| Background:Bone is an important part of human body, play an important role in locomotion, support, protect internal organs, storeage calcium and phosphate and etc in human body. Recently a whole-organism study of physiology found that bone has more functions than expected. For example bone is closely relate to the function of the brain, pancreas and intestinal. It also reveals that the bone is in contact with the pathogenesis of various diseases. So keep bones tissue relatively steady state has great significance in maintain the basic function of the human body. Bone is the dynamic equilibrium through continuous process of bone remodeling with a new bone substitution old bone. Bone remodeling is to achieve the balance between bone-resorbing and bone-forming through the interaction between osteoclasts and osteoblasts.In recent years, the aging phenomenon is increasingly serious in our country, the proportion of the elderly population growth, coupled with the rapid economic development and people’s lifestyle changes, the number of people suffering from type 2 diabetes mellitus increased year by year. Osteoporosis is one of common complications of type 2 diabetes mellitus, which is caused by the imbalance between bone-resorbing and bone-forming at the stage of bone remodeling. Relevant studies have reported that exercise intervention can affect bone metabolism, play an important role in prevention and treatment of osteoporosis by regulate the expression of some cytokines in order to improve bone-resorbing and bone-forming in the process of bone remodeling. The bone remodeling is a very complex process, each of the bone remodeling cycle through three stages:In the first stage, it produce a large number of internal voids in the process of bone-resorbing osteoclast; In the second stage, the bone voids is filled through the transition of phase; In the finally stage, mineral deposition in the bone and osteoblasts play their functions to form new bones. Therefore, the study about the process of bone-resorbing osteoclast is the primary factor in order to solution the imbalance of bone-resorbing and bone-forming in the process of bone remodeling in patients with type 2 diabetes mellitus. But now about the mechanism of exercise regulate bone-resorbing osteoclast through p38MAPK signal pathway is unclear.Objective:In this study, we constructed a model of type 2 diabetes mellitus mice, and the successful type 2 diabetes mellitus mice were respectively applied of swimming and downhill running exercise intervention. The expression of p38MAPK signal pathway in bone tissue and osteoclast differentiation and bone-resorbing were detrcted, aiming to analyze the effect of the metabolic disorder induced by type 2 diabetes mellitus on bone metabolism. Further inquiry the effect of exercise intervention regulate of bone metabolism in type 2 diabetes mellitus, and provide theoretical basis and feasibility of motion scheme for the prevention and treatment of type 2 diabetes mellitus osteoporosis in the future.Methods:60 C57BL/6 male mice of 6 weeks were fed with high fat diet and injected with STZ, to build type 2 diabetes mellitus model mice, and 20 C57BL/6 male mice of 6 weeks were fed with normal diet as normal control mice, with other breeding conditions were the same. The successful of type 2 diabetes mellitus mice were randomly divided into three groups, namely group of type 2 diabetes mellitus control, group of type 2 diabetes mellitus with swimming, and group of type 2 diabetes mellitus with downhill running.Group of type 2 diabetes mellitus with swimming and group of type 2 diabetes mellitus downhill running mice respectively exercise for 8 weeks,6 days a week,50 minutes a day. The treadmill gradient for downhill running was -9°, running speed was 0.8km/h. Type 2 diabetes mellitus mice during the exercise intervention still eat high fat diet and normal control mice were fed with normal diet, every Monday afternoon at about six o’clock mice were weighed in the experimental period.After the end of the exercise intervention within 12 to 24 hours, the cervical vertebra was severed to kill mice. Mice body length was measured with a flexible rule, mice and their the humerus were weighed with electronic balance, humerus length and each cross-sectionals diameter of humerus were measured with vernier caliper, the right distal femur bone mineral density was detected with Micro CT, the left femur mRNA relatively expression quantity of p38MAPK signaling pathway and bone resorb relate factors were detected with RT-PCR, the lumbar vertebra p38MAPK and p-p38MAPK protein relatively expression quantity were detected with western blot, the number of osteoclasts differentiated by bone marrow hematopoietic stem cells in vitro in each group were compared.Results:(1)The body weight of mice were fed with high-fat diet for 8 weeks significantly heavier than the body weight of mice were fed with normal diet (P<0.01),8 weeks exercise intervention significantly decrease the body weight of type 2 diabetes mellitus mice(P<0.01).(2)The obese mice index of type 2 diabetes mellitus mice significantly higher than that of normal mice (P<0.05), downhill running exercise intervention can significantly decrease the obese mice index of type 2 diabetes mellitus mice(P<0.05), and the effect of downhill on the obesity index of type 2 diabetes mellitus mice better than swimming(P<0.05).(3)The bone mineral density in cortical bone and cancellous bone of Type 2 diabetes mellitus mice significantly lower than that of normal mice(P<0.01). Swimming and downhill running exercise intervention are able to increase bone mineral density of type 2 diabetes mellitus mice, especially downhill running exercise intervention significantly increase the cancellous bone mineral density of type 2 diabetes mellitus mice (P<0.05). However, exercise intervention only weaken but not reverse the trend of bone mineral density decrease of type 2 diabetes mellitus mice.(4)The mRNA relative expression quantity of MAP3K1, MAP2K6, p38MAPK except for MAP2K3 in p38MAPK signaling pathway and IRF-3 and IFN-β with inhibitory effect on osteoclast differentiation in bone tissue of type 2 diabetes mellitus mice significantly less than that of normal mice(P<0.05). Swimming and downhill running exercise intervention could activate the p38MAPK signaling pathway in bone tissue of type 2 diabetes mellitus mice, increase the mRNA relative expression quantity of MAP3K1, MAP2K3, MAP2K6, p38MAPK, especially downhill running exercise intervention could significantly increase the mRNA relative expression quantity of MAP3K1 and p38MAPK(P<0.05); Swimming and downhill running exercise intervention can also upregulate the mRNA expression of IRF-3 and IFN-β in bone tissue of the type 2 diabetes mellitus mice, significantly increase the mRNA relative expression quantity of IRF-3 and IFN-β (P<0.05).(5)The content of p38MAPK protein in bone tissue of type 2 diabetes mellitus mice significantly less than that of normal mice(P<0.01), the content of have biological activity p-p38MAPK protein in bone tissue of type 2 diabetes mellitus mice was also significantly less than that of normal mice(P<0.05); Swimming and downhill running exercise intervention significantly increase the content of p38MAPK protein in bone tissue of type 2 diabetes mellitus mice(P<0.05), and downhill running exercise intervention also significantly increase the content of p-p38MAPK protein in bone tissue of type 2 diabetes mellitus mice(P<0.05).(6)Compared with normal mice, the mRNA relative expression quantity of inducing osteoclast differentiation TRAF-6 in bone tissue of type 2 diabetes mellitus mice significantly increase(P<0.05), swimming and downhill running exercise intervention can down regulate the expression of TRAF-6 mRNA in bone tissue of the type 2 diabetes mellitus mice, the mRNA relative expression quantity of osteoclasts specific secretion bone absorb factors TRAP and Cts K in bone tissue of the type 2 diabetes mellitus mice significantly more than that of normal mice (P<0.05), swimming and downhill running exercise intervention can down regulate the expression of TRAP and Cts K mRNA in bone tissue of the type 2 diabetes mellitus mice, especially downhill running exercise intervention can significantly reduce the mRNA relative expression quantity of TRAP in bone tissue of the type 2 diabetes mellitus mice(P<0.05).(7)The number of osteoclast differentiated by bone marrow hematopoietic stem cells in vitro in each group were different, the number of osteoclast in type 2 diabetes mellitus mice significantly increase than normal mice(P<0.01), swimming and downhill running exercise intervention can significantly reduce the number of osteoclast in type 2 diabetes mellitus mice(P<0.01).Conclusion:(1)The body weight and obesity index of mice were fed with high-fat diet for 8 weeks significantly heavier than the body weight and obesity index of mice were fed with normal diet.(2) The p38MAPK signaling pathway in bone tissue of the type 2 diabetes mellitus mice is inhibited, the activity of p38MAPK protein decline, the inhibitory effect on osteoclast differentiation of p38MAPK decrease, bone absorb increase and bone mineral density decrease.(3)The exercise intervention decrease the body weight of the type 2 diabetes mellitus mice, downhill running exercise significantly decrease the obesity index of type 2 diabetes mellitus mice.(4)The exercise intervention can activate p38MAPK signaling pathway in bone tissue of type 2 diabetes mellitus mice, increase the inhibitory effect of p38MAPK on osteoclast differentiation, reduce the number of osteoclasts and the bone absorption ability, so that to increase the bone mineral density. |
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