Effect of oral sodium bicarbonate supplementation on urine TFG-β in normal serum bicarbonate CKD, a randomized controlled trial

Abstract

The consequences of chronic subclinical metabolic acidosis, characterized by an increase in single nephron ammonium generation, contribute to the progression of chronic kidney disease (CKD). Therefore, sodium bicarbonate (NaHCO₃) supplementation in CKD with normal serum bicarbonate patients may reduce kidney fibrosis and slow CKD progression. This study aimed to evaluate the impact of high-dose NaHCO₃ supplementation on urinary transforming growth factor-beta (TGF-β), a biomarker of kidney fibrosis, in non-diabetic CKD patients with normal serum bicarbonate levels. We conducted a single-center, randomized, open-label controlled trial in patients with non-diabetic CKD stage 3–4 and normal serum bicarbonate (22–26 mEq/L). Participants were randomized to receive high-dose NaHCO₃ (0.8 mEq/kg/day) or standard care for 12 weeks. The primary outcome was the change in urinary TGF-β-to-creatinine ratio from baseline. Secondary outcomes included changes in urinary albumin-to-creatinine ratio (UACR), urine pH, serum electrolytes, blood pressure, and adverse events. A total of 64 participants were randomized (NaHCO₃ group: n = 32; control group: n = 32). There was no significant difference in the percentage change of urinary TGF-β (NaHCO₃: −1.86% vs. control: 5.75%; p = 0.477). However, the NaHCO₃ group demonstrated a significant increase in urine pH mean difference (0.56; 95% CI: 0.3,0.82 vs. 0,95% CI −0.24,0.24; p = 0.002) compared to the control group. Similarly, no significant differences were observed in UACR, serum electrolytes, blood pressure, or body weight between groups. No serious adverse events were reported. High-dose NaHCO₃ supplementation in non-diabetic CKD patients with normal serum bicarbonate levels did not significantly reduce urinary TGF-β over 12 weeks but effectively increased urine pH without adverse effects. These findings suggest that NaHCO₃ is safe; however, its role in modulating profibrotic biomarkers in CKD requires further investigation. Longer-term studies and alternative alkali therapies should be explored to determine the optimal strategies for preserving kidney function in this population. Clinical trial registration: TCTR20240817007 (17/08/2024).