Studies on adipogenic and antiadipogenic factors in serum of beef cattle

本研究利用培养的小鼠3 T3-L1前脂肪细胞对肉牛血清的成脂活性进行了评价。脂肪生成活性在农场之间存在显著差异，并且受到性别差异的影响（即，来自育肥小母牛的血清比来自阉牛的血清更有效地诱导3 T3-L1细胞的脂肪分化）。血清成脂活性与牛肉大理石花纹性能呈正相关，表明血清因子在肌内脂肪沉积的形成中起一定作用。成脂活性与血清视黄醇浓度呈负相关。血清胆固醇、三酰甘油和非酯化脂肪酸均与成脂活性无关。此外，血清视黄醇浓度与牛肉大理石花纹性能呈负相关。这些数据表明，育肥期血液中的视黄醇水平可能通过其对肌肉组织中存在的前脂肪细胞的抗脂肪形成作用而影响肉牛肌内脂肪沉积。血清保存至测定期间的温度影响脂肪形成活性。血清的解冻和再冷冻增加了脂肪形成活性，这表明血清中的一些抗脂肪形成因子在这种处理过程中可能会失活或降解。血清超滤分级显示> 100 kDa的组分明显抑制脂肪细胞分化。此外，该组分的成脂活性似乎大大有助于全血清的成脂活性。

In this study, adipogenic activity in sera of beef cattle was evaluated using cultured mouse 3T3-L1 preadipocytes. Adipogenic activity was significantly different among the farms, and was affected by sex difference (i.e., sera from fattened heifers induced adipose differentiation of 3T3-L1 cells more effectively than those from steers). There was a positive correlation between adipogenic activity in serum and beef marbling performance, suggesting that serum factor (s) play a role in development of intramuscular fat deposition. Adipogenic activity was negatively correlated with serum retinol concentration. Neither serum cholesterol, triacylglycerol nor non-esterified fatty acid was related to adipogenic activity. Furthermore, serum retinol concentration was negatively correlated with beef marbling performance. These data imply that retinol level in blood during fattening period may influence intramuscular fat deposition of beef cattle through its antiadipogenic action on preadipocytes present in muscle tissues. Temperature during preservation of serum until assay affected adipogenic activity. Thawing and re-freezing of serum increased adipogenic activity, suggesting that some antiadipogenic factor (s) in serum may be subject to inactivation or degradation during such handling. Fractionation of serum by ultrafiltration revealed that the fraction of>100kDa markedly inhibited adipocyte differentiation. In addition, adipogenic activity of this fraction seemed to greatly contribute to adipogenic activity of whole serum.