Green Michael H, Green Joanne Balmer
Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, United States.
Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, United States.
J Nutr. 2024 Oct;154(10):3151-3156. doi: 10.1016/j.tjnut.2024.08.007. Epub 2024 Aug 21.
As currently applied, the paired retinol isotope dilution (RID) test, which is used to assess the impact of a vitamin A intervention on vitamin A total body stores (TBS), requires 2 doses of stable isotope-labeled vitamin A.
The objectives of this study were to evaluate use of a single isotope dose (4 μmol) to assess TBS by RID before and after intervention in theoretical children with low/moderate TBS.
We selected 6 theoretical children with assigned values for TBS ranging from 82 to 281 μmol. Using Simulation, Analysis and Modeling software, we simulated the variable [plasma retinol specific activity (SA)] and coefficients (Fa and S) used in the RID equation TBS (μmol) = FaS × 1/SA in both the unsupplemented steady state at day 14 postdosing and during the subsequent 4 mo without or with vitamin A supplementation [2.8 μmol retinol/d (801 μg retinol activity equivalents/d)].
Fraction of dose in plasma on day 150 compared with day 14 was similar in the unsupplemented and supplemented conditions [geometric mean, 32% (range, 20%-48%) and 30% (20%-48%), respectively] and simulated values for FaS were similar under the 2 conditions. After 2 and 4 mo of daily vitamin A supplementation with 2.8 μmol/d, TBS was 78% and 128% higher, respectively, than without supplementation.
Results indicate that the paired RID method can successfully be done using a single 4 μmol dose of stable isotope. Furthermore, because values for the RID coefficient FaS were similar in the unsupplemented and vitamin A-supplemented conditions, these results in theoretical children indicate that FaS determined by population ("super-subject") modeling of steady state vitamin A kinetic data could be used to predict TBS by RID after a vitamin A intervention in individuals from the same or a similar group.
目前应用的配对视黄醇同位素稀释（RID）试验用于评估维生素A干预对维生素A全身储存量（TBS）的影响，该试验需要两剂稳定同位素标记的维生素A。
本研究的目的是评估在理论上TBS低/中度的儿童中，使用单剂量同位素（4 μmol）通过RID评估干预前后的TBS。
我们选择了6名理论儿童，其TBS赋值范围为82至281 μmol。使用模拟、分析和建模软件，我们模拟了在给药后第14天的未补充稳态以及随后4个月内未补充或补充维生素A [2.8 μmol视黄醇/天（801 μg视黄醇活性当量/天）] 期间，RID方程TBS（μmol）= FaS × 1/SA中使用的变量 [血浆视黄醇比活性（SA）] 和系数（Fa和S）。
在未补充和补充条件下，第150天与第14天相比血浆中剂量分数相似 [几何平均值分别为32%（范围为20% - 48%）和30%（20% - 48%）]，并且在两种条件下模拟的FaS值相似。在每天补充2.8 μmol/d维生素A 2个月和4个月后，TBS分别比未补充时高78%和128%。
结果表明，使用单剂量4 μmol稳定同位素可以成功完成配对RID方法。此外，由于在未补充和补充维生素A的条件下，RID系数FaS的值相似，这些理论儿童的结果表明，通过对稳态维生素A动力学数据进行群体（“超级受试者”）建模确定的FaS可用于预测来自相同或相似群体的个体在维生素A干预后通过RID得出的TBS。
