Increases in plasma n-3 tetracosapentaenoic acid and tetracosahexaenoic acid following 12 weeks of EPA, but not DHA, supplementation in women and men

Abstract

Dietary feeding and stable isotope studies in rodents support that the 24-carbon omega-3 polyunsaturated fatty acids, tetracosapentaenoic acid (24:5n-3, TPAn-3) and tetracosahexaenoic acid (24:6n-3, THA), are immediate precursors to docosahexaenoic acid (DHA, 22:6n-3). In this study, we assessed for the first time, changes in TPAn-3 or THA levels following omega-3 PUFA supplementation in humans, providing insight into human omega-3 PUFA metabolism. In this secondary analysis of a double-blind randomized control trial, women and men (19 – 30 years, n = 10 – 14 per sex, per diet) were supplemented with 3 g/day EPA, DHA, or olive oil control for 12 weeks. Plasma TPAn-3 and THA concentrations were determined by gas chromatography-mass spectrometry to determine changes following supplementation in a sex-specific manner (sex x time). EPA supplementation significantly increased (p < 0.0001) plasma TPAn-3 by 215% (1.3 ± 0.1 – 4.1 ± 0.7, nmol/mL ± SEM) and THA by 112% (1.7 ± 0.2 – 3.6 ± 0.5, nmol/mL ± SEM). Furthermore, women had 111% and 99% higher plasma TPAn-3 and THA in the EPA supplemented group compared to men (p < 0.0001). There were no significant effects of time on plasma TPAn-3 or THA concentrations in the DHA supplemented or olive oil supplemented groups. In conclusion, EPA, but not DHA, supplementation in humans increased plasma TPAn-3 and THA levels, suggesting that THA accumulates prior to conversion to DHA in the n-3 PUFA synthesis pathway. Furthermore, women generally exhibit higher plasma TPAn-3 and THA concentrations compared with men, suggesting that women have a greater ability to accumulate 24-carbon n-3 PUFA in plasma via EPA and DPAn-3 elongation, which may explain the known higher DHA levels in women.

Summary: In this secondary analysis of a double-blind randomized control trial, we assessed changes in omega-3 (n-3) tetracosapentaenoic acid (24:5n-3, TPAn-3) and tetracosahexaenoic acid (24:6n-3, THA) plasma levels in women and men (19 – 30 years, n = 10 – 14 per sex, per diet) following 12-weeks of n-3 PUFA supplementation (3 g/day EPA, DHA or olive oil). Women had higher plasma TPAn-3 in all supplementation groups and higher THA levels in the EPA and olive oil groups (p < 0.0001) compared to men. EPA supplementation increased (p < 0.0001) plasma TPAn-3 by 215% (1.3 ± 0.1 – 4.1 ± 0.7, nmol/mL ± SEM) and THA by 112% (1.7 ± 0.2 – 3.6 ± 0.5, nmol/mL ± SEM), but DHA supplementation had no effect. For the first time in humans, we show that plasma TPAn-3 and THA levels are higher in women and increased with EPA, but not DHA supplementation, suggesting an accumulation of THA prior to conversion to DHA in the n-3 PUFA synthesis pathway.