Ann Mertens

Circulating Oxidized LDL Is a Useful Marker for Identifying Patients With Coronary Artery Disease

Abstract—Our aim was to determine the usefulness of circulating oxidized low density lipoprotein (LDL) in the identification of patients with coronary artery disease (CAD). A total of 304 subjects were studied: 178 patients with angiographically proven CAD and 126 age-matched subjects without clinical evidence of cardiovascular disease. The Global Risk Assessment Score (GRAS) was calculated on the basis of age, total and high density lipoprotein cholesterol, blood pressure, diabetes mellitus, and smoking. Levels of circulating oxidized LDL were measured in a monoclonal antibody 4E6-based competition ELISA. Compared with control subjects, CAD patients had higher levels of circulating oxidized LDL (P <0.001) and a higher GRAS (P <0.001). The sensitivity for CAD was 76% for circulating oxidized LDL (55% for men and 81% for women) compared with 20% (24% for men and 12% for women) for GRAS, with a specificity of 90%. Logistic regression analysis revealed that the predictive value of oxidized LDL was additive to that of GRAS (P <0.001). Ninety-four percent of the subjects with high (exceeding the 90th percentile of distribution in control subjects) circulating oxidized LDL and high GRAS had CAD (94% of the men and 100% of the women). Thus, circulating oxidized LDL is a sensitive marker of CAD. Addition of oxidized LDL to the established risk factors may improve cardiovascular risk prediction.

Adenovirus-Mediated Gene Transfer of Human Platelet-Activating Factor–Acetylhydrolase Prevents Injury-Induced Neointima Formation and Reduces Spontaneous Atherosclerosis in Apolipoprotein E–Deficient Mice

Background—Atherosclerosis is characterized by an early inflammatory response involving proinflammatory mediators such as platelet-activating factor (PAF)-like phospholipids, which are inactivated by PAF-acetylhydrolase (PAF-AH). The effect of adenovirus-mediated expression of PAF-AH on injury-induced neointima formation and spontaneous atherosclerosis was studied in apolipoprotein E–deficient mice. Methods and Results—Intravenous administration of an adenovirus (5×108 plaque-forming units) directing liver-specific expression of human PAF-AH resulted in a 3.5-fold increase of plasma PAF-AH activity at day 7 (P <0.001); this was associated with a 2.4- and 2.3-fold decrease in malondialdehyde-modified LDL autoantibodies and the lysophosphatidylcholine/phosphatidylcholine ratio, respectively (P <0.001 for both). Non-HDL and HDL cholesterol levels in PAF-AH-treated mice were similar to those of control virus-treated mice. Seven days after virus injection, endothelial denudation of the common left carotid artery was induced with a guidewire. Neointima formation was assessed 18 days later. PAF-AH gene transfer reduced oxidized lipoproteins by 82% (P <0.001), macrophages by 69% (P =0.006), and smooth muscle cells by 84% (P =0.002) in the arterial wall. This resulted in a 77% reduction (P <0.001) of neointimal area. Six weeks after adenovirus-mediated gene transfer, spontaneous atherosclerotic lesions in the aortic root were analyzed. PAF-AH gene transfer reduced atherosclerotic lesions by 42% (P =0.02) in male mice, whereas a nonsignificant 14% reduction was observed in female mice. Basal and PAF-AH activity after gene transfer were higher in male mice than in female mice (P =0.01 and P =0.04, respectively). Conclusions—Gene transfer of PAF-AH inhibited injury-induced neointima formation and spontaneous atherosclerosis in apolipoprotein E–deficient mice. Our data indicate that PAF-AH, by reducing oxidized lipoprotein accumulation, is a potent protective enzyme against atherosclerosis.

Increased Low-Density Lipoprotein Oxidation and Impaired High-Density Lipoprotein Antioxidant Defense Are Associated With Increased Macrophage Homing and Atherosclerosis in Dyslipidemic Obese Mice LCAT Gene Transfer Decreases Atherosclerosis

Background—Obesity-associated dyslipidemia in humans is associated with increased low-density lipoprotein (LDL) oxidation. Mice with combined leptin and LDL receptor deficiency are obese and show severe dyslipidemia and insulin resistance. We investigated the association between oxidation of apolipoprotein B–containing lipoproteins, high-density lipoprotein (HDL) antioxidant defense, and atherosclerosis in these mice. Methods and Results—LDL receptor knockout (LDLR−/−), leptin-deficient (ob/ob), double-mutant (LDLR−/−;ob/ob), and C57BL6 mice were fed standard chow. Double-mutant mice had higher levels of non-HDL (P <0.001) and HDL (P <0.01) cholesterol and of triglycerides (P <0.001). They also had higher oxidative stress, evidenced by higher titers of autoantibodies against malondialdehyde-modified LDL (P <0.001). C57BL6 and ob/ob mice had no detectable lesions. Lesions covered 20% of total area of the thoracic abdominal aorta in double-mutant mice compared with 3.5% in LDLR−/− mice (P <0.01). Higher macrophage homing and accumulation of oxidized apolipoprotein B-100–containing lipoproteins were associated with larger plaque volumes in the aortic root of double-mutant mice (P <0.01). The activity of the HDL-associated antioxidant enzymes paraoxonase and lecithin:cholesterol acyltransferase (LCAT) (ANOVA;P <0.0001 for both) was lower in double-mutant mice. Adenovirus-mediated LCAT gene transfer in double-mutant mice increased plasma LCAT activity by 64% (P <0.01) and reduced the titer of autoantibodies by 40% (P <0.01) and plaque volume in the aortic root by 42% (P <0.05) at 6 weeks. Conclusions—Dyslipidemia and insulin resistance in obese LDL receptor–deficient mice are associated with increased oxidative stress and impaired HDL-associated antioxidant defense, evidenced by decreased paraoxonase and LCAT activity. Transient LCAT overexpression was associated with a reduction of oxidative stress and atherosclerosis.

Weight-loss-associated induction of peroxisome proliferator-activated receptor-alpha and peroxisome proliferator-activated receptor-gamma correlate with reduced atherosclerosis and improved cardiovascular function in obese insulin-resistant mice.

Background—Weight loss in obese insulin-resistant but not in insulin-sensitive persons reduces coronary heart disease risk. To what extent changes in gene expression are related to atherosclerosis and cardiovascular function is unknown. Methods and Results—We studied the effect of diet restriction–induced weight loss on gene expression in the adipose tissue, the heart, and the aortic arch and on atherosclerosis and cardiovascular function in mice with combined leptin and LDL-receptor deficiency. Obesity, hypertriglyceridemia, and insulin resistance are associated with hypertension, impaired left ventricular function, and accelerated atherosclerosis in those mice. Compared with lean mice, peroxisome proliferator–activated receptors (PPAR)-&agr; and PPAR-&ggr; expression was downregulated in obese double-knockout mice. Diet restriction caused a 45% weight loss, an upregulation of PPAR-&agr; and PPAR-&ggr;, and a change in the expression of genes regulating glucose transport and insulin sensitivity, lipid metabolism, oxidative stress, and inflammation, most of which are under the transcriptional control of these PPARs. Changes in gene expression were associated with increased insulin sensitivity, decreased hypertriglyceridemia, reduced mean 24-hour blood pressure and heart rate, restored circadian variations of blood pressure and heart rate, increased ejection fraction, and reduced atherosclerosis. PPAR-&agr; and PPAR-&ggr; expression was inversely related to plaque volume and to oxidized LDL content in the plaques. Conclusions—Induction of PPAR-&agr; and PPAR-&ggr; in adipose tissue, heart, and aortic arch is a key mechanism for reducing atherosclerosis and improving cardiovascular function resulting from weight loss. Improved lipid metabolism and insulin signaling is associated with decreased tissue deposition of oxidized LDL that increases cardiovascular risk in persons with the metabolic syndrome.

The effect of atorvastatin on postprandial lipaemia in overweight or obese women homozygous for apo E3.

Objective — To determine the effect of atorvastatin on postprandial lipaemia in overweight or obese women with the apoprotein (apo) E3/E3 genotype. Design — Double-blind randomised, placebo-controlled 8-week single-centre study. Subjects — Twenty-two healthy women, homozygous for apo E3 with a BMI ranging from 27.6 to 41.1 kg/m2 and normal or moderately elevated fasting triglycerides (53-184 mg/dl). Treatment — After a 4-week isocaloric single-blind, placebo lead-in period, subjects were randomly assigned to receive either placebo (n = 7) or atorvastatin 20 mg once daily in the evening (n = 15) for 4 weeks. Results — Atorvastatin significantly reduces fasting total cholesterol, LDL-cholesterol and postprandial triglycerides in obese women, homozygous for apo E3 with normal or near-normal fasting triglyceride levels. No significant effect on fasting triglycerides was observed. Conclusion — Atorvastatin decreases postprandial hyperlipidaemia, an independent cardiovascular risk factor, in normolipidaemic obese women.This effect of atorvastatin may, therefore, represent a cardioprotective mechanism.

At similar weight loss, dietary composition determines the degree of glycemic improvement in diet-induced obese C57BL/6 mice

Background Achieving weight loss is the cornerstone of the treatment of the metabolic consequences of obesity, in particular of glucose intolerance. Objective To determine whether improvement in glucose control depends on dietary macronutrient composition of the diet at identical weight loss. Materials and methods Twenty-two weeks old diet-induced obese C57BL/6 mice lost weight through caloric restriction on normal chow (R-NC) or high fat diet (R-HF). Control mice were fed normal chow (LEAN) or high fat diet (OBESE) ad libitum. Body weight and composition were assessed after 8 weeks of dietary intervention. Glucose homeostasis was evaluated by intraperitoneal glucose tolerance tests (IPGTT). Epididymal white adipose (eWAT) and hepatic tissues were analyzed by immunohistochemistry and RT-qPCR. Results By 30 weeks of age, the body weight of the mice on R-NC (31.6±1.7g, mean±SEM) and R-HF (32.3±0.9g) was similar to LEAN mice (31.9±1.4g), while OBESE mice weighed 51.7±2.4g. Glucose tolerance in R-NC was better than in LEAN mice (69% AUC IPGTT, P 0.0168) whereas R-HF mice remained significantly less glucose tolerant (125% AUC IPGTT, P 0.0279 vs LEAN), despite identical weight loss. The eWAT pads and adipocyte size were similar in LEAN and R-NC mice, while the eWAT pad size of R-HF was 180% of R-NC (P < 0.0001) and the average adipocyte size of R-HF mice was 134% of R-NC fed mice (P 0.0285). No LEAN or R-NC mice had hepatic steatosis, in contrast to 28.6% of R-HF mice. Compared to OBESE mice, inflammatory markers were lower in eWAT and liver tissue of R-NC, but not in R-HF mice. Measures of visceral adiposity correlated well with glucose tolerance parameters. Conclusions In mice, caloric restriction on a normal chow diet improved glucose tolerance significantly more when identical weight loss was achieved on a high fat diet.