Measuring Peripheral Tissue DHA Turnover Using a Novel ¹³C Enrichment Technique

Recently, through the use of compound-specific isotope analysis (CSIA), our lab validated the utility of ¹³C enrichment (δ¹³C) of docosahexaenoic acid (DHA) by using a very high δ¹³C in a diet switch study by measuring brain, liver, and plasma DHA turnover and half-lives via high-precision gas chromatography combustion isotope ratio mass spectrometry (GC/C/IRMS). Using this novel enrichment technique, the present study extends measures of DHA turnover in the peripheral tissues, including red blood cells (RBC), perirenal adipose tissue (PRAT), muscle, heart, and skin. Mice were fed a low δ¹³C diet (fish-DHA control) for 3 months, then switched to either a high δ¹³C treatment diet (algal-DHA) or a very high δ¹³C treatment diet (¹³C enriched-DHA), while some remained on the fish-DHA control diet as a reference group for the remainder of the study time course. In mice fed the algal and ¹³C enriched-DHA diets, the RBC DHA half-life was 22.8 and 19.5 days, the PRAT DHA half-life was 6.0 and 8.2 days, the muscle DHA half-life was 38.2 and 42.2 days, the heart DHA half-life was 12.4 and 10.5 days, and the skin DHA half-life was 13.6 and 13.0 days, respectively. Future studies could employ the ¹³C enrichment method to examine how DHA metabolism is altered in peripheral tissues according to genetics, stress, and development.