HDL Subspecies Research Articles

Abstract 4138473: Detailed Lipoprotein Profiling in Assessing Coronary Calcium Score Progression and Atherosclerotic Risk

Background: Coronary calcium scoring (CCS) evaluates atherosclerotic burden and cardiovascular risk, correlating with coronary artery disease (CAD) severity. Advances in Nuclear Magnetic Resonance ( 1 H-NMR) spectroscopy for lipoprotein fraction analysis highlight precise atherogenic lipid parameter estimation. Enhanced lipid testing, including sub-fractionation assays, improves risk assessment and identifies new biochemical markers for CAD burden. Hypothesis: Specific lipid fractions and subfractions are significantly associated with CCS progression, serving as biochemical markers of CAD progression. Aim: To evaluate the association between lipid fractions and subfractions with CCS progression, aiming to improve CAD risk stratification. Methods: This study used data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). CCS progression was any positive change in CCS values over 5 years. High-field 1 H-NMR spectroscopy assessed lipoprotein fractions and subfractions, including plasma concentration, particle size, cholesterol, and triglyceride content. Descriptive and inferential statistics compared baseline characteristics. Multivariable binary logistic regression models, both unadjusted and propensity score-adjusted, assessed associations between plasma levels of lipoprotein fractions and CCS progression. Statistical significance was set at p <0.05. Results/Data: In this study of 2,986 participants, 1,008 (33.8%) experienced CCS progression over 5 years. Significant associations were found between plasma lipoprotein fractions and CCS progression. Large, medium, and very small TRLP (89-37 and 29-24 nm) were linked to increased CCS risk, while small TRLP (36-30 nm) had an inverse association. Small cLDLP (20.4-19 nm) were directly associated with CCS progression, while medium and large cLDLP (23-20.5 nm) were inversely associated. Small cHDLP (7.4-8.0 nm) increased CCS risk, whereas medium to large cHDLP (8.1-13.0 nm) had an inverse association. Specific HDL subspecies (H7P to H3P, 12.0-8.7 nm) were inversely associated with CCS progression, while H2P and H1P (7.8-7.4 nm) increased CCS risk. TRLZ (30-100 nm) levels were positively associated with CCS progression, whereas LDLZ (19-22.5 nm) and HDLZ (7.1-13 nm) were inversely associated. Conclusion(s): Plasma levels of specific lipoprotein fractions and subfractions are associated with CCS progression, providing insights into the complexity of lipoprotein characteristics in CAD.

Effect of Empagliflozin with or without the Addition of Evolocumab on HDL Subspecies in Individuals with Type 2 Diabetes Mellitus: A Post Hoc Analysis of the EXCEED-BHS3 Trial.

Evolocumab and empagliflozin yield a modest rise in plasma high-density lipoprotein cholesterol (HDL-C) through unknown mechanisms. This study aims to assess the effect of evolocumab plus empagliflozin vs. empagliflozin alone on HDL subspecies isolated from individuals with type 2 diabetes mellitus (T2D). This post hoc prespecified analysis of the EXCEED-BHS3 trial compared the effects of a 16-week therapy with empagliflozin (E) alone or in combination with evolocumab (EE) on the lipid profile and cholesterol content in HDL subspecies in individuals with T2D divided equally into two groups of 55 patients. Both treatments modestly increased HDL-C. The cholesterol content in HDL subspecies 2a (7.3%), 3a (7.2%) and 3c (15%) increased from baseline in the E group, while the EE group presented an increase from baseline in 3a (9.3%), 3b (16%) and 3c (25%). The increase in HDL 3b and 3c was higher in the EE group when compared to the E group (p < 0.05). No significant interactive association was observed between changes in hematocrit and HDL-C levels after treatment. Over a 16-week period, empagliflozin with or without the addition of evolocumab led to a modest but significant increase in HDL-C. The rise in smaller-sized HDL particles was heterogeneous amongst the treatment combinations.

Alcohol Consumption, High-Density Lipoprotein Particles and Subspecies, and Risk of Cardiovascular Disease: Findings from the PREVEND Prospective Study.

The associations of HDL particle (HDL-P) and subspecies concentrations with alcohol consumption are unclear. We aimed to evaluate the interplay between alcohol consumption, HDL parameters and cardiovascular disease (CVD) risk. In the PREVEND study of 5151 participants (mean age, 53 years; 47.5% males), self-reported alcohol consumption and HDL-P and subspecies (small, medium, and large) by nuclear magnetic resonance spectroscopy were assessed. Hazard ratios (HRs) with 95% CIs for first CVD events were estimated. In multivariable linear regression analyses, increasing alcohol consumption increased HDL-C, HDL-P, large and medium HDL, HDL size, and HDL subspecies (H3P, H4P, H6 and H7) in a dose-dependent manner. During a median follow-up of 8.3 years, 323 first CVD events were recorded. Compared with abstainers, the multivariable adjusted HRs (95% CIs) of CVD for occasional to light, moderate, and heavy alcohol consumers were 0.72 (0.55-0.94), 0.74 (0.54-1.02), and 0.65 (0.38-1.09), respectively. These associations remained consistent on additional adjustment for each HDL parameter. For CVD, only HDL-C was associated with a statistically significant decreased risk of CVD in a fully adjusted analysis (HR 0.84, 95% CI 0.72-0.97 per 1 SD increment). For coronary heart disease, HDL-C, HDL-P, medium HDL, HDL size, and H4P showed inverse associations, whereas HDL-C and HDL size modestly increased stroke risk. Except for H6P, alcohol consumption did not modify the associations between HDL parameters and CVD risk. The addition of HDL-C, HDL size, or H4P to a CVD risk prediction model containing established risk factors improved risk discrimination. Increasing alcohol consumption is associated with increased HDL-C, HDL-P, large and medium HDL, HDL size, and some HDL subspecies. Associations of alcohol consumption with CVD are largely independent of HDL parameters. The associations of HDL parameters with incident CVD are generally not attenuated or modified by alcohol consumption.

Abstract 17049: Specific Subspecies of High Density Lipoprotein are Associated With Arterial Stiffness in Youth With and Without Diabetes

Introduction: Early vascular aging (EVA), a risk factor for cardiovascular disease (CVD), is evident in youth with diabetes. The mechanisms responsible for EVA are not well understood. Causal relationship of HDL-C with CVD is doubtful, but HDL particle concentration (HDL-P) and HDL function (cholesterol efflux capacity, CEC) are associated with incident and prevalent CVD independent of HDL-C. We investigated whether these metrics associate with EVA in youth. Methods: We studied three cohorts of youth with T1D (n=173), T2D (n=214) and healthy controls (n=116). We quantified total HDL-P and 6 HDL subspecies by differential ion mobility, serum HDL CEC (total and ABCA1-specific), and investigated their association with arterial stiffness (tonometric carotid-femoral pulse wave velocity, PWV) with multivariate regression. Results: PWV was not associated with total HDL-P in any of the three groups, but was associated positively with concentration of extra-small (xsHDL, 7.6nm, r=0.22, P=0.004) in T1D, small (sHDL, 8.2nm) particles in T1D (r=0.31, P&lt;0.0001) and T2D (r=0.17, P=0.02), and negatively with large HDL particles (lHDL, 11.5 nm) in T1D (r=-0.19, P=0.01). None of the HDL subspecies associated with PWV in healthy subjects. The association of sHDL with PVW remained significant after adjustment for age, sex, BMIz, mean arterial pressure (MAP), and diabetes status when analyzing T1D and controls or T2D and control subjects (Table 1). Both HDL-CEC metrics were significantly associated with higher PWV in T1D cohort but not T2D cohort, however, in multivariate models neither remained significant after adjusting the model for MAP (Table 1). Conclusions: A specific population of small HDL particles, but not HDL CEC, is associated with EVA, a predictor of CVD, independent of traditional risk factors and distending pressure (MAP). How the small HDL particles relate to EVA and whether they may be a novel target for intervention to prevent EVA in youth remains to be investigated.

Novel Size-Based High-Density Lipoprotein Subspecies and Incident Vascular Events.

Background High-density lipoprotein (HDL) particle concentration likely outperforms HDL cholesterol in predicting atherosclerotic cardiovascular events. Whether size-based HDL subspecies explain the atheroprotective associations of HDL particle concentration remains unknown. Our objective was to assess whether levels of specific size-based HDL subspecies associate with atherosclerotic cardiovascular disease in a multiethnic pooled cohort and improve risk prediction beyond traditional atherosclerotic cardiovascular disease risk factors. Methods and Results Seven HDL size-based subspecies were quantified by nuclear magnetic resonance (LP4 algorithm; H1=smallest; H7=largest) among participants without prior atherosclerotic cardiovascular disease in ARIC (Atherosclerosis Risk in Communities), MESA (Multi-Ethnic Study of Atherosclerosis), PREVEND (Prevention of Renal and Vascular Endstage Disease), and DHS (Dallas Heart Study) cohorts (n=15 371 people). Multivariable Cox proportional hazards models were used to evaluate the association between HDL subspecies and incident myocardial infarction (MI) or ischemic stroke at follow-up (average 8-10 years) adjusting for HDL cholesterol and risk factors. Improvement in risk prediction was assessed via discrimination and reclassification analysis. Within the pooled cohort (median age 57 years; female 54%; Black 22%) higher H1 (small) and H4 (medium) concentrations were inversely associated with incident MI (hazard ratio [HR]/SD, H1 0.88 [95% CI, 0.81-0.94]; H4 0.89 [95% CI, 0.82-0.97]). H4 but not H1 improved risk prediction indices for incident MI. Increasing H2 and H4 were inversely associated with improved risk prediction indices for composite end point of stroke, MI, and cardiovascular death (HR/SD, H2 0.94 [95% CI, 0.88-0.99]; H4 0.91 [95% CI, 0.85-0.98]). Levels of the large subspecies (H6 and H7) were not associated with any vascular end point. Conclusions Two of 7 HDL size-based subspecies modestly improved risk prediction for MI and composite vascular end points in a large multiethnic pooled cohort. These findings support assessment of precise HDL subspecies for future studies regarding clinical utility.

Low concentrations of medium-sized HDL particles predict incident CVD in chronic kidney disease patients

Patients with chronic kidney disease (CKD) are at high risk for CVD. However, traditional CVD risk factors cannot completely explain the increased risk. Altered HDL proteome is linked with incident CVD in CKD patients, but it is unclear whether other HDL metrics are associated with incident CVD in this population. In the current study, we analyzed samples from two independent prospective case-control cohorts of CKD patients, the Clinical Phenotyping and Resource Biobank Core (CPROBE) and the Chronic Renal Insufficiency Cohort (CRIC). We measured HDL particle sizes and concentrations (HDL-P) by calibrated ion mobility analysis and HDL cholesterol efflux capacity (CEC) by cAMP-stimulated J774 macrophages in 92 subjects from the CPROBE cohort (46 CVD and 46 controls) and in 91 subjects from the CRIC cohort (34 CVD and 57 controls). We tested associations of HDL metrics with incident CVD using logistic regression analysis. No significant associations were found for HDL-C or HDL-CEC in either cohort. Total HDL-P was only negatively associated with incident CVD in the CRIC cohort in unadjusted analysis. Among the six sized HDL subspecies, only medium-sized HDL-P was significantly and negatively associated with incident CVD in both cohorts after adjusting for clinical confounders and lipid risk factors with odds ratios (per 1-SD) of 0.45 (0.22–0.93, P = 0.032) and 0.42 (0.20–0.87, P = 0.019) for CPROBE and CRIC cohorts, respectively. Our observations indicate that medium-sized HDL-P—but not other-sized HDL-P or total HDL-P, HDL-C, or HDL-CEC—may be a prognostic cardiovascular risk marker in CKD.

Abstract 13404: Novel Sized-Based HDL Subspecies Demonstrate Inverse Associations With Incident Vascular Events

Recent studies suggest that total high-density lipoprotein particle concentration (HDL-P) outperforms HDL cholesterol (HDL-C) in predicting atherosclerotic cardiovascular disease (ASCVD). Whether specific size-based HDL subspecies contribute to the atheroprotective effects of HDL-P remains unknown. Our objective was to assess size-based HDL subspecies for association with both incident myocardial infarction (MI) and ischemic stroke in a large, diverse cohort, expecting heterogeneous associations regarding subspecies and vascular endpoints. Participants without prior ASCVD enrolled in the Dallas Heart Study, MESA, ARIC, and PREVEND were included as a single pooled cohort (N=15,371). Seven HDL size-based subspecies were quantified by NMR (LP4 algorithm; H1=smallest; H7=largest). The primary adjudicated outcomes over an average of 8-10 years of follow up were first MI and first ischemic stroke. Cox proportional hazards models included traditional ASCVD risk factors (except HDL-C) and all seven HDL subspecies. As continuous variables, higher H1, H2 and H4 concentrations were associated with lower risk of MI (Panel A), whereas higher H2 and H4 concentrations were associated with lower risk of ischemic stroke (Panel B). The top vs bottom quartiles of H2 and H4 had 27-32% lower incidence of MI (HR Q4 vs. Q1 [95% CI]: H1 0.73 [0.58-0.91]; H2 0.69 [0.54-0.89]; H4 0.68 [0.54-0.86]) and no significant associations with ischemic stroke. Serial adjustment for HDL-C attenuated all associations with ischemic stroke. However, H1 and H4 retained significant inverse associations with MI adjusted for HDL-C (HR/SD [95% CI]: H1 0.88 [0.81-0.94]; H4 0.89 [0.82-0.97]). H1 (small HDL) and H4 (medium HDL), but no large subspecies, demonstrated inverse associations with MI in a large multi-ethnic pooled cohort. Next steps include assessment of interactions by sex and race as well as incremental clinical utility of H1 and H4 compared to both HDL-C and total HDL-P in predicting MI.

Effect of Selective Androgen Receptor Modulator on Cholesterol Efflux Capacity, Size, and Subspecies of HDL Particles.

ContextSelective androgen receptor modulators (SARMs), because of their preferential muscle vs prostate selectivity, are being developed for muscle-wasting conditions. Oral SARMs suppress high-density lipoprotein cholesterol (HDL-C) but their effects on functional capacity and atherogenic potential of HDL particles are unknown.ObjectiveTo determine the effects of an oral SARM (OPK-88004) on cholesterol efflux capacity, HDL particle number and size, apolipoprotein particle number and size and HDL subspeciesMethodsWe measured cholesterol efflux capacity (CEC); HDL particle number and size; APOB; APOA1; and protein-defined HDL subspecies associated with coronary heart disease (CHD) risk in men, who had undergone prostatectomy for low-grade prostate cancer during 12-week treatment with placebo or 1, 5, or 15 mg of an oral SARM (OPK-88004).ResultsSARM significantly suppressed HDL-C (P < .001) but HDL particle size did not change significantly. SARM had minimal effect on CEC of HDL particles (change + 0.016, –0.036, +0.070, and –0.048%/µmol-HDL/L–1 at 0, 1, 5, and 15 mg SARM, P = .045). SARM treatment suppressed APOAI (P < .001) but not APOB (P = .077), and reduced APOA1 in HDL subspecies associated with increased (subspecies containing α2-macroglobulin, complement C3, or plasminogen) as well as decreased (subspecies containing APOC1 or APOE) CHD risk; relative proportions of APOA1 in these HDL subspecies did not change. SARM increased hepatic triacylglycerol lipase (HTGL) (P < .001).ConclusionSARM treatment suppressed HDL-C but had minimal effect on its size or cholesterol efflux function. SARM reduced APOA1 in HDL subspecies associated with increased as well as decreased CHD risk. SARM-induced increase in HTGL could contribute to HDL-C suppression. These data do not support the simplistic notion that SARM-associated suppression of HDL-C is necessarily proatherogenic; randomized trials are needed to determine SARM’s effects on cardiovascular events.

Effect of olezarsen targeting APOC-III on lipoprotein size and particle number measured by NMR in patients with hypertriglyceridemia

Olezarsen is a hepatocyte-targeted, GalNAc-modified antisense oligonucleotide that decreases plasma levels of apolipoprotein C-III (apoC-III) and triglyceride-rich lipoproteins (TRLs). To define the effect of olezarsen on NMR-derived lipoprotein particle size and concentration. Patients (n=114) with or at risk for atherosclerotic cardiovascular disease and fasting triglycerides ≥200 and <500 mg/dL received olezarsen (10 or 50 mg every 4 weeks, 15 mg every 2 weeks, or 10 mg every week) or saline placebo subcutaneously for 6-12 months. NMR LipoProfile® analysis was performed in frozen EDTA plasma samples collected at baseline and at the primary analysis timepoint (PAT) at 6 months. A dose-dependent relationship was generally noted with increasing cumulative doses of olezarsen in TRL particle (TRLP), LDL particle (LDL-P) and HDL (HDL-P) particle concentrations. In the 50 mg every 4 weeks dose, compared to placebo, olezarsen resulted in a significant reduction in total TRL-P (51%, P<0.0001) with largest reductions in large-size (68%, P<0.0001) and medium-size (63%, P<0.0001) TRL-P. Total LDL-P concentration was not changed, but large LDL-P increased by 186% (p=0.0034), and small LDL-P decreased by 39% (p=0.0713). Total HDL-P concentration increased by 15% (P=0.0006), driven primarily by a 32% increase in small HDL subspecies (diameters <8.3 nm) (P=0.0008). Olezarsen results in favorable changes in lipoprotein concentration and particle size, primarily manifested by reduction in TRLs, remodeling to larger LDL particles, and increase in small HDL-P. These findings suggest that apoC-III inhibition improves the overall atherogenic risk profile.

Protein-based HDL subspecies: Rationale and association with cardiovascular disease, diabetes, stroke, and dementia

HDL-cholesterol is associated with reduced risk of cardiovascular disease, and is used in clinical practice for risk stratification. HDL is composed of many protein-defined subspecies that each comprises just a few percent of the total, some associated with lower and some with higher risk of CVD. HDL that contains apoC3 or apoE are subspecies that have opposing actions on HDL reverse cholesterol transport and opposing associations with risk of future CVD, apoC3 adverse and apoE beneficial. In addition to coronary heart disease, HDL that contains apoC3 is associated with risk of future type 2 diabetes and insulin resistance; ischemic stroke and cerebral infarction; dementia and the deposition of beta-amyloid in the brain. HDL that contains apoE and apoE itself are associated with lower risk of dementia. Other HDL subspecies that contain complement C3, alpha-2 macroglobulin, plasminogen, or haptoglobin are associated with higher future risk of coronary heart disease, whereas others such as HDL that contains apoC1 are associated with lower risk. At this time, these findings provide improved understanding of the multifaceted HDL system to better determine risk and targeting of therapy for the most prevalent chronic lifestyle diseases in our society.

Abstract 11174: Effect of APOCIII-L Rx on Lipoprotein Size and Particle Numbers Measured by NMR in Patients with Hypertriglyceridemia: Results of the AKCEA-APOCIII-L Rx Trial

Background: APOCIII-L Rx is a hepatocyte-targeted, GalNAc-modified antisense oligonucleotide that decreases plasma levels of apoC-III and triglyceride-rich lipoproteins (TRLs). We examined the effect of APOCIII-L Rx on a variety of lipoprotein fractions measured by nuclear magnetic resonance (NMR) spectroscopy. Methods: The AKCEA-APOCIII-L Rx trial was a dose-ranging study in 114 patients with, or at risk for, ASCVD and fasting serum triglycerides 200-500 mg/dL. Patients (n=114) received AKCEA-APOCIII-L Rx (10 or 50 mg every 4 weeks, 15 mg every 2 weeks, or 10 mg every week) or saline placebo subcutaneously for 6-12 months. Comprehensive NMR LipoProfile ® analysis was performed by LipoScience/LabCorp in frozen EDTA plasma samples collected at baseline and at the primary analysis timepoint (PAT) at 6 months. Results: Results are reported as change from baseline to PAT for the 50 mg every 4 weeks dose versus placebo. APOCIII-L Rx resulted in a significant reduction in total TRL particle (TRLP) concentration by 51% (P&lt;0.0001) with largest reductions in large-size (by 68%, P&lt;0.0001) and medium-size (by 63%, P&lt;0.0001) TRLPs. Total LDL particle (LDLP) concentration was not changed, small LDLP numerically decreased by 39% (P= 0.0713) while medium LDLP increased by 187% (P=0.0119), accompanied by an increase in average LDL size by xx 2% (p=0.0039xx). Total HDL particle (HDLP) concentration increased by 15% (P=0.0006), represented primarily by an increase in small HDL subspecies (particle diameters &lt;8.3 mm) of 32% (P=0.0008). Lower cumulative doses of APOCIII-L Rx generally reflected a dose-dependent relationship in the above parameters. Conclusion: APOCIII-L Rx results in favorable changes in lipoprotein concentration and particle size, primarily manifested by reduction in TRLs, remodeling to larger LDL particles, and increase in small HDLP. These findings suggest an improvement in overall atherogenic risk profile.

HDL Containing Apolipoprotein C-III is Associated with Insulin Sensitivity: A Multicenter Cohort Study.

High density lipoprotein (HDL) in humans is composed of a heterogeneous group of particles varying in protein composition as well as biological effects. We investigated the prospective associations between HDL subspecies containing and lacking apolipoprotein (apo) C-III at baseline and insulin sensitivity at year 3. A prospective cohort study of 864 healthy volunteers drawn from the relationship between insulin sensitivity and cardiovascular disease (RISC) study, a multicenter European clinical investigation, whose recruitment initiated in 2002, with a follow-up of 3 years. Insulin sensitivity was estimated from an oral glucose tolerance test at baseline and year 3, and by euglycemic-hyperinsulinemic clamp at baseline only. The apolipoprotein concentrations were measured at baseline by a sandwich enzyme-linked immunosorbent assay (ELISA)-based method. The 2 HDL subspecies demonstrated significantly opposite associations with insulin sensitivity at year 3 (P-heterogeneity = 0.004). The highest quintile of HDL containing apoC-III was associated with a 1.2% reduction in insulin sensitivity (P-trend = 0.02), while the highest quintile of HDL lacking apoC-III was associated with a 1.3% increase (P-trend = 0.01), compared to the lowest quintile. No significant association was observed for total HDL, and very low density lipoprotein (VLDL) and low density lipoprotein (LDL) containing apoC-III. ApoC-III contained in HDL was associated with a decrease in insulin sensitivity even more strongly than plasma total apoC-III. Both HDL containing apoC-III and apoC-III in HDL adversely affect the beneficial properties of HDL on insulin response to glucose. Our results support the potential of HDL-associated apoC-III as a promising target for diabetes prevention and treatment.

HDL Particle Subspecies and Their Association With Incident Type 2 Diabetes: The PREVEND Study.

ContextHigh-density lipoproteins (HDL) may be protective against type 2 diabetes (T2D) development, but HDL particles vary in size and function, which could lead to differential associations with incident T2D. A newly developed nuclear magnetic resonance (NMR)-derived algorithm provides concentrations for 7 HDL subspecies.ObjectiveWe aimed to investigate the association of HDL particle subspecies with incident T2D in the general population.MethodsAmong 4828 subjects of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study without T2D at baseline, HDL subspecies with increasing size from H1P to H7P were measured by NMR (LP4 algorithm of the Vantera NMR platform).ResultsA total of 265 individuals developed T2D (median follow-up of 7.3 years). In Cox regression models, HDL size and H4P (hazard ratio [HR] per 1 SD increase 0.83 [95% CI, 0.69-0.99] and 0.85 [95% CI, 0.75-0.95], respectively) were inversely associated with incident T2D, after adjustment for relevant covariates. In contrast, levels of H2P were positively associated with incident T2D (HR 1.15 [95% CI, 1.01-1.32]). In secondary analyses, associations with large HDL particles and H6P were modified by body mass index (BMI) in such a way that they were particularly associated with a lower risk of incident T2D, in subjects with BMI < 30 kg/m2.ConclusionGreater HDL size and lower levels of H4P were associated with a lower risk, whereas higher levels of H2P were associated with a higher risk of developing T2D. In addition, large HDL particles and H6P were inversely associated with T2D in nonobese subjects.

1569-P: Cholesterol Efflux Capacity (CEC) and HDL Subspecies Associate with Estimated Insulin Sensitivity (eIS) in Type 1 Diabetes (T1D)

People with T1D have higher HDL cholesterol (HDLc) yet are more insulin resistant and have increased cardiovascular disease (CVD) risk than people without diabetes. We hypothesized that HDL is dysfunctional in people with T1D, explaining this paradox. We examined the association between eIS, serum HDL CEC, and HDL subspecies in adults with T1D. This study was conducted in a sub-cohort (N=134) randomly selected from the Coronary Artery Calcification in type 1 diabetes study (N=652). eIS was calculated using a validated equation that includes waist circumference, triglycerides, adiponectin, diastolic blood pressure and insulin dose. We quantified CEC from a macrophage cell line (J774) and through the cholesterol transport proteins ABCA1 and ABCG1 and HDL particle concentration and size using calibrated ion mobility analysis. The analyzed HDLs were extra small (XS-HDL), small (S-HDL), medium (M-HDL) and large (L-HDL) populations. Associations were assessed by multivariable linear regression. J774 and ABCA1 CEC were negatively associated with eIS, as was S-HDL (Table). eIS positively associated with L-HDL, whereas other HDL metrics were not associated with eIS. Higher eIS associated with fewer S-HDL particles and reduced macrophage- and ABCA1-mediated CEC, suggesting novel interactions among insulin sensitivity and HDL metrics, which may contribute to CVD risk in T1D. Disclosure T. Buckner: None. K. Bornfeldt: None. J. Heinecke: None. T. Vaisar: Consultant; Self; MedImmune. Research Support; Self; MedImmune. J.K. Snell-Bergeon: None. Funding American Diabetes Association (7-13-CD-10 to J.K.S-B.)

Dietary unsaturated fat increases HDL metabolic pathways involving apoE favorable to reverse cholesterol transport.

HDL that contains apolipoprotein E (apoE) is a subspecies especially active in steps in reverse cholesterol transport, a process that brings cholesterol from peripheral cells to the liver. Here, we studied the effect of dietary unsaturated fat compared with carbohydrate on the metabolism of HDL containing apoE. We enrolled 9 adults who were overweight or obese and had below-average HDL-cholesterol in a crossover study of a high-fat diet, primarily unsaturated, and a low-fat, high-carbohydrate diet. A metabolic tracer study was performed after each diet period. Dietary fat increased the secretion, metabolism, and clearance of HDL subspecies containing apoE. Dietary fat increased the rate of clearance of large cholesterol-rich HDL containing apoE and increased their conversion to small HDL containing apoE, indicating selective cholesterol ester delivery to the liver. The high-unsaturated-fat diet did not affect the metabolism of HDL lacking apoE. HDL containing apoE is a diet-responsive metabolic pathway that renders HDL more biologically active in reverse cholesterol transport. This may be a mechanism by which unsaturated fat protects against coronary heart disease. Protein-based HDL subspecies such as HDL containing apoE may be used to identify additional atheroprotective treatment targets not evident in the total HDL-cholesterol measurement. ClinicalTrials.gov NCT01399632. NIH and the National Center for Advancing Translational Science.

Apolipoprotein C-III and its defined lipoprotein subspecies in relation to incident diabetes: the Multi-Ethnic Study of Atherosclerosis.

Apolipoprotein C-III (apoC-III) is a small proinflammatory protein that may play a key role in diabetes pathophysiology. However, prior observational studies have been limited to predominantly white populations, and the biological links between apoC-III and diabetes, particularly the role of apoC-III on specific lipoprotein particles, are not yet well understood. We therefore investigated associations of total apoC-III and apoC-III-defined lipoprotein subspecies with incident diabetes and glucose metabolism measures in a multi-ethnic cohort. For the current analyses, baseline (2000-2002) plasma total apoC-III and apolipoprotein A-I concentrations of HDL containing or lacking apoC-III were newly measured via sandwich ELISA in 4579 participants from the Multi-Ethnic Study of Atherosclerosis. Multivariable Cox regression was used to examine associations of apolipoproteins with incident diabetes until early 2012 (567 cases), and linear mixed models were used to estimate associations with longitudinally assessed continuous measures of glucose metabolism. Similar exploratory analyses of plasma apolipoprotein B concentrations of LDL and VLDL containing or lacking apoC-III were performed in a subset of participants (LDL, n = 1545; VLDL, n = 1526). In the overall population, elevated total apoC-III concentrations were associated with a higher rate of diabetes (top vs bottom quintile, HR 1.88; 95% CI 1.42, 2.47; ptrend = 0.0002). ApoC-III-defined HDL subspecies displayed opposing associations with incidence of diabetes (p for heterogeneity = 0.02). While HDL lacking apoC-III was inversely associated with incidence of diabetes (top vs bottom quintile, HR 0.66; 95% CI 0.46, 0.93; ptrend = 0.002), HDL containing apoC-III was not associated (HR 1.11; 95% CI 0.78, 1.58; ptrend = 0.61). Similarly, only HDL lacking apoC-III was beneficially associated with plasma glucose (ptrend = 0.003), HbA1c (ptrend = 0.04) and insulin sensitivity (ptrend < 0.0001), and higher HDL containing apoC-III was associated with lower insulin sensitivity (ptrend = 0.04). Neither of the apoC-III-defined LDL subspecies was associated with incident diabetes, while VLDL was more strongly associated with the incidence of diabetes when it lacked apoC-III. Further adjustment for plasma triacylglycerols as a potential intermediate attenuated the associations of total apoC-III and apoC-III-defined lipoprotein subspecies. No statistically significant differences were observed across racial/ethnic groups. Our findings in a multi-ethnic population support the involvement of apoC-III in the development of diabetes, potentially through its association with circulating triacylglycerols. The presence of apoC-III on HDL also diminished the protective association of HDL with incident diabetes. Further investigation of apoC-III and apoC-III-defined HDL subspecies may inform the development of novel diabetes treatment and prevention strategies.

Abstract P200: Unsaturated Fat Replacing Carbohydrate or Protein Affects Protein-Based HDL Subspecies of Different Functionality

Introduction: HDL is a heterogeneous group of protein-lipid complexes comprised of stable subspecies defined by their protein content whose functions and associations with cardiovascular disease (CVD) are likely driven by their proteome. The Optimal Macronutrient Intake Trial to Prevent Heart Disease (OMNI Heart) found that unsaturated fat replacing carbohydrate or protein increased HDL cholesterol, but nothing is known about the effect of macronutrient composition on HDL subspecies concentrations. Hypothesis: Dietary unsaturated fat (UNSAT) replacing carbohydrate (CARB) or protein (PROT) affects protein-based HDL subspecies. Methods: The OMNI Heart Trial employed a randomized cross-over design that fed sequentially each of three study diets emphasizing CARB, PROT, or UNSAT to the participants. The apolipoprotein (apo) A1 concentrations of 16 HDL subspecies, selected to represent the major functions of HDL, were measured in plasma samples from 141 participants collected after 4 weeks on each diet. Results and Conclusions: UNSAT replacing CARB or PROT affected the levels of different HDL subspecies involved in lipid metabolism, anti-oxidation, anti-inflammation, and homeostasis (figure). UNSAT replacing PROT increased HDL that contains apoC1, apoL1, PON1, or plasminogen. UNSAT replacing CARB increased HDL that contains apoC1 and HDL that contains apoE, an HDL subspecies associated with protection against CVD. PROT replacing CARB decreased HDL that contains apoE. UNSAT replacing CARB or PROT increased HDL cholesterol, total apoA1, and HDL that contains apoA2, as expected. In conclusion, macronutrients affect HDL subspecies that vary in their functionality, which may contribute to the effects of dietary inventions on the risk of cardiovascular and other diseases.

HDL modification: recent developments and their relevance to atherosclerotic cardiovascular disease.

In the last 2 years, significant advances in the understanding of HDL particle structure and the associations between particle structure, function, and atherosclerosis have been made. We will review and provide clinical and epidemiological context to these recent advances. Several recent studies have analyzed the associations between HDL particle size distribution, number, and particle function and specific environmental, behavioral, and pharmacologic exposures. Detailed phenotyping of HDL-associated protein complements, particularly apolipoproteins, strongly suggests structural subspecies of HDL exist with differential associations with HDL function and ASCVD risk. The recent data on biological and structural variation in HDL suggests the existence of relatively discrete particle species, which share a similar structure and function. We propose that the classical taxonomy that clusters HDL particles by cholesterol content is incomplete. Detailed phenotyping of HDL subspecies in clinical and epidemiological research may yield insights into new risk markers and biochemical pathways that could provide targets for atherosclerotic cardiovascular disease (ASCVD) therapy and prevention in the future.

Abstract 557: The Effect of Dietary Fat and Carbohydrate on the Metabolism of HDL Subspecies Containing ApoE in Humans

Background: The effect of diet on the metabolism of HDL subspecies defined by protein content remains undetermined. ApoE forms subspecies on HDL with unique metabolic properties. HDL containing apoE have dramatically increased clearance from plasma compared to HDL not containing apoE, and also participate in size expansion from small to large HDL (a marker of cholesterol uptake). Methods: We enrolled ten adults who were overweight or obese and had low HDL-C ( &lt; 45 mg/dl for men, &lt; 55 mg/dl for women). Each participant received two diets in a random-crossover design: a high-unsaturated fat diet (40% fat [10% sat, 23% MUFA, 7% PUFA], 45% carbohydrate) and a low fat diet (65% carbohydrate, 20% fat [10% sat, 8% MUFA, 7% PUFA]), each for 28 days. At the end of each diet period, participants received a bolus infusion of tri-deuterated (D3-) leucine, a stable isotope tracer, to label apoA1, and plasma was collected at 18 time points up to 94 hours post-tracer infusion. We isolated from plasma HDL subspecies containing or not containing apoE, and used compartmental modeling of apoA1 tracer enrichment and pool size to study the kinetic behavior of each HDL subspecies during each diet. Results: HDL containing apoE comprises about 5% of apoA1 HDL mass in plasma. On both diets, apoA1 in HDL containing apoE turns over about ten times more quickly than in HDL not containing apoE. The high-unsaturated fat diet increased the synthesis and clearance of apoA-I on HDL containing apoE by about 250% compared to the low fat diet. There was also greater evidence of HDL size interconversion in this subspecies on the high fat diet. In contrast, the high-unsaturated fat diet did not significantly affect the metabolism of apoA1 of HDL not containing apoE. Conclusions: Dietary unsaturated fat compared to carbohydrate increases the secretion of HDL subspecies containing apoE, and renders them more biologically active in metabolic pathways that involve reverse cholesterol transport.

Apolipoproteins E and CIII interact to regulate HDL metabolism and coronary heart disease risk

Subspecies of HDL contain apolipoprotein E (apoE) and/or apoCIII. Both proteins have properties that could affect HDL metabolism. The relation between HDL metabolism and risk of coronary heart disease (CHD) is not well understood. Eighteen participants were given a bolus infusion of [D3]L-leucine to label endogenous proteins on HDL. HDL was separated into subspecies containing apoE and/or apoCIII and then into 4 sizes. Metabolic rates for apoA-I in HDL subspecies and sizes were determined by interactive modeling. The concentrations of apoE in HDL that contain or lack apoCIII were measured in a prospective study in Denmark including 1,949 incident CHD cases during 9 years. HDL containing apoE but not apoCIII is disproportionately secreted into the circulation, actively expands while circulating, and is quickly cleared. These are key metabolic steps in reverse cholesterol transport, which may protect against atherosclerosis. ApoCIII on HDL strongly attenuates these metabolic actions of HDL apoE. In the epidemiological study, the relation between HDL apoE concentration and CHD significantly differed depending on whether apoCIII was present. HDL apoE was associated significantly with lower risk of CHD only in the HDL subspecies lacking apoCIII. ApoE and apoCIII on HDL interact to affect metabolism and CHD. ApoE promotes metabolic steps in reverse cholesterol transport and is associated with lower risk of CHD. ApoCIII, when coexisting with apoE on HDL, abolishes these benefits. Therefore, differences in metabolism of HDL subspecies pertaining to reverse cholesterol transport are reflected in differences in association with CHD. Clinicaltrials.gov NCT01399632. This work was supported by NIH grant R01HL095964 to FMS and by a grant to the Harvard Clinical and Translational Science Center (8UL1TR0001750) from the National Center for Advancing Translational Science.