251 Impacts of different levels of dietary zinc oxide on mitochondrial energy metabolism and oxidative stress conditions in post-weaned piglets

Abstract

Abstract Zinc oxide (ZnO) is commonly added to weanling piglet diets for its documented benefits as growth promoting agent and usefulness for preventing diarrhea. We have recently reported the occurrence of mitochondrial energetic deficiencies and oxidative stress conditions in post-weaned piglets. In cells, Zn is known to be primarily located in mitochondria, where it is involved in mitochondrial function. The objective of this study was to determine the impacts of different levels of dietary ZnO on mitochondrial function and oxidative stress. One hundred twenty suckling piglets (5.65 ± 0.68 kg) were selected at d14. After weaning (d21), they were fed a basal diet supplemented with 100 mg/kg (low; L), 1000 mg/kg (medium; M) or 3000 mg/kg (high; H) of ZnO until d42 (n = 40/treatment). Piglets were sacrificed at d21, d23, d35, and d42 of age (n = 10/treatment/d) for sample collection. Mitochondrial respiration was evaluated using an extracellular flux analyzer and our results showed higher oxygen consumption rates in liver mitochondria from H group (P < 0.05) at d42. The cellular energy status was characterized by measuring liver adenosine 5’-triphosphate (ATP) content, and lower levels were reported in H group (P < 0.01) at d42. These observations were concomitant with a decrease in activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) in cytosol and mitochondria. Quantitative RT-PCR analyses revealed that expression of genes implicated in oxidative stress response such as glutathione synthase (GSS), heme oxygenase 1 (HO1) and metallothionein 3 (MT3) is increased in H group at d42 (P < 0.05). In plasma, GPx activity and oxidative damage to proteins (carbonyls) was higher in H group (P < 0.05). These findings indicate that ZnO affects mitochondrial function and oxidative stress in post-weaned piglets and provide insights to guide the prophylactic practices using high levels of dietary ZnO.