Cross-regulation of Immunometabolism and Circadian Pathways in Obesity Pathophysiology

项目摘要 肥胖和糖尿病在轮班工作、睡眠减少和社会时差的人群中增加。 高脂饮食（HFD）使内在的昼夜节律周期与光/暗周期不一致，并改变了代谢的振荡。 内脏脂肪组织是控制能量平衡、葡萄糖调节和炎症反应的关键部位， 紊乱相反，将HFD限制在黑暗期只会使进餐时间与昼夜节律重新对齐， 增强胰岛素敏感性，促进健康肥胖。内脏脂肪组织的昼夜节律紊乱 导致肥胖的病理生理学仍然未知。令人兴奋的新数据显示， 脂肪细胞线粒体呼吸的节律，在活动期开始时具有最大解偶联， 取决于功能时钟。此外，13 C-葡萄糖进入三羧酸（TCA）循环也是一个重要的因素。 在活跃期开始时最高，表明WAT代谢通量的自主昼夜节律控制 在白天/黑夜的循环中。令人惊讶的是，在Bmal 1-/-脂肪细胞中，我们观察到脂肪细胞的重编程， 代谢增加，琥珀酸中的13 C标记增加，其他TCA中间体水平降低，这是一个特征， 压力和ROS积累。在这里，我们试图测试的假设，生物钟控制 在燃料进入TCA循环的水平上，内脏脂肪组织内的能量通量通过一个过程 被HFD破坏。在目标1中，我们将检验喂养时间和脂肪的昼夜协调的假设， 能量利用循环促进健康的脂肪扩张，使用遗传谱系示踪动物和代谢 表型分析我们将评估脂肪组织重塑和13 C葡萄糖流入TCA循环， 自由进食或限时进食普通食物或HFD的小鼠中， 在热中性（30 ℃）下，将其置于光照（不定时喂食）或黑暗（最佳喂食时间）时期。我们还将测试 WAT时钟的要求和HFD中脂肪特异性BMAL 1过表达对脂肪代谢的影响 重塑、炎症、纤维化和葡萄糖稳态。目标1的结果将建立相互作用 WAT时钟和喂养时间之间的能量通量，代谢健康和健康的能力 脂肪膨胀，特别是与黑暗相比， 只有和AL队列。在目标2中，我们将测试HFD废除昼夜能量周期的假设， 内脏脂肪组织，并诱导表观遗传重塑朝向促炎细胞命运。我们将执行 串联染色质和表达谱分析，以确定时间特征和分子驱动因素， 内脏WAT重塑随意和光和黑暗喂养的HFD小鼠。最后，我们将研究是否 HFD期间BMAL 1过表达保留了常规食物喂养小鼠的健康染色质景观。 目标2的结果将确定染色质活性和转录的时钟控制如何有助于 健康的肥胖总的来说，这些研究将定义一天中的时间在脂肪生成和营养通量中的作用， 发现新的目标，以打击肥胖和昼夜节律紊乱的免疫代谢并发症。

Project Summary Obesity and diabetes are increased among individuals subjected to shiftwork, reduced sleep, and social jetlag. High fat diet (HFD) misaligns intrinsic circadian cycles with the light/dark cycle and alters oscillations of metabolic genes in visceral adipose tissue, a key site in the control of energy balance, glucose regulation, and inflammatory disorders. Conversely, restricting HFD to the dark period only realigns meal time with circadian rhythms and enhances insulin sensitivity, promoting healthful obesity. How circadian disruption in visceral adipose tissue contributes to obesity pathophysiology remains unknown. In exciting new data, we show strong day/night rhythms in adipocyte mitochondrial respiration with maximal uncoupling at the onset of the active period that is dependent upon a functional clock. Further, 13C-glucose entry into the tricarboxylic acid (TCA) cycle is also highest at the beginning of the active period, indicating autonomous circadian control of WAT metabolic flux across the day/night cycle. Surprisingly, in Bmal1-/- adipocytes, we observe reprogramming of adipocyte metabolism with increased 13C labeling in succinate and reduced levels of other TCA intermediates, a signature of stress and ROS accumulation. Here we seek to test the hypothesis that the circadian clock controls energy flux within visceral adipose tissue at the level of fuel entry into the TCA cycle through a process disrupted by HFD. In Aim 1, we will test the hypothesis that circadian coordination of feeding time and adipose energy utilization cycles promote healthful adipose expansion using genetic lineage tracer animals and metabolic phenotyping. We will assess adipose tissue remodeling and 13C glucose flux into the TCA cycle in addition to lipid and organic acids across the light-dark cycle in mice fed regular chow or HFD either ad lib or time-restricted to the light (misttimed feeding) or dark (optimal time feeding) period at thermoneutrality (30oC). We will also test the requirement of the WAT clock and the effect of adipose-specific BMAL1 overexpression in HFD on adipose remodeling, inflammation, fibrosis, and glucose homeostasis. Aim 1 results will establish the interplay between the WAT clock and feeding time in energy flux, metabolic health, and capacity for healthful adipose expansion, particularly with the new addition of the light-only feeding group for comparison to the dark- only and AL cohorts. In Aim 2, we will test the hypothesis that HFD abrogates circadian energetic cycles in visceral adipose tissue and induces epigenetic remodeling towards a proinflammatory cell fate. We will perform tandem chromatin and expression profiling in adipocytes to identify the time signature and molecular drivers of visceral WAT remodeling in ad lib and light- and dark-only-fed mice on HFD. Finally, we will examine whether BMAL1 overexpression during HFD preserves the healthful chromatin landscape of regular chow fed mice. Results of Aim 2 will determine how clock control of chromatin activity and transcription contributes to healthful obesity. Collectively, these studies will define the role of time-of-day in adipogenesis and nutrient flux, uncovering novel targets to combat the immunometabolic complications of obesity and circadian disruption.