Oral administration of Weissella cibaria Wikim0187 — a probiotic isolated from kimchi — at 1×10⁹ CFU daily for four months significantly increased gastrocnemius and quadriceps muscle mass, absolute grip strength, and mean muscle fiber cross-sectional area in 18-month-old male C57BL/6J mice. Mechanistically, the intervention suppressed the ubiquitin-proteasome degradation markers MuRF-1 and Atrogin-1 while upregulating the myogenic transcription factors MyoD and Myogenin. Western blot confirmed reduced Atrogin-1 protein alongside elevated phospho-Akt, signaling enhanced anabolic signaling and attenuated proteolysis. Gut microbiota composition shifted substantially, with enriched taxa correlating positively with improved muscle parameters.
This finding sits at a productive intersection of the gut-muscle axis and sarcopenia research — an area gaining momentum but still mechanistically undercharacterized. The dual action on protein degradation (MuRF-1/Atrogin-1 suppression) and synthesis (Akt phosphorylation, MyoD/Myogenin induction) is pharmacologically coherent and mirrors pathways targeted by experimental myostatin inhibitors and leucine supplementation. However, the limitations are significant: this is an all-male rodent study with no human validation, no dose-response curve, and no head-to-head comparison with established interventions like resistance training or leucine. The gut microbiota correlations are associative, not causal. For aging adults, the findings are biologically plausible but premature for clinical guidance. Confirmatory human trials are essential before Weissella cibaria earns a place in sarcopenia prevention protocols. Consider this incremental but directionally important.
