The metabolism of linoleic acid in healthy subjects after intake of a single dose of 13C-linoleic acid

Abstract

Objective: To investigate the in vivo oxidation of 13 C18X2n-6 and its conversion into longer-chain polyunsaturates (LCPs) in healthy subjects. Design: Blood samples were collected from six subjects before (fasted) and 7, 11 (non-fasted), 24, 48, 72, 168 and 336 h (fasted) after ingestion of a single bolus of 45 mg uniformly labeled 13 C18X2n-6 dissolved in 8 g olive oil. In three subjects, breath was also sampled and CO 2 production measured every hour during the ®rst 12 h. Subjects consumed their habitual diets. Plasma 13 C-enrichments were measured by GC-C-IRMS and fatty acid compositions by GCaFID. Setting: Maastricht University, Department of Human Biology. Subjects: Three men and three women, recruited by local advertisement. Results: The traceratracee ratio (TTR) of C18X2n-6 in plasma total lipids was already increased 5 h after tracer intake. The mean peak amount (AE s.e.m) of 13 C18X2n-6 (3.4AE 0.8 mg; 7.6% of dose) was found after about 17 h, 13 C18X3n-6 (0.018 AE 0.008 mg; 0.04% of dose) after 7 ± 48 h, and 13 C20X3n-6 (0.028 AE 0.011 mg; 0.06% of dose) after 48 ± 336 h. Time to peak TTRs of C20X4n-6 varied between subjects and were on average 0.022 AE 0.006 mg (0.05% of dose). The proportion of 13 C18X2n-6 recovered in breath after 12 h ranged between 16.8 and 25.1%. Conclusions: These ®ndings suggest that a single bolus of 45 mg U-13 C18X2n-6 can be used to study the oxidation of 13 C18X2n-6. However, because of the low TTRs for C20X4n-6, a higher dose is recommended for studying the conversion of 13 C18X2n-6 into LCPs. In addition, since only about 35% of the tracer was found in plasma total lipids and as 13 CO 2 in breath, it might be necessary to study other accessible lipid fractions as well to study the overall conversion of linoleic acid.

A comparison of the metabolism of eighteen-carbon 13C-unsaturated fatty acids in healthy women

“…Our results concerning the quantitative recovery of 13 C in breath CO 2 during the first 24 h postdose and the rank order of oxidation of these four common dietary fatty acids agree with similar previously published results (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). Tracer studies reporting breath data do not often extend beyond 24 h, but in 22 of the 24 breath tracer profiles in the present study, 13 C enrichment in breath CO 2 was still above baseline at 168 h (8 days) postdose.…”

“…Maximal incorporation of tracer into plasma ranged from 3% to 8% depending on the tracer administered. The 3 and 6 long-chain PUFAs in plasma had a maximum value of less than 0.1% of the administered dose, values that agree with other recent data (22)(23)(24)(25)(26)49). These net desaturation chain-elongation values are derived from the plasma pool but should at least qualitatively mirror the tissue incorporation of these fatty acids and their long-chain products.…”

“…Previously, several deuterated fatty acids were administered to compare incorporation into plasma lipid classes as well as the conversion of linoleate and ␣-linolenate to their desaturated and chain elongated products (17)(18)(19)(20). Using 13 C or 14 C as the tracer, the simultaneous measurement of oxidation and plasma lipid enrichment of linoleate (21,22) and ␣-linolenate (23-26) and their desaturated and elongated products was performed. However, in each case only a single fatty acid was studied.…”

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

“…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). Present study has suggested that abalone has certain conversion of dietary LA to muscle ARA.…”

Status Epilepticus Associated with Borage Oil Ingestion

“…GLA is then converted to DGLA and then to arachidonic acid (AA). In a single-dose study of radio-labeled LA metabolism in healthy subjects, the percent of LA recovered as AA was very low (0.05% of the radio-labeled dose) [10].…”