Acute increases in serum colonic short-chain fatty acids elicited by inulin do not increase GLP-1 or PYY responses but may reduce ghrelin in lean and overweight humans

BACKGROUND: Colonic fermentation of dietary-fibre to short-chain-fatty-acids (SCFA) influences appetite hormone secretion in animals, but SCFA production is excessive in obese animals. This suggests there may be resistance to the effect of SCFA on appetite-hormones in obesity. OBJECTIVES: to determine the effects of inulin (IN) and resistant-starch (RS) on postprandial SCFA, and gut hormone (GLP-1, PYY, and ghrelin) responses in healthy overweight/obese (OWO) vs lean (LN) humans. METHODS: Overnight fasted participants (13 OWO, 12 LN) consumed 300mL water containing 75g glucose (GLU) as Control, or 75g glucose plus 24g IN, or 28.2g RS using a randomized, single-blind, cross-over design. Blood for appetite-hormones and SCFA was collected at intervals over 6h. A standard lunch was served 4h after the test drink. RESULTS: Relative to GLU, IN, but not RS, significantly increased SCFA AUC from 4–6h (AUC(4-6)). Neither IN nor RS affected GLP-1 or PYY-AUC(4-6). Although neither IN nor RS reduced ghrelin-AUC(4-6) compared to GLU, ghrelin at 6h after IN was significantly lower than that after GLU (p<0.05). After IN, relative to GLU, the changes in SCFA-AUC(4-6) were negatively related to the changes in ghrelin-AUC(4-6) (p=0.017). SCFA and hormone responses did not differ significantly between LN and OWO. CONCLUSIONS: Acute increases in colonic SCFA do not affect GLP-1 or PYY responses in LN or OWO subjects, but may reduce ghrelin. The results do not support the hypothesis that SCFA acutely stimulate PYY and GLP-1 secretion; however, a longer adaptation to increased colonic fermentation or a larger sample size may yield different results.