Elucidating the therapeutic mechanism of Orthosiphon aristatus in hyperuricemic nephropathy: An integrated microbiome-metabolomics approach

Abstract

Ethnopharmacological relevance: Hyperuricemic nephropathy (HN) remains challenging to treat due to the limitations, including variable efficacy and side effects, of conventional drugs. Orthosiphon aristatus (O. aristatus), used for over 2000 years in Dai medicine to treat kidney disorders by "clearing heat and promoting diuresis," shows strong potential for HN management. However, its mechanisms of action against HN remain unclear.

Aim of the study: This study aimed to elucidate the nephroprotective effects and underlying mechanisms of O. aristatus against HN using an integrated strategy focusing on the gut-kidney axis.

Methods: A rat model of HN was established by combined oral administration of potassium oxonate (750 mg/kg) and uric acid (300 mg/kg) daily for 7 weeks. Model rats were treated with a low- or high-dose aqueous extract of O. aristatus (3.125 or 6.25 g/kg/day), using allopurinol (5 mg/kg/day) as a positive control. Renal function was assessed by measuring serum levels of uric acid, creatinine, and urea nitrogen. Renal pathological injury and fibrosis were evaluated through histopathological examination (H&E and Masson's trichrome staining), immunohistochemistry (α-SMA, vimentin), and transmission electron microscopy. To elucidate the underlying mechanisms, an integrated multi-omics approach was employed: gut microbiota composition was profiled by metagenomic sequencing, and metabolic alterations in cecal content and kidney tissue were characterized using UPLC-MS-based metabolomics. Furthermore, the protein expression of key targets involved in intestinal barrier function (Occludin, Claudin-1) and the IDO1/AhR signaling pathway was validated by Western blot analysis.

Results: O. aristatus treatment significantly ameliorated renal dysfunction and pathological injury, as demonstrated by marked reductions in serum uric acid (sUA), creatinine (Scr), and blood urea nitrogen (BUN) levels (all p < 0.001), alongside attenuated tubular injury and fibrosis. Concurrently, it restored gut microbiota diversity (e.g., increased Shannon index, p < 0.05) and composition, characterized by an enrichment of beneficial Prevotella and a reduction in Bacteroides. Integrated metabolomics analysis further linked these effects to the rectification of tryptophan metabolism, manifested by decreased renal kynurenine levels (p < 0.01) and enhanced intestinal barrier integrity (e.g., elevated Occludin and Claudin-1, p < 0.05). Collectively, our results delineate that the renoprotective effect of O. aristatus is mediated through the suppression of the renal IDO1/kynurenine/AhR pro-fibrotic signaling axis, unveiling a novel gut microbiota-metabolite-kidney interaction mechanism.

Conclusion: This study elucidates that the renoprotective effect of O. aristatus against HN is mediated through modulation of the gut-kidney axis, by restoring microbial ecology, reprogramming host tryptophan metabolism, and subsequently inhibiting the IDO1/kynurenine/AhR pro-fibrotic pathway.

Keywords: Aryl hydrocarbon receptor; Gut microbiota; Gut-kidney axis; Hyperuricemic nephropathy; Metabolomics; Orthosiphon aristatus; Tryptophan metabolism.