Fig. 6. Validation experiments of DHAP, OAA and SCS levels in serum of DKDs. (A) DHAP levels were increased in DKDs (n=60) compared to HCs (n=65), (B) OAA levels were not significantly changed, and (C) the activity of SCS was significantly increased in DCs (n=48) compared to HCs (n=65), and decreased in DKDs (n=60) compared to DCs. (D-F) Correlation analysis of 3 metabolites with tubular injury. DHAP (D) and OAA levels (E) were positively correlated with tubular injury respectively, SCS levels (F) were negatively correlated with tubular injury. r, correlation coefficient. RBP, retinol-binding protein; Cr, creatinine; HC, healthy control; DC, diabetic control; DKD, diabetic kidney disease; SCS, succinyl-CoA synthetase; DHAP, dihydroxyacetone phosphate; OAA, oxaloacetate.