Is HDL function as important as HDL quantity in the coronary artery disease risk assessment?

Cardiovascular Disease in South Asian Immigrants: a Review of Dysfunctional HDL as a Potential Marker

South Asians (SAs) account for a quarter of the world's population and are one of the fastest-growing immigrant groups in the United States (US). South Asian Immigrants (SAIs) are disproportionately more at risk of developing cardiovascular disease (CVD) than other ethnic/racial groups. Atherosclerosis is a chronic inflammatory disorder and is the major cause of CVD. Traditional CVD risk factors, though important, do not fully explain the elevated risk of CVD in SAIs. High-density lipoproteins (HDLs) are heterogeneous lipoproteins that modify their composition and functionality depending on physiological or pathological conditions. With its cholesterol efflux, anti-inflammatory, and antioxidant functions, HDL is traditionally considered a protective factor for CVD. However, its functions can be compromised under pathological conditions, such as chronic inflammation, making it dysfunctional (Dys-HDL). SAIs have a high prevalence of type 2 diabetes and metabolic syndrome, which may further promote Dys-HDL. This review explores the potential association between Dys-HDL and CVD in SAIs and presents current literature discussing the role of Dys-HDL in CVD.

Determinants of high-density lipoprotein (HDL) functions beyond proteome in Asian Indians: exploring the fatty acid profile of HDL phospholipids

Impaired high-density lipoprotein (HDL) functions are associated with development of coronary artery disease. In this study, we explored the quantitative differences in HDL (i.e. HDL proteome and fatty acid profile of HDL phospholipids) underlying the functional deficits associated with acute coronary syndrome (ACS). The relationship between HDL function and composition was assessed in 65 consecutive ACS patients and 40 healthy controls. Cholesterol efflux capacity (CEC) of HDL and lecithin cholesterol acyl transferase (LCAT) activity were significantly lower in patients with ACS compared to controls. In HDL proteome analysis, HDL isolated from ACS individuals was enriched in apolipoprotein C2 (inhibitor of LCAT), apolipoprotein C4 and serum amyloid A proteins and was deficient in apolipoprotein A-I and A-II. The fatty acid profile of HDL phospholipids analyzed using gas chromatography showed significantly lower percentages of stearic acid (17.4 ± 2.4 vs 15.8 ± 2.8, p = 0.004) and omega-3 fatty acids [eicosapentaenoic acid (1.0 (0.6-1.4) vs 0.7 (0.4-1.0), p = 0.009) and docosahexaenoic acid (1.5 ± 0.7 vs 1.3 ± 0.5, p = 0.03)] in ACS patients compared to controls. Lower percentages of these fatty acids in HDL were associated with higher odds of developing ACS. Our results suggest that distinct phospholipid fatty acid profiles found in HDL from ACS patients could be one of the contributing factors to the deranged HDL functions in these patients apart from the protein content and the inflammatory conditions.

Cuban Sugar Cane Wax Acid and Policosanol Showed Similar Atheroprotective Effects with Inhibition of LDL Oxidation and Cholesteryl Ester Transfer via Enhancement of High-Density Lipoproteins Functionality

Background

Cuban sugarcane wax acids (SCWA) and policosanol (PCO) are mixtures of higher aliphatic acids and alcohols, respectively, purified from sugarcane wax with different chief components. Although it has been known that they have antioxidant and anti-inflammatory activities, physiological properties on molecular mechanism of SCWA have been less studied than PCO.

Methods

In this study, we compared antiatherogenic activities of SCWA and PCO via encapsulation with reconstituted high-density lipoproteins (rHDL).

Results

After reconstitution, SCWA-rHDL showed smaller particle size than PCO-rHDL with increase of content. PCO-rHDL or SCWA-rHDL showed distinct inhibition of glycation with similar extent in the presence of fructose. PCO-rHDL or SCWA-rHDL showed strong antioxidant activity against cupric ion-mediated oxidation of low-density lipoproteins (LDL), and inhibition of oxLDL uptake into macrophages. Although PCO-rHDL showed 1.2-fold stronger inhibition against cholesteryl ester transfer protein (CETP) activity than SCWA-rHDL, SCWA-rHDL enhanced 15% more brain cell (BV-2) growth and 23% more regeneration of tail fin in zebrafish.

Conclusion

PCO and SCWA both enhance the beneficial functions of HDL to maximize its antioxidant, antiglycation, and antiatherosclerotic activities and the inhibition of CETP. These enhancements of HDL functionality by PCO and SCWA could exert antiaging and rejuvenation activity.

Impact of Lifestyle Intervention on HDL-Induced eNOS Activation and Cholesterol Efflux Capacity in Obese Adolescent

Background. Endothelial dysfunction occurs in obese children and adolescent and is regarded as a key step in the development of atherosclerosis. Important components for the development of endothelial dysfunction are reduced activity of endothelial nitric oxide synthase (eNOS) and an increase in cholesterol deposition in the vessel wall, due to reduced reverse cholesterol transport (RCT) activity. High density lipoprotein (HDL) exhibits antiatherosclerotic properties including modulation of eNOS activity and cholesterol efflux capacity. Lifestyle intervention programs can modify endothelial dysfunction in obese adolescents, but their impact on HDL-mediated eNOS activation and RCT is unknown so far. Methods. Obese adolescents (15 ± 1 years, BMI > 35 kg/m²) where randomized either to an intervention group (IG, n = 8; restricted diet and exercise) or to a usual care group (UC, n = 8). At the beginning and after 10 months of treatment HDL-mediated eNOS phosphorylation and cholesterol efflux capacity were evaluated. Results. Ten months of treatment resulted in a substantial weight loss (−31%), an improvement of endothelial function, and an increase in HDL-mediated eNOS-Ser¹¹⁷⁷ phosphorylation and RCT. A correlation between change in eNOS-Ser¹¹⁷⁷ phosphorylation or RCT and change in endothelial function was noted. Conclusion. A structured lifestyle intervention program improves antiatherosclerotic HDL functions, thereby positively influencing endothelial function.

Proteome profiles of HDL particles of patients with chronic heart failure are associated with immune response and also include bacteria proteins

Besides modulation of reverse cholesterol transport, high density lipoprotein (HDL) is able to modulate vascular function by stimulating endothelial nitric oxide synthase. Recently, it could be documented that this function of HDL was significantly impaired in patients with chronic heart failure (CHF). We investigated alterations in the HDL proteome in CHF patients. Therefore, HDL was isolated from 5 controls (HDLhealthy) and 5 CHF patients of NYHA-class IIIb (HDLCHF). Proteome analysis of HDL particles was performed by two-dimensional liquid chromatography-mass spectrometry (SCX/RP LC-MS/MS). In total, we identified 494 distinct proteins, of which 107 proteins were commonly found in both groups (HDLCHF and HDLhealthy) indicating a high inter-subject variability across HDL particles. Several important proteins (e.g. ITGA2, APBA1 or A2M) varied in level. Functional analysis revealed regulated pathways. A minor proportion of bacteria-derived proteins were also identified in the HDL-particles. The extension of the list of HDL-associated proteins allows besides their mere description new insights into alterations in HDL function in diseases. In addition, the detection of bacterial proteins bound to HDL will broaden our view of HDL not only as a cholesterol carrier but also as a carrier of proteins.

Cholesterol Metabolism in CKD

Patients with chronic kidney disease (CKD) have a substantial risk of developing coronary artery disease. Traditional cardiovascular disease (CVD) risk factors such as hypertension and hyperlipidemia do not adequately explain the high prevalence of CVD in CKD. Both CVD and CKD are inflammatory states and inflammation adversely affects lipid balance. Dyslipidemia in CKD is characterized by elevated triglyceride levels and high-density lipoprotein levels that are both decreased and dysfunctional. This dysfunctional high-density lipoprotein becomes proinflammatory and loses its atheroprotective ability to promote cholesterol efflux from cells, including lipid-overloaded macrophages in the arterial wall. Elevated triglyceride levels result primarily from defective clearance. The weak association between low-density lipoprotein cholesterol level and coronary risk in CKD has led to controversy over the usefulness of statin therapy. This review examines disrupted cholesterol transport in CKD, presenting both clinical and preclinical evidence of the effect of the uremic environment on vascular lipid accumulation. Preventative and treatment strategies are explored.

High-density lipoprotein oxidation in type 2 diabetic patients and young patients with premature myocardial infarction

BACKGROUND AND AIMS

ApoA-I can undergo oxidative changes that reduce anti-atherogenic role of HDL. The aim of this study was to seek any significant differences in methionine sulfoxide (MetO) content in the ApoA-I of HDL isolated from young patients with coronary heart disease (CHD), type 2 diabetics and healthy subjects.

METHODS AND RESULTS

We evaluated the lipid profile of 21 type 2 diabetic patients, 23 young patients with premature MI and 21 healthy volunteers; we determined in all patients the MetO content of ApoA-I in by MALDI/TOF/TOF technique. The typical MALDI spectra of the tryptic digest obtained from HDL plasma fractions all patients showed a relative abundance of peptides containing Met(112)O in ApoA-I in type 2 diabetic and CHD patients. This relative abundance is given as percentages of oxidized ApoA-I (OxApoA-I). OxApoA-I showed no significant correlations with lipoproteins in all patients studied, while a strong correlation emerged between the duration of diabetic disease and OxApoA-I levels in type 2 diabetic patients.

CONCLUSIONS

The most remarkable finding of our study lies in the evidence it produced of an increased HDL oxidation in patients highly susceptible to CHD. Levels of MetO residues in plasma ApoA-I, measured using an accurate, specific method, should be investigated and considered in prospective future studies to assess their role in CHD.

Rosiglitazone attenuates atherosclerosis and increases high-density lipoprotein function in atherosclerotic rabbits

Rosiglitazone has been found to have anti-atherogenic effects and to increase serum high-density lipoprotein (HDL) cholesterol (HDL-C) levels. However, in vivo studies investigating the regulation of adenosine triphosphate-binding cassette transporter A1 (ABCA1) and scavenger receptor class B type I (SR-BI) by rosiglitazone are limited. Moreover, the effects of rosiglitazone on the function and levels of HDL are unclear. In the present study, we investigated the effects of rosiglitazone on HDL function and its mechanisms of action in atherosclerotic rabbits. Our results revealed that rosiglitazone induced a significant increase in serum HDL-C levels, paraoxonase 1 (PON1) activity, [³H]cholesterol efflux rates, and the expression of ABCA1 and SR-BI in hepatocytes and peritoneal macrophages. The expression of ABCA1 was also increased in aortic lesions. Rosiglitazone markedly reduced serum myeloperoxidase (MPO) activity, aortic intima-media thickness (IMT) and the percentage of plaque area in the aorta. It can thus be concluded that in atherosclerotic rabbits, rosigitazone increases the levels of HDL-C and hinders atherosclerosis. Thus, it improves HDL quality and function, as well as the HDL-induced cholesterol efflux, exerting anti-inflammatory and antioxidant effects.

HDL anti-oxidant function associates with LDL level in young adults

OBJECTIVES

The primary objective was to evaluate predictors of HDL anti-oxidant function in young adults.

BACKGROUND

High-density lipoprotein (HDL) cholesterol is considered a protective factor for cardiovascular disease (CVD). However, increased levels are not always associated with decreased cardiovascular risk. A better understanding of the importance of HDL functionality and how it affects CVD risk is needed.

METHODS

Fifty non-Hispanic white subjects from the Testing Responses on Youth (TROY) study were randomly selected to investigate whether differences in HDL anti-oxidant function are associated with traditional cardiovascular risk factors, including carotid intima media thickness (CIMT), arterial stiffness and other inflammatory/metabolic parameters. HDL anti-oxidant capacity was evaluated by assessing its ability to inhibit low-density lipoprotein (LDL) cholesterol oxidation by air using a DCF-based fluorescent assay and expressed as a HDL oxidant index (HOI). The associations between HOI and other variables were assessed using both linear and logistic regression.

RESULTS

Eleven subjects (25%) had an HOI ≥ 1, indicating a pro-oxidant HDL. Age, LDL, high sensitivity C-reactive protein (hsCRP), and paraoxonase activity (PON1), but not HDL, were all associated with HOI level in univariate linear regression models. In multivariate models that mutually adjusted for these variables, LDL remained the strongest predictor of HOI (0.13 increase in HOI per 1 SD increase in LDL, 95% CI 0.04, 0.22). Atherogenic index of plasma, pulse pressure, homocysteine, glucose, insulin, CIMT and measurements of arterial stiffness were not associated with HOI in this population.

CONCLUSIONS

These results suggest LDL, hsCRP and DBP might predict HDL anti-oxidant function at an early age.

Myeloperoxidase-derived oxidants modify apolipoprotein A-I and generate dysfunctional high-density lipoproteins: comparison of hypothiocyanous acid (HOSCN) with hypochlorous acid (HOCl)

Oxidative modification of HDLs (high-density lipoproteins) by MPO (myeloperoxidase) compromises its anti-atherogenic properties, which may contribute to the development of atherosclerosis. Although it has been established that HOCl (hypochlorous acid) produced by MPO targets apoA-I (apolipoprotein A-I), the major apolipoprotein of HDLs, the role of the other major oxidant generated by MPO, HOSCN (hypothiocyanous acid), in the generation of dysfunctional HDLs has not been examined. In the present study, we characterize the structural and functional modifications of lipid-free apoA-I and rHDL (reconstituted discoidal HDL) containing apoA-I complexed with phospholipid, induced by HOSCN and its decomposition product, OCN− (cyanate). Treatment of apoA-I with HOSCN resulted in the oxidation of tryptophan residues, whereas OCN− induced carbamylation of lysine residues to yield homocitrulline. Tryptophan residues were more readily oxidized on apoA-I contained in rHDLs. Exposure of lipid-free apoA-I to HOSCN and OCN− significantly reduced the extent of cholesterol efflux from cholesterol-loaded macrophages when compared with unmodified apoA-I. In contrast, HOSCN did not affect the anti-inflammatory properties of rHDL. The ability of HOSCN to impair apoA-I-mediated cholesterol efflux may contribute to the development of atherosclerosis, particularly in smokers who have high plasma levels of SCN− (thiocyanate).

Lipids and lipoproteins and risk of different vascular events in the MRC/BHF Heart Protection Study

BACKGROUND

Low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol are established risk factors for vascular disease, but lipoprotein particle concentrations may be stronger determinants of risk.

METHODS AND RESULTS

Associations between vascular events and baseline concentrations of cholesterol fractions, apolipoproteins B and A(1), and lipoprotein particles assessed by nuclear magnetic resonance were considered in the Heart Protection Study randomized trial of simvastatin versus placebo (>5000 vascular events during 5.3 years of follow-up among 20 000 participants). Major occlusive coronary events were equally strongly associated with the cholesterol- and particle-based total LDL measures; adjusted hazard ratios per 1-SD-higher level were 1.25 (95% confidence interval [CI], 1.16-1.34) for LDL cholesterol, 1.22 (95% CI, 1.14-1.32) for non-HDL cholesterol, 1.23 (95% CI, 1.15-1.33) for apolipoprotein B, and 1.25 (95% CI, 1.16-1.35) for LDL particle number. Given the total LDL particle number, the distribution between small and large particles did not add predictive value. Associations of these different LDL-related measures were similar with arterial revascularization procedures but much weaker or nonexistent with ischemic stroke and other cardiac events (mainly heart failure). After adjustment for LDL particle number, the hazard ratios for major occlusive coronary event per 1-SD-higher level were 0.91 (95% CI, 0.86-0.96) for HDL cholesterol and 0.89 (95% CI, 0.85-0.93) for HDL particle number. Other cardiac events were inversely associated with total (hazard ratio, 0.84; 95% CI, 0.79-0.90) and small (0.82; 95% CI, 0.76-0.89) HDL particle number but only very weakly associated with HDL cholesterol (0.94; 95% CI, 0.88-1.00).

CONCLUSIONS

In a population at 2% average coronary event risk per year, cholesterol, apolipoprotein, and particle measures of LDL were strongly correlated and had similar predictive values for incident major occlusive vascular events. It is unclear whether the associations between HDL particle numbers and other cardiac events represent a causal or reverse-causal effect.

Laboratory investigation of dysfunctional HDL

High-density lipoprotein (HDL) particles are anti-atherosclerotic, by virtue of their functions in reverse cholesterol transportation, anti-inflammation and anti-oxidation. However, recent studies have cast doubt on the cardio-protective role of HDL. Structural modification and composition alteration of HDL due to chronic inflammation and acute phase responses may result in loss of normal biological function and even convert HDL into a pro-inflammatory and pro-oxidative agent. Therefore, the assessment of dysfunctional HDL has become a novel target to investigate the association between HDL and coronary artery disease risk. This review article summarizes the laboratory assessment of dysfunctional HDL.