Aldose reductase deficiency significantly ameoliorates development of diabetic nephropathy in C57BL/6 mice

Abstract

Objective To study the roles of aldose reductase in the development of diabetic nephropathy using mouse models which were deficient for aldose reductase (AR). Methods Eight-week-old homozygous male AR-knockout (KO), bitransgenic (BT) and wild-type (WT) background C57BL/6 mice were treated with or without 40 μg/g streptozotocin by intraperitoneal injection. After 2 weeks, blood glucose was measured and hyperglycemia was confirmed. Diabetic and control mice were further maintained for 17 weeks, then sacrificed. Body weight, kidney weight, serum glucose, triglyceride, cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, blood urea nitrogen, serum creatinine, glomerular filtration rate and urinary albumin parameters were determined. PAS staining was performed for kidney histological analyses. Western blot and immunohistochemistry were used to determine the expression of collagen Ⅳ and transforming growth factor-beta1 (TGF-β1). Protein kinase C (PKC) activities for the cytoplasm and cell membrane fractions of the renal cortex were assayed with the kit of PepTag® Assay for non-radioactive detection of PKC. One-way ANOVA was used for multiple comparisons. Results In comparison with the diabetic mice with normal aldose reductase activity, most serum and urinary parameters as well as renal histological and functional parameters were significantly improved in diabetic mice deficient in aldose reductase. For instance, loss of AR in the KO mice results in 43% reduction in urine albumin ((1.49±0.26) vs (2.62±0.34)mg/g creatinine, F=20.8, P<0.01) whereas a 48% reduction was resulted in the BT mice ((1.36±0.12) vs (2.62±0.34) mg/g creatinine, F=20.8, P<0.01). Further, aldose reductase deficiency prevented hyperglycemia-induced activation of PKC and TGF-β1. Conclusion AR contributes to the development of diabetic nephropathy in vivo. The inhibition of AR may be beneficial for the prevention and treatment of the disease. Key words: Aldose reductase; Diabetic nephropathy; Glomerula; Protein kinase C; Transforming growth factor-beta1