鱼类的葡萄糖感知与糖代谢调节研究进展

为加深对鱼类糖的感知与代谢调控的认识,本文综述了鱼类的葡萄糖感知与摄食调控、糖代谢调控等领域的研究进展。鱼类的下丘脑不仅是中枢葡萄糖感受器所处的主要部位,同时也是食欲调节中枢。leptin、ghrelin、CCK、NPY等内分泌因子均能调控鱼类对糖的感知与摄食。另一方面,鱼类糖代谢受到胰岛素、GLP-1、ghrelin、CCK、NPY、SS等内分泌因子和糖、脂、蛋白质等营养素的双重调节。尽管鱼类对糖的利用能力低于陆生动物,但鱼体内亦存在较完善的糖的感知、摄食与代谢调节机制。因此,将来的重点工作应在于研究鱼类中枢神经系统整合营养和内分泌等信号的机制,研究草食性鱼类、杂食性鱼类在糖耐受力及糖异生调控机制上与肉食性鱼类存在的差异。

Progress in research on the regulation of glucose sensing and carbohydrate metabolism in fish

The utilization of carbohydrate in fish seems low compared with terrestrial animals,with intolerance to hyperglycemia,but the glucose regulation mechanism does exist in fish.In order to update the studies on glucosensing and carbohydrate metabolism in fish,and provide basic information for getting a better understanding about these physiological mechanisms,this review briefly introduced the progress of research on glucose sensing and its relationship with appetite,and the regulation of glucose metabolism in fish.The piscine glucose sensors were located in the different parts of the body,including central nervous system(CNS)and peripheral tissues.It is worth noting that both the glucose sensors and appestat are located in the hypothalamus,and they are also both regulated by some endocrine factors,such as leptin,ghrelin,cholecystokinin(CCK),neuropeptide Y(NPY),and so on.In mammals,the glucose sensing and appetite regulation were linked by AMP-activated protein kinase(AMPK)and mammalian target of rapamycin(mTOR)signaling pathways.Although this link has not been identified yet in fish,it was found that the energy state or some endocrine factors of fish were highly related with AMPK or mTOR phosphorylation levels.Probably this link was presumably similar to that in mammalian.In addition,the blood glucose levels of fish were regulated by some endocrine factors such as insulin,glucagon-like peptide-1(GLP-1),ghrelin,CCK,NPY,somatostatin(SS),etc.Besides,the glycometabolism and utilization in fish was aslo regulated by dietary nutrients including carbohydrate,lipid and protein.High-carbohydrate diet increased the activity and mRNA expression of glucose kinase(GK)in the liver of fish,and the glycolysis were also strengthened,even in the early development.Moreover,the hepatic gluconeogenesis in omnivorous species was inhibited by high-carbohydrate diet,but unaffected in carnivorous.Furthermore,High-fat diet promoted the glycolysis in some species,and the gluconeogenesis was also promoted both by high-fat and high-protein diets.However,there are still some questions that need further research.Finally,the development tendency and research hotspot in the carbohydrate metabolism of fish were discussed.For example,how the CNS integrate the nutritional,endocrine and other signals to regulate food intake in fish? what is the mechanism behind the differences between herbivorous,omnivorous and carnivorous species in glucose tolerance and the regulation of hepatic gluconeogenesis,etc.