PGC-1 & Muscle Mitochondrial Dysfunction in Diabetes

描述（由申请人提供）：我们发现了一种被称为“运动抵抗”的现象，即胰岛素抵抗个体对单次运动的PGC-1α和其他基因的表达不正常。为了产生关于为什么会发生这种情况的假设，正常的葡萄糖耐受性志愿者在休息和运动后30分钟进行了一次运动肌肉活检。我们发现，运动后，130个基因对应的216个mrna发生了显著变化。转录调控因子的比例明显过高。对受影响基因的5'非翻译区进行分析，发现转录因子应答元件显著富集，包括NFKB1、RELA、SP1/KLF家族和EGR1的基序。对这些转录因子的5' UTR分析发现了一个共同的潜在转录调节因子，髓系锌指1 （MZF1）。运动后MZF1表达变化与胰岛素敏感性呈正相关。MZF1在胰岛素抵抗型肥胖和糖尿病患者中的表达也明显增加，提示该系统失调。我们利用这些实验对调节mRNA和蛋白质丰度的更多因素进行了更仔细的检查。其中，microRNAs （miRNAs）调控着许多基因表达和翻译事件。初步数据显示，在健康人群中，运动增加了针对FOXO1 mRNA的microrna，并且FOXO1蛋白在肥胖和2型糖尿病肌肉中增加，同时FOXO1磷酸化降低，表明FOXO1转录程序在胰岛素抵抗肌肉中可能被激活。关于运动和胰岛素敏感性如何在骨骼肌中与人类肌肉中全局miRNA表达事件相互作用的数据很少。最后，急性运动30分钟后，PPARα及其下游靶点的表达以胰岛素敏感性相关的方式下降。小鼠肌肉中PPARα过表达恶化，敲除PPARα可改善胰岛素敏感性。因此，肌肉中PPARα的激活可能对胰岛素敏感性有害，并提出了用贝特类药物治疗降低血浆脂质的问题，是否可以对抗骨骼肌运动的胰岛素增敏作用。本项目的总体目标是了解骨骼肌运动时胰岛素敏感性与基因表达反应之间的相互作用。虽然在小鼠和体外系统中有大量的数据，但需要将这些数据适用于人类疾病。我们建议：1。确定2型糖尿病患者肌肉中运动后转录因子表达反应是否失调；2. 研究胰岛素抵抗如何改变SP1/KLF家族和MZF1转录因子的翻译后修饰对2型糖尿病患者肌肉急性运动的反应；3. 探讨肥胖和2型糖尿病患者健康和胰岛素抵抗肌肉中mirna对急性运动的反应；4. 确定PPARα激动剂贝特衍生物治疗是否抑制正常基因表达对急性运动的反应。

DESCRIPTION (provided by applicant): We discovered a phenomenon called "exercise resistance", where insulin resistant individuals do not respond normally to a single bout of exercise with respect to expression of PGC-1α and other genes). To generate hypotheses regarding why this happens, normal glucose tolerant volunteers had one exercise bout with muscle biopsies at rest and 30 min after exercise. We found that 216 mRNAs corresponding to 130 genes changed significantly after exercise. Transcriptional regulators were significantly over-represented. Analysis of the 5' untranslated regions of the affected genes showed significant enrichment in transcription factor response elements, including motifs for NFKB1, RELA, SP1/KLF family, and EGR1. Analysis of the 5' UTR of these transcription factors revealed one common potential transcriptional regulator, myeloid zinc finger 1 (MZF1). The change in MZF1 expression after exercise was positively correlated with insulin sensitivity. MZF1 expression also was increased markedly in insulin resistant obese and diabetic patients, suggesting dysregulation of this system. We used these experiments to conduct a closer examination of more factors that regulate mRNA and protein abundance. Among these, microRNAs (miRNAs) regulate much of gene expression and translation events. Preliminary Data shows that, in healthy people, exercise increases microRNAs that target FOXO1 mRNA, and FOXO1 protein is increased in obese and type 2 diabetic muscle, accompanied by decreased FOXO1 phosphorylation, indicating potential activation of the FOXO1 transcriptional program in insulin resistant muscle. There are few data on how exercise and insulin sensitivity interact in skeletal muscle with regard to global miRNA expression events in human muscle. Finally, the expression of PPARα and its downstream targets decreased 30 minutes after acute exercise in an insulin sensitivity-related manner. In mice PPARα overexpression in muscle worsens and PPARα knockout improves insulin sensitivity. Thus, PPARα activation in muscle may detrimental to insulin sensitivity, and begs the question of whether treatment with fibrates to lower plasma lipids could work against insulin sensitizing effects of exercise in skeletal muscle. The overall goal of this project is to understand the interplay between insulin sensitivity and the gene expression response to exercise in skeletal muscle. Although substantial data is available in mice and in vitro systems, the applicability of these data to human disease is required. We propose: 1. To determine whether the transcription factor expression response to exercise is dysregulated in muscle from type 2 diabetic patients; 2. To determine how insulin resistance changes the response of posttranslational modifications of SP1/KLF family and MZF1 transcription factors to acute exercise in muscle from type 2 diabetic patients; 3. To define the response of miRNAs to acute exercise in healthy and insulin resistant muscle from obese and type 2 diabetic patients; 4. To determine whether treatment with PPARα agonist fibrate derivatives suppresses the normal gene expression response to acute exercise.