Fatty Liver Model Construction and Its Effectiveness Evaluation Induced by Dexamethasone in Broilers

Excessive abdominal fat deposition and fatty liver syndrome are important industrial problems of lipid metabolism disorder in poultry breeding. The liver is the main site of de novo fatty acid synthesis in poultry, which plays a vital function in nutrients metabolism, formation of bile acids and detoxication. Therefore, the mechanism analysis of lipid metabolism disorder will provide reference for the healthy development of poultry industry, but the disease model is necessary for pathogenesis research.

This experiment was conducted to evaluate the effect of dexamethasone-induced fatty liver in broilers, aiming to provide the reference for the construction of lipid metabolism disorder model in poultry.

Sixteen 35-day-old AA broilers with similar body weight were randomly divided into control group and dexamethasone group (DXM), with 8 replicates in each group. The birds in the DXM were injected subcutaneously with dexamethasone sodium phosphate (4.5 mg·kg^-1) for 7 days, and the birds in the control group were given the administration of normal saline injection. After 7 days, oil red O staining was used to analyze the histopathological changes of the liver, and serum biochemical and antioxidant indexes were detected. RT-PCR was applied to detect genes expression related to lipid metabolism and inflammatory response in the liver.

Compared with the control group, the liver index of broilers in the DXM was significantly increased (P<0.05). Oil red O sections showed a large number of red lipid droplets, and the contents of TG and TC in the liver were higher than those in the control group (P<0.05). Serum biochemical results showed that aspartate amino transferase (AST), total bilirubin (TBIL), uric acid (UA), total protein (TP), high density lipoprotein cholesterol (HDL-c), low density lipoprotein cholesterol (LDL-c), total cholesterol (TC) and triglyceride (TG) levels in the DXM were significantly higher than those in the control group (P<0.05), but there was no significant difference about alanine aminotransferase (ALT) and glucose (GLU) (P>0.05). Dexamethasone injection significantly increased genes expression about lipid synthesis, such as ACC, FAS, SCD1, PPARγ, ChREBP, SREBP-1c, IGF2 and GR in the liver (P<0.05), but ELOVL6 expression was not affected (P>0.05). In addition, genes expression about lipid catabolism such as CPT1, LPL and PPARα were deceased in DXM group (P<0.05). However, the expression of ATGL gene related to lipid hydrolysis, CETP and MTTP gene related to lipid transport were significantly higher in DXM group (P<0.05). On the other hand, DXM injection significantly increased the genes expression of MyD88, NFκB, IL-6, TNF-α in the liver of broilers (P<0.05). Antioxidant analysis showed that there was no significant change in the total antioxidant capacity of liver and serum (P>0.05), but the content of malondialdehyde in serum was significantly higher in DXM group (P<0.05).

Neck subcutaneous injection of DXM could cause lipid metabolism disorders in broilers, and lead to oxidative stress and liver inflammation, which was similar to the characteristics of fatty liver disease, indicating that this method could be used to establish the fatty liver model in broilers quickly.