Lipoprotein Subfraction Concentrations Research Articles

Distinct metabolomic and lipidomic profiles in serum samples of patients with primary sclerosing cholangitis.

Identification of specific metabolome and lipidome profile of patients with primary sclerosing cholangitis (PSC) is crucial for diagnosis, targeted personalized therapy, and more accurate risk stratification. Nuclear magnetic resonance (NMR) spectroscopy revealed an altered metabolome and lipidome of 33 patients with PSC [24 patients with inflammatory bowel disease (IBD) and 9 patients without IBD] compared with 40 age-, sex-, and body mass index (BMI)-matched healthy controls (HC) as well as 64 patients with IBD and other extraintestinal manifestations (EIM) but without PSC. In particular, higher concentrations of pyruvic acid and several lipoprotein subfractions were measured in PSC in comparison to HC. Of clinical relevance, a specific amino acid and lipid profile was determined in PSC compared with IBD and other EIM. These results have the potential to improve diagnosis by differentiating PSC patients from HC and those with IBD and EIM.

Lipoprotein subfraction patterns throughout gestation in The Gambia: changes in subfraction composition and their relationships with infant birth weights

BackgroundLipoprotein subfraction concentrations have been shown to change as gestation progresses in resource-rich settings. The objective of the current study was to evaluate the impact of pregnancy on different-sized lipoprotein particle concentrations and compositions in a resource-poor setting.MethodSamples were collected from pregnant women in rural Gambia at enrollment (8–20 weeks), 20 weeks, and 30 weeks of gestation. Concentrations of different-sized high-density, low-density, and triglyceride-rich lipoprotein particles (HDL, LDL, and TRL, respectively) were measured by nuclear magnetic resonance in 126 pooled plasma samples from a subset of women. HDL was isolated and the HDL proteome evaluated using mass spectroscopy. Subfraction concentrations from women in The Gambia were also compared to concentrations in women in the U.S. in mid gestation.ResultsTotal lipoprotein particles and all-sized TRL, LDL, and HDL particle concentrations increased during gestation, with the exception of medium-sized LDL and HDL particles which decreased. Subfraction concentrations were not associated with infant birth weights, though relationships were found between some lipoprotein subfraction concentrations in women with normal versus low birth weight infants (< 2500 kg). HDL’s proteome also changed during gestation, showing enrichment in proteins associated with metal ion binding, hemostasis, lipid metabolism, protease inhibitors, proteolysis, and complement activation. Compared to women in the U.S., Gambian women had lower large- and small-sized LDL and HDL concentrations, but similar medium-sized LDL and HDL concentrations.ConclusionsMost lipoprotein subfraction concentrations increase throughout pregnancy in Gambian women and are lower in Gambian vs U.S. women, the exception being medium-sized LDL and HDL particle concentrations which decrease during gestation and are similar in both cohorts of women. The proteomes of HDL also change in ways to support gestation. These changes warrant further study to determine how a lack of change or different changes could impact negative pregnancy outcomes.

Effect of Delayed Centrifugation on the Levels of NMR-Measured Lipoproteins and Metabolites in Plasma and Serum Samples.

Metabolic profiling is widely used for large-scale association studies, based on biobank material. The main obstacle to the translation of metabolomic findings into clinical application is the lack of standardization, making validation in independent cohorts challenging. One reason for this is sensitivity of metabolites to preanalytical conditions. We present a systematic investigation of the effect of delayed centrifugation on the levels of NMR-measured metabolites and lipoproteins in serum and plasma samples. Blood was collected from 20 anonymous donors, of which 10 were recruited from an obesity clinic. Samples were stored at room temperature until centrifugation after 30 min, 1, 2, 4, or 8 h, which is within a realistic time scenario in clinical practice. The effect of delaying centrifugation on plasma and serum metabolic concentrations, and on concentrations of lipoprotein subfractions, was investigated. Our results show that lipoproteins are only minimally affected by a delay in centrifugation while metabolite levels are more sensitive to a delay. Metabolites significantly increased or decreased in concentration depending on delay duration. Further, we describe differences in the stability of serum and plasma, showing that plasma is more stable for metabolites, while lipoprotein subfractions are equally stable for both types of matrices.

Lipoprotein subfractions in patients with sarcopenia and their relevance to skeletal muscle mass and function.

Loss of skeletal muscle mass is a characteristic of aging. Growing evidence suggests the role of fatty acids and their derived lipid intermediates in the regulation of skeletal muscle and function. However, the exact association between lipoprotein subfractions and sarcopenia in elderly individuals remains unclear. In this study, we aimed to investigate the levels of lipoprotein subfractions in sarcopenia patients and their relationship with skeletal muscle mass and function. A total of 84 elderly Chinese subjects aged ≥65years who did not have diseases that obviously affected lipid metabolism were included. Concentrations of lipoprotein subfractions, including total cholesterol (TC), high-density lipoprotein cholesterol (HDLC), HDL2, HDL3, low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), VLDL3, LDL-particle (LDL-P), lipoprotein(a) and remnant-like particle cholesterol (RLP-C), were determined by vertical auto profile. Triglyceride (TG) was measured by an enzymatic colorimetric assay. The skeletal muscle index (SMI) was assessed by bioelectrical impedance analysis. Handgrip strength was measured using a hand-held dynamometer. The levels of TC, TG, LDL-C, LDL-P, IDL, VLDL, VLDL3, RLP-C and C-reactive protein were significantly higher in sarcopenia patients than in controls (p<0.05). Pearson Product-Moment Correlation Coefficient analysis showed that the TC, TG, LDL-C, IDL, VLDL, VLDL3, and RLP-C levels were negatively associated with the SMI; The TG, IDL, VLDL, VLDL3, and RLP-C were negatively correlated with handgrip strength. In multivariate stepwise regression analysis, the VLDL and RLP-C levels were significantly correlated with the SMI. The sensitivity and specificity of the combined measurement of VLDL and RLP-C in predicting sarcopenia were 69.8% and 92.5% (AUC: 0.831; 95% CI:(0.739, 0.924); p<0.05). The occurrence of sarcopenia is associated with disorders of lipid metabolism, particularly VLDL and RLP-C.

Effects of a low-carbohydrate diet on insulin-resistant dyslipoproteinemia—a randomized controlled feeding trial

ABSTRACTBackgroundCarbohydrate restriction shows promise for diabetes, but concerns regarding high saturated fat content of low-carbohydrate diets limit widespread adoption.ObjectivesThis preplanned ancillary study aimed to determine how diets varying widely in carbohydrate and saturated fat affect cardiovascular disease (CVD) risk factors during weight-loss maintenance.MethodsAfter 10–14% weight loss on a run-in diet, 164 participants (70% female; BMI = 32.4 ± 4.8 kg/m2) were randomly assigned to 3 weight-loss maintenance diets for 20 wk. The prepared diets contained 20% protein and differed 3-fold in carbohydrate (Carb) and saturated fat as a proportion of energy (Low-Carb: 20% carbohydrate, 21% saturated fat; Moderate-Carb: 40%, 14%; High-Carb: 60%, 7%). Fasting plasma samples were collected prerandomization and at 20 wk. Lipoprotein insulin resistance (LPIR) score was calculated from triglyceride-rich, high-density, and low-density lipoprotein particle (TRL-P, HDL-P, LDL-P) sizes and subfraction concentrations (large/very large TRL-P, large HDL-P, small LDL-P). Other outcomes included lipoprotein(a), triglycerides, HDL cholesterol, LDL cholesterol, adiponectin, and inflammatory markers. Repeated measures ANOVA was used for intention-to-treat analysis.ResultsRetention was 90%. Mean change in LPIR (scale 0–100) differed by diet in a dose-dependent fashion: Low-Carb (–5.3; 95% CI: –9.2, –1.5), Moderate-Carb (–0.02; 95% CI: –4.1, 4.1), High-Carb (3.6; 95% CI: –0.6, 7.7), P = 0.009. Low-Carb also favorably affected lipoprotein(a) [–14.7% (95% CI: –19.5, –9.5), –2.1 (95% CI: –8.2, 4.3), and 0.2 (95% CI: –6.0, 6.8), respectively; P = 0.0005], triglycerides, HDL cholesterol, large/very large TRL-P, large HDL-P, and adiponectin. LDL cholesterol, LDL-P, and inflammatory markers did not differ by diet.ConclusionsA low-carbohydrate diet, high in saturated fat, improved insulin-resistant dyslipoproteinemia and lipoprotein(a), without adverse effect on LDL cholesterol. Carbohydrate restriction might lower CVD risk independently of body weight, a possibility that warrants study in major multicentered trials powered on hard outcomes. The registry is available through ClinicialTrials.gov: https://clinicaltrials.gov/ct2/show/NCT02068885.

Effects of a Low-Carbohydrate Diet on Cardiometabolic Risk Factors During Weight-Loss Maintenance: A Randomized Controlled Feeding Trial

Abstract Objectives To compare effects of diets varying in carbohydrate (carb) and fat on plasma lipids and lipoprotein subfractions. Methods Participants (N = 164, 70% female, 18–65 y, BMI ≥ 25 kg/m2) achieved 10–14% weight loss on a run-in diet and then were randomized to 3 test diets for 20 weeks of weight-loss maintenance. Percentages of total energy from carb-fat-protein for high-, moderate-, and low-carb diets were 60-20-20 (HI), 40-40-20 (MOD), and 20–60-20 (LO). Relative amounts of added sugar (15% total carb) and saturated fat (35% total fat) were fixed across diets. Plasma was collected at START (post-weight loss) and END of trial. The primary outcome for this ancillary study was lipoprotein insulin resistance (LPIR) – a 6-component weighted score of triglyceride-rich, high-density, and low-density lipoprotein particle (TRL-P, HDL-P, LDL-P) sizes and subfraction concentrations (large/very large TRL-P, large HDL-P, small LDL-P) (NMR spectroscopy, LabCorp). Other outcomes included large LDL-P concentration, triglycerides (TG), and cholesterol (HDL-C, LDL-C). Means (±SE) and END–START changes (mean [95% CI]) were constructed and compared from repeated measures ANOVA. Results Retention was 90% and 147 participants provided evaluable data, with no difference in body weight by diet after randomization. LPIR was 32.6 ± 1.5 at START. Change in LPIR differed by diet (P = 0.009): LO (−5.3 [−9.2, −1.5]), MOD (−0.02 [−4.1, 4.1]), HI (3.6 [−0.6, 7.7]). Diet effects favoring LO compared to HI were observed for large/very large TRL-P (P = 0.005), large HDL-P (P = 0.045), TG (P = 0.006), and HDL-C (P = 0.04). There were no mean differences between diets for particle sizes, LDL-P subfraction concentrations, and LDL-C (START: 79.3 ± 1.8 mg/dL; END–START: HI, 8.2 [4.2, 12.2]; MOD, 11.7 [7.8, 15.7]; LO, 10.0 [6.3, 13.7]). Conclusions With 3-fold higher saturated fat content (21% vs 7% total energy), a low- vs high-carb diet improved LPIR, a biomarker of diabetes risk, and several other components of the metabolic syndrome, with no adverse effects on LDL-P or LDL-C. These results from a large feeding study suggest that carb restriction may help prevent cardiometabolic disease independent of body weight. Funding Sources Nutrition Science Initiative (gifts from Arnold Ventures and Robert Lloyd Corkin Charitable Foundation), New Balance Foundation, Many Voices Foundation, Blue Cross Blue Shield.

Colchicine's effects on lipoprotein particle concentrations in adults with metabolic syndrome: A secondary analysis of a randomized controlled trial

Colchicine has received renewed interest for its potential beneficial effects in secondary prevention of cardiovascular disease. This was presumed to be primarily because of its anti-inflammatory effects; however, limited data exist regarding colchicine's impact on other cardiovascular risk factors. The aim of this study was to examine if colchicine's anti-inflammatory actions would lead to reduced circulating concentrations of oxidized low-density lipoprotein (oxLDL) in metabolically unhealthy individuals. We also examined if colchicine would improve concentrations of other atherogenic lipoprotein subfractions. This is a secondary analysis of a double-blind, randomized, placebo-controlled pilot study in which 40 adults with metabolic syndrome were randomized to colchicine 0.6mg or placebo twice daily for 3 months. Blood samples were collected in the fasted state. OxLDL was measured using enzyme-linked immunosorbent assay. Nuclear magnetic resonance spectroscopy was used to measure other lipoprotein particle subfraction concentrations. Compared with placebo, colchicine reduced markers of inflammation, including C-reactive protein, erythrocyte sedimentation rate, and GlycA (P<.01). Concentrations of oxLDL (P=.019) and small LDL (P=.022) appeared significantly increased in the colchicine arm. Colchicine had no significant effect on other lipoprotein subfractions or lipoprotein particle sizes (all P>.05). Although colchicine may have benefit in secondary prevention of cardiovascular disease in at-risk individuals, we found no evidence that these effects are because of improvements in circulating atherogenic lipoprotein particle concentrations. Further studies are needed to confirm whether colchicine increases circulating oxLDL and small LDL levels in adults with metabolic syndrome. If true, additional research is warranted to elucidate the mechanisms underlying these associations.

Effect Of Dapagliflozin And Sitagliptin On Serum Lipids And Lipoprotein Subfractions

Background and Aims: Type 2 Diabetes Mellitus (DM2) is associated with important disturbances in lipoprotein metabolism. There is little evidence regarding the effect of sodium-glucose co-transporter 2 (SGLT-2) inhibitors and dipeptidyl-peptidase 4 (DPP-4) inhibitors on serum lipid metabolism. The aim of the study was to compare the effects of dapagliflozin and sitagliptin on serum lipid and apolipoprotein-B containing lipoprotein subfraction concentrations.

Plasma lipoprotein subfraction concentrations are associated with lipid metabolism and age-related macular degeneration

Disturbance in lipid metabolism has been suggested as a major pathogenic factor for age-related macular degeneration (AMD). Conventional lipid measures have been inconsistently associated with AMD. Other factors that can alter lipid metabolism include lipoprotein phenotype and genetic mutations. We performed a case-control study to examine the association between lipoprotein profile and neovascular AMD (nAMD) and whether the cholesterylester transfer protein (CETP) D442G mutation modulates these associations. Patients with nAMD had significantly higher concentrations of HDL and IDL compared with controls. The increase in HDL particles in nAMD patients was driven by an excess of medium-sized particles. Concurrently, patients with nAMD also had lower Apo A-1, lower VLDL and chylomicron lipoprotein. Many of these associations showed a dose-dependent association between controls, early AMD cases, and nAMD cases. Adjustment for the presence of the D442G mutation at the CETP locus did not significantly alter the increased AMD risk associated with HDL particle concentration. AMD is associated with variation in many lipoprotein subclasses, including increased HDL and IDL particles and decreased Apo A-1, VLDL, and chylomicron particles. These data suggest widespread systemic disturbance in lipid metabolism in the pathogenesis of AMD, including possible alterations in lipoprotein carrier capacity.

Human knockouts and phenotypic analysis in a cohort with a high rate of consanguinity.

A major goal of biomedicine is to understand the function of every gene in the human genome.1 Loss-of-function (LoF) mutations can disrupt both copies of a given gene in humans and phenotypic analysis of such ‘human knockouts’ can provide insight into gene function. Consanguineous unions are more likely to result in offspring who carry LoF mutations in a homozygous state. In Pakistan, consanguinity rates are notably high.2 Here, we sequenced the protein-coding regions of 10,503 adult participants in the Pakistan Risk of Myocardial Infarction Study (PROMIS) designed to understand the determinants of cardiometabolic diseases in South Asians.3 We identified individuals carrying predicted LoF (pLoF) mutations in the homozygous state, and performed phenotypic analysis involving >200 biochemical and disease traits. We enumerated 49,138 rare (<1 % minor allele frequency) pLoF mutations. These pLoF mutations are predicted to knock out 1,317 genes in at least one participant. Homozygosity for pLoF mutations at PLAG27 was associated with absent enzymatic activity of soluble lipoprotein-associated phospholipase A2; at CYP2F1, with higher plasma interleukin-8 concentrations; at TREH, with lower concentrations of apoB-containing lipoprotein subfractions; at either A3GALT2 or NRG4, with markedly reduced plasma insulin C-peptide concentrations; and at SLC9A3R1, with mediators of calcium and phosphate signaling. Finally, APOC3 is a gene which retards clearance of plasma triglyceride-rich lipoproteins and where heterozygous deficiency confers protection against coronary heart disease.4,5 In Pakistan, we now observe APOC3 homozygous pLoF carriers; we recalled these knockout humans and challenged with an oral fat load. Compared with wild-type family members, APOC3 knockouts displayed marked blunting of the usual post-prandial rise in plasma triglycerides. Overall, these observations provide a roadmap for a ‘human knockout project’, a systematic effort to understand the phenotypic consequences of complete disruption of genes in humans.

Effect of short term aerobic exercise on fasting and postprandial lipoprotein subfractions in healthy sedentary men.

BackgroundOur goal was to investigate the effect of short term exercise on fasting and postprandial lipoprotein profile.MethodsHealthy sedentary men exercised 20 min for four days. The intensity of exercise was modulated to maintain 75–80 % of a calculated HRmax. Before and after the exercise program, fasting and postprandial (4 h after standard meal) concentrations of lipoprotein subfractions were measured by an electrophoresis in polyacrylamide gel and total concentrations of TAG, LDL and HDL by enzymatic colorimetric method. After 2 days of rest, fasting and postprandial concentrations of lipoprotein fractions and subfractions were measured to determine a persistency of a changes in the lipoprotein profile.Results4 days of physical exercise led to statistically significant decrease of concentration of triacylglycerol in fasting (76.29 ± 20.07, 53.92 ± 10.90, p < 0.05) and postprandial state (139.06 ± 23.72, 96.55 ± 25.21, p < 0.05) VLDL in fasting (21.88 ± 3.87, 18.00 ± 3.93, p < 0.05) and postprandial state (23.88 ± 3.52, 19.25 ± 3.62, p < 0.05), total cholesterol in fasting (162.26 ± 23.38, 148.91 ± 17.72, p < 0.05) and postprandial state (163.73 ± 23.02, 150.08 ± 18.11, p < 0.05). Atherogenic medium LDL decreased also in fasting (9.89 ± 3.27, 6.22 ± 2.55, p < 0.001) and postprandial state (8.88 ± 6.51, 6.88 ± 5.57, p < 0.001). However decrease of large IDL (25.38 ± 3.54, 23.88 ± 3.91, p < 0.05) and large LDL particles (42.89 ± 11.40, 38.67 ± 9.30) was observed only in postprandial state. Total HDL concentration remained unchanged but we observed statistically significant decrease of small HDL particles in fasting (6.11 ± 2.89, 4.22, p < 0.05) and postprandial state (6.44 ± 3.21, 4.56 ± 1.33, p < 0.05). Concentration of these particles are associated with progression of atherosclerosis. All changes of fasting and postprandial lipoprotein profile disappeared after 2 days of rest.ConclusionJust 4 daily settings of 20 min of physical exercise can lead to significant positive changes of fasting and postprandial lipoprotein profile.

Genetic risk scores associated with baseline lipoprotein subfraction concentrations do not associate with their responses to fenofibrate.

Lipoprotein subclass concentrations are modifiable markers of cardiovascular disease risk. Fenofibrate is known to show beneficial effects on lipoprotein subclasses, but little is known about the role of genetics in mediating the responses of lipoprotein subclasses to fenofibrate. A recent genomewide association study (GWAS) associated several single nucleotide polymorphisms (SNPs) with lipoprotein measures, and validated these associations in two independent populations. We used this information to construct genetic risk scores (GRSs) for fasting lipoprotein measures at baseline (pre-fenofibrate), and aimed to examine whether these GRSs also associated with the responses of lipoproteins to fenofibrate. Fourteen lipoprotein subclass measures were assayed in 817 men and women before and after a three week fenofibrate trial. We set significance at a Bonferroni corrected alpha <0.05 (p < 0.004). Twelve subclass measures changed with fenofibrate administration (each p = 0.003 to <0.0001). Mixed linear models which controlled for age, sex, body mass index (BMI), smoking status, pedigree and study-center, revealed that GRSs were associated with eight baseline lipoprotein measures (p < 0.004), however no GRS was associated with fenofibrate response. These results suggest that the mechanisms for changes in lipoprotein subclass concentrations with fenofibrate treatment are not mediated by the genetic risk for fasting levels.

Comparison of four methods of analysis of lipoprotein particle subfractions for their association with angiographic progression of coronary artery disease

BackgroundCompare gradient gel electrophoresis (GGE), vertical auto profile ultracentrifugation (VAP-II), nuclear magnetic resonance spectroscopy (NMR), and ion mobility for their ability to relate low- (LDL), intermediate- (IDL), very-low-density (VLDL) and high-density lipoprotein (HDL) subfraction concentrations to atherosclerotic progression. Methods and resultsRegression analyses of 136 patients who received baseline and follow-up coronary angiographies and subfraction measurements by all four methods in the HDL Atherosclerosis Treatment Study. Prior analyses have shown that the intervention primarily affected disease progression in proximal arteries with <30% stenoses at baseline.Three-year increases in percent stenoses were consistently associated with higher on-study plasma concentrations of small, dense LDL as measured by GGE (LDLIIIb, P = 10−6; LDLIVa, P = 0.006; LDLIVb, P = 0.02), VAP-II (LDL4, P = 0.002), NMR (small LDL, P = 0.001), and ion mobility (LDL IIb, P = 0.04; LDLIIIa, P = 0.002; LDLIIIb, P = 0.0007; LDLIVa, P = 0.05). Adjustment for triglycerides, HDL-cholesterol, and LDL-cholesterol failed to eliminate the statistical significance for on-study GGE estimated LDLIIIb (P = 10−5) and LDLIVa (P = 0.04); NMR-estimated small LDL (P = 0.03); or ion mobility estimated large VLDL (P = 0.02), LDLIIIa (P = 0.04) or LDLIIIb (P = 0.02). All methods show that the effects were significantly greater for the on-study than the baseline small, dense LDL concentrations, thus establishing that the values concurrent to the progression of disease were responsible. The rate of disease progression was also related to individual VLDL, IDL, and HDL subclasses to differing extents among the various analytic methods. ConclusionFour methodologies confirm the association of small, dense LDL with greater coronary atherosclerosis progression, and GGE, NMR, and ion mobility confirm that the associations were independent of standard lipid measurements.Clinical Trial Registration: clinicaltrials.gov/ct2/show/NCT00000553.

Abstract 397: Changes in Lipoprotein Subfraction Concentrations After Treatment with the Cholesteryl Ester Transfer Protein Inhibitor Anacetrapib Alone or in Combination with Atorvastatin

Background Anacetrapib (ANA), a cholesteryl ester transfer protein inhibitor, has been shown to increase plasma HDL cholesterol and reduce LDL cholesterol, both as monotherapy and in combination with atorvastatin (ATORVA). The effects of these regimens on lipoprotein subfractions have not been reported. Methods ApoB-containing lipoprotein particle subfractions were measured by ion mobility in a post-hoc analysis of baseline and 8 week on-treatment samples from 464 dyslipidemic participants who had been randomized to placebo, ATORVA 20 mg/d, or to ANA at several doses administered with and without ATORVA ( clinicaltrials.gov NCT00325455 ). Results ANA (combined 150 mg/d and 300 mg/d groups) significantly reduced total LDL particle concentration by 51%, and levels of large, medium, and small LDL particles (LDL 1, 2, and 3a) by 43-72% but significantly increased levels of the less abundant cholesterol-depleted very small LDL 4a and 4b species by ~64%. In contrast, ATORVA, despite producing a similar reduction of total LDL particle concentration (50%), reduced the levels of all LDL particle subfractions, although the magnitude was smaller for LDL 4a, with a much smaller non-significant reduction for LDL 4b. Compared with ANA monotherapy, results for combination treatment were generally consistent with additive effects. Notably, for individuals with baseline triglyceride (TG) above the median (&gt;154 mg/dL), increases of very small LDL after ANA were markedly attenuated, whereas after ATORVA there was greater reduction of LDL 4a in the higher TG group. Conclusions Similar reductions of LDL levels after ANA or ATORVA were not associated with comparable effects on all LDL particle subfractions, and neither drug was effective in lowering levels of the smallest LDL particles. Assessment of the clinical impact of the effects of ANA on LDL subfractions, and the differential changes in very small LDL in individuals with normal versus elevated TG, await cardiovascular outcome data from REVEAL.

Changes in lipoprotein subfraction concentration and composition in healthy individuals treated with the CETP inhibitor anacetrapib

We investigated the effects of the cholesteryl ester (CE) transfer protein inhibitor anacetrapib (ANA) on plasma lipids, lipoprotein subfraction concentrations, and lipoprotein composition in 30 healthy individuals. Participants (n = 30) were randomized to ANA 20 mg/day, 150 mg/day, or placebo for 2 weeks. Changes in concentration of lipoprotein subfractions were assessed using ion mobility, and compositional analyses were performed on fractions separated by density gradient ultracentrifugation. ANA 150 mg/day versus placebo resulted in significant decreases in LDL-cholesterol (26%) and apo B (29%) and increases in HDL-cholesterol (82%). Concentrations of medium and small VLDL, large intermediate density lipoprotein (IDL), and medium and small LDL (LDL2a, 2b, and 3a) decreased whereas levels of very small and dense LDL4b were increased. There was enrichment of triglycerides and reduction of CE in VLDL, IDL, and the densest LDL fraction. Levels of large buoyant HDL particles were substantially increased, and there was enrichment of CE, apo AI, and apoCIII, but not apoAII or apoE, in the mid-HDL density range. Changes in lipoprotein subfraction concentrations and composition with ANA 20 mg/day were similar to those for ANA 150 mg/day but were generally smaller in magnitude. The impact of these changes on cardiovascular risk remains to be determined.

Novel Lipoprotein Subfraction and Size Measurements in Prediction of Mortality in Maintenance Hemodialysis Patients

Conventional lipid profiles usually cannot predict cardiovascular outcomes in chronic disease states. We hypothesized that novel lipoprotein subfraction concentrations and LDL particle size measurements better predict mortality in maintenance hemodialysis (MHD) patients. Mortality-predictability of LDL particle diameter and lipoprotein subfraction concentrations, measured by novel ion mobility, was examined in a cohort of 235 hemodialysis patients who were followed for up to 6 years using Cox models with adjustment for important covariables. Patients were 54 ± 14 years old (mean ± SD) and included 45% women with total, LDL and HDL cholesterol levels of 143 ± 42, 76 ± 29, and 37 ± 12 mg/dl, respectively. Over 6 years, 71 patients (31%) died. Conventional lipid profile was not associated with mortality. The death hazard ratio (HR, 95% confidence interval) of the highest versus lowest quartiles of very small and large LDL particle concentrations were 2.43 (1.03 to 5.72) and 0.38 (0.15 to 0.96), respectively. Across increasing quartiles of LDL particle diameter, death HRs were 1.00, 0.93 (0.46 to 1.87), 0.43 (0.21 to 0.89), and 0.45 (0.31 to 1.00), respectively. Whereas conventional lipid profile cannot predict mortality in MHD patients, larger novel LDL particle diameter or higher large LDL particle concentrations appear predictive of greater survival, whereas higher very small LDL particle concentration is associated with higher death risk. Examining lipoprotein subfraction modulation in chronic diseases is indicated.

Advanced diagnostic support in lipidology project: role for phenotypic and functional evaluation of lipoproteins in dyslipidemias

The term ‘dyslipidemia’ includes a wide family of lipoprotein metabolic defects often related to cardiovascular diseases. Despite the complexity of lipid disorders, current guidelines indicate LDL-C as the single most important therapeutic target; however, other lipido–proteic parameters, such as the concentration of lipoprotein subfractions (e.g., small-dense LDL) or their functional capacity (e.g., HDL reverse cholesterol transport), may display direct pro- or anti-atherogenic properties. Traditional lipid profiles may therefore be inadequate in representing dyslipidemia complexity and may prove to be ineffective in estimating the overall patient’s risk in this context. We designed a research project attempting to provide a coherent framework integrating traditional lipid profiling and advanced diagnostics, to assess qualitative and functional lipoprotein features in relevant clinical conditions and to correlate them with preclinical atherosclerosis.

Advanced Lipoprotein Testing and Subfractionation Are Not (Yet) Ready for Routine Clinical Use

Standard lipid tests measure the cholesterol or triglyceride content of lipoproteins, expressed as mg/dL (or mmol/L) of cholesterol or triglyceride. A standard lipid panel includes total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides. These lipids are carried within lipoprotein particles that are heterogeneous in size, density, charge, core lipid composition, specific apolipoproteins, and function.1 A variety of lipoprotein assays have been developed that subfractionate lipoprotein particles according to some of these properties such as size, density, or charge.2 These lipoprotein assays have been proposed for improving assessment of risk of cardiovascular disease (CVD) and for guiding lipid-lowering therapies. They are mostly used today in specialized lipid clinics or research studies, and their general utility for clinical practice is not well delineated.3 In this review, I first provide a summary of current guideline statements that address this topic. Then I give a brief overview of the different laboratory methods available for clinical use and discuss the literature evaluating these methods. Finally, I discuss current limitations to the widespread clinical application of these methods. Response by Superko on p 2404 The Third Adult Treatment Panel of the National Cholesterol Education Program4 and the American Heart Association5 recommend measuring a standard lipid panel in adults and targeting lipid-lowering therapy on the basis of levels of LDL cholesterol, and non-HDL cholesterol in subjects with hypertriglyceridemia. European and Canadian guidelines recommend measuring standard lipids while also emphasizing the total/HDL cholesterol ratio in risk assessment.6,7 Current guidelines do not recommend routine use of advanced lipoprotein tests, mainly because it is unclear how much incremental prognostic information is provided by these tests beyond that available from a standard lipid panel.4,6,7 Recently, an international panel proposed that cardiovascular risk may be more closely related to atherogenic lipoprotein …

EFFECT OF EZETIMIBE ON LIPOPROTEIN SUBFRACTION CONCENTRATIONS: THE ROLE OF ATORVASTATIN PRETREATMENT

Introduction: Recently published data indicate that the effect of ezetimibe on lipoprotein subfraction distribution in patients receiving statin therapy may differ substantially from that observed in patients treated with ezetimibe monotherapy. The aim of our study was to directly compare the effects of ezetimibe added to established atorvastatin treatment on lipoprotein subfractions with those obtained by ezetimibe monotherapy. Material and methods: Forty dyslipidaemic patients who failed to reach their assigned LDL-C target while on atorvastatin therapy (20 mg/day) for at least 6 months were included in the study. Ezetimibe (10 mg/day) was added to atorvastatin in all patients. The concentrations of the individual lipoprotein subfractions were determined using the Lipoprint method at baseline (prior to the addition of ezetimibe) as well as after 16 weeks of combination treatment. The changes in lipoprotein subfraction concentrations were compared with those observed in 40 age- and sex-matched statin-naive patients receiving ezetimibe monotherapy for 16 weeks. Results: Ezetimibe administration reduced VLDL concentrations either when used as monotherapy or when added to established atorvastatin treatment. However, in contrast to ezetimibe monotherapy, which reduced the concentrations of all LDL subfractions, the addition of ezetimibe in patients receiving atorvastatin decreased LDL cholesterol values exclusively by reducing the concentrations of large, buoyant LDL subfractions. In addition, while ezetimibe monotherapy reduced mainly the concentrations of small, dense LDL subspecies, the addition of ezetimibe in patients receiving atorvastatin equally reduced the concentration of all HDL particles. Conclusions: The effect of ezetimibe on lipoprotein subfractions is significantly affected by previous atorvastatin treatment.

Effect of ezetimibe monotherapy on the concentration of lipoprotein subfractions in patients with primary dyslipidaemia

ABSTRACTBackground: Recent studies suggest that the distribution of lipoprotein subfractions is an independent predictor of vascular events. Therefore, we evaluated the effect of ezetimibe (a selective cholesterol transport inhibitor) on the concentrations of lipoprotein subfractions in patients with primary dyslipidaemia.Materials and methods: Patients (n = 50) with primary dyslipidaemias were recruited. The concentrations of the individual lipoprotein subfractions were measured using the Lipoprint system at baseline and after 16 weeks of treatment.Results: Ezetimibe reduced total, low-density lipoprotein cholesterol (LDL‑C) and non-high-density lipoprotein cholesterol (HDL‑C) values as well as apolipoprotein B concentrations. Subfractionation of apolipoprotein B-containing lipoproteins showed that the reduction in LDL‑C values was due to a fall in the concentrations of all LDL subfractions. However, a more pronounced trend towards a decrease in the concen­trations of dense LDL subfractions was observed. Patients with triglyceride values >1.7 mmol/L had significantly greater reductions in the concentrations of small, dense LDL particles compared with those with normal triglyceride levels (49 vs. 19%, respectively; p < 0.05). Ezetimibe decreased the concentrations of HDL‑C mainly due to a fall in the concentration of dense HDL subfractions.Conclusion: Ezetimibe can favourably affect the distribution of LDL subfractions, especially in patients with elevated triglyceride values. Further studies are needed to clarify the significance of the ezetimibe-induced reduction in the concentrations of dense HDL particles.