Effects of SGLT2 Inhibition in Human Kidney Proximal Tubular Cells—Renoprotection in Diabetic Nephropathy?

Abstract

Sodium/glucose cotransporter 2 (SGLT2) inhibitors are oral hypoglycemic agents used to treat patients with diabetes mellitus. SGLT2 inhibitors block reabsorption of filtered glucose by inhibiting SGLT2, the primary glucose transporter in the proximal tubular cell (PTC), leading to glycosuria and lowering of serum glucose. We examined the renoprotective effects of the SGLT2 inhibitor empagliflozin to determine whether blocking glucose entry into the kidney PTCs reduced the inflammatory and fibrotic responses of the cell to high glucose. We used an in vitro model of human PTCs. HK2 cells (human kidney PTC line) were exposed to control 5 mM, high glucose (HG) 30 mM or the profibrotic cytokine transforming growth factor beta (TGFβ1; 0.5 ng/ml) in the presence and absence of empagliflozin for up to 72 h. SGLT1 and 2 expression and various inflammatory/fibrotic markers were assessed. A chromatin immunoprecipitation assay was used to determine the binding of phosphorylated smad3 to the promoter region of the SGLT2 gene. Our data showed that TGFβ1 but not HG increased SGLT2 expression and this occurred via phosphorylated smad3. HG induced expression of Toll-like receptor-4, increased nuclear deoxyribonucleic acid binding for nuclear factor kappa B (NF-κB) and activator protein 1, induced collagen IV expression as well as interleukin-6 secretion all of which were attenuated with empagliflozin. Empagliflozin did not reduce high mobility group box protein 1 induced NF-κB suggesting that its effect is specifically related to a reduction in glycotoxicity. SGLT1 and GLUT2 expression was not significantly altered with HG or empagliflozin. In conclusion, empagliflozin reduces HG induced inflammatory and fibrotic markers by blocking glucose transport and did not induce a compensatory increase in SGLT1/GLUT2 expression. Although HG itself does not regulate SGLT2 expression in our model, TGFβ increases SGLT2 expression through phosphorylated smad3.

The effect of sodium glucose cotransporter 2 inhibition with empagliflozin on microalbuminuria and macroalbuminuria in patients with type 2 diabetes

“…In vitro and in vivo work has suggested that sodium glucose cotransport inhibition reduces markers of inflammation and fibrosis [18,19,[29][30][31]. Although we did not measure inflammatory markers in the present trials, future studies should assess the effect of SGLT2 inhibition on pro-inflammatory and pro-fibrotic mechanisms in diabetes and associated kidney disease.…”

Fatty Liver and Chronic Kidney Disease: Novel Mechanistic Insights and Therapeutic Opportunities

“…The consequent reduction in NaCl distal delivery to the macula densa decreases tubuloglomerular feedbackmediated afferent arteriolar vasoconstriction, thereby increasing glomerular afferent-to-efferent arteriolar tone, intraglomerular ultrafiltration pressure, and glomerular filtration rate (124). Proximal tubule SGLT2 upregulation and increased NaCl reabsorption also have been documented in obesity-related CKD as a result of enhanced sympathetic activity (33,125) and TGF-b1/SMAD3 axis activation (126). By virtue of these actions, SGLT2 inhibitors synergize with renin-angiotensin-aldosterone system (RAAS) inhibitors, and their combination may confer incremental renal benefits (127).…”

SGLT2 Inhibitors and the Diabetic Kidney

“…The increase in glucose trafficking through the proximal tubular cells, consequent of an increased transport of glucose by SGLT2, could promote inflammation and fibrosis. In immortalized human proximal tubular cells, empagliflozin reduced the glucoseinduced Toll-like receptor 2 and 4 and nuclear factor-kB expression, both wellknown mediators of inflammatory and fibrotic responses in animal models of DN (42). Thus, it is tempting to hypothesize that in patients with type 2 diabetes and tubulointerstitial lesions SGLT2 inhibitors might be particularly useful in reducing tubulointerstitial fibrosis and inflammation.…”