Mechanisms Underlying Adipose Tissue Thermogenesis

在与波士顿Joslin糖尿病中心/哈佛医学院的Tseng博士的小组合作中，我们从人颈部脂肪中产生克隆细胞系，并在移植到免疫缺陷裸鼠后在体外和体内表征其成脂分化和代谢功能。使用克隆分析和基因表达谱分析，我们确定了人类前脂肪细胞中独特的基因特征集，这些基因特征集可以预测这些细胞在培养中成熟为脂肪细胞后的产热潜力。这些数据突出了人类BAT和WAT中的细胞异质性，并提供了新的基因靶点来引发前脂肪细胞的产热分化。 在过去的一年里，我们还使用这些永生化的人类脂肪细胞来描述肾上腺素能受体的表达和功能谱，这将指导可用于激活人类BAT和治疗肥胖和代谢疾病的药理学化合物的开发。 与ATCC，我们正在开发一个额外的收集人类脂肪组织细胞群和细胞系从其他仓库。 这些将有助于丰富人体脂肪组织的功能和解剖学映射。 同时，我们测试了饮食诱导的肥胖（DIO）对棕色脂肪组织（BAT）的影响。 我们给6周龄的C57 BL/6小鼠喂食正常食物饮食（NCD）或高脂肪饮食（HFD）。再过16周后，我们测量了体脂、WAT和BAT mRNA表达、葡萄糖耐量以及对胰岛素和β 3-AR激动剂米拉贝隆的葡萄糖摄取率。 我们发现，与NCD相比，HFD增加了体脂和糖耐量受损。WAT和BAT均具有较高的炎症标志物mRNA水平，包括TNF和F4/80。BAT和WAT中的胰岛素信号传导减少，Akt磷酸化减少。饮食标准化的BAT葡萄糖摄取率对米拉贝隆的反应较低。 这些结果支持DIO导致BAT炎症和胰岛素抵抗的模型，导致BAT功能更广泛的损害。

In collaboration with Dr. Tseng's group at the Joslin Diabetes Center / Harvard Medical School in Boston, we generated clonal cell lines from human neck fat and characterized their adipogenic differentiation and metabolic function in vitro and in vivo after transplantation into immune deficient nude mice. Using clonal analysis and gene expression profiling, we identified unique sets of gene signatures in human preadipocytes that could predict the thermogenic potential of these cells once matured in culture into adipocytes. These data highlight the cellular heterogeneity in human BAT and WAT and provide novel gene targets to prime preadipocytes for thermogenic differentiation. This past year, we also used these immortalized human adipocytes to describe the adrenergic receptor expression and functional profiling that will guide the develop of pharmacological compounds that can be used to activate human BAT and treat obesity and metabolic disease. With ATCC, we are developing an additional collection of human adipose tissue cell populations and cell lines from additional depots. These will help enrich the functional and anatomical mapping of human adipose tissue. In parallel, we tested the effects of diet-induced obesity (DIO) on brown adipose tissue (BAT). We fed 6-week-old C57BL/6 mice either a normal chow diet (NCD) or a high-fat diet (HFD). After 16 additional weeks, we measured body fat, WAT, and BAT mRNA expression, glucose tolerance, and rates of glucose uptake in response to insulin and the beta3-AR agonist mirabegron. We saw that compared with NCD, HFD increased body fat and impaired glucose tolerance. Both WAT and BAT had higher mRNA levels of markers of inflammation, including TNF and F4/80. Insulin signaling in BAT and WAT was reduced, with decreased Akt phosphorylation. Diet-normalized BAT glucose uptake rates were lower in response to mirabegron. These results support a model in which DIO leads to BAT inflammation and insulin resistance, leading to a broader impairment of BAT function.