Apolipoprotein A5 inhibits adipogenesis of human adipose-derived mesenchymal stem cells through modulating CIDEC expression

[GW30-e0029]

Authors: Xin Su, Daoquan Peng

The Second Xiangya Hospital of Central South University

OBJECTIVES Obesity is associated with 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 A5 (ApoA5) is a novel apolipoprotein. Recently, evidence indicates that lower plasma level of ApoA5 was found in obese subjects and was inversely correlated with BMI. However, the underlying mechanisms are ambiguous. On the other hand, it is noteworthy that ApoA5 could also modulate TG storage in hepatocytes, indicating a crucial intracellular role of ApoA5 in TG metabolism. Since adipocytes provide the largest storage depot for TG, we hypothesized apoA5 might also target to adipocytes and regulate TG storage. The aims of this research were to explore the effect of ApoA5 in AMSCs adipogenesis and the underlying mechanisms.

METHODS We isolated AMSCs from the epigastric adipocyte tissue of the patients underwent abdominal surgery. The pre-adipocytes were treated with adipogenesis medium and human recombinant ApoA5 protein. Then we harvested cells at 7^th, 14^th, 21^st days after adipogenesis. The following tests were performed: (1) effects of ApoA5 on morphological changes of intracellular lipid droplets were observed under microscope; (2) effects of ApoA5 on intracellular TG content were observed by spectrophotometry; (3) effects of ApoA1 on modulating the gene expression levels of the adipogenesis-related markers, such as C/EBPα, C/EBPβ, PPARγ, aP2 and FAS, were detected by PCR; (4) effects of ApoA1 on modulating the gene expression levels of CIDEC were detected by PCR; (5) distribution of ApoA5 and CIDEC were observed by confocal microscope; (6) ApoA5 antibody and CIDEC antibody were used for CO-IP observe whether ApoA5 interacts with CIDEC; (7) we silenced and over-expressed the CIDEC gene in AMSCs. The function of CIDEC in AMSCs adipogenesis was investigated and the effects of ApoA5 on CIDEC expression were detected; (8) the effect of ApoA5 on adipogenesis was further detected in AMSCs with CIDEC-silenced or over-expressed.

RESULTS The main results were listed as follows: (1) ApoA5 could reduce the amount of lipid droplets and decrease the TG content in adipocytes during the adipogenesis; (2) ApoA5 could down-regulate the gene expression level of C/EBPα, C/EBPβ, PPARγ, aP2 and FAS during the adipogenesis; (3) ApoA5 could down-regulate the gene and protein expression level of CIDEC during the adipogenesis; (4) ApoA5 co-localized and had interaction with CIDEC in the surface of lipid droplets; (5) the effect of ApoA5 on inhibiting adipogenesis was attenuated in AMSCs with SORT1 gene over-expression.

CONCLUSIONS In conclusions, our results confirm that CIDEC plays an important role in the adipogenesis of human AMSCs. Furthermore, the results indicate that apoA5 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 CIDEC. The present data provide insight into the mechanisms of the inhibitory effects of ApoA5 and suggest that the inhibitory activity of ApoA5 indicates a potential pharmacological intervention specifically directed toward obesity.