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

Abstract

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.

Effects of feeding steers extruded flaxseed on its own before hay or mixed with hay on animal performance, carcass quality, and meat and hamburger fatty acid composition

“…conversion rate of ALA to LCn-3 PUFA) and the ratio of triacylglycerol to phospholipids in beef. The increase in ALA in LT of non-TMR compared to TMR steers in the present study (from 1.13% to 1.26 %; of total fatty acids) may not have been great enough to support increased synthesis of LCn-3 PUFA, given the very low conversion rate of ALA to LCn-3 PUFA in cattle (Gruffat, Gobert, Durand, & Bauchart, 2011).…”

The labile lipid fraction of meat: From perceived disease and waste to health and opportunity

“…In this regard, future strategies for improving the FA composition of beef, and limiting its variation amongst animals, must address how diet, animal management, physiology, and behavior influence the rumen environment and microbial populations in individual animals, and to what extent individual animal variation in lipid metabolism may also play a role. To this end, it will be important to understand the rumen environment, including potential regulators of PUFA metabolism pathways, and to characterize rumen ecology using high throughput molecular biology techniques (Duan, Guo, & Liu, 2006;Qi et al, 2011), and to extend studies looking at fundamental biochemical aspects of lipid metabolism on a species and tissue specific basis (Gruffat, Gobert, Durand, & Bauchart, 2011). Currently available cost-effective molecular techniques utilized by either animal geneticists or rumen microbiologists, if focused on the understanding of inter-animal variation of FA composition, could help in advancing in the production of FA enriched beef.…”

Is hepatic lipid metabolism of beef cattle influenced by breed and dietary silage level?

“…Uptake of NEFA is the predominant route by which fatty acids are supplied to the liver [3] and, thus, plasma lipid fatty acid composition should influence the liver fatty acid metabolism and composition [2]. Consequently, the regulation of these liver metabolic pathways may affect fatty acid deposition into lipids of ruminant products [4]. …”

“…The activity of these enzymes is currently regarded as potential limiting steps in this biosynthesis, possibly in a tissue dependent manner. However, recent studies addressed the role of the liver in ruminants’ lipid metabolism, either using in vitro experiments [4] or in vivo assays [11]. These experiments raised some interesting clues on hepatic lipid metabolism, namely the extensive catabolism of α-linolenic acid [4] and the low or negligible expression level of genes encoding for enzymes of fatty acid desaturation and elongation [11].…”