Metabolism of uniformly labeled 13C-eicosapentaenoic acid and 13C-arachidonic acid in young and old men [Lipids]

Background: Plasma eicosapentaenoic acid (EPA) and arachidonic acid (AA) concentrations increase with age.

Objective: The aim of this study was to evaluate EPA and AA metabolism in young and old men by using uniformly labeled carbon-13 (¹³C) fatty acids.

Design: 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 ¹³C-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 ¹³C-AA and its metabolism was followed for 28 d in plasma and breath.

Results: There was a time x age interaction for ¹³C-EPA (P_{time x age} = 0.008), and the shape of the postprandial curves was different between young and old men. The ¹³C-EPA plasma half-life was ~2 d for both young and old men (P = 0.485). The percentage dose recovered of ¹³C-EPA per hour as ¹³CO₂ and the cumulative β-oxidation of ¹³C-EPA did not differ between young and old men. At 7 d, however, old men had a >2.2-fold higher plasma ¹³C-DHA concentration synthesized from ¹³C-EPA compared with young men (P_age = 0.03). ¹³C-AA metabolism was not different between young and old men. The ¹³C-AA plasma half-life was ~4.4 d in both young and old participants (P = 0.589).

Conclusions: The metabolism of ¹³C-AA was not modified by age, whereas ¹³C-EPA metabolism was slightly but significantly different in old compared with young men. The higher plasma ¹³C-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 .

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