Comparison of gene expression and fatty acid profiles in concentrate and forage finished beef1

Abstract

Fatty acid profiles and intramuscular expression of genes involved in fatty acid metabolism were characterized in concentrate- (CO) and forage- (FO) based finishing systems. Intramuscular samples from the adductor were taken at slaughter from 99 heifers finished on a CO diet and 58 heifers finished on a FO diet. Strip loins were obtained at fabrication to evaluate fatty acid profiles of LM muscle for all 157 heifers by using gas chromatography fatty acid methyl ester analysis. Composition was analyzed for differences by using the General Linear Model (GLM) procedure in SAS. Differences in fatty acid profile included a greater atherogenic index, greater percentage total MUFA, decreased omega-3 to omega-6 ratio, decreased percentage total PUFA, and decreased percentage omega-3 fatty acids in CO- compared with FO-finished heifers (P<0.05). Fatty acid profiles from intramuscular samples were ranked by the atherogenic index, and 20 heifers with either a high (HAI; n=10) or low (LAI; n=10) atherogenic index were selected for gene expression analysis using real-time PCR (RT-PCR). Gene expression data for the 20 individuals were analyzed as a 2 by 2 factorial arrangement of treatments using the GLM procedure in SAS. There was no significant diet × atherogenic index interaction identified for any gene (P>0.05). Upregulation was observed for PPARγ, fatty acid synthase (FASN), and fatty acid binding protein 4 (FABP4) in FO-finished compared with CO-finished heifers in both atherogenic index categories (P<0.05). Upregulation of diglyceride acyl transferase 2 (DGAT2) was observed in FO-finished heifers with a HAI (P<0.05). Expression of steroyl Co-A desaturase (SCD) was upregulated in CO-finished heifers with a LAI, and downregulated in FO-finished heifers with a HAI (P<0.05). Expression of adiponectin (ADIPOQ) was significantly downregulated in CO-finished heifers with a HAI compared with all other categories (P<0.05). The genes identified in this study which exhibit differential regulation in response to diet or in animals with extreme fatty acid profiles may provide genetic markers for selecting desirable fatty acid profiles in future selection programs.

Gene expression profile of intramuscular muscle in Nellore cattle with extreme values of fatty acid

“…In this sense, the DGAT2 (diacylglycerol O-acyltransferase 2) gene, upregulated for palmitic and downregulated for linoleic acid and PUFA/SFA ratio, is essential for the triglycerides synthesis and intracellular storage [40] found negative correlations between marbling and concentrations of stearic, linoleic acid, and PUFA [24] reported a positive and moderate correlation between the level of marbling and the expression of DGAT2 gene. The DGAT2 gene is an important contributor to the triacylglycerol synthesis through their acyltransferase activity.…”

“…Costa et al [23] used bulls from different genetic groups of Alentejana and Barrosã breeds with divergent diets, high and low concentration of silage, to identify DEG associated with lipid metabolism in subcutaneous adipose tissue and in the longissimus lumborum muscle. Recently, [24] studied the gene expression pattern in taurine cattle finished in different diets with extreme phenotypes for FA profile in the intramuscular fat.…”

Constraints and potentials for the nutritional modulation of the fatty acid composition of ruminant meat

“…Some experimental data on nutritional factors that might modulate the SCD activity , SCD protein , or gene expression in ruminants are available, but the overwhelming majority of studies reporting meat FA composition do not report the SCD activity or expression data. The lack of widespread reports of SCD activity as influenced by dietary factors, prevent a more clear understanding of the potential impact of nutritional strategies to modulate the SCD activity and the FA composition of adipose tissue and muscle neutral fat in ruminants.…”

“…The direct activity assays are difficult to conduct as SCD protein is labile and all the complex procedures must be conducted very quickly after tissue sampling . The quantification of SCD gene expression is easier to conduct, and has been more extensively applied . However, at least in rodents, transcription of SCD1 gene is known to respond to circadian nutrient absorption cycles, with fast postprandial stimulation followed by under‐expression periods .…”

“…The close association between SCDi17 and 18:0 in neutral lipid deposits become weaker when dietary lipid supplementation, or other factors that modify the RBH are present, probably due to the highly variable fraction of dietary C18 FA that are absorbed as trans ‐18:1 or 18:0. Although a careful use of SCDi17 is necessary, the consistence of its results with the theoretical expectations are notorious although generally not correlated to single point SCD expression at slaughter or activity data. For that, we believe that the adequate use of SCDi17 (i.e., using muscle TAG concentrations of 17:0 and c 9‐17:1) might be a useful indicator of the impact of experimental dietary strategies on the average SCD activity during the whole finishing period.…”