Study On The Function Of Cidec Gene In Small Intestinal Lipid Metabolism

Cidec（Cell death-inducing DFF45-like effector C）is a lipid droplet（LD）-related protein.There are two tissue-specific isoforms,namely long isoform cidec-l and short isoform cidec-s.Overexpression of Cidec can increase levels of triglyceride（TG）in adipocytes.However,there are few studies on the expression of this gene in pigs and its correlation with triglyceride content.At the same time,the function of Cidec in small intestinal lipid metabolism has not been reported.In this study,we first take Duroc pigs and Luchuan pigs as the research objects,and the content of triglyceride in liver,small intestine,longissimus dorsi muscle,abdominal fat and subcutaneous fat and m RNA expression of two isoforms of cidec-l and cidec-s correlation analysis.Then,using porcine small intestinal epithelial cells IPEC-J2 as an in vitro model to explore the regulation of cidec-l in lipid metabolism in the small intestine.Wild-type C57/BL6 mice and Cidec knockout(Cidec^-/-)mice were used as in vivo models to study the regulation of Cidec on the digestion and absorption of exogenous fat in the small intestine.The results of the study provide a theoretical basis for further elucidating the molecular mechanism of Cidec regulating lipid metabolism in the small intestine,and for the biotechnology control of fat deposition.The experiment randomly selected 6 months Duroc and Luchuan pigs（n=5;5）for slaughter sampling to determine the triglyceride content of the liver,small intestine,longissimus dorsi muscle,abdominal fat and subcutaneous fat tissue and the m RNA of two isoforms of Cidec the amount of expression,Statistical analysis by pig breed showed that the m RNA expression levels of the two isoform of Cidec in lean Duroc pigs and obese Luchuan pigs are positively correlated with triglyceride content,in which cidec-l showed an extremely significant positive correlation in the liver of Luchuan pigs（p<0.01）and a positive correlation in the small intestine（p=0.059）;cidec-s was significantly positively correlated with the longissimus dorsi muscle and abdominal fat in Duroc pigs（p<0.05）.According to the statistical analysis of the tissues,the results showed that the m RNA expression levels of the two isoforms of Cidec in pig liver and other 4 tissues were significantly positively correlated with the content of triglycerides,in which the intestinal and abdominal adipose tissues were extremely positively correlated,with p values of 0.0029 and 0.0021,respectively.Subsequently,using IPEC-J2 as a model,the regulatory function of the isoform cidec-1 in the small intestine in lipid metabolism was studied.The results showed that overexpression of cidec-l significantly increased the extracellular triglyceride content of IPEC-J2 cells（p<0.01）,enhanced lipase activity（p<0.05）,increased fatty acid intake（p<0.05）,and upregulated fatty acids Absorption and transport related genes FATP4,FABPm,CD36,APO-AI and other genes m RNA expression levels（p<0.05）.In order to further study the regulation of Cidec on the digestion and absorption of exogenous fat in the small intestine,12-week-old wild-type C57/BL6 mice and Cidec knockout(Cidec^-/-)mice were used as in vivo research models.and serum triglycerides were measured after gavage with olive oil.The results showed that the serum triglyceride level of wild-type mice after gavage was higher than that of Cidec^-/-mice,and the serum triglyceride level reached the highest level 1hour after gavage.The serum lipoprotein lipase inhibitor Triton WR-1339was intraperitoneally injected 30 minutes before gavage of olive oil.After gavage,it was found that the accumulation rate of serum triglycerides in Cidec^-/-mice was significantly lower than that of wild-type mice（p<0.05）.Subsequently,16-week-old wild-type and Cidec^-/-mice were gavaged with olive oil,and samples were collected to determine digestion and absorption related indicators.The results showed that the fecal triglyceride level increased significantly（p<0.05）,and the triglyceride level and lipase activity of small intestine decreased significantly（p<0.05）,and total bile acid level of liver increased significantly（p<0.05）in Cidec^-/-mice.In summary,the m RNA expression of Cidec in pigs is positively correlated with the content of triglycerides in tissues,and Cidec plays an important regulatory role in the digestion,absorption and transport of small intestinal fat.