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Abstract: SA-PO076

Renal Quinolinate Accumulation May Reduce Cellular NAD+

Session Information

  • AKI: Mechanisms - III
    November 05, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
    Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Clark, Amanda J., The University of Texas Southwestern Medical Center, Dallas, Texas, United States
  • Saade, Marie Christelle, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
  • Mendoza Flores, Brenda, The University of Texas Southwestern Medical Center, Dallas, Texas, United States
  • Parikh, Samir M., The University of Texas Southwestern Medical Center, Dallas, Texas, United States
Background

Tubule energy metabolism is required for renal health, and its impairment is a feature of acute kidney injury (AKI). We previously reported that the biosynthesis of NAD+, an essential cofactor for oxidative energy metabolism, becomes suppressed during experimental and clinical AKI. A critical enzyme in this biosynthetic pathway is quinolinate phosphoribosyltransferase (QPRT), whose suppression leads to an accumulation of quinolinate (Quin) in kidneys during AKI along with a reduction in renal NAD+ despite the existence of non-QPRT dependent pathways to generate NAD+. Therefore, we hypothesized that accumulation of quin may also contribute to NAD+ reduction in AKI.

Methods

Intracellular NAD+ was assessed using a recently developed NAD+ biosensor. The effect of Quin on glycolytic flux was measured using a Seahorse XX96 flux analyzer. Intracellular lactate was measured using a commercial assay. Studies were conducted in HK2, human proximal tubule cells.

Results

Quin addition (1uM) for 12 hours reduced cytoplasmic NAD+ (Fig1 B-C, p < 0.0001). Consistent with a reduced cellular NAD+, quin-exposed cells exhibited increased glycolysis (Fig1 E-F p < 0.0001) and increased intracellular lactate.

Conclusion

These data suggest that QPRT suppression during AKI may have distinct contributions to NAD+ reduction, both via NAD+ biosynthesis attenuation and through quin accumulation. Cellular NAD+ reduction led to expected effects on fuel utilization with increased glycolytic acidification. There is no known mechanism where quin may exact these metabolic changes, though many studies have described quin as a non-inert metabolite capable of receptor activation and potential allosteric modulation of enzymes. Underatnding NAD+ homeostasis, its role in quin accumuation, and the activity of quin in the kidney may be critical to understanding AKI physiology, and developing novel therapies.

A) Hypothesis. B-C) Quinolinate reduces cytoplasmic NAD+. D) Seahorse illustration. E-F) Quinoliniate increases glycolysis.

Funding

  • NIDDK Support