Deposition and metabolism of dietary n-3 very-long-chain PUFA in different organs of rat, mouse and Atlantic salmon

Abstract

There is limited knowledge about the metabolism and function of n-3 very-long-chain polyunsaturated fatty acids (n-3 VLC-PUFAs) with chain lengths ≥24. They are known to be produced endogenously in certain tissues from eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and not considered to originate directly from dietary sources. The aim of this study was to investigate whether n-3 VLC-PUFAs from dietary sources are bio-available and deposited in tissues of rat, fish and mouse. Rats were fed diets supplemented with a natural fish oil as source of low dietary levels of n-3 VLC-PUFAs, while Atlantic salmon and mice were fed higher dietary levels of n-3 VLC-PUFAs from a fish oil concentrate. In all experiments, n-3 VLC-PUFA incorporation in organs was investigated. We found that natural fish oil, due to its high EPA content, to a limited extent increased endogenous production of n-3 VLC-PUFAs in brain and eye of mice with neglectable amounts of n-3 VLC-PUFA originating from diet. When higher dietary levels were given in the form of concentrate, these fatty acids were bio-available and deposited in both phospholipids (PL) and triacylglycerol (TAG) fractions of all tissues studied, including skin, eye, brain, testis, liver and heart, and their distribution appeared to be tissue-dependent, but not species-specific. When dietary EPA and DHA were balanced and n-3 VLC-PUFA increased, the major n-3 VLC-PUFAs from the concentrate increased significantly in the organs studied, showing that these fatty acids can be provided through diet and thereby provide a tool for functional studies of these VLC-PUFAs.

Increasing dietary levels of the n-3 long-chain PUFA, EPA and DHA, improves the growth, welfare, robustness and fillet quality of Atlantic salmon in sea cages

“…In line with these results, analysis of internal organ health scores and external welfare indicators revealed the same tendency toward improved welfare with increased dietary EPA and DHA content, especially for liver colour, which is considered a visual indicative of fat accumulation [59] and is therefore associated with nutritional disorders [60]. On the other hand, the welfare scorings for skin damage appeared to be marginally higher (worse condition) but not significant in the 3.5% EPA and DHA group, which was unexpected given the demonstrated positive impact of n-3 PUFAs in barrier tissues, such as skin [61]. Although only anecdotical, one potential explanation for these results could be that the fish in the 3.5% EPA and DHA group were substantially bigger and more active at the time of the final sampling and handling may have slightly damaged the skin and had a negative influence on the scoring.…”

Dietary fish oil enriched in very-long-chain polyunsaturated fatty acid reduces cardiometabolic risk factors and improves retinal function

“…Dietary VLCPUFA-oil showed no adverse effects, using doses comparable with previous animal studies of VLCPUFAs. 11 , 16 The single-dose oral administration of the VLCPUFA-oil caused a rapid increase in plasma levels of 24:5, followed by increased tissue levels in the retina. Despite the relatively low content of 24:6 in the VLCPUFA-oil, it also increased in the retina, possibly due to conversion of 24:5 by delta-6 desaturase.…”

“…Overall, our results confirm the previous studies’ findings concerning the bioavailability and tissue incorporation of orally administered VLCPUFAs. 11 , 16 Until now, most studies on dietary PUFA metabolism have focused on shorter-chain fatty acids (C18-C22), so the detailed metabolism of dietary VLCPUFAs remains largely unknown. 20 Further studies using isotopic labeled VLCPUFAs are needed to better understand their possible interconversion and degradation in various tissues.…”

“… 44 The dose and feeding period are comparable with previous animal metabolism studies, using fish oil-derived VLCPUFA concentrate in triglyceride form or dietary DHA. 16 , 45 Each diet contained equally 18.8% kcal from protein, 63.9% kcal from carbohydrate, and 17.2% kcal from fat. After 8 weeks of diet consumption, the 5-h fasted mice were euthanized via intraperitoneal injection of tribromoethanol.…”

Investigation of the functions of n-3 very-long-chain PUFAs in skin using in vivo Atlantic salmon and in vitro human and fish skin models

“…The severity of these conditions indicates that VLC-FA play an essential role in animals. We have previously demonstrated deposition of n -3 VLC-PUFA in skin tissue after dietary supplementation in Atlantic salmon ( Salmo salar ) and mice ( 29 ) , which may indicate a role of VLC-PUFA in skin. This is an interesting finding, as the importance of VLC-FA in skin has mostly been examined in relation to very-long-chain SFA (VLC-SFA), while the role of VLC-PUFA remains unclear ( 25 , 27 , 29 ) .…”