Peripheral chemoreceptor, a new player in metabolic sensing during physical exertion: a hypothetical scenario

The cardiorespiratory and metabolic response to exercise has been associated with meeting the organism's metabolic demands during physical exertion. Of note, an incremental exercise is characterized by 1) cardiodynamic phase related to cardiac output enhancement mainly determined by a positive chronotropic response, 2) ventilatory threshold one, associated with a significant contribution of cardiovascular and pulmonary ventilation, and 3) ventilatory threshold two, correlated with a tremendous increase in breathing and metabolic responses to exercise. Notably, it has been shown that the ventilatory response to exercise increases concomitantly with the release and accumulation of metabolites (i.e., lactate released from skeletal muscle). The principal peripheral chemoreceptors are the carotid bodies (CBs), allocated into the carotid bifurcation and demonstrated to respond to several stimuli, triggering autonomic and ventilatory responses. Indeed, in past and recent years, it has been shown that CB could respond to lactate in in vitro and in vivo preparations, eliciting an increase in CB activity and ventilation. However, not all evidence indicates that peripheral chemoreceptors respond to lactate. Thus, considering that CB chemoreceptors' role in lactate-dependent breathing response is not completely clear and their potential preponderance as metabolic sensors during exercise has not been thoroughly explored, the present review was focused on the possible role of CB chemoreceptors as metabolic sensors during physical exertion in a physiological context, proposing it as a new actor in exercise physiology.