The Influence of Variation in the Catechol-O-methyltransferase Gene on Perceptual Response to Exercise

THE INFLUENCE OF VARIATION IN THE CATECHOL-O-METHYLTRANSFERASE GENE ON PERCEPTUAL RESPONSE TO EXERCISENikhil Satchidanand, PhDUniversity of Pittsburgh, 2010INTRODUCTION: Exercise is a psycho-physiological stressor that activates the hypothalamic-pituitary-adrenal axis, eliciting increased catecholamine production. The catechol-O-methyltransferase (COMT) gene codes for the enzyme that catabolizes catecholamines as part of antinonciception. Haplotypes of COMT are implicated in interindividual differences in sensation of pain and possibly exertional perception.PURPOSE: To examine the influence of haplotypes of COMT on exertional perceptions and lower-body pain (LBP) during a sub-maximal graded exercise test (GXT) among adults.METHODS: Subjects (n=169, 55% female, mean age: 29.16 + 4.10 yrs) completed one sub-maximal GXT to 85% of age-adjusted maximal heart-rate. Oxygen uptake (VO2), minute ventilation (VE) and heart rate were measured at each stage. Ratings of perceived exertion (RPE; OMNI Scale) were estimated for the overall body (RPE-O), legs (RPE-L), and chest (RPE-C) at 2:45 of each stage. Exercise-induced LBP (Cook Pain Scale) was assessed at 2:55. One sample for DNA extraction was collected. Subject categories were Low Responder (LR), Average Responder (AR), or High Responder (HR). For each subject, linear regression models were generated for RPE or Pain expressed as a function of each physiological criterion variable. A separate slope was calculated for each regression model. Slopes were compared among subgroups via ANCOVA, controlling for age and physical activity.RESULTS: For males when RPE (Legs, Chest) was expressed as a function of %VO2max, HR subjects exhibited higher (p < .001) slopes than LR subjects. When RPE-L was expressed as a function of VE, HR subjects exhibited higher (p <.001) slopes than LR subjects. Finally, among males when RPE (Legs, Chest) was expressed as a function of heart rate, HR subjects exhibited higher (p < .001) slopes than LR subjects. No significant differences existed among females for any of the associations. For both males and females, when LBP was expressed as a function of each physiological criterion variable, HR subjects exhibited significantly higher slopes than LR subjects (p < .001).CONCLUSIONS: Haplotypes of the COMT gene appear to influence interindividual differences in exertional perceptions and LBP during a sub-maximal GXT. Subjects with the HR genotype exhibited higher RPEs and LBP than LR subjects at a given workload