Wim van Duyvenvoorde

Supplementation With Low Doses of Vitamin E Protects LDL From Lipid Peroxidation in Men and Women

There is accumulating evidence that oxidative modification of LDL is an important step in the process of atherogenesis and that antioxidants may protect LDL from oxidation. We and others have previously shown that ingestion of pharmacological doses of the antioxidant D,L-alpha-tocopherol (vitamin E), far above the recommended daily intake (ie, 12 to 15 IU/d for adults), increases the oxidation resistance of LDL. In this study, we ascertained the minimal supplementary dose of vitamin E necessary to protect LDL against oxidation in vitro. Twenty healthy volunteers (10 men and 10 women, aged 21 to 31 years) ingested consecutively 25, 50, 100, 200, 400, and 800 IU/d, D,L-alpha-tocopherol acetate during six 2-week periods. No changes were observed in LDL triglyceride content, fatty acid composition of LDL, or LDL size during the intervention. Concentrations of alpha-tocopherol in plasma and LDL were both 1.2 times the baseline values after the first period (25 IU/d) and 2.6 and 2.2 times, respectively, after the last period (800 IU/d). There was a linear increase in LDL alpha-tocopherol levels up to an intake of 800 IU/d (r = .79, P < .0001) and a good correlation between alpha-tocopherol in plasma and LDL (r = .66, P < .0001). Simultaneously, the resistance of LDL to oxidation was elevated dose-dependently (+28% after the last period) and differed significantly from the baseline resistance time even after ingestion of only 25 IU/d.(ABSTRACT TRUNCATED AT 250 WORDS)

Acyl-CoA:Cholesterol Acyltransferase Inhibitor Avasimibe Reduces Atherosclerosis in Addition to Its Cholesterol-Lowering Effect in ApoE*3-Leiden Mice

BackgroundThe present study investigated whether the ACAT inhibitor avasimibe can reduce atherogenesis independently of its cholesterol-lowering effect in ApoE*3-Leiden mice. Methods and ResultsTwo groups of 15 female ApoE*3-Leiden mice were put on a high-cholesterol (HC) diet; 1 group received 0.01% (wt/wt) avasimibe mixed into the diet. The HC diet resulted in a plasma cholesterol concentration of 18.7±2.6 mmol/L. Addition of avasimibe lowered plasma cholesterol by 56% to 8.1±1.2 mmol/L, caused mainly by a reduction of and composition change in VLDL and LDL. In a separate low-cholesterol (LC) control group, plasma cholesterol was titrated to a level comparable to that of the avasimibe group (10.3±1.4 mmol/L) by lowering the amount of dietary cholesterol. After 22 weeks of intervention, atherosclerosis in the aortic root area was quantified. Treatment with avasimibe resulted in a 92% reduction of lesion area compared with the HC control group. Compared with the LC control, avasimibe reduced lesion area by 78%. After correction for the slight difference in cholesterol exposure between the LC control and avasimibe groups, the effect of avasimibe on lesion area (73% reduction) remained highly significant. In addition, monocyte adherence to the endothelium, free cholesterol accumulation, and lesion severity were reduced by avasimibe treatment. ConclusionsTreatment with avasimibe potently lowered plasma cholesterol levels in ApoE*3-Leiden mice and considerably reduced atherosclerotic lesion area in addition to its cholesterol-lowering effect. Because monocyte adherence to the endothelium and lesion severity were also reduced by avasimibe, treatment with avasimibe may result in higher plaque stability and therefore a reduced risk of plaque rupture.

Effect of 17β-Estradiol on Plasma Lipids and LDL Oxidation in Postmenopausal Women With Type II Diabetes Mellitus

In type II diabetes mellitus the altered hormonal state after menopause may represent an additional cardiovascular risk factor. Estrogen replacement therapy (ERT) is associated with a decreased cardiovascular risk, at least in nondiabetic post-menopausal women. We studied the effect of ERT on plasma lipids and lipoproteins and on LDL oxidation in 40 postmenopausal women with type II diabetes but with minimal vascular complications in a randomized placebo-controlled trial. Twenty patients were treated orally with 2 mg/d micronized 17β-estradiol and 20 patients with placebo for 6 weeks. Plasma total cholesterol (-6%, P=.04), LDL cholesterol (-16%, P=.0001), and apoB (- 11%, P=.001) levels decreased and HDL cholesterol (20%, P=.0001) and apoA-I (14%, P=.0001) levels increased after ERT compared with placebo. Glycated hemoglobin (HbA1c) decreased significantly after ERT (-3%, P=.03), the cholesterol content of the LDL particles decreased (-5%, P=.006), triglyceride content increased (16%, P=.01), and LDL particle size did not change significantly. ERT had no effect on parameters of LDL oxidation. We conclude that plasma levels of HDL cholesterol, apoA-I, LDL cholesterol, apoB, and glycated hemoglobin are improved in postmenopausal women with type II diabetes mellitus after treatment with 17β-estradiol, indicative of a better metabolic control, and that ERT has no effect on LDL oxidizability.

Effects of Fish Oil on Oxidation Resistance of VLDL in Hypertriglyceridemic Patients

In hypertriglyceridemic (HTG) patients the addition of fish oil to the diet causes a marked reduction in the concentration of triglyceride-rich lipoproteins in the serum. To investigate the effects of fish oil on the oxidation resistance of VLDL and LDL in HTG patients, nine male patients received 1 g/d fish oil (containing 55.7% n-3 polyunsaturated fatty acids [PUFAS] and l U alpha-tocopherol/g fish oil) for 6 weeks followed by 5 g/d fish oil for an additional 6 weeks. Cu(2+)-induced oxidation of VLDL and LDL was measured by continuous monitoring of conjugated dienes. Supplementation with 1 g/d fish oil caused hardly any changes in the n-3 PUFA content of lipoproteins or lipoprotein concentrations in serum. However, supplementation with 5 g/d fish oil resulted in a significant increase of n-3 PUFA content in VLDL (from 2.5% to 6.4% of total fatty acids) and LDL (from 3.2% to 6.4% of total fatty acids), decreases in serum triglyceride, VLDL triglyceride, and VLDL cholesterol concentrations of 54%, 56%, and 40%, respectively, and an increase in LDL cholesterol of 23%. The lag times of VLDL and LDL oxidation decreased from 197 to 140 minutes (-29%) and 101 to 86 minutes (-15%), respectively. At the end of the 5 g/d fish oil supplementation the lag times of VLDL and LDL oxidation were correlated with their respective n-3 PUFA content (r = -.67; P < .05 and r = -.79; P < .02, respectively). Before and at the end of supplementation with 5 g/d fish oil the lag times and propagation rates of VLDL oxidation also correlated with the total number of double bonds in all PUFAs of VLDL. We conclude that fish oil supplementation strongly reduces serum concentrations of total triglycerides, VLDL triglycerides, and VLDL cholesterol. However, in HTG patients fish oil supplementation increased the serum LDL cholesterol concentration and the susceptibility of VLDL and LDL to oxidation.

LDL oxidation and extent of coronary atherosclerosis

Accumulated evidence indicates that oxidative modification of LDL plays an important role in the atherogenic process. Therefore, we investigated the relation between coronary atherosclerosis and susceptibility of LDL to oxidation in a case-control study in men between 45 and 80 years of age. Case subjects and hospital control subjects were selected from subjects undergoing a first coronary angiography. Subjects with severe coronary stenosis (> or = 85% stenosis in one and > or = 50% stenosis in a second major coronary vessel) were classified as case subjects (n=91). Hospital control subjects with no or minor stenosis (< or = 50% stenosis in no more than two of the three major coronary vessels, n=94) and population control subjects free of plaques in the carotid artery (n=85) were pooled for the statistical analysis into one control category. Enrollment procedures allowed for similar distributions in age and smoking habits. Case subjects had higher levels of total and LDL cholesterol and triglycerides and lower levels of HDL cholesterol. Resistance time, maximum rate of oxidation, and maximum diene production were measured ex vivo using copper-induced LDL oxidation. A borderline significant inverse trend was observed for coronary atherosclerosis risk at increasing resistance time. Odds ratios (95% confidence interval) for the successive quartiles were 1.0 (reference), 0.77 (0.39 to 1.53), 0.67 (0.33 to 1.34), and 0.55 (0.27 to 1.15) (ptrend=0.07). No relation with maximum rate of oxidation was found, and higher maximum diene levels were found in control subjects (P<.01). The main determinant of oxidation was the fatty acid composition of LDL. No effect of smoking or use of medication was observed. We conclude that although LDL resistance to oxidation may be a factor in atherogenesis, the ex vivo measure is not a strong predictor of severity of coronary atherosclerosis.

A Dietary Mixture Containing Fish Oil, Resveratrol, Lycopene, Catechins, and Vitamins E and C Reduces Atherosclerosis in Transgenic Mice

Chronic inflammation and proatherogenic lipids are important risk factors of cardiovascular disease (CVD). Specific dietary constituents such as polyphenols and fish oils may improve cardiovascular risk factors and may have a beneficial effect on disease outcomes. We hypothesized that the intake of an antiinflammatory dietary mixture (AIDM) containing resveratrol, lycopene, catechin, vitamins E and C, and fish oil would reduce inflammatory risk factors, proatherogenic lipids, and endpoint atherosclerosis. AIDM was evaluated in an inflammation model, male human C-reactive protein (CRP) transgenic mice, and an atherosclerosis model, female ApoE*3Leiden transgenic mice. Two groups of male human-CRP transgenic mice were fed AIDM [0.567% (wt:wt) powder and 0.933% (wt:wt oil)] or placebo for 6 wk. The effects of AIDM on basal and IL-1β–stimulated CRP expression were investigated. AIDM reduced cytokine-induced human CRP and fibrinogen expression in human-CRP transgenic mice. In the atherosclerosis study, 2 groups of female ApoE*3Leiden transgenic mice were fed an atherogenic diet supplemented with AIDM [0.567% (wt:wt) powder and 0.933% (wt:wt oil)] or placebo for 16 wk. AIDM strongly reduced plasma cholesterol, TG, and serum amyloid A concentrations compared with placebo. Importantly, long-term treatment of ApoE*3Leiden mice with AIDM markedly reduced the development of atherosclerosis by 96% compared with placebo. The effect on atherosclerosis was paralleled by a reduced expression of the vascular inflammation markers and adhesion molecules inter-cellular adhesion molecule-1 and E-selectin. Dietary supplementation of AIDM improves lipid and inflammatory risk factors of CVD and strongly reduces atherosclerotic lesion development in female transgenic mice.

Differential effects of drug interventions and dietary lifestyle in developing type 2 diabetes and complications: a systems biology analysis in LDLr-/- mice.

Excess caloric intake leads to metabolic overload and is associated with development of type 2 diabetes (T2DM). Current disease management concentrates on risk factors of the disease such as blood glucose, however with limited success. We hypothesize that normalizing blood glucose levels by itself is insufficient to reduce the development of T2DM and complications, and that removal of the metabolic overload with dietary interventions may be more efficacious. We explored the efficacy and systems effects of pharmaceutical interventions versus dietary lifestyle intervention (DLI) in developing T2DM and complications. To mimic the situation in humans, high fat diet (HFD)-fed LDLr−/− mice with already established disease phenotype were treated with ten different drugs mixed into HFD or subjected to DLI (switch to low-fat chow), for 7 weeks. Interventions were compared to untreated reference mice kept on HFD or chow only. Although most of the drugs improved HFD-induced hyperglycemia, drugs only partially affected other risk factors and also had limited effect on disease progression towards microalbuminuria, hepatosteatosis and atherosclerosis. By contrast, DLI normalized T2DM risk factors, fully reversed hepatosteatosis and microalbuminuria, and tended to attenuate atherogenesis. The comprehensive beneficial effect of DLI was reflected by normalized metabolite profiles in plasma and liver. Analysis of disease pathways in liver confirmed reversion of the metabolic distortions with DLI. This study demonstrates that the pathogenesis of T2DM towards complications is reversible with DLI and highlights the differential effects of current pharmacotherapies and their limitation to resolve the disease.