mTOR–Gut Microbiome Interaction in Aging: <i>Fusobacterium nucleatum</i> , Resistance Training and Multi‐nutrient Supplementation Effects in Aged Male Rats

We investigated the mTOR pathway in relation to gut microbiome composition and Fusobacterium nucleatum (Fn) in aged male Wistar rats undergoing resistance exercise and multi-nutrient supplementation. Thirty-five male rats (OC, YC, OS, OR, ORS; n = 7/group) underwent 8-week moderate-intensity resistance training and/or supplementation (Lactobacillus plantarum, Bifidobacterium bifidum, vitamin D, leucine). Muscle samples were analyzed by RT-PCR and Western blot; fecal DNA by 16S rRNA sequencing (p < 0.05). Finding revealed significant increases in the mTOR/IGF-1/S6K1 protein content and gene expression in the ORS group compared to OS and OR groups (mTORC1: ORS vs. OR, p = 0.011; ORS vs. OS, p < 0.001; IGF-1: ORS vs. OR, p = 0.008; ORS vs. OS, p = 0.001), which showed only mild increases. The F/B ratio decreased in all intervention groups, with ORS reaching levels comparable to YC (p = 0.207). Resistance training alone did not significantly affect Fn, but the ORS group had the lowest Fn levels, comparable to YC (p = 0.069) and significantly lower than OR and OS (p = 0.001). The study provides novel evidence that combined resistance training and multi-nutrient supplementation (L. plantarum, B. bifidum, vitamin D, leucine) upregulates mTOR/IGF-1/S6K1 signaling and reduces Fusobacterium nucleatum in aged male rats. The ORS group outperformed either intervention alone; Fn correlates strongly with S6K1 (r = -0.85) and IGF-1 (r = -0.81), supporting the gut-muscle axis as a therapeutic target for sarcopenia.