In the first step of the project, an in vitro model systems closely mimicking the intestinal epithelium was developed by co-culturing different human cell lines. The model was then validated for the presence of key features found in human enterocytes, including M-cells, using scanning electron microscopy. Following validation, the model system was used on its own to investigate the intestinal transport of a number of commonly consumed and emerging protein sources such as those from milk, quinoa, hemp and lesser mealworm. Additionally, it was used in combination with immunes cells such as macrophages to investigate the immunomodulating properties of the transported proteins/peptides as well as their impact on enzymes, particularly dipeptidyl-peptidase IV (DPP-IV), found in the gastrointestinal tract and expressed on the membrane of various type of lymphocytes.
While un-treated proteins showed low intestinal permeability and displayed no or weak immunological effect, peptides generated from their in vitro gastrointestinal digestion were able to generate immune responses, such as influencing cell proliferation and cytokine secretion, and this ability was retained following their intestinal transport. Some active peptides were transported intact across the intestinal epithelium, while other where hydrolyzed by intestinal brush border enzymes into fragments of various potency levels. Protein digests and hydrolysates, particularly those from milk and mealworm proteins, were shown to have inhibitory activity against the DPP-IV enzyme, suggesting that they may play a dual role in preventing the degradation of chemokines as well as the incretin hormones which are involved in blood glucose regulation.
The work performed, and results obtained, during this project were shared at training and networking events organized at the University of British Columbia (Vancouver, Canada) and the European Molecular Biology Laboratory (Heidelberg, Germany) as well as at scientific meetings such as the American Diary Science Association (ADSA) annual meeting (Knoxville, United States) and the XI ISIN conference on immunonutrition (London, England).
