| In recent years,with the global aging increasing year by year,the rate of primary senile osteoporosis is rising rapidly,which has been considered as a major public health problem.China is accelerating to become a country with a large number of elderly people.Therefore,it is urgent to find an effective and safe method to prevent and treat primary senile osteoporosis.Irisin was discovered by bostr? M in 2012.As a muscle factor,it is released into the blood circulation after exercise,and has been considered to change metabolism by communicating with other endocrine organs.As a bridge between skeletal muscle and peripheral tissue,irisin plays an important role in the metabolism of adipose tissue,bone tissue and nervous system.Objective: in this study,male SD rats with osteoporosis induced by natural aging were taken as the research object to study the effect of swimming with different intensity for8 weeks on the expression of Irisin in male senile SD rats with osteoporosis,to explore the correlation between the expression of Irisin and primary senile osteoporosis,and to clarify the key role of Irisin in improving osteoporosis by exercise.Methods: 20-month-old male SD rats were randomly divided into four groups:control group（C）,aerobic swimming group（SA）,high interval swimming group（SH）and resistance swimming group（SR）,and 8 10-month-old SD rats were selected as young control group（YC）.All the experiments were intervened for 9 weeks,the first week was adaptive exercise,and the second week was 8 weeks of formal exercise intervention.Firstly,the bone turnover of SD-treated rats was determined by measuring the contents of Irisin,Tartrate-resistant acid phosphatase（TRAP）,Serum phosphorus（SP）,Osteoclastogenesis inhibitory factor（OPG）and Alkaline phosphatase（ALP）in serum.Then the bone mineral density and bone stress of left femur and left tibia were measured by bone mineral density and bone stress to judge the condition of osteoporosis in SD rats.Finally,the gene transcription levels of fibronectin type III domain-containing protein 5（FNDC5）,Peroxisome proliferator-activated receptor-γ coactivator-1α（PGC-1α）in gastrocnemius muscle and Bone alkaline phosphatase（BALP）,Runt-related Transcription Factor 2（RUNX2）,OPG and Receptor Activator of Nuclear Factor-κ B Ligand（RANKL）in femur were determined by fluorescence quantitative PCR（q RTPCR）.The protein expressions of BALP,RUNX2,OPG and RANKL in femur were detected by Western Blot.Results: 1.The results of bone mineral density and bone stress were as follows:（1）compared with group C,the bone mineral density of femur in SH group and SR group increased significantly,but there was no significant difference in SA group,and tibia bone mineral density in SR group increased significantly compared with group C,while there was no significant difference between SH group and SA group.（2）compared with group C,the bone stress of femur in SH group and SR group was significantly higher than that in SA group,but there was no significant difference between SR group and C group,and there was no significant difference between SA group and SH group.2.HE staining: observed by optical microscope,the trabeculae of group C and SA became thinner and disordered.Compared with SR group and SH group,the trabecular structure of SR group and SH group was more regular and closely reticular,and the whole structure was complete.3.Biochemical markers of serum bone turnover: compared with group C,the expressions of SP,ALP and OPG in group SR and SH were extremely significant,TRAP in group SR was significantly lower than that in group C,and that in group SH was significantly lower than that in group C.The SC of SR group was significantly higher than that of C group,and that of SH group was significantly higher than that of C group.There was no significant difference in the expression of SC,SP,TRAP,ALP and OPG between SR group and SH group,but it was significantly higher in SR group and SH group than in SA group.4.Serum Irisin: compared with group C,there was significant difference between SR group and SH group,but there was no significant difference in SA group.It was significantly higher in SR group and SH group than that in SA group,but there was no significant difference between SR group and SH group.5.Gene transcriptional level and protein expression: compared with C group,the transcriptional levels of FNDC5 and PGC-1 α in gastrocnemius muscle of SR group and SH group were extremely significant,and the transcriptional level of PGC1 α in gastrocnemius muscle of SA group was significantly higher than that of C group.There was no significant difference in FNDC5 transcriptional level.There was no significant difference in the gene transcription level of FNDC5 and PGC-1 α between SR group and SH group,but the gene transcription level of SR group and SH group was significantly higher than that of SA group.Compared with group C,the gene transcription and protein expression of RUNX2,BALP and OPG in femur of SR group and SH group were significantly higher than those of group C（P < 0.05）.The gene transcription levels of RUNX2 and ALP in femur of SA group were significantly higher than those of group C,while the protein expressions of RUNX2,BALP and OPG were not significantly increased in SA group.The gene transcription and protein expression of RANKL in SR group and SH group were significantly lower than those in group C（P < 0.0l）.The transcription level of RANKL gene in SA group was significantly lower than that in group C（P < 0.05）,but the expression of RANKL protein was not significant.The results of comparison between exercise groups showed that there was no significant difference in gene transcription and protein expression of RUNX2,BALP and OPG between SR group and SH group,but it was significantly higher in SR group and SH group than in SA group.The gene transcription level and protein expression of RANKL in SR group were significantly lower than those in SH group and SA group,but there was no significant difference between SH group and SA group.6.Serum Irisin was positively correlated with serum OPG,serum ALP,bone mineral density（femur and tibia）,bone stress（femur and tibia）,RUNX2,BALP and OPG,and negatively correlated with serum TRAP and RANKL.Conclusion: 1.Resistance and high interval swimming have more obvious effect on osteoporosis than aerobic swimming.2.It is considered that resistance and high interval swimming exercise can increase the content of serum Irisin more than aerobic swimming exercise.In swimming exercise,adding certain weight bearing and increasing exercise intensity can promote the increase of serum Irisin concentration.3.Irisin can up-regulate the expression of RUNX2,BALP and OPG,inhibit the expression of RANKL and increase the ratio of OPG/RANKL,so as to promote the proliferation and differentiation of osteoblasts,promote bone formation,inhibit the maturation of osteoclasts and reduce bone resorption. |
