Abstract
The renoprotective effects of SLC5A2/SGLT2 (solute carrier 5 (sodium/glucose cotransporter), member 2) inhibitors have recently been demonstrated in non-diabetic chronic kidney disease (CKD), even without overt albuminuria. However, the mechanism underlying this renoprotection is largely unclear. We investigated the renoprotective mechanisms of the SLC5A2 inhibitor empagliflozin with a focus on ALB (albumin) reabsorption and macroautophagy/autophagy in proximal tubules using wild-type or drug-inducible lrp2/Megalin or atg5 knockout mice with high-fat diet (HFD)-induced obesity or 5/6 nephrectomy that elevated intraglomerular pressure without overt albuminuria. Empagliflozin treatment of HFD-fed mice reduced several hallmarks of lipotoxicity in the proximal tubules, such as phospholipid accumulation in the lysosome, inflammation and fibrosis. Empagliflozin, which decreases intraglomerular pressure, not only reduced the HFD-induced increase in ALB reabsorption via LRP2 in the proximal tubules (i.e. total nephron ALB filtration), as assessed by urinary ALB excretion caused by genetic ablation of Lrp2, but also ameliorated the HFD-induced imbalance in circulating ALB-bound fatty acids. Empagliflozin alleviated the HFD-induced increase in autophagic demand and successfully prevented autophagic stagnation in the proximal tubules. Similarly, empagliflozin decreased ALB exposure and autophagic demand in 5/6 nephrectomized mice. Finally, empagliflozin reduced HFD-induced vulnerability to ischemia-reperfusion injury, whereas LRP2 blockade and atg5 ablation separately diminished this effect. Our findings indicate that empagliflozin reduces ALB exposure and prevents autophagic stagnation in the proximal tubules even without overt albuminuria. Autophagy improvement may be critical for the renoprotection mediated by SLC5A2 inhibition.
Keywords:
Albuminuria; LRP2/Megalin; SLC5A2/SGLT2 inhibitors; autophagic stagnation; lipotoxicity; lysosome.