乳脂肪球膜的研究进展

脂肪以液滴或球状形态稳定分散于乳中。这些脂肪球被一层薄膜包裹,称为乳脂肪球膜(MFGM)。MFGM是由磷脂、鞘脂及多种蛋白质组成的复杂三层结构。奶牛的生理状况、泌乳期、挤奶操作、加工处理等,都会对MFGM产生影响。此外,MFGM中的蛋白质和脂质组分也被证明具有特殊营养价值。本文总结了近年来关于MFGM的研究,旨在描述MFGM的组成及结构、影响因素及其营养价值,并对未来的研究方向提出建议。     

乳脂肪球膜的研究进展

乳脂肪球膜(milk fat globule membrane,MFGM)是包裹乳脂肪球的薄膜,由于其含有蛋白质和极性脂质的特殊组成被广泛用作食品或非食品领域中的乳化剂、稳定剂及营养物质载体等。此外,MFGM被证明具有丰富的营养价值。本文综述MFGM的结构、组成成分、分离制备及营养功能的研究进展,介绍MFGM制备脂质体包埋生物活性物质的新技术,为开发利用MFGM提供一定的参考依据。     

马乳脂肪球膜蛋白组鉴定及潜在功能分析

试验旨在研究马乳脂肪球膜（milk fat globule membrane，MFGM）蛋白组成及潜在的生物学功能。选取12匹5岁左右、平均体重为450~500 kg的健康纯血母马作为试验动物，主要饲喂干牧草，所有马匹饲养和管理条件均相同。将12份样品以每组4份进行混合，分离提取产后第60天马乳中MFGM蛋白，进行高分辨质谱仪鉴定和生物信息学分析。结果显示，马MFGM组分中共鉴定出310种表达蛋白，这些蛋白主要参与的生物过程为生物调节、刺激应答、定位、多细胞生物过程、运输、信号、细胞通讯、发育过程、细胞分化和免疫系统过程等；细胞成分主要为胞外区域、膜、囊泡、核仁和线粒体等；分子功能主要为催化活性、蛋白质结合、碳水化合物衍生物结合和小分子结合等。KEGG通路分析表明，MFGM蛋白主要参与血小板活化通路、内吞、脂肪酸生物合成和Ras信号通路等。马乳MFGM蛋白的蛋白质互作网络分析图中共包含215种蛋白质。本研究结果揭示了马乳MFGM蛋白质组的复杂性，为解析其营养和生物学功能提供了科学数据。     

牛奶和山羊奶中乳脂球膜蛋白的比较研究

试验旨在分析牛奶与山羊奶中乳脂肪球膜（milk fat globule membrane,MFGM）蛋白组成及潜在的生物学功能。采集牛奶和山羊奶各30份,离心分离牛奶和山羊奶中脂肪,提取MFGM蛋白,液相色谱串联质谱分析结合数据库搜索鉴定,比较了奶牛和山羊MFGM蛋白的差异,分析了MFGM蛋白参与的生物过程、分子功能及相关代谢通路。结果显示,奶牛和山羊MFGM中分别鉴定了284和334个蛋白,奶牛和山羊中蛋白参与的生物学过程的模式非常相似,主要涉及生物调控、定位、转运、信号转导和应激反应等。分子功能方面二者存在一定的差异,奶牛MFGM蛋白主要涉及蛋白结合和核苷酸结合,而山羊MFGM蛋白主要涉及蛋白结合和结构分子活性。奶牛和山羊中差异表达的MFGM蛋白主要涉及结构分子活性。通路分析发现,奶牛和山羊MFGM蛋白涉及的生物学通路稍有差异,其中紧密接头、轴突导向、抗原加工与递呈、补体和凝血级联反应通路在奶牛MFGM蛋白中得到富集,而调节肌动蛋白细胞骨架通路在山羊奶中得到富集。研究结果展示了奶牛和山羊MFGM蛋白的表达模式及差异,为进一步探索两种奶畜乳腺合成脂肪球的分子机制的异同提供科学依据。     

乳脂球膜结构、化学组成与潜在生物活性功能研究进展

乳脂球膜(MFGM)是乳脂球的保护膜,是泌乳过程和泌乳后储藏过程中维持乳的乳化稳定状态的主要功能成分。MFGM类似细胞膜结构,主要由脂类和蛋白质构成。MFGM具有潜在的生物活性功能,包括抗炎、调节免疫、抗癌、抗菌和抗病毒等。本文综述了MFGM的形成与结构、化学组成和潜在生物活性功能的研究进展,并讨论了未来研究趋势,旨在为进一步研究与应用MFGM营养生理作用提供参考。     

乳脂肪球膜中的脂类及其在婴儿配方乳粉中的应用

母乳被认为是新生婴儿早期所需营养的黄金标准。改善婴儿配方乳粉的最好办法除了模拟母乳的成分外,越来越多的关注点集中在乳脂肪球的结构上,并且对乳脂肪球膜(milkfatglobulemembrane,MFGM)的研究越来越深入。本文综述MFGM的结构与组成以及近年来在婴儿配方乳粉中补充MFGM对婴儿生长发育的影响,并得到近期临床研究的支持。基于啮齿动物的研究表明,在婴儿配方乳粉中添加MFGM对肠道消化、生理健康和炎症保护有好处,同时,大量人体实验表明,补充MFGM对婴儿的神经认知发育具有积极作用。但是,婴儿配方乳粉中MFGM的添加量及安全性问题仍是不确定的。     

乳脂球膜蛋白的研究进展

乳脂球膜蛋白是乳腺在泌乳时包被在脂肪滴外的膜蛋白。乳脂肪球膜（milk fat globule membrane,MFGM）是磷脂、鞘脂和多种蛋白质组成的3层膜结构。乳脂球膜蛋白包含100余种蛋白质,含量最丰富的8种蛋白质为黏液素1、黄嘌呤氧化还原酶、黏液素15、CD36、嗜乳脂蛋白、乳凝集素、脂肪分化相关蛋白和脂肪酸结合蛋白。乳脂球膜蛋白已被证明具有丰富的开发利用价值,包括：反映奶牛母体的生理状态;作为幼体的营养和免疫来源,会影响犊牛的发育和母源抗体;会影响人和动物的免疫调节和体质,未来可能应用于疾病的治疗。作者介绍了乳脂球膜蛋白的来源、组成及一种新建立的乳脂球膜蛋白结构,阐述了几个主要蛋白的生理特性及乳脂球膜蛋白的研究进展,并对未来的研究方向提出建议。     

最新脂肪球膜上蛋白质排列模型被提出

比利时科学家近日从牛乳中分离乳脂肪球膜，用特异性胰蛋白酶和非特异性链霉蛋白酶水解，以研究脂肪球膜上蛋白质的不对称排列结构。学者利用二维电泳和基质辅助激光解析电离飞行时间质谱法，鉴定脂肪球膜经胰蛋白酶酶解后的产物。     

牛初乳与牛常乳中乳脂肪球膜蛋白质的组成及功能的对比研究

利用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate polyacrylamide gel electropheresis,SDS-PAGE)将牛初乳与牛常乳中乳脂肪球膜蛋白质的组成部分进行分离鉴定,发现牛初乳与牛常乳中乳脂肪球膜蛋白质的组成存在较大的差异,且在牛初乳中鉴定出628种乳脂肪球膜蛋白质,牛常乳中鉴定出487种乳脂肪球膜蛋白质.由基因本体(gene ontology,GO)功能注释分析发现,在生物过程中生物调控作用是牛初乳和牛常乳中乳脂肪球膜的主要生物过程.在分子功能上,牛初乳的乳脂肪球膜蛋白质的绑定作用大于牛常乳.在细胞组成上,牛初乳乳脂肪球膜蛋白质参与细胞外区域远远大于牛常乳.通过京都基因与基因组百科全书系统(Kyoto Encyclopedia of Genes and Genomes,KEGG)代谢通路分析可知,牛初乳和牛常乳乳脂肪球膜蛋白质参与的代谢途径不同,表明牛初乳在日后的生产加工中更具有利用价值.     

乳中黄嘌呤氧化还原酶的研究进展

黄嘌呤氧化还原酶属于含钼脱氢酶黄素蛋白家族，是组成乳脂肪球膜的主要蛋白，通过硫酸胺分级沉淀和DEAE-Sepharose柱可从乳脂肪球膜中纯化。XOR作为乳脂肪球膜的膜结合蛋白，在脂肪滴的包裹和分泌中起到重要的结构作用，并且在肠道能够起到一定的抗菌作用。     

过滤器辅助样品前处理法测定乳脂肪球膜蛋白质的研究

牛乳是世界上消费最广泛的乳类,并为消费者提供必需的营养物质。牛乳包括蛋白质,脂肪,糖类,维生素和矿物质。蛋白质是牛乳的重要组成部分,包括酪蛋白、乳清蛋白及乳脂肪球膜蛋白质。牛乳乳脂肪球被乳脂肪球膜覆盖,乳脂肪球膜是一个含有3层膜的膜结构,其上附着或者包含蛋白质。近些年来,对于乳中蛋白质的鉴定成为新的研究热点。随着蛋白质组学技术的发展,鉴定出的蛋白质的种类和数量都在增加。但是由于乳脂肪球膜的特殊性质,在牛乳乳脂肪球膜蛋白质的鉴定中,缺乏方便快捷及效果好的方法。作者运用过滤器辅助样品前处理法（FASP）结合纳升液相质谱（NanoLC-MS/MS）测定牛乳乳脂肪球膜蛋白质的种类和数量,共鉴别出169种蛋白质,是目前鉴别数量最大的一种方法。此方法的建立为今后乳脂肪球膜蛋白质研究领域提供一种方便快捷准确的试验工具。     

Association of bovine secretory immunoglobulins with milk fat globule membranes

Milk IgA was seen to be largely associated with milk fat globules ( of the sIgA in whole milk). Isolated fat globules became agglutinated by anti-IgA and to a lesser degree by anti-IgM but not by anti-IgG₁ or anti-IgG₂ (microscopic plate agglutination). Absorption studies using anti-bovine sIgA showed that the cream contained some 16 times more IgA than the repective whey. Isolated milk fat globule membranes released IgA and SC when treated by Triton X 100 as demonstrated by double gel diffusion. IgA was the only membrane-associated component showing cross-reactivity with serum proteins in immunoelectrophoresis. An antiserum prepared against fat globule membranes showed strong anti-IgA activity. IgA from whey became absorbed into washed cream. The specificity of MFGM associated immunity was demonstrated by analysing the capacity of cream, isolated from mastitic cows, to bind homologous labelled bacteria (cream-rising test).     

乳脂肪球膜主要膜蛋白功能的研究进展

嗜乳脂蛋白（butyrophilin，Btn）、黄嘌呤氧化还原酶（XOR）和乳脂肪球表面生长因子8 （MFG-E8）是乳脂肪球膜的３种主要膜蛋白。最近的研究发现，Btn和XOR在乳脂肪的分泌阶段是必不可少的。而MFG E8在乳腺泌乳晚期及衰退期，对清除凋亡的乳腺上皮细胞起着重要作用。     

Comparison of Milk Fat Globule Membrane Proteins in Milk Samples of Dairy Cow and Goat

In order to compare the difference of milk fat globule membrane（MFGM）proteins between dairy cow and goat milk,30 milk samples were collected in a dairy farm and a goat farm from Anhui area,respectively.Extracted proteins from the MFGM-enriched fractions were identified and quantified by LC/MS approach.The results showed that 284 and 334 proteins of MFGM from dairy cow and goat were identified,the biological processes of MFGM proteins were similar between dairy cow and goat which were mainly related to biological regulation,localization,transport,signal transduction and response to stimulus.Meanwhile,there were some differences in molecular functions,and protein binding and nucleotide binding were the most prevalent molecular functions in dairy cow MFGM proteins,while protein binding and structural molecule activity were the most prevalent molecular functions in goat MFGM proteins.And structural molecule activity was the main molecular functions among the difference proteins.Pathway analysis revealed that tight junction,axon guidance,antigen processing and presentation,complement and coagulation cascades were enrichment in dairy cow MFGM proteins,and regulation of actin cytoskeleton was enrichment in goat MFGM proteins.Those results revealed the protein expression pattern difference between MFGM protein of dairy cow and goat milk,and provide reference data for further exploring the molecular mechanism of synthetic milk fat globule.     

Shifts in the Holstein dairy cow milk fat globule membrane proteome that occur during the first week of lactation are affected by parity

Background: The milk fat globule membrane(MFGM) proteomes of colostrum and transition milk are rich sources of proteins that are likely important for neonatal calf health. In addition, characterization of these proteomes could also yield valuable information regarding mammary gland physiology of the early postpartum lactating cow. The objectives of this research were to characterize the MFGM proteomes of colostrum and transition milk through sample collections at four timepoints postpartum, including the first milking(M1, colostrum), second milking(M2, transition milk), fourth milking(M4, transition milk), and fourteenth milking(M14, mature milk), and compare these proteomes between multiparous(MP; n = 10) and primiparous(PP; n = 10) Holstein dairy cows. Isolated MFGM proteins were labeled using Tandem Mass tagging and analyzed using liquid chromatography-tandem mass spectrometry(LC-MS/MS). Protein identification was completed using MASCOT and Sequest in Proteome Discoverer 2.2. The scaled abundance values were analyzed using PROC MIXED in SAS to determine the effects of milking(MIL), parity(PAR), and MIL × PAR. The adaptive false-discovery rate(FDR)-adjusted P values were determined using PROC MULTTEST. Protein characterization and bioinformatic analysis were completed using a combination of PANTHER, Blast, and Uniprot.Results: A total of 104 common proteins were identified in each of the MFGM samples. Statistical analysis revealed that70.2% of identified proteins were affected by MIL. Of these, 78.1% were lower in M14 compared with M1, including immune-related proteins lactotransferrin, lactadherin and hemopexin. Parity affected 44.2% of proteins. Of the proteins affected by PAR, 84.8% were higher in MP cows compared with PP cows, including apolipoprotein E and histones 2 A, 2 B, 3,and 4 b. Butyrophilin subfamily 1 member 1 A and annexin 5 were higher in samples from PP cows. Milking × parity affected32.7% of identified proteins, including lactotransferrin, gelsolin, vitamin D binding protein, and S100 proteins.Conclusions: This research supports previous findings that the Holstein MFGM proteome changes rapidly during the first week of lactation. In addition, this research identifies the impact of parity on the colostrum and transition milk MFGM proteomes, which may be important for milk-fed calf health or for the identification of protein biomarkers for mammary functionality.     

乳极性脂质组成及其功能性研究进展

乳中含有2％～5％的脂质,乳中的脂质由乳腺上皮细胞分泌并以乳脂肪球的形式分散在乳中.大部分乳脂(约98％)以甘油酯的形式存在于乳脂肪球内部,其余(约2％)包括甘油磷脂、鞘脂、糖脂等在内的少部分极性脂质则主要分布在乳脂肪球膜表面.乳极性脂质虽然在乳脂中占比较少,但却对哺乳动物的生长发育有着不可或缺的作用.本文首先介绍乳中...     

Fat globule membrane of sow milk as a target for adhesion of K88-positive Escherichia coli

Membrane adhesion of K88-positive Escherichia coli was studied on intestinal brush-border membranes on 237 Finnish Landrace pigs. Forty-one per cent of the brush-border membrane preparations aggregated E. coli (positive adhesion). Similar dualism of adherence/nonadherence was observed on sow milk fat globule membranes. Washed milk fat globules (washed cream) can be used as a convenient source of material for adhesion studies. Bacterial adherence on to milk fat globules is evident as agglutination of the globules (dark-field microscopy). By this procedure the sows can be typed according to their receptor phenotype. This simple principle of fat globule agglutination due to receptors for K88-positive E. coli might be complicated by SigA-mediated bacterial adherence. Fat globule membranes were shown to contain SigA, which may act as a mediator of bacterial adherence onto fat globules. The significance of this adhesive property of milk fat globule might be to provide alternative receptors for E. coli thus preventing bacterial adhesion on to gastro-intestinal epithelium of the offspring. Sow milk fat globules can be used for typing E. coli for membrane adhesiveness. The adhesiveness of the strains showed a good correlation with the presence of the K88 antigen, as well as the hydrophobicity of the bacterial strain as determined by an association on Phenyl-Sepharose beads.