Abstract
The intramuscular fat (IMF) content and fatty acid composition are important meat quality traits that are mostly affected by the cattle breed. Muscle, adipose tissue and liver are important organs involved in the development of intramuscular adipose tissue. Thus, we hypothesized that there were marked differences in the adipogenesis and lipid metabolism of these tissues between Wagyu-cross and Holstein steers during the finishing phases. To test this hypothesis, we analyzed the expression levels of adipogenesis- and lipid metabolism-related genes in longissimus muscle (LM), subcutaneous fat (SCF) and liver from Wagyu-cross and Holstein steers at 26 months of age. The IMF content and fatty acid profile of LM were determined. Wagyu-cross steers had a higher IMF content and MUFA percentages in the LM than Holstein steers (P<0.05). The relative expression of FGF2, COL1A1, SREBP1c, SCD1, GRP78 and LEP was greater in the LM of Wagyu-cross steers than in Holstein steers (P<0.05). In contrast, Holstein steer SCF had higher (P<0.05) mRNA expression levels of FABP4 and ADIPOQ than Wagyu-cross steers. In the liver, the expression of SREBP1c and GRP78 in Wagyu-cross steers was significantly higher than that in Holstein steers (P<0.05). The results demonstrate that both intramuscular adipogenesis and fibrogenesis are enhanced in Wagyu-cross steers compared with Holstein steers during the finishing phase and that IMF deposition is positively correlated with the maturity of SCF and hepatic lipid accumulation in Wagyu-cross steers.