High-intensity interval training and glycine interventions ameliorate intestinal homeostasis via modulation of gut microbiota and metabolism in aged mice

High-intensity interval training (HIIT) and glycine (Gly) have received much attention for demonstrating resistance to age-related effects, and the combination of exercise and nutritional strategies is thought to produce more favorable outcomes for the organism. However, it is unclear whether HIIT and/or glycine supplementation improves intestinal homeostasis in the aged. The study aimed to investigate the effects and mechanisms of HIIT and Gly interventions on intestinal homeostasis in aged mice. The results showed that HIIT and Gly interventions increased small intestinal villus length and cuprocyte density, improved intestinal aging markers, decreased pro-inflammatory factor expression, and improved age-related intestinal barrier integrity. The HIIT combined with Gly intervention was more beneficial in slowing down intestinal aging than a single intervention. In addition, HIIT and Gly interventions remodeled the gut microbiota structure, with HIIT intervention increased <em>Alistipes</em> and <em>Akkermansia</em>, Gly intervention increased <em>Lachnospiraceae</em>, <em>Desulfovibrio</em>, and HIIT combined with Gly intervention increasing <em>Dubosiella</em>, Faecalibacterium, <em>Oscillospiraceae_g_uncultured</em>, <em>Blautia</em>, <em>Staphylococcus</em>. Meanwhile, HIIT and Gly interventions to improve body metabolites, including arachidonic acid, indoleacetic acid, methionine, and L-serine, have been associated with the modulation of lipid peroxidation and the expression of ferroptosis resistance. Finally, we observed correlations between gut microbiota, metabolites, inflammation, intestinal barrier integrity, lipid peroxidation, and ferroptosis-related phenotypes in each group. In conclusion, HIIT and Gly improve intestinal homeostasis in aged mice by remodeling gut microbiota and metabolites.