The effect of levels and of various combinations of Zn and Cu sources on their homeostasis and gene expression in different tissues of post-weaned piglets

This study evaluated the effects of levels and of different combinations of dietary sources of zinc (Zn) and copper (Cu) on mineral homeostasis and gene expression in post-weaned piglets. At weaning (d21; 7.79 ± 0.49 kg), 110 piglets were randomly allocated to 5 dietary treatments consisting of different combinations of inorganic (I) and organic (O) Zn and Cu at 300 and 130 mg/kg, respectively (IZnICu, OZnOCu, IZnOCu, OZnICu) and an additional treatment with high levels of inorganic Zn and Cu (HZnHCu; 3000 and 250 mg/kg, respectively). Plasma, jejunal mucosa and liver samples were collected at day 21, 28 and 35 and analyzed for Zn and Cu concentrations as well as the mRNA expression of genes of interest. Statistical analysis compared all treatments versus d21, the different combinations of Zn and Cu versus the high level, and a 2 x 2 factorial contrast among the different combinations of Zn and Cu at each time point. Plasma, jejunal mucosa and liver Zn concentrations were higher for HZnHCu at d28 and 35 compared to d21 (P < 0.01) and to the different combinations (P ≤ 0.02). For all the different combinations, plasma and liver Zn concentrations at d28 and 35 were lower than at d21 (P ≤ 0.05), except for IZn groups in plasma at d35 (P ≥ 0.45). Jejunal mucosa Cu concentrations were higher than d21 only in HZnHCu groups (P < 0.04). At d28 and d35, HZnHCu piglets had higher jejunal mucosa Cu concentrations than the different combinations (P < 0.02). No treatment effect was detected on plasma Cu concentrations (P ≥ 0.18) whereas in liver IZn tended to be higher than OZn (P = 0.07). In the jejunal mucosa, the mRNA expression of ZIP4 was downregulated in HZnHCu compared to the different combinations (P < 0.01) whereas ZNT1 and MT3 were upregulated (P < 0.01). The MT3 expression tended to be highest for IZnICu and lowest for OZnOCu at d28 and 35 (interaction effect; P ≤ 0.09). In liver, d28 and 35, the mRNA expression of ZNT1, MT3 and ATP7B (d35 only) were upregulated in HZnHCu compared to the different combinations (P ≤ 0.02). Among the combinations of Zn and Cu, MT3 expression was lower in OZn compared to IZn at d28 and d35 (P ≤ 0.05). In conclusion, HZnHCu stimulated the mechanisms of Zn and Cu homeostasis in jejunal mucosa and liver, increased Zn concentrations in all tissues, and enhanced Cu concentrations in jejunal mucosa. Among the different combinations of Zn and Cu sources, IZn supplementation appeared to stimulate higher concentrations of Zn in plasma and Cu in jejunal mucosa and liver compared to OZn via a greater expression of MT3 in tissues.