oxygen is essential for maintaining homeostatic function , but small amounts of active 
 oxygen species are constantly produced in all cells with aerobic metabolism .
they are 
 normally reduced in an organism s scavenging system , but with breakdown of the scavenging 
 system or accumulation of active oxygen species when the amount of active oxygen produced 
 exceeds the capacity of the scavenging system , highly reactive active oxygen species are 
 produced and oxidative stress occurs1 . 

oxidative stress is thus a state in which the balance between oxidation reactions ( degree of 
 oxidative stress ) and anti - oxidation reactions ( antioxidant capacity ) in a body is disrupted 
 and shifts toward oxidation reactions , which is unfavorable for the body .
generally , oxygen 
 flux to tissues increases during exercise2 , leading to generation of a marked increase in oxidative stress . 

oxidative stress contributes to senescence3 and induces lifestyle - related diseases and various other 
 diseases4 .
therefore , the level to which 
 defense systems ( antioxidant capacity ) against oxidative stress can be enhanced through 
 antioxidant enzyme systems and consumption of antioxidant substances becomes important .
the 
 effects on oxidative stress and antioxidant capacity in small animals ( rats ) exposed to 
 exercise have been investigated5 , but few 
 reports have investigated the relationships of consumption of vitamin c , which is sensitive 
 to oxidative stress , or foods containing ubiquinol ( reduced form of coenzyme q10 , 
 h2coq10 : qh ) radical - scavenging antioxidants6 , 7 with exercise ability , the 
 oxidative stress defense system , and senescence8 , 
 9 . moreover , there are no reports on the 
 effects of long - term consumption of different foods ( antioxidants ) on exercise capacity and 
 degree of oxidative stress .
coenzyme q ( coq ) is synthesized in the same mevalonate pathway 
 as cholesterol and is present in all organs and cells .
it has the two following major 
 actions : activation of energy production and antioxidant action10 . in humans and other mammals ,
the main forms of coq are 
 plasma ubiquinone ( plasma oxidized form of coq10 ) and qh , but nearly all coq is present in a 
 reduced form ubiquinol .
the oxidized form is converted to the reduced form by nad(p)h 
 oxidase ( oxidation - reduction enzyme ) in the body , and the ability to perform this conversion 
 decreases with age11 .
consumption of coq 
 by mice is reported to increase plasma coq10 values12 , 13 , but there are no reports 
 on the effects of long - term consumption of different foods on the reduced ratio . in this study
, the effects of differences in the amount of qh consumed over a long period 
 on oxidative stress defense systems , including exercise capacity and degree of oxidative 
 stress , and senescence were investigated in an animal experiment .
twenty - three senescence - accelerated mouse p1 ( samp1/sku slc ) ( 39 weeks old ) mice were 
 randomly divided into two groups : one consuming a relatively high amount of qh ( 300  mg / kg , 
 n=12 : group a ) and the other a relatively low amount ( 30  mg / kg , n=11 : group b ) . at 39 weeks 
 of age
, all mice were made to perform running exercise twice to become acclimated to the 
 treadmill ( model tm - r - n1 , osaka microsystems , ibaraki , japan ) ( i , speed 20 m / min , tilt 0 
 degrees , time 30  min ; ii , speed 20 m / min , tilt 10 degrees , time 30  min ) . the first running 
 exercise ( i )
was done five days before measurement of running time , and the second exercise 
 ( ii ) was performed four days before measurement .
all of the samp1 mice were kept at room 
 temperature ( 201c ) , with a relative humidity of about 50% and a light - dark cycle of 12 
 hours ; food ( ce-2 , clea japan , inc .
the samp1 mice used in this study were useful in that senescence was accelerated after the 
 mice grew up , and they were assumed to live for 50% of their survival time ( 297 days on 
 average)10 . in this study , running time ( exercise capacity ) , the oxidative stress regulation system , 
 senescence grading scores , and weight were measured at 39 to 76 weeks of age .
the number of 
 dropouts by 10 months of qh consumption ( age 76 weeks ) was eight ( 35% ) overall .
the reasons 
 were unknown in six cases and other in two ( time of blood sampling or time of senescence 
 level determination ) ( fig .
the study was 
 performed on 23 male samp1 mice ( 39 weeks old ) , which were randomly divided into two 
 groups : one consuming a high amount of qh ( 300  mg / kg , n=12 , group a ) and the other 
 consuming a low amount of qh ( 30  mg / kg , n=11 , group b ) .
the study was 
 performed on 23 male samp1 mice ( 39 weeks old ) , which were randomly divided into two 
 groups : one consuming a high amount of qh ( 300  mg / kg , n=12 , group a ) and the other 
 consuming a low amount of qh ( 30  mg / kg , n=11 , group b ) .
eight mice were excluded 
 ( 35% ) . a treadmill with the speed set to 25 m / min and tilt at 20 degrees was used for the exercise 
 load .
both groups were made to run on the treadmill until exhaustion , and the total running 
 duration was measured .
the termination criterion for the limit of running was decided as the 
 point at which the time interval of electrostimulation delivered to the back of the running 
 surface of the treadmill fell below 5 seconds8 , 9 . using analytical equipment for reactive oxygen and free radicals ( model fras4 , h&d , 
 parma , italy ) , the d - rom test value ( reactive oxygen metabolites test : degree of oxidative 
 stress ) and bap test value ( biological antioxidant potential ) were measured in a resting 
 state , and then the latent antioxidant potential ( b / r ratio ) was calculated . as an oxidative 
 stress marker , the values of plasma qh and plasma ubiquinone (
plasma oxidized form of coq10 , 
 plasma q10 ) were measured using an electrochemical detector ( shiseido co. , ltd . ,
tokyo , 
 japan ) , and the reduced ratio ( plasma qh value / plasma qh value + plasma q10 value ) was 
 calculated . for the d - rom and bap measurements ,
blood was extracted from the tail vein and 
 centrifuged immediately ( for five minutes at 6,000  rpm ) to obtain blood plasma for 
 analysis . in the d - rom test ,
the levels of free radicals in the body , especially hydrogen peroxide 
 concentrations , were measured ( unit : u.carr , 1 u.carr = 0.08 bmg / dl of hydrogen peroxide ) 
 according to the optical measurement method ( color reaction ) , and the measured values 
 indicated the degree of oxidative stress ( oxidative reaction)14 , 15 . meanwhile , in the bap 
 test , the levels were measured ( unit : m ) by the reduction action of antioxidant materials 
 in blood plasma , and the measured values indicated the degree of antioxidant potential 
 ( antioxidant reaction ) .
that is , the amount of blood plasma reduced to ferrous ions when 
 mixed with reagents containing ferric ions was measured as the decoloring level of the color 
 reaction liquid according to the optical measurement method .
the content of iron ions to 
 which blood plasma is reduced is the antioxidant potential14 , 15 .
the b / r ratio , which 
 was calculated on the basis of the values obtained in the bap test and the d - rom test , 
 indicates the degree of latent antioxidant potential . in other words ,
the 
 reduced ratio is affected by decreases ( or increases ) in the plasma qh value due to 
 oxidative stress and the amount of nad(p)h oxidase ( oxidation - reduction enzyme ) needed for 
 re - reduction of the plasma oxidized form of coq107 , 
 16 , 17 .
thus , the reduced ratio reflects the ability to convert the plasma 
 oxidized form of coq10 to plasma qh , which indicates anti - oxidation and is present in 
 abundance in the body .
senescence grading scores , which were designed to evaluate senescence more objectively , 
 were graded according to changes in hair luster , lesions around the eyes , curve of the 
 spine , and so on10 .
senescence grading 
 scores are generally used as an acceptance criterion for the aging process .
higher scores 
 mean that the aging process is accelerated . in the present study ,
weight was measured in a resting state at the age of 38 weeks 
 using scales for animals ( kn type manufactured by natsume seisakusho co. , ltd . ,
qh ( 30% stabilized powder ) was mixed in the animals 
 water bottles and consumed daily .
running time , the d - rom test , the bap test , and the senescence score were measured three 
 times : at the start of the study ( age 39 weeks ; baseline ) , after consumption of qh for seven 
 months ( age 63 weeks ; 7 mo ) , and after consumption of qh for 10 months ( age 76 weeks ; 10 
 mo ) .
plasma qh values and plasma q10 values were measured twice , at baseline and at 10 
 mo .
spss ( ibm , tokyo , 
 japan , ver 19.0 for windows ) was used for statistical analyses , and the wilcoxon signed - rank 
 test was used to test the significance of the differences .
this study was conducted with the 
 approval of the animal research committee of saitama prefectural university ( approval 
 number : 39 ) .
the running time , senescence score , and weight were compared between the two groups . at 10 
 mo ,
only the senescence score was significantly lower in group a , and thus inhibition of 
 senescence was seen ( p<0.05 ) ( table 
 1table 1 .
changes in running time and senescence grading scoresbaseline7 months of qh consumption10 months of qh consumptionn(39 weeks old)(63 weeks old ) : 7 mo(76 weeks old ) : 10 morunning times ( min)group a21.886.099.594.047.883.987group b19.926.817.582.534.282.428senescence grading scores ( points)group a2.40.47.10.89.10.97group b2.50.58.10.510.61.1 * 8weight ( g)group a36.22.033.03.534.63.07group b33.72.131.92.434.72.88d - rom test ( u.carr ) group a113.63.8114.220.9125.810.77group b115.18.7118.211.6163.342.4 * 8bap test ( m / l)group a2286.484.22098.5546.02601.2280.67group b2189.858.8 * 2606.7225.4 * 2537.2154.28bap / d - rom ( ratio)group a20.21.218.43.020.82.77group b19.11.422.33.2 * 16.53.8 * 8group a , high amount of qh ( 300  mg / kg ) ; group b , low amount of qh ( 30  mg / kg ) ; qh , 
 ubiquinol ( reduced form of coenzyme q10 , h2coq10 ) ; d - rom test , reactive oxygen 
 metabolites test ; bap test , biological antioxidant potential ; bap / d - rom ratio , 
 calculated on the basis of the values obtained in the bap test and d - rom test ; values 
 are meanssd . * p<0.05 compared with the value in the intergroup comparison by the 
 wilcoxon signed - rank test . )
. the mean rate of change in running time from baseline to 10 mo was 
 62.620.6% in group a and 77.713.8% in group b ( difference in mean percentage change 
 between the groups : 15.1% ) .
the d - rom test value , bap test value , and b / r ratio were 
 compared between the two groups . at 10 mo ,
the d - rom test value was significantly higher in 
 group b , and the bap / d - rom ratio was significantly lower ( both p<0.05 ) ( table 1 ) . for the bap test value and the b / r ratio 
 at 7 mo , a significant decrease was seen in group a ( both p<0.05 ) , and thus , variation 
 was seen .
group a , high amount of qh ( 300  mg / kg ) ; group b , low amount of qh ( 30  mg / kg ) ; qh , 
 ubiquinol ( reduced form of coenzyme q10 , h2coq10 ) ; d - rom test , reactive oxygen 
 metabolites test ; bap test , biological antioxidant potential ; bap / d - rom ratio , 
 calculated on the basis of the values obtained in the bap test and d - rom test ; values 
 are meanssd . * p<0.05 compared with the value in the intergroup comparison by the 
 wilcoxon signed - rank test .
comparisons of the plasma qh values , plasma oxidized form of coq10 value , and the reduced 
 ratios between the two groups showed significant increases in the plasma qh value and 
 reduced ratio at 10 mo in group a ( both p<0.001 ) ( table 2table 2 .
changes in oxidative stressbaseline10 months of qh consumptionn(39 weeks old)(76 weeks old):10 moplasma qh ( g / ml)group a 0.0350.024 0.2200.0937group b 0.0330.023 0.0410.017***8plasma q10 ( g / ml)group a 0.0250.005 0.0650.0157group b 0.0300.014 0.0480.0158reduced ratio ( % ) group a55.1147.90075.339 6.2007group b50.77711.60046.22710.300***8group a , high amount of qh ( 300  mg / kg ) ; group b , low amount of qh ( 30  mg / kg ) ; qh , 
 ubiquinol ( reduced form of coenzyme q10 , h2coq10 ) ; plasma qh , plasma concentration of 
 qh ; plasma q10 , plasma concentration of ubiquinone ; reduced ratio , calculated from 
 plasma qh and plasma q10 ; values are meanssd .
* * * p<0.001 compared with the value 
 in the intergroup comparison by the wilcoxon signed - rank test . p<0.05 
 compared with the value in the baseline by the wilcoxon signed - rank test . ) . in group
b , a significant increase only in the plasma q10 value was seen at 
 10 mo compared with baseline ( p<0.05 ) .
group a , high amount of qh ( 300  mg / kg ) ; group b , low amount of qh ( 30  mg / kg ) ; qh , 
 ubiquinol ( reduced form of coenzyme q10 , h2coq10 ) ; plasma qh , plasma concentration of 
 qh ; plasma q10 , plasma concentration of ubiquinone ; reduced ratio , calculated from 
 plasma qh and plasma q10 ; values are meanssd . * * * p<0.001 compared with the value 
 in the intergroup comparison by the wilcoxon signed - rank test .
p<0.05 
 compared with the value in the baseline by the wilcoxon signed - rank test .
ubiquinol ( qh ) has engendered interest as a supplement ingredient that has both an energy 
 production activating effect and an antioxidant action .
its physiological effects have been 
 verified in various investigations12 , 17,18,19 ; however , its effects on exercise capacity 
 and the oxidative stress defense system when consumed in different amounts over a long 
 period remain unknown .
the importance of this study lies in the fact that it was a basic 
 study to investigate measures to raise exercise capacity , taking into account the oxidative 
 stress defense system .
coq10 shows an antifatigue effect and has been widely used by athletes to increase physical 
 strength19 .
when running time was 
 compared in the two groups in this study at 10 mo , no significant difference was seen ; 
 however , the mean percentage change from baseline to 10 mo was a decrease of 62.6% in group 
 a , compared with a decrease of 77.7% in group b. thus , a difference of 15.1% was seen 
 between the groups .
this suggests that high - dose consumption of qh inhibits decreases in 
 running time , and a relationship is thought to exist between dosage and maintenance of 
 physiological effects associated with running time .
these physiological effects related to 
 running showed similar tendencies as in a previous study20 with consumption of the oxidized form of coq10 .
in other words , not 
 only does cardiac muscle metabolism increase with mitochondrial activation ( increase in 
 cardiac output ) , but oxygen demand to active muscle is also adequately compensated by 
 actions such as decreased peripheral vascular resistance ( increased oxygen availability in 
 the periphery ) , and the effect is thought to be maintained . in general exercise ,
oxygen uptake in the body occurs with the purpose of continuous atp 
 production , and so the generation of oxidative stress increases with prolonged running time 
 ( or a decrease is inhibited)21 .
it has 
 also been reported that exercise , through promotion of oxidative stress , may increase the 
 expression of enzymes and proteins in the body s defense systems , including antioxidant 
 enzymes , and may inhibit expression of inflammation - related enzymes22 .
such activation of antioxidant enzymes has been indicated 
 to have a compensatory effect against increased generation of oxidative stress23 .
the body has defense mechanisms using the 
 elimination action of vitamin c24 and the 
 coq10 redox cycle19 , 25 against continuous exposure to oxidative stress .
the coq10 redox 
 cycle is a mechanism that maintains qh in the body by reductase , and it is an important 
 defense mechanism that reduces the oxidative stress produced by exercise . despite the 
 suggestion in this study that the decrease in running time at 10 mo was inhibited in group 
 a , a significant decrease was seen in the d - rom test value .
this suggests the possibility 
 that exercise - induced oxidative stress was mitigated in group a , and that the coq10 redox 
 cycle defense mechanism was activated .
it therefore stands to reason that the increase in 
 exercise - induced oxidative stress is inhibited by activation of biological defense systems . 
 in this study ,
the senescence score at 10 mo was significantly lower in group a than in 
 group b , and the d - rom test value and b / r ratio were significantly lower .
this suggests an 
 association between the senescence score and the d - rom test vaiue and b / r ratio .
generally , 
 the main factors related to the effects of senescence on the body are deterioration of the 
 elimination function with respect to continuous oxidative stress and promotion of senescence 
 by the resulting augmentation of oxidative stress3 .
consequently , the significantly decreased senescence score ( senescence inhibition effect ) 
 is thought to result from a decrease in oxidative stress from the antioxidant action of qh 
 itself7 , and maintenance of the 
 antioxidant system with the production of atp26 .
group a is therefore thought to have maintained the oxidative 
 stress elimination function and latent antioxidant function better than group b , with 
 delayed senescence as a result .
group a showed a significant increase in the plasma qh value and the reduced ratio at 10 mo 
 compared with group b. the general energy state is thus thought to have improved due to 
 activation of energy production in group a , leading to the improvement of the reduced ratio 
 during exposure to exercise - induced oxidative stress . in group
b , a significant increase was 
 seen only in ubiquinone at 10 mo compared with baseline .
the plasma qh value is therefore 
 thought to indicate oxidation from exposure to exercise - induced oxidative stress . 

investigations of 
 qh levels in organs and other factors will be needed in the future .
group a showed a significant decrease in the b / r ratio at 7 mo , but variation was seen . 
 considering that reduction of ferric ion
is evaluated using plasma in the bap test , it is 
 possible that the level of reduction reflects the effects from qh consumption together with 
 a general improvement in the antioxidative state ( for example , effects from vitamin c or 
 other antioxidants ) .
comprehensive evaluations of antioxidant activity based on 
 investigations of plasma vitamin c levels and other factors will be needed in the 
 future .
   [ purpose ] this study examined how exercise capacity and the 
 oxidative stress regulation system are affected by different amounts of dietary ubiquinol 
 ( reduced form of coenzyme q10 , h2coq10 : qh ) over the long term . 
 [ subjects and 
 methods ] twenty - three senescence - accelerated mouse p1 ( samp1 ) mice were randomly divided 
 into two groups : one consuming a relatively high amount of qh ( 300  mg / kg ; group a ) and the 
 other a relatively low amount ( 30  mg / kg , group b ) . 
 food and tap water were provided ad 
 libitum . 
 both groups were made to run on a treadmill until exhaustion , and total running 
 duration was measured . 
 for the oxidative stress regulation system , the d - rom test value 
 ( degree of oxidative stress ) and bap test value ( antioxidant potential ) were measured in a 
 resting state , and then the bap / d - rom ratio ( b / r ratio ) was calculated . 
 the values of 
 plasma qh and plasma ubiquinone ( plasma oxidized form of coq10 ) were also measured , and 
 the reduced ratio was calculated . 
 measurements were taken 3 times : at the start of the 
 study when the animals were 39 weeks old ( baseline ) , after consumption of qh for 7 months 
 ( 7 mo ) , and after consumption of qh for 10 months ( 10 mo ) . 
 [ results ] the senescence score 
 at 10 mo was significantly lower in group a. comparison of the mean percentage change in 
 running time showed a difference of 15.1% between the 2 groups . at 10 mo , the d - rom test 
 value was significantly increased and the b / r ratio was significantly decreased in group 
 b. significant increases in the plasma qh value and reduced ratio were seen in group a. 
 [ conclusion ] group a showed a greater decrease in the d - rom test and increase in the 
 reduced ratio than group b. thus , a dose - dependent effect of qh consumption was 
 demonstrated . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION