Apolipoprotein CIII-induced THP-1 cell adhesion to endothelial cells involves pertussis toxin-sensitive G protein- and protein kinase C alpha-mediated nuclear factor-kappaB activation

Mapping the gut microecological multi-omics signatures to serum metabolome and their impact on cardiometabolic health in elderly adults

BACKGROUND

Mapping gut microecological features to serum metabolites (SMs) will help identify functional links between gut microbiome and cardiometabolic health.

METHODS

This study encompassed 836-1021 adults over 9.7 year in a cohort, assessing metabolic syndrome (MS), carotid atherosclerotic plaque (CAP), and other metadata triennially. We analyzed mid-term microbial metagenomics, targeted fecal and serum metabolomics, host genetics, and serum proteomics.

FINDINGS

Gut microbiota and metabolites (GMM) accounted for 15.1% overall variance in 168 SMs, with individual GMM factors explaining 5.65%-10.1%, host genetics 3.23%, and sociodemographic factors 5.95%. Specifically, GMM elucidated 5.5%-49.6% variance in the top 32 GMM-explained SMs. Each 20% increase in the 32 metabolite score (derived from the 32 SMs) correlated with 73% (95% confidence interval [CI]: 53%-95%) and 19% (95% CI: 11%-27%) increases in MS and CAP incidences, respectively. Among the 32 GMM-explained SMs, sebacic acid, indoleacetic acid, and eicosapentaenoic acid were linked to MS or CAP incidence. Serum proteomics revealed certain proteins, particularly the apolipoprotein family, mediated the relationship between GMM-SMs and cardiometabolic risks.

INTERPRETATION

This study reveals the significant influence of GMM on SM profiles and illustrates the intricate connections between GMM-explained SMs, serum proteins, and the incidence of MS and CAP, providing insights into the roles of gut dysbiosis in cardiometabolic health via regulating blood metabolites.

FUNDING

This study was jointly supported by the National Natural Science Foundation of China, Key Research and Development Program of Guangzhou, 5010 Program for Clinical Research of Sun Yat-sen University, and the 'Pioneer' and 'Leading goose' R&D Program of Zhejiang.

Role of APOC3 3238C/G, APOB 12669G/A and SCARB1 1050C/T polymorphisms, their expression in patients of HIV-associated lipodystrophy

Apolipoproteins and Scavenger Receptor Class B1 (SCARB1) proteins are involved in the etiology of HIV-associated lipodystrophy (HIVLD). APOC3 3238C/G, APOB 12669G/A and SCARB1 1050C/T polymorphisms were linked with increased level of APOB, TG, HDL-C and risk of cardiovascular diseases (CVDs). Hence, we evaluated the genetic variations of APOC3 3238C/G, APOB 12669G/A and SCARB1 1050C/T in 187 patients of HIV (64 with HIVLD, 123 without HIVLD) and 139 healthy controls using PCR-RFLP and expression by qPCR. The genotypes of SCARB1 1050 TT and APOB 12669AA showed a risk to severe HIVLD (P = 0.23, OR = 4.95; P = 0.16, OR = 2.02). The APOC3 3238 GG genotype was associated with a lesser risk of severe HIVLD (P = 0.07, OR = 0.22). The APOB 12669 GA genotype was associated with a greater risk of HIVLD severity in patients with impaired LDL, triglyceride (TG), and cholesterol levels (P = 0.34, OR = 4.13; P = 0.25, OR = 3.64; P = 0.26, OR = 5.47). Similarly, APOB 12669AA genotypes in the presence of impaired triglyceride levels displayed the susceptibility to severity of HIVLD (P = 0.77, OR = 2.91). APOB 12669 GA genotype along with impaired HDL and cholesterol levels indicated an increased risk for HIVLD acquisition among patients without HIVLD (P = 0.42, OR = 2.42; P = 0.26, OR = 2.27). In patients with and without HIVLD, APOC3 3238CG genotypes having impaired cholesterol and glucose levels had higher risk for severity and development of HIVLD (P = 0.13, OR = 2.84, P = 0.34, OR = 1.58; P = 0.71, OR = 1.86; P = 0.14, OR = 2.30). An increased expression of APOB and SCARB1 genes were observed in patients with HIVLD (+0.51 vs. -0.93; +4.78 vs. +3.29), and decreased expression of APOC3 gene was observed in patients with HIVLD (-0.35 vs. -1.65). In conclusion, the polymorphisms mentioned above were not associated with the modulation of HIVLD. However, in the presence of impaired triglyceride, HDL, cholesterol and glucose levels, APOB 12669AA and 12669 GA, APOC3 3238CG genotypes indicated a risk for the development and severity of HIVLD.

Unraveling the Impact of Extracellular Vesicle-Depleted Serum on Endothelial Cell Characteristics over Time

Extracellular vesicles (EVs) are produced by all kinds of cells, including endothelial cells. It has been observed that EVs present in fetal bovine serum (FBS), broadly used in cell culture, can be a confounding factor and lead to misinterpretation of results. To investigate this phenomenon, human brain microvascular endothelial cells (HBMECs) were cultured for 2 or 24 h in the presence of EV-depleted FBS (EVdS). Cell death, gene and protein expression, and the presence of EVs isolated from these cells were evaluated. The uptake of EVs, intercellular adhesion molecule 1 (ICAM-1) expression, and monocyte adhesion to endothelial cells exposed to EVs were also evaluated. Our results revealed higher apoptosis rates in cells cultured with EVdS for 2 and 24 h. There was an increase in interleukin 8 (IL8) expression after 2 h and a decrease in interleukin 6 (IL6) and IL8 expression after 24 h of culture. Among the proteins identified in EVs isolated from cells cultured for 2 h (EV2h), several were related to ribosomes and carbon metabolism. EVs from cells cultured for 24 h (EV24h) presented a protein profile associated with cell adhesion and platelet activation. Additionally, HBMECs exhibited increased uptake of EV2h. Treatment of endothelial cells with EV2h resulted in greater ICAM-1 expression and greater adherence to monocytes than did treatment with EV24h. According to our data, HBMEC cultivated with EVdS produce EVs with different physical characteristics and protein levels that vary over time.

Lipidomics of triglyceride-rich lipoproteins derived from hyperlipidemic patients on inflammation

BACKGROUND AND AIM

Triglyceride-rich lipoproteins (TRLs) can have an important role in atherosclerosis development due to their size and ability to penetrate the endothelium. While high plasma triglyceride (TG) levels and chronic inflammation are relevant in metabolic diseases, it remains unclear whether TGs are atherogenic or which TRL-TG-derived metabolites are responsible for inflammation. Here, we aimed to study the lipidome modifications of TRL particles enriched in TG in patients with hyperlipidemia and their associations with a proinflammatory status both in vivo and in vitro.

METHODS

Using proton nuclear magnetic resonance (1 H-NMR), we analysed the plasma levels of glycoprotein acetyls and the TRL lipidomic profile of 307 patients with dyslipidemia. THP-1-derived macrophages were used as an in vitro model to explore the molecular inflammatory effects mediated by TRL.

RESULTS

In vivo, higher TRL-TG levels were associated with higher circulating levels of NMR-measured glycoproteins (Glyc-A, Glyc-B and Glyc-F; p < .001). Lipidomic analysis showed that TRL-TG enrichment led to decreased cholesterol and phospholipid content (p < .01), an increase in omega-9, and a decrease in saturated fatty acids (p < .001). THP-1 macrophages exposed to increasing TRL particle concentrations augmented the secretion of IL-1β and TNF-α, which varied based on particle composition. Particles with higher cholesterol and phospholipid contents exerted higher cytokine secretion. The activation of MAPK, Akt/NFκB, and caspase-1 was concurrent with this proinflammatory response.

CONCLUSIONS

High TRL-TG levels are associated with a higher systemic inflammatory status and increased particle concentrations. In vitro, higher particle numbers increase proinflammatory cytokine secretion, with cholesterol and phospholipid-rich TRL being more proinflammatory.

RNA interference-based therapies for atherosclerosis: Recent advances and future prospects

Atherosclerosis represents a pathological state that affects the arterial system of the organism. This chronic, progressive condition is typified by the accumulation of atheroma within arterial walls. Modulation of RNA molecules through RNA-based therapies has expanded the range of therapeutic options available for neurodegenerative diseases, infectious diseases, cancer, and, more recently, cardiovascular disease (CVD). Presently, microRNAs and small interfering RNAs (siRNAs) are the most widely employed therapeutic strategies for targeting RNA molecules, and for regulating gene expression and protein production. Nevertheless, for these agents to be developed into effective medications, various obstacles must be overcome, including inadequate binding affinity, instability, challenges of delivering to the tissues, immunogenicity, and off-target toxicity. In this comprehensive review, we discuss in detail the current state of RNA interference (RNAi)-based therapies.

Phosphatidylcholine-Specific Phospholipase C as a Promising Drug Target

Phosphatidylcholine-specific phospholipase C (PC-PLC) is an enzyme that catalyzes the formation of the important secondary messengers phosphocholine and diacylglycerol (DAG) from phosphatidylcholine. Although PC-PLC has been linked to the progression of many pathological conditions, including cancer, atherosclerosis, inflammation and neuronal cell death, studies of PC-PLC on the protein level have been somewhat neglected with relatively scarce data. To date, the human gene expressing PC-PLC has not yet been found, and the only protein structure of PC-PLC that has been solved was from Bacillus cereus (PC-PLCBc). Nonetheless, there is evidence for PC-PLC activity as a human functional equivalent of its prokaryotic counterpart. Additionally, inhibitors of PC-PLCBc have been developed as potential therapeutic agents. The most notable classes include 2-aminohydroxamic acids, xanthates, N,N'-hydroxyureas, phospholipid analogues, 1,4-oxazepines, pyrido[3,4-b]indoles, morpholinobenzoic acids and univalent ions. However, many medicinal chemistry studies lack evidence for their cellular and in vivo effects, which hampers the progression of the inhibitors towards the clinic. This review outlines the pathological implications of PC-PLC and highlights current progress and future challenges in the development of PC-PLC inhibitors from the literature.

Role of APOC3 3238C/G polymorphism in HIV-associated neurocognitive disorder

Apolipoprotein not only have a role in cholesterol metabolism but also play a role in normal brain function. Apolipoprotein gene polymorphisms are known risk factors for a number of mental and neurological disorders. The expression of brain apolipoproteins is significantly altered in several brain disorders. Therefore, we assed ApoC33238C/G polymorphism in a total of 248 patient infected with HIV (45 with HAND, 89 without HAND, 114 without ART) and 134 healthy controls using PCR-RFLP. ApoC3 3238CG, 3238GG genotypes and 3238G allele showed a non-significant increased risk for severity of HAND (P = 0.16, OR = 1.83; P = 0.32, OR = 2.78; P = 0.10, OR = 1.65) while comparing individuals with and without HAND. ApoC3 3238GG genotype and 3238G allele revealed an increased risk for disease progression when compared between HIV patients with and without ART (P = 0.55, OR = 1.76; P = 0.65, OR = 1.12) though risk could not reach statistical significance. ApoC3 3238GG genotype and 3238G allele were associated with the reduced risk of acquiring HIV infection when comparing HIV patients who are not on ART with healthy controls (P = 0.05, OR = 0.29; P = 0.04, OR = 0.66). In HIV patients on ART,ApoC3 3238GG genotype showed an increased susceptibility to development of HAND (P = 0.48, OR = 2.24) when comparing alcohol drinkers and non-drinkers however risk could not reach statistical significance. In conclusion, the genotype ApoC33238GG displayed an inclination of risk for the severity of HAND and HIV disease progression. The polymorphism of APOC3 3238C/G may have a role to reduce the risk for acquisition of HIV infection. ApoC33238GG genotype in presence of alcohol may increase susceptibility to development of HAND.

New Therapeutic Approaches to the Treatment of Dyslipidemia 1: ApoC-III and ANGPTL3

Low-density lipoprotein cholesterol (LDL-C)-lowering therapy that increases LDL receptor expression in several ways robustly reduces the risk of atherosclerotic cardiovascular disease (CVD). However, a substantial risk of CVD still remains after intensive LDL-C reduction, which requires new treatment modalities for dyslipidemia and cardiovascular risk management. Triglycerides (TGs) and triglyceride-rich lipoproteins (TRLs) have received attention as indicators of residual cardiovascular risk and as direct causal factors for atherosclerosis and CVDs. Advances in understanding TG and TRL metabolism and their association with clinically evident CVDs have led to the development of novel therapeutic targets, including apolipoprotein C-III (apoC-III) and angiopoietin-like protein 3 (ANGPTL3). Genetic association studies have indicated that both apoC-III and ANGPTL3 play a causal role in the development of atherosclerotic CVD. Both molecules contribute to lipid dysregulation and atherosclerosis primarily by inhibiting lipoprotein lipase; however, recent evidence has shown that novel pathways exist in relation to their lipid-modifying activities. Notably, recent progress in therapeutic approaches, such as monoclonal antibodies or antisense oligonucleotides, has led to several novel therapeutics targeting apoC-III and ANGPTL3. This review summarized the recent updates and discussions related to apoC-III and ANGPTL3 expression.

Apolipoprotein C3 and necrotic core volume are correlated but also associated with future cardiovascular events

We aimed to clarify the relationship between apolipoprotein C3 (apo-C3) and the vascular composition of lesion plaque in stable coronary disease (SCD) before percutaneous coronary intervention (PCI), and to investigate major adverse cardiovascular events (MACEs) within 4 years. Data of 98 consecutive patients with SCD who underwent PCI between November 1, 2012, and March 10, 2015, were analyzed. Laboratory and virtual histology-intravascular ultrasound (VH-IVUS) examinations of culprit lesions were conducted before PCI. Patients were divided according to median apo-C3 into low apo-C3 (≤ 8.5 mg/dL) and high apo-C3 (> 8.5 mg/dL) groups. VH-IVUS data indicated that the percentage of necrotic core volume (%NC) was significantly higher in the high apo-C3 group than in the low apo-C3 group. Moreover, the %NC significantly correlated with the apo-C3 level (R = 0.2109, P = 0.037). Kaplan–Meier curve analysis revealed that freedom from MACEs exhibited a greater decrease in the high apo-C3 group than in the low apo-C3 group, and in the high %NC group than in the low %NC group. Multivariate Cox hazards analysis showed that the %NC and high apo-C3 were independent predictors of 4 year MACEs. Apo-C3 may be a useful marker of future MACEs in patients with SCD after PCI and contribute to %NC growth.

Hypertriglyceridemia, a causal risk factor for atherosclerosis, and its laboratory assessment

Epidemiological and clinical studies show a causal association between serum triglyceride (TG) level, the number of triglyceride-rich lipoproteins (TRLs) and their remnants, and the increased risk of atherosclerosis and cardiovascular disease (CVD) development. In light of current guidelines for dyslipidemia management, the laboratory parameters reflecting TRL content are recommended as part of the routine lipid analysis process and used for CVD risk assessment, especially in people with hypertriglyceridemia (HTG), diabetes mellitus, obesity and low levels of low-density lipoprotein cholesterol (LDL-C), in which high residual CVD risk is observed. The basic routinely available laboratory parameters related with TRL are serum TG and non-high-density lipoprotein cholesterol (non-HDL-C) levels, but there are also other biomarkers related to TRL metabolism, the determination of which can be helpful in identifying the basis of HTG development or assessing CVD risk or can be the target of pharmacological intervention. In this review, we present the currently available laboratory parameters related to HTG. We summarise their link with TRL metabolism and HTG development, the determination methods as well as their clinical significance, the target values and interpretation of the results in relation to the current dyslipidemia guidelines.

Apolipoproteins in vascular biology and atherosclerotic disease

Apolipoproteins are important structural components of plasma lipoproteins that influence vascular biology and atherosclerotic disease pathophysiology by regulating lipoprotein metabolism. Clinically important apolipoproteins related to lipid metabolism and atherogenesis include apolipoprotein B-100, apolipoprotein B-48, apolipoprotein A-I, apolipoprotein C-II, apolipoprotein C-III, apolipoprotein E and apolipoprotein(a). Apolipoprotein B-100 is the major structural component of VLDL, IDL, LDL and lipoprotein(a). Apolipoprotein B-48 is a truncated isoform of apolipoprotein B-100 that forms the backbone of chylomicrons. Apolipoprotein A-I provides the scaffolding for lipidation of HDL and has an important role in reverse cholesterol transport. Apolipoproteins C-II, apolipoprotein C-III and apolipoprotein E are involved in triglyceride-rich lipoprotein metabolism. Apolipoprotein(a) covalently binds to apolipoprotein B-100 to form lipoprotein(a). In this Review, we discuss the mechanisms by which these apolipoproteins regulate lipoprotein metabolism and thereby influence vascular biology and atherosclerotic disease. Advances in the understanding of apolipoprotein biology and their translation into therapeutic agents to reduce the risk of cardiovascular disease are also highlighted.

Novel RNAi-Based Therapies for Atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis, defined by inflammation and accumulation of cholesterol, extracellular matrix, and cell debris into the arteries is a common factor behind cardiovascular diseases (CVD), such as coronary artery disease, peripheral artery disease, and stroke. In this review, we discuss and describe novel RNA interference (RNAi)-based therapies in clinical trials and on the market.

RECENT FINDINGS

The first RNAi-based therapies have entered clinical use for the control of atherosclerosis risk factors, i.e., blood cholesterol levels. The most advanced treatment is silencing of proprotein convertase subtilisin/kexin type 9 (PCSK9) with a drug called inclisiran, which has been approved for the treatment of hypercholesterolemia in late 2020, and results in a robust decrease in plasma cholesterol levels. As the new RNAi therapies for atherosclerosis are now entering markets, the usefulness of these therapies will be further evaluated in larger patient cohorts. Thus, it remains to be seen how fast, effectively and eminently these new drugs consolidate their niche within the cardiovascular disease drug palette.

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.

Non-alcoholic fatty liver disease: a metabolic burden promoting atherosclerosis

Non-alcoholic fatty liver disease (NAFLD) has become the fastest growing chronic liver disease, with a prevalence of up to 25% worldwide. Individuals with NAFLD have a high risk of disease progression to cirrhosis, hepatocellular carcinoma (HCC), and liver failure. With the exception of intrahepatic burden, cardiovascular disease (CVD) and especially atherosclerosis (AS) are common complications of NAFLD. Furthermore, CVD is a major cause of death in NAFLD patients. Additionally, AS is a metabolic disorder highly associated with NAFLD, and individual NAFLD pathologies can greatly increase the risk of AS. It is increasingly clear that AS-associated endothelial cell damage, inflammatory cell activation, and smooth muscle cell proliferation are extensively impacted by NAFLD-induced systematic dyslipidemia, inflammation, oxidative stress, the production of hepatokines, and coagulations. In clinical trials, drug candidates for NAFLD management have displayed promising effects for the treatment of AS. In this review, we summarize the key molecular events and cellular factors contributing to the metabolic burden induced by NAFLD on AS, and discuss therapeutic strategies for the improvement of AS in individuals with NAFLD.

Apolipoprotein CIII Is an Important Piece in the Type-1 Diabetes Jigsaw Puzzle

It is well known that type-2 diabetes mellitus (T2D) is increasing worldwide, but also the autoimmune form, type-1 diabetes (T1D), is affecting more people. The latest estimation from the International Diabetes Federation (IDF) is that 1.1 million children and adolescents below 20 years of age have T1D. At present, we have no primary, secondary or tertiary prevention or treatment available, although many efforts testing different strategies have been made. This review is based on the findings that apolipoprotein CIII (apoCIII) is increased in T1D and that in vitro studies revealed that healthy β-cells exposed to apoCIII became apoptotic, together with the observation that humans with higher levels of the apolipoprotein, due to mutations in the gene, are more susceptible to developing T1D. We have summarized what is known about apoCIII in relation to inflammation and autoimmunity in in vitro and in vivo studies of T1D. The aim is to highlight the need for exploring this field as we still are only seeing the top of the iceberg.

Apolipoprotein C-III and cardiovascular diseases: when genetics meet molecular pathologies

Cardiovascular diseases (CVD) have overtaken infectious diseases and are currently the world's top killer. A quite strong linkage between this type of ailments and elevated plasma levels of triglycerides (TG) has been always noticed. Notably, this risk factor is mired in deep confusion, since its role in atherosclerosis is uncertain. One of the explanations that aim to decipher this persistent enigma was provided by apolipoprotein C-III (apoC-III), a small protein historically recognized as an important regulator of TG metabolism. Preeminently, hundreds of studies have been carried out in order to explore the APOC3 genetic background, as well as to establish a correlation between its variants and dyslipidemia-related disorders, pointing to an earnest predictive power for future outcomes. Among several polymorphisms reported within the APOC3, the SstI site in its 3'-untranslated region (3'-UTR) was the most consistently and robustly associated with an increased CVD risk. As more genetic data supporting its importance in cardiovascular events aggregate, it was declared, correspondingly, that apoC-III exerts various atherogenic effects, either by intervening in the function and catabolism of many lipoproteins, or by inducing endothelial inflammation and smooth muscle cells (SMC) proliferation. This review was designed to shed the light on the structural and functional aspects of the APOC3 gene, the existing association between its SstI polymorphism and CVD, and the specific molecular mechanisms that underlie apoC-III pathological implications. In addition, the translation of all these gathered knowledges into preventive and therapeutic benefits will be detailed too.

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.

Current Understanding of the Relationship of HDL Composition, Structure and Function to Their Cardioprotective Properties in Chronic Kidney Disease

In the general population, the ability of high-density lipoproteins (HDLs) to promote cholesterol efflux is a predictor of cardiovascular events, independently of HDL cholesterol levels. Although patients with chronic kidney disease (CKD) have a high burden of cardiovascular morbidity and mortality, neither serum levels of HDL cholesterol, nor cholesterol efflux capacity associate with cardiovascular events. Important for the following discussion on the role of HDL in CKD is the notion that traditional atherosclerotic cardiovascular risk factors only partially account for this increased incidence of cardiovascular disease in CKD. As a potential explanation, across the spectrum of cardiovascular disease, the relative contribution of atherosclerotic cardiovascular disease becomes less important with advanced CKD. Impaired renal function directly affects the metabolism, composition and functionality of HDL particles. HDLs themselves are a heterogeneous population of particles with distinct sizes and protein composition, all of them affecting the functionality of HDL. Therefore, a more specific approach investigating the functional and compositional features of HDL subclasses might be a valuable strategy to decipher the potential link between HDL, cardiovascular disease and CKD. This review summarizes the current understanding of the relationship of HDL composition, metabolism and function to their cardio-protective properties in CKD, with a focus on CKD-induced changes in the HDL proteome and reverse cholesterol transport capacity. We also will highlight the gaps in the current knowledge regarding important aspects of HDL biology.

Serum Glycoproteomic Alterations in Patients with Diabetic Retinopathy

The precise molecular mechanisms of diabetic retinopathy (DR) pathogenesis are unclear, and treatment options are limited. There is an urgent need to discover and develop novel therapeutic targets for the treatment of this disease. Glycosylation is a post-translational modification that plays a critical role in determining protein structure, function, and stability. Recent studies have found that serum glycoproteomic changes are associated with the presence or progression of several inflammatory diseases. However, very little is known about the glycoproteomic changes associated with DR. In this study, glycoproteomic profiling of the serum of diabetic patients with and without DR was performed. A total of 15 glycopeptides from 11 glycoproteins were found to be significantly altered (5 upregulated and 10 downregulated) within the serum glycoproteome of DR patients. These glycoproteins are known to be involved in the maintenance of the extracellular matrix and complement system through peptidolytic activity or regulation.

Urinary Apolipoprotein C3 Is a Potential Biomarker for Alzheimer's Disease

INTRODUCTION

Biomarkers of Alzheimer's disease (AD) that can easily be measured in routine health checkups are desirable. Urine is a source of biomarkers that can be collected easily and noninvasively. We previously reported on the comprehensive profile of the urinary proteome of AD patients and identified proteins estimated to be significantly increased or decreased in AD patients by a label-free quantification method. The present study aimed to validate urinary levels of proteins that significantly differed between AD and control samples from our proteomics study (i.e., apolipoprotein C3 [ApoC3], insulin-like growth factor-binding protein 3 [Igfbp3], and apolipoprotein D [ApoD]).

METHODS

Enzyme-linked immunosorbent assays (ELISAs) were performed using urine samples from the same patient and control groups analyzed in the previous proteomics study (18 AD and 18 controls, set 1) and urine samples from an independent group of AD patients and controls (13 AD, 5 mild cognitive impairment [MCI], and 32 controls) from the National Center for Geriatrics and Gerontology Biobank (set 2).

RESULTS

In set 1, the crude urinary levels of ApoD, Igfbp3, and creatinine-adjusted ApoD were significantly higher in the AD group relative to the control group (p = 0.003, p = 0.002, and p = 0.019, respectively), consistent with our previous proteomics results. In set 2, however, the crude urinary levels of Igfbp3 were significantly lower in the AD+MCI group than in the control group (p = 0.028), and the levels of ApoD and ApoC3 did not differ significantly compared to the control group. Combined analysis of all samples revealed creatinine-adjusted ApoC3 levels to be significantly higher in the AD+MCI group (p = 0.015) and the AD-only group (p = 0.011) relative to the control group.

CONCLUSION

ApoC3 may be a potential biomarker for AD, as validated by ELISA. Further analysis of ApoC3 as a urinary biomarker for AD is warranted.

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).

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).

Electronegative LDL: An Active Player in Atherogenesis or a By- Product of Atherosclerosis?

Low-density lipoproteins (LDLs) are the major plasma carriers of cholesterol. However, LDL particles must undergo various molecular modifications to promote the development of atherosclerotic lesions. Modified LDL can be generated by different mechanisms, but as a common trait, show an increased electronegative charge of the LDL particle. A subfraction of LDL with increased electronegative charge (LDL(-)), which can be isolated from blood, exhibits several pro-atherogenic characteristics. LDL(-) is heterogeneous, due to its multiple origins but is strongly related to the development of atherosclerosis. Nevertheless, the implication of LDL(-) in a broad array of pathologic conditions is complex and in some cases anti-atherogenic LDL(-) properties have been reported. In fact, several molecular modifications generating LDL(-) have been widely studied, but it remains unknown as to whether these different mechanisms are specific or common to different pathological disorders. In this review, we attempt to address these issues examining the most recent findings on the biology of LDL(-) and discussing the relationship between this LDL subfraction and the development of different diseases with increased cardiovascular risk. Finally, the review highlights the importance of minor apolipoproteins associated with LDL(-) which would play a crucial role in the different properties displayed by these modified LDL particles.

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.

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.

Association between Genetic Variant of Apolipoprotein C3 and Incident Hypertension Stratified by Obesity and Physical Activity in Korea

Apolipoprotein C3 (APOC3) is an important regulator of lipoprotein metabolism, and has been shown to be strongly associated with hypertriglyceridemia. We tested whether triglyceride-influencing genetic variants at APOC3 (T-455C, C-482T, C1100T, and SstI) are associated with the onset of hypertension (HTN) among Korean adults stratified by lifestyle-related factors in the Ansung–Ansan cohort within the Korean Genome and Epidemiology Study. After excluding participants with preexisting cancer, cardiovascular diseases, diabetes, and HTN, a total of 5239 men and women were included at baseline (2001–2002), and followed up for a median of 9.8 years. Carriers of the C allele of C1100T with body mass index <25 kg/m² showed a significantly lower HTN risk (hazard ratio (HR) than non-carriers: 0.87, 95% confidence interval (CI): 0.77–0.98) after adjusting for covariates. In addition, carriers of the C allele of T-455C and the T allele of C-482T with low physical activity had lower incident HTN than non-carriers (HR: 1.14, 95% CI: 1.03–1.26; HR: 1.13, 95% CI: 1.02–1.25). Our results suggest that genotype effects in APOC3 on HTN risk have been shown in lean carriers of the C allele of C1100T and in less active people having the C allele of T-455C and T allele of C-482T in a large sample of the Korean population.

Association of plasma apolipoprotein CIII, high sensitivity C-reactive protein and tumor necrosis factor-α contributes to the clinical features of coronary heart disease in Li and Han ethnic groups in China

Background

Apolipoprotein CIII (apoCIII) is an independent risk for coronary heart disease (CHD). In this study, we investigated the associations among plasma apoCIII, hs-CRP and TNF-α levels and their roles in the clinical features of CHD in the Li and Han ethnic groups in China.

Methods

A cohort of 474 participants was recruited (238 atherosclerotic patients and 236 healthy controls) from the Li and Han ethnic groups. Blood samples were obtained to evaluate apoCIII, TNF-α, hs-CRP and lipid profiles. Chi-squared, t-tests, and Kruskal–Wallis or Wilcoxon–Mann–Whitney tests, Pearson or Spearman correlation tests and multiple unconditional logistic regression were employed to analyze lipid profiles and variations in plasma apoCIII, TNF-α, hs-CRP in subgroups of CHD and their contributions to CHD using SPSS version 20.0 software.

Results

Compared to healthy participants, unfavorable lipid profiles were identified in CHD patients with enhanced systolic pressure, diastolic pressure, fasting blood sugar (FBS), TG, TC, LDL-C, apoB, Lp(a) (P < 0.05, TC and Lp(a); P < 0.01, FBS, TG, LDL-C, apoB); and lower HDL-C and apoAI (P < 0.05). Plasma apoCIII, TNF-α and hs-CRP levels were higher in CHD individuals (16.77 ± 5.98 mg/dL vs. 10.91 ± 4.97 mg/dL; 17.23 ± 6.34 pg/mL vs. 9.49 ± 3.88 pg/mL; 9.55 ± 7.32 mg/L vs. 2.14 ± 1.56 mg/L; P < 0.01 vs. healthy participants). Identical patterns were obtained in the Li and Han groups (16.46 ± 6.08 mg/dL vs. 11.72 ± 5.16 mg/dL; 15.71 ± 5.52 pg/mL vs. 9.74 ± 4.31 pg/mL; 8.21 ± 7.09 mg/L vs. 2.15 ± 1.51 mg/L in Li people; 17.05 ± 5.90 mg/dL vs. 10.07 ± 4.63 mg/dL; 18.59 ± 6.73 pg/mL vs. 9.23 ± 3.38 pg/mL; 10.75 ± 7.44 mg/L vs. 2.12 ± 1.63 mg/L in Han people; P < 0.01). Paired comparisons of subgroups with stable angina, unstable angina, and acute myocardial infarction (AMI) revealed significant variation in plasma levels of apoCIII, TNF-α and hs-CRP (P < 0.01), but not among subgroups with mild, moderate and severe stenosis (P > 0.05). Plasma apoCIII, TNF-α and hs-CRP contributed to the development of CHD (OR = 2.554, 7.252, 6.035, P < 0.01) with paired correlations in CHD patients (apoCIII vs. TNF-α, r = 0.425; apoCIII vs. hs-CRP, r = 0.319; TNF-α vs. hs-CRP, r = 0.400, P < 0.01).

Conclusions

Association among plasma apoCIII, hs-CRP and TNF-α interacts with unfavorable lipid profiles to contribute to the clinical features of CHD with stable angina, unstable angina, and AMI in the Li and Han ethnic groups in China.

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.

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.

RNA-seq analysis provide new insights into mapk signaling of apolipoproteinciii-induced inflammation in porcine vascular endothelial cells

Apolipoprotein CIII (ApoCIII) has been shown to be associated with the inflammatory response, but the mechanism of its inflammatory effects remains unclear. Because vascular endothelial cells (VECs) play a key role in the development of inflammation, the present study was performed to investigate inflammatory mechanisms induced by ApoCIII in VECs. In this study, we screened differentially expressed genes (DEGs) using RNA-sequencing. The results identified 390 up-regulated genes and 257 down-regulated genes. We performed GO functional classification and KEGG pathway analysis for DEGs. Analysis of sequencing data showed that 21 genes were related to the MAPK pathway. Finally, we investigated whether ApoCIII regulates the expression of pro-inflammatory cytokines via MAPK signaling pathway. The results showed that ApoCIII increased the expression levels of IL-6, TNF-α, VCAM-1 and ICAM-1 in VECs. ApoCIII activated the phosphorylation of ERK1/2 and p38 MAPK. An inhibitor of ERK1/2 and p38 MAPK decreased the protein levels of IL-6 and TNF-α. Our findings demonstrate that ApoCIII induces pro-inflammatory cytokine production in VECs via activation of ERK1/2 and p38 MAPK phosphorylation.

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.

ApoCIII enrichment in HDL impairs HDL-mediated cholesterol efflux capacity

Apolipoprotein CIII (apoCIII) has been reported to be tightly associated with triglyceride metabolism and the susceptibility to coronary artery disease (CAD). Besides, apoCIII has also been found to affect the anti-apoptotic effects of HDL. However, the effect of apoCIII on HDL-mediated cholesterol efflux, the crucial function of HDL, has not been reported. A hospital-based case-control study was conducted to compare the apoCIII distribution in lipoproteins between CAD patients and nonCAD controls and to explore the relationship between HDL-associated apoCIII (apoCIII_HDL) and HDL-mediated cholesterol efflux. One hundred forty CAD patients and nighty nine nonCAD controls were included. Plasma apoCIII, apoCIII_HDL and cholesterol efflux capacity was measured. The apoCIII_HDL ratio (apoCIII_HDL over plasma apoCIII) was significantly higher in CAD patients than that in control group (0.52 ± 0.24 vs. 0.43 ± 0.22, P = 0.004). Both apoCIII_HDL and apoCIII_HDL ratio were inversely correlated with cholesterol efflux capacity (r = −0.241, P = 0.0002; r = −0.318, P < 0.0001, respectively). Stepwise multiple regression analysis revealed that the apoCIII_HDL ratio was an independent contributor to HDL-mediated cholesterol efflux capacity (standardized β = −0.325, P < 0.001). This study indicates that the presence of apoCIII in HDL may affect HDL-mediated cholesterol efflux capacity, implying the alternative role of apoCIII in the atherogenesis.

Trimethylamine N-oxide in atherogenesis: impairing endothelial self-repair capacity and enhancing monocyte adhesion

Several studies have reported a strong association between high plasma level of trimethylamine N-oxide (TMAO) and atherosclerosis development. However, the exact mechanism underlying this correlation is unknown. In the present study, we try to explore the impact of TMAO on endothelial dysfunction. After TMAO treatment, human umbilical vein endothelial cells (HUVECs) showed significant impairment in cellular proliferation and HUVECs-extracellular matrix (ECM) adhesion compared with control. Likewise, TMAO markedly suppressed HUVECs migration in transwell migration assay and wound healing assay. In addition, we found TMAO up-regulated vascular cell adhesion molecule-1 (VCAM-1) expression, promoted monocyte adherence, activated protein kinase C (PKC) and p-NF-κB. Interestingly, TMAO-stimulated VCAM-1 expression and monocyte adherence were diminished by PKC inhibitor. These results demonstrate that TMAO promotes early pathological process of atherosclerosis by accelerating endothelial dysfunction, including decreasing endothelial self-repair and increasing monocyte adhesion. Furthermore, TMAO-induced monocyte adhesion is partly attributable to activation of PKC/NF-κB/VCAM-1.

Apolipoprotein CIII is a new player in diabetes

PURPOSE OF REVIEW

Type-1 and type-2 diabetes are diseases with an increasing number of patients and a complex, multifactorial pathogenesis. Apolipoprotein (apo) CIII is increased in both types of diabetes and interventions preventing the increase have effects on the development of diabetes.

RECENT FINDINGS

ApoCIII affects intracellular Ca-handling by activating voltage-gated Ca-channels. ApoCIII is produced within the pancreatic islets and it increases in parallel with the development of insulin resistance and type-2 diabetes. Preventing the increase maintains a normal glucose tolerance as well as Ca-handling and no signs of inflammation can be seen in islets wherein the augmented local production of the apolipoprotein is absent.

SUMMARY

ApoCIII has been found to interfere with both function and survival of the β-cell and thereby promote the development of diabetes. Increased levels of this apolipoprotein affects intracellular Ca-handling and insulin sensitivity, which finally results in impaired glucose homeostasis and diabetes. Interestingly, in a type-1 diabetes rat model lowering of apoCIII delays onset of diabetes. In type-2 diabetes insulin resistance within the pancreatic islets leads to a local increase in apoCIII that promotes inflammation and β-cell dysfunction. Hence, targeting apoCIII may constitute a novel pharmacological strategy to treat both type-1 and type-2 diabetes.

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.

APOC3 induces endothelial dysfunction through TNF-α and JAM-1

Background

The fatality rate for cardiovascular disease (CVD) has increased in recent years and higher levels of triglyceride have been shown to be an independent risk factor for atherosclerotic CVD. Dysfunction of endothelial cells (ECs) is also a key factor of CVD. APOC3 is an important molecule in lipid metabolism that is closely associated with hyperlipidemia and an increased risk of developing CVD. But the direct effects of APOC3 on ECs were still unknown. This study was aimed at determining the effects of APOC3 on inflammation, chemotaxis and exudation in ECs.

Methods

ELISA, qRT-PCR, immunofluorescence, flow cytometry and transwell assays were used to investigate the effects of APOC3 on human umbilical vein endothelial cells (HUVECs). SiRNA-induced TNF-α and JAM-1 silencing were used to observe how APOC3 influenced the inflammatory process in the ECs.

Results

Our results showed that APOC3 was closely associated with the inflammatory process in ECs, and that this process was characterized by the increased expression of TNF-α. Inflammatory processes further disrupted the tight junctions (TJs) between HUVECs by causing increased expression of JAM-1. JAM-1 was involved in maintaining the integrity of TJs, and it promoted the assembly of platelets and the exudation of leukocytes. Changes in its expression promoted chemotaxis and the exudation of ECs, which contributed to atherosclerosis. While the integrity of the TJs was disrupted, the adhesion of THP-1 cells to HUVECs was also increased by APOC3.

Conclusions

In this study, we describe the mechanism by which APOC3 causes inflammation, chemotaxis and the exudation of ECs, and we suggest that controlling the inflammatory reactions that are caused by APOC3 may be a new method to treat CVD.

The HCMV US28 vGPCR induces potent Gαq/PLC-β signaling in monocytes leading to increased adhesion to endothelial cells

US28 transcripts have been detected in primary monocytes and in THP-1 monocytes infected with HCMV but US28 protein expression has not yet been demonstrated in these cell types. Moreover, the mechanism(s) by which US28 signals and contributes to viral pathogenesis in monocytes remains unclear. Here, we show that US28 protein is robustly expressed in HCMV infected THP-1 monocytes and that US28 can trigger Gαq dependent signaling in THP-1 cells infected with HCMV and in THP-1 cells stably expressing US28. US28 signaling in these cells is dependent on G-protein coupling, but independent of chemokine binding. Importantly, we demonstrate that this US28 signaling is functionally important as it stimulates the adhesion of monocytes to an endothelial monolayer. Our studies, which demonstrate that US28-driven Gαq signaling has profound effects on monocyte biology, suggest that US28 driven phenotypic changes in HCMV infected monocytes may play important roles in HCMV dissemination and/or pathogenesis.

Apoprotein C-III: A review of its clinical implications

Apoprotein C-III (apoC-III), originating from the apoA-I/C-III/A-IV gene cluster affected by multiple regulating factors, has been demonstrated to have a validated link with hypertriglyceridemia in humans. Following genome studies establishing the impact of apoC-III on both plasma triglyceride (TG) level and cardiovascular disease (CVD), apoC-III offers us a novel explanation attempting to resolve the long-existing confusion with regard to the atherogenic effect of TG. Notably, apoC-III exerts its atherogenic effect by means of not only intervening in the function and metabolism of various lipid molecules, but also accelerating pro-inflammatory effects between monocytes and endothelial cells. Data have suggested that diabetes, a common endocrine disease, also correlates closely with apoC-III in its apoptosis process of islet βcells. In fact, apoC-III genes, with various mutations among individuals, are also found to have relevance to other diseases, including fatty liver disease. Fortunately, besides present day therapeutic strategies, such as lifestyle changes and lipid-lowering drug treatments, a promising new antisense drug specifically targeting on apoC-III gene expression opens up new avenues. This article mainly summarizes the clinical implication of apoC-III and its future directions of treatment.

Aggravated restenosis and atherogenesis in ApoCIII transgenic mice but lack of protection in ApoCIII knockouts: the effect of authentic triglyceride-rich lipoproteins with and without ApoCIII

AIM

Previously, our group and others have demonstrated a causative relationship between severe hypertriglyceridaemia and atherogenesis in mice. Furthermore, clinical investigations have shown high levels of plasma Apolipoprotein C-III (ApoCIII) associated with hypertriglyceridaemia and even cardiovascular disease. However, it remains unclear whether ApoCIII affects restenosis in vivo, and whether such an effect is mediated by ApoCIII alone, or in combination with hypertriglyceridaemia. We sought to investigate ApoCIII in restenosis and clarify how smooth muscle cells (SMCs) respond to authentic triglyceride-rich lipoproteins (TRLs) with or without ApoCIII (TRLs ± ApoCIII).

METHODS AND RESULTS

ApoCIII transgenic (ApoCIIItg) and knockout (ApoCIII-/-) mice underwent endothelial denudation to model restenosis. Here, ApoCIIItg mice displayed severe hypertriglyceridaemia and increased neointimal formation compared with wild-type (WT) or ApoCIII-/- mice. Furthermore, increased proliferating cell nuclear antigen (PCNA)-positive cells, Mac-3, and vascular cell adhesion protein-1 (VCAM-1) expression, and 4-hydroxynonenal (4HNE) production were found in lesion sites. ApoCIIItg and ApoCIII-/- mice were then crossed to low-density lipoprotein receptor-deficient (Ldlr-/-) mice and fed an atherogenic diet. ApoCIIItg/Ldlr-/- mice had significantly increased atherosclerotic lesions. However, there was no statistical difference in restenosis between ApoCIII-/- and WT mice, and in atherosclerosis between ApoCIII/Ldlr double knockout and Ldlr-/- mice. SMCs were then incubated in vitro with authentic TRLs ± ApoCIII isolated from extreme hypertriglyceridaemia glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1-deficient (GPIHBP1-/-) mice crossed with ApoCIIItg or ApoCIII-/- mice. It was shown that TRLs + ApoCIII promoted SMC proliferation, VCAM-1 expression, and reactive oxygen species (ROS) production, and activated the Akt pathway. Scavenging ROS significantly reduced SMC activation caused by TRLs + ApoCIII.

CONCLUSIONS

Severe hypertriglyceridaemia resulting from ApoCIII overexpression promotes restenosis and atherosclerosis. Furthermore, we demonstrated that TRLs + ApoCIII promotes SMC proliferation.

Islet inflammation in plain sight

Although, diabetes is reaching pandemic proportions, the exact aetiology of either type 1 (T1D) or type 2 diabetes (T2D) remains to be determined. Mounting evidence, however, suggests that islet inflammation is a likely common denominator during early development of either type of the disease. In this review, we highlight some of the inflammatory mechanisms that appear to be shared between T1D and T2D, and we explore the utility of intravital imaging in the study of islet inflammation. Intravital imaging has emerged as an indispensable tool in biomedical research and a variety of in vivo imaging approaches have been developed to study pancreatic islet physiology and pathophysiology in the native environment in health and disease. However, given the scattered distribution of the islets of Langerhans within the 'sea' of the exocrine pancreas located deep within the body and the fact that the islets only constitute 1-2% of the total volume of pancreatic tissue, studying the pancreatic islet in situ has been challenging. Here, we focus on a new experimental approach that enables studying local islet inflammation with single-cell resolution in the relevant context of the in vivo environment non-invasively and longitudinally and, thereby improving our understanding of diabetes pathogenesis.

Apolipoprotein CIII hyperactivates β cell CaV1 channels through SR-BI/β1 integrin-dependent coactivation of PKA and Src

Apolipoprotein CIII (ApoCIII) not only serves as an inhibitor of triglyceride hydrolysis but also participates in diabetes-related pathological events such as hyperactivation of voltage-gated Ca(2+) (CaV) channels in the pancreatic β cell. However, nothing is known about the molecular mechanisms whereby ApoCIII hyperactivates β cell CaV channels. We now demonstrate that ApoCIII increased CaV1 channel open probability and density. ApoCIII enhanced whole-cell Ca(2+) currents and the CaV1 channel blocker nimodipine completely abrogated this enhancement. The effect of ApoCIII was not influenced by individual inhibition of PKA, PKC, or Src. However, combined inhibition of PKA, PKC, and Src counteracted the effect of ApoCIII, similar results obtained by coinhibition of PKA and Src. Moreover, knockdown of β1 integrin or scavenger receptor class B type I (SR-BI) prevented ApoCIII from hyperactivating β cell CaV channels. These data reveal that ApoCIII hyperactivates β cell CaV1 channels through SR-BI/β1 integrin-dependent coactivation of PKA and Src.

ApoE derived from adipose tissue does not suppress atherosclerosis or correct hyperlipidemia in apoE knockout mice

The synthesis of apoE by adipocytes has profound effects on adipose tissue lipid flux and gene expression. Using adipose tissue transplantation from wild-type (WT) to apoE knockout (EKO) mice, we show that adipose tissue also contributes to circulating apoE. Different from circulating apoE produced by bone marrow transplantation (BMT), however, adipose tissue-derived apoE does not correct hyperlipidemia or suppress atherosclerosis. ApoE secreted by macrophages has a more acidic isoform distribution, and it increases binding of reconstituted VLDL particles to hepatocytes and fibroblasts more effectively than apoE secreted by adipocytes. The incremental binding can be entirely accounted for by binding to the LDL receptor. After BMT into EKO hosts, plasma cholesterol and macrophage-derived apoE are largely within IDL/LDL- and HDL-sized particles. After adipose tissue transplantation, most cholesterol and adipocyte apoE remain in VLDL. After BMT, circulating apoE no longer demonstrates predominance of acidic isoforms compared with that circulating after fat transplantation. In conclusion, fat transplantation provides circulating apoE levels similar to those provided by bone marrow transplantation, but it does not suppress hyperlipidemia or atherosclerosis. A potential mechanism contributing to this difference is differential binding to cell surface lipoprotein receptors.

Effects of dietary saturated fat on LDL subclasses and apolipoprotein CIII in men

Background/Objectives

Small dense LDL particles and apolipoprotein (apo) CIII are risk factors for cardiovascular disease (CVD) that can be modulated by diet, but there is little information regarding the effects of dietary saturated fat on their plasma levels. We tested the effects of high vs. low saturated fat intake in the context of a high beef protein diet on levels and composition of LDL subclasses and on apoCIII levels in plasma and LDL.

Subjects/Methods

Following consumption of a baseline diet (50% CHO, 13% protein, 38% total fat, 15% saturated fat) for 3 wk, 14 healthy men were randomly assigned to two reduced carbohydrate high beef protein diets (31% CHO, 31% protein, 38% fat) that differed in saturated fat content (15% vs. 8%) for 3 wk each in a crossover design.

Results

The high saturated fat diet resulted in higher mass concentrations of buoyant LDL I, medium density LDL II and dense LDL III, but not the very dense LDL IV; and significant increases in plasma and LDL apoCIII concentration of 9.4% and 33.5%, respectively. The saturated fat-induced changes in LDL apoCIII were specifically correlated with changes in apoCIII content of LDL IV.

Conclusions

Taken together with previous observations, these findings suggest that, at least in the context of a lower carbohydrate high beef protein diet, high saturated fat intake may increase CVD risk by metabolic processes that involve apoCIII.