Effects of the isoflavone prunetin on gut health and stress response in male Drosophila melanogaster

The traditional Asian diet is rich in fruits, vegetables and soy, the latter representing a significant source of dietary isoflavones. The isoflavone prunetin was recently identified to improve intestinal epithelial barrier function in vitro and to ameliorate general survival and overall health state in vivo in male Drosophila melanogaster. However, the prunetin-mediated health benefits in the fruit fly were ascertained under standard living conditions. As the loss of intestinal integrity is closely related to a reduction in Drosophila lifespan and barrier dysfunction increases with age, effects on prunetin-modulated gut health under oxidative or pathogenic stress provocation remain to be elucidated. In this study, male adult D. melanogaster were administered either a prunetin or a control diet. Gut-derived junction protein expression and pathogen-induced antimicrobial peptide expressions as well as the stem cell proliferation in the gut were evaluated. Furthermore, survival following exposure to hydrogen peroxide was assessed. Prunetin ingestion did not attenuate bacterial infection and did not protect flies from oxidative stress. Intestinal mRNA expression levels of adherence and septate junction proteins as well as the stem cell proliferation were not altered by prunetin intake. Prunetin does not improve the resistance of flies against severe injuring, exogenous stress and therefore seems to function in a preventive rather than a therapeutic approach since the health-promoting benefits appear to be exclusively restricted to normal living circumstances.