Guangdong Academy of Agricultural Sciences, Sericultural & Agri-Food Research Institute /Key Laboratory of Functional Foods, Ministry of Agriculture and Rural Affairs/Guangdong Key Laboratory of Agricultural Products Processing, Guangzhou 510610, China.
Food Funct. 2020 Feb 26;11(2):1835-1844. doi: 10.1039/c9fo01345h.
The present study attempted to evaluate the mechanism of action and bioactivity of mulberry leaf polyphenols (MLPs) in type-2 diabetes prevention via inhibition of disaccharidase and glucose transport. MLPs were purified with D101 resin and the main composition was determined as chlorogenic acid, rutin, benzoic acid and hyperoside. MLPs demonstrated a strong inhibitory effect on disaccharidases derived from both mouse and Caco-2 cells, and the order of IC50 value was: murine sucrase (7.065 mg mL-1) > murine maltase (4.037 mg mL-1) > Caco-2 cell maltase (0.732 mg mL-1) > Caco-2 cell sucrase (0.146 mg mL-1). MLPs showed the strongest inhibitory effect on sucrase derived from Caco-2 cells and played a role in lowering postprandial glucose mainly by inhibiting sucrase activity. The Caco-2 monolayer cell model was established to simulate the glucose transport process in the human small intestine. We found that within the concentration range of 0.5-2 mg mL-1, MLPs significantly inhibited glucose transport, and the inhibition rate increased with time and dose. The effect of phlorizin (SGLT1 inhibitor) in the control group showed a similar effect on glucose transport, revealing that MLPs may inhibit glucose transport mainly by inhibiting the SGLT1 transporter. RT-qPCR analysis confirmed that MLPs inhibited glucose absorption by suppressing the SGLT1-GLUT2 pathway via downregulation of the mRNA expression of phospholipase, protein kinase A and protein kinase C.
本研究旨在通过抑制双糖酶和葡萄糖转运来评估桑叶多酚（MLPs）在 2 型糖尿病预防中的作用机制和生物活性。采用 D101 树脂对 MLPs 进行纯化，主要成分被确定为绿原酸、芦丁、苯甲酸和金丝桃苷。MLPs 对来源于小鼠和 Caco-2 细胞的双糖酶表现出强烈的抑制作用，IC50 值的顺序为：鼠蔗糖酶（7.065 mg mL-1）>鼠麦芽糖酶（4.037 mg mL-1）>Caco-2 细胞麦芽糖酶（0.732 mg mL-1）>Caco-2 细胞蔗糖酶（0.146 mg mL-1）。MLPs 对来源于 Caco-2 细胞的蔗糖酶表现出最强的抑制作用，主要通过抑制蔗糖酶活性来发挥降低餐后血糖的作用。建立 Caco-2 单层细胞模型模拟人小肠中的葡萄糖转运过程，我们发现，在 0.5-2 mg mL-1 的浓度范围内，MLPs 显著抑制葡萄糖转运，且抑制率随时间和剂量增加而增加。对照组的根皮苷（SGLT1 抑制剂）的作用对葡萄糖转运显示出相似的效果，表明 MLPs 可能主要通过抑制 SGLT1 转运体来抑制葡萄糖转运。RT-qPCR 分析证实，MLPs 通过下调磷脂酶、蛋白激酶 A 和蛋白激酶 C 的 mRNA 表达，抑制 SGLT1-GLUT2 途径，从而抑制葡萄糖吸收。
