Plasma phenylalanine concentrations are associated with hepatic iron content in a murine model for phenylketonuria

Abstract

Individuals with phenylketonuria (PKU) have been reported to have altered trace mineral status. In this study, we evaluated in a murine PKU model whether protein level and level of phenylalanine (PHE) restriction could modulate iron, copper, and zinc status. Fifty-four male weanling PKU and control mice were assigned to receive for 56 days an elemental low or normal protein diet; PKU mice also were assigned to receive PHE restriction (treated) or no restriction (untreated). PHE-restricted mice consumed a prescribed dietary PHE to maintain plasma PHE concentrations between 120 and 480 μmol/L. PHE-unrestricted and control mice received equal amounts of dietary PHE. Intestinal and hepatic copper, iron, and zinc were measured at day 56 and fecal minerals measured at baseline and day 56. Mean plasma PHE concentrations were significantly greater in PKU PHE-unrestricted versus PKU PHE-restricted mice and control mice. Mean intestinal weights when normalized for body weight were significantly greater in PKU mice versus control mice. PKU PHE-unrestricted mice had significantly lower hepatic copper and zinc than PKU PHE-restricted mice, and significantly greater hepatic iron than control and PKU PHE-restricted mice. PKU PHE-unrestricted mice on a low protein diet had hepatic iron concentrations about 1.5 times that of the other mice. Fecal iron concentrations in all mice were significantly greater at day 56 than at baseline. No animal group effects or protein level effects were found for fecal copper, iron, or zinc contents. We conclude that hyperphenylalaninemia alters the metabolism of iron, copper, and zinc in PKU mice.