Increased Colonic Propionate Reduces Anticipatory Food Reward Responses in the Human Striatum

Abstract

Short chain fatty acids produced by colonic fermentation of non‐digestible carbohydrates have been associated with suppression in appetite. Using a novel system, inulin‐propionate ester (IPE), which delivers propionate directly to the colon, we have previously shown that propionate stimulates release of the satiety hormones GLP‐1 and PYY, and suppresses appetite in humans. In this study, we hypothesised that brain responses during evaluation of food pictures, a measure of food cue reactivity, would be reduced after ingestion of IPE. In a randomised, crossover design, 15 healthy men underwent a functional MRI food‐picture evaluation task 300 minutes after oral ingestion of either 10 g/d IPE (treatment) or inulin (control) with a standard meal. Five a priori regions of interest (ROIs; amygdala, anterior insula, caudate, nucleus accumbens, orbitofrontal cortex) involved in reward processing were defined. Compared to inulin, IPE resulted in lower % blood oxygen level dependent (BOLD) signal for food vs. object pictures in the caudate nucleus (mean ± SD: 0.078 ± 0.109 vs. ‐0.005 ± 0.085, P = 0.02), with a similar trend in the nucleus accumbens (0.118 ± 0.148 vs. 0.030 ± 0.121, P = 0.07). % BOLD signal in the other ROIs was similar between visits (P = 0.16‐0.54). IPE reduces striatal responses to anticipatory food reward, an effect that may be mediated by enhancement of the postprandial rise in plasma PYY and GLP‐1 or direct action of propionate on the CNS.