Amiloride and hydrochlorothiazide affect metabolites and ammonium excretion in CKD patients

Recent clinical trials have shown that distal nephron-acting diuretics are effective in managing fluid retention and salt-sensitive hypertension in people with chronic kidney disease (CKD). However, their use may be complicated by diuretic-induced hyponatremia. This study aimed to characterize the metabolomic effects of distal diuretics in people with CKD, including those who develop hyponatremia. Therefore, we analyzed plasma and 24-h urine samples from a previously completed randomized controlled trial including individuals with CKD (mean estimated glomerular filtration rate = 39 ± 13 mL/min/1.73 m) treated with amiloride/hydrochlorothiazide (5 mg/50 mg daily) for 2 wk. The study included 26 participants in whom we analyzed a set of targeted metabolites. Global untargeted metabolomics was performed in a subcohort of 12 participants, including four patients who developed hyponatremia (plasma sodium <136 mmol/L) and eight diuretic-treated controls with stable sodium levels. Distal diuretic therapy decreased plasma glutamine levels and the excretion of several tricarboxylic acid cycle-related metabolites. Furthermore, distal diuretics significantly increased urinary ammonium excretion in the absence of hypokalemia or metabolic acidosis. Untargeted metabolomic analysis revealed 988 unique metabolites in the urine. Among those with hyponatremia, we observed a metabolomic signature of oxidative stress, likely due to altered glutamine and carnitine metabolism. These findings suggest that distal diuretics not only act locally in the distal convoluted tubule but also influence proximal tubular metabolism. In conclusion, our results highlight that distal diuretics induce significant metabolic changes in CKD, with urine metabolomics offering valuable insights into the physiological pathways and mechanisms underlying both therapeutic effects and adverse responses. We assessed the urinary metabolomic fingerprint of treatment with amiloride and hydrochlorothiazide in individuals with CKD stages G3-G4. We identified enhanced ammoniagenesis in the absence of hypokalemia or metabolic acidosis. Patients who developed diuretic-induced hyponatremia exhibited a urinary metabolomic signature of oxidative stress. Our study highlights the interplay between "electrolyte and fluid balance" and "metabolic adaptations" in individuals with CKD who are treated with distal diuretics.