Age Related Insulin Resistance, Akt/PKB, and Skeletal Muscle Proteolysis

年龄相关的胰岛素抵抗、Akt/PKB 和骨骼肌蛋白水解

• 批准号: 7363050
• 负责人: THOMAS H REYNOLDS
• 金额: $ 16.59万
• 依托单位: SKIDMORE COLLEGE
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-30 至 2011-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7363050
• 关键词: Ablation; Age; Apoptosis; Boxing; Cell Size; Cell physiology; Data; Defect; Elderly; Genetic Transcription; Glycogen; Goals; Growth; Growth Factor; In Vitro; Individual; Insulin; Insulin Resistance; Knockout Mice; Lead; Measures; Mediating; Metabolism; Modeling; Mus; Muscle; Muscular Atrophy; Non-Insulin-Dependent Diabetes Mellitus; Nuclear; Numbers; Other Resources; Pathway interactions; Phosphorylation; Phosphotransferases; Prevention intervention; Protein Biosynthesis; Protein Isoforms; Proteins; Proteolysis; Proto-Oncogene Proteins c-akt; Rate; Regulation; Research Activity; Role; Signal Pathway; Signal Transduction; Signaling Molecule; Skeletal Muscle; Soleus Muscle; Specificity; Students; Thinking; Transgenic Mice; Transgenic Organisms; Ubiquitin; Ubiquitination; Work; age effect; age related; aged; glucose uptake; human TYRP1 protein; insulin signaling; middle age; multicatalytic endopeptidase complex; novel; prevent; protein degradation; sarcopenia; senescence; size; transcription factor; ubiquitin ligase; wasting

DESCRIPTION (provided by applicant): Decreases in muscle size and strength are associated with advancing age and type 2 diabetes. Since insulin resistance and type 2 diabetes are commonly observed in older individuals, a good portion of the age-related loss of muscle mass may be due to a decrease in insulin action. A major action of insulin is to suppress skeletal muscle proteolysis, in part, by activating protein kinase B (PKB). PKB is a critical insulin signaling molecule that controls a plethora of cellular functions including glucose uptake, glycogen synthesis, protein synthesis, protein degradation, and gene transcription. Activation of PKB reduces skeletal muscle proteolysis by phosphorylating forkhead box O (FOXO) transcription factors and thereby repressing the expression of atrogin-1 and MURF1, two ubiquitin ligases thought to mediate skeletal muscle proteolysis. Our preliminary data demonstrates increases in total protein degradation rates and ubiquitin-protein conjugates in skeletal muscles of aged mice compared to younger mice. Therefore, our first goal of this AREA proposal is to demonstrate that an increase in the ubiquitin-proteasome proteolytic pathway is responsible for the increase in total protein degradation observed in aged skeletal muscle. Our preliminary data also demonstrates decreases in PKB activity and FOXO transcription factor phosphorylation in aged muscle compared to young muscle. In this regard, our second goal is to demonstrate that the ability of insulin to activate PKB and promote FOXO transcription factor phosphorylation is reduced in aged skeletal muscle. Because PKB controls several critical cellular functions relating to both growth and metabolism, different isoforms of the kinase may provide signaling specificity. Since PKB-1 null transgenic mice are smaller than wildtype or PKB-2 null mice, we believe that PKB-1 controls skeletal muscle proteolysis to a greater extent than PKB-2. Therefore, our third goal of this AREA application is to demonstrate that PKB-1 exerts a greater control of ubiquitin-proteasome dependent proteolysis than PKB-2 by using isoform specific PKB knockout mice. Accomplishing these goals will establish a novel mechanism connecting insulin resistance to age-related loss of muscle mass as well as identify an isoform specific function of PKB. In accordance with the NIH-AREA initiative the goals of this R15 proposal will be accomplished by making undergraduate students an integral part of all research activities.

描述（由申请人提供）：肌肉尺寸和力量的减少与年龄增长和 2 型糖尿病有关。由于胰岛素抵抗和 2 型糖尿病常见于老年人，因此与年龄相关的肌肉质量损失很大一部分可能是由于胰岛素作用下降所致。胰岛素的主要作用是部分通过激活蛋白激酶 B (PKB) 来抑制骨骼肌蛋白水解。 PKB 是一种关键的胰岛素信号分子，控制多种细胞功能，包括葡萄糖摄取、糖原合成、蛋白质合成、蛋白质降解和基因转录。 PKB 的激活通过磷酸化叉头框 O (FOXO) 转录因子来减少骨骼肌蛋白水解，从而抑制 atrogin-1 和 MURF1（两种被认为介导骨骼肌蛋白水解的泛素连接酶）的表达。我们的初步数据表明，与年轻小鼠相比，老年小鼠骨骼肌中的总蛋白质降解率和泛素-蛋白质缀合物有所增加。因此，我们该 AREA 提案的首要目标是证明泛素-蛋白酶体蛋白水解途径的增加是导致衰老骨骼肌中观察到的总蛋白质降解增加的原因。我们的初步数据还表明，与年轻肌肉相比，老年肌肉中的 PKB 活性和 FOXO 转录因子磷酸化有所降低。在这方面，我们的第二个目标是证明胰岛素激活 PKB 和促进 FOXO 转录因子磷酸化的能力在衰老的骨骼肌中降低。由于 PKB 控制与生长和代谢相关的多种关键细胞功能，因此激酶的不同亚型可能提供信号特异性。由于 PKB-1 缺失转基因小鼠比野生型或 PKB-2 缺失小鼠小，我们认为 PKB-1 比 PKB-2 更大程度地控制骨骼肌蛋白水解。因此，我们该 AREA 应用的第三个目标是通过使用同工型特异性 PKB 敲除小鼠来证明 PKB-1 比 PKB-2 对泛素蛋白酶体依赖性蛋白水解具有更强的控制能力。实现这些目标将建立一种将胰岛素抵抗与年龄相关的肌肉质量损失联系起来的新机制，并确定 PKB 的亚型特异性功能。根据 NIH-AREA 倡议，R15 提案的目标将通过让本科生成为所有研究活动不可或缺的一部分来实现。

项目成果

Disassociation of insulin action and Akt/FOXO signaling in skeletal muscle of older Akt-deficient mice.

• DOI: 10.1152/ajpregu.00358.2012
• 发表时间: 2012-12
• 期刊: American journal of physiology. Regulatory, integrative and comparative physiology
• 作者: T. Reynolds;Erin Merrell;Nicholas Cinquino;Megan Gaugler;L. Ng