龙虾壳聚糖干预后糖尿病小鼠血糖和糖耐量的变化

Influence of lobster chitosan on blood sugar and glucose tolerance in diabetic mice

目的:观察龙虾壳聚糖对四氧嘧啶致糖尿病小鼠的降血糖作用。方法:实验于2005-04/12在江苏大学医学技术学院生化研究室和江苏大学医学部实验动物中心完成。实验动物选用45d的健康雄性ICR清洁级小鼠100只。①龙虾壳聚糖对正常小鼠空腹血糖的影响:取正常小鼠20只,禁食3h后测定空腹血糖,按血糖水平的高低随机抽签法分成龙虾壳聚糖组和正常对照组,每组10只。龙虾壳聚糖用10g/L醋酸配制,龙虾壳聚糖组小鼠按剂量200mg/(kg·d)连续灌胃;正常对照组以10g/L醋酸20mL/kg灌胃,连续30d。30d后禁食3h测定其空腹血糖值。②制备糖尿病模型:取正常小鼠80只,用四氧嘧啶生理盐水溶液尾静脉注射制备糖尿病小鼠模型,剂量100mg/kg,容积10mL/kg,6d后测定禁食3h后各小鼠的空腹血糖,以血糖值≥25mmol/L者确定为高血糖模型成功动物。③龙虾壳聚糖对尿病小鼠空腹血糖的影响:取高血糖模型成功大鼠40只,随机分成龙虾壳聚糖50,100和200mg/kg3个剂量组和高血糖模型对照组,每组10只。模型对照组给予10g/L醋酸灌胃,剂量20mL/kg,连续30d;龙虾壳聚糖50,100和200mg/kg剂量组分别给予龙虾壳聚糖50,100和200mg/(kg·d)(用10g/L醋酸配制),连续30d。第31天禁食3h后测定各组小鼠的空腹血糖值,比较各组动物血糖值及血糖下降百分率。血糖下降百分率=[(实验前血糖值一实验后血糖值)/实验前血糖值]×100%。④龙虾壳聚糖对糖尿病小鼠糖耐量的影响:在各组小鼠测定空腹血糖值后,龙虾壳聚糖50,100和200mg/kg剂量组分别继续给予龙虾壳聚糖50,100和200mg/(kg·d);模型对照组给予10g/L醋酸灌胃,剂量20mL/kg。15～20min后经口给予葡萄糖溶液2.0g/kg,于0,0.5,2h分别测定各组小鼠的血糖值。观察模型对照组与龙虾壳聚糖50,100和200mg/kg剂量组在给予葡萄糖后各时间点血糖曲线下面积的变化。血糖曲线下面积=0.25×(0h血糖值+4×0.5h血糖值+3×2h血糖值)。结果:实验小鼠100只均进入结果分析,无脱失值。①龙虾壳聚糖在50,100和200mg/kg的剂量下,糖尿病小鼠的空腹血糖值明显低于模型对照组(P<0.01,P<0.001),血糖降低百分率分别达16.08%、19.05和25.00%,模型对照组小鼠的血糖值仅降低9.92%。②龙虾壳聚糖100和200mg/kg剂量组均具有不同程度地增强糖尿病小鼠的糖耐量作用,血糖曲线下面积:模型对照组为(57.6±3.69)mm2,龙虾壳聚糖100和200mg/kg剂量组分别为[(52.1±3.06),(49.2±2.52)mm2],明显低于模型对照组(P<0.05和P<0.001)。③龙虾壳聚糖对正常小鼠的血糖水平无明显影响(P>0.05)。④模型制备和行为学结果:糖尿病小鼠模型制备6d测定禁食3h后各小鼠的空腹血糖值为25～28mmol/L,并出现了明显的多饮多尿消瘦等糖尿病症状。结论:龙虾壳聚糖对糖尿病小鼠具有降血糖和增强糖耐量的作用,且不影响正常糖代谢。

AIM： To observe the action of lobster chitosan in declining the blood sugar （BS） of alloxan-induced diabetic mice. METHODS： The experiment was completed in the Biochemical Laboratory, College of Medical Science Technology and the Experimental Animal Center, Medical College of Jiangsu University from April to December in 2005. Totally 100 healthy male mice with ICR cleanness class and 45 days old were adopted in the experiment.①Effects of lobster chitosan on fasting BS of normal mice： Twenty normal mice were selected to measure the BS value after fasting 3 hours, and were divided into lobster chitosan grbup and normal control group according to the BS levels, every group had 10 mice. The mice of lobster chitosan group were treated continuously with intragastric infusion of 200 mg/kg lobster chitosan every day, which was prepared with 10 g/L acetic acid. While＇ the mice of normal control group were infused into the stomach by 10 g/L acetic acid （20 mL/kg） every day, continuously for 30 days. Then the BS values of all the mice were .estimated after fasting 3 hours. ②Preparations of diabetic models： Eighty normal mice were injected intravenously with alloxan saline via caudal veins to prepare the diabetic models, and the dose was 100 mg/kg while volume was 10 mL/kg. Six days later, the fasting BS were measured after fasting 3 hours in all the mice, who was taken as successful model of hyperglycemia if the BS value was 1〉 25 mmol/L, ③Effects of lobster chitosan on fasting BS of diabetic mice： Forty successful rat models of hyperglycemia were randomly divided into three lobster chitosan groups with doses of 50, 100 and 200 mg/kg and the control group of hyperglycemia model, with 10 mice in every group. The rat of model control group were administrated intragastrically by 10 g/L acetic acid at the dose of 20 mg/kg per day, continuously for 30 days; The mice of lobster chitosan groups were administrated with 50, 100 and 200 mg/kg lobster chitosan separately （prepared with 10 g/L acetic acid）, and the duration was also continuous 30 days. Thirty days later, all the mice were used to assay BS after fasting 3 hours. And the BS value and BS descent percent were compared among groups. BS descent percent=[（BS value before experiment-BS value after experiment）/BS value before experiment]×100%.④Effects of lobster chitosan on sugar endurance in diabetic mice： After the fasting BS value detections, the mice of three lobster chitosan groups were treated with daily intragastric injection of 50, 100 and 200 mg/kg lobster chitosan; The control mice models were given 10 g/L acetic acid （20 mL/kg） by stomach infusion; All the mice were administrated orally with 2.0 g/kg glucose liquid after 15-20 minutes, then every mouse＇s BS value was measured after 0, 0.5 and 2 hours separately. The change of area under the BS curve （AUC） at every time point was observed after glucose administration and compared between model control group and three lobster chitosan groups. AUC = 0.25×（BS value at 0 hour ＋ 4×BS value at 0.5 hours ＋ 3 ×BS value at 2 hours） RESULTS： Totally 100 mice were involved in the result analysis without any drop.①The lobster chitosan of 50 mg/kg, 100 mg/kg and 200 mg/kg decreased BS value in diabetic mice evidently, compared with model control group （P 〈 0.01, P 〈 0.001）. The BS decent percents were 16.08%, 19.05% and 25.00% respectively in lobster chitosan groups, but only lowered 9.92% in model coutrol group. ②Lobster chitosan of 100 and 200 mg/kg strengthened the sugar tolerance of the diabetic mice to some extents, and decreased obviously the AUC of BS： model control group： （57.6±3.69） mm^2; lobster chitosan group of 100 and 200 mg/kg were [（52.1±3.06）,（49.2 ±2.52） mm^2], and obvious lower than control group （P 〈 0.05, P 〈 0.001）. ③Lobster chitosan had no obvious influence on the BS value of normal mice （P 〉 0.05）.④Medel preparations and behavioral results： After 6 days of diabetic model establishment, the fasting BS value of diabetic mice were 25-28 mmol/L after fasting 3 hours, and appeared the obvious polydipsia, polyuria and emaciation, etc. CONCLUSION： The lobster chitosan has the functions of declining the BS value and strengthening the sugar tolerance whereas unaffecting the normal glycogen metabolism in diabetic mice.