Nutritional Modulation of the Gut–Kidney Axis

Background: Chronic kidney disease (CKD) represents a state of persistent, sterile low-grade inflammation in which sustained innate immune activation accelerates renal decline and cardiovascular complications. Diet-induced gut dysbiosis and intestinal barrier dysfunction lower mucosal immune tolerance, promote metabolic endotoxemia, and position the gut as an upstream modulator of systemic inflammatory signaling along the gut–kidney axis. Scope: Most studies address microbiota-derived metabolites, food-derived bioactive peptides, or omega-3 fatty acids separately. This review integrates evidence across these domains and examines their convergent actions on epithelial barrier integrity, immune polarization, oxidative-inflammatory stress, and inflammasome-dependent pathways relevant to CKD progression. Key mechanisms: CKD-associated dysbiosis is characterized by reduced short-chain fatty acid (SCFA) production and increased generation and accumulation of uremic toxins and co-metabolites, including indoxyl sulfate, p-cresyl sulfate, trimethylamine N-oxide, and altered bile acids. Reduced SCFA availability weakens tight junction-dependent barrier function and regulatory immune programs, favoring Th17-skewed inflammation and endotoxin translocation. Bioactive peptides modulate inflammatory mediator networks and barrier-related pathways through effects on NF-κB/MAPK signaling and redox balance, while omega-3 fatty acids and specialized pro-resolving mediators support resolution-phase immune responses. Across these modalities, shared control points include barrier integrity, metabolic endotoxemia, oxidative stress, and NLRP3 inflammasome activation. Conclusions: Although evidence remains heterogeneous and largely preclinical, combined nutritional modulation targeting these convergent pathways may offer greater immunomodulatory benefit than isolated interventions. Future multi-omics-guided, factorial trials are required to define responder phenotypes and translate precision immunonutrition strategies into clinical CKD care.