Chemopreventive Effects of Flax Seed Oil and Flax Seed Meal on Azoxymethane-Induced Colon Tumors in Fisher 344 Male Rats

Abstract

This study was designed to evaluate the anticarcinogenic effect of Flax Seed Meal (FSM) (10 and 20%) and Flax Seed Oil (FSO) (7 and 14%) on Azoxymethane (AOM)-induced colon tumors in Fisher 344 male rats during initiation (I), promotion (P) and Initiation + Promotion (I+P) stages of carcinogenesis. After an acclimatization period of 1 week, 14 groups of Fisher 344 male weanling rats, 3-4 week old (15 per group) were assigned to 2 control groups fed AIN 93G diet and AIN 93G + 14% soybean oil (SBO) (high fat control). The remaining 12 groups were assigned to 10 and 20% FSM (I, P and I+P) and 7 and 14% FSO (I, P and I+P). All rats received 16 mg kg-1 body weight of AOM at 7 and 8 week of age. At 20 weeks of age all animals were switched to AIN-93 M diets and at 45 week of age all rats were killed by CO2 asphyxiation. Tumor incidence (%) in colon of rats fed C (7 and 14%) was both 100. Tumor incidences for rats fed FSO (7 and 14%) at I, P and I+P were: 100, 100, 61, 60, 58 and 61, respectively and 80, 80, 66.6, 66.6, 66.6 and 31, respectively for rats fed FSM (10 and 20%) at I, P and I+P. Tumors per tumor-bearing ratios for groups fed C; 10 and 20% FSM (I, P and I + P) were 3.86, 1.28, 1.70, 1.75 and 1.0, 0.94, 0.64, respectively. In rats fed C (7 and 14%) and 7 and 14% FSO (I, P and I + P) T/TBR ratios were 3.86, 5.96; 1.4, 0.6, 0.6; 1.90, 0.8, 0.8, respectively. Glutathione-S-Transferase activity (a phase II detoxification enzyme) was significantly (p<0.05) higher in rats fed 10 and 20% FSM and 7 and 14% FSO compared to controls. The results of this study indicate that bioactive phytochemicals such as dietary fiber and lignans such as secoisolariciresinol diglycoside (SDG) found in flax seed meal and essential fatty acids such as α-linolenic acid (ALA) found in flax seed oil suppress colon tumors, particularly at the promotion stage and flax seed products may therefore be effective chemopreventive agents.