Biol. Pharm. Bull. 28(8) 1539—1541 (2005)

served in Japan. PR has been developed industrially in order to enhance the nutritional functions of its source material, brown rice (BR). PR is produced by soaking BR in water for slight germination. Amounts of some constituents including g-aminobutyric acid (GABA) are remarkably increased in PR. GABA is also known to potentiate the insulin secretion in pancreas. Thus PR is thought to ameliorate the disorders such as diabetes, although there is little scientific evidence regarding nutritional function of BR. We have reported that the feeding of PR diet to streptozotocin-induced type 1 diabetic rats ameliorated the elevation of blood glucose, type-1 plasminogen activator inhibitor (PAI-1) and lipid peroxide concentrations in comparison with rats fed white rice (WR) diet. These results suggest that intake of PR instead of WR is effective for the prevention of diabetic vascular complications including macrovascular complications such as myocardial infarction and microvascular complications, retinopathy and nephropathy. It has been reported that the glycemic index (GI) obtained from volunteers who took PR was significantly lower than that of those who were taking WR, however, there was no significant difference between the groups PR and BR. These results suggest that the PR-specific component which is found only in PR would not be involved in the suppression of post prandial glucose levels, because PR and BR showed almost identical effect. In the present study we tried to identify which component(s) in PR is responsible for these benefits to control the blood glucose levels by using destarched and defatted PR bran (DB) in an animal model. We now report that dietary fiber, but not GABA is a major active component responsible for the suppression of post-prandial glucose level. MATERIALS AND METHODS