Objectives: Kidney stone disease (KSD), particularly calcium oxalate (CaOx) type, remains a global health problem. Many efforts have been made to prevent KSD, including the use of some dietary supplements. However, mechanisms underlying their anti-KSD properties remain poorly understood. Herein, we addressed the modulatory effects of five well-known dietary supplements on CaOx crystals.
Methods: Caffeine, epigallocatechin-3-gallate (EGCG), N-acetylcysteine (NAC), resveratrol and trigonelline (at 1, 10 and 100 µM, which are within their physiologic range in the urine) were subjected to CaOx crystallization, growth and aggregation assays. Their CaOx crystal-modulatory effects were then compared.
Results: Caffeine inhibited crystal formation, EGCG inhibited crystal formation and growth, NAC inhibited crystal aggregation, resveratrol inhibited crystal growth, and trigonelline inhibited crystal growth and aggregation. However, resveratrol promoted crystal aggregation and thus served as a dual modulator (acting as inhibitor and promoter at different steps of stone formation). Almost all of these modulatory effects were concentration-dependent. Comparing the CaOx-inhibitory activities of these compounds revealed that EGCG was the most potent inhibitor against CaOx crystal formation, whereas resveratrol was the most potent inhibitor against CaOx crystal growth. NAC was the only inhibitor against CaOx crystal aggregation.
Conclusions: These data have shown the direct inhibitory effects of various dietary supplements against CaOx crystal formation, growth and aggregation, and therefore support their roles for KSD prevention.
