Dose-dependent effect of rosuvastatin on VLDL-apolipoprotein C-III kinetics in the metabolic syndrome

Unravelling lipoprotein metabolism with stable isotopes: tracing the flow

Dysregulated lipoprotein metabolism is a major cause of atherosclerotic cardiovascular disease (ASCVD). Use of stable isotope tracers and compartmental modelling have provided deeper understanding of the mechanisms underlying lipid disorders in patients at high risk of ASCVD, including familial hypercholesterolemia (FH), elevated lipoprotein(a) [Lp(a)] and metabolic syndrome (MetS). In patients with FH, deficiency in low-density lipoprotein (LDL) receptor activity not only impairs the catabolism of LDL, but also induces hepatic overproduction and decreases catabolism of triglyceride-rich lipoproteins (TRLs). Patients with elevated Lp(a) are characterized by increased hepatic secretion of Lp(a) particles. Atherogenic dyslipidemia in MetS patients relates to a combination of overproduction of very-low density lipoprotein-apolipoprotein (apo) B-100, decreased catabolism of apoB-100-containing particles, and increased catabolism of high-density lipoprotein-apoA-I particles, as well as to impaired clearance of TRLs in the postprandial state. Kinetic studies show that weight loss, fish oils, statins and fibrates have complementary modes of action that correct atherogenic dyslipidemia. Defining the kinetic mechanisms of action of proprotein convertase subtilisin/kexin type 9 and angiopoietin-like 3 inhibitors on lipid and lipoprotein mechanism in dyslipidemic subjects will further our understanding of these therapies in decreasing the development of ASCVD. "Everything changes but change itself. Everything flows and nothing remains the same... You cannot step twice into the same river, for other waters and yet others go flowing ever on." Heraclitus (c.535- c. 475 BCE).

Metabolism of Triglyceride-Rich Lipoproteins

Triglycerides are critical lipids as they provide an energy source that is both compact and efficient. Due to its hydrophobic nature triglyceride molecules can pack together densely and so be stored in adipose tissue. To be transported in the aqueous medium of plasma, triglycerides have to be incorporated into lipoprotein particles along with other components such as cholesterol, phospholipid and associated structural and regulatory apolipoproteins. Here we discuss the physiology of normal triglyceride metabolism, and how impaired metabolism induces hypertriglyceridemia and its pathogenic consequences including atherosclerosis. We also discuss established and novel therapies to reduce triglyceride-rich lipoproteins.

Lipids and Lipoproteins in Health and Disease: Focus on Targeting Atherosclerosis

Despite advances in pharmacotherapy, intervention devices and techniques, residual cardiovascular risks still cause a large burden on public health. Whilst most guidelines encourage achieving target levels of specific lipids and lipoproteins to reduce these risks, increasing evidence has shown that molecular modification of these lipoproteins also has a critical impact on their atherogenicity. Modification of low-density lipoprotein (LDL) by oxidation, glycation, peroxidation, apolipoprotein C-III adhesion, and the small dense subtype largely augment its atherogenicity. Post-translational modification by oxidation, carbamylation, glycation, and imbalance of molecular components can reduce the capacity of high-density lipoprotein (HDL) for reverse cholesterol transport. Elevated levels of triglycerides (TGs), apolipoprotein C-III and lipoprotein(a), and a decreased level of apolipoprotein A-I are closely associated with atherosclerotic cardiovascular disease. Pharmacotherapies aimed at reducing TGs, lipoprotein(a), and apolipoprotein C-III, and enhancing apolipoprotein A-1 are undergoing trials, and promising preliminary results have been reported. In this review, we aim to update the evidence on modifications of major lipid and lipoprotein components, including LDL, HDL, TG, apolipoprotein, and lipoprotein(a). We also discuss examples of translating findings from basic research to potential therapeutic targets for drug development.

Development of Antisense Oligonucleotide Gapmers for the Treatment of Dyslipidemia and Lipodystrophy

Although technological advances in molecular genetics over the last few decades have greatly expedited the identification of mutations in many genetic diseases, the translation of the genetic mechanisms into a clinical setting has been quite challenging, with a minimum number of effective treatments available. The advancements in antisense therapy have revolutionized the field of neuromuscular disorders as well as lipid-mediated diseases. With the approval of splice-switching antisense oligonucleotide (AO) therapy for nusinersen and eteplirsen for the treatment of spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD), several modified AOs are now being evaluated in clinical trials for the treatment of a number of disorders. In order to activate RNase H-mediated cleavage of the target mRNA, as well as to increase the binding affinity and specificity, gapmer AOs are designed that have a PS backbone flanked with the modified AOs on both sides. Mipomersen (trade name Kynamro), a 2'-O-methoxyethyl (MOE) gapmer, was approved by the Food and Drug Administration (FDA) for the treatment of homozygous familial hypercholesterolemia (HoFH) in 2013. Volanesorsen, another 20-mer MOE gapmer has shown to be successful in lowering the levels of triglycerides (TGs) in several lipid disorders and has received conditional approval in the European Union for the treatment of Familial chylomicronemia syndrome (FCS) in May 2019 following successful results from phase II/III clinical trials. This chapter focuses on the clinical applications of gapmer AOs for genetic dyslipidemia and lipodystrophy.

ANGPTL3 and Apolipoprotein C-III as Novel Lipid-Lowering Targets

PURPOSE OF REVIEW

Despite significant progress in plasma lipid lowering strategies, recent clinical trials highlight the existence of residual cardiovascular risk. Angiopoietin-like protein 3 (ANGPTL3) and apolipoprotein C-III (Apo C-III) have been identified as novel lipid-lowering targets.

RECENT FINDINGS

Apo C-III and ANGPTL3 have emerged as novel regulators of triglyceride (TG) and low-density lipoprotein-cholesterol (LDL-C) levels. ANGPTL3 is an inhibitor of lipoprotein lipase (LPL), reducing lipolysis of Apo B-containing lipoproteins. Loss-of-function ANGPLT3 mutations are associated with reduced plasma cholesterol and TG, while novel ANGPLT3 inhibition strategies, including monoclonal antibodies (evinacumab), ANGPLT3 antisense oligonucleotides (IONIS-ANGPTL3-L_Rx), and small interfering RNA (siRNA) silencing techniques (ARO-ANG3), result in increased lipolysis and significant reductions of LDL-C and TG levels in phase I and II clinical trials. Similarly, Apo C-III inhibits LPL while promoting the hepatic secretion of TG-rich lipoproteins and preventing their clearance. Loss-of-function APOC3 mutations have been associated with reduced TG levels. Targeting of Apo C-III with volanesorsen, an APOC3 siRNA, results in significant reduction in plasma TG levels but possibly also increased risk for thrombocytopenia, as recently demonstrated in phase I, II, and III clinical trials. ARO-APOC3 is a novel siRNA-based agent targeting Apo C-III which is currently under investigation with regard to its lipid-lowering efficiency. ANGPTL3 and Apo C-III targeting agents have demonstrated striking lipid-lowering effects in recent clinical trials; however, more thorough safety and efficacy data are required. Here, we evaluate the role of ANGPLT3 and Apo C-III in lipid metabolism, present the latest clinical advances targeting those molecules, and outline the remaining scientific challenges on residual lipid-associated cardiovascular risk.

Investigation of the synergistic effect of glimepiride and rosuvastatin on alloxan-induced diabetic rat

Purpose

Diabetes mellitus is characterized by having a multitude of life-threatening secondary complications, particularly dyslipidemia, which ultimately leads to the development of comorbid diseases, such as cardiovascular diseases. This research work was designed to investigate the synergistic effect of glimepiride (1 mg/kg b.w.) and rosuvastatin (10 mg /kg b.w.) on alloxan-induced diabetic rats having dyslipidemia.

Methods

Diabetes was induced by injecting alloxan (120 mg/kg b.w.) intraperitoneally. The experiment was conducted to determine the level of blood glucose, HbA1c, lipid profile, and body weight variation of rats.

Results

This study's outcomes suggested that the combination therapy showed more statistically significant effect on blood glucose level, HbA1c level, lipid profile, and body weight variation than any single therapy. While the glimepiride monotherapy showed a statistically considerable effect on blood glucose level, HbA1c level, and body weight variation, the rosuvastatin treated group gave statistically non-significant effect on these parameters except body weight variation, which was found as downward trend. In addition, the rosuvastatin treated group showed a healthy lipid profile compared to glimepiride treated group.

Conclusions

Concluding the results of this study, it can be said that the treatment of glimepiride in combination with rosuvastatin may be more efficacious than monotherapy for preventing diabetes in rats with dyslipidemia.

Exploration of Serum Marker Proteins in Mice Induced by Babesia microti Infection Using a Quantitative Proteomic Approach

Babesia microti is a protozoan that mainly parasitizes rodent and human erythrocytes. B. microti infection can result in changes in the expression levels of various proteins in the host serum. To explore the mechanism underlying the regulation of serum proteins by the host during B. microti infection, this study used a data-independent acquisition (DIA) quantitative proteomic approach to perform comprehensive quantitative proteomic analysis on the serum of B. microti-infected mice. We identified and analysed 333 serum proteins during the infectious stage and recovery stage within 30 days of infection by B. microti in mice. Through quantitative analysis, we found 57 proteins differentially expressed in the infection stage and 69 proteins differentially expressed in the recovery stage. Bioinformatics analysis revealed that these differentially expressed proteins were mainly concentrated in organelles, cell parts, and extracellular regions that are mainly involved in immune system, metabolic, and cellular processes. Additionally, the differentially expressed proteins mainly had catalytic activity. Kyoto Encyclopedia of Genes and Genome (KEGG) pathway analysis showed that many of the differentially expressed proteins participate in the complement and coagulation cascade reaction, including complement C3, complement FP, and coagulation factor XII. The results of this study can provide more information for the selection of biomarkers for the early clinical monitoring of babesiosis and help in the treatment of babesiosis.

The Roles of ApoC-III on the Metabolism of Triglyceride-Rich Lipoproteins in Humans

Cardiovascular disease (CVD) is the leading cause of death globally. It is well-established based on evidence accrued during the last three decades that high plasma concentrations of cholesterol-rich atherogenic lipoproteins are causatively linked to CVD, and that lowering these reduces atherosclerotic cardiovascular events in humans (1-9). Historically, most attention has been on low-density lipoproteins (LDL) since these are the most abundant atherogenic lipoproteins in the circulation, and thus the main carrier of cholesterol into the artery wall. However, with the rise of obesity and insulin resistance in many populations, there is increasing interest in the role of triglyceride-rich lipoproteins (TRLs) and their metabolic remnants, with accumulating evidence showing they too are causatively linked to CVD. Plasma triglyceride, measured either in the fasting or non-fasting state, is a useful index of the abundance of TRLs and recent research into the biology and genetics of triglyceride heritability has provided new insight into the causal relationship of TRLs with CVD. Of the genetic factors known to influence plasma triglyceride levels variation in APOC3- the gene for apolipoprotein (apo) C-III - has emerged as being particularly important as a regulator of triglyceride transport and a novel therapeutic target to reduce dyslipidaemia and CVD risk (10).

Role of apolipoprotein C-III overproduction in diabetic dyslipidaemia

AIMS

To investigate how apolipoprotein C-III (apoC-III) metabolism is altered in subjects with type 2 diabetes, whether the perturbed plasma triglyceride concentrations in this condition are determined primarily by the secretion rate or the removal rate of apoC-III, and whether improvement of glycaemic control using the glucagon-like peptide-1 analogue liraglutide for 16 weeks modifies apoC-III dynamics.

MATERIALS AND METHODS

Postprandial apoC-III kinetics were assessed after a bolus injection of [5,5,5-² H₃ ]leucine using ultrasensitive mass spectrometry techniques. We compared apoC-III kinetics in two situations: in subjects with type 2 diabetes before and after liraglutide therapy, and in type 2 diabetic subjects with matched body mass index (BMI) non-diabetic subjects. Liver fat content, subcutaneous abdominal and intra-abdominal fat were determined using proton magnetic resonance spectroscopy.

RESULTS

Improved glycaemic control by liraglutide therapy for 16 weeks significantly reduced apoC-III secretion rate (561 ± 198 vs. 652 ± 196 mg/d, P = 0.03) and apoC-III levels (10.0 ± 3.8 vs. 11.7 ± 4.3 mg/dL, P = 0.035) in subjects with type 2 diabetes. Change in apoC-III secretion rate was significantly associated with the improvement in indices of glucose control (r = 0.67; P = 0.009) and change in triglyceride area under the curve (r = 0.59; P = 0.025). In line with this, the apoC-III secretion rate was higher in subjects with type 2 diabetes compared with BMI-matched non-diabetic subjects (676 ± 208 vs. 505 ± 174 mg/d, P = 0.042).

CONCLUSIONS

The results reveal that the secretion rate of apoC-III is associated with elevation of triglyceride-rich lipoproteins in subjects with type 2 diabetes, potentially through the influence of glucose homeostasis on the production of apoC-III.

Emerging Evidence that ApoC-III Inhibitors Provide Novel Options to Reduce the Residual CVD

Purpose of Review

Apolipoprotein C-III (apoC-III) is known to inhibit lipoprotein lipase (LPL) and function as an important regulator of triglyceride metabolism. In addition, apoC-III has also more recently been identified as an important risk factor for cardiovascular disease. This review summarizes the mechanisms by which apoC-III induces hypertriglyceridemia and promotes atherogenesis, as well as the findings from recent clinical trials using novel strategies for lowering apoC-III.

Recent Findings

Genetic studies have identified subjects with heterozygote loss-of-function (LOF) mutations in APOC3, the gene coding for apoC-III. Clinical characterization of these individuals shows that the LOF variants associate with a low-risk lipoprotein profile, in particular reduced plasma triglycerides. Recent results also show that complete deficiency of apoC-III is not a lethal mutation and is associated with very rapid lipolysis of plasma triglyceride-rich lipoproteins (TRL). Ongoing trials based on emerging gene-silencing technologies show that intervention markedly lowers apoC-III levels and, consequently, plasma triglyceride. Unexpectedly, the evidence points to apoC-III not only inhibiting LPL activity but also suppressing removal of TRLs by LPL-independent pathways.

Summary

Available data clearly show that apoC-III is an important cardiovascular risk factor and that lifelong deficiency of apoC-III is cardioprotective. Novel therapies have been developed, and results from recent clinical trials indicate that effective reduction of plasma triglycerides by inhibition of apoC-III might be a promising strategy in management of severe hypertriglyceridemia and, more generally, a novel approach to CHD prevention in those with elevated plasma triglyceride.

Effect of statin therapy on plasma apolipoprotein CIII concentrations: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Statins are well-established low-density lipoprotein cholesterol-lowering drugs. Elevated apolipoprotein CIII (Apo CIII) levels are associated with elevated triglyceride-rich particles, which are also considered to be a possible risk factor for cardiovascular disease.

OBJECTIVE

The aim of this meta-analysis of randomized placebo-controlled clinical trials was to assess the effect of statins on Apo CIII concentrations.

METHODS

Randomized placebo-controlled trials investigating the impact of statin treatment on cholesterol lowering that include lipoprotein measurement were searched in PubMed, MEDLINE, Scopus, Web of Science, and Google Scholar databases (up to July 31, 2017). A random-effects model and generic inverse variance method were used for quantitative data synthesis. Sensitivity analysis was conducted using the leave-one-out method. A weighted random-effects meta-regression was performed to evaluate the impact of potential confounders on Apo CIII concentrations.

RESULTS

This meta-analysis of data from 6 randomized placebo-controlled clinical trials (10 statin arms) involving 802 subjects showed that statin therapy significantly decreased circulating Apo CIII concentrations (weighted mean difference [WMD]: -2.71, 95% confidence interval [CI]: -3.74 to -1.68, P < .001; I²: 73.83%). The effect size was robust in the leave-one-out sensitivity analysis and not driven by any single study. Subgroup analysis showed a reduction of Apo CIII concentrations by atorvastatin (WMD: -4.74, 95% CI: -3.74 to -1.68, P = .002; I²: 84.02%), rosuvastatin (WMD: -2.68, 95% CI: -4.52 to -0.84, P = .004; I²: 0%), and lovastatin (WMD: -1.64, 95% CI: -2.22 to -1.07, P < .001; I²: 0%).

CONCLUSION

This meta-analysis suggests that statin treatment significantly reduces plasma Apo CIII levels.

ApoCIII as a Cardiovascular Risk Factor and Modulation by the Novel Lipid-Lowering Agent Volanesorsen

PURPOSE OF REVIEW

Apolipoprotein CIII (ApoCIII) is now recognized as a key regulator in severe hypertriglyceridemia, chylomicronemia, and conditions of triglyceride-rich lipoprotein (TRL) remnant excess due to its inhibition of lipoprotein lipase (LPL) and hepatic lipase, leading to decreased hepatic reuptake of TRLs, as well as enhanced synthesis and secretion of VLDL from the liver. ApoCIII gain-of-function mutations are associated with atherosclerosis and coronary heart disease (CHD), and contribute to the development of cardiometabolic syndrome, hypertriglyceridemia, and type 2 diabetes mellitus. Conversely, loss-of-function mutations in ApoCIII are associated with lower levels of plasma triglycerides (TG), attenuation of vascular inflammatory processes such as monocyte adhesion and endothelial dysfunction, and potentially, a reduction in the incidence and progression of atherosclerosis and cardioprotection.

RECENT FINDINGS

Evidence is now emerging that volanesorsen, a second-generation antisense oligonucleotide drug targeting ApoCIII messenger RNA resulting in decreases in TG in patients with familial chylomicronemia syndrome, severe hypertriglyceridemia, and metabolic dyslipidemia with type 2 diabetes giving support to the hypothesis that ApoCIII is a powerful inhibitor of LPL, and when reduced, endogenous clearance of TRLs can result in substantial reductions in TG levels. Discovery of the ApoCIII inhibitor volanesorsen opens a new era of lipid-lowering drugs for reduction in TG and potentially for reduction in LDL-C. Herein, this review will provide an update on the pathophysiology of ApoCIII-linked atherosclerosis and the development of the first drug to target ApoCIII, volanesorsen, as a promising lipid-lowering agent.

Targeting ApoC-III to Reduce Coronary Disease Risk

Triglyceride-rich lipoproteins (TRLs) are causal contributors to the risk of developing coronary artery disease (CAD). Apolipoprotein C-III (apoC-III) is a component of TRLs that elevates plasma triglycerides (TGs) through delaying the lipolysis of TGs and the catabolism of TRL remnants. Recent human genetics approaches have shown that heterozygous loss-of-function mutations in APOC3, the gene encoding apoC-III, lower plasma TGs and protect from CAD. This observation has spawned new interest in therapeutic efforts to target apoC-III. Here, we briefly review both currently available as well as developing therapies for reducing apoC-III levels and function to lower TGs and cardiovascular risk. These therapies include existing options including statins, fibrates, thiazolidinediones, omega-3-fatty acids, and niacin, as well as an antisense oligonucleotide targeting APOC3 currently in clinical development. We review the mechanisms of action by which these drugs reduce apoC-III and the current understanding of how reduction in apoC-III may impact CAD risk.

The role of antisense oligonucleotide therapy against apolipoprotein-CIII in hypertriglyceridemia

Increased triglyceride levels (higher than ∼1000 mg/dL) are associated with an increased risk for pancreatitis. Apolipoprotein-CIII (apo-CIII) plays a key role in the metabolism of triglycerides and triglyceride-rich lipoproteins. While loss of function mutations in the gene encoding apo-CIII (APOC3) are associated with low triglyceride levels and a decreased risk for cardiovascular disease (CVD), overexpression of APOC3 is associated with hypertriglyceridemia. Although many drugs such as fibrates, statins and omega-3 fatty acids modestly decrease triglyceride levels (and apo-CIII concentrations), there are many patients who still have severe hypertriglyceridemia and are at risk for pancreatitis and potentially CVD. The antisense oligonucleotide (ASO) against APOC3 mRNA volanesorsen (previously called ISIS 304801, ISIS-ApoCIIIRx and IONIS-ApoCIIIRx) robustly decreases both, apo-CIII production and triglyceride concentrations and is being currently evaluated in phase 3 trials. In this narrative review we present the currently available clinical evidence on the efficacy and safety of volanesorsen for the treatment of hypertriglyceridemia.

The metabolic vascular syndrome - guide to an individualized treatment

In ancient Greek medicine the concept of a distinct syndrome (going together) was used to label 'a group of signs and symptoms' that occur together and 'characterize a particular abnormality and condition'. The (dys)metabolic syndrome is a common cluster of five pre-morbid metabolic-vascular risk factors or diseases associated with increased cardiovascular morbidity, fatty liver disease and risk of cancer. The risk for major complications such as cardiovascular diseases, NASH and some cancers develops along a continuum of risk factors into clinical diseases. Therefore we still include hyperglycemia, visceral obesity, dyslipidemia and hypertension as diagnostic traits in the definition according to the term 'deadly quartet'. From the beginning elevated blood pressure and hyperglycemia were core traits of the metabolic syndrome associated with endothelial dysfunction and increased risk of cardiovascular disease. Thus metabolic and vascular abnormalities are in extricable linked. Therefore it seems reasonable to extend the term to metabolic-vascular syndrome (MVS) to signal the clinical relevance and related risk of multimorbidity. This has important implications for integrated diagnostics and therapeutic approach. According to the definition of a syndrome the rapid global rise in the prevalence of all traits and comorbidities of the MVS is mainly caused by rapid changes in life-style and sociocultural transition resp. with over- and malnutrition, low physical activity and social stress as a common soil.

Increased Rosuvastatin Dose versus Concomitant Fenofibrate and Rosuvastatin Therapy to Achieve Lipid Goal in Patients with Diabetes or Atherosclerosis with Metabolic Syndrome

PUPOSE

We aimed to ascertain whether increased rosuvastatin dose is non-inferior to concomitant fenofibrate and rosuvastatin therapy in patients with diabetes or atherosclerosis with metabolic syndrome.

METHODS

After treatment with rosuvastatin 5 mg/day for 12 weeks, 112 patients were randomly assigned to receive either 10 mg/day rosuvastatin (group A) or 80 mg/day supra-film coated fenofibrate plus 5 mg/day rosuvastatin (group B). The therapy effects were evaluated by measuring the serum lipid profile, liver and muscle enzymes, and renal function after the treatment period.

RESULTS

After the treatment, the total cholesterol, high-density-lipoprotein cholesterol (HDL-C), non HDL-C, low-density-lipoprotein cholesterol (LDL-C), and triglyceride were comparable between the 2 groups. The change in the non-HDL-C were -7.39 ± 26.58 (-6.62%) and -0.68 ± 24.49 (-1.19%) mg/dl (p = 0.28); and the change in the triglyceride were -36.61 ± 62.51 (-14.00%) and -44.77 ± 77.35 (-23.17%) mg/dl (p = 0.64), respectively. While 41.37% of group A and 38.69% of group B achieved their LDL-C goal (< 100 mg/dl) (p = 0.79), 37.26% of group A and 42.31% of group B achieved their triglyceride goal (< 150 mg/dl) (p = 0.53), respectively. The changes in the serum transaminase and creatinine phosphokinase were similar between the 2 groups.

CONCLUSIONS

After 5 mg/day of rosuvastatin, the lipid profile in patients with diabetes or atherosclerotic vascular diseases with metabolic syndrome could be improved by increasing rosuvastatin dose, and the resultant decrease of non-HDL and triglyceride were similar to those obtained with combination therapy. Both therapies were safe and feasible.

KEY WORDS

Combination therapy; Diabetes; Fenofibrate; Metabolic syndrome; Monotherapy; Statin.

Altered activation of endothelial anti- and proapoptotic pathways by high-density lipoprotein from patients with coronary artery disease: role of high-density lipoprotein-proteome remodeling

BACKGROUND

Endothelial dysfunction and injury are thought to play an important role in the progression of coronary artery disease (CAD). High-density lipoprotein from healthy subjects (HDL(Healthy)) has been proposed to exert endothelial antiapoptotic effects that may represent an important antiatherogenic property of the lipoprotein. The present study therefore aimed to compare effects of HDL(CAD) and HDL(Healthy) on the activation of endothelial anti- and proapoptotic pathways and to determine which changes of the lipoprotein are relevant for these processes.

METHODS AND RESULTS

HDL was isolated from patients with stable CAD (HDL(sCAD)), an acute coronary syndrome (HDL(ACS)), and healthy subjects. HDL(Healthy) induced expression of the endothelial antiapoptotic Bcl-2 protein Bcl-xL and reduced endothelial cell apoptosis in vitro and in apolipoprotein E-deficient mice in vivo. In contrast, HDL(sCAD) and HDL(ACS) did not inhibit endothelial apoptosis, failed to activate endothelial Bcl-xL, and stimulated endothelial proapoptotic pathways, in particular, p38-mitogen-activated protein kinase-mediated activation of the proapoptotic Bcl-2 protein tBid. Endothelial antiapoptotic effects of HDL(Healthy) were observed after inhibition of endothelial nitric oxide synthase and after delipidation, but not completely mimicked by apolipoprotein A-I or reconstituted HDL, suggesting an important role of the HDL proteome. HDL proteomics analyses and subsequent validations and functional characterizations suggested a reduced clusterin and increased apolipoprotein C-III content of HDL(sCAD) and HDL(ACS) as mechanisms leading to altered effects on endothelial apoptosis.

CONCLUSIONS

The present study demonstrates for the first time that HDL(CAD) does not activate endothelial antiapoptotic pathways, but rather stimulates potential endothelial proapoptotic pathways. HDL-proteome remodeling plays an important role for these altered functional properties of HDL. These findings provide novel insights into mechanisms leading to altered vascular effects of HDL in coronary disease.

Mechanism of action of a peroxisome proliferator-activated receptor (PPAR)-delta agonist on lipoprotein metabolism in dyslipidemic subjects with central obesity

CONTEXT

Dyslipidemia increases the risk of cardiovascular disease in obesity. Peroxisome proliferator-activated receptor (PPAR)-δ agonists decrease plasma triglycerides and increase high-density lipoprotein (HDL)-cholesterol in humans.

OBJECTIVE

The aim of the study was to examine the effect of GW501516, a PPAR-δ agonist, on lipoprotein metabolism. Design, Setting, and Intervention: We conducted a randomized, double-blind, crossover trial of 6-wk intervention periods with placebo or GW501516 (2.5 mg/d), with 2-wk placebo washout between treatment periods.

PARTICIPANTS

We recruited 13 dyslipidemic men with central obesity from the general community.

MAIN OUTCOME MEASURES

We measured the kinetics of very low-density lipoprotein (VLDL)-, intermediate-density lipoprotein-, and low-density lipoprotein (LDL)-apolipoprotein (apo) B-100, plasma apoC-III, and high-density lipoprotein (HDL) particles (LpA-I and LpA-I:A-II).

RESULTS

GW501516 decreased plasma triglycerides, fatty acid, apoB-100, and apoB-48 concentrations. GW501516 decreased the concentrations of VLDL-apoB by increasing its fractional catabolism and of apoC-III by decreasing its production rate (P < 0.05). GW501516 reduced VLDL-to-LDL conversion and LDL-apoB production. GW501516 increased HDL-cholesterol, apoA-II, and LpA-I:A-II concentrations by increasing apoA-II and LpA-I:A-II production (P < 0.05). GW501516 decreased cholesteryl ester transfer protein activity, and this was paralleled by falls in the triglyceride content of VLDL, LDL, and HDL and the cholesterol content of VLDL and LDL.

CONCLUSIONS

GW501516 increased the hepatic removal of VLDL particles, which might have resulted from decreased apoC-III concentration. GW501516 increased apoA-II production, resulting in an increased concentration of LpA-I:A-II particles. This study elucidates the mechanism of action of this PPAR-δ agonist on lipoprotein metabolism and supports its potential use in treating dyslipidemia in obesity.

Plasma apolipoprotein C-III metabolism in patients with chronic kidney disease

Moderate chronic kidney disease (CKD) (defined by an estimated glomerular filtration rate of 30-60 ml/min) is associated with mild hypertriglyceridemia related to delayed catabolism of triglyceride-rich lipoprotein particles. Altered apolipoprotein C-III (apoC-III) metabolism may contribute to dyslipidemia in CKD. To further characterize the dyslipidemia of CKD, we investigated the kinetics of plasma apoC-III in 7 nonobese, nondiabetic, non-nephrotic CKD subjects and 7 age- and sex-matched healthy controls, using deuterated leucine ([5, 5, 5, ²H₃]leucine), gas chromatography-mass spectrometry, and multicompartmental modeling. Compared with controls, CKD subjects had higher concentrations of plasma and VLDL triglycerides and plasma and VLDL apoC-III (P < 0.05). The increased plasma apoC-III concentration was associated with a decreased apoC-III fractional catabolic rate (FCR) (1.21 ± 0.15 vs. 0.74 ± 0.12 pools/day, P = 0.03). There were no differences between apoC-III production rates of controls and those of CKD subjects. In CKD subjects, plasma apoC-III concentration was significantly and negatively correlated with apoC-III FCR (r = -0.749, P = 0.05) but not with apoC-III production rate. Plasma apoC-III concentration was positively correlated with plasma and VLDL triglycerides and VLDL apoB concentrations and negatively correlated with VLDL apoB FCR (P < 0.05 for all). ApoC-III FCR was negatively correlated with plasma and VLDL triglycerides and VLDL apoB concentration and positively correlated with VLDL apoB FCR (P < 0.05 for all). Altered plasma apoC-III metabolism is a feature of dyslipidemia in moderate CKD. Modification of apoC-III catabolism may be an important therapeutic target for reducing cardiovascular disease risk in moderate CKD.

Mechanisms for therapeutic correction of dyslipidaemia in insulin resistance and diabetes

Dyslipidaemia is a common cardiovascular risk factor in insulin resistant subjects with obesity, type 2 diabetes mellitus and the metabolic syndrome. Lipoprotein metabolism is complex and abnormal plasma concentrations result from alterations in the rates of production and/or catabolism of diverse lipoprotein particles. Understanding the dysregulation and therapeutic correction of lipoprotein transport in insulin resistant states has relied on the use of stable isotope tracers and modelling methods. The effects of lifestyle and therapeutic interventions on the kinetics of apolipoproteins B-100 and A-I containing lipoproteins are reviewed.

Effects of atorvastatin and n-3 fatty acid supplementation on VLDL apolipoprotein C-III kinetics in men with abdominal obesity

BACKGROUND

Disturbed apolipoprotein (apo) C-III metabolism in obese subjects may account for hypertriglyceridemia and increased risk of cardiovascular disease. Atorvastatin and fish oils decrease plasma triglycerides and VLDL concentrations, but the underlying mechanisms are not fully understood.

OBJECTIVE

We studied the independent and combined effects of atorvastatin and fish oils on the metabolism of VLDL apo C-III in obese men.

DESIGN

We carried out a 6-wk randomized, placebo-controlled, 2 x 2 factorial intervention study of atorvastatin (40 mg/d) and fish oils (4 g/d) on VLDL apo C-III kinetics in the postabsorptive state in 39 abdominally obese men using intravenous administration of d(3)-leucine. VLDL apo C-III isotopic enrichments were measured by using gas chromatography-mass spectrometry with kinetic parameters derived by using a multicompartmental model.

RESULTS

Atorvastatin significantly (P < 0.05, main effect) increased the VLDL apo C-III fractional catabolic rate (+0.06 +/- 0.003 pools/d) without significantly altering its production rate (-0.14 +/- 0.18 mg . kg(-1) . d(-1)), accounting for a significant reduction in plasma VLDL apo C-III pool size (-44 +/- 17 mg/L). Fish-oil supplementation significantly decreased plasma triglycerides but did not significantly alter plasma VLDL apo C-III concentrations or kinetic parameters. Combination treatment provided no additional effect on VLDL apo C-III concentrations or kinetics compared with atorvastatin alone.

CONCLUSIONS

In obesity, the triglyceride-lowering effect of atorvastatin, but not fish oils, is associated with increased VLDL apo C-III fractional catabolism and hence lower VLDL apo C-III concentrations. Combination treatment provided no significant additional improvement in VLDL apo C-III metabolism compared with atorvastatin alone.

Effects of ezetimibe and simvastatin on apolipoprotein B metabolism in males with mixed hyperlipidemia

Sixteen hyperlipidemic men were enrolled in a randomized, placebo-controlled, double-blind, cross-over study to evaluate the effect of ezetimibe 10 mg and simvastatin 40 mg, coadministered and alone, on the in vivo kinetics of apolipoprotein (apo) B-48 and B-100 in humans. Subjects underwent a primed-constant infusion of a stable isotope in the fed state. The coadministration of simvastatin and ezetimibe significantly reduced plasma concentrations of cholesterol (-43.0%), LDL-C (-53.6%), and triglycerides (-44.0%). Triglyceride-rich lipoproteins (TRL) apoB-48 pool size (PS) was significantly decreased (-48.9%) following combination therapy mainly through a significant reduction in TRL apoB-48 production rate (PR) (-38.0%). The fractional catabolic rate (FCR) of VLDL and LDL apoB-100 were significantly increased with all treatment modalities compared with placebo, leading to a significant reduction in the PS of these fractions. We also observed a positive correlation between changes in TRL apoB-48 PS and changes in TRL apoB-48 PR (r = 0.85; P < 0.0001) with combination therapy. Our results indicate that treatment with simvastatin plus ezetimibe is effective in reducing plasma TRL apoB-48 levels and that this effect is most likely mediated by a reduction in the intestinal secretion of TRL apoB-48. Our study also indicated that the reduction in LDL-C concentration following combination therapy is mainly driven by an increase in FCR of apoB-100 containing lipoproteins.