인슐린 저항성 특이 골격근육 유래의 분비 단백질체 발굴 및 체계적인 연구

Abstract

Skeletal muscle plays major function in the regulation of energy metabolism in the whole body. Secretomic studies to identify secretory proteins from metabolic cells/tissues have detected several candidate cytokines but skeletal muscle-derived cytokines have not been studied seriously yet.This study sought to provide lists of skeletal muscle-derived secretory proteins that have the potential to play a role in insulin resistance and to characterize insulin resistance through systematic analysis of the secretomes from different causes of insulin resistance. By novel label-free methods for secretomics using G-statistics, this study found 33 insulin-modulated skeletal muscle secretory proteins. After establishment of cell-based insulin resistant condition by TNF-alpha and palmitate, subsequent studies provided the lists of insulin resistant-modulated skeletal muscle secretory proteins using reliable quantitative methods: 28 TNF-alpha-modulated secretory proteins and 42 palmitate-modulated secretory proteins.This study found candidate myokines by clear verification. In insulin-treated secretome study, MMP-2 and PAI-1 were found that are highly related with metabolic disease especially with atherosclerotic complications. In TNF-alpha-treated secretome study, clusterin, nucleobindin-2, IGFBP-4 and DJ-1 were found. Clusterin and nucleobindin-2 are novel factors to explain roles skeletal muscle in anti-atherogenic responses and food intake, relatively. Annexin A1 was screened from palmitate-treated secretome study, which able to explain insulin resistance of skeletal muscle by autocrine pathway. From individual secretome analysis, several of novel skeletal muscle-derived insulin resistant-modulated secretory proteins that have not yet been reported as the proteins related with metabolic disease were discovered: 26 of insulin-modulated, 23 of TNF-alpha modulated and 23 of palmitate-modulated secretory proteins.In systematic analysis, TNF-alpha secretome study combined analysis with transcriptome of skeletal muscle of diabetic fatty rat suggested TNF-alpha-mediated inflammation is an important cause of diabetic skeletal muscle phenotypes. In systematic study of the secretomes from three different insulin resistant conditions, 7 proteins were common and 3 proteins of these were commonly modulated by the given insulin resistant conditions (Alpha-enolase, Nucleobindin-1, Metalloproteinase inhibitor 2). Those are identified as the common insulin resistance-dependent secretory proteins. Systematic bioinformatics analysis found common terms in biological process and molecular function of functional annotation that become foothold to further characterization of insulin resistance of skeletal muscle.This study revealed that insulin, TNF-alpha and palmitate-treated skeletal muscle secrete a variety of cytokines disparately and the extracellular environment affects cytokine secretion by skeletal muscle tissue. Therefore, the lists of identified proteins provides useful information for designing further metabolic disease studies, such as studies to identify potential communication mediators involving endo-/para-/auto-crines, as well as biomarkers for irregular states like obesity induced insulin resistance.