Increasing Dietary Iron Intake Perturbs Copper Metabolism in a Dose‐Dependent Fashion in Growing Sprague‐Dawley Rats
Authors: Ha Jung‐Heun , Doguer Caglar , Flores Shireen R , Wang Tao , Jeong Sun Young , Collins James F 
Published: November 2023

High‐iron feeding (1–2% Fe) is a commonly used approach to induce iron overload in rodents, modeling genetic iron‐loading disorders in humans. We recently utilized this approach to create a rat model of iron overload. To our surprise though, high dietary iron (0.8%; 8800 ppm) consumption impaired growth and caused copper‐deficiency anemia and cardiac hypertrophy in growing rats (Ha et. al. PLoS One, 11(8): e0161033, 2016). Interestingly, adding extra copper to this high‐iron diet prevented these copper‐related physiologic perturbations. Since the iron content in this diet was extreme, the current study was designed to test the hypothesis that lower iron levels would similarly perturb copper metabolism in growing rats. The experimental design was to feed three‐week‐old, male, weanling Sprague‐Dawley rats 6 different AIN‐93G‐based diets for 7–8 weeks. The diets varied only in iron content (88 [adequate Fe], 320, 756, 1475, 3021, and 8834 ppm) with copper being held constant at adequate levels (i.e. ~8 ppm). Subsequently, iron and copper‐related biochemical and physiologic parameters were quantified in experimental rats. All data reported in this study were from 6 rats per group and all reached statistical significance (p<0.05; 1‐way ANOVA with Tukey's post hoc analysis), unless otherwise stated. Consumption of the diet with 8834 ppm Fe caused growth retardation, severe anemia, cardiac hypertrophy, and hematomegaly and nephromegaly, confirming observations from our previous study. A noticeable trend towards heart and liver enlargement was also noted in rats consuming the diets with 1475 and 3021 ppm Fe. Moreover, tissue copper levels gradually decreased as iron content of the diets increased. For example, hepatic, splenic and cardiac copper depletion was noted when rats consumed the diets with the 2 highest iron levels. Representing a more subtle biomarker of body copper levels, serum ceruloplasmin (Cp) (i.e. amine oxidase) activity also trended lower as the iron content of the diets increased, with the decrease in the rats consuming the diets with the 3 highest Fe levels reaching statistical significance. Complementary molecular analyses demonstrated that expression of copper transporter 1 mRNA decreased as the iron content of the diets increased, possibly providing an explanation for hepatic copper depletion and depressed Cp activity with high‐iron feeding. Overall then, this investigation supports our contention that higher iron intake dose‐dependently perturbs copper metabolism. The suggestion that copper can antagonize iron absorption has been proposed previously (Klevay, Nutr. Res. Rev., 28:1–8, 2016), and our studies support this possibility. Although longer‐term feeding studies are required to assess the impact of more moderate iron levels on copper metabolism, it seems likely that iron supplementation in humans could also cause similar physiologic perturbations.Support or Funding InformationSupported by NIH grant 1R01 DK074867 (to J.F.C.).