Effects of Ghrelin on the Proliferation and Differentiation of 3T3-L1 Preadipocytes

The effects of ghrelin on the proliferation and differentiation of 3T3-L1 preadipocytes and the possible mechanisms were investigated in this study. 3T3-L1 preadipocytes were cultured in vitro and treated with different concentrations of ghrelin. Proliferation of 3T3-L1 preadipocytes was evaluated by MTT method and mRNA levels of c-myc and thymidine kinase were detected by RT-PCR. Morphological changes of 3T3-L1 preadipocytes were observed and cell differentiation was measured by oil red O staining. The mRNA levels of peroxisome proliferator-activated receptor γ （PPARγ） and CAAT/enhancer binding protein （C/EBPa） in the cells at different differentiation stages were detected by RT-PCR. The results showed that ghrelin at concentrations of 10^-7 to 10^-15 mol/L could significantly promote preadipocyte proliferation （P〈0.05）, with the most pronounced effect observed at 10^-11 mol/L （P〈0.01）. Treatment of 3T3-L1 preadipocytes with ghrelin significantly increased the mRNA levels of c-myc and thymidine kinase （P〈0.01）. Morphological findings demonstrated that the great amount of lipid droplets appeared in the 3T3-L1 preadipocytes treated with ghrelin. Ghrelin could morphologically induce the differentiation of 3T3-L1 preadipocytes into mature adipocytes. Ghrelin significantly increased the mRNA levels of PPAR7 and C/EBPα during the differentiation, when compared with control group （P〈0.05）. The mRNA levels of PPARγ and C/EBPα were obviously up-regulated with the differentiation of preadipocytes after the treatment of ghrelin. There were significant difference in the mRNA levels of PPARγ and C/EBPu on day 2 and day 8 of the differentiation of 3T3-L1 preadipocytes （P〈0.01）. In conclusion, ghrelin could promote the proliferation and differentiation of 3T3-L1 preadipocytes by increasing the mRNA levels of PPARγ and C/EBPα and therefore enhance the sensitivity of adipocytes against insulin.