沙葱提取物对肉羊机体脂肪分布及其脂肪酸组成影响的表观遗传学机理研究

In our previous research supported by NSFC, it was found that the Allium Mongolicum Regel and its water-soluble extractives could change the fatty acid composition and distribution of carcass fat in sheep and improve the flavor and quality of mutton by restraining the activity of fatty acid synthase and increasing the activity of hormone sensitive lipase. The results in the recent research suggested that the fatty acid composition and distribution of fat in the animal body could be modified and optimized by balance diet and moderate exercise which change the epigenetic modifications of related gene. According those results, therefore, this study intends to analyze the component of fat and methylation level of LPL and PPARγ gene in the carcass of sheep fed a diet without the water-soluble extractives from Allium Mongolicum Regel, then investigate the effect of the water-soluble extractives to the fatty acid composition and distribution of carcass fat, gene methylation level of LPL and PPARγ, and related gene expressions in the sheep, and find the relationship among the water-soluble extractives, the fatty acid composition and distribution of carcass fat, and gene methylation level of LPL and PPARγ, in order to reveal the epigenetic mechanisms of the water-soluble extractives regulate the modification of composition and redistribution of fat in the sheep body, and supply references for advanced exploiture and scientific application of the Allium Mongolicum Regel and its water-soluble extractives in sheep husbandry.

课题组在前期的研究中发现，沙葱及其提取物通过降低肉羊机体内脂肪酸合成酶的活性和提高激素敏感脂酶的活性影响舍饲肉羊胴体脂肪的沉积部位和脂肪中脂肪酸的组成，并显著改善羊肉风味和品质。最新的研究发现，机体中脂肪的组成与分布是可以通过适当的运动以及合理的膳食来改变基因的表观遗传特征而得到优化与改变。所以，本项目将通过对正常肉羊脂肪组织中的组成成分以及LPL、PPAR-γ基因甲基化谱相对表达水平的分析明确羊肉脂肪组成成分，继而在饲料中添加沙葱水溶性提取物，探讨沙葱水溶性提取物对肉羊机体脂肪分布和脂肪中脂肪酸组成的影响、探究沙葱水溶性提取物对肉羊脂肪组织LPL、PPARγ基因的甲基化水平的影响以及对相关基因表达的作用，建立脂肪组织与LPL、PPARγ基因甲基化及表达水平的关联，从表观遗传学角度揭示沙葱提取物对羊机体脂肪分布及组成成分的调控机制，为沙葱及其提取物在养羊业中的进一步开发与应用提供科学依据。

沙葱及其提取物可以提高肉羊生产性能，改善羊肉风味，为了阐明其作用机制，本项目通过在日粮中添加沙葱及其提取物，分析肉羊脂肪代谢相关基因的甲基化水平变化和mRNA表达差异，从表观遗传学角度解释沙葱及其提取物对羊肉脂肪的沉积与分布的调控机制。获得了如下研究成果：（1）日粮中添加沙葱及其提取物提高了肉羊屠宰率，增加了眼肌面积，升高了血中GH的含量，表明其可以提高产肉量，改善肉羊生产性能；（2）沙葱及其提取物可以增加肉羊肌内脂肪的含量，影响脂肪酸的组成，降低与羊肉膻味相关的支链脂肪酸4-甲基辛酸的含量，使瘦素（LEP）的含量增多，从而影响羊肉中脂肪的沉积分布，改善肉的品质和风味；（3）沙葱水提物可作用于部分脂肪合成和代谢相关基因，提升LPL基因甲基化水平，下调LPL、DGAT1、ACC和FAS基因的转录，上调PPARγ、ACACA、SCD、SREBF1 和HSL基因的表达，进而调控脂肪代谢；（4）通过全基因组DNA甲基化测序和转录组RNA-seq测序，筛选出了一些羊肌肉和脂肪组织响应沙葱提取物的关键靶基因和lncRNA，且明确了它们参与的不同信号通路；（5）发现了沙葱水提取物的摄入可以降低羊肌肉和脂肪组织间的mRNA和lncRNA的差异表达，引起两种组织之间出现更多的甲基化差异；（6）沙葱及其提取物可影响羊瘤胃发酵相关指标，改变微生物群系结构，可能进而影响脂肪的代谢。以上研究的重要发现，对沙葱及其提取物在养殖业中科学使用提供了理论依据，为羊肉生产产业的发展提供了科学指导。