Influence of Dietary Linoleic Acid Intake with Different Fat Intakes on Arachidonic Acid Concentrations in Plasma and Platelet Lipids and Eicosanoid Biosynthesis in Female Volunteers

Abstract

Background/Aim: N-6 fatty acids are considered to promote diseases prevalent in industrialized countries and characterized by an increased eicosanoid biosynthesis from arachidonic acid (AA). We investigated the impact of the linoleic acid (LA) intake on AA levels in humans. Methods: Six healthy female volunteers (age range 23–34 years) were given liquid formula diets (LFD) devoid of AA for 6 weeks, providing a constant intake of zero energy% (LFD 0: protein 15%, carbohydrates 85%) or 20 energy% (LFD 20: protein 15%, carbohydrates 55%, fat 30%) LA, for 3 weeks each. Fatty acids of plasma cholesteryl esters and platelet lipids were determined each week, and the prostaglandin biosynthesis was measured in 24-hour urine samples. Results: LFD 0 increased (+31% of initial value) and LFD 20 lowered (–30% of initial value) the percentage of AA in plasma cholesteryl esters and platelet lipids. Moreover, absence of dietary AA lowered the percentages of AA in plasma (–31% week 0 vs. week 6) and platelet (–11%) lipids, indicating a low transformation of LA. LFD 0 reduced urinary metabolite levels of prostaglandins D, E, and F in 24-hour urine samples (–48%, p < 0.001) within 24 h, but did not significantly affect platelet aggregation (–10%) and thromboxane formation (–25%). LFD 20 significantly lowered platelet aggregation (–25%) and thromboxane formation (–43%). The prostaglandin metabolite levels increased during the first 10 days, declined thereafter, and were lower than the preexperimental values at the end of the 3-week period. Conclusions: The results show that dietary LA does not increase the AA levels in plasma or platelet lipids and does not persistently contribute to prostaglandin biosynthesis which is increased by AA intake with Western diets.

Effects of dietary grape seed oil and linseed oil on growth, muscle fatty acid composition and expression of putative Δ5 fatty acyl desaturase in abalone Haliotis discus hannai Ino

“…1C). However, other papers on human concluded that increasing dietary LA has no effect on increase of plasma phospholipid ARA level, or even may have an inverse relationship (Adam et al, 2003(Adam et al, , 2008Liou and Innis, 2009;Liou et al, 2007;Rett and Whelan, 2011;Thijssen and Mensink, 2005). The possible reason for no response of tissue ARA content by dietary increasing LA in those studies was considered to be related to fractional conversion from LA to ARA and limited catalysis of Δ6 Fad on LA (Demmelmair et al, 1999;Rett and Whelan, 2011;Vermunt et al, 2001).…”

Plasma n-6 and n-3 polyunsaturated fatty acids as biomarkers of their dietary intakes: a cross-sectional study within a cohort of middle-aged French men and women

“…This is likely due to the low bioconversion rate of linoleic and a-linolenic acids in humans (Burdge, 2004). A 3-week interventional study in women has shown that in the absence of dietary arachidonic acid, even a very high level of intake of linoleic acid (20% of energy) did not increase the percentage of arachidonic in plasma cholesteryl esters (Adam et al, 2003). The inverse correlations found in men between the intakes of long-chain n-3 PUFA and the plasma levels of some n-6 PUFA (20:2n-6, 20:3n-6 and 22:4n-6) suggests that long-chain n-3 PUFA can inhibit one or several steps of the bioconversion of linoleic acid (D-6-and D-5-desaturases, elongase) (Burdge and Calder, 2005).…”

Fat and Fatty Acid Terminology, Methods of Analysis and Fat Digestion and Metabolism: A Background Review Paper

“…In human studies in different population groups, higher dietary levels of LA also do not appear to be correlated with higher AA levels in platelets and RBC [Dougherty et al, 1987]. Controlled studies with the administration of liquid formulas devoid of AA and containing either 0 or 20% of LA showed that enhancement of dietary LA intakes does not consistently contribute to PG biosynthesis [Adam et al, 2003a]. Possible mechanisms underlying these types of effects are:…”