3.0 to 47.5 +/- 2.8 ml/min per 100 ml tissue; and low-dose group, from 35.2 +/- 2.2 to 46.8 +/- 3.4 ml/min per 100 ml tissue, P < 0.01). FBF levels in the control group were unchanged. Treatment did not affect nitroglycerin-induced dilation. The incidences of vaginal bleeding and breast tenderness were lower with the low-dose group than with the standard-dose group. Low-dose CEE plus MPA augments endothelial function in forearm resistance arteries and decreased MDA-modified LDL levels similarly to standard doses of CEE plus MPA, with fewer side effects.     

Hormone replacement effects on endothelial function measured in the forearm resistance artery in normocholesterolemic and hypercholesterolemic postmenopausal women

We investigated whether forearm resistance artery endothelial function differed between hypercholesterolemic postmenopausal women (n = 41) and normocholesterolemic postmenopausal women (n = 37), both generally and in terms of effects of long-term hormone replacement therapy (HRT) on endothelial function. Both menopause and hypercholesterolemia are associated with endothelial dysfunction and increased coronary risk. Forearm blood flow (FBF) during reactive hyperemia and after sublingual nitroglycerin (NTG) administration was measured by strain-gauge plethysmography. Treated women received conjugated equine estrogen (0.625 mg) plus medroxyprogesterone acetate (2.5 mg) daily for 6 months. Nitrite/nitrate, angiotensin-converting enzyme, and lipids were measured in serum. FBF during reactive hyperemia as well as serum nitrite/nitrate concentrations were significantly lower in hypercholesterolemic than normocholesterolemic subjects. Increases in the FBF induced by NTG were similar in the two groups. HRT significantly increased estradiol, high-density lipoprotein cholesterol, and serum nitrite/nitrate, while decreasing circulating angiotensin-converting enzyme activity in both groups. Reduction in total and low-density lipoprotein cholesterol was seen only in hypercholesterolemic subjects. After 6 months of HRT, maximal FBF response during reactive hyperemia increased in both groups. Augmentation of this response was greater in hypercholesterolemic than in normocholesterolemic subjects (maximal FBF, 55.4 +/- 11.2 vs. 25.9 +/- 11.5%; P < 0.05). Changes in the FBF with NTG were not altered by HRT in either group. Long-term HRT augments endothelial function in forearm resistance artery. This beneficial effect is greater in patients with hypercholesterolemia.     

Endogenous testosterone and endothelial function in postmenopausal women

OBJECTIVE: It is well known that coronary heart disease incidence increases in women after menopause. This phenomenon was related to reduced levels of female sex hormones. Estrogen decline, however, is not the only hormonal change during the postmenopausal period and estrogen administration did not protect women from cardiovascular disease. Therefore, it is justified to explore other hormonal changes. The role of androgens is still controversial. The aim of the present study was to investigate the relationship between endogenous sex hormones and endothelial function, measuring the brachial artery flow-mediated dilation. METHODS AND RESULTS: Sixty postmenopausal women were consecutively enrolled and underwent a clinical and biochemical examination. Brachial artery flow-mediated dilation was also evaluated by ultrasound. After correction for confounding variables, testosterone was positively correlated to flow-mediated dilation (beta=0.277, P=0.03). Indeed, women in the lowest testosterone tertile had a flow-mediated dilation smaller than that in the highest tertile (P=0.02). CONCLUSIONS: This result could suggest that the development of cardiovascular disease after menopause is due not only to estrogen decline but also to androgen decline. More studies are needed to evaluate the role of androgen replacement therapy on postmenopausal women with low level of this hormone.     

Apolipoprotein E gene determines serum testosterone and dehydroepiandrosterone levels in postmenopausal women

OBJECTIVE: Apolipoprotein E (ApoE) is believed to play an important role in lipid metabolism and has been found to be related to diseases associated with ageing, the important characteristic of which is decline in circulating sex steroids, including androgen. DESIGN: To find the relationships of levels of serum testosterone and its precursor, dehydroepiandrosterone (DHEA), to ApoE polymorphism in 113 postmenopausal Caucasian women. METHODS: The ApoE genotype was assessed by polymerase chain reaction and CfoI endonuclease digestion. ApoE genotype distribution was as follows: E2/3, 15%; E3/3, 71.7%; E2/4, 1.8%; E3/4, 10.6; and E4/4, 0.89%. The differences in serum androgen levels between genotypes were evaluated by ANCOVA and least significant difference (LSD) multiple comparisons test after adjustment for body mass index, age and/or years since menopause. RESULTS: Significant intergroup differences between the most frequent allele combination (2/3, 3/3 and 3/4) in serum DHEA levels were found (P<0.05, ANCOVA). DHEA levels were higher in women with the E3/4 allele combination than in the E3/3 genotype (P<0.01, LSD multiple comparisons). In serum testosterone levels, borderline intergroup differences were found (P<0.07, ANCOVA). Higher testosterone levels were found in the E3/4 allele combination as compared with E3/3 (P<0.05, LSD multiple comparisons). Dose effect of E4 allele analysis indicated higher serum DHEA and testosterone levels in women with the E4 allele present than in women with the E4 allele absent (P<0.003 for DHEA, P<0.007 for testosterone, ANCOVA). CONCLUSIONS: Circulating testosterone and DHEA are associated with the ApoE genotype, which may render women carrying the allele E4 more susceptible to the development of some diseases associated with ageing and menopause [corrected].     

Racial differences in endothelial function in postmenopausal women

Objective

Racial differences in cardiovascular mortality among women remain largely unexplained. Preliminary data suggest that African American and Caucasian differences in endothelial function may parallel differential cardiovascular disease (CVD) risk in women. To further study differences in endothelial function between African American and Caucasian women, we analyzed measures of brachial artery flow-mediated dilation (FMD) in women enrolled in the Cardiovascular Health Study (CHS).

Methods and results

Brachial artery FMD was measured in the fasting state using established ultrasound techniques in 1330 Caucasian and 297 African American female participants in CHS (mean age 78.4 ± 4.4 years). General linear models were used to compare FMD between African American and Caucasian women after adjusting for baseline brachial diameter, hypertension, diabetes, smoking, cholesterol, systolic blood pressure, body mass index, waist/hip ratio, age, education, income level; use of angiotensin-converting enzyme inhibitors, β-blockers, nitroglycerin, estrogens and lipid-lowering drugs; and presence of clinical or subclinical disease. Adjusted absolute change and percent change in brachial artery diameter was significantly reduced in African American women compared with Caucasian women (P < .0001 and P = .0002, respectively). Similar results were found when the women were stratified by history of CVD (− CVD, P = .02; + CVD, P = .001) and CVD or subclinical vascular disease (− disease, P = .01, + disease, P = .03).

Conclusions

In this cohort, brachial artery FMD was lower in African American women compared to Caucasian women, and this difference persisted after adjustment by multivariable analysis. The increased CVD risk in African American women may be related to impaired endothelial function. It remains to be determined whether African American women may uniquely benefit by interventions designed to improve endothelial health.     

Forearm endothelial function and bone mineral loss in postmenopausal women

It is widely believed that the vasculature plays an important role in bone remodeling. We investigated the relationship between forearm endothelial function and bone mass in the lumbar spine in early postmenopausal women without a history of smoking or diabetes mellitus. We studied the forearm resistance artery endothelial function in 110 Japanese women-52 postmenopausal women with normal spinal bone mineral density (BMD), 36 postmenopausal women with osteopenia, and 22 osteoporotic postmenopausal women. Forearm blood flow (FBF) during reactive hyperemia and after sublingual nitroglycerin (NTG) administration was measured by strain-gauge plethysmography. BMD of the lumbar spine (L2-L4) was measured by dual-energy X-ray absorptiometry. After adjustment for age, body mass index, years since the start of menopause, and basal FBF, women with osteoporosis had a lower maximal FBF response to reactive hyperemia (28.4 +/- 3.8 mL/min per 100 mL tissue) than those with normal BMD (39.8 +/- 2.8 mL/min per 100mL tissue) or osteopenia (35.6 +/- 2.5 mL/min per 100mL tissue) (P = 0.029). A significant increase in serum angiotensin-converting enzyme (ACE) activity (P = 0.042) and a significant decrease in the serum concentrations of nitrite/nitrate (P = 0.041) were noted in osteoporotic women compared to women with normal BMD or osteopenia. The present findings suggest that postmenopausal women with low BMD, especially those with osteoporosis, have impaired endothelial function in the forearm resistance arteries.     

Raloxifene,conjugated oestrogen and endothelial function in postmenopausal women

OBJECTIVES: To study the long-term effects of raloxifene, a potential designer oestrogen, and oestrogen monotherapy on endothelial function in healthy postmenopausal women. DESIGN: A 2-year double-blind, randomized and placebo-controlled study in an Academic Medical Center. Fifty-six hysterectomized but otherwise healthy postmenopausal women randomly received raloxifene hydrochloride 60 mg day-1 (n = 15) or 150 mg day-1 (n = 13), conjugated equine oestrogen (CEE) 0.625 mg day-1 (n = 15), or placebo (n = 13). MAIN OUTCOME MEASURES: Endothelial function as estimated from brachial artery flow-mediated, endothelium-dependent vasodilation and nitroglycerine-induced endothelium-independent vasodilation, and plasma levels of the endothelium-derived regulatory proteins, von Willebrand factor (vWF) and endothelin (ET). RESULTS: Raloxifene 60 mg did not significantly affect endothelial function. As compared with placebo, at 6 months of therapy, raloxifene 150 mg and CEE were associated with a mean increase in vWF of 25.5% point (95% CI 3.6-47.3) and 26.6% point (95% CI 6.9-46.3), respectively. At 24 months of therapy, raloxifene 150 mg was associated with a mean decrease in ET of 0.96 pg mL-1 (95% CI -1.57 to -0.36). Raloxifene nor CEE significantly affected endothelium-dependent and/or -independent vasodilation. CONCLUSIONS: Our results suggest that long-term therapy with raloxifene or oral CEE does not affect endothelium-dependent vasodilation in healthy postmenopausal women. Raloxifene 150 mg day-1 might have both positive and negative effects on endothelium. The clinical significance of these findings remains to be investigated.     

Apolipoprotein E 4 allele is associated with low bone density in postmenopausal women

Apolipoprotein E (Apo E) genotypes have been associated with a number of involutional disorders. Recently some studies have examined whether the Apo E 4 allele might play a role in the pathophysiology of postmenopausal osteoporosis. However, association analysis between Apo E genotypes, BMD, bone loss or fracture risk have not brought universal findings. The aim of this study was, therefore, to determine the relationship between the presence or absence of Apo E 4 allele and BMD in postmenopausal women of Caucasian origin. We studied 113 women, age 62.5 +/- 8.9 yr, who underwent measurement of hip and spine BMD by dual-energy absorptiometry (DXA, g/cm2). Apo E genotypes were assessed by PCR amplification and by restriction typing with Cfol enzyme. The Apo E allele frequencies in the study population were as follows: E2 0.084, E3 0.845, E4 0.071. Because the Apo E 4 allele was associated with osteoporosis in previous studies, the probands were dichotomized by the presence or absence of Apo E 4 allele. After adjustment for BMI and years since menopause BMD at the lumbar spine varied significantly by Apo E 4 status. Women with Apo E 4 allele had significantly lower BMD at the lumbar spine than women with no Apo E 4 allele (p<0.003, ANCOVA). In contrast, there were no significant differences in BMD at the hip comparing women with or without the Apo E 4 allele. To conclude, these data may support the importance of Apo E 4 allele in determining postmenopausal spine bone mass.     

Tamoxifen improves endothelial function and reduces carotid intima-media thickness in postmenopausal women

Background

Tamoxifen is a selective estrogen-receptor modulator shown to improve several cardiovascular risk factors in postmenopausal women with breast cancer. In animal studies tamoxifen inhibits the progression of atherosclerosis. Although the presence of a history with tamoxifen treatment is related to a lower intima-media thickness (IMT) of the common carotid artery, data from controlled follow-up studies are lacking to support this observation.

Methods

We examined 14 postmenopausal women with early stage breast cancer with indication for tamoxifen treatment (20 mg/d) and 13 healthy postmenopausal women. Flow-mediated dilatation (FMD) of the brachial artery, combined carotid IMT, and aortic pulse wave were measured before and 6 months after treatment in the tamoxifen group and at the same times in the control group.

Results

FMD and IMT were significantly increased and decreased, respectively, in the treatment group compared to the control group (FMD: +2.2% ± 0.9% vs +0.085% ± 1%, P = .012; IMT: −0.088 ± 0.03 mm vs +0.04 ± 0.03 mm, P = .018, mean ± standard error of the mean, treatment vs control group). These differences remained significant even when adjusted for age, duration of menopause, and cardiovascular risk factors. Low-density lipoprotein cholesterol was also significantly reduced after tamoxifen treatment.

Conclusions

Tamoxifen treatment slows the progression of atherosclerosis in postmenopausal women with breast cancer as assessed by changes in carotid IMT. An improvement in endothelial function and blood lipid profile may be the reason for this beneficial effect.     

Apolipoprotein E phenotype and cholesterol metabolism in familial hypercholesterolemia

Serum lipids, lipoproteins, cholesterol absorption and parameters of cholesterol metabolism were related to apolipoprotein E phenotypes in 38 patients with familial xanthomatous hypercholesterolemia. Serum lipids and lipoproteins were similar in 2 most frequent apo E phenotypes E 3/3 and E 4/3. Coronary artery disease was not related to the apo E phenotypes. Cholesterol absorption efficiency was significantly lower in the apo E 3/3 patients than in the apo E 4/3 group. A high serum level of cholesterol precursor lathosterol, a high lathosterol/sitosterol ratio and sterol balance data suggest that cholesterol synthesis may be slightly higher in the apo E 3/3 than E 4/3 group. The findings indicate that the genetically determined apo E polymorphism contributes to cholesterol absorption efficiency in FH patients, but serum total and lipoprotein cholesterol levels are poorly related to apo E isoforms.     

Combined hormone replacement therapy improves endothelial function in healthy postmenopausal women

OBJECTIVES: Large scale epidemiological studies suggest that hormone replacement therapy (HRT) reduces cardiovascular events in postmenopausal women. Improvement in endothelial function may contribute to this protective effect. DESIGN: In a prospective, double blind study, 61 healthy postmenopausal women were randomized to receive either oral continuous combined HRT [oestradiol 2 mg and norethisterone acetate (NETA) 1 mg per day] or placebo. Endothelial function, assessed by flow-mediated vasodilation (FMD) of the brachial artery and expression of soluble endothelial cell adhesion molecules (CAM) were determined before, after 3 and 6 months of therapy. RESULTS: The FMD was significantly improved in women on combined HRT (from 5.97% to 10.94% after 3 months and to 10.58% after 6 months; both P < 0.01 versus baseline values) and did not change in the placebo group (6.92% at baseline, 5.86% after 3 and 6.26% after 6 months). After 3 months of combined HRT, significant decreases of 24.6% for E-selectin and 13.9% for intercellular adhesion molecule-1 (ICAM-1) were observed (both P < 0.01 versus baseline values) and were sustained after 6 months of therapy, whilst no differences emerged in the placebo group. CONCLUSIONS: Oestradiol and norethisterone acetate improve endothelial function by both enhancing FMD and reducing the levels of soluble E-selectin and ICAM-1 in healthy postmenopausal women.     

Apolipoprotein E and Paraoxonase 1 polymorphisms are associated with lower serum thyroid hormones in postmenopausal women

Objective  Autoimmune thyroiditis and overt or subclinical hypothyroidism have been associated with increased prevalence of cardiovascular disease (CVD).
Design  Cross-sectional investigation of the association between gene polymorphisms related to CVD with thyroid function and autoimmunity.
Patients  In total 84 healthy postmenopausal women aged 49–69 years.
Measurements  FT3, FT4, anti-TPO and anti-TG were assessed in the sera of participants. The following polymorphisms were assessed from peripheral lymphocyte DNA: Apolipoprotein E E2/E3/E4, paraoxonase 1 A/B, Glycoprotein IIIa leu33pro, MTHFR ala222val, ApoBarg3500gln, plasminogen activator inhibitor 1 4G/5G, cholesterol 7-α hydroxylase A204C and cholesterol ester transfer protein B1/B2.
Results  A statistically significant correlation was found between Apolipoprotein E and paraoxonase1 polymorphisms and serum thyroid hormones: carriers of the E2 or E4 allele of the ApoE gene had lower levels of FT4 ( P  = 0·0005) than women with the E3/E3 genotype. Carriers of the B allele of paraoxonase 1 gene had lower levels of FT3 compared to women with the wild-type genotype ( P =  0·047). A statistically significant positive association ( P =  0·049) was also observed between anti-TG antibodies and the presence of the E2 allele of the Apolipoprotein E gene.
Conclusions  Polymorphisms of apolipoprotein E and paraoxonase 1 are associated with different levels of thyroid hormone and anti-Tg antibody levels in the study population in this pilot study. The mechanism underlying this association remains to be elucidated.     

Circulating leptin is associated with oxidized LDL in postmenopausal women

Recently, leptin has been suggested as a possible cause of atherosclerotic disease. In the present study, we have investigated in postmenopausal women (n = 60; age: 52 +/- 13) the relationship between circulating levels of leptin, oxidized LDL (Ox-LDL) and other biochemical and anthropometric variables of atherosclerotic risk. In addition, we have evaluated soluble thrombomodulin (sTM) as a marker of endothelial damage. An additional study was conducted in a subgroup of obese subjects to determine the short-term effects of weight loss on selected variables. Ox-LDL showed a positive correlation with leptin circulating levels (r = 0.65, P < 0.0001). A significant association was also found between Ox-LDL and body mass index (r = 0.69, P < 0.0001), waist-to-hip ratio (r = 0.50, P < 0.0001), insulin levels (r = 0.65, P < 0.0001), HOMA index (r = 0.55, p < 0.0001) and sTM (r = 0.74, P < 0.0001) levels. After multivariate regression analysis leptin was still related to Ox-LDL levels (P = 0.007). In obese women who completed the program of weight reduction, leptin changes persisted as a significant predictor of plasma changes in Ox-LDL levels. These findings suggested a novel link between leptin and Ox-LDL, possibly involved in atherosclerotic disease.     

Lipoprotein (a) is associated with endothelial function in healthy postmenopausal women

BACKGROUND: Lipoprotein (a) (Lp(a)) is an independent risk factor for atherosclerotic cardiovascular disease. The atherogenic potential of Lp(a) may be by impairment of endothelial function. Objectives. We investigated the relation of Lp(a) plasma levels to endothelium dependent and independent dilatation of the brachial artery in healthy postmenopausal women. METHODS: One hundred and five healthy postmenopausal women aged 52-67 years were included in the study. Endothelial function was assessed non-invasively by measuring percent lumen diameter change in the brachial artery after reactive hyperemia and sublingual nitroglycerine spray. RESULTS: Flow mediated dilatation was inversely related to the plasma logLp(a) level. Mean change per unit logLp(a) increase:-2.83% (95% CI: -5.22--0.43). Elevated Lp(a) (>239 mg/l) (upper quartile) was associated with an impaired flow mediated vasodilatation (2.4%+/-1. 2) compared to Lp(a) < or =239 mg/l (5.2%+/-0.7). Adjustment for other cardiovascular risk factors did not change the magnitude of the association. Nitroglycerine-induced vasodilatation was not significantly lower in the high Lp(a) level group, compared to the group with normal levels of Lp(a) (< or =239 mg/l) (8.0+/-1.2 vs. 11.4%+/-0.8). CONCLUSION: Elevated lipoprotein (a) levels are associated with an impaired endothelial function in healthy postmenopausal women, independent of conventional risk factors for cardiovascular disease. Since Lp(a) may be pathogenetically important for early vascular damage, elevated Lp(a) levels might contribute to the increased cardiovascular risk seen in postmenopausal women.