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Abstract: PO1084

Calcium-Sensing Receptor-Mediated Activation of the WNK4-SPAK-NCC Pathway by Glucose/Fructose In Vivo and Ex Vivo

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 901 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

  • Bahena-López, Jessica Paola, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Tlalpan, Mexico
  • Rojas, Lorena Leonor, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Tlalpan, DF, Mexico
  • Chavez-Canales, Maria, Instituto de Investigaciones Biomedicas, UNAM, Mexico City, Mexico
  • Lee, Ju Hye, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Tlalpan, DF, Mexico
  • Bazua-Valenti, Silvana, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Tlalpan, DF, Mexico
  • Bautista, Rocio, Instituto Nacional de Cardiologia Ignacio Chavez, Mexico City, Mexico
  • Vázquez, Norma Hilda, Instituto de Investigaciones Biomedicas, UNAM, Mexico City, Mexico
  • Castañeda-Bueno, Maria, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Tlalpan, DF, Mexico
  • Gamba, Gerardo, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Tlalpan, Mexico
Background

NCC is activated via the CaSR-WNK4-SPAK pathway. Glucose and other sugars act as positive allosteric modulators of the CaSR. In vitro data from our lab (ASN 2019-2020) showed that extracellular glucose or fructose increases activity of the WNK4-SPAK-NCC pathway via the CaSR. Since glucose reabsorption occurs proximally in the nephron, delivery to the distal convoluted tubule (DCT) is negligible. Fructose delivery depends largely on intake. Thus, sugars delivery to DCT could result in NCC activation via CaSR-WNK4-SPAK pathway.

Methods

We used wild-type mice treated with vehicle, oral fructose +/- calcilytic NPS2143, or a single dose of dapagliflozin 1mg/kg ip to induce transient glycosuria +/- NPS2143. Kidneys were extracted after 3 hours to assess activation of the WNK4-SPAK-NCC pathway by immunoblotting. To rule out an effect of dapagliflozin in the WNK4-SPAK-NCC by angiotensin II, we pre-treated mice with losartan. The response to a thiazide challenge in vehicle, fructose or dapagliflozin treated mice was assessed. Finally, we used an ex vivo Langerhans rat kidney preparation to evaluate the effect of different concentrations of glucose infusion in the renal artery.

Results

In WT mice, we observed increased activity of the WNK4-SPAK-NCC pathway in the kidney after exposure to 20% fructose or administration of dapagliflozin (p<0.01). These effects were abrogated by NPS2143 (p<0.01) and was not observed in WNK4-KO mice (p<0.001). Additionally, the effect of dapagliflozin was present in mice pre-treated with losartan (p<0.01). Natriuresis induced by a thiazide challenge was significantly higher in fructose or dapagliflozin, than in vehicle treated mice, suggesting activation of NCC. Finally, we observed increased NCC and SPAK phosphorylation by infusing glucose above proximal tubule reabsorption threshold levels to ex vivo rat kidney preparations (p<0.001); notably, this effect was prevented by NPS2143.

Conclusion

Glycosuria or fructosuria increases NCC, SPAK and WNK4 phosphorylation in a CaSR-dependent fashion. Our data thus suggest a calcimimetic-like behavior for sugars in the DCT. This effect may have implications for salt-retention mechanisms induced by disorders of glucose metabolism and increased dietary fructose intake.

Funding

  • NIDDK Support