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

Abstract

Altered use of different dietary fatty acids may contribute to several chronic diseases, including obesity, noninsulin-dependent diabetes mellitus, and cardiovascular disease. However, few comparative data are available to support this link, so the goal of the present study was to compare the metabolism of [13C]oleate, [13C]α-linolenate, [ 13C]elaidate, and [13C]linoleate through oxidation and incorporation into plasma lipid fractions and adipose tissue. Each tracer was given as a single oral bolus to six healthy women. Samples were collected over 8 days, and 13C was analyzed using isotope ratio mass spectrometry. At 9 h post-dose, cumulative oxidation was similar for [13C]elaidate, [13C]oleate, and [13C]α-linolenate (19 ± 1%, 20 ± 4%, and 19 ± 3% dose, respectively). Significantly lower oxidation of [13C]linoleate (12 ± 4% dose; P < 0.05) was accompanied by its higher incorporation into plasma phospholipids and cholesteryl esters. Abdominal adipose tissue was enriched with [ 13C]α-linolenate, [13C]elaidate, or [ 13C]linoleate within 6 h. The percentage linoleate in plasma phospholipids correlated positively with [13C]linoleate and [ 13C]elaidate oxidation, indicating a potential role of background diet. Conversion of [13C]linoleate and [13C]α -linolenate to longer chain polyunsaturates was a quantitatively minor route of utilization.