α葡萄糖苷酶抑制剂桑枝总生物碱的抗糖尿病作用研究

Anti-diabetic effects of the fraction of alkaloids from Ramulus Mori,an innovative Sangzhi alkaloids as an α-glucosidase inhibitor

桑枝总生物碱(Sangzhi alkaloids,SZ-A)是来源于中药桑枝的具有α葡萄糖苷酶抑制活性的有效组分。本研究在酶学和整体动物水平,考察SZ-A对几种糖苷酶的抑制特点和抗糖尿病作用。基于酶活性评价体系,分别考察了SZ-A对蔗糖酶、麦芽糖酶及淀粉酶的抑制作用,计算半数抑制浓度(IC50)值;在正常小鼠和四氧嘧啶(alloxan)高血糖小鼠中,考察单次灌胃SZ-A对多糖和葡萄糖负荷后血糖升高的影响;在链脲霉素(STZ)糖尿病大鼠和高脂喂养的肥胖C57小鼠(HFC57)中,考察长期给予SZ-A对糖脂代谢紊乱的改善作用。动物实验操作过程依照中国医学科学院、北京协和医学院药物研究所实验动物管理与动物福利委员会的要求执行。结果显示,SZ-A对蔗糖酶和麦芽糖酶活性抑制的IC50分别为21.9和40.4 ng·mL^-1,对淀粉酶几乎无抑制作用。SZ-A能显著降低正常和高血糖小鼠蔗糖和淀粉负荷后的血糖峰值和血糖时间曲线下面积,抑制餐后血糖的升高;但对葡萄糖负荷后的血糖升高无影响。在STZ糖尿病大鼠中,SZ-A给药3周后,可显著降低其随机及空腹血糖、血甘油三酯(TG)和胆固醇(TC)、糖化血清蛋白及尿糖水平。在糖尿病前期动物模型HFC57小鼠中,SZ-A给药6周后,可显著降低随机和空腹血糖、血TC及基础胰岛素水平,改善糖脂代谢紊乱和胰岛素抵抗状态,改善葡萄糖刺激的胰岛素分泌功能。综上,SZ-A是一种高选择性的双糖酶抑制剂;单次给药可显著抑制正常及糖尿病小鼠多糖负荷后的血糖升高,长期给药可改善糖尿病前期及糖尿病动物的糖脂代谢紊乱。SZ-A通过抑制α葡萄糖苷酶活性控制糖尿病状态下的餐后血糖的波动,长期应用可能有益于减缓糖尿病及其并发症的发生和发展。

Sangzhi alkaloids(SZ-A) are derived from traditional Chinese medicine Ramulus Mori,serving well as an innovative antidiabetic drug,due to α-glucosidase inhibition.To evaluate the potency of glucosidase inhibitory effect of SZ-A,the enzyme-based screening platforms,including sucrase,maltase and amylase were established,and IC50 was calculated.The effects of SZ-A on postprandial blood glucose at a single dose,oral sucrose,starch and glucose loading were determined in normal ICR mice and alloxan-induced hyperglycemic mice.To confirm the anti-diabetic effects of SZ-A on glucose and lipid metabolism after long-term administration,the postprandial and fasting blood glucose,serum insulin,urinary glucose levels,glycosylated serum proteins and blood lipid levels were determined in high-fat fed C57 obese mice(pre-diabetic HFC57 mice) and diabetic rats induced by streptozotocin(STZ).The Experimental Animal Welfare Ethics Committee of the Institute of Materia Medica,Chinese Academy of Medical Sciences and Peking Union Medical College approved all of the protocols for this research.We found that SZ-A exhibited a significant inhibitory effect on the sucrase and maltase.SZ-A showed no effect on amylase.In normal ICR mice and alloxan-induced hyperglycemic mice,SZ-A at a single dose significantly delayed and reduced the peak of blood glucose after sucrose or starch loading,but showed no effect on the increase of blood glucose after glucose loading.In STZ diabetic rats,SZ-A significantly reduced the postprandial or fasting blood glucose levels,glycosylated serum proteins and urinary glucose.SZ-A also reduced serum triglyceride(TG) and cholesterol(TC) levels after 3 weeks of treatment.SZ-A ameliorated the postprandial blood glucose or the fasting blood glucose elevation,and reduced the incidence of hyperglycemia in HFC57 mice.SZ-A decreased the basal insulin level,improved insulin sensitivity,and ameliorated glucose intolerance in prediabetic HFC57 mice.Our results indicated that SZ-A had a novel inhibitory activity on α-glucosidase,especially on disaccharidases.SZ-A at a single dose significantly reduced the peak of blood glucose elevation and delayed the increase of blood glucose in normal and diabetic mice after disaccharide and polysaccharide loading.Long-term SZ-A treatment improved glucose and lipid metabolic profiles by delaying carbohydrate absorption from the intestine and reduced the postprandial blood glucose levels in both pre-diabetic and diabetic animal models.Therefore,SZ-A application may display a beneficial role in preventing the development and complications of diabetes.