Kidney Week

Abstract: SA-PO0328

Macula Densa NKCC2 Deletion Impairs Tubuloglomerular Feedback and Promotes RAAS Activation and Glomerular Hyperfiltration in Type 1 Diabetic Mice

Session Information

• Diabetic Kidney Disease: Basic and Translational Science Advances - 2
  November 08, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Diabetic Kidney Disease

• 701 Diabetic Kidney Disease: Basic

Authors

• Williams, Kristof, Department of Molecular Pharmacology and Physiology, USF-TGH Transplant Research Center, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States

Kristof Williams

• Qu, Stanley, Department of Molecular Pharmacology and Physiology, USF-TGH Transplant Research Center, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States

Stanley Qu

• Zheleznova, Nadezhda N., Department of Molecular Pharmacology and Physiology, USF-TGH Transplant Research Center, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States

Nadezhda N. Zheleznova, PhD

• Hall, Nathan, Department of Molecular Pharmacology and Physiology, USF-TGH Transplant Research Center, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States

Nathan Hall, MS

• Ni, Runze, Department of Molecular Pharmacology and Physiology, USF-TGH Transplant Research Center, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States

Runze Ni

• Staruschenko, Alexander, Department of Molecular Pharmacology and Physiology, USF-TGH Transplant Research Center, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States

Alexander Staruschenko, PhD, FASN

• Zhang, Jie, Boston University, Boston, Massachusetts, United States

Jie Zhang, PhD

• Wei, Jin, Boston University, Boston, Massachusetts, United States

Jin Wei, PhD

• Wang, Lei, Department of Molecular Pharmacology and Physiology, USF-TGH Transplant Research Center, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States

Lei Wang, PhD

• Liu, Ruisheng, Department of Molecular Pharmacology and Physiology, USF-TGH Transplant Research Center, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States

Ruisheng Liu, MD, PhD, FASN

Background

SGLT2 inhibitors reduce serum glucose levels, providing cardiovascular and renal protective benefits. One proposed mechanism involves the tubuloglomerular feedback (TGF) response due to increased NaCl delivery to the macula densa (MD), leading to a reduction of glomerular filtration rate (GFR). However, direct evidence is lacking. Here, we investigate the role of TGF in SGLT2 inhibition using a novel mouse model lacking a functional TGF response.

Methods

We generated a novel MD-specific NKCC2 deletion line (MD-NKCC2KO) by crossing NKCC2^flox mice with tamoxifen-inducible NOS1cre mice. NKCC2 was induced by tamoxifen (i.p., 5 days). Type 1 diabetes was then induced via alloxan (55 mg/kg, i.v.). Serum glucose was measured biweekly for 2 weeks. TGF was assessed via double-perfused juxtaglomerular apparatus, GFR via FITC-sinistrin clearance, and plasma renin from tail-tip blood samples to track the renin-angiotensin-aldosterone system (RAAS) activity. After two weeks of sustained hyperglycemia, mice received dapagliflozin (5 mg/kg/day, orally) for 14 days. Kidneys were collected at the endpoint for immunofluorescence, Western blotting, RT-PCR, cytokine array, and histological analysis.

Results

TGF was abolished in the MD-NKCC2KO mice (0.3±0.8 µm in the KO vs 3.7±0.4 µm in the control). Diabetic MD-NKCC2KO mice exhibited significantly higher GFR and elevated plasma renin activity compared to diabetic controls. Dapagliflozin reduced serum glucose concentration similarly in both groups. SGLT2 inhibition led to a marked reduction in WT diabetic mice, consistent with enhanced TGF. In contrast, GFR remained unchanged in MD-NKCC2KO mice. Plasma renin levels remained elevated in both groups.

Conclusion

These findings demonstrate an essential role of TGF in mediating the renal effects of SGLT2 inhibition. Loss of TGF response by deletion of MD-NKCC2 diminishes the beneficial effects of SGLT2 inhibition on hyperfiltration in type 1 diabetic mice. Therefore, the impact of SGLT2 inhibition on GFR is dependent on intact TGF mechanisms. TGF response also plays a significant role in enhancing renin activity in diabetes. The TGF mechanism seems to play a minimal role in the glucose-lowering effect of SGLT2 inhibition.

Funding

• NIDDK Support

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025qv1vk6c7