| The content of fat in dietary has been attracting more and more attention. Animal products with higher lean meat while less adipose are much more popular now. Adipose tissue of human and animal is not only the organ for reservation and endocrine, it is also a major target for different kinds of disease, such as obesity, metabolic disorders and energy metabolism complications and other diseases. Over deposition of adipose can cause obesity, which is usually an important reason of metabolic disorders. Metabolic disorders can further induce production of diabetes, ketosis which promote fatty liver and metabolic disorder syndrome. Meanwhile, obesity also can reduce immune response, trigger chronic inflammation and increase the risk of infectious disease, thus severely affact human and animal health and performance. Adipose tissue can be classified as two gropus: whit adipose tissue(WAT) and brown adipose tissue(BAT). WAT is the largest endocrine organ in the body and is mainly function as a reservoir of excess energy in the form of lipid. BAT contributes to the energy dissipation to maintain body temperature through producing heat under the situation of cold and stress, BAT is an important thermogenesis organ, especially for young mammals. Diet is the main source of energy and carbohydrate is the major substrate for lipogenesis. Fatty acids are the most important component of lipids and the linoleic acid, linolenic acid, α-linolenic acid and arachidonic acid are essential fatty acids. α-linolenic acid(ALA) is the precursor fatty acid of omega-3(ω-3) polyunsaturated fatty acids(PUFAs) family. ALA can synthesis long-chain fatty acids, such as Eicosapetaenoic acid(EPA), Docosapentaenoic acid(DPA) and Docosahexaeoic acid(DHA) through elongation and desaturation,. Raw materials containing abundant ω-3 PUFAs can be used to produce meat products with high amount of ω-3 PUFAs to improve quality of human diet. The aim of this research is to study the effect of monomer fatty acid of ω- 3 on the differentiation of adipocytes and construction of ω- 3 PUFAs, which will provide a theoretical basis for investigation of the metabolism and regulation of ω- 3 PUFAs in adipose tissue and provide new perspectives to improve meat quality and performance.In this study, mature WAT and BAT adipocytes were produced through inducing differentiation of WAT and BAT preadipocytes in mice. The fatty acids content and the expression level of adipokines biomarkers were investigated in adipose tissues from different gender and different location. Then, the effect of ALA and DPA on unsaturated fatty acids was investigated during the differentiation of WAT and BAT. After that, the isotope labeling was used to verify the changing of synthesis of ω- 3 polyunsaturated fatty acid derivative. In the end, white preadipocyte browning was induced by rosiglitazone to investigate the effect of it induced by on fatty acid metabolism.The results were shown as following. Firstly, there are more lipid droplets in fully differentiated brown adipocytes than in white adipocytes. DHA was accumulated faster in differentiated BAT than in total fat. However, compare to DHA, total fat was accumulated much faster in differentiated WAT. BAT is a highly metabolically active tissue with a high level of mitochondria, which normally contains DHA and other PUFA. Secondly, fatty acids content is different in fat tissues between WAT and BAT. In different gender, the fatty acid content is also different. The expression of adipose tissue biomarker is associated with the gender of mice and location of adipose. Brown adipose specific marker gene Prdm16, Zic1, UCP1 were specifically expressed only in brown adipocyte. Thirdly, undifferentiated BAT and WAT were treated with ALA and DPA. After 24 hours incubation, ALA increased accumulation of DHA during BAT differentiation. The treatment of DPA increased the content of EPA in differentiated BAT, but decreased the level of EPA in differentiated WAT compared to undifferentiated cells. Fourthly, the m RNA expression of FADS1 and FADS2 was siginificantly decreased in mature brown adipocytes after treatment of d5-ALA in mature brown adipocytes compare to undifferentiated brown adipocytes. The m RNA expression of FADS1 was also significantly decreased in mature WAT, however, the m RNA expression of FADS2 was not changed. The m RNA expression of PPARGC-1a and PDK4 was increased significantly in mature BAT. However, the m RNA expression of PPARGC-1a in mature WAT was not changed but PDK4 was dramatically decreased. d5-DHA was synthesied fasted during BAT differentiation while d5-DPA was synthesized much faster in mature WAT than in undifferentiated adipocytes. In addition, mature WAT had less amount of d5-EPA than undifferentiated WAT. The data also showed that the lipid content is dependent on cell type and gender. Isotope labeling study demonstrated that the differences of lipid biosynthesis existed in different gender and location of fat deposit. Lastly, Rosiglitazone(RZ) could significantly accelerate lipid droplets accumulation during white adipocyte differentiation. After incubate with RZ, less saturated fatty acid, more monounsaturated fatty acid and unchanged polyunsaturated fatty acid were detected in WAT compared to other groups, which suggesting PUFAs is not the fatty acids that promote browning of WAT.In conclusion: ALA increased the biosynthesis rate of DHA in BAT during differentiation. This study provides a basis for further exploring the metabolism and regulation mechanism of DHA in adipose tissue in animal meat, improving meat quality and ameliorating the constitute of unsaturated fatty acids in human dietary. |
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