MIR-27B Regulates Differential Lipid Accumulation Between Intramuscular And Subcutaneous Adipocyte Via Suppressing Pparg Expression

Intramuscular fat (IMF) content is one of the most important factors which affect the quality of pork. It is well documented that IMF content was decreased significantly due to long-term intensive selection for increased leanness. Increasing marbling IMF content while not influence other fat content, especially the subcutaneous (SC) adipose content, is the aim of modern pig breeding. Mature adipocytes of various depot origins have distinct metabolic behaviors, and preadipocytes in different adipose tissues have various capacities of differentiation. Biological differences among various depots might give a clue to depot-specific regulation of fat tissues. In order to understand the differential mechanisms regulating the fat deposition between intramuscular (IM) and SC tissues, we compared the differentiation ability of preadipocytes which from IM and SC adipose tissues. The expression level of PPARy, which is a critical factor in adipocyte differentiation, was also detected between the adipocytes, which from IM and SC preadipocyte. And potential microRNAs (miRNAs) targeting PPARy were predicted and their expression level were also compared, at last we verified the differential expression miRNA through dual luciferase report system.The main results achieved were as follows:1. In vitro context, the differentiation ability of preadipocytes from IM adipose tissue had stronger differentiation ability than from SC fat tissues. After 9 days induction and differentiation when added DMI, intramuscular preadipocytes lipid accumulation level was significantly higher than subcutaneous fat cells (P<0.05). When comparing the expression level of genes which have a relation with lipid metabolism in the two kinds of fatty cells, the results showed the expression level of ACC、FAS、ATGL and HSL in IM adipose cells were significantly higher than which in subcutaneous fat cells (P<0.05). PPARy is a key gene during adipocyte differentiation and its expression level of mRNA and protein in intramuscular fat cell was significantly higher than which in subcutaneous fat (P<0.05).2. We got six miRNAs which regulate PPARy through bioinformatics prediction, they are miR-130a、miR-130b、miR128、miR-301、miR-27a and miR-27b. Quantitative analysis indicated that the expression level of miR-27a and miR-27b in SC cells were significantly higher than which in IM cells (P<0.05). But the expression level of miR-130a、miR-130b、miR128 and miR-301 have no difference between SC cells and IM cells (P>0.05). Constructing pGL3-Control/PPARy expression plasmids which contained 3’-UTR of PPARy and dual luciferase activity analysis revealed that miR-27b can regulate the 3’-UTR of PPARy.This study showed that intramuscular preadipocytes have a stronger differentiation ability than subcutaneous preadipocytes in vitro. miR-27b can regulate PPARy and it can lead to difference in the expression of PPAR y in the two kinds of adipocytes when it have a difference expression in the two kinds of adipocytes. Then it cause difference of adipoctye differentiation in distinct parts.