Physical activity, body mass index, and prostaglandin E-2 levels in rectalmucosa

Background: Evidence suggests a relationship between prostaglandin levels i n colonic mucosa and risk of colon cancer. Physical inactivity and a higher body mass index (BMI; weight in kilograms divided by [height in meters](2) ) have been consistently shown to increase risk of this cancer. We investig ated whether higher levels of leisure-time physical activity or a Lower BMI was associated with lower concentrations of prostaglandin E-2 (PGE(2)) in rectal mucosa, Methods: This study was conducted in 41 men and 22 women, 42 -78 years of age, with a history of polyps, who participated in a randomize d clinical trial testing the effects of piroxicam on rectal mucosal PGE(2) levels, An [I-125]PGE(2) radioimmunoassay kit Mras used to determine PGE(2) levels in samples of extracted rectal mucosa collected before randomizatio n. Leisure-time physical activity was assessed through a self-administered questionnaire collected at baseline, The reported time spent at each activi ty per week was multiplied by its typical energy expenditure, expressed in metabolic equivalents (METs), to yield a MET-hours per week score. A repeat ed measures model was used to assess the effect of BMI and physical activit y as predictors of PGE(2) concentration. All statistical tests were two-sid ed. Results: After adjustment for age, a higher BMI was associated with hig her PGE(2) levels (P =.001), A higher level of leisure-time physical activi ty was inversely associated with PGE(2) concentration (P<.03). An increase in BMI from 24.2 to 28.8 kg/m(2) was associated with a 27% increase in PGE( 2), An increase in activity level from 5.2 to 27.7 MET-hours per week was a ssociated with a 28% decrease in PGE(2), Conclusions: Physical activity and obesity may alter the risk of colon cancer through their effects on PGE(2) synthesis.