Differential expression of genes associated with lipid metabolism in longissimus dorsi of Korean bulls and steers.

The objective of this study was to compare expression of genes associated with lipid deposition and removal between bulls and steers in the longissimus dorsi muscle (LM) tissue of Korean cattle. Castration increased the expression of lipid uptake lipoprotein lipase, fatty acid translocase, and fatty acid transport protein 1 in LM. Castration increased lipogenic gene expression of both acetyl-CoA carboxylase and fatty acid synthase. In contrast, castration downregulated lipolytic gene expression of both adipose triglyceride lipase (ATGL) and monoglyceride lipase. Steers showed higher expression levels of insulin signaling phospho-v-akt murine thymoma viral oncogene homolog 1 than bulls but lower protein levels of nuclear Forkhead box O 1 (FoxO1) than bulls, suggesting that increased insulin signaling following castration decreases nuclear FoxO1 levels, leading to downregulation of ATGL gene expression. These findings suggest that castration contributes to increases in lipid uptake and lipogenesis and a decrease in lipolysis, resulting in improved marbling.