Empagliflozin protects glomerular endothelial cell architecture in experimental diabetes through the VEGF‐A/caveolin‐1/PV‐1 signaling pathway

Abstract

In addition to having blood glucose-lowering effects, inhibitors of sodium glucose cotransporter 2 (SGLT2) afford renoprotection in diabetes. We sought to investigate which components of the glomerular filtration barrier could be involved in the antiproteinuric and renoprotective effects of SGLT2 inhibition in diabetes. BTBR (black and tan, brachyuric) ob/ob mice that develop a type 2 diabetic nephropathy received a standard diet with or without empagliflozin for 10 weeks, starting at 8 weeks of age, when animals had developed albuminuria. Empagliflozin caused marked decreases in blood glucose levels and albuminuria but did not correct glomerular hyperfiltration. The protective effect of empagliflozin against albuminuria was not due to a reduction in podocyte damage as empagliflozin did not affect the larger podocyte filtration slit pore size nor the defective expression of nephrin and nestin. Empagliflozin did not reduce the thickening of the glomerular basement membrane. In BTBR ob/ob mice, the most profound abnormality seen using electron microscopy was in the endothelial aspect of the glomerular capillary, with significant loss of endothelial fenestrations. Remarkably, empagliflozin ameliorated the subverted microvascular endothelial ultrastructure. Caveolae and bridging diaphragms between adjacent endothelial fenestrae were seen in diabetic mice and associated with increased expression of caveolin-1 and the appearance of PV-1. These endothelial abnormalities were limited by the SGLT2 inhibitor. Although no expression of SGLT2 was found in glomerular endothelial cells, SGLT2 was expressed in the podocytes of diabetic mice. VEGF-A, which is a known stimulus for endothelial caveolin-1 and PV-1, was increased in podocytes of BTBR ob/ob mice and normalized by SGLT2 inhibitor treatment. Thus, empagliflozin's protective effect on the glomerular endothelium of diabetic mice could be due to a limitation of the paracrine signaling of podocyte-derived VEGF-A that resulted in a reduction of the abnormal endothelial caveolin-1 and PV-1, with the consequent preservation of glomerular endothelial function and permeability.

SGLT2 inhibitors suppress epithelial–mesenchymal transition in podocytes under diabetic conditions via downregulating the IGF1R/PI3K pathway

“…Several studies recently reported a direct role of SGLT2 in interfering with podocyte dysfunction. For instance, in mice with DN, the reno-protective effect of empagliflozin against proteinuria was primarily due to the decreased release of Frontiers in Pharmacology frontiersin.org substances that damaged endothelial cells after SGLT2 downregulation in podocytes (Locatelli et al, 2022). Particularly, Cassis et al (2018) reported increased SGLT2 expression in the HPC of proteinuric CKD patients as well as podocytes cultured with repeated BSA exposure.…”

“…For instance, dapagliflozin dilates the efferent arteriole, reduces intravascular pressure, and alleviates shear force injury to the filtration barrier ( van Bommel et al, 2020 ). In BTBR ob/ob mice, empagliflozin decreased the expression of SGLT2 in podocytes and further improved the microvascular endothelial ultrastructure by inhibiting the secretion of podocyte-derived VEGF-A ( Locatelli et al, 2022 ). Cassis et al (2018 ) reported a high level of SGLT2 in protein-overloaded human podocytes (HPC), and inhibition of SGLT2 could help normalize podocyte cytoskeleton and function.…”

KITLG Promotes Glomerular Endothelial Cell Injury in Diabetic Nephropathy by an Autocrine Effect

“…Moreover, accumulating evidence suggests that SGLT2 inhibitors attenuate oxidative stress and inflammation in vivo and in vitro models of DN in several ways [ 43 ]. Although SGLT2 expression was not found in GECs, empagliflozin protected GECs by limiting podocyte-secreted vascular endothelial growth factor A in DN mice [ 44 ]. Further experiments to explore the function and molecular pathways of GECs specifically affected by SGLT2 inhibitors are necessary.…”

The importance of caveolin as a target in the prevention and treatment of diabetic cardiomyopathy

“…Since Cav-2 will not exist independently in the absence of Cav-1, we focus on Cav-1 and Cav-3 here. Of note, as stated in the European Society of Cardiology Guidelines on diabetes, pre-diabetes and cardiovascular diseases ( 79 ), empagliflozin, among others, has been newly recommended as one of the first line options for glucose lowing treatment, while its protective mechanism involves Cav-1 signaling ( 80 ). This signifies the importance of caveolins in the treatment of diabetic complications including diabetic cardiomyopathy.…”