Welsh M, Hellerström C, Andersson A
Biochim Biophys Acta. 1982 Oct 11;721(2):178-84. doi: 10.1016/0167-4889(82)90066-0.
In order to further evaluate the importance of B-cell metabolism for the stimulation of insulin release, respiration and insulin release were studied in mouse pancreatic islets. Leucine and 2-ketoisocaproate stimulated insulin release during an initial 1-h period, whereas there was no stimulation during two subsequent 1-h periods. This effect was in contrast to that of 16.7 mM glucose, which was a potent stimulator through all the 3 h. Furthermore, the presence of glucose (5.6 mM) or glutamine together with either leucine or 2-ketoisocaproate enhanced the insulin release and prolonged the stimulation. When the kinetics of islet respiration were studied both leucine and 2-ketoisocaproate exerted an initial stimulation on the O2 uptake which, however, was short-lived (less than 30 min). The presence of 5.6 mM glucose strongly delayed the respiratory retardation seen after the initial stimulation. Similarly, glutamine enhanced the leucine- and 2-ketoisocaproate-stimulated respiratory rates and prevented the respiratory retardation otherwise observed. Leucine (20 mM) and 2-ketoisocaproate (10 and 20 mM) stimulated the oxidation of glucose (5.6 mM). It is concluded that there is a strong correlation between respiratory stimulation and the enhancement of insulin release and that leucine and 2-ketoisocaproate depend on the presence of endogenous fuels for their ability to stimulate islet functions in vitro.
为了进一步评估B细胞代谢对胰岛素释放刺激的重要性，对小鼠胰岛的呼吸作用和胰岛素释放进行了研究。亮氨酸和2-酮异己酸在最初1小时内刺激胰岛素释放，而在随后的两个1小时内则无刺激作用。这种效应与16.7 mM葡萄糖的效应相反，葡萄糖在整个3小时内都是强效刺激物。此外，葡萄糖（5.6 mM）或谷氨酰胺与亮氨酸或2-酮异己酸共同存在时，可增强胰岛素释放并延长刺激时间。当研究胰岛呼吸动力学时，亮氨酸和2-酮异己酸均对氧气摄取产生初始刺激作用，然而这种刺激是短暂的（不到30分钟）。5.6 mM葡萄糖的存在强烈延迟了初始刺激后出现的呼吸抑制。同样，谷氨酰胺提高了亮氨酸和2-酮异己酸刺激的呼吸速率，并防止了原本会观察到的呼吸抑制。亮氨酸（20 mM）和2-酮异己酸（10 mM和20 mM）刺激了（5.6 mM）葡萄糖的氧化。得出的结论是，呼吸刺激与胰岛素释放增强之间存在很强的相关性，并且亮氨酸和2-酮异己酸在体外刺激胰岛功能的能力取决于内源性燃料的存在。
