Effect of Aging on Preadipocyte Differentiation

描述（由申请人提供）：新的脂肪细胞在一生中由前脂肪细胞发育而来。随着年龄的增长，脂肪组织的功能和分布发生了巨大的变化。中年后，脂肪从皮下重新分布到代谢有害的内脏储存器，脂质在肌肉、骨髓和肝脏积累，而不是脂肪储存器，增加了患糖尿病和动脉粥样硬化的易感性。我们的假设是，随着年龄的增长，脂肪细胞祖细胞的过度利用会产生衰老的前脂肪细胞，其分泌表型会损害脂肪的形成。这在不同的仓库中以不同的速率发生，被重复复制和代谢压力加速，并在肥胖中过早发生。我们发现前脂肪细胞分化随着衰老和炎症细胞因子的产生以及对代谢应激的易感性的增加而受损。我们证明了来自不同脂肪库的前脂肪细胞本质上是不同的。我们发现衰老的前脂肪细胞随着年龄的增长和体外和体内（肥胖）的重复复制而以储存依赖的方式积累。这些发现开辟了一种全新的方式来看待脂肪组织的重新分配和衰老的功能障碍。目的1是测试功能失调的前脂肪细胞随着年龄的增长而积累的假设，并剖析相关机制，并测试人类脂肪储存依赖性。我们将测试细胞衰老介质（DNA损伤相关的foci/ 3-H2AX/ p53/p21组分；衰老相关的foci/p16/Rb组分），并区分可能介导衰老前脂肪细胞生成的过程。我们将通过改变前脂肪细胞的复制历史、随着年龄增长而增加的细胞因子以及引发代谢应激来扰乱它们。目的2是确定衰老前脂肪细胞分泌表型，复制史和储存来源对其的影响，及其对趋化性的影响。传代晚期人类皮肤成纤维细胞获得异常的促炎分泌表型。我们将定义老年受试者与年轻受试者、体外晚期与早期前体脂肪细胞以及肥胖患者前体脂肪细胞的分泌谱。我们将测试这种异常的分泌表型是否会引起邻近细胞的功能障碍，从而放大影响。目的3是验证功能失调的前脂肪细胞导致衰老导致脂肪生成受损的假设，确定相关机制，并在此基础上测试分子干预。C/EBP1和PPAR3对脂肪形成至关重要。C/EBP1和PPAR3的表达随着年龄的增长而减弱。我们发现，暴露于老年动物的前脂肪细胞，随着年龄的增长，前脂肪细胞释放的TNF1增加，以及应激反应性抗脂肪生成调节因子（CUGBP， CHOP）都会阻碍老年大鼠的脂肪生成。将使用老年受试者前脂肪细胞的共同培养和条件培养基来干扰这些过程。我们将定义人类衰老中的抗脂肪生成机制及其与前脂肪细胞衰老的关系。我们将测试恢复老年大鼠前脂肪细胞脂肪生成的干预措施是否也适用于人类。这些研究代表了一种全新的方式来思考导致老年人常见的脂肪再分配和代谢功能障碍的机制。公共卫生相关性：脂肪组织功能随着年龄的增长而显著改变。中年后，脂肪从皮肤下的区域重新分配到腹部代谢有害的仓库。脂肪在肌肉、骨髓、肝脏和其他部位的脂肪组织外积聚。这种变化增加了患糖尿病和动脉粥样硬化的易感性。越来越多的证据表明，在动物模型中，脂肪组织功能是影响最大寿命和年龄相关疾病发病时间的过程的纽带，这使我们不禁要问：1)随着年龄的增长，脂肪细胞祖细胞的过度利用会导致功能失调的细胞产生阻碍邻近细胞功能的蛋白质；2)这是否可能是老年脂肪功能失调的基础。这代表了一种全新的方式来思考导致脂肪再分配、糖尿病及其并发症在老年人中如此常见的机制。

DESCRIPTION (provided by applicant): New fat cells develop from preadipocytes throughout life. Fat tissue function and distribution change dramatically with aging. After middle age, fat is redistributed from subcutaneous to metabolically deleterious visceral depots and lipid accumulates in muscle, marrow, and liver instead of fat depots, with increased predisposition to diabetes and atherosclerosis. Our hypothesis is that fat cell progenitor overutilization with aging generates senescent preadipocytes with a secretory phenotype that impairs adipogenesis. This occurs at different rates in different depots, is accelerated by repeated replication and metabolic stress, and occurs prematurely in obesity. We found preadipocyte differentiation is impaired with aging and inflammatory cytokine generation and susceptibility to metabolic stress increase. We demonstrated preadipocytes from different fat depots are inherently distinct. We found senescent preadipocytes accumulate with aging and after repeated replication in vitro and in vivo (in obesity) in a depot-dependent manner. These findings open an entirely new way of looking at fat tissue redistribution and dysfunction with aging. Aim 1 is to test the hypothesis that dysfunctional preadipocytes accumulate with aging and dissect responsible mechanisms, and test fat depot-dependence in humans. We will test cellular senescence mediators (DNA damage-associated foci/ 3-H2AX/ p53/p21 components; senescence associated foci/p16/Rb components) and distinguish between processes that potentially mediate senescent preadipocyte generation. We will perturb them by varying preadipocyte replicative history, with cytokines that increase with aging, and by eliciting metabolic stress. Aim 2 is to define the aging preadipocyte secretory phenotype, the impact of replicative history and depot origin upon it, and its effect on chemotaxis. Late passage human skin fibroblasts acquire an aberrant, pro-inflammatory secretory phenotype. We will define the secretory profile of preadipocytes from old vs. younger subjects, later vs. early passage preadipocytes in vitro, and in obesity. We will test if this aberrant secretory phenotype induces dysfunction in neighboring cells, magnifying impact. Aim 3 is to test the hypothesis that dysfunctional preadipocytes contribute to impaired adipogenesis with aging, define responsible mechanisms and, based on these, test molecular interventions. C/EBP1 and PPAR3 are essential for adipogenesis. C/EBP1 and PPAR3 expression are impaired with aging. We found exposure to preadipocytes from old animals, increased TNF1 release by preadipocytes with aging, and stress-responsive, anti-adipogenic regulators (CUGBP, CHOP) all impede adipogenesis in old rats. Co-culture and conditioned medium from preadipocytes of old subjects will be used to perturb these processes. We will define anti-adipogenic mechanisms in human aging and their relation to preadipocyte senescence. We will test if interventions that restore adipogenesis in preadipocytes from old rats do so in humans. These studies represent an entirely new way of thinking about mechanisms causing the fat redistribution and metabolic dysfunction common in old age. PUBLIC HEALTH RELEVANCE: Fat tissue function changes dramatically with aging. After middle age, fat is redistributed from regions under the skin to metabolically deleterious depots in the abdomen. Fat accumulates outside of fat tissue in muscle, marrow, the liver, and other sites. This change increases the predisposition to diabetes and atherosclerosis. The mounting evidence placing fat tissue function at the nexus of processes impacting maximum lifespan and timing of age-related disease onset in animal models has led us to ask if: 1) fat cell progenitor overutilization with aging results in dysfunctional cells that produce proteins that impede function of neighboring cells and 2) if this may underlie fat dysfunction in old age. This represents an entirely new way of thinking about mechanisms causing the fat redistribution, diabetes, and their complications so common in old age.