3，5-二碘-L-甲状腺素对白色脂肪棕色化的作用

Effects of 3,5-diiodo-L-thyronine on browning of white adipose tissue

目的探究3，5-二碘-L-甲状腺素（T2）诱导白色脂肪棕色化的作用。方法31、3-L1脂肪前体细胞诱导分化并用油红O染色进行鉴定；细胞分化过程中予不同浓度梯度（1nmol／L、10nmol／L、100nmol／L）的T2处理，待细胞分化成熟后，分别用实时荧光定量PCR、Western印迹检测解耦联蛋白-1（UCP-1）表达水平的变化；仅予高浓度（100nmol／L）T2处理，Western印迹法检测其他棕色脂肪功能性基因，包括诱导细胞死亡DNA片段化因子α样效应因子A（CIDEA）、过氧化物酶体增殖物活化受体吖协同刺激因子-1α（PGC-1α）蛋白表达变化。结果3T3-L1脂肪前体细胞呈成纤维细胞样形态，胞浆中无脂滴；诱导分化成熟后光镜下油红O染色可见细胞内大量环状脂滴。在细胞分化过程中予不同浓度T2干预后，分化成熟的脂肪细胞上UCP-1mRNA水平均有升高（t=3．97、11．77、17．7，P均〈0．05），蛋白表达水平也均有改变（t=13．31、14．55、23．62，P均〈0．05），且在高浓度（100nmol／L）下最明显。在高浓度T2（100nmol／L）干预下，成熟脂肪细胞的棕色脂肪其他功能性基因蛋白CIDEA、PGC-1α水平表达增加（t=15．92、17．36，P均〈0．05）。结论T2可诱导由3T3-L1脂肪前体细胞分化而来的成熟白色脂肪细胞表达棕色脂肪功能性基因。

Objective To explore the effects of 3,5-diiodo-L-thyronine（ T2 ） on browning of white adipose tissue. Methods Differentiation of 3T3-L1 adipose precursor cells were induced and identified by oil red O staining. During the differentiation process, 3T3-L1 were treated by different concentrations of T2 （ 1 nmol/L, 10 nmol/L, 100 nmol/L）. After the maturation of 3T3-L1, the level of uncoupling protein-1 （ UCP-1） mRNA and protein were detected by RT-PCR and Western blotting, respectively. Specific proteins of brown adipose tissue including cell death-inducing DNA fragmentation factor alpha like effector A （CIDEA） and peroxisome proliferator-activated receptor γ coactivator-1 α （PGC-1 α） were detected by Western blotting only in cells treated by 100 nmol/L T2. Results 3T3-L1 adipose precursor cells were fibroblast-like without liquid droplets in the cytoplasm, but after maturation, a large number of annular lipid drops were observed under light microscope by oil red O staining. The level of UCP-1 mRNA in mature fat cells were increased （ t = 3.97, 11.77,17.7 ; all P 〈 0.05 ） and the level of protein were also changed （ t = 13.31, 14.55, 23.62; all P 〈 0.05）, especially in cells treated by 100 nmol/L T2. The brown adpose tissue specific proteins CIDEA and PGC-1α were also increased in cells treated by 100 nmol/L T2 （t = 15.92,17.36; all P 〈 0.05）. Conclusion T2 induces the expression of specific genes of brown adipose tissue in mature fat cells which are differentiated from 3T3-L1 adipose precursor cells.