The Effects And Potential Mechanisms Of Human Adipocytes On The Expression Of Apolipoprotein A5 In HepG2 Cells

ObjectivesWe developed an in vitro coculture system composed of human adipocytes and HepG2 cells, to investigate the effects and potential mechanisms of human adipocytes on the expression of apolipoprotein A5(apoA5) in HepG2 cells.MethodsUsing a stromal vascular fraction(SVF)cells culture metheod, preadipocytes from human subcutaneous adipose tissue differentiated into mature adipocytes after stimulation by a standard inducer which containing 3-isobutyl-1-methylxanthine(IBMX), insulin, and dexamethasone. Then mature adipocytes were stimulated by lipopolysaccharide(LPS) into inflammatory adipocytes. Mature adipocytes and inflammatory adipocytes cocultured with HepG2 cells by transwell syetem respectively. RNAs extracted from collected HepG2 cells, then reverse transcription polymerase chain reaction (RT-PCR) was used to evaluate mRNA expression of apoA5, serum amyloid A (SAA), peroxisome proliferator-activated receptor-alpha (PPAR-α) and liver X receptor-alpha(LXR-α). MK886, a PPAR-αinhibitor, was used to evaluated its influence on the expressions of apoA5 and PPAR-αin HepG2 cells.Results1. Cocultured with mature adipocytes(24h,48h), the expression levels of apoA5, PPAR-αand SAA mRNA in HepG2 cells increased compared with control group (uncocultured group) (all P＜0.05). Compared with cocultured for 24h,The HepG2 cells had higher expression of apoA5,PPAR-αand SAA mRNA in cocultured with mature adipocytes for 48h (all P<0.05).But there were no changes in the expression of LXR-αin HepG2 cells both in cocultured with mature adipocytes for 24h and 48h(all P>0.05).2. Cocultured with HepG2 cells for 48h, inflammatory adipocytes had stronger effect on upregulation of apoA5,PPAR-a and SAA mRNA in HepG2 cells than mature adipocytes(P<0.05).but there were no differences in LXR-αmRNA between them(P>0.05).3. Upregulation of apoA5 mRNA in HepG2 cells by mature adipocytes as well as inflammatory adipocytes can be inhibited by PPAR-αinhibitor MK886(P<0.05).Conclusions1. Mature adipocytes could upregulate the expression of apoA5 mRNA in HepG2 cells in a time-dependent manner.2. Inflammatory adipocytes upregulate the expression of apoA5 mRNA in HepG2 cells stronger than mature adipocytes.3. The upregulation of apoA5 mRNA in HepG2 cells by adipocytes, probably due to the inflammatory cytokines secreted by adipocytes, and it is also associated with the timing and the intensity of the inflammation.4. Adipocytes may regulate the expression of apoA5 in HepG2 cells by PPAR-αbut not LXR-αpathyway.