Targeting IMAT-derived Extracellular Matrix Proteins as Mediators of Skeletal Muscle Insulin Resistance

肥胖症和2型糖尿病在全球范围内的流行率在美国继续大幅上升 以及全球范围内。在考虑肥胖时，区域性脂肪分布和异位脂肪沉积是至关重要的。 相关代谢功能障碍，因为我们现在知道脂肪组织是一个重要的内分泌器官， 分泌各种影响附近组织的生物活性因子。一个这样的异位脂肪储存库，肌肉间 脂肪组织(IMAT)，聚集在骨骼肌间、肌纤维之间。而当 先前的研究表明，IMAT与胰岛素抵抗和2型糖尿病直接相关。 缺乏旨在解决IMAT如何参与代谢性疾病发展的研究。 越来越多的证据表明，细胞外基质(ECM)蛋白沉积与重构有关。 骨骼肌中存在胰岛素抵抗，我们实验室最近的研究表明，IMAT可能会分泌更多的 与内脏脂肪组织(VAT)和其他脂肪储藏相比，ECM蛋白质的含量 皮下脂肪组织(SAT)。但是，从未在中研究过IMAT派生的ECM组件 与骨骼肌胰岛素敏感性的关系。因此，这项提议的目标是确定新的机制 IMAT通过什么影响2型糖尿病的发展，重点是IMAT的中心假设 分泌细胞外基质蛋白，促进骨骼肌胰岛素抵抗。这项提案的第一个目标将检验这一点。 通过扩展初步数据并评估IMAT、VAT和SAT的程度来进行假设 分泌与人类胰岛素敏感性有关的细胞外基质蛋白。条件媒体使用 将产生人IMAT、SAT和VAT组织活检，并分泌纤维连接蛋白(FN)、VI型胶原 (COLVI)、纤维蛋白原-β(FGB)和转化生长因子-β1(TGFB1)将用 多重酶联免疫吸附试验和蛋白质组学分析相结合。这项提案的第二个目标将决定 这些特定的细胞外基质蛋白在体外增加骨骼肌胰岛素抵抗的能力。 将IMAT、SAT和VAT条件培养液应用于分化的L6肌管培养物以测量 胰岛素敏感性的变化。此外，FN、Colvi、Fgb和TGFB1单独调制的能力 胰岛素敏感性将通过隔离处理重组蛋白以及给予 FN、COLVI、FGB和TGFB1-条件培养液为空。总而言之，这些研究将探索潜在的新颖性 调节骨骼肌胰岛素敏感性的机制，强调IMAT在 胰岛素抵抗和2型糖尿病的发展。

The worldwide prevalence of obesity and type 2 diabetes continue to increase substantially in the United States and globally. Regional fat distribution and ectopic adipose deposition are paramount when considering obesity- associated metabolic dysfunction, as we now know that adipose tissue is an important endocrine organ, secreting a variety of bioactive factors that impact nearby tissues. One such ectopic adipose depot, intermuscular adipose tissue (IMAT), accumulates within the skeletal muscle compartment, between muscle fibers. While previous research has shown that IMAT directly relates to insulin resistance and type 2 diabetes, mechanistic studies aimed at addressing how IMAT is involved in the development of metabolic disease are lacking. Mounting evidence suggests that extracellular matrix (ECM) protein deposition and remodeling is associated with insulin resistance in skeletal muscle, and recent studies in our lab indicate that IMAT may secrete a greater amount of ECM proteins compared to other adipose depots such as visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT). However, IMAT-derived ECM components have never been investigated in relation to skeletal muscle insulin sensitivity. Therefore, the goal of this proposal is to identify novel mechanisms by which IMAT impacts the development of type 2 diabetes, focusing on the central hypothesis that IMAT secretes ECM proteins that promote skeletal muscle insulin resistance. The first aim of this proposal will test this hypothesis by expanding upon preliminary data and evaluating the degree to which IMAT, VAT and SAT secrete extracellular matrix proteins that relate to insulin sensitivity in humans. Conditioned media using human IMAT, SAT and VAT tissue biopsies will be generated, and secreted Fibronectin (FN), Collagen VI (ColVI), Fibrinogen-beta (FGB) and Transforming growth factor beta-1 (TGFB1) will be measured using a combination of multiplex ELISA and proteomic analyses. The second aim of this proposal will determine the ability of these specific extracellular matrix proteins to increase skeletal muscle insulin resistance in vitro. IMAT, SAT, and VAT conditioned media will be administered to differentiated L6 myotube cultures to measure changes in insulin sensitivity. In addition, the ability of FN, ColVI, FGB, and TGFB1 to individually modulate insulin sensitivity will be measured by isolated treatment of recombinant proteins as well as administration of FN, ColVI, FGB and TGFB1-null conditioned media. To summarize, these studies will explore potentially novel mechanisms regulating skeletal muscle insulin sensitivity, highlighting the essential role of IMAT in the development of insulin resistance and type 2 diabetes.