Hirofumi Koyama

Inhibitory Effect of Dietary Perilla Oil Rich in the n-3 Polyunsaturated Fatty Acid α-Linolenic Acid on Colon Carcinogenesis in Rats

The inhibitory effect of dietary perilla oil rich in the n‐3 polyunsaturated fatty acid α‐linolenic acid against colon carcinogenesis was investigated in rats. Four groups of 26 F344 rats each received an intrarectal dose of 2 mg of N‐methyl‐N‐nitrosourea 3 times a week for 2 weeks, and received a diet containing 12% perilla oil, 6% or 12% safflower oil (rich in the n‐6 polyunsaturated fatty acid linoleic acid), or 12% palm oil (rich in saturated and monounsaturated fatty acids). At week 35, the incidence of colon cancer was significantly lower in perilla oil‐fed rats than in other dietary groups; 19% vs. 46%, 56% and 58%. When examined at week 10, the concentration of fecal bile acids, known to be tumor promoters, was not significantly different among the dietary groups, and the intrarectal deoxycholic acid‐induced colonic mucosal ornithine decarboxylase activity, a marker of tumor promotion, was significantly lower in perilla oil‐fed group than in other groups. The serum and colonic mucosal fatty acid compositions and the blood plasma prostaglandin E2 level directly reflected the fatty acid composition of each dietary fat. The results suggest that the anti‐tumor‐promoting effect of dietary perilla oil was a result of a decreased sensitivity of colonic mucosa to tumor promoters arising from the altered fatty acid composition in membrane phospholipid of colonic epithelial cells, and was not a consequence of a decrease of promoters such as bile acids.

Chemoprevention of Large Bowel Cancer in Animal Models and Its Possibility in Humans

Indomethacin (prostaglandin synthesis inhibitor), sarcophytol A (product from marine soft coral) and perilla oil (rich in α-linolenic acid) suppressed large bowel mucosal ornithine decarboxylase induction as a biomarker of tumor promotion and inhibited methylnitrosourea-induced large bowel tumor development in rats. The elevated level of this enzyme activity in large bowel cancer patients lowered by indomethacin treatment. Thus, it was expected that those agents may prevent large bowel carcinogenesis in individuals at high risk, probably through the mechanism involving in changes of biologic property of the large bowel mucosa.

Abstracts of selected papers presented at the 29th annual meeting of the japanese society of gastroenterology

S OF SELECTED PAPERS PRESENTED AT THE 29TH A N N U A L MEETING OF THE JAPANESE SOCIETY OF GASTROENTEROLOGY K0fu, Japan, November 5--7, 1987 Chairman: Katsuhiko SUGAHARA, M.D.