Isoflavone enteric bacterial metabolite equol conjugate acts on the digestive tract and suppresses appetite in female rats

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07738
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Food science
• Research Institution: Ehime University
• Principal Investigator: Kishida Taro 愛媛大学, 農学研究科, 教授 (80304658)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 大豆イソフラボン / 食欲抑制 / ラット / 視床下部 / 胃排泄 / 腸肝循環

Outline of Final Research Achievements

The prevention of overeating is important in the prevention and treatment of many lifestyle-related diseases including obesity. We previously found that dietary daidzein, a major soy isoflavone, reduced food intake in female rats and revealed from the blood and bile levels that equol, an enteric bacterial metabolite of daidzein, is the active substance. Because the bile concentration is higher level, it is possible to suppress the appetite through the digestive tract while circulating in the enterohepatic circulation. In this study, it was suggested that bile equol was conjugated with glucuronic acid and sulfuric acid, and the conjugation type had sex difference and involved in the sex-specific action. In addition, it was suggested that equol might have an effect via gastric emptying delay, and changes in hypothalamic gene expression associated with gastric emptying were also seen.

Free Research Field

栄養科学

Academic Significance and Societal Importance of the Research Achievements

過食は肥満をはじめ多くの生活習慣病のもっとも大きな原因のひとつであり、過食の防止は生活習慣病の予防・治療において重要である。先に我々は大豆イソフラボンを雌ラットに与えると（50～150 mg/kg飼料）飼料摂取量が低下することを見出した。大豆イソフラボンはエストロゲン作用を持ち、食欲抑制はエストロゲン作用の一つだが大豆イソフラボンが卵巣摘出メスラットの飼料摂取量を低下させた際、卵巣摘出による子宮重量の萎縮は全く改善されなかった。我々はエストロゲン作用とは全く異なる機構が存在すると考えた。本研究は大豆イソフラボンが、腸肝循環しながら消化管を介して食欲を抑制する新しい機構の解明を目指すものである。