Impact of dietary conjugated linoleic acid on the oxidative stability of rat liver microsomes and skeletal muscle homogenates

Dietary conjugated linoleic acid (CLA; 0-2.0%) increased CLA concentrations in liver microsomes and skeletal muscle homogenates from rats. Dietary CLA decreased oleic and arachadonic acid concentrations in both liver microsom es and skeletal muscle. The presence of CLA in liver microsomes had no impa ct on linoleic acid, arachadonic acid, and alpha-tocopherol oxidation rates . Dietary CLA (2.0%) also did not alter alpha-tocopherol oxidation rates in liver microsomes or muscle homogenates. Formation of malonaldehyde (MDA) i n oxidizing liver microsomes decreased with increasing CLA concentration as determined by measurement of thiobarbituric acid-MBA complexes by HPLC. Th e ability of CLA to decrease MDA formation without impacting other lipid ox idation markers such as the disappearance of fatty acid and alpha-tocophero l suggests that decreased MBA concentration was the result of CLA's ability to lower polyenoic fatty acids such as arachadonic acid. While CLA does no t appear to act as an antioxidant, its ability to decrease polyenoic fatty acid concentrations could decrease the formation of highly cytotoxic lipid oxidation products such as MDA.