Conjugated linoleic acid and oxidative stress |
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Authors: | Sebastiano Banni Elisabetta Angioni Maria Stefania Contini Gianfranca Carta Viviana Casu Giorgio Amedeo Iengo Maria Paola Melis Monica Deiana Maria Assunta Dessì Francesco P Corongiu |
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Affiliation: | (1) Dipartimento di Biologia Sperimentale, Sezione Patologia Sperimentale, Universita’ degli Studi di Cagliari, Cittadella Universitaria, Km. 4.500 S.S. 554, 09040 Monserrato (Cagliari), Italy |
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Abstract: | At the present time, conjugated linoleic acid (CLA) is the subject of a growing number of studies since it has been demonstrated
to possess anticarcinogenic and antiatherogenic activities in experimental animal models and to increase in some pathological
states in humans. In both situations, CLA has been claimed to be involved in oxidative stress, as an antioxidant in the first
case and as a primary product of a free-radical attack on polyunsaturated fatty acids (PUFA) in the other. The controversial
results are due mostly to a lack of a suitable methodology because the presence of conjugated dienes (CD) in lipid moiety
has been taken for years as evidence of lipid peroxidation due to the occurrence of this structure in fatty acid hydroperoxides.
We have recently developed a new methodology that consists of the extraction of fatty acids, including CD fatty acid hydroperoxides,
by mild saponification and their separation and identification by high-performance liquid chromatography with diode array
detector. Fatty acid analyses of liver homogenate, oxidized in vitro either with Fe-ADP or t-butyl hydroperoxide (t-ButylHP), of lamb and rats fed CLA at levels known to prevent carcinogenesis, showed that CLA and its metabolites steadily
decreased during oxidative stress and that they are more prone to oxidation than their corresponding methylene-interrupted
fatty acids. No significant antioxidant effect of CLA was detected in any model tested. However, CD fatty acid hydroperoxides
increased in the t-ButylHP model but not in the Fe-ADP model, owing probably to the degradation of CD fatty acid hydroperoxides induced by this
oxidative agent. In conclusion, CLA and its metabolites seem to behave, under oxidative stress, as regular PUFA. Thus, it
is highly unlikely that the peculiar effects of CLA are directly related to interference in lipoperoxidative processes. |
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Keywords: | Conjugated dienes conjugated linoleic acid diode array detector HPLC hydroperoxides oxidative stress second derivative UV spectrophotometry |
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