在输注[1-(13)C]乙酸盐、[2-(13)C]乙酸盐和NaH(13)CO3后静息和运动期间(13)CO2的恢复情况。
Recovery of (13)CO2 during rest and exercise after [1-(13)C]acetate, [2-(13)C]acetate, and NaH(13)CO3 infusions.
作者信息
Trimmer J K, Casazza G A, Horning M A, Brooks G A
机构信息
Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California 94720-3140, USA.
出版信息
Am J Physiol Endocrinol Metab. 2001 Oct;281(4):E683-92. doi: 10.1152/ajpendo.2001.281.4.E683.
For estimating the oxidation rates (Rox) of glucose and other substrates by use of (13)C-labeled tracers, we obtained correction factors to account for label dilution in endogenous bicarbonate pools and TCA cycle exchange reactions. Fractional recoveries of (13)C label in respiratory gases were determined during 225 min of rest and 90 min of leg cycle ergometry at 45 and 65% peak oxygen uptake (VO(2 peak)) after continuous infusions of [1-(13)C]acetate, [2-(13)C]acetate, or NaH(13)CO(3). In parallel trials, [6,6-(2)H]glucose and [1-(13)C]glucose were given. Experiments were conducted after an overnight fast with exercise commencing 12 h after the last meal. During the transition from rest to exercise, CO(2) production increased (P < 0.05) in an intensity-dependent manner. Significant differences were observed in the fractional recoveries of (13)C label as (13)CO(2) at rest (NaH(13)CO(3), 77.5 +/- 2.8%; [1-(13)C]acetate, 49.8 +/- 2.4%; [2-(13)C]acetate, 26.1 +/- 1.4%). During exercise, fractional recoveries of (13)C label from [1-(13)C]acetate, [2-(13)C]acetate, and NaH(13)CO(3) were increased compared with rest. Magnitudes of label recoveries during both exercise intensities were tracer specific (NaH(13)CO(3), 93%; [1-(13)C]acetate, 80%; [2-(13)C]acetate, 65%). Use of an acetate-derived correction factor for estimating glucose oxidation resulted in Rox values in excess (P < 0.05) of glucose rate of disappearance during hard exercise. We conclude that, after an overnight fast: 1) recovery of (13)C label as (13)CO(2) from [(13)C]acetate is decreased compared with bicarbonate; 2) the position of (13)C acetate label affects carbon dilution estimations; 3) recovery of (13)C label increases in the transition from rest to exercise in an isotope-dependent manner; and 4) application of an acetate correction factor in glucose oxidation measurements results in oxidation rates in excess of glucose disappearance during exercise at 65% of VO(2 peak). Therefore, bicarbonate, not acetate, correction factors are advocated for estimating glucose oxidation from carbon tracers in exercising men.
为了利用（13）C标记示踪剂估算葡萄糖和其他底物的氧化速率（Rox），我们获得了校正因子，以考虑内源性碳酸氢盐池中的标记稀释和三羧酸循环交换反应。在连续输注[1-（13）C]乙酸盐、[2-（13）C]乙酸盐或NaH（13）CO3后，在静息225分钟以及腿部周期测力计运动90分钟期间，分别在45%和65%的峰值摄氧量（VO（2峰值））下测定呼吸气体中（13）C标记的分数回收率。在平行试验中，给予[6,6-（2）H]葡萄糖和[1-（13）C]葡萄糖。实验在禁食过夜后进行，运动在最后一餐12小时后开始。在从静息到运动的过渡过程中，二氧化碳产生量以强度依赖的方式增加（P<0.05）。在静息时，观察到作为（13）CO2的（13）C标记的分数回收率存在显著差异（NaH（13）CO3，77.5±2.8%；[1-（13）C]乙酸盐，49.8±2.4%；[2-（13）C]乙酸盐，26.1±1.4%）。在运动期间，与静息相比，[1-（13）C]乙酸盐、[2-（13）C]乙酸盐和NaH（13）CO3的（13）C标记的分数回收率增加。在两种运动强度下，标记回收率的幅度具有示踪剂特异性（NaH（13）CO3，93%；[1-（13）C]乙酸盐，80%；[2-（13）C]乙酸盐，65%）。使用源自乙酸盐的校正因子估算葡萄糖氧化，导致在剧烈运动期间Rox值超过（P<0.05）葡萄糖消失率。我们得出结论，在禁食过夜后：1）与碳酸氢盐相比，[（13）C]乙酸盐中作为（13）CO2的（13）C标记回收率降低；2）（13）C乙酸盐标记的位置影响碳稀释估计；3）在从静息到运动的过渡过程中，（13）C标记的回收率以同位素依赖的方式增加；4）在VO（2峰值）的65%运动时，在葡萄糖氧化测量中应用乙酸盐校正因子导致氧化速率超过葡萄糖消失率。因此，提倡使用碳酸氢盐而非乙酸盐校正因子，从运动男性的碳示踪剂估算葡萄糖氧化。
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