Dietary polysaccharide from Mung bean [Vigna radiate (Linn.) Wilczek] skin modulates gut microbiota and short-chain fatty acids in mice

Cumulative evidence revealed that the gut microbiota play important role in human health. Polysaccharide from Mung bean [Vigna radiate (Linn.) Wilczek] skin has been confirmed to have a variety of biological activities, but its effect on the gut microbiota has not been considered. This study aimed to investigate the effect of hot water extraction of mung bean skin water-soluble polysaccharides (MBP-2) on the gut microbiota of Balb/c mice and its main metabolite short-chain fatty acids (SCFAs). The results showed that supplementation with MBP-2 increased the colon length and the production of SCFAs in Balb/c mice, and improved the intestinal microenvironment by producing SCFAs, which is beneficial to the intestinal health of mice. MBP-2 increased the Chao1 index and ACE index in a dose-depended manner, and changed the structure of the gut microbiota and significantly promoted the growth of probiotic bacteria in Balb/c mice. The faecal bacterial flora of mice is mainly composed of nine phyla and twenty-seven genera, MBP-2 can regulate the composition of intestinal flora by increasing Firmicutes, Bacteroidetes, Clostridium and decreasing TM7, thereby maintaining intestinal health.     

枸杞多糖体外调节人体肠道菌群的功能研究

为研究枸杞多糖(LBP)对人体肠道菌群结构和代谢产物的影响,对6名健康人的粪便提取物进行单独样本与混合样本的体外模拟厌氧发酵,利用16S rRNA基因高通量测序技术对发酵后肠道菌群进行结构和功能分析,并利用超高效液相色谱(UPLC)检测发酵液中的短链脂肪酸(SCFAs)浓度。结果表明,LBP能够明显改变人体肠道菌群结构与功能,提高肠道菌群中益生菌乳酸杆菌属与双歧杆菌属的丰度,并促进了SCFAs的产生。因此,LBP能够显著影响人体肠道菌群结构与功能。     

Functional properties of curry paste in relation to digestibility and fermentation by gut microbiota

The prebiotic properties of sour curry paste in the upper gut and the gut microbiota were investigated in vivo during digestion. The effect of the addition of garcinia as souring agent in curry paste was studied. Curry paste without garcinia (P1) and curry paste with garcinia (P2) increased the number of beneficial bacteria in the gut microbiota, especially bifidobacteria and lactobacilli, and significantly (p < 0.05) decreased the number of harmful bacteria (Clostridia). Fecal fermentation with P1 resulted in a prebiotic index (PI) of 1.19, whereas fermentation with P2 resulted in a PI of 2.75. The fermented metabolites produced were lactic acid; vitamins; and short-chain fatty acids (SCFAs) such as acetic acid, propionic acid, and butyric acid. P1 produced metabolites including lactic acid, SCFAs, and B vitamins in higher amounts than P2. After a 24 h fermentation period with colonic microbiota, P1 produced vitamins B1 (18.38 ± 0.10 µg/ml) and B2 (45.28 ± 2.02 µg/ml) but not folic acid, whereas P2 produced only vitamin B1 (5.99 ± 0.48 µg/ml).     

微生态制剂调节便秘、腹泻人群肠道菌群结构与产短链脂肪酸关键菌属的相关性

为探究微生态制剂对健康、便秘和腹泻人群肠道菌群结构的调节能力。本研究以健康、便秘和腹泻人群 为对象,令其定时、定量摄入水苏糖（stachyose tetrahydrate,Sta）、益生菌纯粉（probiotics power,PP）、益生 菌剂（probotic preparations,PPrs）3 种微生态制剂,共6 周,采集新鲜粪便样本并提取DNA,利用Ion torrent PGM 二代测序技术进行16S rRNA V3区扩增子测序,并用气相色谱检测粪便中的短链脂肪酸（short-chain fatty acids, SCFAs）表达水平,最后联合多变量统计学分析方法对测序数据进行多样性分析。结果表明：绝大多数序列属 于硬壁菌门（Firmicutes）和拟杆菌门（Bacteroidetes）,约占总序列数的94.37%。随着微生态制剂的摄入,受 试人群肠道菌群的群落结构多样性明显增加,毛螺菌科（Lachnospiraceae）中的Blautia、Lachnospira以及瘤胃菌 科（Ruminococcaceae）中的Faecalibacterium、Oscillospir等与产SCFAs相关的菌属都明显地增长,其中Blautia和 Faecalibacterium与SCFAs含量呈显著正相关。SCFAs的含量以及肠道中相应菌群的增长与减少都与微生态制剂的成 分相关,在3 组受试人群中,服用Sta组,丙酸含量显著增加,乙酸与丁酸含量也在2 周左右有所增加,并伴随产 SCFAs的菌属快速且大量增长;PP组肠道中只有乙酸含量有所增加,丙酸和丁酸含量呈现降低的趋势,而产SCFAs 的菌属增长较明显;服用PPrs组,乙酸和丁酸含量明显增加,且便秘和腹泻人群在停止服用后,其SCFAs的含量 接近于健康人群,常见的Bifidobacterium、Lactobacillus、Parabacteroides等外源性益生菌均明显增长,可能性致病 菌相对丰度降低,表明服用PPrs对肠道菌群结构的调节作用以及影响更大。此外,根据肠型的分析,Bacteroides和 Prevotella在饮食的共同驱动下会调整并改变肠型,而仅通过所选择的微生态制剂的作用,在驱动肠型改变方面不 显著。综上所述,肠道疾病状态的人群服用微生态制剂后,肠道菌群结构向正常人群的状态调整,菌群多样性和 SCFAs表达水平提高,表现出持续抑制肠道有害细菌生长,促进有益菌的增殖,以此来维持肠道菌群结构的稳态。 经扩增子测序分析获得初步结论为：微生态制剂有改变腹泻、便秘人群肠道菌群整体结构的功效,并且PPrs要比单 一的Sta或PP调整肠道菌群的能力更突出。     

低分子量硫酸软骨素体外酵解特征及其对肠道菌群的调节作用

硫酸软骨素（Chondroitin sulfate,CS）具有调节肠道微生物的作用,但不同分子量对其益生活性的影响鲜有报道。该研究比较了硫酸软骨素（80 ku）及其光催化降解产物（Low Molecular Weight Chondroitin Sulfate,LWCS,4 ku）体外酵解特征及其对肠道代谢物的影响。通过化学法、气相色谱质谱联用、高通量测序等方法测定了不同时间发酵液中pH值、CS和LWCS含量、还原糖含量、短链脂肪酸浓度以及肠道微生物的变化。结果显示,在发酵48 h内,CS、LWCS以及还原糖含量均显著降低（P<0.05）,说明肠道微生物能够降解利用硫酸软骨素及其降解产物。且降解后的硫酸软骨素更显著地增加了拟杆菌门和副杆菌属等有益菌的丰度（P<0.05）,更明显的抑制了潜在致病菌型埃希氏-志贺氏菌属（P<0.05）。此外,LWCS发酵能维持24 h的酸性环境,并产生更多的乙酸、丙酸和总短链脂肪酸（分别增加1.15、1.03和1.09倍）。以上结果表明,光催化降解后的硫酸软骨素具有更强的肠道益生作用,该研究为硫酸软骨素的开发应用提供了科学依据。     

海藻糖基麦芽五糖及其微球的体外消化和酵解

为研究包埋前后的海藻糖基麦芽五糖(N-G7)在模拟消化液及体外酵解过程中的变化,采用口腔、胃部及小肠的体外消化模型分析消化前后溶液中N-G7的质量和N-G7微球(ALGCa)中的糖组成变化,应用体外发酵技术评价N-G7微球的发酵行为,检测不同时间点的pH值、菌体浓度(OD₆₀₀)、产气量、短链脂肪酸(SCFA)浓度等指标的变化,并探究其对人体肠道微生物构成的影响。结果表明：N-G7在口腔消化2 min后在强酸性的胃部环境中几乎不被水解,在小肠中N-G7的水解率达到了82.70%。采用不同质量分数(1%、2%、3%)的海藻酸钙对其进行包埋,形成的微球保留80%以上的N-G7到达结肠。在体外酵解中,各实验组的pH随时间延长逐渐降低,OD600随时间延长逐渐增加。质量分数2%的ALG-Ca组产气量和碳源消耗率在0～6 h内达到最低,而后逐渐增加,证明包埋后的N-G7发酵体系属于缓慢发酵。与对照相比,质量分数2%的ALG-Ca组产生大量SCFA,肠道菌群组成发生变化,更有利于益生菌的生长。     

Metabolic and microbial modulation of phenolic compounds from raspberry leaf extract under in vitro digestion and fermentation

Raspberry leaves, by-products in raspberry production, are also a rich source of bioactive phytochemicals. In this study, the changes of phenolic compounds in raspberries leaf extract (RLE) under in vitro digestion and colonic fermentation were further studied by HPLC-MS analysis and 16S rRNA. The results showed that the phenolic compounds in RLE were relatively stable during in vitro gastric digestion; however, in the subsequent intestinal digestion and colonic fermentation, their content decreased sharply. A large amount of hydroxyphenylpropionic acid, hydroxyphenylacetic acid and urolithins were produced under the action of gut microbiota. Moreover, compared with corresponding control, RLE significantly reduced the ratio of Firmicutes/Bacteroidetes in all volunteers, increased the relative abundances of some beneficial bacteria, Enterococcus, Prevotella, and decreased the relative abundances of potential pathogens, Clostridium and Faecalibacterium. These findings suggest that RLE during in vitro digestion and fermentation has positive effects on gut microbiota and potential value of maintaining intestinal health.     

Influence of Intestinal Microbiota on the Catabolism of Flavonoids in Mice

Although in vitro studies have shown that flavonoids are metabolized into phenolic acids by the gut microbiota, the biotransformation of flavonoids by intestinal microbiota is seldom studied in vivo. In this study, we investigated the impact of the gut microbiota on the biotransformation of 3 subclasses of flavonoids (flavonols, flavones, and flavanones). The ability of intestinal microbiota to convert flavonoids was confirmed with an in vitro fermentation model using mouse gut microflora. Simultaneously, purified flavonoids were administered to control and antibiotic‐treated mice by gavage, and the metabolism of these flavonoids was evaluated. p‐Hydroxyphenylacetic acid, protocatechuic acid, p‐hydroxybenzoic acid, vanillic acid, hydrocaffeic acid, coumaric acid, and 3‐(4‐hydroxyphenyl)propionic acid were detected in the serum samples from the control mice after flavonoid consumption. The serum flavonoid concentrations were similar in both groups, whereas the phenolic metabolite concentrations were lower in the antibiotic‐treated mice than in the control mice. We detected markedly higher flavonoids excretion in the feces and urine of the antibiotic‐treated mice compared to the controls. Moreover, phenolic metabolites were upregulated in the control mice. These results suggest that the intestinal microbiota are not necessary for the absorption of flavonoids, but are required for their transformation.     

Fabrication of quercetin-loaded nanoparticles based on Hohenbuehelia serotina polysaccharides and their modulatory effects on intestinal function and gut microbiota in vivo

This research was aimed to construct the nanoparticles based on Hohenbuehelia serotina polysaccharides for encapsulation of quercetin (QC-HSP NPs), and investigate their effects on intestinal function and gut microbiota in mice. Results showed that in comparison with HSP and control, QC-HSP NPs significantly improved immune organ indexes, colon length, fecal moisture content and intestinal peristalsis capacity of mice. The productions of short-chain fatty acids (SCFAs) in colon were also increased after treatment with QC-HSP NPs, while the colonic fecal pH was decreased and defecation time was shortened. Through analysis of 16S rRNA sequencing, QC-HSP NPs could increase α and β diversities of gut microbiota, modulate their structure and composition, and increase the relative abundance of beneficial bacteria together with reducing the richness of harmful bacteria. In addition, QC-HSP NPs ameliorated the metabolic functions of gut microbiota by modulating metabolic pathways. This study suggested that QC-HSP NPs might be served as a prebiotic for protecting intestinal health.     

应用Illumina NovaSeq测序技术比较3 种杂粮对大鼠肠道菌群的影响

为探究燕麦、荞麦和小米对健康大鼠肠道结构、肠道菌群及肠道中短链脂肪酸（short-chain fatty acids,SCFAs）含量的影响,本实验将48 只SPF级雄性SD大鼠随机分为4 组（空白对照组（饲喂标准维持饲料）、燕麦组（饲喂含22%（质量分数,下同）燕麦的饲料）、荞麦组（饲喂含22%荞麦的饲料）和小米组（饲喂含22%小米的饲料））,每周测定大鼠体质量,12 周后处死大鼠,取肝脏、结肠组织及结肠内容物,对大鼠肝脏和结肠组织进行病理学检测;应用Illumina NovaSeq高通量测序技术检测大鼠肠道菌群变化;利用液相色谱-质谱联用仪检测大鼠结肠内容物SCFAs含量。结果表明,燕麦可增加大鼠肠道菌群多样性,提高大鼠结肠乳杆菌属（Lactobacillus）和阿克曼氏菌属（Akkermansia）丰度;荞麦和小米可增加厚壁菌门（Firmicutes）相对丰度,降低疣微菌门（Verrucomicrobia）和拟杆菌门（Bacteroidetes）相对丰度;燕麦、荞麦和小米均可降低拟杆菌属（Bacteroides）丰度;燕麦和小米可显著提高大鼠结肠内乙酸和总SCFAs含量（P＜0.05）,小米可显著提高丙酸和异丁酸含量（P＜0.05）。综上,燕麦对大鼠肠道菌群具有一定的改善作用,荞麦和小米对肠道菌群的影响相似度较高,相关研究结果可为谷物功能食品的开发提供科学依据。     

肠源性短链脂肪酸生成机制及其饮食调控

短链脂肪酸(short chain fatty acids, SCFAs)作为肠道微生物的重要代谢产物,将宿主饮食与肠道微生物之间复杂的相互作用关系有机地联系在一起。SCFAs是近年来微生物代谢产物与人体健康科研领域研究热点,SCFAs不仅作为肠道上皮细胞的重要能源物质,也是游离脂肪酸受体的天然配体,因此发挥着多种健康作用,如调节脂质代谢、免疫、炎症反应和食欲等。阐述了肠源性SCFAs前体物质的主要食物来源,详细探讨了参与SCFAs生成的肠道微生物及代谢途径,并提出了肠源性SCFAs的饮食调控策略。从化学结构上看,SCFAs是一类碳原子数小于7的挥发性有机酸,肠源性SCFAs主要包括乙酸、丙酸、丁酸,它们主要是由SCFAs前体物质在肠道菌群的酵解作用下转化生成。SCFAs前体物质的食物来源多种多样,不易消化的碳水化合物是SCFAs的主要食物前体,包含抗性淀粉、非淀粉多糖、低聚糖等。肠道中的多种微生物能够通过不同代谢途径独立或者协同利用SCFAs前体物质产生SCFAs。补充富含SCFAs前体物质的食物,不仅能够影响肠源性SCFAs的含量,还可选择性地促进肠道中有益菌的生长,从质和量上维护肠道微生态稳态、直接或者间接地调节机体多种生理功能,促进人体健康功能。希望可为预防和治疗相关代谢和免疫疾病提供新的思路。     

青稞膳食纤维和多酚对肠道微生物的协同调节作用

以青稞面粉(hulless barley flour,HBF)、不可溶膳食纤维-多酚复合物(insoluble dietary fiber-phenolic compounds,IDF-PC)和可溶性膳食纤维-多酚复合物(soluble dietary fiber-phenolic compounds,SDF-PC)为材料,以阿魏酸(ferulic acid,FA)为对照,采用酶解法制备IDF-PC和SDF-PC,Folin-Ciocalteu法测定多酚含量,利用体外结肠发酵,结合16S rRNA高通量测序,根据微生物的丰度和多样性分析青稞膳食纤维和多酚对肠道微生物协同调节作用,并利用高效液相色谱法进行短链脂肪酸分析。结果表明,HBF、IDF-PC和SDF-PC中含有丰富的膳食纤维和多酚。经体外结肠发酵后,3种样品能够提高肠道微生物的丰度和多样性,明显促进乳杆菌属(Lactobacillus)、艾克曼菌属(Akkermansia)、瘤胃菌科UCG-005(Ruminococcaceae-UCG-005)和瘤胃菌科NK4A214-(Ruminococcaceae-NK4A214-group)的生长,调节作用优于FA。HBF、IDF-PC和SDF-PC经体外结肠发酵后,能够产生较多的短链脂肪酸,乙酸含量最高,分别为(0.29±0.21)、(0.15±0.05)和(0.14±0.10)mg/mL,说明青稞膳食纤维和多酚对肠道微生物有较好的协同调节作用,可为青稞促进机体健康和预防疾病提供科学依据。     

Characteristic of polysaccharides from Flammulina velutipes in vitro digestion under salivary,simulated gastric and small intestinal conditions and fermentation by human gut microbiota

In this study, in vitro digestion and fermentation of Flammulina velutipes -derived polysaccharides (FVP) were investigated. It was found that FVP mainly consisted of 48.45% glucose, 15.40% mannose, 14.60% xylose, 11.80% fucose and 9.90% galactose. The -human saliva, simulated gastric and small intestinal juices conditions did not break down the FVP. Based on in vitro fermentation tests, FVP modulated the composition of gut microbiota by elevating the amounts of Bifidobacteriaceae and Bacteroidaceae and reducing the numbers of genera Lachnospiraceae and Enterococcaceae. Meanwhile, FVP affected the synthesis of short-chain fatty acids derived from gut microbiota.     

乳酸菌发酵香菇对肠道菌群的调节作用及其产品研制

将香菇经乳酸菌发酵后,通过小鼠灌胃实验和16S rRNA高通量测序,研究其对肠道菌群结构和多样性的影响,并研制调味即食产品。结果表明,中等剂量（10 g/kg,以小鼠质量计）的发酵香菇改变了小鼠肠道菌群的物种多样性,其特有物种和稀有物种数量增加,且个体差异减小,物种分布更均匀。发酵香菇可不同程度地增加小鼠肠道内有益菌群,如Muribaculaceae、乳杆菌属（Lactobacillus）、Dubosiella、Lachnospiraceae等的定殖,降低螺杆菌属（Helicobacter）、支原体（Mycoplasma）等致病菌的相对丰度,从而改善肠道健康。通过单因素和响应面优化实验,获得乳酸菌发酵香菇调味即食产品的最佳配方为：发酵香菇块81.5%、甜面酱1.0%、豆瓣酱1.5%、白砂糖6.0%、藤椒油3.0%、芝麻2.0%、辣椒油4.0%、姜汁1.0%（均为质量分数）。为乳酸菌发酵技术在香菇深加工中的应用提供了有益参考。     

西洋参多糖对克林霉素磷酸酯诱导的抗生素相关性腹泻的改善作用

目的:研究西洋参多糖对抗生素（克林霉素磷酸酯）所诱导的肠道相关副作用的改善作用,包括腹泻、肠道结构完整性及肠道菌群组成和多样性。方法:通过水提、醇沉、脱蛋白后,从西洋参根中得到水溶性西洋参多糖（water-soluble Panax quinquefolius polysaccharide,WQP）。通过灌胃克林霉素磷酸酯建立抗生素相关副作用模型,随后利用生理盐水（自然恢复组,NR）或WQP（WQP组）进行干预。结果:WQP主要由半乳糖醛酸、葡萄糖、半乳糖和阿拉伯糖组成;其产率、总糖含量、糖醛酸含量、蛋白质含量分别为6.71%、85.2%、31.9%、2.1%。药理实验结果表明:WQP能够减轻大鼠腹泻症状,改善结肠组织水肿,增加肠绒毛长度,恢复肠道菌群多样性。与NR组相比,门水平上,WQP可降低肠道菌群中的厚壁菌门（Firmicutes）和变形菌门（Proteobacteria）的相对丰度,增加拟杆菌门（Bacteroidetes）的相对丰度;属水平上,WQP降低拟杆菌属（Bacteroides）和梭菌属（Clostridium）的相对丰度。结论:WQP可通过促进大鼠肠道结构修复,改善肠道菌群丰富度和多样性,进而缓解克林霉素磷酸酯所造成的腹泻和菌群失调等抗生素相关副作用。     

基于体外发酵研究仙人掌果实花色苷对肠道菌群及代谢物SCFAs的影响

仙人掌果中富含多种活性物质,其中含有的花色苷在调节肠道菌群中起着重要作用,为了进一步探讨仙人掌果实中花色苷与人体肠道内菌群的关系,本文研究了仙人掌果实花色苷体外模拟消化和体外厌氧发酵K组（空白）、花色苷H组（高剂量15 mg/mL）、M组（中剂量10 mg/mL）、L组（低剂量5 mg/mL）对人体肠道微生物和代谢物短链脂肪酸（SCFAs）的影响。结果表明:采用pH示差法,以消化率为指标,仙人掌果实花色苷（10 mg/mL）,经胃消化3 h后消化率为11.4%;经肠消化4 h后消化率为23.5%;剩余65.1%的花色苷未经胃肠道消化。采用高通量测序方法,通过α多样性和β多样性分析,与K组相比,花色苷H、M、L组均能显著提高肠道菌群多样性（P<0.05）。在菌群组成上,基于门水平分析,与空白组比较,花色苷各剂量组,变形菌门（Proteobacteria）相对丰度显著降低（P<0.05）,厚壁菌门/拟干菌门（Firmicutes/Bacteroidetes,F/B值）的比例均显著减少（P<0.05）;基于属水平中,与K组相比H、M、L组均能显著降低大肠杆菌志贺属（Escherichia-Shigella）、脱硫弧菌属（Desulfovibrio）致病菌相对丰度（P<0.05）,能够显著增高有益菌的丰度（P<0.05）,其中,中剂量组中普氏菌属（Prevotella）相对丰度最高,达到41.8%。高剂量组中乳酸杆菌属（Lactobacillus）、双歧杆菌属（Bifidobacterium）相对丰度最高,分别达到7.9%、5.9%,低剂量组中光冈菌属（Mitsuokella）相对丰度大幅提高,达到37.7%。通过气相色谱分析短链脂肪酸变化,与K组相比,H、M、L组总短链脂肪酸含量均显著提升（P<0.05）,且分别为K组的7.8、5.0和1.1倍。其中乙酸、丙酸、丁酸含量上升最显著（P<0.05）,乙酸上升最高为K组的10.0倍,丙酸为4.6倍,丁酸为10.7倍。综上,仙人掌果实花色苷在胃中少量消化,在小肠中大量消化,绝大部分剩余,其能够改变肠道的微生物的多样性及菌群组成,促进短链脂肪酸的产生,为后续花色苷对肠道微生物群的调节作用以及开发功能性食品建立基础。     

Dietary Casein and Soy Protein Isolate Modulate the Effects of Raffinose and Fructooligosaccharides on the Composition and Fermentation of Gut Microbiota in Rats

Although diet has an important influence on the composition of gut microbiota, the impact of dietary protein sources has only been studied to a minor extent. In this study, we examined the influence of different dietary protein sources regarding the effects of prebiotic oligosaccharides on the composition and metabolic activity of gut microbiota. Thirty female rats were fed casein and soy protein isolate with cellulose, raffinose (RAF), and fructooligosaccharides (FOS). Microbiota composition was examined by real‐time qPCR and denaturing gradient gel electrophoresis. Dietary protein source affected cecum microbiota; acetic acid concentration and Lactobacillus spp. populations were greater with soy protein than with casein. Prebiotic oligosaccharides had distinctive effects on gut microbiota; RAF increased the acetic acid concentration and Bifidobacterium spp. populations, and FOS increased the butyric acid concentration regardless of the dietary protein. Likewise, Bifidobacterium sp., Collinsella sp., and Lactobacillus sp. were detected in microbiota of the rats fed RAF, and Bacteroides sp., Roseburia sp., and Blautia sp. were seen in microbiota of the rats fed FOS. Interactions between dietary proteins and prebiotic oligosaccharides were observed with Clostridium perfringens group populations and cecum IgA concentration. RAF and FOS decreased C. perfringens group populations in casein‐fed rats, and the combination of soy protein and RAF substantially increased cecum IgA concentration. These results indicate that dietary proteins can differentially modulate the effects of prebiotic oligosaccharides on gut fermentation and microbiota, depending on the type of carbohydrate polymers involved.     

金柚幼果膳食纤维改善糖尿病小鼠的肠道健康

为了研究金柚幼果膳食纤维对小鼠肠道健康的影响。将小鼠随机分为6组,按照0.2mL/10g体重的剂量进行灌胃。灌胃4周后,HE染色观察结肠组织损伤情况,收集小鼠粪便及结肠,测定水分、pH值和短链脂肪酸(SCFAs)含量。通过试剂盒提取各组小鼠粪便细菌总DNA,利用高通量测序技术对16S rRNA基因的V4区域进行测序,最后通过生物信息学方法对测序数据进行分析,并结合前期研究进行血糖相关指标与肠道菌群的相关性分析。结果显示:金柚幼果膳食纤维实验组可提高糖尿病小鼠在结肠及粪便中的水分含量,SCAFs含量,降低pH值水平,其中水分含量以TDF组上升最为显著,分别提高了8.04%和21.36%;SCAFs含量在结肠、粪便中均在TDF组有显著变化,分别升高475.19%(乙酸)和702.56%(正丁酸)。同时HE染色实验表明金柚幼果膳食纤维在一定程度上可以减缓因糖尿病导致的肠道黏膜损伤;其能够促进有益菌群繁殖,同时抑制有害微生物增殖;该膳食纤维调节小鼠的血糖水平可能与其进入肠道后被益生菌发酵,产生短链脂肪酸有关。结果表明金柚幼果膳食纤维可以维持肠粘膜屏障的完整性,调节肠道菌群的结构,对小鼠的肠道健康具有改善调节的作用。     

In Vitro Fermentation Behavior of Isomalto/Malto‐Polysaccharides Using Human Fecal Inoculum Indicates Prebiotic Potential

1 Scope

This study characterize intestinal fermentation of isomalto/malto‐polysaccharides (IMMPs), by monitoring degradation of IMMPs, production of short chain fatty acids (SCFAs), lactic acid, and succinic acid as well as enzyme activity and microbiota composition.

2 Methods and results

IMMP‐94 (94% α‐(1→6) glycosidic linkages), IMMP‐96, IMMP‐27, and IMMP‐dig27 (IMMP‐27 after removal of digestible starch segments) are fermented batchwise in vitro using human fecal inoculum. Fermentation digesta samples are taken for analysis in time up till 48 h. The fermentation of α‐(1→6) glycosidic linkages in IMMP‐94, IMMP‐96, and IMMP‐dig27 starts after 12 h and finishes within 48 h. IMMP‐27 fermentation starts directly after inoculation utilizing α‐(1→4) linked glucosyl residues; however, the utilization of α‐(1→6) linked glucoses is delayed and start only after the depletion of α‐(1→4) linked glucose moieties. SCFAs are produced in high amounts with acetic acid and succinic acid being the major products next to propionic acid and butyric acid. The polysaccharide fraction is degraded into isomalto‐oligosaccharides (IMOs) mainly by extracellular enzymes. The smaller IMOs are further degraded by cell‐associated enzymes. Overall microbial diversity and the relative abundance of Bifidobacterium and Lactobacillus, significantly increase during the fermentation of IMMPs.

3 Conclusion

IMMP containing segments of α‐(1→6) linked glucose units are slowly fermentable fibers with prebiotic potential.     

山药多糖对2型糖尿病小鼠胰岛素抵抗的影响及作用机制

为研究山药多糖对2型糖尿病(type 2 diabetes mellitus,T2DM)小鼠胰岛素抵抗的影响及作用机制,选取SPF级C57BL/6小鼠,随机分为正常组、模型组、山药多糖(低、中、高剂量)组、二甲双胍组,采用链脲佐菌素(streptozocin,STZ)结合高脂饲料喂养法建立 T2DM 小鼠模型,连续灌胃多糖6周后取血清测定空腹血糖(fasting blood glucose,FBG)、空腹血清胰岛素(fasting insulin,FINS)、胰岛素抵抗指数(homeostasis model assessment for insulin resistance,HOMA-IR)及胰岛素耐量(insulin tolerance test,ITT)。取肝脏进行油红O染色,观察脂肪沉积情况,16S rRNA基因测序检测肠道菌群丰度,代谢组学检测其短链脂肪酸的含量。研究结果表明,各剂量山药多糖均能够显著降低小鼠的FBG、FINS、HOMA-IR(P＜0.01)。相比于模型组小鼠,山药多糖组小鼠的肠道菌群物种总量及多样性增加,厚壁菌门与拟杆菌门比值、变形菌门水平显著降低,乳酸菌属、阿克曼氏菌属水平显著提高,肠杆菌属、脱硫弧菌属水平显著降低。山药多糖显著提升小鼠肠道中短链脂肪酸含量 (P＜0.01),其中以丙酸、丁酸的上升趋势较为显著(P＜0.01)。研究结果表明,山药多糖可改善 T2DM 小鼠的糖脂代谢紊乱及胰岛素抵抗,其可能通过增加菌群物种总量及多样性,并改变其菌群群落比例及增加短链脂肪酸的含量,发挥生物活性。研究旨在为山药多糖的开发利用提供理论参考。