Microbiota protect against frailty, loss of skeletal muscle, and maintain inflammatory tone during aging in mice

We showed that germ-free mice had increased frailty, lower muscle mass, and lower circulating inflammatory monocytes. Therefore, lower systemic inflammation coincided with worse frailty and muscle loss. Microbial colonization decreased frailty, restored muscle mass, and increased circulating inflammatory monocytes while lowering transcripts in inflammatory TNF and NF-kB pathways within muscle. Hence, microbiota can increase circulating inflammation but decrease muscle inflammation to protect against frailty.