Dopamine D2 receptor genotypes and physical activity levels
Nugent, Colleen Ann
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Objective . Dopamine influences physical activity via effects on motivation, reward, participation in physical activity and locomotion. Taq1 A1 allele of the DRD2 gene is related to a reduction in the number of D2 receptors. The reduced density is directly associated with reduced physical activity. The DRD2 A1 allele is associated with reduced D2 receptors; therefore, this genotype may be related to a more sedentary lifestyle. Methods . We examined the association between DRD2 genotypes and objectively measured physical fitness and physical activity. The 31 adult subjects (13 females, 18 males) who had previous DRD2 genotyping, performed a submaximal cycle ergometer test to approximate activity and aerobic fitness. Wearing an accelerometer, subjects walked on a treadmill at an exercise intensity of 3 Mets to determine the intensity (g) value associated with each subject's moderate to vigorous physical activity level (MVPA, ≥3 Mets). They then wore the accelerometers for 2 weekdays and one weekend day to determine free-living physical activity levels. Group differences in physical activity and aerobic fitness were analyzed using a 2 sex by 2 genotype ANOVA. Results . Females with an A1 allele participated in 33% less physical activity than females without an A1 allele (866.2 ± 120.0 vs.1291.0 ± 96.0min, p =0.01) attributed to less low intensity (≤3 Mets) physical activity (766.8 ± 100.9 vs.1150.1 ± 80.1min, p =0.005). There was no effect of genotype on MVPA or fitness in females. There was no effect of DRD2 genotype on the males total activity time, low intensity physical activity, MVPA or fitness. Conclusions . Females with a dopamine A1 allele that is associated with fewer D2 receptors have lower objectively measured physical activity levels than females with a genotype associated with a greater number of D2 receptors.