Abstract (eng)
Up to now homoeriodictyol, a flavanone from Eriodictyon californicum has been known mainly for its bitter-masking and health-promoting effects. Here, another physiological aspect, the influence of homoeriodictyol sodium salt (NaHED) on glucose uptake and serotonin release, as well as a possible interaction between these two systems in Caco-2 cells were investigated. This human colonic cell line sharing similarities with enterocytes is adapted to imitate the intestinal barrier. To determine a potential NaHED-mediated effect on glucose uptake as well as the possible involvement of the intestinal glucose transporters in Caco-2 cells, a fluorescence-based glucose uptake assay with use of specific inhibitors of GLUT2 and SGLT1 was carried out. Moreover, the influence of NaHED at the level of gene expression of GLUT2 and SGLT1 was investigated by means of qRT-PCR. The hypothesis of a decreased serotonin release in Caco-2 cells after treatment with NaHED, which is also based on preliminary studies, showing a NaHED mediated reduced serotonin release in neural cells and a decreased serotonin level in plasma after treatment with NaHED in a human intervention study, was tested by means of a serotonin sensitive ELISA kit. In addition, several studies already suggest a relationship between peripheral serotonin and glucose metabolism. The results of this master thesis show both, glucose uptake increasing effects after 30 minutes incubation of Caco-2 cells with NaHED in a concentration of 100 µM, and a decreased serotonin release after 5 minutes incubation, respectively. The use of GLUT2 and SGLT1 inhibitors Phloretin and Phlorizin indicated the contribution of the sodium dependent glucose transporter 1 in the increased glucose, while NaHED did not show any effects on apical GLUT2 levels in Caco-2 cells under the mentioned conditions. On the level of gene expression of SGLT1 and GLUT2 the treatment of Caco-2 cells with NaHED neither resulted in an up- nor in a down-regulation of these transporters.
The influence of NaHED in the same concentration of 100 µM on glucose uptake and serotonin release in Caco-2 cells could be interpreted as an indication of a possible relationship between peripheral serotonin und glucose metabolism, while the decreased serotonin release could be understood as appetite stimulating effect of NaHED.