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Abstract: FR-PO996

Urate Regulates Mitochondrial Function in a URAT1 Dependent Manner in Renal Epithelial Cells

Session Information

  • CKD: Pathobiology - I
    November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
    Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

  • 2203 CKD (Non-Dialysis): Mechanisms

Authors

  • Woodward, Owen M., University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Halperin Kuhns, Victoria L., University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Lane-Harris, Allison C., University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Zapf, Ava M., University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Bamberg, Krister, AstraZeneca Translational Sciences and Experimental Medicine, Early Cardiovascular, Renal and Metabolism (CVRM), Biopharmaceuticals R&D, Gothenburg, Sweden
Background

Alterations in cell metabolism in the proximal tubule are a recognized component in the initiation and progression of chronic kidney disease (CKD). Previously, we used whole kidney RNAseq to determine genes and pathways that were differential expressed in a genetic mouse model of hyperuricemia (Uox-iKO). The pathways most effected in the Uox-iKO males were related to metabolism and oxidative phosphorylation. The Uox-iKO male animals also showed significant increases in urinary lactate excretion after induction of Uox KO. Here, we focused on the role of renal urate handling in controlling lactate secretion and mitochondrial function in human renal epithelial cells. Lactate is a substrate of URAT1 (SLC22A12) moving in trans with the apical entry of urate from the renal tubule lumen. We hypothesized that increased extracellular urate will promote the secretion of lactate via URAT1 and alter cellular respiration and mitochondrial function.

Methods

Using cultured primary normal human cortical renal epithelial cells (NHCRE) we measured the effect of chronic extracellular urate on intracellular lactate and oxygen consumption rate using the Seahorse XFe96 analyzer.

Results

In NHCRE cells we found that chronic exposure to increased extracellular urate (500μM from 24hrs to 2 weeks) significantly lowered intracellular lactate in the presence of either high (4.5g/l) or reduced glucose (1g/l), and that additional extracellular lactate rescued intracellular levels. Further, the application of probenecid, a general anion transporter blocker with affinity for URAT1, or verinurad, a specific URAT1 inhibitor, abolished the effects of extracellular urate on lactate levels, though URAT1 inhibition alone had no effect. Next, we measured the oxygen consumption rate (OCR, normalized to cell number) in NHCRE cells using the Seahorse analyzer. We found chronic exposure to increased extracellular urate (500μM for 24 hours) significantly increased basal respiration and the maximum respiratory capacity. Both effects were abolished in the presence 0.5μM of verinurad.

Conclusion

We conclude that increased tubular urate alters intracellular lactate levels and mitochondrial function in a URAT1 dependent manner, providing mechanistic evidence that urate alters cell metabolism in the proximal tubule and may contribute to kidney disease progression.

Funding

  • NIDDK Support