Volume 89, Issue 1, January (2003), pp. 19-28 © The Author 2003
doi:10.1079/BJN2002731

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Relationship between tissue lipid peroxidation and peroxidizability index after α-linolenic, eicosapentaenoic, or docosahexaenoic acid intake in rats

Morio Saito^1* and Kazuhiro Kubo^1,2
1Division of Food Science, Independent Administrative Institution, National Institute of Health and Nutrition,  Shinjuku-ku, Tokyo 162-8636, Japan
²Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012, Japan

 (Received 18 December 2001–Revised 11 July 2002–Accepted 11 August 2002)

In a previous study, we found that the extent of dietary n-3 docosahexaenoic acid (DHA)-stimulated tissue lipid peroxidation was less than expected from the relative peroxidizability index of the total tissue lipids in rats with adequate vitamin E nutritional status. This suppression of lipid peroxidation was especially prominent in the liver. To elucidate whether this phenomenon was unique to DHA, we compared the peroxidation effects of n-3 α-linolenic acid (α-LN) and n-3 eicosapentaeonic acid (EPA) with those of DHA in rats. Either α-LN (8·6 % of total energy), EPA (8·2 %), or DHA (8·0 %) and one of two levels of dietary vitamin E (7·5 and 54 mg/kg diet) were fed to rats for 22 d. Levels of conjugated diene, chemiluminescence emission and thiobarbituric acid (TBA)-reactive substance in the liver, kidney, and testis were determined as indicators of lipid peroxidation. In rats fed the DHA diet deficient in vitamin E (7·5 mg/kg diet), TBA values in the liver, kidney, and testis correlated well with the tissues’ relative peroxidizability indices. In rats fed the α-LN diet with an adequate level of vitamin E (54 mg/kg diet), a close association between relative peroxidizability indices and lipid peroxide levels was observed in all the tissues analysed. However, in rats fed either the EPA diet or the DHA diet with an adequate level of vitamin E, the extent of lipid peroxidation in each tissue was less than expected from the relative peroxidizability index. This suppression was particularly marked in the liver. We concluded that suppression of lipid peroxidation below the relative peroxidizability index was not unique to DHA, but was also seen with EPA, which has five double bonds, in rats with adequate vitamin E nutritional status, but not with α-LN, which has three double bonds.

*Corresponding author: Dr Morio Saito, fax þ 81 3 3202 3278, email msaito@nih.go.jp

Keywords:
Docosahexaenoic acid: Eicosapentaeonic acid: Lipid peroxidation: Peroxidizability index