obesity is a serious health threat not only for metabolic diseases , but also for several 
 types of cancers1 , 2 .
oxidative stress has been reported as one of the chief causes of 
 the onset of various obesity - related diseases3 . in brief , obesity is accompanied by increased levels of free fatty 
 acids ( ffa ) and hyperglycemia ; which , in turn , leads to increased reactive oxygen species 
 ( ros ) production and oxidative stress4 . 
 increased oxidative stress could initiate cancer not only by damaging dna directly , but also 
 by inducing error - prone dna repair5 .
it has been reported that physical activities such as regular exercise can reduce the 
 oxidative stress level in the body that is elevated by obesity6 .
konopka et al . suggested that exercise could reduce dna oxidative 
 damage in obese females by significantly decreasing exercise - induced 8-oxo-2deoxyguanosine 
 ( 8-oxo - dg)7 formation .
however , there 
 has been limited research investigating the effects of obesity and exercise on dna damage by 
 using the comet assay8 , which enables 
 rapid and sensitive measurement of dna damage .
it has been reported that , although regular 
 aerobic exercise could be effective for obesity prevention and alleviation6 , 9 , 
 walking and running , the representative modes of aerobic exercise , could cause temporary 
 cartilage deformation and degradation by increasing the load on the lower extremity joints 
 ( e.g. , knee joint ) , as reflected by elevated serum cartilage oligomeric matrix protein 
 ( comp ) levels10 , 11 . therefore , two aspects should be considered for obese subjects who exercise regularly : 
 while it is effective for maintenance and promotion of health by reducing dna damage , it can 
 induce cartilage deformation by repetitively increasing the load on the lower extremity 
 joints .
accordingly , the present 
 research aims to identify the effect of aerobic exercise on lymphocyte dna damage in obese 
 subjects by using the comet assay , as well as the stress level of the lower extremity 
 articular cartilage by analyzing serum comp levels .
all subjects had 
 a body mass index ( bmi ) above 25  kg / m , and waist circumference above 80  cm . 

minimum acceptable values for bmi and waist circumference were based on the criteria for 
 class i obesity for adult asians , established by the world health organization ( who ) . 

subjects also had to be free from any orthopedic or cardiovascular problems that would limit 
 exercise .
the research conformed to the standards set by the latest revision of the 
 declaration of helsinki .
all subjects read and signed a written informed consent statement 
 consistent with the guidelines set by the department of physical education at yonsei 
 university .
anthropometric measurements included height , body composition , and waist circumference , 
 measured using a stadiometer ( seca 213 ; seca , hamburg , germany ) , a bioimpedance analysis 
 ( bia ) device ( inbody 720 ; biospace , seoul , korea ) , and a circumference measuring tape ( seca 
 200 ; seca , hamburg , germany ) , respectively .
after the anthropometric measurements , subjects were randomly and equally assigned to 
 either an 8-member control ( con ) group ( age : 62.3  4.8  years , height : 159.0  5.0  cm , 
 weight : 71.0  3.6  kg , bmi : 28.1  2.2  kg / m , percent body fat : 35.9  2.7% , 
 waist circumference : 86.7  3.8  cm ) or an 8-member exercise ( ex ) group ( age : 63.8  
 4.0  years , height : 158.3  5.4  cm , weight : 69.9  6.6  kg , bmi : 27.9  1.9  kg / m , 
 percent body fat : 35.0  3.0% , waist circumference : 87.6  4.6  cm ) .
the ex group 
 participated in sessions of 60  min per day , 3 days per week , for a period of 8 weeks .
each 
 session began with a 10-min warm - up , continued with a main set of 40-min treadmill running 
 at their individual target heart rate zone ( 70% of heart rate reserve ) , and finished with a 
 10-min cool - down period .
the individual target heart - rate zone was determined according to 
 the guidelines for exercise testing and prescription of the american college of sport 
 medicines12 . before and after the 8 weeks of intervention , 8  ml of blood was collected from the 
 antecubital vein of each subject with a 22-gauge needle and sst tubes .
the serum comp levels 
 were determined by an enzyme - linked immunosorbent assay ( elisa ) using a commercially 
 available human comp elisa kit ( anamar ab , lund , sweden ) .
the absorbance was 
 measured at 450  nm with a microplate reader ( molecular device , sunnyvale , ca , usa ) .
the 
 lymphocyte dna damage was determined by using a comet assay as described by singh et al . , 
 which showed single- or double - strand dna breaks13 .
statistical analyses were performed using the statistical package for the social sciences 
 software , version 21.0 ( spss inc .
experimental analysis was performed with a 2  2 
 repeated - measures analysis of variance ( anova ) model to determine differences within and 
 between groups over time .
the changes of anthropometric and biochemical characteristics for the two groups before and 
 after intervention are shown in table 
 1table 1.changes of anthropometric and biochemical characteristics before and after 
 interventionvariablescon ( n=8)ex ( n=8)beforeafterbeforeafterweight ( kg)71.0  3.670.9  3.069.9  6.666.7  5.1*bmi ( kg / m)28.1  2.228.1  2.127.9  1.926.6  1.3*body fat ( % ) 35.9  2.736.0  2.635.0  3.032.5  2.2wc ( cm)86.7  3.886.8  4.887.6  4.685.5  3.5*comp ( u / l)11.5  2.411.6  2.910.9  2.110.4  2.2dna in tail ( % ) 8.2  2.18.2  1.98.8  2.27.9  1.7tail length ( m)49.8  14.148.0  6.749.8  4.547.1  5.2tail moment4.9  2.35.1  2.05.1  1.14.2  0.9*data are presented as mean  sd .
con : control ; ex : exercise ; wc : waist circumference ; 
 * significantly lower than before within the group ( p<0.05 ) ; 
 significantly lower than con within the time point ( p<0.05 ) .. the weight , bmi , body fat , waist circumference , and tail moment were 
 significantly decreased after intervention , as compared with those before intervention , in 
 the ex group ( p<0.05 ) .
in addition , body fat after intervention was significantly lower 
 in the ex group than in the con group ( p<0.05 ) .
in contrast , serum comp , dna in tail , and 
 tail length were not significantly different among any groups or time points ( table 1 ) .
con : control ; ex : exercise ; wc : waist circumference ; 
 * significantly lower than before within the group ( p<0.05 ) ; 
 significantly lower than con within the time point ( p<0.05 ) .
measuring dna damage in cells has been suggested as a method not only for detecting the 
 occurrence of genotoxicity caused by toxic materials that are harmful to the human body , but 
 also for the early prediction of the presence of severe diseases such as cancer14 .
the research described herein used the 
 comet assay to investigate the effect of a regular aerobic exercise intervention on 
 lymphocyte dna damage in obese , elderly females .
the result showed that after intervention , 
 the ex group showed a significant decrease in tail moment , a reflection dna damage .
this 
 result supports preceding research that showed reduced dna damage , based on the comet assay , 
 after aerobic exercise training 15 , 16 .
another result of the present research 
 was a significant decrease in obesity - related indexes ( weight , bmi , body fat , and waist 
 circumference ) in the ex group after intervention .
taken together , the results of the 
 present research indicate that obesity reduction , due to exercise , alleviates dna damage . 

, who reported obesity as a cause of dna damage , 
 based on significantly high levels of dna strand breaks and oxidized purines and pyrimidines 
 in morbidly obese females compared with that in eutrophic females17 . additionally , karaman et al . , suggested that comet - tail 
 length had positive correlations with waist circumference and bmi18 .
in contrast , it has been reported that comp , a protein component of cartilage , was released 
 into the blood when cartilage was damaged , because of repetitive training or physical stress 
 on a joint ; and that joint diseases , such as osteoarthritis , also led to elevated blood comp 
 levels10 , 11 , 19 .
the present research 
 analyzed serum comp to examine the change in the level of stress on lower extremity 
 articular cartilage in obese , elderly females , according to regular aerobic exercise 
 intervention .
the result showed no significant difference in serum comp levels before or 
 after intervention .
therefore , it is considered that the aerobic exercise regimen of the 
 present research did not exert deleterious stress on the lower extremity articular 
 cartilages of the subjects .
however , it is known that serum comp levels , elevated by walking 
 or running , return to baseline levels within 30 minutes after exercise10 , 11 . for this 
 reason , follow - up
research for investigating change in circulating comp levels would need to 
 employ an acute exercise protocol for stimulating articular cartilage before and after 
 intervention . in conclusion
, it is suggested that the regular aerobic exercise involved in this research , 
 may be effective for reducing obesity - induced high dna damage levels in obese , elderly 
 female subjects , without causing deformation or degradation of lower extremity articular 
 cartilage .
 [ purpose ] the aim of the reported research was to investigate the effects of regular 
 aerobic exercise on cartilage oligomeric matrix protein and oxidative dna damage in obese , 
 elderly females . [ subjects and methods ] sixteen class i obese , elderly females , according 
 to world health organization criteria , were randomly and equally assigned to a control 
 group ( n=8 ) or an exercise group ( n=8 ) . 
 the exercise group participated in exercise 
 sessions of 60 minutes per day , 3 days per week , for a period of 8 weeks . 
 [ results ] after 
 aerobic exercise intervention , weight , body mass index , body fat , waist circumference , and 
 dna damage ( tail moment ) were significantly decreased , compared with baseline values . in 
 contrast , 
 serum cartilage oligomeric matrix protein levels were not significantly 
 different among any groups or time - points . 
 [ conclusion ] regular aerobic exercise may be 
 effective for reducing obesity - induced high dna damage levels in obese females , without 
 causing the deformation or degradation of lower extremity articular cartilage . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION