VMAT1 also has effects on the modulation of gastrin processing in G cells.  These intestinal endocrine cells process amine precursors, and VMAT1 pulls them into vesicles for storage.  The activity of VMAT1 in these cells has a seemingly inhibitory effect on the processing of gastrin.  Essentially, this means that certain compounds in the gut can be taken into these G cells and either amplify or inhibit the function of VMAT1, which will impact gastrin processing (conversion from G34 to G17).
Additionally, VMAT1 is known to play a role in the uptake and secretion of serotonin in the gut.  Enterochromaffin cells in the intestines will secrete serotonin in response to the activation of certain mechanosensors.  The regulation of serotonin in the gut is critically important, as it modulates appetite and controls intestinal contraction.