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Abstract: TH-PO187

Association of Serum Bicarbonate Levels with Serum Fibroblast Growth Factor-23 Levels

Session Information

Category: Bone and Mineral Metabolism

  • 402 Bone and Mineral Metabolism: Clinical

Authors

  • Kendrick, Jessica B., University of Colorado School of Medicine, Aurora, Colorado, United States
  • You, Zhiying, UC Denver, Aurora, Colorado, United States
  • Gitomer, Berenice Y., Div. Renal Diseases and Hypertension,, Aurora, Colorado, United States
  • Chonchol, Michel, University of Colorado, Aurora, Colorado, United States
  • Blaine, Judith, University of Colorado Denver , Aurora, Colorado, United States
Background

The regulation of fibroblast growth factor-23 (FGF23) is not understood. In vitro studies have found that metabolic acidosis increases FGF23. However, small pilot studies have found that treatment of low bicarbonate levels with sodium bicarbonate increases FGF23 levels. We tested the hypothesis that lower serum bicarbonate levels are associated with higher levels of FGF23.

Methods

We included 822 patients from the HALT-PKD Study A (n=540; mean eGFR = 91±17 ml/min per 1.73 m2) and B (n=462; mean eGFR = 48±12 ml/min per 1.73 m2) with serum bicarbonate and FGF23 levels measured at baseline. Bicarbonate was examined as a continuous variable and in categories (≤ 24, 25-28 and >28 mEq/L, with 25-28 mEq/L as the reference group). We used linear regression models to examine the cross-sectional association between baseline serum bicarbonate and FGF23 levels.

Results

The mean (SD) age and estimated glomerular filtration rate (eGFR) was 43 ± 10 years and 70 ± 26 ml/min/1.73m2. The mean (SD) serum bicarbonate level was 26.7 ± 2.4 mEq/L and the median (IQR) serum FGF23 level was 53 (39-74) pg/mL. Participants with bicarbonate levels ≤ 24 mEq/L had lower baseline eGFR and higher systolic blood pressure. In unadjusted analysis, every 1 mEq/L increase in serum bicarbonate was associated with a decrease of 1.25 pg/mL in FGF23 levels (β -1.25, 95% CI -2.48 to -0.01). However, after adjustment for demographics, randomization group, baseline eGFR, smoking, cardiac history, body mass index, blood pressure, serum calcium and phosphorus, the association was no longer significant (p=0.20). A serum bicarbonate ≤ 24 mEq/L trended towards an increased risk of higher FGF23 in unadjusted analysis but it did not reach statistical significance (p=0.05).

Conclusion

Serum bicarbonate levels are not associated with FGF23 levels in patients with polycystic kidney disease. Further studies are needed to examine the relationship between metabolic acidosis and FGF23 in other causes of kidney disease.

Funding

  • Other NIH Support