Role of the Renal Nerves in Regulating SGLT2 inhibitor‐induced Diuresis and Natriuresis in rats with Heart Failure

Abstract

Sodium‐glucose cotransporter 2 (SGLT2) inhibitors promoting glucose excretion are widely used to treat type 2 diabetes. Recently, the clinical trial in both diabetic and non‐diabetic heart failure (HF) patients with reduced ejection fraction demonstrated that SGLT2 inhibitor prevents worsening HF. However, the underlying mechanisms have not been fully elucidated. The present study was conducted to assess whether the effects of SGLT2 inhibitor on urine flow, sodium and glucose excretions are changed in HF. To address the underlying mechanisms the mRNA and protein levels of renal SGLT2 are investigated. HF was induced in rats by left coronary artery ligation. Further, to assess the contribution of renal nerves in the regulation of renal SGLT2, four weeks after ligation surgery, surgical bilateral renal denervation (RDN) was performed. Acute experiments were performed one week after RDN (five weeks after coronary ligation). Urine flow, sodium and glucose excretion responses to SGLT2 inhibitor dapagliflozin (0.5 mg/kg, i.v.) were greater in HF than Sham (Urine flow 15.8 ± 1.8 vs. 8.3 ± 1.1 μl/min/gkw, Sodium excretion 2.23 ± 0.35 vs. 1.13 ± 0.18 μEq/min/gkw, Glucose excretion 0.84 ± 0.06 vs. 0.52 ± 0.08 mg/min/gkw at 120 min, P<0.05, n=5–7). RDN significantly attenuated these responses to dapagliflozin in HF (Urine flow 9.8 ± 1.2 vs. 15.8 ± 1.8 μl/min/gkw, Sodium excretion 1.31 ± 0.17 vs. 2.23 ± 0.35 μEq/min/gkw, Glucose excretion 0.66 ± 0.04 vs. 0.84 ± 0.06 mg/min/gkw at 120 min, P<0.05, n=5–7). Western blot analysis indicated that SGLT2 protein expressions in the renal cortex were higher in HF than Sham (SGLT2/GAPDH 0.83 ± 0.06 vs. 0.58 ± 0.05, P<0.05, n=6). RDN significantly reduced enhanced protein levels of SGLT2 in the renal cortex of rats with HF (SGLT2/GAPDH 0.60 ± 0.07 vs. 0.83 ± 0.06, P<0.05, n=6). In contrast, RT‐PCR analysis indicated that RDN increased mRNA levels of SGLT2 in the renal cortex of rats with HF (SGLT2/18sRNA 1.08 ± 0.28 vs. 0.23 ± 0.06, P<0.05, n=6), possibly a compensatory change to SGLT2 protein expressions. Immunohistochemistry of renal sections confirmed the enhanced staining for SGLT2 in HF. These findings suggest that increases in urine flow, sodium and glucose excretion responses to SGLT2 inhibitor are enhanced in HF due to the upregulation of renal SGLT2. Renal sympathoexcitation in HF might enhance the expression and functional activity of renal SGLT2, thereby contribute to subsequent pathophysiology of renal sodium and water retention associated with HF.Support or Funding InformationSupported by Japan Heart Foundation and NIH grants DK 114663 and HL62222.