Subchronic treatment with grape-seed phenolics inhibits ghrelin production despite a short-term stimulation of ghrelin secretion produced by bitter-sensing flavanols

Abstract

Scope: Grape-seed phenolic compounds have recently been described as satiating agents in rats when administered as a whole phenolic extract (GSPE). This satiating effect may involve the release of satiating gut hormones such as GLP-1, although a short-term increase in the orexigenic hormone ghrelin was also reported. In this study, we investigated the short- and long-term effects of GSPE in rats, focusing on the role of the main grape-seed phenolics in ghrelin secretion.

Methods and results: GSPE produced a short-term increase in plasma ghrelin in rats after an acute treatment. A mouse ghrelinoma cell line was used to test the effects of the main pure grape-seed phenolic compounds on ghrelin release. Monomeric flavanols stimulated ghrelin secretion by activating bitter taste receptors. In contrast, gallic acid (GA) and oligomeric flavanols inhibited ghrelin release. The ghrelin-inhibiting effects of GA were confirmed in rats and in rat duodenal segments. One day after the last dose of a subchronic treatment, GSPE decreased plasma ghrelin in rats, ghrelin secretion in intestinal segments, and ghrelin mRNA expression in stomach.

Conclusion: The sustained satiating effects of GSPE are related to a long-term decrease in ghrelin expression. GA and oligomeric flavanols play a ghrelin-inhibiting role in this process.

Keywords: Bitter agonists; Flavanols; Food intake; Gallic acid; Ghrelin.