chemokines are a family of small cytokines that regulate leukocyte migration by inducing 
 chemotaxis of specific cells .
chemokines are produced in almost all eukaryotic cells that 
 constitute blood and other tissues .
for example , chemokines of the cc subfamily are secreted 
 by epithelial cells and fibroblasts during inflammatory reactions1 .
eotaxin-1 ( ccl11 ) , a member of the cc chemokine family 
 secreted by epithelial cells , fibroblasts , macrophages , and eosinophils , has been reported 
 to play an important role in eosinophil infiltration during allergic inflammation1 .
accordingly , majority of previous studies 
 on the function and role of ccl11 focused mainly on inflammatory airway diseases , such as 
 asthma1 , 2 .
however , recently , studies have provided evidence regarding the 
 neurobiological relevance of ccl113 . for 
 example , in the study of villeda et al . , a decrease in long - term potentiation of synaptic 
 transmission ,
a neurophysiological index related to learning ability , has been observed in 
 the brains of mice injected with ccl114 . 

in addition , that study revealed that ccl11 is a blood - borne factor inhibiting 
 neurogenesis4 . on the other hand
, it has been reported that regular exercise not only reduces high 
 oxidative stress level caused by obesity , but also induces neurogenesis by increasing 
 expression of neurotrophic factors , such as brain - derived neurotrophic factor ( bdnf)5 , 6 . 

dramatic changes in oxidative stress levels could play an important role in neurotrophic 
 factor expression as well as in ccl11 release7 , 8 .
in addition , loughrey et al . revealed 
 increased circulating ccl11 levels in patients with a metabolic syndrome that included 
 obesity as a clinical manifestation9 .
choi 
 et al . reported that although ccl11 levels were significantly higher in patients with 
 central obesity , regular exercise training could reduce their plasma ccl11 levels10 .
however , there has been very limited 
 research into dynamics of neurogenesis in obese human subjects and the relationship between 
 ccl11 levels and regular exercise has not been properly studied . therefore , for the present study , obese young men were recruited with the objective of 
 defining the effect of regular aerobic exercise intervention on the content of malonaldehyde 
 ( mda ) , an oxidative stress marker , and on the resulting changes in peripheral bdnf and ccl11 
 levels .
sixteen obese young men between 2026  years of age volunteered as subjects for the present 
 study .
all subjects had to meet the following criteria before enrollment in the study : 1 ) 
 bmi above 25  kg / m and waist circumference above 90  cm , 2 ) no participation in 
 regular physical activity programs , and 3 ) no history of cardiovascular , metabolic , or 
 respiratory diseases .
subjects were randomly assigned into a control ( con ) group or an 
 exercise ( ex ) group , with 8 subjects in each group .
the characteristics of the subjects are 
 shown in table 1table 1.characteristics of the subjectsvariablescon ( n = 8)ex ( n = 8)age ( years)22.32.122.92.5height ( cm)173.66.3172.84.4weight ( kg)83.810.385.68.3fat mass ( kg)24.34.524.65.2bmi ( kg / m)27.72.228.72.5body fat ( % ) 28.82.328.74.4waist circumference ( cm)99.84.8100.05.8resting sbp ( mmhg)126.07.3126.99.4resting dbp ( mmhg)81.45.383.85.9vo2max ( ml / kg / min)43.97.242.45.9data are presented as mean  sd .
bmi : body mass index ; sbp : systolic blood pressure ; 
 dbp : diastolic blood pressure .
the study 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 .
bmi : body mass index ; sbp : systolic blood pressure ; 
 dbp : diastolic blood pressure anthropometric measurements included measurements of height , body composition , resting 
 blood pressure ( bp ) , and maximal oxygen uptake ( vo2max ) .
height and body 
 composition were measured using a stadiometer ( seca213 ; seca , hamburg , germany ) and a 
 bioimpedance analysis ( bia ) device ( inbody720 ; biospace , seoul , korea ) , respectively .
bp was 
 measured in a seated position using standard auscultation procedures and a mercury 
 sphygmomanometer ( trimline ; pymah , somerville , nj , usa ) .
each subject was wearing a gas 
 analyzer ( metamax 3b ; cortex , leipzig , germany ) that evaluated respiratory parameters using 
 the breath - by - breath method and vo2max was measured on a treadmill ( q65 ; quinton , 
 seattle , wa , usa ) according to the bruce protocol .
all subjects in the ex group had undergone the supervised treadmill running exercise [ 70% 
 of the heart rate reserve ( hrr ) , 40  min each ] sessions 3 times a week for 8 weeks , while 
 those in the con group just maintained their usual lifestyles .
ten milliliters of blood was collected from the antecubital vein of each subject before and 
 after the intervention using a 22-gauge needle , a serum separator tube ( becton dickinson , 
 franklin lakes , nj , usa ) , and an ethylenediamine tetra - acetic acid tube ( becton dickinson , 
 franklin lakes , nj , usa ) . collected blood samples were centrifuged for 15  min at 1,000  g 
 and then stored at 80  c until further analysis .
serum glucose was determined by the 
 hexokinase method using a commercially available glucose / hexokinase assay kit ( pointe 
 scientific , canton , mi , usa ) . the analyses of plasma mda , serum bdnf , and plasma ccl11 
 levels were carried out using an oxiselect mda adduct competitive elisa kit 
 ( cell biolabs , san diego , ca , usa ) , a human bdnf elisa kit ( r&d systems , minneapolis , 
 mn , usa ) , and a human ccl11/eotaxin immunoassay kit ( r&d systems , minneapolis , mn , usa ) , 
 respectively . a microplate reader ( emax ; molecular device , sunnyvale , ca , usa ) was used to 
 measure absorbance at 450  nm . statistical analyses were performed with spss version 21.0 for windows ( spss inc . ,
data are presented as the means  standard deviation ( sd ) , unless otherwise 
 stated .
independent student s t - tests were conducted to compare baseline levels of all 
 variables between the con and ex groups . to reveal differences between normally distributed 
 data , the two - way repeated analysis of variance ( anova ) was employed .
when significant time 
 by group interactions occurred , simple main effects were assessed using independent and 
 paired student s t - tests .
the comparison of anthropometric and biochemical characteristics for the two groups before 
 and after intervention is shown in table 
 2table 2.comparison of anthropometric and biochemical characteristics before and after 
 interventionvariablescon ( n = 8)ex ( n = 8)beforeafterbeforeafterweight ( kg)83.810.383.510.085.68.379.57.3bmi ( kg / m)27.72.227.62.128.72.526.61.9fat mass ( kg)24.34.524.04.724.65.219.14.5body fat ( % ) 28.82.328.72.028.74.425.14.4waist circumference ( cm)99.84.899.04.4100.05.891.64.3vo2max ( ml / kg / min)43.97.243.45.442.45.949.14.3glucose ( mg / dl)94.62.694.53.294.44.291.74.3mda ( mmol / ml)5.70.55.70.65.70.45.10.8bdnf ( ng / ml)24.84.925.14.924.84.129.95.3ccl11 ( pg / ml)71.712.572.710.972.814.268.511.9data are presented as the mean  sd .
symbols * and 
 indicate significantly lower or significantly higher values , respectively , in the same 
 subjects compared to the values obtained before the start of the intervention period 
 ( p < 0.05 ) . following intervention , repeated measures anova demonstrated a significant 
 effect of treatment for weight ( f = 29.546 , p < 0.001 ) , bmi ( f = 26.859 , p < 0.001 ) , 
 fat mass ( f = 31.632 , p < 0.001 ) , body fat ( f = 19.947 , p = 0.001 ) , waist circumference 
 ( f = 29.126 , p < 0.001 ) , vo2max ( f = 18.613 , p = 0.001 ) , serum glucose levels 
 ( f = 12.754 , p = 0.003 ) , plasma mda levels ( f = 5.218 , p = 0.038 ) , serum bdnf levels ( f = 
 12.834 , p = 0.003 ) , and plasma ccl11 levels ( f = 9.178 , p = 0.009 ) . following the 
 intervention , bmi , fat mass ,
body fat , waist circumference , serum glucose levels , plasma mda 
 levels , and plasma ccl11 levels were significantly lower , while vo2max and serum 
 bdnf levels were significantly higher when compared to values prior to the intervention in 
 the ex group ( p < 0.05 ) .
symbols * and 
 indicate significantly lower or significantly higher values , respectively , in the same 
 subjects compared to the values obtained before the start of the intervention period 
 ( p < 0.05 )
obesity not only increases the rate of occurrence of type 2 diabetes mellitus , 
 hypertension , and cardiovascular disease11 , 12 , but it has also been recently reported to 
 be closely associated with the development of neurodegenerative disorders13 , 14 .
one of plausible causes of neurodegeneration is obesity - induced 
 increase in the level of high oxidative stress in the body15 . in our study , to examine the effect of regular aerobic exercise on 
 oxidative stress level and neurogenesis in obese subjects , the peripheral levels of mda , 
 bdnf , and ccl11 were measured .
it was found that plasma mda and ccl11 levels were decreased , 
 whereas serum bdnf levels were significantly increased after 8 weeks of aerobic exercise . 

this result corroborates observations in previous studies that showed significantly lower 
 plasma mda and ccl11 levels and , at the same time , significantly higher serum bdnf levels 
 after regular exercise training in patients with a metabolic syndrome that included obesity 
 as a clinical feature .
reported that 8 weeks of low - intensity exercise 
 significantly decreased plasma mda levels in overweight patients with type 2 diabetes5 , while choi et al .
found that 12 weeks of 
 exercise training significantly reduced plasma ccl11 levels in patients with obesity10 .
in addition , lee et al . observed 
 significantly increased serum bdnf levels in obese patients after 12 weeks of aerobic 
 exercise6 . in the present study , changes in the indexes related to obesity and levels of serum glucose 
 and
plasma mda suggested that the significantly lower plasma ccl11 levels and significantly 
 higher serum bdnf content were due to regular aerobic exercise . by inducing the improvement 
 of body composition and reducing fasting glucose level , regular exercise alleviated 
 oxidative stress in the body .
this interpretation is supported by previous studies , which 
 had reported that obesity elevates oxidative stress levels and induces ccl11 release 
 following the increase in the reactive oxygen species ( ros ) production8 , 15 . increased 
 oxidative stress could , in turn , induce down - regulation of neurotrophic factors7 .
in addition , it was reported that high 
 blood glucose concentration induces ros production via various biochemical signaling 
 cascades , such as glucose autoxidation , increase in advanced glycation end - products 
 synthesis , and activation of the polyol pathway , thereby leading to increased oxidative 
 stress in a variety of tissues16 . on the 
 other hand
, it has been reported that in addition to improving obesity symptoms , regular 
 exercise could reduce fasting glucose concentration and levels of mda , an indirect oxidative 
 stress marker17 , 18 . in conclusion
, it is suggested that regular exercise can induce neurogenesis in obese 
 individuals by increasing bdnf levels , while concomitantly reducing ccl11 levels . 

alleviation of oxidative stress could be a principal mediator of these physiological and 
 biochemical changes .
 [ purpose ] the aim of the present study was to investigate the effects of aerobic exercise 
 training on the levels of peripheral brain - derived neurotrophic factor and eotaxin-1 in 
 obese young men . [ subjects and methods ] the subjects included sixteen obese young men with 
 a body mass index greater than 25  kg / m2 . 
 they were randomly divided between 
 control and exercise groups ( n = 8 in each group ) . 
 the exercise group performed treadmill 
 exercise for 40  min , 3 times a week for 8 weeks at the intensity of 70% heart rate 
 reserve . 
 blood collection was performed to examine the levels of serum glucose , plasma 
 malonaldehyde , serum brain - derived neurotrophic factor , and plasma eotaxin-1 before and 
 after the intervention ( aerobic exercise training ) . 
 [ results ] following the intervention , 
 serum bdnf levels were significantly higher , while serum glucose , plasma mda , and plasma 
 eotaxin-1 levels were significantly lower than those prior to the intervention in the 
 exercise group . [ conclusion ] aerobic exercise training can induce neurogenesis in obese 
 individuals by increasing the levels of brain - derived neurotrophic factor and reducing the 
 levels of eotaxin-1 . 
 alleviation of oxidative stress is possibly responsible for such 
 changes . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION