Analysis of liver transcriptome in broilers with ascites and regulation by L-carnitine

Two experiments were conducted using male Ross-308 broilers. Exp. 1 was to determine the differences in liver transcriptomic profile of healthy broilers at 39 days (D39) vs. 21 days of age (D21), and of ascites vs. healthy broilers at D39 by GeneChips, under a low-temperature environment. Differentially expressed genes related to liver antioxidative capacity and energy metabolism were screened. Exp. 2 was to analyze the regulatory roles of L-carnitine on genes and biochemical parameters involved in liver oxidoreduction and energy metabolism. The results showed that the expression of 790 genes in D39 vs D21 healthy broilers (386 up- and 404 down-regulated) and expression of 178 genes in ascites vs. healthy broilers on D39 (128 up- and 50 down-regulated) was changed. The analysis of pathway and GO indicated that genes related to amino acid metabolism, fatty acid metabolism, Krebs cycle, carbohydrate metabolism, vitamin metabolism, cell apoptosis, immune response, oxidoreduction, angiogenesis, nitric oxide formation and erythrocyte differentiation were involved in the development of ascites. Liver MDA level of ascites broilers was significantly increased, but the activity of T-SOD was significantly decreased than healthy broilers. The activity of liver HK, MDH, PK and Nasup(+) -Ksup(+) -ATPase was significantly lower in ascites broilers. The expression of liver HKDC1 and PCK1 was significantly down-regulated, and that of HNF-4alpha and AKR1B10 expression was significantly up-regulated. L-carnitine supplementation significantly increased the activity of T-SOD and PK, and significantly up-regulated HKDC1 and HNF-4alpha expression. It can be concluded that genes involved in many biological processes are differentially expressed due to ascites. Liver oxidation damage and energy generation obstruction were found in broilers with ascites. L-carnitine can alleviate the liver oxidative damage and promote the generation and utilization of energy. The present results demonstrated that L-carnitine could serve as a potential regulatory agent to reduce ascites susceptibility and mortality.