Effect of vitamin e supplementation on intestinal barrier function in rats exposed to high altitude hypoxia environment

Abstract

The study was conducted to investigate the role of vitamin E in the high altitude hypoxia-induced damage to the intestinal barrier in rats. Sprague-Dawley rats were divided into control (Control), high altitude hypoxia (HH), and high altitude hypoxia+vitamin E (250 mg/kg BW*d) (HV) groups. After the third day, the HH and HV groups were placed in a hypobaric chamber at a stimulated elevation of 7000 m for 5 days. The rats in the HV group were given vitamin E by gavage daily for 8 days. The other rats were given equal volume saline. The results showed that high altitude hypoxia caused the enlargement of heart, liver, lung and kidney, and intestinal villi damage. Supplementation with vitamin E significantly alleviated hypoxia-caused damage to the main organs including intestine, increased the serum superoxide dismutase (SOD) (p< 0.05), diamino oxidase (DAO) (p< 0.01) levels, and decreased the serum levels of interleukin-2 (IL-2) (p< 0.01), interleukin-4 (IL-4) (p<0.001), interferon-gamma (IFN-γ) (p<0.01) and malondialdehyde (MDA) (p<0.001), and decreased the serum erythropoietin (EPO) activity (p<0.05). Administration of vitamin E significantly increased the S-IgA (p<0.001) in ileum and significantly improved the expression levels of occludin and IκBα, and decreased the expression levels of hypoxia-inducible factor 1 alpha and 2 alpha (HIF-1α and HIF-2α), Toll-like receptors (TLR4), P-IκBα and nuclear factor-κB p65(NF-κB P65) in ileum compared to the HH group. This study suggested that vitamin E protectis from intestinal injury caused by high altitude hypoxia environment. These effects may be related to the HIF and TLR4/NF-κB signaling pathway.

Keywords: Hypoxia; Intestinal mucosa; Occludin; TLRs; Vitamin E.

Fig. 1

Effects of vitamin E and hypoxia on body weight in rats. Control, Control group; HH, High altitude hypoxia group; HV, High altitude hypoxia plus vitamin E group.

Fig. 2

Effect of vitamin E on intestinal morphology in rats from different groups. Control, Control group; HH, High altitude hypoxia group; HV, High altitude hypoxia plus vitamin E group (H&E, ×200).

Fig. 3

Serum total SOD activity and MDA concentration. ^##p<0.01, ^###p<0.001 vs Control; ^*p<0.05, ^***p<0.001 vs HH. Values are expressed as mean±S.E.M. (n=10). SOD, superoxide dismutase; MDA, malondialdehyde; Control, Control group; HH, High altitude hypoxia group; HV, High altitude hypoxia plus vitamin E group.

Fig. 4

Serum IL-2, IL-4, IFN-γ, EPO and DAO levels, and intestinal S-IgA levels. ^#p<0.05, ^##p<0.01, ^###p<0.001 vs Control; ^*p<0.05, ^**p<0.01, ^***p<0.001 vs HH. Values are expressed as mean±S.E.M. (n=10). IL-2, interleukin-2; IL-4, interleukin-4; IFN-γ, interferon-gamma; DAO, diamine oxidase; EPO, erythropoietin; S-IgA, secretory Immunoglobulin A; Control, Control group; HH, High altitude hypoxia group; HV, High altitude hypoxia plus vitamin E group.

Fig. 5

occludin mRNA levels in ileum. Values present means±S.E.M. (n=10). ^#p<0.05 vs. Control. ^*p<0.05 vs. HH. Control, Control group; HH, High altitude hypoxia group; HV, High altitude hypoxia plus vitamin E group.

Fig. 6

Occludin, HIFs, TLR4 and NF-κB p65 protein expression in ileum. ^#p<0.01, ^##p<0.01, ^###p<0.001 vs Control; ^*p<0.05, ^***p<0.001 vs HH. Values are expressed as mean±S.E.M. (n=10). Values present means±S.E.M. (n=10). Control, Control group; HH, High altitude hypoxia group; HV, High altitude hypoxia plus vitamin E group.