The Hepatoprotective Effects of Zinc Glycine on Liver Injury in Meat Duck Through Alleviating Hepatic Lipid Deposition and Inflammation

Dietary zinc status was recently approved to exert a powerful influence on liver health, and zinc deficiency results in hepatic injury caused by fat deposition, inflammation, and oxidant stress, but the effect of zinc on hepatic lipid metabolism and liver injury in meat duck has not been well defined. To determine the hepatoprotective effects of graded zinc glycine in meat ducks. A total of 384 1-day-old male meat ducks were subjected to 5 weeks feeding program with three experimental diets: (1) low-zinc diet, (2) adequate-zinc diet, and (3) high-zinc diet. Blood and liver samples were collected for biochemical analysis, gene expression analysis, and histopathological study. Diet with low zinc increased hepatic lipid content and triglyceride concentration. Meat ducks fed low-zinc diet exhibited considerably increased serum alanine aminotransferase (ALT) activity than birds fed other diets among all groups (P < 0.05). Low zinc administration also notably induced hepatocyte apoptosis and stimulated hepatic inflammatory gene expression. Adequate or high zinc supplementation increased hepatic zinc level, reduced hepatic lipid deposition and hepatosomatic indices through suppressing the expression of lipogenic genes including fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC) (P < 0.05), and upregulated the mRNA expression of both fatty acid secretion and beta-oxidation, including carnitine palmitoyltransferase 1a (Cpt1a), peroxisome proliferator-activated receptor (PPAR)alpha, and apolipoprotein B (ApoB) (P < 0.05). Dietary zinc addition also declined hepatic mRNA expression of interleukin (IL)-1 beta and IL-6 (P < 0.05). Furthermore, diets with adequate or high zinc significantly decreased serum ALT activity and hepatocyte apoptosis. These data revealed that supplementing adequate- or high-zinc glycine efficiently protects liver injury by attenuating lipid deposition and hepatic inflammation.