Submitted to: Journal of Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/21/2003
Publication Date: 2/1/2004
Citation: Reeves, P.G., Ralston, N.V., Idso, J.P., Lukaski, H.C. 2004. Contrasting and cooperative effects of copper and iron deficiencies in male rats fed different concentrations of manganese and different sources of sulfur amino acids in an AIN-93-G-based diet. Journal of Nutrition. 134:416-425. Interpretive Summary: It is important to know the concentration of a mineral nutrient in the diet, and to know if the nutrient is available for absorption. Many factors affect absorption, and one of the most important ones is the interaction between specific minerals where one affects the absorption and utilization of the other. Copper, iron, and manganese are three mineral nutrients that interact in the intestine to affect the utilization of the other. The type of sulfur amino acid in the diet also affects mineral metabolism. In this experiment, we used what is called a factorial design so we could study the interaction of all 3 of these mineral nutrients at the same time. The concentration of copper in the diet was either less than 1 or 6 mg/kg (deficient or adequate); the amount of iron was 10 or 35 mg/kg (deficient or adequate); and the amount of manganese was 10 or 50 (adequate or excessive); and the type of sulfur amino acid was either L-cystine or DL-methionine. The diets were fed to laboratory rats, and after 6 weeks, low dietary copper given to rats getting adequate iron reduced the utilization of iron and caused anemia. When dietary iron was also low, low dietary copper reduced iron utilization even more. Of course, low dietary iron by itself caused anemia, and low dietary copper alone caused some specific effects such as lowering the activity of copper-dependent enzymes, liver and red cell superoxide dismutase-1, serum superoxide dismutase-3, and serum ceruloplasmin. Changing the amount of manganese in the diet had very little effect on most parameters studies, except that the higher amount in the diet reduced the amount of copper in the intestine when rats were fed an adequate amount of copper but not when the rats were fed a low amount. High dietary manganese by itself increased the amount of manganese in the intestine and liver. Feeding DL-methionine instead of L-cystine tended to increase iron in the liver and also to reduce the severity of anemia observed with both copper and iron deficiency. The study shows the importance of having a balanced intake of various nutrients, because too much or too little of one might reduce or enhance the utilization of another.
Technical Abstract: Dietary nutrient interactions are important factors to consider in the study of nutrient status and requirements. Here, the effect of dietary interactions among copper (Cu), iron (Fe), manganese (Mn), and sulfur amino acids (SAA) on blood cell characteristics and enzyme activities were observed. Male rats (N=8) were used in a 2x2x2x2 factorial design and fed an AIN-93G-based diet containing dietary Cu (<1 and 5 mg/kg), Fe (10 and 35 mg/kg), Mn (10 and 50 mg/kg), and either L-cystine or DL-methionine. Blood was analyzed by automated hematology cell counting and by flow cytometry. Severe Cu deficiency was verified by reductions in the activities of serum ceruloplasmin (1% of control), red cell SOD1 (14% of control), liver cytochrome c oxidase activity (25% of control), and serum extracellular SOD (SOD3) activity (20% of controls). Because Cu is required for Fe absorption and utilization, many physiologic responses that require Fe were affected by both deficiencies, including lowered blood hemoglobin, low RBC volume, and low RBC hemoglobin concentration, and elevated number of reticulocytes. Cu and Fe deficiencies together worsened some conditions: lower hemoglobin, lower RBC hemoglobin, increased RBC distribution width, increased number of reticulocytes and nucleated RBCs, and elevated platelet count. Elevating dietary Mn had little effect on most parameters, except to reduce serum Cu when dietary Cu was adequate but not when it was low, and to reduce RBC SOD1 activity when dietary Fe was low but not when it was adequate. Feeding methionine instead of cystine tended to elevate hemoglobin but lowered reticulocyte count when dietary Fe was low but reduced these two parameters when dietary Cu was low. Although the anemia of Cu deficiency produced by feeding the AIN-93G-based diet was not as pronounced as that reported in rats fed the AIN-76A, other manifestations of the deficiency were prominent.