Preproinsulin expression, insulin release, and hepatic glucose metabolism after a glucose load in the omnivorous GIFT tilapia Oreochromis niloticus
Preproinsulin expression, insulin release, and hepatic glucose metabolism after a glucose load in the omnivorous GIFT tilapia Oreochromis niloticus
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杂食性 GIFT 罗非鱼 Oreochromis niloticus 葡萄糖负荷后前胰岛素原表达、胰岛素释放和肝脏葡萄糖代谢
DOI：
10.1016/j.aquaculture.2017.10.001
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发表时间：
2018-01-01
期刊：
影响因子：
4.5
通讯作者：
Wang, De-Shou
中科院分区：
文献类型：
--
作者：
Chen, Yong-Jun;Wang, Xin-Ya;Wang, De-Shou
本研究旨在探讨改良尼罗罗非鱼（Oreochromis niloticus）葡萄糖耐量试验（GTT）后胰岛素前原（ins）和胰岛素降解酶（ide）表达、血浆胰岛素水平和肝脏糖代谢的时间变化。剥夺食物24 h后，雄性成鱼腹腔注射1 g /kg体重的葡萄糖，然后在GTT后0、1、2、4、6和12 h取样。与对照组（4.3 mM/L）相比，血浆葡萄糖水平在1 h达到峰值（14.8 mM/L），在2 ~ 4 h下降（5.7 ~ 8.3 mM/L），在GTT治疗6 h后恢复。虽然在Brockman体中，ins1、ins2和ide的表达不受影响，但在葡萄糖注射后1 ~ 4小时内，血浆胰岛素水平随血浆葡萄糖水平的升高而升高。葡萄糖转运蛋白1的表达在GTT后1 h急剧升高，表明肝脏葡萄糖摄取受到刺激。葡萄糖激酶mRNA水平在1 ~ 4 h内上调，磷酸果糖激酶活性在2 ~ 4 h内升高，说明葡萄糖给药后1 ~ 4 h肝糖酵解处于活跃状态。糖原合成酶1 mRNA水平在GTT后1 h升高，肝糖原水平在GTT后4 h积累。虽然葡萄糖-6-磷酸酶催化亚基a2的表达在1 ~ 2 h内受到抑制，但葡萄糖注射并未影响磷酸烯醇丙酮酸羧激酶2的mRNA水平及其活性，这可能延长了罗非鱼对葡萄糖的清除时间。GTT同时上调ATP柠檬酸裂解酶a （1-4 h）、乙酰辅酶a羧化酶α (4-12 h)和脂肪酸合成酶（2-12 h） mRNA水平，有效刺激肝脏脂肪生成以处理肝细胞吸收的多余葡萄糖。综上所述，葡萄糖是罗非鱼有效的胰岛素分泌剂，肝脏通过刺激葡萄糖摄取、糖酵解、糖生成和脂肪生成，在清除葡萄糖负荷方面发挥了重要作用。
This study was performed to investigate the time course of changes in the expression of preproinsulin (ins) and insulin-degrading enzyme (ide), plasma insulin level and hepatic glucose metabolism after a glucose tolerance test (GTT) in genetically improved farmed Nile tilapia (GIFT), Oreochromis niloticus. Male adult fish were intraperitoneally injected with 1 g glucose/kg of body weight after 24 h of food deprivation, and then subjected to sampling at 0, 1, 2, 4, 6 and 12 h after the GTT. Compared with the control (4.3 mM/L), plasma glucose level peaked at 1 h (14.8 mM/L), decreased during 2-4 h (5.7-8.3 mM/L), and was restored after 6 h of the GTT. Although the expression of ins1, ins2 and ide were not affected in the Brockman body, plasma insulin level concomitantly increased with the increase of plasma glucose level during 1-4 h after the glucose injection. The expression of glucose transporter 1 sharply increased at 1 h after the GTT, indicating that hepatic glucose uptake was stimulated. The mRNA level of glucokinase was up-regulated during 1-4 h, and the activity of phosphofructokinase increased during 2-4 h, suggesting that hepatic glycolysis was active during 1-4 h after the glucose administration. The mRNA level of glycogen synthase 1 increased at 1 h, and liver glycogen level accumulated at 4 h after the GTT. Although the expression of glucose-6-phosphatase catalytic subunit a2 was suppressed during 1-2 h, neither the mRNA level of phosphoenolpyruvate carboxykinase 2 nor its activity was impacted by the glucose injection, which might have prolonged the glucose clearance of tilapia. Hepatic lipogenesis was effectively stimulated to dispose excess glucose absorbed by the hepatocytes, as up-regulation of mRNA levels of ATP citrate lyase a (during 1-4 h), acetyl-CoA carboxylase alpha (during 4-12 h) and fatty acid synthase (during 2-12 h) were accompanied by the GTT. Taken together, it was concluded that glucose was an effective insulin secretagogue in tilapia, and liver played an important role to clear the glucose load through stimulation of glucose uptake, glycolysis, glycogenesis and lipogenesis.