Metabolism of uniformly labeled C-eicosapentaenoic acid and C-arachidonic acid in young and old men.

Plasma eicosapentaenoic acid (EPA) and arachidonic acid (AA) concentrations increase with age. The aim of this study was to evaluate EPA and AA metabolism in young and old men by using uniformly labeled carbon-13 (C) fatty acids. Six young (∼25 y old) and 6 old (∼75 y old) healthy men were recruited. Each participant consumed a single oral dose of 35 mg C-EPA and its metabolism was followed in the course of 14 d in the plasma and 28 d in the breath. After the washout period of ≥28 d, the same participants consumed a single oral dose of 50 mg C-AA and its metabolism was followed for 28 d in plasma and breath. There was a time × age interaction for C-EPA ( = 0.008), and the shape of the postprandial curves was different between young and old men. The C-EPA plasma half-life was ∼2 d for both young and old men ( = 0.485). The percentage dose recovered of C-EPA per hour as CO and the cumulative β-oxidation of C-EPA did not differ between young and old men. At 7 d, however, old men had a >2.2-fold higher plasma C-DHA concentration synthesized from C-EPA compared with young men ( = 0.03). C-AA metabolism was not different between young and old men. The C-AA plasma half-life was ∼4.4 d in both young and old participants ( = 0.589). The metabolism of C-AA was not modified by age, whereas C-EPA metabolism was slightly but significantly different in old compared with young men. The higher plasma C-DHA seen in old men may be a result of slower plasma DHA clearance with age. This trial was registered at clinicaltrials.gov as NCT02957188.