Abstract: BACKGROUND: The relationship between insulin resistance and intestinal mucosal permeability may be related to excess fat, inflammation and oxidative stress. At present, the influence of different kinds of exercise on this relationship has not been fully studied, and the relevant mechanism needs to be further studied.
OBJECTIVE: To study the effects of continuous exercise and cumulative exercise on intestinal mucosal permeability of insulin-resistant mice induced by high fat diet, and to compare the effects of different intensities of exercise, thereby evaluating the health-promoting effects of cumulative exercise.
METHODS: Four-week-old male C57BL/6J mice were fed high-fat diet to induce insulin resistance, and mice with successful modeling were randomly divided into five groups: high-fat insulin resistance group, general dietary insulin resistance group, moderate-intensity continuous exercise group, moderate-intensity cumulative exercise group, and high-intensity cumulative exercise group. Mice in the high-fat insulin resistance group received high-fat diet and mice in the other groups were fed normally. All the exercise groups received 8 weeks of different forms of treadmill training. Mice in the moderate-intensity sustained exercise group exercised for 50 minutes at a speed of 11 m/min. Mice in the moderate-intensity cumulative exercise group were subjected to 12.5 minutes of exercise, four times a day (3 hours between sessions), at a speed of 11 m/min. Mice in the high-intensity cumulative exercise group exercised for 7.5 minutes once, four times a day (3 hours between sessions), at a speed of 19 m/min. At 48 hours after the final session, the levels of lipopolysaccharide and D-lactic acid in serum of mice were detected, the pathological changes of ileal tissue were observed by hematoxylin-eosin staining, and the expression of intestinal compact linking protein was detected by western blot. The expression of interleukin-10, tumor necrosis factor αin blood and ileum and intestinal secreted immunoglobulin A were detected by ELISA.
RESULTS AND CONCLUSION: High-fat diet-induced insulin resistance was associated with body mass gain. The serum levels of endotoxin and D-lactic acid significantly increased, and the levels of tumor necrosis factor-α in serum and small intestine were significantly increased. Long-term regular cumulative exercise and continuous exercise could reduce the body mass of insulin-resistant mice, significantly improve glucose metabolism, and correct or improve insulin resistance symptoms. Both long-term regular cumulative exercise and continuous exercise could increase the expression of zonula occludens protein 1 and increase the secretion of secreted immunoglobulin A in intestinal mucosal tissue, thereby improving intestinal mucosal permeability, enhancing intestinal immune function, reducing the content of lipopolysaccharide in serum, and reducing the expression of pro-inflammatory factors in circulating blood and intestinal tissue. Finally, it could protect the intestinal mucosal barrier of insulin-resistant mice. Compared with medium-intensity cumulative exercise and continuous exercise, high-intensity cumulative exercise had more obvious effects on reducing body mass, improving insulin resistance symptoms and protecting intestinal mucosal barrier in insulin-resistant mice.

Key words: continuous exercise, cumulative exercise, insulin resistance, mouse, intestinal mucosa, permeability, barrier function, inflammation