Effect of diets fortified with tomatoes or onions with variable quercetin-glycoside content on azoxymethane-induced aberrant crypt foci in the colon of rats.
BACKGROUND
Onion and tomato are vegetables widely consumed by humans and epidemiological studies show an inverse association between vegetable consumption and colon cancer risk; however, the effect on colon cancer of diets containing high levels of vegetables like onion and tomato are not clear.


OBJECTIVE
To investigate whether tomatoes and onions,with low or high quercetin-glycoside content, could reduce azoxymethane (AOM)-induced Aberrant Crypt Foci (ACF), preneoplastic lesions in the colon of rats.


METHODS
Male Fisher 344 rats were fed the following diets: a) high fat (HF) diet (control diet); b) HF diet containing 20 % (w/w) tomatoes with a low quercetin-glycoside content (final concentration in the diet: 5 mg/kg of quercetin aglycone equivalents); c) HF diet containing 20% (w/w) high quercetin-glycoside tomatoes (100 mg/kg final concentration of quercetin aglycone equivalents); d) HF diet containing 20 % (w/w) low quercetin-glycoside onions (14 mg/kg of quercetin aglycone equivalents in the diet); e) HF diet containing 20 % (w/w) high quercetin-glycoside onions (360 mg/kg quercetin aglycone equivalents in the diet). After 2 wks of feeding, all rats were treated twice, 1 wk apart, with AOM (12 mg/kg, s. c.). The dietary treatments continued until sacrifice, 7 wks after the first injection with AOM.


RESULTS
ACF induction did not vary in animals fed low or high quercetin-glycoside tomatoes relative to controls. On the contrary, rats fed 20% (w/w) onion-based diets, with low or high quercetin-glycoside content, showed an increase in number, multiplicity and "large" ACF compared to the control group (number of ACF/colon 145 +/- 15 (SE), 255 +/- 11 and 218 +/- 16 in controls, low and high-quercetin-glycoside groups, respectively; p < 0.01). Proliferative activity of the colon did not vary between animals fed control and high quercetin-glycoside tomato diet. The height of the crypts in normal mucosa of rats fed high quercetinglycoside onions was significantly increased compared to control rats (cells/emicrypt 38.4 +/- 1.2 (SE) and 41.3 +/- 0.6 in controls and high quercetin-glycoside onions group, p < 0.05).


CONCLUSIONS
None of the diets supplemented with onion or tomato with variable quercetin-glycoside content demonstrated a potential chemopreventive effect on ACF-induction by AOM in rats.
Femia
Angelo Pietro
AP
Dept. of Pharmacology, University of Florence, Viale Pieraccini 6, 50139, Florence, Italy. angelo.pietro@unifi.it
Caderni
Giovanna
G
Ianni
Maura
M
Salvadori
Maddalena
M
Schijlen
Elio
E
Collins
Geoff
G
Bovy
Arnaud
A
Dolara
Piero
P
D000818:Animals; D016588:Anticarcinogenic Agents / Q000008:administration & dosage*; D001397:Azoxymethane / Q000633:toxicity; D002273:Carcinogens / Q000633:toxicity; D003110:Colonic Neoplasms / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D004305:Dose-Response Relationship, Drug; D005527:Food, Fortified; D006027:Glycosides / Q000008:administration & dosage*; D018551:Solanum lycopersicum / Q000737:chemistry*; D008297:Male; D019697:Onions / Q000737:chemistry*; D011794:Quercetin / Q000008:administration & dosage*; D011897:Random Allocation; D051381:Rats; D011916:Rats, Inbred F344
D016588:Anticarcinogenic Agents; D002273:Carcinogens; D006027:Glycosides; D011794:Quercetin; D001397:Azoxymethane