Introduction
Inflammatory bowel disease (IBD) is a chronic inflammatory condition involving the gut primarily, encompasses two major groups of idiopathic disorders: Crohn’s disease (CD) and ulcerative colitis (UC) 1 . Extraintestinal manifestations are also frequently observed and involve the joints, eyes, hepatobiliary tract as well as skin2 . CD is characterized by transmural inflammation of the intestine. Studies have shown that approximately 50% of the CD patients have ileocolitis and the incidence is 3.1–20.2 per 100 000. Furthermore, UC is more prevalent than CD with incidence of 9-20 per 100 000 3 . It starts in the rectum and usually extends proximally through part or the entire colon in a continuous manner4 . Currently, there is a general agreement that IBD is a result of an interaction of genetic, gut microbiota, intestinal mucosal immune response factors and surrounding environment 5 , and causes suffering, mortality and economic loss every year6 . Immunopathogenesis of IBD induces an inflammatory response involving both the innate immune cells and the adaptive immune cells7 . In particular, T-helper 1 and T-helper 2 responses are thought to drive the pathogenesis of CD and UC, respectively 8 .
Furthermore, adipose tissues can secrete adipokines that play major roles in metabolism, immunity, and inflammation. Meanwhile, resistin is one of the adipokine, mainly produced by macrophages and detectable in human serum. It is a cysteine-rich peptide with different biological effects and initially proposed to regulate obesity, glucose metabolism and insulin sensitivity 9 . Some researchers reported that human resistin may also play a major role in regulating inflammation 10 . Resistin expression has been identified in the non-adipocyte stromal vascular parts of white adipose tissue 11 , moreover, IBD is typically characterized by malnutrition, body composition changes and mesenteric white adipose tissue hypertrophy12 . And previous studies have investigated the serum levels of resistin in IBD patients and healthy controls13-22 . However, the results are inconsistent. In light of these inconsistent findings, we made a meta-analysis of published studies that studied serum levels of resistin in patients with CD and UC compared with healthy controls.