title: 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.
authors: Department of Medicine, The University of Sydney, Renal Research Group, Kolling Institute of Medical Research, Royal North Shore Hospital, St. Leonards, New South Wales, Australia. usha.panchapakesan@sydney.edu.au
authors: Usha
authors: U
authors: Panchapakesan
authors: Kate
authors: K
authors: Pegg
authors: Simon
authors: S
authors: Gross
authors: Muralikrishna Gangadharan
authors: MG
authors: Komala
authors: Harshini
authors: H
authors: Mudaliar
authors: Josephine
authors: J
authors: Forbes
authors: Carol
authors: C
authors: Pollock
authors: Amanda
authors: A
authors: Mather
mesh_terms: D001559:Benzhydryl Compounds / Q000494:pharmacology*; D024141:Collagen Type IV / Q000235:genetics / Q000378:metabolism; D003920:Diabetes Mellitus / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D003928:Diabetic Nephropathies / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D005960:Glucosides / Q000494:pharmacology*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051297:Sodium-Glucose Transporter 2 / Q000235:genetics* / Q000378:metabolism; D000077203:Sodium-Glucose Transporter 2 Inhibitors; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
chemical_list: D001559:Benzhydryl Compounds; D024141:Collagen Type IV; D005960:Glucosides; D007004:Hypoglycemic Agents; C508600:IL6 protein, human; D015850:Interleukin-6; D016328:NF-kappa B; C495674:SLC5A1 protein, human; C089180:SLC5A2 protein, human; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D051269:Sodium-Glucose Transporter 1; D051297:Sodium-Glucose Transporter 2; D000077203:Sodium-Glucose Transporter 2 Inhibitors; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D018808:Transcription Factor AP-1; D053773:Transforming Growth Factor beta1; C570240:empagliflozin; D005947:Glucose
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