The role of the y(+)L-type amino acid transporter 2 in promoting zinc absorption as zinc proteinate with moderate chelation strength in broiler primary duodenal epithelial cells

No study is currently available regarding the roles of the amino acid transporters in promoting mineral absorption in animals. To study whether the y(+)L-type amino acid transporter 2 (y+LAT2) participates in enhancing Zn absorption as Zn proteinate with moderate chelation strength (Zn-Prot M) in broilers, three experiments were carried out to investigate the effects of y+LAT2 silencing and overexpression on zinc (Zn) absorption as Zn-Prot M and related gene expressions in broiler primary duodenal epithelial cells (BPDECs) contrasted with Zn sulfate (ZnSO4). In experiment 1, three pairs of siRNAs (si-494, si-834, and si-1153) targeting y+LAT2 were synthesized and transfected within the cells to identify the optimal siRNA for silencing y+LAT2 mRNA expression, and the data were analyzed by one-way ANOVA. In experiment 2, cells were incubated for 2 h in either a DMEM/F12 complete medium without Zn supplementation (Control) or the same medium enriched with 400 μmol Zn/liter as ZnSO4 or Zn-Prot M, with or without the only one effective siRNA targeting y+LAT2, and the data were analyzed by two-way ANOVA. In experiment 3, with or without the recombinant adenovirus plasmid encoding y+LAT2, cells were also treated for 2 h with the same media as in experiment 2, and the data were analyzed by two-way ANOVA. The results demonstrated that in experiment 1, the si-494 was the only one effective (P < 0.0001) siRNA for inhibiting y+LAT2 mRNA expression. In experiment 2, y+LAT2 silencing reduced its own mRNA and protein abundances (P < 0.0001) by 46% and 14% and Zn absorption from Zn-Prot M by 34% (P < 0.05), with no effect (P > 0.05) on Zn absorption from ZnSO4. In experiment 3, y+LAT2 overexpression elevated its own mRNA and protein expressions by 949% and 18% (P < 0.0001) and Zn absorption from Zn-Prot M by 73% (P < 0.05), but didn't affect (P > 0.05) Zn absorption from ZnSO4. Additionally, Zn-Prot M upregulated (P < 0.05) the y+LAT2 protein expression compared to the Control and ZnSO4 by 12 to 17%, with no impact (P > 0.07) on the y+LAT2 mRNA expression, regardless of y+LAT2 silencing or overexpression. In conclusion, the y+LAT2 took part in promoting Zn absorption as Zn-Prot M in BPDECs.