Methionine deficiency decreases hepatic lipid exportation and induces liver lipid accumulation in broilers

The objective of the study was to investigate the effects of deficiency or high level addition of methionine (Met) in diet on homocysteine (Hcy) metabolism and hepatic lipid metabolism in broiler. A completely random design was used with 3 dietary treatments with the addition of Met from DLmethionine (DLM) at 0%, 0.22%, and 0.32% in a basal diet. The analyzed dietary Met was 0.271%, 0.485%, and 0.584% respectively for the Met-deficient, sufficient, and excessive diet. A total of 360 one-day-old male Ross 308 broiler chicks were randomly assigned to the treatments. The trial was last for 21 d. Compared to the Met-sufficient diet, the Met-deficient diet significantly resulted the decrease of 1 to 21 d growth performance and the increase of liver ether extract (EE). Compared to the Met-sufficient group, the expression of lipid transport gene apolipoprotein B (APOB) in both Met-deficient and Met-excessive group was decreased (P < 0.05). However, compared to the Met-sufficient group, a decreased of serum low-density lipoprotein cholesterol (LDLC) was only shown in birds fed a Met-deficient diet (P < 0.05). Although the plasma Hcy content was decreased, the expression of Cystathionine beta-synthase (C beta S) and hepatic inflammatory cytokines included interleukin-1 (IL-1) and interleukin-8 (IL-8) was significantly decreased in birds fed the Metdeficient diet when compared to those in Met-sufficient group (P < 0.05). When compared to the Met-sufficient group, the broilers in high dietary Met group had increased levels of catabolic enzyme genes expression especially acyl-coenzyme A oxidase 1 (ACOX1) and carbohydrate response element-binding protein (CHREBP) (P < 0.05), and a decreased content of liver EE. In conclusion, dietary Met deficiency decreased the hepatic lipid export and subsequently increased the hepatic lipid accumulation. High dietary Met addition increased the hepatic lipid catabolism and subsequently decreased the liver lipid accumulation.