Growth and growth rate influences bovine intramuscular adipose tissue gene expression in a differential manner

Abstract Text: Intramuscular (IM) adipose tissue is the last adipose depot to mature in the growing bovine, and nutrition and management practices that influence growth and growth rate can influence IM adipose tissue deposition. Diet leading to changes in rumen VFA profile can influence substrates utilized for fatty acid synthesis, but diet has a greater effect on subcutaneous (SC) than IM adipose tissue. Subcutaneous adipose tissue has a greater ability to utilize glucose and lactate to produce reducing equivalents and to use lactate and acetate for lipid synthesis than IM adipose tissue regardless of diet. The greater ability of SC adipose tissue to utilize glucose to produce reducing equivalents and acetate and lactate for fatty acid synthesis indicates limited ability to manipulate site of fat deposition through changes in rumen fermentation. Our data suggests that differentiation and lipid synthesis in IM adipose tissue are primarily related to BW whereas differentiation and lipid synthesis in SC and perirenal (PR) adipose tissue are influenced by energy intake and rate of gain. It is perplexing as to why differentiation and lipid synthesis of IM adipose tissue is not affected by rate of gain as in SC and PR adipose tissue. The close proximity of IM adipose tissue to muscle tissue during development suggests that intercellular signaling between these 2 tissues might be crucial for development of IM adipose tissue. Early in the development of IM adipose tissue, changes in gene expression in muscle that effect remodeling of the extracellular matrix along with angiogenesis appear to be critical for development of IM adipose tissue. The strong correlation of angiogenic growth factors in LM with angiogenic growth factors and markers of adipocyte differentiation in immature IM adipose tissue suggest that there is a highly coordinated change that occurs between skeletal muscle and IM during the early stage of adipose development. However, the mechanisms of IM adipose tissue development are still not fully clear and more in vitro and in vivo studies are needed to further elucidate the pathways and mechanisms involved in IM adipose tissue development. Further understanding the interactions between skeletal muscle and adipose tissue during IM development could allow for development of management strategies that optimize carcass quality in bovine.

Keywords: bovine, growth, intramuscular adipose tissue