S100A16 Regulates Adipocyte Differentiation And Its Mechanism Through Wnt/β-Catenin Signaling Pathway

Objective:To investigate the role of S100A16 in adipocyte and to explore the effect and molecular mechanism of S100A16 on obesity and adipogenesis.METHODS:Twenty male mice of 5 weeks-old adipocyte-specific-S100A16overexpression transgenic mice(aP2-S100A16^Tg-/+)and Twenty male mice of C57BL/6 mice were randomly divided into normal diet group and high-fat diet group.There were 4 groups:C57BL/6 mice with normal diet group（n=10）;C57BL/6 mice with high-fat diet group（n=10）;aP2-S100A16^Tg-/+mice with normal diet group（n=10）;aP2-S100A16^Tg-/+mice with high-fat diet group（n=10）.Mice were fed for12 weeks.The weight of the mice was recorded weekly and random blood glucose was measured.Intraperitoneal glucose tolerance test（IPGTT）and insulin tolerance test（ITT）were performed at appropriate time.Mice were sacrificed after feeding 12weeks,and the weight of body and visceral fat were measured,hematoxylin-eosin staining（HE）was subsequently used to assess the degree of fat vacuoles change.The levels of triglyceride,cholesterol,LDL and HDL were also detected.Expression of S100A16 and some markers associated with Wnt signaling pathway were analyzed by Western blotting and Quantitative Real-time PCR.The interaction between S100A16 and GSK-3βwhich is a mark of Wnt/β-Catenin signaling pathway,was detected by immunofluorescence（IF）and co-immunoprecipitation（co-IP）.S100A16 overexpression plasmid was constructed and 3T3-L1 preadipocytes were treated by upregulating the expression of S100A16,or adding ICG001,Wnt/β-Catenin signaling pathway inhibitor.Then 3T3-L1 preadipocytes were differentiated in MDI medium under different treatment,and adipocyte differentiation was examined on day 8 by ORO staining.RESULTS:The protein levels of S100A16 in the adipose tissue of aP2-S100A16^Tg-/+mice was significantly higher than that of C57BL/6 mice,indicating that the model mice were successfully constructed.There was no significant difference in body weight,visceral fat weight between the two genotype mice,but the aP2-S100A16^Tg-/+mice increased concentrations of serum glucose and size of adipocyte,and decreased glucose tolerance and insulin sensitivity,compared with the control group,especially with high-fat diet.The protein levels of S100A16 in the adipose tissue of aP2-S100A16^Tg-/+mice was higher than that of C57BL/6 mice,and the high-fat diet also increased the expression of S100A16 andβ-Catenin.Simultaneously,the expression of GSK-3βwas decreased.There is a potential interaction between S100A16 and GSK-3βand they are colocalized in the cytoplasm.Upregulation of S100A16 expression promoted the formation of lipid droplets in 3T3-L1preadipocytes,but lipid accumulation was decreased significantly after adding ICG001.Conclusion:The adipocyte-specific-S100A16 overexpression transgenic mice can promote lipid accumulation,reduce glucose tolerance and induce insulin resistance.S100A16 overexpression can activate the Wnt/β-Catenin signaling pathway.S100A16 promotes adipocyte differentiation through the Wnt/β-Catenin signaling pathway.