Longissimus Thoracis and subcutaneous fat transcriptome study in lambs

Feeding animals with either concentrates supplemented with vitamin E or alfalfa grazing has been proven to reduce the oxidative process that occurs in meat products. Indoor-kept lambs were fed a standard concentrate (n=7, C) or concentrate supplemented with vitamin E (n=7, VE) for 30 days before slaughtering all animals at 22–24 kg of live weight. Simultaneously, 7 unweaned lambs grazed in alfalfa paddocks (ALF) with their dams. Global transcriptomic data of longissimus thoracis (LT) muscle and subcutaneous fat (SF) with the Affymetrix® Ovine Gene 1.1 microarray was used. In LT muscle when ALF group was compared with C group, were identified 41 genes differentially expressed. Among these genes 32 were down- regulated and 9 were up- regulated. Meanwhile when VE treatment was compared with C group were identified a total of 29 genes, 26 were down- regulated and 3 genes were up- regulated. In SF when ALF treatment was compared with C, were identified only 4 genes differentially expressed, all of them up-regulated in ALF group. Meanwhile when VE treatment was compared with C group, were identified a total of 330 genes. Among them, 295 genes were up- regulated and 35 were down- regulated. In LT muscle the clusters corresponding to gene expression profiles from treatments ALF, C and VE were clearly separated from each other. In SF, ALF group, overlap with VE and C treatments, however, VE and C clearly were separate in different clusters. These differentially expressed genes were selected for a functional analysis by using DAVID. In LT muscle some of the identified significant biological processes were catabolic and lipid process (down-regulated, except CPT1B) (CPT1B, PLA2G16, SPSB1, LRTOMT, PLCD4, FBXO9, CNBP and CYP27A1) and muscle organ differentiation (down-regulated) (CPT1B, MYOD1, MYLK2 and MSTN) in ALF; whereas intracellular signaling cascade (IGF1R, DEF8, AKAP7 and CISH) was down-regulated. In SF, vitamin E supplementation had an important effect; most of the genes were up-regulated. DAVID analysis showed that biosynthesis lipid pathway was the most represented with 20 genes, such as EBP, MVD, CYP51A1, DHCR7, HMGCS1, LSS and FDFT1 implicated in cholesterol synthesis. Further exploration of the links between these genes and vitamin E will lead to a better understanding of how vitamin E affects the oxidative process that occurs in meat products. 21 male lambs were employed. 7 animals were fed basal concentrate, 7 animals were fed concentrate supplemented with 500 mg dl-α-tocopheryl acetate/kg concentrate and 7 animals grazed in alfalfa paddocks. Animals were slaughtered at 22-24 kg of live weight. Just after slaughter, a piece of Longissimus Thoracis muscle and a piece of subcutaneous fat were sampled from each animal.