College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, 712100, China.
College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, China.
Sci Rep. 2018 Feb 14;8(1):3012. doi: 10.1038/s41598-018-20168-9.
Castration increases fat deposition, improving beef quality in cattle. Here, the steer group exhibited a significantly higher intramuscular fat (IMF) content than the bull group. To determine the potential roles of microRNAs (miRNAs) in castration-induced fat deposition, differential expression patterns of miRNA in liver tissue were investigated in bulls and steers. A total of 7,827,294 clean reads were obtained from the bull liver library, and 8,312,483 were obtained from the steer liver library; 452 conserved bovine miRNAs and 20 novel miRNAs were identified. The results showed that the expression profiles of miRNA in liver tissue were changed by castration, and 12 miRNAs that were differentially expressed between bulls and steers were identified. Their target genes were majorly involved in the metabolic, PI3K-Akt, and MAPK signaling pathways. Furthermore, six differentially expressed miRNAs were validated by quantitative real-time PCR, and luciferase reporter assays verified that calcium-sensing receptor (CASR) was the direct target of miR-27a-5p. Meantime, we found that the expression level of CASR was significantly higher in steers than in bulls, and revealed that CASR gene silencing in bovine hepatocytes significantly inhibited triacylglycerol (TAG) accumulation and reduced secretion of very low density lipoprotein (VLDL). These results obtained in the liver indicate that miR-27a-5p may increase fat deposition partly by targeting CASR in steers.
去势会增加脂肪沉积，从而改善牛的牛肉质量。在这里，阉牛组的肌肉内脂肪（IMF）含量明显高于公牛组。为了确定微小 RNA（miRNA）在去势诱导脂肪沉积中的潜在作用，我们研究了公牛和阉牛肝脏组织中 miRNA 的差异表达模式。从公牛肝脏文库中获得了 7827294 条清洁读数，从阉牛肝脏文库中获得了 8312483 条清洁读数；鉴定出 452 个保守的牛 miRNA 和 20 个新的 miRNA。结果表明，miRNA 在肝脏组织中的表达谱因去势而发生变化，鉴定出 12 个在公牛和阉牛之间差异表达的 miRNA。它们的靶基因主要参与代谢、PI3K-Akt 和 MAPK 信号通路。此外，通过定量实时 PCR 验证了 6 个差异表达的 miRNA，荧光素酶报告基因实验验证了钙敏感受体（CASR）是 miR-27a-5p 的直接靶基因。同时，我们发现 CASR 基因在阉牛中的表达水平明显高于公牛，并且表明在牛肝细胞中沉默 CASR 基因可显著抑制三酰甘油（TAG）的积累并减少极低密度脂蛋白（VLDL）的分泌。这些在肝脏中获得的结果表明，miR-27a-5p 可能通过靶向 CASR 来增加阉牛的脂肪沉积。
