Mechanism of Activation of Probiotic Bifidobacteria by Prebiotic Milk Glycans

描述（由申请人提供）：益生菌和益生元是美国公众经常使用的CAM干预措施，以促进肠道健康和健康。乳酸菌和双歧杆菌等有益细菌的存在，无论是作为益生菌外源传递还是通过益生元富集，都与积极的健康影响有关，包括减少肠道炎症、腹泻和过敏反应。然而，目前我们对这些生物效应背后的作用机制的理解还很缺乏。牛奶低聚糖是自然进化的益生元底物，促进双歧杆菌在婴儿宿主内的富集和相互作用。加州大学戴维斯分校牛奶生物活性项目的研究表明，母乳中的低聚糖被婴儿携带的双歧杆菌菌株所利用，这些菌株在低聚糖消费方面表现出独特的偏好。此外，对婴儿双歧杆菌和两歧双歧杆菌这两种在牛奶低聚糖上生长良好的菌株的基因组分析揭示了在这些聚糖上生长时特异性诱导的独特基因簇。进一步的分析表明，乳聚糖的生长导致双歧杆菌与宿主上皮的相互作用增强。我们假设牛奶低聚糖和同源婴儿双歧杆菌之间的进化驱动关系为增强益生菌在人类宿主内的持久性和与人类宿主的相互作用提供了一个模型。为了解决这一假设，我们将通过以下具体目标获得双歧杆菌对这些独特乳聚糖的特定分解代谢的机制见解，并全面绘制其对双歧杆菌-宿主相互作用的影响：全面表征人乳和牛乳低聚糖，并开发其大规模分离和生产方法，用于功能研究。2. 为了完全表征双歧杆菌的转运体和糖基水解酶，有必要解构这些复杂的牛奶低聚糖。3. 探讨乳低聚糖对双歧杆菌与宿主相互作用的影响。这些特异性目标的成功完成将揭示母乳低聚糖促进母乳喂养婴儿胃肠道双歧杆菌保护性富集的具体机制。此外，我们将把这些发现转化为结构和功能相当的牛奶低聚糖，这是一种商业上可获得的底物，可以很容易地输送到CAM食品和针对肠道健康的疗法中。这一应用的意义在于对合成菌（牛奶低聚糖和同源双歧杆菌）应用的有益作用有了更深入的机制理解，从而为更好地解决以肠道生态失调为标志的各种疾病提供了策略和诊断措施。

DESCRIPTION (provided by applicant): Probiotics and prebiotics are CAM interventions frequently employed by the American public to promote intestinal health and wellness. The presence of beneficial bacteria such as lactobacilli and bifidobacteria, whether delivered exogenously as probiotics or enriched via prebiotics, has been linked to positive health effects including reduction of gut inflammation, diarrhea and allergic reactions. At present however, our understanding of the mechanism of action underlying these biological effects is significantly lacking. Milk oligosaccharides are naturally-evolved prebiotic substrates that facilitate bifidobacterial enrichment and interaction within the infant host. Work from the UC Davis Milk Bioactives Program has shown that human milk oligosaccharides are utilized by select infant-borne bifidobacterial strains that demonstrated unique preferences in oligosaccharide consumption. In addition, genomic analysis of Bifidobacterium infantis and Bifidobacterium bifidum, two strains that grow well on milk oligosaccharides, has revealed unique gene clusters that are specifically induced during growth on these glycans. Further analysis has revealed that growth on milk glycans results in enhanced bifidobacterial interaction with the host epithelium. We hypothesize that the evolutionarily-driven relationship between milk oligosaccharides and cognate infant-borne bifidobacteria provides a model for enhanced probiotic persistence within, and interaction with, the human host. To address this hypothesis we will gain mechanistic insight into the specific catabolism of these unique milk glycans by bifidobacteria and comprehensively map their influence on bifidobacteria-host interaction via the following Specific Aims: 1. To comprehensively characterize human and bovine milk oligosaccharides and develop methods for their large scale fractionation and production for functional studies. 2. To completely characterize the bifidobacterial transporters and glycosyl hydrolases necessary to deconstruct these complex milk oligosaccharides. 3. To examine the influence of milk oligosaccharides on the interaction between bifidobacteria and the host. Successful completion of these Specific Aims will reveal specific mechanisms by which human milk oligosaccharides facilitate a protective enrichment of bifidobacteria in the gastrointestinal tract of breast fed infants. In addition, we will translate these findings to structurally and functionally equivalent bovine milk oligosaccharides, a commercially accessible substrate that can be easily delivered into CAM foods and therapies aimed at gut health. The significance of this application is a greater mechanistic understanding of the beneficial effects of synbiotic (milk oligosaccahrides plus cognate bifidobacteria) applications thereby providing both strategies and diagnostic measures to better address a variety of disorders marked by intestinal dysbiosis.