新疆褐牛与安格斯肉牛体脂代谢关键基因和产物时空表达的品种差异性及其与肉品质的相关性研究

Beef cattle production is one of the predominant enterprises in Xinjiang. There are about 1.8 million Xinjiang brown cattle and its cross breeds representing the main body and accounting for the 40% of all cattle population kept in the end of 2012. However, in caparison with those fine-foreign beef cattle breeds, Xinjiang brown cattle has significant disadvantages in some lipid-metabolic related beef quality traits, such as intramuscular fat or marblling, etc thus restricting the improvement of beef quality of Xinjiang brown cattle. Our previous study has revealed that the relative expression of leptin (LEP), lipoprotein lipase (LPL) genes was extremly lower in subcutaneous fat than in intramuscular fat, whereas the relative expression of fatty acid synthase(FAS) gene tend to be opposite,which were different from that expressed in Angus and other beef cattle breads reported suggesting there were breeds difference regarding lipid metabolic regulating related genes' expression. Therefore, in the present proposal taking Angus beef cattle as comparison with Xinjiang brown cattle, the temporal and spatial expression of LEP, FAS, hormone sensitive-lipase (HSL) and adipose fatty acid binding protein (FABP4) genes and the products in different adipose tissues (intramuscular, subcutaneous and KPH fat) will be investigated; then the adipocyte morphometry, physiology and biochemistry as well as the composition of fatty acids in different adipose tussues will be measured in relation to those changes of genes expression; the correlation of those genes expression and phenotypic change of adipose tissue morphology, physiology and biochemistry with lipid-metabolic related beef quality traits will be approached thoroughly. The goal of the proposal is to reveal "from moelcule to integration", age-dependent mechanisms in regulating adipose metabolic - related beef quality traits in Xinjiang brown cattle. The research will be beneficial for the development of a novel molecular marker and biological technique for "managing" animal fat and improving beef quality in Xinjiang brown cattle.

新疆褐牛及其杂交牛是新疆肉牛养殖业的主体品种，2013年末存栏180余万头，约占新疆牛存栏总数的40%，但新疆褐牛存在肌内脂肪沉积能力差，大理石纹含量少，与国内外优良肉牛品种有显著差异，制约了新疆褐牛肉用新类型的培育提高。本课题组前期研究表明，瘦素（LEP）、脂蛋白脂酶（LPL）基因在皮下脂肪组织中的表达极显著低于肌间脂肪组织，而脂肪酸合成酶（FAS）基因则呈现相反趋势，与文献报道的安格斯牛等品种间不同，提示其品种差异性。本课题拟将新疆褐牛与安格斯肉牛进行比较，研究LEP、FAS、LPL、激素敏感酯酶（HSL）和脂肪型脂肪酸结合蛋白（FABP4）等基因及其产物的时空表达品种差异性；测定脂肪细胞数量组织学、脂肪酸组成、脂代谢相关生理生化指标；进而与肉品质性状进行相关分析。探明新疆褐牛与脂代谢相关肉品质从"分子到整体"的形成机制，为采用生物技术调控脂肪分配、改善新疆褐牛肉品质奠定基础。

新疆褐牛及其杂交牛是新疆肉牛养殖业的主体品种，约占新疆牛存栏总数的40%。但其牛肉品质与国内外优良肉牛品种间尚有一定差异。新疆褐牛肉品质性状的生长发育变化及其分子调控机理缺乏研究。本课题采用相同饲养条件下3月龄健康新疆褐牛和安格斯公犊各11头为对象，对其脂代谢相关肉品质性状关键调控因子（Regulators of fat metabolism related meat quality traits，RFMRMQT）瘦素（leptin）、关键酶脂肪酸合成酶（FAS）、激素敏感酯酶（HSL）、脂蛋白脂酶（LPL）和脂肪酸结合蛋白（FABP4）基因及其产物在肌肌间脂、皮下脂肪和KPH脂肪的表达的生长发育（3、7、12和24月龄）变化进行了比较研究，并与其产肉及肉皮质性状进行相关分析。研究结果显示：3月龄新疆褐牛公犊体脂沉积能力大于安格斯公犊，而产肉率有低于安格斯公犊的趋势。体脂代谢相关基因及其蛋白表达的品种间差异主要体现在背最长肌、肾周和心周脂肪等组织。背最长肌脂代谢相关基因的表达似有与肾周脂肪相似而与心周脂肪相反的关系。5 RFMRMQT 基因mRNA表达均呈现显著的年龄变化，以7月龄和12月龄变化剧烈。品种间差异也主要体现在7和12月龄。leptin和LPL基因mRNA表达与肌间脂肪和心周脂肪中脂肪细胞面积呈显著中等程度负相关，该特点为新疆褐牛肌肉脂肪调控提供了可能的分子标记。Leptin基因外显子II多态位点E2JW与肌纤维细度显著相关有望作为肌肉嫩度性状选育的分子标记之一。FABP4主要参与调节背膘厚度。而FASN、LPL和leptin基因主要参与调节眼肌面积性状，以及与HSL基因共同参与调节肌肉嫩度。提示其肉品质成因的基因调控有所不同。两品种牛肌肉蛋白组学（TMT）初步研究发现新疆褐牛肌肉有51个蛋白上调，而安格斯肉牛有15个蛋白下调。两品种之间差异蛋白主要表现在生物进程、细胞组成和分子功能等方面，该结果为进一步探查脂代谢相关肉品质性状相关的差异蛋白，以及揭示其对牛骨骼肌脂肪沉积过程中的作用奠定了科学基础。