Abstract
BackgroundAcidosis-induced kidney injury is mediated by the intrarenal renin-angiotensin system, for which urinary renin is a potential marker. Therefore, we hypothesized that sodium bicarbonate supplementation reduces urinary renin excretion in patients with chronic kidney disease (CKD) and metabolic acidosis.MethodsPatients with CKD stage G4 and plasma bicarbonate 15–24 mmol/l were randomized to receive sodium bicarbonate (3 × 1000 mg/day, ~ 0.5 mEq/kg), sodium chloride (2 × 1,00 mg/day), or no treatment for 4 weeks (n = 15/arm). The effects on urinary renin excretion (primary outcome), other plasma and urine parameters of the renin-angiotensin system, endothelin-1, and proteinuria were analyzed.ResultsForty-five patients were included (62 ± 15 years, eGFR 21 ± 5 ml/min/1.73m2, plasma bicarbonate 21.7 ± 3.3 mmol/l). Sodium bicarbonate supplementation increased plasma bicarbonate (20.8 to 23.8 mmol/l) and reduced urinary ammonium excretion (15 to 8 mmol/day, both P < 0.05). Furthermore, a trend towards lower plasma aldosterone (291 to 204 ng/L, P = 0.07) and potassium (5.1 to 4.8 mmol/l, P = 0.06) was observed in patients receiving sodium bicarbonate. Sodium bicarbonate did not significantly change the urinary excretion of renin, angiotensinogen, aldosterone, endothelin-1, albumin, or α1-microglobulin. Sodium chloride supplementation reduced plasma renin (166 to 122 ng/L), and increased the urinary excretions of angiotensinogen, albumin, and α1-microglobulin (all P < 0.05).ConclusionsDespite correction of acidosis and reduction in urinary ammonium excretion, sodium bicarbonate supplementation did not improve urinary markers of the renin-angiotensin system, endothelin-1, or proteinuria. Possible explanations include bicarbonate dose, short treatment time, or the inability of urinary renin to reflect intrarenal renin-angiotensin system activity.Graphic abstract
Highlights
Metabolic acidosis is a common complication in patients with chronic kidney disease (CKD)
After 4 weeks, there was a trend towards a reduction in plasma potassium with sodium bicarbonate (P = 0.06 for difference baseline versus 4 weeks), which was not observed with sodium chloride and without treatment. In this open-label, three-arm randomized controlled trial (RCT) we investigated whether sodium bicarbonate supplementation in patients with CKD and metabolic acidosis lowers urinary renin, as a potential measure of the intrarenal renin-angiotensin systems (RAS)
Sodium bicarbonate had no significant effect on the urinary excretion of angiotensinogen, aldosterone, endothelin-1, albumin, or α1-microglobulin
Summary
Metabolic acidosis is a common complication in patients with chronic kidney disease (CKD). Current understanding of how acidosis contributes to kidney injury suggests that acid retention triggers an adaptive response to increase ammoniagenesis [7]. This process is orchestrated by activation of the circulating and intrarenal renin-angiotensin systems (RAS) and endothelin-1. We hypothesized that sodium bicarbonate supplementation reduces urinary renin excretion in patients with chronic kidney disease (CKD) and metabolic acidosis. Sodium chloride supplementation reduced plasma renin (166 to 122 ng/L), and increased the urinary excretions of angiotensinogen, albumin, and α1-microglobulin (all P < 0.05). Conclusions Despite correction of acidosis and reduction in urinary ammonium excretion, sodium bicarbonate supplementation did not improve urinary markers of the renin-angiotensin system, endothelin-1, or proteinuria. Possible explanations include bicarbonate dose, short treatment time, or the inability of urinary renin to reflect intrarenal renin-angiotensin system activity
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