Natural flavonoid ombuin significantly down-regulated the expression of TGF-β1, Notch 1, and Hes 1 and up-regulated the expression of peroxisome proliferator-activated receptor γ (PPAR γ), significantly improved renal function and pathological damage in DKD rats, and improved renal interstitial fibrosis. Here, NOTCH1 is linked to diabetic kidney disease.