Abstract: FR-PO307
Acid Retention Decreases Urine Citrate Excretion Through Reduced Kidney Clearance and Reduced Plasma Concentration of Citrate
Session Information
- CKD: Epidemiology and Risk Factors
November 08, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 2101 CKD (Non-Dialysis): Epidemiology, Risk Factors, and Prevention
Authors
- Goraya, Nimrit, Texas A&M HSC College of Medicine, Temple, Texas, United States
- Simoni, Jan, Texas Tech University Health Sciences Center, Lubbock, Texas, United States
- Mamun, Abdullah A., Baylor Scott & White Health, Dallas, Texas, United States
- Madias, Nicolaos E., Tufts University School of Medicine, Boston, Massachusetts, United States
- Wesson, Donald E., Baylor Scott and White Health and Wellness Center, Dallas, Texas, United States
Background
Decreased urine excretion of the pH-sensitive metabolite citrate is a potential biomarker of H+ retention in patients with CKD and reduced eGFR but no metabolic acidosis (Goraya.KI 95:1190, 2019). We explored contributions of reduced plasma citrate (Pcit) and/or reduced kidney citrate clearance (UV/Pcit) to decreasing urine citrate excretion associated with increasing H+ retention over time.
Methods
We measured H+ retention, 8-hour urine citrate excretion (UcitrateV), Pcit, and UV/Pcit in macroalbuminuric, non-diabetic CKD 2 patients with hypertension associated nephropathy without metabolic acidosis (plasma total CO2 >24 mM) at baseline and after treatment with 0.5 meq/kg bw/day NaHCO3 (HCO3, n=40), 0.5 meq/kg bw/day NaCl (NaCl, n=40), or usual care (UC, n=40) and assessed after 5 years.
Results
Baseline H+ retention, UcitrateV, Pcit, and UV/Pcit were not different among groups. The 5-year vs. respective baseline value in HCO3 patients was not different for H+ retention (16.1±12.9 vs 18.1±14.8 mmol, p=0.46) or UcitrateV (1.063±0.244 vs 1.032±0.259 mmol, p=0.69). However, the 5-year vs respective baseline value in NaCl patients was higher for H+ retention (23.2±14.0 vs 19.2±16.7 mmol, p<0.01) and lower for UcitrateV (0.910±0.233 vs 1.021±0.275 mmol, p<0.01). Similarly, 5-year vs baseline value in UC was higher for H+ retention (22.1±11.2 vs. 17.4±9.9 mmol, p<0.01) and lower for UcitrateV (0.899±0.217 vs 0.989±0.212 mmol, p<0.01). Five-year vs.baseline value for Pcit was not different for HCO3 (0.050±0.016 vs. 0.048±0.016 mM, p=0.46) and NaCl (0.051±0.023 vs. 0.054±0.025 mM, p=0.08) but was lower for UC (0.050±0.020 vs. 0.052±0.020 mM, p<0.02). Five-year vs. baseline value for UV/Pcit was not different for HCO3 (0.048±0.011 vs. 0.047±0.008 ml/min/1.73m2, p=0.94) but was lower for NaCl (0.043±0.016 vs. 0.047±0.018 ml/min/1.73m2, p<0.002) and UC (0.045±0.024 vs. 0.048±0.024 ml/min/1.73m2, p<0.004)
Conclusion
Both reduced UV/Pcit and reduced Pcit mediated decreased UcitrateV in CKD patients without metabolic acidosis whose H+ retention increased after 5 years without alkali therapy but both parameters were unchanged in those treated with alkali in whom H+ retention did not increase. Increasing H+ retention initiates kidney and extra-kidney mechanisms for citrate conservation.