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

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 (C-13) fatty acids. Design: Six young (similar to 25 y old) and 6 old (similar to 75 y old) healthy men were recruited. Each participant consumed a single oral dose of 35 mg C-13-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-13-AA and its metabolism was followed for 28 d in plasma and breath. Results: There was a time x age interaction for C-13-EPA (P-time x age = 0.008), and the shape of the postprandial curves was different between young and old men. The C-13-EPA plasma half-life wasw2 d for both young and old men (P = 0.485). The percentage dose recovered of C-13-EPA per hour as (CO2)-C-13 and the cumulative beta-oxidation of C-13-EPA did not differ between young and old men. At 7 d, however, old men had >2.2-fold higher plasma C-13-DHA concentration synthesized from C-13-EPA compared with young men (P-age = 0.03). C-13-AA metabolism was not different between young and old men. The C-13-AA plasma half-life was similar to 4.4 d in both young and old participants (P = 0.589). Conclusions: The metabolism of C-13-AA was not modified by age, whereas C-13-EPA metabolism was slightly but significantly different in old compared with young men. The higher plasma C-13-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.