Exercise intensity-mediated regulation of gut epithelial cells and immune function in gut microbiota dysbiosis

The gut epithelium and resident microbiota critically regulate intestinal barrier integrity, immune homeostasis, and systemic health. Emerging evidence from human studies and clinical trials indicates that exercise intensity modulates these components differentially. This narrative review synthesizes human and clinical trial data on exercise intensity effects on gut epithelial function, immune responses, and microbiota dynamics. Moderate-intensity continuous training (MICT; 30–60 min at 50–70% VO₂ max) enhances tight junction proteins (e.g., ZO-1, occludin; ↑15–20% in RCTs), reduces oxidative stress, and shifts cytokines toward anti-inflammatory profiles (IL-10 ↑, TNF-α ↓), improving barrier integrity and microbial diversity (alpha-diversity ↑10–20% over 8–12 weeks; e.g., enrichment of Lactobacillus, Bifidobacterium, Faecalibacterium prausnitzii, Roseburia hominis). Clinical trials in metabolic syndrome and mild IBD confirm these benefits. In contrast, high-intensity interval training (HIIT; >70% VO₂ max for > 90 min) transiently elevates permeability (zonulin/LPS ↑ in 20–30% of untrained participants), dysbiosis (SCFA-producers ↓, Escherichia coli/Fusobacterium ↑), and inflammation (CRP/IL-6 ↑), particularly under confounders like dehydration or poor diet. HIIT improves insulin sensitivity but risks microbial imbalance without recovery. A bidirectional gut-exercise axis emerges, with MICT linked to IBS symptom relief and reduced colitis severity in trials; probiotics/prebiotics mitigate HIIT risks. Gaps include cellular mechanisms, inter-individual variability (genetics, diet, hydration), and long-term impacts. Multi-omics trials are needed for personalized exercise prescriptions in disease states.