Research On The Regulating Mechanism Of Hypoxia Exposure And Exercise On Muscle Glycogen Synthesis

Purpose:The purpose of this study was to explore the regulating mechanism of hypoxia exposure and exercise on muscle glycogen synthesis.The main study was the signaling pathway of insulin regulating muscle glycogen synthesis,and we researched on AMPK which was also an important signaling way of regulating glucose transport.Meanwhile, their downstream signals-GLUT4 and GN were studied.Methods:As the subjects of this study,male Sprague-Dawley rats were divided into four groups:Control group,Hypoxia exposure group,Exerxise group and Living high training low(HiLo) group.The mode of exercise was to run on the treadmill,The grade of which was 5,and the speed was 20m/min, lasting for 6 days every week.At night,Hypoxia exposure and HiLo group were exposured in normobaric hypoxic tent where the concentration of oxygen was 13.6%for 12 hours.All these had been lasting 4 weeks,then the rats of each group were killed after the experiment lasting lday, 7days,28days and 35days(7days after restored normal oxygen),and the sample were collected.We observed and analysed the shape and function of pancreas beta cells,measured the affinity of insulin receptors and explored the mRNA and protein expression changes of PI3K,AMPK,GLUT4 and GN which regulated muscle glycogen synthesis in the hypoxia exposure and exercise.Results:(1) The pancreas cells of Hypoxia exposure and HiLo,were obviously and moderately degenerated with adipic shape at lday and 7days after experiment.As the experiment were prolonged,the degeneration were to be lessen.(2) The results of image analysis indicated:exercise increased the numbers of pancreas beta cells,the percentage of beta cells and the area of pancreas were also increased.But all these of Hypoxia exposure and HiLo group were decreased.(3) As the ratio of I/G and C/G, we observed that there was no difference between exercise and HiLo.(4) The effects of hypoxia and/or exercise on insulin receptor of low affinity were more noticeable,hypoxia and/or exercise decreased the affinity of insulin receptor,but obviously increased the number of insulin receptor. (5) Hypoxia and/or exercise increased the content of muscle glycogen, and exercise increased more obviously.(6) Hypoxia and/or exercise increased the protein of AMPK and PI3k,and the protein of AMPK of 7days group and the protein of PI3k of 28 days group increased more obviously. (7) Hypoxia and/or exercise increased the gene expression of GLUT4 and GN,and which of the 28 days groups,were increased more obviously.Conclusions:(1) Hypoxia made the pancreas cells degenerated with adipic shape,,but hypoxia and /or exercise did not obviously change the endocrine fuction of pancreas beta cells.(2) Hypoxia and /or exercise induced or increased the numbers of insulin receptor,which indicated that the responses of insulin to hypoxia and /or exercise were enhanced. (3) Hypoxia and/or exercise increased the content of muscle glycogen,and exercise increased more obviously.The mechanism of which included two signaling way:one was through changing the affinity and the numbers of insulin receptor,increasing the protein of PI3K,and then enhancing the action of insulin signaling pathway;the other was through increasing the protein of AMPK which promoted glucose transport.Moreover hypoxia and/or exercise also increased the gene expression of GLUT4 and GN,which played important roles on promoting muscle glycogen synthesis of hypoxia and/or exercise.