Dora B. Balogh1,4, Judit Hodrea1,4, Lilla Lenart1,4, Adam Hosszu1,4, Csenge Mezei1,4, Tamas Lakat1,4, Agnes Molnar1,4, Laszlo J. Wagner3, Attila J. Szabo2,4, Andrea Fekete1,4
1. MTA-SE „Lendület” Diabetes Research Group, Budapest
2. MTA-SE Pediatrics and Nephrology Research Group, Budapest
3. Department of Transplantation and Surgery, Semmelweis University, Budapest
4. 1st Department of Pediatrics, Semmelweis University Budapest
Introduction: Identification of novel therapeutic strategies that reduce the risk of diabetic kidney disease (DKD) is a research priority. Tubular hypoxia has a major pathogenic role in DKD. Hypoxia is in strong association with elevated glucose reabsorption and increased protein O-GlcNAcylation which could contribute to renal fibrosis. We recently described that SGLT2 inhibitors (SGLT2i) are renoprotective in experimental type 1 diabetes.
Aims: Considering emerging evidence of proximal tubular involvement in DKD and the major role of SGLT2 in glucose metabolism, here we investigated the direct effects of SGLT2i on hypoxia and O-GlcNAcylation.
Methods: Renal function and fibrosis were evaluated. The effect of hyperglycaemia was tested in human proximal tubular epithelial cells (HK-2) kept under normal glucose (5.5 mM), high glucose (35 mM) or high mannitol (osmotic control, 35 mM) conditions for 24 hours. HG cells were treated with 10 µM DAPA. O-GlcNAc, O‑GlcNAc transferase (OGT) and O‑GlcNAcase (OGA) were measured. To test the effect of hypoxia cells were treated with 10 µM DAPA and were placed in a hypoxic chamber for 2 hours (1% O2, 5% CO2, 94% N2). HIF-1α, EPO, VEGFA and PAI-1 were measured. Immunocytochemistry (ICC) staining for HIF-1α was performed.
Results: DAPA minimized hyperglycemia-induced total protein O-GlcNAcylation and OGT, while OGA which removes O-GlcNAc moieties was elevated in HK-2 cells. Hypoxia-induced HIF-1α elevation was suspended by DAPA treatment. Abolishment of HIF-1α upregulation by DAPA was confirmed by ICC staining. EPO, VEGFA and PAI-1 levels were also increased in hypoxia and DAPA prevented EPO and PAI-1 elevation.
Conclusions: Here we identified a novel mechanism of SGLT2i by which the direct reduction of tubular hypoxia and inhibition of OGT by DAPA results in decreased O-GlcNAcylation in proximal tubular cells. These processes could contribute to improved renal function and alleviated kidney fibrosis.
Funding: LP008/2017, OTKA-K112629-FK124491-NN-114607, VKE-2017-00006, FIKP, ÚNKP-18-3
Doctoral School: Clinical Medicine
Program: Prevention of Chronic Diseases in Childhood
Supervisor: Andrea Fekete, MD Phd
E-mail address: email@example.com