Scientific concept
Gut–Kidney Axis
The gut–kidney axis is the bidirectional relationship between the intestinal environment and kidney health.
What is the gut–kidney axis?
In chronic kidney disease (CKD) research, scientists study how gut-microbiota composition, intestinal-barrier function, microbial metabolites, inflammation, uremic toxins, and kidney function may affect one another.
How does the gut–kidney axis work?
In CKD, an altered intestinal environment may be associated with microbial dysbiosis and reduced intestinal-barrier integrity. Some gut microbes metabolize dietary substrates into precursors of compounds such as indoxyl sulfate (IS) and p-cresyl sulfate (PCS). When kidney clearance is impaired, these and other uremic toxins can accumulate. Uremia and its associated metabolic environment may, in turn, further affect the intestinal environment, creating a potentially self-reinforcing cycle.
Kidney dysfunction and uremic milieu → changes in the intestinal environment and microbiota → dysbiosis, barrier dysfunction, and altered microbial metabolites → gut-derived uremic toxins and inflammatory signalling → potential contribution to kidney and systemic complications → back to the start.
Are probiotics and prebiotics proven CKD therapies?
No general conclusion can be made for all probiotics or prebiotics. Diet, prebiotics, probiotics, synbiotics, oral adsorbents, and other microbiome-directed approaches are active areas of CKD research. Some clinical studies and evidence syntheses report changes in selected uremic-toxin measures, but studies vary in their populations, interventions, methods, and outcomes.
The gut-kidney axis is a scientific framework, not a demonstrated therapy. Larger, well-designed trials are still needed to establish clinical benefits such as slower CKD progression, reduced need for dialysis, cardiovascular benefit, or improved survival. Human CKD literature and preclinical models cannot be treated as clinical evidence in dogs or cats.
Why is this relevant to companion-animal renal health?
The gut–kidney axis provides a scientific rationale for investigating microbiome-based approaches in companion-animal renal health. It is the rationale behind Tailored Bio's BP121 programme. Ligilactobacillus salivarius BP121 (formerly Lactobacillus salivarius BP121) has been investigated in preclinical research involving a rat acute-kidney-injury model and Caco-2 cells; that work does not establish clinical efficacy in people, dogs, or cats.
Sources
- Alobaidi H. The gut-kidney axis in chronic kidney disease: mechanisms, microbial metabolites, and microbiome-targeted therapeutics. Frontiers in Medicine. 2025. PubMed
- Matsumoto T, et al. Kidney-Gut Axis in Chronic Kidney Disease: Therapeutic Perspectives from Microbiota Modulation and Nutrition. 2025. PubMed
- Poesen R, et al. Altered microbiome in chronic kidney disease: systemic effects of gut-derived uremic toxins. Clinical Science. 2018. PubMed
- Impact of Gut Microbiome Modulation on Uremic Toxin Reduction in Chronic Kidney Disease: A Systematic Review and Network Meta-Analysis. Nutrients. 2025. PubMed