COMPREHENSIVE METABOLOMIC ANALYSIS OF ANEMIA IN PATIENTS WITH CHRONIC KIDNEY DISEASE

Anemia is a major complication of chronic kidney disease (CKD), and its presence significantly affects the prognosis and quality of life of CKD patients. The primary cause of anemia in CKD is considered to be a relative deficiency in erythropoietin (EPO) production, although other contributors likely play a role. In this study, we identified novel metabolic factors involved in anemia in CKD patients through metabolite analysis and explored their mechanisms.

We used two independent cohorts. J-Kidney-Biobank (JKB) included 380 participants covering all CKD stages with 630 metabolites measured, and UT-DKD included 135 participants with diabetic kidney disease at CKD stage G3 with 416 metabolites. Analyses were restricted to the 84 metabolites quantified in both cohorts. Each metabolite was treated as the exposure. In JKB, we fitted multivariable logistic regression with anemia (hemoglobin (Hb) < 10.0 g/dL or use of an erythropoiesis-stimulating agent) as the outcome; in UT-DKD, we fitted multivariable linear regression with Hb (continuous) as the outcome. All models were adjusted for age, sex, and serum creatinine. For each metabolite, p-values were obtained and Benjamini-Hochberg false discovery rate (FDR) control was applied to account for multiple testing. Analyses were performed in R (version 4.2.3; R Foundation for Statistical Computing, Vienna, Austria) using the base stats. We primarily focused on metabolites meeting p < 0.05 with FDR < 0.05, and additionally reported those with FDR < 0.10.

Across the 84 shared metabolites, symmetric dimethylarginine (SDMA) was the only metabolite that remained significant in both cohorts after covariate adjustment and FDR control. In JKB, SDMA showed inverse correlations with eGFR (r = −0.62) and Hb (r = −0.48), and was independently associated with clinical anemia (Hb < 10.0 g/dL or ESA use). In UT-DKD, the associations were directionally concordant (eGFR r = −0.47; Hb r = −0.29). In contrast, other methylarginines−including the structural isomer asymmetric dimethylarginine (ADMA)−and representative uremic toxins did not show reproducible significance under identical multiple-comparison control. Across both cohorts, serum creatinine and ADMA emerged as the principal determinants of SDMA, whereas contributions from other arginine-related metabolites were minimal. We also assessed the effect of SNPs which affect SDMA concentration in general population, and found that rs37369 C>T increases SDMA concentration in CKD patients.

We identified SDMA as a metabolite consistently associated with anemia through comprehensive metabolomics analysis in two independent CKD cohorts. Given that SDMA is predominantly renally cleared, its accumulation with declining kidney function may contribute to lower hemoglobin concentrations. Moreover, our determinant analyses and genetic evidence are consistent with a pathway-specific involvement within methylarginine metabolism that may influence the SDMA-anemia association in patients with CKD. This study suggests that SDMA serves as an integrative indicator of CKD-related anemia and may represent a useful biomarker implicated in novel mechanistic pathways underlying its pathophysiology.

Acknowledgement

This work was supported by the Japan Agency for Medical Research and Development (AMED, 25tm0424230h0002) and KAKENHI (25K11536).