School of Biomedical Sciences, Ulster University, Coleraine, BT52 1SA, Co. Londonderry, Northern Ireland, UK.
Br J Nutr. 2021 Oct 28;126(8):1149-1163. doi: 10.1017/S0007114520005085. Epub 2020 Dec 17.
Anti-diabetic actions of Camellia sinensis leaves, used traditionally for type 2 diabetes (T2DM) treatment, have been determined. Insulin release, membrane potential and intra-cellular Ca were studied using the pancreatic β-cell line, BRIN-BD11 and primary mouse pancreatic islets. Cellular glucose-uptake/insulin action by 3T3-L1 adipocytes, starch digestion, glucose diffusion, dipeptidyl peptidase-4 (DPP-IV) activity and glycation were determined together with in vivo studies assessing glucose homoeostasis in high-fat-fed (HFF) rats. Active phytoconstituents with insulinotropic activity were isolated using reversed-phase HPLC, LCMS and NMR. A hot water extract of C. sinensis increased insulin secretion in a concentration-dependent manner. Insulinotropic effects were significantly reduced by diazoxide, verapamil and under Ca-free conditions, being associated with membrane depolarisation and increased intra-cellular Ca2+. Insulin-releasing effects were observed in the presence of KCl, tolbutamide and isobutylmethylxanthine, indicating actions beyond K+ and Ca2+ channels. The extract also increased glucose uptake/insulin action in 3T3L1 adipocyte cells and inhibited protein glycation, DPP-IV enzyme activity, starch digestion and glucose diffusion. Oral administration of the extract enhanced glucose tolerance and insulin release in HFF rats. Extended treatment (250 mg/5 ml per kg orally) for 9 d led to improvements of body weight, energy intake, plasma and pancreatic insulin, and corrections of both islet size and β-cell mass. These effects were accompanied by lower glycaemia and significant reduction of plasma DPP-IV activity. Compounds isolated by HPLC/LCMS, isoquercitrin and rutin (464·2 Da and 610·3 Da), stimulated insulin release and improved glucose tolerance. These data indicate that C. sinensis leaves warrant further evaluation as an effective adjunctive therapy for T2DM and source of bioactive compounds.
已确定传统上用于治疗 2 型糖尿病（T2DM）的茶叶具有抗糖尿病作用。使用胰岛β细胞系 BRIN-BD11 和原代小鼠胰腺胰岛研究了胰岛素释放、膜电位和细胞内 Ca。通过 3T3-L1 脂肪细胞研究细胞葡萄糖摄取/胰岛素作用、淀粉消化、葡萄糖扩散、二肽基肽酶-4（DPP-IV）活性和糖化作用，并进行了体内研究以评估高脂肪喂养（HFF）大鼠的葡萄糖体内平衡。使用反相 HPLC、LCMS 和 NMR 分离具有胰岛素促分泌作用的活性植物成分。茶叶的热水提取物以浓度依赖的方式增加胰岛素分泌。胰岛素促分泌作用被二氮嗪、维拉帕米和无 Ca 条件显著降低，与膜去极化和细胞内 Ca2+增加有关。在 KCl、甲苯磺丁脲和异丁基甲基黄嘌呤存在下观察到胰岛素释放作用，表明作用超出 K+和 Ca2+通道。提取物还增加了 3T3L1 脂肪细胞中的葡萄糖摄取/胰岛素作用，并抑制蛋白质糖化、DPP-IV 酶活性、淀粉消化和葡萄糖扩散。提取物的口服给药增强了 HFF 大鼠的葡萄糖耐量和胰岛素释放。延长治疗（每天 250mg/5ml/kg 口服）9 天导致体重、能量摄入、血浆和胰腺胰岛素增加，以及胰岛大小和β细胞质量的改善。这些作用伴随着较低的血糖和血浆 DPP-IV 活性的显著降低。通过 HPLC/LCMS 分离的化合物，异槲皮苷和芦丁（464.2Da 和 610.3Da），刺激胰岛素释放并改善葡萄糖耐量。这些数据表明，茶叶值得进一步评估，作为 T2DM 的有效辅助治疗方法和生物活性化合物的来源。
