Chen Pei, Wu Xiufeng, Gu Xu, Han Juan, Xue Min, Liang Xiaofang
National Aquafeed Safety Assessment Center, Institute of Feed Research, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
Institute of Food and Nutrition Development, Ministry of Agriculture and Rural Affairs, Beijing 100081, China.
Gen Comp Endocrinol. 2021 Sep 1;310:113811. doi: 10.1016/j.ygcen.2021.113811. Epub 2021 May 9.
Forkhead box O1 (FoxO1), a nuclear transcription factor, plays an important role in insulin-mediated glucose metabolism. In this study, FoxO1 gene from largemouth bass (Micropterus salmoides) was cloned and characterized, and its effects on hepatic glucose metabolism regulated by insulin-AKT pathway were investigated in response to glucose or insulin-glucose injection. The full-length cDNA of FoxO1 consisted of 2541 bp and encoded 680 amino acids. Sequence alignments and phylogenetic analysis revealed that FoxO1 exhibited a high degree of conservation among teleost, retaining one forkhead domain, one transactivation domain, and three phosphorylation sites. FoxO1 mRNA was expressed in a wide range of tissues, and high in the brain and liver. Glucose loading resulted in persistent hyperglycemia, and plasma insulin levels remained unchanged except at 1 h. After the insulin-glucose injection, insulin levels were significantly elevated and glucose levels recovered to the basal value after 6 h, which indicated insufficient insulin secretion caused persistent hyperglycemia in this species. Compared with the glucose injection group, transcript levels and enzyme activities of hepatic glycolysis-related genes (GK and PK) were significantly activated, and gluconeogenesis-related genes (PEPCK and G6Pase) were significantly depressed at 3 h after the insulin-glucose injection. Besides, phosphorylation of AKT-FoxO1 pathway was significantly activated. Therefore, insulin improved glucose metabolism by activating the AKT-FoxO1 phosphorylation to decrease hyperglycemia stress after the meal, which indicated insufficient insulin secretion was the reason for glucose intolerance in largemouth bass. Meanwhile, conserved S267 and S329 phosphorylation sites of FoxO1 were confirmed to be regulated by AKT and mediated the glucose metabolism. In conclusion, activation of insulin-AKT-FoxO1 pathway improved glucose tolerance through mediating glucose metabolism in largemouth bass.
叉头框O1（FoxO1）是一种核转录因子，在胰岛素介导的葡萄糖代谢中发挥重要作用。在本研究中，克隆并鉴定了大口黑鲈（Micropterus salmoides）的FoxO1基因，并研究了其在葡萄糖或胰岛素-葡萄糖注射后对胰岛素-AKT途径调节的肝脏葡萄糖代谢的影响。FoxO1的全长cDNA由2541个碱基对组成，编码680个氨基酸。序列比对和系统发育分析表明，FoxO1在硬骨鱼中具有高度保守性，保留了一个叉头结构域、一个反式激活结构域和三个磷酸化位点。FoxO1 mRNA在多种组织中表达，在脑和肝脏中表达较高。葡萄糖负荷导致持续性高血糖，除1小时外血浆胰岛素水平保持不变。胰岛素-葡萄糖注射后，胰岛素水平显著升高，6小时后血糖水平恢复到基础值，这表明胰岛素分泌不足导致该物种持续性高血糖。与葡萄糖注射组相比，胰岛素-葡萄糖注射后3小时，肝脏糖酵解相关基因（GK和PK）的转录水平和酶活性显著激活，糖异生相关基因（PEPCK和G6Pase）显著下调。此外，AKT-FoxO1途径的磷酸化显著激活。因此，胰岛素通过激活AKT-FoxO1磷酸化改善葡萄糖代谢，以减轻餐后高血糖应激，这表明胰岛素分泌不足是大口黑鲈葡萄糖不耐受的原因。同时，证实FoxO1保守的S267和S329磷酸化位点受AKT调节并介导葡萄糖代谢。总之，胰岛素-AKT-FoxO1途径的激活通过介导大口黑鲈的葡萄糖代谢改善了葡萄糖耐受性。
