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Metabolic dysfunction drives a mechanistically distinct proinflammatory phenotype in adipose tissue macrophages.

ABSTRACT: Adipose tissue macrophage (ATM)-driven inflammation plays a key role in insulin resistance; however, factors activating ATMs are poorly understood. Using a proteomics approach, we show that markers of classical activation are absent on ATMs from obese humans but are readily detectable on airway macrophages of patients with cystic fibrosis, a disease associated with chronic bacterial infection. Moreover, treating macrophages with glucose, insulin, and palmitate-conditions characteristic of the metabolic syndrome-produces a "metabolically activated" phenotype distinct from classical activation. Markers of metabolic activation are expressed by proinflammatory ATMs in obese humans/mice and are positively correlated with adiposity. Metabolic activation is driven by independent proinflammatory and anti-inflammatory pathways, which regulate balance between cytokine production and lipid metabolism. We identify PPAR? and p62/SQSTM1 as two key proteins that promote lipid metabolism and limit inflammation in metabolically activated macrophages. Collectively, our data provide important mechanistic insights into pathways that drive the metabolic-disease-specific phenotype of macrophages.

SUBMITTER: Kratz M

PROVIDER: S-EPMC4192131 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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Metabolic dysfunction drives a mechanistically distinct proinflammatory phenotype in adipose tissue macrophages.

Kratz Mario M Coats Brittney R BR Hisert Katherine B KB Hagman Derek D Mutskov Vesco V Peris Eduard E Schoenfelt Kelly Q KQ Kuzma Jessica N JN Larson Ilona I Billing Peter S PS Landerholm Robert W RW Crouthamel Matthew M Gozal David D Hwang Seungmin S Singh Pradeep K PK Becker Lev L

Cell metabolism 20140918 4

Adipose tissue macrophage (ATM)-driven inflammation plays a key role in insulin resistance; however, factors activating ATMs are poorly understood. Using a proteomics approach, we show that markers of classical activation are absent on ATMs from obese humans but are readily detectable on airway macrophages of patients with cystic fibrosis, a disease associated with chronic bacterial infection. Moreover, treating macrophages with glucose, insulin, and palmitate-conditions characteristic of the me ...[more]

PMID: 25242226

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Project description:The roles of adipokines, proinflammatory cytokines, and adipose tissue macrophages in obesity-associated insulin resistance have been explored in both animal and human studies. However, our current understanding of obesity-associated insulin resistance relies on studies of artificial metabolic extremes. The purpose of this study was to explore the roles of adipokines, proinflammatory cytokines, and adipose tissue macrophages in human patients with modest obesity and early metabolic dysfunction. We obtained omental adipose tissue and fasting blood samples from 51 females undergoing gynecologic surgery. We investigated serum concentrations of proinflammatory cytokines and adipokines as well as the mRNA expression of proinflammatory and macrophage phenotype markers in visceral adipose tissue using ELISA and quantitative RT-PCR. We measured adipose tissue inflammation and macrophage infiltration using immunohistochemical analysis. Serum levels of adiponectin and leptin were significantly correlated with HOMA-IR and body mass index. The levels of expression of MCP-1 and TNF-α in visceral adipose tissue were also higher in the obese group (body mass index ≥ 25). The expression of mRNA MCP-1 in visceral adipose tissue was positively correlated with body mass index (r = 0.428, p = 0.037) but not with HOMA-IR, whereas TNF-α in visceral adipose tissue was correlated with HOMA-IR (r = 0.462, p = 0.035) but not with body mass index. There was no obvious change in macrophage phenotype or macrophage infiltration in patients with modest obesity or early metabolic dysfunction. Expression of mRNA CD163/CD68 was significantly related to mitochondrial-associated genes and serum inflammatory cytokine levels of resistin and leptin. These results suggest that changes in the production of inflammatory biomolecules precede increased immune cell infiltration and induction of a macrophage phenotype switch in visceral adipose tissue. Furthermore, serum resistin and leptin have specific roles in the regulation of adipose tissue macrophages in patients with modest obesity or early metabolic dysfunction.

Project description:ObjectiveThe human adaptive fasting response enables survival during periods of caloric deprivation. A crucial component of the fasting response is the shift from glucose metabolism to utilization of lipids, underscoring the importance of adipose tissue as the central lipid-storing organ. The objective of this study was to investigate the response of adipose tissue to a prolonged fast in humans.MethodsWe performed RNA sequencing of subcutaneous adipose tissue samples longitudinally collected during a 10-day, 0-calorie fast in humans. We further investigated observed transcriptional signatures utilizing cultured human monocytes and Thp1 cells. We examined the cellularity of adipose tissue biopsies with transmission electron microscopy and tested for associated changes in relevant inflammatory mediators in the systemic circulation by ELISA assays of longitudinally collected blood samples.ResultsCoincident with the expected shift away from glucose utilization and lipid storage, we demonstrated downregulation of pathways related to glycolysis, oxidative phosphorylation, and lipogenesis. The canonical lipolysis pathway was also downregulated, whereas fasting drove alternative lysosomal paths to lipid digestion. Unexpectedly, the dominant induced pathways were associated with immunity and inflammation, although this only became evident at the 10-day time point. Among the most augmented transcripts were those associated with macrophage identity and function, such as members of the erythroblast transformation-specific (ETS) transcription factor family. Key components of the macrophage transcriptional signal in fasting adipose tissue were recapitulated with induced expression of two of the ETS transcription factors via cultured macrophages, SPIC and SPI1. The inflammatory signal was further reflected by an increase in systemic inflammatory mediators.ConclusionsCollectively, this study demonstrates an unexpected role of metabolic inflammation in the human adaptive fasting response.

Project description:Aims/hypothesisRecent studies have identified intracellular metabolism as a fundamental determinant of macrophage function. In obesity, proinflammatory macrophages accumulate in adipose tissue and trigger chronic low-grade inflammation, that promotes the development of systemic insulin resistance, yet changes in their intracellular energy metabolism are currently unknown. We therefore set out to study metabolic signatures of adipose tissue macrophages (ATMs) in lean and obese conditions.MethodsF4/80-positive ATMs were isolated from obese vs lean mice. High-fat feeding of wild-type mice and myeloid-specific Hif1α-/- mice was used to examine the role of hypoxia-inducible factor-1α (HIF-1α) in ATMs part of obese adipose tissue. In vitro, bone marrow-derived macrophages were co-cultured with adipose tissue explants to examine adipose tissue-induced changes in macrophage phenotypes. Transcriptome analysis, real-time flux measurements, ELISA and several other approaches were used to determine the metabolic signatures and inflammatory status of macrophages. In addition, various metabolic routes were inhibited to determine their relevance for cytokine production.ResultsTranscriptome analysis and extracellular flux measurements of mouse ATMs revealed unique metabolic rewiring in obesity characterised by both increased glycolysis and oxidative phosphorylation. Similar metabolic activation of CD14+ cells in obese individuals was associated with diabetes outcome. These changes were not observed in peritoneal macrophages from obese vs lean mice and did not resemble metabolic rewiring in M1-primed macrophages. Instead, metabolic activation of macrophages was dose-dependently induced by a set of adipose tissue-derived factors that could not be reduced to leptin or lactate. Using metabolic inhibitors, we identified various metabolic routes, including fatty acid oxidation, glycolysis and glutaminolysis, that contributed to cytokine release by ATMs in lean adipose tissue. Glycolysis appeared to be the main contributor to the proinflammatory trait of macrophages in obese adipose tissue. HIF-1α, a key regulator of glycolysis, nonetheless appeared to play no critical role in proinflammatory activation of ATMs during early stages of obesity.Conclusions/interpretationOur results reveal unique metabolic activation of ATMs in obesity that promotes inflammatory cytokine release. Further understanding of metabolic programming in ATMs will most likely lead to novel therapeutic targets to curtail inflammatory responses in obesity.Data availabilityMicroarray data of ATMs isolated from obese or lean mice have been submitted to the Gene Expression Omnibus (accession no. GSE84000).

Project description:BackgroundMetabolic disorders such as obesity and diabetes mellitus can cause dysfunction of endothelial cells (ECs) and vascular rarefaction in adipose tissues. However, the modulatory role of ECs in adipose tissue function is not fully understood. Other than vascular endothelial growth factor-vascular endothelial growth factor receptor-mediated angiogenic signaling, little is known about the EC-derived signals in adipose tissue regulation. We previously identified Argonaute 1 (AGO1; a key component of microRNA-induced silencing complex) as a crucial regulator in hypoxia-induced angiogenesis. In this study, we intend to determine the AGO1-mediated EC transcriptome, the functional importance of AGO1-regulated endothelial function in vivo, and the relevance to adipose tissue function and obesity.MethodsWe generated and subjected mice with EC-AGO1 deletion (EC-AGO1-knockout [KO]) and their wild-type littermates to a fast food-mimicking, high-fat high-sucrose diet and profiled the metabolic phenotypes. We used crosslinking immunoprecipitation- and RNA-sequencing to identify the AGO1-mediated mechanisms underlying the observed metabolic phenotype of EC-AGO1-KO. We further leveraged cell cultures and mouse models to validate the functional importance of the identified molecular pathway, for which the translational relevance was explored using human endothelium isolated from healthy donors and donors with obesity/type 2 diabetes mellitus.ResultsWe identified an antiobesity phenotype of EC-AGO1-KO, evident by lower body weight and body fat, improved insulin sensitivity, and enhanced energy expenditure. At the organ level, we observed the most significant phenotype in the subcutaneous and brown adipose tissues of KO mice, with greater vascularity and enhanced browning and thermogenesis. Mechanistically, EC-AGO1 suppression results in inhibition of thrombospondin-1 (THBS1/TSP1), an antiangiogenic and proinflammatory cytokine that promotes insulin resistance. In EC-AGO1-KO mice, overexpression of TSP1 substantially attenuated the beneficial phenotype. In human endothelium isolated from donors with obesity or type 2 diabetes mellitus, AGO1 and THBS1 are expressed at higher levels than the healthy controls, supporting a pathological role of this pathway.ConclusionsOur study suggests a novel mechanism by which ECs, through the AGO1-TSP1 pathway, control vascularization and function of adipose tissues, insulin sensitivity, and whole-body metabolic state.

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Metabolic dysfunction drives a mechanistically distinct proinflammatory phenotype in adipose tissue macrophages.

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Metabolic dysfunction drives a mechanistically distinct proinflammatory phenotype in adipose tissue macrophages.

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