小肽的营养作用及其吸收转运研究进展

小肽营养是蛋白质营养理论的发展与重要补充,研究小肽营养作用与吸收代谢特点,对全面理解小肽营养具有重要意义,文章将对该方面研究进展做一概括性总结。     

肠道小肽吸收利用机制及其营养功能

小肽是动物降解蛋白质过程中的中间产物,是由2个或2个以上的氨基酸以肽键相连的化合物,其吸收在总饲粮蛋白质的吸收中有重要作用。本文综述肠道对小肽的吸收利用及其调控机制,肠道小肽感应与胃肠激素分泌和摄食调控,肠道小肽利用对肠道健康的调控,以及小肽在动物营养中的应用。     

小肽营养与生理调控机制

小肽营养是蛋白质营养理论的发展与重要补充,研究小肽营养作用与吸收代谢特点,对全面理解小肽营养具有重要意义,文章将对该方面研究进展做一概括性总结。     

小肽的吸收机制与营养作用

上世纪五、六十年代，Agor（１９５３）首先观察到肠道能完整地吸收转运双苷肽。此后，Neway和Smith证实了肽可以完整转运吸收的观点。近２０年来，研究表明：蛋白质降解后的产物大部分是２个或３个氨基酸残基组成的小肽，可以完整形式被吸收进入循环系统，被机体利用。至此，肽的研究空前活跃，取得了不少的成就，Hara等（１９８４）在小肠粘膜上发现了小肽载体；Fei等（１９９４）克隆了小肽的１型载体；Adi－di（１９９６）克隆了小肽的２型载体等。１小肽的吸收血液循环中肽类的来源主要有：（１）消化道吸收（２）体蛋白质分解（３…     

小肽的吸收机制与营养功能的研究进展

小肽拥有许多特殊的营养生理作用,在蛋白质代谢过程中的地位十分重要,优势也十分明显。就小肽的吸收机制和特殊的营养功能进行了综述。     

小肽转运载体(PepT1和PepT2)研究进展

由小肽转运载体介导的小肽吸收对动物的生长和发育有着特殊的作用,因此,对小肽转运载体的深入研究在生理、药理和临床上都有着非常重要的意义。文中主要从小肽转运载体(PepT1和PepT2)的蛋白质分子结构与功能、主要的组织分布和影响其活性的因素三方面进行简要综述。     

蛋鸡小肠肽转运载体PepT1表达差异性的评定

本试验旨在研究蛋鸡十二指肠、空肠、回肠小肽转运载体mRNA表达的差异性.选用相同背景的健康成年蛋鸡10只,从十二指肠、空肠、回肠组织提取RNA样品,采用相对定量RT-PCR,对蛋鸡小肠各段肽转运载体mRNA表达的差异性进行评定.结果表明,蛋鸡空肠PepT1 mRNA的表达水平显著高于十二指肠(P＜0.05),与回肠比差异不显著(P＞0.05),十二指肠PepT1 mRNA的表达水平与回肠之间无显著差异(P＞0.05).     

肽的吸收与营养

本文介绍了近年来国内外肽的吸收与营养的研究概况,对肽的吸收特点、转运、利用及营养作用等进行了初步探讨,最后就反刍动物肽吸收与营养作用的研究进展及其前景,做了进一步的分析和展望。 引言 近年来,肽(主要指二肽和三肽)被胃肠道吸收己作为一种重要的生理现象被人们所接受,国外许多学者对肽的吸收和营养作用做了大量研究,取得了令人满意的成果,一些新的成果向传统的理论提出了挑战。本文就肽吸收     

小肽在动物营养中的研究新动态及展望

小肽（主要指二、三肽）作为蛋白质的主要消化产物，它在氨基酸（AA）消化、吸收和蛋白质代谢中的作用已被许多研究所证实。本文旨在就小肽的吸收机制、转运系统的特点、影响其吸收与释放的因素及其营养作用等方面的国内外研究新动态及展望作一综述。     

微量元素铬的营养调控及吸收转运模式探讨

铬作为葡萄糖耐受因子的重要活性成分,可以刺激胰岛素与跨膜胰岛素受体结合,增强胰岛素活性,并参与碳水化合物、脂肪、蛋白质和核酸代谢。本文主要综述铬的研究概况、营养调控机制及吸收转运模式。     

Creep feed intake during lactation enhances net absorption in the small intestine after weaning

The aim of the study was to measure the effect of creep feeding during lactation on net absorption in the small intestine at 4 days after weaning. Intermittent suckling was used to increase creep feed intake during lactation. Creep feed containing chromic oxide was provided. Based on the colour of the faeces, piglets were classified as ‘eaters’ or ‘non-eaters’, respectively. At day 4 after weaning, an in vivo small intestine segment perfusion test was performed at 5 sites along the small intestine in 24 piglets (12 eaters and 12 non-eaters). At both sides of each intestinal segment a tube was fitted to perfuse and drain fluid in order to assess net absorption. Net absorption was higher in eaters than in non-eaters (P < 0.001). Net absorption varied greatly between and within piglets and was highest in the caudal segments of the small intestine (P < 0.001). These data suggest that creep feeding could be a useful tool in the prevention of post-weaning diarrhoea.     

鲤鱼肠道中小肽与血液中肽的关系研究

为了研究鲤鱼肠道完整吸收小肽与肠道中小肽的关系,用6．25％酶解酪蛋白、酸解酪蛋白、酪蛋白溶液和生理盐水对鲤鱼进行肠道灌注试验(1ml／100g体重),20min后尾静脉采血制备血浆,用高效液相色谱仪分析。结果表明,鲤鱼血浆中肽量的增加与肠道提供的肽种类和数量有关,鲤鱼肠道能够完整地吸收某些小肽进入血液循环。     

十二指肠大豆小肽梯度灌注对泌乳奶山羊血液指标、乳成分及肽转运载体在小肠中表达丰度的影响

本试验通过十二指肠大豆小肽梯度灌注,旨在研究不同水平的小肽对泌乳中期奶山羊乳成分、血液生化指标、激素水平及小肠肽转运载体(PepT1)表达活性的影响.试验选用12只平均体重为(38±2)kg、带有十二指肠瘘管的泌乳奶山羊,分成4组,分别灌注小肽0、60、120、180 g/d,试验日粮相同,连续灌注14 d.结果表明:通过小肽的灌注,(1)增加了乳蛋白产量(P＜0.05),乳蛋白含量也有所增加,但仅在120 g/d试验组差异显著(P＜0.05).乳脂产量与乳脂含量随着灌注量的升高呈显著下降趋势(P＜0.05).乳中尿素氮含量随着灌注量的升高而增加(P＜0.05);(2)血清中总蛋白和球蛋白含量均高于对照组,但仅在120 g/d试验组差异显著(P＜0.05).白蛋白含量反而较对照组相比有所降低(P＜0.05),尿素氮的含量显著升高(P＜0.05).血清中生长激素浓度随着大豆小肽灌注量的增加而升高(P＜0.05),胰岛素浓度也表现出增加趋势,但只有在180 g/d试验组差异显著(P＜0.05);(3)PepT1表达在十二指肠、空肠、回肠随着灌注量的增加而升高.小肽灌注组PepT1在十二指肠表达丰度分别是对照组的1.6、2.6、5.4倍;回肠表达丰度是对照组的1.1、1.4、3.3倍;在空肠中表达是对照组的1.1、1.8、2.4倍.随着灌注量的增加,PepT1在十二指肠表达的增加尤为显著,在180 g/d试验组,PepT1十二指肠表达量分别为空肠、回肠的1.5、1.6倍.本研究揭示,小肽的灌注可以提高PepT1表达活性,增加小肽吸收,促进乳蛋白合成,并在120 g/d试验组表现尤为显著.     

小肽在动物营养中的应用

小肽是蛋白质降解为氨基酸过程中的中间产物,是动物蛋白质营养中的重要物质;小肽的吸收部位除小肠外,还有瘤胃、瓣胃等;小肽的转运机制与氨基酸明显不同;小肽吸收具有耗能低、速度快、载体不易饱和等优点,小肽吸收具有降低游离氨基酸间的吸收竞争、促进氨基酸(除蛋氨酸外)的吸收等作用;小肽还能促进蛋白质的合成和矿物质元素的吸收代谢。蛋白质的种类、消化酶的活性、小肽本身的性质都会影响小肽的释放、吸收及代谢。     

Improvement of small dairy producers in the central coast of Peru

The objective of this study was to characterize a group of small dairy producers in the central coast of Peru and determine the most important limiting factors that affect animal productivity, using Participatory Rural Appraisal methodologies. The information collected during a year included biological and socio-economic characteristics. Inappropriate nutrition, management, health and reproduction were observed in most farms. The average number of animals per family was 17.3, of which 40% were bulls and growing calves. Milk production and net cash income were reduced in the summer. The feeding programme for lactating and growing females of forage exchanged for labour and purchased concentrates did not theoretically or practically meet the cows’ needs. All water was carried to the site on donkeys from one kilometre distance. All cows were negative for a number of potential infectious diseases. By California Mastitis Test of routine samples 7.1% of cows had clinical mastitis and 66.1% subclinical. Taking notional labour and forage costs into account, milk production was at a loss but the farmers considered neither and were satisfied with a net cash income from milk sales three times the average agricultural wage.     

小肽添加剂对生长猪生长性能的影响

试验研究三种不同的小肽添加剂制品对生长猪生长性能的影响。试验选用72头初始体重在(34.64±8.32)kg的杜×长×大三元阉公猪,随机分为4个处理,每个处理6个重复,每个重复3头猪试验各组分别饲喂基础日粮(对照组),基础日粮加100mg/kg小肽A(小肽A组),基础日粮加100mg/kg小肽B(小肽B组),基础日粮加50mg/kg小肽C(小肽C组),试验期28d。测定其对生长猪的生长性能的影响,结果表明,与对照组相比,小肽A组、小肽B组和小肽C组的生长猪的平均采食量分别提高了9.8%、7.0%和12.5%(P0.05),平均日增重分别提高了15.8%、12.8%和21.7%(P0.05),料肉比分别降低了5.1%、6.3%和8.5%(P0.05)。     

Electrophysiological characterization of electrolyte and nutrient transport across the small intestine in horses

The aim of this study was to characterize the transport mechanisms of electrolytes and nutrients across the jejunum of nine healthy horses electrophysiologically. The stripped mucosa was mounted in Ussing chambers and tissue conductances (G_t) and short circuit currents (I_sc) were continuously monitored. After blocking the sodium and potassium channels with amiloride, tetraethylammonium chloride (TEA) and barium, chloride secretion was stimulated by carbachol and forskolin. Subsequently, chloride channels were inhibited by 4,4′‐diisothiocyanato‐stilbene‐2,2′‐disulfonic acid, 5‐nitro‐2‐(3‐phenylpropylamino)benzoic acid, CFTR_inh‐172, N‐(2‐naphtalenyl)‐(3.5‐dibromo‐2.4‐dihydroxyphenyl)methylene glycine hydrazide (GlyH‐101) and glibenclamide and their dose–response effect was investigated. The response to glucose, l ‐alanine and glycyl‐l ‐glutamine was determined at two different mucosal pH values (pH 7.4 and 5.4 respectively). Mean basal I_sc was ?0.47 ± 0.31 μEq/cm²h and mean G_t was 22.17 ± 1.78 mS/cm². Amiloride and TEA did not alter the baseline I_sc. Barium, carbachol and forskolin significantly increased I_sc. Irrespective of the dose, none of the chloride inhibitors changed I_sc. All nutrients induced a significant increase in I_sc with the increase being significantly higher at pH 7.4 than at pH 5.4. In conclusion, there is evidence that chloride secretion in horses may be different from respective transport mechanisms in other species. The glucose absorption is suggestive of a sodium‐dependent glucose cotransporter 1. However, a decrease in luminal pH did not stimulate current response to peptides as shown for other mammals.