title: Muscle transcriptomic profiles in pigs with divergent phenotypes for fatness traits.
abstract: BACKGROUND
  Selection for increasing intramuscular fat content would definitively improve the palatability and juiciness of pig meat as well as the sensorial and organoleptic properties of cured products. However, evidences obtained in human and model organisms suggest that high levels of intramuscular fat might alter muscle lipid and carbohydrate metabolism. We have analysed this issue by determining the transcriptomic profiles of Duroc pigs with divergent phenotypes for 13 fatness traits. The strong aptitude of Duroc pigs to have high levels of intramuscular fat makes them a valuable model to analyse the mechanisms that regulate muscle lipid metabolism, an issue with evident implications in the elucidation of the genetic basis of human metabolic diseases such as obesity and insulin resistance.
  
  
  RESULTS
  Muscle gene expression profiles of 68 Duroc pigs belonging to two groups (HIGH and LOW) with extreme phenotypes for lipid deposition and composition traits have been analysed. Microarray and quantitative PCR analysis showed that genes related to fatty acid uptake, lipogenesis and triacylglycerol synthesis were upregulated in the muscle tissue of HIGH pigs, which are fatter and have higher amounts of intramuscular fat than their LOW counterparts. Paradoxically, lipolytic genes also showed increased mRNA levels in the HIGH group suggesting the existence of a cycle where triacylglycerols are continuously synthesized and degraded. Several genes related to the insulin-signalling pathway, that is usually impaired in obese humans, were also upregulated. Finally, genes related to antigen-processing and presentation were downregulated in the HIGH group.
  
  
  CONCLUSIONS
  Our data suggest that selection for increasing intramuscular fat content in pigs would lead to a shift but not a disruption of the metabolic homeostasis of muscle cells. Future studies on the post-translational changes affecting protein activity or expression as well as information about protein location within the cell would be needed to to elucidate the effects of lipid deposition on muscle metabolism in pigs.
authors.affiliation: IRTA, Genètica i Millora Animal, 191 Av Alcalde Rovira Roure, 25198 Lleida, Spain.
authors.forename: Angela
authors.initials: A
authors.lastname: Cánovas
authors.forename: Raquel
authors.initials: R
authors.lastname: Quintanilla
authors.forename: Marcel
authors.initials: M
authors.lastname: Amills
authors.forename: Ramona N
authors.initials: RN
authors.lastname: Pena
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D005260:Female; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks / Q000235:genetics; D014644:Genetic Variation; D008297:Male; D053858:Metabolic Networks and Pathways / Q000235:genetics; D009132:Muscles / Q000166:cytology* / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D016133:Polymerase Chain Reaction; D015203:Reproducibility of Results; D013552:Swine / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism