Figure 1.

Metformin suppresses the maturation of human visceral preadipocytes with no suppression of cell growth. (A) Metformin suppresses lipid droplet accumulation in human visceral preadipocytes. Oil Red O staining of HPrAD-vis cells was performed after 2 weeks of culture with or without metformin. The stained area was reduced in metformin-treated cells compared to non-treated cells, ×200. (B) The relative stained area of metformin-treated cells and non-treated cells. Cells were cultured for 1 or 2 weeks with or without metformin. The stained areas per ×200 field were measured using Image J. (C) Adiponectin secretion from HPrAD-vis cells is decreased following treatment with metformin. The cells were cultured for 1 or 2 weeks with or without metformin (n=3). The adiponectin concentration in the culture media was determined by ELISA with the specific antibody Acrp30. (D) Metformin did not suppress the growth of fatty cells. Cells were incubated with or without metformin for 1 week. Cell proliferation was measured using a WST-8 assay (n=6). (E) Genes involved in the differentiation and maturation of preadipocytes are downregulated by metformin. Cells were incubated for 1 week with or without metformin. The relative expression of PPARγ and C/EBPα in metformin-treated cells compared to non-treated cells was determined using RT-qPCR with relative quantification (n=3). β-actin was used as an internal control gene. (F) Effect of metformin on gene expression was confirmed by western blot analysis. The cells were incubated for 1 week with or without metformin. The protein expression level of C/EBPα decreased after treatment. HPrAD-vis, human visceral preadipocytes; ELISA, enzyme-linked immunosorbent assay; PPARγ, peroxisome proliferator-activated receptor γ; C/EBPα, CCAAT-enhancer-binding protein α.