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

描述（由申请人提供）：目前迫切需要了解骨骼肌中热休克蛋白（HSPs）的基本抗氧化特性，并建立新的热休克蛋白治疗方法来预防胰岛素抵抗。长期目标是阐明肌肉胰岛素抵抗导致2型糖尿病随年龄增长而增加的机制。这个特殊应用的目的是确定在多大程度上增加HSP表达可以调节骨骼肌中的应激激酶和胰岛素信号通路。我们的中心假设是HSP72和HSP25的表达增加会降低应激激酶的激活并改善胰岛素信号传导。我们提出这项研究的基本原理是，可以开发新的策略来调节热休克蛋白依赖途径，作为治疗胰岛素抵抗的治疗方法。在强有力的初步数据的指导下，这一假设将通过追求三个具体目标来验证：1)确定hsp依赖的机制，以改善骨骼肌胰岛素信号传导；2)确定胰岛素抵抗骨骼肌中调节HSP表达的信号通路；3)确定改善老年骨骼肌HSP激活和胰岛素信号的治疗干预措施。在Specific Aim 1中，我们将确定HSP72和HSP25的表达增加是否分别抑制应激激酶c-jun末端激酶（JNK）和kappa B激酶2抑制剂（IKK2），并改善幼龄（6和12月龄）和老年（18和24月龄）Fischer 344大鼠的胰岛素信号传导。我们将使用热处理和通过质粒转染特异性过表达热休克蛋白来实现这一目标。在Specific Aim 2中，我们将确定糖原合成酶激酶3 （GSK-3）和JNK信号通路在胰岛素抵抗骨骼肌中调节HSP表达的程度。GSK-3和JNK的药理抑制剂将用于修饰主要热休克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增加年轻人和老年人胰岛素抵抗骨骼肌HSP反应的能力。我们的工作假设是，运动训练将通过独立于热处理的途径触发热休克反应，并且热应激和运动将导致胰岛素信号和胰岛素抵抗骨骼肌中葡萄糖摄取的添加剂改善。作为提出的目标的结果，我们期望建立热休克蛋白在对抗胰岛素抵抗中的新的治疗作用，并确定调节热休克蛋白在老年胰岛素抵抗骨骼肌中的表达的分子机制。这个项目是创新的，因为它旨在通过增加骨骼肌中热休克蛋白的表达来确定一种以前未被探索的改善胰岛素抵抗的机制。这项研究具有重要意义，因为它将有助于建立预防胰岛素抵抗的重要新候选靶点，并增强我们对随着年龄和疾病而发生的细胞防御能力下降的理解。

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.