Objective:To study the changes in long non-coding RNA C2dat1 expression in kidney tissues of rats at different stages of diabetic kidney disease (DKD) and its relationship with renal interstitial fibrosis.Methods:Forty-eight male SD rats were randomly divided into two groups with 24 rats in each group: control group and DKD group. The rats in the control group were fed with ordinary diet, while those in the DKD group were fed with high-fat diet and drank water freely. After eight weeks of feeding, the rats were fasted for 12 h with free access to water. Then, the DKD group was given a one-time intrabitoneal injection of streptozotocin and the control group was given an equal dose of sodium citrate buffer. After 72 h, the random peripheral blood glucose concentration (≥ 16.7 mmol/L for three consecutive days) and urine sugar (positive) were tested to assess the establishment of the diabetes model. Urine, blood and kidney samples were collected at 3, 6, 9 and 12 weeks. The urinary protein excretion rate within 24 h, urinary creatinine and serum total cholesterol were measured by automatic biochemical apparatus. Pathological changes in kidney tissues were observed by HE staining. The expression of calcium/calmodulin-dependent protein kinase Ⅱ delta (CaMK2D), p65, p50, α-SMA and E-cardherin was detected by immunohistochemistry. Quantitative real-time PCR (qPCR) was used to detect the expression of lncRNA C2dat1 and CaMK2D. The relationship of lncRNA C2dat1 with α-SMA, E-cardherin and CaMK2D was analyzed by correlation analysis. In in vitro experiment, renal tubular epithelial cells HK-2 were induced by high glucose. The expression of lncRNA C2dat1 and CaMK2D in HK-2 cells was detected by qPCR after 24, 48 and 72 h of intervention. Results:The rats in the DKD group showed typical symptoms such as polydipsia, polyphagia, significant weight loss and increased blood glucose as compared with the rats in the control group. Results of the biochemical tests revealed that compared with the control group, the DKD group had increased 24 h excretion rate of urinary protein, decreased urinary creatinine and up-regulated total cholesterol. HE staining showed that the rats in the control group had intact glomeruli, normal basement membrane and no mesangial hyperplasia or inflammatory cell infiltration. However, enlarged glomeruli and evenly thickened basement membrane were observed in the DKD group. Immunohistochemistry indicated that the expression of CaMK2D, p50 and α-SMA was higher in the DKD group than in the control group, while the expression of E-cardherin was lower in the DKD group. qPCR results showed that the expression of lncRNA C2dat1 and CaMK2D at mRNA level was higher in the DKD group than in the control group. In in vitro experiment, the expression of lncRNA C2dat1 and CaMK2D at mRNA level was also higher in HK-2 cells induced by high glucose than in the control group. Correlation analysis indicated that lncRNA C2dat1 was positively correlated with α-SMA and CaMK2D, but negatively correlated with E-cardherin. Conclusions:During the progression of DKD, the high expression of lncRNA C2dat1 might promote diabetic renal interstitial fibrosis by regulating the expression of CaMK2D to activate the NF-κB signaling pathway.

Objective To investigate the effect of 1, 25-(OH)₂-VitD3 (VitD3) on renal tubuleinterstitial fibrosis in diabetic kidney disease. Methods NRK-52E renal tubular epithelial cells were divided into control group (5.5 mmol/L glucose medium treatment), high glucose group (25 mmol/L glucose medium treatment) and high glucose with added VitD3 group (25 mmol/L glucose medium combined with 10^-8 mmol/L VitD3). The mRNA and protein expression of Snail1, SMAD3, SMAD4, α-SMA and E-cadherin in NRK-52E cells were detected by real-time quantitative PCR and Western blot analysis respectively. The expression and localization of Snail1, SMAD3 and SMAD4 were detected by immunofluorescence cytochemical staining. The binding of Snail1 with SMAD3/SMAD4 complex to the promoter of Coxsackie-adenovirus receptor (CAR) was detected by chromatin immunoprecipitation. The interaction among Snail1, SMAD3/SMAD4 and E-cadherin were detected by luciferase assay. Small interfering RNA (siRNA) was used to inhibit the expression of Snail1 and SMAD4, and the expression of mRNA of E-cadherin was detected by real-time quantitative PCR. SD rats were randomly divided into control group, DKD group and VitD3-treated group. DKD model was established by injection of streptozotocin (STZ) in DKD group and VitD3-treated group. After DKD modeling, VitD3-treated group was given VitD3 (60 ng/kg) intragastric administration. Control group and DKD group were given normal saline intragastric administration. In the DKD group and VitD3-treated group, insulin (1-2 U/kg) was injected subcutaneously to control blood glucose for 8 weeks. The mRNA and protein levels of Snail1, SMAD3, SMAD4, α-SMA and E-cadherin in renal tissues were detected by real-time quantitative PCR and Western blot analysis respectively. Immunohistochemistry was used to detect the expression and localization of Snail1, SMAD3, SMAD4, α-SMA and E-cadherin in renal tissue. Results Compared with the control group, the mRNA and protein expressions of Snail1, SMAD3, SMAD4 and α-SMA in NRK-52E cells cultured with high glucose and in DKD renal tissues were up-regulated, while E-cadherin expression was down-regulated. After the intervention of VitD3, the expression levels of Snail1, SMAD3, SMAD4, α-SMA and E-cadherin in the DKD model improved to be close to those in the control group. Chromatin immunoprecipitation showed that Snail1 and SMAD3/SMAD4 bound to CAR promoter IV, while VitD3 prevented Snail1 and SMAD3/SMAD4 from binding to CAR promoter IV. Luciferase assay confirmed the interaction among Snail1, SMAD3/SMAD4 and E-cadherin. After the mRNA of Snail1 and SMAD4 was inhibited by siRNA, the expression of E-cadherin induced by high glucose was up-regulated. Conclusion VitD3 could inhibit the formation of Snail1-SMAD3/SMAD4 complex and alleviate the renal tubulointerstitial fibrosis in DKD.
Animals ; Rats ; Cadherins/genetics* ; Diabetes Mellitus/pathology* ; Diabetic Nephropathies/pathology* ; Epithelial-Mesenchymal Transition ; Fibrosis/pathology* ; Glucose/pharmacology* ; Kidney/pathology* ; Rats, Sprague-Dawley ; RNA, Messenger ; RNA, Small Interfering ; Transforming Growth Factor beta1/metabolism* ; Vitamin D/pharmacology*