HDL metabolism in hypertriglyceridemic states: an overview

Effects of a dietary intervention with Mediterranean vs lacto-ovo vegetarian diets on HDL function: Results from the CARDIVEG study

BACKGROUND AND AIM

HDL-cholesterol efflux capacity (CEC) has been shown to be a better cardiovascular (CVD) risk marker than serum HDL concentration. Several foods and nutrients have been shown to improve HDL functions, however no effective dietetic nor pharmacological strategy is available to increase CEC. This study aims to evaluate the possible effect of Mediterranean diet (MD) and lacto-ovo-vegetarian diet (VD) on HDL function in a group of clinically healthy subjects at low-to-moderate CVD risk.

METHODS AND RESULTS

Thirty apparently healthy subjects with a low-to-moderate cardiovascular risk profile (21 F; mean age: 51.3 ± 9.7 years) were randomly assigned to a 3-month MD or VD diet and then crossed. Participants on VD showed a reduction in total HDL CEC by 8.99% (p < 0.001) as well as a reduction in ABCA1 mediated-CEC by 18.62% (p < 0.001) compared to participants on MD. Regarding CEC mediated by aqueous diffusion, no significant changes were observed after treatment with either diet. Finally, a significant positive association between CEC mediated by the ABCA1 transporter and adiponectin was found (r = 0.462; p = 0.010).

CONCLUSION

The results of this study suggest that HDL activity in promoting cholesterol efflux and thereby reducing the concentration of pro-atherogenic lipoproteins was more effective in participants undergoing MD than VD. Based on these findings, the MD could be considered a better therapeutic strategy for cardiovascular prevention than VD.

CLINICAL TRIAL REGISTRATION URL

http://www.

CLINICALTRIALS

gov. Unique identifier: NCT02641834.

Expanding the Molecular Disturbances of Lipoproteins in Cardiometabolic Diseases: Lessons from Lipidomics

The increasing global burden of cardiometabolic diseases highlights the urgent clinical need for better personalized prediction and intervention strategies. Early diagnosis and prevention could greatly reduce the enormous socio-economic burden posed by these states. Plasma lipids including total cholesterol, triglycerides, HDL-C, and LDL-C have been at the center stage of the prediction and prevention strategies for cardiovascular disease; however, the bulk of cardiovascular disease events cannot be explained sufficiently by these lipid parameters. The shift from traditional serum lipid measurements that are poorly descriptive of the total serum lipidomic profile to comprehensive lipid profiling is an urgent need, since a wealth of metabolic information is currently underutilized in the clinical setting. The tremendous advances in the field of lipidomics in the last two decades has facilitated the research efforts to unravel the lipid dysregulation in cardiometabolic diseases, enabling the understanding of the underlying pathophysiological mechanisms and identification of predictive biomarkers beyond traditional lipids. This review presents an overview of the application of lipidomics in the study of serum lipoproteins in cardiometabolic diseases. Integrating the emerging multiomics with lipidomics holds great potential in moving toward this goal.

Effect of Clinical and Laboratory Parameters on HDL Particle Composition

The functional status of High-Density Lipoprotein (HDLs) is not dependent on the cholesterol content but is closely related to structural and compositional characteristics. We reported the analysis of HDL lipidome in the healthy population and the influence of serum lipids, age, gender and menopausal status on its composition. Our sample comprised 90 healthy subjects aged between 30 and 77 years. HDL lipidome was investigated by Nuclear Magnetic Resonance (NMR) spectroscopy. Among serum lipids, triglycerides, apoAI, apoB and the ratio HDL-C/apoAI had a significant influence on HDL lipid composition. Aging was associated with significant aberrations, including an increase in triglyceride content, lysophosphatidylcholine, free cholesterol, and a decrease in esterified cholesterol, phospholipids, and sphingomyelin that may contribute to increased cardiovascular risk. Aging was also associated with an atherogenic fatty acid pattern. Changes occurring in the HDL lipidome between the two genders were more pronounced in the decade from 30 to 39 years of age and over 60 years. The postmenopausal group displayed significant pro-atherogenic changes in HDLs compared to the premenopausal group. The influence of serum lipids and intrinsic factors on HDL lipidome could improve our understanding of the remodeling capacity of HDLs directly related to its functionality and antiatherogenic properties, and also in appropriate clinical research study protocol design. These data demonstrate that NMR analysis can easily follow the subtle alterations of lipoprotein composition due to serum lipid parameters.

Progressive, Qualitative, and Quantitative Alterations in HDL Lipidome from Healthy Subjects to Patients with Prediabetes and Type 2 Diabetes

Prediabetes is a clinically silent, insulin-resistant state with increased risk for the development of type 2 diabetes (T2D) and cardiovascular disease (CVD). Since glucose homeostasis and lipid metabolism are highly intersected and interrelated, an in-depth characterization of qualitative and quantitative abnormalities in lipoproteins could unravel the metabolic pathways underlying the progression of prediabetes to T2D and also the proneness of these patients to developing premature atherosclerosis. We investigated the HDL lipidome in 40 patients with prediabetes and compared it to that of 40 normoglycemic individuals and 40 patients with established T2D using Nuclear Magnetic Resonance (NMR) spectroscopy. Patients with prediabetes presented significant qualitative and quantitative alterations, potentially atherogenic, in HDL lipidome compared to normoglycemic characterized by higher percentages of free cholesterol and triglycerides, whereas phospholipids were lower. Glycerophospholipids and ether glycerolipids were significantly lower in prediabetic compared to normoglycemic individuals, whereas sphingolipids were significantly higher. In prediabetes, lipids were esterified with saturated rather than unsaturated fatty acids. These changes are qualitatively similar, but quantitatively milder, than those found in patients with T2D. We conclude that the detailed characterization of the HDL lipid profile bears a potential to identify patients with subtle (but still proatherogenic) abnormalities who are at high risk for development of T2D and CVD.

Hypertriglyceridemia in young adults with a 22q11.2 microdeletion

OBJECTIVE

Mild to moderate hypertriglyceridemia is a condition often associated with obesity and diabetes, with as yet incomplete knowledge of underlying genetic architecture. The 22q11.2 microdeletion is associated with multimorbidity, including increased risk of obesity and diabetes. In this study, we sought to investigate whether the 22q11.2 microdeletion was associated with mild to moderate hypertriglyceridemia (1.7-10 mmol/L).

DESIGN

This was a cohort study comparing 6793 population-based adults and 267 with a 22q11.2 microdeletion aged 17-69 years, excluding those with diabetes or on statins.

METHODS

We used binomial logistic regression modeling to identify predictors of hypertriglyceridemia, accounting for the 22q11.2 microdeletion, male sex, BMI, ethnicity, age, and antipsychotic medications.

RESULTS

The 22q11.2 microdeletion was a significant independent predictor of mild to moderate hypertriglyceridemia (odds ratio (OR): 2.35, 95% CI: 1.70-3.26). All other factors examined were also significant predictors (OR: 1.23-2.10), except for antipsychotic medication use. Within the 22q11.2 microdeletion subgroup, only male sex (OR: 3.10, 95% CI: 1.77-5.44) and BMI (OR: 1.63, 95% CI: 1.14-1.98) were significant predictors of hypertriglyceridemia, evident at mean age 31.2 years.

CONCLUSIONS

The 22q11.2 microdeletion is associated with hypertriglyceridemia even when accounting for other known risk factors for elevated triglycerides. This effect is seen in young adulthood (76.6% were <40 years), in the absence of diabetes, and irrespective of antipsychotics, suggesting that the 22q11.2 microdeletion may represent an unrecognized genetic risk factor for hypertriglyceridemia, providing novel opportunities for animal and cellular models. Early dyslipidemia screening and management strategies would appear prudent for individuals with 22q11.2 microdeletions.

Modification of High-Density Lipoprotein Functions by Diet and Other Lifestyle Changes: A Systematic Review of Randomized Controlled Trials

High-density lipoprotein (HDL) functional traits have emerged as relevant elements that may explain HDL antiatherogenic capacity better than HDL cholesterol levels. These properties have been improved in several lifestyle intervention trials. The aim of this systematic review is to summarize the results of such trials of the most commonly used dietary modifications (fatty acids, cholesterol, antioxidants, alcohol, and calorie restriction) and physical activity. Articles were screened from the Medline database until March 2021, and 118 randomized controlled trials were selected. Results from HDL functions and associated functional components were extracted, including cholesterol efflux capacity, cholesteryl ester transfer protein, lecithin-cholesterol acyltransferase, HDL antioxidant capacity, HDL oxidation status, paraoxonase-1 activity, HDL anti-inflammatory and endothelial protection capacity, HDL-associated phospholipase A2, HDL-associated serum amyloid A, and HDL-alpha-1-antitrypsin. In mainly short-term clinical trials, the consumption of monounsaturated and polyunsaturated fatty acids (particularly omega-3 in fish), and dietary antioxidants showed benefits to HDL functionality, especially in subjects with cardiovascular risk factors. In this regard, antioxidant-rich dietary patterns were able to improve HDL function in both healthy individuals and subjects at high cardiovascular risk. In addition, in randomized trial assays performed mainly in healthy individuals, reverse cholesterol transport with ethanol in moderate quantities enhanced HDL function. Nevertheless, the evidence summarized was of unclear quality and short-term nature and presented heterogeneity in lifestyle modifications, trial designs, and biochemical techniques for the assessment of HDL functions. Such findings should therefore be interpreted with caution. Large-scale, long-term, randomized, controlled trials in different populations and individuals with diverse pathologies are warranted.

Prognostic significance of preoperative serum triglycerides and high-density lipoproteins cholesterol in patients with non-small cell lung cancer: a retrospective study

Background

Abnormalities in serum lipids and lipoproteins have been documented to link to the risk of cancers in recent years, but its prognostic value for cancer is not known. This study retrospectively evaluated the significance of preoperative serum lipids and lipoproteins for NSCLC’s prognosis.

Methods

A retrospective review was implemented of 551 patients succumbed to NSCLC. A ROC curve was utilized to determine the best cut-off value and area under the ROC curve. Kaplan-Meier and a Cox proportional hazards model were utilized to perform survival analysis.

Results

With a median follow-up of 42 months, the NSCLC patients in the high TG (> 1.21 mmol/L) and low HDL-C (≤ 1.26 mmol/L) two groups exhibited shorter OS and DFS. In multivariable analysis, preoperative HDL-C and TG can work as independent prognosis factors for OS (P<0.001 for both) and DFS (P<0.05 for both) in patients succumbed to NSCLC.

Conclusion

Abnormalities of serum lipids and lipoproteins metabolism linked to the survival outcomes of NSCLC. Preoperative serum HDL-C and TG may be promising biomarkers to predict the NSCLC patients’ prognosis.

HDL Dysfunctionality: Clinical Relevance of Quality Rather Than Quantity

High-density lipoproteins (HDLs) represent a class of lipoproteins very heterogeneous in structure, composition, and biological functions, which carry out reverse cholesterol transport, antioxidant, anti-inflammatory, antithrombotic, and vasodilator actions. Despite the evidence suggesting a clear inverse relationship between HDL cholesterol (HDL-c) concentration and the risk for cardiovascular disease, plasma HDL cholesterol levels do not predict the functionality and composition of HDLs. The importance of defining both the amount of cholesterol transported and lipoprotein functionality has recently been highlighted. Indeed, different clinical conditions such as obesity, diabetes mellitus type 2 (T2DM), and cardiovascular disease (CVD) can alter the HDL functionality, converting normal HDLs into dysfunctional ones, undergoing structural changes, and exhibiting proinflammatory, pro-oxidant, prothrombotic, and proapoptotic properties. The aim of the current review is to summarize the actual knowledge concerning the physical-chemical alteration of HDLs related to their functions, which have been found to be relevant in several pathological conditions associated with systemic inflammation and oxidative stress.

Early Signs of Atherogenic Features in the HDL Lipidomes of Normolipidemic Patients Newly Diagnosed with Type 2 Diabetes

Cardiovascular disease (CVD) is the major cause of death in patients with type-2 diabetes mellitus (T2DM), although the factors that accelerate atherosclerosis in these patients are poorly understood. The identification of the altered quantity and quality of lipoproteins, closely related to atherogenesis, is limited in routine to a pattern of high triglycerides and low HDL-cholesterol (HDL-C) and in research as dysfunctional HDLs. We used the emerging NMR-based lipidomic technology to investigate compositional features of the HDLs of healthy individuals with normal coronary arteries, drug-naïve; recently diagnosed T2DM patients with normal coronary arteries; and patients with recent acute coronary syndrome. Patients with T2DM and normal serum lipid profiles even at diagnosis presented significant lipid alterations in HDL, characterized by higher triglycerides, lysophosphatidylcholine and saturated fatty acids; and lower cholesterol, phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, plasmalogens and polyunsaturated fatty acids, an atherogenic pattern that may be involved in the pathogenesis of atherosclerosis. These changes are qualitatively similar to those found, more profoundly, in normolipidemic patients with established Coronary Heart Disease (CHD). We also conclude that NMR-based lipidomics offer a novel holistic exploratory approach for identifying and quantifying lipid species in biological matrixes in physiological processes and disease states or in disease biomarker discovery.

Consumption of two whole kiwifruit (Actinide chinensis) per day improves lipid homeostasis, fatty acid metabolism and gut microbiota in healthy rats

Golden kiwifruit (Actinidia chinensis) peel is a by-product enriched with polyphenols. The effects of fleshes of two Actinidia chinensis fruits (ACF) and fleshes with peels of two Actinidia chinensis fruits (ACFP) on lipid homeostasis, fatty acid metabolism and gut microbiota was investigated in healthy rats. Intervention of ACF and ACFP for 4 weeks significantly reduced total cholesterol, total triglycerides, and increased the high-density lipoprotein levels in rats. ACF and ACFP ameliorated lipid peroxidation in rats, by the lowering hepatic MDA level and enhancing GSH-Px and SOD activities. In addition, ACFP significantly decreased the saturated fatty acids in serum and increased the polyunsaturated fatty acids in hepatic and serum of rats. Analysis of gut microbiota revealed that ACF and ACFP evidently increased the microbial richness and diversity of gut microbiota. The Firmicutes/Bacteroidetes ratio was significantly reduced from 3.04 in ND group to 1.34 and 2.12 in ACF and ACFP groups, respectively. Moreover, ACF and ACFP significantly increased the abundance of beneficial bacteria (Lactobacillus and Barnesiella) and reduced harmful bacteria (Enterococcus, Escherichia, and Staphylococcus). Overall, ACFP exerts more potent health-improving effects than ACF. Our study provides a scientific basis for the development of kiwifruit (including pericarp)-based novel natural products with significant health benefits.

Dysfunctional High-Density Lipoproteins Are Associated With a Greater Incidence of Acute Coronary Syndrome in a Population at High Cardiovascular Risk: A Nested Case-Control Study

BACKGROUND

Studies have failed to establish a clear link between high-density lipoprotein (HDL) cholesterol and cardiovascular disease, leading to the hypothesis that the atheroprotective role of HDL lies in its biological activity rather than in its cholesterol content. However, to date, the association between HDL functional characteristics and acute coronary syndrome has not been investigated comprehensively.

METHODS

We conducted a case-control study nested within the PREDIMED (Prevención con Dieta Mediterránea) cohort, originally a randomized trial in which participants followed a Mediterranean or low-fat diet. Incident acute coronary syndrome cases (N=167) were individually matched (1:2) to control patients by sex, age, intervention group, body mass index, and follow-up time. We investigated 2 individual manifestations (myocardial infarction, unstable angina) as secondary outcomes. We measured the following functional characteristics: HDL cholesterol concentration (in plasma); cholesterol efflux capacity; antioxidant ability, measured by the HDL oxidative-inflammatory index; phospholipase A2 activity; and sphingosine-1-phosphate, apolipoproteins A-I and A-IV, serum amyloid A, and complement 3 protein (in apolipoprotein B-depleted plasma). We used conditional logistic regression models adjusted for HDL cholesterol levels and cardiovascular risk factors to estimate odds ratios (ORs) between 1-SD increments in HDL functional characteristics and clinical outcomes.

RESULTS

Low values of cholesterol efflux capacity (OR_1SD, 0.58; 95% CI, 0.40-0.83) and low levels of sphingosine-1-phosphate (OR_1SD, 0.70; 95% CI, 0.52-0.92) and apolipoprotein A-I (OR_1SD, 0.58; 95% CI, 0.42-0.79) were associated with higher odds of acute coronary syndrome. Higher HDL oxidative inflammatory index values were marginally linked to acute coronary syndrome risk (OR_1SD, 1.27; 95% CI, 0.99-1.63). Low values of cholesterol efflux capacity (OR_1SD, 0.33; 95% CI, 0.18-0.61), sphingosine-1-phosphate (OR_1SD: 0.60; 95% CI: 0.40-0.89), and apolipoprotein A-I (OR_1SD, 0.59; 95% CI, 0.37-0.93) were particularly linked to myocardial infarction, whereas high HDL oxidative-inflammatory index values (OR_1SD, 1.53; 95% CI, 1.01-2.33) and low apolipoprotein A-I levels (OR_1SD, 0.52; 95% CI, 0.31-0.88) were associated with unstable angina.

CONCLUSIONS

Low cholesterol efflux capacity values, pro-oxidant/proinflammatory HDL particles, and low HDL levels of sphingosine-1-phosphate and apolipoprotein A-I were associated with increased odds of acute coronary syndrome and its manifestations in individuals at high cardiovascular risk.

CLINICAL TRIAL REGISTRATION

URL: https://www.controlled-trials.com/ISRCTN35739639. Unique identifier: ISRCTN35739639.

Altered lipoprotein profiles in cats with hepatic lipidosis

OBJECTIVES

The aim of this study was to assess serum lipoprotein profiles using rapid single-spin continuous lipoprotein density profiling (CLPDP) in healthy control cats and cats with hepatic lipidosis (HL).

METHODS

Analysis of serum lipoprotein profiles using the CLPDP was performed in 23 cats with HL and 20 healthy control cats. The area under the curve for each lipoprotein fraction, triglyceride (TG)-rich lipoproteins (TRLs), low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs), was calculated. Serum cholesterol and TG concentrations were measured using a clinical chemistry analyzer.

RESULTS

Serum cholesterol and TG concentrations were not significantly different between healthy control cats and cats with HL ( P = 0.5075 and P = 0.2541, respectively). LDL content was significantly higher in cats with HL than in healthy control cats ( P = 0.0001), while HDL content was significantly lower in cats with HL than in healthy control cats ( P = 0.0032). TRL content was not significantly different between the two groups ( P = 0.0699). The specific fraction (1.037-1.043 g/ml) within nominal LDL in serum distinguished healthy control cats from cats with HL with a sensitivity of 87% and a specificity of 90%.

CONCLUSIONS AND RELEVANCE

Serum lipoprotein profiles were altered in cats with HL, even though serum cholesterol and TG concentrations were not significantly different compared with healthy control cats. The CLPDP might be a useful tool for assessing lipid metabolism in cats with HL.

Rethinking reverse cholesterol transport and dysfunctional high-density lipoproteins

Human plasma high-density lipoprotein cholesterol concentrations are a negative risk factor for atherosclerosis-linked cardiovascular disease. Pharmacological attempts to reduce atherosclerotic cardiovascular disease by increasing plasma high-density lipoprotein cholesterol have been disappointing so that recent research has shifted from HDL quantity to HDL quality, that is, functional vs dysfunctional HDL. HDL has varying degrees of dysfunction reflected in impaired reverse cholesterol transport (RCT). In the context of atheroprotection, RCT occurs by 2 mechanisms: one is the well-known trans-hepatic pathway comprising macrophage free cholesterol (FC) efflux, which produces early forms of FC-rich nascent HDL (nHDL). Lecithin:cholesterol acyltransferase converts HDL-FC to HDL-cholesteryl ester while converting nHDL from a disc to a mature spherical HDL, which transfers its cholesteryl ester to the hepatic HDL receptor, scavenger receptor B1 for uptake, conversion to bile salts, or transfer to the intestine for excretion. Although widely cited, current evidence suggests that this is a minor pathway and that most HDL-FC and nHDL-FC rapidly transfer directly to the liver independent of lecithin:cholesterol acyltransferase activity. A small fraction of plasma HDL-FC enters the trans-intestinal efflux pathway comprising direct FC transfer to the intestine. SR-B1^-/- mice, which have impaired trans-hepatic FC transport, are characterized by high plasma levels of a dysfunctional FC-rich HDL that increases plasma FC bioavailability in a way that produces whole-body hypercholesterolemia and multiple pathologies. The design of future therapeutic strategies to improve RCT will have to be formulated in the context of these dual RCT mechanisms and the role of FC bioavailability.

The role and function of HDL in patients with diabetes mellitus and the related cardiovascular risk

BACKGROUND

Diabetes mellitus (DM) is a major public health problem which prevalence is constantly raising, particularly in low- and middle-income countries. Both diabetes mellitus types (DMT1 and DMT2) are associated with high risk of developing chronic complications, such as retinopathy, nephropathy, neuropathy, endothelial dysfunction, and atherosclerosis.

METHODS

This is a review of available articles concerning HDL subfractions profile in diabetes mellitus and the related cardiovascular risk. In this review, HDL dysfunction in diabetes, the impact of HDL alterations on the risk diabetes development as well as the association between disturbed HDL particle in DM and cardiovascular risk is discussed.

RESULTS

Changes in the amount of circulation lipids, including triglycerides and LDL cholesterol as well as the HDL are frequent also in the course of DMT1 and DMT2. In normal state HDL exerts various antiatherogenic properties, including reverse cholesterol transport, antioxidative and anti-inflammatory capacities. However, it has been suggested that in pathological state HDL becomes "dysfunctional" which means that relative composition of lipids and proteins in HDL, as well as enzymatic activities associated to HDL, such as paraoxonase 1 (PON1) and lipoprotein-associated phospholipase 11 (Lp-PLA2) are altered. HDL properties are compromised in patients with diabetes mellitus (DM), due to oxidative modification and glycation of the HDL protein as well as the transformation of the HDL proteome into a proinflammatory protein. Numerous studies confirm that the ability of HDL to suppress inflammatory signals is significantly reduced in this group of patients. However, the exact underlying mechanisms remains to be unravelled in vivo.

CONCLUSIONS

The understanding of pathological mechanisms underlying HDL dysfunction may enable the development of therapies targeted at specific subpopulations and focusing at the diminishing of cardiovascular risk.

Targeted Proteomics Identifies Paraoxonase/Arylesterase 1 (PON1) and Apolipoprotein Cs as Potential Risk Factors for Hypoalphalipoproteinemia in Diabetic Subjects Treated with Fenofibrate and Rosiglitazone

Low levels of high-density lipoprotein cholesterol (HDL-C) and high triglyceride levels contribute to the excess rate of cardiovascular events seen in subjects with type 2 diabetes. Fenofibrate treatment partially reverses dyslipidemia in these subjects. However, a paradoxical marked reduction in HDL-C and HDL's major protein, apolipoprotein A-I, is a complication of fenofibrate in combination with rosiglitazone, an insulin-sensitizing agent. Risk factors for this condition, termed hypoalphalipoproteinemia, have yet to be identified. Using a case-control study design with subjects enrolled in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial, we tested the hypothesis that alterations in HDL's protein cargo predispose diabetic subjects to fenofibrate/rosiglitazone-induced hypoalphalipoproteinemia. HDL was isolated from blood obtained from controls (no decreases or increase in HDL-C while receiving fenofibrate/rosiglitazone therapy) and cases (developed hypoalphalipoproteinemia after fenofibrate/rosiglitazone treatment) participating in the ACCORD study before they began fenofibrate/rosiglitazone treatment. HDL proteins were quantified by targeted parallel reaction monitoring (PRM) and selected reaction monitoring (SRM) with isotope dilution. This approach demonstrated marked increases in the relative concentrations of paraoxonase/arylesterase 1 (PON1), apolipoprotein C-II (APOC2), apolipoprotein C-I, and apolipoprotein H in the HDL of subjects who developed hypoalphalipoproteinemia. The case and control subjects did not differ significantly in baseline HDL-C levels or other traditional lipid risk factors. We used orthogonal biochemical techniques to confirm increased levels of PON1 and APOC2. Our observations suggest that an imbalance in HDL proteins predisposes diabetic subjects to develop hypoalphalipoproteinemia on fenofibrate/rosiglitazone therapy.

Defective functionality of small, dense HDL3 subpopulations in ST segment elevation myocardial infarction: Relevance of enrichment in lysophosphatidylcholine, phosphatidic acid and serum amyloid A

BACKGROUND

Low plasma levels of high-density lipoprotein-cholesterol (HDL-C) are typical of acute myocardial infarction (MI) and predict risk of recurrent cardiovascular events. The potential relationships between modifications in the molecular composition and the functionality of HDL subpopulations in acute MI however remain indeterminate.

METHODS AND RESULTS

ST segment elevation MI (STEMI) patients were recruited within 24h after diagnosis (n=16) and featured low HDL-C (-31%, p<0.05) and acute-phase inflammation (determined as marked elevations in C-reactive protein, serum amyloid A (SAA) and interleukin-6) as compared to age- and sex-matched controls (n=10). STEMI plasma HDL and its subpopulations (HDL2b, 2a, 3a, 3b, 3c) displayed attenuated cholesterol efflux capacity from THP-1 cells (up to -32%, p<0.01, on a unit phospholipid mass basis) vs.

CONTROLS

Plasma HDL and small, dense HDL3b and 3c subpopulations from STEMI patients exhibited reduced anti-oxidative activity (up to -68%, p<0.05, on a unit HDL mass basis). HDL subpopulations in STEMI were enriched in two proinflammatory bioactive lipids, lysophosphatidylcholine (up to 3.0-fold, p<0.05) and phosphatidic acid (up to 8.4-fold, p<0.05), depleted in apolipoprotein A-I (up to -23%, p<0.05) and enriched in SAA (up to +10.2-fold, p<0.05); such changes were most marked in the HDL3b subfraction. In vitro HDL enrichment in both lysophosphatidylcholine and phosphatidic acid exerted deleterious effects on HDL functionality.

CONCLUSIONS

In the early phase of STEMI, HDL particle subpopulations display marked, concomitant alterations in both lipidome and proteome which are implicated in impaired HDL functionality. Such modifications may act synergistically to confer novel deleterious biological activities to STEMI HDL.

SIGNIFICANCE

Our present data highlight complex changes in the molecular composition and functionality of HDL particle subpopulations in the acute phase of STEMI, and for the first time, reveal that concomitant modifications in both the lipidome and proteome contribute to functional deficiencies in cholesterol efflux and antioxidative activities of HDL particles. These findings may provide new biomarkers and new insights in therapeutic strategy to reduce cardiovascular risk in this clinical setting where such net deficiency in HDL function, multiplied by low circulating HDL concentrations, can be expected to contribute to accelerated atherogenesis.

Amyloid-Forming Properties of Human Apolipoproteins: Sequence Analyses and Structural Insights

Apolipoproteins are protein constituents of lipoproteins that transport cholesterol and fat in circulation and are central to cardiovascular health and disease. Soluble apolipoproteins can transiently dissociate from the lipoprotein surface in a labile free form that can misfold, potentially leading to amyloid disease. Misfolding of apoA-I, apoA-II, and serum amyloid A (SAA) causes systemic amyloidoses, apoE4 is a critical risk factor in Alzheimer's disease, and apolipoprotein misfolding is also implicated in cardiovascular disease. To explain why apolipoproteins are over-represented in amyloidoses, it was proposed that the amphipathic α-helices, which form the lipid surface-binding motif in this protein family, have high amyloid-forming propensity. Here, we use 12 sequence-based bioinformatics approaches to assess amyloid-forming potential of human apolipoproteins and to identify segments that are likely to initiate β-aggregation. Mapping such segments on the available atomic structures of apolipoproteins helps explain why some of them readily form amyloid while others do not. Our analysis shows that nearly all amyloidogenic segments: (i) are largely hydrophobic, (ii) are located in the lipid-binding amphipathic α-helices in the native structures of soluble apolipoproteins, (iii) are predicted in both native α-helices and β-sheets in the insoluble apoB, and (iv) are predicted to form parallel in-register β-sheet in amyloid. Most of these predictions have been verified experimentally for apoC-II, apoA-I, apoA-II and SAA. Surprisingly, the rank order of the amino acid sequence propensity to form amyloid (apoB>apoA-II>apoC-II≥apoA-I, apoC-III, SAA, apoC-I>apoA-IV, apoA-V, apoE) does not correlate with the proteins' involvement in amyloidosis. Rather, it correlates directly with the strength of the protein-lipid association, which increases with increasing protein hydrophobicity. Therefore, the lipid surface-binding function and the amyloid-forming propensity are both rooted in apolipoproteins' hydrophobicity, suggesting that functional constraints make it difficult to completely eliminate pathogenic apolipoprotein misfolding. We propose that apolipoproteins have evolved protective mechanisms against misfolding, such as the sequestration of the amyloidogenic segments via the native protein-lipid and protein-protein interactions involving amphipathic α-helices and, in case of apoB, β-sheets.

Association between triglyceride and high-density lipoprotein cholesterol change following fibrate therapy

BACKGROUND

Debate surrounding the role of fibrates has followed mixed outcomes from several randomised controlled trials. Subgroup analysis of even the negative trials reveals significant reduction in cardiovascular risk amongst patients with low HDL-C and high TG. We previously described factors associated with HDL-C change following fibrates. As fibrates influence both HDL-C and TG levels via their action on PPAR-α, we now wished to study TG change following fibrate therapy and any associations with baseline and change in HDL-C and TC levels.

METHODS

Data was collected from case notes of patients started on fibrates (n=248) between 2002 and 2008 in the lipid clinics at Heart of England NHS Foundation Trust. Regression analyses were carried out to determine factors associated with changes in TG.

RESULTS

Multiple regression analysis revealed that TG change was associated with pre-treatment TG (p<0.001) and TC levels (p=0.029). The association between TG change and pre-treatment TG remained significant when all factors including gender, concurrent statin treatment, diabetes and baseline HDL-C were entered into the regression model. Our previous study demonstrated significant post-fibrate HDL-C change in the group with baseline HDL-C values <1.0mmol/l. In our present study significant TG reduction was observed regardless of the baseline patient characteristics including HDL-C levels.

CONCLUSIONS

The actions of fibrates are considered to be mediated via PPAR-α, but our data suggest that the effects on TG and HDL-C are different. Thus, the mechanisms mediating the changes of these lipids following fibrate treatment may vary.

The Effect of Residing Altitude on Levels of High-Density Lipoprotein Cholesterol: A Pilot Study From the Omani Arab Population

Lower mortality rates from coronary heart disease and higher levels of serum high-density lipoprotein cholesterol (HDL-C) have been observed in populations residing at high altitude. However, this effect has not been investigated in Arab populations, which exhibit considerable genetic homogeneity. We assessed the relationship between residing altitude and HDL-C in 2 genetically similar Omani Arab populations residing at different altitudes. The association between the levels of HDL-C and other metabolic parameters was also investigated. The levels of HDL-C were significantly higher in the high-altitude group compared with the low-altitude group. Stepwise regression analysis showed that altitude was the most significant factor affecting HDL-C, followed by gender, serum triglycerides, and finally the 2-hour postprandial plasma glucose. This finding is consistent with previously published studies from other populations and should be taken into consideration when comparing cardiovascular risk factors in populations residing at different altitudes.

Binding of human apoA-I[K107del] variant to TG-rich particles: implications for mechanisms underlying hypertriglyceridemia

We found earlier that apoA-I variants that induced hypertriglyceridemia (HTG) in mice had increased affinity to TG-rich lipoproteins and thereby impaired their catabolism. Here, we tested whether a naturally occurring human apoA-I mutation, Lys107del, associated with HTG also promotes apoA-I binding to TG-rich particles. We expressed apoA-I[Lys107del] variant in Escherichia coli, studied its binding to TG-rich emulsion particles, and performed a physicochemical characterization of the protein. Compared with WT apoA-I, apoA-I[Lys107del] showed enhanced binding to TG-rich particles, lower stability, and greater exposure of hydrophobic surfaces. The crystal structure of truncated, Δ(185-243), apoA-I suggests that deletion of Lys107 disrupts helix registration and disturbs a stabilizing salt bridge network in the N-terminal helical bundle. To elucidate the structural changes responsible for the altered function of apoA-I[Lys107del], we studied another mutant, apoA-I [Lys107Ala]. Our findings suggest that the registry shift and ensuing disruption of the inter-helical salt bridges in apoA-I[Lys107del] result in destabilization of the helical bundle structure and greater exposure of hydrophobic surfaces. We conclude that the structural changes in the apoA-I[Lys107del] variant facilitate its binding to TG-rich lipoproteins and thus, may reduce their lipolysis and contribute to the development of HTG in carriers of the mutation.

Amyloidogenic mutations in human apolipoprotein A-I are not necessarily destabilizing - a common mechanism of apolipoprotein A-I misfolding in familial amyloidosis and atherosclerosis

High-density lipoproteins and their major protein, apolipoprotein A-I (apoA-I), remove excess cellular cholesterol and protect against atherosclerosis. However, in acquired amyloidosis, nonvariant full-length apoA-I deposits as fibrils in atherosclerotic plaques; in familial amyloidosis, N-terminal fragments of variant apoA-I deposit in vital organs, damaging them. Recently, we used the crystal structure of Δ(185-243)apoA-I to show that amyloidogenic mutations destabilize apoA-I and increase solvent exposure of the extended strand 44-55 that initiates β-aggregation. In the present study, we test this hypothesis by exploring naturally occurring human amyloidogenic mutations, W50R and G26R, within or close to this strand. The mutations caused small changes in the protein's α-helical content, stability, proteolytic pattern and protein-lipid interactions. These changes alone were unlikely to account for amyloidosis, suggesting the importance of other factors. Sequence analysis predicted several amyloid-prone segments that can initiate apoA-I misfolding. Aggregation studies using N-terminal fragments verified this prediction experimentally. Three predicted N-terminal amyloid-prone segments, mapped on the crystal structure, formed an α-helical cluster. Structural analysis indicates that amyloidogenic mutations or Met86 oxidation perturb native packing in this cluster. Taken together, the results suggest that structural perturbations in the amyloid-prone segments trigger α-helix to β-sheet conversion in the N-terminal ~ 75 residues forming the amyloid core. Polypeptide outside this core can be proteolysed to form 9-11 kDa N-terminal fragments found in familial amyloidosis. Our results imply that apoA-I misfolding in familial and acquired amyloidosis follows a similar mechanism that does not require significant structural destabilization or proteolysis. This novel mechanism suggests potential therapeutic interventions for apoA-I amyloidosis.

Origin and therapy for hypertriglyceridaemia in type 2 diabetes

Hypertriglyceridaemia (HTG) is a risk factor for cardiovascular disease (CVD) in type 2 diabetes and is caused by the interaction of genes and non-genetic factors, specifically poor glycaemic control and obesity. In spite of statin treatment, residual risk of CVD remains high in type 2 diabetes, and this may relate to HTG and atherogenic dyslipidemia. Treatment of HTG emphasises correcting secondary factors and adverse lifestyles, in particular, diet and exercise. Pharmacotherapy is also required in most type 2 diabetic patients. Statins are the first-line therapy to achieve recommended therapeutic targets of plasma low-density lipoprotein cholesterol and non-high-density lipoprotein cholesterol. Fibrates, ezetimibe and n-3 fatty acids are adjunctive treatment options for residual and persistent HTG. Evidence for the use of niacin has been challenged by non-significant CVD outcomes in two recent large clinical trials. Further investigation is required to clarify the use of incretin-based therapies for HTG in type 2 diabetes. Extreme HTG, with risk of pancreatitis, may require insulin infusion therapy or apheresis. New therapies targeting HTG in diabetes need to be tested in clinical endpoint trials. The purpose of this review is to examine the current evidence and provide practical guidance on the management of HTG in type 2 diabetes.

Familial aggregation of metabolic syndrome indicators in Portuguese families

Background and Aims. Family studies are well suited to investigate the genetic architecture underlying the metabolic syndrome (MetS). The purposes of this paper were (i) to estimate heritabilities for each of the MetS indicators, and (ii) to test the significance of familial intratrait and cross-trait correlations in MetS markers. Methods and Results. This study included 1,363 individuals from 515 Portuguese families in which five MetS components, including waist circumference (WC), blood pressure (BP), HDL-cholesterol, triglycerides (TG), and glucose (GLU), were measured. Intratrait and cross-trait familial correlations of these five components were estimated using Generalized Estimating Equations. Each MetS component was significantly heritable (h² ranged from 0.12 to 0.60) and exhibited strong familial resemblance with correlations between biological relatives of similar magnitude to those observed between spouses. With respect to cross-trait correlations, familial resemblance was very weak except for the HDL-TG pair. Conclusions. The present findings confirm the idea of familial aggregation in MetS traits. Spousal correlations were, in general, of the same magnitude as the biological relatives' correlations suggesting that most of the phenotypic variance in MetS traits could be explained by shared environment.

Proprotein convertases in high-density lipoprotein metabolism

The proprotein convertase subtilisin/kexins (PCSKs) are a serine endopeptidase family. PCSK members cleave amino acid residues and modulate the activity of precursor proteins. Evidence from patients and animal models carrying genetic alterations in PCSK members show that PCSK members are involved in various metabolic processes. These studies further revealed the molecular mechanism by which genetic alteration of some PCSK members impairs normal molecular and physiological functions, which in turn lead to cardiovascular disease. High-density lipoprotein (HDL) is anti-atherogenic as it removes excessive amount of cholesterol from blood and peripheral tissues. Several PCSK members are involved in HDL metabolism. PCSK3, PCSK5, and PCSK6 process two triglyceride lipase family members, endothelial lipase and lipoprotein lipase, which are important for HDL remodeling. Recent studies in our lab found evidence that PCSK1 and PCSK9 are also involved in HDL metabolism. A mouse model carrying an amino acid substitution in PCSK1 showed an increase in serum apolipoprotein A1 (APOA1) level. Another mouse model lacking PCSK9 showed a decrease in APOE-containing HDL. In this review, we summarize the role of the five PCSK members in lipid, glucose, and bile acid (BA) metabolism, each of which can influence HDL metabolism. We propose an integrative model in which PCSK members regulate HDL metabolism through various molecular mechanisms and metabolic processes and genetic variation in some PCSK members may affect the efficiency of reverse cholesterol transport. PCSK members are considered as attractive therapeutic targets. A greater understanding of the molecular and physiological functions of PCSK members will improve therapeutic strategies and drug efficacy for cardiovascular disease where PCSK members play critical role, with fewer adverse effects.

High density lipoprotein is positively correlated with the changes in circulating total adiponectin and high molecular weight adiponectin during dietary and fenofibrate treatment

OBJECTIVE

The investigation of the relationship between high density lipoprotein (HDL) and adiponectin.

DESIGN

Thirty-seven obese or overweight [body mass index ≥27 Kg/m(2)], hypertriglyceridemic patients underwent one of the following interventions for 3 months: 1) Low-calorie diet (n=19), 2) Low-calorie diet plus fenofibrate (n=18).

RESULTS

Circulating total adiponectin did not change significantly in the low-calorie diet group. However, in the subgroup of patients whose high density lipoprotein cholesterol (HDL-C) decreased over the first month of diet, a statistically significant reduction of the circulating total adiponectin was observed (p=0.010), while in the subgroup of patients whose HDL-C increased over the latter 2 months of the diet, an increase in circulating total adiponectin over the 2 months was found (p=0.043). The percentage change of HDL-C over the first month of diet was positively correlated with the percentage change of circulating total adiponectin (r=0.579, p=0.019). The percentage change of HDL-C over the 3 months of diet was positively correlated with the percentage changes of circulating total adiponectin (r=0.527, p=0.030) and high molecular weight (HMW) adiponectin (r=0.524, p=0.031). The change in circulating total adiponectin over the first month of diet was positively correlated with the HDL-C at 1 month (r=0.606, p=0.013). The change in HMW adiponectin over the 3 months of diet was positively correlated with the HDL-C at 3 months (r=0.602, p=0.011). The percentage change of circulating HMW adiponectin over the first month of fenofibrate treatment was positively correlated with the percentage change of HDL-C (r=0.594, p=0.012).

CONCLUSIONS

HDL is positively correlated with the changes in circulating adiponectin during dietary and fenofibrate treatment.

Unraveling the complexities of the HDL lipidome

Plasma high density lipoproteins (HDL) are small, dense, protein-rich particles compared with other lipoprotein classes; roughly half of total HDL mass is accounted for by lipid components. Phospholipids predominate in the HDL lipidome, accounting for 40-60% of total lipid, with lesser proportions of cholesteryl esters (30-40%), triglycerides (5-12%), and free cholesterol (5-10%). Lipidomic approaches have provided initial insights into the HDL lipidome with identification of over 200 individual molecular lipids species in normolipidemic HDL. Plasma HDL particles, however, reveal high levels of structural, compositional, and functional heterogeneity. Establishing direct relationships between HDL structure, composition, and atheroprotective functions bears the potential to identify clinically relevant HDL subpopulations. Furthermore, development of HDL-based therapies designed to target beneficial subspecies within the circulating HDL pool can be facilitated using this approach. HDL lipidomics can equally contribute to the identification of biomarkers of both normal and deficient HDL functionality, which may prove useful as biomarkers of cardiovascular risk. However, numerous technical issues remain to be addressed in order to make such developments possible. With all technical questions resolved, quantitative analysis of the molecular components of the HDL lipidome will contribute to expand our knowledge of cardiovascular and metabolic diseases.

Mitotane-induced hyperlipidemia: a retrospective cohort study

Limited data are available about mitotane-nduced hyperlipidemia. We retrospectively analyzed lipid data in 38 patients with adrenocortical carcinoma (ACC) who received mitotane therapy with emphasis on HDL cholesterol (HDL-c) and clinical predictors of lipid changes. At baseline, the mean levels of HDL-c, LDL-c, and triglycerides were 53.3 mg/dL, 114.4 mg/dL, and 149 mg/dL, respectively. HDL-c, LDL-c, and triglyceride concentrations significantly increased with mitotane therapy to a mean HDL peak (HDL-P) of 86.3 mg/dL (P < 0.001), a mean LDL peak of 160.1 mg/dL (P < 0.001), and a mean triglyceride peak (Tg-P) of 216.7 mg/dL (P = 0.042). HDL-P positively correlated with mitotane concentration (r = 0.52, P < 0.001), while LDL-P levels and Tg-P did not. Gender, body mass index, cortisol overproduction, baseline levels of HDL-c, and triglyceride did not predict change in HDL-c. Similar changes were noticed in subgroup analysis after excluding patients who were using lipid-lowering agents. In conclusion, in ACC patients, mitotane caused significant increases in HDL-c that may counteract the deleterious atherosclerotic effects of LDL-c and Tg rise. Understanding the mechanism of HDL change may lead to the discovery of novel HDL-c-elevating drugs.

Kiwifruit consumption favourably affects plasma lipids in a randomised controlled trial in hypercholesterolaemic men

The unique composition of green kiwifruit has the potential to benefit CVD risk. The aim of the present study was to investigate the effect of consuming two green kiwifruits daily in conjunction with a healthy diet on plasma lipids and other metabolic markers and to examine response according toAPOEgenotype in hypercholesterolaemic men. After undergoing a 4-week healthy diet, eighty-five hypercholesterolaemic men (LDL-cholesterol (LDL-C) >3·0 mmol/l and TAG < 3 mmol/l) completed an 8-week randomised controlled cross-over study of two 4-week intervention sequences of two green kiwifruits per d plus healthy diet (intervention) or healthy diet alone (control). Anthropometric measures, blood pressure (BP) and fasting blood samples (plasma lipids, serum apoA1 and apoB, insulin, glucose, high-sensitivity C-reactive protein (hs-CRP)) were taken at baseline, and at 4 and 8 weeks. After the kiwifruit intervention, plasma HDL-cholesterol (HDL-C) concentrations were significantly higher (mean difference 0·04; 95 % CI 0·01, 0·07 mmol/l;P= 0·004) and the total cholesterol (TC):HDL-C ratio was significantly lower (mean difference − 0·15; 95 % CI − 0·24, − 0·05 mmol/l;P= 0·002) compared with the control. In carriers of theAPOE4allele, TAG decreased significantly (mean difference − 0·18; 95 % CI − 0·34, − 0·02 mmol/l;P= 0·03) with kiwifruit compared with control. There were no significant differences between the two interventions for plasma TC, LDL-C, insulin, glucose, hs-CRP and BP. The small but significant increase in HDL-C and decrease in TC:HDL-C ratio and TAG (inAPOE4carriers) suggest that the regular inclusion of green kiwifruit as part of a healthy diet may be beneficial in improving the lipid profiles of men with high cholesterol.

Association between liver insulin resistance and cardiovascular risk factors

OBJECTIVES

The objective of this study was to examine the associations between indices of liver insulin resistance (IR) and whole-body insulin sensitivity and different cardiovascular disease (CVD) risk factors.

DESIGN AND SUBJECTS

A total of 8750 nondiabetic men (age 57.2 ± 7.1 years, body mass index 26.8 ± 3.8 kg m(-2) ) were included in this study from the population-based cross-sectional Metabolic Syndrome In Men (METSIM) cohort. Liver IR index and Matsuda insulin sensitivity index (ISI) were used as markers of liver IR and whole-body insulin sensitivity, respectively. Pearson correlation analysis was performed to examine the associations between these indices and various CVD risk factors.

RESULTS

Total cholesterol (r = -0.088 vs. r = 0.020; P < 0.0019), high-sensitivity C-reactive protein (CRP) (r = 0.284 vs. r = -0.219; P < 0.0019) and total triglycerides (r = 0.507 vs. r = -0.477; P < 0.05) were more highly correlated with liver IR index than with Matsuda ISI. By contrast, Matsuda ISI was nominally more highly correlated with systolic and diastolic blood pressure (r = -0.234 and r = -0.275 vs. r = 0.202 and r = 0.239, respectively) compared to liver IR index. Furthermore, the variance explained by liver IR index was larger than that explained by Matsuda ISI for the majority of CVD risk factors measured.

CONCLUSIONS

Liver IR index correlated more strongly than Matsuda ISI with levels of total cholesterol, CRP and triglycerides. Therefore, liver IR might be a significant indicator of CVD risk amongst men.

HDL dysfunction in diabetes: causes and possible treatments

HDL is known to be inversely correlated with cardiovascular disease due to its diverse antiatherogenic functions. These functions include cholesterol efflux and reverse cholesterol transport, antioxidative and anti-inflammatory activities. However, HDL has been shown to undergo a loss of function in several pathophysiological states, as in the acute phase response, obesity and chronic inflammatory diseases. Some of these diseases were also shown to be associated with increased risk for cardiovascular disease. One such disease that is associated with HDL dysfunction and accelerated atherosclerosis is diabetes mellitus, a disease in which the HDL particle undergoes diverse structural modifications that result in significant changes in its function. This review will summarize the changes that occur in HDL in diabetes mellitus and how these changes lead to HDL dysfunction. Possible treatments for HDL dysfunction are also briefly described.

Postprandial lipoprotein metabolism in familial hypercholesterolemia: thinking outside the box

Familial hypercholesterolemia (FH) is a dominantly inherited disorder principally due to mutations in the low-density lipoprotein (LDL) receptor that classically cause markedly elevated plasma LDL cholesterol concentrations and premature coronary heart disease (CHD). However, elevated plasma LDL cholesterol alone does not fully account for the increase or variation in risk of CHD. We propose a hypothetical model for the role of postprandial dyslipoproteinemia based on the overproduction and decreased catabolism of triglyceride-rich lipoproteins, which may be a consequence of LDL receptor deficiency. Expression of postprandial dyslipoproteinemia in FH may also depend on the type of pathogenic gene variants and on coexistent conditions, particularly obesity and insulin resistance. Further research is required to investigate our model proposed and to test whether treating postprandial dyslipoproteinemia decreases CHD risk in FH incremental to standard therapy.

Association between Perchlorate and Indirect Indicators of Thyroid Dysfunction in NHANES 2001-2002, a Cross-Sectional, Hypothesis-Generating Study

BACKGROUND

A previous study based on NHANES 2001-2002 observed that increased levels of urinary perchlorate were associated with increased levels of thyroid stimulating hormone among all women, and with decreased levels of thyroxine among women with low urinary iodine. No associations were observed for men.

METHODS

Using the same NHANES 2001-2002 data, associations of urinary perchlorate with indirect biomarkers of thyroid hormone disruption were investigated. Decreased levels of hemoglobin (HGB), hematocrit (HCT), and high density lipoprotein (HDL) have been observed among subjects with subclinical hypothyroidism. To investigate the suitability of these indicators for use in observational studies, subjects were divided into six groups: boys, age 6-19; men, age 20-85; girls, age 6-14; non-pregnant women, age 15-49; women, age 50-85; and pregnant women. Use of perchlorate quintiles (Q1-Q5) and continuous log-transformed perchlorate in the regression models allowed investigation of both non-linear and linear associations. Adjustments were made for age, urinary creatinine, race/ethnicity, body mass index, cotinine, poverty index, hours of fasting, thiocyanate, nitrate, daily kcal intake, C-reactive protein. Adjustment for alcohol consumption depended on availability. Adjustment for prescription drugs (beta-blockers, sex hormones, antihyperlipidemic and antidiabetic drugs) was made if it changed the perchlorate estimate by ≥10%.

RESULTS

Statistically significant decreases were observed for HGB and HCT among boys, men, women age 15-49, and pregnant women, and for HDL among men.

CONCLUSIONS

Although the mean response biomarkers were within normal range, their association with urinary perchlorate is of interest. HGB and HCT among pregnant women showed a stronger association with urinary perchlorate than non-pregnant women age 15-49. Statistically significant associations were observed for individual perchlorate quintiles. Assumption of linearity of log-transformed perchlorate may result in underestimation of some associations.

Effects of 34 risk loci for type 2 diabetes or hyperglycemia on lipoprotein subclasses and their composition in 6,580 nondiabetic Finnish men

OBJECTIVE

We investigated the effects of 34 genetic risk variants for hyperglycemia/type 2 diabetes on lipoprotein subclasses and particle composition in a large population-based cohort.

RESEARCH DESIGN AND METHODS

The study included 6,580 nondiabetic Finnish men from the population-based Metabolic Syndrome in Men (METSIM) study (aged 57 ± 7 years; BMI 26.8 ± 3.7 kg/m(2)). Genotyping of 34 single nucleotide polymorphism (SNPs) for hyperglycemia/type 2 diabetes was performed. Proton nuclear magnetic resonance spectroscopy was used to measure particle concentrations of 14 lipoprotein subclasses and their composition in native serum samples.

RESULTS

The glucose-increasing allele of rs780094 in GCKR was significantly associated with low concentrations of VLDL particles (independently of their size) and small LDL and was nominally associated with low concentrations of intermediate-density lipoprotein, all LDL subclasses, and high concentrations of very large and large HDL particles. The glucose-increasing allele of rs174550 in FADS1 was significantly associated with high concentrations of very large and large HDL particles and nominally associated with low concentrations of all VLDL particles. SNPs rs10923931 in NOTCH2 and rs757210 in HNF1B genes showed nominal or significant associations with several lipoprotein traits. The genetic risk score of 34 SNPs was not associated with any of the lipoprotein subclasses.

CONCLUSIONS

Four of the 34 risk loci for type 2 diabetes or hyperglycemia (GCKR, FADS1, NOTCH2, and HNF1B) were significantly associated with lipoprotein traits. A GCKR variant predominantly affected the concentration of VLDL, and the FADS1 variant affected very large and large HDL particles. Only a limited number of risk loci for hyperglycemia/type 2 diabetes significantly affect lipoprotein metabolism.

Visceral adipocyte hypertrophy is associated with dyslipidemia independent of body composition and fat distribution in women

OBJECTIVE

We assessed whether subcutaneous and omental adipocyte hypertrophy are related to metabolic alterations independent of body composition and fat distribution in women.

RESEARCH DESIGN AND METHODS

Mean adipocyte diameter of paired subcutaneous and omental adipose tissue samples was obtained in lean to obese women. Linear regression models predicting adipocyte size in both adipose tissue depots were computed using body composition and fat distribution measures (n = 150). In a given depot, women with larger adipocytes than predicted by the regression were considered as having adipocyte hypertrophy, whereas women with smaller adipocytes than predicted were considered as having adipocyte hyperplasia.

RESULTS

Women characterized by omental adipocyte hypertrophy had higher plasma and VLDL triglyceride levels as well as a higher total-to-HDL cholesterol ratio compared with women characterized by omental adipocyte hyperplasia (P < 0.05). Conversely, women characterized by subcutaneous adipocyte hypertrophy or hyperplasia showed a similar lipid profile. In logistic regression analyses, a 10% enlargement of omental adipocytes increased the risk of hypertriglyceridemia (adjusted odds ratio [OR] 4.06, P < 0.001) independent of body composition and fat distribution measures. A 10% increase in visceral adipocyte number also raised the risk of hypertriglyceridemia (adjusted OR 1.55, P < 0.02). Associations between adipocyte size and homeostasis model assessment of insulin resistance were not significant once adjusted for adiposity and body fat distribution.

CONCLUSIONS

These results suggest that omental, but not subcutaneous, adipocyte hypertrophy is associated with an altered lipid profile independent of body composition and fat distribution in women.

Adipose tissue lamin A/C messenger RNA expression in women

Mutations in the lamin A/C gene (LMNA) cause lipodystrophy. However, little data are available on lamin A/C expression in various fat depots in women. We recruited 34 women scheduled for gynecologic surgery. Blood samples were collected on the morning of surgery to obtain a detailed lipid profile. Radiological examinations were performed to measure total body fat mass and abdominal fat accumulation. Fat samples were taken from the subcutaneous (SC) fat depot and from the greater omentum (OM) during the surgical procedure. Whole adipose tissue samples were used for total messenger RNA (mRNA) extraction and real-time polymerase chain reaction quantification of the LMNA transcript. No association was observed between lamin A/C mRNA expression, either in SC or OM fat tissue, and adiposity measures. Women with low SC lamin A/C expression, identified on the basis of the median value of SC lamin A/C mRNA expression, had a significantly altered lipid profile including lower levels of high-density lipoprotein (HDL) cholesterol and HDL(2) cholesterol and reduced HDL(2) cholesterol to HDL(3) cholesterol ratio (P < .05 for all). These women were also characterized by higher cholesterol to HDL cholesterol, low-density lipoprotein-triglycerides, very low-density lipoprotein-apolipoprotein B, and low-density lipoprotein cholesterol to HDL cholesterol (P < .05 for all). Low SC lamin A/C mRNA expression levels were also associated with significantly increased lipolysis in isolated fat cells from this fat depot. Specifically, the response to lipolytic agent isoproterenol was significantly increased at doses ranging from 10(-5) to 10(-10) mol/L (P < .05). A similar trend was observed in OM fat cells but did not reach significance. In conclusion, low lamin A/C expression in SC adipose tissue is associated with significant alterations in the lipid profile and increased fat cell lipolysis, independent of the level of total or abdominal adiposity.

Dyslipidaemia in the metabolic syndrome and type 2 diabetes: pathogenesis, priorities, pharmacotherapies

IMPORTANCE OF THE FIELD

Dyslipoproteinaemia is a cardinal feature of the metabolic syndrome that accelerates atherosclerosis. It is usually characterized by high plasma concentrations of triglyceride-rich and apolipoprotein B (apoB)-containing lipoproteins, with depressed concentrations of high-density lipoprotein (HDL). Drug interventions are essential for normalizing metabolic dyslipidaemia.

AREAS COVERED IN THIS REVIEW

This review discusses the mechanisms and treatment for dyslipidaemia in the metabolic syndrome and type 2 diabetes.

WHAT THE READER WILL GAIN

A comprehensive understanding of the pathophysiology and pharmacotherapy of dyslipidaemia in the metabolic syndrome and diabetes.

TAKE HOME MESSAGE

Dysregulation of lipoprotein metabolism may be due to a combination of overproduction of triglyceride-rich lipoproteins, decreased catabolism of apoB-containing particles, and increased catabolism of HDL particles. These abnormalities may be consequent on a global metabolic effect of insulin resistance and an excess of both visceral and hepatic fat. Lifestyle modifications may favourably alter lipoprotein transport in the metabolic syndrome. Patients with dyslipidaemia and established cardiovascular disease should receive a statin as first-line therapy. Combination with other lipid-regulating agents, such as ezetimibe, fibrates, niacins and fish oils may optimize the benefit of statin on atherogenic dyslipidaemia.

In vivo efficacy of acyl CoA: diacylglycerol acyltransferase (DGAT) 1 inhibition in rodent models of postprandial hyperlipidemia

Postprandial serum triglyceride concentrations have recently been identified as a major, independent risk factor for future cardiovascular events. As a result, postprandial hyperlipidemia has emerged as a potential therapeutic target. The purpose of this study was two-fold. Firstly, to describe and characterize a standardized model of postprandial hyperlipidemia in multiple rodent species; and secondly, apply these rodent models to the evaluation of a novel class of pharmacologic agent; acyl CoA:diacylglycerol acyltransferase (DGAT) 1 inhibitors. Serum triglycerides were measured before and for 4h after oral administration of a standardized volume of corn oil, to fasted C57BL/6, ob/ob, apoE(-/-) and CD-1 mice; Sprague-Dawley and JCR/LA-cp rats; and normolipidemic and hyperlipidemic hamsters. Intragastric administration of corn oil increased serum triglycerides in all animals evaluated, however the magnitude and time-course of the postprandial triglyceride excursion varied. The potent and selective DGAT-1 inhibitor A-922500 (0.03, 0.3 and 3 mg/kg, p.o.), dose-dependently attenuated the maximal postprandial rise in serum triglyceride concentrations in all species tested. At the highest dose of DGAT-1 inhibitor, the postprandial triglyceride response was abolished. This study provides a comprehensive characterization of the time-course of postprandial hyperlipidemia in rodents. In addition, the ability of DGAT-1 inhibitors to attenuate postprandial hyperlipidemia in multiple rodent models, including those that feature insulin resistance, is documented. Exaggerated postprandial hyperlipidemia is inherent to insulin-resistant states in humans and contributes to the substantially elevated cardiovascular risk observed in these patients. Therefore, by attenuating postprandial hyperlipidemia, DGAT-1 inhibition may represent a novel therapeutic approach to reduce cardiovascular risk.