Up-regulation of bone morphogenetic protein and its signaling molecules following castration of bulls and their association with intramuscular fat content in Korean cattle

Abstract

AbstractWe evaluated whether castration affects bone morphogenetic protein 2 (BMP2) level and the expression of its signaling molecules in Korean cattle bulls. We also checked whether castration affects the expression of muscle fiber type and oxidative and glycolytic enzyme genes. Enzyme-linked immunosorbent assays revealed that steers had higher plasma BMP2 and leptin concentrations than bulls. Quantitative real-time PCR showed that steers had higher mRNA levels of thelysyl oxidasegene, a downstream target of the BMP signaling pathway, in thelongissimus thoracis(LT) muscle. Steers had higher adipogenicperoxisome proliferator-activated receptor gammaand lipogenicfatty acid binding protein 4mRNA levels in the LT than bulls. Steers had lower mRNA levels for several muscle fiber type 1 genes and fiber type 2A myosin heavy chain 2 gene than bulls. Steers had higher mRNA levels of the glycolytic enzymephosphoglycerate kinase 1gene than bulls. Transcript levels of oxidative enzyme genes did not differ between bulls and steers. Regression analysis revealed a positive association between plasma BMP2 levels and intramuscular fat (IMF) content in the steer group. These findings suggest that upregulation of the BMP signaling pathway in response to castration induces increased adipogenic gene expression, contributing to the increased IMF deposition observed in castrated animals.