Interferon γ Attenuates Insulin Signaling, Lipid Storage, and Differentiation in Human Adipocytes via Activation of the JAK/STAT Pathway

Abstract

Recent reports demonstrate T-cell infiltration of adipose tissue in early obesity. We hypothesized that interferon (IFN) γ, a major T-cell inflammatory cytokine, would attenuate human adipocyte functions and sought to establish signaling mechanisms. Differentiated human adipocytes were treated with IFNγ ± pharmacological inhibitors prior to insulin stimulation. [3H]Glucose uptake and AKT phosphorylation were assessed as markers of insulin sensitivity. IFNγ induced sustained loss of insulin-stimulated glucose uptake in human adipocytes, coincident with reduced Akt phosphorylation and down-regulation of the insulin receptor, insulin receptor substrate-1, and GLUT4. Loss of adipocyte triglyceride storage was observed with IFNγ co-incident with reduced expression of peroxisome proliferator-activated receptor γ, adiponectin, perilipin, fatty acid synthase, and lipoprotein lipase. Treatment with IFNγ also blocked differentiation of pre-adipocytes to the mature phenotype. IFNγ-induced robust STAT1 phosphorylation and SOCS1 mRNA expression, with modest, transient STAT3 phosphorylation and SOCS3 induction. Preincubation with a non-selective JAK inhibitor restored glucose uptake and Akt phosphorylation while completely reversing IFNγ suppression of adipogenic mRNAs and adipocyte differentiation. Specific inhibition of JAK2 or JAK3 failed to block IFNγ effects suggesting a predominant role for JAK1-STAT1. We demonstrate that IFNγ attenuates insulin sensitivity and suppresses differentiation in human adipocytes, an effect most likely mediated via sustained JAK-STAT1 pathway activation. Recent reports demonstrate T-cell infiltration of adipose tissue in early obesity. We hypothesized that interferon (IFN) γ, a major T-cell inflammatory cytokine, would attenuate human adipocyte functions and sought to establish signaling mechanisms. Differentiated human adipocytes were treated with IFNγ ± pharmacological inhibitors prior to insulin stimulation. [3H]Glucose uptake and AKT phosphorylation were assessed as markers of insulin sensitivity. IFNγ induced sustained loss of insulin-stimulated glucose uptake in human adipocytes, coincident with reduced Akt phosphorylation and down-regulation of the insulin receptor, insulin receptor substrate-1, and GLUT4. Loss of adipocyte triglyceride storage was observed with IFNγ co-incident with reduced expression of peroxisome proliferator-activated receptor γ, adiponectin, perilipin, fatty acid synthase, and lipoprotein lipase. Treatment with IFNγ also blocked differentiation of pre-adipocytes to the mature phenotype. IFNγ-induced robust STAT1 phosphorylation and SOCS1 mRNA expression, with modest, transient STAT3 phosphorylation and SOCS3 induction. Preincubation with a non-selective JAK inhibitor restored glucose uptake and Akt phosphorylation while completely reversing IFNγ suppression of adipogenic mRNAs and adipocyte differentiation. Specific inhibition of JAK2 or JAK3 failed to block IFNγ effects suggesting a predominant role for JAK1-STAT1. We demonstrate that IFNγ attenuates insulin sensitivity and suppresses differentiation in human adipocytes, an effect most likely mediated via sustained JAK-STAT1 pathway activation. IntroductionObesity has emerged as a major pandemic in Western society. Adipose inflammation is a key component of the pathophysiology in obesity-related insulin resistance, type 2 diabetes, and downstream complications (1.Kahn B.B. Flier J.S. J. Clin. Invest. 2000; 106: 473-481Crossref PubMed Scopus (2411) Google Scholar, 2.Goossens G.H. Physiol. Behav. 2008; 94: 206-218Crossref PubMed Scopus (379) Google Scholar, 3.Ferrante Jr., A.W. J. Intern. Med. 2007; 262: 408-414Crossref PubMed Scopus (412) Google Scholar, 4.Shoelson S.E. Lee J. Yuan M. Int. J. Obes. Relat. Metab. Disord. 2003; 27: S49-S52Crossref PubMed Scopus (381) Google Scholar). Recent work has revealed a role for adipose tissue macrophages in adiposity (5.Lumeng C.N. Bodzin J.L. Saltiel A.R. J. Clin. Invest. 2007; 117: 175-184Crossref PubMed Scopus (3255) Google Scholar, 6.Weisberg S.P. McCann D. Desai M. Rosenbaum M. Leibel R.L. Ferrante Jr., A.W. J. Clin. Invest. 2003; 112: 1796-1808Crossref PubMed Scopus (7317) Google Scholar). In early obesity, resident macrophages shift from a non-inflammatory, regulatory M2 phenotype toward the classical, pro-inflammatory M1 (CCR2+) phenotype (5.Lumeng C.N. Bodzin J.L. Saltiel A.R. J. Clin. Invest. 2007; 117: 175-184Crossref PubMed Scopus (3255) Google Scholar). A high-fat diet increases circulating and adipose MCP1 (7.Chen A. Mumick S. Zhang C. Lamb J. Dai H. Weingarth D. Mudgett J. Chen H. MacNeil D.J. Reitman M.L. Qian S. Obes. Res. 2005; 13: 1311-1320Crossref PubMed Scopus (178) Google Scholar) and promotes monocyte recruitment/retention in adipose (6.Weisberg S.P. McCann D. Desai M. Rosenbaum M. Leibel R.L. Ferrante Jr., A.W. J. Clin. Invest. 2003; 112: 1796-1808Crossref PubMed Scopus (7317) Google Scholar, 8.Lumeng C.N. Deyoung S.M. Bodzin J.L. Saltiel A.R. Diabetes. 2007; 56: 16-23Crossref PubMed Scopus (759) Google Scholar). Paracrine adipose tissue macrophage-adipocyte cross-talk induces adipocyte inflammation, modulates adipocytokines (9.Permana P.A. Menge C. Reaven P.D. Biochem. Biophys. Res. Commun. 2006; 341: 507-514Crossref PubMed Scopus (238) Google Scholar), and drives local and systemic insulin resistance and type 2 diabetes (10.Antuna-Puente B. Feve B. Fellahi S. Bastard J.P. Diabetes Metab. 2008; 34: 2-11Crossref PubMed Scopus (573) Google Scholar).The triggers for adipose macrophage switching are poorly understood. Emerging reports demonstrate loss of regulatory T-cells (Treg) (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. 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Med. 2009; 15: 914-920Crossref PubMed Scopus (1586) Google Scholar) and infiltration of inflammatory T-cells, particularly interferon (IFN) γ 2The abbreviations used are: IFNinterferonPPARperoxisome proliferator-activated receptorJAK1 and 2Janus family kinases 1 and 2STATsignal transducers and activator of transcriptionSOCSsuppressor of cytokine signalingSGBSSimpson-Golabi-Behmel syndromeELISAenzyme-linked immunosorbent assaySFMserum-free mediumBSAbovine serum albuminPBSphosphate-buffered salineIRinsulin receptorIRSinsulin receptor substrateMAPKmitogen-activated protein kinaseILinterleukin. -secreting T helper type 1 (TH1) cells (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. Med. 2009; 15: 921-929Crossref PubMed Scopus (1021) Google Scholar) and effector CD8+ T-cells (13.Nishimura S. Manabe I. Nagasaki M. Eto K. Yamashita H. Ohsugi M. Otsu M. Hara K. Ueki K. Sugiura S. Yoshimura K. Kadowaki T. Nagai R. Nat. Med. 2009; 15: 914-920Crossref PubMed Scopus (1586) Google Scholar, 14.Rausch M.E. Weisberg S. Vardhana P. Tortoriello D.V. Int. J. Obes. 2008; 32: 451-463Crossref PubMed Scopus (424) Google Scholar), with increasing adipose expression of T-cell chemokines (15.Wu H. Ghosh S. Perrard X.D. Feng L. Garcia G.E. Perrard J.L. Sweeney J.F. Peterson L.E. Chan L. Smith C.W. Ballantyne C.M. Circulation. 2007; 115: 1029-1038Crossref PubMed Scopus (504) Google Scholar). Furthermore, infiltration of T-cells into adipose tissue during obesity has been shown to precede macrophage recruitment (16.Kintscher U. Hartge M. Hess K. Foryst-Ludwig A. Clemenz M. Wabitsch M. Fischer-Posovszky P. Barth T.F. Dragun D. Skurk T. Hauner H. Bluher M. Unger T. Wolf A.M. Knippschild U. Hombach V. Marx N. Arterioscler. Thromb. Vasc. Biol. 2008; 28: 1304-1310Crossref PubMed Scopus (543) Google Scholar). T-cell cytokines, in particular pro-inflammatory IFNγ (17.Schoenborn J.R. Wilson C.B. Adv. Immunol. 2007; 96: 41-101Crossref PubMed Scopus (1165) Google Scholar), promote the macrophage M1 phenotype (18.Mantovani A. Sozzani S. Locati M. Allavena P. Sica A. Trends Immunol. 2002; 23: 549-555Abstract PubMed Scopus Google Scholar). G. K. I. P. Res. 2008; PubMed Scopus Google Scholar) a role for IFNγ in adipose inflammation, obesity, and glucose in the role and of IFNγ of adipocyte functions are poorly IFNγ receptor of and that to of family kinases 1 and 2 and phosphorylation of transducers and activator of with to the M. Immunol. 15: PubMed Scopus Google Scholar). of induces of cytokine signaling 1 and and Nat. Immunol. 2002; PubMed Scopus Google Scholar), been in insulin resistance in adipocyte and insulin resistance in and in L. Yuan M. D. Shoelson S. J. Biol. 2002; PubMed Scopus Google Scholar, K. T. Biol. PubMed Scopus Google Scholar, B. P. C. C. K. D.J. E. J. Biol. PubMed Scopus Google Scholar). IFNγ and signaling are for adipocyte inflammation and insulin resistance in the demonstrate that IFNγ induces insulin resistance in mature human effect was and with suppression of insulin signaling markers of adipocyte differentiation and reduced triglyceride Furthermore, IFNγ completely differentiation to mature of the pathway with a non-selective JAK inhibitor effects of IFNγ in mature In inhibition of JAK2 failed to IFNγ effects suggesting an role for establish the pathway as a and a for of adipose inflammation and insulin resistance in human obesity and type 2 was from human cells were a from of human pre-adipocytes were from adipose during the of the of JAK inhibitor and JAK3 inhibitor human and serum were from human IFNγ was from and human was from was a from of was from were from human adipocytes were as M. I. M. P. E. Hauner H. Int. J. Obes. Relat. Metab. Disord. PubMed Scopus Google Scholar). human pre-adipocytes were from adipose Adipose was and with were and the in pre-adipocytes were to cells were in differentiation insulin human and for was with and for a were to adipocytes as J.S. Chen D. J. Biol. PubMed Scopus Google human adipocytes were treated with IFNγ in serum for the cells were in cells was and with were and prior to the glucose uptake was In mature adipocytes were treated with increasing of IFNγ in for and glucose uptake was In cells were for 2 ± inhibitors or ± and with IFNγ ± inhibitors or ± for a the of cells were glucose in for prior to insulin for of glucose was to cells prior to with were in and uptake was were for in glucose uptake is were treated ± IFNγ differentiation in differentiation in effects insulin-stimulated glucose uptake and were assessed the of the differentiation was the acid protein of protein were to and blocked in in prior to in were with to JAK2 or were in and and adipocytes ± the were in and was to the and and were from and the cells were was an of were assessed an and were from the mRNA were to for the for from the for the of a for was with the for the to and were treated with IFNγ ± inhibitors ± prior to in were with for 1 and was were a cells were to was of and In treated cells were in prior to triglyceride the adipocytes were in or and were as adipocytes were treated for to cells were with for to for cells were with and in for and cells were a for adipocytes were treated as and was the a for were with are as ± S.E. with of was used to for in of was were for were that loss of cells (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. Med. 2009; 15: 921-929Crossref PubMed Scopus (1021) Google Scholar, 12.Feuerer M. Herrero L. Cipolletta D. Naaz A. Wong J. Nayer A. Lee J. Goldfine A.B. Benoist C. Shoelson S. Mathis D. Nat. Med. 2009; 15: 930-939Crossref PubMed Scopus (1484) Google Scholar, 13.Nishimura S. Manabe I. Nagasaki M. Eto K. Yamashita H. Ohsugi M. Otsu M. Hara K. Ueki K. Sugiura S. Yoshimura K. Kadowaki T. Nagai R. Nat. Med. 2009; 15: 914-920Crossref PubMed Scopus (1586) Google Scholar) coincident with of inflammatory T-cells in adipose (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. Med. 2009; 15: 921-929Crossref PubMed Scopus (1021) Google Scholar, 13.Nishimura S. Manabe I. Nagasaki M. Eto K. Yamashita H. Ohsugi M. Otsu M. Hara K. Ueki K. Sugiura S. Yoshimura K. Kadowaki T. Nagai R. Nat. Med. 2009; 15: 914-920Crossref PubMed Scopus (1586) Google Scholar, 14.Rausch M.E. Weisberg S. Vardhana P. Tortoriello D.V. Int. J. Obes. 2008; 32: 451-463Crossref PubMed Scopus (424) Google Scholar) are early in obesity that adipose inflammation and adipocyte insulin resistance prior to macrophage infiltration (16.Kintscher U. Hartge M. Hess K. Foryst-Ludwig A. Clemenz M. Wabitsch M. Fischer-Posovszky P. Barth T.F. Dragun D. Skurk T. Hauner H. Bluher M. Unger T. Wolf A.M. Knippschild U. Hombach V. Marx N. Arterioscler. Thromb. Vasc. Biol. 2008; 28: 1304-1310Crossref PubMed Scopus (543) Google Scholar). We demonstrate that a inflammatory T-cell cytokine, induced insulin resistance, markers of and reduced storage in human adipocytes via the most likely mediated sustained activation. establish and the as and for inflammatory human adipose inflammation and insulin tissue inflammation has emerged as a of diet and insulin resistance S.E. Lee J. Yuan M. Int. J. Obes. Relat. Metab. Disord. 2003; 27: S49-S52Crossref PubMed Scopus (381) Google Scholar, Diabetes. PubMed Google Scholar). systemic of and P.A. M. R. J. Clin. Invest. PubMed Scopus Google Scholar, S. S. N. Y. A. B. J. Med. 2006; PubMed Scopus Google Scholar) are in obesity, glucose in PubMed Scopus Google Scholar, V. I. Smith U. J. Biol. 2003; PubMed Scopus Google Scholar), and attenuate insulin sensitivity in C. PubMed Scopus Google Scholar, S. I. V. T. I. J. J. F. Smith U. 2008; PubMed Scopus Google Scholar). adipocytes, observed in obesity, monocyte promote macrophage recruitment into adipose P. D.J. 2003; PubMed Scopus Google Scholar). Furthermore, resident M2 macrophages to a pro-inflammatory M1 phenotype adipose tissue inflammation (5.Lumeng C.N. Bodzin J.L. Saltiel A.R. J. Clin. Invest. 2007; 117: 175-184Crossref PubMed Scopus (3255) Google Scholar, 8.Lumeng C.N. Deyoung S.M. Bodzin J.L. Saltiel A.R. Diabetes. 2007; 56: 16-23Crossref PubMed Scopus (759) Google Scholar). that adipose macrophage phenotype switching is poorly understood. a cytokine, macrophages toward an M1 phenotype (18.Mantovani A. Sozzani S. Locati M. Allavena P. Sica A. Trends Immunol. 2002; 23: 549-555Abstract PubMed Scopus Google Scholar). is that inflammatory T-cell infiltration of with of a role in and switching to pro-inflammatory work and inflammatory T-cells and IFNγ in early adipose inflammation and adipocyte (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. Med. 2009; 15: 921-929Crossref PubMed Scopus (1021) Google Scholar, 12.Feuerer M. Herrero L. Cipolletta D. Naaz A. Wong J. Nayer A. Lee J. Goldfine A.B. Benoist C. Shoelson S. Mathis D. Nat. Med. 2009; 15: 930-939Crossref PubMed Scopus (1484) Google Scholar, 13.Nishimura S. Manabe I. Nagasaki M. Eto K. Yamashita H. Ohsugi M. Otsu M. Hara K. Ueki K. Sugiura S. Yoshimura K. Kadowaki T. Nagai R. Nat. Med. 2009; 15: 914-920Crossref PubMed Scopus (1586) Google Scholar, U. Hartge M. Hess K. Foryst-Ludwig A. Clemenz M. Wabitsch M. Fischer-Posovszky P. Barth T.F. Dragun D. Skurk T. Hauner H. Bluher M. Unger T. Wolf A.M. Knippschild U. Hombach V. Marx N. Arterioscler. Thromb. Vasc. Biol. 2008; 28: 1304-1310Crossref PubMed Scopus (543) Google Scholar, G. K. I. P. Res. 2008; PubMed Scopus Google Scholar). G. K. I. P. Res. 2008; PubMed Scopus Google Scholar) an of and CD8+ cells in adipose tissue of Furthermore, of inflammatory cells in adipose tissue and glucose of T-cells, observed with early insulin resistance, the of macrophages was (16.Kintscher U. Hartge M. Hess K. Foryst-Ludwig A. Clemenz M. Wabitsch M. Fischer-Posovszky P. Barth T.F. Dragun D. Skurk T. Hauner H. Bluher M. Unger T. Wolf A.M. Knippschild U. Hombach V. Marx N. Arterioscler. Thromb. Vasc. Biol. 2008; 28: 1304-1310Crossref PubMed Scopus (543) Google Scholar). reports (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. Med. 2009; 15: 921-929Crossref PubMed Scopus (1021) Google Scholar, 12.Feuerer M. Herrero L. Cipolletta D. Naaz A. Wong J. Nayer A. Lee J. Goldfine A.B. Benoist C. Shoelson S. Mathis D. Nat. Med. 2009; 15: 930-939Crossref PubMed Scopus (1484) Google Scholar, 13.Nishimura S. Manabe I. Nagasaki M. Eto K. Yamashita H. Ohsugi M. Otsu M. Hara K. Ueki K. Sugiura S. Yoshimura K. Kadowaki T. Nagai R. Nat. Med. 2009; 15: 914-920Crossref PubMed Scopus (1586) Google Scholar) demonstrate an of T cells in adipose tissue with obesity and that resident adipose T cells particular and obesity and insulin resistance (13.Nishimura S. Manabe I. Nagasaki M. Eto K. Yamashita H. Ohsugi M. Otsu M. Hara K. Ueki K. Sugiura S. Yoshimura K. Kadowaki T. Nagai R. Nat. Med. 2009; 15: 914-920Crossref PubMed Scopus (1586) Google Scholar) also that of CD8+ T-cells macrophage infiltration and adipose tissue inflammation while insulin sensitivity. Winer and (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. Med. 2009; 15: 921-929Crossref PubMed Scopus (1021) Google Scholar) adipose of IFNγ CD8+ T-cells and that with T-cells in with obesity and insulin resistance, M. Herrero L. Cipolletta D. Naaz A. Wong J. Nayer A. Lee J. Goldfine A.B. Benoist C. Shoelson S. Mathis D. Nat. Med. 2009; 15: 930-939Crossref PubMed Scopus (1484) Google Scholar) that a of adipose inflammation, are in adipose in adipose of of cells in reduced adipose insulin sensitivity M. Herrero L. Cipolletta D. Naaz A. Wong J. Nayer A. Lee J. Goldfine A.B. Benoist C. Shoelson S. Mathis D. Nat. Med. 2009; 15: 930-939Crossref PubMed Scopus (1484) Google of T-cell in adipose inflammation, is of the of IFNγ of adipocyte In the the effects of IFNγ insulin and differentiation in human We that IFNγ induced a of insulin-stimulated glucose uptake and AKT of insulin that IFNγ-induced insulin resistance as as suggesting of adipocyte functions local observed in and in reduced glucose uptake was suggesting that of insulin signaling as phosphorylation of is to the of the IFNγ IFNγ reduced expression of insulin signaling and reduced protein were observed coincident with reduced glucose mature adipocytes, IFNγ reduced triglyceride coincident with and sustained suppression of mRNAs for adipogenic fatty acid synthase, lipoprotein adiponectin, and Furthermore, during the with differentiation of IFNγ to pre-adipocytes completely blocked and insulin-stimulated glucose of adipocyte is for adipocyte differentiation and insulin sensitivity Y. J. N. M. 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Diabetes. 2006; PubMed Scopus Google Scholar). that suppression of insulin signaling and of adipocyte that of to the effects of IFNγ insulin JAK inhibition the effects of IFNγ insulin sensitivity and storage while also effects of In inhibitors of JAK2 or STAT3 as as inhibitors of JAK3 and failed to attenuate the effects of pharmacological for the that is for IFNγ in human sought in human adipocytes to an signaling that as and phosphorylation of STAT3 STAT1 C. J.L. C.M. Jr., M. Nat. PubMed Scopus Google Scholar, P. P. F. R. 2000; PubMed Scopus Google Scholar, Y. D. B. J. Biol. PubMed Scopus Google Scholar). We that a JAK2 induced SOCS3 expression to a SOCS1 with STAT3 activation. Furthermore, induced a in human adipocytes to IFNγ with a effect markers of differentiation and suppression of that STAT1 with the that is to N. J. E. Y. S. Res. 2006; PubMed Scopus Google Scholar) and that of JAK2 STAT1 phosphorylation C.M. Google Scholar, C. J.L. C.M. Jr., M. Nat. PubMed Scopus Google Scholar, P. P. F. R. 2000; PubMed Scopus Google Scholar), that the major role in IFNγ effects human in that a insulin resistance and glucose in L. G. H. Y. G. Diabetes Obes. Metab. 2007; PubMed Scopus Google Scholar) an role for pathway in insulin demonstrate that IFNγ attenuates insulin and differentiation in human adipocytes, an effect likely mediated via sustained STAT1 activation. T-cell cytokines, particularly an role in T-cell of obesity, insulin resistance, and type 2 diabetes via of the adipocyte IntroductionObesity has emerged as a major pandemic in Western society. Adipose inflammation is a key component of the pathophysiology in obesity-related insulin resistance, type 2 diabetes, and downstream complications (1.Kahn B.B. Flier J.S. J. Clin. Invest. 2000; 106: 473-481Crossref PubMed Scopus (2411) Google Scholar, 2.Goossens G.H. Physiol. Behav. 2008; 94: 206-218Crossref PubMed Scopus (379) Google Scholar, 3.Ferrante Jr., A.W. J. Intern. Med. 2007; 262: 408-414Crossref PubMed Scopus (412) Google Scholar, 4.Shoelson S.E. Lee J. Yuan M. Int. J. Obes. Relat. Metab. Disord. 2003; 27: S49-S52Crossref PubMed Scopus (381) Google Scholar). Recent work has revealed a role for adipose tissue macrophages in adiposity (5.Lumeng C.N. Bodzin J.L. Saltiel A.R. J. Clin. Invest. 2007; 117: 175-184Crossref PubMed Scopus (3255) Google Scholar, 6.Weisberg S.P. McCann D. Desai M. Rosenbaum M. Leibel R.L. Ferrante Jr., A.W. J. Clin. Invest. 2003; 112: 1796-1808Crossref PubMed Scopus (7317) Google Scholar). In early obesity, resident macrophages shift from a non-inflammatory, regulatory M2 phenotype toward the classical, pro-inflammatory M1 (CCR2+) phenotype (5.Lumeng C.N. Bodzin J.L. Saltiel A.R. J. Clin. Invest. 2007; 117: 175-184Crossref PubMed Scopus (3255) Google Scholar). A high-fat diet increases circulating and adipose MCP1 (7.Chen A. Mumick S. Zhang C. Lamb J. Dai H. Weingarth D. Mudgett J. Chen H. MacNeil D.J. Reitman M.L. Qian S. Obes. Res. 2005; 13: 1311-1320Crossref PubMed Scopus (178) Google Scholar) and promotes monocyte recruitment/retention in adipose (6.Weisberg S.P. McCann D. Desai M. Rosenbaum M. Leibel R.L. Ferrante Jr., A.W. J. Clin. Invest. 2003; 112: 1796-1808Crossref PubMed Scopus (7317) Google Scholar, 8.Lumeng C.N. Deyoung S.M. Bodzin J.L. Saltiel A.R. Diabetes. 2007; 56: 16-23Crossref PubMed Scopus (759) Google Scholar). Paracrine adipose tissue macrophage-adipocyte cross-talk induces adipocyte inflammation, modulates adipocytokines (9.Permana P.A. Menge C. Reaven P.D. Biochem. Biophys. Res. Commun. 2006; 341: 507-514Crossref PubMed Scopus (238) Google Scholar), and drives local and systemic insulin resistance and type 2 diabetes (10.Antuna-Puente B. Feve B. Fellahi S. Bastard J.P. Diabetes Metab. 2008; 34: 2-11Crossref PubMed Scopus (573) Google Scholar).The triggers for adipose macrophage switching are poorly understood. Emerging reports demonstrate loss of regulatory T-cells (Treg) (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. Med. 2009; 15: 921-929Crossref PubMed Scopus (1021) Google Scholar, 12.Feuerer M. Herrero L. Cipolletta D. Naaz A. Wong J. Nayer A. Lee J. Goldfine A.B. Benoist C. Shoelson S. Mathis D. Nat. Med. 2009; 15: 930-939Crossref PubMed Scopus (1484) Google Scholar, 13.Nishimura S. Manabe I. Nagasaki M. Eto K. Yamashita H. Ohsugi M. Otsu M. Hara K. Ueki K. Sugiura S. Yoshimura K. Kadowaki T. Nagai R. Nat. Med. 2009; 15: 914-920Crossref PubMed Scopus (1586) Google Scholar) and infiltration of inflammatory T-cells, particularly interferon (IFN) γ 2The abbreviations used are: IFNinterferonPPARperoxisome proliferator-activated receptorJAK1 and 2Janus family kinases 1 and 2STATsignal transducers and activator of transcriptionSOCSsuppressor of cytokine signalingSGBSSimpson-Golabi-Behmel syndromeELISAenzyme-linked immunosorbent assaySFMserum-free mediumBSAbovine serum albuminPBSphosphate-buffered salineIRinsulin receptorIRSinsulin receptor substrateMAPKmitogen-activated protein kinaseILinterleukin. -secreting T helper type 1 (TH1) cells (11.Winer S. Chan Y. Paltser G. Truong D. Tsui H. Bahrami J. Dorfman R. Wang Y. Zielenski J. Mastronardi F. Maezawa Y. Drucker D.J. Engleman E. Winer D. Dosch H.M. Nat. Med. 2009; 15: 921-929Crossref PubMed Scopus (1021) Google Scholar) and effector CD8+ T-cells (13.Nishimura S. Manabe I. Nagasaki M. Eto K. Yamashita H. Ohsugi M. Otsu M. Hara K. Ueki K. 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