This study was to investigate the mechanism of intestinal physical and immune barriers in the occurrence of high-intensive exercise-induced gastrointestinal symptoms.
An overtraining model of male C57BL/6 mice was established by running-to-exhaustive exercise. Then, the mice were sacrificed, and a series of evaluation indicators, including the routine blood analysis as well as histological examinations, inflammatory factors, ultrastructure observation, and intestinal permeability of the gut, were measured based on this model. The expressions of inflammatory factors tumor necrosis factor α, interferon-γ, and interleukin (IL)-6 as well as the tight junction and adherence junction proteins ZO-1, Occludin, Claudin-1, and E-cadherin were measured, respectively. Furthermore, the mRNA level of IL-22 and the proportion of ILC3 and IL-22 produced in CD4+ T cells in lamina propria lymphocytes (LPL) were analyzed by flow cytometry. Besides, the liver glycogen and the expressions of sirtuins-3 and hypoxia-inducible factor-1a, which were associated with the intestinal metabolism phenotype, were analyzed by Western blotting.
Exhaustive exercise induced a disrupted intestinal barrier integrity, an aggravated intestinal inflammation, increased gut permeability, and the reduced IL-22 mRNA level. Compared with the nonexercise mice, the IL-22 produced in LPL was reduced followed by exhaustive exercise, whereas the proportion of IL-22 produced in CD4+ T cells was still unchanged. Significantly, the proportion of ILC3 in the LPL was decreased obviously, including the NCR+ ILC3. Furthermore, the intestinal metabolism phenotype assessment showed lower liver glycogen and blood glucose as well as higher blood lactic acid and hypoxia-inducible factor-1a, respectively.
The data indicated that the acute high-intensity running-induced gastrointestinal symptom is closely associated with a reduced percentage of ILC3 and IL-22 level in the LPL, possibly due to the glycogen exhaustion and intestinal mucosa hypoperfusion.