Palmitate induces insulin resistance in H4IIEC3 hepatocytes through reactive oxygen species produced by mitochondria.
Palmitate induces insulin resistance in H4IIEC3 hepatocytes through reactive oxygen species produced by mitochondria.
复制标题
DOI：
10.1074/jbc.m901488200
复制
发表时间：
2009-05-29
期刊：
影响因子：
--
通讯作者：
Kaneko S
中科院分区：
文献类型：
--
作者：
Nakamura S;Takamura T;Matsuzawa-Nagata N;Takayama H;Misu H;Noda H;Nabemoto S;Kurita S;Ota T;Ando H;Miyamoto K;Kaneko S
肥胖症的内脏肥胖导致过量的游离脂肪酸（FFA）通过门静脉流入肝脏，并可能导致脂肪肝疾病和肝脏胰岛素抵抗。然而，由于脂质输注或高脂肪饮食诱导的胰岛素抵抗的动物模型是复杂的，并且可能伴随着不限于肝脏的改变，因此难以确定FFA对肝脏胰岛素抵抗的贡献。因此，我们用单不饱和脂肪酸（油酸酯）和饱和脂肪酸（棕榈酸酯）处理H4 IIEC 3细胞（一种大鼠肝细胞系），以研究FFA对肝细胞的直接和初始影响。我们发现，棕榈酸酯，而不是油酸酯，抑制胰岛素刺激的酪氨酸磷酸化的胰岛素受体底物2和丝氨酸磷酸化的Akt，通过c-Jun氨基末端激酶（JNK）的激活。在JNK激活的既定刺激中，活性氧（ROS）在棕榈酸酯诱导的JNK激活中发挥了因果作用。此外，依托莫西（肉毒碱棕榈酰转移酶-1的抑制剂，肉毒碱棕榈酰转移酶-1是线粒体脂肪酸β-氧化的限速酶）以及线粒体呼吸链复合物（噻吩甲酰三氟丙酮和羰基氰间氯苯腙）的抑制剂降低了棕榈酸诱导的ROS产生。总之，我们在肝细胞中的发现表明棕榈酸酯通过JNK活化抑制胰岛素信号转导，并且棕榈酸酯的加速β-氧化引起线粒体呼吸链中的过量电子通量，导致ROS产生增加。因此，棕榈酸酯诱导的拟南芥衍生的ROS可能是JNK激活和细胞胰岛素抵抗的主要贡献者。
Visceral adiposity in obesity causes excessive free fatty acid (FFA) flux into the liver via the portal vein and may cause fatty liver disease and hepatic insulin resistance. However, because animal models of insulin resistance induced by lipid infusion or a high fat diet are complex and may be accompanied by alterations not restricted to the liver, it is difficult to determine the contribution of FFAs to hepatic insulin resistance. Therefore, we treated H4IIEC3 cells, a rat hepatocyte cell line, with a monounsaturated fatty acid (oleate) and a saturated fatty acid (palmitate) to investigate the direct and initial effects of FFAs on hepatocytes. We show that palmitate, but not oleate, inhibited insulin-stimulated tyrosine phosphorylation of insulin receptor substrate 2 and serine phosphorylation of Akt, through c-Jun NH2-terminal kinase (JNK) activation. Among the well established stimuli for JNK activation, reactive oxygen species (ROS) played a causal role in palmitate-induced JNK activation. In addition, etomoxir, an inhibitor of carnitine palmitoyltransferase-1, which is the rate-limiting enzyme in mitochondrial fatty acid β-oxidation, as well as inhibitors of the mitochondrial respiratory chain complex (thenoyltrifluoroacetone and carbonyl cyanide m-chlorophenylhydrazone) decreased palmitate-induced ROS production. Together, our findings in hepatocytes indicate that palmitate inhibited insulin signal transduction through JNK activation and that accelerated β-oxidation of palmitate caused excess electron flux in the mitochondrial respiratory chain, resulting in increased ROS generation. Thus, mitochondria-derived ROS induced by palmitate may be major contributors to JNK activation and cellular insulin resistance.