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Impact of methods used to express levels of circulating fatty acids on the degree and direction of associations with blood lipids in humans.

Sergeant S, Ruczinski I, Ivester P, Lee TC, Morgan TM, Nicklas BJ, Mathias RA, Chilton FH - Br. J. Nutr. (2015)

Bottom Line: This reversal pattern was replicated in serum samples from both human cohorts.The correlations between blood lipids and fatty acids expressed as a percentage of total could be mathematically modelled from the concentration data.These data reveal that the different methods of expressing fatty acids lead to dissimilar correlations between blood lipids and certain fatty acids.

View Article: PubMed Central - PubMed

Affiliation: 1Center for Botanical Lipids and Inflammatory Disease Prevention,Wake Forest School of Medicine,Medical Center Blvd,Winston-Salem,NC 27157,USA.

ABSTRACT
Numerous studies have examined relationships between disease biomarkers (such as blood lipids) and levels of circulating or cellular fatty acids. In such association studies, fatty acids have typically been expressed as the percentage of a particular fatty acid relative to the total fatty acids in a sample. Using two human cohorts, this study examined relationships between blood lipids (TAG, and LDL, HDL or total cholesterol) and circulating fatty acids expressed either as a percentage of total or as concentration in serum. The direction of the correlation between stearic acid, linoleic acid, dihomo-γ-linolenic acid, arachidonic acid and DHA and circulating TAG reversed when fatty acids were expressed as concentrations v. a percentage of total. Similar reversals were observed for these fatty acids when examining their associations with the ratio of total cholesterol:HDL-cholesterol. This reversal pattern was replicated in serum samples from both human cohorts. The correlations between blood lipids and fatty acids expressed as a percentage of total could be mathematically modelled from the concentration data. These data reveal that the different methods of expressing fatty acids lead to dissimilar correlations between blood lipids and certain fatty acids. This study raises important questions about how such reversals in association patterns impact the interpretation of numerous association studies evaluating fatty acids and their relationships with disease biomarkers or risk.

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Related in: MedlinePlus

Impact of fatty acid (FA) expression method on the TAG relationship with oleic acid (OA, C18 : 1n-9) and linoleic acid (LA, C18 : 2n-6). The relationship between TAG and the most abundant circulating FA, LA (31 %), differs (, C18 : 2n-6) on the basis of the method of FA expression: concentration (mmol/l) (a); or as percentage of total (b) in the Diet, Exercise, Metabolism and Obesity in Older Women (DEMO) cohort. The same relationships were also examined in the replicate population (the diabetes/metabolic syndrome cohort; right panels) as concentration (mmol/l) (c); or as percentage of total (d). The relationship between TAG and OA (19–20 %) is unaffected (, C18 : 1n-9) by the method of FA expression. For visualisation, the linear regression line is shown for each data set.
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fig1: Impact of fatty acid (FA) expression method on the TAG relationship with oleic acid (OA, C18 : 1n-9) and linoleic acid (LA, C18 : 2n-6). The relationship between TAG and the most abundant circulating FA, LA (31 %), differs (, C18 : 2n-6) on the basis of the method of FA expression: concentration (mmol/l) (a); or as percentage of total (b) in the Diet, Exercise, Metabolism and Obesity in Older Women (DEMO) cohort. The same relationships were also examined in the replicate population (the diabetes/metabolic syndrome cohort; right panels) as concentration (mmol/l) (c); or as percentage of total (d). The relationship between TAG and OA (19–20 %) is unaffected (, C18 : 1n-9) by the method of FA expression. For visualisation, the linear regression line is shown for each data set.

Mentions: Fig. 1 shows the statistically significant associations between TAG and the two most abundant circulating fatty acids, LA (31 %) and oleic acid (OA) (19–20 %), calculated as a percentage of total and as concentrations. However, the direction of the relationship between TAG and LA was negative when expressed as a percentage of total (Fig. 1(b); r −0·53; P<0·0001), but positive when expressed as the serum concentration (mmol/l) of LA (Fig. 1(a); r 0·60; P<0·0001). In contrast, the association between TAG and OA was positive using either fatty acid expression method (r 0·71 with P<0·0001 for percentage of total, Fig. 1(b); and r 0·90 with P<0·0001 for absolute concentration, Fig. 1(a)).Fig. 1


Impact of methods used to express levels of circulating fatty acids on the degree and direction of associations with blood lipids in humans.

Sergeant S, Ruczinski I, Ivester P, Lee TC, Morgan TM, Nicklas BJ, Mathias RA, Chilton FH - Br. J. Nutr. (2015)

Impact of fatty acid (FA) expression method on the TAG relationship with oleic acid (OA, C18 : 1n-9) and linoleic acid (LA, C18 : 2n-6). The relationship between TAG and the most abundant circulating FA, LA (31 %), differs (, C18 : 2n-6) on the basis of the method of FA expression: concentration (mmol/l) (a); or as percentage of total (b) in the Diet, Exercise, Metabolism and Obesity in Older Women (DEMO) cohort. The same relationships were also examined in the replicate population (the diabetes/metabolic syndrome cohort; right panels) as concentration (mmol/l) (c); or as percentage of total (d). The relationship between TAG and OA (19–20 %) is unaffected (, C18 : 1n-9) by the method of FA expression. For visualisation, the linear regression line is shown for each data set.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697295&req=5

fig1: Impact of fatty acid (FA) expression method on the TAG relationship with oleic acid (OA, C18 : 1n-9) and linoleic acid (LA, C18 : 2n-6). The relationship between TAG and the most abundant circulating FA, LA (31 %), differs (, C18 : 2n-6) on the basis of the method of FA expression: concentration (mmol/l) (a); or as percentage of total (b) in the Diet, Exercise, Metabolism and Obesity in Older Women (DEMO) cohort. The same relationships were also examined in the replicate population (the diabetes/metabolic syndrome cohort; right panels) as concentration (mmol/l) (c); or as percentage of total (d). The relationship between TAG and OA (19–20 %) is unaffected (, C18 : 1n-9) by the method of FA expression. For visualisation, the linear regression line is shown for each data set.
Mentions: Fig. 1 shows the statistically significant associations between TAG and the two most abundant circulating fatty acids, LA (31 %) and oleic acid (OA) (19–20 %), calculated as a percentage of total and as concentrations. However, the direction of the relationship between TAG and LA was negative when expressed as a percentage of total (Fig. 1(b); r −0·53; P<0·0001), but positive when expressed as the serum concentration (mmol/l) of LA (Fig. 1(a); r 0·60; P<0·0001). In contrast, the association between TAG and OA was positive using either fatty acid expression method (r 0·71 with P<0·0001 for percentage of total, Fig. 1(b); and r 0·90 with P<0·0001 for absolute concentration, Fig. 1(a)).Fig. 1

Bottom Line: This reversal pattern was replicated in serum samples from both human cohorts.The correlations between blood lipids and fatty acids expressed as a percentage of total could be mathematically modelled from the concentration data.These data reveal that the different methods of expressing fatty acids lead to dissimilar correlations between blood lipids and certain fatty acids.

View Article: PubMed Central - PubMed

Affiliation: 1Center for Botanical Lipids and Inflammatory Disease Prevention,Wake Forest School of Medicine,Medical Center Blvd,Winston-Salem,NC 27157,USA.

ABSTRACT
Numerous studies have examined relationships between disease biomarkers (such as blood lipids) and levels of circulating or cellular fatty acids. In such association studies, fatty acids have typically been expressed as the percentage of a particular fatty acid relative to the total fatty acids in a sample. Using two human cohorts, this study examined relationships between blood lipids (TAG, and LDL, HDL or total cholesterol) and circulating fatty acids expressed either as a percentage of total or as concentration in serum. The direction of the correlation between stearic acid, linoleic acid, dihomo-γ-linolenic acid, arachidonic acid and DHA and circulating TAG reversed when fatty acids were expressed as concentrations v. a percentage of total. Similar reversals were observed for these fatty acids when examining their associations with the ratio of total cholesterol:HDL-cholesterol. This reversal pattern was replicated in serum samples from both human cohorts. The correlations between blood lipids and fatty acids expressed as a percentage of total could be mathematically modelled from the concentration data. These data reveal that the different methods of expressing fatty acids lead to dissimilar correlations between blood lipids and certain fatty acids. This study raises important questions about how such reversals in association patterns impact the interpretation of numerous association studies evaluating fatty acids and their relationships with disease biomarkers or risk.

Show MeSH
Related in: MedlinePlus