Role In Adipose Tissue Inflammation Research Articles

Contribution of NKT cells and CD1d-expressing cells in obesity-associated adipose tissue inflammation.

Natural killer T (NKT) cell are members of the innate-like T lymphocytes and recognizes lipid antigens presented by CD1d-expressing cells. Obesity-associated inflammation in adipose tissue (AT) leads to metabolic dysfunction, including insulin resistance. When cellular communication is properly regulated among AT-residing immune cells and adipocytes during inflammation, a favorable balance of Th1 and Th2 immune responses is achieved. NKT cells play crucial roles in AT inflammation, influencing the development of diet-induced obesity and insulin resistance. NKT cells interact with CD1d-expressing cells in AT, such as adipocytes, macrophages, and dendritic cells, shaping pro-inflammatory or anti-inflammatory microenvironments with distinct characteristics depending on the antigen-presenting cells. Additionally, CD1d may be involved in the inflammatory process independently of NKT cells. In this mini-review, we provide a brief overview of the current understanding of the interaction between immune cells, focusing on NKT cells and CD1d signaling, which control AT inflammation both in the presence and absence of NKT cells. We aim to enhance our understanding of the mechanisms of obesity-associated diseases.

Adipose tissue lymphocytes and obesity.

Obesity is associated with chronic inflammation in adipose tissue (AT), mainly evidenced by infiltration and phenotypic changes of various types of immune cells. Macrophages are the major innate immune cells and represent the predominant immune cell population within AT. Lymphocytes, including T cells and B cells, are adaptive immune cells and constitute another important immune cell population in AT. In obesity, CD8+ effector memory T cells, CD4+ Th1 cells, and B2 cells are increased in AT and promote AT inflammation, while regulatory T cells and Th2 cells, which usually function as immune regulatory or type 2 inflammatory cells, are reduced in AT. Immune cells may regulate the metabolism of adipocytes and other cells through various mechanisms, contributing to the development of metabolic diseases, including insulin resistance and type 2 diabetes. Efforts targeting immune cells and inflammation to prevent and treat obesity-linked metabolic disease have been explored, but have not yielded significant success in clinical studies. This review provides a concise overview of the changes in lymphocyte populations within AT and their potential role in AT inflammation and the regulation of metabolic functions in the context of obesity.

Ablation of Siglec-E enhances adipose tissue inflammation through CXCR3 activation and induces monocytic myeloid-derived suppressor cells

Abstract Obesity is a worldwide epidemic associated with dysregulated metabolism and chronic low-grade inflammation in adipose tissue (AT). AT infiltrates with several immune cells, which secrete proinflammatory cytokines that mediate the severity of AT inflammation during obesity. During our ongoing studies, we observed the downregulation of various genes, particularly sialic acid-binding Ig-like lectin E (Siglec-E) by RNA-seq analysis in AT immune cells isolated from high-fat diet (HFD) fed mice as compared to normal diet (ND) mice. Siglec-E is mainly expressed in the cells of myeloid lineages, including macrophages, dendritic cells (DCs), and neutrophils. We confirmed the RNA-seq data of downregulation of Siglec-E in AT derived from HFD-fed mice by RT-PCR analysis. To determine the role of Siglec-E in mediating AT inflammation, we fed ND and HFD to wild-type (WT) and Siglec-E knockout mice (Siglec-E −/−), respectively. HFD consumption increased the body weight and blood glucose levels in Siglec-E −/−mice as compared to WT mice. Further, we observed increased infiltration of macrophages and decreased frequency of DCs in HFD-fed Siglec-E −/−mice AT compared to WT HFD-fed mice. We also noticed an increase in the frequency of CD8 +CXCR3 +cells and monocytic myeloid-derived suppressor cells (M-MDSCs) in AT of HFD-fed Siglec-E −/−mice as compared to WT HFD-fed mice. We also noticed the increased expression of AKT, and TNF receptor-associated factor 3 (TRAF3) in HFD-fed Siglec-E −/−mice. These results suggest that Siglec-E deletion plays a role in AT inflammation and obesity through the activation of CXCR3 and M-MDSCs. This study supports the notion that modulating Siglec-E pathways protect from AT inflammation and metabolic disorders. This research is supported by NIH grant R01 AI140405

Macrophage Polarization Mediated by Mitochondrial Dysfunction Induces Adipose Tissue Inflammation in Obesity.

Obesity is one of the prominent global health issues, contributing to the growing prevalence of insulin resistance and type 2 diabetes. Chronic inflammation in adipose tissue is considered as a key risk factor for the development of insulin resistance and type 2 diabetes in obese individuals. Macrophages are the most abundant immune cells in adipose tissue and play an important role in adipose tissue inflammation. Mitochondria are critical for regulating macrophage polarization, differentiation, and survival. Changes to mitochondrial metabolism and physiology induced by extracellular signals may underlie the corresponding state of macrophage activation. Macrophage mitochondrial dysfunction is a key mediator of obesity-induced macrophage inflammatory response and subsequent systemic insulin resistance. Mitochondrial dysfunction drives the activation of the NLRP3 inflammasome, which induces the release of IL-1β. IL-1β leads to decreased insulin sensitivity of insulin target cells via paracrine signaling or infiltration into the systemic circulation. In this review, we discuss the new findings on how obesity induces macrophage mitochondrial dysfunction and how mitochondrial dysfunction induces NLRP3 inflammasome activation. We also summarize therapeutic approaches targeting mitochondria for the treatment of diabetes.

Adipokines, Hepatokines and Myokines: Focus on Their Role and Molecular Mechanisms in Adipose Tissue Inflammation.

Chronic low-grade inflammation in adipose tissue (AT) is a hallmark of obesity and contributes to various metabolic disorders, such as type 2 diabetes and cardiovascular diseases. Inflammation in ATs is characterized by macrophage infiltration and the activation of inflammatory pathways mediated by NF-κB, JNK, and NLRP3 inflammasomes. Adipokines, hepatokines and myokines — proteins secreted from AT, the liver and skeletal muscle play regulatory roles in AT inflammation via endocrine, paracrine, and autocrine pathways. For example, obesity is associated with elevated levels of pro-inflammatory adipokines (e.g., leptin, resistin, chemerin, progranulin, RBP4, WISP1, FABP4, PAI-1, Follistatin-like1, MCP-1, SPARC, SPARCL1, and SAA) and reduced levels of anti-inflammatory adipokines such as adiponectin, omentin, ZAG, SFRP5, CTRP3, vaspin, and IL-10. Moreover, some hepatokines (Fetuin A, DPP4, FGF21, GDF15, and MANF) and myokines (irisin, IL-6, and DEL-1) also play pro- or anti-inflammatory roles in AT inflammation. This review aims to provide an updated understanding of these organokines and their role in AT inflammation and related metabolic abnormalities. It serves to highlight the molecular mechanisms underlying the effects of these organokines and their clinical significance. Insights into the roles and mechanisms of these organokines could provide novel and potential therapeutic targets for obesity-induced inflammation.

1417-P: Gut Microbiome Translocation to Visceral Adipose Tissue Promotes Recruitment of Adipose-Specific Neutrophils in Human Obesity

Neutrophils protect against invading bacteria, and their unique role in adipose tissue inflammation and insulin resistance (IR) in obesity is increasingly recognized. We found that visceral adipose tissue (VAT) of obese (n=83) compared to lean (n=13) individuals had higher neutrophil abundance, correlating with IR. The obese subjects had elevated circulating plasma zonulin, a marker of intestinal permeability, and lipopolysaccharide-binding protein (LPSBP) , a marker of bacterial presence, consistent with evidence suggesting that changes in the microbiome and gut permeability in obesity permits the entry of gut bacteria and bacterial products into the circulation. Therefore, we tested for bacterial presence in VAT under sterile conditions. 16s rRNA analyses revealed that the family Streptococcaceae and an unnamed genus in the family Ruminococaceae were enriched in obese VAT contrary to order Bacilliales and genus Marvinobryantia in lean VAT, majorly originating from the GI tract. To confirm whether higher bacterial load is causal for VAT neutrophil abundance in obesity, we gavaged high-fat diet fed mice with fecal material from an obese human, which increased neutrophil, but not macrophage recruitment to VAT. As VAT is highly vascularized, we used RNA-seq to compare the gene expression signature of VAT neutrophils to peripheral blood neutrophils to eliminate the possibility that VAT neutrophils were circulating cells. Evidently, VAT neutrophils had a differential activation state compared to the circulating neutrophils, with a distinct gene expression pattern representing upregulated inflammatory, chemotactic, extracellular matrix, and ROS generation pathways. Overall, we find that that increased gut bacterial translocation enhances the recruitment of VAT specific neutrophils in obesity offering novel targets for managing VAT inflammation and comorbidities of obesity. Disclosure D.Shantaram: None. N.F.Williams: None. D.Spakowicz: None. W.Hsueh: None. A.M.Blaszczak: None. R.Hoyd: None. A.Smith: None. L.Antwi: None. J.Z.Liu: None. V.P.Wright: None. D.Bradley: None. Y.Liu: None.

Myeloid Cell-Specific IL-4 Receptor Knockout Partially Protects from Adipose Tissue Inflammation.

IL-4 receptor signaling is supposed to play a major role in anti-inflammatory polarization and proliferation of adipose tissue macrophages. In this study, we examined the metabolic and inflammatory phenotype of C57BL/6J mice (IIl4ra) with LysM-dependent knockout (IIl4ra Δmyel) of the IL-4 receptor α-chain (IL-4Rα), the mandatory signaling component of IL-4 and IL-13, on chow and high-fat diet. Lean IIl4ra Δmyel mice showed decreased insulin sensitivity, no divergent adipose tissue macrophage polarization, but an increased percentage of CD8+ T cells in visceral adipose tissue. After 20 wk of a high-fat diet, IIl4ra Δmyel mice exhibited higher glucose tolerance, no changes in the lymphocyte compartment and fewer M1 macrophages in visceral adipose tissue. In vivo adipose tissue macrophage proliferation measured by BrdU incorporation was unaffected by Il4ra knockout. Interestingly, we show that IL-4Rα signaling directly augmented Itgax (Cd11c) gene expression in bone marrow-derived macrophages and increased the amount of CD11c+ macrophages in adipose tissue explants. Myeloid cell-specific knockout of Il4ra deteriorated insulin sensitivity in lean mice but improved parameters of glucose homeostasis and partially protected from adipose tissue inflammation in obese mice. Hence, IL-4Rα signaling probably plays a minor role in maintaining the macrophage M2 population and proliferation rates in vivo. Moreover, our data indicate that IL-4 signaling plays a proinflammatory role in adipose tissue inflammation by directly upregulating CD11c on adipose tissue macrophages.

E-Selectin-Dependent Inflammation and Lipolysis in Adipose Tissue Exacerbate Steatosis-to-NASH Progression via S100A8/9.

Background & AimsNonalcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease, characterized by steatosis and hallmark liver neutrophil infiltration. NASH also is associated with adipose tissue inflammation, but the role of adipose tissue inflammation in NASH pathogenesis remains obscure. The aim of this study was to investigate the interplay between neutrophil recruitment in adipose tissue and the progression of NASH.MethodsA mouse model of NASH was obtained by high-fat diet (HFD) feeding plus adenovirus-Cxcl1 overexpression (HFD+AdCxcl1). Genetic deletion of E-selectin (Sele) and treatment with an S100A9 inhibitor (Paquinimod) were investigated using this model.ResultsBy analyzing transcriptomic data sets of adipose tissue from NASH patients, we found that E-selectin, a key adhesion molecule for neutrophils, is the highest up-regulated gene among neutrophil recruitment-related factors in adipose tissue of NASH patients compared with those in patients with simple steatosis. A marked up-regulation of Sele in adipose tissue also was observed in HFD+AdCxcl1 mice. The HFD+AdCxcl1-induced NASH phenotype was ameliorated in Sele knockout mice and was accompanied by reduced lipolysis and inflammation in adipose tissue, which resulted in decreased serum free fatty acids and proinflammatory adipokines. S100A8/A9, a major proinflammatory protein secreted by neutrophils, was highly increased in adipose tissue of HFD+AdCxcl1 mice. This increase was blunted in the Sele knockout mice. Therapeutically, treatment with the S100A9 inhibitor Paquinimod reduced lipolysis, inflammation, and adipokine production, ameliorating the NASH phenotype in mice.ConclusionsE-selectin plays an important role in inducing neutrophil recruitment in adipose tissue, which subsequently promotes inflammation and lipolysis via the production of S100A8/A9, thereby exacerbating the steatosis-to-NASH progression. Targeting adipose tissue inflammation therefore may represent a potential novel therapy for treatment of NASH.

Adipocyte calcium sensing receptor is not involved in visceral adipose tissue inflammation or atherosclerosis development in hyperlipidemic Apoe\u2212/\u2212 mice

The calcium sensing receptor (CaSR) is a G-protein coupled receptor that especially plays an important role in the sensing of extracellular calcium to maintain its homeostasis. Several in-vitro studies demonstrated that CaSR plays a role in adipose tissue metabolism and inflammation, resulting in systemic inflammation and contributing to atherosclerosis development. The aim of this study was to investigate whether adipocyte CaSR plays a role in adipose tissue inflammation in-vivo and atherosclerosis development. By using a newly established conditional mature adipocyte specific CaSR deficient mouse on a hyperlipidemic and atherosclerosis prone Apoe−/− background it could be shown that CaSR deficiency in adipocytes does neither contribute to initiation nor to progression of atherosclerotic plaques as judged by the unchanged lesion size or composition. Additionally, CaSR deficiency did not influence gonadal visceral adipose tissue (vAT) inflammation in-vivo, although a small decrease in gonadal visceral adipose cholesterol content could be observed. In conclusion, adipocyte CaSR seems not to be involved in vAT inflammation in-vivo and does not influence atherosclerosis development in hyperlipidemic Apoe−/− mice.

Multiple Parallel Hits Hypothesis in Nonalcoholic Fatty Liver Disease: Revisited After a Decade.

A decade ago, we hypothesised that multiple parallel hits constitute the pathophysiology of non-alcoholic fatty liver disease (NAFLD). We proposed that hepatic lipotoxicity and multiple events beyond the liver, such as adipose tissue inflammation and gastrointestinal hits including dysbiosis, fuel the evolution of NAFLD. Over the last decade, a plethora of studies have evolved this hypothesis into an established concept. First, adipose tissue serves as a cytokine sink in NAFLD which contributes substantially to the systemic inflammatory state in obesity-related disorders. The degree of adipose tissue inflammation directly correlates with the severity of NAFLD and tissue-specific knockout mice established a critical role of adipose tissue inflammation in experimental NAFLD. The most compelling advance in the last decade fostered our understanding of the gut microbiome in NAFLD. Several NAFLD-associated commensals and metabolites have been identified that influence susceptibility to NAFLD. Furthermore, the diet is increasingly emerging as a fuel of metabolic inflammation in obesity-related disorders and NAFLD which is partly mediated by bacterial communites in the gut. Collectively, the multiple parallel hits concept has gained momentum in NAFLD.

The role of immune dysfunction in obesity-associated cancer risk, progression, and metastasis.

Obesity has been linked to an increased risk of and a worse prognosis for several types of cancer. A number of interrelated mediators contribute to obesity's pro-tumor effects, including chronic adipose inflammation and other perturbations of immune cell development and function. Here, we review studies examining the impact of obesity-induced immune dysfunction on cancer risk and progression. While the role of adipose tissue inflammation in obesity-associated cancer risk has been well characterized, the effects of obesity on immune cell infiltration and activity within the tumor microenvironment are not well studied. In this review, we aim to highlight the impact of both adipose-mediated inflammatory signaling and intratumoral immunosuppressive signaling in obesity-induced cancer risk, progression, and metastasis.

Insulin-sensitizing effects of vitamin D repletion mediated by adipocyte vitamin D receptor: Studies in humans and mice

ObjectiveAdipose tissue inflammation and fibrosis appear to contribute to insulin resistance in obesity. Vitamin D receptor (Vdr) genes are expressed by adipocytes, macrophages, and fibroblasts, all of which could potentially play a role in adipose tissue inflammation and fibrosis. As vitamin D has been shown to have direct anti-inflammatory effects on adipocytes, we determined whether specific vitamin D receptor-mediated effects on adipocytes could impact adipose tissue inflammation and fibrosis and ultimately insulin resistance. MethodsWe examined the effects of repleting vitamin D in 25(OH)D-deficient, insulin resistant, overweight-to-obese human subjects (n = 19). A comprehensive assessment of whole-body insulin action was undertaken with stepped euglycemic (∼90 mg/dL) hyperinsulinemic clamp studies both before and after the administration of vitamin D or placebo. Adipose tissue fibrosis and inflammation were quantified by real-time rt-PCR and immunofluorescence in subcutaneous abdominal adipose tissue.To determine whether vitamin D's effects are mediated through adipocytes, we conducted hyperinsulinemic clamp studies (4 mU/kg/min) and adipose tissue analysis using an adipocyte-specific vitamin D receptor knockout (VDR-KO) mouse model (adiponectin-Cre + VDR+/fl) following high-fat diet feeding for 12 weeks. Results25(OH)D repletion was associated with reductions in adipose tissue expression of pro-inflammatory and pro-fibrotic genes, decreased collagen immunofluorescence, and improved hepatic insulin sensitivity in humans. Worsening trends after six months on placebo suggest progressive metabolic effects of 25(OH)D deficiency. Ad-VDR-KO mice mirrored the vitamin D-deficient humans, displaying increased adipose tissue fibrosis and inflammation and hepatic insulin resistance. ConclusionsThese complementary human and rodent studies support a beneficial role of vitamin D repletion for improving hepatic insulin resistance and reducing adipose tissue inflammation and fibrosis in targeted individuals, likely via direct effects on adipocytes. These studies have far-reaching implications for understanding the role of adipocytes in mediating adipose tissue inflammation and fibrosis and ultimately impacting insulin sensitivity.

Adipocyte-Derived Versican and Macrophage-Derived Biglycan Control Adipose Tissue Inflammation in Obesity

Obesity is characterized by adipose tissue inflammation. Because proteoglycans regulate inflammation, here we investigate their role in adipose tissue inflammation in obesity. We find that adipose tissue versican and biglycan increase in obesity. Versican is produced mainly by adipocytes and biglycan by adipose tissue macrophages. Both proteoglycans are also present in adipose tissue from obese human subjects undergoing gastric bypass surgery. Deletion of adipocyte-specific versican or macrophage-specific biglycan in mice reduces macrophage accumulation and chemokine and cytokine expression, although only adipocyte-specific versican deletion leads to sustained improvement in glucose tolerance. Macrophage-derived biglycan activates inflammatory genes in adipocytes. Versican expression increases in cultured adipocytes exposed to excess glucose, and adipocyte-conditioned medium stimulates inflammation in resident peritoneal macrophages, in part because of a versican breakdown product, versikine. These findings provide insights into the role of adipocyte- and macrophage-derived proteoglycans in adipose tissue inflammation in obesity.

Preliminary evidence for reduced adipose tissue inflammation in vegetarians compared with omnivores

BackgroundThere are links between obesity and inflammation that may relate activation of pro-inflammatory pathways by dietary factors. Because dietary fat intake of vegetarians is thought to be more beneficial than that of omnivores, we hypothesized that obese vegetarians would have less adipose tissue inflammation and lower intramyocellular ceramide concentrations than equally obese omnivores.MethodsEight obese vegetarian (1 male) and 8 obese omnivore volunteers (1 male) completed a Food Frequency Questionnaire, underwent body composition measures, subcutaneous adipose tissue and muscle biopsies. We used immunohistochemistry to measure adipose macrophage (ATM) and senescent cells. Plasma free fatty acid (FFA), adipose FA and muscle ceramide profiles were measured using liquid chromatography/mass spectrometry. Student t tests were used for the comparison of primary outcomes; univariate regression analysis was used to test for associations between dietary patterns and ATMs (secondary analysis).ResultsThere were no differences in age (38 ± 8 vs. 39 ± 8 years), BMI (32.2 ± 2.6 vs. 33.3 ± 1.9 kg/m2) or percent body fat (44 ± 8 vs. 45 ± 4) between the vegetarians and omnivores. Vegetarians consumed 42% (P = 0.02) less saturated fat and 50% (P = 0.04) less cholesterol than the omnivores. Plasma FFA of vegetarians had lesser proportions of palmitic acid (24 ± 3 vs. 29 ± 4%, P = 0.02) and vegetarians had fewer femoral pro-inflammatory ATMs than omnivores (3.6 ± 2.8 vs. 7.9 ± 4.4 per 100 adipocytes, respectively; P = 0.02). Omnivores had 50% greater (P = 0.01) expression of TNF mRNA in abdominal fat. We found no significant between group differences in muscle ceramide concentrations.ConclusionsAlthough the sample size is small, these results may indicate that dietary patterns play a role in adipose tissue inflammation, as reflected by reduced number of femoral ATMs in obese vegetarians than obese omnivores.

Role of adipose tissue inflammation in fat pad loss induced by fasting in lean and mildly obese mice

Inflammation induced by obesity contributes to insulin resistance and atherosclerosis. Indeed, high levels of proinflammatory cytokines trigger chronic low-grade inflammation and promote detrimental metabolic effects in the adipose tissue. On the other hand, inflammation seems to control fat pad expansion and to have important functions on lipolysis and glucose metabolism. Thus, it is possible that inflammation may also drive fat pad loss, as seen during long-fast periods. Herein, we have used fasting as a strategy to induce weight loss and evaluate the possible role of inflammation on adipose tissue remodeling. Male BALB-c mice were fed with chow diet (lean mice) or with high-carbohydrate refined diet (mildly obese mice) for 8 weeks. After that, animals were subjected to 24 h of fasting. There was a 63% reduction of adiposity in lean mice following fasting. Furthermore, the adipose tissue was enriched of immune cells and had a higher content of IL-6, TNF-alpha, IL-10, TGF-β and CXCL-1. Interestingly, mildly obese mice, subjected to the same 24-h fasting period, lost only 33% of their adiposity. Following fasting, these mice did not show any increment in leukocyte recruitment and cytokine levels, as did lean mice. Our findings indicate that inflammation participates in fat mass loss induced by fasting. Although the chronic low-grade inflammation seen in obesity is associated with metabolic diseases, a lower inflammatory response triggered by fasting in mildly obese mice impairs fat pad mobilization.

Pentraxin 3 deficiency exacerbates lipopolysaccharide-induced inflammation in adipose tissue

Background/objectivesPentraxin 3 (PTX3) has been characterized as a soluble and multifunctional pattern recognition protein in the regulation of innate immune response. However, little is known about its role in adipose tissue inflammation and obesity. Herein, we investigated the role of PTX3 in the regulation of lipopolysaccharide (LPS)-induced inflammation in adipocytes and adipose tissue, as well as high-fat diet (HFD)-induced metabolic inflammation in obesity.MethodsPtx3 knockdown 3T3-L1 Cells were generated using shRNA for Ptx3 gene and treated with different inflammatory stimuli. For the in vivo studies, Ptx3 knockout mice were treated with 0.3 mg/kg of LPS for 6 h. Adipose tissues were collected for gene and protein expression by qPCR and western blotting, respectively. Ptx3 knockout mice were fed with HFD for 12 week since 6 week of age.ResultsWe observed that the expression of PTX3 in adipose tissue and serum PTX3 were markedly increased in response to LPS administration. Knocking down Ptx3 in 3T3-L1 cells reduced adipogenesis and caused a more profound and sustained upregulation of proinflammatory gene expression and signaling pathway activation during LPS-stimulated inflammation in 3T3-L1 adipocytes. In vivo studies showed that PTX3 deficiency significantly exacerbated the LPS-induced upregulation of inflammatory genes and downregulation of adipogeneic genes in visceral and subcutaneous adipose tissue of mice. Accordingly, LPS stimulation elicited increased activation of nuclear factor-κB (NF-κB) and p44/42 MAPK (Erk1/2) signaling pathways in visceral and subcutaneous adipose tissue. The expression of PTX3 in adipose tissue was also induced by HFD, and PTX3 deficiency led to the upregulation of proinflammatory genes in visceral adipose tissue of HFD-induced obese mice.ConclusionsOur results suggest a protective role of PTX3 in LPS- and HFD-induced sustained inflammation in adipose tissue.

A Possible Role of Perivascular Adipocyte Stress in Cardiovascular Dysfunction Prior to the Onset of Diabetes

Cardiovascular disease is the leading cause of morbidity and mortality among diabetic patients. Although prolonged exposure to hyperglycemia is implicated in the pathogenesis of cardiovascular dysfunction, a significant proportion of patients show established diabetic microvascular complications at initial diagnosis of diabetes, before overt hyperglycemia. Moreover, recent studies from our laboratory have shown that cardiovascular dysfunction is evident in animal models of metabolic challenge before the onset of hyperglycemia and diabetes, thus placing the etiology of this early cardiovascular dysfunction in question. Given the role of adipose tissue inflammation in the pathophysiology of metabolic syndrome, we hypothesized that interactions between perivascular adipose tissue and vascular smooth muscle cells may play a role in early cardiovascular dysfunction. To test this hypothesis, 3T3‐L1 cells were differentiated to adipocyte‐like cells and treated with 1600 μM free fatty acids and 40 mIU/L insulin, mimicking the levels of these mediators in the plasma of rats challenged with 12 weeks of hyper‐caloric diet feeding. The conditioned medium from these cells was used to treat rat aortic vascular smooth muscle cells (VSMC). VSMC metabolic activity and expression of contractile phenotype markers were assessed. A decrease in metabolic activity in MTS assays was observed in cells treated with conditioned media from challenged 3T3 cells compared to those exposed to control media containing the same levels of fatty acids and/or insulin and to those exposed to conditioned media from control 3T3‐L1 cells. This was paralleled with a significant decrease in alpha‐smooth muscle actin in cells treated with conditioned media from stressed 3T3‐L1 cells. Significantly, media with high free fatty acids and/or insulin did not have a direct effect on VSMCs, supporting the idea that metabolic dysfunction‐evoked vascular impairment was induced by adipose tissue inflammation and suggesting the potential involvement of a soluble adipose tissue mediator triggered by the early insult on adipocytes. Furthermore, adipocyte‐differentiated human bone marrow mesenchymal stem cells challenged with the same concentrations of free fatty acids and insulin recruited a greater number of THP‐1 monocytes compared to cells exposed to control medium, suggesting an upregulation of monocyte attractant properties of stressed adipocytes consistent with an inflammatory phenotype. Our preliminary results indicate a possible mechanistic framework whereby metabolic challenge may mediate early VSMC dysfunction prior to overt hyperglycemia.Support or Funding InformationSupported by AUB MPP fund #320148.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Role of Natural Killer T Cells in the Development of Obesity and Insulin Resistance: Insights From Recent Progress.

Natural killer T (NKT) cells play important roles in adipose tissue inflammation, and thus influence the development of diet-induced obesity and insulin resistance. The interactions between cluster of differentiation (CD)1d and NKT T cell receptor are thought to be critical in this process, as demonstrated in two NKT cell-deficient mouse models—systemic CD1d gene knockout (KO) and prototypic Jα18 KO mice. The latter lacks some repertoires besides invariant (i)NKT cells due to manipulation of the Jα18 gene segment; therefore, the role of iNKT vs. variant NKT cells must be reinterpreted considering the availability of new Jα18 KO mice. NKT cells have varied roles in the development of obesity; indeed, studies have reported contradictory results depending on the mouse model, diet, and rearing conditions, all of which could affect the microbiome. In this mini-review, we discuss these points considering recent findings from our laboratory and others as well as the role of NKT cells in the development of obesity and insulin resistance based on data obtained from studies on conditional CD1d1 KO and new Jα18 KO mice generated through gene editing.

1,3,6,7-Tetrahydroxy-8-prenylxanthone ameliorates inflammatory responses resulting from the paracrine interaction of adipocytes and macrophages.

Chronic inflammation in adipose tissue is critical in the onset and development of insulin resistance and type 2 diabetes. Macrophage infiltration into adipose tissue and pro-inflammatory polarization play key roles in adipose tissue inflammation. The fruit hull of mangosteen (Garcinia mangostana) is used in traditional medicine to treat various inflammatory diseases. However, its role in regulating adipose tissue inflammation is unexplored. This study was designed to identify xanthones from G.mangostana, which could ameliorate adipose tissue inflammation. Expressions of inducible NOS, cytokines, chemokines and components of the NF-κB and MAPKs pathways were evaluated using Western blotting, immunofluorescence, quantitative real-time PCR or ELISA. The migration of macrophages towards adipocytes was tested using Transwell experiments in vitro. A murine model of LPS-induced acute inflammation was used to examine effects of 1,3,6,7-tetrahydroxy-8-prenylxanthone (TPX) on inflammatory responses in adipose tissue in vivo. From a series of xanthones isolated from G.mangostana, TPX was identified as a potent inhibitor of LPS-induced NO production and IL-6 secretion in RAW264.7 macrophages. TPX ameliorated LPS-induced inflammatory responses in RAW264.7 macrophages, and TNF-α-mediated inflammation in 3T3-L1 adipocytes, through inhibiting MAPKs and NF-κB activation and promoting sirtuin 3 expression. TPX also blocked RAW264.7 macrophages migration towards 3T3-L1 adipocytes in co-cultures. Furthermore, TPX alleviated LPS-induced adipose tissue inflammation in vivo by reducing pro-inflammatory cytokines and preventing the pro-inflammatory polarization of macrophages. Taken together, our results indicate that TPX disrupts the inflammatory responses between macrophages and adipocytes, and attenuates adipose tissue inflammation.

Obesity-Associated Adipose Tissue Inflammation and Transplantation.

Obesity is often associated with the development of adipose tissue (AT) inflammation, resulting in metabolic dysfunction and an increased risk for developing type 2 diabetes. It is also associated with multiple chronic diseases, including cardiovascular, liver, and kidney disease, and thus can contribute to organ failure. Several studies have investigated whether there is a correlation between obesity and outcomes in transplantation, but there is currently very limited information on the specific role of AT inflammation in the rejection process or on the overall function of the transplanted organ. Here, we provide a brief review of the current understanding of the cellular mechanisms that control obesity-associated AT inflammation and summarize knowledge about how obesity affects clinical outcomes following solid organ or hematopoietic stem cell transplantation. We also highlight opportunities for more research to better understand how obesity affects outcomes of transplantation.