Vitamin E content in fish oil emulsion does not prevent lipoperoxidative effects on human colorectal tumors

Abstract

a b s t r a c tObjective: The anticancer action exerted by polyunsaturated fatty acid peroxidation may not be reproduced by commercially available lipid emulsions rich in vitamin E. Therefore, we evaluated the effects of fish oil (FO) emulsion containing a-tocopherol 0.19 g/L on human colorectal adenocarcinoma cells and tumors. Methods: HT-29 cell growth, survival, apoptosis, and lipid peroxidation were analyzed after a 24-h incubation with FO 18 to 80 mg/L. Soybean oil (SO) emulsion was used as an isocaloric and isolipidic control. In vivo, nude mice bearing HT-29 tumors were sacrificed 7 d after an 11-d treatment with intravenous injections of FO or SO 0.2 g • kg À1 • d À1 FO or SO to evaluate tumor growth, necrosis, and lipid peroxidation. Results: The FO inhibited cell viability and clonogenicity in a dose-dependent manner, whereas SO showed no significant effect compared with untreated controls. Lipid peroxidation and cell apoptosis after treatment with FO 45 mg/L were increased 2.0-fold (P < 0.01) and 1.6-fold (P ¼ 0.04), respectively. In vivo, FO treatment did not significantly affect tumor growth. However, immunohistochemical analyses of tumor tissue sections showed a decrease of 0.6-fold (P < 0.01) in the cell proliferation marker Ki-67 and an increase of 2.3-fold (P ¼ 0.03) in the necrotic area, whereas malondialdehyde and total peroxides were increased by 1.9-fold (P ¼ 0.09) and 7.0-fold (P < 0.01), respectively, in tumors of FO-treated compared with untreated mice. Conclusion: These results suggest that FO but not SO has an antitumor effect that can be correlated with lipid peroxidation, despite its vitamin E content.

Tocopherol and tocotrienol homologs in parenteral lipid emulsions

“…Thus, there may have been less evolutionary need for a lipid antioxidant in olive oil. As reported by others [36,40], our investigation also found atocopherol to be the predominant vitamin E homolog in the fish oil-containing emulsions. Despite Omegaven 1 being a 10% lipid emulsion while the other emulsions were all 20% emulsions, its content of vitamin E (mostly a-tocopherol) was comparable or higher than most of the other lipid emulsions.…”

“…The content of vitamin E homologs in oils are also further influenced by harvesting, processing, and storage. Thus, the vitamin E homolog composition profile of commercially available lipid emulsions made from different oils by different manufactures may exhibit large variations in vitamin E content . The vitamin E contents of the lipid emulsions may also be influenced by the addition of exogenous vitamin E (usually α‐tocopherol), which may be added to the lipid emulsions to minimize oxidation of the fatty acids.…”