Dietary oxalate induces monocyte mitochondrial dysfunction and crystalluria in healthy subjects: A role of spinach in kidney stone disease?

Abstract

Dietary oxalate contributes significantly to urinary oxalate excretion and is linked to calcium oxalate kidney stone formation. Oxalate is a common component found in kidney stones and in plants such as spinach. We have previously shown that patients with calcium oxalate kidney stone disease have decreased mitochondrial function and increased IL‐6 levels compared to healthy subjects. The purpose of this study was to investigate whether a dietary oxalate load has any effect on monocyte mitochondrial function and urinary oxalate levels in healthy subjects. Nine healthy subjects between the ages of 21 and 31 with an average BMI of 24.6 ±1.2 were included in the study. Participants consumed a low oxalate diet for 3 days prior to drinking a high dietary oxalate load (spinach smoothie). Blood and urine was collected from participants prior to consuming a high oxalate spinach load (pre‐smoothie) and 5 hours following smoothie consumption (post‐smoothie). Monocyte mitochondrial function was measured using Seahorse XF96 technology. Urinary oxalate levels (both crystalline and soluble) were determined using ion chromatography‐mass spectrometry. The high dietary oxalate load caused a significant decrease in monocyte mitochondrial function in healthy subjects. These responses were similar to levels previously found in patients with calcium oxalate kidney stone disease. In addition, both crystalline and soluble urinary oxalate levels were significantly increased in post‐smoothie samples compared to pre‐smoothie samples. These findings suggest that a high dietary oxalate could affect monocyte mitochondrial function in patients. Future studies will investigate potential mechanisms responsible for these findings.Support or Funding InformationThis work was supported by NIH K01DK106284 and the UAB Department of Urology.