循环磷脂脂肪酸的测量：相对重量百分比与绝对浓度之间的关联
Measurement of Circulating Phospholipid Fatty Acids: Association between Relative Weight Percentage and Absolute Concentrations.
作者信息
Song Xiaoling, Schenk Jeannette M, Diep Pho, Murphy Rachel A, Harris Tamara B, Eiriksdottir Gudny, Gudnason Vilmundur, Casper Corey, Lampe Johanna W, Neuhouser Marian L
机构信息
a Public Health Sciences Division , Fred Hutchinson Cancer Research Center , Seattle , Washington.
b Laboratory of Epidemiology and Population Sciences , National Institute on Aging , Bethesda , Maryland.
出版信息
J Am Coll Nutr. 2016 Sep-Oct;35(7):647-656. doi: 10.1080/07315724.2015.1116417. Epub 2016 Jun 17.
OBJECTIVE
Most epidemiologic studies of circulating phospholipid fatty acids (PLFAs) and disease risk have used the relative concentration (percentage of total) of each fatty acid as the measure of exposure. Using relative concentrations, the total of all fatty acids is summed to 100% and thus the values of individual fatty acid are not independent. This has led to debate, along with the suggestion to use absolute concentrations of fatty acids. We aimed to examine the relationship between relative (weight percentage) and absolute (mg/L) concentrations of individual circulating PLFAs.
METHODS
Relative and absolute concentrations of 41 circulating PLFAs were measured by gas chromatography in samples from 3 diverse populations. Correlations between the relative and absolute concentrations for each fatty acid were used to measure agreement. Unadjusted correlations and correlations adjusting absolute PLFA concentrations for total cholesterol were calculated.
RESULTS
Unadjusted correlations between relative and absolute concentrations, as well as correlations adjusting absolute PLFA concentrations for total cholesterol, were high for most PLFAs in all 3 studies. Across the 3 studies, 28 of the 41 analyzed PLFAs had unadjusted correlations > 0.6 and 39 had adjusted correlations > 0.6.
CONCLUSIONS
Choice of relative vs absolute concentration may not affect interpretation of results for most circulating PLFAs in studies of association between individual PLFAs and disease outcomes, especially if a covariate reflecting total lipids, such as total circulating cholesterol, is included in the model. However, for fatty acids, such as 16:0 (palmitic acid), with low correlation between the 2 metrics, using relative vs absolute concentration may lead to different inferences regarding their association with the outcome. Because both concentrations could be obtained simultaneously from the same laboratory assay, use of both metrics is warranted to better understand PLFA-disease relationships.
目的
大多数关于循环磷脂脂肪酸（PLFAs）与疾病风险的流行病学研究都将每种脂肪酸的相对浓度（占总量的百分比）用作暴露量的衡量指标。使用相对浓度时，所有脂肪酸的总和为100%，因此各脂肪酸的值并非相互独立。这引发了争论，同时有人建议使用脂肪酸的绝对浓度。我们旨在研究个体循环PLFAs的相对（重量百分比）浓度与绝对（mg/L）浓度之间的关系。
方法
通过气相色谱法测量了来自3个不同人群样本中41种循环PLFAs的相对和绝对浓度。每种脂肪酸的相对浓度与绝对浓度之间的相关性用于衡量一致性。计算了未调整的相关性以及针对总胆固醇调整绝对PLFA浓度后的相关性。
结果
在所有3项研究中，大多数PLFAs的相对浓度与绝对浓度之间的未调整相关性，以及针对总胆固醇调整绝对PLFA浓度后的相关性都很高。在这3项研究中，41种分析的PLFAs中有28种的未调整相关性>0.6，39种的调整相关性>0.6。
结论
在个体PLFAs与疾病结局关联的研究中，对于大多数循环PLFAs而言，选择相对浓度还是绝对浓度可能不会影响结果的解读，特别是如果模型中纳入了反映总脂质的协变量，如总循环胆固醇。然而，对于16:0（棕榈酸）等两种指标之间相关性较低的脂肪酸，使用相对浓度还是绝对浓度可能会导致关于它们与结局关联的不同推断。由于两种浓度可以通过同一实验室检测同时获得，因此有必要同时使用这两种指标，以更好地理解PLFA与疾病的关系。
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