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Objectives The co-stimulatory CD40L–CD40 dyad exerts a critical role in atherosclerosis by modulating leukocyte accumulation into developing atherosclerotic plaques. The requirement for cell-type specific expression of both molecules, however, remains elusive. Here, we evaluate the contribution of CD40 expressed on endothelial cells (ECs) in a mouse model of atherosclerosis. Methods and Results Atherosclerotic plaques of apolipoprotein E-deficient (Apoe −/− ) mice and humans displayed increased expression of CD40 on ECs compared with controls. To interrogate the role of CD40 on ECs in atherosclerosis, we induced EC-specific (BmxCreERT2-driven) deficiency of CD40 in Apoe −/− mice. After feeding a chow diet for 25 weeks, EC-specific deletion of CD40 (iEC-CD40) ameliorated plaque lipid deposition and lesional macrophage accumulation but increased intimal smooth muscle cell and collagen content, while atherosclerotic lesion size did not change. Leukocyte adhesion to the vessel wall was impaired in iEC-CD40-deficient mice as demonstrated by intravital microscopy. In accord, expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) in the vascular endothelium declined after deletion of CD40. In vitro, antibody-mediated inhibition of human endothelial CD40 significantly abated monocyte adhesion on ECs. Conclusion Endothelial deficiency of CD40 in mice promotes structural features associated with a stable plaque phenotype in humans and decreases leukocyte adhesion. These results suggest that endothelial-expressed CD40 contributes to inflammatory cell migration and consecutive plaque formation in atherogenesis.

Statins induce plaque regression characterized by reduced macrophage content in humans, but the underlying mechanisms remain speculative. Studying the translational APOE*3-Leiden.CETP mouse model with a humanized lipoprotein metabolism, we find that systemic cholesterol lowering by oral atorvastatin or dietary restriction inhibits monocyte infiltration, and reverses macrophage accumulation in atherosclerotic plaques. Contrary to current believes, none of (1) reduced monocyte influx (studied by cell fate mapping in thorax-shielded irradiation bone marrow chimeras), (2) enhanced macrophage egress (studied by fluorescent bead labeling and transfer), or (3) atorvastatin accumulation in murine or human plaque (assessed by mass spectrometry) could adequately account for the observed loss in macrophage content in plaques that undergo phenotypic regression. Instead, suppression of local proliferation of macrophages dominates phenotypic plaque regression in response to cholesterol lowering: the lower the levels of serum LDL-cholesterol and lipid contents in murine aortic and human carotid artery plaques, the lower the rates of in situ macrophage proliferation. Our study identifies macrophage proliferation as the predominant turnover determinant and an attractive target for inducing plaque regression. Supplementary Information The online version contains supplementary material available at 10.1007/s00395-020-00838-4.

In einer grosen Anzahl wissenschaftlicher Publikationen des letzten Jahrzehnts wurde die Inflammation als wesentlicher Kausalfaktor des Diabetes mellitus und der Atherosklerose identifiziert. Im Vergleich zum nicht an Diabetes leidenden Patienten fuhrt der durch Hyperglykamie und Insulinresistenz/-defizienz gekennzeichnete Diabetes mellitus zu einer verstarkten Aktivierung inflammatorischer Zytokine und Zellen und damit einer beschleunigten Atherosklerose. In dieser Ubersichtsarbeit werden die wesentlichen Faktoren der diabetesassoziierten Inflammation beschrieben. Im Weiteren wird auf mogliche antiinflammatorische Therapieansatze eingegangen, die moglicherweise das Risiko der diabetischen Makroangiopathie vermindern konnen. Die multifaktorielle Therapie des Diabetes mellitus konnte in Zukunft neben Blutzucker- und Cholesterinspiegel- sowie Bluthochdruckkontrolle durch eine antientzundliche Therapie erganzt werden.

Integrin-based therapeutics have garnered considerable interest in the medical treatment of inflammation. Integrins mediate the fast recruitment of monocytes and neutrophils to the site of inflammation, but are also required for host defense, limiting their therapeutic use. Here, we report a novel monoclonal antibody, anti-M7, that specifically blocks the interaction of the integrin Mac-1 with its pro-inflammatory ligand CD40L, while not interfering with alternative ligands. Anti-M7 selectively reduces leukocyte recruitment in vitro and in vivo. In contrast, conventional anti-Mac-1 therapy is not specific and blocks a broad repertoire of integrin functionality, inhibits phagocytosis, promotes apoptosis, and fuels a cytokine storm in vivo. Whereas conventional anti-integrin therapy potentiates bacterial sepsis, bacteremia, and mortality, a ligand-specific intervention with anti-M7 is protective. These findings deepen our understanding of ligand-specific integrin functions and open a path for a new field of ligand-targeted anti-integrin therapy to prevent inflammatory conditions., Integrin-based therapeutics could block inflammatory processes but they also impair host defence, limiting their usefulness. Here the authors report an anti-Mac1 antibody that blocks its interaction with pro-inflammatory ligand CD40L but not other ligands, and show that it can protect against sepsis in mice.

ZUSAMMENFASSUNGDer Diabetes mellitus ist mit einem erhöhten Risiko für kardiovaskuläre Erkankungen assoziiert. Die aktuellen Leitlinien der European Society of Cardiology (ESC) und der American Heart Association (AHA) sprechen sich gegen ein Routinescreening aller Diabetiker aus und empfehlen stattdessen abhängig von weiteren Risikofaktoren ein differenziertes Vorgehen. Hierbei können Biomarker, Kardio-CT, Stressbildgebung und Risikorechner helfen, jedoch hat bisher keines dieser Untersuchungen beim asymptomatischen Diabetiker in Studien eine Überlegenheit zeigt.

Background: Extracellular adenosine triphosphate (ATP) binds as a danger signal to purinergic receptor P2X 7 and promotes inflammasome assembly and interleukin-1β expression. We hypothesized a functional role of the signal axis ATP–P2X 7 in inflammasome activation and the chronic inflammation driving atherosclerosis. Methods: P2X 7 -competent and P2X 7 -deficient macrophages were isolated and stimulated with lipopolysaccharide, ATP, or both. To assess whether P2X 7 may have a role in atherosclerosis, P2X 7 expression was analyzed in aortic arches from low density lipoprotein receptor -/- mice consuming a high-cholesterol or chow diet. P2X 7 +/+ and P2X 7 −/− low density lipoprotein receptor −/− mice were fed a high-cholesterol diet to investigate the functional role of P2X 7 knockout in atherosclerosis. Human plaques were derived from carotid endarterectomy and stained against P2X 7 . Results: Lipopolysaccharide or ATP stimulation alone did not activate caspase 1 in isolated macrophages. However, priming with lipopolysaccharide, followed by stimulation with ATP, led to an activation of caspase 1 and interleukin-1β in P2X 7 -competent macrophages. In contrast, P2X 7 -deficient macrophages showed no activation of caspase 1 after sequential stimulation while still expressing a basal amount of interleukin-1β. P2X 7 receptor was higher expressed in murine atherosclerotic lesions, particularly by lesional macrophages. After 16 weeks of a high-cholesterol diet, P2X 7 -deficient mice showed smaller atherosclerotic lesions than P2X 7 -competent mice (0.162 cm 2 ±0.023 [n=9], P2X 7 −/− low density lipoprotein receptor −/− : 0.084 cm 2 ±0.01 [n=11], P =0.004) with a reduced amount of lesional macrophages. In accord with our in vitro findings, lesional caspase 1 activity was abolished in P2X 7 −/− mice. In addition, intravital microscopy revealed reduced leukocyte rolling and adhesion in P2X 7 -deficient mice. Last, we observe increased P2X 7 expression in human atherosclerotic lesions, suggesting that our findings in mice are relevant for human disease. Conclusions: P2X 7 deficiency resolved plaque inflammation by inhibition of lesional inflammasome activation and reduced experimental atherosclerosis. Therefore, P2X 7 represents an interesting potential new target to combat atherosclerosis.

Diabetes worsens atherosclerosis progression and leads to a defect in repair of arteries after cholesterol reduction, a process termed regression. Empagliflozin reduces blood glucose levels via inhibition of the sodium glucose cotransporter 2 (SGLT-2) in the kidney and has been shown to lead to a marked reduction in cardiovascular events in humans. To determine whether glucose lowering by empagliflozin accelerates atherosclerosis regression in a mouse model, male C57BL/6J mice were treated intraperitoneally with LDLR- and SRB1- antisense oligonucleotides and fed a high cholesterol diet for 16 weeks to induce severe hypercholesterolemia and atherosclerosis progression. At week 14 all mice were rendered diabetic by streptozotocin (STZ) injections. At week 16 a baseline group was sacrificed and displayed substantial atherosclerosis of the aortic root. In the remaining mice, plasma cholesterol was lowered by switching to chow diet and treatment with LDLR sense oligonucleotides to induce atherosclerosis regression. These mice then received either empagliflozin or vehicle for three weeks. Atherosclerotic plaques in the empagliflozin treated mice were significantly smaller, showed decreased lipid and CD68+ macrophage content, as well as greater collagen content. Proliferation of plaque resident macrophages and leukocyte adhesion to the vascular wall were significantly decreased in empagliflozin-treated mice. In summary, plasma glucose lowering by empagliflozin improves plaque regression in diabetic mice.

Introduction Many clinical and experimental observations have established an association between visceral obesity and chronic adipose tissue inflammation. Potent pro-inflammatory mediators such as TNFα, CD40 and IL-1β are regulated by Tumor necrosis factor (TNF) receptor-associated factors (TRAFs). TRAF5 deficiency accelerates atherogenesis in mice by increasing inflammatory leukocyte recruitment. Since inflammatory cell invasion is also a prerequisite of adipose tissue inflammation, we tested the hypothesis that deficient TRAF5 signaling aggravates adipose tissue inflammation and its metabolic complications in a murine diet-induced obesity (DIO) model. Purpose We aimed to clarify the role of TRAF5 in adipose tissue inflammation and metabolic syndrome. Methods TRAF5−/− mice and gender- and age-matched wild-type (WT) mice consumed a high fat diet (HFD, 45%kcal from fat) or a matched low-fat diet (LFD, 10%kcal from fat) for 18 weeks to induce DIO and adipose tissue inflammation. All mice were then subjected to subsequent analysis, including glucose and insulin tolerance testing, body composition assessment by MRI imaging, flow cytometry, gene expression of different tissues, plasma analysis and histology. Finally, we studied if TRAF5 expression was associated with metabolic syndrome in humans by analyzing plasma and adipocytes samples from 62 patients of the Tumor-Necrosis-Factor Receptor Associated in Cardiovascular Risk Study (TRAFICS). Results TRAF5 expression was significantly attenuated in isolated WT-adipocytes and WT-macrophages after 18 weeks of HFD compared to LFD-fed controls. TRAF5−/− mice on HFD gained significantly more weight compared to TRAF5-competent mice and showed an aggravated metabolic phenotype, including impaired insulin tolerance, hyperinsulinemia and increased fasting glucose plasma levels. The weight gain in TRAF5−/− mice was attributable to a significant increase in adipose tissue and liver weight. Further analysis of the visceral adipose tissue revealed enhanced macrophage accumulation and increased pro-inflammatory CD11c+ subset polarization in HFD-fed TRAF5−/− mice. In line with an increased migratory capacity of inflammatory cells, we observed enhanced peritoneal invasion of leukocytes and subsets in TRAF5−/− mice. Accordingly, TRAF5 deficiency increased inflammatory cytokine expression and ameliorated parameters of insulin sensitivity in adipose tissue. Finally, patients with metabolic syndrome displayed decreased TRAF5 expression in blood and adipocytes compared to humans without metabolic syndrome. Conclusion We show that genetic deficiency of TRAF5 aggravates metabolic syndrome in murine diet-induced obesity. Enhanced accumulation of leukocytes subsets in adipose tissue serves as the likely mechanism. We conclude that TRAF5 signaling properties may favorably affect metabolic disease. Acknowledgement/Funding Forschungskommission Medizinische Fakultät Universität Freiburg, MOTI-VATE Promotionskolleg der Medizinischen Fakultät Freiburg (EKFS)

Background Inflammation drives atherosclerosis and its complications. Anti-inflammatory therapy with interleukin 1 beta (IL-1β) antibody reduces cardiovascular events in patients with elevated high-sensitive C-reactive protein (hsCRP). This study aims to identify the share of patients with coronary heart disease (CHD) and residual inflammation who may benefit from anti-inflammatory therapy. Methods hsCRP and low-density lipoprotein (LDL) levels were determined in 2741 all-comers admitted to the cardiological ward of our tertiary referral hospital between June 2016 and June 2018. Patients without CHD, with acute coronary syndrome, chronic or recurrent systemic infection, use of immunosuppressant or anti-inflammatory agents, chronic inflammatory diseases, chemotherapy, terminal organ failure, traumatic injury and pregnancy were excluded. Results 856 patients with stable CHD were included. 42.7% of those had elevated hsCRP ≥ 2 mg/l. Within the group of patients with LDL-cholesterol

Sterile inflammation of visceral fat, provoked by dying adipocytes, links the metabolic syndrome to cardiovascular disease. Danger-associated molecular patterns, such as adenosine triphosphate (ATP), are released by activated or dying cells and orchestrate leukocyte infiltration and inflammation via the purinergic receptor P2Y2. The gene expression of ATP receptor P2Y2 did not change in several tissues in the course of obesity, but was increased within epididymal fat. Adipose tissue from P2Y 2 −/− mice consuming high-fat diet (HFD) contained less crown-like structures with a reduced frequency of adipose tissue macrophages (ATMs). This was likely due to decreased leukocyte migration because of missing VCAM-1 exposition on P2Y2 deficient hypertrophic adipose tissue endothelial cells. Accordingly, P2Y 2 −/− mice showed blunted traits of the metabolic syndrome: they gained less weight compared to P2Y 2 +/+ controls, while intake of food and movement behaviour remained unchanged. Liver and adipose tissue were smaller in P2Y 2 −/− animals. Insulin tolerance testing (ITT) performed in obese P2Y 2 −/− mice revealed a better insulin sensitivity as well as lower plasma C-peptide and cholesterol levels. We demonstrate that interfering with somatic P2Y2 signalling prevents excessive immune cell deposition in diet-induced obesity (DIO), both attenuating adipose tissue inflammation and ameliorating the metabolic phenotype. Thus, blocking the P2Y2 cascade may be a promising strategy to limit metabolic disease and its sequelae.

Rationale: The coincidence of inflammation and metabolic derangements in obese adipose tissue has sparked the concept of met-inflammation. Previous observations, however, suggest that inflammatory pathways may not ultimately cause dysmetabolism. Objective: We have revisited the relationship between inflammation and metabolism by testing the role of TRAF (tumor necrosis receptor-associated factor)-1, an inhibitory adapter of inflammatory signaling of TNF (tumor necrosis factor)-a, IL (interleukin)-1ß, and TLRs (toll-like receptors). Methods and Results: Mice defcient for TRAF-1, which is expressed in obese adipocytes and adipose tissue lymphocytes, caused an expected hyperinflammatory phenotype in adipose tissue with enhanced adipokine and chemokine expression, increased leukocyte accumulation, and potentiated proinflammatory signaling in macrophages and adipocytes in a mouse model of diet-induced obesity. Unexpectedly, TRAF-1-/-mice were protected from metabolic derangements and adipocyte growth, failed to gain weight, and showed improved insulin resistance-an effect caused by increased lipid breakdown in adipocytes and UCP (uncoupling protein)-1-enabled thermogenesis. TRAF-1-dependent catabolic and proinflammatory cues were synergistically driven by ß3-adrenergic and inflammatory signaling and required the presence of both TRAF-1-defcient adipocytes and macrophages. In human obesity, TRAF-1-dependent genes were upregulated. Conclusions: Enhancing TRAF-1-dependent inflammatory pathways in a gain-of-function approach protected from metabolic derangements in diet-induced obesity. These fndings identify TRAF-1 as a regulator of dysmetabolism in mice and humans and question the pathogenic role of chronic inflammation in metabolism. Fil: Michel, Nathaly Anto. University of Freiburg. University Medical Center; Alemania Fil: Colberg, Christian. University of Freiburg. University Medical Center; Alemania Fil: Buscher, Konrad. La Jolla Institute for Allergy and Immunology; Estados Unidos Fil: Sommer, Björn. Universitat Erlangen-Nuremberg; Alemania Fil: Pramod, Akula Bala. La Jolla Institute for Allergy and Immunology; Estados Unidos Fil: Ehinger, Erik. La Jolla Institute for Allergy and Immunology; Estados Unidos Fil: Dufner, Bianca. University of Freiburg. University Medical Center; Alemania Fil: Hoppe, Natalie. University of Freiburg. University Medical Center; Alemania Fil: Pfeiffer, Katharina. University of Freiburg. University Medical Center; Alemania Fil: Marchini, Timoteo Oscar. University of Freiburg. University Medical Center; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentina Fil: Willecke, Florian. University of Freiburg. University Medical Center; Alemania Fil: Stachon, Peter. University of Freiburg. University Medical Center; Alemania Fil: Hilgendorf, Ingo. University of Freiburg. University Medical Center; Alemania Fil: Heidt, Timo. University of Freiburg. University Medical Center; Alemania Fil: Von Zur Muhlen, Constantin. University of Freiburg. University Medical Center; Alemania Fil: Von Elverfeldt, Dominik. University of Freiburg. University Medical Center; Alemania Fil: Pfeifer, Dietmar. University of Freiburg; Alemania Fil: Schüle, Roland. University of Freiburg; Alemania Fil: Kintscher, Ulrich. University of Freiburg; Alemania Fil: Brachs, Sebastian. Center For Cardiovascular Research; Alemania Fil: Ley, Klaus. La Jolla Institute for Allergy and Immunology; Estados Unidos Fil: Bode, Christoph. University of Freiburg. University Medical Center; Alemania Fil: Zirlik, Andreas. University of Freiburg. University Medical Center; Alemania Fil: Wolf, Dennis. La Jolla Institute for Allergy and Immunology; Estados Unidos

Sterile inflammation of visceral fat, provoked by dying adipocytes, links the metabolic syndrome to cardiovascular disease. Danger-associated molecular patterns, such as adenosine triphosphate (ATP), are released by activated or dying cells and orchestrate leukocyte infiltration and inflammation via the purinergic receptor P2Y

Movement of circulating fatty acids (FAs) to parenchymal cells requires their transfer across the endothelial cell (EC) barrier. The multiligand receptor cluster of differentiation 36 (CD36) facilitates tissue FA uptake and is expressed in ECs and parenchymal cells such as myocytes and adipocytes. Whether tissue uptake of FAs is dependent on EC or parenchymal cell CD36, or both, is unknown. Using a cell-specific deletion approach, we show that EC, but not parenchymal cell, CD36 deletion increased fasting plasma FAs and postprandial triglycerides. EC-Cd36-KO mice had reduced uptake of radiolabeled long-chain FAs into heart, skeletal muscle, and brown adipose tissue; these uptake studies were replicated using [11C]palmitate PET scans. High-fat diet-fed EC-CD36-deficient mice had improved glucose tolerance and insulin sensitivity. Both EC and cardiomyocyte (CM) deletion of CD36 reduced heart lipid droplet accumulation after fasting, but CM deletion did not affect heart glucose or FA uptake. Expression in the heart of several genes modulating glucose metabolism and insulin action increased with EC-CD36 deletion but decreased with CM deletion. In conclusion, EC CD36 acts as a gatekeeper for parenchymal cell FA uptake, with important downstream effects on glucose utilization and insulin action.

Introduction: Inflammation drives atherosclerosis and its complications. Thus, CANTOS as the first anti-inflammatory outcome trial in this population produced positive results. However, it is unclear how many patients qualify for an anti-inflammatory therapy in everyday practice. Hypothesis: This study analyzes how many patients with coronary heart disease (CHD) on guideline conform therapy show an increased residual inflammatory as opposed to an increased residual lipid risk in order to define the need for an anti-inflammatory treatment in a real world setting. Methods: High sensitive C-reactive protein (hsCRP) and low density lipoprotein (LDL) levels were determined in 700 all comer patients between June 2016 and June 2017 in our center. Patients lacking CHD, such with chronic-inflammatory diseases, acute inflammation, and on immunosuppressive medication were excluded. Patients were divided in the following groups: elevated hsCRP (≥2mg/dl), normal hsCRP ( Results: From 700 patients 221 fulfilled the inclusion and exclusion criteria. HsCRP was increased in 45% of these patients. Patients with on target LDL Levels showed lower hsCRP concentrations than those with off target values of LDL confirming a positive association between both (1,92mg/dl vs. 3,15mg/dl, p=0.005). However, despite guideline-conform LDL-control 34% of patients with a LDL-cholesterol Conclusions: A substantial part of patients with CHD shares a residual inflammatory risk defining a need for an anti-inflammatory therapy. Residual inflammation is particularly prevalent in patients with heart failure and diabetes.

Rationale: Animal models have been used to explore factors that regulate atherosclerosis. More recently, they have been used to study the factors that promote loss of macrophages and reduction in lesion size after lowering of plasma cholesterol levels. However, current animal models of atherosclerosis regression require challenging surgeries, time-consuming breeding strategies, and methods that block liver lipoprotein secretion. Objective: We sought to develop a more direct or time-effective method to create and then reverse hypercholesterolemia and atherosclerosis via transient knockdown of the hepatic LDLR (low-density lipoprotein receptor) followed by its rapid restoration. Methods and Results: We used antisense oligonucleotides directed to LDLR mRNA to create hypercholesterolemia in wild-type C57BL/6 mice fed an atherogenic diet. This led to the development of lesions in the aortic root, aortic arch, and brachiocephalic artery. Use of a sense oligonucleotide replicating the targeted sequence region of the LDLR mRNA rapidly reduced circulating cholesterol levels because of recovery of hepatic LDLR expression. This led to a decrease in macrophages within the aortic root plaques and brachiocephalic artery, that is, regression of inflammatory cell content, after a period of 2 to 3 weeks. Conclusions: We have developed an inducible and reversible hepatic LDLR knockdown mouse model of atherosclerosis regression. Although cholesterol reduction decreased early en face lesions in the aortic arches, macrophage area was reduced in both early and late lesions within the aortic sinus after reversal of hypercholesterolemia. Our model circumvents many of the challenges associated with current mouse models of regression. The use of this technology will potentially expedite studies of atherosclerosis and regression without use of mice with genetic defects in lipid metabolism.

Extracellular adenosine triphosphate (ATP) binds as a danger signal to purinergic receptor P2XP2XLipopolysaccharide or ATP stimulation alone did not activate caspase 1 in isolated macrophages. However, priming with lipopolysaccharide, followed by stimulation with ATP, led to an activation of caspase 1 and interleukin-1β in P2XP2X

Diabetes mellitus is a multifactorial disease that substanially increases the risk for cardiovascular disease. Increased platelet activation has been indentified as a major factor contributing to increased CVD risk in diabetes by enhancing platelet adhesion and aggregation. The exact contribution of factors such as insulin resistance, hyperglycemia, inflammation, and hyperlipidemia is still under investigation. Here, we review these factors and how they contribute to platelet hyperreactivity in patients with diabetes mellitus and highlight possible pharmacological interventions.

Objective - A solid body of evidence supports a role of extracellular ATP and its P2 receptors in innate and adaptive immunity. It promotes inflammation as a danger signal in various chronic inflammatory diseases. Thus, we hypothesize contribution of extracellular ATP and its receptor P2Y 2 in vascular inflammation and atherosclerosis. Approach and Results - Extracellular ATP induced leukocyte rolling, adhesion, and migration in vivo as assessed by intravital microscopy and in sterile peritonitis. To test the role of extracellular ATP in atherosclerosis, ATP or saline as control was injected intraperitoneally 3× a week in low-density lipoprotein receptor -/- mice consuming high cholesterol diet. Atherosclerosis significantly increased after 16 weeks in ATP-treated mice (n=13; control group, 0.26 mm2; ATP group, 0.33 mm2; P=0.01). To gain into the role of ATP-receptor P2Y 2 in ATP-induced leukocyte recruitment, ATP was administered systemically in P2Y 2 -deficient or P2Y 2 -competent mice. In P2Y 2 -deficient mice, the ATP-induced leukocyte adhesion was significantly reduced as assessed by intravital microscopy. P2Y 2 expression in atherosclerosis was measured by real-time polymerase chain reaction and immunohistochemistry and demonstrates an increased expression mainly caused by influx of P2Y 2 -expressing macrophages. To investigate the functional role of P2Y 2 in atherogenesis, P2Y 2 -deficient low-density lipoprotein receptor -/- mice consumed high cholesterol diet. After 16 weeks, P2Y 2 -deficient mice showed significantly reduced atherosclerotic lesions with decreased macrophages compared with P2Y 2 -competent mice (n=11; aortic arch: control group, 0.25 mm 2; P2Y 2 -deficient, 0.14 mm2; P=0.04). Mechanistically, atherosclerotic lesions from P2Y 2 -deficient mice expressed less vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 RNA. Conclusions - We show that extracellular ATP induces vascular inflammation and atherosclerosis via activation of P2Y 2. Fil: Stachon, Peter. Albert Ludwigs University of Freiburg; Alemania Fil: Geis, Serjosha. Albert Ludwigs University of Freiburg; Alemania Fil: Peikert, Alexander. Albert Ludwigs University of Freiburg; Alemania Fil: Heidenreich, Adrian. Albert Ludwigs University of Freiburg; Alemania Fil: Anto Michel, Nathaly. Albert Ludwigs University of Freiburg; Alemania Fil: Üenal, Fatih. Albert Ludwigs University of Freiburg; Alemania Fil: Hoppe, Natalie. Albert Ludwigs University of Freiburg; Alemania Fil: Dufner, Bianca. Albert Ludwigs University of Freiburg; Alemania Fil: Schulte, Lisa. Albert Ludwigs University of Freiburg; Alemania Fil: Marchini, Timoteo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentina Fil: Cicko, Sanja. Albert Ludwigs University of Freiburg; Alemania Fil: Korcan Ayata, Cemil. Albert Ludwigs University of Freiburg; Alemania Fil: Zech, Andreas. Albert Ludwigs University of Freiburg; Alemania Fil: Wolf, Dennis. Albert Ludwigs University of Freiburg; Alemania Fil: Hilgendorf, Ingo. Albert Ludwigs University of Freiburg; Alemania Fil: Willecke, Florian. Albert Ludwigs University of Freiburg; Alemania Fil: Reinöhl, Jochen. Albert Ludwigs University of Freiburg; Alemania Fil: von zur Muhlen, Constantin. Albert Ludwigs University of Freiburg; Alemania Fil: Bode, Christoph. Albert Ludwigs University of Freiburg; Alemania Fil: Idzko, Marco. Albert Ludwigs University of Freiburg; Alemania Fil: Zirlik, Andreas. Albert Ludwigs University of Freiburg; Alemania

Rationale: CD40L figures prominently in chronic inflammatory diseases such as atherosclerosis. However, since CD40L potently regulates immune function and hemostasis by interaction with CD40 receptor and the platelet integrin GPIIb/IIIa, its global inhibition compromises host defense and generated thromboembolic complications in clinical trials. We recently reported that CD40L mediates atherogenesis independently of CD40 and proposed Mac-1 as an alternate receptor. Objective: Here, we molecularly characterized the CD40L-Mac-1 interaction and tested whether its selective inhibition by a small peptide modulates inflammation and atherogenesis in vivo. Methods and Results: CD40L concentration-dependently bound to Mac-1 I-domain in solid phase binding assays, and a high-affinity interaction was revealed by surface-plasmon-resonance analysis. We identified the motif EQLKKSKTL, an exposed loop between the α1 helix and the β-sheet B, on Mac-1 as binding site for CD40L. A linear peptide mimicking this sequence, M7, specifically inhibited the interaction of CD40L and Mac-1. A cyclisized version optimized for in vivo use, cM7, decreased peritoneal inflammation and inflammatory cell recruitment in vivo. Finally, LDLr -/- mice treated with intraperitoneal injections of cM7 developed smaller, less inflamed atherosclerotic lesions featuring characteristics of stability. However, cM7 did not interfere with CD40L-CD40 binding in vitro and CD40L-GPIIb/IIIa-mediated thrombus formation in vivo. Conclusions: We present the novel finding that CD40L binds to the EQLKKSKTL motif on Mac-1 mediating leukocyte recruitment and atherogenesis. Specific inhibition of CD40L-Mac-1 binding may represent an attractive anti-inflammatory treatment strategy for atherosclerosis and other inflammatory conditions, potentially avoiding the unwanted immunologic and thrombotic effects of global inhibition of CD40L. Fil: Wolf, Dennis. Albert-Ludwigs-Universität Freiburg; Alemania. Baker IDI Heart and Diabetes Institute; Australia Fil: Hohmann, Jan David. Baker IDI Heart and Diabetes Institute; Australia Fil: Wiedemann, Ansgar. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Bledzka, Kamila. Cleveland Clinic. Department of Molecular Cardiology; Estados Unidos Fil: Blankenbach, Hermann. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Marchini, Timoteo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentina. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Gutte, Katharina. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Zeschky, Katharina. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Bassler, Nicole. Baker IDI Heart and Diabetes Institute; Australia Fil: Hoppe, Natalie. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Rodriguez, Alexandra Ortiz. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Herr, Nadine. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Hilgendorf, Ingo. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Stachon, Peter. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Willecke, Florian. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Duerschmied, Daniel. Albert-Ludwigs-Universität Freiburg; Alemania Fil: von zur Muhlen, Constantin. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Soloviev, Dmitry A.. Cleveland Clinic. Department of Molecular Cardiology; Estados Unidos Fil: Zhang, Li. University of Maryland; Estados Unidos Fil: Bode, Christoph. Albert-Ludwigs-Universität Freiburg; Alemania Fil: Plow, Edward F.. Cleveland Clinic. Department of Molecular Cardiology; Estados Unidos Fil: Libby, Peter. Harvard Medical School; Estados Unidos Fil: Peter, Karlheinz. Baker IDI Heart and Diabetes Institute; Australia Fil: Zirlik, Andreas. Albert-Ludwigs-Universität Freiburg; Alemania

Objective— Spleen tyrosine kinase (SYK) has come into focus as a potential therapeutic target in chronic inflammatory diseases, such as rheumatoid arthritis and asthma, as well as in B-cell lymphomas. SYK has also been involved in the signaling of immunoreceptors, cytokine receptors, and integrins. We therefore hypothesized that inhibition of SYK attenuates the inflammatory process underlying atherosclerosis and reduces plaque development. Methods and Results— Low-density lipoprotein receptor–deficient mice consuming a high-cholesterol diet supplemented with 2 doses of the orally available SYK inhibitor fostamatinib for 16 weeks showed a dose-dependent reduction in atherosclerotic lesion size by up to 59±6% compared with the respective controls. Lesions of fostamatinib-treated animals contained fewer macrophages but more smooth muscle cells and collagen—characteristics associated with more stable plaques in humans. Mechanistically, fostamatinib attenuated adhesion and migration of inflammatory cells and limited macrophage survival. Furthermore, fostamatinib normalized high-cholesterol diet –induced monocytosis and inflammatory gene expression. Conclusion— We present the novel finding that the SYK inhibitor fostamatinib attenuates atherogenesis in mice. Our data identify SYK inhibition as a potentially fruitful antiinflammatory therapeutic strategy in atherosclerosis.

SummaryCD40L figures prominently in atherogenesis. Recent data demonstrate elevated levels of sCD40L in the serum of patients with the metabolic syndrome (MS). This study investigated the role of CD40L in pro-inflammatory gene expression and cellular differentiation in adipose tissue to obtain insight into mechanisms linking the MS with atherosclerosis. Human adipocytes and preadipocytes expressed CD40 but not CD40L. Stimulation with recombinant CD40L or membranes over-expressing CD40L induced a time- and dose-dependent expression of IL-6, MCP-1, IL-8, and PAI-1. Supernatants of CD40L-stimulated adipose cells activated endothelial cells, suggesting a systemic functional relevance of our findings. Neutralising antibodies against CD40L attenuated these effects substantially. Signalling studies revealed the involvement of mitogen-activated protein kinases and NFκB. Furthermore, stimulation with CD40L resulted in enhanced activation of C/EBPα and PPARγ and promoted adipogenesis of preadipose cells in the presence and absence of standard adipogenic conditions. Finally, patients suffering from the metabolic syndrome with high levels of sCD40L also displayed high levels of IL-6, in line with the concept that CD40L may induce the expression of inflammatory cytokines in vivo in this population. Our data reveal potent metabolic functions of CD40L aside from its known pivotal pro-inflammatory role within plaques. Our data suggest that CD40L may mediate risk at the interface of metabolic and atherothrombotic disease.

SummaryPlasminogen activator inhibitor type-1 (PAI-1), an established marker and mediator of cardiovascular risk, is produced extensively in adipose tissue. Fibrates are hypolipidemic peroxisome proliferator activated receptor-alpha (PPARα) agonists. Recent laboratory and clinical observations indicate that they are also anti-atherosclerotic. Mechanisms responsible, however, remain to be fully understood. The present study was designed to elucidate modulation of PAI-1 expression in adipose cells by fibrates as a potential mechanism. Expression of PPARα was verified by PCR, immunohistochemistry, and Western blotting. In cultured preadipocytes and adipocytes gemfibrozil and fenofibrate significantly reduced PAI-1 protein expression by up to 55 ± 5% and 34 ± 4% under basal conditions and up to 56 ± 6% and 31 ± 6% under conditions of stimulation of the cells with 40 pM trans-Keywords forming growth factor (TGF)β, respectively. Quantification of mRNA showed that the gemfibrozil-induced effect was at least in part regulated at the transcriptional level. Incubations with non-fibrate PPARα agonists showed similar reductions in PAI-1 expression. The decrease in PAI-1 expression induced by gemfibrozil was inhibited by MK886, a PPARα inhibitor. Furthermore, preadipocytes isolated from PPARα-deficient mice produced significantly more PAI-1 than those from wild-type mice upon stimulation with TGFβ. Finally, fenofibrate reduced PAI-1 expression both in plasma and adipose tissue of hyperlipidemic mice. Our data support the view that PPARα activation down-regulates PAI-expression in adipose cells that may contribute in part to the reduction in cardiovascular mortality seen with fibrates in clinical trials.

Macrophages in the arterial intima sustain chronic inflammation during atherogenesis. Under hypercholesterolemic conditions murine Ly6Chigh monocytes surge in the blood and spleen, infiltrate nascent atherosclerotic plaques, and differentiate into macrophages that proliferate locally as disease progresses. Spleen tyrosine kinase (SYK) may participate in downstream signaling of various receptors that mediate these processes. We tested the effect of the SYK inhibitor fostamatinib on hypercholesterolemia-associated myelopoiesis and plaque formation in Apoe−/− mice during early and established atherosclerosis. Mice consuming a high cholesterol diet supplemented with fostamatinib for 8 weeks developed less atherosclerosis. Histologic and flow cytometric analysis of aortic tissue showed that fostamatinib reduced the content of Ly6Chigh monocytes and macrophages. SYK inhibition limited Ly6Chigh monocytosis through interference with GM-CSF/IL-3 stimulated myelopoiesis, attenuated cell adhesion to the intimal surface, and blocked M-CSF stimulated monocyte to macrophage differentiation. In Apoe−/− mice with established atherosclerosis, however, fostamatinib treatment did not limit macrophage accumulation or lesion progression despite a significant reduction in blood monocyte counts, as lesional macrophages continued to proliferate. Thus, inhibition of hypercholesterolemia-associated monocytosis, monocyte infiltration, and differentiation by SYK antagonism attenuates early atherogenesis but not established disease when local macrophage proliferation dominates lesion progression. Electronic supplementary material The online version of this article (doi:10.1007/s00395-016-0535-8) contains supplementary material, which is available to authorized users.

Rationale: Fatty acid oxidation is transcriptionally regulated by peroxisome proliferator–activated receptor (PPAR)α and under normal conditions accounts for 70% of cardiac ATP content. Reduced Ppara expression during sepsis and heart failure leads to reduced fatty acid oxidation and myocardial energy deficiency. Many of the transcriptional regulators of Ppara are unknown. Objective: To determine the role of Krüppel-like factor 5 (KLF5) in transcriptional regulation of Ppara . Methods and Results: We discovered that KLF5 activates Ppara gene expression via direct promoter binding. This is blocked in hearts of septic mice by c-Jun, which binds an overlapping site on the Ppara promoter and reduces transcription. We generated cardiac myocyte–specific Klf5 knockout mice that showed reduced expression of cardiac Ppara and its downstream fatty acid metabolism–related targets. These changes were associated with reduced cardiac fatty acid oxidation, ATP levels, increased triglyceride accumulation, and cardiac dysfunction. Diabetic mice showed parallel changes in cardiac Klf5 and Ppara expression levels. Conclusions: Cardiac myocyte KLF5 is a transcriptional regulator of Ppara and cardiac energetics.

Circulating fatty acids must cross the endothelial cell (EC) barrier to supply cardiomyocytes (CM). How this occurs is unknown. Cluster of differentiation (CD) 36 is a membrane associated protein whose total body deletion leads to reduced uptake of non-esterified fatty acids by heart, skeletal muscle and adipose tissue. To determine the contribution of EC versus CM CD36 in heart lipid uptake, we floxed CD36 and created EC- and CM-specific knockout (KO) mice. CD36 mRNA was reduced >50% in the heart, lung and skeletal muscle of EC-CD36 KO mice; CM-CD36 KO mice also had an ~50% reduction of CD36 mRNA levels in the heart. Both CM- and EC-specific CD36 ablation altered heart mRNA levels of glucose transport and oxidation genes (e.g. Glut1 ~2-fold increased, PDK4 ~0.5-fold decreased); these changes were similar to those found in mice with total body CD36 deletion. Loss of EC-CD36 led to increased plasma free fatty acid levels and prevented heart lipid droplet accumulation after an overnight fast (assessed by EM and oil red O staining). Lipid droplet accumulation was less affected in CM-CD36 KO hearts. To quantify the role of CD36 in the uptake of short chain vs. long chain fatty acids we simultaneously injected mice with radiolabeled [14C]hexanoic acid and [3H]oleic acid. Compared to both floxed-CD36 and CM-CD36 KO mice, plasma clearance of oleic acid was significantly delayed, and heart and quadriceps muscle uptake of oleic acid was reduced >50% in EC-CD36 KO and total-CD36 KO mice. Hexanoic acid uptake was not decreased by either deletion. Therefore, CD36 in EC is needed for the accumulation of long chain fatty acids in the heart and appears to be required for movement of fatty acids across the EC barrier.

Krüppel-like factors (KLF) affect metabolism. Lipopolysaccharide-induced sepsis reduced cardiac PPARα and increased KLF5 (8-fold) more than any cardiac KLF isoform detected by whole genome microarray analysis. In silico analysis of ppara gene promoter predicted two KLF5 binding sites that overlap with c-Jun (AP-1) binding sites: -792/-772 bp and -719/-698 bp. Infection of a mouse cardiomyocyte cell line (HL-1) with adenovirus expressing constitutively active c-Jun reduced, while Ad-KLF5 increased PPARα mRNA in a dose-dependent manner. Chromatin immunoprecipitation (ChIP) showed that c-Jun binds both -792/-772 bp and -719/-698 on ppara promoter while KLF5 binds on -792/-772 bp. ChIP on LPS-treated HL-1 cells showed that c-Jun binding on -792/-772 bp prohibits KLF5 binding. We generated a cardiomyocyte-specific KLF5 knockout mouse (αMHC-KLF5-/-), which had 50% normal cardiac function. Cardiomyocyte-specific KLF5 ablation reduced PPARα (50%) and several fatty acid metabolism-associated genes such as CD36 (40%), LpL (20%), PGC1α (45%), AOX (28%) and Cpt1 (45%). As PPARα regulates cardiac fatty acid metabolism, we tested whether cardiac KLF5 is modulated in diabetes, when cardiac PPARα and lipid changes occur. I.p. injection of streptozotocin (STZ) in C57BL/6 mice increased plasma glucose (2.9-fold) and reduced cardiac KLF5 and PPARα gene expression; similar to STZ-treated rats but unlike what had been found in a different mouse strain (C57BL/6 x DBA2) treated with STZ. Treatment of HL-1 cells with increased glucose-containing medium (1 mg/ml) reduced KLF5 (80%) and PPARα (65%), as well as fatty acid metabolism markers, such as AOX (85%), Cpt1β (70%), LCAD (80%) and VLCAD (85%). On the other hand GLUT1 and GLUT4 were increased (30% and 20%) and PDK4 was reduced (65%) indicating increased glucose utilization. A model of non-insulin dependent hyperglycemia (ob/ob mice) had reduced cardiac KLF5 (60%) and PPARα (65%). Correction of hyperglycemia in STZ-treated C57BL/6 mice by pharmacological (dapagliflozin) or antisense oligonucleotide inhibition of kidney’s sodium glucose transporter 2 (SGLT2), restored KLF5 and PPARα gene expression. Thus, KLF5 is a transcriptional regulator of cardiac PPARα that is driven by changes in plasma glucose levels

Objective— Diabetic hypertriglyceridemia is thought to be primarily driven by increased hepatic de novo lipogenesis. However, experiments in animal models indicated that insulin deficiency should decrease hepatic de novo lipogenesis and reduce plasma triglyceride levels. Approach and Results— To address the discrepancy between human data and genetically altered mouse models, we investigated whether insulin-deficient diabetic mice had triglyceride changes that resemble those in diabetic humans. Streptozotocin-induced insulin deficiency increased plasma triglyceride levels in mice. Contrary to the mouse models with impaired hepatic insulin receptor signaling, insulin deficiency did not reduce hepatic triglyceride secretion and de novo lipogenesis-related gene expression. Diabetic mice had a marked decrease in postprandial triglycerides clearance, which was associated with decreased lipoprotein lipase and peroxisome proliferator-activated receptor α mRNA levels in peripheral tissues and decreased lipoprotein lipase activity in skeletal muscle, heart, and brown adipose tissue. Diabetic heterozygous lipoprotein lipase knockout mice had markedly elevated fasting plasma triglyceride levels and prolonged postprandial triglycerides clearance. Conclusions— Insulin deficiency causes hypertriglyceridemia by decreasing peripheral lipolysis and not by an increase in hepatic triglycerides production and secretion.

Background— Costimulatory cascades such as the CD40L-CD40 dyad enhance immune cell activation and inflammation during atherosclerosis. Here, we tested the hypothesis that CD40 directly modulates traits of the metabolic syndrome in diet-induced obesity in mice. Methods and Results— To induce the metabolic syndrome, wild-type or CD40 −/− mice consumed a high-fat diet for 20 weeks. Unexpectedly, CD40 −/− mice exhibited increased weight gain, impaired insulin secretion, augmented accumulation of inflammatory cells in adipose tissue, and enhanced proinflammatory gene expression. This proinflammatory and adverse metabolic phenotype could be transplanted into wild-type mice by reconstitution with CD40-deficient lymphocytes, indicating a major role for CD40 in T or B cells in this context. Conversely, therapeutic activation of CD40 signaling by the stimulating antibody FGK45 abolished further weight gain during the study, lowered glucose levels, improved insulin sensitivity, and suppressed adipose tissue inflammation. Mechanistically, CD40 activation decreased the expression of proinflammatory cytokines in T cells but not in B cells or macrophages. Finally, repopulation of lymphocyte-free Rag1 −/− mice with CD40 −/− T cells provoked dysmetabolism and inflammation, corroborating a protective role of CD40 on T cells in the metabolic syndrome. Finally, levels of soluble CD40 showed a positive association with obesity in humans, suggesting clinical relevance of our findings. Conclusions— We present the surprising finding that CD40 deficiency on T cells aggravates whereas activation of CD40 signaling improves adipose tissue inflammation and its metabolic complications. Therefore, positive modulation of the CD40 pathway might describe a novel therapeutic concept against cardiometabolic disease.

Rupture of the ventricular myocardium is an often lethal complication after myocardial infarction. Due to the dramatic hemodynamics and the short time frame between ventricular rupture and surgical closure of the defect, additional therapeutic strategies are needed. Here we report the successful therapy of ventricular rupture by percutaneous intrapericardial instillation of fibrin glue in a 72-year-old male patient with postinfarct angina secondary to anterior myocardial infarction.

BackgroundAdipose tissue inflammation fuels the metabolic syndrome. We recently reported that CD40L--an established marker and mediator of cardiovascular disease--induces inflammatory cytokine production in adipose cells in vitro. Here, we tested the hypothesis that CD40L deficiency modulates adipose tissue inflammation in vivo.Methodology/principal findingsWT or CD40L(-/-) mice consumed a high fat diet (HFD) for 20 weeks. Inflammatory cell recruitment was impaired in mice lacking CD40L as shown by a decrease of adipose tissue macrophages, B-cells, and an increase in protective T-regulatory cells. Mechanistically, CD40L-deficient mice expressed significantly lower levels of the pro-inflammatory chemokine MCP-1 both, locally in adipose tissue and systemically in plasma. Moreover, levels of pro-inflammatory IgG-antibodies against oxidized lipids were reduced in CD40L(-/-) mice. Also, circulating low-density lipoproteins and insulin levels were lower in CD40L(-/-) mice. However, CD40L(-/-) mice consuming HFD were not protected from the onset of diet-induced obesity (DIO), insulin resistance, and hepatic steatosis, suggesting that CD40L selectively limits the inflammatory features of diet-induced obesity rather than its metabolic phenotype. Interestingly, CD40L(-/-) mice consuming a low fat diet (LFD) showed both, a favorable inflammatory and metabolic phenotype characterized by diminished weight gain, improved insulin tolerance, and attenuated plasma adipokine levels.ConclusionWe present the novel finding that CD40L deficiency limits adipose tissue inflammation in vivo. These findings identify CD40L as a potential mediator at the interface of cardiovascular and metabolic disease.

BACKGROUND:Strong evidence supports a protective role of the cannabinoid receptor 2 (CB(2)) in inflammation and atherosclerosis. However, direct proof of its involvement in lesion formation is lacking. Therefore, the present study aimed to characterize the role of the CB(2) receptor in Murine atherogenesis. METHODS AND FINDINGS:Low density lipoprotein receptor-deficient (LDLR(-/-)) mice subjected to intraperitoneal injections of the selective CB(2) receptor agonist JWH-133 or vehicle three times per week consumed high cholesterol diet (HCD) for 16 weeks. Surprisingly, intimal lesion size did not differ between both groups in sections of the aortic roots and arches, suggesting that CB(2) activation does not modulate atherogenesis in vivo. Plaque content of lipids, macrophages, smooth muscle cells, T cells, and collagen were also similar between both groups. Moreover, CB(2) (-/-)/LDLR(-/-) mice developed lesions of similar size containing more macrophages and lipids but similar amounts of smooth muscle cells and collagen fibers compared with CB(2) (+/+)/LDLR(-/-) controls. While JWH-133 treatment reduced intraperitoneal macrophage accumulation in thioglycollate-elicited peritonitis, neither genetic deficiency nor pharmacologic activation of the CB(2) receptor altered inflammatory cytokine expression in vivo or inflammatory cell adhesion in the flow chamber in vitro. CONCLUSION:Our study demonstrates that both activation and deletion of the CB(2) receptor do not relevantly modulate atherogenesis in mice. Our data do not challenge the multiple reports involving CB(2) in other inflammatory processes. However, in the context of atherosclerosis, CB(2) does not appear to be a suitable therapeutic target for reduction of the atherosclerotic plaque.

Objective: The accumulation of inflammatory leukocytes is a prerequisite of adipose tissue inflammation during cardiometabolic disease. We previously reported that a genetic deficiency of the intracellular signaling adaptor TRAF5 (TNF [tumor necrosis factor] receptor–associated factor 5) accelerates atherosclerosis in mice by increasing inflammatory cell recruitment. Here, we tested the hypothesis that an impairment of TRAF5 signaling modulates adipose tissue inflammation and its metabolic complications in a model of diet-induced obesity in mice. Approach and Results: To induce diet-induced obesity and adipose tissue inflammation, wild-type or Traf5 −/− mice consumed a high-fat diet for 18 weeks. Traf5 −/− mice showed an increased weight gain, impaired insulin tolerance, and increased fasting blood glucose. Weight of livers and peripheral fat pads was increased in Traf5 −/− mice, whereas lean tissue weight and growth were not affected. Flow cytometry of the stromal vascular fraction of visceral adipose tissue from Traf5 −/− mice revealed an increase in cytotoxic T cells, CD11c + macrophages, and increased gene expression of proinflammatory cytokines and chemokines. At the level of cell types, expression of TNFα, MIP (macrophage inflammatory protein)-1α, MCP (monocyte chemoattractant protein)-1, and RANTES (regulated on activation, normal T-cell expressed and secreted) was significantly upregulated in Traf5 -deficient adipocytes but not in Traf5 -deficient leukocytes from visceral adipose tissue. Finally, Traf5 expression was lower in adipocytes from obese patients and mice and recovered in adipose tissue of obese patients one year after bariatric surgery. Conclusions: We show that a genetic deficiency of TRAF5 in mice aggravates diet-induced obesity and its metabolic derangements by a proinflammatory response in adipocytes. Our data indicate that TRAF5 may promote anti-inflammatory and obesity-preventing signaling events in adipose tissue.