Research of Novel Mechanism in the Genesis of Diabetes Mellitus: The Dysfunction of pancreatic beta cell by the Increase of Blood Lipid Peroxides

通过对脂质过氧化物与血管细胞关系的研究，认为脂质过氧化是动脉粥样硬化的主要机制。然而，其对其他细胞类型的影响尚未被研究。胰脏的胰岛素分泌细胞（β-细胞）对氧化应激的反应较弱。因此，我们激发了来源于仓鼠胰腺肿瘤细胞的β-细胞Hit-T15细胞，以阐明磷脂过氧化物对胰岛素分泌的影响。我们在HIT-T15细胞培养中加入天然磷脂酰胆碱（PC）、过氧化磷脂酰胆碱（PCOOH）和溶血磷脂酰胆碱（LysoPC）。LysoPC显著降低胰岛素前原mRNA的表达、细胞内胰岛素含量和胰岛素分泌。PCOOH效应不影响胰岛素前原mRNA表达，但降低细胞内胰岛素水平和胰岛素分泌。这些氧化磷脂将成为氧化LDL （oxLDL）的组成部分。因此，我们在与LysoPC培养hit - t15细胞类似的实验中，研究了oxLDL与天然LDL （nLDL）和乙酰化LDL （AcLDL）的作用。与LysoPC一样，OxLDL显著降低胰岛素前原mRNA的表达、细胞内胰岛素含量和胰岛素分泌。另一方面，nLDL或AcLDL没有影响。LysoPC和oxLDL不影响MTT法评价细胞活力。提示oxLDL干扰β细胞胰岛素代谢，通过PCOOH和PC降低胰岛素分泌。我们认为氧化应激可能通过氧化低密度脂蛋白的作用而致糖尿病。

It is believed that lipid peroxidation is a main mechanism in atherogenesis from the various studies on the relationships between lipid peroxides and vascular cells. However, its effect on the other cell types has not been studied. It has been suggested that insulin secretary cell of pancreas (β-cell) was weak for oxidized stress. Therefore we challenged Hit-T15 cell, which is a β-cell derived from hamster pancreatic tumor cell, to clarify the effect of phospholipid peroxides on insulin secretion. We added native phosphatidylcholine (PC), phosphatidylcholine hydroperoxide (PCOOH) and lysophosphatidylcholine (LysoPC) in the culture of HIT-T15 cell. LysoPC significantly decreased the expression of preproinsulin mRNA, intracellular insulin content, and insulin secretion. PCOOH effect did not affect on the preproinsulin mRNA expression, but decreased intracellular insulin level and insulin secretion. These oxidized phospholipids would be the components of oxidized LDL (oxLDL). Therefore we studied the effect of oxLDL in the similar experiments as Hit-T15cell culture with LysoPC as comparison with native LDL (nLDL) and acerylated LDL (AcLDL). OxLDL significantly decreased the expression of preproinsulin mRNA, intracellular insulin content, and insulin secretion as same as LysoPC. On the other hand nLDL or AcLDL had no effects. LysoPC and oxLDL did not affect MTT assay as evaluation of cell viability. These results suggested that oxLDL disturbed insulin metabolism of β-cell to decrease insulin secretion via PCOOH and PC. We proposed that oxidized stress would be diabetogenic by the effect of oxLDL.