Polygonati Rhizoma Polysaccharides Ameliorated Diabetic Kidney Disease in db/db Mice via Inhibiting TGF β /Smad2 Signaling Pathway

Polygonati Rhizoma polysaccharides (PP) are the active components isolated from medicine food homology (MFH) Chinese herb Polygonati Rhizoma. Diabetic kidney disease (DKD) is a serious diabetic complication occurring in the later stage of diabetes. We have previously reported the hypoglycemic effect of PP on early-stage type 2 diabetes (T2D). This study evaluated the effect of PP on DKD and investigated the underlying mechanisms. PP was mainly composed of L-fucose, L-rhamnose, D-glucose, and D-mannose. Ten-week-old Leprdb/Leprdb (db/db) compared with control Leprdb/Lepr+ (db/+) mice were given vehicle or PP for 16 weeks. Our results showed that PP alleviated renal dysfunction (BUN, Cr, microalbumin) and pathological damage in db/db mice. PP improved lipid homeostasis (TG, NEFA, and HDL) and reversed oxidative stress (CAT, MDA, SOD, and GSH) in the serum of db/db mice. Besides, PP reduced the Masson-positive area and expression of TGFβ in the kidneys from db/db mice. Furthermore, PP upregulated the expression of Smad7 and abrogated the phosphorylation of Smad2 in the kidneys from db/db mice. In conclusion, PP ameliorated kidney dysfunction and fibrosis through attenuating dyslipidemia, anti-oxidative stress, and inhibiting the activation of TGFβ/Smad2 signaling pathway in db/db mice. The study provides a theoretical basis for further elucidation of the effect and mechanism of PP in attenuating DKD.