High Dietary Iron Intake Impairs Growth and Causes Copper Deficiency in Sprague‐Dawley Rats
Authors: Ha Jung‐Heun , Doguer Caglar , Zhao Shaomin , Wang Xiaoyu , Flores Shireen R , Collins James F 
Published: November 2023

Introduction

Iron‐copper interactions in humans were reported more than a century ago; however, the molecular mechanism(s) underlying the link between iron absorption and copper status are just beginning to be understood. Although absorption of these two metals is closely related, copper status in iron‐deficient and iron‐overload rodent models has not been critically evaluated. This study was intended to test the hypothesis that changes in dietary copper intake would have differential influences on iron absorption and distribution in iron‐deficient, iron‐adequate and iron‐loaded rats.

Methods

Male, weanling Sprague‐Dawley rats were housed in overhanging cages with wire mesh bottoms and were fed one of 9 different AIG‐93G‐based diets for 4 weeks, containing low (11 ppm), adequate (79 ppm) or high (8820 ppm) iron in combination with low (0.9 ppm), adequate (8 ppm) or high (183 ppm) copper. Except for differences in iron and copper concentration, the diets were otherwise identical. Tissue and blood mineral levels were determined by ICP/MS. Serum ceruloplasmin (CP) levels were determined by a pPD assay which measures the amine oxidase activity of CP. All data reported below were from 6–11 rats per group and all reached statistical significance (p<0.05; 2‐way ANOVA with Tukey's analysis).

Results

Unexpectedly, several homeostatic perturbations were noted in rats consuming the high‐iron diets with low or adequate copper levels (all in comparison to rats consuming the adequate iron diets with low or adequate copper), including the following: growth retardation; anemia; low copper concentrations in blood, liver, heart and bone; cardiac hypertrophy; and low serum ferroxidase (i.e. CP) activity. Interestingly, none of these symptoms developed in the rats fed the high‐iron diets with higher copper content. In fact, this dietary treatment led to increased liver/body weight, non‐heme iron levels in serum, transferrin saturation and CP activity (as compared to the other 8 groups). Liver iron content was also higher in all 3 high‐iron fed groups, with the most significant increase seen in the group consuming higher copper. Furthermore, expression of hepcidin mRNA, encoding the iron‐regulatory hormone, increased in rats fed the high‐iron diet with higher copper content but not in the rats consuming the high‐iron diets with low or adequate copper (as compared to all 3 iron adequate groups). And lastly, expression of erythropoietin mRNA (encoding the erythropoeitic hormone EPO) was induced in the high‐iron‐fed rats with low copper content, but was not different in the 2 other high‐iron‐fed groups.

Conclusions

High dietary iron intake impairs growth and causes copper‐deficiency anemia in growing rats. These physiologic perturbations could be avoided by adding extra copper to the high‐iron diets. This investigation may have implications for iron supplementation in humans in which extra copper may be beneficial, although additional studies would be required to support this supposition.

Support or Funding Information

NIH grant 1R01 DK074867 (to J.F.C.)