Orally administered [14C]DPA and [14C]DHA are metabolised differently to [14C]EPA in rats

Abstract

Previous studies have revealed that C20 PUFA are significantly less oxidised to CO2in whole-body studies compared with SFA, MUFA and C18 PUFA. The present study determined the extent to which three long-chain PUFA, namely 20 : 5n-3 EPA, 22 : 5n-3 docosapentaenoic acid (DPA) and 22 : 6n-3 DHA, were catabolised to CO2or, conversely, incorporated into tissue lipids. Rats were administered a single oral dose of 2·5 μCi [1-14C]DPA, [1-14C]EPA, [1-14C]DHA or [1-14C]oleic acid (18 : 1n-9; OA), and were placed in a metabolism chamber for 6 h where exhaled14CO2was trapped and counted for radioactivity. Rats were euthanised after 24 h and tissues were removed for analysis of radioactivity in tissue lipids. The results showed that DPA and DHA were catabolised to CO2significantly less compared with EPA and OA (P< 0·05). The phospholipid (PL) fraction was the most labelled for all threen-3 PUFA compared with OA in all tissues, and there was no difference between C20 and C22n-3 PUFA in the proportion of label in the PL fraction. The DHA and DPA groups showed significantly more label than the EPA group in both skeletal muscle and heart. In the brain and heart tissue, there was significantly less label in the cholesterol fraction from the C22n-3 PUFA group compared with the C20n-3 PUFA group. The higher incorporation of DHA and DPA into the heart and skeletal muscle, compared with EPA, suggests that these C22n-3 PUFA might play an important role in these tissues.