Influència d’una dieta rica en cacau sobre el sistema immunitari intestinal de rates sensibilitzades
- Autores: Mariona Camps Bossacoma
- Directores de la Tesis: Margarida Castell Escuer (dir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2017
- Idioma: español
- Tribunal Calificador de la Tesis: Patrocinio Vergara Esteras (presid.), Mireia Urpi Sarda (secret.), Franziska Roth Walter (voc.)
- Materias:
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- Resumen
Due to the rising prevalence of food allergy, the development of animal models of oral food sensitization is of interest in studying the mechanisms involved in this sensitization and its possible treatments.
Previous studies have reported that cocoa influences the intestinal and systemic immune systems, modifying lymphoid tissue composition and functionality and the synthesis of intestinal and systemic antibodies.
On these bases, the aim of the current thesis was to study in depth the immunomodulatory properties of cocoa, in particular to ascertain the effect and possible mechanisms induced by a cocoa diet on a rat oral sensitization model and also to determine which compound/s is/are responsible for such effect.
To achieve the initial part of the goal, a rat oral sensitization model was developed using ovalbumin as allergen and cholera toxin as adjuvant. Afterwards, three-week-old female Lewis rats from the successful model developed were fed for four weeks with a 10% cocoa diet. With regard to the results, the 10% cocoa diet was able to prevent the synthesis of the anti-ovalbumin antibodies. Moreover, the cocoa intake decreased intestinal IgA concentration due to fewer IgA cells reaching the lamina propia. In terms of the gutassociated lymphoid tissues (GALT), cocoa diet increased the proportion of TCRγδ+ cells and NK cells in mesenteric lymph nodes, Peyer’s patches and epithelium together with some modifications in gene expression of various molecules and cytokines in the mesenteric lymph nodes and small intestine. Cocoa intake also influenced gut microbiota in this rat oral sensitization model.
To attain the second part of the goal, the determination of the compounds responsible for the immunoregulatory effect of cocoa, two different approaches were made. Firstly, approximations were carried out in order to determine the effect of hesperidin, a flavonoid not found in cocoa, on rat immune response. However, with the dosages and the immunization process used, we were unable to detect changes on specific antibody production, although some modifications were evident in intestinal lymphocyte composition and functionality.
On the other hand, in order to determine whether theobromine, the main methylxanthine in cocoa, was responsible for the cocoa’s effects on microbiota, antibody immune response and on lymphocyte composition, the effects of the cocoa diet were compared with those obtained from rats fed a 0.25% theobromine diet (the same amount of theobromine provided by the cocoa diet). Theobromine affected microbiota composition but not in the same manner as cocoa intake, suggesting that other cocoa compounds, such as polyphenols and fibre, may have an effect on the intestinal bacteria. Nevertheless, theobromine was responsible for the short-chain fatty acid increase and the lower proportion of IgA-coated bacteria. Moreover, theobromine seems to be the main component responsible for the decrease in cocoa antibodies together with almost all modifications to the lymphoid tissues.
To sum up, cocoa, due to its theobromine content, is able to prevent the development of a rat oral sensitization model, contributing towards oral tolerance. These results suggest the role of cocoa as a potential nutraceutical for avoiding or preventing food allergies.
