Yeganeh Azadeh, Taylor Carla G, Poole Jenna, Tworek Leslee, Zahradka Peter
Department of Physiology and Pathophysiology, University of Manitoba, Canada; Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Canada.
Department of Physiology and Pathophysiology, University of Manitoba, Canada; Department of Human Nutritional Sciences, University of Manitoba, Canada; Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg, Canada.
Biochim Biophys Acta. 2016 Apr;1861(4):363-70. doi: 10.1016/j.bbalip.2016.01.004. Epub 2016 Jan 9.
Trans-10, cis-12 (t10-c12) CLA treatment reduces lipid accumulation in differentiating mouse and human adipocytes, and decreases fat mass in mice, yet the mechanism of action remains unknown.
This study investigated the effect of the cis-9, trans-11 (c9-t11) and t10-c12 CLA isomers on the Wnt/β-catenin pathway, which has been reported to inhibit adipogenesis by down-regulating PPARγ.
We observed that t10-c12 CLA treatment of 3T3-L1 adipocytes increases the levels of β-catenin and Ser-675 phosphorylated β-catenin due to inhibition of its degradation. These changes in β-catenin were not linked to either the Wnt/β-catenin agonist Wnt10b or other upstream effectors such as SFRP-5. Paradoxically, the presence of higher amounts of β-catenin did not elevate cyclin D1 levels, which is recognized as a critical target gene. Neither of the CLA isomers affected the localization of β-catenin in the cytosol and nucleus as determined by immunofluorescence microscopy. However, subcellular fractionation suggested the level of cytosolic β-catenin was reduced in t10-c12 CLA treated cells. Immunoprecipitation revealed that t10-c12 CLA increased the interaction of β-catenin and PPARγ.
t10-c12-CLA inhibits adipocyte differentiation by increasing β-catenin stability in 3T3-L1 adipocytes, thus enhancing sequestration of PPARγ in an inactive complex, which prevents progression of adipogenesis.
反式-10，顺式-12（t10-c12）共轭亚油酸（CLA）处理可减少分化中的小鼠和人脂肪细胞中的脂质积累，并降低小鼠的脂肪量，但其作用机制尚不清楚。
本研究调查了顺式-9，反式-11（c9-t11）和t10-c12 CLA异构体对Wnt/β-连环蛋白信号通路的影响，该信号通路据报道可通过下调过氧化物酶体增殖物激活受体γ（PPARγ）来抑制脂肪生成。
我们观察到，用t10-c]2 CLA处理3T3-L1脂肪细胞可增加β-连环蛋白和丝氨酸675磷酸化β-连环蛋白的水平，这是由于其降解受到抑制。β-连环蛋白的这些变化与Wnt/β-连环蛋白激动剂Wnt10b或其他上游效应分子如分泌型卷曲相关蛋白5（SFRP-5）均无关。矛盾的是，较高水平的β-连环蛋白并未提高细胞周期蛋白D1的水平，而细胞周期蛋白D1是一个关键的靶基因。免疫荧光显微镜检查显示，CLA异构体均未影响β-连环蛋白在细胞质和细胞核中的定位。然而，亚细胞分级分离表明，t10-c12 CLA处理的细胞中细胞质β-连环蛋白水平降低。免疫沉淀显示，t10-c12 CLA增加了β-连环蛋白与PPARγ的相互作用。
t10-c12-CLA通过增加3T3-L1脂肪细胞中β-连环蛋白的稳定性来抑制脂肪细胞分化，从而增强PPARγ在无活性复合物中的隔离，阻止脂肪生成的进程。
