A role for dopamine neurotransmission in the regulation of motor activity and reinforcement of behavior is supported by considerable evidence. We studied the association between a marker in the dopamine D2 receptor gene (DRD2) and physical activity level in two cohorts. A first cohort consisted of 721 participants from 161 families of the Quebec Family Study (QFS). Physical activity phenotypes were obtained from a three-day diary and a questionnaire probing physical activity during the past year. The second cohort was the HERITAGE Family Study (HERITAGE), which included 275 Black and 497 White participants from 228 families, among whom past year leisure time and occupational physical activity were probed. A fragment length polymorphism in exon 6 of the DRD2 gene was detected by the polymerase chain reaction (PCR) and NcoI digestion. Frequencies for the T and C alleles were 28% and 72% in the QFS. In the QFS, TT homozygote women had 25% and 34% lower age and BMI-adjusted physical activity level during the past year, compared to CC homozygotes and CT heterozygotes (F=4.42, P=.016). The DRD2 genotype was not associated with the QFS phenotypes obtained from the three-day diary. In the HERITAGE, the frequency of the T allele was 30% among Whites and 63% among Blacks. Similarly, the TT homozygote White women had 29-38% lower sports index (F=4.09, P=.023) and 27-33% lower work index (F=6.23, P=.004) than the CC homozygotes and CT heterozygotes. The results suggest that DNA sequence variation in the DRD2 gene is associated with physical activity levels among White women.
Bibliographical noteFunding Information:
The Quebec Family Study has been supported by multiple grants from the Medical Research Council of Canada (PG-11811, MT-13960, and GR-15187). The HERITAGE Family Study is supported by the National Heart, Lung, and Blood Institute through grants HL-45670 (to Dr. Bouchard), HL-47323 (to Dr. Leon), HL-47317 (to Dr. Rao), HL-47327 (to Dr. Skinner), and HL-47321 (to Dr. Wilmore). Dr. Leon is partially supported by the Henry L. Taylor Endowed Professorship in Exercise Science and Health Enhancement. Dr. Bouchard is partially supported by the George A Bray Chair in Nutrition. This study was also supported by training grants from the Academy of Finland and the Finnish Ministry of Education to Dr. Simonen.
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