Circadian regulation of adipose tissue; the role of the myeloid system

重要性：维持能量平衡和新陈代谢健康正在成为我们这个时代的一项重大挑战。肥胖的后果包括心血管和代谢疾病(如2型糖尿病)、癌症增加、肌肉骨骼疾病(如骨关节炎)和传染病风险，尤其是冠状病毒死亡。体重调节的治疗方法一直集中在大脑中的食欲通路或肠道中的营养吸收；这两种方法都不能产生足够的成功。因此，需要新的、有效的和安全的战略。大多数系统和细胞的能量代谢与生物钟的调节网络密切相关。值得注意的是，核糖体生物发生表现出强烈的日常振荡，受昼夜节律和摄食节律的调节，通过翻译控制(例如核糖体蛋白和翻译因子的生物合成)发挥作用。节律性也影响线粒体的动力学(合成、分裂/融合)和氧化活性，部分原因是时钟与包括PGC1a在内的线粒体生物发生调节因子之间的紧密耦合。考虑到时间在能量代谢中所起的作用，在分析脂肪功能时考虑昼夜节律因素是必要的。假设：脂肪组织床的时间调节反映了交感神经系统的输入，交感神经系统与视交叉上核的中央大脑时钟密切相关，并流动着外部的明暗周期；脂肪细胞中的时钟跟随着进食和禁食周期。这打开了内部去同步化的可能性，在脂肪组织中昼夜节律振荡器运行不同步，结果未知。来源：我们将使用小鼠作为临床前模型。我们有一系列带有生物钟成分的转基因小鼠，以允许组织特异性基因敲除。我们可以操纵光周期和摄食时间，以推动脂肪细胞和交感神经系统昼夜节律的变化。我们可以使用组织特异性的TNFa表达来驱动脂肪床上的炎症，模拟人类肥胖的炎症条件，或者在患有系统性炎症(如类风湿性关节炎)的人的脂肪床上。计划：我们将分析昼夜节律失调对脂肪组织中脂肪细胞和髓细胞隔间的影响，重点是昼夜节律功能、基因表达和能量代谢功能(脂肪分解/脂肪生成，线粒体功能)。我们将首先关注破坏巨噬细胞的昼夜节律功能，靶向脂肪组织相关的巨噬细胞和新发现的交感神经系统相关的巨噬细胞(由A Domingos博士发现)。然后我们将转向光周期操作，以及有时间限制的喂食方案，以驱动未对准。我们将通过外科手术去神经来阻断交感神经对脂肪床的支配，并在交感神经元中转基因定向丢失生物钟。我们也可以使用β-肾上腺素能系统的药物阻断。我们将使用一种新的有条件表达TNFa的小鼠模型，通过将脂联素-CRERET小鼠与ROSA26停滞型TNFa小鼠杂交，限制在脂肪床上。这个模型将测试脂肪床炎症的流行情况，我们可以在标准和高脂肪肥胖条件下进行测试。我们将寻求调查脂肪床细胞的异质性，并将选择性地利用单细胞RNA-SEQ和ATAC-SEQ，可以在相同的细胞中完成，以确定这种错位对脂肪床细胞类型特定分化的后果。我们与NN的联系将主要集中在科学讨论、我们的模型的商业背景和我们的发现。这将通过共同商定的项目更新会议加以促进。根据进展情况，我们可能会在个案的基础上寻求具体的合作安排

Importance: Maintenance of energy balance and metabolic health is emerging as a major challenge of our time. The consequences of obesity include cardiovascular and metabolic disease (e.g. type 2 diabetes), as well as increased cancer, musculoskeletal (e.g. osteoarthritis), and infectious disease risk, notably coronavirus mortality. Therapeutic approaches to body weight regulation have focussed on appetitive pathways in the brain or nutrient absorption in the gut; with neither approach yielding adequate success. Therefore, new, effective and safe strategies are needed. Most systemic and cellular energy metabolism is closely tied into the regulatory network of the circadian clock. Notably, ribosome biogenesis shows strong daily oscillations that are regulated by both circadian and feeding rhythms, acting through the translation control (e.g. ribosomal protein and translation factor biosynthesis). Rhythmicity also affects mitochondrial dynamics (synthesis, fission/fusion) and oxidative activity, in part due to the close coupling between the clock and regulators of mitochondrial biogenesis including Pgc1a. Given the role played by timing in energy metabolism it is essential to consider circadian factors in analysis of adipose function. Hypotheses: Regulation of timing in adipose tissue beds reflects inputs from the sympathetic nervous system, which is closely linked to the central brain clock in the suprachiasmatic nucleus, and flows external light-dark cycles; and the clock in the adipocyte which follows feeding and fasting cycles. This opens the possibility of internal desynchrony, with circadian oscillators running out of phase in adipose tissue, with unknown consequences.Resources: we will use mouse as a pre-clinical model. We have a range of transgenic mice with circadian clock components floxed, to allow tissue-specific gene knockout. We can manipulate light cycles, and feeding times, in order to drive changes in circadian phase in adipocytes, and the sympathetic nervous system. We can use tissue specific TNFa expression to drive inflammation to adipose beds, to model conditions of inflammation seen in human obesity, or in human adipose beds in patients with systemic inflammation eg rheumatoid arthritis.Plans: We will analyse the impact of circadian misalignment on adipocyte and myeloid cell compartments in adipose tissue, focussed on circadian function, gene expression, and energy metabolic function (lipolysis/lipogenesis, mitochondrial function).We will initially focus on disrupting circadian function in macrophages, to target the adipose tissue associated macrophage, and the newly-identified sympathetic nervous system associated macrophages (discovered by Dr A Domingos).We will then move to light cycle manipulation, and time-restricted feeding protocols to drive misalignment. We will block sympathetic innervation to the adipose beds using surgical denervation, and transgenic directed loss of the circadian clock in the sympathetic neurones. We can also use beta adrenergic system pharmacological blockade. We will use a new mouse model of conditional TNFa expression, confined to adipose beds by crossing adiponectin-creERET mice with a ROSA26 stop-flox TNFa mouse. This model will test the prevalent condition of adipose bed inflammation, which we can test under standard and high fat obesity conditions.We will seek to investigate cellular heterogeneity in the adipose beds and will make selective use of single cell RNA-seq and ATAC-seq, which can be done in the same cells, to establish the consequences of such misalignment for cell type-specific differentiation in adipose beds.Our links with NN will mainly focus on scientific discussions, and the commercial context of our models, and our findings. This will be facilitated by mutually agreed project update meetings. Depending on progress we may seek specific collaborative arrangements, on a case-by-case basis