Roles of BMAL1 in adipocytes

脂肪分化受多种转录因子调控，如C/EBP家族和PPARγ2。在这项研究中，我们研究了BMAL 1在脂肪形成中的作用。在3 T3-L1细胞的脂肪分化过程中，BMAL mRNA的水平开始增加，在分化的细胞中高度表达。在从C57 BL/6 J小鼠分离的白色脂肪组织中，与基质-血管部分相比，BMALI主要在脂肪细胞部分中表达。通过RNAi技术敲低3 T3-L1细胞中的BMAL 1 mRNA表达允许细胞在细胞中积累最少量的脂滴。分化7天后，对照细胞中脂肪细胞相关基因的表达被极大地诱导。与形态学观察结果一致，在BMAL 1敲低细胞中诱导了最少量的脂肪细胞相关基因。腺病毒介导的BMAL 1在成熟脂肪细胞中的表达诱导了脂质代谢所需的几个基因。这些结果表明BMAL 1在3 T3-L1细胞中的脂肪形成中起作用。那我们希望检测BMALI是否具有促进NIH 3 T3细胞（一种相对非脂肪形成的细胞系）中脂肪形成的能力。用表达高水平全长BMALI mRNA的载体或对照载体稳定转染NIH 3 T3细胞。为了评价克隆的分化效力，将细胞培养至汇合，然后用含有PPAR γ2配体（曲格列酮或ETYA）的标准分化诱导培养基处理。与对照细胞相比，BMAL 1在NIH 3 T3细胞中的过表达诱导了显著量的脂质积累。通过测量脂肪细胞相关基因的表达也证实了这一结果。这些结果表明，BMAL 1在脂肪分化的调节中起重要作用。

Adipose differentiation is regulated by several transcription factors, such as a C/EBP family and PPARγ2. In this study, we have studied the roles of the BMAL1 in adipogenesis. During adipose differentiation in 3T3-L1 cells, the level of the BMAL mRNA began to increase is highly expressed in differentiated cells. In white adipose tissues isolated from C57BL/6J mice, BMALI is predominantly expressed in adipocytes fraction compared with stromal-vascular fraction. Knock down of BMAL1 mRNA expression in 3T3-L1 cells by RNAi technique allowed the cells to accumulate minimum amounts of lipid droplets in the cells. Expression of adipocytes-related genes was greatly induced in the control cells after 7 days of differentiation. Consistent with the morphological observations, a minimum amount of adipocytes-related genes was induced in the BMAL 1 knock down cells. Adenovirus-mediated expression of BMAL1 in mature adipocytes induced several genes required for lipid metabolism. These results indicated that BMAL1 play roles in adipogenesis in 3T3-L1 cells. Then. we wished to examine if BMALI has the ability to promote adipogenesis in NIH 3T3 cells, a relatively nonadipogenic cell line. NIH 3T3 cells were stably transfected with a vector expressing high levels of full length BMALI mRNA, or a control vector. To evaluate the differentiation potency of the clones, the cells were cultured to confluence and then treated with a standard differentiation-induction medium containing and PPAR γ2 ligands (troglitazone or ETYA). Overexpression of BMAL1 in NIH 3T3 cells induced significant amounts of lipids accumulation compared with the control cells. The results were also confirmed by measuring the expression of adipocyte-related genes. These results suggest that BMAL1 plays important role in the regulation of adipose differentiation.