Nunes Patricia M, Jarak Ivana, Heerschap Arend, Jones John G
Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Magn Reson Med. 2014 Apr;71(4):1368-73. doi: 10.1002/mrm.24789. Epub 2013 May 28.
After a glucose load, futile glucose/glucose-6-phosphate (G6P) cycling (FGC) generates [2-(2) H]glucose from (2)H(2)O thereby mimicking a paradoxical glycogenolytic contribution to plasma glucose levels. Contributions of load and G6P derived from gluconeogenesis, FGC, and glycogenolysis to plasma glucose levels need resolution. A simple methodology is proposed integrating the administration of (2)H(2)O with a glucose load containing [1-(2)H, 1-(13)C]glucose and [2-(2)H, 2-(13)C]glucose.
Mice fasted for 6 (n = 7) or 24 h (n = 5) were intraperitoneally injected with 2 mg/g 10% enriched glucose in 35 µL/g (2)H(2)O. Plasma glucose enrichment was analyzed by (2)H NMR after 30 min.
For 6-h fasted mice, 12.3 ± 1.5% of plasma glucose was pre-existing, 44.3 ± 2.7% was load derived, and 43.4 ± 1.8% G6P derived. G6P origins were 26.0 ± 2.0% gluconeogenesis, 10.9 ± 2.6% FGC, and 6.5 ± 3.4% glycogenolysis. For 24-h fasted mice, 18.2 ± 8.5% was pre-existing, 41.1 ± 5.0 % was load derived, and 40.8 ± 4.3% G6P derived. G6P origins were 27.1 ± 3.3% gluconeogenesis, 13.1 ± 2.8% FGC, and 0.6 ± 2.4% glycogenolysis.
After a glucose load, glycogenolytic contribution to plasma glucose was negligible, whereas FGC was significant for both 6- and 24-h fasted mice.
在给予葡萄糖负荷后，无效的葡萄糖/葡萄糖-6-磷酸（G6P）循环（FGC）可从H₂O生成[2-(²)H]葡萄糖，从而模拟糖原分解对血糖水平产生的矛盾作用。源自糖异生、FGC和糖原分解的负荷及G6P对血糖水平的贡献需要明确。本文提出一种简单的方法，即将给予H₂O与含有[1-(²)H, 1-(¹³)C]葡萄糖和[2-(²)H, 2-(¹³)C]葡萄糖的葡萄糖负荷相结合。
将禁食6小时（n = 7）或24小时（n = 5）的小鼠腹腔注射2 mg/g 10%富集葡萄糖（溶于35 µL/g H₂O中）。30分钟后通过²H NMR分析血浆葡萄糖富集情况。
对于禁食6小时的小鼠，12.3±1.5%的血浆葡萄糖为预先存在的，44.3±2.7%源自负荷，43.4±1.8%源自G6P。G6P的来源分别为：26.0±2.0%来自糖异生，10.9±2.6%来自FGC，6.5±3.4%来自糖原分解。对于禁食24小时的小鼠，18.2±8.5%为预先存在的，41.1±5.0%源自负荷，40.8±4.3%源自G6P。G6P的来源分别为：27.1±3.3%来自糖异生，13.1±2.8%来自FGC，0.6±2.4%来自糖原分解。
给予葡萄糖负荷后，糖原分解对血糖的贡献可忽略不计，而FGC对禁食6小时和24小时的小鼠均有显著作用。
