C/EBPα and PPARγ-specific transcriptional programs in mature adipocytes in vivo

We took a systematic approach to determine the transcriptional programs that are specifically regulated by C/EBPα in mature white adipocytes of mice on chow diet or high fat diet. The hypothesis tested in the present study was that C/EBPα, as a lipogenic transcription factor, has unique direct targets compared to PPARγ. Our inducible adipocyte specific knockout system allows us to test the direct targets of C/EBPα and PPARγ in adipocytes by short-term C/EBPα or PPARγ elimination in mature adipocytes in vivo. Results indicate that although it has been shown that C/EBPα and PPARγ cross-regulate each other, they have distinct direct responsive targets. Moreover, there are very few C/EBPα specific targets in mice on a chow diet, most of the C/EBPα targets in mature adipocytes are genes modulated by HFD feeding. Total RNA obtained from subcutaneous adipose tissue of Adn-C/EBPα-/- mice on doxycycline chow diet for 3 days, doxycycline high fat diet for 3 days or 1 month and Adn-PPARγ-/- mice on doxycycline chow diet for 3 days, compared to control littermates.

本研究采用系统性研究方法，旨在明确基础饲料饮食（chow diet）或高脂饮食（high fat diet, HFD）喂养小鼠的成熟白色脂肪细胞中，受C/EBPα特异性调控的转录程序。本研究验证的假说为：作为脂肪生成型转录因子的C/EBPα，与PPARγ相比，拥有独特的直接调控靶基因。本研究构建的可诱导脂肪细胞特异性敲除系统，可通过在体内对成熟脂肪细胞进行短期C/EBPα或PPARγ敲除，从而检测脂肪细胞中二者的直接靶基因。研究结果显示：尽管已有研究证实C/EBPα与PPARγ可相互交叉调控，但二者的直接响应靶基因存在显著差异。此外，在基础饲料饮食喂养的小鼠中，C/EBPα的特异性靶基因极少；成熟脂肪细胞中的绝大多数C/EBPα靶基因，均为受HFD调控的基因。本研究提取的总RNA来自以下各组小鼠的皮下脂肪组织：分别经强力霉素（doxycycline）喂养3天的基础饲料饮食Adn-C/EBPα基因敲除（Adn-C/EBPα-/-）小鼠、经强力霉素喂养3天或1个月的高脂饮食Adn-C/EBPα-/-小鼠，以及经强力霉素喂养3天的基础饲料饮食Adn-PPARγ基因敲除（Adn-PPARγ-/-）小鼠，所有样本均以同窝野生型对照小鼠为对照。