Association of Serum Irisin with Metabolic Syndrome in Obese Chinese Adults

Citation: Yan B, Shi X, Zhang H, Pan L, Ma Z, et al. ( Association of Serum Irisin with Metabolic Syndrome in Obese Chinese Adults Bing Yan 0 Xiulin Shi 0 Huijie Zhang 0 Lingling Pan 0 Zhimin Ma 0 Suhuan Liu 0 Yongwen Liu 0 Xiaoying Li 0 Shuyu Yang 0 Zhibin Li 0 Pantelis G. Bagos, University of Central Greece, Greece 0 1 Xiamen Diabetes Institute , Xiamen , China , 2 Department of Endocrinology and Diabetes, The First Affiliated Hospital, Xiamen University , Xiamen , China , 3 Shanghai Institute of Endocrinology and Metabolism, Rui-Jin Hospital, School of Medicine, Shanghai Jiaotong University , Shanghai , China , 4 Department of Endocrinology, The Second Affiliated Hospital of Soochow University , Suzhou , China , 5 Department of Nursing, The First Affiliated Hospital, Xiamen University , Xiamen , China , 6 Epidemiology Research Unit, The First Affiliated Hospital, Xiamen University , Xiamen , China Irisin, a recently identified novel myokine, drives brown-fat-like conversion of white adipose tissues and has been proposed to mediate beneficial effects of exercise on metabolism. Circulating irisin was significantly reduced in type 2 diabetes patients; however, no evidence is available about its association with metabolic syndrome (MetS) and effects of adiposity and muscle mass on circulating irisin have been controversial. Cross-sectional data on socio-demographic, lifestyle, clinical characteristics and serum irisin were collected for 1,115 community-living Chinese adults with central obesity. Associations of serum irisin with MetS (central obesity plus any two of the following four factors (raised blood pressure (BP), raised fasting plasma glucose (FPG), raised triglyceride (TG), and reduced HDL cholesterol) and each component of MetS were analyzed using multivariable logistic regression. Among the 1,115 obese Chinese adults with a mean age of 53.2(67.2) years, serum irisin levels (log-transformed) were significantly reduced in subjects with MetS and raised FPG than their control groups (p = 0.034 and 0.041, respectively). After adjustment for potential confounders, serum irisin was significantly associated with reduced risks of MetS and raised FPG, with odds ratios (ORs) (95% CI) per standard deviation of log-transformed irisin of 0.796 (0.505-0.959, p = 0.027) and 0.873 (0.764-0.998, p = 0.046), respectively. Associations of irisin with raised BP, raised TG and reduced HDL were not statistically significant ((ORs) (95% CI): 0.733(0.454-1.182, p = 0.202), 0.954(0.838-1.086, p = 0.478) and 1.130(0.980-1.302, p = 0.092), respectively). Stepwise multivariable linear regression analysis showed that fasting insulin, HbA1c and albumin/globulin ratio were negatively associated with serum irisin level with statistical significance (all p-values ,0.05) and waist circumference was negatively associated with serum risin with marginally statistical significance (p = 0.055). These results imply that irisin may play an important role in insulin resistance and MetS and should be confirmed in future prospective studies. - Funding: This study is supported by the grants from the Xiamen Systems Biology Research Program for Metabolic Disease and National Nature Science Foundations (No. 81000320 and No. 81073113). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. . These authors contributed equally to this work. Metabolic syndrome (MetS) represents a cluster of atherogenic risk factors including hypertension, insulin resistance, obesity and dyslipidemia, and is now considered as a major public health problem because of its rapidly increasing prevalence worldwide and its association with type 2 diabetes and cardiovascular disease [13]. Insulin resistance plays an important role in the pathogenesis of MetS although the mechanisms underlying insulin resistance are not fully understood [1]. Physical exercise, as a lifestyle intervention approach, has been consistently shown to be effective in reducing incidence of type 2 diabetes [4,5] and MetS [6], which made the discovery that physical exercise provokes increases in a number of cytokines from skeletal muscle as a potential mechanism sound plausible. Irisin, a recently identified novel myokine, is proteolytically processed from the product of the FNDC5 gene prior to being released into the circulation and regulated by PPAR-c coactivator1(PGC1)-a [7]. Irisin drives brown-fat-like conversion of white adipose tissues, and has been proposed to mediate the beneficial effects of exercise on metabolism [7]. Circulating irisin was found to be significantly reduced in long-term [8], new onset [9] and undefined [10] type 2 diabetes patients compared with nondiabetic controls, which suggested either the diabetic state itself or the metabolic condition that caused progression to type 2 diabetes is accompanied by lower circulating irisin [11]. However, no evidence is available on whether circulating irisin is involved in metabolic syndrome in adults. Available evidence about the effect of adiposity on circulating irisin has been controversial. Liu and co-workers found a positive association of irisin with BMI and glucose in non-diabetic subjects but not in diabetes patients, even after adjustment for multiple covariates [8]. The positive association of circulating irisin with BMI has also been found in two other non-diabetic populations [12,13]. Huh and co-workers further found that muscle mass was the main predictor for circulating irisin [12]. In contrast to these reports above, Moreno-Navarrete et al. found a negative association of circulating irisin with BMI, waist-hip ratio and fat mass in men; although they did find FNDC5 expression in human muscle positively correlated with BMI as well as PGC-1a expression [10]. Therefore, further studies are warranted to address this discrepancy on the effect of adiposity on circulating irisin. In the present cross-sectional study of 1,115 obese Chinese adults without any previously diagnosed chronic diseases, we aimed to examine the independent effect of circulating irisin on MetS and further determine the association of adiposity with circulating irisin level. Materials and Methods Subjects Obese adults were local residents aged 40 years or older living in the Lianqian community, Xiamen, China, and were screened with physical examination from April 2011 to August 2011. Subject sampling, recruitment and evaluation have been described earlier [14]. Briefly, a total of 1,523 subjects with central obesity (waist circumference greater than 90 cm for men and 80 cm for women) were included. Of them, 1,115 (73.2%) subjects with the complete data on the entire examination were left for further analysis. Ethics Statement The study was approved by the Human Research Ethics Committee of the First Affiliated Hospital of Xiamen University (Xiamen, Chin (...truncated)