ANGPTL3 (Angiopoietin-Like 3) Preferentially Resides on High-Density Lipoprotein in the Human Circulation, Affecting Its Activity.

Background ANGPTL3 (angiopoietin-like protein 3) is an acknowledged crucial regulator of lipid metabolism by virtue of its inhibitory effect on lipoprotein lipase and endothelial lipase. It is currently unknown whether and to which lipoproteins ANGPTL3 is bound and whether the ability of ANGPTL3 to inhibit lipase activity is affected by binding to lipoproteins. Methods and Results Incubation of ultracentrifugation-isolated low-density lipoprotein (LDL) and high-density lipoprotein (HDL) fractions from healthy volunteers with recombinant ANGPTL3 revealed that ANGPTL3 associates with both HDL and LDL particles ex vivo. Plasma from healthy volunteers and a patient deficient in HDL was fractionated by fast protein liquid chromatography, and ANGPTL3 distribution among lipoprotein fractions was measured. In healthy volunteers, ≈75% of lipoprotein-associated ANGPTL3 resides in HDL fractions, whereas ANGPTL3 was largely bound to LDL in the patient deficient in HDL. ANGPTL3 activity was studied by measuring lipolysis and uptake of 3H-trioleate by brown adipocyte T37i cells. Unbound ANGPTL3 did not suppress lipase activity, but when given with HDL or LDL, ANGPTL3 suppressed lipase activity by 21.4±16.4% (P=0.03) and 25.4±8.2% (P=0.006), respectively. Finally, in a subset of the EPIC (European Prospective Investigation into Cancer) Norfolk study, plasma HDL cholesterol and amount of large HDL particles were both positively associated with plasma ANGPTL3 concentrations. Moreover, plasma ANGPTL3 concentrations showed a positive association with incident coronary artery disease (odds ratio, 1.25 [95% CI, 1.01-1.55], P=0.04). Conclusions Although ANGPTL3 preferentially resides on HDL, its activity was highest once bound to LDL particles.

Lipoproteins act as vehicles for lipid antigen delivery and activation of invariant natural killer T cells.

Invariant natural killer T (iNKT) cells act at the interface between lipid metabolism and immunity because of their restriction to lipid antigens presented on CD1d by antigen-presenting cells (APCs). How foreign lipid antigens are delivered to APCs remains elusive. Since lipoproteins routinely bind glycosylceramides structurally similar to lipid antigens, we hypothesized that circulating lipoproteins form complexes with foreign lipid antigens. In this study, we used 2-color fluorescence correlation spectroscopy to show, for the first time to our knowledge, stable complex formation of lipid antigens α-galactosylceramide (αGalCer), isoglobotrihexosylceramide, and OCH, a sphingosine-truncated analog of αGalCer, with VLDL and/or LDL in vitro and in vivo. We demonstrate LDL receptor-mediated (LDLR-mediated) uptake of lipoprotein-αGalCer complexes by APCs, leading to potent complex-mediated activation of iNKT cells in vitro and in vivo. Finally, LDLR-mutant PBMCs of patients with familial hypercholesterolemia showed impaired activation and proliferation of iNKT cells upon stimulation, underscoring the relevance of lipoproteins as a lipid antigen delivery system in humans. Taken together, circulating lipoproteins form complexes with lipid antigens to facilitate their transport and uptake by APCs, leading to enhanced iNKT cell activation. This study thereby reveals a potentially novel mechanism of lipid antigen delivery to APCs and provides further insight into the immunological capacities of circulating lipoproteins.

Proteomics and lipidomics in atherosclerotic cardiovascular disease risk prediction.

Given the limited accuracy of clinically used risk scores such as the Systematic COronary Risk Evaluation 2 system and the Second Manifestations of ARTerial disease 2 risk scores, novel risk algorithms determining an individual's susceptibility of future incident or recurrent atherosclerotic cardiovascular disease (ASCVD) risk are urgently needed. Due to major improvements in assay techniques, multimarker proteomic and lipidomic panels hold the promise to be reliably assessed in a high-throughput routine. Novel machine learning-based approaches have facilitated the use of this high-dimensional data resulting from these analyses for ASCVD risk prediction. More than a dozen of large-scale retrospective studies using different sets of biomarkers and different statistical methods have consistently demonstrated the additive prognostic value of these panels over traditionally used clinical risk scores. Prospective studies are needed to determine the clinical utility of a biomarker panel in clinical ASCVD risk stratification. When combined with the genetic predisposition captured with polygenic risk scores and the actual ASCVD phenotype observed with coronary artery imaging, proteomics and lipidomics can advance understanding of the complex multifactorial causes underlying an individual's ASCVD risk.

Apolipoprotein C-III Inhibition - Killing Two Birds with One Stone?

In this issue of NEJM Evidence, Gaudet et al.1 report on safety and efficacy of a strategy targeting apolipoprotein C-III (APOC3) using a silencing ribonucleic acid (RNA; ARO-APOC3). In a phase I trial comprising 52 healthy volunteers (triglycerides [TG], >80 mg/dl), 40 patients with hypertriglyceridemia (TG, >300 mg/dl), and 20 patients with chylomicronemia (TG, >880 mg/dl), ARO-APOC3 or placebo was administered subcutaneously either once or twice, with doses given on days 1 and 29. The primary goal was to examine the safety of ARO-APOC3. Injection site reactions were the most commonly observed adverse clinical event; no adverse effects led to discontinuation of the study drug.

Lp(a): a New Pathway to Target?

PURPOSE OF REVIEW: Over the past decades, genetic and observational evidence has positioned lipoprotein(a) as novel important and independent risk factor for cardiovascular disease (ASCVD) and aortic valve stenosis. RECENT FINDINGS: As Lp(a) levels are determined genetically, lifestyle interventions have no effect on Lp(a)-mediated ASCVD risk. While traditional low-density lipoprotein cholesterol (LDL-C) can now be effectively lowered in the vast majority of patients, current lipid lowering therapies have no clinically relevant Lp(a) lowering effect. There are multiple Lp(a)-directed therapies in clinical development targeting LPA mRNA that have shown to lower Lp(a) plasma levels for up to 90%: pelacarsen, olpasiran, and SLN360. Pelacarsen is currently investigated in a phase 3 cardiovascular outcome trial expected to finish in 2024, while olpasiran is about to proceed to phase 3 and SLN360's phase 1 outcomes were recently published. If proven efficacious, Lp(a) will soon become the next pathway to target in ASCVD risk management.

Lipoprotein(a): An underestimated inflammatory mastermind.

Lipoprotein(a) [Lp(a)] has been established as an independent and causal risk factor for cardiovascular disease. Individuals with elevated levels of Lp(a) (>125 nmol/L; >50 mg/dl) display increased arterial wall inflammation characterized by activation of the endothelium by Lp(a)-carried oxidized phospholipids and recruitment of circulating monocytes. This results in increased secretion of chemoattractants and cytokines, upregulation of adhesion molecules and increased migration of leukocytes through the vessel wall. In addition, Lp(a) is also pivotal in the initiation phase of aortic valve stenosis. The oxidized phospholipids associated, in part, with the apolipoprotein(a) [apo(a)] moiety of Lp(a) stimulate the aortic valve residential cell, the valve interstitial cells (VICs), to either induce osteoblastic differentiation or apoptosis, thereby initiating the process of aortic valve calcification. Lastly, Lp(a) has been linked to systemic inflammation, including the acute phase response. Specifically, the cytokine interleukin 6 (IL-6) has a unique relationship with Lp(a), since the LPA gene contains IL-6 response elements. In this review, we will discuss the pathways and cell types affected by Lp(a) in the context of atherosclerosis, aortic valve stenosis and the acute phase response, highlighting the role of Lp(a) as an inflammatory mastermind.

Interleukin 6 in diabetes, chronic kidney disease, and cardiovascular disease: mechanisms and therapeutic perspectives.

INTRODUCTION: Diabetes, chronic kidney disease (CKD) and cardiovascular disease (CVD) are cardiometabolic diseases that remain amongst the leading causes of morbidity and premature mortality. Here, we review the current understanding of how anti-inflammatory intervention via inhibition of the pro-inflammatory but pleiotropic cytokine interleukin (IL) 6 may benefit patients with these or related diseases or complications. AREAS COVERED: Based on a PubMed literature search, this review integrates and contextualizes evidence regarding the clinical utility of anti-IL-6 intervention in the treatment of cardiometabolic diseases, as well as of the associated condition nonalcoholic hepatosteatosis. EXPERT OPINION: Evidence implicates the pro-inflammatory effects of IL-6 in the pathophysiology of diabetes, CKD and CVD. Thus, targeting the IL-6 pathway holds a therapeutic potential in these cardiometabolic disorders. However, because IL-6 has multiple homeostatic roles, antagonizing this cytokine may be associated with side effects, such as increased risk of infection as seen with other anti-inflammatory drugs. Additional studies are required to establish the benefit-risk profile of anti-IL-6 intervention in the cardiometabolic diseases, whilst also considering alternative interventions such as lifestyle changes. IL-6 is also elevated in NASH, but the clinical usefulness of targeting IL-6 in this hepatic disorder remains largely unexplored.

Targeted proteomics improves cardiovascular risk prediction in secondary prevention.

AIMS: Current risk scores do not accurately identify patients at highest risk of recurrent atherosclerotic cardiovascular disease (ASCVD) in need of more intensive therapeutic interventions. Advances in high-throughput plasma proteomics, analysed with machine learning techniques, may offer new opportunities to further improve risk stratification in these patients. METHODS AND RESULTS: Targeted plasma proteomics was performed in two secondary prevention cohorts: the Second Manifestations of ARTerial disease (SMART) cohort (n = 870) and the Athero-Express cohort (n = 700). The primary outcome was recurrent ASCVD (acute myocardial infarction, ischaemic stroke, and cardiovascular death). Machine learning techniques with extreme gradient boosting were used to construct a protein model in the derivation cohort (SMART), which was validated in the Athero-Express cohort and compared with a clinical risk model. Pathway analysis was performed to identify specific pathways in high and low C-reactive protein (CRP) patient subsets. The protein model outperformed the clinical model in both the derivation cohort [area under the curve (AUC): 0.810 vs. 0.750; P < 0.001] and validation cohort (AUC: 0.801 vs. 0.765; P < 0.001), provided significant net reclassification improvement (0.173 in validation cohort) and was well calibrated. In contrast to a clear interleukin-6 signal in high CRP patients, neutrophil-signalling-related proteins were associated with recurrent ASCVD in low CRP patients. CONCLUSION: A proteome-based risk model is superior to a clinical risk model in predicting recurrent ASCVD events. Neutrophil-related pathways were found in low CRP patients, implying the presence of a residual inflammatory risk beyond traditional NLRP3 pathways. The observed net reclassification improvement illustrates the potential of proteomics when incorporated in a tailored therapeutic approach in secondary prevention patients.

The iterative lipid impact on inflammation in atherosclerosis.

PURPOSE OF REVIEW: Lipid-mediated atherogenesis is hallmarked by a chronic inflammatory state. Low-density lipoprotein cholesterol (LDL-C), triglyceride rich lipoproteins (TRLs), and lipoprotein(a) [Lp(a)] are causally related to atherosclerosis. Within the paradigm of endothelial activation and subendothelial lipid deposition, these lipoproteins induce numerous pro-inflammatory pathways. In this review, we will outline the effects of lipoproteins on systemic inflammatory pathways in atherosclerosis. RECENT FINDINGS: Apolipoprotein B-containing lipoproteins exert a variety of pro-inflammatory effects, ranging from the local artery to systemic immune cell activation. LDL-C, TRLs, and Lp(a) induce endothelial dysfunction with concomitant activation of circulating monocytes through enhanced lipid accumulation. The process of trained immunity of the innate immune system, predominantly induced by LDL-C particles, hallmarks the propagation of the low-grade inflammatory response. In concert, bone marrow activation induces myeloid skewing, further contributing to immune cell mobilization and plaque progression. SUMMARY: Lipoproteins and inflammation are intertwined in atherogenesis. Elucidating the inflammatory pathways will provide new opportunities for therapeutic agents.

HIV and Cognitive Impairment in Clinical Practice: The Evaluation of a Stepwise Screening Protocol in Relation to Clinical Outcomes and Management.

Neurocognitive impairment (NCI) is an increasingly important comorbidity in an ageing HIV+ population. Despite the lack of available treatment modalities, screening for NCI is recommended. In the UMC Utrecht, yearly NCI screening is done using the Montreal Cognitive Assessment (MoCA) tool and the HIV Dementia Scale (HDS). The aim of this study was to evaluate this screening protocol in relation to clinical outcomes and management. A retrospective cohort study was performed in suppressed adult HIV+ patients. Apart from the MoCa and the HDS, the Utrecht Scale for Evaluation of Rehabilitation-Participation (USER-P) and the Hospital Anxiety and Depression Scale (HADS) were performed. Patients scoring below average on cognitive screening tests or with subjective cognitive complaints were further evaluated using a standardized protocol, including optimizing cART and checking for somatic disorders. In patients with cognitive complaints and participation restrictions, cognitive rehabilitation was proposed. Two hundred eighty-six patients were screened. The vast majority were MSM with an average age of 49 years. One hundred forty-four out of 286 patients (50%) had an abnormal test score and/or had subjective cognitive complaints. Restrictions in participation were present in 23% of patients. Six patients on Efavirenz switched their regimes, as this drug is known for its potential central nervous system (CNS) side effects. A depressive component was present in 58 patients (40%). Five patients had a clinical relevant laboratory abnormality. Moreover, six patients were referred for cognitive rehabilitation, which resulted in a 100% success rate in set goals in the five evaluable patients. Although the protocol was not fully adhered to in all patients, it did result in detectable underlying causes of NCI in 59% of patients, and 21% was referred for further treatment. Moreover, cognitive rehabilitation appears to be a very successful intervention for patients with NCI who experience subjective complaints and participation restrictions.