Zhongguo quanke yixue (Jul 2022)
Effect of Myostatin Gene Knockout on Browning of White Fat and Related Gene Expression Levels in a Mouse Model of Type 2 Diabetes Mellitus
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.
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