Identification of mechanisms of beneficial effects of dietary clays in pigs and chicks during an enteric infection

dietary clays;goblet cells;smectite

Almeida, Juliana

关键词: dietary clays;    goblet cells;    smectite;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/45324/Juliana_Almeida.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Dietary clays can reduce diarrhea in pigs, but the mechanisms are unknown. Of several candidates, strengthening of the intestinal barrier is most solidly supported by the literature. Three approaches were taken in order to elucidate some of those mechanisms. First, pigs were challenged with a pathogenic E.coli in order to determine how the challenge and 3 different dietary clays affect the intestinal barrier of pigs. The challenge reduced the barrier integrity as indicated by increased bacterial translocation from the intestinal lumen to mesenteric lymph nodes (from 0.76 log10CFU/g of lymph node for the sham group to 1.93 log10CFU/g of lymph node on average), increased crypt depth in the ileum (from 210.9 um in the sham group to 227.3 um in the challenged group on average), and increased goblet cell size (from 30.36 µm2 in the sham group to 32.38 µm2 in the challenged group on average) and number (from 24.60 in the sham group to 27.93 in the challenged group) in the ileum , thus reducing growth performance. One of the clays, smectite A (SMA) increased goblet cell size (from 29.58 µm2 in the sham group to 35.96 µm2 in the challenged group) during the acute phase of the infection, indicating increased mucus production. Second, chicks were challengedwith Salmonella enterica serovar Typhimuriumwith the objective to test the beneficial effects of 3 different dietary clays on growth performance and barrier function during the chronic phase of infection. Challenge with Salmonella enterica serovar Typhimurium reduced performance by 11%; during d 3-7 post infection the ADG was reduced from 54.83 g in the sham group to 48.82 g in the challenged group. The challenge increased goblet cell size (from 23.3 µm2 in the sham group to 29.7 µm2 in the challenged group fed basal diet) and number (from 99.50 in the sham group to 131.98 in the challenged group fed the basal diet), and reduced villus height. The clays restored performance in the challenged group. One of the clays (SMA) reduced goblet cell size (from 29.7 µm2 in the challenge group fed basal diet to 23.4 µm2 in the challenged group fed SMA) and number (from iii131.98 in the challenge group fed basal diet to 99.78 in the challenged group fed SMA), indicating increased secretion of mucus in the chronic phase of infection, thus strengthening the barrier. The apparent difference in results between the 2 experiments can be explained by the fact that measurements were done during different phases of infection in the pigs and chicks. When pigs were challenged with E.coli the measurements were done during the acute phase of infection and when the chicks were challenged with Salmonella enterica serovar Typhimurium the measurements were done during the chronic phase of infection. Different clays appeared to work through different mechanisms. All 3 clays restored performance (ADG and ADFI) in the chick experiment but not all 3 clays seemed to enhance the intestinal barrier. Third, a human colorectal adenocarcinoma cell line (LS174T) was grown in the presence or absence of different concentrations of SMA in order to explore potential mechanisms through which SMA may produce the beneficial effects previously observed in vivo. The mucin 2 (MUC2) expression was down-regulated by SMA and the reason is unclear. The resistin like molecule beta (RELMβ) expression was up-regulated by SMA. The magnitude of the up-regulation of RELMβ (41%) was greater than the magnitude of the down-regulation of MUC2 (25%) when LS174T cells were grown in the presence of 0.10% SMA (combined results of 3 cell cultures), thus the further focus was onRELMβ. The secretion of RELMβ by LS174T cells was increased by SMA, with depletion of goblet cells. These observations are in agreement with the results from the enteric challenge in chicks and indicate strenghtening of the mucus barrier.