组蛋白H3甲基转移酶Ezh2与小鼠脂肪细胞分化关系研究

Study on the Relationship between Histone H3 Methyltransferase Ezh2and Adipocyte Differentiation in Mice

目的:探索组蛋白H3K27me3甲基转移酶Ezh2对小鼠白色、棕色和米色脂肪细胞分化的影响。方法:构建诱导型Ezh2全身敲除小鼠(Ezh2flox/flox CAGcre)并于6周龄时腹腔注射他莫昔芬诱导敲除,以同窝、同性别、相同基因型假诱导(腹腔注射玉米油)小鼠作为对照。诱导完成后在光镜下观察脂肪细胞形态,采用Western Blot法检测脂肪组织中H3K27me3、Ezh2和Ucp1的蛋白表达量。采用Realtime PCR法检测不同部位脂肪组织的脂肪分化相关基因(Pparγ、Adipoq和Fabp4)、棕色脂肪标志基因(Ucp1、Cidea和Prdm16)和米色脂肪标志基因(CD137、Tmem26和Tbx1)的表达。检测敲除组小鼠的冷耐受能力,并予以高脂饮食诱导肥胖,观察小鼠体重增长情况、诱导结束后小鼠的糖耐量和胰岛素敏感性指标。结果:Ezh2敲除小鼠Ezh2和H3K27me3的蛋白含量降低,背部棕色脂肪细胞脂滴明显小于对照组,Ucp1的基因和蛋白表达明显高于对照组(P<0.05);敲除组小鼠白色脂肪细胞分化较差,米色脂肪分化增加,米色脂肪的Ucp1和Tbx1基因表达增加(P<0.05)。敲除小鼠可以更好地耐受冷刺激,并抵抗高脂饮食诱导的肥胖和胰岛素抵抗。结论:Ezh2在体内促进白色脂肪细胞的分化,抑制棕色和米色脂肪细胞分化。

Objective: To explore the effect of histone H3 K27 me3 methyltransferase Ezh2 on the differentiation of white, brown and beige adipocytes in mice. Methods: Ezh2 whole body knockout mice(Ezh2flox/flox CAGcre) were constructed and induced by intraperitoneal injection of tamoxifen at the age of 6 weeks. The same litter, same sex and same genotype pseudoinduction mice(intraperitoneal injection of corn oil) were used as control. After induction completion, the morphology of adipocytes was observed under light microscope, and the expression of H3 K27 me3, Ezh2 and Ucp1 in adipose tissue was detected by Western Blot method. Realtime PCR was used to detect the expression of adipose differentiation-related genes(Pparγ, Adipoq and Fabp4), brown adipocyte markers(Ucp1, Cidea and Prdm16) and beige adipocyte markers(CD137, Tmem26 and Tbx1) in different parts of adipose tissues. The cold tolerance of knockout mice was tested, and obesity was induced by high fat diet. The weight gain, glucose tolerance and insulin sensitivity of mice were observed after induction. Results: The protein content of Ezh2 and H3 K27 me3 in Ezh2 knockout mice decreased, the lipid droplets of brown adipocytes in interscapular region were significantly smaller than those in control group, and the gene and protein expression of Ucp1 were significantly higher than those in control group(P<0.05);the differentiation of white adipocytes in Ezh2 knockout mice was poor, the differentiation of beige adipocytes increased, and the expression of Ucp1 and Tbx1 genes in beige adipocytes increased(P<0.05).Ezh2 knockout mice were better able to tolerate cold stimulation and resist obesity and insulin resistance induced by a high-fat diet.Conclusion: Ezh2 promotes the differentiation of white adipocytes and inhibits the differentiation of brown and beige adipocytes in vivo.