Obesity and its associated metabolic diseases are a major public health burden. Consumption of dietary fibre is associated with appetite suppression, reduced weight gain and elevated plasma levels of the anorectic gut hormones peptide YY (PYY) and glucagon-like peptide-1 (GLP-1). Bacterial fermentation of dietary fibre in the colon yields short-chain fatty acids (SCFAs) including acetate (C2), propionate (C3) and butyrate (C4). In humans, luminal concentrations of SCFAs are low in the small intestine but higher than 100mmol/L in the colon, and rise even further following increased fibre consumption. SCFAs have recently been shown to stimulate GLP-1 release from mouse primary enteroendocrine L cells via the FFAR2 receptor. The effects of SCFAs on gut hormone release from human L cells have not been demonstrated. To investigate the effect of SCFAs on PYY release from human L cells, a primary human colonic cell model was developed. Colonic crypts were isolated from healthy human colonic tissue obtained from patients undergoing diagnostic colonoscopy. All participants provided informed, written consent (2000/5795). Colonic crypts were isolated following repeated digests using 0.4mg/ml collagenase at 37oC. The colonic crypt cultures were incubated for 2 hours with increasing concentrations (0, 100, 200 and 400mmol/L) of SCFAs. PYY levels in supernatants and lysed cells were measured by radioimmunoassay and percentage PYY release was calculated. Cell viability following the treatments was confirmed using a lactate dehydrogenase cytotoxicity assay. Values represent means ± S.E.M. (n=4-6), compared by one-way ANOVA. All three SCFAs significantly increased PYY release from human colonic L cells compared to control (400mmol/L acetate and butyrate vs. control, P<0.05; 400mmol/L propionate vs. control, P<0.01). At 200 and 400mmol/L, propionate increased PYY secretion 2-fold and 3-fold compared to control, respectively (7.4±1.2% and 13.8±1.3% PYY released vs. 4.1±0.5%). Similarly, 200 and 400mmol/L acetate also increased PYY secretion 2-fold and 3-fold, respectively, compared to control (6.5±1.6% and 10.5±1.9% PYY released vs. 3.6±1.3%). These data, obtained using a novel human colonic cell model, demonstrate for the first time that SCFAs act directly on human primary colonic cells to stimulate the release of the anorectic gut hormone PYY. These results offer a mechanism by which dietary fibre may suppress appetite and reduce food intake in humans.