Single-nucleus RNA-sequencing reveals NRF1/NFE2L1 as a key determining metabolic state and fate decision of brown adipocytes in mice [bulk RNA-seq]

Brown adipose tissue (BAT) is a major site of nonshivering thermogenesis (NST) in mammals and might play an important role in human obesity and energy homeostasis. Recent single-cell/nucleus RNA-sequencing studies have revealed heterogeneity in thermogenesis among brown adipocytes, such as the findings of low thermogenesis and regulated thermogenesis in brown adipocytes. Activating and enhancing function adipocytes (BAC) has acquired attention as a possible therapeutic intervention for metabolic diseases. Nuclear factor-erythroid 2-related factor 1 (NFE2L1, also known as Nrf1), a CNC-bZIP protein, is a master regulator of multiple cellular functions and responds to various stress in many cells and tissues. NFE2L1 acts as a guardian role in BAC function providing increased proteometabolic quality control for adapting to cold or obesity. Our previous studies demonstrated that NFE2L1-dependent lipolytic activity is crucial for white adipose tissue (WAT) plasticity and lipid homeostasis. To further clarify the role of NFE2L1 in adipocytes, we focused on the phenotype and gene expression profiling of BAT in adipocyte-specific Nfe2l1-knockout [Nfe2l1(f)-KO] mice. We found that deletion of Nfe2l1 decreased core body temperature and cold intolerance under cold exposure. Compared with floxed mice, the BAT of Nfe2l1(f)-KO mice expressed substantially lower levels of many genes related to lipolysis, thermogenesis, oxidative capacity of mitochondria, cellular respiration while higher genes related to inflammation, pyroptosis. By snRNA-seq, we found that Nfe2l1-knockout resulted in increased antigen processing and presentation (APP), necroptosis and NOD-like receptor signal pathway (NOD) signaling pathways in most subpopulations of BAC, with devastating effects on a normal subpopulation of BAC with low thermogenesis and high necroptosis genes expression. Absent of Nfe2l1 impairs the function of BAC, causing a morphological "whitening" phenotype with adipocyte hypertrophy and severe inflammation. Moreover, the adipose inflammation and pyroptosis in Nfe2l1(f)-KO mice could be mitigated by cold exposure or beta3-agonist treatment. These findings provided a deeper insight into the function of NFE2L1 in the metabolic programming of brown adipocytes. Bulk RNA-sequencing profiles of BAT from Flox and Nfe2l1(f)-KO mice at 4 and 14~16 weeks.棕色脂肪组织（brown adipose tissue, BAT）是哺乳动物非战栗产热（nonshivering thermogenesis, NST）的主要部位，可能在人类肥胖与能量稳态调控中发挥关键作用。近期的单细胞/单细胞核RNA测序（single-cell/nucleus RNA-sequencing）研究揭示了棕色脂肪细胞产热功能的异质性，例如发现棕色脂肪细胞存在低产热型与调节型产热两种亚群。功能活化增强的棕色脂肪细胞（Activating and enhancing function brown adipocytes, BAC）作为代谢疾病的潜在治疗靶点，已受到学界广泛关注。核因子红细胞系2相关因子1（Nuclear factor-erythroid 2-related factor 1, NFE2L1，又称Nrf1）属于CNC-bZIP蛋白家族，是多种细胞功能的核心调控因子，可响应多种细胞与组织中的应激信号。NFE2L1作为BAC功能的监护因子，通过增强蛋白代谢质量控制以适应寒冷或肥胖状态。我们既往研究证实，依赖NFE2L1的脂解活性对白色脂肪组织（white adipose tissue, WAT）的可塑性与脂质稳态至关重要。为进一步明确NFE2L1在脂肪细胞中的生物学功能，本研究聚焦于脂肪细胞特异性Nfe2l1基因敲除[Nfe2l1(f)-KO]小鼠的BAT表型与基因表达谱分析。研究发现，在寒冷暴露条件下，Nfe2l1基因敲除会降低小鼠核心体温并引发寒冷不耐受。与floxed对照小鼠相比，Nfe2l1(f)-KO小鼠的BAT中，众多与脂解、产热、线粒体氧化能力及细胞呼吸相关的基因表达水平显著降低，而与炎症、焦亡相关的基因表达水平则显著升高。通过单细胞核RNA测序（single-nucleus RNA sequencing, snRNA-seq），我们发现Nfe2l1基因敲除会使大多数BAC亚群中抗原加工呈递（antigen processing and presentation, APP）、坏死性凋亡以及NOD样受体信号通路（NOD-like receptor signal pathway, NOD）的富集程度显著升高，并对低产热且高坏死性凋亡基因表达的正常BAC亚群造成毁灭性影响。Nfe2l1缺失会损伤BAC的功能，引发脂肪细胞肥大与严重炎症的形态学“白色化”表型。此外，寒冷暴露或β3受体激动剂（beta3-agonist）处理可缓解Nfe2l1(f)-KO小鼠的脂肪组织炎症与焦亡。本研究结果为阐明NFE2L1在棕色脂肪细胞代谢编程中的功能提供了更深入的科学认识。本数据集包含4周龄及14~16周龄floxed对照小鼠与Nfe2l1(f)-KO小鼠的BAT组织批量RNA测序（bulk RNA-sequencing）转录组谱数据。