Buoyant Low-density Lipoprotein Research Articles

Serum Levels of Adiponectin Are Strongly Associated with Lipoprotein Subclasses in Healthy Volunteers but Not in Patients with Metabolic Syndrome.

Metabolic syndrome (MS) is a widespread disease in developed countries, accompanied, among others, by decreased adiponectin serum levels and perturbed lipoprotein metabolism. The associations between the serum levels of adiponectin and lipoproteins have been extensively studied in the past under healthy conditions, yet it remains unexplored whether the observed associations also exist in patients with MS. Therefore, in the present study, we analyzed the serum levels of lipoprotein subclasses using nuclear magnetic resonance spectroscopy and examined their associations with the serum levels of adiponectin in patients with MS in comparison with healthy volunteers (HVs). In the HVs, the serum levels of adiponectin were significantly negatively correlated with the serum levels of large buoyant-, very-low-density lipoprotein, and intermediate-density lipoprotein, as well as small dense low-density lipoprotein (LDL) and significantly positively correlated with large buoyant high-density lipoprotein (HDL). In patients with MS, however, adiponectin was only significantly correlated with the serum levels of phospholipids in total HDL and large buoyant LDL. As revealed through logistic regression and orthogonal partial least-squares discriminant analyses, high adiponectin serum levels were associated with low levels of small dense LDL and high levels of large buoyant HDL in the HVs as well as high levels of large buoyant LDL and total HDL in patients with MS. We conclude that the presence of MS weakens or abolishes the strong associations between adiponectin and the lipoprotein parameters observed in HVs and disturbs the complex interplay between adiponectin and lipoprotein metabolism.

How good can HDL Cholesterol be? Recent Evidence and way forward for Clinical Practice

The science of “Lipidology” is flourishing in endless ways. The services included under the lipid testingdo not provide generalised risk assessment for possibleatherosclerotic cardiovascular disease (ASCVD) butprovide specialised services, including genomic andmolecular biomarkers for personalised care. The seminal discovery of lipoprotein fractions seems like a stepnext door in the much wider cosmos of metabolomicsand proteomics, where knowledge of lipoprotein subfractions as villains or saviours seems like the trailer ofthe Larger Amphitheatre. Low-density lipoproteins(LDL) though differently defined in the literature, werecategorised as “large buoyant LDL” (lbLDL) and“small dense LDL” (sdLDL).1 Over time, the knowledge base evolved to incorporate different fractionsamong lipoproteins based upon size and density withhigh-density lipoproteins (HDL) to incorporate nascentHDL, HDL2 and HDL3

Lipid Profile Changes Associated with SGLT-2 Inhibitors and GLP-1 Agonists in Diabetes and Metabolic Syndrome.

The introduction of sodium glucose transporter-2 inhibitors and glucagon-like peptide-1 receptor agonists in type 2 diabetes mellitus treatment has shown an unexpectedly significant improvement in heart disease outcome trials. Although they have very different modes of action, a portion of the salutary cardiovascular disease improvement may be related to their impact on diabetic dyslipidemia. As discussed in this focused review, the sodium glucose transporter-2 inhibitors as a class show a mild increase in low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels, while triglycerides (TG) decrease inconsistently. In particular, the rise in LDL appears to be related to the less atherogenic, large buoyant LDL particles. The glucagon-like peptide-1 receptor agonists show more of an impact on weight loss and improvement in the underlying low HDL and high TG dyslipidemia. The effect of sodium glucose transporter-2 inhibitors and glucagon-like peptide 1 receptor agonists when used in combination remains largely unknown. Also unexplored is difference in effect of these medications among various ethnicities and metabolic syndrome.

Oxidative Modification of Lipoproteins: A Potential Role of Oxidized Small dense LDL in Enhanced Atherogenicity

Atherosclerosis (AS) is a multifaceted inflammatory syndrome of the arterial wall to which number of mediators have been implicated in lesion progression. Triglyceride (TG)-rich lipoproteins consist of the large diversity of lipoprotein particles that fluctuate in density, size, and apolipoprotein composition. Two foremost phenotypes, on basis of size, chemical configuration, and density, of low-density-lipoprotein (LDL) have been recognized i.e., pattern A, having LDL diameter greater than 25.5nm (large buoyant LDL or lb-LDL) and pattern B, having LDL diameter less than or equal to 25.5nm (small-dense LDL or sd-LDL). Small-dense low-density-lipoprotein (sd-LDL) particles are produced by potential intravascular hydrolysis of TG-rich VLDL particles via lipoprotein lipases (LPLs), hepatic lipases (HLs) and cholesterol ester transfer protein (CETP). sd-LDL is more atherogenic due to its smaller size, increased penetration into the arterial wall, extended plasma half-life, lesser binding affinity for LDL receptors (LDL-R) as well as lower resistance to oxidative stress when equated with lb-LDL. The higher atherogenic potential of sd-LDL is due to its enhanced susceptibility to oxidation, owing to high polyunsaturated fatty acids (PUFA), low cholesterol and Apoprotein B (ApoB) content. An enhanced understanding of sd-LDL metabolism at the molecular level, transport and clearance may result in the development of sd-LDL as an independent predictive marker for AS events and may be used to maintain cholesterol homeostasis and prevent the succession of AS.

A Ketogenic Low-Carbohydrate High-Fat Diet Increases LDL Cholesterol in Healthy, Young, Normal-Weight Women: A Randomized Controlled Feeding Trial.

Ketogenic low-carbohydrate high-fat (LCHF) diets are popular among young, healthy, normal-weight individuals for various reasons. We aimed to investigate the effect of a ketogenic LCHF diet on low-density lipoprotein (LDL) cholesterol (primary outcome), LDL cholesterol subfractions and conventional cardiovascular risk factors in the blood of healthy, young, and normal-weight women. The study was a randomized, controlled, feeding trial with crossover design. Twenty-four women were assigned to a 4 week ketogenic LCHF diet (4% carbohydrates; 77% fat; 19% protein) followed by a 4 week National Food Agency recommended control diet (44% carbohydrates; 33% fat; 19% protein), or the reverse sequence due to the crossover design. Treatment periods were separated by a 15 week washout period. Seventeen women completed the study and treatment effects were evaluated using mixed models. The LCHF diet increased LDL cholesterol in every woman with a treatment effect of 1.82 mM (p < 0.001). In addition, Apolipoprotein B-100 (ApoB), small, dense LDL cholesterol as well as large, buoyant LDL cholesterol increased (p < 0.001, p < 0.01, and p < 0.001, respectively). The data suggest that feeding healthy, young, normal-weight women a ketogenic LCHF diet induces a deleterious blood lipid profile. The elevated LDL cholesterol should be a cause for concern in young, healthy, normal-weight women following this kind of LCHF diet.

Abstract P181: Atherogenic Lipoproteins and Incident Atherosclerotic Cardiovascular Disease in the Framingham Offspring Study

Introduction: Elevated plasma low-density lipoprotein cholesterol (LDL-C), small-dense LDL-C (sdLDL-C), LDL-triglyceride (LDL-TG), triglycerides (TG), remnant-lipoprotein cholesterol (RLP-C), triglyceride-rich lipoprotein-C (TRL-C), very low-density lipoprotein cholesterol (VLDL-C), and lipoprotein(a) [Lp(a)] levels have been associated with increased atherosclerotic cardiovascular disease (ASCVD) risk. However, these parameters have not been included in risk factors for ASCVD in the pooled cohort equation (PCE). Hypothesis: We assessed the hypothesis that these atherogenic lipoprotein parameters add significant information for ASCVD risk prediction in the Framingham Offspring Study. Methods: We evaluated 3,147 subjects without ASCVD at baseline (mean age 58 years) from participants of Framingham Offspring Study cycle 6, 677 (21.5%) of whom developed inclusive ASCVD over 16 years. Biomarkers of risk were assessed in frozen plasma samples. Total cholesterol, TG, HDL-C, direct LDL-C, sdLDL-C, LDL-TG, Lp(a), RLP-C, and TRL-C were measured by standardized automated analysis. Calculated LDL-C, large buoyant low-density lipoprotein cholesterol (lbLDL-C), VLDL-C, and non-HDL-C values were calculated. Data were analyzed using Cox proportional regression analysis and net reclassification improvement (NRI) analysis to identify parameters significantly associated with the incidence of ASCVD after controlling for standard ASCVD risk factor and applying the PCE model. Results: All specialized lipoprotein parameters were significant ASCVD risk factors on univariate analysis, but only direct LDL-C, sdLDL-C, and Lp(a) were significant on multivariate analysis with standard risk factors in the model. Together these parameters significantly improved the model c statistic (0.716 vs 0.732, P &lt; 0.05) and net risk reclassification (mean NRI 0.104, P &lt; 0.01) for ASCVD risk. Using the ASCVD risk pooled cohort equation, sdLDL-C, TG, LDL-TG, LDL-C, RLP-C, and TRL-C individually added significant information, but no other parameter added significant information with sdLDL-C (hazard ratio 1.30 for 75th vs 25th percentile, P &lt; 0.0001) in the model. Conclusions: In multivariate analysis, sdLDL-C, direct LDL-C, and Lp(a) contributed significantly to ASCVD risk, but only sdLDL-C added significant risk information to the PCE model, indicating that sdLDL-C may be the most atherogenic lipoprotein particle.

The small dense LDL particle/large buoyant LDL particle ratio is associated with glucose metabolic status in pregnancy

BackgroundThe lipoprotein subfraction particle profile can be used to improve clinical assessments of cardiovascular disease risk and contribute to early detection of atherogenic dyslipidemia. Lipid alterations in gestational diabetes have been extensively studied, but the results have been inconsistent. Here, we investigated serum lipoprotein subfraction particle levels and their association with glucose metabolic status in pregnancy.MethodsTwenty-eight pregnant women with gestational diabetes and 56 pregnant women with normal glucose tolerance matched for body mass index were enrolled in this study. We assessed fasting serum lipid concentrations and lipoprotein subfraction particle levels in participants between 24 and 28 weeks of gestation.ResultsThe level of low-density lipoprotein (LDL) cholesterol was significantly lower in women with gestational diabetes than in those with normal glucose tolerance, but the triglyceride and high-density lipoprotein (HDL) cholesterol levels of the two groups were similar. Lipoprotein particle analysis showed that very-low-density lipoprotein (VLDL) particle number and the small dense LDL particle/large buoyant LDL particle (sdLDL-P/lbLDL-P) ratio were significantly higher in women with gestational diabetes than in those with normal glucose tolerance (P = 0.013 and P = 0.015, respectively). In multivariate analysis, fasting glucose was independently and positively associated with sdLDL-P/lbLDL-P ratio even after adjustment for maternal age, gestational weight gain, BMI and LDL cholesterol (standardized Beta = 0.214, P = 0.029).ConclusionsThe sdLDL-P/lbLDL-P ratio is higher in GDM compared with non-diabetic pregnant women, and positively and independently associated with fasting glucose in pregnant women.

Bariatric surgery improves lipoprotein profile in morbidly obese patients by reducing LDL cholesterol, apoB, and SAA/PON1 ratio, increasing HDL cholesterol, but has no effect on cholesterol efflux capacity

Bariatric surgery has been shown to reduce cardiovascular events and cause-specific mortality for coronary artery disease in obese patients. Lipoprotein biomarkers relating to low-density lipoprotein (LDL), high-density lipoprotein (HDL), their subfractions, and macrophage cholesterol efflux have all been hypothesized to be of value in cardiovascular risk assessment. The objective of this study was to examine the effect of a lifestyle intervention followed by bariatric surgery on the lipid profile of morbidly obese patients. Thirty-four morbidly obese patients were evaluated before and after lifestyle changes and then 1 year after bariatric surgery. They were compared with 17 lean subjects. Several lipoprotein metrics, serum amyloid A (SAA), serum paraoxonase-1 (PON1), and macrophage cholesterol efflux capacity (CEC) were assessed. Average weight loss after the lifestyle intervention was 10.5% and 1 year after bariatric surgery was 33.9%. The lifestyle intervention significantly decreased triglycerides (TGs; -28.7mg/dL, P<.05), LDL cholesterol (LDL-C; -32.3mg/dL, P<.0001), and apolipoprotein B (apoB; -62.9μg/mL, P<.001). Bariatric surgery further reduced TGs (-36.7mg/dL, P<.05), increased HDL cholesterol (+12mg/dL, P<.0001), and reductions in LDL-C and apoB were sustained. Bariatric surgery reduced large, buoyant LDL (P<.0001), but had no effect on the small, dense LDL. The large HDL subfractions increased (P<.0001), but there was no effect on the smaller HDL subfractions. The ratio for SAA/PON1 was reduced after the lifestyle intervention (P<.01) and further reduced after bariatric surgery (P<.0001). Neither the lifestyle intervention nor bariatric surgery had any effect on CEC. Lifestyle intervention followed by bariatric surgery in 34 morbidly obese patients showed favorable effects on TGs, LDL-C, and apoB. HDL cholesterol and apoA1 was increased, apoB/apoA1 ratio as well as SAA/PON1 ratio reduced, but bariatric surgery did not influence CEC.

Association of low-density lipoprotein pattern with mortality after myocardial infarction: Insights from the TRIUMPH study

Studies of incident coronary heart disease risk within low-density lipoprotein (LDL) subclass (small, dense vs large, buoyant) have shown mixed results. No prospective cohort study has examined the association of small, dense, or large, buoyant LDL with mortality after myocardial infarction (MI). The objective of the study was to examine association of LDL pattern after MI and death. In 2476 patients hospitalized for MI, LDL pattern (A [large, buoyant], A/B [mixed], and B [small, dense]) was established by ultracentrifugation using Vertical Auto Profile. Using time-to-event analysis, we examined the association with 5-year mortality within LDL patterns, after adjusting for important patient and treatment characteristics. We additionally adjusted for LDL cholesterol (LDL-C) and triglyceride levels and used directly measured LDL-C and non-high-density lipoprotein cholesterol as exposures. Patterns A, A/B, and B were present in 39%, 28%, and 33% of patients, respectively, with incident rates (per 1000 patient-years) of 50, 34, and 24 for all-cause and 24, 19, and 10 for CV mortality. The hazard ratios (95% confidence interval) with LDL patterns A/B and B compared with pattern A were 0.77 (0.61, 0.99) and 0.67 (0.51, 0.88) for all-cause, 0.94 (0.67, 1.33) and 0.69 (0.46, 1.03) for cardiovascular, and 0.64 (0.45, 0.91) and 0.65 (0.45, 0.93) for noncardiovascular mortalities, respectively. Results were similar when further adjusted for LDL-C and triglycerides, or with LDL-C and non-high-density lipoprotein cholesterol as exposures. Compared with LDL pattern A, pattern B was significantly associated with reduced all-cause and non-CV mortalities with a trend for lower CV mortality after MI, independent of LDL-C and triglycerides.

Comprehensive assessment of lipoprotein subfraction profiles according to glucose metabolism status, and association with insulin resistance in subjects with early-stage impaired glucose metabolism

BackgroundEarly detection of atherogenic dyslipidemia is crucial. We investigated lipoprotein subfraction parameters according to glucose metabolism status. MethodsWe recruited 1255 lipid-lowering drug-naïve subjects with normal fasting glucose (NFG; n=200, 15.9%), impaired fasting glucose (IFG; n=443, 35.3%), or type 2 diabetes (T2D; n=612, 48.8%). Lipoprotein subfractions (1–7) were determined by polyacrylamide gel electrophoresis, separating low-density lipoprotein (LDL) into large buoyant LDL (lbLDL, LDL1–2) and small dense LDL (sdLDL, LDL3–7). Lipoprotein subfraction parameters including the sdLDL% (LDL3–7/LDL1–7), the sdLDL/lbLDL ratio (LDL3–7/LDL1–2), and weighted LDL subfraction (LDLSF) scores, were compared between groups. Their associations with insulin resistance, estimated using the homeostasis model assessment of insulin resistance, were examined. ResultsThe concentrations of sdLDL particles were significantly higher in subjects with T2D and IFG than in those with NFG (15.78±13.47mg/dl and 14.60±14.33mg/dl, respectively, vs. 12.22±12.31mg/dl). Compared with those with NFG, subjects with IFG or T2D had significantly a higher sdLDL% (15.98±15.26% vs. 19.50±16.21% or 21.46±16.81%, respectively), a higher sdLDL/lbLDL ratio (0.24±0.30 vs. 0.31±0.37 or 0.35±0.39), and a higher LDLSF score (2.08±0.91 vs. 2.30±1.14 or 2.36±1.17). These lipoprotein subfraction parameters had stronger associations with insulin resistance compared to conventional lipid profiles in the IFG and T2D groups. ConclusionsAtherogenic dyslipidemia is initiated in an early stage of impaired glucose metabolism, when early intervention might be required.

Abstract P107: Small Dense Low Density Lipoprotein Subfractions are Independently Associated with Subclinical Atherosclerosis: The ELSA-Brasil study

Introduction: Low-density lipoproteins (LDL) are established risk factors for cardiovascular disease and a therapy target. Prior studies suggest that among the pool of plasma LDL, the small and dense subfractions are more strongly associated with risk. In the present study, we investigated whether LDL particle density is associated with the presence of subclinical atherosclerosis detected by coronary artery calcium score. Methods: We included 2869 (50.3±8.5 years, 54% women) participants from the ELSA-Brasil study who had no prior history of CVD, were not currently using lipid-lowering medications, and underwent CAC evaluation. We measured the fasting lipoprotein cholesterol fractions (in mg/dL) using the vertical auto profile (VAP) ultracentrifugation method. We analyzed the independent predictive values of LDL-1, LDL-2, LDL-3 and LDL-4, as well as the ln transformed ratio of small and dense (LDL-3 and LDL-4) to larger and more buoyant LDL particles (LDL-1 and LDL-2) (LLDR (Logarithmic of LDL Density Ratio)) using logistic regression. Results: Overall 749 (26%) of the participants had a CAC &gt;0, and 241 (8.1%) had a CAC &gt; 100. The mean LDL-1, LDL-2, LDL-3 and LDL-4 cholesterol were respectively (mg/dL): 22.5±9.4, 32.7±17.9, 47.1±20.4 and 10.4±10.8. Individuals with CAC&gt;0 had higher LDL-1, LDL-3 and LDL-4, but LDL-2 was not significantly different between groups. LLDLR was also significantly higher in those with CAC&gt;0. LLDR was associated with CAC&gt;0 even after multivariable adjustment for age, gender, smoking, diabetes, hypertension, systolic blood pressure and Friedwald LDL-cholesterol. (p&lt;0.01). Conclusion: In a large cohort of asymptomatic individuals, the ratio of small and dense to larger buoyant LDL-C particles is associated with CAC score. This association is independent and complementary to the calculated LDL-cholesterol levels.

Understanding of Diabetic Dyslipidemia by Using the Anion-Exchange High Performance Liquid Chromatography Data.

Type 2 diabetes and dyslipidemia are cardiovascular risk factors which should be managed [1]. However, the precise lipoprotein profiles and the underlying mechanisms for diabetic dyslipidemia remain largely unknown. We previously developed an anion-exchange liquid chromatographic method (AEX-HPLC) which can measure cholesterol levels of triglyceride (TG)-rich lipoproteins such as very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL) and chylomicron (CM) in addition to low-density lipoprotein (LDL) and high-density lipoprotein (HDL) [2]. Here we compared lipoprotein profiles obtained by our previous studies using AEX-HPLC in young lean men [3], subjects with low Framingham risk score (FRS) [4, 5], type 2 diabetic patients without obesity and type 2 diabetic patients with obesity [6, 7]. The mean ± SD values of age, body mass index, HbA1c in in young lean men (n = 7) [3], low FRS subjects (n = 304) [4], type 2 diabetic patients without obesity (n = 194) [6], and type 2 diabetic patients with obesity (n = 5) [7] were 24 ± 2, 51 ± 8, 63 ± 13, and 60 ± 9 years old, 20.8 ± 2.2, 23.8 ± 3.0, 23.1 ± 2.0, and 29.5 ± 7.0 kg/m2, 5.0 ± 0.2, 5.4 ± 0.5, 6.3 ± 1.0, and 9.1±2.1%, respectively. HDL-cholesterol (HDL-C) in type 2 diabetes (49.9 ± 16.6 mg/dL (1.29 ± 0.43 mmol/L)), especially in type 2 diabetic patients with obesity (36.4 ± 5.3 mg/dL (0.94 ± 0.14 mmol/L)) was lower than young lean men (59.4 ± 10.1 mg/dL (1.54 ± 0.26 mmol/L)) and low FRS subjects (57.6 ± 14.7 mg/dL (1.49 ± 0.38 mmol/L)). IDL-C in type 2 diabetes was higher than other two groups, and IDL-C was higher in the order of type 2 diabetic patients with obesity (9.8 ± 3.0 mg/dL (0.25 ± 0.08 mmol/L)), type 2 diabetic patients without obesity (9.3 ± 4.6 mg/dL (0.24 ± 0.12 mmol/L)), low FRS subjects (7.3 ± 3.1 mg/ dL (0.19 ± 0.08 mmol/L)), young lean men (4.3 ± 2.2 mg/dL (0.11 ± 0.06 mmol/L)). VLDL-C clearly showed higher values in the order of type 2 diabetic patients with obesity (27.3 ± 22.7 mg/dL (0.71 ± 0.59 mmol/L)), type 2 diabetic patients without obesity (20.1 ± 16.2 mg/dL (0.52 ± 0.42 mmol/L)), low FRS subjects (16.6 ± 12.8 mg/dL (0.43 ± 0.33 mmol/L)), and young lean men (4.0 ± 4.6 mg/dL (0.10 ± 0.12 mmol/L)). LDL-C and CM-C did not show the characteristic profile for diabetes. According to accumulation of our previous AEX-HPLC data [3, 4, 6, 7], the characteristics in diabetic dyslipidemia is reduced HDL-C, and increased IDL-C and VLDL-C, which is further deteriorated by complication with obesity. Relative insulin deficiency due to insulin resistance increases activity and expression of hormone-sensitive lipase (HSL) in adipose tissue, which catalyzes the breakdown of TG, releasing free fatty acids (FFA) (Fig. 1) [8]. Insulin promotes apoB100 degradation, and hepatic insulin resistance causes reduction of apoB100 degradation [9]. Insulin resistance also induces an enhanced expression of microsomal TG transfer protein (MTP), a key enzyme involved in VLDL assembly [10]. In type 2 diabetes, increased FFA entry to liver, reduced degradation of apoB100 and enhanced expression of MTP may elevate hepatic production of VLDL. Relative insulin deficiency also decreases the activity of lipoprotein lipase (LPL), the rate-limiting enzyme of the catabolism of TG-rich lipoproteins such as CM, VLDL and IDL [11]. The formation of HDL is related with the catabolism of TG-rich lipoproteins by LPL [12]. Therefore, reduced LPL activity increases IDL and VLDL, and reduces HDL. The activity of hepatic TG lipase (HTGL), the enzyme that facilitates the catabolism of HDL, is correlated with insulin requirement [13]. In type 2 diabetes, low serum HDL-C may be partially due to an increased rate of clearance by HTGL [13]. LDL size and buoyancy are inversely proportional to HTGL activity [14], and patients with high HTGL have smaller, denser LDL particles, as compared with subjects with low HTGL activity [15]. Increased HTGL activity due Manuscript accepted for publication March 03, 2016

Exchanging carbohydrate or protein for fat improves lipid-related cardiovascular risk profile in overweight men and women when consumed ad libitum.

The impact of low-fat diets on the plasma lipoprotein profile is incompletely understood. We conducted two 16-week dietary studies to compare the effects of a moderate-fat (mod-FAT) baseline diet with isocaloric and ad libitum low-fat diets rich in either carbohydrates (high-CHO, n = 16) or protein (high-PRO, n = 19) on plasma lipids, post-heparin lipase activities, cholesteryl ester transfer protein, and phospholipid transfer protein. Switching from the mod-FAT to the isocaloric high-CHO diet lowered plasma high-density lipoprotein cholesterol concentrations (P < 0.001) and tended to increase triglyceride levels (P = 0.087). Cholesterol content in the larger, buoyant low-density lipoprotein (LDL) fractions decreased, whereas those of the very-low-density lipoprotein, intermediate-density lipoprotein, and smaller, denser LDL fractions tended to increase. These changes were largely reversed when subjects lost weight by consuming this high-CHO diet ad libitum. Switching from the mod-FAT diet to the isocaloric high-PRO diet did not increase cholesterol content in the small-dense LDL fraction and led to decreases in both LDL and high-density lipoprotein cholesterol in plasma (P < 0.001 for both).Consumption of the high-protein ad libitum diet accompanied by weight loss did not change plasma lipids further, except for a shift of cholesterol from dense low-density lipoprotein fractions to more buoyant low-density lipoprotein fractions. Cholesteryl ester transfer protein concentrations decreased with high-cholesterol feeding, whereas cholesteryl ester transfer protein concentrations and hepatic lipase and phospholipid transfer protein activities all decreased during high-protein feeding. Both high-CHO and high-PRO diets improve plasma lipid-related risk of cardiovascular disease when consumed ad libitum.

Prevalence of plasma small dense LDL is increased in obesity in a Thai population.

BackgroundPlasma low density lipoprotein (LDL) particles vary in size, density, electrical charge and chemical composition. An increased presence of small dense LDL (sdLDL), along with raised triglyceride concentrations and decreased high density lipoprotein (HDL) cholesterol concentrations is commonly known as the atherogenic triad and has been observed in some cases of obesity, principally in Europe and America. This study examines the prevalence of sdLDL in the plasma of an obese (BMI ≥ 25 kg/m2) Thai population.MethodsPlasma from fasted obese (n = 48) and non-obese (n = 16) Thai participants was subjected to density gradient ultracentrifugation in iodixanol to separate lipoproteins. Gradients were unloaded top-to-bottom into 20 fractions which were assayed for cholesterol, triglyceride, apo B and apo A-1 to identify lipoprotein types and subtypes.ResultsLDL cholesterol was subfractionated into LDL I + II (fractions 3–6, ρ = 1.021-1.033 g/ml) which was considered to represent large buoyant LDL (lbLDL), LDL III (fractions 7–9, ρ = 1.036-1.039 g/ml) which was considered to represent sdLDL, and, LDL IV (fractions 10–12, ρ = 1.044-1.051 g/ml) which was considered to represent very sdLDL. Concentrations of LDL III and IV were increased by 15-20% in obese participants whilst that of LDL I + II was concomitantly decreased by 10%. This was accompanied by a 50% increase in plasma triglyceride concentrations and 15% decrease in HDL cholesterol concentrations. Only 3/16 (19%) non-obese participants had a pattern B LDL cholesterol profile (peak density of >1.033 g/ml), whilst 28/48 (58%) obese participants were pattern B. When expressed as a fraction of the LDL concentration, total sdLDL (i.e. LDL III + IV) showed highly significant correlations to plasma triglyceride concentrations and the triglyceride/HDL cholesterol ratio.ConclusionsThe prevalence of sdLDL is increased in obesity in a Thai population such that they demonstrate a similar atherogenic triad to that previously observed in European and American populations.

Effect of Ezetimibe on Low‐and High‐Density Lipoprotein Subclasses in Sitosterolemia

Sitosterolemia (STSL) is a rare sterol disease manifested by very high plasma phytosterols (PS) with normal to high total cholesterol (TC) levels and increased atherosclerosis risk. Low density lipoprotein (LDL), intermediate density lipoprotein (IDL) and very lowdensity lipoprotein (VLDL) cholesterols are proatherogenic while high density lipoprotein (HDL) cholesterol is antiatherogenic. Ezetimibe (EZ), a sterol absorption inhibitor, can reduce plasma PS and TC levels in STSL but its effect on lipoprotein subclasses has not been studied. We evaluated the effect of EZ on lipoprotein subclasses in STSL patients (pts, n=8) taken off EZ for 14 wks then placed on EZ (10 mg/d) for 14 wks. Serum total lipids and subfractions were measured enzymatically or with the Lipoprint system. Data (mean±SEM) were analyzed by paired t‐test. EZ reduced serum TC (‐13±4%, p=0.02), VLDL (‐24±4%, p=0.002) and total LDL (‐17±6%, p=0.03) levels vs off EZ. Reduced LDL values were due to decreased IDLB and C (‐22±7 and ‐21±8%, p&lt;0.05), not to large, buoyant LDL subclasses (LDL1: ‐8±8%, p=0.23 and LDL2: +35±55%, p=0.17). LDL size did not change with EZ (275±0 vs 274±1 Å, p=0.18). EZ increased HDL levels (26±8%, p=0.008) due to increased intermediate (34±14%, p=0.02) and large (33±16%, p=0.06) HDL subclasses. These data suggest EZ can favorably affect LDL and HDL subfractions distribution, thus providing potential clinical benefit in STSL beyond reducing TC and PS accrual.Funded by NIH and CIHR

Metabolic alterations, HFE gene mutations and atherogenic lipoprotein modifications in patients with primary iron overload.

Iron overload (IO) has been associated with glucose metabolism alterations and increased risk of cardiovascular disease (CVD). Primary IO is associated with mutations in the HFE gene. To which extent HFE gene mutations and metabolic alterations contribute to the presence of atherogenic lipoprotein modifications in primary IO remains undetermined. The present study aimed to assess small, dense low-density lipoprotein (LDL) levels, chemical composition of LDL and high-density lipoprotein (HDL) particles, and HDL functionality in IO patients. Eighteen male patients with primary IO and 16 sex- and age-matched controls were recruited. HFE mutations (C282Y, H63D and S65C), measures of insulin sensitivity and secretion (calculated from the oral glucose tolerance test), chemical composition and distribution profile of LDL and HDL subfractions (isolated by gradient density ultracentrifugation) and HDL functionality (as cholesterol efflux and antioxidative activity) were studied. IO patients compared with controls exhibited insulin resistance (HOMA-IR (homoeostasis model assessment-estimated insulin resistance): +93%, P< 0.001). Metabolic profiles differed across HFE genotypes. C282Y homozygotes (n=7) presented a reduced β-cell function and insulin secretion compared with non-C282Y patients (n=11) (-58% and -73%, respectively, P< 0.05). In addition, C282Y homozygotes featured a predominance of large, buoyant LDL particles (C282Y: 43±5; non-C282Y: 25±8; controls: 32±7%; P< 0.001), whereas non-C282Y patients presented higher amounts of small, dense LDL (C282Y: 23±5; non-C282Y: 39±10; controls: 26±4%; P< 0.01). HDL particles were altered in C282Y homozygotes. However, HDL functionality was conserved. In conclusion, metabolic alterations and HFE gene mutations are involved in the presence of atherogenic lipoprotein modifications in primary IO. To what extent such alterations could account for an increase in CVD risk remains to be determined.

Effects of Niacin Combination Therapy With Statin or Bile Acid Resin on Lipoproteins and Cardiovascular Disease

Two large studies in populations selected for cardiovascular disease (CVD) demonstrated that raising high-density lipoprotein (HDL) cholesterol with niacin added to statin therapy did not decrease CVD. We examine the association of lipoprotein subfractions with niacin and changes in coronary stenosis and CVD event risk. One hundred and seven patients from 2 previous studies using niacin in combination with either statin or bile acid-binding resin were selected to evaluate changes in lipoproteins separated by density-gradient ultracentrifugation to progression of coronary artery disease as assessed by quantitative coronary angiography. Improvement in coronary stenosis was significantly associated with the decrease of cholesterol in the dense low-density lipoprotein (LDL) particles and across most of the intermediate density lipoprotein (IDL) and very low density lipoprotein particle density range, but, not with any of the HDL fraction or of the more buoyant LDL fractions. Event-free survival was significantly associated with the decrease of cholesterol in the dense LDL and IDL; there was no association with changes in cholesterol in the HDL and buoyant LDL fractions. Niacin combination therapy raises HDL cholesterol and decreases dense LDL and IDL cholesterol levels. Changes in LDL and IDL are related to improvement in CVD. Lipoprotein subfraction analysis should be performed in larger studies utilizing niacin in combination with statins.

Small dense LDL is more susceptible to glycation than more buoyant LDL in Type 2 diabetes

Glycation of apoB (apolipoprotein B) of LDL (low-density lipoprotein) increases its atherogenicity. Concentrations of both serum glyc-apoB (glycated apoB) and SD-LDL (small dense LDL) (syn LDL3; D=1.044-1.063 g/ml) are increased in diabetes and are closely correlated. We studied whether SD-LDL is more susceptible to glycation in vitro than more buoyant LDL in statin- and non-statin-treated Type 2 diabetes mellitus. Serum SD-LDL apoB and glyc-apoB on statins was 20±2 (means±S.D.) and 3.6±0.41 compared with 47±3 and 5.89±0.68 mg/dl in those not receiving statins (P<0.001 and <0.01, respectively). There was a dose-dependent increase in glycation on incubation of LDL subfractions with glucose, which was accompanied by an increase in LPO (lipid peroxide) and electrophoretic mobility and a decrease in free amino groups. SD-LDL was more susceptible to these changes than more buoyant LDL. Both SD-LDL and more buoyant LDL from statin-treated patients were less susceptible to glycation. There were fewer free amino groups on LDL subfractions from statin-treated patients, which may contribute to this resistance. In conclusion, greater susceptibility of SD-LDL to glycation is likely to contribute to the raised levels of circulating glyc-apoB in diabetes. Statins are associated with lower levels of both SD-LDL and glyc-apoB.

Simultaneous Determination of High-Density Lipoprotein, Very Low-Density Lipoprotein and Low-Density Lipoprotein Subclass in Human Serum by Microchip CE

Lipoproteins, especially high-density lipoproteins (HDL), very low-density lipoproteins (VLDL) and small, dense low-density lipoprotein (sdLDL), are believed to play an important role in the development of atherosclerosis. In this work, a simple, selective and sensitive method for the simultaneous monitoring of these lipoproteins in human serum using microchip capillary electrophoresis was developed. Gold nanoparticles were used as an additive to the running buffer to obtain the absolute separation of the lipoproteins. Under optimised conditions, the linear ranges of large buoyant low-density lipoproteins, sdLDL, VLDL and HDL were 10–800, 10–800, 40–1,000 and 20–800 μg L−1, and their limits of detection were 5, 5, 15 and 8 μg L−1, respectively. The intraassay and interassay relative standard deviation of lipoprotein peak areas were in the range of 3.8–7.4%. For practical application, variations in the serum lipoprotein of coronary heart disease patients were monitored by microchip-based CE. The results showed that the method was applicable for routine clinical use and allowed the rapid detection of different lipoprotein classes as well as their subclasses, thus greatly improving the analysis of atherosclerotic risk factors.

Antiatherogenic effects of newly developed apolipoprotein A-I mimetic peptide/phospholipid complexes against aortic plaque burden in Watanabe-heritable hyperlipidemic rabbits

This study analyzed the antiatherogenic effects of newly developed apolipoprotein A-I (ApoA-I) mimetic peptide/phospholipid complexes (ETC-642) against the aortic plaque burden in vivo. We used human macrophage cells to analyze cholesterol efflux by ETC-642. Watanabe-heritable hyperlipidemic (WHHL) rabbits were divided into 3 groups: low- (15mg/kg) and high-dose ETC-642 (50mg/kg), and placebo. The test material was injected twice/week for 12 weeks. The aortic plaque burden was assessed by intravascular ultrasound (IVUS) at 0 and 12 weeks. Plasma lipid profiles were analyzed by capillary isotachophoresis every 4 weeks. ETC-642 had an effect on cholesterol efflux comparable to that of conventional rHDL. In WHHL rabbits, high-dose ETC-642 inhibited the progression of aortic atherosclerosis compared to placebo. There was no change in the percentage of plaque volume (%PV) in the high-dose group between before (30.9%) and after infusion (28.6%), whereas there was a significant increase in the control group from 27.8% to 37.9%. ETC-642 significantly reduced charge-modified low-density lipoprotein (LDL) by converting more negative-charged modified LDL to less negative-charged LDL, and reduced small dense (sd) LDL by converting it into large, buoyant (lb) LDL. Changes in the %PV were positively correlated with changes in negative-charged modified LDL (r=0.61, p<0.01) and sdLDL (r=0.59, p<0.01), and negatively correlated with changes in less negative-charged LDL (r=−0.43, p<0.01) and lbLDL (r=−0.57, p<0.01). In conclusion, the ETC-642-induced remodeling of sdLDL to large and lbLDL and the enhancement of cholesterol efflux may prevent progression of the aortic plaque burden. HDL-based therapy may be useful for preventing the progression of plaque volume.