SGLT2 Inhibitor Empagliflozin Reduces Renal Growth and Albuminuria in Proportion to Hyperglycemia and Prevents Glomerular Hyperfiltration in Diabetic Akita Mice
Published online on November 13, 2013
Abstract
Our previous work has shown that gene-knockout of the sodium-glucose cotransporter SGLT2 modestly lowered blood glucose in streptozotocin-diabetic mice (BG; from 470 to 300mg/dl) and prevented glomerular hyperfiltration, but did not attenuate albuminuria or renal growth and inflammation. Here we determined effects of the SGLT2 inhibitor empagliflozin (300mg/kg of diet for 15 weeks; corresponding to 60-80mg/kg/d) in type 1 diabetic Akita mice that, opposite to streptozotocin-diabetes, upregulate renal SGLT2 expression. Akita-diabetes, empagliflozin, and Akita+empagliflozin similarly increased renal membrane SGLT2 expression (by 38-56%) and reduced the expression of SGLT1 (by 33-37%) vs. vehicle-treated wild-type controls (WT). The diabetes-induced changes in SGLT2/SGLT1 protein expression are expected to enhance the BG lowering potential of SGLT2 inhibition, and empagliflozin strongly lowered BG in Akita (means of 187-237 vs. 517-535mg/dl in vehicle group; 100-140mg/dl in WT). Empagliflozin modestly reduced GFR in WT (250 vs. 306µl/min), and completely prevented the diabetes-induced increase in GFR (255 vs. 397µl/min). Empagliflozin attenuated increases in kidney weight and urinary albumin/creatinine ratio in Akita in proportion to hyperglycemia. Empagliflozin did not increase urinary glucose/creatinine ratios in Akita, indicating the reduction in filtered glucose balanced the inhibition of glucose reabsorption. Empagliflozin attenuated/prevented the increase in systolic blood pressure, glomerular size, and molecular markers of kidney growth, inflammation, and gluconeogenesis in Akita. We propose that SGLT2 inhibition can lower GFR independent of reducing BG (consistent with the tubular hypothesis of diabetic glomerular hyperfiltration), while attenuation of albuminuria, kidney growth, and inflammation in the early diabetic kidney may mostly be secondary to lower BG.