Effect of Dapagliflozin Treatment on the Expression of Renal Sodium Transporters/Channels on High-Fat Diet Diabetic Mice

Abstract

Background: Inhibition of the Na⁺/glucose co-transporter 2 is a new therapeutic strategy for diabetes. It is unclear how proximal loss of Na⁺ (and glucose) affects the subsequent Na⁺ transporters in the proximal tubule (PT), thick ascending limb of loop of Henle (TAL), distal convoluted tubule (DCT) and collecting duct (CD). Methods: Mice on a high fat diet were administered 3 doses streptozotocin 6 days prior to oral dapagliflozin administration or vehicle for 18 days. A control group of lean mice were also included. Body weight and glucose were recorded at regular intervals during treatment. Renal Na⁺ transporters expression in nephron segments were analyzed by RT-qPCR and Western blot. Results: Dapagliflozin treatment resulted in a significant reduction in body weight and blood glucose compared to vehicle-treated controls. mRNA results showed that Na⁺-hydrogen antiporter 3 (NHE3), Na⁺/phosphate cotransporter (NaPi-2a) and epithelial Na⁺ channel expression was increased, Ncx1, ENaCβ and ENaCγ expression declined (p all < 0.05), respectively, in dapagliflozin-treated mice when compared with saline vehicle mice. Na-K-2Cl cotransporters and Na-Cl cotransporter mRNA expression was not affected by dapagliflozin treatment. Na⁺/K⁺-ATPase (Atp1b1) expression was also increased significantly by dapagliflozin treatment, but it did not affect Atp1a1 and glucose transporter 2 expression. Western blot analysis showed that NaPi-2a, NHE3 and ATP1b1 expression was upregulated in dapagliflozin-treated diabetic mice when compared with saline vehicle mice (p < 0.05). Conclusion: Our findings suggest that dapagliflozin treatment augments compensatory changes in the renal PT in diabetic mice.