No abstract

Manganese (Mn) and iron (Fe) are transition metals that are crucial to the appropriate growth, development, function, and maintenance of biological organisms. Because of their chemical similarity, in organisms ranging from bacteria to mammals they share and compete for many protein transporters, such as the divalent metal transporter-1. As such, during conditions of low Fe, abnormal Mn accumulation occurs. Conversely, when Mn concentrations are altered, the homeostasis and deposition of Fe and other transition metals are disrupted. Our lab has undertaken a series of studies in rats involving pregnant dams, neo- and perinatal pups, and adult animals. Animals were exposed to various concentrations of dietary Fe and/or Mn, and protein transporter expression, blood Mn and Fe concentrations, brain transition metal concentrations, and temporal brain deposition patterns were examined. As a result, we have demonstrated the importance of the interdependence of the transport of Mn and Fe, and established brain metal concentrations in several longitudinal studies. The purpose of this review is to examine these studies in their entirety and highlight the importance of monitoring the deposition and accumulation of both Mn and Fe when designing future studies related to either dietary or environmental changes in transition metal levels. Finally, this review will provide information about various transport proteins currently under investigation in the research community related to Fe and Mn regulation and transport.

No abstract

Manganese (Mn) neurotoxicity in adults can result in psychological and neurological disturbances similar to Parkinson's disease, including extrapyramidal motor system defects and altered behaviors. Iron (Fe) deficiency is one of the most prevalent nutritional disorders in the world, affecting approximately 2 billion people, especially pregnant and lactating women, infants, toddlers, and adolescents. Fe deficiency can enhance brain Mn accumulation even in the absence of excess Mn in the environment or the diet. To assess the neurochemical interactions of dietary Fe deficiency and excess Mn during development, neonatal rats were exposed to either a control diet, a low-Fe diet (ID), or a low-Fe diet supplemented with Mn (IDMn) via maternal milk during the lactation period (postnatal days [PN] 4-21). In PN21 pups, both the ID and IDMn diets produced changes in blood parameters characteristic of Fe deficiency: decreased hemoglobin (Hb) and plasma Fe, increased plasma transferrin (Tf), and total iron binding capacity (TIBC). Treated ID and IDMn dams also had decreased Hb throughout lactation and ID dams had decreased plasma Fe and increased Tf and TIBC on PN21. Both ID and IDMn pups had decreased Fe and increased copper brain levels; in addition, IDMn pups also had increased brain levels of several other essential metals including Mn, chromium, zinc, cobalt, aluminum, molybdenum, and vanadium. Concurrent with altered concentrations of metals in the brain, transport proteins divalent metal transporter-1 and transferrin receptor were increased. No significant changes were determined for the neurotransmitters gamma aminobutyric acid and glutamate. The results of this study confirm that there is homeostatic relationship among several essential metals in the brain and not simply between Fe and Mn.