Exercise and intestinal polyp development in APCMin mice.
OBJECTIVE
Epidemiological evidence suggests that physical activity protects against colon cancer. We previously used a mouse predisposed to intestinal polyps (APCMin) to evaluate this association and found the suggestion of fewer polyps in exercised males but not females. The present study was designed to further explore the potential exercise x sex interaction on polyp development and to begin to look at potential mechanisms.


METHODS
Six-week-old APCMin mice (N = 60 males; 60 females) were randomly assigned to one of two groups by sex: treadmill running at 20 m.min-1, 5% grade, 45 min.d-1, 5 d.wk-1 (EX) or nonrunning controls (CON) (N = 30 per group). EX mice ran in running wheels while in quarantine (weeks 0-3), followed by treadmill running weeks 3-8. Body weights were measured weekly. Urine was collected at 5 wk and fasting blood at 7.5 wk. Body composition was measured, serum was frozen, and polyp number and size were measured at sacrifice.


RESULTS
EX resulted in lower body weights (P < 0.01) and reduced fat mass (P < 0.01). Fasting glucose was lower in EX (P < 0.01), and leptin was lower in EX (P = 0.05) compared with CON. EX did not affect serum insulin-like growth factor-1 or urinary corticosterone. Total polyp number and size were not statistically different between groups; however, there were fewer jejunal polyps in EX (3.6 +/- 0.7, mean +/- SE) versus CON males (5.2 +/- 0.8; P = 0.04) and an even larger difference when only the consistent runners were kept in the analysis (2.7 +/- 0.5 in EX; P = 0.01).


CONCLUSIONS
Despite favorable changes in body composition, blood glucose, and leptin, 8 wk of running resulted in only minor changes related to polyp development in male but not female APCMin mice.
Colbert
Lisa H
LH
National Institute on Aging/NIH, Bethesda, MD 20892, USA.
Mai
Volker
V
Perkins
Susan N
SN
Berrigan
David
D
Lavigne
Jackie A
JA
Wimbrow
Heather H
HH
Alvord
W Gregory
WG
Haines
Diana C
DC
Srinivas
Pothur
P
Hursting
Stephen D
SD
D000818:Animals; D001823:Body Composition; D001835:Body Weight; D004195:Disease Models, Animal; D005260:Female; D006728:Hormones / Q000097:blood; D007417:Intestinal Polyps / Q000517:prevention & control*; D020738:Leptin / Q000097:blood; D008297:Male; D051379:Mice; D012420:Running; D012727:Sex Characteristics
D006728:Hormones; D020738:Leptin