A short amphipathic alpha helix in scavenger receptor BI facilitates bidirectional HDL-cholesterol transport.

During reverse cholesterol transport, high-density lipoprotein (HDL) carries excess cholesterol from peripheral cells to the liver for excretion in bile. The first and last steps of this pathway involve the HDL receptor, scavenger receptor BI (SR-BI). While the mechanism of SR-BI-mediated cholesterol transport has not yet been established, it has long been suspected that cholesterol traverses through a hydrophobic tunnel in SR-BI's extracellular domain. Confirmation of a hydrophobic tunnel is hindered by the lack of a full-length SR-BI structure. Part of SR-BI's structure has been resolved, encompassing residues 405 to 475, which includes the C-terminal transmembrane domain and its adjacent extracellular region. Within the extracellular segment is an amphipathic helix (residues 427-436, referred to as AH(427-436)) that showed increased protection from solvent in NMR-based studies. Homology models predict that hydrophobic residues in AH(427-436) line a core cavity in SR-BI's extracellular region that may facilitate cholesterol transport. Therefore, we hypothesized that hydrophobic residues in AH(427-436) are required for HDL cholesterol transport. Here, we tested this hypothesis by mutating individual residues along AH(427-436) to a charged residue (aspartic acid), transiently transfecting COS-7 cells with plasmids encoding wild-type and mutant SR-BI, and performing functional analyses. We found that mutating hydrophobic, but not hydrophilic, residues in AH(427-436) impaired SR-BI bidirectional cholesterol transport. Mutating phenylalanine-430 was particularly detrimental to SR-BI's functions, suggesting that this residue may facilitate important interactions for cholesterol delivery within the hydrophobic tunnel. Our results support the hypothesis that a hydrophobic tunnel within SR-BI mediates cholesterol transport.

The Potential Role of Electronegative High-Density Lipoprotein H5 Subfraction in RA-Related Atherosclerosis.

Although the heterogeneity of high-density lipoprotein-cholesterol (HDL-c) composition is associated with atherosclerotic cardiovascular risk, the link between electronegative subfractions of HDL-c and atherosclerosis in rheumatoid arthritis (RA) remains unknown. We examined the association of the percentage of the most electronegative subfraction of HDL-c (H5%) and RA-related atherosclerosis. Using anion-exchange purification/fast-protein liquid chromatography, we demonstrated significantly higher H5% in patients (median, 7.2%) than HC (2.8%, p < 0.005). Multivariable regression analysis revealed H5% as a significant predictor for subclinical atherosclerosis. We subsequently explored atherogenic role of H5 using cell-based assay. The results showed significantly higher levels of IL-1ß and IL-8 mRNA in H5-treated (mean ± SD, 4.45 ± 1.22 folds, 6.02 ± 1.43-folds, respectively) than H1-treated monocytes (0.89 ± 0.18-folds, 1.03 ± 0.26-folds, respectively, both p < 0.001). In macrophages, H5 upregulated the mRNA and protein expression of IL-1ß and IL-8 in a dose-dependent manner, and their expression levels were significantly higher than H1-treated macrophages (all p < 0.001). H5 induced more foam cell formation compared with H1-treated macrophages (p < 0.005). In addition, H5 has significantly lower cholesterol efflux capacity than H1 (p < 0.005). The results of nanoLC-MS/MS approach reveal that the best discriminator between high-H5% and normal-H5% is Apo(a), the main constituent of Lp(a). Moreover, Lp(a) level is a significant predictor for high-H5%. These observations suggest that H5 is involved in RA-related atherosclerosis.

New insights into the emerging effects of inflammatory response on HDL particles structure and function.

According to the increasing results, it has been well-demonstrated that the chronic inflammatory response, including systemic lupus erythematosus, rheumatoid arthritis, and inflammatory bowel disease are associated with an increased risk of atherosclerotic cardiovascular disease. The mechanism whereby inflammatory response up-regulates the risk of cardio-metabolic disorder disease is multifactorial; furthermore, the alterations in high density lipoprotein (HDL) structure and function which occur under the inflammatory response could play an important modulatory function. On the other hand, the serum concentrations of HDL cholesterol (HDL-C) have been shown to be reduced significantly under inflammatory status with remarked alterations in HDL particles. Nevertheless, the potential mechanism whereby the inflammatory response reduces serum HDL-C levels is not simply defined but reduces apolipoprotein A1 production. The alterations in HDL structure mediated by the inflammatory response has been also confirmed to decrease the ability of HDL particle to play an important role in reverse cholesterol transport and protect the LDL particles from oxidation. Recently, it has been shown that under the inflammatory condition, diverse alterations in HDL structure could be observed which lead to changes in HDL function. In the current review, the emerging effects of inflammatory response on HDL particles structure and function are well-summarized to elucidate the potential mechanism whereby different inflammatory status modulates the pathogenic development of dyslipidemia.

Apolipoprotein A-I modulates HDL particle size in the absence of apolipoprotein A-II.

Human high-density lipoproteins (HDLs) are a complex mixture of structurally related nanoparticles that perform distinct physiological functions. We previously showed that human HDL containing apolipoprotein A-I (APOA1) but not apolipoprotein A-II (APOA2), designated LpA-I, is composed primarily of two discretely sized populations. Here, we isolated these particles directly from human plasma by antibody affinity chromatography, separated them by high-resolution size-exclusion chromatography and performed a deep molecular characterization of each species. The large and small LpA-I populations were spherical with mean diameters of 109 Å and 91 Å, respectively. Unexpectedly, isotope dilution MS/MS with [15N]-APOA1 in concert with quantitation of particle concentration by calibrated ion mobility analysis demonstrated that the large particles contained fewer APOA1 molecules than the small particles; the stoichiometries were 3.0 and 3.7 molecules of APOA1 per particle, respectively. MS/MS experiments showed that the protein cargo of large LpA-I particles was more diverse. Human HDL and isolated particles containing both APOA1 and APOA2 exhibit a much wider range and variation of particle sizes than LpA-I, indicating that APOA2 is likely the major contributor to HDL size heterogeneity. We propose a ratchet model based on the trefoil structure of APOA1 whereby the helical cage maintaining particle structure has two "settings"-large and small-that accounts for these findings. This understanding of the determinants of HDL particle size and protein cargo distribution serves as a basis for determining the roles of HDL subpopulations in metabolism and disease states.

Particle size and cholesterol content of circulating HDL correlate with cardiovascular death in chronic heart failure.

Evidence regarding any association of HDL-particle (HDL-P) derangements and HDL-cholesterol content with cardiovascular (CV) death in chronic heart failure (HF) is lacking. To investigate the prognostic value of HDL-P size (HDL-Sz) and the number of cholesterol molecules per HDL-P for CV death in HF patients. Outpatient chronic HF patients were enrolled. Baseline HDL-P number, subfractions and HDL-Sz were measured using 1H-NMR spectroscopy. The HDL-C/P ratio was calculated as HDL-cholesterol over HDL-P. Endpoint was CV death, with non-CV death as the competing event. 422 patients were included and followed-up during a median of 4.1 (0-8) years. CV death occurred in 120 (30.5%) patients. Mean HDL-Sz was higher in CV dead as compared with survivors (8.39 nm vs. 8.31 nm, p < 0.001). This change in size was due to a reduction in the percentage of small HDL-P (54.6% vs. 60% for CV-death vs. alive; p < 0.001). HDL-C/P ratio was higher in the CV-death group (51.0 vs. 48.3, p < 0.001). HDL-Sz and HDL-C/P ratio were significantly associated with CV death after multivariable regression analysis (HR 1.22 [95% CI 1.01-1.47], p = 0.041 and HR 1.04 [95% CI 1.01-1.07], p = 0.008 respectively). HDL-Sz and HDL-C/P ratio are independent predictors of CV death in chronic HF patients.

Efeito do treinamento aeróbio em parâmetros cardiorrespiratórios, hemodinâmicos e autonômicos de pacientes com doença renal crônica em hemodiálise / Effect of aerobic training on cardiorespiratory, hemodynamic, and autonomic parameters of chronic kidney disease patients on hemodialysis

A doença renal crônica (DRC) é uma condição clínica de alto risco cardiovascular e os pacientes nos estágios mais avançados da doença que dependem de terapia renal substitutiva frequentemente tem prejuízo cardiorespiratório, níveis elevados de pressão arterial (uso de múltiplas medicações para controle), modulação autonômica prejudicada e graus variados de inflamação. Deste modo este estudo tem como objetivo verificar se o exercício físico aeróbio intradialítico tem impacto em modificar estas alterações. Os pacientes foram selecionados em duas unidades de hemodiálise em São Luís do Maranhão, Brasil, entre junho de 2016 e outubro de 2019, e foram alocados conforme aceitação em grupo controle (GC) e grupo exercício (GE). O GE foi submetido a treinamento aeróbio com bicicleta por um período de 12 semanas. Avaliação física antropométrica, teste de caminhada de 6 minutos (TC6m), ecocardiograma, eletrocardiograma com análise da variabilidade da frequência cardíaca e medidas laboratoriais foram realizadas incluindo interleucina 6 (IL6) antes e após 12 semanas em ambos os grupos. Trinta e um pacientes foram avaliados 15 pacientes no grupo controle (GC) e 16 pacientes no grupo exercício (GE). Após 12 semanas de treinamento houve diminuição da pressão arterial sistólica do grupo exercício em relação ao basal (129,8 ± 9,41mmHg vs 112,00 ± 12,0 mmHg p = 0,03). Não houve alterações na composição corporal e na maioria dos exames laboratoriais, exceto pelo aumento do KTV (índice de adequação de diálise) e diminuição do LDL colesterol no grupo exercício em relação ao grupo controle. No entanto, os níveis de HDL colesterol aumentaram (39,92 ± 6,1 mg/dL vs 48,00 ± 7,85 mg/dL p = 0,02) e IL6 diminuíram (4,56 ± 1,2 pg / mL vs 2,14 ± 1,0 pg / mL p = 0,02). Houve aumento da distância percorrida no teste de caminhada no grupo exercício (473,80 ± 98,6 metros vs 573,50 ± 74,22 metros p = 0,01). Na avaliação ecocardiográfica, verificou-se que no GE houve diminuição da pressão da artéria pulmonar estimada (31,38 ± 2,9 mmhg vs 24,2 ± 1,7 mmhg p = 0,001). Houve melhora na modulação autonômica no GE (RMSSD 11,7 ± 4,2 vs 18,4 ± 5,7 p=0,02), LFnu (52,9 ± 17,2 vs 32,0 ± 18,2 p=0,02) e HFnu (48,1 ± 17,2 vs 68,0 ± 18,2 p=0,01). Não foram evidenciados efeitos adversos e não houve abandono do treinamento. Baseados nestes resultados, é possível concluir que o exercício aeróbio intradialítico por 12 semanas pode melhorar parâmetros cardiorrespiratórios, hemodinâmicos e autonômicos, com boa aderência e sem eventos adversos, podendo ser usado como medida coadjuvante para melhora clínica destes pacientes.

Chronic kidney disease (CKD) is a clinical condition of high cardiovascular risk and patients in the more advanced stages of the disease who depend on renal replacement therapy often experience cardiorespiratory impairment, high blood pressure levels (use of multiple medications for control), modulation impaired autonomy and varying degrees of inflammation. Thus, this study aims to verify whether intradialytic aerobic exercise has an impact on modifying these variables. The patients were selected in two hemodialysis units in São Luís do Maranhão, Brazil, between May 2016 and October 2019, and were allocated according to acceptance in the control group (CG) and exercise group (EG). The group exercise was submitted to aerobic exercise with bicycle for a period of 12 weeks. Anthropometric physical evaluation, 6-minute walk test (6MWT), echocardiogram, electrocardiogram with analysis of heart rate variability (VFC) and laboratory measurements were performed including interleukin 6 (IL6) before and after 12 weeks in both groups. Thirty-one patients were evaluated 15 patients in the control group (CG) and 16 patients in the exercise group (EG). After 12 weeks of training, there was a decrease in systolic blood pressure in the exercise group compared to baseline (129.8 ± 9.41 mmHg vs 112.00 ± 12.0 mmhg p = 0.03). There were no changes in body composition and in most laboratory tests, except for an increase in KTV (dialysis adequacy index) and a decrease in LDL cholesterol in the exercise group compared to the control group. However, HDL cholesterol levels increased (39.92 ± 6.1 mg / dL vs 48.00 ± 7.85 mg / dL p = 0.02) and IL6 decreased (4.56 ± 1.2 pg / mL vs 2.14 ± 1.0 pg / mL p = 0.02). There was an increase in the distance covered in the walking test in the exercise group (473.80 ± 98.6 m vs 573.50 ± 74.22 m p = 0,01). In the echocardiographic evaluation, it was found that in the EG there was a decrease in the estimated pulmonary artery pressure (31.38 ± 2.9 mmhg vs 24.2 ± 1.7 mmhg p = 0.001). There was an improvement in autonomic modulation in the EG (RMSSD 11.7 ± 4.2 vs 18.4 ± 5.7 p = 0.02), LFnu (52.9 ± 17.2 vs 32.0 ± 18.2 p = 0.02) and HFnu (48.1 ± 17.2 vs 68.0 ± 18.2 p = 0.01). There were no adverse effects and training was not abandoned. Based on these results, it is possible to conclude that intradialytic aerobic exercise for 12 weeks can improve cardiorespiratory, hemodynamic, and autonomic parameters, with good adherence and without adverse events, and can be used as a supporting measure for the clinical improvement of these patients.

Nascent HDL (High-Density Lipoprotein) Discs Carry Cholesterol to HDL Spheres: Effects of HDL Particle Remodeling on Cholesterol Efflux.

OBJECTIVE: To characterize the fate of protein and lipid in nascent HDL (high-density lipoprotein) in plasma and explore the role of interaction between nascent HDL and mature HDL in promoting ABCA1 (ATP-binding cassette transporter 1)-dependent cholesterol efflux. Approach and Results: Two discoidal species, nascent HDL produced by RAW264.7 cells expressing ABCA1 (LpA-I [apo AI containing particles formed by incubating ABCA1-expressing cells with apo AI]), and CSL112, human apo AI (apolipoprotein AI) reconstituted with phospholipids, were used for in vitro incubations with human plasma or purified spherical plasma HDL. Fluorescent labeling and biotinylation of HDL were employed to follow the redistribution of cholesterol and apo AI, cholesterol efflux was measured using cholesterol-loaded cells. We show that both nascent LpA-I and CSL112 can rapidly fuse with spherical HDL. Redistribution of the apo AI molecules and cholesterol after particle fusion leads to the formation of (1) enlarged, remodeled, lipid-rich HDL particles carrying lipid and apo AI from LpA-I and (2) lipid-poor apo AI particles carrying apo AI from both discs and spheres. The interaction of discs and spheres led to a greater than additive elevation of ABCA1-dependent cholesterol efflux. CONCLUSIONS: These data demonstrate that although newly formed discs are relatively poor substrates for ABCA1, they can interact with spheres to produce lipid-poor apo AI, a much better substrate for ABCA1. Because the lipid-poor apo AI generated in this interaction can itself become discoid by the action of ABCA1, cycles of cholesterol efflux and disc-sphere fusion may result in net ABCA1-dependent transfer of cholesterol from cells to HDL spheres. This process may be of particular importance in atherosclerotic plaque where cholesterol acceptors may be limiting.

Organ-specific lymphatics play distinct roles in regulating HDL trafficking and composition.

Recently, peripheral lymphatic vessels were found to transport high-density lipoprotein (HDL) from interstitial tissues to the blood circulation during reverse cholesterol transport. This function is thought to be critical to the clearance of cholesterol from atherosclerotic plaques. The role of organ-specific lymphatics in modulating HDL transport and composition is, however, incompletely understood. This study aimed to 1) determine the contribution of the lymphatics draining the intestine and liver (which are major sites of HDL synthesis) to total (thoracic) lymph HDL transport and 2) verify whether the HDLs in lymph are derived from specific organs and are modified during trafficking in lymph. The mesenteric, hepatic, or thoracic lymph duct was cannulated in nonfasted Sprague-Dawley rats, and lymph was collected over 5 h under anesthesia. Whole lymph and specific lymph lipoproteins (isolated by ultracentrifugation) were analyzed for protein and lipid composition. The majority of thoracic lymph fluid, protein, and lipid mass was sourced from the mesenteric, and to a lesser extent, hepatic lymph. Mesenteric and thoracic lymph were both rich in chylomicrons and very low-density lipoprotein, whereas hepatic lymph and plasma were HDL-rich. The protein and lipid mass in thoracic lymph HDL was mostly sourced from mesenteric lymph, whereas the cholesterol mass was equally sourced from mesenteric and hepatic lymph. HDLs were compositionally distinct across the lymph sources and plasma. The composition of HDL also appeared to be modified during passage from the mesenteric and hepatic to the thoracic lymph duct. Overall, this study demonstrates that the lipoproteins in lymph are organ specific in composition, and the intestine and liver appear to be the main source of HDL in the lymph.NEW & NOTEWORTHY High-density lipoprotein in lymph are organ-specific in composition and derive mostly from the intestine and liver. High-density lipoprotein also appears to be remodeled during transport through the lymphatics. These findings have implications to cardiometabolic diseases that involve perturbations in lipoprotein distribution and metabolism.

HDL Subclass Analysis in Predicting Metabolic Syndrome in Koreans With High HDL Cholesterol Levels.

BACKGROUND: High-density lipoprotein cholesterol (HDL-C) is a complex mixture of subclasses with heterogeneous atheroprotective activities. We analyzed HDL-C subclass in relation to cardiovascular risk and metabolic syndrome (MetS) in a population with high HDL-C levels. METHODS: A total of 300 Korean individuals with high HDL-C levels (≥2.331 mmol/L) were enrolled following a comprehensive general medical examination including body composition analysis. HDL3-C levels were measured using the HDL3-EX SEIKEN kit (Randox Ltd., Crumlin, UK) and non-HDL3-C levels were calculated by subtracting HDL3-C levels from total HDL-C levels. RESULTS: HDL3-C levels and HDL3-C proportion had a weak positive correlation with low-density lipoprotein cholesterol (LDL-C) and triglycerides (r=0.21, r=0.25; r=0.26, r=0.34, respectively, all P<0.001); in contrast, non-HDL3-C levels had a weak negative correlation with these parameters (r=-0.17 and r=-0.25, respectively, both P<0.005). HDL3-C levels and HDL3-C proportion were significantly higher in the MetS group (N=8) than in the non-MetS group (0.71 vs 0.63 mmol/L, P=0.001; 29.7 vs 25.8%, P=0.001, respectively); these were the only predictors of MetS among the lipid variables (areas under the curves [AUC]=0.84 and 0.83, respectively, both P=0.001). CONCLUSIONS: In populations with high HDL-C levels, HDL-C subclass may provide a greater amount of information on cardiovascular risk and MetS than HDL-C levels alone.

Reconstituted High-density Lipoprotein Therapy Improves Survival in Mouse Models of Sepsis.

BACKGROUND: High-density lipoproteins exert pleiotropic effects including antiinflammatory, antiapoptotic, and lipopolysaccharide-neutralizing properties. The authors assessed the effects of reconstituted high-density lipoproteins (CSL-111) intravenous injection in different models of sepsis. METHODS: Ten-week-old C57BL/6 mice were subjected to sepsis by cecal ligation and puncture or intraperitoneal injection of Escherichia coli or Pseudomonas aeruginosa pneumonia. CSL-111 or saline solution was administrated 2 h after the sepsis. Primary outcome was survival. Secondary outcomes were plasma cell-free DNA and cytokine concentrations, histology, bacterial count, and biodistribution. RESULTS: Compared with saline, CSL-111 improved survival in cecal ligation and puncture and intraperitoneal models (13 of 16 [81%] survival rate vs. 6 of 16 [38%] in the cecal ligation and puncture model; P = 0.011; 4 of 10 [40%] vs. 0 of 10 [0%] in the intraperitoneal model; P = 0.011). Cell-free DNA concentration was lower in CSL-111 relative to saline groups (68 [24 to 123] pg/ml vs. 351 [333 to 683] pg/ml; P < 0.001). Mice injected with CSL-111 presented a decreased bacterial count at 24 h after the cecal ligation and puncture model both in plasma (200 [28 to 2,302] vs. 2,500 [953 to 3,636] colony-forming unit/ml; P = 0.021) and in the liver (1,359 [360 to 1,648] vs. 1,808 [1,464 to 2,720] colony-forming unit/ml; P = 0.031). In the pneumonia model, fewer bacteria accumulated in liver and lung of the CSL-111 group. CSL-111-injected mice had also less lung inflammation versus saline mice (CD68+ to total cells ratio: saline, 0.24 [0.22 to 0.27]; CSL-111, 0.07 [0.01 to 0.09]; P < 0.01). In all models, no difference was found for cytokine concentration. Indium bacterial labeling underlined a potential hepatic bacterial clearance possibly promoted by high-density lipoprotein uptake. CONCLUSIONS: CSL-111 infusion improved survival in different experimental mouse models of sepsis. It reduced inflammation in both plasma and organs and decreased bacterial count. These results emphasized the key role for high-density lipoproteins in endothelial and organ protection, but also in lipopolysaccharide/bacteria clearance. This suggests an opportunity to explore the therapeutic potential of high-density lipoproteins in septic conditions.

Ramadan fasting improves liver function and total cholesterol in patients with nonalcoholic fatty liver disease.

Background: Nonalcoholic fatty liver disease (NAFLD) is a serious global health problem, thus the prevention and management of the disease is necessary. This study aimed to determine the effects of Ramadan Fasting (RF) on liver function, Visceral Adiposity Index (VAI) and Atherogenic Index of Plasma (AIP) in these patients. METHODS: Eighty-three NAFLD patients (57 males and 26 females) were enrolled in the study, 42 patients who practiced RF, between Jun 18 through July 17, 2015 and 41 patients in non-fasting groups. Anthropometric parameters and Ultrasound grading were measured before and after Ramadan. The biochemical parameters including lipid profiles (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides), liver enzymes (Aspartate aminotransferase, SGOT and Alanine aminotransferase, SGPT) were evaluated before and after Ramadan. AIP and VAI were calculated based on formula. RESULTS: The mean decreases in anthropometric indices were significantly different between groups. Similarly, the mean decrease in the total cholesterol values in the fasting group was remarkably greater than in the control group (p = 0.02). The values of AIP and VAI decreased at the end of the study in both group and the mean of changes showed no differences between groups (p = 0.79 and p = 0.65 for AIP and VAI, respectively). The changes in the concentrations of liver enzymes, as well as the severity of hepatic steatosis, showed remarkable differences between groups (p = 0.03, p = 0.05, and p = 0.02 for SGOT and SGPT, and Liver steatosis, respectively). CONCLUSION: RF improved liver steatosis in NAFLD patients and might be useful in the management of NAFLD.

Participation of white adipose tissue dysfunction on circulating HDL cholesterol and HDL particle size in apparently healthy humans.

OBJECTIVE: To use the combined presence of the elevated insulin resistance index in adipose tissue (Adipo-IR) and low values of adiponectin as a marker of dysfunctional adipose tissue, and to analyze its possible association with low values of high-density lipoprotein cholesterol (HDL-C) and small size of HDL particles. RESEARCH DESIGN AND METHODS: The analysis included 253 subjects with functional adipose tissue and 253 with dysfunctional adipose tissue, considering similar gender, age, and body mass index (BMI). Adipo-IR was considered when index values (free fatty acids × insulin concentrations) were ≥75th percentile. Low levels of adiponectin were considered when concentration in serum was <25th percentile (determined by ELISA). HDL size was estimated by a quantitative validated equation. Small HDL size was considered when values were <25th percentile. RESULTS: When comparing subjects with functional adipose tissue with those of dysfunctional adipose tissue, the latter had a higher prevalence of low HDL-C (51.4% vs. 64.0%; p = 0.004) and small HDL (56.9% vs. 67.6%; p = 0.009). Multivariate analysis indicated that independently from other metabolic risk factors, dysfunction of adipose tissue is significantly associated with low HDL-C (OR: 1.624 [CI 95%: 1.100-2.397]) and small HDL (OR: 1.462 [CI 95%: 1.000-2.139]). Adding BMI, waist circumference, and subcutaneous or visceral adipose tissue did not modify the association. CONCLUSIONS: Dysfunction of adipose tissue is associated with a 65 and 50% higher probability of having low HDL-C and small HDL. Identification of dysfunctional adipose tissue could be a useful tool in the clinical setting to prevent the cardiometabolic risk independently from adiposity.

Usefulness of apolipoprotein B-depleted serum in cholesterol efflux capacity assays using immobilized liposome-bound gel beads.

Cholesterol efflux capacity (CEC) in atherosclerotic lesions is the main anti-atherosclerotic function of high-density lipoprotein (HDL). In recent studies, apolipoprotein (apo) B-depleted serum (BDS) obtained with the polyethylene glycol (PEG) precipitation method is used as a cholesterol acceptor (CA) substitution for HDL isolated by ultracentrifugation. However, the suitability of BDS as a CA is controversial. In the present study, CEC obtained from BDS (BDS-CEC) was evaluated based on a parameter, defined as whole-CEC, which was calculated by multiplying CEC obtained using fixed amounts of HDL by cholesterol concentration to HDL-cholesterol (HDL-C) levels in the serum. Significant correlation (r = 0.633) was observed between both CECs. To eliminate systematic errors from possible contamination with serum proteins and low-density lipoprotein (LDL) or very-LDL (VLDL) in BDS-CEC, the deviation of each CEC-BDS from the regression equation was compared with serum protein, LDL, and triglyceride (TG) levels. No correlation was observed between the deviation and the levels of each of these serum components, indicating that the deviations do not derive from systematic error. Further, to evaluate the effects of serum protein on the results, we measured BDS-CEC of reconstituted serum samples prepared using combinations of five levels of serum proteins with five levels of HDL-C. No significant change in BDS-CEC was observed in any combination. These results indicate that BDS-CEC reflects not only the function of HDL but also its concentration in serum.

Serum amyloid A does not affect high-density lipoprotein cholesterol measurement by a homogeneous assay.

BACKGROUND: Serum amyloid A (SAA), which is one of the acute phase proteins, alters the structure of HDL by associating with it during circulation. We focused on whether SAA influences the values of HDL-cholesterol (HDL-C) measurements when using a homogeneous assay. METHODS: HDLs were isolated by ultracentrifugation from serum samples of 248 patients that were stratified into three groups based on their serum SAA concentrations (low: SAA ≤ 8 µg/mL; middle: 8 < SAA ≤ 100 µg/mL; and high: SAA > 100 µg/mL). HDL-C concentrations of the serum samples measured by the homogeneous assay were compared with the total cholesterol concentrations of HDL fractions isolated by ultracentrifugation. RESULTS: HDLs obtained from patients with low SAA concentrations were separated into their general particle sizes and classified as HDL2 and HDL3 by native-gel electrophoresis. On the other hand, HDLs obtained from patients with high SAA concentrations occasionally showed distributions different from the typical sizes of HDL2 and HDL3, such as extremely small or large particles. Nevertheless, HDL-C concentrations measured using the homogeneous assay were strongly correlated with those measured using the ultracentrifugation method, regardless of the SAA concentrations. However, the ratios of HDL-C concentrations obtained by the homogeneous assay to those obtained by the ultracentrifugation method for patients with high SAA concentrations were significantly lower than those of patients with low SAA concentrations. CONCLUSIONS: A large amount of SAA attached to HDL altered the HDL particle size but did not essentially affect HDL-C measurement by homogeneous assay.

Lipoprotein Particle Profiles, Standard Lipids, and Peripheral Artery Disease Incidence.

BACKGROUND: Despite strong and consistent prospective associations of elevated low-density lipoprotein (LDL) cholesterol concentration with incident coronary and cerebrovascular disease, data for incident peripheral artery disease (PAD) are less robust. Atherogenic dyslipidemia characterized by increased small LDL particle (LDL-P) concentration, rather than total LDL cholesterol content, along with elevated triglyceride-rich lipoproteins and low high-density lipoprotein (HDL) cholesterol (HDL-C), may be the primary lipid driver of PAD risk. METHODS: The study population was a prospective cohort study of 27 888 women ≥45 years old free of cardiovascular disease at baseline and followed for a median of 15.1 years. We tested whether standard lipid concentrations, as well as nuclear magnetic resonance spectroscopy-derived lipoprotein measures, were associated with incident symptomatic PAD (n=110) defined as claudication and/or revascularization. RESULTS: In age-adjusted analyses, while LDL cholesterol was not associated with incident PAD, we found significant associations for increased total and small LDL-P concentrations, triglycerides, and concentrations of very LDL (VLDL) particle (VLDL-P) subclasses, increased total cholesterol (TC):HDL-C, low HDL-C, and low HDL particle (HDL-P) concentration (all P for extreme tertile comparisons <0.05). Findings persisted in multivariable-adjusted models comparing extreme tertiles for elevated total LDL-P (adjusted hazard ratio [HRadj] 2.03; 95% CI, 1.14-3.59), small LDL-P (HRadj 2.17; 95% CI, 1.10-4.27), very large VLDL-P (HRadj 1.68; 95% CI, 1.06-2.66), medium VLDL-P (HRadj 1.98; 95% CI, 1.15-3.41), and TC:HDL-C (HRadj, 3.11; 95% CI, 1.67-5.81). HDL was inversely associated with risk; HRadj for extreme tertiles of HDL-C and HDL-P concentration were 0.30 ( P trend < 0.0001) and 0.29 ( P trend < 0.0001), respectively. These components of atherogenic dyslipidemia, including small LDL-P, medium and very large VLDL-P, TC:HDL-C, HDL-C, and HDL-P, were more strongly associated with incident PAD than incident coronary and cerebrovascular disease. Finally, the addition of LDL-P and HDL-P concentration to TC:HDL-C measures identified women at heightened PAD risk. CONCLUSIONS: In this prospective study, nuclear magnetic resonance-derived measures of LDL-P, but not LDL cholesterol, were associated with incident PAD. Other features of atherogenic dyslipidemia, including elevations in TC:HDL-C, elevations in triglyceride-rich lipoproteins, and low standard and nuclear magnetic resonance-derived measures of HDL, were significant risk determinants. These data help clarify prior inconsistencies and may elucidate a unique lipoprotein signature for PAD compared to coronary and cerebrovascular disease. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov/ . Unique Identifier: NCT00000479.

Unravelling HDL-Looking beyond the Cholesterol Surface to the Quality Within.

High-density lipoprotein (HDL) particles have experienced a turbulent decade of falling from grace with widespread demotion from the most-sought-after therapeutic target to reverse cardiovascular disease (CVD), to mere biomarker status. HDL is slowly emerging from these dark times due to the HDL flux hypothesis wherein measures of HDL cholesterol efflux capacity (CEC) are better predictors of reduced CVD risk than static HDL-cholesterol (HDL-C) levels. HDL particles are emulsions of metabolites, lipids, protein, and microRNA (miR) built on the backbone of Apolipoprotein A1 (ApoA1) that are growing in their complexity due to the higher sensitivity of the respective "omic" technologies. Our understanding of particle composition has increased dramatically within this era and has exposed how our understanding of these particles to date has been oversimplified. Elucidation of the HDL proteome coupled with the identification of specific miRs on HDL have highlighted the "hormonal" characteristics of HDL in that it carries and delivers messages systemically. HDL can dock to most peripheral cells via its receptors, including SR-B1, ABCA1, and ABCG1, which may be a critical step for facilitating HDL-to-cell communication. The composition of HDL particles is, in turn, altered in numerous disease states including diabetes, auto-immune disease, and CVD. The consequence of changes in composition, however, on subsequent biological activities of HDL is currently poorly understood and this is an important avenue for the field to explore in the future. Improving HDL particle quality as opposed to HDL quantity may, in turn, prove a more beneficial investment to reduce CVD risk.

Effect of liquid ubiquinol supplementation on glucose, lipids and antioxidant capacity in type 2 diabetes patients: a double-blind, randomised, placebo-controlled trial.

Ubiquinone is a lipid antioxidant, and a novel liquid ubiquinol (a hydro-soluble, reduced form of coenzyme Q10) supplement was recently developed. The purpose of this study was to examine the levels of glucose, lipids and antioxidant capacity of type 2 diabetes patients after liquid ubiquinol supplementation. This study was designed as a randomised, double-blind, placebo-controlled trial. In all, fifty participants were randomly assigned to a placebo (n 25) or liquid ubiquinol (100 mg/d, n 25) group, and the intervention lasted for 12 weeks. Plasma coenzyme Q10, glucose homoeostasis parameters, lipid profiles, oxidative stress and antioxidative enzyme activities were measured during the study. After 12 weeks of supplementation, glyco Hb (HbA1c) value was significantly decreased in the liquid ubiquinol group (P=0·03), and subjects in the liquid ubiquinol group had significantly lower anti-glycaemic medication effect scores (MES) compared with those in the placebo group (P=0·03). The catalase (P<0·01) and glutathione peroxidase (P=0·03) activities were increased significantly after supplementation. Plasma coenzyme Q10 was correlated with the insulin level (P=0·05), homoeostatic model assessment-insulin resistance (P=0·07), quantitative insulin sensitivity check index (P=0·03) and the anti-hyperglycaemic agents' MES (P=0·03) after supplementation. Lipid profiles did not change after supplementation; however, the subjects in the placebo group had a significantly lower level of HDL-cholesterol after 12 weeks of intervention. In conclusion, oral intake of 100 mg/d liquid ubiquinol might benefit type 2 diabetes patients by increasing antioxidant enzyme activity levels, reducing HbA1c levels and maintaining HDL-cholesterol levels.

HDL Mimetics Infusion and Regression of Atherosclerosis: Is It Still Considered a Valid Therapeutic Option?

PURPOSE OF REVIEW: This review aims to summarize and discuss the recent findings in the field of using HDL mimetics for the treatment of patients with coronary artery disease. RECENT FINDINGS: Following the largely disappointing results with the cholesteryl ester transfer protein inhibitors, focus moved to HDL functionality rather than absolute HDL cholesterol values. A number of HDL/apoA-I mimicking molecules were developed, aiming to enhance reverse cholesterol transport that has been associated with an atheroprotective effect. Three HDL mimetics have made the step from bench-testing to clinical trials in humans and are discussed here: apoA-I Milano, CSL-112, and CER-001. Unfortunately, with the exception of CSL-112 where the results of the clinical trial are not yet known, none of the agents was able to demonstrate a clinical benefit. HDL mimetics have failed to date to prove a beneficial effect in clinical practice. Reverse cholesterol transport remains a challenging therapeutic pathway to be explored.

HDL functionality and cardiovascular outcome among nondialysis chronic kidney disease patients.

CVD remains the leading cause of morbidity and mortality in patients with chronic kidney disease (CKD). CKD profoundly affects HDL composition and functionality, but whether abnormal HDL independently contributes to cardiovascular events in CKD patients remains elusive. In the present study, we assessed whether compositional and functional properties of HDL predict cardiovascular outcome among 526 nondialysis CKD patients who participate in the CARE FOR HOMe study. We measured HDL cholesterol, the content of HDL-associated proinflammatory serum amyloid A (SAA), and activities of the HDL enzymes paraoxonase and lipoprotein-associated phospholipase A2 (Lp-PLA2). In addition, we assessed the antioxidative activity of apoB-depleted serum. During a mean follow-up of 5.1 ± 2.1 years, 153 patients reached the predefined primary endpoint, a composite of atherosclerotic cardiovascular events including cardiovascular mortality and death of any cause. In univariate Cox regression analyses, lower HDL-cholesterol levels, higher HDL-associated SAA content, and lower paraoxonase activity predicted cardiovascular outcome, while Lp-PLA2 activity and antioxidative capacity did not. HDL-cholesterol and HDL-paraoxonase activity lost their association with cardiovascular outcome after adjustment for traditional cardiovascular and renal risk factors, while SAA lost its association after further adjustment for C-reactive protein. In conclusion, our data suggest that neither HDL quantity nor HDL composition or function independently predict cardiovascular outcome among nondialysis CKD patients.