The Study Of Regulatory Mechanisms Of Cattle Ppar γ In Adipocyte Proliferation And Differentiation

ABSTRACT According to some advantageous such as rich resources and geographical situations, China is standing on a rapid expansion in beef industry as the future. But, compared to the beef industry developed countries, the lower quality of beef which is becoming a major restricting factor for output of high-grade beef in China. According to the basic principle of beef evaluation, intramuscular fat content is a major determinant of meat quality in cattle. In our country, the major cattle breeds is local cattle which low rate of meat fat is the leading reason for poor per-formance and low slaughter. For the reason that, improving intramuscular China local cattle intramuscular fat content and the quality of beef are an important work to promote the development of China beef industry.The peroxisome-proliferations actirated receptor γ (PPARγ), a member of the nuclear receptor superfamily of ligand activated trianscription factors, plays a pivotal role in adipocyte differentiation and lipid storage. Con-sistent with the different pathways they regulate, PPARs were shown to be expressed in a wide range of tissues of the adult organism. Whereas PPARy is restricted mainly to adipose tissue, with PPARy mRNAs were detected in BAT, at very high levels. The localization of PPARy gene transcripts and proteins and the nature of their target genes indicates that they play roles in adipogenesis and lipid storage. Interestingly, PPARy which induces differ-entiation of adipocytes, also markedly upregulates lipid anabolism mRNAs, including LPL、PLIN1、GATA2、 CEBPA、FABPA、FAS、IGFBP and SREBP1. Thus, as in adipocyte differentiation, the induction of PPARy expression during adipocytes differentiation may important for initiation and maintenance of lipid storage.PPARy were shown to be activated by substances that induce peroxisome proliferation as well as by matural fatty acids. These date suggest that both natural and synthetic PPARy agonists induce time-and dose-dependent increases in PPARy mRNA in both primary human adipocytes and primary animal adipocytes. In addition, treatment of preaipocytes with pioglitazone, which induces differentiation, also markedly upregulated the expre-ssion of PPARy.To characterize the effect of PPARy on fatty deposits, intramuscular fat tissue of Henan native cattle——Nanyan cattle was used for experimental material to establish cattle primary precursor fat cells in vitro model; RT-PC1approach was conducted to investigate the expreein of PPARy in differentiation of adipocyte in cattle; The expressio of PPARy gene was enhenced in cattle adipocytes using pigtitazone drug intervention technology, and the roles c PPARy gene in the adipocytes proliferation and differentiation were investigated by MTT assay and Oil Red O stainin extraction assay, respectively. After PPARy gene was upregulated, the expression level of other transcript factors an marker genes related to the adipocyte differentiation was detected by Real-time PCR analyses; Aim to explore th centrol role of PPARy gene in adipocyte differentiation regulatory networks in bovine adipocyte differentiatio process, and lay the foundation for improving quality of beef. The results are as follows:(1) Creation bovine preadipocytes culture model in vitroTo explore the involement of cattle PPARy gene in lipid metabolism, NanYan cattle adipose tissue specimens were obtained from the subcutaneous adipose tissue regions within the sixth and seventh ribs.The isolation and differentiation of preadipocytes was performed according to the method described by Haunner et al. with some modification, which will lay the foundation for the further study of bovine preadipocytes proliferation and differentiation mechanisms and cattle body fat deposition.(2) The effects of pioglietazone on PPARy expression in cattle adipocytesWe analyzed the effects of piolietazone to cattle adipocytes throughout the cause of the differentiation process, between0day and8day. In this case, we used a fixed concentration of pioglietazone (1μm) and harvested RNA everyday. Expression of PPARy increased in response to pioglietazone.Compared to vehicle in non-pioglietazone adipocytes. PPARy mRNA levels were slightly reduced by pioglietazone in adipocytes.(3)The effect of PPARy in cattle adipocyte proliferation and differentiationThe expression of PPARy gene was enhenced in cattle adipocytes using piglitazone drug intervention technology, and the roles of PPARy gene in the adipocytes proliferation and differentiation were investigated by MTT assay and Oil Red O staining extraction assay, respectively. After PPARy gene was upregulated, the expression level of other transcript factors and marker genes related to the adipocyte differentiation was detected by Real-time PCR analyses. The results showed that upregulating PPARy gene increased cattle adipocyte proliferateion and decreased cell differentiation,while we demonstrated that the expression levels of classic PPARy target gene CEBPA, SREBP1, FABPA, Perilipinl, LPL, and IGFBP2is also significantly induced in adipocytes in response to PPARy agonists (P<0.05). In summary, PPARy gene may be related to the broiler abdominal fat deposition, and be probably a key regulator of cattle adipocyte proliferationnd differentiation.