By proteomic screening of sera obtained from patients with rheumatoid arthritis (RA), we previously identified leucine rich α2 glycoprotein (LRG) as a possible marker for inflammation. Unlike C-reactive protein (CRP), a biomarker widely used to evaluate inflammation, LRG is induced not only by IL-6 but also by other proinflammatory cytokines. In addition, LRG is upregulated not only in liver but also in local inflammatory sites. Therefore, serum LRG is a novel inflammatory marker applicable to evaluate inflammation in many diseases including ulcerative colitis in which serum CRP often fails to reflect disease activity and RA to which IL-6-blocking biologic agents such as tocilizumab are given as a first line therapy. Interestingly, evidence indicates that LRG is functionally involved in pathogenesis of inflammation, by promoting cellular proliferation, differentiation and angiogenesis via modulating TGF-β signaling.
Keywords: CRP; LRG; biomarker.