Comprehensive proteomic profile in newly diagnosed patients with inflammatory bowel disease: identification of potential biomarkers

OBJECTIVE: Identifying proteomic signatures in treatment-naïve individuals newly diagnosed with inflammatory bowel disease (IBD) may provide insights into the underlying pathophysiological mechanisms of the disease and aid in distinguishing Crohn's disease (CD) from ulcerative colitis (UC). DESIGN: In the discovery phase, label-free quantitative proteomics was performed to analyze proteomic profiles in serum extracellular vesicles (EVs), serum, urine, and intestinal tissue from 100 newly diagnosed IBD patients (50 CD and 50 UC), and 51 healthy controls (HC). Serum candidate biomarkers were validated using ELISA in a separate subset cohort (87 CD, 134 UC, and 99 HC), and immunohistochemistry was performed on biopsies from the discovery cohort to confirm findings. RESULTS: We identified 419 proteins in serum EVs, 468 in serum, 683 in urine, and 2603 in intestinal tissue. ELISA results showed lower levels of TTR and APOC3 and higher levels of ATRN in UC patients compared to HC. Similarly, CD patients showed lower TTR and higher ATRN levels compared to HC. Moreover, serum protein S10A9 was differentially upregulated in CD vs UC. Immunohistochemistry revealed increased PRDX4 and AZU1 expression in the ileum of CD patients, whereas AOFB expression was lower in the ileum of CD and in the left colon of both CD and UC compared to HC. CONCLUSION: This comprehensive proteomic study has identified a set of proteins differentially expressed in IBD, which may contribute to a better understanding of its mechanisms and hold promise as candidate biomarkers. Although these findings are preliminary, they warrant further investigation to evaluate their diagnostic and therapeutic relevance.