Serum high-density lipoprotein-cholesterol levels modify the association between plasma levels of oxidatively modified low-density lipoprotein and coronary artery disease in men

Elevated concentration of oxidized LDL together with poor cardiorespiratory and abdominal muscle fitness predicts metabolic syndrome in young men

BACKGROUND

Metabolic syndrome (MetS) is associated with increased oxidized LDL (ox-LDL), systemic inflammation, and poor cardiorespiratory fitness. We examined affiliations of these factors and the effect of muscular fitness on MetS in young healthy men.

METHODS

Physical fitness, ox-LDL, tumor necrosis factor α (TNFα), interleukin-6 (IL-6) and serum lipids were measured in a nationally representative sample of Finnish young men with and without MetS. Participants (mean age 25.1years) performed tests of maximal oxygen uptake (VO₂max) and muscle fitness, and were divided into MetS (n=54, IDF 2007 criteria) and non-MetS (n=790). Age, smoking and leisure-time physical activity were used as covariates (ANCOVA).

RESULTS

The MetS group had lower results in VO₂max and all of the muscular fitness tests (excluding grip strength) (P<0.0001, in all). Ox-LDL, ox-LDL/HDL-cholesterol, ox-LDL/LDL-cholesterol, TNFα and IL-6 were all higher in the MetS group than in the non-MetS group (P<0.01, in all). In stepwise multivariate logistic regression analysis (adjusted to MetS criteria), higher ox-LDL (OR 1.118, 95% CI 1.078-1.160), lower VO₂max (OR 0.938, 95% CI 0.901-0.977) and lower sit-ups (OR 0.898, 95% CI 0.844-0.956) predicted MetS (p<0.05, in all).

CONCLUSIONS

Young men with MetS possess significantly poorer cardiorespiratory and muscle fitness, together with elevated systemic levels of ox-LDL, TNFα and IL-6 compared to non-MetS young men. Of these variables, ox-LDL, VO₂max and sit-ups predicted MetS. Based on these findings, poor physical fitness and elevated concentration of ox-LDL are significant predisposing factors in the development of MetS.

High-density lipoprotein cholesterol and residual cardiometabolic risk in metabolic syndrome

It has long been recognized that elevated levels of low-density lipoprotein cholesterol (LDL-C) increase the risk of cardiovascular disease (CVD) and that pharmacologic therapy to decrease LDL-C significantly reduces cardiovascular events. Despite the effectiveness of statins for CVD risk reduction, even optimal LDL-lowering therapy alone fails to avert approximately 60% to 70% of CVD cases, and the incidence of CVD mortality continues to grow. A low plasma concentration of high-density lipoprotein cholesterol (HDL-C) is also associated with increased risk of CVD and is 1 component of metabolic syndrome, a cluster of interrelated CVD risk factors. HDL stimulates reverse cholesterol transport from the peripheral tissues to the liver for removal from the body, prevents deleterious effects of LDL on endothelial function, acts as an antioxidant, and also possesses anti-inflammatory, antithrombotic, and antiapoptotic effects. Some of the treatments that increase HDL-C concentrations have been shown to reduce atheroma volume and may prevent the formation of new atherosclerotic lesions, thereby reducing the risk of CVD. For these reasons, increasing HDL-C concentrations has become a potentially attractive therapeutic target for individuals who are at increased risk of CVD, including those with metabolic syndrome. Traditional strategies to increase HDL-C include the use of niacin, statins, and fibric acid derivatives. Pharmacotherapies that have recently been developed and are currently being evaluated include inhibition of the enzyme cholesteryl ester transfer protein (CETP) and antagonism of the endocannabinoid CB1 receptor. Initial studies of CETP inhibitors suggest that these agents may markedly increase HDL-C concentrations. Clinical trials with rimonabant, a CB1 receptor antagonist, have demonstrated significant weight loss as well as increased HDL-C levels and reduced triglyceride levels.

C-Reactive Protein and Other Emerging Blood Biomarkers to Optimize Risk Stratification of Vulnerable Patients

Several emerging plasma biomarkers may ultimately prove useful in risk stratification and prognosis of cardiovascular disease. The clinical utility of these biomarkers will depend on their ability to provide a reflection of the underlying atherosclerotic burden or activity; the ability to provide reliable, accurate, and cost-effective information; and the ability to predict future events. High-sensitivity C-reactive protein (hs-CRP) fulfills many, if not all, of these criteria, and blood levels of hs-CRP are now commonly used in clinical practice to improve vascular risk prediction in primary and secondary prevention across all levels of low-density lipoprotein-cholesterol (LDL-C), all levels of the Framingham Risk Score, and all levels of metabolic syndrome. High-sensitivity C-reactive protein may also have clinical relevance as an adjunct to LDL-C for both the targeting and monitoring of statin therapy. Accumulating evidence suggests that several other selected emerging biomarkers may also potentially prove useful in the diagnosis and prognosis of cardiovascular disease. Specifically, data are accumulating on the potential clinical utility of lipoprotein-associated lipoprotein-associated phospholipase A2, myeloperoxidase, oxidized LDL, lipoprotein (a), isoprostanes, and small, dense LDL. This review focuses on hs-CRP and these emerging plasma biomarkers, and their potential diagnostic and prognostic utility in cardiovascular disease. Plasma biomarkers that reflect the clinical potential of atherothrombotic disease may allow more precise risk stratification and prognostication in high-risk populations, and perhaps earlier diagnosis and intervention in patients at risk for or with occult cardiovascular disease.

Oxidized low-density lipoprotein biomarkers in atherosclerosis

The concept that the oxidation of lipoproteins is central in the pathogenesis of atherosclerosis was first reported over 25 years ago, initially by in vitro studies and subsequently through experimental models of atherosclerosis. The innate immune system plays a key role in atherogenesis as manifested by its atherosclerosis-modulating properties, the immunogenicity of oxidized low-density lipoprotein (LDL), and the presence of oxidized LDL autoantibodies in plasma and lesions of humans. In the past 10 years it has been possible to generate monoclonal antibodies to oxidized LDL to directly measure oxidized LDL in plasma. This has led to a rapidly accelerating pace of new reports on the relationship of circulating oxidized LDL and various cardiovascular pathologic processes, which are the focus of this review.