PGC-1 & Muscle Mitochondrial Dysfunction in Diabetes

描述(申请人提供)：我们发现了一种称为“运动抵抗”的现象，即胰岛素抵抗的个体对单次运动没有正常的反应(PGC-1α和其他基因的表达)。为了解释为什么会发生这种情况，正常糖耐量志愿者进行了一轮锻炼，分别在休息时和锻炼后30分钟进行肌肉活组织检查。我们发现，运动后，与130个基因对应的216个mRNAs发生了显著变化。转录调控因子的比例明显偏高。对受影响基因5‘非翻译区的分析表明，转录因子反应元件显著丰富，包括NFKB1、RELA、SP1/KLF家族和Egr1基序。对这些转录因子5‘端非编码区的分析揭示了一个共同的潜在转录调控因子，髓系锌指1(MZF1)。运动后MZF1表达的变化与胰岛素敏感性呈正相关。在胰岛素抵抗的肥胖和糖尿病患者中，MZF1的表达也显著增加，提示这一系统的失调。我们利用这些实验对更多调节mRNA和蛋白质丰度的因素进行了更仔细的检查。其中，microRNAs(MiRNAs)调控大部分基因表达和翻译事件。初步数据显示，在健康人中，运动增加了靶向FOXO1 mRNA的microRNAs，肥胖和2型糖尿病肌肉中FOXO1蛋白增加，同时FOXO1磷酸化降低，这表明胰岛素抵抗肌肉中FOXO1转录程序可能被激活。关于运动和胰岛素敏感性在骨骼肌中如何与人类肌肉中的全局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与胰岛素敏感性相关的方式减少。在小鼠中，PPARα在肌肉中的过度表达恶化，PPARα基因敲除提高了胰岛素敏感性。因此，肌肉中PPARα的激活可能不利于胰岛素敏感性，并回避了贝特类降脂治疗是否可以对抗运动对骨骼肌的胰岛素增敏作用的问题。这个项目的总体目标是了解骨骼肌中胰岛素敏感性和运动基因表达反应之间的相互作用。尽管在小鼠和体外系统中可以获得大量数据，但这些数据对人类疾病的适用性是必需的。我们建议：1.确定2型糖尿病患者肌肉对运动的转录因子表达反应是否失调；2.确定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型糖尿病患者肌肉对急性运动的反应；3.确定健康人和肥胖和2型糖尿病患者的胰岛素抵抗肌肉对急性运动的反应；4.确定PPARα激动剂贝特衍生物治疗是否抑制对急性运动的正常基因表达反应。

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.