ELSEVIER Nutrition Research, Vol. 19, No. 8, pp. 1233-124331999 copyright 0 1999 Elsevier Science Inc. Printed in the USA. All rights reserved 0271-53 17/99/&see front matter zyxwvu PII !SO271-5317(!N)OOO8~6 SHORT-TERM FEEDING OF FLAXSEED OR ITS LIGNAN HAS MINOR INFLUENCE ON IN VZVO HEPATIC ANTIOXIDANT STATUS IN YOUNG RATS Yvonne V. Yuan, Ph.D.‘, Sharon E. Richard, M.Sc. and Lilian U. Thompson, Ph.D.* Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, 150 College Street, Toronto, Ontario Canada M5S 3E2 ABSTRACT 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 mammalii 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 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED (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. 0 1959 Elsevia Science Inc KEY WORDS: Flaxseed, lignans, antioxidant enzymes, secoisolariciresinol, enterodiol. * Corresponding author: Dr. L.U. Thompson, Dept. of Nutritional Sciences, University of Toronto, 150 College Street, Toronto, ON Canada M5S 3E2 Telephone: (416) 978-3523, Fax (416) 978-5882, e-mail: lilian.thomnson@utoronto.ca ’ Present address: School of Nutrition, Ryerson Polytechnic University, 350 Victoria Street, Toronto, ON Canada M5B 2R3 1233