Zinc-induced upregulation of metallothionein (MT)-2A is predicted by gene expression of zinc transporters in healthy adults

The usefulness of zinc transporter and metallothionein (MT) gene expressions to detect changes in zinc intake remains unclear. This pilot study aimed to determine the effects of zinc supplementation on zinc transporter and MT gene expressions in humans. Healthy adults (n = 39) were randomised to zinc treatment (ZT), receiving 22 mg Zn/day (n = 19), or no treatment (NT) (n = 20). Blood samples were collected on Days 0, 2, 7, 14, and 21. Plasma zinc and serum C-reactive protein concentrations were analysed. Gene expression of zinc transporters and MT in peripheral blood mononuclear cells was analysed using real-time PCR. Using repeated-measures ANOVA, MT-2A gene expression and fold change were found to be higher in the ZT group (P = 0.025 and P = 0.016, respectively) compared to the NT group, specifically at Day 2 (40 +/- 18 % increase from baseline, P = 0.011), despite no significant increase in plasma zinc concentration. In a multiple regression model exploring the changes in gene expressions between Days 0 and 21, the change in MT-2A gene expression was correlated with changes in all zinc transporter expressions (r(2) = 0.54, P = 0.029); the change in ZIP1 expression emerged as a univariate predictor (P = 0.003). Dietary zinc intake was predictive of zinc transporter and MT expressions (P = 0.030). Physical activity level was positively correlated with baseline ZIP7 expression (r = 0.36, P = 0.029). The present study shows that MT-2A expression is related to changing expression of zinc transporter genes, specifically ZIP1, in response to zinc supplementation. The current report adds to our understanding of MT in the coordinated nature of cellular zinc homeostasis.