Obesity-associated microbiomes instigate visceral adipose tissue inflammation by recruitment of distinct neutrophils.

Neutrophils are increasingly implicated in chronic inflammation and metabolic disorders. Here, we show that visceral adipose tissue (VAT) from individuals with obesity contains more neutrophils than in those without obesity and is associated with a distinct bacterial community. Exploring the mechanism, we gavaged microbiome-depleted mice with stool from patients with and without obesity during high-fat or normal diet administration. Only mice receiving high-fat diet and stool from subjects with obesity show enrichment of VAT neutrophils, suggesting donor microbiome and recipient diet determine VAT neutrophilia. A rise in pro-inflammatory CD4+ Th1 cells and a drop in immunoregulatory T cells in VAT only follows if there is a transient spike in neutrophils. Human VAT neutrophils exhibit a distinct gene expression pattern that is found in different human tissues, including tumors. VAT neutrophils and bacteria may be a novel therapeutic target for treating inflammatory-driven complications of obesity, including insulin resistance and colon cancer.

Interferon gamma mediates the reduction of adipose tissue regulatory T cells in human obesity.

Decreased adipose tissue regulatory T cells contribute to insulin resistance in obese mice, however, little is known about the mechanisms regulating adipose tissue regulatory T cells numbers in humans. Here we obtain adipose tissue from obese and lean volunteers. Regulatory T cell abundance is lower in obese vs. lean visceral and subcutaneous adipose tissue and associates with reduced insulin sensitivity and altered adipocyte metabolic gene expression. Regulatory T cells numbers decline following high-fat diet induction in lean volunteers. We see alteration in major histocompatibility complex II pathway in adipocytes from obese patients and after high fat ingestion, which increases T helper 1 cell numbers and decreases regulatory T cell differentiation. We also observe increased expression of inhibitory co-receptors including programmed cell death protein 1 and OX40 in visceral adipose tissue regulatory T cells from patients with obesity. In human obesity, these global effects of interferon gamma to reduce regulatory T cells and diminish their function appear to instigate adipose inflammation and suppress adipocyte metabolism, leading to insulin resistance.

Characterization of inflammatory changes in the breast cancer associated adipose tissue and comparison to the unaffected contralateral breast.

BACKGROUND: Adipose tissue has emerged as an important window into cancer pathophysiology, revealing potential targets for novel therapeutic interventions. The goal of this study was to compare the breast adipose tissue (BrAT) immune milieu surrounding breast carcinoma and contralateral unaffected breast tissue obtained from the same patient. MATERIALS AND METHODS: Patients undergoing bilateral mastectomy for unilateral breast cancer were enrolled for bilateral BrAT collection at the time of operation. After BrAT was processed, adipocyte and stromal vascular fraction (SVF) gene expression was quantified by PCR. SVF cells were also processed for flow cytometric immune cell characterization. RESULTS: Twelve patients underwent bilateral mastectomy for unilateral ductal carcinoma. BrAT adipocyte CXCL2 gene expression trended higher in the tumor-affected breast as compared to the unaffected breast. Macrophage MCP-1 and PPARγ gene expression also tended to be higher in the tumor-affected breasts. T cell gene expression of FOXP3 (p = 0.0370) were significantly greater in tumor-affected breasts than unaffected breasts. Affected BrAT contained higher numbers of Th2 CD4+ cells (p = 0.0165) and eosinophils (p = 0.0095) while trending towards increased macrophage and lower Th1 CD4+ cells infiltration than tumor-affected BrAT. CONCLUSION: This preliminary study aimed to identify the immunologic environment present within BrAT and is the first to directly compare this in individual patients' tumor-associated and unaffected BrAT. These findings suggest that cancer-affected BrAT had increased levels of T cell specific FOXP3 and higher levels of anti-inflammatory/regulatory cells compared to the contralateral BrAT.

Low visceral adipose tissue regulatory T cells are associated with higher comorbidity severity in patients undergoing bariatric surgery.

BACKGROUND: Adipose tissue (AT) inflammation is linked to the development of type 2 diabetes (T2DM) and atherosclerosis in murine models of obesity. Reduced AT regulatory T cells (Tregs), which are anti-inflammatory immune cells, play an important part in this pathogenesis, and we have shown that AT-Tregs are inversely correlated to increasing body-mass-index. The purpose of this study was to evaluate the association between AT-Treg abundance and comorbidity status in patients undergoing bariatric surgery (BS). METHODS: Visceral (intra-abdominal) AT was harvested at that time of primary BS (n = 80) and collagenase digested. AT-Treg abundance (CD4+/CD25+/FOXP3+) was characterized using flow cytometry from the AT stromal vascular fraction. The median AT-Treg abundance (3.03%) was utilized to define high (High-Tregs, n = 39) and low AT-Treg (low-Tregs, n = 38) abundance within this cohort. These two groups were compared in terms of baseline demographic data, preoperative obesity-related comorbidities, glycemic parameters, including insulin resistance (HOMA-IR). RESULTS: Age, excess body weight, and sex were not different between groups. Prevalence of hypertension, hyperlipidemia, or T2DM preoperatively were not different between groups. Compared to High-Tregs, patients with low-Tregs were more likely to have insulin-dependent type 2 diabetes (12.5% vs 2.9%, p = 0.04). Within patients with T2DM, low-Treg patients had higher plasma insulin levels compared to high-Tregs (31.8 (28.4-56.5) vs 15.5 (10.1-23.1), p = 0.04) and trended towards higher insulin resistance (HOMA-IR) (9.0 (5.3-18.3) vs 3.5 (2.2-7.7), p = 0.08). Within those diagnosed with hyperlipidemia, preoperative statin use was higher in Low-Treg patients compared to the control cohort (91% vs 50%, p = 0.056). Low-Treg patients with hypertension were more likely to need 2 + anti-hypertensive agents preoperatively compared to their counterparts (71% vs 44%, p = 0.058). CONCLUSION: Within bariatric candidates, lower visceral AT-Treg abundance was associated with increased baseline medication requirements for type 2 diabetes, hypertension, and hyperlipidemia. This suggests that reduced AT-Tregs may be associated with higher obesity-related comorbidity severity.

Obesogenic Memory Maintains Adipose Tissue Inflammation and Insulin Resistance.

BACKGROUND: Obesity is characterized by visceral adipose tissue (AT) inflammation. Immunosuppressive regulatory T cells (Tregs), phagocytic M2-like macrophages, and innate lymphoid cells type 2 (ILC2) control lean AT inflammation to maintain systemic insulin sensitivity, while the loss of these cells in obesity leads to AT inflammation and insulin resistance (IR). OBJECTIVE: The objective of this study was to determine if weight loss following obesity would correct AT inflammation and systemic metabolism. RESULTS: After six months of high fat diet (HFD) in male C57/Bl6 mice, flow analyses of epidydimal AT stromal vascular fraction (SVF) revealed depleted Tregs by 50%, doubling of CD8+ T cells, tripling of pro-inflammatory M1-like macrophages, and an 80% drop in ILC2 cells associated with changes in pro-inflammatory adipocyte and macrophage gene expression. Despite normalization of body weight, fat, and adipocyte size, mice ingesting 3 months of high-fat diet (HFD) followed by 3 months of chow-diet remained more insulin resistant and glucose intolerant than chow-fed animals. Adipocytes, AT Tregs, CD8+ T cells, ILC2 cells, and M1-like macrophages all failed to normalize with weight loss. CONCLUSIONS: Persistent AT inflammation contributes to the maintenance of IR despite body weight and fat normalization in previously obese mice. These findings highlight the importance of obesity prevention to avoid the consequences of "obesogenic memory."

Loss of Antigen Presentation in Adipose Tissue Macrophages or in Adipocytes, but Not Both, Improves Glucose Metabolism.

Macrophages, B cells, and adipocytes are among the adipose tissue (AT) APCs that differentiate and activate naive CD4+ T cells. Mice with adipocyte loss of MHC class II (MHC II) are more insulin sensitive. Because macrophages are professional APCs, mice with genetic myeloid MHC II depletion (myeloid MHC II knockout [mMHCII-/-]) were created and metabolically characterized. FITC+ glucan-coated particles (glucan-encapsulated small interfering RNA [siRNA] particles [GeRPs]) were also used to target MHC II knockout specifically in AT macrophages (ATMs). Mice with total body mMHCII-/- were generated by crossing LyzMCre with H2Ab1 floxed mice. For specific ATM depletion of H2Ab1, GeRPs containing H2Ab1 siRNA were administered to high-fat diet-fed C57BL/6 mice. Unexpectedly, mMHCII-/- mice had loss of both macrophage and adipocyte H2Ab1, one of only two Ag-presenting arms; thus, neither cell could present Ag and activate CD4+ T cells. This inability led to a reduction in AT immunosuppressive regulatory T cells, increased AT CD8+ T cells, and no improvement in systemic metabolism. Thus, with combined systemic myeloid and adipocyte MHC II loss, the impact of ATM-specific alterations in APC activity could not be delineated. Therefore, GeRPs containing H2Ab1 siRNA were administered to specifically reduce ATM H2Ab1 which, in contrast, revealed improved glucose tolerance. In conclusion, loss of either ATM or adipocyte APC function, but not both, improves systemic glucose metabolism because of maintenance of AT regulatory T cells.

Human Visceral Adipose Tissue Macrophages Are Not Adequately Defined by Standard Methods of Characterization.

Obesity is associated with a state of chronic low-grade inflammation both systemically and within specific tissues, including adipose tissue (AT). In murine models of obesity, there is a shift in the inflammatory profile of the AT immune cells, with an accumulation of proinflammatory M1 macrophages that surround the expanding adipocyte. However, much less is known about the immune cell composition and how to best define AT macrophages in humans. Objective. The goals of the current study were to determine the contribution of macrophages to the stromal vascular fraction (SVF) in lean versus obese human visceral AT (VAT); examine the expression of common M1, M2, and pan macrophage markers; and determine the association of specific macrophage types with known biomarkers of obesity-related cardiometabolic disease. Research Design and Methods. VAT biopsies were obtained from obese (n = 50) and lean (n = 8) patients during elective surgery. Adipocytes and SVF were isolated, and the SVF was subjected to flow cytometry analyses. Results. Our results indicate that VAT macrophages are increased in obesity and associate with biomarkers of CVD but that many macrophages do not fall into currently defined M1/M2 classification system based on CD206 receptor expression levels. Conclusions. VAT macrophages are increased in obese subjects, but the current markers used to define macrophage populations are inadequate to distinguish differences in human obesity. Further studies are needed to delineate the function of AT macrophages in the maintenance and progression of human AT inflammation in obesity.

Clusterin Impairs Hepatic Insulin Sensitivity and Adipocyte Clusterin Associates With Cardiometabolic Risk.

OBJECTIVE: Components of the adipose tissue (AT) extracellular matrix (ECM) are recently discovered contributors to obesity-related cardiometabolic disease. We identified increased adipocyte expression of ECM-related clusterin (apolipoprotein J) in obese versus lean women by microarray. Our objective was to determine 1) whether subcutaneous AT adipocyte (SAd) clusterin and serum clusterin are associated with insulin resistance (IR) and known markers of cardiometabolic risk and 2) how clusterin may contribute to increased risk. RESEARCH DESIGN AND METHODS: We validated increased clusterin expression in adipocytes from a separate group of 18 lean and 54 obese individuals. The relationship of clusterin gene expression and plasma clusterin with IR, cardiovascular biomarkers, and risk of cardiovascular disease (CVD) was then determined. Further investigations in human cultured cells and in aged LDLR-/- mice prone to development of obesity-associated complications were performed. RESULTS: SAd clusterin correlated with IR, multiple CVD biomarkers, and CVD risk, independent of traditional risk factors. Circulating human clusterin exhibited similar associations. In human adipocytes, palmitate enhanced clusterin secretion, and in human hepatocytes, clusterin attenuated insulin signaling and APOA1 expression and stimulated hepatic gluconeogenesis. LRP2 (megalin), a clusterin receptor, highly expressed in liver, mediated these effects, which were inhibited by LRP2 siRNA. In response to Western diet feeding, an increase in adipocyte clusterin expression was associated with a progressive increase in liver fat, steatohepatitis, and fibrosis in aged LDLR-/- mice. CONCLUSIONS: Adipocyte-derived clusterin is a novel ECM-related protein linking cardiometabolic disease and obesity through its actions in the liver.

Adipocyte DIO2 Expression Increases in Human Obesity but Is Not Related to Systemic Insulin Sensitivity.

Deiodinase type II (D2), encoded by DIO2, catalyzes the conversion of T4 to bioactive T3. T3 not only stimulates adaptive thermogenesis but also affects adipose tissue (AT) lipid accumulation, mitochondrial function, inflammation, and potentially systemic metabolism. Although better defined in brown AT, the precise role of DIO2 expression in white AT remains largely unknown, with data derived only from whole fat. Therefore, the purpose of this study was to determine whether subcutaneous (SAT) and visceral (VAT) adipocyte-specific gene expression of DIO2 differs between obese and lean patients and whether these differences relate to alterations in mitochondrial function, fatty acid flux, inflammatory cytokines/adipokines, and ultimately insulin sensitivity. Accordingly, adipocytes of 73 obese and 21 lean subjects were isolated and subjected to gene expression analyses. Our results demonstrate that obese compared to lean human individuals have increased adipocyte-specific DIO2 expression in both SAT and VAT. Although higher DIO2 was strongly related to reduced fatty acid synthesis/oxidation and mitochondrial function, we found no relationship to proinflammatory cytokines or insulin resistance and no difference based on diabetic status. Our results suggest that adipocyte-derived DIO2 may play a role in weight maintenance but is likely not a major contributor to obesity-related insulin resistance.

Ontology-Driven Semantic Search for Brazilian Portuguese Clinical Notes.

The emerging penetration of Health IT in Latin America (especially in Brazil) has exacerbated the ever-increasing amount of Electronic Health Record (EHR) clinical free text documents.This imposes a workflow efficiency challenge on clinicians who need to synthesize such documents during the typically time-constrained patient care. We propose an ontology-driven semantic search framework that effectively supports clinicians' information synthesis at the point of care.

Osteocalcin protects against nonalcoholic steatohepatitis in a mouse model of metabolic syndrome.

Nonalcoholic fatty liver disease, particularly its more aggressive form, nonalcoholic steatohepatitis (NASH), is associated with hepatic insulin resistance. Osteocalcin, a protein secreted by osteoblast cells in bone, has recently emerged as an important metabolic regulator with insulin-sensitizing properties. In humans, osteocalcin levels are inversely associated with liver disease. We thus hypothesized that osteocalcin may attenuate NASH and examined the effects of osteocalcin treatment in middle-aged (12-mo-old) male Ldlr(-/-) mice, which were fed a Western-style high-fat, high-cholesterol diet for 12 weeks to induce metabolic syndrome and NASH. Mice were treated with osteocalcin (4.5 ng/h) or vehicle for the diet duration. Osteocalcin treatment not only protected against Western-style high-fat, high-cholesterol diet-induced insulin resistance but substantially reduced multiple NASH components, including steatosis, ballooning degeneration, and fibrosis, with an overall reduction in nonalcoholic fatty liver disease activity scores. Further, osteocalcin robustly reduced expression of proinflammatory and profibrotic genes (Cd68, Mcp1, Spp1, and Col1a2) in liver and suppressed inflammatory gene expression in white adipose tissue. In conclusion, these results suggest osteocalcin inhibits NASH development by targeting inflammatory and fibrotic processes.

Class II major histocompatibility complex plays an essential role in obesity-induced adipose inflammation.

Adipose-resident T cells (ARTs) regulate metabolic and inflammatory responses in obesity, but ART activation signals are poorly understood. Here, we describe class II major histocompatibility complex (MHCII) as an important component of high-fat-diet (HFD)-induced obesity. Microarray analysis of primary adipocytes revealed that multiple genes involved in MHCII antigen processing and presentation increased in obese women. In mice, adipocyte MHCII increased within 2 weeks on HFD, paralleling increases in proinflammatory ART markers and decreases in anti-inflammatory ART markers, and preceding adipose tissue macrophage (ATM) accumulation and proinflammatory M1 polarization. Mouse 3T3-L1 and primary adipocytes activated T cells in an antigen-specific, contact-dependent manner, indicating that adipocyte MHCII is functional. HFD-fed MHCII(-/-) mice developed less adipose inflammation and insulin resistance than did wild-type mice, despite developing similar adiposity. These investigations uncover a mechanism whereby a HFD-induced adipocyte/ART dialog involving MHCII instigates adipose inflammation and, together with ATM MHCII, escalates its progression.

Myeloid deletion of nuclear factor erythroid 2-related factor 2 increases atherosclerosis and liver injury.

OBJECTIVE: To determine the impact of hematopoietic deletion of nuclear factor- (erythroid-derived 2) like 2 factor (Nrf2) on the development of atherosclerosis and liver injury in an obese, hypercholesterolemic mouse model. METHODS AND RESULTS: Two-month-old male low-density lipoprotein receptor-deficient mice were lethally irradiated and transplanted with either wild type or Nrf2-deficient (Nrf2(-/-)) bone marrow cells. At 3 months of age, mice were placed on an obesogenic high-fat diet (HFD), high-cholesterol diet for 7 months. Despite no differences in body weight, body fat percentage, liver fat, plasma glucose, lipids, or insulin, the HFD-fed Nrf2(-/-) bone marrow recipients had increased proinflammatory vascular gene expression, a significant increase in atherosclerosis area (18% versus 28%; P=0.018) and lesion complexity, and a marked increase in liver fibrosis. The acceleration of vascular and liver injury may arise from enhanced macrophage migration, inflammation, and oxidative stress resulting from myeloid Nrf2 deficiency. CONCLUSIONS: Myeloid-derived Nrf2 activity attenuates atherosclerosis development and liver inflammation and fibrosis associated with obesity. Prevention of oxidative stress in macrophage and other myeloid lineage cells may be an important therapeutic target to reduce inflammation-driven complications of obesity.

Rosiglitazone attenuates age- and diet-associated nonalcoholic steatohepatitis in male low-density lipoprotein receptor knockout mice.

UNLABELLED: Nonalcoholic fatty liver disease (NAFLD) is a common complication of obesity that can progress to nonalcoholic steatohepatitis (NASH), a serious liver pathology that can advance to cirrhosis. The mechanisms responsible for NAFLD progression to NASH remain unclear. Lack of a suitable animal model that faithfully recapitulates the pathophysiology of human NASH is a major obstacle in delineating mechanisms responsible for progression of NAFLD to NASH and, thus, development of better treatment strategies. We identified and characterized a novel mouse model, middle-aged male low-density lipoprotein receptor (LDLR)(-/-) mice fed a high-fat diet (HFD), which developed NASH associated with four of five metabolic syndrome (MS) components. In these mice, as observed in humans, liver steatosis and oxidative stress promoted NASH development. Aging exacerbated the HFD-induced NASH such that liver steatosis, inflammation, fibrosis, oxidative stress, and liver injury markers were greatly enhanced in middle-aged versus young LDLR(-/-) mice. Although expression of genes mediating fatty acid oxidation and antioxidant responses were up-regulated in young LDLR(-/-) mice fed HFD, they were drastically reduced in MS mice. However, similar to recent human trials, NASH was partially attenuated by an insulin-sensitizing peroxisome proliferator-activated receptor-gamma (PPARγ) ligand, rosiglitazone. In addition to expected improvements in MS, newly identified mechanisms of PPARγ ligand effects included stimulation of antioxidant gene expression and mitochondrial ß-oxidation, and suppression of inflammation and fibrosis. LDLR-deficiency promoted NASH, because middle-aged C57BL/6 mice fed HFD did not develop severe inflammation and fibrosis, despite increased steatosis. CONCLUSION: MS mice represent an ideal model to investigate NASH in the context of MS, as commonly occurs in human disease, and NASH development can be substantially attenuated by PPARγ activation, which enhances ß-oxidation.

Critical role for osteopontin in diabetic nephropathy.

The profibrotic adhesion molecule, osteopontin (OPN), is upregulated in kidneys of humans and mice with diabetes. The thiazolidinedione (TZD) insulin sensitizers decrease albuminuria in diabetic nephropathy (DN) and reduce OPN expression in vascular and cardiac tissue. To examine whether OPN is a critical mediator of DN we treated db/db mice with insulin, rosiglitazone, or pioglitazone to achieve similar fasting plasma glucose levels. The urine albumin-to-creatinine ratio and glomerular OPN expression were increased in diabetic mice, but both were reduced by the TZDs more than by insulin. We administered streptozotocin to OPN-null and OPN-wild-type mice, and OPN-null mice were bred into both type 1 (Ins2(akita/+)) and 2 (db/db) diabetic mice. In each case, OPN deletion decreased albuminuria, mesangial area, and glomerular collagen IV, fibronectin and transforming growth factor (TGF)-beta in the diabetic mice compared with their respective controls. In cultured mouse mesangial cells, TZDs but not insulin decreased angiotensin II-induced OPN expression, while recombinant OPN upregulated TGF-beta, ERK/MAPK, and JNK/MAPK signaling. These studies show that OPN expression in DN mouse models enhances glomerular damage, likely through the expression of TGF-beta, while its deletion protects against disease progression, suggesting that OPN might serve as a therapeutic target.

Age-accelerated atherosclerosis correlates with failure to upregulate antioxidant genes.

Excess food intake leads to obesity and diabetes, both of which are well-known independent risk factors for atherosclerosis, and both of which are growing epidemics in an aging population. We hypothesized that aging enhances the metabolic and vascular effects of high fat diet (HFD) and therefore examined the effect of age on atherosclerosis and insulin resistance in lipoprotein receptor knockout (LDLR(-/-)) mice. We found that 12-month-old (middle-aged) LDLR(-/-) mice developed substantially worse metabolic syndrome, diabetes, and atherosclerosis than 3-month-old (young) LDLR(-/-) mice when both were fed HFD for 3 months, despite similar elevations in total cholesterol levels. Microarray analyses were performed to analyze the mechanism responsible for the marked acceleration of atherosclerosis in middle-aged mice. Chow-fed middle-aged mice had greater aortic expression of multiple antioxidant genes than chow-fed young mice, including glutathione peroxidase-1 and -4, catalase, superoxide dismutase-2, and uncoupling protein-2. Aortic expression of these enzymes markedly increased in young mice fed HFD but decreased or only modestly increased in middle-aged mice fed HFD, despite the fact that systemic oxidative stress and vascular reactive oxygen species generation, measured by plasma F2alpha isoprostane concentration (systemic) and dihydroethidium conversion and p47phox expression (vascular), were greater in middle-aged mice fed HFD. Thus, the mechanism for the accelerated vascular injury in older LDLR(-/-) mice was likely the profound inability to mount an antioxidant response. This effect was related to a decrease in vascular expression of 2 key transcriptional pathways regulating the antioxidant response, DJ-1 and forkhead box, subgroup O family (FOXOs). Treatment of middle-aged mice fed HFD with the antioxidant apocynin attenuated atherosclerosis, whereas treatment with the insulin sensitizer rosiglitazone attenuated both metabolic syndrome and atherosclerosis. Both treatments decreased oxidative stress. A novel effect of rosiglitazone was to increase expression of Nrf2 (nuclear factor [erythroid-derived 2]-like 2), a downstream target of DJ-1 contributing to enhanced expression of vascular antioxidant enzymes. This investigation underscores the role of oxidative stress when multiple atherosclerotic risk factors, particularly aging, converge on the vessel wall and emphasizes the need to develop effective strategies to inhibit oxidative stress to protect aging vasculature.

A Dominant-Negative PPARgamma Mutant Promotes Cell Cycle Progression and Cell Growth in Vascular Smooth Muscle Cells.

PPARgamma ligands have been shown to have antiproliferative effects on many cell types. We herein report that a synthetic dominant-negative (DN) PPARgamma mutant functions like a growth factor to promote cell cycle progression and cell proliferation in human coronary artery smooth muscle cells (CASMCs). In quiescent CASMCs, adenovirus-expressed DN-PPARgamma promoted G1-->S cell cycle progression, enhanced BrdU incorporation, and increased cell proliferation. DN-PPARgamma expression also markedly enhanced positive regulators of the cell cycle, increasing Rb and CDC2 phosphorylation and the expression of cyclin A, B1, D1, and MCM7. Conversely, overexpression of wild-type (WT) or constitutively-active (CA) PPARgamma inhibited cell cycle progression and the activity and expression of positive regulators of the cell cycle. DN-PPARgamma expression, however, did not up-regulate positive cell cycle regulators in PPARgamma-deficient cells, strongly suggesting that DN-PPARgamma effects on cell cycle result from blocking the function of endogenous wild-type PPARgamma. DN-PPARgamma expression enhanced phosphorylation of ERK MAPKs. Furthermore, the ERK specific-inhibitor PD98059 blocked DN-PPARgamma-induced phosphorylation of Rb and expression of cyclin A and MCM7. Our data thus suggest that DN-PPARgamma promotes cell cycle progression and cell growth in CASMCs by modulating fundamental cell cycle regulatory proteins and MAPK mitogenic signaling pathways in vascular smooth muscle cells (VSMCs).

Differential roles of cardiomyocyte and macrophage peroxisome proliferator-activated receptor gamma in cardiac fibrosis.

OBJECTIVE: Cardiac fibrosis is an important component of diabetic cardiomyopathy. Peroxisome proliferator-activated receptor gamma (PPARgamma) ligands repress proinflammatory gene expression, including that of osteopontin, a known contributor to the development of myocardial fibrosis. We thus investigated the hypothesis that PPARgamma ligands could attenuate cardiac fibrosis. RESEARCH DESIGN AND METHODS: Wild-type cardiomyocyte- and macrophage-specific PPARgamma(-/-) mice were infused with angiotensin II (AngII) to promote cardiac fibrosis and treated with the PPARgamma ligand pioglitazone to determine the roles of cardiomyocyte and macrophage PPARgamma in cardiac fibrosis. RESULTS: Cardiomyocyte-specific PPARgamma(-/-) mice (cPPARgamma(-/-)) developed spontaneous cardiac hypertrophy with increased ventricular osteopontin expression and macrophage content, which were exacerbated by AngII infusion. Pioglitazone attenuated AngII-induced fibrosis, macrophage accumulation, and osteopontin expression in both wild-type and cPPARgamma(-/-) mice but induced hypertrophy in a PPARgamma-dependent manner. We pursued two mechanisms to explain the antifibrotic cardiomyocyte-PPARgamma-independent effects of pioglitazone: increased adiponectin expression and attenuation of proinflammatory macrophage activity. Adenovirus-expressed adiponectin had no effect on cardiac fibrosis and the PPARgamma ligand pioglitazone did not attenuate AngII-induced cardiac fibrosis, osteopontin expression, or macrophage accumulation in monocyte-specific PPARgamma(-/-) mice. CONCLUSIONS: We arrived at the following conclusions: 1) both cardiomyocyte-specific PPARgamma deficiency and activation promote cardiac hypertrophy, 2) both cardiomyocyte and monocyte PPARgamma regulate cardiac macrophage infiltration, 3) inflammation is a key mediator of AngII-induced cardiac fibrosis, 4) macrophage PPARgamma activation prevents myocardial macrophage accumulation, and 5) PPARgamma ligands attenuate AngII-induced cardiac fibrosis by inhibiting myocardial macrophage infiltration. These observations have important implications for potential interventions to prevent cardiac fibrosis.

PPARdelta-mediated antiinflammatory mechanisms inhibit angiotensin II-accelerated atherosclerosis.

Activation of the nuclear hormone receptor peroxisome proliferator-activated receptor delta (PPARdelta) has been shown to improve insulin resistance, adiposity, and plasma HDL levels. However, its antiatherogenic role remains controversial. Here we report atheroprotective effects of PPARdelta activation in a model of angiotensin II (AngII)-accelerated atherosclerosis, characterized by increased vascular inflammation related to repression of an antiinflammatory corepressor, B cell lymphoma-6 (Bcl-6), and the regulators of G protein-coupled signaling (RGS) proteins RGS4 and RGS5. In this model, administration of the PPARdelta agonist GW0742 (1 or 10 mg/kg) substantially attenuated AngII-accelerated atherosclerosis without altering blood pressure and increased vascular expression of Bcl-6, RGS4, and RGS5, which was associated with suppression of inflammatory and atherogenic gene expression in the artery. In vitro studies demonstrated similar changes in AngII-treated macrophages: PPARdelta activation increased both total and free Bcl-6 levels and inhibited AngII activation of MAP kinases, p38, and ERK1/2. These studies uncover crucial proinflammatory mechanisms of AngII and highlight actions of PPARdelta activation to inhibit AngII signaling, which is atheroprotective.

Rosiglitazone inhibits acyl-CoA synthetase activity and fatty acid partitioning to diacylglycerol and triacylglycerol via a peroxisome proliferator-activated receptor-gamma-independent mechanism in human arterial smooth muscle cells and macrophages.

Rosiglitazone is an insulin-sensitizing agent that has recently been shown to exert beneficial effects on atherosclerosis. In addition to peroxisome proliferator-activated receptor (PPAR)-gamma, rosiglitazone can affect other targets, such as directly inhibiting recombinant long-chain acyl-CoA synthetase (ACSL)-4 activity. Because it is unknown if ACSL4 is expressed in vascular cells involved in atherosclerosis, we investigated the ability of rosiglitazone to inhibit ACSL activity and fatty acid partitioning in human and murine arterial smooth muscle cells (SMCs) and macrophages. Human and murine SMCs and human macrophages expressed Acsl4, and rosiglitazone inhibited Acsl activity in these cells. Furthermore, rosiglitazone acutely inhibited partitioning of fatty acids into phospholipids in human SMCs and inhibited fatty acid partitioning into diacylglycerol and triacylglycerol in human SMCs and macrophages through a PPAR-gamma-independent mechanism. Conversely, murine macrophages did not express ACSL4, and rosiglitazone did not inhibit ACSL activity in these cells, nor did it affect acute fatty acid partitioning into cellular lipids. Thus, rosiglitazone inhibits ACSL activity and fatty acid partitioning in human and murine SMCs and in human macrophages through a PPAR-gamma-independent mechanism likely to be mediated by ACSL4 inhibition. Therefore, rosiglitazone might alter the biological effects of fatty acids in these cells and in atherosclerosis.