Abstract: FR-PO320

Decreased Urinary Citrate Excretion Associates with Disease Severity in Autosomal Dominant Polycystic Kidney Disease

Session Information

Category: Genetic Diseases of the Kidney

  • 801 Cystic Kidney Diseases

Authors

  • Chapman, Arlene B., University of Chicago, Chicago, Illinois, United States
  • Harris, Peter C., Mayo Clinic , Rochester, Minnesota, United States
  • Bae, Kyongtae Ty, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
  • Landsittel, Doug, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
  • Reddy, Bharathi V., University of Chicago, Chicago, Illinois, United States
  • Lanktree, Matthew, None, Dundas, Ontario, Canada
  • Shen, Chengli, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
  • Torres, Vicente E., Mayo Clinic , Rochester, Minnesota, United States
  • Mrug, Michal, University of Alabama at Birmingham , Birmingham, Alabama, United States
  • Rahbari-Oskoui, Frederic F., Emory University School of Medicine, Atlanta, Georgia, United States
  • Yu, Alan S.L., University of Kansas Medical Center, Kansas City, Kansas, United States
  • Bennett, William M., Legacy Good Samaritan Medical Center, Portland, Oregon, United States
Background

Autosomal dominant polycystic kidney disease (PKD) is characterized by increased cyst burden measured by total kidney volume (TKV) and loss of kidney function. Urinary citrate excretion (UCE), known to be decreased in PKD associates with complications of disease including nephrolithiasis and urinary acidification defects. In the observational longitudinal Consortium for Radiologic Studies in Polycystic Kidney Disease (CRISP), 24 hour UCE was measured annually during the first three years of study. We postulate that decreased UCE is an independent marker of disease severity in PKD and associates with genotype, increased TKV, decreased eGFR and decreases over time.

Methods

224 of 241 participating CRISP subjects with baseline creatinine clearance >70 ml/min had 24 hr UCE as well as DNA, TKV and corrected iothalamate clearance (CIC) measurements completed in a Clinical Research Center setting.

Results

UCE correlated inversely with TKV (r=-0.26, P<0.001) and directly with CIC (r=0.16, P<0.02). Irazabal Class 1A subjects (n=14) had greater UCE (653+257 mg/day) than Class 1C (n=68, 449+241 mg/day, P<0.03), 1D (n=54, 452+295 mg/day, P<0.02) or 1E (n=35, 393+198 mg/day P<0.008). UCE was significantly lower in PKD1 vs. PKD2 patients (276 +269 vs.682+ 523 mg/day, P<0.01) No differences (P=NS) were seen in UCE between PKD1 truncating and non-truncating mutations (275+211 vs. 278+289 mg/day). UCE decreased 19.1 mg/day/year over 3 years (P<0.03), and significantly declined in PKD1 patients only. A forward linear regression selection method with an entry criteria of p=0.1 demonstrated that PKD1 genotype, urine volume, TKV and age, associated negatively with baseline UCE, while increasing sodium excretion, CIC and male gender associated with UCE. When baseline UCE was combined with TKV, area under the receiver operator characteristic curve for predicting CKD stage 3 in 8 years was 0.83.

Conclusion

TKV and CIC associate with decreased UCE early in PKD. Reductions in UCE in PKD1 patients showed no difference between truncating and non-truncating mutations. Decline in UCE occurred over three years and UCE may be a biomarker that associates with disease severity and progression in PKD.

Funding

  • NIDDK Support