Glucose metabolism in aquatic animals

水生动物的葡萄糖代谢

• 批准号: RGPIN-2018-05160
• 负责人: Driedzic, William
• 金额: $ 2.4万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=684744
• 关键词: Glucose; metabolism; aquatic; animals

Glucose metabolism has been studied in aquatic animals for over 100 years yet there remain important questions to be resolved. 1) Glucose metabolism in Atlantic cod gas gland. Many fish utilize a gas filled swim bladder to maintain neutral buoyancy. As fish dive pressure increases by 1 atm for every 10 m of depth. This causes the swim bladder to compress and in order to maintain buoyancy increased gas must be deposited. In most species the swim bladder is filled primarily with O2 via a gas gland that clusters around a network of blood vessels. The glandular cells generate H+ that causes O2 to unload from haemoglobin. H+ and O2 accumulate in the plasma and O2 moves by diffusion into the swim bladder. H+ is produced from anaerobic glycolysis with the production of lactic acid. There are many studies on the physiology and biochemistry of swim bladder and gas gland function but none have been conducted at pressures that occur in real life. The present experiments will address for the first time the biochemistry of gas deposition and glucose metabolism under physiologically relevant conditions. Novel experiments will be possible with the use of a newly constructed chamber that is capable of developing pressures of 300 atm with flow through water at controlled temperatures. Cod will be utilized since they have a discrete gas gland that is easy to harvest. Cod may travel between 50 and 275 m in 2 hr and may also occur at depths greater than 500 m. Work will focus on the first critical steps in glucose metabolism, i.e. transport into the cell via glucose transporter 1 and phosphorylation of glucose by hexokinase. The objectives of the program will be to assess the importance of glucose metabolism and control of the process in gas gland in animals undergoing normal pressure changes. 2) Is extracellular glucose required to maintain intracellular pH? Hearts from some species of fish (e.g. Armoured catfish, white sturgeon) are able to maintain intracellular pH at decreased extracellular pH allowing maintenance of contraction. The mechanisms of pH defense are unknown but likely involve Na+ exchange which places demands on Na+/K+ ATPase (NKA) to maintain Na+ balance. In mammalian heart, NKA is fueled primarily by glycolysis. In fish hearts, extracellular glucose is directed primarily if not exclusively to lactate production even under normal O2, suggesting a necessity for glycolysis consistent with fueling membrane ATPases. This leads to the hypothesis that anaerobic glycolysis is necessary to maintain pHi. Heart cells will be isolated from fish and exposed to low pHe with or without glucose in the medium. pHi, oxygen consumption, lactate production, and glucose metabolism will be tracked. This program will articulate roles of glucose metabolism that are specific to particular functions as opposed to being a general fuel source for ATP production. This will result in a paradigm shift with respect to how we think about the role of glucose.**********.************

人们对水生动物的葡萄糖代谢的研究已有 100 多年的历史，但仍有一些重要问题有待解决。 1）大西洋鳕鱼气腺中的葡萄糖代谢。 许多鱼利用充气的鱼鳔来保持中性浮力。鱼每潜深 10 m，压力就会增加 1 个大气压。这会导致鱼鳔受到压缩，为了维持浮力，必须沉积更多的气体。在大多数物种中，鱼鳔主要通过聚集在血管网络周围的气腺充满氧气。 腺细胞产生 H+，导致 O2 从血红蛋白中释放出来。 H+ 和 O2 在血浆中积聚，O2 通过扩散进入鱼鳔。 H+ 由无氧糖酵解和乳酸产生。 关于鱼鳔和气腺功能的生理学和生物化学的研究有很多，但没有一项是在现实生活中发生的压力下进行的。 本实验将首次研究生理相关条件下气体沉积和葡萄糖代谢的生物化学。使用新建的腔室可以进行新颖的实验，该腔室能够在受控温度下流过水时产生 300 atm 的压力。鳕鱼将被利用，因为它们具有易于捕获的离散气体腺体。鳕鱼可能在 2 小时内游动 50 至 275 m，也可能出现在大于 500 m 的深度。工作将集中在葡萄糖代谢的第一个关键步骤，即通过葡萄糖转运蛋白 1 转运到细胞中并通过己糖激酶磷酸化葡萄糖。该计划的目标是评估正常压力变化的动物中葡萄糖代谢和气腺过程控制的重要性。 2) 维持细胞内pH值是否需要细胞外葡萄糖？ 某些鱼类（例如鲶鱼、白鲟）的心脏能够在细胞外 pH 值降低的情况下维持细胞内 pH 值，从而维持收缩。 pH 防御机制尚不清楚，但可能涉及 Na+ 交换，这需要 Na+/K+ ATP 酶 (NKA) 来维持 Na+ 平衡。在哺乳动物心脏中，NKA 主要由糖酵解提供能量。在鱼心脏中，即使在正常的 O2 条件下，细胞外葡萄糖也主要（如果不是完全）产生乳酸，这表明糖酵解的必要性与为膜 ATP 酶提供能量一致。这导致了无氧糖酵解对于维持 pHi 是必要的假设。从鱼中分离出心脏细胞，并将其暴露于低 pHe 培养基中，培养基中含有或不含葡萄糖。 pHi、耗氧量、乳酸生成和葡萄糖代谢将被跟踪。该计划将阐明葡萄糖代谢的作用，这些作用特定于特定功能，而不是作为 ATP 生产的一般燃料来源。这将导致我们如何看待葡萄糖的作用发生范式转变。************.************