The metabolic basis for impaired bile acid synthesis in malnutrition

营养不良胆汁酸合成受损的代谢基础

• 批准号: 10501037
• 负责人: Geoffrey A Preidis
• 金额: $ 42.74万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-15 至 2027-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10501037
• 关键词: Acute; Address; Albumins; Amino Acids; Anorexia Nervosa; Bile Acid Biosynthesis Pathway; Bile Acids; Blood Coagulation Disorders; Blood Coagulation Factor; CYP7A1 gene; Cell Line; Cessation of life; Child; Child Malnutrition; Child Mortality; Cholesterol; Citric Acid Cycle; Complement; Data; Dependence; Dependovirus; Diet; Dietary Proteins; Enteral; Enzymes; Exhibits; Fat-Restricted Diet; Fat-Soluble Vitamin; Fatty acid glycerol esters; Functional disorder; Generations; Genes; Glucose; Goals; Growth; Health; Heme; Hepatocyte; Homeostasis; Hydroxycholesterols; Impairment; Intestines; Iron; Label; Lead; Life; Link; Liver; Liver Dysfunction; Malabsorption Syndromes; Malnutrition; Mass Spectrum Analysis; Measures; Metabolic; Metabolism; Mus; Nuclear; Nuclear Receptors; Nutrient; Nutritional; Outcome; Pathology; Pathway interactions; Process; Production; Protein-Restricted Diet; Proteins; Publishing; Receptor Activation; Refractory; Regimen; Reporting; Research; Role; Signal Transduction; Small Interfering RNA; Small for Gestational Age Infant; Sulfur; Supplementation; Testing; Therapeutic; Transcriptional Regulation; Vitamin K; Weight Gain; base; cofactor; dietary; dietary control; enzyme biosynthesis; experimental study; feeding; ferrochelatase; heme biosynthesis; improved outcome; intraperitoneal; iron deficiency; knock-down; mouse model; novel; novel therapeutics; nutrient absorption; overexpression; postnatal; prevent; protoporphyrin IX; receptor; response; succinyl-coenzyme A; therapy outcome; transcription factor

Malnutrition contributes to half of all global child deaths. Severe malnutrition interferes with the liver’s synthesis of albumin, complement and coagulation factors, and bile acids (BAs). BA deficiency impairs nutrient absorption and growth and alters signaling through nuclear receptors including farnesoid-X-receptor (FXR) to impact a wide range of processes. Using a mouse model of early postnatal malnutrition, we reported that decreased BA synthesis in malnutrition causes decreased FXR activation and decreased expression of FXR target genes including coagulation factors. The resulting malnutrition-induced coagulopathy can cause child mortality. It is not known why BA synthesis is impaired in malnutrition. Our published data and new preliminary data indicate malnutrition impairs the activity (not expression) of the rate-determining enzyme (CYP7A1) in the classic pathway of BA synthesis due to depletion of the essential cofactor heme. We present novel evidence that restoring heme increases BA synthesis. We now seek to understand why heme synthesis is impaired in malnutrition. Heme is generated from tricarboxylic acid (TCA) cycle products and enzymes that require iron- sulfur (Fe-S) clusters for stability. Fe-S clusters are derived from both Fe and S-containing amino acids (AAs), which are found in dietary protein or generated by transsulfuration. Like most low-protein diets, our mouse malnourishing diet is deficient in S-containing AAs. The mice exhibit decreased expression of transsulfuration and Fe-S cluster-dependent TCA cycle enzymes, suggesting that deficiency of S-containing AAs and Fe-S clusters drives liver dysfunction in malnutrition. Indeed, we decreased BA synthesis by 50% by maintaining hepatocytes in low-AA media, and we restored BA production by adding S-containing AAs (but not other AAs). Thus, we hypothesize that deficiency of S-containing AAs in malnutrition impairs BA synthesis by disrupting TCA cycle function, heme biosynthesis, and CYP7A1 activity. Our Specific Aims are to 1) Characterize in AA- deficient hepatocytes TCA cycle dysfunction by quantifying flux of labeled glucose through the TCA cycle and measuring expression levels and activity of Fe-S cluster-dependent TCA cycle enzymes before and after heme treatment; 2) Define the role of S-containing AAs and heme in BA synthesis by measuring BA synthesis by hepatocytes maintained in low-AA media and treated in a high-throughput manner with combinations of AAs and heme and using adeno-associated virus or siRNA to manipulate levels of transsulfuration and Fe-S cluster- dependent enzymes; and 3) Determine whether a novel nutritional therapeutic can rescue BA synthesis in malnutrition by feeding mice the malnourishing diet supplemented by S-containing AAs, then quantifying TCA cycle function, heme synthesis, and BA production in primary hepatocytes. Expected outcomes include elucidation of a novel link between malnutrition, TCA cycle and heme homeostasis, and BA synthesis. The research is significant because of its potential to develop a scalable AA-based therapeutic to restore liver synthetic function and treat malnutrition in children.

营养不良占全球儿童死亡总数的一半。严重营养不良干扰肝脏合成 白蛋白、补体和凝血因子以及胆汁酸(BAs)。BA缺乏损害营养吸收 并通过包括法尼类X受体(FXR)在内的核受体生长和改变信号来影响广泛的 流程的范围。使用出生后早期营养不良的小鼠模型，我们报告了降低BA 营养不良的合成导致FXR活性降低和FXR靶基因表达减少 包括凝血因子。由此导致的营养不良引起的凝血障碍可能会导致儿童死亡。它是 不知道营养不良时BA合成受损的原因。我们公布的数据和新的初步数据 表明营养不良损害了经典的速度决定酶(CYP7A1)的活性(而不是表达 基本辅因子血红素耗尽所致的BA合成途径。我们提出了新的证据 恢复血红素可增加BA的合成。我们现在试图了解为什么血红素的合成在 营养不良。血红素是由三羧酸(TCA)循环产物和需要铁的酶产生的- 硫(铁-S)团簇为稳定。铁-S簇合物由含铁和S的氨基酸组成 (AAS)，在饮食蛋白质中发现或通过硫化产生。像大多数低蛋白质饮食一样，我们的小鼠 含S的氨基酸缺乏营养不良的饮食。小鼠表现出转硫化的表达减少 和铁-S簇状依赖的三氯乙酸循环酶，提示S-AAs和铁-S缺乏 在营养不良时，聚集性会导致肝功能障碍。事实上，我们通过维持BA合成减少了50% 在低AA的培养液中培养肝细胞，我们通过添加含S的氨基酸(而不是其他氨基酸)来恢复BA的产生。 因此，我们假设营养不良时，含有S的氨基酸缺乏会通过干扰BA的合成而损害BA的合成。 TCA循环功能、血红素生物合成和细胞色素P7A1活性。我们的具体目标是1)在AA- 缺陷肝细胞TCA循环功能障碍通过TCA循环定量标记葡萄糖的流量和 测定血红素前后铁-S簇依赖的三氯乙酸循环酶的表达水平和活性 处理；2)确定含有S的氨基酸和血红素在BA合成中的作用，通过测量BA合成 肝细胞在低AA培养液中维持，并以高通量方式与AAS和 血红素和使用腺相关病毒或小干扰RNA来操纵硫化和铁-S簇的水平- 依赖的酶；以及3)确定一种新的营养疗法是否可以挽救BA的合成 用含S氨基酸的营养不良饲料喂养小鼠的营养不良，然后定量测定三氯乙酸 原代肝细胞的循环功能、血红素合成和BA的产生。预期结果包括 阐明营养不良、TCA循环、血红素动态平衡和BA合成之间的新联系。 这项研究意义重大，因为它有潜力开发一种可扩展的基于AA的治疗方法来恢复肝脏 综合功能与治疗儿童营养不良。