体内糖异生作用的质量同位素异构体分布分析的批判性评估。

A critical evaluation of mass isotopomer distribution analysis of gluconeogenesis in vivo.

作者信息

Previs S F, Cline G W, Shulman G I

机构信息

Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8020, USA.

出版信息

Am J Physiol. 1999 Jul;277(1):E154-60. doi: 10.1152/ajpendo.1999.277.1.E154.

DOI:10.1152/ajpendo.1999.277.1.E154

PMID:10409139

Abstract

There are conflicting reports concerning the reliability of mass isotopomer distribution analysis (MIDA) for estimating the contribution of gluconeogenesis to total glucose production (f) during [(13)C]glycerol infusion. We have evaluated substrate-induced effects on rate of appearance (R(a)) of glycerol and glucose and f during [2-(13)C]glycerol infusion in vivo. Five groups of mice were fasted for 30 h and then infused with [2-(13)C]glycerol at variable rates and variable (13)C enrichments (group I: 20 micromol. kg(-1). min(-1), 99% (13)C; group II: 60 micromol. kg(-1). min(-1), 60% (13)C; group III: 60 micromol. kg(-1). min(-1), 99% (13)C; group IV: 120 micromol. kg(-1). min(-1), 40% (13)C; or group V: 120 micromol. kg(-1). min(-1), 99% (13)C). The total glycerol R(a) increased from approximately 104 to approximately 157 and to approximately 210 micromol. kg(-1). min(-1) as the infusion of [2-(13)C]glycerol increased from 20 to 60 and to 120 micromol. kg(- 1). min(-1), respectively. As the amount of 99% enriched [2-(13)C]glycerol increased from 20 to 60 and to 120 micromol. kg(-1). min(-1) (groups I, III, and V, respectively), plasma glycerol enrichment increased from approximately 21 to approximately 42 and to approximately 57% and the calculated f increased from approximately 27 to approximately 56 and to approximately 87%, respectively. Similar plasma glycerol enrichments were observed in groups I, II, and IV (i. e., approximately 21-24%), yet f increased from approximately 27 to approximately 57 and to approximately 86% in groups II and IV, respectively. Estimates of absolute gluconeogenesis increased from approximately 14 to approximately 33 and approximately 86 micromol. kg(-1). min(-1) as the infusion of [2-(13)C]glycerol increased from 20 to 60 and 120 micromol. kg(-1). min(-1). Plausible estimates of f were obtained only under conditions that increased total glycerol R(a) approximately 2-fold (P < 0.001) and increased glucose R(a) approximately 1.5-fold (P < 0.01) above basal. We conclude that in 30-h fasted mice, 1) estimates of f by MIDA with low infusion rates of [2-(13)C]glycerol yield erroneous results and 2) reasonable estimates of f are obtained at glycerol infusion rates that perturb glycerol and glucose metabolism.

摘要

关于在[¹³C]甘油输注期间，用质量同位素异构体分布分析（MIDA）来估算糖异生对总葡萄糖生成（f）的贡献的可靠性，存在相互矛盾的报道。我们在体内[2-(¹³C)]甘油输注期间，评估了底物对甘油和葡萄糖的出现率（R(a)）以及f的影响。将五组小鼠禁食30小时，然后以不同速率和不同¹³C丰度输注[2-(¹³C)]甘油（第一组：20微摩尔·千克⁻¹·分钟⁻¹，99%¹³C；第二组：60微摩尔·千克⁻¹·分钟⁻¹，60%¹³C；第三组：60微摩尔·千克⁻¹·分钟⁻¹，99%¹³C；第四组：120微摩尔·千克⁻¹·分钟⁻¹，40%¹³C；或第五组：120微摩尔·千克⁻¹·分钟⁻¹，99%¹³C）。随着[2-(¹³C)]甘油输注速率分别从20增加到60以及再到120微摩尔·千克⁻¹·分钟⁻¹，总甘油R(a)从约104增加到约157以及再到约210微摩尔·千克⁻¹·分钟⁻¹。当99%富集的[2-(¹³C)]甘油量从20增加到60以及再到120微摩尔·千克⁻¹·分钟⁻¹（分别为第一组、第三组和第五组）时，血浆甘油丰度从约21%增加到约42%以及再到约57%，计算得到的f分别从约27%增加到约56%以及再到约87%。在第一组、第二组和第四组中观察到相似的血浆甘油丰度（即约21% - 24%），然而第二组和第四组中的f分别从约27%增加到约57%以及再到约86%。随着[2-(¹³C)]甘油输注从20增加到60以及再到120微摩尔·千克⁻¹·分钟⁻¹，绝对糖异生的估计值从约14增加到约33以及再到约86微摩尔·千克⁻¹·分钟⁻¹。只有在总甘油R(a)比基础值增加约2倍（P < 0.001）且葡萄糖R(a)比基础值增加约1.5倍（P < 0.01）的条件下，才能获得合理的f估计值。我们得出结论，在禁食30小时的小鼠中，1）用低输注速率的[2-(¹³C)]甘油通过MIDA估算f会产生错误结果，2）在扰动甘油和葡萄糖代谢的甘油输注速率下可获得合理的f估计值。