PGC-1 & Muscle Mitochondrial Dysfunction in Diabetes

描述（由申请人提供）：我们发现了一种称为“运动抵抗”的现象，其中胰岛素抵抗个体在PGC-1α和其他基因的表达方面对单次运动没有正常反应。为了产生关于为什么会发生这种情况的假设，正常葡萄糖耐受的志愿者在休息时和运动后30分钟进行了一次运动，并进行了肌肉活检。我们发现，运动后，对应于130个基因的216个mRNA发生了显著变化。转录调节因子的比例明显过高。对受影响基因的5'非翻译区的分析显示转录因子应答元件显著富集，包括NFKB 1、RELA、SP1/KLF家族和EGR 1的基序。对这些转录因子的5' UTR的分析揭示了一个共同的潜在转录调节因子，髓样锌指1（MZF 1）。运动后MZF 1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，MZF 1表达也显著增加，表明该系统失调。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，microRNA（miRNAs）调节许多基因表达和翻译事件。初步数据显示，在健康人群中，运动增加了靶向FOXO 1 mRNA的microRNA，FOXO 1蛋白在肥胖和2型糖尿病肌肉中增加，伴随着FOXO 1磷酸化减少，表明胰岛素抵抗肌肉中FOXO 1转录程序的潜在激活。关于运动和胰岛素敏感性如何在骨骼肌中相互作用，以及人类肌肉中的总体miRNA表达事件的数据很少。急性运动后30 min，PPARα及其下游靶点的表达降低，且与胰岛素敏感性相关。在小鼠中，肌肉中的PPARα过表达和PPARα敲除改善了胰岛素敏感性。因此，肌肉中的PPARα激活可能对胰岛素敏感性有害，并回避了贝特类药物治疗降低血脂是否可以对抗骨骼肌运动的胰岛素增敏作用的问题。本项目的总体目标是了解骨骼肌胰岛素敏感性和运动基因表达反应之间的相互作用。虽然在小鼠和体外系统中获得了大量数据，但需要这些数据对人类疾病的适用性。我们建议：1.目的：1.确定2型糖尿病患者骨骼肌中转录因子表达对运动的反应是否失调。研究胰岛素抵抗如何改变2型糖尿病患者肌肉中SP1/KLF家族和MZF 1转录因子的翻译后修饰对急性运动的反应。明确miRNAs在肥胖和2型糖尿病患者健康和胰岛素抵抗肌肉中对急性运动的反应; 4.确定用PPARα激动剂贝特类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.