linoleic-acid and nitrosobis(2-oxopropyl)amine

Type and composition of dietary fat intake is supposed to play an important role in carcinogenesis. Thus we investigated the effects of n-3, n-6 and n-9 polyunsaturated fatty acids (PUFA) on oxidative stress (lipidperoxidation) and tumour growth in ductal pancreatic cancer.. Ninety male hamsters were randomized into 6 groups (gr.) (n=15) and allocated to 3 main dietary categories: gr. 1 and 2 received a standard high fat diet (SHF, rich in n-6 PUFA), while gr. 3 and 4 were fed with a diet containing a mixture of n-3, n-6 and n-9 PUFA (SMOF) and gr. 5 and 6 had free access to a diet rich in n-3 PUFA (FISH-OIL). Gr. 1, 3 and 5 received weekly subcutaneous (s.c.) injections of 10 mg N-nitrosobis-2-oxypropylamine (BOP)/kg body weight in order to induce ductal pancreatic adenocarcinoma. Healthy control gr. 2, 4 and 6 were treated with 0.5 ml 0.9% sodium chloride s.c. After 32 weeks all animals were sacrificed. Removed pancreata were weighed and analysed histologically and biochemically. Activities of glutathionperoxidase (GSH-Px), superoxiddismutase (SOD) and levels of lipidperoxidation were measured in samples of pancreatic carcinoma as well as in tumour-free pancreatic tissue.. While different diets did not significantly alter the overall incidence of histologically proven pancreatic adenocarcinoma, the number of macroscopically visible tumours was decreased in the FISH-OIL-gr.. Different diets did not significantly influence the incidence of histologically proven pancreatic adenocarcinoma. However, administration of a diet rich in n-3 PUFA (FISH-OIL) resulted in a decrease of macroscopically visible tumours, thus indicating its beneficial effects in respect to attenuation of tumour growth.

Topics: Animals; Carcinogens; Carcinoma, Pancreatic Ductal; Cricetinae; Dietary Fats, Unsaturated; Docosahexaenoic Acids; Eicosapentaenoic Acid; Enteral Nutrition; Fatty Acids, Unsaturated; Fish Oils; Glutathione Peroxidase; Linoleic Acid; Male; Mesocricetus; Nitrosamines; Oleic Acid; Olive Oil; Oxidative Stress; Pancreas; Pancreatic Neoplasms; Plant Oils; Random Allocation; Soybean Oil; Superoxide Dismutase; Survival Rate; Thiobarbituric Acid Reactive Substances; Triglycerides

In the present study the chemopreventive potential of 25% fat (HF) diets containing 2 wt% linoleic acid (LA) and including 0.0, 1.2, 2.4, 4.7, 7.1 or 9.4 wt% dietary fish oil (MaxEPA) has been investigated using the N-nitrosobis(2-oxopropyl)amine (BOP)-hamster model for pancreatic cancer. The number of pancreatic borderline lesions (BLL) was significantly higher (P < 0.05) in the HF groups containing 1.2, 2.4 or 9.4 wt% MaxEPA in comparison with the HF group without MaxEPA. MaxEPA inhibited the metabolism of LA to arachidonic acid (AA) and of AA to prostaglandins (PGs) in both blood plasma and pancreatic microsomes. The pancreatic levels of PGE2 (P < 0.05), 6-keto-PGF1 alpha (P < 0.01) and PGF2 alpha (P < 0.05) decreased significantly with increasing dietary MaxEPA. The levels of PGE2 (P < 0.001), 6-keto-PGF1 alpha (P < 0.05), PGF2 alpha (P < 0.001) and thromboxane (TX) B2 (P < 0.001) in pancreatic adenocarcinomas were higher than in non-tumorous pancreas. The MaxEPA had no significant effect on the BrdU labeling index (LI) in acinar, ductular or centroacinar cells, nor on the LI in BOP-induced pancreatic lesions. It is concluded that (i) dietary fish oil has a slight enhancing effect on BOP-induced pancreatic carcinogenesis in hamsters and (ii) dietary fish oil dose-dependently inhibits the conversion of LA to AA and of AA to certain PGs and (iii) dietary fish oil does not influence the cell proliferation in hamster pancreas.

Topics: Animals; Arachidonic Acid; Carcinogens; Cell Division; Cricetinae; Dinoprostone; Fish Oils; Linoleic Acid; Linoleic Acids; Male; Mesocricetus; Nitrosamines; Pancreatic Neoplasms

It has been suggested that linoleic acid (LA) is responsible for the promoting effect of dietary polyunsaturated fat on pancreatic carcinogenesis via an accelerated prostaglandin synthesis, caused by metabolism of LA-derived arachidonic acid in (pre)neoplastic tissue. The purpose of the present study was to investigate whether dietary LA is the cause of pancreatic tumor promotion by a high fat diet. Five groups of 30 azaserine-treated rats and 5 groups of 30 N-nitrosobis(2-oxopropyl)amine-treated hamsters were maintained for 6 months (rats) and 12 months (hamsters) on high fat (25 weight %) AIN diets containing 2, 4, 6, 10, or 15 weight % LA. The results indicated that the strongest enhancing effect on the growth of pancreatic (pre)neoplastic lesions in rats and hamsters was obtained with 4 and 2 weight % of dietary LA, respectively. At higher LA levels the tumor response seemed to decrease rather than increase. In both rats and hamsters the fatty acid profiles of blood plasma and pancreas showed an accurate reflection of the dietary fatty acid profiles: a proportional increase in LA levels was observed in plasma and pancreas with increasing dietary LA. In both species plasma and pancreatic AA levels remained constant, except for arachidonic acid levels in rat plasma, which significantly increased with increasing dietary LA levels. Fatty acid profiles in hamster pancreatic tumors did not differ from fatty acid profiles in nontumorous pancreatic tissue from hamsters fed the same diet. Prostaglandin (PG) E2, 6-keto-PGF1 alpha, PGF2 alpha, and thromboxane B2-concentrations in nontumorous pancreatic tissue were similar among the diet groups. Ductular adenocarcinomas from hamster pancreas showed significantly higher levels of 6-keto-PGF1 alpha, PGF2 alpha, and thromboxane B2, but not of PGE2 in comparison with nontumorous pancreas. It is concluded that the strongest pancreatic tumor promotion by dietary LA is 4 weight % in rats and 2 weight % or less in hamsters, and that PGs may be involved in the development of ductular adenocarcinomas induced in hamster pancreas by N-nitrosobis(2-oxopropyl)amine.

Topics: Animals; Arachidonic Acid; Azaserine; Carcinogens; Cricetinae; Dietary Fats; Fatty Acids; Linoleic Acid; Linoleic Acids; Male; Mesocricetus; Microsomes; Nitrosamines; Pancreas; Pancreatic Neoplasms; Plant Oils; Precancerous Conditions; Rats; Rats, Wistar; Reference Values; Safflower Oil; Species Specificity; Sunflower Oil