BACKGROUND: Trimethylamine N-oxide (TMAO), a gut microbiota metabolite, is a risk factor for chronic kidney disease (CKD) progression. Suyin Detoxification Granule (SDG) is a traditional Chinese medicine preparation that has been proven to significantly reduce renal function damage and serum TMAO levels in patients with CKD. However, its specific mechanism remains unclear.
PURPOSE: This study investigated the role of TMAO-induced ferroptosis in CKD, and further explored the mechanism of SDG in improving TMAO-induced kidney injury.
METHODS: A TMAO renal tubular epithelial cell injury model was constructed in vitro. After using freeze-dried powder of Suyin Detoxification Prescription (SDP), proteomic analysis, Western blotting, ferroptosis phenotype-related detection, and ELISA were performed to explore its mechanism. In vivo, a adenine-induced CKD model was established, with or without a high-choline diet to observe the impact of TMAO on CKD, and SDG or 3,3-Dimethyl-1-butanol (DMB, a TMAO inhibitor) was used for intervention. The composition of gut microbiota was analyzed using 16SrRNA sequencing, and the effect of SDG on gut-derived TMAO-induced kidney injury under the background of CKD was evaluated by pathological staining, immunoblotting, immunohistochemistry, and fluorescence staining.
RESULTS: In vitro, TMAO could induce ferroptosis and secrete profibrotic factors in NRK-52E cells. SDP could inhibit TMAO-induced ferroptosis and reduce the secretion of profibrotic factors. The amelioration of ferroptosis by SDP was also verified in RSL3-induced cells. In vivo, our results demonstrated that gut-derived TMAO could promote CKD progression by inducing tubular ferroptosis, profibrotic factors expression and renal fibrosis. In addition, we illustrated that SDG might reduce circulating TMAO levels by down-regulating the gut microbiota related to TMAO (including Muribaculaceae, Bacteroides and Ruminococcaceae_UCG-010). Furthermore, SDG could prevent CKD progression by reducing TMAO-induced renal damage.
CONCLUSION: SDG reduced circulating TMAO levels by regulating gut microbiota and inhibited TMAO-induced renal tubular ferroptosis, profibrotic factors secretion, and renal fibrosis to prevent CKD progression.
