Microbial provision of essential amino acids: protein conservation in hibernation

微生物提供必需氨基酸：冬眠中蛋白质的保存

• 批准号: 10455080
• 负责人: Khrystyne Duddleston
• 金额: $ 20.44万
• 依托单位: UNIVERSITY OF ALASKA FAIRBANKS
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-16 至 2024-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10455080
• 关键词: Address; Amino Acids; Anabolism; Attention; Bacteria; Collection; Communities; Data; Deposition; Development; Diet; Dietary Proteins; Diffuse; Disease; Elderly; Essential Amino Acids; Family suidae; Fasting; Fatty acid glycerol esters; Future; Gastrointestinal tract structure; Gene Expression Profile; Genes; Genetic; Goals; Growth; Health; Hibernation; Human; Impairment; In Vitro; Injury; Isotope Labeling; Knowledge; Label; Life Style; Liver; Measures; Metabolic; Metabolism; Metagenomics; Microbe; Muscle; Muscular Atrophy; Nitrogen; Obesity; Pathway interactions; Peritoneal; Phenotype; Physiological; Physiology; Plasma; Play; Process; Production; Protein Biosynthesis; Proteins; Rattus; Reproducibility; Research; Risk; Role; Salvelinus; Sampling; Seasons; Squirrel; Structure; Techniques; Testing; Thinness; Tissues; Urea; Urea Nitrogen; Wasting Syndrome; Work; age-related muscle loss; aminoacid biosynthesis; arctic ground squirrel; density; design; effective intervention; experimental study; fight against; gene synthesis; gut microbes; gut microbiome; gut microbiota; in vivo; member; metabolomics; metatranscriptomics; microbial; microbial community; microbiota; muscle form; next generation sequencing; nitrogen metabolism; preservation; prevent; sarcopenia; sarcopenic obesity; therapeutic target

Project Summary Project 2 – Microbially-liberated urea nitrogen and host essential amino acids. The elderly are particularly susceptible to sarcopenic obesity (SAO), whereby a loss of lean mass (e.g., muscle) accompanies an increase in fat, and which is difficult to treat via life style changes (e.g., diet) designed to target obesity. Although numerous studies have addressed the role of diet and gut microbes as factors in diseases such as obesity, the potential beneficial role of gut microbes in preventing loss of lean mass in disorders such as SAO has received comparably less attention. Urea-nitrogen salvage (UNS) is the process whereby urea is degraded by gut microbes releasing nitrogen that can be utilized by gut microbes to produce amino acids, or be reabsorbed and used by the host. UNS likely plays an important role in nitrogen metabolism in humans, and evidence suggests both UNS and the production of essential amino acids (EAAs) by gut microbes may have important impacts on human health. Yet, despite the availability of microbially-liberated urea-nitrogen (MLUN) for EAA synthesis in the gut, these two microbial components of host nitrogen metabolism have been studied primarily independently and with little focus on the structure and function of the gut microbial community. The goal of this project is to determine the gut microbiota potential for use of MLUN in synthesis of EAAs, and demonstrate the provision of microbially-synthesized EAAs for host protein synthesis. We use the arctic ground squirrel (AGS) as a study species, as AGS are able to preserve lean mass during their long hibernation season. Our hypothesis is that MLUN in the gut of AGS is utilized by gut microbes for synthesis of EAAs which are incorporated into host tissues during hibernation. Our approach relies upon simultaneous analyses of the structure and function of the gut microbial community, microbial production of EAAs using MLUN, and incorporation of microbial-derived EAAs in host tissues under varying conditions of host dietary protein availability and physiological state. In Specific Aims 1 and 2 we utilize isotopically labeled urea (13C and 15N), which when injected intra-peritoneally diffuses into the gut and becomes available for urea degrading microbes. After injecting hibernating squirrels with labeled urea, we will measure 13CO2 in breath (to confirm ureolytic activity), determine the EAA synthesis potential of the gut microbiota using next generation sequencing techniques (metagenomics and metatranscriptomics to look for EAA biosynthesis genes) and metabolomics (15N-NMR to search for labeled EAAs in gut contents), and determine if AGS incorporate microbially-derived EAAs into host tissues (15N-NMR). In Specific Aim 3, we will isolate and characterize bacteria from the GI tract of AGS and determine culture conditions necessary for growth to experiment with mock gut communities in the future. Our approach promises to yield an increased knowledge of the role of the gut microbial community in host nitrogen metabolism and protein conservation, contributing to our understanding of the relationship between the gut microbial community and human health.

项目摘要项目 2 – 微生物释放的尿素氮和宿主必需氨基酸。 老年人特别容易患肌肉减少性肥胖（SAO），即瘦体重减少（例如， 肌肉）伴随着脂肪的增加，并且很难通过设计的生活方式改变（例如饮食）来治疗 以针对肥胖。尽管许多研究已经探讨了饮食和肠道微生物作为影响因素的作用 肥胖等疾病、肠道微生物在预防瘦体重损失方面的潜在有益作用 SAO 等疾病受到的关注相对较少。尿素氮回收（UNS）过程 尿素被肠道微生物降解，释放出氮，肠道微生物可以利用氮来生产尿素 氨基酸，或被宿主重新吸收和利用。 UNS 可能在氮代谢中发挥重要作用 在人类中，有证据表明 UNS 和肠道产生必需氨基酸 (EAA) 微生物可能对人类健康产生重要影响。然而，尽管可以获得微生物释放的 尿素氮 (MLUN) 用于肠道内 EAA 合成，宿主氮的这两种微生物成分 代谢主要是独立研究的，很少关注代谢的结构和功能 肠道微生物群落。该项目的目标是确定使用 MLUN 的肠道微生物群潜力 参与 EAA 的合成，并证明为宿主蛋白提供微生物合成的 EAA 合成。我们使用北极地松鼠 (AGS) 作为研究物种，因为 AGS 能够保留瘦体重 在他们漫长的冬眠季节。我们的假设是 AGS 肠道中的 MLUN 被肠道微生物利用 用于合成 EAA，并在冬眠期间掺入宿主组织中。我们的方法依赖于 同时分析肠道微生物群落的结构和功能、微生物生产 使用 MLUN 的 EAA，以及在不同条件下将微生物衍生的 EAA 掺入宿主组织中 宿主膳食蛋白质的可用性和生理状态。在具体目标 1 和 2 中，我们利用同位素标记 尿素（13C 和 15N），腹膜内注射时会扩散到肠道中并可用于 尿素降解微生物。向冬眠松鼠注射标记尿素后，我们将测量 13CO2 呼吸（确认尿素分解活性），使用下一步确定肠道微生物群的 EAA 合成潜力 世代测序技术（宏基因组学和宏转录组学，寻找 EAA 生物合成 基因）和代谢组学（15N-NMR，用于搜索肠道内容物中标记的 EAA），并确定 AGS 是否 将微生物衍生的 EAA 掺入宿主组织中 (15N-NMR)。在具体目标 3 中，我们将隔离并 表征来自 AGS 胃肠道的细菌，并确定生长所需的培养条件 未来尝试模拟肠道社区。我们的方法有望增加知识 肠道微生物群落在宿主氮代谢和蛋白质保护中的作用，有助于 我们对肠道微生物群落与人类健康之间关系的理解。