Effect of dietary n − 3 and n − 6 fatty acids on fatty acid desaturation in rat liver

Christiansen, Erling N.; Lund, J S; Rørtveit, Torill; Rustan, Arild C.

doi:10.1016/0005-2760(91)90299-w

Cited by 137 publications

(61 citation statements)

References 20 publications

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“…These results agree with the general observation of a very low biosynthesis of DHA (,1%) in mammalian liver (Igarashi et al, 2006). It is well known that members of the n-6 and n-3 families compete for the elongation-desaturation pathway (Sprecher, 1981), the conversion of LA and ALA into their longer chain homologues being significantly influenced by the composition of dietary fats (Christiansen et al, 1991). In this context, bioconversion of n-3 FA into higher homologues depends on the ratio of ingested n-6/n-3 FA, a ratio of 1/1 being proposed to lead to the highest formation of long-chain n-3 PUFA (Harnack et al, 2009).…”

Section: Discussionsupporting

confidence: 91%

Distinct metabolism of linoleic and linolenic acids in liver and adipose tissues of finishing Normande cull cows

Gruffat

Gobert

Durand

et al. 2011

Animal

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Feeding strategies based on the addition of plant lipids rich in polyunsaturated fatty acids (PUFAs) in diets of bovines during the finishing period are common to enhance the nutritional value of meat. However, following rumen biohydrogenations, these FAs could still be metabolised in various tissues/organs involved in the FA metabolism such as the liver and adipose tissues (ATs), thus affecting their subsequent deposition in muscles. In this context, the objective of this study was to characterise the various metabolic pathways of linoleic acid (LA) and a-linolenic acid (ALA) in the liver and ATs (subcutaneous (SC) and inter-muscular (IM)) of Normande cull cows fed a diet supplemented (LR) or not (C) with extruded linseeds and rapeseeds, using the ex vivo incubated tissue slice method. Hepatic uptake of both FAs was higher with the LR than with the C diet ( P 5 0.02). For the two diets, ALA uptake was higher than that of LA (146%, P 5 0.04). ALA was much more degraded by b-oxidation (.50% of ALA present in cells) than LA (, 27%) with both diets ( P 5 0.015). Whatever the diet, ALA was not converted into longer and/or more unsaturated FA, whereas about 14% of LA was converted into 20:4n-6. The intensity of the esterification pathway was higher (170%, P 5 0.004) with the LR than with the C diet, for both FAs. Hepatic secretion of ALA as part of the very-low-density lipoprotein particles was lower than that of LA (258% and 223% for C and LR diets respectively, P 5 0.02). In SC and IM ATs, dietary lipid supplementation did not alter metabolic pathways of LA and ALA. They were efficiently taken up by ATs (.68% of FA present in the medium), with uptake being higher for IM than for SC AT (112%, P 5 0.01). Moreover, LA uptake by ATs was higher than ALA uptake (110.7%, P 5 0.027). Both FAs were mainly esterified (.97% of FA present in adipocytes) into neutral lipids (.85% of esterified FA). Around 9.5% of LA was converted into 20:4n-6, whereas only around 1.3% of ALA was converted into 20:5n-3. We concluded that, in our experimental conditions, liver was highly active in ALA catabolism limiting its subsequent deposition in muscles. However, bovine liver and ATs were inefficient at converting ALA into long-chain n-3 PUFA, but actively converted LA into 20:4n-6.

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Section: Discussionsupporting

confidence: 91%

Distinct metabolism of linoleic and linolenic acids in liver and adipose tissues of finishing Normande cull cows

Gruffat

Gobert

Durand

et al. 2011

Animal

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“…These acids found mainly in fish oils markedly depress A6-desaturase enzyme (Choi et al, 1989;Christiansen et al, 1991 ). They also depress A5-desaturase activity (Garg et al, 1988b figure 2 confirm what was previously demonstrated (Blond et al, 1989) phospholipids of rats fed the fish oil diet.…”

Section: Dietary Sources Of Essential Fatty Acidssupporting

confidence: 87%

The metabolism and availability of essential fatty acids in animal and human tissues

Bézard

Blond²,

Bernard³

et al. 1994

Reprod. Nutr. Dev.

191

109

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Summary ― Essential fatty acids (EFA), which are not synthesized in animal and human tissues, belong to the n-6 and n-3 families of polyunsaturated fatty acids (PUFA), derived from linoleic acid (LA,) and a-linolenic acid (LNA,. Optimal requirements are 3-6% of ingested energy for LA and 0.5-1% for LNA in adults. Requirements in LNA are higher in development. Dietary sources of LA and LNA are principally plants, while arachidonic acid (AA,) is found in products from terrestrian animals, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)

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“…However, when the diet is supplemented with polyenoic fatty acids of the (n-6) and (n-3) families, these enzymatic activities are reduced (26,28). Consistent with the enzymatic activity changes, we found that supplementing a high glucose fat-free diet with safflower oil (65% 18:2(n-6)) or fish oil (35% 20:5 and 22:6(n-3)) suppressed the hepatic abundance of ⌬-5 desaturase 60% (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, dietary and hormonal studies indicate that the two enzymes may be coordinately regulated (25)(26)(27)(28). For example, the enzymatic activity of both desaturases is reduced by diabetes, and this is associated with a reduced tissue content of 20:4(n-6) (27,29,30).…”

mentioning

confidence: 99%

Cloning, Expression, and Fatty Acid Regulation of the Human Δ-5 Desaturase

Cho

Nakamura

Clarke

1999

Journal of Biological Chemistry

454

377

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Arachidonic (20:4(n-6)), eicosapentaenoic (20:5(n-3)), and docosahexaenoic (22:6(n-3)) acids are major components of brain and retina phospholipids, substrates for eicosanoid production, and regulators of nuclear transcription factors. One of the two rate-limiting steps in the production of these polyenoic fatty acids is the desaturation of 20:3(n-6) and 20:4(n-3) by ⌬-5 desaturase. This report describes the cloning and expression of the human ⌬-5 desaturase, and it compares the structural characteristics and nutritional regulation of the ⌬-5 and ⌬-6 desaturases. The open reading frame of the human ⌬-5 desaturase encodes a 444-amino acid peptide which is identical in size to the ⌬-6 desaturase and which shares 61% identity with the human ⌬-6 desaturase. The ⌬-5 desaturase contains two membrane-spanning domains, three histidine-rich regions, and a cytochrome b 5 domain that all align perfectly with the same domains located in the ⌬-6 desaturase. Expression of the open reading frame in Chinese hamster ovary cells instilled the ability to convert 20:3(n-6) to 20:4(n-6). Northern analysis revealed that many human tissues including skeletal muscle, lung, placenta, kidney, and pancreas expressed ⌬-5 desaturase mRNA, but ⌬-5 desaturase was most abundant in the liver, brain, and heart. However, in all tissues, the abundance of ⌬-5 desaturase mRNA was much lower than that observed for the ⌬-6 desaturase. When rats were fed a diet containing 10% safflower oil or menhaden fish oil, the level of hepatic mRNA for ⌬-5 and ⌬-6 desaturase was only 25% of that found in the liver of rats fed a fat-free diet or a diet containing triolein. Finally, a BLAST and Genemap search of the human genome revealed that the ⌬-5 and ⌬-6 desaturase genes reside in reverse orientation on chromosome 11 and that they are separated by <11,000 base pairs.

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Effect of dietary n − 3 and n − 6 fatty acids on fatty acid desaturation in rat liver

Cited by 137 publications

References 20 publications

Distinct metabolism of linoleic and linolenic acids in liver and adipose tissues of finishing Normande cull cows

Distinct metabolism of linoleic and linolenic acids in liver and adipose tissues of finishing Normande cull cows

The metabolism and availability of essential fatty acids in animal and human tissues

Cloning, Expression, and Fatty Acid Regulation of the Human Δ-5 Desaturase

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