Kather H, Rivera M, Brand K
Biochem J. 1972 Aug;128(5):1089-96. doi: 10.1042/bj1281089.
In order to study the quantitative relationship between fatty acid synthesis and pentose phosphate-cycle activity under different hormonal and dietary conditions affecting the extent of glucose uptake, cells isolated from rat epididymal adipose tissue were incubated in bicarbonate buffer containing [U-(14)C]-, [1-(14)C]- or [6-(14)C]-glucose. From the amount of glucose taken up, the production of lactate and pyruvate, and the incorporation of (14)C from differently labelled [(14)C]glucose into CO(2), fatty acids and glyceride glycerol, the rates of glucose metabolism via different pathways and the extent of lipogenesis under various experimental conditions were determined. The contribution of the pentose phosphate-cycle to glucose metabolism under normal conditions was calculated to be 8%. Starvation and re-feeding, and the presence of insulin, caused an enhancement of glucose uptake, pentose phosphate-cycle activity and fatty acid synthesis. Plots of both pentose phosphate-cycle activity and fatty acid synthesis versus glucose uptake revealed that the extent of glucose uptake, over a wide range, determines the rates of fatty acid synthesis and glucose metabolism via the pentose phosphate cycle. A balance of formation and production of nicotinamide nucleotides in the cytoplasm was established. The total amount of cytoplasmic NADH and NADPH formed was only in slight excess over the hydrogen equivalents required for the synthesis of fatty acids, glyceride glycerol and lactate. Except in cells from starved animals, the pentose phosphate cycle was found to provide only about 60% of the NADPH required for fatty acid synthesis. The results are discussed with respect to an overall control of the different metabolic and biosynthetic reactions in the fat-cells by the amount of glucose transported into the cell.
为了研究在影响葡萄糖摄取程度的不同激素和饮食条件下脂肪酸合成与磷酸戊糖循环活性之间的定量关系，将从大鼠附睾脂肪组织分离的细胞在含有[U-(14)C]-、[1-(14)C]-或[6-(14)C]-葡萄糖的碳酸氢盐缓冲液中孵育。根据摄取的葡萄糖量、乳酸和丙酮酸的生成量，以及不同标记的[(14)C]葡萄糖中(14)C掺入二氧化碳、脂肪酸和甘油酯甘油的情况，确定了在各种实验条件下通过不同途径的葡萄糖代谢速率和脂肪生成程度。正常条件下磷酸戊糖循环对葡萄糖代谢的贡献经计算为8%。饥饿与再喂食以及胰岛素的存在导致葡萄糖摄取、磷酸戊糖循环活性和脂肪酸合成增强。磷酸戊糖循环活性和脂肪酸合成与葡萄糖摄取的关系图表明，在很宽的范围内，葡萄糖摄取程度决定了脂肪酸合成速率和通过磷酸戊糖循环的葡萄糖代谢速率。细胞质中烟酰胺核苷酸的生成与产生达到了平衡。细胞质中形成的NADH和NADPH总量仅略高于脂肪酸、甘油酯甘油和乳酸合成所需的氢当量。除了饥饿动物的细胞外，发现磷酸戊糖循环仅提供脂肪酸合成所需NADPH的约60%。针对细胞内转运的葡萄糖量对脂肪细胞中不同代谢和生物合成反应的总体控制对结果进行了讨论。
