Abstract
BackgroundSince oleic acid (OA, 18:1 c9) and arachidonic acid (AA, 20:4 n6) may have antagonistic actions, it is of interest to assess their relative abundances. We previously reported an inverse correlation between % OA and %AA. However, percentages of the same sum may be correlated without involving biology. We now investigate whether random numbers, generated within the true concentration distributions for OA and AA, may be correlated.MethodsWe reanalysed data from a previous diet trial in chickens. Breast muscle was collected, and the concentration of fatty acids in muscle lipids was determined using gas chromatography. We computed R = S – OA – AA, where S is the sum of all fatty acids (g/kg) and R is concentration of all fatty acids, except OA and AA. From histograms we found physiological distributions of OA, AA and R. Then we generated random numbers for each of 3 variables (n = 163), within the distributions (g/kg) for OA (1–7), AA (0.25–0.39), and R (4–10). Next we made scatterplots of % OA vs. % AA, and studied how a narrowing or broadening of distributions might change the relationship.ResultsAlso with random numbers, generated within true concentration distributions for OA and AA, we found an inverse relationship between their percentages (r = − 0.356, p < 0.001; r = 163); however, the points were not close to the regression line. The %OA vs. %AA relationship changed appreciably in response to slightly altering concentration distributions of OA and AA, and a negative association could be changed to become positive.ConclusionUsing random numbers, generated within the biological distributions for OA, AA, and sum of the remaining fatty acids, we found an inverse relationship between “% OA” and “% AA”, but the scatterplot was poor compared with that obtained with real values. The association between relative abundances of random numbers of OA and AA was very sensitive to changes in distributions, and a negative association could be changed to become positive by slightly altering the distributions. Thus, the association between relative abundances of OA and AA could be partly caused by the particular distribution of the fatty acid concentration: a Distribution Dependent Correlation.
Highlights
Since oleic acid (OA, 18:1 c9) and arachidonic acid (AA, 20:4 n6) may have antagonistic actions, it is of interest to assess their relative abundances
In spite of high significance (p < 0.001) with random numbers, Fig. 3 demonstrates a poor scatter as compared with that obtained with real values
For fatty acids in breast muscle lipids of chickens, it seems that the distribution per se may partly explain the inverse %OA vs. %AA correlation, but apparently not in our two previous studies, one in sera of human subjects, and another in sera of rats. In this context we may add that distribution alone does seem to completely explain the positive association observed between percentages of AA and EPA in breast muscle lipids of chickens [27, 28], a finding strongly suggesting that there might be a Distribution Dependent Regulation of the correlation between percentages of some fatty acids. These analyses suggest that the distribution per se of three random scale variables can determine whether the association between their relative abundances is negative, positive, or not significant
Summary
Since oleic acid (OA, 18:1 c9) and arachidonic acid (AA, 20:4 n6) may have antagonistic actions, it is of interest to assess their relative abundances. When considering the beneficial health effects of oils rich in oleic acid, we previously suggested [1,2,3] that many of the positive effects would be anticipated if the fatty acid works to counteract effects of arachidonic acid (AA, 20:4 n6). This fatty acid is formed in the body from linoleic acid (LA, 18:2 n6), a major constituent in many plant oils, and is converted by cyclooxygenase and lipoxygenase into various eicosanoids, i.e. prostacyclines, thromboxanes and leukotrienes [14]. Endocannabinoides, which are derived from arachidonic acid, may have a role in adiposity and inflammation [17]
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