2 porcine skeletal muscle in a genotype-dependent manner

15 Abstract 16 Skeletal muscle is a major site for the oxidation of fatty acids (FA) in mammals, including humans. Using a swine model, we tested the 17 hypothesis that dietary protein intake regulates the expression of key genes for lipid metabolism in skeletal muscle. A total of ninety- 18 six barrows (forty-eight pure-bred Bama mini-pigs (fatty genotype) and forty-eight Landrace pigs (lean genotype)) were fed from 19 5 weeks of age to market weight. Pigs of fatty or lean genotype were randomly assigned to one of two dietary treatments (low- or ade- 20 quate-protein diet), with twenty-four individually fed pigs per treatment. Our data showed that dietary protein levels affected the 21 expression of genes involved in the anabolism and catabolism of lipids in the longissimus dorsi and biceps femoris muscles in a geno- 22 type-dependent manner. Specifically, Bama mini-pigs had more intramuscular fat, SFA and MUFA, as well as elevated mRNA expression 23 levels of lipogenic genes, compared with Landrace pigs. In contrast, Bama mini-pigs had lower mRNA expression levels of lipolytic 24 genes than Landrace pigs fed an adequate-protein diet in the growing phase. These data are consistent with higher white-fat deposition 25 in Bama mini-pigs than in Landrace pigs. In conclusion, adequate provision of dietary protein (amino acids) plays an important role in 26 regulating the expression of key lipogenic genes, and the growth of white adipose tissue, in a genotype- and tissue-specific manner. 27 These findings have important implications for developing novel dietary strategies in pig production.