Soy protein was known to have renal-protective effects. The aim of this study was to investigate the effects of different doses of soybean β-conglycinin, one of the main storage proteins in soy, on diabetic nephropathy in the rat. We used 40 Wistar rats with eight rats in each group. Diabetes mellitus was induced in rats by an intravenous injection of streptozotocin. The groups included a control group (Ctrl) fed with the standard AIN93-M diet, while other groups were fed with AIN-93M with the addition of NaCl to induce diabetic nephropathy (DN). DN rats were divided into the DN control (DN) group, the soy protein (DN + SP) group, the low-dose β-conglycinin (DN + B) group, and the high-dose β-conglycinin (DN + 2B) group. After a 27 weeks experimental period, we found that soy protein and β-conglycinin decreased blood glucose via increasing the insulin sensitivity, with an enhanced cholesterol-lowering effect of β-conglycinin-mediated hepatic LDL receptor protein expression. Otherwise, there were beneficial effects of soy protein and β-conglycinin on renal function markers. Through the inhibition of angiotensin-converting enzyme (ACE), soy protein and β-conglycinin retarded the progression of diabetic nephropathy by decreasing the blood pressure and histological changes. In conclusion, soy protein and β-conglycinin may retard the progression of diabetic nephropathy by increasing insulin sensitivity, regulating lipid metabolism, improving renal function markers, and inhibiting ACE activity.
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