Abstract: FR-PO275
SGLT2-Independent Effects of Canagliflozin on NHE3 and Mitochondrial Complex I Activity Inhibit Proximal Tubule Fluid Transport and Albumin Uptake
Session Information
- Diabetic Kidney Disease: Basic - 1
October 25, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Diabetic Kidney Disease
- 701 Diabetic Kidney Disease: Basic
Authors
- Albalawy, Wafaa N., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Youm, Elynna B., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Shipman, Katherine E., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Long, Kimberly R., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Rbaibi, Youssef, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Jurczak, Michael J., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Kashlan, Ossama B., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
- Weisz, Ora A., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
Background
Beyond glycemic control, SGLT2 inhibitors have protective effects on cardiorenal function. Renoprotection has been suggested to involve inhibition of NHE3 leading to reduced ATP-dependent tubular workload and mitochondrial oxygen consumption. NHE3 activity is also important for regulation of endosomal pH, but the effects of SGLT2i on endocytosis are unknown
Methods
We used a highly differentiated cell culture model of proximal tubule (PT) cells to determine the direct effects of SGLT2i on Na+-dependent fluid transport and endocytic uptake in this nephron segment. BCECF-AM were used to measure intracellular pH. The effect of gliflozins on albumin uptake and on fluid transport was quantified in opossum kidney (OK) PT cells; cana vs the NHE3 inhibitor S3226 effect on early endosome pH in OK cells was measured using fluorescence ratio imaging. Effects of gliflozins on AMPK pathway were determined by immunoblotting. 10 week-old male C57BL/6 mice were given cana or empa by oral gavage daily following vehicle gavage. Urine was collected via metabolic cages at baseline and after 24h and 48h. Creatinine and albumin were measured by ELISA
Results
Canagliflozin but not empagliflozin reduced fluid transport across cell monolayers and dramatically inhibited endocytic uptake of albumin. These effects were independent of glucose and occurred at clinically relevant concentrations of drug. Cana acutely inhibited surface NHE3 activity, consistent with a direct effect, but did not affect endosomal pH or NHE3 phosphorylation. In addition, canagliflozin rapidly and selectively inhibited mitochondrial complex I activity. Inhibition of mitochondrial complex I by metformin recapitulated the effects of cana on endocytosis and fluid transport, whereas modulation of downstream effectors AMPK and mTOR did not. Mice given a single dose of cana excreted twice as much urine over 24 h compared with empa-treated mice despite similar water intake
Conclusion
We conclude that cana selectively suppresses Na+-dependent fluid transport and albumin uptake in PT cells via direct inhibition of NHE3 and of mitochondrial function upstream of the AMPK/mTOR axis. These additional targets of cana contribute significantly to reduced PT Na+-dependent fluid transport in vivo
Funding
- Government Support – Non-U.S.