Glucocorticoids & adipocyte function in human obesity

说明(申请人提供)：肥胖，特别是内脏和上半身皮下肥胖，与肥胖相关的共病风险较高，包括2型糖尿病和心血管疾病。糖皮质激素(GC)是脂肪沉积和脂肪分布的强大调节剂。肥胖与皮下和内脏脂肪组织中局部皮质醇产生的增加有关。此外，内脏(大网膜)脂肪组织在体外对GC更敏感，这表明GC作用的不同导致了脂肪细胞代谢和内分泌功能的不同。我们的初步基因芯片研究表明，GCs对人类脂肪组织的慢性处理在体外调节了许多与新陈代谢和炎症相关的基因，并发现了几个潜在的重要GC靶点，这些靶点可能有助于不同基因网络的仓库特异性激活。这些变化与体内生理学的相关性以及GC协调调节脂肪细胞代谢和内分泌功能的不同基因网络的活动的潜在机制尚不清楚。因此，当前提案的具体目标1将集中在确定腹部皮下脂肪组织中受体内糖皮质激素调节的基因。由于GC效应取决于营养状态/胰岛素，我们将比较在禁食状态下或与膳食联合使用氢化可的松对全球基因表达的影响(AffyMatrix基因阵列)。脂肪组织将在服用氢化可的松3.5h后(有或没有进餐)进行采样，以确定主要的GC靶基因。为了阐明GC在内脏脂肪中的不同作用机制，Special Aim 2将使用候选基因方法比较体外培养的ABD sc和大网膜脂肪组织以及原代脂肪细胞中GC调控的基因表达。具体目标3将通过分析候选基因和基因阵列分析下游靶标的表达变化，以及脂肪细胞代谢和脂肪因子分泌的功能变化，在脂肪细胞水平上测试表观主要GC靶标的功能重要性。总而言之，这些数据将通过指出内脏肥胖及其代谢并发症的治疗干预的新靶点，加强对GC促进肥胖，特别是内脏脂肪沉积的机制的理解。与公共卫生有关：“肥胖”流行病及其代谢并发症降低了大多数美国人的生活质量。我们建议的工作涉及糖皮质激素，即应激期间分泌的激素，调节人类脂肪组织中沉积的脂肪量的机制，以及脂肪是否主要沉积在中央(腹部)或外周仓库，从而增加患糖尿病和心血管疾病的风险。这些数据将为揭开GC在人类脂肪组织中的复杂、多效性作用提供关键的第一步。此外，识别脂肪中GC作用的关键靶点可能为GC在协调脂肪细胞的内分泌、免疫和代谢功能的整合中的作用提供新的见解。

DESCRIPTION (provided by applicant): Obesity, particularly visceral and upper body subcutaneous obesity, is associated with higher risk for obesity-related co-morbidities, including type 2 diabetes and cardiovascular disease. Glucocorticoids (GC) are powerful regulators of fat deposition and fat distribution. Obesity is associated with an increase in local cortisol production within both subcutaneous and visceral adipose tissues. In addition, visceral (omental) adipose tissue is more responsive to GC in vitro, suggesting depot differences in GC action contribute to depot differences in fat cell metabolism and endocrine function. Our preliminary gene array studies show that chronic treatment of human adipose tissue with GCs regulates numerous genes related to metabolism and inflammation in vitro, and identified several potentially important GC targets that could contribute to the depot-specific activation of different gene networks. The relevance of these changes to in vivo physiology and the underlying mechanisms by which GC coordinate the activity of different gene networks that regulate the metabolic and endocrine functions of the adipocyte remain unclear. Thus, Specific Aim 1 of the current proposal will focus on identifying the genes in abdominal subcutaneous adipose tissue that are regulated by glucocorticoids in vivo. Because GC effects depend on nutritional state/insulin, we will compare the effects of hydrocortisone administered in the fasted state or in combination with meals, on global gene expression (Affymatrix gene arrays). Adipose tissue will be sampled 3.5h after hydrocortisone administration (with or without a meal) to determine primary GC target genes. To elucidate the mechanisms underlying the differential effects of GC in visceral fat, Specific Aim 2 will compare GC-regulated gene expression in organ cultures of Abd sc and omental adipose tissue and primary adipocytes in vitro using a candidate gene approach. Specific Aim 3 will test the functional importance of apparent primary GC targets at the level of the adipocyte with analysis of alterations in the expression of downstream targets using analysis of candidate genes and gene arrays, and functional changes in adipocyte metabolism and adipokine secretion. Collectively, these data will enhance understanding of the mechanisms by which GC promote obesity, particularly visceral fat deposition, by pointing to novel targets for therapeutic intervention for visceral obesity and its metabolic complications. PUBLIC HEALTH RELEVANCE: The `diabesity' epidemic and its metabolic complications detract from the quality of life of the majority of Americans. Our proposed work addresses the mechanisms by which glucocorticoids, hormones secreted during stress, regulate the amount of fat deposited in human adipose tissues, and whether the fat is mainly deposited in central (abdominal) or peripheral depots and hence contribute to risk for developing diabetes and cardiovascular disease. These data will provide a critical first step to unraveling the complex, pleiotropic effects of GC in human adipose tissues. Furthermore, identifying the key targets of GC action in fat may provide novel insights into the effects of GC in orchestrating the integration of the endocrine, immune and metabolic functions of the adipocyte.