Antioxidant characterization of soy derived products in vitro and the effect of a soy diet on peripheral markers of oxidative stress in a heart disease model.

This study analyzed and compared the content of isoflavones in 2 soy products, the effectiveness of isoflavones as antioxidants, in vitro, and demonstrated the antioxidant effect of a soy diet in rats with myocardial infarction (MI). Isoflavone content was analyzed in soybean hypocotyl (SH) and isolated soy protein (ISP). The quality (TAR) and quantity (TRAP) of antioxidants present in the samples was quantified. The amount of daidzin was higher in SH (9 times) and genistein in ISP (5 times). SH presented a 3-fold increase in TAR, while both products exhibited same TRAP. The rats were fed an ISP diet for 9 weeks. Animals were distributed among 6 treatment groups: (i) Sham Casein; (ii) Infarct Casein < 25%; (iii) Infarct Casein > 25%; (iv) Sham Soy; (v) Infarct Soy < 25%; and (vi) Infarct Soy > 25%. MI was induced 5 weeks after the commencement of the diets. Lipid peroxidation (LPO), antioxidant enzyme activity, and levels of nitrites/nitrates were determined in blood. Rats receiving the ISP diet demonstrated increased activity of antioxidant enzyme activity and nitrite/nitrate content. In addition, the increase in LPO seen in rats subjected to MI was significantly mitigated when the ISP diet was given. These findings suggest a nutritional approach of using a soy-based diet for the prevention of oxidative-stress-related diseases such as heart failure.

Diet with isolated soy protein reduces oxidative stress and preserves ventricular function in rats with myocardial infarction.

We investigated the effects of an isolated soy protein (ISP) diet offered over a 9-week period to rats in whom myocardial infarction (MI) had been induced, and a casein diet given as a control. Male Wistar rats were assigned to six groups after infarct size determination (n=8/group): Sham Casein (SC); Infarct Casein <25% (IC<25%); Infarct Casein >25% (IC>25%); Sham Soy (SS); Infarct Soy <25% (IS<25%); and Infarct Soy >25% (IS>25%). MI surgery was performed at the fifth week, and one month later, the animals were hemodynamically assessed to evaluate left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), contractility and relaxation indexes (+/-dP/dt). Lung and liver specimens were also collected for the estimation of organ congestion. Oxidative stress was evaluated in heart homogenates through chemiluminescence (CL), carbonyl groups, and antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). Infarcted groups treated with casein showed cardiac hypertrophy, lung and liver congestion, increased LVEDP and decreased LVSP and +/-dP/dt, all typical signals of heart failure. Ventricular dysfunction was correlated with increased myocardial oxidative damage as seen by CL and carbonyl groups data in the groups IC<25% and IC>25% (3 and 10-fold increase, respectively). The ISP diet was able to improve ventricular systolic and diastolic function in the groups IS<25% and IS>25% (LVEDP was reduced by 44% and 24%, respectively) and to decrease myocardial oxidative stress. The overall results confirm the preventive role of soy-derived products in terms of post-MI myocardial dysfunction probably by an antioxidant action.