Regulation and mechanism of mannose-binding lectin on autophagy during the differentiation of 3T3-L1 adipocytes / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To investigate the regulatory effects and mechanism of mannose-binding lectin(MBL) on autophagy during the differentiation of 3T3-L1 adipocytes, and provide the feasibility for targeting autophagy to prevent obesity and related pathological conditions in natural immunity.Methods:3T3-L1 preadipocytes were cultured in vitro and induced to differentiation. Cell differentiation and lipid accumulation were analyzed by oil red O staining and CCK-8 was used to detect the effect of different concentrations of MBL (0, 1, 5, 10 μg/ml) on cell proliferation ability at different differentiation stages. Western blot was used to analyze the expression of MBL(10 μg/ml) on the key autophagy factors LC3B, Beclin1 and p62 protein at different stages of differentiation, and the changes of lipid droplet accumulation under the intervention of MBL were observed by oil red O staining. The protein and mRNA expression of autophagy key factors under the intervention of different concentrations of MBL were detected by Western blot and qRT-PCR. And autophagy flow analysis based on autophagic degradation was used to further illustrate the autophagic activity. The expression and phosphorylation of adenosine monophosphate-activated protein kinase(AMPK)/mammalian target of rapamycin(mTOR) signaling molecules were analyzed by Western blot. Results:The results of oil red O staining showed that 3T3-L1 preadipocytes could achieve complete differentiation after 10 days of induction. CCK-8 showed that the concentration of MBL (1-10 μg/ml) in the experimental group had no effect on cell proliferation at different differentiation stages. During the differentiation of 3T3-L1 preadipocytes, Western blot and qRT-PCR showed that the expression of autophagy-related proteins and mRNA levels was enhanced in the MBL treated group, and presented a concentration-dependent relationship. Oil red O staining showed that the lipid droplets in adipocytes at different stages of differentiation are reduced to varying degrees under the intervention of MBL. Fluorescence microscopy results further confirmed that MBL enhanced the autophagy activity of adipocytes by increasing the synthesis of autophagosomes. Moreover, under the intervention of MBL, the phosphorylation level of AMPK was significantly up-regulated, while the phosphorylation level of mTOR was significantly down-regulated, also showing a concentration-dependent relationship.Conclusions:MBL accelerates the autophagy process during the differentiation of 3T3-L1 adipocytes through AMPK/mTOR signaling pathway, reduces lipid accumulation, providing a possible functional pathway for the treatment of obesity and related metabolic diseases.