Glucagon-like peptide 1 regulates adipogenesis in 3T3-L1 preadipocytes.

Glucagon-like peptide 1 (GLP-1), a gut-derived peptide, has been reported to have profound effects on metabolism and to reduce insulin resistance. Adipocyte hyperplasia stimulated by preadipocyte differentiation has a positive effect on adipose tissue insulin sensitivity. However, it remains less clear whether GLP-1 plays a role in adipogenesis. In this study, we examined the effect of GLP-1 on preadipocyte differentiation and investigated the mechanisms that may be involved in this effect. In our 3T3-L1 cell study, we tested the levels of adipocyte-specific markers and signaling pathways during preadipocyte differentiation. In addition, Oil Red O staining was used to examine lipid accumulation. Image Pro Plus 5.02 was used to analyze the size and number of lipid droplets. We found that GLP-1 elevated the protein expression levels of free fatty acid-binding protein 4 (aP2) and the transcription factor peroxisome proliferator-activated receptor-γ (PPAR‑γ) in a dose-dependent manner during 3T3‑L1 preadipocyte differentiation. Furthermore, RT‑PCR results showed that GLP-1 promoted CCAAT/enhancer-binding protein α (C/EBPα) and lipoprotein lipase (LPL) expression at the transcriptional level. These data suggest that GLP-1 promotes preadipocyte differentiation. Our study also found that treatment of the cells with 100 nM GLP-1 enhanced the phosphorylation of Akt signaling during the first 24 h of differentiation. Although Oil Red O staining showed that GLP‑1 had no significant effect on lipid accumulation, there were increased numbers of small adipocytes in the cells treated with 100 nM GLP‑1. Taken together, these results indicate that GLP-1 regulates 3T3‑L1 adipogenesis and the Akt signaling pathway may be involved in this process. The differentiated small adipocytes may have a positive effect against insulin resistance and obesity.