Effect and potential mechanisms of apolipoprotein A1 on adipogenesis of human adipose-derived mesenchymal stem cells

[GW30-e0030]
Authors: Xin Su, Shuai Wang, Daoquan Peng

The Second Xiangya Hospital of Central South University

OBJECTIVES Obesity is associated with a series of metabolic syndromes. The hallmark of obesity is excessive lipid storage in adipose tissue. As is known, the adipose tissue has such abundant adipose-derived mesenchymal stem cells (AMSCs), which can differentiate into mature adipocytes by imbalance between energy intake and expenditure.

Apolipoprotein A1 (ApoA1) is the major protein component of HDL. In addition to anti-atherogenic function of ApoA1, recent works focused on ApoA1 in affecting the process of obesity and the lipid metabolism in mature adipocytes, demonstrating that APOA1 gene SNPs were related to obesity and reduced plasma ApoA1 level was associated with increased prevalence of obesity. However, the underlying mechanisms are ambiguous. The aim of this study was to examine the anti-obesity effect of ApoA1 and the potential mechanisms by which ApoA1 influencing human AMSCs adipogenesis.

METHODS We isolated AMSCs from the epigastric adipocyte tissue of the patients underwent abdominal surgery. The pre-adipocytes were treated with adipogenesis medium and ApoA1 protein. Then we harvested cells at 7^th, 14^th days after adipogenesis. The following tests were performed separately: (1) effects of ApoA1 on the morphological changes of intracellular lipid droplets were observed by Oil red O staining under microscope; (2) effects of ApoA1 on the intracellular TG content were observed by spectrophotometry; (3) effects of ApoA1 on modulating the expression levels of the adipogenesis-related markers, such as C/EBPα, C/EBPβ, FABP4 and FAS, were detected by PCR and Western Blot; (4) by lentiviral transfection technology, we silenced and over-expressed the SORT1 gene in AMSCs. The function of sortilin in AMSCs adipogenesis was investigated and the effects of ApoA1 on sortilin expression were detected by PCR and Western blot; (5) the effect of apoA1 on adipogenesis was further detected in AMSCs with SORT1-silenced or over-expressed.

RESULTS The main results were listed as follows: (1) ApoA1 could reduce the amount of lipid droplets and decrease the TG content synergistically in adipocytes during the adipogenesis; (2) ApoA1 could down-regulate the gene and protein expression level of C/EBPα, C/EBPβ, FABP4 and FAS during the adipogenesis; (3) Sortilin plays an important role in AMSCs adipogenesis. Silencing SORT1 gene could promote excessive adipogenesis of AMSCs, while over-expression of SORT1 gene inhibits the AMSCs adipogenesis; (4) ApoA1 could up-regulate the gene and protein level of sortilin during the adipogenesis; (5) the effect of ApoA1 on inhibiting adipogenesis was attenuated in AMSCs with silencing SORT1 gene; however, there was no significant changes of the effect of ApoA1 on inhibiting adipogenesis in AMSCs with overexpressed SORT1 gene.

CONCLUSIONS In conclusions, our results confirm that sortilin plays an important role in the adipogenesis of human AMSCs. Furthermore, the results indicate that ApoA1 acts as a negative regulator of adipogenesis differentiation in human AMSCs through the inhibition of adipogenesis differentiation-related factors and the promotion the intracellular gene and expression level of sortilin. The present data provide insight into the mechanisms of the inhibitory effects of ApoA1 and suggest that the inhibitory activity of ApoA1 indicates a potential pharmacological intervention specifically directed toward obesity.