Crtc1 deficiency aggravates fat accumulation in the white adipose tissue

Obesity is described as excessive fat accumulation that drives the development of glucose and lipid metabolism disorders, which is linked to multiple diseases. Crtc1, known as a transducer to regulate Creb activity, plays an important role in several basic physiological functions. Previous studies have shown visible hyperappetite and obesity in Crtc1 knockout (Crtc1-/-) mice. To investigate the effect of Crtc1 on fat accumulation in different organs, we generated Crtc1-/- mice by CRISPR/Cas9 system and regarded Crtc1+/+ as control under the normal feeding conditions. Compared with Crtc1+/+ mice, Crtc1-/- mice exhibited increase of bodyweight which was resulted from the abnormal expansion of white adipocyte. In addition, Crtc1-/- mice were more prone to hyperglycemia and dyslipidemia, supported by the levels of plasma glucose and FABP4. The results of RNA-seq and qRT-PCR in liver and epididymal white adipose tissue (eWAT) showed that the fat accumulation caused by Crtc1 deletion was mainly related to the lipid metabolism of adipose tissue, not liver. Moreover, the up-regulation of lipid metabolism in eWAT induced by Crtc1 deficiency was closely related to the up-regulation of Ppar? signaling pathway. Our findings suggested that endogenous Crtc1 had a protective role in obesity development and Crtc1 deficiency aggravates the progression of fat accumulation and related co-morbidities, which introduced a new insight for treatment of obesity. Overall design: 12 weeks old male Crtc1-/- mice and Crtc1+/+ mice were euthanatized by cervical dislocation. A piece of liver and eWAT were used to extracted RNA according to the manufacturer's instructions. Transcriptome sequencing of RNA was completed by Beijing Genomics Institution (BGI). Two independent biological replicate samples were sequenced for each group.

肥胖被定义为过量脂肪堆积，可诱发糖脂代谢紊乱，且与多种疾病密切相关。Crtc1作为调控Creb活性的转导因子，在多项基础生理功能中发挥关键作用。既往研究显示，Crtc1敲除（Crtc1-/-）小鼠存在明显的食欲亢进与肥胖表型。为探究Crtc1对不同器官脂肪堆积的影响，本研究通过CRISPR/Cas9系统构建了Crtc1-/-小鼠，并将正常饲喂条件下的Crtc1野生型（Crtc1+/+）小鼠设为对照。与Crtc1+/+小鼠相比，Crtc1-/-小鼠体重显著升高，该现象源于白色脂肪细胞的异常增殖与扩张。此外，通过血浆葡萄糖与脂肪酸结合蛋白4（FABP4）水平验证，Crtc1-/-小鼠更易出现高血糖与血脂异常。对肝脏与附睾白色脂肪组织（eWAT）开展RNA测序（RNA-seq）与实时定量反转录聚合酶链反应（qRT-PCR）检测，结果显示Crtc1缺失所致的脂肪堆积主要与脂肪组织脂代谢相关，而非肝脏。此外，Crtc1缺失诱导的eWAT脂代谢上调与Ppar信号通路的上调密切相关。本研究结果表明，内源性Crtc1在肥胖发生发展中具有保护作用，而Crtc1缺失会加重脂肪堆积及相关并发症的进展，为肥胖的治疗提供了全新的研究视角。实验整体设计：选取12周龄雄性Crtc1-/-与Crtc1+/+小鼠，采用颈椎脱臼法处死。取部分肝脏与eWAT组织，按照试剂盒说明书提取RNA。RNA转录组测序工作由北京基因组研究所（BGI）完成，每组设置2个独立生物学重复样本并进行测序。