Molecular mechanisms of bovine intramuscular fat deposition

Abstract Text: Intramuscular fat (IMF) content in the longissimus dorsi muscle (LM), also known as marbling fat, is one of most important factors that determine beef quality in Korea and Japan as well as in USA. IMF deposition is influenced by both genetic (e.g., breed, genotype) and non-genetic factors (e.g., gender, castration, nutrition, stresses, age). Castration markedly increases IMF deposition, resulting in improved beef quality in Korean cattle. We present comparative approach in gene expression between bulls and steers in bovine tissues. Marling trait has relatively higher heritability compared to other phenotypes such as feed efficiency and body weight and is quantitative being influenced by variety of genes involved in nutrient metabolism. The identification of genes associated with IMF deposition is an important area for elucidating mechanisms of IMF deposition. IMF deposition is determined by a balance between fat deposition and fat removal in the LM. Fat deposition is determined by lipogenesis, fatty acid uptake and transport, and fatty acid esterification, and fat removal is regulated by lipolysis and fatty acid oxidation. Studies on these lipid metabolic gene expression pattern provide understanding of role and relative significance of lipid metabolic genes in IMF deposition. Several peripheral tissues, including LM, adipose as well as liver, are involved in lipid metabolism. Thus, understanding of significance of tissue-network on lipid metabolism is important. Our studies with several peripheral tissues provide involvement of many lipid metabolic genes in the IMF deposition as well as body fat deposition in beef cattle. Application of newly-developed functional genomic tools is very efficient for elucidation of molecular aspect of metabolism. We present detail molecular events associated with IMF deposition through the application of functional genomics tools, including microarray, RNA sequencing analyses and bioinformatics. Expression of gene is also influenced by epigenetic factors such DNA methylation and histone modification. Possible involvement of DNA methylation levels in regulating bovine gene expression will be discussed. New information on molecular mechanisms of bovine IMF deposition could be applicable to design nutritional or genetic methods to increase IMF deposition and to modify fatty acid composition in the LM of beef cattle.

Keywords: beef quality, intramuscular fat, functional genomics