Empagliflozin Inhibits NHE3 Activity in the Proximal Tubule of Normotensive and Hypertensive Rats

Abstract

BackgroundA growing body of evidence suggests an interplay between extracellular volume and glucose homeostasis. NHE3 is the main pathway for Na reabsorption in the proximal tubule (PT). The sodium glucose cotransporter SGLT2 reabsorbs most of the glucose filtered by the kidneys and colocalizes with NHE3 in the apical membrane of PT. Thus, we tested the hypothesis that SGLT2 and NHE3 functionally interact. Given that SGLT2 inhibitors confer blood‐pressure lowering effects in T2DM patients, we also tested the hypothesis that the antihypertensive effects of SGLT2 inhibitors may be associated with PT NHE3 inhibition.MethodsThe acute and long‐term effects of the SGLT2 inhibitor empagliflozin on PT NHE3 activity were determined by in vivo stationary microperfusion in fourteen‐week‐old male Wistar rats and SHR‐treated rats. Additionally, twelve‐week‐old SHRs were treated with empagliflozin (10 mg/kg/day) or vehicle (control) for two weeks. Tail‐cuff blood pressure and renal function were measured before (baseline) and after treatment (post‐treatment). NHE3 expression and phosphorylation levels were evaluated by immunoblotting.ResultsEmpagliflozin acutely inhibited PT NHE3 activity in both Wistar (1.73 ± 0.07 vs. 2.55 ± 0.14 nmol/cm2.s, P < 0.001) and SHR (0.82 ± 0.07 vs. 1.21 ± 0.10 nmol/cm2.s, P < 0.01). Blood pressure (BP) of empagliflozin‐treated SHR was lower than baseline levels (176 ± 4 vs. 194 ± 4 mm Hg, P < 0.01) whereas no change in BP was observed in vehicle‐treated SHR (194 ± 6 vs. 192 ± 5 mm Hg). Compared to baseline, empagliflozin‐treatment enhanced cumulative urinary flow, calcium, sodium and glucose excretion whereas in vehicle‐treated SHR these parameters remained unchanged. Lower BP in empagliflozin‐treated SHR was associated with lower PT NHE3 activity (0.67 ± 0.10 vs. 1.18 ± 0.10 nmol/cm2.s, P < 0.001). No differences were observed on renal cortical NHE3 protein expression or NHE3 phosphorylation levels between the two groups of rats.ConclusionThese results suggest that NHE3 and SGLT2 functionally interact in the PT. Inhibition of NHE3 by SGLT2 inhibitors may underlie, at least in part, the antihypertensive effect of empagliflozin.Support or Funding InformationFAPESPThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

New insights into cellular links between sodium–glucose cotransporter‐2 inhibitors and ketogenesis

“…This study demonstrated that chronic empagliflozin therapy induced an acute bicarbonaturia in an NHE3‐dependent manner possibly through adaptations to urinary glucose and Na+ excretion 61 . Other evidence provided recently demonstrated that empagliflozin inhibits NHE3 activity in renal proximal tubules of rats 89 . In this study, 2 weeks of empagliflozin therapy significantly reduced NHE3 activity in both normal and hypertensive Wistar rats 89 .…”

“…89 In this study, 2 weeks of empagliflozin therapy significantly reduced NHE3 activity in both normal and hypertensive Wistar rats. 89 Collectively, this evidence highly suggests that SGLT2 inhibitors are potent NHE3 inhibitors and decrease their activity. 91,92 Although this effect may be attenuated by inducing ammoniagenesis by SGLT2 inhibitors, 93 however, may represent another potential link between SGLT2 inhibition and acidosis.…”

“…they functionally interact. 60,63,87,89,90 The activity of NHE3 is increased in response to higher levels of insulin and glucose, while SGLT2 inhibitors reduce both of them and so reduce NHE3 activity indirectly. 60,63 NHE3-dependent renal bicarbonate reabsorption is related to glucose metabolism in proximal tubules.…”

“…There may be interactions via scaffolding proteins, such as MAP17, which is known to be a potent SGLT2 activator 61 . Abundant expression of these antiporters on proximal tubule segments expressing SGLT2 highly suggests that SGLT2 inhibitors may be able to modify these exchangers and that they functionally interact 60,63,87,89,90 . The activity of NHE3 is increased in response to higher levels of insulin and glucose, while SGLT2 inhibitors reduce both of them and so reduce NHE3 activity indirectly 60,63 .…”

Renoprotective mechanisms of sodium‐glucose co‐transporter 2 (SGLT2) inhibitors against the progression of diabetic kidney disease

“…SGLT2 inhibition causes blood volume depletion and dehydration, part of which could be attributed to inhibition of NHE3, which causes natriuresis due to inhibition of sodium reabsorption in the proximal tubules (Silva Dos Santos et al, 2020). A study by Borges et al (2018) showed that empagliflozin lowered blood pressure in spontaneously hypertensive rats by inhibiting NHE3 activity in renal proximal tubular cells (RPTCs). The co‐localization of SGLT2 and NHE3 and the enhanced natriuresis following SGLT2 inhibition suggests that SGLT2‐NHE3 interaction is significant in maintaining the acid–base balance in kidneys (Thomson & Vallon, 2019).…”