| Adipose tissue is not merely an organ designed to passively store excess carbon in the form of fatty acids esterified to glycerol (triacylglycerols). In essence, it’s also a major secretory and endocrine organ involved in a range of adipokines, such as adiponectin, leptin and resistin, they involved in various diseases such as obesity, type Ⅱ diabetes mellitus, cardiovascular disease, hyperlipidemia, and metabolic syndrome. At the same time, to understand the mechanism of pig fat tissue growth and development will help improve the efficiency of pork production. At present, the studies of adipose tissue are more focused in the human body, which is due to obesity has become a major diseasea effect the human health, but studies on pig fat tissue is still relatively limited, so we can learn humans studies that complementarity each other. Adipose tissue can be divided into subcutaneous fat and visceral fat, they exhibit a significant difference in the structure and function, the subcutaneous adipose tissue primarily as an energy storage and regulation of energy balance, however, the anatomical location and veins reflux model of visceral adipose tissue, and its nature and specific features are prone to abnormal lipid metabolism, leading to cardiovascular disease and metabolic disorders. Furthermore, subcutaneous fat comprising 60%-70% of the total body fat, so weight loss are based on the basis of reduction of subcutaneous fat. In this study, four different developmental stages of porcine subcutaneous adipose tissue was studied, the differences between adipocytes volume was analysis using paraffin sections; the content of cytokines was determined by liquid chromatography to explore the differences of cytokine in adipose tissue growth and developmental processes; utilization DGE method to identified new mRNA transcripts and transcripts that high expressed; analysis of differentially expressed genes between the different developmental stages of adipose tissue; analysis of mitochondrial genes expression in adipose tissue growth and development; association analysisof the transcriptome data and fat phenotype index to reveals the biological processes caused by adipose tissue growth and development.We used paraffin sections to analyze the cell morphology and structure of the back subcutaneous adipose tissue in four developmental stages, the result show that, from birth to 7 years(7 y), the volume of fat cells always show very significant growth pattern (P< 0.01); the volume of fat cell was very small when the pig was born; the speed of growth was significant (P< 0.01) from birth to 30 days (30 d); it also showed a very significant increase (P< 0.01) from each other in this two process:30 days to 180 days (180 d) and 180 days to seven years (7 y).The measurement of metabolic factors associated with porcine fat in four developmental stages, from birth to seven years, the level of metabolism factors associated with fat showed a significant decrease (P <0.05), and fat metabolism factors have a significant correlation (r> 0.6, P< 0.05) from each other.We have done a subcutaneous adipose tissue transcriptome sequencing by 12 DGE,each library were given 3.66-6.5 M (million)original data, about 3.32-6.06 M clean tags and 141,865-270,124 distinct clean tags; By comparison,12,618 genes have been identified to do a subsequent analysis; the highest expression of the 10 genes in four developmental stages library were analyzed and seven common high expression of genes (TUBA1B, ND2, COX2, ATP8, COX3, ND1, SCD) in the four developmental stage was found, just sort of changed.To assess the reliability of the experimental results and the operational stability.we have done correlation analysis to the results of parallel experiments.the result show that.correlation coefficient between biological replicates was r> 0.95 (P< 0.05).This study indicates that biological individuals have very strong repeatability, mRNA expression profiles is very low various between different biological individuals, the experimental operation have strong stability and reliability, and the results of subsequent analysis are credible and reliable.Screenning differentially expressed genes in adipose tissue from Birth to 30 d, we got a total of 807 genes. There were a total of 649 differentially expressed genes between Birth and 180 d,1,263 genes between Birth and 7 y,708 genes between 30 d and 180 d,266 genes between 0 d and 7 y, and 767 genes between 180 d and 7 y. Through GO and Pathway analysis, the differentially expressed genes enriched in the oxidative stress, immune processes, apoptosis, energy metabolism, insulin stimulation, cell cycle, angiogenesis, gene translation path, and other biological processes. Analysis the distribution of differentially expressed genes, we found that 13 genes encoded in the mitochondrial DNA, nine of which were differentially expression; QTL analysis showed that 298 (9.11%) differentially expressed genes located in the QTL that affected fat and meat.We adopted STEM (short time series method) analysis for transcriptome data. Five types of gene expression were significantly enriched by differentially expressed genes. Based on these, correlation analysis was adopted between fat metabolism factors and transcriptome data. The result indicated that the significant enrichment of differentially expressed genes were significant related to the level of fat metabolism factors. Among these, upregulated genes enriched in energy metabolism and angiogenesis. The downregulated genes enriched in the biological processes of the cell cycle, steroids, cholesterol, ribosome biogenesis and metabolic processes.Analysing whether theses differentially expressed genes are known aging genes,288 genes potentially relevant to human aging in HAGE database, of which 61 genes were identified of differential expressed genes in our study, reaching significant levels of enrichment (P= 3.17×10-6); functional enrichment analysis found that these genes are associated with DNA repair, apoptosis, transcription and immune processes. DGE results were verified by Q-PCR. we found a good correlation (r> 0.7, P< 0.05) with each other, indicating that the DGE results are accurate and reliable.Through this study, we explored the molecular mechanisms of porcine adipose tissue growth and development at different developmental stages, screend out the differentially expressed genes and the valuable GO and Pathway, revealed the molecular basis of morphology and function of adipose tissue at different developmental stages. Our study provide scientific basis for the mechanism of diseases and obesity, provide theoretical guidance for clinical treatment, and also provide a theoretical basis for the deposition of pig fat tissue. |
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