Liver-Gut-Microbiome Axis and Fatty acid absorption in Preterm Infants

项目摘要/摘要 目前的营养策略不能满足极低出生体重儿的需求，超过一半的婴儿正在发育。 营养不良、生长障碍和其他不良后果。长链多不饱和脂肪酸(LCPUFA) 对大脑和视网膜发育、免疫功能、炎症调节和健康至关重要。胎盘移位 LCPUFA的含量在妊娠晚期最高，但这种转移在早产时突然停止。当前 营养策略不能纠正出生后LCPUFA的不足。肝脏-肠道-微生物组轴对肠道的调节 脂肪和脂肪酸的消化、同化和吸收。肠道细菌代谢肠道脂肪和分泌物 通过胆盐水解酶和其他微生物改变脂质摄取和形成胆汁酸稳态的分子 酵素。反过来，饮食中的脂肪酸，包括LCPUFAs，直接和通过塑造肠道影响生理。 微生物群落组成和功能。目前还不清楚VLBW中未成熟的肠道微生物区系和胆汁酸 婴儿导致脂肪酸和LCPUFA吸收受损。我们已经证明，极低出生体重儿喂养供体 母乳损害了生长，肠道微生物区系的阿尔法多样性比喂养母乳的要少。我们 假设生长受损和α多样性降低是由于缺乏完整的脂肪酶引起的 供体乳的巴氏杀菌和脂肪酸吸收受损。我们已经证明了来自胆汁淤积剂的大便 生长受损的极低出生体重儿的微生物胆盐水解酶活性较低， 与未结合的极低出生体重儿相比，未结合的粪便胆汁酸和二次胆汁酸合成受损 胆汁淤积症。总而言之，这些结果表明，脂肪酸吸收受损、不成熟的 肝脏-肠道-微生物组轴，以及胆汁酸代谢改变。我们假设一个未成熟的肝脏-肠道- 微生物群轴缺乏关键的微生物胆汁酸修饰基因，导致胆汁酸组成改变 并损害脂肪酸和LCPUFAs的吸收。目的1：建立脂肪酸的纵向系数 未来极低出生体重儿队列中关键脂肪酸的吸收。脂肪吸收系数(CFA)将为 使用GC-MS计算72小时饮食摄入量和排泄量中不同的个体脂肪酸。 随着时间的推移，我们将使用线性建模来确定CFA的临床决定因素。目标2：量化亲属 微生物胆汁酸修饰基因和活性的丰度及其对胆汁酸的影响 早产儿的成分和脂肪酸吸收系数。总胆汁酸浓度和个体胆汁酸浓度 极低出生体重儿血清和粪便中胆汁酸修饰基因的检测 使用全基因组鸟枪法测序，基因拷贝数将通过qPCR进行确认。胆盐 水解酶活性将在体外进行定量测定。使用最先进的技术和分析工具，我们的 专家团队将促进我们对肠道微生物变化、胆汁酸动态平衡和脂肪酸的理解 极低出生体重婴儿的吸收，以确定增强营养的新机制和未来的治疗目标 并改善极低出生体重儿的脂肪吸收、生长和健康结局。

PROJECT SUMMARY/ABSTRACT Current nutritional strategies fail to meet the needs of very low birth weight infants, with more than half developing malnutrition, growth failure, and other poor outcomes. Long Chain Polyunsaturated Fatty Acids (LCPUFAs) are vital for brain and retinal development, immune function, inflammatory regulation, and health. Placental transfer of LCPUFAs is highest in the third trimester, but this transfer abruptly stops upon premature birth. Current nutritional strategies do not correct postnatal LCPUFA deficits. The Liver-Gut-Microbiome Axis regulates enteral fat and fatty acid digestion, assimilation, and absorption. Gut bacteria metabolize intestinal lipids and secrete molecules that alter lipid uptake and shape bile acid homeostasis via bile salt hydrolases and other microbial enzymes. In turn, dietary fatty acids including LCPUFAs impact physiology both directly and by shaping gut microbial community composition and function. It is unclear how immature gut microbiota and bile acids in VLBW infants contribute to impaired fatty acid and LCPUFA absorption. We have shown that VLBW infants fed donor milk have impaired growth and less alpha-diversity of gut microbiota than those fed maternal milk. We hypothesize that impaired growth and decreased alpha-diversity is caused by the lack of intact lipase due to pasteurization of donor milk and by impaired fatty acid absorption. We have shown that stool from cholestatic VLBW infants with impaired growth contains less microbial bile salt hydrolase enzymatic activity, fewer unconjugated fecal bile acids, and impaired secondary bile acid synthesis compared to VLBW infants without cholestasis. Together, these results suggest an association between impaired fatty acid absorption, an immature Liver-Gut-Microbiome Axis, and altered bile acid metabolism. We hypothesize that an immature Liver-Gut- Microbiome Axis lacks key microbial bile acid modifying genes, resulting in altered bile acid composition and impaired fatty acid and LCPUFAs absorption. Aim 1: Establish the longitudinal coefficient of fatty acid absorption of key fatty acids in a prospective VLBW infant cohort. Coefficients of fat absorption (CFA) will be calculated using GC-MS to measure different individual fatty acids from 72-hour dietary intakes and fecal losses. We will use linear modeling to identify clinical determinants of CFA over time. Aim 2: Quantify relative abundances of microbial bile acid modifying genes and activity and determine their impact on bile acid composition and fatty acid absorption coefficients in preterm infants. Total and individual bile acid concentrations in serum and stool from VLBW infants using MS. Microbial bile acid modifying genes will be identified in stool using whole metagenome shotgun sequencing and gene copy numbers will be confirmed by qPCR. Bile salt hydrolase enzyme activity will be quantified in vitro. Using state-of-the-art technologies and analytic tools, our expert team will advance our understanding of gut microbial alterations, bile acid homeostasis, and fatty acid absorption in VLBW infants to define novel mechanisms and future therapeutic targets to enhance nutrient uptake and to improve fat absorption, growth, and health outcomes in VLBW infants.