Targeting stress-mediated pathways in the treatment of muscle insulin resistance

描述(由申请人提供)：迫切需要了解骨骼肌中热休克蛋白(HSP)的基本抗氧化特性，并建立预防胰岛素抵抗的新HSP疗法。长期目标是阐明肌肉胰岛素抵抗导致2型糖尿病患病率随年龄增长而增加的机制。这一特殊应用的目的是确定HSP表达增加可以在多大程度上调节骨骼肌中的应激蛋白激酶和胰岛素信号通路。我们的中心假设是，HSP72和HSP25的表达增加将减少应激激酶的激活，并改善胰岛素信号转导。我们建议这项研究的基本原理是，可以开发新的策略来调节HSP依赖的通路，作为治疗胰岛素抵抗的方法。在强大的初步数据的指导下，这一假说将通过追求三个具体目标来验证：1)确定能够改善骨骼肌胰岛素信号转导的HSP依赖机制；2)确定调节胰岛素抵抗骨骼肌中HSP表达的信号通路；以及3)确定改善老年骨骼肌HSP激活和胰岛素信号转导的治疗干预措施。在具体目标1中，我们将确定HSP72和HSP25的表达增加是否分别抑制了应激性激酶c-jun末端激酶(JNK)和kappa B激酶2抑制物(IKK2)，并改善了年轻(6和12个月)和老年(18和24个月)Fischer 344大鼠的胰岛素信号转导。为了达到这一目的，我们将同时使用热处理和通过质粒转染实现HSPs的特异性过表达。在特定的目标2中，我们将确定糖原合成酶激酶-3(GSK-3)和JNK信号通路在多大程度上调节胰岛素抵抗骨骼肌中HSP的表达。GSK-3和JNK的药物社会抑制剂将用于修改主要的HSP转录因子-热休克因子1(HSF-1)的激活。在具体目标3中，我们将检查运动训练提高年轻和老年胰岛素抵抗骨骼肌HSP反应的能力。我们的工作假设是，运动训练将通过一条独立于热处理的途径触发HSP反应，热应激和运动将导致老年胰岛素抵抗骨骼肌的胰岛素信号和葡萄糖摄取的相加改善。作为拟议目标的结果，我们期望建立热休克蛋白在对抗胰岛素抵抗方面的新的治疗作用，并确定调节老年胰岛素抵抗骨骼肌中热休克蛋白表达的分子机制。该项目具有创新性，因为它旨在确定一种以前未被探索的机制，通过增加骨骼肌中热休克蛋白的表达来改善胰岛素抵抗。这项拟议的研究具有重要意义，因为它将有助于为预防胰岛素抵抗建立重要的新候选靶点，并增强我们对随着年龄和疾病而出现的细胞防御能力下降的理解。 公共卫生相关性：在这些研究完成后，我们希望增加我们对骨骼肌中热休克蛋白的基本抗氧化特性的了解，并确定热处理对胰岛素作用的保护作用背后的热休克蛋白依赖机制。这些结果将通过确定新的治疗干预目标来对公共健康产生重要的积极影响，这些干预措施将帮助美国越来越多的面临胰岛素抵抗和2型糖尿病风险的老年人。

DESCRIPTION (provided by applicant): There is a critical need to understand the fundamental antioxidant properties of heat shock proteins (HSPs) in skeletal muscle and establish novel HSP therapies for preventing insulin resistance. The long-term goal is to elucidate the mechanisms of muscle insulin resistance that lead to increased prevalence of type 2 diabetes with advancing age. The objective of this particular application is to determine the extent to which increased HSP expression can modulate stress kinase and insulin signaling pathways in skeletal muscle. Our central hypothesis is that increased expression of HSP72 and HSP25 will decrease stress kinase activation and improve insulin signaling. Our rationale for the proposed research is that new strategies could be developed to modulate HSP-dependent pathways as a therapeutic approach to treat insulin resistance. Guided by strong preliminary data, this hypothesis will be tested by pursuing three specific aims: 1) Identify HSP-dependent mechanisms that function to improve skeletal muscle insulin signaling; 2) Identify signaling pathways that modulate HSP expression in insulin-resistant skeletal muscle; and 3) Identify therapeutic interventions to improve HSP activation and insulin signaling in aged skeletal muscle. In Specific Aim 1, we will determine whether increased expression of HSP72 and HSP25 inhibit the stress kinases c-jun terminal kinase (JNK) and inhibitor of kappa B kinase 2 (IKK2), respectively, and improve insulin signaling in young (6- and 12-month-old) and aged (18- and 24-month-old) Fischer 344 rats. We will use both heat treatment and specific overexpression of HSPs via plasmid transfection to accomplish this aim. In Specific Aim 2, we will determine the extent to which glycogen synthase kinase-3 (GSK-3) and JNK signaling pathways modulate HSP expression in insulin-resistant skeletal muscle. Pharmacolgocial inhibitors of GSK-3 and JNK will be used to modify activation of the primary HSP transcription factor, heat shock factor 1 (HSF-1). In Specific Aim 3, we will examine the ability of exercise training to increase the HSP response in young and aged, insulin-resistant skeletal muscle. Our working hypothesis is that exercise training will trigger the HSP response through a pathway independent of heat treatment, and that heat stress and exercise will result in an additive improvement of insulin signaling and glucose uptake in aged, insulin-resistant skeletal muscle. As an outcome of the proposed aims, we expect to establish a novel therapeutic role for HSPs in combating insulin resistance and identify molecular mechanisms that regulate HSP expression in aged, insulin-resistant skeletal muscle. This project is innovative, because it is designed to identify a previously unexplored mechanism for improving insulin resistance via increased expression of HSPs in skeletal muscle. The proposed research is significant because it will help to establish important new candidate targets for prevention of insulin resistance as well as enhance our understanding of the decline in cellular defenses that occurs with age and disease. PUBLIC HEALTH RELEVANCE: At the completion of these studies, we expect to increase our understanding of the fundamental antioxidant properties of heat shock proteins in skeletal muscle and to identify the heat shock protein-dependent mechanisms underlying the protective effect of heat treatment on insulin action. Such results would have an important positive impact on public health by identifying new targets for therapeutic interventions that will aid the growing number of elderly persons in the U.S. at risk for developing insulin resistance and type 2 diabetes.