Abstract: SA-PO647

Effect of the Microbiota-Derived Uremic Toxin Indoxyl Sulfate on FMO Expression and TMAO Formation: A Pilot Study

Session Information

Category: Pharmacokinetics, Pharmacodynamics, and Pharmacogenetics

  • 1601 Pharmacokinetics, Pharmacodynamics, Pharmacogenomics

Authors

  • Prokopienko, Alexander J., University of Pittsburgh, Pittsburgh, Pennsylvania, United States
  • Joshi, Anand, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
  • Venkataramanan, Raman, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
  • Nolin, Thomas D., University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Background

Cardiovascular disease (CVD) is the leading cause of death in kidney disease. Microbiota-derived uremic toxins likely contribute to CVD progression and may be modifiable risk factors. The microbiota-derived uremic toxins indoxyl sulfate and trimethylamine-N-oxide (TMAO) are associated with poor CVD outcomes. Indoxyl sulfate activates the aryl hydrocarbon receptor (AhR) transcription factor, which partially regulates flavin-containing monooxygenase (FMO) expression. FMOs are an important class of hepatic enzymes that oxidize trimethylamine to TMAO. We hypothesize that indoxyl sulfate induces hepatic FMO expression and activity, thereby increasing TMAO formation. The aim of this pilot study was to assess the effect of indoxyl sulfate on the expression and activity of FMO.

Methods

Primary cultures of human hepatocytes (n=1 donor) were pre-treated with 0.1% dimethylsulfoxide (vehicle control), rifampin (induction control), PCB-77 (AhR agonist) and indoxyl sulfate (1, 25, 100 and 250 μM) for 72 hours. All treatments were run in duplicate. Hepatocytes were then incubated for 3 hours with trimethylamine and formation rate of TMAO was used as an indicator of hepatic FMO activity. TMAO was measured via LC-MS. Gene expression was determined by RT-qPCR using specific Taqman® probes and master mix. All data was analyzed using one-way ANOVA.

Results

FMO3 mRNA expression increased by 2.4-fold, 2.1-fold, 2.9-fold and 5.1-fold compared to vehicle control with indoxyl sulfate 1, 25, 100 and 250 μM, respectively (p<0.0055). CYP1A2 mRNA expression increased by 2.7-fold, 16-fold, 96-fold and 254-fold compared to vehicle control with indoxyl sulfate 1, 25, 100 and 250 μM, respectively (p<0.0003). AhR mRNA expression was not significantly changed compared to control. Indoxyl sulfate 1, 25, 100 and 250 μM increased TMAO formation by 1.2-fold, 1.6-fold, 1-fold, and 3-fold compared to vehicle control, respectively (p<0.0049).

Conclusion

These results suggest that indoxyl sulfate induces FMO3 mRNA expression and activity, leading to increased FMO-mediated TMAO formation. This novel metabolic interaction may contribute to dramatically increased systemic exposure of TMAO and CVD progression in kidney disease patients.

Funding

  • NIDDK Support