HOW VALID ARE ISOTOPIC MEASUREMENTS OF FATTY-ACID OXIDATION
HOW VALID ARE ISOTOPIC MEASUREMENTS OF FATTY-ACID OXIDATION
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DOI：
10.1152/ajpendo.1991.261.5.e572
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发表时间：
1991-11-01
影响因子：
--
通讯作者：
JENSEN, MD
中科院分区：
文献类型：
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作者：
HEILING, VJ;MILES, JM;JENSEN, MD
这些研究进行了1)比较两种同位素方法(（H2O)-H-3和(CO2)-C-14生产）测量游离脂肪酸（FFA）氧化；2)确定与间接量热法相比，低胰岛素血症期间脂肪酸氧化的同位素估计是否合理；3)研究从血浆中排出[C-14]游离脂肪酸与呼吸中出现(CO2)-C-14之间的延迟是否完全由碳酸氢盐动力学引起。对11名健康志愿者的研究表明，[C-14]-和[H-3]FFA示踪剂提供了相似的FFA周转和氧化估计。脂肪酸氧化的同位素估计值在基础条件下低于间接量热法，但在急性低胰岛素血症（生长抑素诱导）3小时后等于或超过间接量热法估计值。停用示踪剂后，血浆[C-14]FFA半衰期为3.7±0.1 min。[C-14]碳酸氢盐(CO2)-C-14衰变的半衰期为37 +/- 1 min， [C-14]FFA输注停止后(CO2)-C-14衰变的半衰期为141 +/- 10 min。细胞内预氧化脂肪酸池（可能是甘油三酯）很可能解释了血浆中游离脂肪酸示踪剂的排出与可测量空间中氧化同位素标记物的出现之间的显著延迟。这种延迟可能导致对“FFA氧化”的错误估计。我们得出结论，在大多数情况下，示踪剂测量FFA氧化是无效的。
These studies were performed 1) to compare two isotopic methods ((H2O)-H-3 and (CO2)-C-14 production) of measuring free fatty acid (FFA) oxidation; 2) to determine whether isotopic estimates of fatty acid oxidation during hypoinsulinemia are plausible when compared with those obtained using indirect calorimetry; and 3) to examine whether the delay between the exit of [C-14]FFA from plasma and the appearance of (CO2)-C-14 in breath is accounted for solely by bicarbonate kinetics. Studies in 11 healthy volunteers revealed that [C-14]- and [H-3]FFA tracers provide similar estimates of FFA turnover and oxidation. Isotopic estimates of fatty acid oxidation were less than those of indirect calorimetry under basal conditions but equaled or exceeded indirect calorimetry estimates after 3 h of acute hypoinsulinemia (somatostatin induced). After stopping tracer infusions, the half-life of plasma [C-14]FFA was 3.7 +/- 0.1 min. The half-life of (CO2)-C-14 decay from [C-14]bicarbonate was 37 +/- 1 min, and the half-life of (CO2)-C-14 decay after discontinuation of [C-14]FFA infusion was 141 +/- 10 min. Intracellular preoxidative fatty acid pools (possibly triglycerides) most probably account for the marked delay between the exit of FFA tracers from plasma and the appearance of isotopic markers of oxidation in measurable spaces. This delay can result in erroneous estimates of "FFA oxidation." We conclude that tracer measurements of FFA oxidation are invalid under most circumstances.