The present study investigated the anti-diabetic activity and potential mechanisms of the polyphenol rich extract from Phellinus igniarius (PI-PRE) in vitro and in vivo. Four main phenolic compounds of PI-PRE were purified and identified as 7,8-dihydroxycoumarin, 3,4-dihydroxybenzalacetone, 7,3′-dihydroxy-5′-methoxyisoflavone and inoscavin C by the off-line semipreparative liquid chromatography-nuclear magnetic resonance protocol. In vitro, PI-PRE stimulated GLUT4 translocation by 2.34-fold and increased glucose uptake by 1.73-fold in L6 cells. However, the selective AMP-activated protein kinase (AMPK) inhibitor, compound C, completely reversed the PI-PRE-induced GLUT4 translocation. In vivo, KK-Ay mice treated with PI-PRE for four weeks had lower fasting blood glucose levels, as well as other blood–lipid indexes, compared with the vehicle control group. Mechanistic studies showed that the expressions of p-AMPKα and GLUT4 were significantly increased by treatment with PI-PRE in L6 cells. In KK-Ay mice, the expression of p-AMPKα was enhanced in the liver and skeletal muscle, and the expression of GLUT4 was increased in skeletal muscle. These findings suggest that PI-PRE possesses potential anti-diabetic effects including improving glucose tolerance, reducing hyperglycemia, and normalizing insulin levels. These effects are partly due to the activation of GLUT4 translocation via the modulation of the AMPK pathway.

中文翻译：

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桑黄 富含多酚的提取物对自发性2型糖尿病的KK-Ay小鼠的抗糖尿病活性†

本实验研究的抗糖尿病活性和从富含多酚的提取物的潜在机制桑黄（PI-PRE）在体外和体内。离线半制备液相色谱-核磁法纯化并鉴定了PI-PRE的四种主要酚类化合物，分别为7,8-二羟基香豆素，3,4-二羟基苯丙酮，7,3'-二羟基-5'-甲氧基异黄酮和inoscavin C共振协议。在体外，PI-PRE在L6细胞中刺激GLUT4移位2.34倍，并增加葡萄糖摄取1.73倍。但是，选择性AMP激活的蛋白激酶（AMPK）抑制剂化合物C完全逆转了PI-PRE诱导的GLUT4易位。体内与媒介物对照组相比，用PI-PRE治疗4周的KK-Ay小鼠的空腹血糖水平以及其他血脂指数更低。机理研究表明，用PI-PRE处理L6细胞后，p-AMPKα和GLUT4的表达显着增加。在KK-Ay小鼠中，肝脏和骨骼肌中p-AMPKα的表达增加，骨骼肌中GLUT4的表达增加。这些发现表明PI-PRE具有潜在的抗糖尿病作用，包括改善葡萄糖耐量，降低高血糖症和使胰岛素水平正常化。这些影响部分归因于通过AMPK途径的调节激活GLUT4易位。