Mechanisms of adipocyte loss in laminopathy-induced lipodystrophy in mice and humans

摘要 脂肪营养不良是一种以脂肪组织损失和再分布为特征的疾病， 相关的代谢并发症，包括糖尿病。最常见的单基因 脂肪营养不良是家族性部分脂肪营养不良2型（FPLD 2），其由以下突变引起： LMNA基因，编码核纤层蛋白A和C。脂肪组织 在青春期正常发育后丢失，是未知的。为了弥补这一不足， 我们选择性地删除小鼠脂肪细胞中的Lmna（LmnaADKO）。我们观察到一个惊人的损失， 成年LmnaADKO小鼠中的白色脂肪组织，沿着肝脏中脂肪沉积增加， 空腹和进食状态下血糖水平升高，循环胰岛素水平升高 与Lmnafl/fl对照相比。对年轻小鼠的分析显示白色 LmnaADKO小鼠的脂肪组织，其与青春期同时进行性丢失。这些 表型密切反映了在患有FPLD 2的人类患者中观察到的那些。为了进一步研究 核纤层蛋白A/C在脂肪组织中的功能和脂肪细胞丢失的机制，我们 现在已经开发出了诱导型LmnaiADKO小鼠以及7个基因敲入小鼠品系，每个品系 含有导致脂肪代谢障碍的突变我们假设，核纤层蛋白A/C是必需的， 保持成熟的脂肪细胞特征，我们将确定分子和细胞 在小鼠模型和人类患者中成熟脂肪细胞丢失的机制。到 为了验证我们的假设，我们提出：1）确定在诱导型LmnaiADKO小鼠中是否缺失 具有核纤层蛋白A/C缺乏的脂肪组织是由于与以下相关的基因失调 脂肪生成、脂肪分解或炎症。2)来描述七个品系的小鼠， Lmna的脂肪营养不良变体，并测试这些脂肪细胞损失的机制是否 小鼠中的表达反映了在诱导型LmnaADKO小鼠以及患有FPLD 2的人类患者中发现的那些。 3)为了研究LMNA变体对脂肪细胞和核形态、基因表达 年轻人脂肪组织库的细胞组成和染色质纵向结构 不具有所有疾病体征的患者，以及健康对照和患有FPLD 2的父母。

Abstract Lipodystrophy is a disorder characterized by adipose tissue loss and redistribution, with associated metabolic complications including diabetes. The most common form of monogenic lipodystrophy is familial partial lipodystrophy type 2 (FPLD2), which is caused by a mutation in the LMNA gene, encoding nuclear lamins A and C. The mechanisms for how adipose tissues are lost, after developing normally through adolescence are unknown. To address this shortfall, we selectively deleted Lmna in adipocytes (LmnaADKO) of mice. We observed a striking loss of white adipose tissue in adult LmnaADKO mice, along with increased fat deposition in the liver, elevated blood glucose levels in both fasting and fed states, increased circulating insulin levels compared to the Lmnafl/fl controls. Analyses of young mice revealed development of white adipose tissue in LmnaADKO mice, which is progressively lost coincident with puberty. These phenotypes closely mirror those observed in human patients with FPLD2. To further investigate the function of lamin A/C in adipose tissue and mechanisms by which adipocytes are lost, we have now developed inducible LmnaiADKO mice as well as seven knock-in mouse lines, each containing a mutation that causes lipodystrophy. We hypothesize that lamin A/C is required to maintain mature adipocyte characteristics, and we will ascertain molecular and cellular mechanisms that underly loss of mature adipocytes in mouse models and human patients. To test our hypotheses, we propose 1) to determine in inducible LmnaiADKO mice whether loss of adipose tissues with lamin A/C deficiency is due to dysregulation of genes associated with lipogenesis, lipolysis, or inflammation. 2) to characterize seven lines of mice that contain lipodystrophic variants across Lmna, and test whether mechanisms of adipocyte loss in these mice reflect those found in inducible LmnaADKO mice, as well as in human patients with FPLD2. 3) to study effects of LMNA variant on adipocyte and nuclear morphology, gene expression, cellular composition of adipose tissue depots, and chromatin architecture longitudinally in young patients who do not have all signs of disease, and in healthy controls and parents with FPLD2.