染色质重塑因子BAF60s介导的糖脂代谢重塑在2型糖尿病胰岛β细胞功能损伤中的作用与机制研究

Emerging evidence suggests that metabolic regulation and signaling play an important role in pancreatic β dedifferentiation, reprogramming and dysfunction in type 2 diabetes. However, the underlying mechanism is unclear. Our previous studies identified BAF60s chromatin remodeling factors, including three members BAF60a, BAF60b and BAF60c, as key players in nutrient sensing and metabolic regulation in skeletal muscle and liver, as well as the maintenance of systemic energy homeostasis. In the preliminary studies, using β cell specific BAF60s deficient mice, we found that BAF60s may play key roles in the development of pancreatic β dedifferentiation, reprogramming and dysfunction in type 2 diabetes. Mechanistically, inactivation of BAF60s differentially regulated metabolic gene expression and signaling, leading to impaired glucose sensing, calcium response, and insulin secretion from β cells. Based on these data, we hypothesize that BAF60s, through transcriptional regulation of metabolic gene expression and signaling, may play a critical role in pancreatic β cell dedifferentiation, reprogramming and dysfunction in type 2 diabetes. In this proposal, using a combination of β cell specific knockout and transgenic mouse models, pancreatic tissue samples from diabetic patients and non-human primates, and cultured primary pancreatic islets and β cell lines, we plan to elucidate the role and mechanism of BAF60s-mediated epigenetic regulation of metabolic reprogramming and signaling in the control of β cell dedifferentiation, reprogramming and dysfunction in type 2 diabetes. Successful completion of this study will provide new insights into the mechanisms of β cell failure, and form the basis for the development of new therapeutic targets for diabetes.

最近许多研究提示糖脂代谢重塑和稳态失衡在2型糖尿病胰岛β细胞去分化、重编程和功能损伤中发挥重要作用，但其具体机制仍不清楚。申请人过去研究发现染色质重塑因子BAF60s对骨骼肌和肝脏的营养感受、代谢调控和全身糖脂稳态的维持至关重要。利用β细胞特异性BAF60s敲除和转基因小鼠，我们前期研究发现BAF60s对胰岛β细胞去分化、重编程和胰岛素分泌功能具有重要调控作用。进一步机制研究提示BAF60s可能通过影响细胞葡萄糖感受和代谢重塑，调控胰岛β细胞的去分化和重编程，从而在2型糖尿病胰岛β细胞功能损伤中发挥重要作用。本项目我们将以糖脂代谢时空网络调控为研究核心，围绕本年度重点资助研究方向四，以β细胞特异性BAF60s敲除和转基因小鼠为动物模型，结合人和灵长类动物组织样本，在体内、胰岛、细胞和分子水平重点研究糖脂代谢重塑和稳态失衡在2型糖尿病胰岛β细胞去分化、重编程和功能损伤中的作用和分子机制。

胰岛β细胞功能储备和损伤程度是2型糖尿病进程和转归的重要决定因素。2型糖尿病是由遗传和环境因素共同作用引起的。我们近期研究发现SWI/SNF染色质重塑因子BAF60s（包括BAF60a、b、c三个亚型）介导的表观遗传学机制在骨骼肌、肝脏和脂肪的环境感应、糖脂代谢和全身能量稳态的维持中发挥重要调控作用。本项目中，我们成功构建了胰岛β细胞特异性BAF60s基因敲除（BsBKO）和过表达（BsBTg）小鼠模型，从正反两个方面深入研究BAF60s在2型糖尿病胰岛β细胞功能损伤的作用。结果发现BAF60a、b、c基因敲除（BsBKO）小鼠均表现为不同程度的胰岛β细胞功能障碍，尤其是在高脂饮食喂养条件下，均出现高血糖和糖耐量受损，而对胰岛素敏感性没有明显影响。相反，BsBTg均能够显著缓解和改善高脂饮食诱导的小鼠胰岛β细胞功能损伤和2型糖尿病症状。进一步，我们利用ATAC-Seq、CUT&Tag-Seq、RNA-Seq、基于BioID的蛋白质组学、代谢物组学、胰岛动态灌流等多种技术，对上述模型小鼠的原代胰岛和细胞模型，从基因组、转录组、蛋白互作、代谢流和胰岛素分泌功能等多维度进行了整合分析，发现BAF60a、b、c通过不同的转录调控和信号转导机制影响胰岛β细胞糖脂代谢、细胞特性（Identity）、胰岛局部免疫微环境和组织重构，互补协作，精准调节胰岛β细胞的数量、分化和胰岛素分泌功能。我们还发现，高浓度的脂肪酸和炎症因子能够显著抑制胰岛β细胞中BAF60s的表达，提示了胰岛β细胞中BAF60s能够整合肥胖和2型糖尿病相关的脂毒性和慢性炎症等环境信号，通过染色质重塑和转录重编程，在2型糖尿病胰岛β细胞数量、特性（Identity）和功能的动态变化和损伤过程中发挥关键调控作用。本研究有助于进一步阐明2型糖尿病胰岛β细胞去分化、重编程和功能损伤的机制，从而为2型糖尿病的治疗提供新的理论基础。

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