RBP2 Biology and Pathobiology

RBP2 生物学和病理学

• 批准号: 10409772
• 负责人: WILLIAM S BLANER
• 金额: $ 47.97万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-06-15 至 2023-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10409772
• 关键词: 2-arachidonylglycerol; Adipose tissue; Adult; Affect; Affinity; Age; All-Trans-Retinol; Binding; Binding Proteins; Biochemical; Biochemical Pathway; Biology; Biophysics; Body Weight; Carotenoids; Cell Culture Techniques; Cells; Chylomicrons; Crystallization; Data; Development; Diet; Dietary Fats; Eating; Energy Metabolism; Enterocytes; Esters; Fasting; Fatty Liver; Fatty acid glycerol esters; Gene Expression; Glucose; Goals; Health; Hepatic; High Fat Diet; In Vitro; Intestines; Ligand Binding; Lipids; Literature; Maintenance; Mediating; Metabolic; Metabolism; Molecular; Monoglycerides; Mucous Membrane; Mus; Obesity; Oral; Phenotype; Physiological; Process; Property; Proteins; Publishing; Regulation; Research; Retinaldehyde; Retinoids; Retinol Binding Proteins; Role; Serum; Signaling Molecule; Site; Small Intestines; Structure; Study models; Tissues; Tretinoin; Triglycerides; Unsaturated Fats; Vitamin A; Wild Type Mouse; absorption; analog; base; dietary; feeding; impaired glucose tolerance; jejunum; male; metabolic phenotype; mouse model; novel; prevent; reproductive; response; uptake

Retinol-binding protein 2 (RBP2) was originally identified more than 30 years ago as an intracellular binding protein for retinoids (vitamin A and its metabolites). RBP2 is expressed solely in the adult small intestine, primarily in the jejunum, and has been studied only from the context of its actions in dietary retinoid uptake and metabolism. We unexpectedly have identified a role for RBP2 in the maintenance of body weight, normal responses to a glucose challenge, and normal fasting hepatic triglyceride levels. When maintained solely on a control chow diet, 6–7 month-old male Rbp2-deficient (Rbp2-/-) mice accrue significantly more body weight as white adipose tissue, respond significantly less well to a glucose challenge, and possess significantly more hepatic fat than matched wild type littermate controls. These same metabolic phenotypes are observed when 2 month-old male Rbp2-/- mice are fed a high fat diet for 6 weeks or longer. Although we attempted to identify retinoid-dependent mechanisms that might account for these metabolic phenotypes, we did not detect any differences in tissue retinoic acid levels or in retinoid-regulated gene expression that could explain the metabolic phenotypes of the Rbp2-/- mice. Through biochemical studies, we established that RBP2 binds monoacylglycerols (MAGs), including both 1- and 2-arachidonoylglycerol, 2-oleoylglycerol, and 2-linoyleoylglycerol with very high affinities, comparable to that of retinol binding to RBP2. Based on these and other data, we concluded that RBP2 is a physiologically relevant MAG-binding protein. We are proposing to obtain in depth understanding of role(s) that RBP2 has in mediating enterocyte MAG metabolism. We view this as a first step towards our long-term goal of identifying the molecular processes that underlie the metabolic phenotypes we have observed in both chow fed and high fat diet fed male Rbp2-/- mice. We hypothesize that these phenotypes involve the actions of RBP2 as a MAG-binding protein. To this end, we propose 3 Specific Aims. In Specific Aim 1, we will identify non-retinoid lipids that are able to bind RBP2 and establish the structural properties of RBP2 that facilitate or prevent non-retinoid ligand binding to RBP2. In Specific Aim 2, we will elucidate RBP2-mediated biochemical pathways related to MAG uptake and metabolism within intestinal enterocytes. In Specific Aim 3, we will investigate in mice how RBP2 acts within the jejunum to affect metabolic phenotype development in response to feeding of different high fat diets consisting of either predominantly saturated or predominantly unsaturated fat and how these diets affect MAG and retinoid/carotenoid absorption and metabolism.

视黄醇结合蛋白2（RBP 2）最初在30多年前被发现是类维生素A（维生素A及其代谢物）的细胞内结合蛋白。RBP 2仅在成年小肠中表达，主要在空肠中，并且仅从其在膳食类维生素A摄取和代谢中的作用的背景进行了研究。我们出乎意料地确定了RBP 2在维持体重、对葡萄糖挑战的正常反应和正常空腹肝甘油三酯水平中的作用。当仅维持对照食物饮食时，6-7月龄的雄性Rbp 2缺陷（Rbp 2-/-）小鼠以白色脂肪组织的形式累积显著更多的体重，对葡萄糖激发的响应显著更差，并且具有比匹配的野生型同窝对照显著更多的肝脂肪。当给2月龄雄性Rbp 2-/-小鼠喂食高脂肪饮食6周或更长时间时，观察到这些相同的代谢表型。虽然我们试图确定可能解释这些代谢表型的类维生素A依赖性机制，但我们没有检测到组织维甲酸水平或类维生素A调节的基因表达的任何差异，这些差异可以解释Rbp 2-/-小鼠的代谢表型。通过生物化学研究，我们确定了RBP 2以非常高的亲和力结合单酰基甘油（MAG），包括1-和2-花生四烯酰甘油、2-油酰甘油和2-亚油酰甘油，与视黄醇结合RBP 2的亲和力相当。基于这些和其他数据，我们得出结论，RBP 2是一种生理相关的MAG结合蛋白。我们建议深入了解RBP 2在介导肠细胞MAG代谢中的作用。我们认为这是朝着我们的长期目标迈出的第一步，即鉴定我们在普通饲料喂养和高脂肪饮食喂养的雄性Rbp 2-/-小鼠中观察到的代谢表型的分子过程。我们假设这些表型涉及RBP 2作为MAG结合蛋白的作用。为此，我们提出三个具体目标。在具体目标1中，我们将鉴定能够结合RBP 2的非类维生素A脂质，并建立促进或阻止非类维生素A配体与RBP 2结合的RBP 2的结构特性。在具体目标2中，我们将阐明RBP 2介导的生化途径相关的MAG摄取和代谢的肠上皮细胞。在具体目标3中，我们将研究RBP 2如何在小鼠空肠内作用以影响代谢表型发育，以响应由主要饱和或主要不饱和脂肪组成的不同高脂肪饮食的喂养，以及这些饮食如何影响MAG和类维生素A/类胡萝卜素的吸收和代谢。