亮氨酸调节大鼠胰岛素分泌的功能研究

目的:探讨亮氨酸对正常大鼠以及大鼠离体胰岛细胞胰岛素分泌的影响。方法:体外实验采用胆总管内胶原酶灌注膨胀消化胰腺的方法分离大鼠胰岛,在低糖（5.6mmol/L）/高糖（25mmol/L）DMEM培养基,加入0、10、20mmol/L亮氨酸,孵育120min后测定上清中胰岛素水平。体内实验:24只雄性Wistar大鼠随机分为4组,即对照组（Con）、2g/kg葡萄糖组（Glu）、1.5g/kg亮氨酸组（Leu）和葡萄糖+亮氨酸组（Glu+Leu）,禁食过夜后一次性灌胃。灌胃前、灌胃后30、60和120min割尾取血,测定血糖、血浆胰岛素水平并计算其曲线下面积（AUC）。结果:体外实验发现20mmol/L亮氨酸刺激了高糖培养基中胰岛细胞的胰岛素分泌,低糖培养基中添加亮氨酸没有引起胰岛素水平的明显变化（p>0.05）。体内实验发现亮氨酸单独灌胃对大鼠血糖和胰岛素水平无明显影响。和Glu组比较,Glu+Leu组60、120min血糖显著降低,30min胰岛素则显著升高;相应地升高了胰岛素AUC（p<0.01）,降低了葡萄糖AUC（p<0.05）。结论:亮氨酸促进葡萄糖依赖的胰岛素的一过性释放,从而降低血糖水平。 

Effect of leucine on insulin secretion in normal rats

Objective: To investigate the effect of leucine on insulin secretion in normal rats and their isolated islets. Methods: In vitro, islets were isolated from Wistar rats by collagenase digestion. Leucine ( 0, 10, 20mmol /L) was added to low glucose ( 5.6mmol /L) /high glucose ( 25mmol /L) DMEM medium for 120min incubation with islets and the level of insulin in supernatant was measured.In vivo, 24 male Wistar rats were randomly divided into 4 groups. After overnight fasting, rats were intragastrically administered water ( Con) , 2g /kg glucose ( Glu) , 1.5g /kg leucine ( Leu) and glucose combined with leucine ( Leu + Glu) , respectively.Blood glucose and plasma insulin levels were measured at 0, 30, 60 and 120min after administration.Area under the curve ( AUC) of glucose and insulin were also calculated. Results: In vitro, 20mmol /L leucine significantly increased insulin secretion in 25mmol /L glucose medium.In vivo, leucine alone did not affect plasma levels of glucose and insulin.Comparing with Glu group, blood glucose levels at 60min and 120min significantly decreased and plasma insulin significantly increased at 30min in Glu + Leu group.Insulin AUC significantly higher in Glu + Leu group than in Glu group ( p < 0.01) and glucose AUC was significantly lower in Glu + Leu group than in Glu group ( p < 0.05) . Conclusion: Leucine increases insulin secretion in the presence of glucose, leading to the decrease of blood glucose.