| Summary: | 碩士 === 靜宜大學 === 食品營養研究所 === 93 === The antioxidative activity of soy protein has been attributed to soy isoflavone, while the antioxidative activity of isoflavone-free soy protein isolate has been poorly investigated. This study was to investigate the effect of isoflavone-free soy protein on antioxidant defense system in rats. Sixteen four-week-old male Sprague-Dawley rats were fed AIN-93G diets containing 20％ casein (casein group, n=8) or 20％ isoflavone-free soy protein (soy protein group, n=8) for 14 days. No significant difference in body weight, food intake, feed efficiency, cumulative food intake and cumulative body weight. There was no difference in apparent protein digestibility between two groups. There was no difference in organs weight and relative organs weight between two groups. The soy protein group had lower apparent fat digestibility. Significantly greater amounts of feces and fecal fat were excreted by rats fed the soy protein group compared with rats fed the casein group. There was no difference in MDA and homocysteine concentration of plasma between two groups, and the soy protein group had higher vitamin C concentration of plasma (P＜0.05) , while there was no difference in vitamin E concentration of plasma. The SOD activities of RBC was tended to be reduced by soy protein (P=0.053), and the soy protein group had lower catalase activities. The soy protein group had both higher GR and GPX activities in RBC. There was no difference in GSH and GSSG concentration and GSH: GSSG ratio of plasma between two groups. The soy protein may regulate the GSH system to maintain the antioxidant defense system in blood. The liver MDA concentration was tended to be reduced by soy protein (P=0.082) , and the soy protein group had both higher vitamin C and vitamin E concentration of liver (P＜0.05). The concentration of GSH, GSSG and GSH: GSSG ratio in plasma and liver were no difference between two groups. The MDA concentration in brain was lower than casein group (P＜0.05), and the soy protein group had higher vitamin C concentration in brain (P＜0.05), while there was no difference in vitamin E concentration in brain. There was no difference in triglyceride and total cholesterol of plasma between two groups. Significantly greater concentration of liver triglyceride by rats fed the soy protein group compared with rats fed the casein group. There was no difference in total cholesterol of liver between two groups.
In conclusion, when Sprague-Dawley rats were fed AIN-93G diets containing 20% isoflavones-free soy protein, there were higher concentrations in vitamin C, and higher activities in GR and GPX of RBC. Soy protein may affect on antioxidant defense system in Sprague-Dawley rats.
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