Cyanidin-3-glucoside from Black Rice Ameliorates Diabetic Nephropathy via Reducing Blood Glucose, Suppressing Oxidative Stress, Inflammation, and Regulating TGF-β1/Smad Expression.

Diabetic nephropathy (DN) is one of serious complication in diabetes. Cyanidin-3-glucoside (C3G) from black rice was reported has hypoglycemic effects and anti-osteoporosis effect in diabetic rats. Whether it has preventive effects on DN has not been reported. In this study, we established a rat model of DN, and C3G at two doses (10 and 20 mg kg-1 d-1) were administered to see its anti-DN effect. Eight weeks of C3G supplementation decreased blood glucose, serum insulin, improved the renal function, relieved renal glomerular sclerosis and interstitial fibrosis of DN rats. Also, the kidneys of DN rats had improved the oxidative defense system. Pro-inflammatory mediators were markedly reduced in serum and kidneys of the C3G treated groups. Transforming growth factor-β1 (TGF-β1), phosphor-Smad2, phosphor-Smad3 protein expression levels were decreased significantly in the kidney of the C3G treated group, whereas Smad7 expression level was up-regulated by C3G. Our results indicate that the C3G can ameliorate DN via anti-oxidative stress, anti-inflammation, and regulating TGF-β1/Smad2/3 pathway. Our results suggest that C3G from black rice might be used as a renal-protective nutrient in diabetic nephropathy.