Numerous epidemiological studies have indicated that a diet rich in plant based foods reduces the risk of several chronic diseases. The beneficial health effects of eating dietary plants have been proposed to be partly mediated by the phytochemicals found within these foods. Several dietary phytochemicals can induce EpRE-dependent transcription which is essential in up-regulation of cytoprotective proteins, and this has been suggested to be one of the mechanisms by which phytochemicals may provide protection against chronic diseases.
Dietary phytochemicals have been postulated to work in synergistic and additive manners, and thus this thesis investigated the effects of combinations of plant extracts on EpRE-dependent transcription in vitro. A potent inducer from the in vitro studies was furthermore tested in vivo in transgenic mice.
Of 11 extract combinations tested in vitro, 8 gave a statistically significant induction of EpRE-dependent transcription, and 7 of these were also statistically significantly higher than one or both of the separately added extracts. Most of the extract combinations appeared to exert additive effects, although some showed a trend toward a more synergistic or antagonistic effect. One of the combinations with the strongest EpRE induction and a trend towards synergistic effect was tested in a wider range of concentrations. In this extended experiment, trends towards antagonistic effect were observed.
A rosemary extract was used for an in vivo experiment with EpRE-LUC mice. For the mice given rosemary, the EpRE-dependent luciferase activity measured by in vivo imaging was significantly higher than the control mice 5h after gavage feeding. Furthermore, a trend towards increased EpRE activity in the intestine was found for the extract group compared to the control group.
Based on these results, further studies on effects of combinations of dietary plants on EpRE-dependent transcription and dietary effects of EpRE activity in vivo are warranted.