ICA69的表达调控对胰岛β细胞能量代谢的影响机制

Diabetes is the one of the most serious chronic diseases. Insulin, the unique hypoglycemic hormone, is only secreted from pancreatic islets β cells, and the islets function is the important research field in diabetes. It has been reported that Islet cell autoantigen of 69 kDa (ICA69) was involved in vesicular transport of insulin. Deficient of ICA69 decreased insulin secretion but increased the ration of proinsulin. However, the alternation of ICA69 expression and its influence in diabetic islets have not been clearly addressed. Otherwise, ICA69 has a BAR domain with the membrane-binding capability, which infer ICA69 may cross-talk with mitochondria. Our previous data showed that high glucose reduced ICA69 mRNA depended on methyltransferase in INS-1 cell line. Low expression of ICA69 suppressed the mitochondrial member potential, aerobic respiration and ATP production. These results suggested that diabetes may disrupt cell metabolism via epigenetic regulation of ICA69 expression in islets β cells. Based on this, using cell line, diabetes model and ICA69-/- mice ,we sought to explore the underlying mechanisms involved in ICA69 down-regulation in diabetic islets, address the mechanism of ICA69 and its BAR domain on mitochondrial function and energy metabolism in islets β cells. Giving scientific supporting for the pathogenesis diagnosis of diabetes.

糖尿病是威胁人类健康的最重要慢性疾病之一,胰岛素是唯一降血糖激素,仅从胰岛β细胞中分泌，胰岛β细胞功能是糖尿病研究的重要领域。有报道胰岛β细胞中ICA69参与胰岛素囊泡运输,ICA69的缺失导致胰岛素分泌下降;胰岛素原分泌增加,但ICA69在胰岛中的表达调控、影响机制尚不明确。此外ICA69具有BAR结构域可与磷脂膜结合，提示ICA69可能与具有双层膜的线粒体存在相互作用。课题组研究发现高糖可甲基转移酶依赖性下调胰岛细胞ICA69表达;ICA69敲低使线粒体膜电位下调,有氧呼吸和ATP产量下降。结果提示糖尿病可能通过表观遗传学调控β细胞ICA69的表达继而影响细胞能量代谢。为此本课题拟利用细胞、糖尿病动物和ICA69-/-小鼠进一步探索糖尿病内环境对胰岛ICA69表达的调控机制;阐明ICA69及其BAR结构域影响胰岛细胞线粒体功能和能量代谢的具体机制,为探索糖尿病的发病机制提供科学依据。

糖尿病是当前威胁全球人类健康的最重要的慢性非传染性疾病之一，对于胰岛素分泌的研究有着重要的临床意义。ICA69在胰岛细胞表达水平较高，并参与胰岛素分泌，但糖尿病发表过程中ICA69的调控以及对胰岛细胞代谢的影响机制尚不明确。本项目证实ICA69在胰岛细胞代谢中有着重要的作用，ICA69敲除可导致INS-1细胞ATP合成水平降低，乳酸生成增加，细胞代谢转向无氧代谢;发现ICA69与线粒体有很好的共定位分布，线粒体膜电位水平也在ICA69敲除后明显下降。分离ICA69敲除小鼠的原代胰岛，发现ICA69敲除小鼠的原代胰岛胰岛细胞的ATP水平显著下降。细胞和敲除动物实验结果证实ICA69敲除后显著抑制胰岛细胞代谢，可能与ICA69与线粒体间的相互左右有关。ICA69表达调控的研究发现高糖培养后INS-1细胞ICA69表达下调，且可被甲基转移酶抑制剂反转，高糖培养后启动子区甲基化上调明显。同时高糖导致的缺氧环境也导致INS-1细胞ICA69和PICK1 mRNA和蛋白表达水平均显著降低。自发糖尿病GK大鼠模型显示脂肪和胰岛中ICA69表达下降，进一步进行原代胰岛细胞ICA69启动子区测序，显示ICA69启动子区平均甲基化水平明显增加，详细位点甲基化增加明显。本项目结果提示长期糖尿病的高糖和缺氧环境可以诱发ICA69启动子区甲基化水平增加，从而导致ICA69表达下调，影响胰岛细胞代谢水平。