功能糖通过甜味受体信号通路促进GLP-1的分泌

为探究功能糖对肠源性激素分泌的影响,采用基质胶诱导NCI-H716细胞引起内分泌分化建立小肠内分泌模型。通过该模型评价海藻糖、赤藓糖醇、山梨糖醇、木糖醇、异麦芽酮糖醇、L-阿拉伯糖促胰高血糖素样肽-1(GLP-1)、血糖素样肽-2(GLP-2)、酪酪肽(PYY)分泌的能力,并选出促GLP-1分泌能力强的功能糖,探究促GLP-1分泌的机理。结果表明:海藻糖、山梨糖醇可显著促进GLP-1、PYY分泌(P 0.05);赤藓糖醇可显著促进GLP-1、GLP-2分泌(P 0.05);木糖醇可显著促进PYY分泌(P 0.05);异麦芽酮糖醇、L-阿拉伯糖对3种激素的分泌无显著影响。选取海藻糖、赤藓糖醇、山梨糖醇继续研究其促GLP-1分泌机理,发现它们可通过激活T1R2、T1R3、Gα-gustducin、PLCβ2、TRPM5等基因,增加胞内Ca~(2+)浓度,以激活甜味受体信号通路促进GLP-1分泌。结论:海藻糖、山梨糖醇、赤藓糖醇、木糖醇具有促肠源性激素分泌的功能,海藻糖、赤藓糖醇、山梨糖醇通过激活甜味受体信号通路促进GLP-1分泌。     

稳定表达甜味受体蛋白T1R2/T1R3的HEK293细胞系的建立

以小鼠舌组织为对象,提取总mRNA,并以此为模板,使用自行设计的引物通过RT-PCR扩增Gα15、T1R2和T1R3目的片段。构建重组质粒pEGFP-C1-Gα15、pDsRed1-N1-T1R2、pcDNATM6.2/N-YFP-DEST-T1R3。以脂质体介导的方法转染HEK293细胞,经抗性筛选后,通过极限稀释法获得稳定表达T1R2/T1R3的HEK293细胞系,最后通过RT-PCR,荧光显微镜及Western blot方法在基因及蛋白质水平上对建立的稳定表达细胞系进行鉴定。基因及蛋白质水平上的结果均表明,目的基因Gα15、T1R2/T1R3成功导入HEK293细胞中,并且稳定表达。该细胞系的建立为细胞水平上甜味机理的体外研究(如甜味识别热动力学等)提供了稳定的细胞来源。     

味觉感知的人体肠-脑轴信号传导机制研究进展

味觉是人类感知生物摄取能的重要环节,胃肠道亦存在味觉感知现象。本文从胃肠道味觉受体、胃肠道味觉感知通路及肠-脑轴味觉信号传导机制等方面进行了分析,胃肠道中味觉感知表明胃肠道中存在味觉受体第一家族亚型（taste receptor type 1 member,T1R）1、T1R2、T1R3、味觉受体第二家族亚型（taste receptors type 2,T2Rs）等味觉受体,且肠道味觉物质刺激肠内分泌细胞分泌胆囊收缩素（cholecystokinin,CCK）、肽YY（peptide YY,PYY）等脑肠肽激素,与味觉信号在神经元的传递有关;肠道中鲜味物质谷氨酸钠显著激活大脑缰核、杏仁核和下丘脑亚核的神经网络,表明肠-脑轴味觉感知是基于胃肠道受体及脑肠肽、神经元和大脑中枢神经系统之间的共同调控,从而提出肠-脑轴味觉信号传导机制假说,认为甜味受体T1R2/T1R3和鲜味受体T1R1/T1R3具有相似的信号传导通路,味觉物质作用于肠道后,与肠道中相应的味觉受体结合,激活磷脂酶-β2（phospholipase C-β2,PLC-β2）,释放Ca2＋,引起肠道内环境的变化,刺激肠内分泌细胞分泌PYY、CCK等激素,被肠神经元突触特异性识别,将味觉信号传导至大脑神经中枢;而谷氨酸代谢型受体4（metabotropic glutamate receptor 4,mGluR4）和苦味受体T2Rs信号传导通路则是通过激活磷酸二酯酶（phosphodiesterase,PDE）,使细胞质内3’,5’-环腺苷酸（3’,5’-cyclic adenylic acid,cAMP）浓度降低,从而解除环核苷酸（cyclic nucleotide,cNMP）的抑制作用,从而释放Ca2＋。基于肠-脑轴味觉偏好,为味觉发生改变的患者开发治疗新药物、寻找新的药物靶点提供了新的方向。对肠-脑轴味觉信号传导机制的研究将为胃肠道生理的神经控制提供分子框架、精准控制人体对味觉营养物质的生理反应,并对味觉物质在肠-脑轴中的摄入、代谢、调节等及开发新的味觉感知途径提供新的理论依据。     

甜味感受及其影响因素的研究进展

甜味剂种类繁多,按其来源可分为天然甜味剂和人工合成甜味剂两类。甜味感受主要由味蕾中的异性二聚体进行,不同的异性二聚体可以识别不同的味觉分子,甜味是由异性二聚体T1R2、T1R3共同识别作用产生的;影响甜味剂甜味强度的因素有很多,除甜味剂本身差异外,还包括温度、p H、溶剂环境、受试者生理情况等;甜味强度的研究方法很多,其中常用的研究手段有3种:感官分析、电子舌检测分析、培养细胞株研究方法。     

味觉受体研究热点分析

味觉是重要的感知反应，基本的味觉包括甜、酸、苦、咸、鲜5 种。味觉受体是用于感知各种味觉的蛋白质。本文对味觉受体热点关键词、来源、研究手段、受体类型、研究人员等进行分析概述，为开展味觉受体相关研究提供参考。通过文献分析发现，苦味、甜味、酸味、鲜味、大鼠、人类、小鼠、细胞、表达、蛋白质、诱导、基因、信号、神经元和分子等是味觉受体研究的热点关键词，Proceedings of the National Academy of Sciences、Journal of Neuroscience、American Journal of Physiology-Regulatory, Integrative and Comparative Physiology和Journal of Comparative Neurology是味觉受体研究领域的重点期刊。鼠类味觉受体是大多数实验的研究对象，然而鼠类和人类的味觉受体之间仍然存在较大差异，为更准确地探索人类味觉受体，还需对人类本身的味觉受体进行深入的研究。目前对味觉受体的研究已经进入结构生物学和神经生物学水平，主要采用分子生物学实验和计算机模拟技术等手段对受体结构进行探索。研究人员已经解析了青鳉鱼T1R2/T1R3配体识别结构域、斑马鱼Otop1和鸡Otop3的结构以及各味觉受体的信号传导通路，但大多数受体的精确结构还未解析出，也难以区分不同特点的味觉神经刺激。采用蛋白质表达纯化、蛋白质结构解析和信号传导等技术获得G蛋白偶联受体（G protein coupled receptors，GPCRs）的单晶体并解析晶体结构以及阐明各受体间的相互作用机理是目前重点的研究方向。美国目前在味觉受体研究领域处于领先地位，Ryba N. J. P.、Hoon M. A.和Chandrashekar J.等科学家目前引领了该领域的研究方向。本文明确了味觉受体领域发展现状，预测了味觉受体领域发展趋势，可为科研人员提供研究方向和思路。     

链脲佐菌素诱导糖尿病小鼠轮廓状乳头中味蕾特征变化

以ICR小鼠为实验对象,注射180 mg/kg剂量链脲佐菌素构建糖尿病小鼠模型,利用苏木精-伊红染色法及免疫组织化学方法分析了糖尿病小鼠味蕾形态变化和味觉信号转导相关蛋白表达变化。结果表明,对照组小鼠与糖尿病组小鼠轮廓状乳头大小及数量无显著差异;但糖尿病小鼠单个味蕾中味觉信号转导蛋白α-gustducin及磷酸脂酶Cβ2的阳性细胞数显著增加(P<0.05),而synaptobrevin-25(SNAP-25)阳性细胞显著减少(P<0.05)。综上所述,糖尿病引起的味觉变化可能来自于味信号转导蛋白表达的变化,而这些变化导致外周味觉感受信号无法有效地传导到味觉传入神经。     

低聚合度魔芋甘露寡糖对正常小鼠肠道及微生物菌群的影响

研究以有机溶剂沉淀法制备的低聚合度魔芋甘露寡糖(LMOS)对正常小鼠肠道形态、肠道菌群的影响。取ICR小鼠50只,随机分为4组实验组和1组对照组,分别用不同剂量1,2,4,8,8g/(kg·d)的LMOS溶液和等体积的生理盐水灌胃,连续30 d后,观察比较不同LMOS添加量对小鼠肠道形态、盲肠内短链脂肪酸(SCFA)及微生物菌群的影响。实验结果表明,与对照组相比,高剂量的LMOS能显著增加小鼠盲肠内SCFA的含量,并能使肠绒毛高度增加。变性梯度凝胶电泳(DGGE)指纹图谱结果分析表明,与对照组相比,喂食高剂量LMOS能使小鼠肠道中乳杆菌等有益菌含量增加。得出LMOS能够通过促进SCFA的产生、促进乳杆菌的增殖,调节小鼠肠道健康,是一类具有开发前景的益生元。     

乳酸菌BC299的鉴定及其对免疫抑制小鼠肠道菌群的影响

以传统发酵泡菜中分离得到的乳酸菌BC299为研究对象,通过形态观察、生理生化、16S rDNA基因序列分析等方法对其进行鉴定,研究其耐酸、耐胆盐、耐抗生素能力,并以环磷酰胺（CTX）诱导免疫抑制小鼠,研究菌株BC299对小鼠粪便中肠道细菌的多样性和相对丰度的影响。结果表明,菌株BC299被鉴定为植物乳杆菌（Lactobacillus plantarum）,其对pH2.0和0.3%胆盐具有良好的耐受性;对常见抗生素敏感;能改善CTX诱导小鼠的小肠绒毛和组织形态的破坏,对免疫抑制小鼠的肠道菌群具有调节作用,能正向调节与免疫相关菌群的相对丰度,使小鼠肠道内毛螺菌科（Lachnospiraceae）和瘤胃球菌科（Ruminococcaceae）的相对丰度显著降低（P＜0.05）,拟杆菌科（Bacteroidaceae）的相对丰度显著增加（P＜0.05）。     

基于动物模型的大豆球蛋白诱导肠黏膜过敏反应机理研究

目的:探究大豆球蛋白诱导小鼠肠黏膜过敏反应的调控机理。方法:以大豆球蛋白和β-伴球蛋白为试验材料,Balb/c小鼠为受试动物,采用连续灌胃的方式建立肠道过敏动物模型。研究了小鼠小肠绒毛T、B淋巴细胞的数量、肠细胞凋亡率和固有层IgA+浆细胞的数量及小肠液中sIgA的含量。结果:与对照组相比,大豆球蛋白组小肠绒毛固有层淋巴细胞CD3^+、CD4^+数量显著高于对照组(P<0.01);大豆β-伴球蛋白组小肠绒毛固有层及肠上皮细胞中CD3^+、CD8^+、CD4^+及整合素α4β7的数量均显著高于对照。高倍镜下观察显示试验组小鼠小肠固有层中可见大量浆细胞及淋巴细胞等炎性细胞浸润;试验组小鼠小肠固有层IgA+浆细胞呈现明显的阳性染色。结论:大豆球蛋白可以介导细胞免疫为主的过敏反应发生,肠黏膜上皮细胞凋亡亢进是造成肠道通透性加强,进而破坏肠黏膜屏障功能的重要原因。     

林蛙油的雌激素样作用研究

本文探讨了林蛙油对生长、激素水平及性腺激素受体表达的影响。采用雌性昆明小鼠24只,随机分为高剂量组、低剂量组和空白组。给药组灌胃林蛙油,空白组灌胃生理盐水。给药结束后,取各组小鼠的卵巢、子宫及肾上腺称湿重,并对其组织切片进行了病理形态学观察,取血清测激素水平。利用Western Blot方法检测小鼠子宫、卵巢及肾上腺蛋白组织中FSHR、TβRⅠ及TβRⅡ的表达。林蛙油对雌性小鼠体重、子宫湿重、卵巢湿重及肾上腺湿重均无显著影响,血清内E2及P的含量显著增加(p0.05),FSH的含量显著增加(p0.01),T的含量显著增加(p0.001),PRL和LH的含量变化无显著差异。林蛙油高剂量给药组肾上腺蛋白组织FSHR的表达水平升高(p0.05),其他组变化不显著。表明长时间大剂量服用林蛙油,在一定程度上会引起机体内的E2、T、FSH和P激素水平的变化及FSHR蛋白表达的增高,具有一定的雌激素样作用。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.