Circulating plasma phospholipid fatty acid levels as a biomarker of habitual dietary fat intake: The INTERMAP/INTERLIPID Study

BACKGROUND

Accurate assessment of fat intake is essential to examine relationships between diet and disease risk. However, estimating individual intakes of fat quantity by dietary assessment is difficult.

OBJECTIVE

We assessed the association of plasma phospholipid fatty acid levels with dietary intake of fatty acids in the INTERMAP/INTERLIPID study, conducted with a standardized protocol.

METHODS

The study participants were 1339 men and women ages 40-59 years from five Japanese populations one from Hawaii; four from Japan. Fatty acid intake was estimated from four standardized 24-hour dietary recalls. Plasma phospholipid fatty acid composition was analyzed by gas chromatography. We illustrated the relationship between intake and circulating fatty acid levels using Spearman's rank-correlation coefficients, mean, and median values.

RESULTS

Spearman's rank-correlation coefficients between intake (g/d) and circulating fatty acid levels (µg/ml) were -0.03 to 0.21 for saturated fatty acids and monounsaturated fatty acids and -0.04 to 0.32 for trans fatty acids. The coefficients for essential n-3 and n-6 fatty acids were moderate to high, especially for eicosapentaenoic acid (EPA), 0.60; docosahexaenoic acid (DHA), 0.41; and EPA+DHA, 0.51. The circulating levels and intake of marine-derived n-3 fatty acids showed a linear association, at least for the intake of EPA+DHA up to 2.1 g/d.

CONCLUSION

We observed high correlation between intake and circulating levels of marine-derived n-3 fatty acids in participants from Japanese and Japanese-American populations with high and low fish intake. Plasma phospholipid marine-derived n-3 fatty acid measurements are a simple and reliable biomarker for assessing dietary intake.

Plasma phospholipid polyunsaturated fatty acids composition in early pregnancy and fetal growth trajectories throughout pregnancy: Findings from the US fetal growth studies-singletons cohort

Background

We aimed to investigate plasma phospholipid PUFA levels in early pregnancy and fetal growth trajectories throughout pregnancy.

Methods

Within the NICHD Fetal Growth Studies–Singleton Cohort, we enrolled 2,802 pregnant women at gestational weeks 8–13 and randomly assigned them to four ultrasonogram schedules to capture weekly fetal growth throughout pregnancy. Eleven plasma phospholipid PUFAs were measured at early pregnancy using blood samples collected from a subsample of 321 pregnant women. We modeled fetal growth trajectories across tertiles of PUFAs with cubic splines using linear mixed models after adjusting for major confounders. We then compared pairwise weekly fetal growth biometrics referencing the lowest tertile in each PUFA using the Wald test.

Findings

Among plasma n-3 PUFAs in early pregnancy, docosahexaenoic acid (DHA, 22:6n3) and alpha-linolenic acid (ALA, 18:3n3) showed positive associations with all fetal growth measurements. For instance, compared with the lowest tertile, the highest tertile of DHA had greater estimated fetal growth (EFW) and abdominal circumference (AC), starting at 13 weeks of gestation and throughout pregnancy (at gestational week 38: 3235.3 vs. 3089.0 g for EFW; 344.6 vs. 339.2 mm for AC). As for plasma n-6 PUFAs, some showed positive associations (e.g., linoleic acid [LA], 18:2n6) while others (e.g., docosatetraenoic acid [DTA], 22:4n6) showed inverse associations with fetal growth measures.

Interpretation

Our data suggested that higher plasma levels of DHA and ALA in the first trimester were associated with increased fetal size and weight throughout subsequent pregnancy.

Funding

National Institute of Child Health and Human Development intramural funding.

Plasma phospholipid fatty acids are associated with altered fibrin clot properties in a population-based setting

Evidence regarding the relationship of plasma clot properties with fatty acids is contradictory, owing to different experimental protocols employed. The relationship of fibrinogen and plasma fibrin clot properties with plasma phospholipid fatty acids were cross-sectionally investigated in a population-based setting in 900 individuals. Composite saturated fatty acids (driven by stearic acid) and composite n-3 and n-6 polyunsaturated fatty acids (driven by docosahexaenoic and arachidonic acid respectively) were associated with prothrombotic clot properties. Composite monounsaturated fatty acids (driven by oleic acid) were associated with a profibrinolytic clot phenotype. Fibrinogen and BMI partly mediated these relationships. Individual plasma fatty acids from the same composite group had opposing associations with clot properties indicating that associations with composite fatty acid groups is dependent on the relative composition of the comprising fatty acids. The relationship of the plasma phospholipid fatty acid profile with disease should not be interpreted without considering the role of regulatory mechanisms.