Grape seed proanthocyanidins as modulators of the inflammatory response and barrier function in the intestine
- Autores: Katherine Gil Cardoso
- Directores de la Tesis: Mayte Blay Olivé (dir. tes.), Ximena Terra Barbadora (codir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Simon Carding (presid.), Gerard Aragonès Bargalló (secret.), Daniel Closa Autet (voc.)
- Programa de doctorado: Programa de Doctorado en Nutrición y Metabolismo por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Intestinal dysfunction is a clinical sign of chronic intestinal diseases, characterized by a defective mucosal barrier function that increases intestinal permeability, and also by intestinal inflammation. However, intestinal dysfunction has also been described by recent studies in other pathologies, such as obesity. The intestine is a selective nutrient absorption system where signal transduction exchange is produced between nutrients and the body. The currently existing knowledge about the cellular effects exerted by nutrients through the intestine supports the possibility of the deregulation of intestinal homeostasis by some specific dietary components of the Western diet. Additionally, this tissue contains an extensive mucosal immune system that is continually exposed to both microbial and food antigens from the diet. In this regard, the experimental exposure to low doses of antigens like endotoxins has also been shown to induce a similar state of intestinal dysfunction like the state observed in diet-induced obesity (DIO). However, these models are rarely used to examine intestinal dysfunction and the phenotypes have not been completely defined yet, suggesting the need for a more in-depth exploration. In addition, the intestine is also the target of bioactive compounds, remarking flavonoids. The Mediterranean diet is an important source of these flavonoids, and proanthocyanidins are the most representative components. Previous studies in our group have demonstrated an immunomodulatory role of a grape seed extract, rich in proanthocyanidins (GSPE), in non-intestinal models. Other experimental evidence in our group has revealed that the same extract can directly interact with the intestinal cells, modulating several metabolic processes and improving intestinal health. Despite little is known about the role of proanthocyanidins in the mucosal immune system and the barrier function, the information mentioned above together with the protective role of proanthocyanidins improving metabolic alterations associated with obesity and Western diets sheds new clues about proanthocyanidins as possible immunomodulators and barrier protective agents in the intestine. In this framework, the global objective of the present thesis was to evaluate the possible role of proanthocyanidins in the modulation of the intestinal inflammatory response and barrier function in different animal models of intestinal dysfunction. We firstly evaluated this purpose in the obesity context. Previous to analyse the effect of proanthocyanidins, in the first objective we focused on defining a chronic robust model of intestinal dysfunction associated with obesity. For this reason, we analysed the impact of an obesogenic diet on intestinal health status at three time points, and to compare with a model of genetic obesity. To achieve this objective, obesity was induced in healthy female Wistar rats after the chronic cafeteria (CAF) diet administration for 12, 14.5 or 17 weeks, as a model of obesogenic diet. We focused on examining the effect of the diet intervention on morphometric variables, inflammatory response, tight junctions (TJs) and oxidative state in the intestine. Additionally, such effects were compared with genetic obese fa/fa Zucker rats fed a standard diet for 10 weeks, with the aim to distinguish between effects derived from the genetic background or from the diet. We concluded that obesogenic diets, such as CAF diet, have a negative impact on intestinal health, including intestinal inflammation, oxidative stress and TJs gene expression alteration in the intestine in a time-dependent manner, reaching the greatest damage at 17 weeks of diet intervention. In the following part of the thesis we evaluated whether intestinal health is able to sense proanthocyanidins, as bioactive food compounds, in different doses and time conditions of administration, in a situation of obesity-associated intestinal alterations. Particularly, in the second experiment we evaluated whether a corrective treatment with dietary doses of GSPE had a corrective effect on obesity-associated intestinal alterations in response to the CAF diet. In order to obtain an advanced stage of obesity, healthy female Wistar rats were fed a CAF diet for 18 weeks and the last three weeks they were also supplemented with GSPE at three dietary doses (5, 25 and 50 mg/Kg bw) as a corrective treatment of proanthocyanidins. Finally, we checked the effect of the extract on inflammatory response, oxidative stress markers and TJs in the intestine. Taking together all the results obtained in the second study, we concluded that oral treatment with dietary doses of proanthocyanidins has corrective effects on CAF diet-induced intestinal alterations, including the reduction of intestinal inflammation and oxidative stress, and the normalization in TJs gene expression, without substantial differences among the doses. The protective effect of dietary doses of proanthocyanidins, administered in a corrective way, suggested a possible modulation of barrier function by protecting it against TJs alterations. To study it in more depth, we decided to analyse the effect of a pharmacologic dose of GSPE (500 mg/Kg bw), administered at different time points, against diet induced barrier disruption, in vivo and ex vivo. For this purpose, female healthy Wistar rats were fed the CAF diet during 17 weeks and the effect of one preventive and one intermittent treatment with GSPE were evaluated on the modulation of intestinal barrier function (intestinal permeability and metabolic endotoxemia). According to our results, we concluded that the pharmacological dose of proanthocyanidins, administered before or together with an obesogenic diet, ameliorates barrier dysfunction: improving intestinal permeability and preventing metabolic endotoxemia, being the intermittent treatment the most effective after 17 weeks of CAF diet intervention. Once proanthocyanidins were confirmed as potent intestinal anti-inflammatory agents and modulators of barrier function in response to DIO, in the next section of the thesis we evaluated the same properties of these bioactive compounds in a model of acute intestinal inflammation and impaired intestinal permeability induced by lipopolysaccharides (LPS) injection. For this purpose, we analysed inflammatory and permeability markers in the intestine of male Wistar rats supplemented with one dietary (75 mg/Kg bw) and one pharmacological (375 mg/Kg bw) dose of GSPE before the intraperitoneal (IP) injection of LPS to induce intestinal dysfunction. Based on these findings, we concluded IP administration of a low dose of LPS to cause local mild intestinal inflammation and impaired barrier function, similar to the damages found in the DIO-induced model. At the same time, our analyses revealed that dietary and pharmacological doses of proanthocyanidins have a region-dependent protective effect, preventing against intestinal alterations induced by LPS. Summarizing the four manuscripts, we concluded that DIO and LPS exposition trigger intestinal inflammation and an impaired barrier function state, and that the administration of proanthocyanidins improves intestinal homeostasis and health, and these results depend on the dose and time of administration and they are also region-dependent. Therefore, we propose nutritional and therapeutic interventions with proanthocyanidins based on intestinal health modulation should be extensively explored in the context of intestinal dysfunction.
