Endocrine Abstracts

The anorectic gut hormones glucagon-like peptide-1 (GLP-1) and Peptide YY (PYY) are secreted by enteroendocrine L cells in response to short chain fatty acids (SCFAs) produced by gut microbiota following dietary fibre consumption. SCFAs, acetate, propionate and butyrate, activate the G protein-coupled receptors Free Fatty Acid Receptor 2 and 3 (FFAR2, FFAR3). Increasing intestinal levels of propionate can prevent weight gain in overweight adults. In rodents, FFAR2-mediated gut hormone release occurs via both classical calcium signalling and non-canonical Gαi/p38 signalling from intracellular endosomal compartments. However, the underlying mechanisms mediating human FFAR2-dependent gut hormone production and release, is poorly understood. Here, we characterise the effects of SCFAs on FFAR2-G protein signalling mechanisms in a human L cell model and investigate the role of these pathways on gut hormone production. In human colonic NCI-H716 cells, Homogeneous Time-Resolved Fluorescence (HTRF) assays were employed to measure secondary messengers downstream of G protein activation, and quantitative Reverse Transcription PCR (qPCR) for PYY and glucagon mRNA levels. All SCFAs activated Gαi and Gαq responses in a dose-dependent manner, with similar potencies but distinct efficacies. Both Gαi and Gαq signalling was abolished by pre-treatment with an FFAR2-specific antagonist GLPG0974, confirming that FFAR2 is the primary SCFA receptor in this cell type. Interestingly, all SCFA-induced signalling was inhibited by Dyngo-4a, an inhibitor of dynamin-dependent receptor internalisation. Butyrate induced a large upregulation in expression of PYY, but not glucagon, which was reduced by GLPG0974 and the Gαq-inhibitor YM-254890. Overall, the SCFAs activate pharmacologically distinct FFAR2 responses in human colonic cells, which are sensitive to spatial regulation. An FFAR2-Gαq response might underlie the upregulation of PYY expression by butyrate that may suggest each SCFA has distinct roles in regulating gut hormone production and release and could be exploited to promote long-term health properties of SCFA actions in humans.