IL-15 receptor-alpha and IL-15 action in aging skeletal muscle and adipose tissue

IL-15 受体-α 和 IL-15 在衰老骨骼肌和脂肪组织中的作用

• 批准号: 8139059
• 负责人: LEBRIS S QUINN
• 金额: --
• 依托单位: VA PUGET SOUND HEALTHCARE SYSTEM
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2015-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8139059
• 关键词: Adipose tissue; Adult; Affect; Age; Age-Years; Aging; Alzheimer' s Disease; Apoptosis; Apoptotic; Area; Binding; Biochemistry; Biological; Body Composition; Body fat; Caloric Restriction; Cardiovascular Diseases; Cell Culture Techniques; Cell Line; Cells; Chimeric Proteins; Chronic Disease; Complex; Degenerative polyarthritis; Deposition; Diabetes Mellitus; Disease; Drug Design; Economic Burden; Elderly; Electroporation; Epidemic; Exhibits; Fatty acid glycerol esters; Fiber; Fracture; Future; Genes; Genetic Polymorphism; Health; Health Care Costs; Human; Human Biology; In Vitro; Incidence; Infiltration; Insulin Resistance; Interleukin-15; Investigation; Lead; Link; Longevity; Malignant Neoplasms; Mediating; Medical; Medicine; Membrane; Messenger RNA; Molecular; Morbidity - disease rate; Mus; Muscle; Muscle Fibers; Muscle Proteins; Non-Insulin-Dependent Diabetes Mellitus; Obesity; Pathway interactions; Patients; Peptide Signal Sequences; Persons; Plasmids; Population; Prediabetes syndrome; Protein Isoforms; Proteins; Proteolysis; RNA Splicing; Rattus; Research; Retroviral Vector; Risk Factors; Rodent; Role; Sequence Homology; Set protein; Signal Transduction; Single Nucleotide Polymorphism; Skeletal Muscle; Suggestion; System; TNFRSF1A gene; Techniques; Testing; Tissues; Translational Research; Tumor Necrosis Factor-alpha; Variant; Veterans; Visceral; Weight; Work; aging population; cell type; cytokine; design; disability; expression vector; falls; feeding; frailty; functional disability; genetic regulatory protein; human MPP1 protein; human subject; hypertensive heart disease; in vivo; innovation; insulin sensitivity; interleukin-15 receptor; mortality; muscle form; overexpression; patient population; prevent; receptor; response; sarcopenia; skeletal; wasting; young adult

DESCRIPTION (provided by applicant): Aging is characterized by reduced skeletal muscle mass (sarcopenia) and increased visceral adipose tissue deposition. These changes in body composition result in frailty, insulin resistance, and cardiovascular disease, which are major health problems in the aging Veteran population. Interleukin-15 (IL-15) is a muscle-derived cytokine with favorable effects on muscle mass, fat mass, and insulin sensitivity in young mice. Circulating IL-15 levels decline with age, in ad lib-fed, but not calorie- restricted rodents, suggesting declines in IL-15 activity contribute to age-associated changes in body composition. However, while IL-15 has favorable effects on body composition in young mice, IL-15 overexpression in aging mice results in increased fat mass and reduced muscle mass compared to controls. IL-15 secretion and bioactivity are modulated by differential association of IL-15 with several forms of the IL-15 alpha receptor subunit (IL-15R1), which can appear as a membrane-bound form (mbIL-15R1) or as one of two soluble forms (sIL-15R1). The latter can differentially affect IL-15 secretion and activity in a tissue- specific manner. Association of IL-15 with sIL-15R1 variants can also differentially inhibit signaling by tumor necrosis factor-1 (TNF-1), another cytokine involved in muscle wasting and insulin resistance. In human subjects, several single-nucleotide polymorphisms (SNPs) have been described in the IL-15R1 gene which impact muscularity, adiposity, and insulin sensitivity. In skeletal muscle, expression of the alternatively-spliced mRNA variant of IL-15R1 (spliced sIL-15R1) declines with age, suggesting a decrease in IL-15/spliced sIL-15R1 complexes leads to age-associated declines in IL-15 levels and activity. The molecular biochemistry of IL-15 and IL-15R1 interactions are complex, tissue-specific, and have not been well-studied in skeletal muscle or adipose tissue, nor in aging systems. Therefore, this study will test the overall hypothesis that IL-15 has opposing effects on body composition in young and old mice due to decreased expression of spliced sIL-15R1 and increased association of IL-15 with the molecularly distinct, proteolytically-shed sIL-15R1 form. The proposed study will utilize retroviral vectors to overexpress IL-15 and IL-15R1 variants in mouse primary and immortalized skeletal myogenic cultures, in order to define the roles of these molecules in IL-15 secretion and bioactivity in muscle. The effects of IL-15/sIL-15R1 complex variants in mouse immortalized adipogenic cultures will also be determined. The effects of IL-15/sIL-15R1 complex variants on TNFR1- mediated TNF-1 signaling in skeletal myogenic and adipogenic cultures will be determined as well. In vivo, the innovative and translational technique of plasmid electroporation into skeletal muscle (EPM) will be used to induce systemic expression of IL-15, sIL-15R1 variants, and a putative superagonistic IL-15/sIL15R1 fusion protein, in young and normally-aging mice. The effects of these molecules on body composition and insulin sensitivity in response to high-fat feeding, sarcopenia, and TNFR1-mediated skeletal myonuclear apoptosis will be determined. The Specific Aims of the project are: 1. Determine the role of IL-15R1 variants in IL-15 stability, secretion and bioactivity in skeletal myogenic and adipogenic cultures. 2. Determine the role of IL-15R1 variants on IL-15 secretion from muscle, body composition, and insulin sensitivity in vivo. 3. Determine the bioactivity of an IL-15/sIL-15R1 fusion protein in muscle and adipose tissue in young and aging mice. These studies will provide mechanistic information which could be exploited pharmacologically to modulate body composition and the pathological consequences of sarcopenia and adiposity in the elderly. PUBLIC HEALTH RELEVANCE: Aging is characterized by decreases in muscle weight and strength, and increased deposition of fat. These changes lead to frailty and insulin resistance (a kind of pre-diabetes), which are major health problems in aging Veterans. Interleukin-15 (IL-15) is a protein that can prevent muscle wasting, obesity, and insulin resistance in young mice. Also, IL-15 levels are lower in old mice than in young mice. Therefore, IL-15 has been suggested as a therapy for the decreases in muscle and increases in fat in the elderly. This notion is too simplistic, however, because recent findings indicate IL-15 has the opposite effect in aging mice. Another set of proteins regulate IL-15, and the amounts of these regulating proteins change during aging. This project will study the regulatory proteins in mice, to determine whether some help IL-15 and some prevent IL-15 from working, and will study how levels of these substances can be controlled during aging. This information will be used in the future to design drugs which can help prevent muscle wasting, obesity, and insulin resistance in the elderly.

描述（由申请人提供）： 衰老的特征是骨骼肌质量减少（肌肉减少症）和内脏脂肪组织沉积增加。这些身体组成的变化导致虚弱，胰岛素抵抗和心血管疾病，这些都是老年退伍军人群体的主要健康问题。 白细胞介素-15（IL-15）是一种肌源性细胞因子，对幼龄小鼠的肌肉质量、脂肪质量和胰岛素敏感性具有有利的作用。循环IL-15水平随着年龄的增长而下降，在自由进食的啮齿动物中，但不是热量限制的啮齿动物，表明IL-15活性的下降有助于身体组成的年龄相关变化。然而，虽然IL-15对年轻小鼠的身体组成具有有利的影响，但与对照组相比，衰老小鼠中的IL-15过表达导致脂肪量增加和肌肉量减少。 IL-15分泌和生物活性通过IL-15与几种形式的IL-15 α受体亚基（IL-15 R1）的差异缔合来调节，IL-15 α受体亚基可以表现为膜结合形式（mbIL-15 R1）或两种可溶形式之一（sIL-15 R1）。后者可以以组织特异性方式差异地影响IL-15分泌和活性。IL-15与sIL-15 R1变体的结合也可以差异性地抑制肿瘤坏死因子-1（TNF-1）的信号传导，TNF-1是另一种参与肌肉萎缩和胰岛素抵抗的细胞因子。在人类受试者中，IL-15 R1基因中已描述了几种单核苷酸多态性（SNP），其影响肌肉发达、肥胖和胰岛素敏感性。 在骨骼肌中，IL-15 R1的可变剪接mRNA变体（剪接的sIL-15 R1）的表达随年龄增长而下降，表明IL-15/剪接的sIL-15 R1复合物的减少导致IL-15水平和活性的年龄相关性下降。IL-15和IL-15 R1相互作用的分子生物化学是复杂的、组织特异性的，并且在骨骼肌或脂肪组织中以及在衰老系统中尚未得到充分研究。因此，本研究将检验总体假设，即IL-15对年轻和老年小鼠的身体组成具有相反的作用，这是由于剪接的sIL-15 R1表达降低以及IL-15与分子上不同的、蛋白水解脱落的sIL-15 R1形式的关联增加。 拟议的研究将利用逆转录病毒载体在小鼠原代和永生化骨骼肌原代培养物中过表达IL-15和IL-15 R1变体，以确定这些分子在IL-15分泌和肌肉生物活性中的作用。还将确定IL-15/sIL-15 R1复合物变体在小鼠永生化脂肪形成培养物中的作用。还将确定IL-15/sIL-15 R1复合物变体对骨骼肌生成和脂肪生成培养物中TNFR 1介导的TNF-1信号传导的影响。在体内，创新和转化技术的质粒电穿孔到骨骼肌（ESTA）将用于诱导系统表达IL-15，sIL-15 R1变体，和一个假定的超激动IL-15/sIL-15 R1融合蛋白，在年轻和正常老化的小鼠。这些分子对机体组成和胰岛素敏感性的影响，以响应高脂肪喂养，肌肉减少症，和TNFR 1介导的骨骼肌细胞凋亡将被确定。该项目的具体目标是：1。确定IL-15 R1变体在骨骼肌生成和脂肪生成培养物中IL-15稳定性、分泌和生物活性中的作用。 2.确定IL-15 R1变体对IL-15从肌肉分泌、身体组成和体内胰岛素敏感性的作用。 3.测定IL-15/sIL-15 R1融合蛋白在幼龄和老龄小鼠肌肉和脂肪组织中的生物活性。 这些研究将提供机制的信息，可以利用间接调节身体组成和病理后果的肌肉减少症和肥胖的老年人。 公共卫生关系： 衰老的特征是肌肉重量和力量下降，脂肪沉积增加。这些变化导致虚弱和胰岛素抵抗（一种前驱糖尿病），这是老年退伍军人的主要健康问题。白细胞介素-15（IL-15）是一种蛋白质，可以防止年轻小鼠的肌肉萎缩、肥胖和胰岛素抵抗。此外，老年小鼠的IL-15水平低于年轻小鼠。因此，IL-15已被建议作为老年人肌肉减少和脂肪增加的疗法。然而，这种观点过于简单化，因为最近的研究结果表明IL-15在衰老小鼠中具有相反的作用。另一组蛋白质调节IL-15，这些调节蛋白质的数量在衰老过程中发生变化。该项目将研究小鼠中的调节蛋白，以确定是否有些有助于IL-15，有些阻止IL-15工作，并将研究如何在衰老过程中控制这些物质的水平。这些信息将在未来用于设计药物，帮助预防老年人的肌肉萎缩，肥胖和胰岛素抵抗。