International Journal of Obesity (2009) 33, 151–156 & 2009 Macmillan Publishers Limited All rights reserved 0307-0565/09 $32.00 www.nature.com/ijo ORIGINAL ARTICLE Increased activity of -23/interleukin-17 proinflammatory axis in obese women

M Sumarac-Dumanovic1,6, D Stevanovic2,6, A Ljubic3, J Jorga4, M Simic1, D Stamenkovic-Pejkovic1, V Starcevic2, V Trajkovic5 and D Micic1

1Institute of Endocrinology, Diabetes and Diseases of Metabolism, School of Medicine, University of Belgrade, Belgrade, Serbia; 2Institute of Physiology, School of Medicine, University of Belgrade, Belgrade, Serbia; 3Institute for Obstetrics and Gynecology, Clinical Center of Serbia, Belgrade, Serbia; 4Department of Hygiene and Medical Ecology, School of Medicine, University of Belgrade, Belgrade, Serbia and 5Institute of Microbiology and , School of Medicine, University of Belgrade, Belgrade, Serbia

Objective: To compare the concentrations of belonging to Th17 axis (interleukin (IL)-17 and IL-23) and Th1 axis (IL-12 and (IFN)-g) in obese and lean women, and to investigate their relationships with the proinflammatory adipokine leptin, proinflammatory migration inhibitory factor (MIF) and anthropometric and metabolic parameters of obesity. Design: Cross-sectional study. Subjects: Twenty-six obese women (age 20–52 years, body mass index (BMI): 30–48 kg/m2) and 20 healthy lean women (age 23–46 years, BMI: 18–25 kg/m2). Measurements: Plasma levels of cytokines and leptin, BMI, waist circumference (WC) and insulin resistance index HOMA (homeostatic model assessment). Results: Blood concentrations of IL-17, IL-23, MIF and leptin, but not IL-12 or IFN-g, were higher in obese compared with lean women (P ¼ 0.002, 0.046, 0.006 and 0.002, respectively). There was a positive correlation between IL-17 and IL-23 (rs ¼ 0.530), which was at the border of statistical significance (P ¼ 0.065). Neither IL-17 nor IL-23 correlated with leptin or MIF, and there was no association between IL-17 and IL-23 levels with BMI, WC or HOMA index. Conclusion: Interleukin-23/IL-17 axis is stimulated in obese women independently of the increase in abdominal fat, insulin resistance, leptin and MIF levels. International Journal of Obesity (2009) 33, 151–156; doi:10.1038/ijo.2008.216; published online 4 November 2008

Keywords: ; cytokine; IL-17; IL-23; leptin; MIF

Introduction accumulated to support the role of a chronic low-grade inflammation in the pathogenesis of insulin resistance The increase in proinflammatory cytokine production and the metabolic syndrome.2,3 Moreover, inflammation has been recognized as an important marker of obesity is involved in the pathogenesis of atherosclerosis, acute and accompanying metabolic changes. Following the myocardial infarction and stroke,4 while the increased initial demonstration of the involvement of the principal concentration of inflammatory marker clusters with obesity- proinflammatory cytokine -a (TNFa) related cardiovascular risk factors, such as dyslipidemia, in obesity complications,1 a large body of evidence has glucose intolerance and type 2 diabetes.5 Unlike ‘classic’ proinflammatory mediators, such as TNF-a, interleukin-6 (IL-6) and C-reactive protein,2,3 the T-cell- Correspondence: Professor D Micic, Institute of Endocrinology, Diabetes and derived cytokines, such as interferon-g (IFN-g) and IL-17, Diseases of Metabolism, Dr Subotica 13, Belgrade 11000, Serbia. E-mail: [email protected] and have not been extensively investigated in obesity. IFN-g and Dr V Trajkovic, Institute of Microbiology and Immunology, School of IL-17 are mainly induced by /-derived Medicine, Dr Subotica 1, Belgrade 11000, Serbia. IL-12 and IL-23, respectively, and have been implicated not E-mail: [email protected] only in the defense against and infection, but also in 6These authors contributed equally to this work. Received 21 May 2008; revised 2 September 2008; accepted 6 September pathology associated with the inflammatory response in 6,7 2008; published online 4 November 2008 . In addition to stimulating secretion of IL-23/IL-17 axis in obese women M Sumarac-Dumanovic et al 152 other proinflammatory cytokines, both IFN-g and IL-17 are morning, after an overnight fast, using an EDTA-containing involved in the induction of potentially harmful mediators vacutainer (Becton-Dickinson GmbH, Heidelberg, Germany). of inflammation, such as free radical nitric oxide.8 Moreover, The tubes were immediately inverted 7–8 times to mix the some recent findings suggest that inflammation-related anticoagulant, slowly cooled to 4 1C and centrifuged within tissue damage in organ-specific autoimmunity could be 1 h to obtain plasma. The plasma samples were stored associated with the IL-23/IL-17-dependent T-helper cell at À70 1C. Insulin resistance was determined on the basis response (that is, Th17 response), rather than with the of the homeostasis model assessment (HOMA) index, activity of IL-12/IFN-g cytokine axis as the main driving calculated from the fasting glucose and insulin concen- power behind the so-called Th1 response.9 Although there trations: HOMA ¼ fasting insulin (IU mlÀ1) Â fasting glucose are some data indicating that Th1 response might be reduced (mmol lÀ1)/22.5. in malnourished and increased in obese children,10–12 IL-23 and IL-17 have not been investigated as potential markers of the inflammatory syndrome in obesity. Their exploration in Cytokine and hormone measurements obesity is warranted by recent findings indicating that the Insulin was determined by radioimmunoassay kit (Inep proinflammatory adipokine leptin and the proinflammatory Zemun, Belgrade, Serbia). The lower limit of detection for cytokine macrophage migration inhibitory factor (MIF), insulin was 0.6 IU mlÀ1, whereas the intra-assay coefficients both known to be increased in obese humans,13–17 might of variation were 3.84% for the concentration 15.5 IU mlÀ1, stimulate IL-17 production in T cells.18,19 2.51% for the concentration 31.7 IU mlÀ1 and 5.25% for the The aim of this study was to investigate the activity of concentration 117.0 IU mlÀ1. Total leptin was determined by IL-23/IL-17 and IL-12/IFN-g cytokine axis in obesity, as well radioimmunoassay kit (Linco Research, St Charles, MO, USA) as their relationship with the proinflammatory mediators with an intra-assay coefficient of variation of less than 6%. MIF and leptin. The association between cytokine levels and The minimum detectable concentration is estimated to be the major anthropometric and metabolic markers of obesity 1ngmlÀ1. All the above data were stated by the manufac- was also explored. turer. Plasma concentrations of cytokines were measured by commercial ELISA kits (MIFFR&D Systems, Minneapolis, MN, USA; IL-17, IL-23, IL-12, IFN-gFeBioscience, San Diego, Materials and methods CA, USA). Lower limits of detection were 30 pg mlÀ1 (MIF), 8pgmlÀ1 (IL-23) and 4 pg mlÀ1 (IL-17, IL-12, IFN-g), whereas Subjects the intra-assay precision was 6.0% (MIF), 6.2% (IL-17), 3.8% The study group consisted of 26 obese women, whereas the (IL-23), 8.0% (IFN-g) and 6.6% (IL-12). The lower limit control group consisted of 20 lean volunteers. Inclusion detection data for cytokines were reported by the manufac- criteria were as follows: women in reproductive period, no turer (MIF, IL-17, IL-12 and IFN-g) or were obtained in our smoking habits, no alcohol consumption, blood pressure laboratory (IL-23; sensitivity stated by the manufacturer was À1 130/80 mm Hg or less, normal glucose tolerance evaluated by 15 pg ml ). The intra-assay precision data for all cytokines a standard glucose tolerance test, normal thyroid function were obtained in our laboratory. and cortisol secretion, regular menses, no regular physical exercise. All obese subjects included in the study were diagnosed as having simple obesity without additional Statistical analysis disease. Twenty healthy subjects who were matched with Statistical analysis was carried out using the Statistica the study group for age and sex served as controls. The study software package (version 6.1; Statsoft Inc., Tulsa, OK, was conducted after obtaining informed consent from all the USA). For a desired value of Po0.05 and 80% power to subjects. The study was approved by the Ethics Committee of detect an actual difference, a sample size of 20 per group was the School of Medicine, Belgrade. considered satisfactory. All numeric variables were tested for normality of distribution using the Kolmogorov–Smirnov test and, if necessary, were subjected to logarithmic trans- Determination of anthropometric parameters and insulin formation before applying parametric tests (MIF, IL-12 and resistance IFN-g). Unpaired t-test was used to test the significance of the Anthropometric parameters such as body weight, height and difference in parameter values between obese and lean waist circumference (WC) were measured and body mass subjects, whereas the Mann–Whitney test was used for data index (BMI) was calculated by dividing weight (kg) by the that did not conform to normality after logarithmic squared value of height in meters. The reference interval of transformation (IL-23). The differences in frequency of BMI is defined as 18–24.9 kg/m2 (controls) and obesity as a cytokine detection in the two groups were evaluated by w2 BMI of more than 30 kg/m2 (study group). WC was measured test. Pearson correlation analysis or Spearman correlation with a flexible measuring tape, taking as a reference the (for IL-23) was employed to assess the correlation between midway line between the costal inferior border and the iliac different parameters. As multiple tests were performed crest. Samples of venous blood were collected in the (6 involving all samples and 15 on samples from obese

International Journal of Obesity IL-23/IL-17 axis in obese women M Sumarac-Dumanovic et al 153 women), the obtained P-values that were lower than 0.05 levels correlated with BMI in the group of obese women were corrected using the Holm–Bonferroni step-down (r ¼À0.077, P ¼ 0.710 and rs ¼À0.180, P ¼ 0.378, respec- approach. The corrected P-values (Pc) of less than 0.05 were tively). Also, no correlation was observed between IL-17 or considered significant. IL-23 and WC as a marker of central obesity (r ¼À0.042,

P ¼ 0.837 and rs ¼À0.140, P ¼ 0.495, respectively). Expect- edly, both BMI and WC values in the obese women group Results were positively correlated with HOMA index as an indicator of insulin resistance (r ¼ 0.561, Pc ¼ 0.026 and r ¼ 0.736, Blood concentrations of IL-17 and IL-23 are increased in obese Pc ¼ 0.015, respectively). On the other hand, we failed to women demonstrate a similar association between HOMA and the The main clinical parameters assessed in the study are levels of IL-17 (r ¼À0.133, P ¼ 0.518). There was a trend presented in Table 1. In comparison with lean subjects, obese toward negative correlation between IL-23 and HOMA patients presented with increased BMI, WC and HOMA (rs ¼À0.434), but it did not reach the level of statistical index of insulin resistance. Leptin, MIF and IL-12 were significance after the Holm–Bonferroni correction (P ¼ 0.027, detected in all samples tested. IL-17, IL-23 and IFN-g were Pc ¼ 0.301). more frequently detected in overweight (100, 42 and 77%, respectively) than in lean subjects (90, 15 and 65%, respectively), but the difference did not reach the level of Discussion statistical significance (P40.05). The plasma levels of leptin, MIF, IL-17 and IL-23 were significantly higher in obese We here demonstrate for the first time that blood concen- compared with lean women (Figures 1a–d). On the other trations of important proinflammatory cytokines IL-17 and hand, the levels of IL-12 and IFN-g did not significantly differ IL-23 are increased in obese women. Our data also indicate between obese and lean subjects (Figures 1e and f). that the increase in IL-17 and IL-23 in obesity is independent of the production of the proinflammatory mediators leptin and MIF and not directly associated with the increase in Correlation between IL-17 and IL-23 in obese women adipose tissue mass or insulin resistance. To assess the possible associations between the different While introducing IL-17 and IL-23 as additional markers of cytokines that were increased in obese women, we next the inflammatory syndrome that accompanies obesity, our performed correlation analyses in the obese women group. results also confirm earlier reports on the increase in leptin The only association observed was a positive correlation and MIF levels in obese humans.13–17 Both leptin and MIF between concentrations of IL-17 and IL-23 (rs ¼ 0.530), are well known for their ability to stimulate secretion of which was at the border of statistical significance after the various proinflammatory mediators in different experimen- Holm–Bonferroni correction (P ¼ 0.005, Pc ¼ 0.065) (Figure 2). tal systems,17,20 the latter being proposed to function as a On the other hand, neither IL-17 nor IL-23 correlated with master controller of systemic inflammation.20 Moreover, the levels of MIF (r ¼À0.153, P ¼ 0.455 and rs ¼À0.089, some recent studies indicate that leptin and MIF might also P ¼ 0.664, respectively) or leptin (r ¼À0.215, P ¼ 0.292 and stimulate the expression of IL-17 in human and mouse rs ¼À0.133, P ¼ 0.517, respectively), and no association was mononuclear cells, respectively.18,19 Our results, however, observed between MIF and leptin levels in the obese women argue against the possibility that such a link might be group (r ¼À0.005, P ¼ 0.981). operative in human obesity, as no correlation was observed between the levels of IL-17 or IL-23 and those of leptin or MIF in obese women. On the other hand, IL-17 showed a IL-17 and IL-23 do not correlate with anthropometric indices clear tendency toward positive correlation with IL-23 in and insulin resistance in obese women obese subjects, which is consistent with the well-known role In contrast to leptin, which displayed a positive correlation of IL-23 in inducing IL-17 secretion in T lymphocytes and with BMI (r ¼ 0.622, P ¼ 0.014), neither IL-17 nor IL-23 c other cell types.21,22 Therefore, it seems plausible to assume that IL-23, but not leptin or MIF, contributed to the increase in IL-17 production in obese women. Table 1 The values of various parameters in obese and lean women There is a question about the possible cellular source of (mean±s.d.; t-test) IL-17 and IL-23 in obese patients. Adipose tissue is an Obese (n ¼ 26) Lean (n ¼ 20) P-value important source of proinflammatory mediators, and adipo- cyte-secreted leptin is the most prominent example.17 The Age (years) 35.0±8.5 31.3±6.8 0.115 BMI (kg/m2) 35.2±4.0 20.6±2.2 o0.001 adipose origin of leptin is accordingly reflected in a positive WC (cm) 105.1±11.9 74.2±8.9 o0.001 correlation between its blood levels and BMI or WC as an HOMA 4.3±2.5 2.9±2.0 0.038 indicator of abdominal fat content,17 which was confirmed Abbreviations: BMI, body mass index; HOMA, homeostatic model assessment; in the present study. In addition, it has been proposed that WC, waist circumference. the production of MIF in obesity could be partially attributed

International Journal of Obesity IL-23/IL-17 axis in obese women M Sumarac-Dumanovic et al 154

Figure 1 Blood concentrations of different cytokines and leptin in obese vs lean women. The boxplots contain median values (horizontal line), interquartile range (the box length), largest and smallest values that are not outliers (whiskers), and outliers (values between 1.5 and 3 box lengths) represented as open circles. (a, b, c, e, fFt-test; dFMann–Whitney test; b, e, fFlog-transformed before analysis).

to adipocytes and/or non-fat cells present in adipose member that was measured in the present study. On the tissue.23,24 However, although IL-17F is preferentially expres- other hand, human adipose tissue-derived sed in adipose tissue,25 there are no studies confirming that express IL-23 among other proinflammatory cytokines,26 adipose tissue contains IL-17A, a prototype IL-17 family and macrophage infiltration into omental fat is augmented

International Journal of Obesity IL-23/IL-17 axis in obese women M Sumarac-Dumanovic et al 155 aging.36 Moreover, the proinflammatory shift in cytokine profile during the development of ischemic coronary disease is characterized by the increase in numbers of IL-17-producing TcellsandIL-17bloodlevels.37,38 Therefore, the possible involvement of IL-23/IL-17 proinflammatory cytokine axis in cardiovascular complications related to obesity seems worthy of investigation. In addition to IL-23 and IL-17, the activity of another important proinflammatory cytokine axis, comprising IFN-g and its inducer IL-12, was compared in obese and lean women. Although our study may be under-powered to detect differences in IFN-g or IL-12 because of the relatively low number of subjects, our data do not indicate that these Th1 cytokines are increased in obese women. This seems to be in contrast with the findings showing that the systemic immune response in obese children is skewed to Th1 profile, as demonstrated by an increase in numbers of IFN-g- secreting helper T cells.10 In addition to the possibility that the increase in Th1 response in obesity might be age- and/or Figure 2 Correlation between interleukin (IL)-17 and IL-23 in obese women. gender-related, it should be noted that it can also occur through downregulation of Th1 counter-regulatory Th2 response characterized by IL-4 secretion,12 which was not in obesity.27–29 Moreover, it has been shown that assessed in our study. T lymphocytes, which represent the main source of In conclusion, the activity of IL-23/IL-17 cytokine axis IL-17A,30,31 accumulate to a greater extent in adipose seems to be increased in obese women independently of tissue of obese animals and humans, as compared with proinflammatory mediators MIF and leptin. Although our lean controls.32–34 It therefore seems conceivable that the results do not indicate a direct pathogenic role of IL-17 and increased accumulation of inflammatory macrophages and IL-23 in metabolic disturbances that accompany obesity, T cells in adipose tissue might contribute to the production additional studies are required to explore the possible of IL-23 and IL-17 in obese women. Nevertheless, the lack clinical implications of their increase in obese humans. of correlation between IL-23 or IL-17 and central obesity markers (BMI and particularly WC) in obese subjects, though not directly contradicting this hypothesis, suggests that the Acknowledgements accumulation of IL-23/IL-17-producing cells in adipose tissue might not increase in proportion with the buildup This study was supported by the Ministry of Science of the of abdominal fat. Although it is also possible that blood Republic of Serbia (Grants no. 145067, 145073 and 145003). mononuclear cells or some other cell type, rather than We are immensely grateful to late Professor Vojin Sulovic for leukocytes infiltrating the adipose tissue, could be the main his kind support. source of IL-17 and IL-23 in obese subjects, additional research is required to test these assumptions. References While neither IL-17 nor IL-23 displayed a positive correla- tion with insulin resistance in obese patients, the observed 1 Hotamisligil GS, Shargill NS, Spiegelman BM. Adipose expression trend toward negative correlation between IL-23 and HOMA of tumor necrosis factor-alpha: direct role in obesity-linked index requires further attention. Nevertheless, these findings insulin resistance. Science 1993; 259: 87–91. do not support the pathogenic role of IL-23/IL-17 cytokine 2 Dandona P, Aljada A, Bandyopadhyay A. Inflammation: the link between insulin resistance, obesity and diabetes. Trends Immunol axis in the metabolic disturbances associated with obesity. 2004; 25: 4–7. On the other hand, it is possible that IL-17 could promote 3 Shoelson SE, Herrero L, Naaz A. Obesity, inflammation, and low-grade inflammation in obese patients, as it is capable of insulin resistance. Gastroenterology 2007; 132: 2169–2180. inducing other proinflammatory mediators such as TNF, 4 Hansson GK, Robertson AK, Soderberg-Naucler C. Inflammation and atherosclerosis. Annu Rev Pathol 2006; 1: 297–329. IL-1, IL-6 and nitric oxide in various cell types.8 It has recently 5 Rana JS, Nieuwdorp M, Jukema JW, Kastelein JJ. Cardiovascular been proposed that IL-17 upregulation in vascular endothelial metabolic syndromeFan interplay of, obesity, inflammation, and smooth muscle cells could promote proinflammatory diabetes and coronary heart disease. Diabetes Obes Metab 2007; 9: functional and phenotypic alterations in blood vessels contri- 218–232. buting to the development of atherothrombotic vascular 6 Anderson EJ, McGrath MA, Thalhamer T, McInnes IB. Inter- 35 leukin-12 to interleukin ‘infinity’: the rationale for future disease. Accordingly, IL-17 expression in blood vessels seems therapeutic cytokine targeting. Springer Semin Immunopathol to increase several fold in proatherogenic conditions, such as 2006; 27: 425–442.

International Journal of Obesity IL-23/IL-17 axis in obese women M Sumarac-Dumanovic et al 156 7 Langrish CL, McKenzie BS, Wilson NJ, de Waal Malefyt R, 24 Skurk T, Herder C, Kraft I, Muller-Scholze S, Hauner H, Kolb H. Kastelein RA, Cua DJ. IL-12 and IL-23: master regulators of innate Production and release of macrophage migration inhibitory and adaptive immunity. Immunol Rev 2004; 202: 96–105. factor from human adipocytes. Endocrinology 2005; 146: 8 Miljkovic D, Trajkovic V. Inducible nitric oxide synthase activa- 1006–1011. tion by interleukin-17. Cytokine Rev 2004; 15: 21–32. 25 Starnes T, Broxmeyer HE, Robertson MJ, Hromas R. IL-17D, a 9 Hunter CA. New IL-12-family members: IL-23 and IL-27, novel member of the IL-17 family, stimulates cytokine produc- cytokines with divergent functions. Nat Rev Immunol 2005; 5: tion and inhibits hemopoiesis. J Immunol 2002; 169: 642–646. 521–531. 26 Bourlier V, Zakaroff-Girard A, Miranville A, De Barros S, Maumus 10 Pacifico L, Di Renzo L, Anania C, Osborn JF, Ippoliti F, Schiavo E M, Sengenes C et al. Remodeling phenotype of human sub- et al. Increased T-helper interferon-gamma-secreting cells in cutaneous adipose tissue macrophages. Circulation 2008; 117: obese children. Eur J Endocrinol 2006; 154: 691–697. 806–815. 11 Palacio A, Lopez M, Perez-Bravo F, Monkeberg F, Schlesinger L. 27 Cancello R, Henegar C, Viguerie N, Taleb S, Poitou C, Rouault C Leptin levels are associated with immune response in malnour- et al. Reduction of macrophage infiltration and chemoattractant ished infants. J Clin Endocrinol Metab 2002; 87: 3040–3046. expression changes in white adipose tissue of morbidly 12 Svec P, Vasarhelyi B, Paszthy B, Korner A, Kovacs L, Tulassay T obese subjects after surgery-induced weight loss. Diabetes 2005; et al. Do regulatory T cells contribute to Th1 skewness in obesity? 54: 2277–2286. Exp Clin Endocrinol Diabetes 2007; 115: 439–443. 28 Harman-Boehm I, Bluher M, Redel H, Sion-Vardy N, Ovadia S, 13 Church TS, Willis MS, Priest EL, Lamonte MJ, Earnest CP, Avinoach E et al. Macrophage infiltration into omental versus Wilkinson WJ et al. Obesity, macrophage migration inhibitory subcutaneous fat across different populations: effect of regional factor, and weight loss. Int J Obes (Lond) 2005; 29: 675–681. adiposity and the comorbidities of obesity. J Clin Endocrinol Metab 14 Dandona P, Aljada A, Ghanim H, Mohanty P, Tripathy C, 2007; 92: 2240–2247. Hofmeyer D et al. Increased plasma concentration of macrophage 29 Weisberg SP, McCann D, Desai M, Rosenbaum M, Leibel RL, migration inhibitory factor (MIF) and MIF mRNA in mono- Ferrante Jr AW. Obesity is associated with macrophage accumula- nuclear cells in the obese and the suppressive action of tion in adipose tissue. J Clin Invest 2003; 112: 1796–1808. metformin. J Clin Endocrinol Metab 2004; 89: 5043–5047. 30 Fossiez F, Djossou O, Chomarat P, Flores-Romo L, Ait-Yahia S, 15 Ghanim H, Aljada A, Hofmeyer D, Syed T, Mohanty P, Dandona P. Maat C et al. T cell interleukin-17 induces stromal cells to produce Circulating mononuclear cells in the obese are in a proinflam- proinflammatory and hematopoietic cytokines. J Exp Med 1996; matory state. Circulation 2004; 110: 1564–1571. 183: 2593–2603. 16 Sakaue S, Ishimaru S, Hizawa N, Ohtsuka Y, Tsujino I, Honda T 31 Yao Z, Painter SL, Fanslow WC, Ulrich D, Macduff BM, Spriggs MK et al. Promoter polymorphism in the macrophage migration et al. Human IL-17: a novel cytokine derived from T cells. inhibitory factor gene is associated with obesity. Int J Obes (Lond) J Immunol 1995; 155: 5483–5486. 2006; 30: 238–242. 32 Agrewala JN, Brown DM, Lepak NM, Duso D, Huston G, Swain SL. 17 Lago F, Dieguez C, Go´mez-Reino J, Gualillo O. The emerging role Unique ability of activated CD4+ T cells but not rested effectors to of adipokines as mediators of inflammation and immune migrate to non-lymphoid sites in the absence of inflammation. responses. Cytokine Growth Factor Rev 2007; 18: 313–325. J Biol Chem 2007; 282: 6106–6115. 18 Liu L, Yang P, He H, Lin X, Jiang L, Chi W et al. Leptin increases in 33 Caspar-Bauguil S, Cousin B, Andre M, Nibbelink M, Galinier A, Vogt-Koyanagi-Harada (VKH) disease and promotes cell prolifera- Periquet B et al. Weight-dependent changes of immune system in tion and secretion. Br J Ophthalmol 2008; adipose tissue: importance of leptin. Exp Cell Res 2006; 312: 92: 557–561. 2195–2202. 19 Stojanovic I, Cvjeticanin T, Lazaroski S, Stosic-Grujicic S, 34 Wu H, Ghosh S, Perrard XD, Feng L, Garcia GE, Perrard JL et al. Miljkovic D. Macrophage migration inhibitory factor T-cell accumulation and regulated on activation, normal T cell stimulates interleukin-17 expression and production in expressed and secreted upregulation in adipose tissue in obesity. lymph node cells. Immunology 2008; (in press) DOI 10.1111/ Circulation 2007; 115: 1029–1038. j.1365-2567.2008.02879.x. 35 Csiszar A, Ungvari Z. Synergistic effects of vascular IL-17 and 20 Larson DF, Horak K. Macrophage migration inhibitory factor: TNFa may promote coronary artery disease. Med Hypotheses 2004; controller of systemic inflammation. Crit Care 2006; 10: 138. 63: 696–698. 21 Aggarwal S, Ghilardi N, Xie MH, de Sauvage FJ, Gurney AL. 36 Csiszar A, Ungvari Z, Koller A, Edwards JG, Kaley G. Aging- Interleukin-23 promotes a distinct CD4 T cell activation state induced proinflammatory shift in cytokine expression profile in characterized by the production of interleukin-17. J Biol Chem coronary arteries. FASEB J 2003; 17: 1183–1185. 2003; 278: 1910–1914. 37 Cheng X, Yu X, Ding YJ, Fu QQ, Xie JJ et al. The Th17/Treg 22 Kawanokuchi J, Shimizu K, Nitta A, Yamada K, Mizuno T, imbalance in patients with acute coronary syndrome. Clin Takeuchi H et al. Production and functions of IL-17 in microglia. Immunol 2008; 127: 89–97. J Neuroimmunol 2008; 194: 54–61. 38 Hashmi S, Zeng QT. Role of interleukin-17 and interleukin-17- 23 Fain JN. Release of and other inflammatory cyto- induced cytokines interleukin-6 and interleukin-8 in kines by human adipose tissue is enhanced in obesity and unstable coronary artery disease. Coron Artery Dis 2006; 17: primarily due to the nonfat cells. Vitam Horm 2006; 74: 443–477. 699–706.

International Journal of Obesity