Interleukin-10 and Regulation of Skeletal Muscle Insulin Action

描述(申请人提供)：骨骼肌胰岛素抵抗在2型糖尿病的发展中起主要作用，并可能与炎症和脂代谢改变有关。在肥胖和糖尿病患者中，循环中的脂肪酸和促炎细胞因子水平升高，并被证明会导致骨骼肌中的胰岛素抵抗。相比之下，血浆IL-10水平，一种抗炎细胞因子，与胰岛素敏感性呈正相关，并在代谢综合征受试者中降低。我们最近发现，IL-10的急性治疗可以预防肌肉中脂质介导的胰岛素抵抗，这种抵抗与小鼠胰岛素信号的增加有关。为了进一步研究IL-10在骨骼肌胰岛素作用中的作用，我们最近培育了肌肉特异性过表达IL-10的转基因小鼠(MCK-IL10小鼠)。我们的初步数据表明，MCK-IL10小鼠可以免受脂肪介导的胰岛素信号和肌肉中葡萄糖代谢缺陷的影响。我们还发现，饮食诱导的胰岛素抵抗与骨骼肌巨噬细胞浸润的增加有关，并且这些影响在MCK-IL10小鼠中被减弱。我们假设IL-10通过1)阻断脂质介导的PKC-8/JNK/IKK活化和下调胰岛素信号转导，和/或2)抑制肥胖相关的巨噬细胞浸润和抑制巨噬细胞衍生细胞因子对糖代谢的有害影响来预防肌肉胰岛素抵抗。根据我们的初步数据显示，IL-10处理的小鼠肌肉内脂肪水平发生了变化，目标1将检查肌肉IL-10过度表达对葡萄糖和脂肪代谢的影响。在目标2中，我们将通过慢性高脂喂养、急性脂肪输注和遗传性肥胖小鼠模型来确定MCK-IL10小鼠免受脂质介导的胰岛素抵抗的机制。目标3将确定巨噬细胞在饮食诱导肥胖和急性脂肪输注模型中肌肉胰岛素抵抗中的作用。我们还将使用单核细胞标记法观察巨噬细胞的迁移，并检查使用氯屈磷酸钠去除巨噬细胞对脂质介导的胰岛素抵抗的影响。最后，我们将研究交替激活的巨噬细胞在MCK-IL10表型中的作用。总体而言，我们提出的研究将确定IL-10在调节骨骼肌胰岛素作用中的新作用，并发现治疗胰岛素抵抗和2型糖尿病的新靶点。与公共卫生相关。骨骼肌胰岛素抵抗在2型糖尿病的发展中起着重要作用，2型糖尿病影响着全球超过1.7亿人，可能与炎症和脂代谢改变有关。这项拟议的研究将探讨白细胞介素10调节骨骼肌胰岛素作用和防止骨骼肌中脂质介导的胰岛素抵抗的机制。我们的发现将为肥胖和炎症在胰岛素抵抗中的作用提供重要的见解，并进一步确定治疗2型糖尿病的新靶点。

DESCRIPTION (provided by applicant): Skeletal muscle insulin resistance plays a primary role in the development of type 2 diabetes and may be causally associated with inflammation and altered lipid metabolism. Circulating levels of fatty acids and pro-inflammatory cytokines are elevated in obese, diabetic subjects and shown to cause insulin resistance in skeletal muscle. In contrast, plasma levels of IL-10, an anti-inflammatory cytokine, are positively related to insulin sensitivity and reduced in subjects with metabolic syndrome. We have recently shown that acute treatment with IL-10 prevents lipid-mediated insulin resistance in muscle that is associated with increased insulin signaling in mice. To further examine the role of IL-10 in skeletal muscle insulin action, we have recently generated transgenic mice with muscle-specific overexpression of IL-10 (MCK-IL10 mice). Our preliminary data indicate that MCK-IL10 mice are protected from lipid- mediated defects in insulin signaling and glucose metabolism in muscle. We also find that diet-induced insulin resistance is associated with increased macrophage infiltration in skeletal muscle, and these effects are attenuated in MCK-IL10 mice. We hypothesize that IL-10 prevents muscle insulin resistance by 1) blocking lipid-mediated activation of PKC-8/JNK/IKK and down regulation of insulin signaling, and/or 2) suppressing obesity-associated macrophage infiltration and inhibiting the deleterious effects of macrophage-derived cytokines on glucose metabolism. Based on our preliminary data showing altered intramuscular lipid levels in IL-10 treated mice, the Aim 1 will examine the effects of muscle IL-10 overexpression on glucose and lipid metabolism. In Aim 2, we will identify the mechanism by which MCK-IL10 mice are protected from lipid-mediated insulin resistance using chronic high-fat feeding, acute lipid infusion, and genetically obese mouse models. The Aim 3 will determine the role of macrophage infiltration in muscle insulin resistance in diet-induced obesity and acute lipid infusion models. We will also observe macrophage migration using monocyte labeling and examine the effects of macrophage depletion using clodronate on lipid-mediated insulin resistance. Lastly, we will investigate the role of alternatively-activated macrophages in MCK-IL10 phenotypes. Overall, our proposed studies will identify a novel role of IL-10 in the regulation of skeletal muscle insulin action and discover new therapeutic targets in the treatment of insulin resistance and type 2 diabetes. PUBLIC HEALTH RELEVANCE. Skeletal muscle insulin resistance plays a major role in the development of type 2 diabetes, which impacts more than 170 million people worldwide and may be causally associated with inflammation and altered lipid metabolism. The proposed studies will examine the mechanisms by which interleukin-10 regulates skeletal muscle insulin action and prevents lipid-mediated insulin resistance in skeletal muscle. Our findings will provide important insights into the role of obesity and inflammation in insulin resistance and further identify novel therapeutic targets in the treatment of type 2 diabetes.