an elevated plasma level of low - density lipoprotein ( ldl ) is a risk factor for atherosclerosis , mainly because this lipoproteins deposit cholesterol within cells of the arterial wall ( 1 ) .
also , multiple epidemiological studies have shown that plasma level of high - density lipoproteins ( hdl ) , and their main protein constitutive apolipoprotein a - i ( apoa - i ) are inversely correlated with the risk of atherosclerosis .
in addition , the rise of hdl cholesterol prevents atherogenesis in multiple genetic animal models ( 1 ) .
this protective effect of hdl - c against atherosclerosis ( 2 ) is due to the role of hdl - c in reverse cholesterol transport ( rct ) . in rct ,
hdl - c intermediates the elimination of excess free cholesterol from peripheral cells to liver for secretion as bile ( 3 ) . in rct ,
the production and reconstruction of hdl - c in plasma requires various factors , including atp - binding cassette transporters , especially abca1 , known as one of the key elements of the reverse cholesterol transport pathway ( 4 , 5 ) .
abca1 is abundantly expressed in the liver , brain macrophages and other different tissues ( 6 , 7 ) and facilitates delivery of phospholipids from cell membranes to lipid - poor apo a-1 with the formation of apo a - i with hdl .
hence , it plays a key role in plasma hdl formation ( 8 , 9 ) .
generally , it is accepted that an increase in liver abca1 expression will have a strong effect on formation of plasma hdl - c to protect against atherosclerosis ( 10 , 11 ) .
abca1 is responsible for lipidation of lipid - poor apo a - i by cellular cholesterol and phospholipids , a rate - limiting process in both formation of hdl and cholesterol efflux ( 12 ) .
peripheral factors significantly contribute to changes in abca1 expression and plasma hdl - c in the general population ( 13 ) .
previous reports show that an increase of apo - a release in the liver and small intestine and greater abca1 expression in macrophages have a strong effect on rct process , formation of plasma hdl - c and protection against atherosclerosis ( 5 ) . moreover
, abca1 might play a role in inflammation and is unregulated by several factors such as physical activity , cholesterol influx , plasma glucose concentration and nutritional status ( 14 ) .
so far , only three studies have focused on the effect of physical activity on abca1 expression ( 12 , 15 , 16 ) . in the first study ,
abca1expression was measured in human skeletal muscle biopsies and blood with assessment of physical activity ( habitual exercise ) using the international physical activity questionnaire ( ipaq ) ( 12 ) . in the second research , conducted by butcher et al .
the effect of low - intensity exercise training ( eight weeks of low - intensity exercise program consisting of walking 10000 steps , three times a week ) was studied on blood abca1and abcg1 expression ( 16 ) .
the third study showed that a single circuit resistance exercise ( nine exercises , 25 seconds per exercise , three sets of three without interruption circuits and one minute rest interval between the sets ) at three given intensities ( 40% , 60% and 80% one - repetition maximum ) increased abca1 expression in peripheral blood ( 15 ) . to the best of our knowledge , no study has focused on the effect of aerobic exercise on blood abca1and apoa1 in obese women .
thus , this study was conducted to investigate blood abca1 expression in response to 12 weeks of aerobic exercise in inactive women .
all aspects of the use of human subjects in this study were approved by the ethical committee of urmia university , urmia , iran . written informed consent was obtained from all subjects in accordance with the principles of the helsinki declaration .
thirty - six inactive woman were randomly assigned to con ( n = 18 ) and ex ( n = 18 ) groups .
participants were asked to complete medical tests and the health questionnaire to ascertain that they did not use any kind of drug , and were free of cardiorespiratory , renal and metabolic diseases .
the ex group performed three sessions ( morning)/week of aerobic exercise for 12 weeks and the con group remained sedentary during this period .
the exercise program lasted for 12 weeks , three sessions a week with intensity of between 65 to 75% of participants maximum heart rate .
participants in the first three weeks , the fourth and fifth , and ultimately from sixth to twelfth week exercised with 0.65 , 0.70 and 0.75 maximum heart rate , respectively .
the 0.65 , 0.70 and 0.75 maximum heart rates were related to the original exercises , and heart rate for warming up and walking down were lower than these intensities . each training session consisted of a five - minute stretching program , 10 to 15-minute dynamic warm - up program ,
20 to 30 minutes of core exercises including brisk walking , soft and light running , motion and movement , local endurance and relaxation and so on , finally a ten - minute cooling program and recovery . maximum heart rate for each subject was calculated using the formula ( 220 - age ) , and participants heart rate was controlled using a polar watch ( model : pox 1000 , made in japan ) .
all experiments performed on humans were in accordance with the guidelines of the ethical committee for research on humans of urmia university .
the subjects attended the laboratory 48 hours before the first training session and 48 hours after completion of the course , at 8 am , after overnight fasting and having been abstained from exercise ; 10ml fasting venous blood was obtained from the antecubital vein .
participants weights were measured with a ( sensitivity of 0.1 kg ) digital scale before the initial sampling and at the end of the research program .
plasma hdl - c was determined by the direct immunohistochemistry method ( hdl - c immuno fs , pars azmoon , karaj ) .
the intra - assay coefficient of variation and sensitivity of the method were 1.2% and 0.03 mmol / l , respectively .
fat mass , percentage of body fat and lean mass were assessed with bioelectrical impedance systems ( bia-106 , rjl systems , usa ) .
total cholesterol , triglycerides and plasma hdl - c was determined by the direct immunohistochemistry method ( hdl - c immuno fs , pars azmoon , karaj ) .
the intra - assay coefficient of variation and sensitivity of the method were 1.2% and 0.03 mmol / l , respectively .
fasting blood glucose levels were measured by the god photometric method ( using the glucose kit made by pars azmoon with internal measurement degree of 1.28 and sensitivity of 5 mg / dl ) .
total rna was isolated from peripheral blood using trizol ( invitrogen , inc ) and 1ug rna subjected to reverse transcription using the first strand cdna synthesis kit ( fermentas ) , according to the manufacturer s instructions .
to determine mrna expression level , the following primers were used for abca1 , apo- a1 and gapdh ( as an internal control ) based on gene specific sequences .
abca1-forward : 5'-caaacatgtcagctgctgctggaag-3 ' , abca1-reverse : 5'-gagcctccccaggagtcg-3 ' . gapdh - forward : 5-tcaccatcttccaggagcga-3 ' , gapdh - reverse : 5'- agtgatggcatggactgtgg-3 ' , apo - a1- forward : 5'-cctgggatcgagtgaaggac-3 ' , apo - a1- reverse : 5'-cgtgctcagatgctcggtgg-3 ' ( 18 ) .
polymerase chain reaction was performed for 28 cycles , denaturationat 94c for 30 seconds , annealing at 55c for 30 seconds and development at 72c for 50 seconds .
template cdna was standardized by reinforcement of a 700-bp internal control of gapdh , a house keeping gene .
abca1 cdna was amplified giving a 211-bp product , and apo - a1 cdna was amplified giving a 587-bp product .
all pcr products were electrophoresed on agarosegel and bands were visualized by gel documentation ( pro logic 212 imaging system , carestream , usa ) .
the intensity of the bands was measured by computer - integrated densitometry ( pro logic 212 imaging system , carestream , usa ) .
all aspects of the use of human subjects in this study were approved by the ethical committee of urmia university , urmia , iran . written informed consent was obtained from all subjects in accordance with the principles of the helsinki declaration .
thirty - six inactive woman were randomly assigned to con ( n = 18 ) and ex ( n = 18 ) groups .
participants were asked to complete medical tests and the health questionnaire to ascertain that they did not use any kind of drug , and were free of cardiorespiratory , renal and metabolic diseases .
the ex group performed three sessions ( morning)/week of aerobic exercise for 12 weeks and the con group remained sedentary during this period .
the exercise program lasted for 12 weeks , three sessions a week with intensity of between 65 to 75% of participants maximum heart rate .
participants in the first three weeks , the fourth and fifth , and ultimately from sixth to twelfth week exercised with 0.65 , 0.70 and 0.75 maximum heart rate , respectively .
the 0.65 , 0.70 and 0.75 maximum heart rates were related to the original exercises , and heart rate for warming up and walking down were lower than these intensities . each training session consisted of a five - minute stretching program , 10 to 15-minute dynamic warm - up program ,
20 to 30 minutes of core exercises including brisk walking , soft and light running , motion and movement , local endurance and relaxation and so on , finally a ten - minute cooling program and recovery . maximum heart rate for each subject was calculated using the formula ( 220 - age ) , and participants heart rate was controlled using a polar watch ( model : pox 1000 , made in japan ) .
all experiments performed on humans were in accordance with the guidelines of the ethical committee for research on humans of urmia university .
the subjects attended the laboratory 48 hours before the first training session and 48 hours after completion of the course , at 8 am , after overnight fasting and having been abstained from exercise ; 10ml fasting venous blood was obtained from the antecubital vein .
participants weights were measured with a ( sensitivity of 0.1 kg ) digital scale before the initial sampling and at the end of the research program .
plasma hdl - c was determined by the direct immunohistochemistry method ( hdl - c immuno fs , pars azmoon , karaj ) .
the intra - assay coefficient of variation and sensitivity of the method were 1.2% and 0.03 mmol / l , respectively .
fat mass , percentage of body fat and lean mass were assessed with bioelectrical impedance systems ( bia-106 , rjl systems , usa ) .
total cholesterol , triglycerides and plasma hdl - c was determined by the direct immunohistochemistry method ( hdl - c immuno fs , pars azmoon , karaj ) .
the intra - assay coefficient of variation and sensitivity of the method were 1.2% and 0.03 mmol / l , respectively .
fasting blood glucose levels were measured by the god photometric method ( using the glucose kit made by pars azmoon with internal measurement degree of 1.28 and sensitivity of 5 mg / dl ) .
total rna was isolated from peripheral blood using trizol ( invitrogen , inc ) and 1ug rna subjected to reverse transcription using the first strand cdna synthesis kit ( fermentas ) , according to the manufacturer s instructions .
to determine mrna expression level , the following primers were used for abca1 , apo- a1 and gapdh ( as an internal control ) based on gene specific sequences .
gapdh - forward : 5-tcaccatcttccaggagcga-3 ' , gapdh - reverse : 5'- agtgatggcatggactgtgg-3 ' , apo - a1- forward : 5'-cctgggatcgagtgaaggac-3 ' , apo - a1- reverse : 5'-cgtgctcagatgctcggtgg-3 ' ( 18 ) .
polymerase chain reaction was performed for 28 cycles , denaturationat 94c for 30 seconds , annealing at 55c for 30 seconds and development at 72c for 50 seconds .
template cdna was standardized by reinforcement of a 700-bp internal control of gapdh , a house keeping gene .
abca1 cdna was amplified giving a 211-bp product , and apo - a1 cdna was amplified giving a 587-bp product .
all pcr products were electrophoresed on agarosegel and bands were visualized by gel documentation ( pro logic 212 imaging system , carestream , usa ) .
the intensity of the bands was measured by computer - integrated densitometry ( pro logic 212 imaging system , carestream , usa ) .
the control group did not show any significant difference after the period of training in any of the estimated parameters . however , body mass index ( bmi ) levels decreased significantly in the experimental group after training ( 31  3.39 ) compared to before training ( 34  1.48 ) ( p < 0.05 ) .
similarly , fat percentage analysis was significantly differentafter training ( 28.49  2.94 ) compared to levels before training ( 31.4  3.98 ) in the experimental group . also , the weight parameter was significantly different after training ( 79.38  0.14 ) compared to before training ( 83.61  1.49 ) in the experimental group .
total cholesterol and triglyceride levels were also significantly lower after training ( 167.9  49.7 and 155.19  62.8 ) compared to before training ( 173.5  43.9 and 171.9  65.8 ) in the experimental group ( p < 0.05 ) .
interestingly , aerobic training caused a significant increase in the hdl levels of the experimental group ( p < 0.05 ) while ldl and glucose levels decreased significantly after training ( 5.8  0.7and 94.7  52.5 ) compared to before training ( 8.7  0.7 and 103.9  29.8 ) ( p < 0.05 ) .
data analysis revealed that the expression of abca1 in blood remained unchanged in the control group , yet there was a significant difference between post and pre abca1 ( figure 1 and figure 2 a ) and apo - a1 ( figure 1 and figure 2 b ) gene expression levels in the training group , ( abca1 ; p = 0.036 , t = 2.74 ) , ( apo - a1 ; p = 0.04 , t = 3.20 ) ( figure 2 a and figure 2 b ) .
duplex rt - pcr was performed on rna with primers generating fragments of 211 , 587 and 700 bp for abca1 , apo - a1 and gapdh , respectively .
; b , control before training ; c , test after training and d , control after training . different levels of transcript were seen in control and test individuals .
both abca1 and apoa1 were found in control and test groups before and after training with alternative transcripts being highly up regulated in test individuals after 12 weeks of training .
the abca1 mrna level was measured by densitometry and normalized to gapdh mrna expression level .
the results of this study show that 12 weeks of aerobic exercise attended by inactive women significantly reduced ldl , glucose , triglycerides and total cholesterol while it increased abca1 and apo - a1 expression .
previous studies have demonstrated beneficial effects of exercise on abca1 expression ( 13 , 19 , 20 ) .
moreover , the effect of exercise training programs on rct and its main factors exclusive of abca1 has been reviewed by several researchers , yet to the best of our knowledge this is the fourth human research to show that abca1 is expressed due to exercise in peripheral blood ( 12 , 15 ) .
the results of the current study showed that twelve weeks of regular aerobic exercise with 65 - 75% of hrmax , increased abca1 expression of blood in trained women .
our findings on abca1 expression are somewhat similar to previous findings reported by ghanbari - niaki et al .
they investigated the expression of abca1 mrna in peripheral blood and found a significant increase shortly after exercise at all given exercise intensities ( 40% , 60% and 80% of 1rm ) with more noticeable results for 60% of the group .
ghanbari - niaki et al . reported that abca1 was expressed in blood after exercise of different intensities ( 40% , 60% and 80% of 1rm ) ( 15 ) .
abca1 is a cell membrane transporter that facilitates delivery of phospholipids from cell membranes to lipid poor apoa-1 with the formation of discoidalapoa - i - containing hdl , and it plays a central role in formation of plasma hdl .
hoang et al . reported that participants with high physical activity had higher levels of abca1 expression ( 12 ) .
a low - intensity training program ( eight weeks of low - intensity exercise program consisting of walking 10000 steps , three times a week ) resulted in a 3.46 and 3.06 fold increase in blood abca1 and abcg1 expression ( 16 ) .
our data of plasma hdl - c and ldl - c concentrations were also in line with several previous reports ( 21 - 23 ) . in the study of olchawa
25 endurance - trained male athletes were compared with 33 males enjoying an active lifestyle .
plasma concentrations of hdl - c and apoa - i were higher in athletes compared with active participants ( 24 ) . a meta - analysis carried out by kelley et al .
on human subjects , revealed that aerobic exercise causes significant reduction of blood glucose concentration , total cholesterol ( tc ) , ldl - c , triglyceride ( tg ) and bmi whereas an increase in hdl - c level ( 25 ) .
also reported that participants who performed aerobic activities showed a significant decrease of ldl - c and tc , while an increase in hdl - c , vldl and tg levels ( 26 ) .
hepatic over expression of abca1 in mice led to an increase of plasma hdl - c levels .
in contrast , apoa - i and plasma hdl levels are considerably reduced in mice with a liver - specific elimination of abca1 ( 27 , 28 ) .
therefore , hepatic expression of abca1 is a rate - limiting factor for production of plasma hdl ( 29 ) .
although abca1 in macrophages has little influence on plasma hdl levels , it is a major factor in the prevention of excessive cholesterol agglomeration in macrophages of the arterial wall and evolution of foam cells , independent of plasma hdl levels .
our intervention resulted in a significant increase in abca1 and apoa1 expression , decrease in tc and tg levels , and an increase in hdl - c and ldl - c .
therefore , it could be suggested that an aerobic program can improve tc , tg , and hdl - c levels . in conclusion , the results of this study suggest that aerobic exercise would be appropriate for increasing hdl - c and reducing tc / hdl - c with low cost and minimal side effects .
- aerobic exercises can increase the expression of abca1and apo - a1 genes , which are effective factors in the prevention of cardiovascular disease .
- aerobic program participation also improves tc , tg , and hdl - c levels and reduces tc / hdl - c .
- aerobic exercises can increase the expression of abca1and apo - a1 genes , which are effective factors in the prevention of cardiovascular disease .
- aerobic program participation also improves tc , tg , and hdl - c levels and reduces tc / hdl - c .
 background : atherosclerotic cardiovascular disease is currently a cause of mortality in some parts of the world . 
 the atp - binding cassette transporter ( abca1 ) gene prepares instructions to produce the atp - binding cassette transporter protein whose operation is for export of phospholipids and cholesterol , outside cells where they are limited to apolipoprotein a1 ( apoa1 ) . increased abca1 activity could inhibit atherosclerosis.objectives:in the present study , the effect of aerobic exercise was investigated on gene expression and biochemical parameters.patients and methods : the participants included 36 inactive women , which were randomly assigned to control ( con ) and experimental ( ex ) groups . 
 the ex group performed 12 weeks of aerobic exercise and the con group remained inactive . fasting blood samples were collected 24 hours before the first session and 48 hours after completion of the course . 
 the abca1 and apoa1 gene expressions were measured using semi - quantitative - rt - pcr . 
 data were analyzed by the spss software ( version 18).results : a significant increase in blood abca1 ( ex group p < 0.002 , t = - 9.876 ) and apo a - i ( ex group p < 0.05 , t = 2.76 ) gene expression was shown following the 12 weeks of training . 
 plasma high - density lipoprotein - cholesterol ( hdl - c ) concentration increased ( p < 0.001 , t = 4.90 respectively ) while plasma low - density lipoprotein - cholesterol ( ldl - c ) concentration decreased ( p < 0.001 , t = 4.27 ) in the ex group compared with the con group.conclusions:aerobic exercises can increase abca1 and apo - a1 gene expression . 
 induction of these genes can effectively prevent cardiovascular disease . 
1. Background
2. Objectives
3. Patients and Methods
3.1. Study Subjects
3.2. Training Protocol
3.3. Data Collection
3.4. Statistical Analysis
4. Results
5. Discussion
5.1. Practical Implications