2022, Vol. 26 ›› Issue (26): 4173-4179

Exercise effects on myocardial type I, III collagen and angiotensin II/transforming growth factor beta1/Smad2 pathway in diabetic myocardial fibrosis rats

Liu Ya1, 2, Liu Xia1, Deng Penghui1, Ji Wei1, Li Jianping1   

Abstract: BACKGROUND: Recent studies have found that exercise can improve myocardial fibrosis in type II diabetic rats.
OBJECTIVE: To investigate the regulatory role of angiotensin II/transforming growth factor β1/Smad2 signaling pathway and its downstream factors in the process of diabetic myocardial fibrosis through swimming exercises in an animal model of diabetic myocardial fibrosis.
METHODS: Forty male Sprague-Dawley rats were randomly divided into two groups: a blank control group (n=10) and a diabetes model group (n=30). Rats in the blank control group were raised under a normal diet, and rats in the diabetes model group were fed with high-sugar and high-fat diet and treated with a single injection of 1% streptozotocin to establish a diabetic model. After successful modeling, 15 rats were randomly selected from the diabetes model group as a diabetes exercise group. Rats in the diabetes exercise group were subjected to non-weight bearing swimming, 60 minutes per day, 6 days per week. After training for 8 weeks, the fasting blood glucose and fasting insulin levels of rats were tested. Hematoxylin-eosin staining was used to observe the morphological changes of myocardial cells. Masson staining was used to observe the deposition of collagen fibers in the myocardial interstitium. Immunohistochemical staining was used to analyze the content of type I and III collagen fibers in myocardial tissue. Reverse transcription PCR was used to detect the mRNA expression of angiotensin II, type I collagen fiber, type III collagen fiber, transforming growth factor β1, and Smad2.
RESULTS AND CONCLUSION: Compared with the blank control group, the fasting blood glucose level and insulin resistance index were increased in the diabetes model group (P < 0.01). Compared with the diabetes model group, the fasting blood glucose and insulin resistance index were decreased in the diabetes exercise group (P < 0.05). Results of hematoxylin-eosin staining and Masson staining showed that disordered arrangement of myocardial cells, widened intercellular space, inflammatory cell infiltration, and obvious myocardial fibrosis in the diabetic model group. Whereas the arrangement of myocardial cells was still in order, the intercellular space was basically normal, and myocardial fibrosis was significantly relieved in the diabetic exercise group compared with the diabetic model group. The content of type I collagen fibers in rat myocardial tissue was increased in the diabetic model group compared with the blank control group (P < 0.05). There was no significant difference in the content of type I and III collagen fibers in rat myocardial tissue between the diabetic model group and the diabetic exercise group (P > 0.05). Compared with the blank control group, the mRNA expression of type I collagen fibers and transforming growth factor β1 in rat myocardial tissue was increased in the diabetic model group (P < 0.05). Compared with the diabetic model group, the mRNA expression of type I and III collagen fibers and transforming growth factor β1 in rat myocardial tissue was decreased in the diabetic exercise group (P < 0.01). To conclude, swimming can effectively prevent the occurrence and development of diabetic myocardial fibrosis, which may be related to the inhibition of the angiotensin II/transforming growth factor β1/Smad2 pathway.
Key words: aerobic exercise, diabetes, myocardial fibrosis, transforming growth factor β1/Smad2, angiotensin II