Expression of Enzymes and Transcription Factors Involved in n-3 Long Chain PUFA Biosynthesis in Limousin Bull Tissues

Towards Sustainable Sources of Omega-3 Long-Chain Polyunsaturated Fatty Acids in Northern Australian Tropical Crossbred Beef Steers through Single Nucleotide Polymorphisms in Lipogenic Genes for Meat Eating Quality

This study aimed to identify single nucleotide polymorphisms (SNP) in lipogenic genes of northern Australian tropically adapted crossbred beef cattle and to evaluate associations with healthy lipid traits of the Longissimus dorsi (loin eye) muscle. The hypothesis tested was that there are significant associations between SNP loci encoding for the fatty acid binding protein 4 (FABP4), stearoyl-CoA desaturase (SCD) and fatty acid synthase (FASN) genes and human health beneficial omega-3 long-chain polyunsaturated fatty acids (ω3 LC-PUFA) within the loin eye muscle of northern Australian crossbred beef cattle. Brahman, Charbray, and Droughtmaster crossbred steers were fed on Rhodes grass hay augmented with desmanthus, lucerne, or both, for 140 days and the loin eye muscle sampled for intramuscular fat (IMF), fat melting point (FMP), and fatty acid composition. Polymorphisms in FABP4, SCD, and FASN genes with significant effects on lipid traits were identified with next-generation sequencing. The GG genotype at the FABP4 g.44677239C>G locus was associated with higher proportion of linoleic acid than the CC and CG genotypes (p < 0.05). Multiple comparisons of genotypes at the SCD g.21266629G>T locus indicated that the TT genotype had significantly higher eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids than GG genotype (p < 0.05). Significant correlations (p < 0.05) between FASN SNP and IMF, saturated and monounsaturated fatty acids were observed. These results provide insights into the contribution of lipogenic genes to intramuscular fat deposition and SNP marker-assisted selection for improvement of meat-eating quality, with emphasis on alternate and sustainable sources of ω3 LC-PUFA, in northern Australian tropical crossbred beef cattle, hence an acceptance of the tested hypothesis.

Transcriptomic profile of longissimus thoracis associated with fatty acid content in Nellore beef cattle

The beef fatty acid (FA) profile has the potential to impact human health, and displays polygenic and complex features. This study aimed to identify the transcriptomic FA profile in the longissimus thoracis muscle in Nellore beef cattle finished in feedlot. Forty-four young bulls were sampled to assess the beef FA profile by considering 14 phenotypes and including differentially expressed genes (DEG), co-expressed (COE), and differentially co-expressed genes (DCO) analyses. All samples (n = 44) were used for COE analysis, whereas 30 samples with extreme phenotypes for the beef FA profile were used for DEG and DCO. A total of 912 DEG were identified, and the polyunsaturated (n = 563) and unsaturated ω-3 (n = 346) FA sums groups were the most frequently observed. The COE analyses identified three modules, of which the blue module (n = 1776) was correlated with eight of 14 FA phenotypes. Also, 759 DCO genes were listed, and the oleic acid (n = 358) and monounsaturated fatty acids sum (n = 120) were the most frequent. Furthermore, 243 and 13, 319 and seven, and 173 and 12 gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways were enriched respectively for the DEG, COE, and DCO analyses. Combining the results, we highlight the unexplored GIPC2, ASB5, and PPP5C genes in cattle. Besides LIPE and INSIG2 genes in COE modules, the ACSL3, ECI1, DECR2, FITM1, and SDHB genes were signaled in at least two analyses. These findings contribute to understand the genetic mechanisms underlying the beef FA profile in Nellore beef cattle finished in feedlot.

The mechanism through which dietary supplementation with heated linseed grain increases n-3 long-chain polyunsaturated fatty acid concentration in subcutaneous adipose tissue of cashmere kids

The aim of this study was to investigate the effects of dietary supplementation with heated linseed on the fatty acid (FA) composition of the plasma, liver, and subcutaneous adipose tissue (SADT) of Albas white cashmere kids, particularly the effect on n-3 long-chain polyunsaturated FA profiles and the mRNA expression of genes related to lipid metabolism in SADT. Sixty 4-month-old castrated male kids (average BW 18.6 ± 0.1 kg) were selected and randomly allocated into three groups in a randomized block design. Three dietary treatments were used: (1) basal diet without supplementation (Control), (2) basal diet supplemented with linseed oil (LSO), and (3) basal diet supplemented with heated linseed grain (HLS). The diets were fed for 104 d, consisting of 14 d for adaptation followed by 90 d of measurement. Different FA profiles were found in SADT between LSO and HLS. Kids fed HLS had more C18:3n3 (P < 0.0001), C22:6n3 (P = 0.007), and n-3 PUFA (P < 0.0001) and a less (P < 0.0001) n-6/n-3 ratio than LSO kids. These FA differences between LSO and HLS kids were due to the increased expression of elongation of very long chain FA protein 5 (P < 0.0001), delta-6 desaturase (P < 0.0001), and peroxisome proliferator-activated receptor α (P = 0.003) in SADT of HLS kids and was also associated with liver fat metabolism. Together, these results suggest that the consumption of HLS leads to more C22:6n3 than LSO in SADT by increasing liver C22:6n3 content and by increasing SADT mRNA expression of ELOVL5 and FADS2 through promoting PPARα expression.

Quality attributes and composition of meat from red deer (Cervus elaphus), fallow deer (Dama dama) and Aberdeen Angus and Holstein cattle (Bos taurus)

BACKGROUND

The consumption of venison from deer species has increased in recent years owing to presumably positive health effects. Therefore a comparison was made of the physical characteristics, chemical composition and sensory attributes of meat obtained from red deer, fallow deer and Aberdeen Angus and Holstein cattle raised under conditions typical for commercial farming practice and slaughtered at similar ages.

RESULTS

Venison had one-quarter the crude fat content, lower total collagen and a higher proportion of heat-soluble collagen. It was darker and less yellow than beef. Deer species provided meat with higher polyunsaturated/saturated fatty acid ratio and lower atherogenic index. In addition, the venison of red deer contained five times as much n-3 polyunsaturated fatty acids as the beef. Steaks prepared from venison were scored higher than beef for flavour and aroma intensity; they were also tenderer and more easily chewable.

CONCLUSION

Compared with beef, venison from two widely farmed deer species was superior in nutrient composition, thus offering potential benefits for human consumption, and it received higher scores for most of the sensory attributes examined.

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

BACKGROUND

In ruminants, unsaturated dietary fatty acids are biohydrogenated in the rumen and are further metabolised in various tissues, including liver, which has an important role in lipid and lipoprotein metabolism. Therefore, manipulation of muscle fatty acid composition should take into account liver metabolism. In the present study, the influence of breed and diet on liver lipid composition and gene expression was investigated in order to clarify the role of this organ in the lipid metabolism of ruminants. Forty purebred young bulls from two phylogenetically distant autochthonous cattle breeds, Alentejana and Barrosã, were assigned to two different diets (low vs. high silage) and slaughtered at 18 months of age. Liver fatty acid composition, mRNA levels of enzymes and transcription factors involved in lipid metabolism, as well as the plasma lipid profile, were assessed.

RESULTS

In spite of similar plasma non-esterified fatty acids levels, liver triacylglycerols content was higher in Barrosã than in Alentejana bulls. Moreover, the fatty acid composition of liver was clearly distinct from the remaining tissues involved in fatty acid metabolism of ruminants, as shown by Principal Components Analysis. The hepatic tissue is particularly rich in α-linolenic acid and their products of desaturation and elongation. Results indicate that DGAT1, ELOVL2, FADS1 and FADS2 genes influence the fatty acid composition of the liver the most. Moreover, genes such as DGAT1 and ELOVL2 appear to be more sensitive to genetic background than to dietary manipulation, whereas genes encoding for desaturases, such as FADS1, appear to be modulated by dietary silage level.

CONCLUSIONS

Our results indicate that liver plays an important role in the biosynthesis of n-3 LC-PUFA. It is also suggested that dietary silage level influences the hepatic fatty acid metabolism in a breed-dependent manner, through changes in the expression of genes encoding for enzymes associated with the desaturation and elongation pathway. The importance of devising custom-made feeding strategies taking into account the genetic background is, therefore, stressed by the results from this experiment.

A grass-based diet favours muscle n-3 long-chain PUFA deposition without modifying gene expression of proteins involved in their synthesis or uptake in Charolais steers

N-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) are subject of growing interest as they are of particular relevance for meat quality and human health. However, their content in the muscles of cattle is generally low probably as the complex result of their biosynthesis from dietary n-3 PUFA in the muscle and/or in other tissues/organs and of their subsequent uptake by the muscle. In view of this, this study aimed at understanding whether the changes in the muscle n-3 LCPUFA content, depending on the diet (maize silage v. grass) or the muscle type (Rectus abdominis, RA v. Semitendinosus, ST) in 12 Charolais steers, were related to variations in the gene expression of proteins involved in n-3 LCPUFA biosynthesis or cellular uptake. Tissue fatty acid composition was analysed by gas-liquid chromatography and mRNA abundance of proteins by quantitative real-time PCR. The grass-based diet resulted in a 2.3-fold (P < 0.0002) increase in both RA and ST n-3 LCPUFA content compared with the maize silage-based diet, whereas no difference in the expression of genes involved in n-3 LCPUFA biosynthesis and uptake was observed between diets. ST exhibited a 1.5-fold higher n-3 LCPUFA content than RA (P < 0.003), whereas the gene expression of proteins involved in n-3 LCPUFA biosynthesis and uptake was 1.3- to 18-fold higher in RA than in ST (P < 0.05). In conclusion, diet- or muscle type-dependent changes in the muscle n-3 LCPUFA content of Charolais steers did not seem to be mediated by the gene expression regulation of proteins involved in the biosynthesis or uptake of these fatty acids.

Fatty acid profiles and adipogenic gene expression of various fat depots in Japanese Black and Holstein steers

Objective of the study was to assess the breed effect on fatty acid (FA) composition of different adipose tissues and on mRNA expression of genes involved in adipogenesis and fat metabolism. Japanese Black (JB) and Holstein (HS) steers were kept under equivalent conditions with high energy intake resulting in large differences in intramuscular fat (IMF) accumulation in longissimus muscle (LM). The relative FA composition of muscle, intermuscular fat, visceral fat, and perirenal fat was comparable between JB and HS steers. Circulating fatty acids were also similar in both breeds. Most relevant breed effects were identified in IMF, underlining the uniqueness of this adipose tissue site. JB steers had more monounsaturated FA and less saturated FA. Perilipin 1 and adipose differentiation-related protein (ADFP) mRNA levels were higher in IMF of JB. The results suggest advanced maturity of IMF cells in JB and altered local conditions in muscle influencing IMF accumulation and composition.

Functional Role of PPARs in Ruminants: Potential Targets for Fine-Tuning Metabolism during Growth and Lactation

Characterization and biological roles of the peroxisome proliferator-activated receptor (PPAR) isotypes are well known in monogastrics, but not in ruminants. However, a wealth of information has accumulated in little more than a decade on ruminant PPARs including isotype tissue distribution, response to synthetic and natural agonists, gene targets, and factors affecting their expression. Functional characterization demonstrated that, as in monogastrics, the PPAR isotypes control expression of genes involved in lipid metabolism, anti-inflammatory response, development, and growth. Contrary to mouse, however, the PPARγ gene network appears to controls milk fat synthesis in lactating ruminants. As in monogastrics, PPAR isotypes in ruminants are activated by long-chain fatty acids, therefore, making them ideal candidates for fine-tuning metabolism in this species via nutrients. In this regard, using information accumulated in ruminants and monogastrics, we propose a model of PPAR isotype-driven biological functions encompassing key tissues during the peripartal period in dairy cattle.

Selection of reference genes for quantitative real-time PCR normalisation in adipose tissue, muscle, liver and mammary gland from ruminants

The reliability of reverse transcription quantitative real-time PCR (RT-qPCR) depends on normalising the mRNA abundance using carefully selected, stable reference genes. Our aim was to propose sets of reference genes for normalisation in bovine or caprine adipose tissue (AT), mammary gland, liver and muscle. All of these tissues contribute to nutrient partitioning and metabolism and, thus, to the profitability of ruminant productions (i.e. carcasses, meat and milk). In this study, eight commonly used reference genes that belong to different functional classes (CLN3, EIF3K, MRPL39, PPIA, RPLP0, TBP, TOP2B and UXT) were analysed using the geNorm procedure to determine the most stable reference genes in bovine and/or caprine tissues. Abundances and rankings of reference genes varied between tissues, species and the combination of tissues and/or species. Therefore, we proposed 29 sets of reference genes that differed depending on the tissue and/or species. As examples of the 29 sets, EIF3K, TOP2B and UXT were proposed as the most stable reference genes in bovine AT; UXT, EIF3K and RPLP0 were the most stable reference genes in bovine and caprine AT. The optimal number of reference genes for data normalisation was 3 for 27 of the proposed 29 sets. In two of the 29 sets, four to five reference genes were necessary for data normalisation when the number of studied tissues was increased. For example, UXT, EIF3K, TBP, TOP2B and CLN3 were required for data normalisation in bovine mammary gland, AT, muscle and liver. We have evaluated some of our proposed sets of reference genes for the normalisation of CD36 gene expression. Normalisation using the three most stable reference genes has revealed downregulation of CD36 gene expression in bovine mammary gland by a concentrate-based diet that is supplemented with sunflower oil and upregulation of CD36 gene expression in caprine liver by including a rapidly degradable starch in the diet. The dietary regulation of the gene expression of CD36 has been erased by normalisation with the least stable reference genes, which may result in misinterpretation of CD36 gene regulation. To conclude, our results provide valuable reference gene sets for other studies that aim to measure tissue and/or species-specific mRNA abundance in ruminants.

Effects of fish oil and additional starch on tissue fatty acid profile and lipogenic gene mRNA abundance in lactating goats fed a diet containing sunflower-seed oil

In dairy cattle, diet supplementation with oils affects the lipid metabolism in body tissues via changes in the partitioning and deposition of fatty acids (FAs) and lipogenic gene expression; however, limited data are available in goats. Eight Alpine goats were fed a grassland hay diet supplemented with 90 g/day of sunflower-seed oil or 90 g/day of sunflower-seed oil and fish oil (2 : 1) plus additional starch. The goats were slaughtered on day 21 of the treatments and samples of the mammary secretory tissue, liver, omental and perirenal adipose tissues (ATs) were collected to characterise their FA composition and the mRNA abundance of lipogenic genes and transcription factors involved in their regulation, and to examine the impact of the diet composition on the same parameters. The results are in agreement with the specific physiological adaptation in the lipid metabolism of body tissues that is likely to occur during late lactation because of the coexistence of an active lipogenesis in the mammary secretory tissue and a significant anabolic activity in the ATs. These latter tissues were characterised by high concentrations of saturated FA and very low polyunsaturated FA (PUFA) levels. The content of PUFA was relatively higher in the mammary secretory tissue, in particular in the case of polyunsaturated C18. The highest PUFA contents were found in the liver, in accordance with the greater mRNA abundances of the genes that encode the necessary enzymes for very long-chain n-3 and n-6 PUFA synthesis. However, substantial differences between n-3 and n-6 pathways would most likely exist in the goat liver. Overall, differences in diet composition induced limited changes in the mRNA abundance of genes involved in lipid metabolism, and these were not associated with the few variations observed in tissue FA composition.

Different dietary protein and PUFA interventions alter the fatty acid concentrations, but not the meat quality, of porcine muscle

The present study investigated the effect of a reduced protein diet in combination with different vegetable oils (sunflower seed oil or linseed oil) on carcass traits, meat quality and fatty acid profile in porcine muscle. Forty male Landrace pigs were allocated into four experimental groups (each n = 8) and one control group (n = 8) at a live weight of approximately 60 kg. The pigs were fed ad libitum from 60 kg to 100 kg live weight and restricted to 2.8 kg/day until they reached 120 kg. In contrast to other studies, the intramuscular fat content (IMF) did not increase in animals of groups fed a reduced protein diet and vegetable oils. The IMF ranged between 1.2% and 1.4%. The growth performance and meat quality of the longissimus muscle was not affected by the diet, but the average daily gain (ADG) and drip loss were affected. The muscle fatty acid concentrations were significantly affected by the diet, resulting in higher n-3 FA concentrations up to 113 mg/100 g muscle and lower n-6/n-3 PUFA ratio for pigs fed linseed oil-containing high- and reduced protein diets, compared to sunflower seed oil-containing diets.