Figure 1.

EEC function and communication. Intracellular metabolism and activation of chemoreceptors located on the apical cell membrane of EECs, result in calcium influx, which induces the synthesis and release of gut hormones into the sub-epithelial space (1, 4) (Psichas et al., 2015). Various gut-derived hormones are synthesised and secreted in response to luminal constituents and released from EECs systemically to induce an effect on various tissues throughout the body, such as the brain, via, metabolic, local, paracrine (3) and/or endocrine (2) action, as well as the activation of afferent neurons innervating the GIT wall (5, 6, 7, 8) (Psichas et al., 2015). Further, EEC/ENS crosstalk can result from the direct absorption of nutrients through the intestine (7). The production of SCFA by the microbiome, which can be subsequently utilised by colonocytes as an energy source, can activate EECs, thus contributing to gut-brain activation (8).