Physiological and molecular biological studies on functional alterations in ion channels of pancreatic beta cells in diabetes mellitus.

糖尿病胰腺β细胞离子通道功能改变的生理和分子生物学研究。

基本信息

批准号：
05670857
负责人：
ISHIDA Hitoshi
金额：
$ 1.34万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

The selective impairment of glucose-induced insulin secretion has been known as one of the major characteristics of pathogenetic aspects in non-insulin-dependent diabetes mellitus (NIDDM) . We have recently reported that the intracellular calcium responses to glucose are selectively impaired in pancreatic beta cells of NIDDM rat models. In order to clarify the molecular mechanism underlying this impairment, we investigated the activities of ATP sensitive K^+ channels (K_<ATP> channels) and voltage-dependent Ca^<2+> channels (VDCCs) directly using the patch-clamp technique, both of which are known to play an important role in the elevation of intracellular calcium levels after the glucose stimulation. The inhibition of K_<ATP> channels activities by glucose was reduced in beta cells of GK rats, a genetic model of NIDDM,whereas the ATP sensitivity of channels was intact. This clearly indicates that the intracellular glucose metabolism is impaired in NIDDM beta cells. On the other hand, the channels inhibition by glyceraldehyde or ketoisocaproate, which are matabolizad through the intermediates in glucose metabolism, was similar between GK and control rats. However, the inhibition of channel activities by dihydroxyacetone (DHA) -phosphate, an isomer of glyceraldehyde-3-phosphate, was reduced in NIDDM beta cells. Since DHA-phosphate can enter the glycerol phosphate shuttle which is thought to be a direct link in the metaolic pathway between glycolysis and mitochondrial oxidation, the responsible sites for impaired glucose metabolism is speculated to be located in this shuttle. In addition, the direct augmentation of VDCC activities through glucose metabolism was also found to be reduced by perforated-patch recording in beta cells of GK rats. These facts are though to be closely related to the selective impairment of glucose induced insulin secretion from NIDDM beta cells.

葡萄糖诱导的胰岛素分泌的选择性受损已被认为是非胰岛素依赖型糖尿病(NIDDM)发病方面的主要特征之一。我们最近报道，在 NIDDM 大鼠模型的胰腺 β 细胞中，细胞内钙对葡萄糖的反应选择性受损。为了阐明这种损伤的分子机制，我们直接使用膜片钳技术研究了 ATP 敏感的 K^+ 通道（K_<ATP> 通道）和电压依赖性 Ca^<2+> 通道（VDCC）的活性，已知这两者在葡萄糖刺激后细胞内钙水平的升高中发挥重要作用。 NIDDM遗传模型GK大鼠β细胞中葡萄糖对K_<ATP>通道活性的抑制作用减弱，而通道的ATP敏感性完整。这清楚地表明 NIDDM β 细胞的细胞内葡萄糖代谢受损。另一方面，甘油醛或酮异己酸（通过葡萄糖代谢中间体代谢）对通道的抑制作用在 GK 和对照大鼠之间是相似的。然而，在 NIDDM β 细胞中，磷酸二羟丙酮 (DHA)（3-磷酸甘油醛的异构体）对通道活性的抑制作用减弱。由于 DHA-磷酸盐可以进入磷酸甘油穿梭机，而甘油磷酸穿梭机被认为是糖酵解和线粒体氧化之间代谢途径的直接联系，因此推测葡萄糖代谢受损的负责位点位于该穿梭机中。此外，还发现 GK 大鼠 β 细胞中的穿孔贴片记录可以减少通过葡萄糖代谢直接增强的 VDCC 活性。这些事实被认为与 NIDDM β 细胞葡萄糖诱导的胰岛素分泌的选择性损伤密切相关。