饲粮铜调节肉山羊肌内脂肪沉积的分子机制研究

Intramuscular fat (IMF) content is one of the main factors affecting meat quality and positively correlated with meat tenderness, juiciness and flavour, thus more attention have been paid to the IMF content. The accumulation of intramuscular fat is associated with the genetic background, development, and nutrition of an animal. It has become one of the hot topics in current nutrition researches on how to increase IMF content to improve meat quality of goat through nutritional methods. Our preliminary research concluded that dietary copper supplementation could affect lipid metabolism and increased IMF content of meat goats; however, the key regulatory mechanisms are still unknown. To explore the molecular mechanism of copper regulating IMF content and the role of AMPK pathway during this process, a meat goat feeding experiment and an intramuscular preadipocytes culture experiment will be conducted. The effect of copper on mRNA and protein expression of key transcription factors, enzymes and transport protein involved in lipid metabolism, and the signal transduction pathway involved in this regulating process will be investigated by the method of real-time PCR and western-blot. We expect that the results obtained from this project will help us further understanding the potential role of dietary copper in the regulation of lipid metabolism, subsequently proving scientific base and ideas for increasing IMF deposition in meat goat by nutrient manipulations.

羊肉中肌内脂肪含量直接影响羊肉的品质，其含量与肉品的嫩度，多汁性及风味都呈明显的正相关。肌内脂肪的沉积与动物的遗传背景，发育及营养都有密切的关系。如何通过营养手段提高山羊肉中肌内脂肪的含量，从而改善山羊的肉品质已成为动物营养学家关注的问题之一。本实验室前期研究发现，饲粮铜添加可以增加肉山羊肌内脂肪的沉积，但作用机制尚不明确。本课题组在前期工作的基础上，拟开展肉山羊饲养试验和肉山羊肌内前体脂肪细胞培养试验，采用实时荧光定量PCR、Western blot等方法，研究饲粮铜对脂类代谢关键转录因子、酶及转运蛋白基因及蛋白表达的影响及参与其中的信号转导机制，探明AMPK信号通路对肉山羊肌内脂肪沉积的调控机制，阐明铜调节肉山羊肌内脂肪沉积的分子机制，在基础理论方面会有原始性创新，而且可为我国肉山羊生产中通过营养手段增加肌内脂肪沉积，改善羊肉品质提供新的途径和思路。

关于不同水平铜对肉山羊脂类代谢及其分子机制方面的研究，在国内外尚未见报道。本项目通过在肉山羊饲粮中添加不同水平硫酸铜研究了饲粮不同水平铜添加对肉山羊生长性能、肉品质、脂类代谢及与脂类代谢相关基因的基因表达的影响，获得了以下创新性研究结果：（1）肉山羊饲粮低剂量铜添加可增加肉山羊平均日干物质采食量；（2）肉山羊饲粮低剂量铜添加对羊肉肉色有一定影响，降低了肉色亮度L值；（3）肉山羊饲粮低剂量铜添加对降低了乐至黑山羊血清低密度脂蛋白的含量；（4）肉山羊饲粮低剂量铜添加线性增加了乐至黑山羊肌内脂肪含量，随着饲粮铜含量的提高，肝脏铜含量线性上升；（5）肉山羊饲粮低剂量铜添加，增加了乐至黑山羊肌内脂肪中山嵛酸C22:0、顺-8，11，14-二十碳三烯酸cis C20:3n6及花生四烯酸C20:4n6的含量；（6）肉山羊饲粮不同水平铜添加显著降低了背最长肌中FABP 4的基因表达，并有降低LPL和CPT1A基因表达的趋势；（7）肉山羊饲粮不同水平铜添加显著降低了PPARα、CRAT、CPT1A及CPT1B的基因表达。以上研究结果表明，肉山羊饲粮中添加铜可能通过降低PPARα基因的表达，从而降低脂类分解代谢中的关键酶CRAT、CPT1A以及CPT1B的基因表达来降低肉山羊机体脂肪的氧化，增加了其肌内脂肪的沉积。以上研究成果初步揭示了铜对肉山羊脂类代谢的影响及其作用机制，对丰富和发展肉山羊铜营养的现有理论和知识，在肉羊生产中科学应用铜添加剂，改善肉羊肉品质，都具有十分重要的理论和现实指导意义。