Department of Pharmacology, College of Medicine, Chung-Ang University, Seoul, Korea.
Department of Pathology, College of Medicine, Chung-Ang University, Seoul, Korea.
Clin Exp Pharmacol Physiol. 2019 Oct;46(10):898-909. doi: 10.1111/1440-1681.13131. Epub 2019 Jul 21.
The role as well as the molecular mechanisms of protectin DX (PDX) in the prevention of hepatic insulin resistance, a hallmark of type 2 diabetes, remains unknown. Therefore, the present study was designed to explore the direct impact of PDX on insulin resistance and to investigate the expression of fetuin-A and selenoprotein P (SeP), hepatokines that are involved in insulin signalling, in hepatocytes. Human serum levels of PDX as well as fetuin-A and SeP were determined by high-performance liquid chromatography (HPLC). Human primary hepatocytes were treated with palmitate and PDX. NF-κB phosphorylation as well as expression of insulin signalling associated genes and hepatokines were determined by Western blotting analysis. FOXO1 binding levels were measured by quantitative real-time PCR. Selected genes from candidate pathways were evaluated by small interfering (si) RNA-mediated gene suppression. Serum PDX levels were significantly (P < 0.05) downregulated, whereas serum fetuin-A and SeP levels were increased (P < 0.05) in obese subjects compared with healthy subjects. In in vitro experiments, PDX treatment increased AMP-activated protein kinase (AMPK) phosphorylation and SIRT1 expression and attenuated palmitate-induced fetuin-A and SeP expression and insulin resistance in hepatocytes. AMPK or SIRT1 siRNA mitigated the suppressive effects of PDX on palmitate-induced fetuin-A through NF-κB and SeP expression linked to FOXO1 and insulin resistance. Recombinant fetuin-A and SeP reversed the suppressive effects of fetuin-A and SeP expression on palmitate-mediated impairment of insulin signalling. The current finding provides novel insight into the underlying mechanism linking hepatokines to the pathogenesis of hepatic insulin resistance.
保护素 DX（PDX）在预防 2 型糖尿病标志性的肝胰岛素抵抗中的作用及其分子机制尚不清楚。因此，本研究旨在探讨 PDX 对胰岛素抵抗的直接影响，并研究参与胰岛素信号的肝分泌因子胎球蛋白-A 和硒蛋白 P（SeP）在肝细胞中的表达。采用高效液相色谱法（HPLC）测定 PDX、胎球蛋白-A 和 SeP 的人血清水平。用棕榈酸和 PDX 处理人原代肝细胞。通过 Western blot 分析测定 NF-κB 磷酸化以及胰岛素信号相关基因和肝分泌因子的表达。通过定量实时 PCR 测定 FOXO1 结合水平。通过小干扰（si）RNA 介导的基因抑制评估候选途径中的选定基因。与健康受试者相比，肥胖受试者的血清 PDX 水平显著（P < 0.05）降低，而血清胎球蛋白-A 和 SeP 水平升高（P < 0.05）。在体外实验中，PDX 处理增加了 AMP 激活的蛋白激酶（AMPK）磷酸化和 SIRT1 表达，并减弱了棕榈酸诱导的胎球蛋白-A 和 SeP 表达以及肝细胞胰岛素抵抗。AMPK 或 SIRT1 siRNA 减轻了 PDX 通过 NF-κB 和与 FOXO1 和胰岛素抵抗相关的 SeP 表达对棕榈酸诱导的胎球蛋白-A 的抑制作用。重组胎球蛋白-A 和 SeP 逆转了胎球蛋白-A 和 SeP 表达对棕榈酸介导的胰岛素信号损害的抑制作用。这一发现为肝分泌因子与肝胰岛素抵抗发病机制的联系提供了新的见解。
