Effect of SGLT2 Inhibition on the Development of Salt‐sensitive Hypertension, RAAS, and Sodium Channels and Transporters in Dahl SS Rats

Abstract

Hypertension is common among patients with type 2 diabetes mellitus (T2DM). The combination of diabetes and hypertension is associated with high morbidity and mortality because of an increased risk of cardiovascular and renal complications. Effective control of blood glucose levels and blood pressure is essential to prevent the development and progression of diabetic nephropathy in T2DM. Sodium‐Glucose Cotransporter‐2 (SGLT2) inhibitors are the new highly effective drugs for the treatment of T2DM and some cardiovascular diseases. Despite all the remarkable benefits on cardiovascular and renal systems, the molecular mechanisms of how SGLT2 inhibition affects water and electrolyte balance are incompletely understood. We hypothesized that SGLT2 inhibition alters blood pressure via affecting Renin‐Angiotensin‐Aldosterone System (RAAS), sodium channels and transporters. Dahl Salt‐Sensitive (SS) rat, a model for salt‐induced hypertension, was used to test this hypothesis in a hypertensive, non‐diabetic environment. We found that administration of dapagliflozin at a concentration of 2 mg/kg/day via drinking water during 3 weeks blunts the development of salt‐induced hypertension with no changes in the heart rate. Mean arterial pressure in the dapagliflozin treated group compared to the vehicle‐treated group during high salt (4% NaCl) challenge was significantly lower (136 ± 4 vs. 157 ± 6 mmHg; P<0.0001 on 21st day of the experiment). SGLT2 inhibition caused a significant diuretic effect (67 ± 6 vs. 40 ± 4 ml/day, P<0.001 on the 21st day of the experiment). Glucose excretion was dramatically increased in inhibitor‐treated rats compared to vehicle‐treated (747 ± 44 vs. 12 ± 2 mg/dL, P<0.0001 on the 21st day). We also observed increased Na+/creatinine ratios (138 ± 10 vs. 110 ± 6, P<0.004 on the 21st day) and Cl‐/creatinine ratios (133 ± 9 vs. 108 ± 6, P<0.03 on the 21st day). To define potential mechanisms, we first measured levels of hormones involved in the RAAS by using LC‐MS/MS. Despite effects on Na+/creatinine and Cl‐/creatinine ratios, dapagliflozin treatment did not affect RAAS metabolites. Subsequently, we assessed the effects of SGLT2 inhibition on renal Na+ channels and transporters using patch‐clamp, Western blotting, and RT‐PCR. Neither mRNA nor protein expressions levels of all tested Na+ transporters (SGLT2, SGLT1, NHE3, NKCC2, NCC, and α‐, β‐, γ‐ ENaC subunits) were different between groups. Electrophysiological studies did not reveal any difference of SGLT2 inhibition on the conductance and activity of ENaC. Therefore, our data suggest that SGLT2 inhibition blunts the development of salt‐induced hypertension, causes glucosuria and natriuresis but does not affect RAAS and expression and activity of Na+ channels and transporters in a model of non‐diabetic, salt‐sensitive hypertension.