Sidossis L S, Coggan A R, Gastaldelli A, Wolfe R R
Metabolism Unit, Shriners Burns Institute, Galveston, Texas 77550, USA.
Am J Physiol. 1995 Oct;269(4 Pt 1):E649-56. doi: 10.1152/ajpendo.1995.269.4.E649.
The purpose of this study was to acquire a new correction factor for use in tracer estimations of plasma fatty acid oxidation that would fully account for label fixation during the infusion of fatty acid tracers. Thus volunteers were infused with 13C-labeled fatty acids and [1-14C]acetate in the basal state, during hyperinsulinemia-hyperglycemia (clamp), and during 1 h of cycling exercise. The fractional recovery of acetate label (i.e., the acetate correction factor) was 0.56 +/- 0.02, 0.50 +/- 0.03, and 0.80 +/- 0.03 in the basal state and during the clamp and exercise, respectively. Isotopically determined plasma fatty acid oxidation rates (mumol.kg-1.min-1) were 1.7 +/- 0.2, 0.8 +/- 0.2, and 6.4 +/- 0.5 (no correction); 2.1 +/- 0.2, 1.0 +/- 0.2, and 6.7 +/- 0.5 (bicarbonate correction); and 3.1 +/- 0.2, 1.5 +/- 0.2, and 8.2 +/- 0.4 (acetate correction). We conclude that use of the acetate correction factor in place of the bicarbonate correction factor should improve the accuracy of isotopic measurements of plasma fatty acid oxidation, because it accounts for label fixation that might occur at any step between the entrance of labeled acetyl-CoA into the tricarboxylic acid cycle until the recovery of label in breath CO2.
本研究的目的是获得一种新的校正因子，用于血浆脂肪酸氧化的示踪剂估计，该因子将充分考虑脂肪酸示踪剂输注期间的标记固定。因此，在基础状态、高胰岛素血症 - 高血糖（钳夹）状态以及1小时的循环运动期间，向志愿者输注13C标记的脂肪酸和[1-14C]乙酸盐。基础状态、钳夹状态和运动期间乙酸盐标记的分数回收率（即乙酸盐校正因子）分别为0.56±0.02、0.50±0.03和0.80±0.03。同位素测定的血浆脂肪酸氧化率（μmol·kg-1·min-1）分别为1.7±0.2、0.8±0.2和6.4±0.5（未校正）；2.1±0.2、1.0±0.2和6.7±0.5（碳酸氢盐校正）；以及3.1±0.2、1.5±0.2和8.2±0.4（乙酸盐校正）。我们得出结论，使用乙酸盐校正因子代替碳酸氢盐校正因子应能提高血浆脂肪酸氧化同位素测量的准确性，因为它考虑了从标记的乙酰辅酶A进入三羧酸循环到呼吸CO2中标记物回收之间任何步骤可能发生的标记固定。
