人乳寡糖的分离分析

糖是一类重要的生命活性物质,它不仅是细胞能量代谢的源泉,还常作为信号分子参与细胞的各种活动。人乳寡糖（human milk oligosaccharides,HMOs）在人乳干物质中的含量仅次于乳糖和脂肪,高于蛋白质,对婴儿的发育和健康具有重要作用。为了更好的理解人乳寡糖的生物功能和结构的关系,对其组成和结构开展分析研究是必不可少的。对人乳寡糖进行了简要的介绍,并就其预处理方法、分离分析和结构表征方法进行了综述,以期为人乳寡糖的深入研究提供参考。     

Structural Basis for Norovirus Inhibition by Human Milk Oligosaccharides

Histo-blood group antigens (HBGAs) are important binding factors for norovirus infections. We show that two human milk oligosaccharides, 2′-fucosyllactose (2′FL) and 3-fucosyllactose (3FL), could block norovirus from binding to surrogate HBGA samples. We found that 2′FL and 3FL bound at the equivalent HBGA pockets on the norovirus capsid using X-ray crystallography. Our data revealed that 2′FL and 3FL structurally mimic HBGAs. These results suggest that 2′FL and 3FL might act as naturally occurring decoys in humans.     

人乳低寡糖的结构及其特殊功能

人乳低寡糖（HMO）由D-葡萄、D-半乳糖、N-乙酰葡萄糖胺、L-岩藻糖和N-乙酰神经氨酸等5种基本结构构成。基本结构又以不同比例和特殊连接方式形成9种核心结构,再经过多种变化构成人乳中100多种低寡糖。HMO有维护肠道生态平衡、抗御肠道感染、增强人体免疫力,预防癌症发生,防止慢发性结肠炎和促进新生儿大脑发育等功能。     

High Urinary Iodine Concentration Among Breastfed Infants and the Factors Associated with Iodine Content in Breast Milk

Cadmium (Cd) is a highly toxic element, which may cause toxicity to most organs in the body. Zinc (Zn) and magnesium (Mg) are essential minerals with probable benefits on Cd harmful effects. Finding an efficient and non-pathological treatment against Cd toxicity seems promising. Fifty adult rats were divided into ten experimental groups of five rats each. The Cd group was treated with 1 mg Cd/kg and the control group received 0.5 cm³ normal saline. The other eight groups received Zn (0.5 and 1.5 mg/kg) and Mg (0.5 and 1.5 mg/kg) either alone or in combination with 1 mg Cd/kg through IP injection for 3 weeks. Testis malondialdehyde (MDA), sperm parameters, and testis histopathology were investigated. Cd reduced sperm parameters and increased testis MDA. Moreover, Cd exposure caused a significant histological damage in testis of male rats. However, Zn or Mg treatment prevented and reversed Cd toxic alterations in testis. These findings suggest that co-administration of Zn or Mg could improve cadmium testicular toxicity in male Wistar rats.     

人乳寡糖的结构及其分离分析

母乳中存在的人乳寡糖（HMOs）是一类结构高度复杂的低聚糖，对婴儿的肠道菌群、免疫屏障、大脑发育发挥积极作用。由于母乳中基质复杂，寡糖的种类繁多，丰度跨度大，存在众多异构体，这都使得检测面临诸多挑战。现已有多种技术用于HMOs的分析，发现了200多种HMOs，液相色谱和毛细管电泳在分离HMOs方面效果显著，核磁共振、质谱、红外多光子解离光谱推动了对HMOs结构的全面解析。本文回顾了对HMOs实现高灵敏度和高特异性分析的多种技术方法，比较了不同技术的优缺点，还重点介绍了质谱以及不同技术联用在推动HMOs解析和测定方面的突破，为探究寡糖的结构-功能关系、深入理解HMOs的生物学功能提供了全面的技术支持。     

Variation in Consumption of Human Milk Oligosaccharides by Infant Gut-Associated Strains of Bifidobacterium breve

Human milk contains a high concentration of complex oligosaccharides that influence the composition of the intestinal microbiota in breast-fed infants. Previous studies have indicated that select species such as Bifidobacterium longum subsp. infantis and Bifidobacterium bifidum can utilize human milk oligosaccharides (HMO) in vitro as the sole carbon source, while the relatively few B. longum subsp. longum and Bifidobacterium breve isolates tested appear less adapted to these substrates. Considering the high frequency at which B. breve is isolated from breast-fed infant feces, we postulated that some B. breve strains can more vigorously consume HMO and thus are enriched in the breast-fed infant gastrointestinal tract. To examine this, a number of B. breve isolates from breast-fed infant feces were characterized for the presence of different glycosyl hydrolases that participate in HMO utilization, as well as by their ability to grow on HMO or specific HMO species such as lacto-N-tetraose (LNT) and fucosyllactose. All B. breve strains showed high levels of growth on LNT and lacto-N-neotetraose (LNnT), and, in general, growth on total HMO was moderate for most of the strains, with several strain differences. Growth and consumption of fucosylated HMO were strain dependent, mostly in isolates possessing a glycosyl hydrolase family 29 α-fucosidase. Glycoprofiling of the spent supernatant after HMO fermentation by select strains revealed that all B. breve strains can utilize sialylated HMO to a certain extent, especially sialyl-lacto-N-tetraose. Interestingly, this specific oligosaccharide was depleted before neutral LNT by strain SC95. In aggregate, this work indicates that the HMO consumption phenotype in B. breve is variable; however, some strains display specific adaptations to these substrates, enabling more vigorous consumption of fucosylated and sialylated HMO. These results provide a rationale for the predominance of this species in breast-fed infant feces and contribute to a more accurate picture of the ecology of the developing infant intestinal microbiota.     

The Presence of Trehalose-containing Oligosaccharides in Yeast Extract

It was suggested that several trehalose-containing oligosaccharides are present in yeast extract. Among these oligosaccarides a trisaccharides was isolated and identified as β-D-Glcp-(1→6)-α-D-Glcp-(l?1)-α-D-Glcp.     

Automated Speciation of Mercury in the Hair of Breastfed Infants Exposed to Ethylmercury from Thimerosal-Containing Vaccines

A simplified thiourea-based chromatography method, originally developed for methyl and inorganic mercury, was adapted to separate methylmercury (MeHg), ethylmercury (EtHg), and inorganic mercury (Hg^II) in infants' hair. Samples were weighed and leached with an acidic thiourea solution. Leachates were concentrated on a polymeric resin prior to analysis by Hg-thiourea liquid chromatography/cold vapor atomic fluorescence spectrometry. All but one sample showed small amounts of EtHg, and four of the six analyzed samples had proportionally higher Hg^II as a percent of total Hg. Breastfed infants from riverine Amazonian communities are exposed to mercury in breast milk (from high levels of maternal sources that include both fish consumption and dental amalgam) and to EtHg in vaccines (from thimerosal). The method proved sensitive enough to detect and quantify acute EtHg exposure after shots of thimerosal-containing vaccines. Based on work with MeHg and Hg^II, estimated detection limits for this method are 0.050, 0.10, and 0.10 ng g⁻¹ for MeHg, Hg^II, and EtHg, respectively, for a 20-mg sample. Specific limits depend on the amount of sample extracted and the amount of extract injected.     

Significance of Milk pH in Newborn Infants

Bottle-fed infants do not gain weight as rapidly as breast-fed babies during the first week of life. This weight lag can be corrected by the addition of a small amount of alkali (sodium bicarbonate or trometamol) to the feeds. The alkali corrects the acidity of cow''s milk which now assumes some of the properties of human breast milk. It has a bacteriostatic effect on specific Escherichia coli in vitro, and in infants it produces a stool with a preponderance of lactobacilli over E. coli organisms. When alkali is removed from the milk there is a decrease in the weight of an infant and the stools contain excessive numbers of E. coli bacteria.A pH-corrected milk appears to be more physiological than unaltered cow''s milk and may provide some protection against gastroenteritis in early life. Its bacteriostatic effect on specific E. coli may be of practical significance in feed preparations where terminal sterilization and refrigeration are not available. The study was conducted during the week after birth, and no conclusions are derived for older infants. The long-term effects of trometamol are unknown. No recommendation can be given for the addition of sodium bicarbonate to milks containing a higher content of sodium.     

New Archaeological Evidence for an Early Human Presence at Monte Verde,Chile

Questions surrounding the chronology, place, and character of the initial human colonization of the Americas are a long-standing focus of debate. Interdisciplinary debate continues over the timing of entry, the rapidity and direction of dispersion, the variety of human responses to diverse habitats, the criteria for evaluating the validity of early sites, and the differences and similarities between colonization in North and South America. Despite recent advances in our understanding of these issues, archaeology still faces challenges in defining interdisciplinary research problems, assessing the reliability of the data, and applying new interpretative models. As the debates and challenges continue, new studies take place and previous research reexamined. Here we discuss recent exploratory excavation at and interdisciplinary data from the Monte Verde area in Chile to further our understanding of the first peopling of the Americas. New evidence of stone artifacts, faunal remains, and burned areas suggests discrete horizons of ephemeral human activity in a sandur plain setting radiocarbon and luminescence dated between at least ~18,500 and 14,500 cal BP. Based on multiple lines of evidence, including sedimentary proxies and artifact analysis, we present the probable anthropogenic origins and wider implications of this evidence. In a non-glacial cold climate environment of the south-central Andes, which is challenging for human occupation and for the preservation of hunter-gatherer sites, these horizons provide insight into an earlier context of late Pleistocene human behavior in northern Patagonia.     

Novel High-Molecular Weight Fucosylated Milk Oligosaccharides Identified in Dairy Streams

Oligosaccharides are the third largest component in human milk. This abundance is remarkable because oligosaccharides are not digestible by the newborn, and yet they have been conserved and amplified during evolution. In addition to encouraging the growth of a protective microbiota dominated by bifidobacteria, oligosaccharides have anti-infective activity, preventing pathogens from binding to intestinal cells. Although it would be advantageous adding these valuable molecules to infant milk formula, the technologies to reproduce the variety and complexity of human milk oligosaccharides by enzymatic/organic synthesis are not yet mature. Consequently, there is an enormous interest in alternative sources of these valuable oligosaccharides. Recent research has demonstrated that bovine milk and whey permeate also contain oligosaccharides. Thus, a thorough characterization of oligosaccharides in bovine dairy streams is an important step towards fully assessing their specific functionalities. In this study, bovine milk oligosaccharides (BMOs) were concentrated by membrane filtration from a readily available dairy stream called “mother liquor”, and analyzed by high accuracy MALDI FT-ICR mass spectrometry. The combination of HPLC and accurate mass spectrometry allowed the identification of ideal processing conditions leading to the production of Kg amount of BMO enriched powders. Among the BMOs identified, 18 have high-molecular weight and corresponded in size to the most abundant oligosaccharides present in human milk. Notably 6 oligosaccharides contained fucose, a sugar monomer that is highly abundant in human milk, but is rarely observed in bovine milk. This work shows that dairy streams represent a potential source of complex milk oligosaccharides for commercial development of unique dairy ingredients in functional foods that reproduce the benefits of human milk.     

研究: 奶牛与水牛初乳中乳寡糖组分比较研究

乳寡糖是由乳汁中含量丰富的固体物质组成．研究结果表明,乳寡糖有提高免疫、益生元及抗感染等作用,已发现与婴儿肠道发育、神经智力发育等多方面关系密切．水牛奶是除牛奶外的第二大奶源,国际上公认其为营养含量高、口感好的优质乳制品,但目前针对水牛乳寡糖的研究多以美洲水牛为研究对象,尚无中国水牛的相关研究．本研究利用固相萃取对已脱脂和除去蛋白质的广西水牛初乳乳汁样品进行纯化,并采用苯胺 (aniline,Bn)衍生化试剂对其进行衍生化处理,通过UPLC-ESI-Q-TOF-MS液相质谱进行优化后,对水牛初乳中的寡糖组分进行测定并与牛乳进行了对比,最终测得奶牛初乳中19种及水牛初乳中的9种乳寡糖组分,并对二者的种类及含量进行比较,发现在两种初乳的乳寡糖中,中性糖二糖m/z 385.15和中性糖三糖m/z 547.21以及酸性糖m/z 635.23均为其主要寡糖成分,与其他乳寡糖相比含量相对较高．总体而言水牛初乳中的中性寡糖占比比奶牛初乳高,二者中性糖占乳寡糖总量的比例分别为88.88%和63.16%．     

Formation of Oligosaccharides during Enzymic Hydrolysis of Milk Whey Permeates

Lactose present in whey UF-permeates was hydrolysed by an immobilised enzyme reactor and the formation of monosaccharides (glucose + galactose) and oligosaccharides was monitored. The enzyme used was β-galactosidase from A. oryzaeimmobilised in a porous film. The reactor, run in the flow-through mode, allowed large conversions at short residence times (60% conversion in 1 min). The conversion to oligosaccharides as a function of the reaction time (or degree of conversion) reaches a maximum and then declined as oligosaccharides were converted back to mono- and disaccharides. The higher the initial lactose concentration the higher the conversion to oligosaccharides and these maxima appear at higher degrees of conversion. Some trials were carried out on the concentration of the oligosaccharides present in the hydrolysates by means of membrane filtration (nanofiltration) .