Plasma apolipoprotein C-III levels, triglycerides, and coronary artery calcification in type 2 diabetics

Impaired Suppression of Plasma Lipid Extraction and its Partitioning Away from Muscle by Insulin in Humans with Obesity

Context

Humans with obesity and insulin resistance exhibit lipid accumulation in skeletal muscle, but the underlying biological mechanisms responsible for the accumulation of lipid in the muscle of these individuals remain unknown.

Objective

We investigated how plasma insulin modulates the extraction of circulating triglycerides (TGs) and non-esterified fatty acids (NEFAs) from dietary and endogenous sources in the muscle of lean, insulin-sensitive humans (Lean-IS) and contrasted these responses to those in humans with obesity and insulin resistance (Obese-IR).

Methods

The studies were performed in a postprandial state associated with steady-state plasma TG concentrations. The arterio-venous blood sampling technique was employed to determine the extraction of circulating lipids across the forearm muscle before and after insulin infusion. We distinguished kinetics of TGs and NEFAs from dietary sources across muscle from those from endogenous sources by incorporating stable isotope-labeled triolein in ingested fat.

Results

Plasma insulin rapidly suppressed the extraction of plasma TGs from endogenous, but not dietary, sources in the Lean-IS, but same response was absent in the Obese-IR. Furthermore, in the muscle of Lean-IS, plasma insulin decreased the extraction of circulating NEFAs from both dietary and endogenous sources, but in Obese-IR subjects this response was absent for NEFAs from dietary sources.

Conclusions

Partitioning of circulating lipids away from the skeletal muscle when plasma insulin increases, such as during the postprandial period, is impaired in humans with obesity and insulin resistance. Trial Registration: ClinicalTrials.gov ( NCT01860911 ).

Proteomics analysis of coronary atherosclerotic heart disease with different Traditional Chinese Medicine syndrome types before and after percutaneous coronary intervention

OBJECTIVE

To investigate the underlying protein molecular mechanisms of "Qi stagnation and blood stasis syndrome" (QS) and "Qi deficiency and blood stasis syndrome" (QD), as two subtypes of coronary artery disease (CAD) in Traditional Chinese Medicine (TCM), following percutaneous coronary intervention (PCI).

METHODS

In this study, a total of 227 CAD patients with QS and 211 CAD patients with QD were enrolled; all participants underwent PCI. Label-free quantification proteomics were employed to analyze the changes in serum in two subtypes of CAD patients before and 6 months after PCI, aiming to elucidate the intervention mechanism of PCI in treating CAD characterized by two different TCM syndromes.

RESULTS

Biochemical analysis revealed significant changes in tumor necrosis factor-α, high density lipoprotein cholesterol, blood stasis clinical symptoms observation, and Gensini levels in both patient groups post-PCI; Proteomic analysis identified 79 and 95 differentially expressed proteins in the QS and QD patient groups, respectively, compared to their control groups. complement C8 alpha chain, complement factor H, apolipoprotein H, apolipoprotein B, plasminogen, carbonic anhydrase 2, and complement factor I were altered in both comparison groups. Furthermore, enrichment analysis demonstrated that cell adhesion and connectivity-related processes underwent changes in QS patients post-PCI, whereas lipid metabolism-related pathways, including the peroxisome proliferator-activated receptor signaling pathway and extracellular matrix receptor interaction, underwent changes in the QD group. The protein-protein interaction network analysis further enriched 52 node proteins, including apolipoprotein B, lipoprotein (a), complement C5, apolipoprotein A4, complement C8 alpha chain, complement C8 beta chain, complement C8 gamma chain, apolipoprotein H, apolipoprotein A-Ⅱ, albumin, complement C4-B, apolipoprotein C3, among others. The functional network of these proteins is posited to contribute to the pathophysiology of CAD characterized by TCM syndromes.

CONCLUSION

The current quantitative proteomic study has preliminarily identified biomarkers of CAD in different TCM subtypes treated with PCI, potentially laying the groundwork for understanding the protein profiles associated with the treatment of various TCM subtypes of CAD.

APOA1/C3/A4/A5 Gene Cluster at 11q23.3 and Lipid Metabolism Disorders: From Epigenetic Mechanisms to Clinical Practices

The APOA1/C3/A4/A5 cluster is an essential component in regulating lipoprotein metabolism and maintaining plasma lipid homeostasis. A genome-wide association analysis and Mendelian randomization have revealed potential associations between genetic variants within this cluster and lipid metabolism disorders, including hyperlipidemia and cardiovascular events. An enhanced understanding of the complexity of gene regulation has led to growing recognition regarding the role of epigenetic variation in modulating APOA1/C3/A4/A5 gene expression. Intensive research into the epigenetic regulatory patterns of the APOA1/C3/A4/A5 cluster will help increase our understanding of the pathogenesis of lipid metabolism disorders and facilitate the development of new therapeutic approaches. This review discusses the biology of how the APOA1/C3/A4/A5 cluster affects circulating lipoproteins and the current progress in the epigenetic regulation of the APOA1/C3/A4/A5 cluster.

Role of glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 in hypertriglyceridemia and diabetes

In diabetes, the impairment of insulin secretion and insulin resistance contribute to hypertriglyceridemia, as the enzymatic activity of lipoprotein lipase (LPL) depends on insulin action. The transport of LPL to endothelial cells and its enzymatic activity are maintained by the formation of lipolytic complex depending on the multiple positive (glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 [GPIHBP1], apolipoprotein C-II [APOC2], APOA5, heparan sulfate proteoglycan [HSPG], lipase maturation factor 1 [LFM1] and sel-1 suppressor of lin-12-like [SEL1L]) and negative regulators (APOC1, APOC3, angiopoietin-like proteins [ANGPTL]3, ANGPTL4 and ANGPTL8). Among the regulators, GPIHBP1 is a crucial molecule for the translocation of LPL from parenchymal cells to the luminal surface of capillary endothelial cells, and maintenance of lipolytic activity; that is, hydrolyzation of triglyceride into free fatty acids and monoglyceride, and conversion from chylomicron to chylomicron remnant in the exogenous pathway and from very low-density lipoprotein to low-density lipoprotein in the endogenous pathway. The null mutation of GPIHBP1 causes severe hypertriglyceridemia and pancreatitis, and GPIGBP1 autoantibody syndrome also causes severe hypertriglyceridemia and recurrent episodes of acute pancreatitis. In patients with type 2 diabetes, the elevated serum triglyceride levels negatively correlate with circulating LPL levels, and positively with circulating APOC1, APOC3, ANGPTL3, ANGPTL4 and ANGPTL8 levels. In contrast, circulating GPIHBP1 levels are not altered in type 2 diabetes patients with higher serum triglyceride levels, whereas they are elevated in type 2 diabetes patients with diabetic retinopathy and nephropathy. The circulating regulators of lipolytic complex might be new biomarkers for lipid and glucose metabolism, and diabetic vascular complications.

Apolipoprotein C3 induces inflammasome activation only in its delipidated form

Matters arising regarding the lipidation form of plasma APOC3 that induces an alternative NLRP3 activation pathway.

APOC-III: a Gatekeeper in Controlling Triglyceride Metabolism

PURPOSE OF REVIEW

Apolipoprotein C-III (ApoC-III) is a widely known player in triglyceride metabolism, and it has been recently recognized as a polyhedric factor which may regulate several pathways beyond lipid metabolism by influencing cardiovascular, metabolic, and neurological disease risk. This review summarizes the different functions of ApoC-III and underlines the recent findings related to its multifaceted pathophysiological role.

RECENT FINDINGS

The role of ApoC-III has been implicated in HDL metabolism and in the development of atherosclerosis, inflammation, and ER stress in endothelial cells. ApoC-III has been recently considered an important player in insulin resistance mechanisms, lipodystrophy, diabetic dyslipidemia, and postprandial hypertriglyceridemia (PPT). The emerging evidence of the involvement of ApoC-III in the in the pathogenesis of Alzheimer's disease open the way to further study if modification of ApoC-III level slows disease progression. Furthermore, ApoC-III is clearly linked to cardiovascular disease (CVD) risk, and progression of coronary artery disease (CAD) as well as the calcification of aortic valve and recent clinical trials has pointed out the inhibition of ApoC-III as a promising approach to manage hypertriglyceridemia and prevent CVD. Several evidences highlight the role of ApoC-III not only in triglyceride metabolism but also in several cardio-metabolic pathways. Results from recent clinical trials underline that the inhibition of ApoC-III is a promising therapeutical strategy for the management of severe hypertriglyceridemia and in CVD prevention.

Dyslipidemia and coronary artery calcium: From association to development of a risk-prediction nomogram

BACKGROUND AND AIMS

The associations between dyslipidemia and coronary artery calcium (CAC) are controversial. We investigated their cross-sectional relationships and developed a predictive scoring system for prognostically significant coronary calcification (PSCC).

METHODS AND RESULTS

This study evaluated the lipid profiles and the CAC score (CACS) measured through multidetector computed tomography (MDCT) among Taiwanese adult patients in a tertiary hospital between 2011 and 2016. Patients with CACS higher than 100 were classified as having PSCC. Dyslipidemia for each lipid component was defined based on the clinical cutoffs or the use of the lipid-lowering agents. Multivariable logistic regression was used to assess the association between dyslipidemia and PSCC and the model performance was assessed using calibration plot, discrimination, and a decision curve analysis. Of the 3586 eligible patients, 364 (10.2%) had PSCC. Increased age, male sex, higher body mass index (BMI), and higher level of triglyceride (TG) were associated with PSCC. The adjusted odds ratios (95% confidence intervals) of PSCC was 1.15 (0.90-1.47) for dyslipidemia defined by total cholesterol (TC) ≥200 mg/dL, 1.06 (0.83-1.35) for low-density-lipoprotein-cholesterol (LDL-C) ≥130 mg/dL, and 1.36 (1.06-1.75) for TG ≥ 200 mg/dL. The positive association between TG ≥ 200 mg/dL and PSCC was not modified by sex. Incorporating hypertriglyceridemia did not significantly improve the predictive performance of the base model comprising of age, sex, BMI, smoking, hypertension, diabetes, estimated glomerular filtration rate, and fasting glucose.

CONCLUSIONS

Hypertriglyceridemia was significantly associated with the prevalent odds of PSCC. Our proposed predictive model may be a useful screening tool for PSCC.

The daily caloric restriction and alternate-day fasting ameliorated lipid dysregulation in type 2 diabetic mice by downregulating hepatic pescadillo 1

PURPOSE

A possible link between pescadillo 1 (PES1) and lipid metabolism has been reported. However, whether PES1 is involved in the effects of daily caloric restriction (CR) and alternate-day fasting (ADF) interventions on diabetes-related lipid dysregulation is not elucidated. The current study aims are to explore the role of PES1 in effects of CR and ADF on diabetic mice and related mechanism.

METHODS

Eight-week-old male db/db mice with type 2 diabetes mellitus (T2DM) were randomly divided into untreated T2DM, CR and ADF groups. McArdle hepatocytes were treated with 48 h high glucose (HG), 48 h normal glucose (NG) and 24 h HG plus 24 h NG, respectively. Pes1 siRNA and overexpression plasmid were, respectively, transfected into liver cells, and AAV9-Pes1-shRNA was injected into db/db mice.

RESULTS

After 12-week interventions, the peroxisome proliferator-activated receptor alpha (PPAR-α) and carnitine palmitoyltransferase 1A (CPT1A) levels in livers of T2DM mice were enhanced by CR and ADF interventions with reductions of hepatic and plasma triglycerides. Unexpectedly, hepatic PES1 levels were downregulated by two interventions, consistent with the results of 48 h NG and 24 h HG plus 24 h NG-treated cells. Moreover, CPT1A level was upregulated in Pes1-siRNA-treated cells and AAV9-Pes1-shRNA injected murine livers, in contrast to Pes1 overexpression in cultured cells. Mechanistically, 48 h NG or 24 h HG plus 24 h NG treatment increased PPAR-α binding to Pes1 promoter, suppressing the PES1 expression, thereby lowering the PES1-mediated ubiquitination of CPT1A.

CONCLUSION

The present study suggests that CR and ADF may improve lipid dysregulation in diabetic mice by downregulating hepatic PES1.

Liraglutide Improved Cardiometabolic Parameters More in Obese than in Non-obese Patients with Type 2 Diabetes: A Real-World 18-Month Prospective Study

INTRODUCTION

The glucagon-like peptide-1 agonist (GLP1-RA) liraglutide is currently approved for the treatment of both obesity and type 2 diabetes (T2DM). We investigated whether the effect of this agent on cardiometabolic parameters in subjects with T2DM varied in relation to the concomitant presence of obesity.

METHODS

One hundred thirty-five subjects (78 men and 57 women; age: 62 ± 10 years) naïve to incretin-based therapies were treated with low-dose liraglutide (1.2 mg/day) as an add-on to metformin for 18 months. Patients were divided into two subgroups based on their body-mass index (BMI): (a) obese (BMI ≥ 30) and (b) non-obese (BMI < 30). Clinical and laboratory analyses were assessed at baseline and every 6 months.

RESULTS

During follow-up, significant improvements were seen in both groups in fasting glycemia, glycated hemoglobin, waist circumference, and carotid intima-media thickness (cIMT), while body weight, BMI, total cholesterol, and low-density lipoprotein cholesterol decreased significantly in obese subjects only. Correlation analysis revealed that changes in subclinical atherosclerosis (assessed by cIMT) were associated with changes in triglycerides (r = 0.488, p < 0.0001) in the obese group only.

CONCLUSION

Liraglutide had beneficial actions on glycemic parameters and cardiometabolic risk factors in both non-obese and obese patients with T2DM, with a greater efficacy in the latter. These findings reinforce the benefits of liraglutide for the cardiometabolic outcomes of obese patients with T2DM in the real-world setting. This has critical importance during the current pandemic, since patients with diabetes and obesity are exposed globally to the most severe forms of COVID-19, related complications, and death.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT01715428.

Is Apo-CIII the new cardiovascular target? An analysis of its current clinical and dietetic therapies

AIMS

Recently, Apolipoprotein CIII (Apo-CIII) has gained remarkable attention since its overexpression has been strongly correlated to cardiovascular disease (CVD) occurrence. The aim of this review was to summarize the latest findings of Apo-CIII as a CVDs and diabetes risk factor, as well as the plausible mechanisms involved in the development of these pathologies, with particular emphasis on current clinical and dietetic therapies.

DATA SYNTHESIS

Apo-CIII is a small protein (∼8.8 kDa) that, among other functions, inhibits lipoprotein lipase, a key enzyme in lipid metabolism. Apo-CIII plays a fundamental role in the physiopathology of atherosclerosis, type-1, and type-2 diabetes. Apo-CIII has become a potential clinical target to tackle these multifactorial diseases. Dietetic (omega-3 fatty acids, stanols, polyphenols, lycopene) and non-dietetic (fibrates, statins, and antisense oligonucleotides) therapies have shown promising results to regulate Apo-CIII and triglyceride levels. However, more information from clinical trials is required to validate it as a new target for atherosclerosis and diabetes types 1 and 2.

CONCLUSIONS

There are still several pathways involving Apo-CIII regulation that might be affected by bioactive compounds that need further research. The mechanisms that trigger metabolic responses following bioactive compounds consumption are mainly related to higher LPL expression and PPARα activation, although the complete pathways are yet to be elucidated.

Addressing dyslipidemic risk beyond LDL-cholesterol

Despite the success of LDL-lowering drugs in reducing cardiovascular disease (CVD), there remains a large burden of residual disease due in part to persistent dyslipidemia characterized by elevated levels of triglyceride-rich lipoproteins (TRLs) and reduced levels of HDL. This form of dyslipidemia is increasing globally as a result of the rising prevalence of obesity and metabolic syndrome. Accumulating evidence suggests that impaired hepatic clearance of cholesterol-rich TRL remnants leads to their accumulation in arteries, promoting foam cell formation and inflammation. Low levels of HDL may associate with reduced cholesterol efflux from foam cells, aggravating atherosclerosis. While fibrates and fish oils reduce TRL, they have not been uniformly successful in reducing CVD, and there is a large unmet need for new approaches to reduce remnants and CVD. Rare genetic variants that lower triglyceride levels via activation of lipolysis and associate with reduced CVD suggest new approaches to treating dyslipidemia. Apolipoprotein C3 (APOC3) and angiopoietin-like 3 (ANGPTL3) have emerged as targets for inhibition by antibody, antisense, or RNAi approaches. Inhibition of either molecule lowers TRL but respectively raises or lowers HDL levels. Large clinical trials of such agents in patients with high CVD risk and elevated levels of TRL will be required to demonstrate efficacy of these approaches.

Egyptian practical guidance in hypertriglyceridemia management 2021

Hypertriglyceridemia (HTG) is a very common, yet underappreciated problem in clinical practice. Elevated triglyceride (TG) levels are independently associated with atherosclerotic cardiovascular disease (ASCVD) risk. Furthermore, severe HTG may lead to acute pancreatitis. Although LDL-guided statin therapy has improved ASCVD outcomes, residual risk remains. Recent trials have demonstrated that management of high TG levels, in patients already on statin therapy, reduces the rate of major vascular events. Few guidelines were issued, providing important recommendations for HTG management strategies. The goal of treatment is to reduce the risk of ASCVD and acute pancreatitis. The management stands on lifestyle modification, detection of secondary causes of HTG and pharmacological therapy, when indicated. In this guidance we review the causes and classification of HTG and summarize the current methods for risk estimation, diagnosis and treatment. The present guidance provides a focused update on the management of HTG, outlined in a simple user-friendly format, with an emphasis on the latest available data.

Treatment of Hypertriglyceridemia: A Review of Therapies in the Pipeline

BackgroundThe 2018 American College of Cardiology/American Heart Association (ACC/AHA) guidelines and 2021 ACC Expert Consensus Decision Pathway recommend nonpharmacological interventions and initiation of statin therapy for patients with moderate hypertriglyceridemia and addition of fibrates or omega-3 fatty acids in severe hypertriglyceridemia. Although the association between triglyceride (TG) lowering and atherosclerotic cardiovascular disease (ASCVD) risk reduction remains controversial, patients with hypertriglyceridemia may represent a subgroup that require additional therapy to further reduce residual ASCVD risk. Moreover, medications that target novel pathways could provide alternative options for patients who are intolerant of existing therapies or doses needed to provide adequate triglyceride lowering. Objective: Assess recent evidence for TG-lowering agents including omega-3 fatty acid-based therapies, PPARα modulators, apoC-III mRNA antisense inhibitors, angiopoietin-like 3 (ANGPTL3) antibodies, and herbal supplements. Methods: A literature search was performed using PubMed with hypertriglyceridemia specified as a MeSH term or included in the title or abstract of the article along with each individual agent. For inclusion, trials needed to have a primary or secondary outcome of TG levels or TG lowering. Conclusion: Currently, the only US Food and Drug Administration approved medication for CV risk reduction in patients with hypertriglyceridemia is icosapent ethyl. Results from phase 3 trials for CaPre, pemafibrate, and volanesorsen as well as additional evidence for pipeline pharmacotherapies with novel mechanisms of action (e.g., ApoC-III mRNA antisense inhibitors and ANGPTL3 antibodies) will help to guide future pharmacotherapy considerations for patients with hypertriglyceridemia.

Persistence of Lipoproteins and Cholesterol Alterations after Sepsis: Implication for Atherosclerosis Progression

(1) Background: Sepsis is one of the most common critical care illnesses with increasing survivorship. The quality of life in sepsis survivors is adversely affected by several co-morbidities, including increased incidence of dementia, stroke, cardiac disease and at least temporary deterioration in cognitive dysfunction. One of the potential explanations for their progression is the persistence of lipid profile abnormalities induced during acute sepsis into recovery, resulting in acceleration of atherosclerosis. (2) Methods: This is a targeted review of the abnormalities in the long-term lipid profile abnormalities after sepsis; (3) Results: There is a well-established body of evidence demonstrating acute alteration in lipid profile (HDL-c ↓↓, LDL-C -c ↓↓). In contrast, a limited number of studies demonstrated depression of HDL-c levels with a concomitant increase in LDL-C -c in the wake of sepsis. VLDL-C -c and Lp(a) remained unaltered in few studies as well. Apolipoprotein A1 was altered in survivors suggesting abnormalities in lipoprotein metabolism concomitant to overall lipoprotein abnormalities. However, most of the studies were limited to a four-month follow-up and patient groups were relatively small. Only one study looked at the atherosclerosis progression in sepsis survivors using clinical correlates, demonstrating an acceleration of plaque formation in the aorta, and a large metanalysis suggested an increase in the risk of stroke or acute coronary event between 3% to 9% in sepsis survivors. (4) Conclusions: The limited evidence suggests an emergence and persistence of the proatherogenic lipid profile in sepsis survivors that potentially contributes, along with other factors, to the clinical sequel of atherosclerosis.

APOC3 genetic variation, serum triglycerides, and risk of coronary artery disease in Asian Indians, Europeans, and other ethnic groups

BACKGROUND

Hypertriglyceridemia has emerged as a critical coronary artery disease (CAD) risk factor. Rare loss-of-function (LoF) variants in apolipoprotein C-III have been reported to reduce triglycerides (TG) and are cardioprotective in American Indians and Europeans. However, there is a lack of data in other Europeans and non-Europeans. Also, whether genetically increased plasma TG due to ApoC-III is causally associated with increased CAD risk is still unclear and inconsistent. The objectives of this study were to verify the cardioprotective role of earlier reported six LoF variants of APOC3 in South Asians and other multi-ethnic cohorts and to evaluate the causal association of TG raising common variants for increasing CAD risk.

METHODS

We performed gene-centric and Mendelian randomization analyses and evaluated the role of genetic variation encompassing APOC3 for affecting circulating TG and the risk for developing CAD.

RESULTS

One rare LoF variant (rs138326449) with a 37% reduction in TG was associated with lowered risk for CAD in Europeans (p = 0.007), but we could not confirm this association in Asian Indians (p = 0.641). Our data could not validate the cardioprotective role of other five LoF variants analysed. A common variant rs5128 in the APOC3 was strongly associated with elevated TG levels showing a p-value 2.8 × 10- 424. Measures of plasma ApoC-III in a small subset of Sikhs revealed a 37% increase in ApoC-III concentrations among homozygous mutant carriers than the wild-type carriers of rs5128. A genetically instrumented per 1SD increment of plasma TG level of 15 mg/dL would cause a mild increase (3%) in the risk for CAD (p = 0.042).

CONCLUSIONS

Our results highlight the challenges of inclusion of rare variant information in clinical risk assessment and the generalizability of implementation of ApoC-III inhibition for treating atherosclerotic disease. More studies would be needed to confirm whether genetically raised TG and ApoC-III concentrations would increase CAD risk.

Polypeptide N-acetylgalactosaminyltransferase-Associated Phenotypes in Mammals

Mucin-type O-glycosylation involves the attachment of glycans to an initial O-linked N-acetylgalactosamine (GalNAc) on serine and threonine residues on proteins. This process in mammals is initiated and regulated by a large family of 20 UDP-GalNAc: polypeptide N-acetylgalactosaminyltransferases (GalNAc-Ts) (EC 2.4.1.41). The enzymes are encoded by a large gene family (GALNTs). Two of these genes, GALNT2 and GALNT3, are known as monogenic autosomal recessive inherited disease genes with well characterized phenotypes, whereas a broad spectrum of phenotypes is associated with the remaining 18 genes. Until recently, the overlapping functionality of the 20 members of the enzyme family has hindered characterizing the specific biological roles of individual enzymes. However, recent evidence suggests that these enzymes do not have full functional redundancy and may serve specific purposes that are found in the different phenotypes described. Here, we summarize the current knowledge of GALNT and associated phenotypes.

Genetic and Metabolic Determinants of Plasma Levels of ANGPTL8

CONTEXT

ANGPTL8 (A8) plays a key role in determining the tissue fate of circulating triglycerides (TGs). Plasma A8 levels are associated with several parameters of glucose and TG metabolism, but the causality of these relationships and the contribution of genetic variants to differences in A8 levels have not been explored.

OBJECTIVE

To characterize the frequency distribution of plasma A8 levels in a diverse population using a newly-developed enzyme-linked immunosorbent assay (ELISA) and to identify genetic factors contributing to differences in plasma A8 levels.

METHODS

We studied a population-based sample of Dallas County, comprising individuals in the Dallas Heart Study (DHS-1, n = 3538; DHS-2, n = 3283), including 2131 individuals with repeated measurements 7 to 9 years apart (age 18-85 years; >55% female; 52% Black; 29% White; 17% Hispanic; and 2% other). The main outcome measures were associations of A8 levels with body mass index (BMI), plasma levels of glucose, insulin, lipids, and hepatic TGs, as well as DNA variants identified by exome-wide sequencing.

RESULTS

A8 levels varied over a 150-fold range (2.1-318 ng/mL; median, 13.3 ng/mL) and differed between racial/ethnic groups (Blacks > Hispanics > Whites). A8 levels correlated with BMI, fasting glucose, insulin, and TG levels. A variant in A8, R59W, accounted for 17% of the interindividual variation in A8 levels but was not associated with the metabolic parameters correlated with plasma A8 concentrations.

CONCLUSIONS

A8 levels were strongly associated with indices of glucose and TG metabolism, but the lack of association of genetic variants at the A8 locus that impact A8 levels with these parameters indicates that differences in A8 levels are not causally related to the associated metabolic phenotypes.

apoA2 correlates to gestational age with decreased apolipoproteins A2, C1, C3 and E in gestational diabetes

INTRODUCTION

Pregnant women with gestational diabetes mellitus (GDM) are at risk of adverse outcomes, including gestational hypertension, pre-eclampsia, and preterm delivery. This study was undertaken to determine if apolipoprotein (apo) levels differed between pregnant women with and without GDM and if they were associated with adverse pregnancy outcome.

RESEARCH DESIGN AND METHODS

Pregnant women (46 women with GDM and 26 women without diabetes (ND)) in their second trimester were enrolled in the study. Plasma apos were measured and correlated to demographic, biochemical, and pregnancy outcome data.

RESULTS

apoA2, apoC1, apoC3 and apoE were lower in women with GDM compared with control women (p=0.0019, p=0.0031, p=0.0002 and p=0.015, respectively). apoA1, apoB, apoD, apoH, and apoJ levels did not differ between control women and women with GDM. Pearson bivariate analysis revealed significant correlations between gestational age at delivery and apoA2 for women with GDM and control women, and between apoA2 and apoC3 concentrations and C reactive protein (CRP) as a measure of inflammation for the whole group.

CONCLUSIONS

Apoproteins apoA2, apoC1, apoC3 and apoE are decreased in women with GDM and may have a role in inflammation, as apoA2 and C3 correlated with CRP. The fact that apoA2 correlated with gestational age at delivery in both control women and women with GDM raises the hypothesis that apoA2 may be used as a biomarker of premature delivery, and this warrants further investigation.

Association among age, gender, menopausal status and small dense low-density lipoprotein cholesterol: a cross-sectional study

OBJECTIVES

Small dense low-density lipoprotein cholesterol (sdLDL-C) might be a better cardiovascular disease (CVD) indicator than low-density lipoprotein cholesterol (LDL-C); however, details regarding its epidemiology remain elusive. The present study aimed at evaluating the association between the demographic factors, such as age, gender and menopausal status, and sdLDL-C levels and sdLDL-C/LDL-C ratio in the Japanese population.

DESIGN

This was a cross-sectional study.

SETTING

13 rural districts in Japan, 2010-2017.

PARTICIPANTS

This study included 5208 participants (2397 men and 2811 women), who underwent the health mass screening that was conducted in accordance with the medical care system for the elderly and obtained informed consent for this study.

RESULTS

In total, 517 premenopausal women (mean age ±SD, 45.1±4.2 years), 2294 postmenopausal women (66.5±8.8 years) and 2397 men (64.1±11.2 years) were analysed. In men, the sdLDL-C levels and sdLDL-C/LDL-C ratio increased during younger adulthood, peaked (36.4 mg/dL, 0.35) at 50-54 years, and then decreased. In women, relatively regular increasing trends of sdLDL-C level and sdLDL-C/LDL-C ratio until approximately 65 years (32.7 mg/dL, 0.28), followed by a downward or pleated trend. Given the beta value of age, body mass index, fasting glucose and smoking and drinking status by multiple linear regression analysis, standardised sdLDL-C levels and sdLDL-C/LDL-C ratio in 50-year-old men, premenopausal women and postmenopausal women were 26.6, 22.7 and 27.4 mg/dL and 0.24, 0.15 and 0.23, respectively. The differences between premenopausal and postmenopausal women were significant (p<0.001).

CONCLUSIONS

SdLDL-C and sdLDL-C/LDL-C ratios showed different distributions by age, gender and menopausal status. A subgroup-specific approach would be necessary to implement sdLDL-C for CVD prevention strategies, fully considering age-related trends, gender differences and menopausal status.

ApoCIII: A multifaceted protein in cardiometabolic disease

ApoCIII has a well-recognized role in triglyceride-rich lipoproteins metabolism. A considerable amount of data has clearly highlighted that high levels of ApoCIII lead to hypertriglyceridemia and, thereby, may influence the risk of cardiovascular disease. However, recent findings indicate that ApoCIII might also act beyond lipid metabolism. Indeed, ApoCIII has been implicated in other physiological processes such as glucose homeostasis, monocyte adhesion, activation of inflammatory pathways, and modulation of the coagulation cascade. As the inhibition of ApoCIII is emerging as a new promising therapeutic strategy, the complete understanding of multifaceted pathophysiological role of this apoprotein may be relevant. Therefore, the purpose of this work is to review available evidences not only related to genetics and biochemistry of ApoCIII, but also highlighting the role of this apoprotein in triglyceride and glucose metabolism, in the inflammatory process and coagulation cascade as well as in cardiovascular disease.

Circulating Receptor Activator of Nuclear Factor kB Ligand and triglycerides are associated with progression of lower limb arterial calcification in type 2 diabetes: a prospective, observational cohort study

Background

Lower limb arterial calcification is a frequent, underestimated but serious complication of diabetes. The DIACART study is a prospective cohort study designed to evaluate the determinants of the progression of lower limb arterial calcification in 198 patients with type 2 diabetes.

Methods

Lower limb arterial calcification scores were determined by computed tomography at baseline and after a mean follow up of 31.20 ± 3.86 months. Serum RANKL (Receptor Activator of Nuclear factor kB Ligand) and bone remodeling, inflammatory and metabolic parameters were measured at baseline. The predictive effect of these markers on calcification progression was analyzed by a multivariate linear regression model.

Results

At baseline, mean ± SD and median lower limb arterial calcification scores were, 2364 ± 5613 and 527 respectively and at the end of the study, 3739 ± 6886 and 1355 respectively. Using multivariate analysis, the progression of lower limb arterial log calcification score was found to be associated with (β coefficient [slope], 95% CI, p-value) baseline log(calcification score) (1.02, 1.00–1.04, p < 0.001), triglycerides (0.11, 0.03–0.20, p = 0.007), log(RANKL) (0.07, 0.02–0.11, p = 0.016), previous ischemic cardiomyopathy (0.36, 0.15–0.57, p = 0.001), statin use (0.39, 0.06–0.72, p = 0.023) and duration of follow up (0.04, 0.01–0.06, p = 0.004).

Conclusion

In patients with type 2 diabetes, lower limb arterial calcification is frequent and can progress rapidly. Circulating RANKL and triglycerides are independently associated with this progression. These results open new therapeutic perspectives in peripheral diabetic calcifying arteriopathy.

Trial registration NCT02431234

In Vitro Evaluation of the Effects of Commercial Prebiotic GOS and FOS Products on Human Colonic Caco-2 Cells

Prebiotic oligosaccharides are widely used as human and animal feed additives for their beneficial effects on the gut microbiota. However, there are limited data to assess the direct effect of such functional foods on the transcriptome of intestinal epithelial cells. The purpose of this study is to describe the differential transcriptomes and cellular pathways of colonic cells directly exposed to galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS). We have examined the differential gene expression of polarized Caco–2 cells treated with GOS or FOS products and their respective mock-treated cells using mRNA sequencing (RNA-seq). A total of 89 significant differentially expressed genes were identified between GOS and mock-treated groups. For FOS treatment, a reduced number of 12 significant genes were observed to be differentially expressed relative to the control group. KEGG and gene ontology functional analysis revealed that genes up-regulated in the presence of GOS were involved in digestion and absorption processes, fatty acids and steroids metabolism, potential antimicrobial proteins, energy-dependent and -independent transmembrane trafficking of solutes and amino acids. Using our data, we have established complementary non-prebiotic modes of action for these frequently used dietary fibers.

Retinoids Repress Human Cardiovascular Cell Calcification With Evidence for Distinct Selective Retinoid Modulator Effects

OBJECTIVE

Retinoic acid (RA) is a ligand for nuclear receptors that modulate gene transcription and cell differentiation. Whether RA controls ectopic calcification in humans is unknown. We tested the hypothesis that RA regulates osteogenic differentiation of human arterial smooth muscle cells and aortic valvular interstitial cells that participate in atherosclerosis and heart valve disease, respectively. Approach and Results: Human cardiovascular tissue contains immunoreactive RAR (RA receptor)-a retinoid-activated nuclear receptor directing multiple transcriptional programs. RA stimulation suppressed primary human cardiovascular cell calcification while treatment with the RAR inhibitor AGN 193109 or RARα siRNA increased calcification. RA attenuated calcification in a coordinated manner, increasing levels of the calcification inhibitor MGP (matrix Gla protein) while decreasing calcification-promoting TNAP (tissue nonspecific alkaline phosphatase) activity. Given that nuclear receptor action varies as a function of distinct ligand structures, we compared calcification responses to cyclic retinoids and the acyclic retinoid peretinoin. Peretinoin suppressed human cardiovascular cell calcification without inducing either secretion of APOC3 (apolipoprotein-CIII), which promotes atherogenesis, or reducing CYP7A1 (cytochrome P450 family 7 subfamily A member 1) expression, which occurred with cyclic retinoids all-trans RA, 9-cis RA, and 13-cis RA. Additionally, peretinoin did not suppress human femur osteoblast mineralization, whereas all-trans RA inhibited osteoblast mineralization.

CONCLUSIONS

These results establish retinoid regulation of human cardiovascular calcification, provide new insight into mechanisms involved in these responses, and suggest selective retinoid modulators, like acyclic retinoids may allow for treating cardiovascular calcification without the adverse effects associated with cyclic retinoids.

Lipid-Lowering Agents

Several new or emerging drugs for dyslipidemia owe their existence, in part, to human genetic evidence, such as observations in families with rare genetic disorders or in Mendelian randomization studies. Much effort has been directed to agents that reduce LDL (low-density lipoprotein) cholesterol, triglyceride, and Lp[a] (lipoprotein[a]), with some sustained programs on agents to raise HDL (high-density lipoprotein) cholesterol. Lomitapide, mipomersen, AAV8.TBG.hLDLR, inclisiran, bempedoic acid, and gemcabene primarily target LDL cholesterol. Alipogene tiparvovec, pradigastat, and volanesorsen primarily target elevated triglycerides, whereas evinacumab and IONIS-ANGPTL3-L_Rx target both LDL cholesterol and triglyceride. IONIS-APO(a)-L_Rx targets Lp(a).

Combined Effect of Small Dense Low-Density Lipoprotein Cholesterol (sdLDL-C) and Remnant-Like Particle Cholesterol (RLP-C) on Low-Grade Inflammation

Aims: Small dense low-density lipoprotein cholesterol (sdLDL-C) and remnant-like particle cholesterol (RLP-C) are the novel atherosclerotic risk factors and might be strongly associated with inflammation. The basic evidence supports that sdLDL and RLP have some different mechanisms inducing an inflammatory response. Many studies have focused on the mechanism of inflammation of sdLDL-C or RLP-C per se, with limited data on the association between sdLDL-C and RLP-C in the real-world, population-based setting. Thus, the aim of this study was to investigate the association between sdLDL-C and RLP-C with inflammation.

Methods: We examined the baseline cross-sectional data of participants from the Jichi Medical School-II Cohort Study. In total, 5,305 participants (2,439 men and 2,866 women) were included in this study.

Results: Of all quartiles of sdLDL-C, the fourth had the highest high-sensitivity C-reactive protein (hs-CRP) level. Once adjusted for age, sex, smoking status, homeostasis model assessment of insulin resistance, antidyslipidemic and antihyperglycemic medication use, and RLP-C, sdLDL-C was significantly and positively associated with hs-CRP (geometric mean, 95% confidence interval (CI), 0.36 mg/L (0.34–0.38 mg/L), 0.37 mg/L (0.35–0.39 mg/L), 0.40 mg/L (0.37–0.42 mg/L) versus 0.44 mg/L (0.42–0.47 mg/L), P < 0.001 for trend). After stratifying the participants into four sdLDL-C×four RLP-C categories, the group in the fourth sdLDL-C quartile and the forth RLP-C quartile had the highest hs-CRP level (geometric mean, 95% CI, 0.52 mg/L, 0.48–0.57 mg/L, interaction P = 0.75).

Conclusions: SdLDL-C and RLP-C had different associations with inflammation. Our results support sdLDL-C as the potential novel factor of cardiovascular disease, independently of RLP-C.

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.

Serum untargeted lipidomic profiling reveals dysfunction of phospholipid metabolism in subclinical coronary artery disease

Purpose: Disturbed metabolism of cholesterol and triacylglycerols (TGs) carries increased risk for coronary artery calcification (CAC). However, the exact relationship between individual lipid species and CAC remains unclear. The aim of this study was to identify disturbances in lipid profiles involved in the calcification process, in an attempt to propose potential biomarker candidates.

Patients and methods: We studied 70 patients at intermediate risk for coronary artery disease who had undergone coronary calcification assessment using computed tomography and Agatston coronary artery calcium score (CACS). Patients were divided into three groups: with no coronary calcification (NCC; CACS: 0; n=26), mild coronary calcification (MCC; CACS: 1–250; n=27), or severe coronary calcification (SCC; CACS: >250; n=17). Patients’ serum samples were analyzed using liquid chromatography-mass spectrometry in an untargeted lipidomics approach.

Results: We identified 103 lipids within the glycerolipid, glycerophospholipid, sphingolipid, and sterol lipid classes. After false discovery rate correction, phosphatidylcholine (PC)(16:0/20:4) in higher levels and PC(18:2/18:2), PC(36:3), and phosphatidylethanolamine(20:0/18:2) in lower levels were identified as correlates with SCC compared to NCC. There were no significant differences in the levels of individual TGs between the three groups; however, clustering the lipid profiles showed a trend for higher levels of saturated and monounsaturated TGs in SCC compared to NCC. There was also a trend for lower TG(49:2), TG(51:1), TG(54:5), and TG(56:8) levels in SCC compared to MCC.

Conclusion: In this study we investigated the lipidome of patients with coronary calcification. Our results suggest that the calcification process may be associated with dysfunction in autophagy. The lipidomic biomarkers revealed in this study may aid in better assessment of patients with subclinical coronary artery disease.

Triglycerides and triglyceride-rich lipoproteins in the development and progression of atherosclerosis

PURPOSE OF REVIEW

In this review, we intend to show the heterogenicity of the triglyceride group, including the triglyceride-rich lipoproteins and its subparticles, apolipoproteins, and its role in atherogenesis through epidemiological and genetic studies, observing the association of these various components and subclasses with subclinical atherosclerosis and cardiovascular events. Also, we reevaluated the moment of blood collection for the triglyceride measurement and its repercussion in atherosclerosis. Finally, we present the current scenario and new insights about the pharmacologic treatment of hypertriglyceridemia.

RECENT FINDINGS

Recent studies have been observed, a correlation between cardiovascular disease and triglyceride components (as apolipoproteins A-V, C-I, C-III) as well as proteins involved in the metabolism pathway, such as the angiopoietin-like proteins. Also, the triglyceride-rich lipoproteins, also known as remnants, were recently associated with atherogenesis. Another important topic addressed is about nonfasting triglyceride level, which has been postulated as a better predictor of cardiovascular events than fasting collection.

SUMMARY

Regarding hypertriglyceridemia treatment, the drug therapy was updated, as the omega-3 polyunsaturated fatty acids were tested in primary prevention as eicosapentaenoic acid and docosahexaenoic acid combination resulted in no benefit, whereas the administration of icosapent ethyl in secondary prevention and high-risk patients showed a robust decrease of the cardiovascular outcomes.

Tackling Residual Atherosclerotic Risk in Statin-Treated Adults: Focus on Emerging Drugs

Epidemiological studies and meta-analyses have consistently suggested the importance of lowering low-density lipoprotein cholesterol (LDL-C) to reduce cardiovascular (CV) events. However, these studies and mechanistic studies using intracoronary imaging modalities have reported patients who continue to experience CV events or disease progression despite optimal LDL-C levels on statins. These findings, including statin intolerance, have highlighted the importance of exploring additional potential therapeutic targets to reduce CV risk. Genomic insights have presented a number of additional novel targets in lipid metabolism. In particular, proprotein convertase subtilisin/kexin type 9 inhibitors have rapidly developed and recently demonstrated their beneficial impact on CV outcomes. Triglyceride (TG)-rich lipoproteins have been recently reported as a causal factor of atherosclerotic cardiovascular disease (ASCVD). Indeed, several promising TG-targeting therapies are being tested at various clinical stages. In this review, we present the evidence to support targeting atherogenic lipoproteins to target residual ASCVD risk in statin-treated patients.

Relationship between serum apolipoproteins levels and retinopathy risk in subjects with type 2 diabetes mellitus

AIMS

Prognostic significance of apolipoproteins in diabetic retinopathy risk has not been well investigated. The aim of this study was to reveal the relationship between the risk of diabetic retinopathy and the levels of several apolipoproteins and their ratios in a 10-year prospective cohort.

METHODS

A total of 1023 diabetic patients without retinopathy were selected from a 10-year hospital-based diabetic cohort. In this cohort, all subjects had type 2 diabetes. Blood samples were obtained, and serum levels of several apolipoproteins were measured. In the follow-up period, diabetic retinopathy was diagnosed by two ophthalmologists through a series of ophthalmologic examinations. A Cox proportional hazard analysis was adopted to determine the relationship between the risk of diabetic retinopathy and the levels of several apolipoproteins and their ratios.

RESULTS

In the follow-up period, 315 diabetic patients were suffered from diabetic retinopathy, and the remaining 708 patients did not. Baseline serum level of apoAI ≥ 7.4 μmol/L was related to the decreased risk of diabetic retinopathy (HR 0.86, 95% CI 0.70-0.99). Baseline levels of apoCIII ≥ 6.3 μmol/L, apoE ≥ 1.1 μmol/L, apoCIII-to-apoAI ratio ≥ 0.9 and apoE-to-apoAI ratio ≥ 0.2 were associated with the increased risk of this complication (HR 1.25, 95% CI 1.04-1.49; HR 1.23, 95% CI 1.03-1.47; HR 1.34, 95% CI 1.11-1.60; HR 1.21, 95% CI 1.01-1.46).

CONCLUSION

Elevated level of apoAI might be a protective factor for diabetic retinopathy. Increased levels of apoCIII, apoE, apoCIII-to-apoAI and apoE-to-apoAI ratios might be risk factors for this complication.

Vitamin D supplementation and lipoprotein metabolism: A randomized controlled trial

BACKGROUND

Vitamin D deficiency is associated with an unfavorable lipid profile, but whether and how vitamin D supplementation affects lipid metabolism is unclear.

OBJECTIVE

To examine the effects of vitamin D supplementation on lipid and lipoprotein parameters.

METHODS

This is a post hoc analysis of the single-center, double-blind, randomized, placebo-controlled Styrian Vitamin D Hypertension Trial (2011-2014). Two hundred individuals with arterial hypertension and 25-hydroxyvitamin D concentrations of <75 nmol/L were randomized to 2800 IU of vitamin D daily or placebo for 8 weeks.

RESULTS

One hundred sixty-three participants (62.2 [53.1-68.4] years of age; 46% women) had available lipid data and were included in this analysis. Vitamin D supplementation significantly increased total cholesterol, triglycerides, very-low-density lipoprotein (VLDL) triglycerides, low-density lipoprotein (LDL) triglycerides, high-density lipoprotein (HDL) triglycerides, apolipoprotein B (ApoB), LDL-ApoB, ApoCII, ApoCIII, phospholipids, and ApoE (P < .05 for all). Except for ApoCII and ApoCIII and HDL-triglycerides, all other treatment effects remained statistically significant after adjustment for multiple testing with the Benjamini and Hochberg false discovery rate method. There was a nonsignificant increase in LDL cholesterol. Furthermore, no significant effects were seen on free fatty acids, lipoprotein (a), ApoAI, ApoAII, VLDL cholesterol, VLDL-ApoB, HDL cholesterol, LDL diameter, and VLDL diameter.

CONCLUSIONS

The effects of vitamin D on lipid metabolism are potentially unfavorable. They require further investigation in view of the wide use of vitamin D testing and treatment.

High-Density Lipoprotein Subspecies Defined by Apolipoprotein C-III and Subclinical Atherosclerosis Measures: MESA (The Multi-Ethnic Study of Atherosclerosis)

Background

Apolipoprotein C‐III (apoC‐III), a small proinflammatory protein present on 6% to 7% of high‐density lipoprotein (HDL) particles, defines a subspecies of HDL adversely associated with coronary heart disease in primarily white cohorts. In a multi‐ethnic population free of clinical cardiovascular disease, we evaluated the relationship between apoC‐III–defined HDL subspecies and subclinical markers of atherosclerotic pathology.

Methods and Results

We investigated cross‐sectional associations between apolipoprotein A‐I concentrations of apoC‐III–defined HDL subspecies, measured via ELISA and imaging measures of subclinical atherosclerosis, among 4659 participants in the MESA (The Multi‐Ethnic Study of Atherosclerosis) at baseline (2000–2002). HDL particles containing and lacking apoC‐III were divergently associated with coronary artery calcification in women (P‐heterogeneity=0.002) but not in men (P‐heterogeneity=0.31) and with carotid plaque score (P‐heterogeneity=0.02) and intima‐media thickness (P‐heterogeneity=0.06) in the overall study population. HDL lacking apoC‐III was inversely associated with all outcome measures (coronary artery calcification, women: odds ratio per SD=0.81 [95% confidence interval [CI], 0.73–0.90]; carotid plaque, overall: odds ratio per SD=0.92 [95% CI, 0.84–1.00]; intima‐media thickness, overall: mean difference per SD=−14.0 µm [95% CI, −21.1 to −6.7 μm]), whereas HDL containing apoC‐III was positively associated (coronary artery calcification, women: odds ratio=1.10 [95% CI, 0.99–1.22]; plaque, overall: odds ratio=1.10 [95% CI, 1.01–1.19]) or unassociated. Neither total HDL nor HDL subspecies was associated with changes in subclinical atherosclerosis measures up to 10 years later.

Conclusions

The presence of apoC‐III defined a subspecies of HDL not inversely associated with baseline measures of subclinical atherosclerosis, supporting a role of apoC‐III in the pathophysiology of cardiovascular disease.

New medications targeting triglyceride-rich lipoproteins: Can inhibition of ANGPTL3 or apoC-III reduce the residual cardiovascular risk?

Remarkably good results have been achieved in the treatment of atherosclerotic cardiovascular diseases (CVD) by using statin, ezetimibe, antihypertensive, antithrombotic, and PCSK9 inhibitor therapies and their proper combinations. However, despite this success, the remaining CVD risk is still high. To target this residual risk and to treat patients who are statin-intolerant or have an exceptionally high CVD risk for instance due to familial hypercholesterolemia (FH), new therapies are intensively sought. One pathway of drug development is targeting the circulating triglyceride-rich lipoproteins (TRL) and their lipolytic remnants, which, according to the current view, confer a major CVD risk. Angiopoietin-like protein 3 (ANGPTL3) and apolipoprotein C-III (apoC-III) are at present the central molecular targets for therapies designed to reduce TRL, and there are new drugs emerging that suppress their expression or inhibit the function of these two key proteins. The medications targeting these components are biological, either human monoclonal antibodies or antisense oligonucleotides. In this article, we briefly review the mechanisms of action of ANGPTL3 and apoC-III, the reasons why they have been considered promising targets of novel therapies for CVD, as well as the current status and the most important results of their clinical trials.

High density lipoprotein with apolipoprotein C-III is associated with carotid intima-media thickness among generally healthy individuals

BACKGROUND AND AIMS

About 6-7% of high density lipoprotein (HDL) has a protein called apolipoprotein (apo) C-III that regulates lipoprotein metabolism and can provoke an inflammatory response. HDL without apoC-III is inversely associated with coronary heart disease (CHD), whereas HDL with apoC-III is directly associated with CHD. We investigated how the presence of apoC-III affects the association between HDL and early stages of atherosclerosis measured as carotid intima-media thickness (cIMT).

METHODS

We examined the cross-sectional associations between the apoA-I concentrations of HDL subspecies with and without apoC-III and cIMT measured by high resolution B-mode carotid ultrasonography among 847 participants from the European multi-center Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study.

RESULTS

HDL with and without apoC-III demonstrated significantly opposite associations with both cIMT indexes (p-heterogeneity of associations comparing the two subspecies was 0.002 for cIMT at common carotid artery (cIMT at CCA) and 0.006 for the maximum cIMT in any carotid segment (cIMT max)). Compared to the lowest quintile, the highest quintile of apoA-I in HDL without apoC-III was associated with 3.7% lower cIMT at CCA (p-trend = 0.01) or 7.3% lower cIMT max (p-trend = 0.003), while the highest quintile of apoA-I in HDL with apoC-III was associated with 4.4% higher cIMT at CCA (p-trend = 0.001) or 7.9% higher cIMT max (p-trend = 0.002). Total apoA-I as well as total HDL cholesterol was not associated with cIMT whereas higher levels of total apoC-III and apoC-III contained in HDL were significantly associated with higher cIMT (p-trend<0.01).

CONCLUSIONS

HDL apoC-III is a promising target for atherosclerosis prevention and treatment.

A human APOC3 missense variant and monoclonal antibody accelerate apoC-III clearance and lower triglyceride-rich lipoprotein levels

Recent large-scale genetic sequencing efforts have identified rare coding variants in genes in the triglyceride-rich lipoprotein (TRL) clearance pathway that are protective against coronary heart disease (CHD), independently of LDL cholesterol (LDL-C) levels. Insight into the mechanisms of protection of these variants may facilitate the development of new therapies for lowering TRL levels. The gene APOC3 encodes apoC-III, a critical inhibitor of triglyceride (TG) lipolysis and remnant TRL clearance. Here we report a detailed interrogation of the mechanism of TRL lowering by the APOC3 Ala43Thr (A43T) variant, the only missense (rather than protein-truncating) variant in APOC3 reported to be TG lowering and protective against CHD. We found that both human APOC3 A43T heterozygotes and mice expressing human APOC3 A43T display markedly reduced circulating apoC-III levels. In mice, this reduction is due to impaired binding of A43T apoC-III to lipoproteins and accelerated renal catabolism of free apoC-III. Moreover, the reduced content of apoC-III in TRLs resulted in accelerated clearance of circulating TRLs. On the basis of this protective mechanism, we developed a monoclonal antibody targeting lipoprotein-bound human apoC-III that promotes circulating apoC-III clearance in mice expressing human APOC3 and enhances TRL catabolism in vivo. These data reveal the molecular mechanism by which a missense variant in APOC3 causes reduced circulating TG levels and, hence, protects from CHD. This protective mechanism has the potential to be exploited as a new therapeutic approach to reduce apoC-III levels and circulating TRL burden.

Why Is Apolipoprotein CIII Emerging as a Novel Therapeutic Target to Reduce the Burden of Cardiovascular Disease?

ApoC-III was discovered almost 50 years ago, but for many years, it did not attract much attention. However, as epidemiological and Mendelian randomization studies have associated apoC-III with low levels of triglycerides and decreased incidence of cardiovascular disease (CVD), it has emerged as a novel and potentially powerful therapeutic approach to managing dyslipidemia and CVD risk. The atherogenicity of apoC-III has been attributed to both direct lipoprotein lipase-mediated mechanisms and indirect mechanisms, such as promoting secretion of triglyceride-rich lipoproteins (TRLs), provoking proinflammatory responses in vascular cells and impairing LPL-independent hepatic clearance of TRL remnants. Encouraging results from clinical trials using antisense oligonucleotide, which selectively inhibits apoC-III, indicate that modulating apoC-III may be a potent therapeutic approach to managing dyslipidemia and cardiovascular disease risk.

Association of apolipoprotein-CIII (apoC-III), endothelium-dependent vasodilation and peripheral neuropathy in a multi-ethnic population with type 2 diabetes

BACKGROUND

Diabetic peripheral neuropathy (DPN) is a common complication of Type 2 diabetes (T2D). Apart from hyperglycemia, its pathogenesis is poorly understood. Apolipoprotein-CIII (apoC-III) associated with triglyceride metabolism, is a risk factor for cardiovascular disease. Its role in DPN is not well-established. We studied the associations of apoC-III, endothelial function and DPN.

METHODS

In patients with T2D, anthropometric data, fasting blood, and urine were collected for biochemistry and urine albumin/creatinine measurements (uACR). Endothelial function assessments were performed by laser Doppler flowmetry/imaging. DPN was considered present if there was an abnormal finding in monofilament (≤8 of 10 points) or neurothesiometer testing≥25V on either foot. Plasma apoC-III was assessed by ELISA.

RESULTS

Monofilament and neurothesiometer readings were measured in 1981 patients, mean age 57.4±10.8 years old. DPN prevalence was 10.8% (n=214). Patients with DPN compared to those without, were significantly older (p<0.0001), with longer duration of T2D (p<0.0001), had higher BMI (p=0.006), higher glucose (p=0.015) and HbA1c (p<0.0001), Systolic blood pressure (SBP) (p<0.0001), lower eGFR (p<0.0001), higher urine ACR (p<0.0001), poorer endothelium-dependent and endothelium-independent vasodilation (both p<0.0001), higher VCAM-1 (p<0.0001) and higher apoC-III [285.3 (195.2-405.6) vs 242.9(165.0-344.0) μg/ml]. After adjustment, log transformed apoC-III, remained independently associated with the presence of DPN (B=0.965, SE=0.397, p=0.015).

CONCLUSION

Plasma apoC-III is higher in patients with DPN. Apart from its known association with lipids and macrovascular complications, this study suggests its association with DPN. Whether regulating apoC-III metabolism may be an important new therapeutic approach to managing dyslipidemia and microvascular complications in T2D remains to be proven in future mechanistic and clinical studies.

Apolipoprotein C-III Levels and Incident Coronary Artery Disease Risk: The EPIC-Norfolk Prospective Population Study

OBJECTIVE

Apolipoprotein C-III (apoC-III) is a key regulator of triglyceride metabolism. Elevated triglyceride-rich lipoproteins and apoC-III levels are causally linked to coronary artery disease (CAD) risk. The mechanism(s) through which apoC-III increases CAD risk remains largely unknown. The aim was to confirm the association between apoC-III plasma levels and CAD risk and to explore which lipoprotein subfractions contribute to this relationship between apoC-III and CAD risk.

APPROACH AND RESULTS

Plasma apoC-III levels were measured in baseline samples from a nested case-control study in the European Prospective Investigation of Cancer (EPIC)-Norfolk study. The study comprised 2711 apparently healthy study participants, of whom 832 subsequently developed CAD. We studied the association of baseline apoC-III levels with incident CAD risk, lipoprotein subfractions measured by nuclear magnetic resonance spectroscopy and inflammatory biomarkers. ApoC-III levels were significantly associated with CAD risk (odds ratio, 1.91; 95% confidence interval, 1.48-2.48 for highest compared with lowest quintile), retaining significance after adjustment for traditional CAD risk factors (odds ratio, 1.47; 95% confidence interval, 1.11-1.94). ApoC-III levels were positively correlated with triglyceride levels, (r=0.39), particle numbers of very-low-density lipoprotein (r=0.25), intermediate-density lipoprotein (r=0.23), small dense low-density lipoprotein (r=0.26), and high-sensitivity C-reactive protein (r=0.15), whereas an inverse correlation was observed with large low-density lipoprotein particle number (r=-0.11), P<0.001 for each. Mediation analysis indicated that the association between apoC-III and CAD risk could be explained by triglyceride elevation (triglyceride, very-low-density lipoprotein, and intermediate-density lipoprotein particles), small low-density lipoprotein particle size, and high-sensitivity C-reactive protein.

CONCLUSIONS

ApoC-III levels are significantly associated with incident CAD risk. Elevated levels of remnant lipoproteins, small dense low-density lipoprotein, and low-grade inflammation may explain this association.

Relation of Fasting Triglyceride-Rich Lipoprotein Cholesterol to Coronary Artery Calcium Score (from the ELSA-Brasil Study)

Although low-density lipoprotein cholesterol (LDL-C) is widely accepted as the principal lipid fraction associated with atherosclerosis, emerging evidence suggests a causal relation between lifelong elevations in triglyceride-rich lipoprotein cholesterol (TRL-C) and cardiovascular disease (CVD) in genetic studies. To provide further evidence for the potential relevance of TRL-C and atherosclerosis, we have evaluated the relation between TRL-C and coronary artery calcium (CAC) score. We included 3,845 subjects (49.9 ± 8.4 years, 54% women) who had no history of CVD, were not using lipid-lowering medications, and underwent CAC evaluation. We assessed the relation between increasing fasting TRL-C and the graded increase in CAC and to what extent TRL-C were independently associated with CAC over and above LDL-C using logistic regression models. Overall, 973 (25%) of the participants had a CAC >0 and 308 (8%) had a CAC >100. The median TRL-C level was 22 mg/dL (IQR 16 to 32). Subjects with CAC >0 had higher TRL-C levels than those with CAC = 0 (p <0.001). Similarly, subjects with CAC >0 had higher levels of LDL-C, non-high-density lipoprotein cholesterol, and lower high-density lipoprotein cholesterol (all p <0.001). After multivariate adjustment, log-transformed TRL-C remained associated with the presence and severity of CAC (all p <0.05). When TRL-C was added to models that contained demographic factors and conventional lipids, it significantly improved the model to predict the presence of CAC >0 (p = 0.01). In conclusion, in a large cohort of asymptomatic subjects, TRL-C was associated with subclinical atherosclerosis supporting a potentially causal role in CVD.

Using primary murine intestinal enteroids to study dietary TAG absorption, lipoprotein synthesis, and the role of apoC-III in the intestine

Since its initial report in 2009, the intestinal enteroid culture system has been a powerful tool used to study stem cell biology and development in the gastrointestinal tract. However, a major question is whether enteroids retain intestinal function and physiology. There have been significant contributions describing ion transport physiology of human intestinal organoid cultures, as well as physiology of gastric organoids, but critical studies on dietary fat absorption and chylomicron synthesis in primary intestinal enteroids have not been undertaken. Here we report that primary murine enteroid cultures recapitulate in vivo intestinal lipoprotein synthesis and secretion, and reflect key aspects of the physiology of intact intestine in regard to dietary fat absorption. We also show that enteroids can be used to elucidate intestinal mechanisms behind CVD risk factors, including tissue-specific apolipoprotein functions. Using enteroids, we show that intestinal apoC-III overexpression results in the secretion of smaller, less dense chylomicron particles along with reduced triacylglycerol secretion from the intestine. This model significantly expands our ability to test how specific genes or genetic polymorphisms function in dietary fat absorption and the precise intestinal mechanisms that are critical in the etiology of metabolic disease.

Liraglutide improves metabolic parameters and carotid intima-media thickness in diabetic patients with the metabolic syndrome: an 18-month prospective study

Background

Liraglutide, a GLP-1 analogue, exerts several beneficial non-glycemic effects in patients with type-2 diabetes (T2DM), such as those on body weight, blood pressure, plasma lipids and inflammation markers. However, the effects of liraglutide on cardiovascular (CV) risk markers in subjects with the metabolic syndrome (MetS) are still largely unknown. We herein explored its effects on various cardio-metabolic risk markers of the MetS in subjects with T2DM.

Methods

We performed an 18-month prospective, real-world study. All subjects had T2DM and the MetS based on the AHA/NHLBI criteria. Subjects with a history of a major CV event were excluded. One hundred-twenty-one subjects (71 men and 50 women; mean age: 62 ± 9 years) with T2DM and the MetS, who were naïve to incretin-based therapies and treated with metformin only, were included. Liraglutide (1.2 mg/day) was added to metformin (1500–3000 mg/day) for the entire study. Fasting plasma samples for metabolic parameters were collected and carotid-intima media thickness (cIMT) was assessed by B-mode real-time ultrasound at baseline and every 6 months thereafter.

Results

There was a significant reduction in waist circumference, body mass index, fasting glycemia, HbA1c, total- and LDL-cholesterol, triglycerides, and cIMT during the 18-month follow-up. Correlation analysis showed a significant association between changes in cIMT and triglycerides (r = 0.362; p < 0.0001). The MetS prevalence significantly reduced during the study, and the 26% of subjects no longer fulfilled the criteria for the MetS after 18 months.

Conclusions

Liraglutide improves cardio-metabolic risk factors in subjects with the MetS in a real-world study.

Trial Registration ClinicalTrials.gov: NCT01715428.

The emerging role of apolipoprotein C-III: beyond effects on triglyceride metabolism

Apolipoprotein C-III has been referred to as an important participant in the metabolism of triglyceride-rich lipoproteins, leading to hypertriglyceridemia and thereafter cardiovascular disease. Accumulating evidence indicates that apolipoprotein C-III is a multifaceted protein which not only regulates triglyceride metabolism, but also participates in the atherosclerotic lesion formation and several other pathological processes involved in atherosclerosis. Based on data from experiments and clinical trials, some novel therapies such as antisense technology emerge.

An APOC3 3'UTR variant associated with plasma triglycerides levels and coronary heart disease by creating a functional miR-4271 binding site

Apolipoprotein C-III (APOC3) is a key regulator of plasma triglycerides levels. Increasing evidence has shown that loss-of-function mutations in APOC3 is associated with reduction in plasma triglycerides levels and will confer a benefit in patients at high risk for cardiovascular disease. However, these favorable mutations were extremely distribution discrepant among different ethnics. In this study, the APOC3 gene was resequenced and we identified a common variant which located in the microRNA-binding site in APOC3 and would affect its expression and the risk of coronary heart disease (CHD). The molecular mechanism was explored. We found that the T allele of rs4225 suppressed APOC3 translation by facilitating miR-4271 binding, but not the G allele. Subjects carrying the GG genotype had higher plasma APOC3 levels (p for trend = 0.03) than those with the TT genotype. Furthermore, the T allele was significantly associated with decreased triglyceride levels [Beta (SE): -0.024 (0.020), P = 0.03]. Finally, the case-control study suggested that the TT genotype resulted in a significant reduction in overall CHD risk [OR, 0.89 (95% confidence interval, 0.77-0.98), P = 0.009]. In conclusion, our results provide evidence that the rs4225 in the 3'-UTR of APOC3 might contribute to the risk of CHD by interfering with miR-4271 binding.