Gut Microbiota‐Linked Benefits of Low‐Intensity Pulsed Ultrasound Rejuvenate the Ageing Muscle

BACKGROUND: Ageing is an inevitable biological process that contributes to increased prevalence of age-associated diseases, including sarcopenia, defined by progressive loss of muscle mass, functional decline and a heightened risk of injury. Developing effective interventions remains a critical clinical priority. This study employed a natural ageing mouse model to investigate whether noninvasive low-intensity pulsed ultrasound (LIPUS), a therapeutic ultrasound, delivered to the abdomen, could alleviate age-related muscle deterioration and whether its effects were linked to gut microbiota modulation. METHODS: C57BL/6 mice were maintained until 92 weeks of age, after which abdominal LIPUS stimulation was administered for 8 weeks. At 100 weeks, both forelimb and hind limb grip strength were assessed prior to euthanasia. Faecal samples from the distal colon were collected for microbiota profiling, and gastrocnemius muscles were harvested for downstream analyses. RESULTS: Naturally aged mice exhibited sarcopenia-like characteristics, including impaired muscle performance, reduced myofiber diameter and decreased muscle weight (n = 6, p < 0.01, p < 0.001). Age-related renal impairment promoted the accumulation of advanced glycation end products (AGEs) in skeletal muscle, triggering pro-inflammatory signalling cascades characterized by elevated COX-2, phosphorylated NF-κB, NLRP3, IL-1β and Caspase-1 (n = 5-6, p < 0.01). LIPUS treatment significantly improved muscle strength (forelimb and hind limb grip strength, n = 6, p < 0.001, p < 0.01) and muscle mass (n = 6, p < 0.01), while suppressing inflammatory mediators (n = 5-6, p < 0.05). Gut microbiota analysis showed that LIPUS increased microbial diversity (n = 5-6, p < 0.05) and altered taxonomic composition, enriching anti-inflammatory taxa such as Lactobacillus, Bifidobacterium, Faecalibaculum and Coriobacteriaceae_UCG_002 (n = 6, p < 0.05). Correlation analysis indicated that these LIPUS-enriched taxa were positively associated with enhanced muscle performance. These data suggest that LIPUS mitigates sarcopenia in naturally aged mice by restoring muscle integrity and attenuating inflammation, possibly via gut microbiota regulation. CONCLUSIONS: This study shows that natural ageing in mice induces sarcopenia-like features with inflammatory activation and gut microbiota alterations. Abdominal LIPUS treatment alleviated muscle loss, reduced inflammation and promoted beneficial microbes, rejuvenating the ageing muscle. These findings highlight LIPUS as a safe, noninvasive and potentially translatable strategy for sarcopenia, warranting further investigation of its microbiota-muscle interactions.