Evaluation of Glomerular Hemodynamic Function by Empagliflozin in Diabetic Mice using In Vivo Imaging.

Abstract

BACKGROUND\nSodium glucose cotransporter 2 (SGLT2) inhibitors may reduce kidney hyperfiltration, thereby preventing diabetic kidney disease (DKD) progression, which may in turn reduce cardiovascular risk, including heart failure. However, the mechanisms that regulate renal function responses to SGLT2 inhibition are not yet fully understood. We explored the renal protective effects of SGLT2 inhibition with empagliflozin (Empa), with a focus on glomerular hemodynamic effects and tubuloglomerular feedback (TGF) using in vivo multiphoton microscope (MPM) imaging techniques.\n\n\nMETHODS\nC57BL/6 mice and spontaneously diabetic Ins2+/Akita mice were studied. The mice were treated with empagliflozin (20mg/kg/day) and insulin for four weeks, and single-nephron GFR (SNGFR) was measured using MPM. An nNOS inhibitor (7-nitroindazole, 20mg/kg/day) or a COX2 inhibitor (SC58236, 6mg/L), or an adenosine A1 receptor (A1aR) antagonist (8-cyclopentyl-1,3-dipropylxanthine, 1mg/kg/day) were administered to elucidate mechanisms of TGF signaling and SNGFR regulation.\n\n\nRESULTS\nThe urinary excretion of adenosine, nitric oxide metabolites (NOx) and the prostanoid PGE2 was also quantified. SNGFR in the Ins2+/Akita group was higher compared to controls (C57BL/6; 4.9±1.3 nl/min vs. Ins2+/Akita; 15.8±6.8 nl/min) and lower in Ins2+/Akita /Empa to 8.0±3.3 nl/min (p<0.01). In vivo imaging also revealed concomitant afferent arteriolar dilation (p<0.01) and increased glomerular permeability of albumin in the Ins2+/Akita group. Empagliflozin ameliorated these changes (p<0.01). Urinary adenosine excretion in the Ins2+/Akita /Empa group was higher compared to Ins2+/Akita ( Ins2+/Akita; 3.4±1.4 nmol/day, Ins2+/Akita /Empa; 11.2±3.0 nmol/day, p<0.05), while NOx and PGE2 did not differ. A1aR antagonism, but not nNOS or COX2 inhibition, blocked the effect of empagliflozin on renal function. Empagliflozin increased urinary adenosine excretion and reduced hyperfiltration via afferent arteriolar constriction, effects that were abolished by A1aR blockade.\n\n\nCONCLUSIONS\nAdenosine/A1aR pathways play a pivotal role in the regulation of SNGFR via TGF mechanisms in response to SGLT2 inhibition, which may contribute to renal and cardiovascular protective effects reported in clinical trials.