Rewiring Endothelial Sphingolipid Metabolism to Favor S1P Over Ceramide Protects From Coronary Atherosclerosis.

BACKGROUND: Growing evidence correlated changes in bioactive sphingolipids, particularly S1P (sphingosine-1-phosphate) and ceramides, with coronary artery diseases. Furthermore, specific plasma ceramide species can predict major cardiovascular events. Dysfunction of the endothelium lining lesion-prone areas plays a pivotal role in atherosclerosis. Yet, how sphingolipid metabolism and signaling change and contribute to endothelial dysfunction and atherosclerosis remain poorly understood. METHODS: We used an established model of coronary atherosclerosis in mice, combined with sphingolipidomics, RNA-sequencing, flow cytometry, and immunostaining to investigate the contribution of sphingolipid metabolism and signaling to endothelial cell (EC) activation and dysfunction. RESULTS: We demonstrated that hemodynamic stress induced an early metabolic rewiring towards endothelial sphingolipid de novo biosynthesis, favoring S1P signaling over ceramides as a protective response. This finding is a paradigm shift from the current belief that ceramide accrual contributes to endothelial dysfunction. The enzyme SPT (serine palmitoyltransferase) commences de novo biosynthesis of sphingolipids and is inhibited by NOGO-B (reticulon-4B), an ER membrane protein. Here, we showed that NOGO-B is upregulated by hemodynamic stress in myocardial EC of ApoE-/- mice and is expressed in the endothelium lining coronary lesions in mice and humans. We demonstrated that mice lacking NOGO-B specifically in EC (Nogo-A/BECKOApoE-/-) were resistant to coronary atherosclerosis development and progression, and mortality. Fibrous cap thickness was significantly increased in Nogo-A/BECKOApoE-/- mice and correlated with reduced necrotic core and macrophage infiltration. Mechanistically, the deletion of NOGO-B in EC sustained the rewiring of sphingolipid metabolism towards S1P, imparting an atheroprotective endothelial transcriptional signature. CONCLUSIONS: These data demonstrated that hemodynamic stress induced a protective rewiring of sphingolipid metabolism, favoring S1P over ceramide. NOGO-B deletion sustained the rewiring of sphingolipid metabolism toward S1P protecting EC from activation under hemodynamic stress and refraining coronary atherosclerosis. These findings also set forth the foundation for sphingolipid-based therapeutics to limit atheroprogression.

Regional Differences in the Small Intestinal Proteome of Control Mice and of Mice Lacking Lysosomal Acid Lipase.

The metabolic contribution of the small intestine (SI) is still unclear despite recent studies investigating the involvement of single cells in regional differences. Using untargeted proteomics, we identified regional characteristics of the three intestinal tracts of C57BL/6J mice and found that proteins abundant in the mouse ileum correlated with the high ileal expression of the corresponding genes in humans. In the SI of C57BL/6J mice, we also detected an increasing abundance of lysosomal acid lipase (LAL), which is responsible for degrading triacylglycerols and cholesteryl esters within the lysosome. LAL deficiency in patients and mice leads to lipid accumulation, gastrointestinal disturbances, and malabsorption. We previously demonstrated that macrophages massively infiltrated the SI of Lal-deficient (KO) mice, especially in the duodenum. Using untargeted proteomics (ProteomeXchange repository, data identifier PXD048378), we revealed a general inflammatory response and a common lipid-associated macrophage phenotype in all three intestinal segments of Lal KO mice, accompanied by a higher expression of GPNMB and concentrations of circulating sTREM2. However, only duodenal macrophages activated a metabolic switch from lipids to other pathways, which were downregulated in the jejunum and ileum of Lal KO mice. Our results provide new insights into the process of absorption in control mice and possible novel markers of LAL-D and/or systemic inflammation in LAL-D.

Long-Term Follow-Up of Custom-Made Porous Hydroxyapatite Cranioplasties: Analysis of Infections in Adult and Pediatric Patients.

In neurosurgery, cranioplasty (CP) stands as a pivotal surgical intervention, particularly following head trauma or various neurosurgical interventions. This study scrutinizes the intricacies of CP, emphasizing its prevalence and associated complications, with a specific focus on custom-made porous hydroxyapatite (PHA) implants. The investigation spans 687 patients (with 80 patients of pediatric age, less than 14 years old) across 26 neurosurgical centers in five European countries. Methodologically, this study delves into patient characteristics, complications, and infection data through a comprehensive post-marketing on-site surveillance approach. Notably, infections emerged as the primary complication, affecting 41 patients (6% of implants) with a clear distinction in onset patterns between pediatric (with more infections, 10% versus 5.4% in adults and an earlier onset of complications) and adult populations. Out of these 41 cases, cranioplasty explantation was required in 30 patients, 4.4% of the total population. Furthermore, bifrontal decompression correlated with a significantly elevated infection risk as compared to unilateral decompression (12.5% versus 5.1%) which remains after the examination of possible confounding factors. These findings provide substantial insights into the complexities of CP, suggesting the necessity for tailored strategies in pediatric and adult cases and cautioning against bifrontal decompressions. Despite acknowledging limitations and calling for prospective studies with long term follow-up, this research advances our understanding of the use of PHA CP, guiding clinical decision-making and emphasizing the importance of customized approaches for diverse patient cohorts.

The Impact of Red Yeast Rice Extract Use on the Occurrence of Muscle Symptoms and Liver Dysfunction: An Update from the Adverse Event Reporting Systems and Available Meta-Analyses.

Red yeast rice (RYR) has a cholesterol-lowering effect due to the presence of bioactive components (monacolins, mainly monacolin K) that act by inhibiting the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. The European Food Safety Authority (EFSA) assessed the use of RYR and, while pointing out several uncertainties regarding the available data, raised a warning related to the safety of RYR when used as a food supplement at a dose of monacolin as low as 3 mg/day. In their decision in June 2023, EFSA approved the use of monacolins from RYR at doses less than 3 mg/day. We therefore decided to interrogate the different adverse event reporting systems (FAERS and CAERS) and analyse the characteristics of the cases reported to be associated with RYR supplements, and we reviewed the most recent meta-analyses with a focus on the occurrence of muscle symptoms and liver dysfunction. In terms of all musculoskeletal disorders from September 2013 (when the first case related to RYR consumption was recorded) to 30 September 2023, 363,879 cases were reported in the FAERS, with the number of cases related to RYR consumption being very small and accounting for 0.008% of cases. In the same time frame, 27,032 cases of hepatobiliary disorders were reported, and the cases attributable to RYR ingestion accounted for 0.01% of all cases. A low rate of muscle symptoms and liver dysfunction attributed to RYR ingestion was also observed in the CAERS database, where only 34 cases of adverse muscle events and 10 cases of adverse liver events reported RYR as the suspect product, while 19 cases of both muscle events and 10 cases of adverse liver events reported it as a concomitant product. This profile mirrors that of meta-analyses of randomised clinical trials of RYR, in which RYR use was not associated with either liver dysfunction or muscular adverse symptoms.

ASGR1 deficiency diverts lipids toward adipose tissue but results in liver damage during obesity.

BACKGROUND: Asialoglycoprotein receptor 1 (ASGR1), primarily expressed on hepatocytes, promotes the clearance and the degradation of glycoproteins, including lipoproteins, from the circulation. In humans, loss-of-function variants of ASGR1 are associated with a favorable metabolic profile and reduced incidence of cardiovascular diseases. The molecular mechanisms by which ASGR1 could affect the onset of metabolic syndrome and obesity are unclear. Therefore, here we investigated the contribution of ASGR1 in the development of metabolic syndrome and obesity. METHODS: ASGR1 deficient mice (ASGR1-/-) were subjected to a high-fat diet (45% Kcal from fat) for 20 weeks. The systemic metabolic profile, hepatic and visceral adipose tissue were characterized for metabolic and structural alterations, as well as for immune cells infiltration. RESULTS: ASGR1-/- mice present a hypertrophic adipose tissue with 41% increase in fat accumulation in visceral adipose tissue (VAT), alongside with alteration in lipid metabolic pathways. Intriguingly, ASGR1-/- mice exhibit a comparable response to an acute glucose and insulin challenge in circulation, coupled with notably decreased in circulating cholesterol levels. Although the liver of ASGR1-/- have similar lipid accumulation to the WT mice, they present elevated levels of liver inflammation and a decrease in mitochondrial function. CONCLUSION: ASGR1 deficiency impacts energetic homeostasis during obesity leading to improved plasma lipid levels but increased VAT lipid accumulation and liver damage.

The inhibition of inner mitochondrial fusion in hepatocytes reduces non-alcoholic fatty liver and improves metabolic profile during obesity by modulating bile acid conjugation.

AIMS: Mitochondria are plastic organelles that continuously undergo biogenesis, fusion, fission, and mitophagy to control cellular energy metabolism, calcium homeostasis, hormones, sterols, and bile acids (BAs) synthesis. Here, we evaluated how the impairment of mitochondrial fusion in hepatocytes affects diet-induced liver steatosis and obesity. METHODS AND RESULTS: Male mice selectively lacking the key protein involved in inner mitochondrial fusion, optic atrophy 1 (OPA1) (OPA1ΔHep) were fed a high fat diet (HFD) for 20 weeks. OPA1ΔHep mice were protected from the development of hepatic steatosis and obesity because of reduced lipid absorption; a profile which was accompanied by increased respiratory exchange ratio in vivo, suggesting a preference for carbohydrates in OPA1ΔHep compared to controls. At the molecular level, this phenotype emerged as a consequence of poor mitochondria-peroxisome- endoplasmic reticulum (ER) tethering in OPA1 deficient hepatocytes, which impaired BAs conjugation and release in the bile, thus impacting lipid absorption from the diet. Concordantly, the liver of subjects with non-alcoholic fatty liver disease (NAFLD) presented an increased expression of OPA1 and of the network of proteins involved in mitochondrial function when compared with controls. CONCLUSION: Patients with NAFLD present increased expression of proteins involved in mitochondrial fusion in the liver. The selective deficency of OPA1 in hepatocytes protects mice from HFD-induced metabolic dysfunction by reducing BAs secretion and dietary lipids absorption as a consequence of reduced liver mitochondria-peroxisome-ER tethering.

PITX2 gain-of-function mutation associated with atrial fibrillation alters mitochondrial activity in human iPSC atrial-like cardiomyocytes.

Atrial fibrillation (AF) is the most common cardiac arrhythmia worldwide; however, the underlying causes of AF initiation are still poorly understood, particularly because currently available models do not allow in distinguishing the initial causes from maladaptive remodeling that induces and perpetuates AF. Lately, the genetic background has been proven to be important in the AF onset. iPSC-derived cardiomyocytes, being patient- and mutation-specific, may help solve this diatribe by showing the initial cell-autonomous changes underlying the development of the disease. Transcription factor paired-like homeodomain 2 (PITX2) has been identified as a key regulator of atrial development/differentiation, and the PITX2 genomic locus has the highest association with paroxysmal AF. PITX2 influences mitochondrial activity, and alterations in either its expression or function have been widely associated with AF. In this work, we investigate the activity of mitochondria in iPSC-derived atrial cardiomyocytes (aCMs) obtained from a young patient (24 years old) with paroxysmal AF, carrying a gain-of-function mutation in PITX2 (rs138163892) and from its isogenic control (CTRL) in which the heterozygous point mutation has been reverted to WT. PITX2 aCMs show a higher mitochondrial content, increased mitochondrial activity, and superoxide production under basal conditions when compared to CTRL aCMs. However, increasing mitochondrial workload by FCCP or ß-adrenergic stimulation allows us to unmask mitochondrial defects in PITX2 aCMs, which are incapable of responding efficiently to the higher energy demand, determining ATP deficiency.

Genetic deletion of MMP12 ameliorates cardiometabolic disease by improving insulin sensitivity, systemic inflammation, and atherosclerotic features in mice.

BACKGROUND: Matrix metalloproteinase 12 (MMP12) is a macrophage-secreted protein that is massively upregulated as a pro-inflammatory factor in metabolic and vascular tissues of mice and humans suffering from cardiometabolic diseases (CMDs). However, the molecular mechanisms explaining the contributions of MMP12 to CMDs are still unclear. METHODS: We investigated the impact of MMP12 deficiency on CMDs in a mouse model that mimics human disease by simultaneously developing adipose tissue inflammation, insulin resistance, and atherosclerosis. To this end, we generated and characterized low-density lipoprotein receptor (Ldlr)/Mmp12-double knockout (DKO) mice fed a high-fat sucrose- and cholesterol-enriched diet for 16-20 weeks. RESULTS: DKO mice showed lower cholesterol and plasma glucose concentrations and improved insulin sensitivity compared with LdlrKO mice. Untargeted proteomic analyses of epididymal white adipose tissue revealed that inflammation- and fibrosis-related pathways were downregulated in DKO mice. In addition, genetic deletion of MMP12 led to alterations in immune cell composition and a reduction in plasma monocyte chemoattractant protein-1 in peripheral blood which indicated decreased low-grade systemic inflammation. Aortic en face analyses and staining of aortic valve sections demonstrated reduced atherosclerotic plaque size and collagen content, which was paralleled by an improved relaxation pattern and endothelial function of the aortic rings and more elastic aortic sections in DKO compared to LdlrKO mice. Shotgun proteomics revealed upregulation of anti-inflammatory and atheroprotective markers in the aortas of DKO mice, further supporting our data. In humans, MMP12 serum concentrations were only weakly associated with clinical and laboratory indicators of CMDs. CONCLUSION: We conclude that the genetic deletion of MMP12 ameliorates obesity-induced low-grade inflammation, white adipose tissue dysfunction, biomechanical properties of the aorta, and the development of atherosclerosis. Therefore, therapeutic strategies targeting MMP12 may represent a promising approach to combat CMDs.

The glucose transporter 2 regulates CD8+ T cell function via environment sensing.

T cell activation is associated with a profound and rapid metabolic response to meet increased energy demands for cell division, differentiation and development of effector function. Glucose uptake and engagement of the glycolytic pathway are major checkpoints for this event. Here we show that the low-affinity, concentration-dependent glucose transporter 2 (Glut2) regulates the development of CD8+ T cell effector responses in mice by promoting glucose uptake, glycolysis and glucose storage. Expression of Glut2 is modulated by environmental factors including glucose and oxygen availability and extracellular acidification. Glut2 is highly expressed by circulating, recently primed T cells, allowing efficient glucose uptake and storage. In glucose-deprived inflammatory environments, Glut2 becomes downregulated, thus preventing passive loss of intracellular glucose. Mechanistically, Glut2 expression is regulated by a combination of molecular interactions involving hypoxia-inducible factor-1 alpha, galectin-9 and stomatin. Finally, we show that human T cells also rely on this glucose transporter, thus providing a potential target for therapeutic immunomodulation.

Rhabdomyolysis or Severe Acute Hepatitis Associated with the Use of Red Yeast Rice Extracts: an Update from the Adverse Event Reporting Systems.

PURPOSE OF REVIEW: Elevated plasma levels of low-density lipoprotein cholesterol (LDL-C) are a major risk factor for atherosclerotic cardiovascular disease (ASCVD), and lowering LDL-C reduces the risk of cardiovascular adverse events. Among natural approaches known for their lipid-lowering properties, red yeast rice (RYR) has a cholesterol-lowering effect due to the presence of bioactive components (monacolins) that act by inhibiting the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. In August 2018, the European Food Safety Authority (EFSA) concluded in its assessment of the use of RYR (further amended in June 2022) that monacolins from RYR raise significant safety concerns when used as a food supplement at a dose of 10 mg/day. In particular, individual cases of serious adverse effects of monacolins from RYR have been reported at intakes as low as 3 mg/day. The EFSA Panel pointed out several uncertainties regarding the available data. RECENT FINDINGS: We conducted an in-depth and updated analysis of the serious adverse events, with a focus on rhabdomyolysis and acute hepatitis, associated with the consumption of RYR. An analysis of the Food and Drug Administration reporting systems revealed a very small number of cases of rhabdomyolysis or severe acute hepatitis associated with RYR use. In addition, only a few case reports of these serious adverse events associated with RYR use have been published. Based on data from adverse event reporting systems and available case reports, the occurrence of rhabdomyolysis or severe acute hepatitis that could be associated with the use of RYR appears to be extremely rare compared to the occurrence with statins, which is rare to common.

Apolipoprotein E isoforms differentially affect LCAT-dependent cholesterol esterification.

BACKGROUND AND AIMS: LCAT esterifies cholesterol in both HDL (α-activity) and apoB-containing lipoproteins (ß-activity). The main activator of LCAT ß-activity is apoE, which in humans exists in 3 main different isoforms (E2, E3 and E4). Here, to gather insights into the potential role of LCAT in apoB-containing lipoprotein metabolism, we investigated the ability of apoE isoforms to promote LCAT-mediated cholesterol esterification. METHODS: We evaluated the plasma cholesterol esterification rate (CER) in 311 individuals who express functional LCAT and either apoE2, apoE3, or apoE4 and in 28 individuals who also carried LCAT mutations causing selective loss of LCAT α-activity (Fish-Eye Disease (FED)-causing mutations). The association of carrier status with CER was determined using an adjusted linear regression model. The kinetic of LCAT activity towards reconstituted HDLs (rHDLs) containing each apoE isoform was determined using the Michaelis-Menten model. RESULTS: Plasma CER was ∼20% higher in apoE2 carriers compared to apoE3 carriers, and ∼30% higher in apoE2 carriers compared to apoE4 carriers. After adjusting for age, sex, total cholesterol, HDL-C, apoA-I, apoB, chronic kidney disease diagnosis, zygosity, and LCAT concentration, CER remained significantly different among carriers of the three apoE isoforms. The same trend was observed in carriers of FED-causing mutations. rHDLs containing apoE2 were associated with a lower affinity but higher maximal esterification rate, compared to particles containing apoE3 or apoE4. CONCLUSION: The present results suggest that the apoE2 isoform is associated with a higher LCAT-mediated cholesterol esterification. This observation may contribute to the characterization of the peculiar functional properties of apoE2.

Cardiac lipid metabolism, mitochondrial function, and heart failure.

A fine balance between uptake, storage, and the use of high energy fuels, like lipids, is crucial in the homeostasis of different metabolic tissues. Nowhere is this balance more important and more precarious than in the heart. This highly energy-demanding muscle normally oxidizes almost all the available substrates to generate energy, with fatty acids being the preferred source under physiological conditions. In patients with cardiomyopathies and heart failure, changes in the main energetic substrate are observed; these hearts often prefer to utilize glucose rather than oxidizing fatty acids. An imbalance between uptake and oxidation of fatty acid can result in cellular lipid accumulation and cytotoxicity. In this review, we will focus on the sources and uptake pathways used to direct fatty acids to cardiomyocytes. We will then discuss the intracellular machinery used to either store or oxidize these lipids and explain how disruptions in homeostasis can lead to mitochondrial dysfunction and heart failure. Moreover, we will also discuss the role of cholesterol accumulation in cardiomyocytes. Our discussion will attempt to weave in vitro experiments and in vivo data from mice and humans and use several human diseases to illustrate metabolism gone haywire as a cause of or accomplice to cardiac dysfunction.

Fibronectin extra domain a limits liver dysfunction and protects mice during acute inflammation.

Background and aim: The primary transcript of fibronectin (FN) undergoes alternative splicing to generate different isoforms, including FN containing the Extra Domain A (FN_EDA+), whose expression is regulated spatially and temporarily during developmental and disease conditions including acute inflammation. The role of FN_EDA+ during sepsis, however, remains elusive. Methods: Mice constitutively express the EDA domain of fibronectin (EDA+/+); lacking the FN EDA domain (EDA-/-) or with a conditional ablation of EDA + inclusion only in liver produced FN (alb-CRE+EDA floxed mice) thus expressing normal plasma FN were used. Systemic inflammation and sepsis were induced by either LPS injection (70 mg/kg) or by cecal ligation and puncture (CLP) Neutrophils isolated from septic patients were tested for neutrophil binding ability. Results: We observed that EDA+/+ were protected toward sepsis as compared to EDA-/- mice. Also alb-CRE+EDA floxed mice presented reduced survival, thus indicating a key role for EDA in protecting toward sepsis. This phenotype was associated with improved liver and spleen inflammatory profile. Ex vivo experiments showed that neutrophils bind to a larger extent to an FN_EDA + coated surface as compared to FN, thus potentially limiting their over-reactivity. Conclusions: Our study demonstrates that the inclusion of the EDA domain in fibronectin dampens the nflammatoryi consequences of sepsis.

The burden of hypercholesterolemia and ischemic heart disease in an ageing world.

Despite a general improvement in global health conditions in the last decades, cardiovascular diseases (CVDs) are still the first global cause of death and disability worldwide, with ischemic heart disease (IHD) being responsible for half of CVD deaths. Hypercholesterolemia is a major causal risk factor for IHD. Although the availability of effective cholesterol-lowering drugs largely increased in the last few years, we are still facing disparities in the awareness of dyslipidaemia as a CVD-associated risk factor and therefore in health expenditure among different world areas. Although no significant changes have been reported globally in the levels of plasma cholesterol in the last three decades, relevant differences among world areas according to their economic status can be observed. Only high-income countries have experienced an improvement in plasma lipid profile which translated into a substantial decrease in the deaths and disabilities due to IHD, whereas countries in other income groups showed no reduction or even an increase. As expected, most of the deaths for IHD attributable to high LDL-C occur in people aged 60 years and above, although significant differences can be observed according to income. Altogether these observations suggest the need for measures to reduce the gap in treating hypercholesterolemia among income groups, with special attention to women and older people.

Protocol to evaluate the impact of murine MCT1-deficient CD8+ T cells on adipogenesis.

The infiltration of activated T cells, such as CD8+ effector, in metabolic tissues plays a crucial role for the initiation and propagation of obesity-induced inflammation. Given the pivotal role of lactate transporter monocarboxylate transporter 1 (MCT1) in immune cell activation, we present a protocol for the isolation and activation of CD8+ T lymphocytes selectively lacking MCT1. We describe steps for the induction of adipocyte differentiation, CD8+ T isolation and activation, and adipocyte-CD8+ T cell co-culture. We then detail qPCR analysis on differentiated adipocytes. For complete details on the use and execution of this protocol, please refer to Macchi et al.1.

Neutrophil aging exacerbates high fat diet induced metabolic alterations.

BACKGROUND: High fat diet (HFD) chronically hyper-activates the myeloid cell precursors, but whether it affects the neutrophil aging is unknown. PURPOSE: We characterized how HFD impacts neutrophil aging, infiltration in metabolic tissues and if this aging, in turn, modulates the development of metabolic alterations. We immunophenotyped neutrophils and characterized the metabolic responses in physiology (wild-type mice, WT) and in mice with constitutively aged neutrophils (MRP8 driven conditional deletion of CXCR4; herein CXCR4fl/flCre+) or with constitutively fresh neutrophils (MRP8 driven conditional deletion of CXCR2; CXCR2fl/flCre+), following 20 weeks of HFD feeding (45 % kcal from fat). FINDINGS: After 20 weeks HFD, the gluco-metabolic profile of CXCR4fl/flCre+ mice was comparable to that of WT mice, while CXCR2fl/flCre+ mice were protected from metabolic alterations. CXCR4fl/flCre+ infiltrated more, but CXCR2fl/flCre+ neutrophils infiltrated less, in liver and visceral adipose tissue (VAT). As consequence, while CXCR4fl/flCre+ resulted into hepatic "suicidal" neutrophils extracellular traps (NETs) and altered immune cell architecture in VAT, CXCR2fl/flCre+ promoted proresolutive hepatic NETs and reduced accumulation of pro-inflammatory macrophages in VAT. In humans, higher plasma levels of Cxcl12 (CXCR4 ligand) correlated with visceral adiposity while higher levels of Cxcl1 (the ligand of CXCR2) correlated with indexes of hepatic steatosis, adiposity and metabolic syndrome. CONCLUSIONS: Neutrophil aging might contribute to the development of HFD induced metabolic disorders.

Dendritic cell marker Clec4a4 deficiency limits atherosclerosis progression.

Background and aims: Atherogenesis results from altered lipid metabolism and impaired immune response. Emerging evidence has suggested that dendritic cells (DCs) participate to atherosclerosis-related immune response, but their impact is scarcely characterized. Clec4a4 or DCIR2 (Dendritic cell immunoreceptor 2) is a C-type lectin receptor, mainly expressed by CD8α- DCs, able to modulate T cell immunity. However, whether this DC subset could play a role in the atherogenesis is still poorly understood. Thus, the aim of this study is to investigate whether the absence of Clec4a4 could affect atherosclerosis-related immune response and atherosclerosis itself. Methods: Dcir2 -/- Ldlr -/- and Ldlr -/- mice were fed a standard diet or cholesterol-enriched diet for 12 weeks. Subsequently, the profile of circulating and lymph nodes-resident immune cells was investigated together with the analysis of plasma lipid levels and atherosclerotic plaque extension in the aorta. Results: Here, we show that Clec4a4 expression is downregulated under hypercholesterolemia and its deficiency in Ldlr -/- mice results in the reduction of atherosclerotic plaque formation, together with altered lipid metabolism and impaired myeloid immune cell distribution. Conclusions: Our findings suggest a pro-atherosclerotic role of Clec4a4 in experimental atherosclerosis.