Preliminary Study Of The Relation Between MtDNA (Mitochondrial DNA) With Primary Osteoporosis And Its Mechanism Of Oxidative Damage

Objective：1. Begining from the reflections of mtDNA “qualitative change”-missingrate、“quantitative”-copy number to investigate the correlation of primaryosteoporosis with mtDNA.2. Detecting the change of8-OHdG in the serum between two group：osteoporosisgroup and the non-osteoporosis group serum,to further prove the role ofoxidative damage in the development of osteoporosis.3. Further investigate the relationship of patients with mtDNA deletions、copy number changes、and8-OHdG.Method：1. Since July2011-January2012,The author strictly according to theinclusion criteria and exclusion criteria and randomly selecting58patientsin two hospital：the Second Affiliated Hospital of Guangzhou Medical Collegeand The traumatic and Orthopedic Hospital Affiliated to Guang zhou Universityof TCM.Bone density testing were carrying according to the patient’scondition requires,and in the light of bone mineral density results,patientswere divided into the osteoporosis group (experimental group) of40withnon-osteoporosis group (control group)18;in which all patients underwentlumbar spine (L1-4) bone mineral density testing,only45patients(experimental group27, control group18)underwent femoral bonemineral density test at the same time;19cases (experimental group10cases,the control group9cases)ware carryed lumbar spine surgery.all above58patients、19cases of surgical patients were respectively retained inperipheral blood, bone tissue.2. The peripheral blood of58patients and bone tissue retained from19casessurgical patients ware carryed out PCR to qualitative detecting of thefragment deletion of4.9kb (4977bp) and3.7kb, real-time PCR detecting themtDNA copy number. In addition, peripheral blood serum of58patients weredetected by Elisa.3. Statistical analysis were carryed to investigate the correlation in threeindicators of4.9kb (4977bp) and3.7kb deletions、mtDNA copy number、8-OHdGand the correlationin with the other corresponding parameters; an independentrisk factor of primary osteoporosisbe were also evaluated.Results：1．The study includ58patients（40patients in experimental group，18patientsin control group），both group in the lumbar spine (L1-4)BMD、T-values werestatistically significant (p<0.01);45patients (experimental27,controlgroup18) were carryed the femoral bone mineral density test at the same time,two groups of patients in the left and right femur BMD、T-values also werestatistically significant (p<0.01);Both group in age, height, weight, BMIwere not statistically significant (all p>0.05), two groups of patients in the gender differences were significantly different (p<0.05).2. mtDNA4.9kb (4977bp)、3.7kb deletions were not found in the peripheral bloodof all patients and the bone tissue of19cases patients who carrying thelumbar spine surgery.3. Using the2-ΔΔCT to calculate all the patients’mtDNA copy numberrelative to the control sample(selectting the control group, one older andsimultaneously carryed with lumbar spine surgery whose blood sample as thecontrol sample);Spearman’s correlation analysis shows19cases ofpatients’who with lumbar spine surgery mtDNA copy number in peripheral bloodand bone tissue has a nice correlation (r=0.710,p=0.001); Spearmancorrelation analysis showed a negative correlation between58patients’mtDNA copy number in peripheral blood and lumbar spine (L1-4) BMD、T-value(r=-0.341p<0.01,r=-0.396p<0.01); where the femur bone mineraldensity tests were carryed in45patients, mtDNA copy number in peripheralblood also has a negative correlation with the both femur BMD、T value(r=-0.543p<0.01、r=-0.532p<0.01;r=-0.483p <0.01、r=-0.449p <0.01); but this groupof patients with mtDNA copy number with age、BMI were not significantdifference (p>0.05).4. Spearman correlation analysis showed that58patients’8-OHdG inperipheral blood serum has a negative correlation with lumbar spine (L1-4)BMDand T value(r=-0.442p<0.01,r=-0.439,p<0.01);45patients who has bothfemoral bone mineral density at the same time,whose peripheral blood of8-OHdGconcentration also has negative correlation with both femur BMD、T-value(r=-0.397p<0.01、r=-0.458p<0.01;r=-0.423p<0.01、r=-0.455p<0.01)；in this group of patients,The correlation between8-OHdG and age、BMI was nosignificant(p>0.05),with mtDNA copy number is also no obviouscorrelation(p>0.05).5. Logistic regression analysis after adjusting for other factors, gender(female)、8-OHdG、mtDNA copy number were risk factors of primary osteoporosisin the regression model of this experiment,the OR of8-OHdG、copy number were3.410(95%CI:1.011-11.504,P=0.048),33.721(95%CI:2.926-388.600,p=0.005).Conclusion：1. The fragment deletion of mtDNA4.9kb(4977bp) and the3.7kb may not havea close relation with primary osteoporosis for Chinese person.2. The mtDNA copy number in peripheral blood and bone has a significantcorrelation,to a certain extent, it is feasible for the peripheral blood’mtDNA copy number to replace the bone tissue’ mtDNA copy number to detectvariation.3. Peripheral blood mtDNA copy number has a significant correlation with BMD、T value of the lumbar spine (L1-4) and both femur bone, it also proved thatthe mtDNA may be involved in the pathogenesis of primary osteoporosis.4.8-OHdG concentration in peripheral blood has a significant correlationwith BMD、T value of the lumbar spine (L1-4) and both femur bone,indicating that the role of oxidative damage mechanisms in the pathogenesis of primaryosteoporosis5. The correlation between8-OHdG concentration in peripheral blood serumand mtDNA copy number in the peripheral blood was not significant， to acertain extent, mtDNA oxidative damage might not be the main mechanism forthe pathogenesis of primary osteoporosis.6. The8-OHdG of serum and mtDNA copy number in peripheral blood areindependent risk factor for primary osteoporosis,which have a predictivevalue for primary osteoporosis.