Dietary low-fat soy milk powder retards diabetic nephropathy progression via inhibition of renal fibrosis and renal inflammation

Scope: Diabetic nephropathy (DN) is a major cause of end-stage renal disease. Here, we examined the effect of long-term consumption of a low-fat soy milk powder (LFSMP) on the diabetic kidney structure and function. Methods and results: KKAy mice were fed a casein-, LFSMP-, or high-fat soy mixture powder (HFSMP)-based diet for 4 months. Plasma and urine were subjected to a biochemical assay every 2-4 wk. Renal morphology and protein expression were evaluated by histochemical staining and western blots. Although HFSMP-based diet showed no protective effect on DN. LFSMP-fed mice exhibited lower water intake, urine output, and urinary albumin, and glucose excretion. Furthermore, strong preservation of renal structural proteins and low urinary N-acetyl-betaD- glucosaminidase activity were observed in LFSMP-fed mice, indicating alleviation of renal injury. LFSMP-fed mice showed a lesser degree of mesangial matrix expansion, of tubulointerstitial fibrosis, and of myofibroblast differentiation. Finally, milder renal inflammation was found in LFSMP-fed mice, as evidenced by a decrease in urinary monocyte chemoattractant protein-1 excretion and lesser macrophage infiltration into the tubulointerstitium. Conclusion: The present data suggests that long-term consumption of LFSMP but not HFSMP retards DN progression via suppressing renal injury, myofibroblast differentiation, and renal macrophage infiltration in diabetic condition.