Integrated metabolomic profiling identifies citrate as novel diagnostic biomarker for Anti-MDA5-Positive dermatomyositis.

OBJECTIVE: Anti-melanoma differentiation-associated gene 5-positive dermatomyositis (anti-MDA5 + DM) is a unique subtype of idiopathic inflammatory myopathy (IIM) with a poorer prognosis. The immune-metabolic landscape underlying anti-MDA5 + DM pathogenesis remains poorly defined. In our study, we integrated metabolomic profiling of plasma and peripheral blood mononuclear cells (PBMCs) in anti-MDA5 + DM. METHODS: This study enrolled 183 patients with IIM and 104 healthy controls (HCs), comprising a discovery cohort of 150 patients (67 anti-MDA5 + DM patients and 83 anti-MDA5- IIM patients serving as disease controls) and 71 HCs, as well as a validation cohort of 33 patients and 33 HCs. To establish a robust diagnostic model, we implemented a dual analytical approach: seven machine learning algorithms were initially employed to identify key differentially expressed metabolites (DEMs), followed by LASSO regression analysis for optimal feature selection and model construction. Decision curve analysis (DCA) was subsequently conducted to assess their clinical applicability in decision-making scenarios. DHEAS and citrate in plasma were validated using enzyme-linked immunosorbent assay (ELISA) and biochemical assay, respectively. RESULT: Non-targeted metabolomic profiling of plasma identified 90DEMs distinguishing anti-MDA5 + DM patients from HCs, including 65 upregulated and 25 downregulated metabolites. Pathway enrichment analysis revealed the predominant involvement of these plasma DEMs in beta-alanine metabolism. PBMC-derived targeted metabolomics identified 41 DEMs in anti-MDA5 + DM compared with HCs, comprising 21 upregulated and 20 downregulated metabolites. The DEMs in PBMCs also mainly participated in the beta-alanine metabolism pathway. From these DEMs, DHEAS, citrate, dimethylglycine, histidine, PAGN and Melilotate were identified as candidate biomarkers in anti-MDA5 + DM. Clinically, DHEAS levels showed a negative correlation with the prevalence of rapidly progressive interstitial lung disease (RP-ILD), citrate exhibited a negative association with rash, while dimethylglycine displayed a positive association with mortality and RP-ILD. Further combined analysis showed that the expression of plasma and PBMC dehydroepiandrosterone sulfate (DHEAS) and citrate may serve as reliable diagnostic biomarkers. Finally, DHEAS and citrate exhibited concordant variation patterns in the validation cohort. CONCLUSION: Our study underscores the pivotal role of DHEAS and citrate as promising diagnostic biomarkers of IIM and anti-MDA5 + DM, respectively, providing novel insights into the pathogenic mechanism and potential therapeutic targets.