Metabolic programming and intramuscular adipogenesis

Abstract Text:

The study was conducted to clarify how early nutrition as metabolic programming events affected intramuscular adipogenesis of Japanese Black cattle fattened with only roughage. As a control group, the roughage group (R: n=11) was fattened only roughage ad libitum from 4 to 31 months of age (mo) after nursing at standard level (replacer milk intake of 0.6 kg/day) until 3 mo. As a treatment group, the high-energy group of metabolic programming events (MP: n=12) was also fattened only roughage ad libitumfrom 11 to 31 mo after intensively nursing and feeding a high-energy diet until 10 mo. The intramuscular fat content in longissimus muscle was significantly larger in MP (13.2%) than in R (9.4 %) at slaughter (Soxhlet analysis). Expression of the adipogenic genes, C/EBPb, PPARγ, C/EBPa, FASN, SCD, LEP, FABP4, ADIPOQ, IGFBP4, PPARγ2 and PRMT5 were investigated at each stage by quantitative real-time PCR analysis by using longissimus muscle biopsy samples. At 3 mo, the expression levels of PPARγ, C/EBPa, PPARγ2, ADIPOQ, IGFBP4, and PRMT5 were significantly higher in the MP than in the R. At 10 mo, the expression levels of PPARγ, C/EBPa, FASN, SCD and LEP were significantly higher in the MP. At 14 mo, only PPARγ and LEP in the MP showed significantly higher expression. PPARγ, PPARγ2 and C/EBPa, and other adipogenesis markers such as LEP, ADIPOQ, FABP4, IGFBP4 and PRMT5 were expressed at higher levels in the MP compared with the R at 30 mo. This effect may involve several factors including metabolic additivity and response to nutritional stimulus and the unstable nature of expression of these genes. Conversely, at 20 and 30 mo, FASN and SCD were expressed at significantly lower levels in the MP. Nevertheless, according to investigation of fatty acid composition of intramuscular adipose tissue, early metabolic programming events positively affected the relatively higher amounts of C18:1, MUFA, and the US/S ratio in MP at slaughter compared with R. It may be concluded that metabolic programming through high nutrition at neonatal ages can positively change adipogenic gene expression at the molecular level. These effects stimulate the early development of adipocytes at an early age and these changes were maintained over the study period. These suggest that early nutrition affects final meat quality, and early metabolic programming has potential to advance the field of meat sciences and support the meat industry.

Keywords:

cattle, metabolic programming, intramuscular adipogenesis, grass-fed beef cattle