Investigating the effects of diets enriched in PUFA and antioxidants on the gene expression networks and intramuscular fatty acid composition in porcine Longissimus thoracis et lumborum muscle

Western diets are rich in n-6 and deficient in n-3 polyunsaturated fatty acids (PUFAs), resulting in a high n-6/n-3 ratio. Decreasing the n-6/n-3 ratio of meat products with n-3 feeding supplemen- tations in livestock has been suggested as a viable strategy to increase meat nutritional value, but it also rises meat suscepti- bility to lipid oxidation. To date, novel antioxidants are available, and some of them can be obtained from by-products discarded by other food industries, such as grape skins. This study aimed at investigating in medium-heavy pigs the effect of high linolenic acid diets supplemented with synthetic or natural antioxidants on muscle fatty acid (FA) composition, and gene expression of Longissimus thoracis et lumborum (LTL) muscle. For this study, 48 growing-finishing pigs, balanced for sex and weight, were assigned to 4 isoenergetic dietary treatments (12 pigs per treat- ment): barley, soya bean, (control, C); C with 5% linseed (L); L supplemented with vitamin E and selenium; L supplemented with grape skin and oregano extracts rich in polyphenols (L + natural antioxidants, LNA). Total RNA was extracted from LTL muscle and analysed with RNA sequencing. After sequence alignment, 10,169 genes were found expressed in the 48 samples and sub- mitted for Weighted Gene Co-expression Network Analysis to WGCNA package in the R environment. The samples belonging to each treatment were analysed separately and associated with the amounts of FAs found in their LTL muscle. The linseed dietary inclusion significantly reduced the n-6/n-3 ratio and increased the n-3 PUFAs in LTL (p < .05). These changes were also visible at the transcriptome level as the LNA diet caused great changes in the gene expression networks when compared to the gene co-expression structure identified in the LTL muscle of C pigs. In particular, the LNA supplementation stimulated the expression of genes involved in Type I interferon signaling pathway (Bonferroni p = 4.29E-10) and Innate immunity (Bonferroni p = 1.17E-5). This result agrees with the literature, which sug- gests that diets rich in n-3 and polyphenols may stimulate host immunity. On the other hand, the gene networks positively asso- ciated with the n-6/n-3 ratio in the C group were related to mito- chondrial activity and cell energy metabolism. The obtained results support the evidence that supplementing pig diets with extruded linseed and polyphenols can positively influence the nutritional quality of meat products.