This study compared different levels of dietary zinc oxide (ZnO) on mitochondria ATP synthesis and the cellular and systemic redox balance in weaned pigs. One hundred twenty weaned piglets (7.96 ± 1.17kg, 21 days of age) were randomly allocated in one of three diets containing different Zn levels (as ZnO); 100 (100Zn), 1000 (1000Zn) and 3000mg/kg (3000Zn), and were slaughtered at day 21, 23, 35 or 42 for the collection of blood and liver samples. Dietary copper (Cu) levels were constant at 131mg/kg. Hepatic mitochondrial concentrations of Zn and Cu, hepatic mitochondria respiration, antioxidant response and the hepatic expression of related genes were analyzed. Piglets fed 3000Zn had the highest Zn (P < 0.01) and the lowest Cu concentrations (P = 0.01) in hepatic mitochondria. The hepatic oxygen consumption rate for maximal respiration was the highest in 3000Zn piglets (P < 0.05) whereas hepatic cytochrome c oxidase activity tended to be lower (P = 0.06) and intracellular ATP concentrations was the lowest (P = 0.01). Mitochondrial Cu/Zn superoxide dismutase (Cu/Zn-SOD) activity was the lowest (P < 0.01) and glutathione peroxidase (GPx) activity tended to be the lowest (P = 0.07) for 3000Zn piglets. The mRNA expression of the antioxidant related genes copper chaperone for superoxide dismutase (CCS) was highest (P = 0.01) in 3000Zn piglets and tended to be the highest (P = 0.07) for glutathione synthetase (GSS). Plasma carbonyls concentrations (P = 0.02) and GPx activity (P = 0.01) were the highest while SOD activity was not impacted (P = 0.55) in 3000Zn piglets. In conclusion, supplementing 3000mg Zn/kg had detrimental impacts on mitochondria Zn and Cu homeostasis, resulting in a dysfunctional mitochondria respiratory chain and disturbed antioxidant response in post-weaning piglets.
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