The art of targeting gut microbiota for tackling human obesity

Recently, a great deal of interest has been expressed regarding strategies to tackle worldwide obesity because of its accelerated wide spread accompanied with numerous negative effects on health and high costs. Obesity has been traditionally associated with an imbalance in energy consumed when compared to energy expenditure. However, growing evidence suggests a less simplistic event in which gut microbiota plays a key role. Obesity, in terms of microbiota, is a complicated disequilibrium that presents many unclear complications. Despite this, there is special interest in characterizing compositionally and functionally the obese gut microbiota with the help of in vitro, animal and human studies. Considering the gut microbiota as a factor contributing to human obesity represents a tool of great therapeutic potential. This paper reviews the use of antimicrobials, probiotics, fecal microbial therapy, prebiotics and diet to manipulate obesity through the human gut microbiota and reveals inconsistencies and implications for future study.     

肠道微生物多样性与能量代谢调控及肥胖关系的研究进展

肠道微生物与宿主之间相互选择,构成了一个相对稳定的超有机体。宿主基因型和遗传关系影响肠道微生物的生态学特征,而肠道微生物发酵肠道内多糖,为宿主提供可吸收利用的养分,增强肠道对养分吸收的能力。同时,肠道微生物还影响一些转录因子的活性,调控宿主基因的表达,增强宿主甘油三酯的合成和脂肪沉积,减少脂肪酸氧化分解,调控宿主能量代谢。     

Relationship between gut microbiota and development of T cell associated disease

The interplay between the immune response and the gut microbiota is complex. Although it is well-established that the gut microbiota is essential for the proper development of the immune system, recent evidence indicates that the cells of the immune system also influence the composition of the gut microbiota. This interaction can have important consequences for the development of inflammatory diseases, including autoimmune diseases and allergy, and the specific mechanisms by which the gut commensals drive the development of different types of immune responses are beginning to be understood. Furthermore, sex hormones are now thought to play a novel role in this complex relationship, and collaborate with both the gut microbiota and immune system to influence the development of autoimmune disease. In this review, we will focus on recent studies that have transformed our understanding of the importance of the gut microbiota in inflammatory responses.     

Screening for lactobacilli with probiotic properties in the infant gut microbiota

Lactobacilli are believed to be beneficial for the human hosts and are currently being evaluated as potentially probiotic bacteria. In this study, Lactobacillus strains were isolated from infant faeces and were examined in vitro for potential probiotic properties. Faecal specimens from 63 healthy, full-term infants were collected at 4, 30 and 90 days after delivery. Seventy-four Lactobacillus strains were isolated and one or more different phenotypes from each infant (n = 44) were selected for further testing. The bacterial isolates were identified mainly as L. gasseri, L. crispatus, Lactobacillus paracasei, L. salivarius, L. fermentum after amplification and sequencing of 16s rRNA gene. The strains were examined for acid and bile tolerance, adhesion to Caco-2 cells, antibiotic susceptibility and antimicrobial activity against selected enteric pathogens. The great majority of the isolated lactobacilli were susceptible to ampicillin, amoxicillin/clavulanic acid, tetracycline, erythromycin, cephalothin, chloramphenicol and rifampicin. Resistance to vancomycin or bacitracin was detected to 34% of the strains. Twenty strains out of forty-four exhibited significant tolerance to bile salts. Those strains were subsequently tested for resistance to low pH conditions (pH 2 and 3). Interestingly, 85% (17 strains) of the tested lactobacilli remained unaffected at pH 3 after 3 h of incubation, 6 strains were found resistant at pH 2 after 1.5 h and only 2 strains found resistant after 3 h of incubation. Two of the strains were able to adhere to Caco-2 cells. In conclusion, two isolates fulfilled the in vitro probiotic criteria and are good candidates for further in vivo evaluation.     

Therapeutic interventions and mechanisms associated with gut microbiota-mediated modulation of immune checkpoint inhibitor responses

The link between the gut microbiome and responsiveness to immune checkpoint inhibitor (ICI) therapy is now well established. New therapeutic opportunities exploiting this relationship are being developed with the goal of augmenting ICI efficacy. In this review, we summarize the foundational research establishing these interactions and discuss the mechanisms and novel therapeutic options associated with this gut microbiome-ICI connection.     

The impact of bacteriophages on probiotic bacteria and gut microbiota diversity

The human body is colonized by a vast array of bacteria whose diversity is largely affected by predation of bacteriophages. Here, we discussed the impact of bacteriophages on the composition of human intestinal microbiota as well as on the survival and thus efficacy of probiotic bacteria in the human gut.     

肠道硫酸盐还原菌DGGE分析技术的建立

目的 建立分析肠道内硫酸盐还原菌(Sulfate-reducing bacteria,SRB)组成的变性梯度凝胶电泳(Denaturing gradient gel electrophoresis,DGGE)技术,并用于分析10例健康人粪便样品中的SRB组成.方法 从GenBank中下载13株脱硫弧菌科细菌的腺苷酰硫酸还原酶α亚基基因(aprA)的序列,利用Clustal X、Simulated PCR (SPCR)软件比较、评估了2对针对aprA 基因的引物(AprA-3-FW/APS-RV和AprA-1-FW/AprA-5-RV)用于扩增粪便样品中的SRB的特异性.确定PCR引物和条件,进一步摸索并建立DGGE分析体系.结果 Clustal X和SPCR软件分析的结果均表明引物AprA-3-FW/APS-RV优于AprA-1-FW/AprA-5-RV.实际PCR的结果也显示AprA-1-FW/AprA-5-RV扩增效率低并有非特异扩增.建立DGGE体系,对10例健康人肠道中SRB的分析显示,每个个体肠道中SRB的种类有l到5种不等.结论 基于aprA序列的DGGE技术是分析肠道SRB组成的有效方法.     

Comparison of DNA extraction methods for human gut microbial community profiling

The human gut harbors a vast range of microbes that have significant impact on health and disease. Therefore, gut microbiome profiling holds promise for use in early diagnosis and precision medicine development. Accurate profiling of the highly complex gut microbiome requires DNA extraction methods that provide sufficient coverage of the original community as well as adequate quality and quantity. We tested nine different DNA extraction methods using three commercial kits (TianLong Stool DNA/RNA Extraction Kit (TS), QIAamp DNA Stool Mini Kit (QS), and QIAamp PowerFecal DNA Kit (QP)) with or without additional bead-beating step using manual or automated methods and compared them in terms of DNA extraction ability from human fecal sample. All methods produced DNA in sufficient concentration and quality for use in sequencing, and the samples were clustered according to the DNA extraction method. Inclusion of bead-beating step especially resulted in higher degrees of microbial diversity and had the greatest effect on gut microbiome composition. Among the samples subjected to bead-beating method, TS kit samples were more similar to QP kit samples than QS kit samples. Our results emphasize the importance of mechanical disruption step for a more comprehensive profiling of the human gut microbiome.     

肠道菌群代谢作用与人体健康关系的研究进展

人体肠道内寄居的大量共生微生物可以通过多方面作用影响人体健康,特别是肠道内菌群的代谢作用,及与人体自身代谢的交互作用在人类的健康促进与疾病的发生、发展中起着重要作用。本文从正反两面讨论了肠道菌群代谢作用对人体健康的影响,并进一步探讨了肠道菌群代谢在健康监测、疾病的预防与治疗,以及个体化医疗方面的运用。     

Beyond genetics. Influence of dietary factors and gut microbiota on type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease ultimately leading to destruction of insulin secreting β-cells in the pancreas. Genetic susceptibility plays an important role in T1D etiology, but even mono-zygotic twins only have a concordance rate of around 50%, underlining that other factors than purely genetic are involved in disease development. Here we review the influence of dietary and environmental factors on T1D development in humans as well as animal models. Even though data are still inconclusive, there are strong indications that gut microbiota dysbiosis plays an important role in T1D development and evidence from animal models suggests that gut microbiota manipulation might prove valuable in future prevention of T1D in genetically susceptible individuals.     

Similar bifidogenic effects of prebiotic-supplemented partially hydrolyzed infant formula and breastfeeding on infant gut microbiota

The aim of the study was to assess the quantitative and qualitative differences of the gut microbiota in infants. We evaluated gut microbiota at the age of 6 months in 32 infants who were either exclusively breast-fed, formula-fed, nursed by a formula supplemented with prebiotics (a mixture of fructo- and galacto-oligosaccharides) or breast-fed by mothers who had been given probiotics. The Bifidobacterium, Bacteroides, Clostridium and Lactobacillus/Enterococcus microbiota were assessed by the fluorescence in situ hybridization, and Bifidobacterium species were further characterized by PCR. Total number of bifidobacteria was lower among the formula-fed group than in other groups (P=0.044). Total amounts of the other bacteria were comparable between the groups. The specific Bifidobacterium microbiota composition of the breast-fed infants was achieved in infants receiving prebiotic supplemented formula. This would suggest that early gut Bifidobacterium microbiota can be modified by special diets up to the age of 6 months.     

肥胖相关的肠道微生物群落结构动力学与功能解析研究

肥胖及相关的慢性代谢性疾病近年来已经成为威胁全球的公共健康问题。越来越多的证据表明,在宿主的营养、免疫和代谢中有不可替代的作用的肠道菌群不仅可以通过调节宿主脂肪吸收存储相关的基因,影响后者的能量平衡,更重要的是其结构失调导致宿主循环系统中内毒素增加,诱发慢性、低水平炎症,导致肥胖和胰岛素抵抗。运用微生物分子生态学、元基因组学和代谢组学的方法,揭示与代谢性疾病相关的菌群结构失调,并鉴定出相关的特定细菌类群及其功能,使得通过以菌群为靶点的营养干预手段防止慢性代谢性疾病成为可能,将带来代谢性疾病预防和控制策略的革命性的变化。     

Beneficial modulation of the gut microbiota

The human gut microbiota comprises approximately 100 trillion microbial cells and has a significant effect on many aspects of human physiology including metabolism, nutrient absorption and immune function. Disruption of this population has been implicated in many conditions and diseases, including examples such as obesity, inflammatory bowel disease and colorectal cancer that are highlighted in this review. A logical extension of these observations suggests that the manipulation of the gut microbiota can be employed to prevent or treat these conditions. Thus, here we highlight a variety of options, including the use of changes in diet (including the use of prebiotics), antimicrobial-based intervention, probiotics and faecal microbiota transplantation, and discuss their relative merits with respect to modulating the intestinal community in a beneficial way.     

Contribution of gut bacteria to digestion and development of the velvetbean caterpillar, Anticarsia gemmatalis

Bacteria colonies from gut homogenates of fifth instar velvetbean caterpillars (Lepidoptera: Noctuidae) were subjected to antibiotic sensitivity experiments using discs containing 22 antibiotics. The antibiotic tetracycline provided the best results, followed by chloramphenicol. Tetracycline also provided higher inhibition of colony forming units than chloramphenicol and was therefore provided to the caterpillars in increasing diet concentrations to assess the contribution of gut bacteria to their digestion and development. The activity of proteases (general), serine-proteinases and lipases were significantly suppressed by tetracycline. Concentration-inhibition curves were successfully established for tetracycline and this antibiotic was effective in suppressing them, particularly serine-proteinases, suggesting that gut bacteria may significantly contribute with lipid- and mainly protein-digestion in velvetbean caterpillars. Increased diet concentrations of tetracycline led only to mild increase in insect mortality (ca. 20%), with the surviving insects showing faster development (≤4 days) and higher pupa weight (<0.04 mg) with increased concentrations of tetracycline. Therefore, the gut bacteria inhibited by tetracycline does not seem to play a crucial role in the survival and development of the velvetbean caterpillar, but may be important in the adaptation of this pest species to hosts rich in protease inhibitors, such as soybean.     

Oral supplementation of Bifidobacterium longum strain BR-108 alters cecal microbiota by stimulating gut immune system in mice irrespectively of viability

Effect on cecal microbiota and gene expression of various cytokines in ileal Peyer’s patches and cecal tissues were compared between viable and heat-killed Bifidobacterium longum strain BR-108 (BR-108) using a mouse model. Irrespectively of viability, oral supplementation of BR-108 altered the cecal microbiota and stimulated gene expression of cytokines such as IL-6 and IL-10 in ileal Peyer’s patches and cecal tissue of mice. In addition, BR-108 supplementation significantly affected the relative abundance of bacterial genera and family, Oscillospira, Bacteroides and S24-7. The abundance of these bacterial genera and family strongly correlated with gene expression induced by BR-108. This study demonstrated that the effect of heat-killed BR-108 on the mouse cecal microbiota is similar to that of viable BR-108, most likely due to stimulation of the gut immune system by both heat-killed and viable BR-108 is also similar.     

造血干细胞移植术对肠道菌群结构的影响

目的监测造血干细胞移植术（Hematopoietic stem cell transplantation,HSCT）前后肠道菌群结构的动态变化。方法收集3例造血干细胞移植患者手术前后8个时间点的粪便样品,提取样品总DNA进行16S rRNA基因的V3区的bar coded 454焦磷酸测序,并用MANOVA、聚类分析、Pearson相关等统计方法对菌群结构的变化进行动态分析。结果 HSCT移植前,经过放、化疗及预防性抗生素治疗,患者的肠道菌群结构和组成发生显著的改变,多样性明显减少;移植4周后,菌群多样性有恢复的趋势,但菌群结构和组成与治疗前仍有明显的差异。整个HSCT过程中,Escherichia/Shigella及Enterococcus属变成肠道中最优势的细菌类群。结论肠道菌群结构在HSCT术前已发生显著的改变,机会致病菌Escherichia/Shigella及Enterococcus属成为HSCT患者肠道中最优势的细菌类群。     

肠道微生物与1型糖尿病的相关性研究

1型糖尿病(type 1 diabetes, T1D)是一种自身免疫性疾病,越来越多的证据支持肠道菌群是T1D发病的重要因素。在T1D发生前,观察到肠道通透性发生改变,使抗原透过肠黏膜进而攻击胰岛β细胞。患有T1D宿主体内的肠道微生物也与健康宿主的微生物有别,其调节性T细胞、Toll样受体(toll-like receptor, TLR)、丁酸、粘蛋白、胰高血糖素样肽-1(glucagon-likepeptide1,GLP-1)等可能与T1D有关。尽管通过细菌定植促进自身免疫的机制在糖尿病动物模型中虽已发现,但有些问题目前尚不清楚。现就肠道黏膜通透性与T1D的关系、宿主体内微生物组成的变化、肠道微生物与T1D的相关性作一阐述。     

An opportunistic pathogen isolated from the gut of an obese human causes obesity in germfree mice

Lipopolysaccharide endotoxin is the only known bacterial product which, when subcutaneously infused into mice in its purified form, can induce obesity and insulin resistance via an inflammation-mediated pathway. Here we show that one endotoxin-producing bacterium isolated from a morbidly obese human''s gut induced obesity and insulin resistance in germfree mice. The endotoxin-producing Enterobacter decreased in relative abundance from 35% of the volunteer''s gut bacteria to non-detectable, during which time the volunteer lost 51.4 kg of 174.8 kg initial weight and recovered from hyperglycemia and hypertension after 23 weeks on a diet of whole grains, traditional Chinese medicinal foods and prebiotics. A decreased abundance of endotoxin biosynthetic genes in the gut of the volunteer was correlated with a decreased circulating endotoxin load and alleviated inflammation. Mono-association of germfree C57BL/6J mice with strain Enterobacter cloacae B29 isolated from the volunteer''s gut induced fully developed obesity and insulin resistance on a high-fat diet but not on normal chow diet, whereas the germfree control mice on a high-fat diet did not exhibit the same disease phenotypes. The Enterobacter-induced obese mice showed increased serum endotoxin load and aggravated inflammatory conditions. The obesity-inducing capacity of this human-derived endotoxin producer in gnotobiotic mice suggests that it may causatively contribute to the development of obesity in its human host.     

Proteomics,human gut microbiota and probiotics

The various bacterial communities associated with humans have many functions and the gut microbiota has a major role in the host. Bacterial imbalance in the gut, known as dysbiosis, has therefore been linked to several diseases. Probiotics, that is, microbial strains that have beneficial effects on the host, are thought to benefit this intestinal ecosystem. Hence, knowledge of the gut microbiota composition and an understanding of its functionalities are of interest. Recently, efforts have focused on developing new high-throughput techniques for studying microbial cells and complex communities. Among them, proteomics is increasingly being used. The purpose of this article is to focus on the recent development of this technology and its usefulness in analyzing the human gut ecosystem and probiotic strains.     

肠道微生态系统及其与宿主的协同进化

肠道微生态系统是寄生在宿主肠道内的微生物的总和。微生物进入肠道后,通过一个复杂的过程形成群落,与宿主之间相互作用,形成共生关系。宿主客观上为微生物提供生存和进化场所,微生态系统为宿主提供营养物质、刺激肠道组织的发育、刺激宿主肠道免疫系统的发育、影响宿主能量代谢、协助宿主降解有毒物质、影响宿主生殖活动和寿命等功能。作为一个进化的系统,微生态系统的物种多样性和丰富度对维持宿主正常生理功能具有重要作用,但同时又受宿主的影响,物种间相互作用和宿主-微生物间的相互作用是微生态系统进化的动力。进化主要表现在微生物和宿主基因组上发生适应性变化。因此,系统生态学的理论对理解肠道微生态系统的运行机制和临床应用具有重要指导作用。