Knockdown of CTRP6 Reduces Porcine Intramuscular and Subcutaneous Fat Deposition via Different Signaling Pathways

The regulation of porcine subcutaneous (SC) and intramuscular (IM) fat deposition significantly affects pork quality and the lean meat percentage of the carcass, respectively. C1q/tumor necrosis factor-related protein 6 (CTRP6), an adipokine, plays a significant role in regulating animal fat deposition. The purpose of this study is to understand the effects of CTRP6 gene knockdown in IM and SC adipocytes by RNA-seq analysis. A total of 1830 and 2936 differentially expressed genes (DEGs) were identified in SC and IM adipocytes, respectively. 844 were down- and 2092 were upregulated in SC adipocytes, while 648 were down- and 1182 were upregulated in IM adipocytes. Furthermore, 1778 DGEs were detected only in SC adipocytes, 672 DGEs only in IM adipocytes, and 1158 DGEs in both types of adipocytes. GO analysis indicated that DEGs involved in adipocyte differentiation were significantly enriched in both SC and IM adipocytes following treatment with CTRP6-siRNA. In addition, KEGG pathway enrichment analysis revealed differences of metabolic regulation between IM and SC adipocytes. With CTRP6-silencing, the signaling pathways encompassing Ras and arachidonic acid metabolism were significantly enriched in IM adipocytes, while four other signaling pathways encompassing the TNF, MAPK, p53 and adipocytokine pathway were specifically enriched in SC adipocytes. Interestingly, the effect of CTRP6-siRNA treatment was attenuated by ML-097 (a specific Ras activator) in IM adipocytes and SJ-172550 (a specific p53 activator) in SC adipocytes. Based on these findings, we suggest that CTRP6 may be a differential regulator of the development and metabolism of IM and SC adipose tissues.

猪皮下（SC）与肌内（IM）脂肪沉积的调控，分别显著影响猪肉品质与胴体瘦肉率。C1q/肿瘤坏死因子相关蛋白6（CTRP6）作为一种脂肪因子，在调控动物脂肪沉积过程中发挥关键作用。本研究旨在通过RNA测序（RNA-seq）分析，解析CTRP6基因敲低对肌内与皮下脂肪细胞的调控效应。研究共在皮下脂肪细胞与肌内脂肪细胞中分别鉴定出1830个和2936个差异表达基因（DEGs）。其中皮下脂肪细胞内有844个基因下调、2092个基因上调，肌内脂肪细胞内则存在648个下调基因与1182个上调基因。进一步分析显示，仅在皮下脂肪细胞中检测到1778个差异表达基因，仅在肌内脂肪细胞中检测到672个差异表达基因，另有1158个差异表达基因在两类脂肪细胞中均存在。基因本体（GO）分析结果表明，经CTRP6小干扰RNA（siRNA）处理后，两类脂肪细胞中参与脂肪细胞分化的差异表达基因均显著富集。此外，京都基因与基因组百科全书（KEGG）通路富集分析揭示了肌内与皮下脂肪细胞在代谢调控层面的差异：在CTRP6基因敲低后，Ras信号通路与花生四烯酸代谢通路在肌内脂肪细胞中显著富集；而肿瘤坏死因子（TNF）、丝裂原活化蛋白激酶（MAPK）、p53以及脂肪细胞因子通路这四条通路则特异性富集于皮下脂肪细胞。值得注意的是，在肌内脂肪细胞中，ML-097（一种特异性Ras激活剂）可削弱CTRP6小干扰RNA的处理效应；而在皮下脂肪细胞中，SJ-172550（一种特异性p53激活剂）同样可产生此类削弱作用。基于上述研究结果，我们推测CTRP6或可作为肌内与皮下脂肪组织发育及代谢的差异性调控因子。