Real-time Detection of Hepatic Gluconeogenic and Glycogenolytic States Using Hyperpolarized [2-13C]Dihydroxyacetone
Real-time Detection of Hepatic Gluconeogenic and Glycogenolytic States Using Hyperpolarized [2-13C]Dihydroxyacetone
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DOI：
10.1074/jbc.m114.613265
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发表时间：
2014-12-26
影响因子：
4.8
通讯作者：
Merritt, Matthew E.
中科院分区：
文献类型：
--
作者：
Moreno, Karlos X.;Satapati, Santhosh;Merritt, Matthew E.
糖原分解和糖原合成对营养状态敏感，净流量方向受多个酶促步骤控制。肝脏中的这种微妙平衡被各种病理状态破坏，包括癌症和糖尿病。超极化~（13）C磁共振是一种新的代谢成像技术，可以无损地探测中间代谢。目前还没有方法可以快速区分肝的糖原分解状态和糖原分解状态。在这里，我们使用生血管前体二羟丙酮（DHA）提供超极化碳-13灌注小鼠肝脏。DHA在丙糖水平上进入异源生成。灌注条件被设计为建立一个或生血管或糖原分解状态。出乎意料的是，我们发现[2-C-13]DHA在两种条件下在几秒钟内代谢成糖酵解和糖异生的共同中间体和终产物，包括[2，5-C-13]葡萄糖、[2-C-13]甘油3-磷酸、[2-C-13]磷酸烯醇丙酮酸（PEP）、[2-C-13]丙酮酸、[2-C-13]丙氨酸和[2-C-13]乳酸。[2-C-13]磷酸烯醇式丙酮酸是糖异生和糖酵解的关键分支点，首次在功能组织中进行了监测。由于PEP和丙酮酸盐之间的自由能差异较大，因此预期未观察到[2-C-13]PEP。丙酮酸激酶是糖酵解-代谢途径的唯一调节步骤，其似乎对DHA的任何代谢物的动力学施加显著控制。糖酵解产物与糖原分解产物的比率将这些功能性肝脏中的糖原分解状态与糖原分解状态区分开来。
Glycogenolysis and gluconeogenesis are sensitive to nutritional state, and the net direction of flux is controlled by multiple enzymatic steps. This delicate balance in the liver is disrupted by a variety of pathological states including cancer and diabetes mellitus. Hyperpolarized carbon-13 magnetic resonance is a new metabolic imaging technique that can probe intermediary metabolism nondestructively. There are currently no methods to rapidly distinguish livers in a gluconeogenic from glycogenolytic state. Here we use the gluconeogenic precursor dihydroxyacetone (DHA) to deliver hyperpolarized carbon-13 to the perfused mouse liver. DHA enters gluconeogenesis at the level of the trioses. Perfusion conditions were designed to establish either a gluconeogenic or a glycogenolytic state. Unexpectedly, we found that [2-C-13]DHA was metabolized within a few seconds to the common intermediates and end products of both glycolysis and gluconeogenesis under both conditions, including [2,5-C-13]glucose, [2-C-13]glycerol 3-phosphate, [2-C-13]phosphoenolpyruvate (PEP), [2-C-13]pyruvate, [2-C-13]alanine, and [2-C-13]lactate. [2-C-13]Phosphoenolpyruvate, a key branch point in gluconeogenesis and glycolysis, was monitored in functioning tissue for the first time. Observation of [2-C-13]PEP was not anticipated as the free energy difference between PEP and pyruvate is large. Pyruvate kinase is the only regulatory step of the common glycolytic-gluconeogenic pathway that appears to exert significant control over the kinetics of any metabolites of DHA. A ratio of glycolytic to gluconeogenic products distinguished the gluconeogenic from glycogenolytic state in these functioning livers.