Page 54 - 中国全科医学2022-21

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Corresponding author：WANG Yanfang，Chief physician；E-mail：yfwang612@126.com
【Abstract】 Background The browning of white fat is a hot spot in metabolic disease research. Myostatin （Mstn）
inhibits muscle growth，and has correlation with the growth and differentiation of adipocytes，but its effect on the browning of
white fat in type 2 diabetes mellitus（T2DM） is still unclear. Objective To examine changes in expression levels of genes
related to the browning of white fat following Mstn gene knockout to assess the effect of Mstn on the browning of white fat in a mouse
model of T2DM. Methods This study was conducted from January 2019 to January 2020. Thirty-six male，SPF，C57BL/6N
mice were selected. The 12 wild-type（WT） mice were equally randomized into WT group and WT+DM group，12 heterozygous
mice with Mstn gene knockout〔Mstn（+/-）〕 were equally randomized into Mstn（+/-） group and Mstn（+/-）+DM group，
12 homozygous mice with Mstn gene knockout〔Mstn（-/-）〕 were equally randomized into Mstn（-/-） group and Mstn
（-/-）+DM group. The WT group，Mstn（+/-） group，Mstn（-/-） group received a normal diet，and the WT+DM group，
Mstn（+/-）+DM group，Mstn（-/-）+DM group received a high-fat diet and a small dose of streptozotocin to construct T2DM
models. When the intervention was finished in all groups，weight，body length，white fat and brown fat mass，and serum lipids
〔triacylglycerol（TG），total cholesterol（TC），low-density lipoprotein cholesterol（LDL-C） and high-density lipoprotein
cholesterol（HDL-C）measured using automatic biochemical analyzer，and free fatty acid（FFA）measured using ELISA〕
were collected. The Lee's index，white-brown fat ratio and fat mass index were calculated. The morphology of white fat and brown
fat cells was observed using HE staining. The relative expression levels of peroxisome proliferator-activated receptor gamma
（PPAR-γ），peroxisome proliferator-activated receptor gamma coactivator-1 alpha（PGC-1α），uncoupling protein 1（UCP1）
and cluster of differentiation 137（CD137） protein in white and brown fat were determined by Western-blotting. Results Mstn
（-/-） group had lower Lee's index，white-brown fat ratio and levels of serum TG and TC compared with WT group（P<0.05）.
Mstn（-/-） group had lower Lee's index，white-brown fat ratio and level of serum TG than Mstn（+/-） group（P<0.05）.
Compared with WT group，WT+DM group had lower Lee's index and level of serum HDL-C，and higher white-brown fat ratio，
fat mass index，serum TG，TC，LDL-C and FFA levels（P<0.05）. Mstn（-/-）+DM group had lower levels of Lee's index，
white-brown fat ratio，fat mass index，serum TC，TG，LDL-C and FFA，but higher serum HDL-C than did WT+DM group
（P<0.05）. Mstn（-/-）+DM group had lower levels of Lee's index，white-brown fat ratio and serum TC，but higher serum
HDL-C than did Mstn（+/-）+DM group（P<0.05）. Compared with WT group，Mstn（-/-） group had higher relative
expression levels of PPAR-γ，PGC-1α，UCP1 and CD137 protein in white and brown fat（P<0.05）. Mstn（-/-） group
had higher relative expression levels of PPAR-γ，PGC-1α and CD137 protein in white and brown fat than did Mstn（+/-）
group（P<0.05）. The relative expression levels of PPAR-γ，PGC-1α，UCP1 and CD137 protein in white and brown fat in
WT+DM group were lower than those in WT group（P<0.05）. The relative expression levels of PPAR-γ，PGC-1α，UCP1
and CD137 protein in white and brown fat in Mstn（-/-）+DM group were higher than those in WT+DM group or Mstn（+/-）+DM
group（P<0.05）. Conclusion The inhibition of Mstn gene expression may be against T2DM-induced obesity phenotypes such
as white fat accumulation and lipid metabolism disorder，and up-regulate the expression levels of PPAR-γ，PGC-1α，UCP1
and CD137 genes，promoting the browning of white fat.
【Key words】 Diabetes mellitus，type 2；Myostatin；White fat browning；Adipocytes，white；Adipocytes，brown；
Mice

肌肉生长抑制素（Mstn）是 1997 年发现的于骨骼 杂合型 Mstn 基因敲除〔Mstn（+/-）〕小鼠 12 只，纯
肌中高表达的转化生长因子 β 超家族成员之一，又称 合 型 Mstn 基 因 敲 除〔Mstn（-/-）〕 小 鼠 12 只，SPF
为生长分化因子 8，其从小鼠骨骼肌 cDNA 文库克隆， 级，品系 C57BL/6N，6 周龄，雄性，由赛业生物科技
对肌肉量起负调节作用 ［1］ 。除影响肌肉生长分化外， 有限公司提供〔动物实验许可证号：SCXK（苏）2020-
Mstn 还具有调节脂代谢的作用。文献报道，Mstn 可在 0006〕。小鼠适应性饲养 1 周，室内温度 22~24 ℃，湿
体外抑制前体脂肪细胞的分化；特异性敲除 Mstn 基因 度 40%~60%，保持昼夜 12 h 节律，自由进食、饮水。
后，高脂或正常饮食喂养的小鼠均表现为脂肪量减少， 本研究实验过程遵循河南大学实验动物伦理相关规定，
肌肉量增加 ［2-3］ 。本研究观察 Mstn 基因敲除的 2 型糖 符合 3R 原则。本实验时间为 2019 年 1 月至 2020 年 1 月。
尿病（T2DM）小鼠白色脂肪棕色化相关基因表达变化， 1.2 主要仪器与试剂 AU400 全自动生化分析仪（美
探究 Mstn 对 T2DM 小鼠白色脂肪棕色化的影响。 国 Beckman 公司）；酶标仪（美国 BioTeK 公司）；脱
1 材料与方法 水机、包埋机、病理切片机（武汉俊杰电子有限公司）；
1.1 实验动物 野生型（wild type，WT）小鼠 12 只， 光学显微镜及成像系统（日本 Nikon 公司）；脱色摇