Effects of Apelin-13 on proliferation and differentiation of 3T3-L1 preadipocytes

Objective To explore the effects of Apelin-13 on the proliferation and differentiation of 3T3-L1 preadipocytes and its possible mechanisms. Methods 3T3-L1 preadipocytes were cultured in vitro. The logarithmic growth cells were treated with different concentrations of Apelin-13. The effects of Apelin-13 on the proliferation of 3T3-L1 preadipocytes were detected by methyl thiazolyl tetrazolium (MTT) assay. The classical cocktail method was used to induce the differentiation of 3T3-L1 preadipocytes. The logarithmic growth cells were divided into experimental group and control group. In experimental group, the culture mediums were replaced on the 2nd, 4th, 6th and 8th day of differentiation induction, respectively; at the same time cells were intervened with Apelin-13 in a concentration with the strongest inhibitory effect on cell livability. Cells in control group received no intervention. On the 8th day of differentiation induction, the degree of differentiation was detected by Oil red O staining, lipid and triglyceride assessment. Peroxisome proliferator activated receptor γ (PPARγ) mRNA and protein expression were detected by RT-PCR and Western blotting on the 2nd, 4th, 6th and 8th day of differentiation induction, respectively. Results The cell livability of 3T3-L1 preadipocytes was decreased along with the increase of the concentration as well as the intervention time of Apelin-13. The lowest livability of 3T3-L1 preadipocytes was observed after 96 hours of intervention with 100 μmol/L Apelin-13. Compared with control group, the lipid droplets, lipid and triglyceride content of 3T3-L1 preadipocytes treated with Apelin-13 were significantly lower (t=4.526, 5.353, 4.827, all P<0.05). The expression of PPARγ mRNA and protein in 3T3-L1 preadipocytes treated with Apelin-13 were decreased significantly on the 6th and 8th day of differentiation (t=4.962, 5.416, 4.734, 5.627, all P<0.05), compared with control group. Conclusions Apelin-13 inhibits the proliferation of 3T3-L1 preadipocytes in a concentration and time dependent manner. In addition, Apelin-13 could inhibit the formation of lipid droplets, and reduce lipid accumulation and triglyceride content during the differentiation of 3T3-L1 preadipocytes. The possible mechanism is related to inhibit the expression of PPARγ. Key words: Apelin; 3T3-L1 preadipocytes; Cell proliferation; Cell differentiation; Peroxisome proliferator activated receptor γ