Dietary Iron Intake in Excess of Requirements Impairs Intestinal Copper Absorption in Sprague‐Dawley Rat Dams, Causing Copper Deficiency in Neonatal Pups

Abstract

Consumption of a high-iron diet by previously iron-deficient rat dams causes copper insufficiency; however, pathophysiological outcomes in their offspring are unknown. We hypothesized that high-iron consumption by dams would also lead to copper depletion in suckling pups. Accordingly, 8-9-week-old, pregnant Sprague-Dawley rats were randomized and initially fed a low-Fe diet for ≍7 days (to induce iron deficiency), and then switched to one of five AIN-93G-based diets, with variable iron levels (normal [80 ppm] to high [up to 1600 ppm]) and marginal copper content (2 ppm; normal is 6-7 ppm). Dams were fed these diets throughout the remainder of pregnancy and during lactation, until the termination of the experiments (when suckling pups were 13-15 days of age). Subsequently, hematological parameters and serum and tissue iron concentrations were measured, and copper biomarker analyses were performed. Intestinal 64Cu absorption and tissue distribution in dams, and 64Cu delivery to the suckling pups, were also assessed. Results showed that serum para-phenylenediamine (pPD) oxidase activity (reflecting serum ceruloplasmin [Cp]) was suppressed (p<0.05) in dams consuming 5-fold excess iron and in pups suckling dams that consumed iron at 10-fold excess. Hepatic nonheme iron concentrations increased in dams and pups (p<0.05) as dietary iron levels increased (possibly due to inhibition of Cp activity, which is required for iron release from hepatocytes). When dams consumed iron at 20-fold above requirements, pup growth was impaired (p<0.05), possibly due to copper depletion, as also indicated by decreases in erythrocyte SOD activity (which accurately reflects copper status) (p<0.05). Moreover, in iron-supplemented dams, intestinal copper (64Cu) absorption and 64Cu activity in blood, liver, and spleen were all decreased (p<0.05). A similar trend was also noted in pups suckling dams consuming exces iron, with 64Cu accumulation in blood, liver, and spleen (p<0.05) being lower than in controls. We conclude that maternal intake of excessive iron (~10-fold above the dietary recommendation) impairs absorption of dietary copper and concomitantly depletes copper in neonatal pups. Low milk copper content was the most likely explanation for this outcome, although this remains to be experimentally proven.