Time-dependence of the contribution of pyruvate carboxylase versus pyruvate dehydrogenase to rat brain glutamine labelling from [1-13C]glucose metabolism
Time-dependence of the contribution of pyruvate carboxylase versus pyruvate dehydrogenase to rat brain glutamine labelling from [1-13C]glucose metabolism
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DOI：
10.1046/j.1471-4159.2002.00924.x
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发表时间：
2002-07-01
影响因子：
4.7
通讯作者：
Canioni, P
中科院分区：
文献类型：
--
作者：
Merle, M;Bouzier-Sore, AK;Canioni, P
静脉输注标记底物后，研究了大鼠脑中的[1-C-13]葡萄糖代谢。通过NMR波谱分析标记与代谢物的结合作为输注时间的函数：10、20、30或60分钟。纯化的单羧酸和二羧酸氨基酸的具体富集度通过 H-1-观察/C-13-编辑和 C-13-NMR 光谱测定。丙酮酸羧化酶与丙酮酸脱氢酶 (PC/PDH) 对氨基酸标记的相对贡献分别根据 Glu 和 Gln 的 C2 和 C3 或 GABA 的 C4 和 C3 之间的富集差异进行评估。没有证据表明丙酮酸羧化酶对天冬氨酸、谷氨酸或 GABA 标记有贡献。丙酮酸羧化酶对谷氨酰胺标记的贡献随时间而变化。 PC/PDH 从 10 分钟后的 80% 左右下降到 20 至 60 分钟之间的不到 30%。这被解释为反映了两个谷氨酰胺前体谷氨酸池的不同标记动力学：星形胶质细胞谷氨酸和星形胶质细胞通过谷氨酸-谷氨酰胺循环摄取的神经元谷氨酸。根据神经元丙酮酸羧化可能发生的情况讨论结果。重新评估了先前用于测定脑中 PC/PDH 的方法区分星形细胞（通过丙酮酸羧化酶）和神经元（通过苹果酸酶）丙酮酸羧化的能力。
[1-C-13]glucose metabolism in the rat brain was investigated after intravenous infusion of the labelled substrate. Incorporation of the label into metabolites was analysed by NMR spectroscopy as a function of the infusion time: 10, 20, 30 or 60 min. Specific enrichments in purified mono- and dicarboxylic amino acids were determined from H-1-observed/C-13-edited and C-13-NMR spectroscopy. The relative contribution of pyruvate carboxylase versus pyruvate dehydrogenase (PC/PDH) to amino acid labelling was evaluated from the enrichment difference between either C2 and C3 for Glu and Gln, or C4 and C3 for GABA, respectively. No contribution of pyruvate carboxylase to aspartate, glutamate or GABA labelling was evidenced. The pyruvate carboxylase contribution to glutamine labelling varied with time. PC/PDH decreased from around 80% after 10 min to less than 30% between 20 and 60 min. This was interpreted as reflecting different labelling kinetics of the two glutamine precursor glutamate pools: the astrocytic glutamate and the neuronal glutamate taken up by astrocytes through the glutamate-glutamine cycle. The results are discussed in the light of the possible occurrence of neuronal pyruvate carboxylation. The methods previously used to determine PC/PDH in brain were re-evaluated as regards their capacity to discriminate between astrocytic (via pyruvate carboxylase) and neuronal (via malic enzyme) pyruvate carboxylation.