|JI, LI LI|
Submitted to: Nutrition Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2003
Publication Date: 11/12/2003
Citation: Ji, L., Lay, D., Chung, E., Fu, Y., Peterson, D.M. 2003. Effects of avenanthramides on oxidant generation and antioxidant enzyme activity in exercised rats. Nutrition Research. 23:1579-1590.
Interpretive Summary: Free radicals are generated in all aerobic organisms including humans, and can cause tissue damage if not countered by the body's antioxidant defense system. Strenuous physical exercise increases oxidative stress to muscle tissue because of increased free radical generation. It is believed that dietary antioxidants may enhance the endogenous antioxidant defense systems. Oats contain some potent antioxidants called avenanthramides. The purpose of this experiment was to see whether feeding an avenanthramide to rats would increase antioxidant capacity and reduce free radical formation and tissue damage, especially that caused by vigorous physical exercise. Rats were fed an avenanthramide-containing diet or a control diet for 50 days. Prior to killing, half of each diet group were run on a treadmill for an hour while the other half rested. The rats were killed and the tissues removed and examined for indicators of oxidant production, antioxidant enzymes, and lipid peroxidation. The results were mixed. In some tissues, the avenanthramide-fed rats had higher antioxidant enzyme activities. Exercise-induced lipid peroxidation was attenuated by avenanthramide in the heart, but not other tissues. Avenanthramide feeding increased oxidant production in the heart and decreased it in one of the muscles. The impact of this study is the first demonstration that dietary avenanthramide is being absorbed and affecting the metabolism various tissues. The fact that the effects differed among tissues indicates that considerably more research is needed to determine how it is acting.
Technical Abstract: Avenanthramides (AVA) are major phenolic acids in oat (Avena sativa L.) that have potent antioxidant functions. The present study investigated whether dietary AVA supplementation can affect oxidant status and antioxidant defense in rats at rest and in response to exercise-induced oxidative stress. Female Sprague-Dawley rats (n=48, age 6-7 wk) were fed either an AIN-93 based control (C) diet or the same diet containing 0.1 g/kg AVA-Bc [N-(3',4'-dihydroxycinnamoyl)-5-hydroxyanthranilic acid] for 50 days. Each group was further divided into rested (R) and exercised (E, treadmill running at 22.5 m/min, 10% grade for 1 hour) just prior to killing. Reactive oxygen species (ROS) production, measured by 2',7'-dichlorofluorescein as a probe, was increased in the heart (P<0.05), unchanged in liver, kidney and deep vastus lateralis muscle (DVL), and decreased in soleus muscle (P<0.05) with AVA supplementation. AVA-fed rats had higher superoxide dismutase (SOD) activity in DVL, liver and kidney (P<0.05), but lower SOD activity in the heart (P<0.01) compared to C-fed rats. Glutathione peroxidase (GPX) activity was increased (P<0.05) in the heart and tended to be higher in DVL but was unchanged in liver or kidney of AVA vs. C rats. E significantly increased ROS production in DVL and soleus, and also increased lipid peroxidation, measured by malondialdehyde (MDA), in the heart, liver and DVL. AVA prevented E-induced lipid peroxidation in the heart (P<0.05). We concluded that AVA can serve as a potential dietary antioxidant supplement, but its tissue specific pro-oxidant effects require further investigation.