Martin M, Canioni P, Merle M
Unité de Résonance Magnétique des Systèmes Biologiques, UMR 5536 CNRS/Université Victor Segalen Bordeaux 2, France.
Cell Mol Biol (Noisy-le-grand). 1997 Jul;43(5):631-43.
Carbon metabolism was investigated in cerebellar and cortical astrocytes cultured for 15 or 35 days. The consumption rates of exogenous carbon sources--amino acids and glucose--and the production rates of exported metabolites--citrate, lactate, alanine and glutamine--were determined. The specific 13C-enrichment of lactate and glutamine carbons were determined after cell incubation with [1-13C]glucose. These data were used to evaluate the fluxes through metabolic pathways using a monocompartmental model of the cell metabolism including glycolysis and tricarboxylic acid cycle related pathways. The model concluded to a very large contribution of fatty acids as an endogenous carbon source of acetyl-CoA. As a consequence of the high fatty acid turn-over, there was an important recycling (via pyruvate) of the oxaloacetate molecules generated by citrate lyase activity. This recycling represented in fact the major part of the pyruvate carboxylase activity, which therefore was not directly related to metabolite export. Comparing the data from cerebellar and cortical astrocytes evidenced, on the other hand, some differences in metabolite contents which could be related to different cell maturation stages linked to their different tissular origins.
对培养15天或35天的小脑和皮质星形胶质细胞的碳代谢进行了研究。测定了外源性碳源（氨基酸和葡萄糖）的消耗率以及输出代谢产物（柠檬酸、乳酸、丙氨酸和谷氨酰胺）的产生率。在用[1-¹³C]葡萄糖孵育细胞后，测定了乳酸和谷氨酰胺碳的特定¹³C富集度。这些数据用于使用细胞代谢的单室模型（包括糖酵解和三羧酸循环相关途径）评估代谢途径中的通量。该模型得出结论，脂肪酸作为乙酰辅酶A的内源性碳源有很大贡献。由于脂肪酸的高周转率，柠檬酸裂解酶活性产生的草酰乙酸分子存在重要的循环利用（通过丙酮酸）。事实上，这种循环利用代表了丙酮酸羧化酶活性的主要部分，因此它与代谢产物的输出没有直接关系。另一方面，比较小脑和皮质星形胶质细胞的数据表明，代谢产物含量存在一些差异，这可能与它们不同组织来源所关联的不同细胞成熟阶段有关。
