| Objective:In order to explore the effect of hypoxic exposure, intensive training and simulated altitude training is performed on intestinal mucous membrane barrier function of rats. Through nutritional intervention, discuss the changes in the small intestine barrier functi-on of Ala-Gln or Gin in the intervention progress and the possiblemechanism, compare Ala-Gln with Gin, to provide strong experimental evidence for scientific implementation of altitude training.Method:The 5-week-old male SD rats were randomly divided into 6 groups:control group (group C, n=20), Exercise training group (group E, n= 20), altitude control group (group HC, n= 21), hypoxia exercise group (group HE, n= 20), hypoxia exercise+glutamine group (group HEG,n=20), hypoxia exercise+ alanyl-glutamine group (group HEAG, n=20). The rats’weight are measured weekly. According to the grouping requirements of the experiment,13.6% hypoxic exposure and/or 90 min 90% lactate threshold intensity load swimming training was administered to the rats. Assigned Gin or Ala-Gln according to the weight after training.Changes were observed in the small intestine mucosa tissue structure and the ultrastructure under electron microscopy after 2 weeks and 6 weeks, at which point it was detected DAO and D-lactic acid were present in plasma and TNF-a and NF-κB in ileal tissue by Elisa. Expression of occludin mRNA in ileal tissue was measured by RT-PCR.Results:(1) According to two-way ANOVA analysis among C, E, HC and HE groups, it was obvious that after two weeks that the number of intestinal villi was significant reduced through exercise training (P<0.01), the content of plasma DAO and D-LA significantly increase (P<0.05), and increase the content of NF-κB in small intestinal tissue of rats (P<0.01); Although exercise training can make the expression of occludin mRNA in small intestinal tissue decrease, the content of TNF increase, but there was no significant difference. Two weeks later, hypoxic exposure can reduce the number and the height of intestinal villi, but with no significant difference, but the expression of occludin mRNA was greatly reduced, the contents of TNF-a and NF-κB in small intestine tissue of rats were increased(P<0.05, P<0.01), as well as content of plasma DAO and D-LA through regular hypoxic exposure(P<0.05).However, there is no significant interaction between hypoxic exposure and high intensity exercise training in the intestinal villi quantity and height, the content of DAO and D-La in rat plasma, as well as the content of TNF-a and NF-κB in small intestinal tissue of rats(P>0.05).(2) Compared with the group HE, after 2 weeks, the number and the height of intestinal villi increased but there was no significant difference in HEG group, while significantly increased in group HEAG(P<0.05).The contents of DAO and D-La in rat plasma were decreased but no significant difference. While the expression of occludin mRNA was greatly increased(P<0.01) and the contents of TNF-a and NF-κB reduced in small intestine tissue of rats (P<0.05, P<0.01).Compared with the group HEG, there was no significant difference except the expression of occludin mRNA in small intestinal tissue of the group HEAG.(3) According to two-way ANOVA analysis among C, E, HC and HE groups, after 6 weeks, either hypoxic exposure or high intensity exercise training can greatly reduce the number of intestine villi (P<0.01), reduce the height of intestinal villi, but with no significant difference. Significant interaction of exercise training and hypoxia to further reduce the number and height of the rat small intestinal villus (P<0.01, P<0.05). Meanwhile, it was found that hypoxic exposure and high intensity exercise training can increase the DAO and D-La contents in rat plasma significantly (P<0.01), and increase the contents of TNF-a(P<0.01, P<0.05)-. NF-κB(P<0.01) and the expression of occludin mRNA(P<0.01). Combined exercise training and hypoxia exposure could further increasing the DAO and D-La contents in rat plasma, significant interaction between exercise training and hypoxia exposure(P<0.01).However, there is no substantial interaction between exercise training and hypoxia exposure in increasing the contents of TNF-α、NF-κB in rats’ small intestine tissue (P>0.05).(4) 6 weeks later, by electron microscopy observation of the group C of rats, it was found that mucosal microvilli of the small intestine were closely spaced and the arrangement were trim. The epithelial cells connected closely, the number of mitochondria and rough endoplasmic reticulum were rich in cytoplasm, and the morphological structure were normal. In the group E of rats, the microvilli were sparse and the arrangement was chaotic, the number of mitochondria decreased significantly and cristae were vague, some part of the mitochondria had denatured, Part of the mitochondria have exhibited degeneration phenomenon and some cells showed noticeable apoptosis phenomenon. The connections between cells were flabby. In the group HC of rats, the height of microvilli significantly shortened, the arrangement was chaotic, the gap between epithelium cells grows wider. some cells matrix were vacuous with a decreases in density. In the group HE of rats, the number of mucosal epithelium microvilli in the bowels was significantly reduced, the height of micro villi significantly shortened, and the gap between epithelium cells grows wider. There was cellular structure fuzziness and some nuclear chromatin margination. And marked apoptosis, while some of mitochondria had denatured and cristae was vague even disappear. In the group HEG, mucosal micro villi of the small intestine were closely spaced and the arrangements were trim, the height of micro villi significantly increased, the number of mitochondria increased significantly in cytoplasm, and the crisrae were clear. In the group HEAG of rats, mucosal microvilli in the small intestine were closely spaced and the arrangements were trim. Both the length and number of mucosal micro villi were increased compared with group HE, the number of mitochondria and rough endoplasmic reticulum were rich in cytoplasm, more ribosomes attached, and the morphological structures were normal and the epithelial cells connected closely. The intervals of a cell were clear.(5) 6 weeks later, compared with group HE, in the group of HEG, the number of intestine villi increased but with no significant difference, the height of intestine villi was significant increased(P<0.01), the content of plasma DAO and D-LA significant decreased(P<0.05, P<0.01), the expression of occludin mRNA in small intestine tissue of rats was increased significantly (P<0.01) and the contents of TNF-a and NF-κB decreased significantly(P<0.05, P<0.01); In the group HEAG, the number and the average height of intestine villi were both increased(P<0.05, P<0.01), the content of plasma D-LA decreased significantly(P<0.01), but there was no significant difference about reducing rats’plasma DAO. the content of NF-κB and TNF-a were significantly reduced. as well significantly increase the expression of the tight junction protein occludin in the small intestine tissue of simulation altitude training rats (P<0.01). Compared with the group HEG, the number of intestine villi and the expression of occludin mRNA in small intestine tissue of rats were both increased in the group HEAG (P<0.01).Conclusion:(1) Intensive training and hypoxia exposure both can impair intestinal mucosal barrier function, the extent of damage related to the duration of training and hypoxia exposure.(2) Supplying Gin and Ala-Gln could effectively prevent the injury of the intestinal mucosal barrier induced by altitude training, with the effect of supplying Ala-Gln being noticeably better than supplying Gin.(3) Hypoxic exposure and intensive training could increase the contents of TNF-a and NF-κB in the small intestine thus reducing the expression of occludin mRNA. This could ultimately lead to increased intestinal permeability and intestinal mucosa injury.(4) Supplying Gin and Ala-Gin could reduce the contents of TNF-a and NF-κB within the small intestine, while increasing the expression of TJ protein-occluding. Which may be the reason that supplying Gin and Ala-Gln was an effective intervention to the injury of intestinal mucosal barrier which caused by altitude training. |
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