[Involvement of gut bacteria in appetite control]

Animals perceive alternating feelings of hunger and satiety, which constitute their daily rhythms of appetite and drive their feeding behavior. In humans, these rhythms include the onset of satiety about 20 min after meal ingestion and a duration of satiety of about 5 h followed by hunger, triggering food seeking and intake. Molecular mechanisms underlying such appetite cycles involve secretion of intestinal satiety hormones and corresponding activation of the brain anorexigenic and feeding reward pathways. Recent studies showed that gut bacteria can interfere with the host molecular mechanisms regulating appetite at both the intestinal and central sites. In particular, the stable growth dynamics of gut bacteria, determined by host-independent factors such as the time necessary for bacterial DNA replication and quorum sensing, coincide with the host appetite cycles. Integrating the bacterial biology into the host regulation of energy metabolism therefore appears as a new promising strategy to understand the control of appetite in normal and pathological conditions.