Bacterial Quorum Sensing Peptides and their muscle talk

Quorum sensing molecules (QSM) are characteristic bacterial products, constitutively produced by living bacteria and exhibiting an increased and/or altered production in “stress” conditions. Mainly three groups can be distinguished: the N-acyl-homoserine-lactones (AHL, mainly produced by Gram-negative bacteria), the quorum sensing peptides (QSP, mainly produced by Gram-positive bacteria) and the furanosyl borates (AI-2 [autoinducer-2], produced by Gram-positive as well as Gram-negative bacteria). Quorum sensing peptides have long been considered as intra-bacterial communication molecules only [1, 2]. However, nowadays, it is generally accepted that this communication is not limited to the bacteria themselves, but also play a role in for example colorectal cancer and the central nervous system. We recently identified iAM373, a QSP produced by E. faecalis, to be an inducer of sarcopenia [3, 4]. iAM373 was shown to 1) decrease metabolic activity in vitro, 2) induce a sarcopenic phenotype in C. elegans in vivo, 3) be present in murine and human plasma and 4) correlate with muscle mass and gait speed in older people [4]. These findings offer the first demonstration that quorum sensing molecules are involved in muscle wasting diseases such as sarcopenia, opening new diagnostic and therapeutic dimensions.