Relationship between the expression of key lipogenic enzymes, fatty acid composition, and intramuscular fat content of Limousin and Aberdeen Angus cattle

The amount and fatty acid composition of intramuscular fat (IMF) are major factors in determining the nutritional value of beef. Understanding the mechanisms regulating IMF formation is important for designing strategies for manipulation of IMF quantity and quality. The aim of this study was to investigate the contribution of key lipogenic enzymes towards intramuscular fat formation in Aberdeen Angus and Limousin crossbred steers. This study reports the presence of 150 kDa acetyl-CoA-carboxylase α (ACCα), 150 kDa fatty acid synthase (FAS), 37 kDa stearoyl-CoA desaturase (SCD), 50 kDa Δ6-desaturase (Δ6d), and 50 kDa Δ5-desaturase (Δ5d) immunoreactive bands in cattle muscle (as detected by Western blot analyses). A significant positive relationship was established between ACCα protein content and IMF content; FAS protein content and IMF, as well as between expression of these enzymes and the products of their reactions, saturated fatty acid. IMF level was also positively related to the expression of Δ6d and Δ5d proteins. However, no relationship was found between IMF and the amount of SCD protein. It is suggested that the rate of saturated fatty acids and PUFA biosynthesis might have a significant impact on IMF deposition in cattle.