Artificial rearing with docosahexaenoic acid and n-6 docosapentaenoic acid alters rat tissue fatty acid composition

Ken D Stark,Sun-Young Lim,Norman Salem

doi:10.1194/jlr.m700317-jlr200

Abstract

Docosahexaenoic acid (DHA; 22:6n-3) and n-6 docosapentaenoic acid (DPAn-6; 22:5n-6) are components of enriched animal feed and oil derived from Schizochytrium species microalgae. A one generation, artificial rearing model from day 2 after birth onward (AR) and a dam-reared control group (DAM) were used to examine DPAn-6 feeding on the fatty acid composition of various rat tissues at 15 weeks of age. Four AR diets were based on an n-3 fatty acid-deficient, 18:2n-6-based artificial milk with 22:6n-3 and/or 22:5n-6 added: AR-LA, AR-DHA, AR-DPAn-6, and AR-DHA+DPAn-6. The 22:6n-3 levels for the DAM, AR-DHA, and AR-DHA+DPAn-6 groups tended to be similar and higher than in the AR-LA and AR-DPAn-6 groups. The levels of 22:5n-6 tended to be higher only in the absence of dietary 22:6n-3. Adipose levels of 22:5n-6 was the only exception, as 22:5n-6 was significantly higher in AR-DHA+DPAn-6 than was observed in either the DAM or the AR-DHA group. There were no differences in 20:4n-6 levels within the tissues examined. In conclusion, 22:5n-6 replaces 22:6n-3 in the absence of 22:6n-3 only and does not appear to compete with 22:6n-3 in the presence of dietary 22:6n-3, suggesting that oils containing 22:5n-6 and 22:6n-3 may be a good dietary source of 22:6n-3.

Highlights

Docosahexaenoic acid (DHA; 22:6n-3) and n-6 docosapentaenoic acid (DPAn-6; 22:5n-6) are components of enriched animal feed and oil derived from Schizochytrium species microalgae
The Schizochytrium species have a relatively high 22:6n-3 biomass and oil yield for a low cost [6, 7], but they contain considerable amounts of n-6 docosapentaenoic acid (DPAn-6; 22:5n-6) [7]. 22:6n-3 and 22:5n-6 differ by a single, additional carboncarbon double bond at the D19 position of 22:6n-3. 22:6n-3 and 22:5n-6 are largely incorporated into the sn-2 position of phospholipids along with and in competition with other highly unsaturated fatty acids (HUFAs; >20 carbons, >3 double bonds) such as arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) [8]
Dietary groups with 22:6n-3 included (DAM, after birth onward (AR)-DHA, and AR-DHA1DPAn-6) had significantly higher 22:6n-3 in all tissues compared with groups that did not have preformed dietary 22:6n-3 (AR-linoleic acid (LA) and AR-DPAn-6)

Summary

Introduction

Docosahexaenoic acid (DHA; 22:6n-3) and n-6 docosapentaenoic acid (DPAn-6; 22:5n-6) are components of enriched animal feed and oil derived from Schizochytrium species microalgae. A one generation, artificial rearing model from day 2 after birth onward (AR) and a dam-reared control group (DAM) were used to examine DPAn-6 feeding on the fatty acid composition of various rat tissues at 15 weeks of age. Four AR diets were based on an n-3 fatty acid-deficient, 18:2n-6-based artificial milk with 22:6n-3 and/or 22:5n-6 added: AR-LA, AR-DHA, AR-DPAn-6, and AR-DHA1DPAn-6. Jr. Artificial rearing with docosahexaenoic acid and n-6 docosapentaenoic acid alters rat tissue fatty acid composition. 22:6n-3 and 22:5n-6 are largely incorporated into the sn-2 position of phospholipids along with and in competition with other highly unsaturated fatty acids (HUFAs; >20 carbons, >3 double bonds) such as arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) [8]. N-3 fatty acid deficiency studies using 18:2n-6-based control diets have the potential to increase the content of 20:4n-6, which has significant bioactive properties. AR-LA, 18:2n-6 artificially reared diet; AR-DPA, 22:5n-6 artificially reared diet; AR-DHA1DPA, 22:6n-3 plus 22:5n-6 artificially reared diet; AR-DHA, 22:6n-3 artificially reared diet; EE, ethyl ester

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