Diabetic nephropathy is a major risk of end-stage kidney disease. Many complex factors relate to the progression of diabetic nephropathy. Using nonobese type 2 diabetes model rats, we confirmed that oxidative stress was a crucial factor. Because recent studies suggest that vitamin D could suppress oxidative stress, we explored whether the active vitamin D analog, maxacalcitol, could also attenuate oxidative stress and prevent the progression of diabetic nephropathy. Diabetic rats aged 20 weeks were divided into 3 groups and treated with insulin, maxacalcitol, and vehicle. At age 30 weeks, blood and urine analyses, renal histology, immunohistochemistry, real-time polymerase chain reaction, and western blot were performed. Although maxacalcitol reduced albuminuria and mesangial matrix expansion, no significant differences were observed in blood pressure and creatinine clearance among the 3 treatment groups. Systemic and intrarenal oxidative stress was reduced by maxacalcitol therapy. Expressions of nuclear factor-κB and nicotinamide adenine dinucleotide phosphate oxidase in the kidney also decreased in the insulin-treated and maxacalcitol-treated groups but increased in the vehicle-alone group. In addition, the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) decreased and Kelch-like erythroid cell-derived protein with CNC homology (ECH)-associated protein 1 (Keap1) increased in the vehicle-treated group; however, these expressions were restored in the maxacalcitol- and insulin-treated groups. It is suggested that maxacalcitol attenuates the progression of diabetic nephropathy by suppression of oxidative stress and amelioration of the Nrf2–Keap1 pathway in nonobese type 2 diabetes without significant changes in blood pressure and glomerular filtration rate.

With decreasing kidney function, cardiovascular disease (CVD) and mineral bone disorders frequently emerge in patients with chronic kidney disease (CKD). For these patients, in addition to the traditional risk factors, non-traditional CKD-specific risk factors are also associated with such diseases and conditions. One of these non-traditional risk factors is the accumulation of uremic toxins (UTs). In addition, the accumulation of UTs further deteriorates kidney function. Recently, a huge number of UTs have been identified. Although many experimental and clinical studies have reported associations between UTs and the progression of CKD, CVD, and bone disease, these relationships are very complex and have not been fully elucidated. Among the UTs, indoxyl sulfate, asymmetric dimethylarginine, and p-cresylsulfate have been of particular focus, up until now. In this review, we summarize the pathophysiological influences of these UTs on the kidney, cardiovascular system, and bone, and discuss the clinical data regarding the harmful effects of these UTs on diseases and conditions.

Background/Aims: Fibroblast growth factor-23 (FGF23) plays a central role in the development of hypophosphatemia and inappropriately low 1,25-dihydroxyvitamin D induced by iron therapy for iron-deficiency anemia. The aim of this study was to examine the effect of intravenous saccharated ferric oxide on serum FGF23 levels and mineral metabolism in hemodialysis patients. Methods: This prospective study enrolled 27 hemodialysis patients who had iron-deficiency anemia defined by a hemoglobin concentration <10.5 g/dl and serum ferritin <100 ng/ml. Intravenous saccharated ferric oxide at a dose of 40 mg was administered three times weekly over 3 weeks. The dose of active vitamin D and phosphate binders was kept unchanged. Serum FGF23, intact parathyroid hormone (PTH) and other parameters were prospectively monitored for 5 weeks. Results: Serum FGF23 levels were markedly elevated [3,453 (338–6,383) pg/ml] at baseline. After 3 weeks of intravenous saccharated ferric oxide treatment, serum FGF23 further increased to 4,701 (1,251–14,396) pg/ml, and returned to the baseline values after 2 weeks of observation. There was also a significant decrease in intact PTH but no changes in serum calcium and phosphorus. Conclusions: Intravenous saccharated ferric oxide induces further increase in elevated FGF23 levels in hemodialysis patients. This increase does not induce hypophosphatemia and inappropriately low 1,25-dihydroxyvitamin D in the absence of functioning kidney, but may result in transient PTH suppression – possibly by directly acting on the parathyroid.

Background: The role of nitric oxide (NO) is controversial in diabetes nephropathy progression and the mechanisms remain unknown, especially in non-obese type 2 diabetes. To examine mechanisms of nephropathy progression in non-obese type 2 diabetes, we used spontaneously diabetic Torii (SDT) rats, a newly established model of non-obese type 2 diabetes. Methods: Fourteen male Sprague-Dawley rats were used as a control (20 weeks, n = 6; 30 weeks, n = 8), and 20-week-old male SDT rats were divided into 2 groups: diabetic (DM, n = 8) and DM + insulin (n = 8) groups. Twenty- and 36-week-old rats were sacrificed, and blood, urine, and histomorphometric analyses, mRNA expression analysis of endothelial NO synthase (eNOS) and NADPH oxidase, and blood pressure measurement were performed. Results: At 36 weeks, NO metabolites, and 8-hydroxydeoxyguanosine (8-OHdG) were significantly higher in the diabetic group than in the other 2 groups. Further renal studies showed increased glomerular volume and mesangial area, and intensified eNOS, 8-OHdG, and nitrotyrosine immunostaining in the diabetic group. Oxidative and nitrosative stress were positively associated with increased glomerular volume and mesangial area, which were mostly recovered by insulin therapy. Conclusions: NO and oxidative stress increased in SDT rats, suggesting that these play key roles in nephropathy progression in non-obese type 2 diabetes.