Short-term feeding of flaxseed or its lignan has minor influence on in vivo hepatic antioxidant status in young rats

A proposed mechanism underlying the anticarcinogenic and antiatherogenic effects of flaxseed (flax) and its lignan secoisolariciresinol diglycoside (SDG) is the potential antioxidant activity of SDG and its mammalian lignan metabolites enterodiol (ED) and enterolactone (EL). Recent evidence indicates that SDG, ED, and EL scavenge hydroxyl radicals in vitro. This study evaluated the effect of dietary flax on specific antioxidant enzymes and nonenzymatic antioxidant molecules in young rats. After 3 days acclimatization on an AIN-93G basal diet (BD), female Sprague Dawley rats (24 days of age) were randomized into three dietary groups: BD, BD supplemented with 10% flax or 3 mg SDG gavage. At 50 days of age, rats were sacrificed and livers removed for antioxidant enzyme determinations. Body weight gain, feed efficiency ratio, and liver weights were not different between treatment groups indicating that animals grew well on the flax diet. Hepatic reactive oxygen species metabolizing enzymes catalase (CAT) and glutathione peroxidase (GSH-Px) were not different between treatment groups. Hepatic glutathione reductase (GSSG-Red) activity of SDG and flax-fed rats, when combined, were lower (P = 0.037) compared to BD-fed rats. Hepatic acid-soluble sulfhydryl groups as GSH were not influenced by flax or SDG treatment. Total urinary lignan excretion was higher in SDG- and flax-fed groups than in the BD group (P < 0.001). Reduced activity of GSSG-Red and unchanged GSH levels may relate to an antioxidant sparing effect of ED and EL in tissues of flax and SDG-fed rats.