| At present, most attention is focused on obesity because it is associated with an increased risk of developing type 2diabetes and cancer. Despite evidence that genetic factors play a significant role in the etiology of obesity, the percentage of energy derived from fat in the diet is positively correlated with body fat content and obesity. The mechanism which is responsible for the correlation between body fat and dietary fat content is still unknown. Several researches observed that micro-effect polygene determined meat quality and other relative quantitative. To investigate the mechanism of obesity, microarrays can be used to illuminate differences in the expression of genes and within cells from obesity animal models.This study was to develop an obese porcine model and evaluate effects of high-fat induced obesity on gene expression. A total of 20 crossbred, castrated boars (20kg body weight) were fed a corn-soy basal diet (total fat<0.82%) or the diet added with lard at 3% (20-50kg),5%(50-80kg), or 7%(>80kg) for 6 months. The digestible energy levels(MJ/kg) of control diets were 1-13.93,11-13.97 and 111-13.88 respectively. The digestible energy levels (MJ/kg) of high-fat diets were 1-14.55,â…¡-14.97andâ…¢-15.22 respectively. The pigs were slaughtered after 180d feeding, and the effect of dietary energy density on performance, pork quality and biochemical indicators of pigs. Transcription profiles of whole-genome for liver, skeletal muscle, subcutaneous fat tissue and perirenal fat tissue of pigs from control and high-fat diet group. The differentially expressed genes were screened and these data were mined. We used pathway-focused oligo microarry studies to find the target genes of obese pig liver from different expression genes that analyzed by Agilent genome transcript microarray. The results were as followings:(1)Pigs fed the high fat diet showed greater (P<0.05) body weight, back fat thickness, Intramuscular fat and abdominal fat content than that fed the control diet. Blood glucose concentrations, Plasma Insulin, serum triglyceride, total cholesterol were similar between the two group initially (20kg), but became greater (P<0.05) in the high-fat diet fed pigs than the control at 180 d of feeding,so did of serum insulin. Compared with the pigs in control group, the pigs fed high-fat diet showed greater (P<0.05) high level in TNF-a, IL-6, Leptin and Ob-R, but there is no significant change in T3 and T4.(2) The results of porcine genome array:To screen for genes influenced by dietary fat content, we undertook an analysis of transcript expression in 4 tissues (liver, skeletal muscle, subcutaneous fat tissue and perirenal fat) of pigs from control and high-fat diet groups, and compared the expression profiles in 4 tissues between two groups. The results were as followings:1076 differentially expressed genes were screened form liver,478 were up-regulated and 598 were down-regulated.776 differentially expressed genes were screened form skeletal muscle,400 were up-regulated and 376 were down-regulated.852 differentially expressed genes were screened form subcutaneous fat tissue,387 were up-regulated and 465 were down-regulated.1038 differentially expressed genes were screened form perirenal fat tissue,516 were up-regulated and 522 were down-regulated.(3) GO annotation:To aid the overall functional interpretation of the common response to high-fat diet, the induced genes were assigned to several groups according to their GO annotation for biological process. The largest GO category of fat-induced transcripts comprised genes involved in transcriptional regulation, transcription and transport. The up-regulated GO group included genes in lipid biosynthetic process (liver), regulation of insulin secretion (perirenal fat), fatty acid catabolic process (perirenal fat), metabolic process(subcutaneous fat tissue), transport(subcutaneous fat tissue and skeletal muscle), T cell activation involved in immune response (subcutaneous fat tissue) and myofibril assembly(skeletal muscle). The down-regulated GO group included genes in oxidation reduction (liver), protein transport (liver), transport (perirenal fat and skeletal muscle), signal transduction(liver), immune response (perirenal fat), apoptosis (perirenal fat), transcription (subcutaneous fat tissue), transcription (skeletal muscle) and regulation of transcription (skeletal muscle).(4) The significant pathway analysis of differentially expressed genes in 4 tissues (liver, skeletal muscle, subcutaneous fat tissue and perirenal fat) of pigs from control and high-fat diet groups indicated that the pathways belong to steroid biosynthesis (liver and subcutaneous fat tissue), adipocytokine signaling pathway (perirenal fat) and pathway in cancer (skeletal muscle) were significant up-regulated. However, the pathways belong to intestinal immune network for IgA production (liver), prostate cancer (perirenal fat), primary immunodeficiency (subcutaneous fat tissue) and pancreatic secretion (skeletal muscle) were significant down-regulated.(5) The analysis of GO-Tree showed that the regulation of very large numbers of genes was involved in the adaptation process of pigs to the high-fat diet.The significant up-regulated GO of livr was cellular process, and down-regulated were nucleotide metabolic process, negative regulation of protein amino acid phosphorylation,regulation of carbohydrate metabolic process and regulation of polysaccharide biosynthetic process.(6) Construction and analysis of signal-conduct-network initially revealed that there were 7 genes which belong to possessed important regulatory ability, these genes could regulate other genes in signal network. The pathway in cancer, T cell receptor signaling pathway and p53 signaling pathway were significant influenced by high-fat diet induced. (7) Construction and topological analysis of the gene co-expression network:Based on gene co-expression model, gene co-expression network for genes in the control and high-fat diet group were constructed. The network revealed that there were 13 genes and 11 genes which possessed important regulatory ability in gene co-expression network. Moreover,11 genes in these two co-expression network that have higher rank scores were recommended as potential key genes on the obesity induced by high-fat diet.
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