Effects of unilateral nephrectomy on renal function in male Spontaneously Diabetic Torii fatty rats: a novel obese type 2 diabetic model

Characterization of Enlarged Kidneys and Their Potential for Inducing Diabetes in DEK Rats

The kidneys participate in the regulation of systemic glucose metabolism via gluconeogenesis, insulin degradation, and the tubular reabsorption of glucose. The present study characterized rats from a strain of a novel type 2 diabetes model with enlarged kidneys (DEK). Histological and biochemical analyses of DEK rats were performed to assess the relationships between their kidneys and hyperglycemia. The kidney weight of diabetic DEK (DEK-DM) gradually increased over time from the onset of diabetes, with the glomerular number being higher in DEK-DM than in normal DEK (DEK-cont). A positive correlation between blood glucose level and kidney weight was observed in DEK-DM. The similar glomerular size and single glomerular creatinine clearance in DEK-cont and DEK-DM indicated that glomerular hypertrophy and hyperfiltration were not involved in the renal enlargement. Uninephrectomy (1/2Nx) in DEK-DM resulted in a reduction in blood glucose level at 7-28 post-operation days, with this concentration remaining lower than in Sham group until 84 days post-operation. 1/2Nx also improved systemic conditions, including reduced body weight gain, polyuria, polydipsia, and hyperphagia. Plasma concentrations of Na, total cholesterol, albumin, and total protein were higher, and urinary excretion of glucose, urea nitrogen, and proteins were lower, in the 1/2Nx than in the Sham group. Remnant kidney weight was two-fold higher in the 1/2Nx than in the Sham group 84 days later. In addition, 1/2Nx resulted in renal tubular dilatation but not in the progression of fibrosis or glomerular lesions. Taken together, these findings indicate that enlarged kidneys were associated with the onset of diabetes and with the resistance to diabetic nephropathy in DEK-DM.

P2X7 siRNA targeted to the kidneys increases klotho and delays the progression of experimental diabetic nephropathy

Previous studies in our laboratory have suggested that P2X7 could contribute to the progression of diabetic nephropathy and modulated klotho expression. The aim of this study was to investigate if P2X7 receptor is related to the expression of klotho in the onset of diabetic nephropathy in rats. Seven-week-old male Wistar rats weighing 210 g were all uninephrectomized; two-third of the animals were induced to diabetes with 60 mg/kg streptozotocin i.v., and one-third received its vehicle (control rats). At 4th day of the fifth week of the protocol, half of the diabetic rats received a small interfering RNA targeting for P2X7 mRNA, and the other half received its vehicle. Euthanasia was made at the eighth week. Diabetic animals reproduced all classic symptoms of the disease; besides, they showed reduced renal function and low NO bioavailability; also, SOD1, SOD2, and catalase were increased, probably due to the oxidative stress which was elevated in this situation. Metabolic data of diabetic rats did not change by silencing P2X7 receptor. For the other hand, silencing P2X7 was able to contribute to balance oxidative and nitrosative profile, ultimately improving the renal function and increasing plasma and membrane forms of klotho. These findings suggest that the management of P2X7 receptor can benefit the kidneys with diabetic nephropathy. Further studies are needed to show the therapeutic potential of this receptor inhibition to provide a better quality of life for the diabetic patient.

Transplantation of adipose-derived mesenchymal stem cell sheets directly into the kidney suppresses the progression of renal injury in a diabetic nephropathy rat model

AIMS/INTRODUCTION

Adipose-derived mesenchymal stem cell (ASC) transplantation is a promising therapy for diabetic nephropathy (DN). However, intravascular administration of ASCs is associated with low engraftment in target organs. Therefore, we considered applying the cell sheet technology to ASCs. In this study, ASC sheets were directly transplanted into the kidneys of a DN rat model, and therapeutic consequences were analyzed.

MATERIALS AND METHODS

Adipose-derived mesenchymal stem cells were isolated from adipose tissues of 7-week-old enhanced green fluorescent protein rats, and ASC sheets were prepared using a temperature-responsive culture dish. A DN rat model was established from 5-week-old Spontaneously Diabetic Torii fatty rats. Seven-week-old DN rats (n = 21) were assigned to one of the following groups: sham-operated (n = 6); ASC suspension (6.0 × 106  cells/mL) administered intravenously (n = 7); six ASC sheets transplanted directly into the kidney (n = 8). The therapeutic effect of the cell sheets was determined based on urinary biomarker expression and histological analyses.

RESULTS

The ASC sheets survived under the kidney capsule of the DN rat model for 14 days after transplantation. Furthermore, albuminuria and urinary tumor necrosis factor-α levels were significantly lower in the ASC sheets transplanted directly into the kidney group than in the sham-operated and ASC suspension administered intravenously groups (P < 0.05). Histologically, the ASC sheets transplanted directly into the kidney group presented mild atrophy of the proximal tubule and maintained the renal tubular structure.

CONCLUSIONS

Transplantation of ASC sheets directly into the kidney improved transplantation efficiency and suppressed renal injury progression. Therefore, the ASC sheet technology might be a promising novel treatment for DN.

The Possibility of Urinary Liver-Type Fatty Acid-Binding Protein as a Biomarker of Renal Hypoxia in Spontaneously Diabetic Torii Fatty Rats

BACKGROUND

Renal hypoxia is an aggravating factor for tubulointerstitial damage, which is strongly associated with renal prognosis in diabetic kidney disease (DKD). Therefore, urinary markers that can detect renal hypoxia are useful for monitoring DKD.

OBJECTIVE

To determine the correlation between urinary liver-type fatty acid-binding protein (L-FABP) and renal hypoxia using a novel animal model of type 2 diabetes.

METHODS

Male spontaneously diabetic Torii (SDT) fatty rats (n = 6) were used as an animal model of type 2 diabetes. Age- and sex-matched Sprague-Dawley (SD) rats (n = 8) were used as controls. Body weight, systolic blood pressure, and blood glucose levels were measured at 8, 12, 16, and 24 weeks of age. Urine samples and serum and kidney tissues were collected at 24 weeks of age. Microvascular blood flow index (BFI) was measured using diffuse correlation spectroscopy before sampling both the serum and kidneys for the evaluation of renal microcirculation at the corticomedullary junction.

RESULTS

Obesity, hyperglycemia, and hypertension were observed in the SDT fatty rats. Focal glomerular sclerosis, moderate interstitial inflammation, and fibrosis were significantly more frequent in SDT fatty rats than in SD rats. While the frequency of peritubular endothelial cells and phosphoendothelial nitric oxide synthase levels were similar in both types of rats, the degree of renal hypoxia-inducible factor-1α (HIF-1α) expression was significantly higher (and with no change in renal vascular endothelial growth factor expression levels) in the SDT fatty rats. Urinary L-FABP levels were significantly higher and renal microvascular BFI was significantly lower in the SDT fatty rats than in the SD rats. Urinary L-FABP levels exhibited a significant positive correlation with renal HIF-1α expression and a significant negative correlation with renal microvascular BFI.

CONCLUSIONS

Urinary L-FABP levels reflect the degree of renal hypoxia in DKD in a type 2 diabetic animal model. Urinary L-FABP may thus prove useful as a renal hypoxia marker for monitoring DKD in patients with type 2 diabetes in clinical practice.

Codonopsis tangshen Oliv. Amelioration Effect on Diabetic Kidney Disease Rats Induced by High Fat Diet Feeding Combined with Streptozotocin

Diabetic kidney disease (DKD) is the most serious microvascular complication during the development of diabetes with the characterizations of glomerular basement membrane thickening, mesangial expansion, and glomerular sclerosis, eventually leading to end-stage renal disease. This study aimed to investigate the melioration effect of Codonopisis tangshen Oliv. (COD) on the DKD model, which was established by unilateral nephrectomy (UN)-high fat diet feeding (HFD) combined with streptozotocin (STZ). After the DKD rats were oral treated with COD at a dose of 2.7 mg/kg for 4 consecutive weeks, the blood glucose, lipid metabolism, renal function, inflammatory mediators, and fibrosis-associated proteins were examined. In vivo, the COD administration obviously relieved the weight loss, water intake, and blood glucose; decreased the total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels; and improved the renal function by reducing the expression of serum creatinine, uric acid, and urinary protein compared with the model group. The levels of pro-inflammatory cytokines of tumor necrosis factor-α, interleukin-1β, and IL-6 were significantly inhibited by COD. Meanwhile, the deposition of collagen fiber was markedly increased, and the protein and mRNA expressions of transforming growth factor-β1 and α-smooth muscle actin were markedly elevated in DKD rats, but they were decreased to some extent after the COD treatment. In conclusion, COD exhibited a protective effect on the UN-HFD feeding combined with STZ-induced DKD model by improving the blood glucose and lipid metabolism, relieving the inflammatory response, and mitigating the renal fibrosis, which provided scientific evidence for its applications in clinic.