Athletes paradox: Mechanisms evaluated in muscle cell culture

描述(申请人提供)：胰岛素抵抗是发展为2型糖尿病的标志之一，然而，胰岛素抵抗的基本机制尚不清楚。肌内甘油三酯(IMTG)是糖尿病的重要预测指标，因为它在普通人群中具有较高的胰岛素敏感性。矛盾的是，经过耐力训练的运动员体内IMTG浓度较高，但对胰岛素非常敏感，这就是所谓的“运动员悖论”。我在K奖中的研究旨在确定运动员、对照组和2型糖尿病患者(T2D)在休息、运动和康复期间IMTG合成率和利用率有何不同。我希望阐明不同群体之间的差异，这可能有助于解释运动员的悖论。 来自我的K奖的初步数据表明，除了增加胰岛素的作用外，运动员还减少了二酰基甘油(DAG)中的饱和脂肪酸种类，IMTG和DAG的分数合成率提高了两倍。这些变化可能会影响骨骼肌内的胰岛素敏感性。 这份R03中建议的研究将在从运动员、2型糖尿病患者和我的K奖中的久坐对照受试者分离出来的原代人类细胞培养中进行。原代人类细胞培养保留了供者的表型，并将允许对肌肉内脂肪饱和和合成与胰岛素作用之间的潜在联系进行机械性评估。 具体目的1：确定饱和DAG定位对胰岛素敏感性的影响。我们假设，饱和的DAG定位于膜上，通过增加PKC的激活来降低胰岛素敏感性。因此，饱和DAG的位置变化与总浓度无关，可能会改变骨骼肌对胰岛素的敏感性。 特定目的2：确定IMTG和DAG合成的急性变化是否影响胰岛素敏感性。我们的假设是IMTG和DAG的周转，而不是浓度，是肌肉内脂肪和胰岛素作用之间的关键联系。因此，肌肉内脂肪合成率的急剧变化可能会改变骨骼肌对胰岛素的敏感性。 这些研究对于确定饱和DAG和/或肌内脂肪的合成速度是否会改变胰岛素敏感性，或者只是在体内存在相关性是至关重要的。这些研究的结果将进一步加深我们对运动员悖论的理解，并为我第一次提交RO1提供关键的初步数据。 公共卫生相关性：2型糖尿病被认为是我们这个时代最大的健康危机之一，因此对这种疾病有更多的了解是至关重要的。肌肉中储存的脂肪似乎会影响患糖尿病的风险，但具体是如何发生的还不清楚。这项研究将研究脂肪的类型或脂肪储存在肌肉中的速度是否会影响从受试者肌肉活检中分离出来的肌肉细胞患糖尿病的风险。

DESCRIPTION (provided by applicant): Insulin resistance is one of the hallmarks in the progression to Type 2 diabetes, however the fundamental mechanisms that underlie insulin resistance are poorly understood. Intramuscular triglyceride (IMTG) appears an important predictor of diabetes as it is high, with low insulin sensitivity in the general population. Paradoxically, endurance trained athletes have a high concentration of IMTG, but are very insulin sensitive, which has been called the "athlete's paradox". Studies in my K award are aimed at determining how IMTG synthesis rates and utilization are different between athletes, controls, and individuals with type 2 diabetes (T2D) during rest, exercise, and recovery. I hope to elucidate differences between groups which may help explain the athlete's paradox. Preliminary data from my K award indicates that in addition to increased insulin action, athletes have decreased saturated fatty acid species within diacylglycerol (DAG), and 2-fold higher fractional synthesis rates for IMTG and DAG. These changes may influence insulin sensitivity within skeletal muscle. Studies proposed in this RO3 will be carried out in primary human cell cultures isolated from athletes, type 2 diabetics and sedentary control subjects in my K award. Primary human cell cultures retain the phenotype of the donor, and will allow a mechanistic evaluation of the potential links between intramuscular lipid saturation and synthesis and insulin action. Specific Aim 1: To determine the role of saturated DAG localization on insulin sensitivity. We hypothesize that saturated DAG localized to membranes decreases insulin sensitivity by increasing PKC activation. Thus, changes in the location of saturated DAG, independent of total concentration, may alter skeletal muscle insulin sensitivity. Specific Aim 2: To determine whether acute changes in IMTG and DAG synthesis influence insulin sensitivity. Our hypothesis is that IMTG and DAG turnover, rather than concentration, is a critical link between intramuscular lipids and insulin action. Thus, acute changes in intramuscular lipid synthesis rates may alter skeletal muscle insulin sensitivity. These studies are vital to determine if either saturated DAG and/or synthesis rates of intramuscular lipid alter insulin sensitivity, or are simply correlated in vivo. Results from these studies will further our understanding of the athlete's paradox, and provide key preliminary data for my first RO1 submission. PUBLIC HEALTH RELEVANCE: Type 2 diabetes is considered one of the greatest health crises of our time, making it vital to understand more about this disease. Fat stored in muscle appears to influence diabetes risk, but exactly how this happens is not clear. This study will examine if the type of fat, or how quickly fat is stored in muscle can influence diabetes risk in muscle cells that are isolated from muscle biopsies from human subjects.