The influence of different concentrate to forage diets on hepatic protein expression profiles and milk fat synthesis of lactating goat | 不同精粗比日粮对泌乳山羊肝脏蛋白表达谱及乳脂肪合成的影响

Chinese. 采用双向电泳（two-dimensional electrophoresis,2-DE）结合MAIDI-TOF/TOF质谱方法分析不同精粗比日粮条件下肝脏蛋白/酶表达谱的差异,探讨不同精粗比日粮条件下肝脏糖脂代谢与乳脂肪合成的关系及可能机制。8只健康的泌乳中期山羊随机分为2组,日粮精粗比分别为4∶6（低精料）和6∶4（高精料）,采用2×2拉丁方设计,2次重复。取乳样,测定产奶量和乳中甘油三酯（TG）的含量,并进行活体肝脏穿刺取样,应用双向电泳技术对肝脏样品进行蛋白表达谱分析。试验结果表明：与低精料组相比,高精料组山羊日平均产奶量显著增高（P〈0.05）,而乳中TG含量显著降低（P〈0.05）。经PDQuest 7.1软件分析和MAIDI-TOF/TOF质谱分析发现在两种日粮模式下表达量存在3倍以上差异的蛋白点有34个,其中15个得到鉴定。被鉴定的蛋白主要涉及物质代谢和能量转移。其中,当精料比例提高时,脂肪分解代谢的关键酶脂酰CoA合成酶（ACS）和细胞色素b5的表达上调;糖异生作用的关键酶磷酸烯醇丙酮酸羧激酶（PEPCK）表达下调,参与糖分解代谢的烯醇化酶的表达上调。结论：饲喂高精料日粮,产奶量增加而乳中TG含量降低,其机制可能与肝脏中糖脂分解代谢加强,糖异生作用受阻,竞争消耗了乳腺TG合成前体物有关。

English. The purpose of the study was to analyze the differential expression proteins in the goat liver under different concentrate to forage diets by two-dimensional electrophoresis（2-DE）and MAIDI-TOF/TOF,and to investigate the relationship and possible mechanisms between milk fat synthesis and liver fat metabolism under different concentrate to forage fed.8 healthy mid-lactation goats were randomly divided into two groups,using 2×2 Latin square design with two replications.Diet concentrate to forage ratios were 4∶6（low-concentrate group）and 6∶4（high-concentrate group）.Milk samples were taken to measure milk yield and milk triglyceride（TG）levels,and liver samples were collected by living donor liver biopsy.The total liver proteins of 4∶6 group and 6∶4 group were extracted and separated by 2-DE.The determination of high-concentrate group average daily milk yield was significantly higher than the low-concentrate group（P0.05）,while the milk TG content was significantly lower（P0.05）.34 protein spots of more than 3-fold difference in both dietary modes were revealed by PDQuest 7.1 and MAIDI-TOF/TOF,and of which 15 were identified.These proteins which were identified mainly related to metabolism and energy transfer.When the proportion of fine material increased,acyl-CoA synthetase（ACS）and cytochrome b5 involved in fat catabolism had high expression;and phosphoenolpyruvate carboxykinase（PEPCK）involved in gluconeogenesis had low expression,while enolase involved in glucose catabolism had high expression.The results showed that in the high-concentrate group,milk yield increased but milk TG level decreased.The mechanism may be related with the strengthened glucose and lipid catabolism and blocked gluconeogenesis in the liver,which consumed excessive precursors involved in TG synthesis.