Analysis of interaction of phenolic compounds with the cholecystokinin signaling pathway to explain effects on reducing food intake.

Previous animal experiments demonstrated that phenolic compounds can reduce weight and food intake, but the exact mechanism(s) behind these effects remain unknown. For regulation of food intake, the cholecystokinin (CCK) hormone signaling pathway plays an important role as it induces satiety by binding on its specific receptor (CCK1R), hereby reducing food intake. In this study, we investigated the possible interactions of eight phenolic compounds of different classes (tannic acid, gallic acid, benzoic acid, hydroxybenzoic acid, protocatechuic acid, quercetin, kaempferol and resveratrol) with the CCK1R signaling pathway. As major results, the tested phenolic compounds could not activate the CCK1R in a specific cell-based bioassay. In contrast, we observed an anti-CCK1R activity. This antagonistic action might be explained by blocking of the functioning of the CCK1R receptor, although the exact mechanism of interaction remains unknown. For tannic acid, we also measured a sequestration activity of the CCK hormone in vitro. In conclusion, the reported activity of phenolic compounds against food intake and weight is not based on an activation of the CCK1R. Taking into account the complex regulation of food intake, further work is necessary to unravel other essential mechanisms involved to explain the reported effects of phenolic compounds against food intake.