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

基本信息

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
项目类别：
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

项目摘要

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.

营养不良造成了全球儿童死亡的一半。严重的营养不良干扰肝脏的合成白蛋白，完成和凝结因子和胆汁酸（BAS）。 BA缺乏症会损害营养滥用通过包括Farneoid-X受体（FXR）（FXR）的核受体的生长并改变信号传导，以影响广泛过程范围。使用早期产后营养不良的小鼠模型，我们报道了BA降低营养不良中的合成导致FXR激活降低和FXR靶基因表达降低包括凝血因子。由此产生的营养不良诱导的凝血病可引起儿童死亡率。这是不知道为什么在营养不良中会损害BA合成。我们已发布的数据和新的初步数据表明营养不良会损害经典酶（CYP7A1）的活性（非表达）由于必需辅因子血红素的耗竭而导致的BA合成途径。我们提出了新的证据恢复血红素会增加BA合成。我们现在试图了解为什么血红素合成受损营养不良。血红素是由需要铁 - 硫（Fe-S）簇以实现稳定性。 Fe-S簇均来自Fe和S含S的氨基酸（AAS），在饮食蛋白中发现或通过过性产生。像大多数低蛋白饮食一样，我们的鼠标营养不良的饮食缺乏含S的AAS。小鼠暴露于过丝的表达降低和依赖Fe-S聚类依赖性的TCA循环酶，表明含S AS和Fe-S的缺乏簇在营养不良中驱动肝功能障碍。确实，我们通过维护将BA合成提高了50％低AA培养基中的肝细胞，我们通过添加含S的AAS（而不是其他AAS）来恢复BA的生产。这，我们假设营养不良中含有S的AAS的缺乏会破坏BA的合成 TCA循环函数，血红素生物合成和CYP7A1活性。我们的具体目的是1）在AA-中表征通过在TCA循环中量化标记的葡萄糖的通量和测量血红素前后Fe-S簇依赖性TCA循环酶的表达水平和活性治疗; 2）通过测量通过测量BA合成的作用在低AA培养基中保持肝细胞，并以AAS和血红素并使用腺相关病毒或siRNA来操纵过泄殖能和Fe-S簇 - 依赖酶； 3）确定新颖的营养疗法是否可以营救BA合成营养不良，通过喂养用含S的AAS补充的营养不良饮食，然后量化TCA 原发性肝细胞中的周期功能，血红素合成和BA产生。预期结果包括阐明营养不良，TCA循环和血红素稳态和BA合成之间的新联系。这项研究很重要，因为它有可能开发可扩展的基于AA的治疗以恢复肝脏儿童的合成功能和治疗营养不良。