Tagawa Noriko, Kubota Sayaka, Kobayashi Yoshiharu, Kato Ikuo
Department of Medical Biochemistry, Kobe Pharmaceutical University, Kobe, Japan.
Department of Medical Biochemistry, Kobe Pharmaceutical University, Kobe, Japan.
Steroids. 2015 Jan;93:77-86. doi: 10.1016/j.steroids.2014.11.003. Epub 2014 Nov 28.
Excess glucocorticoids promote visceral obesity, hyperlipidemia, and insulin resistance. The main regulator of intracellular glucocorticoid levels is 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts inactive glucocorticoids into bioactive forms such as cortisol in humans and corticosterone in rodents. Hexose-6-phosphate dehydrogenase (H6PD), which is colocalized with 11β-HSD1 in the intralumen of the endoplasmic reticulum, supplies a crucial coenzyme, NADPH, for full reductase activity of 11β-HSD1. Therefore, it is possible that inhibition of 11β-HSD1 will become a considerable medical treatment for metabolic diseases including obesity and diabetes. Genistein, a soy isoflavone, has received attention for its therapeutic potential for obesity, diabetes, and cardiovascular disease, and has been proposed as a promising compound for the treatment of metabolic disorders. However, the mechanisms underlying the pleiotropic anti-obesity effects of genistein have not been fully clarified. Here, we demonstrate that genistein was able to inhibit 11β-HSD1 and H6PD activities within 10 or 20min, in dose- and time-dependent manners. Inhibition of 11β-HSD2 activity was not observed in rat kidney microsomes. The inhibition was not reversed by two estrogen receptor antagonists, tamoxifen and ICI182,780. A kinetic study revealed that genistein acted as a non-competitive inhibitor of 11β-HSD1, and its apparent Km value for 11-dehydrocorticosterone was 0.5μM. Genistein also acted as a non-competitive inhibitor of H6PD, and its apparent Km values for G6P and NADP were 0.9 and 3.3μM, respectively. These results suggest that genistein may exert its inhibitory effect by interacting with these enzymes.
过量的糖皮质激素会导致内脏肥胖、高脂血症和胰岛素抵抗。细胞内糖皮质激素水平的主要调节因子是11β-羟基类固醇脱氢酶1型（11β-HSD1），它可将无活性的糖皮质激素转化为生物活性形式，如人类中的皮质醇和啮齿动物中的皮质酮。己糖-6-磷酸脱氢酶（H6PD）与11β-HSD1在内质网腔内共定位，为11β-HSD1的全还原酶活性提供关键辅酶NADPH。因此，抑制11β-HSD1可能成为治疗包括肥胖症和糖尿病在内的代谢性疾病的重要医学手段。染料木黄酮是一种大豆异黄酮，因其对肥胖症、糖尿病和心血管疾病的治疗潜力而受到关注，并被认为是治疗代谢紊乱的有前景的化合物。然而，染料木黄酮多效性抗肥胖作用的潜在机制尚未完全阐明。在此，我们证明染料木黄酮能够在10或20分钟内以剂量和时间依赖性方式抑制11β-HSD1和H6PD的活性。在大鼠肾脏微粒体中未观察到对11β-HSD2活性的抑制作用。两种雌激素受体拮抗剂他莫昔芬和ICI182,780不能逆转这种抑制作用。动力学研究表明，染料木黄酮作为11β-HSD1的非竞争性抑制剂，其对11-脱氢皮质酮的表观Km值为0.5μM。染料木黄酮也是H6PD的非竞争性抑制剂，其对G6P和NADP的表观Km值分别为0.9和3.3μM。这些结果表明，染料木黄酮可能通过与这些酶相互作用发挥其抑制作用。
