Epidemiologic and laboratory studies suggest a
cancer protective effect and/or lack of a
tumor promoting effect by dietary
olive oil as compared with other types of non-marine
oils.
Squalene, a constituent of
olive oil, and a key intermediate in
cholesterol synthesis may be regarded as partially responsible for the beneficial effects of
olive oil, which include decreased mortality rates among populations with high
olive oil consumption. Thus, in this study we have assessed the chemopreventive efficacy of
squalene on
azoxymethane (AOM)-induced colonic
aberrant crypt foci (ACF). In addition, we measured the effect of
squalene on serum
cholesterol levels in the rats. Male F34 rats (5 weeks old) were fed the control diet (modified AIN-76A) or experimental diets containing 1%
squalene or 320 p.p.m.
sulindac. Two weeks later, all animals except those in vehicle (
normal saline)-treated groups were s.c. injected with AOM (15 mg/kg body wt, once weekly for 2 weeks). At 16 weeks of age, all rats were killed, colons were evaluated for ACF and serum was assayed for the
cholesterol levels. As expected, dietary administration of
sulindac suppressed ACF development and reduced crypt multiplicity, i.e. number of aberrant crypts/focus. Administration of dietary
squalene inhibited total ACF induction and crypt multiplicity by approximately >46% (P < 0.001). Further,
squalene at a level of 1% did not show any significant effect on serum
cholesterol levels. Our finding that
squalene significantly suppresses colonic ACF formation and crypt multiplicity strengthens the hypothesis that
squalene possesses chemopreventive activity against colon
carcinogenesis.