Physical activity, body mass index, and prostaglandin E2 levels in rectal mucosa.
BACKGROUND
Evidence suggests a relationship between prostaglandin levels in 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 investigated whether higher levels of leisure-time physical activity or a lower BMI was associated with lower concentrations of prostaglandin E2 (PGE2) 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 randomized clinical trial testing the effects of piroxicam on rectal mucosal PGE2 levels. An [125I]PGE2 radioimmunoassay kit was used to determine PGE2 levels in samples of extracted rectal mucosa collected before randomization. Leisure-time physical activity was assessed through a self-administered questionnaire collected at baseline. The reported time spent at each activity per week was multiplied by its typical energy expenditure, expressed in metabolic equivalents (METs), to yield a MET-hours per week score. A repeated measures model was used to assess the effect of BMI and physical activity as predictors of PGE2 concentration. All statistical tests were two-sided.


RESULTS
After adjustment for age, a higher BMI was associated with higher PGE2 levels (P = .001). A higher level of leisure-time physical activity was inversely associated with PGE2 concentration (P<.03). An increase in BMI from 24.2 to 28.8 kg/m2 was associated with a 27% increase in PGE2. An increase in activity level from 5.2 to 27.7 MET-hours per week was associated with a 28% decrease in PGE2.


CONCLUSIONS
Physical activity and obesity may alter the risk of colon cancer through their effects on PGE2 synthesis.
Martínez
M E
ME
Arizona Cancer Center and Arizona Prevention Center, University of Arizona, Tucson 85724, USA. emartinez@azcc.arizona.edu
Heddens
D
D
Earnest
D L
DL
Bogert
C L
CL
Roe
D
D
Einspahr
J
J
Marshall
J R
JR
Alberts
D S
DS
D000328:Adult; D000368:Aged; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D015992:Body Mass Index; D015179:Colorectal Neoplasms / Q000209:etiology / Q000517:prevention & control; D015232:Dinoprostone / Q000378:metabolism*; D015444:Exercise; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D007899:Leisure Activities; D008297:Male; D008875:Middle Aged; D010894:Piroxicam / Q000494:pharmacology; D011863:Radioimmunoassay; D016032:Randomized Controlled Trials as Topic; D012007:Rectum; D012306:Risk; D012307:Risk Factors
D000894:Anti-Inflammatory Agents, Non-Steroidal; D010894:Piroxicam; D015232:Dinoprostone