Several studies have demonstrated that the daily intakes of soy foods were associated with a reduced cardiovascular risk. The aim of our study was to investigate the inhibitory effect of black soybeans on low density lipoprotein (LDL) oxidation in comparison to yellow soybeans. The extract from black soybean had a longer LDL oxidation lag time than that from yellow soybean (205 +/- 16 and 65 +/- 3 min, respectively). When both soybeans were divided into the seed coat and the mixture of the germ and cotyledon, the diluted extract solution from the black soybean seed coat prolonged the lag time significantly more than the original extract of the yellow soybean seed coat. On the other hand, antioxidant effects of the extract from the mixture of germs and cotyledons were similar in both soybeans. Regarding total polyphenol contents, the seed coat of black soybean had a higher polyphenol content than that of yellow soybean (29.0 +/- 0.56 and 0.45 +/- 0.02 mg/g, respectively). Interestingly, the mixture of the germ and cotyledon hydrolyzed by beta-glucosidase in both soybeans showed a stronger inhibitory effect on LDL oxidation than that before being hydrolyzed by beta-glucosidase. These results suggest that black soybeans may be more effective in inhibiting LDL oxidation than yellow soybeans because of total polyphenols contents in its seed coat. In addition, aglycones, which are rich in soybeans fermented or hydrolyzed by beta-glucosidase, may play a crucial role in the prevention of oxidation-related diseases.

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To the Editor:Resistin is an adipocytokine that may link obesity with insulin resistance and diabetes. Steppan et al. (1) reported serum resistin levels to be elevated in obese mice and to be decreased by thiazolidinediones. They also showed that administration of antiresistin antibodies improved insulin sensitivity. However, subsequent studies produced disparate findings regarding the role of resistin in obesity and insulin resistance (2). Although serum resistin levels were reported to be elevated in obese (3) and diabetic patients (4,5), conflicting results were also presented (6). Recently, resistin was reported to up-regulate the expression of adhesion molecules, such as vascular cell adhesion molecule-1, in cultured endothelial cells (7). Resistin was also shown to promote smooth muscle cell proliferation (8). Burnett et al. (9) reported resistin messenger ribonucleic acid (mRNA) levels to be elevated in aortas of apo E-deficient mice. However, association between resistin and coronary artery disease (CAD) has not yet been elucidated.We investigated serum resistin levels in 230 patients undergoing coronary angiography. Patients with myocardial infarction, unstable angina, or a history of coronary intervention were excluded. Because antidiabetic medication affects resistin levels (1,2), patients on hypoglycemic medication or insulin were also excluded. Our study was approved by our institutional ethics committee. After written informed consent was obtained, fasting blood samples were taken; CAD was defined as at least one coronary artery having Ͼ50% luminar diameter stenosis. The severity of CAD was represented as the numbers of Ͼ50% stenotic vessels and Ͼ50% and Ͼ25% stenotic segments. Resistin levels were measured by ELISA (BioVendor CAD ϭ coronary artery disease; HDL ϭ high-density lipoprotein; HOMA-IR ϭ homeostasis model assessment for insulin resistance.