Molybdenum absorption, excretion, and retention studied with stable isotopes in young men during depletion and repletion

Biocompatibility and Degradation Behavior of Molybdenum in an In Vivo Rat Model

The biocompatibility and degradation behavior of pure molybdenum (Mo) as a bioresorbable metallic material (BMM) for implant applications were investigated. In vitro degradation of a commercially available Mo wire (ø250 µm) was examined after immersion in modified Kokubo's SBF for 28 days at 37 °C and pH 7.4. For assessment of in vivo degradation, the Mo wire was implanted into the abdominal aorta of female Wistar rats for 3, 6 and 12 months. Microstructure and corrosion behavior were analyzed by means of SEM/EDX analysis. After explantation, Mo levels in serum, urine, aortic vessel wall and organs were investigated via ICP-OES analysis. Furthermore, histological analyses of the liver, kidneys, spleen, brain and lungs were performed, as well as blood count and differentiation by FACS analysis. Levels of the C-reactive protein were measured in blood plasma of all the animals. In vitro and in vivo degradation behavior was very similar, with formation of uniform, non-passivating and dissolving product layers without occurrence of a localized corrosion attack. The in vitro degradation rate was 101.6 µg/(cm2·d) which corresponds to 33.6 µm/y after 28 days. The in vivo degradation rates of 12, 33 and 36 µg/(cm2·d) were observed after 3, 6 and 12 months for the samples properly implanted in the aortic vessel wall. This corresponds with a degradation rate of 13.5 µm/y for the 12-month cohort. However, the magnitude of degradation strongly depended on the implant site, with the wires incorporated into the vessel wall showing the most severe degradation. Degradation of the implanted Mo wire neither induced an increase in serum or urine Mo levels nor were elevated Mo levels found in the liver and kidneys compared with the respective controls. Only in the direct vicinity of the implant in the aortic vessel wall, a significant amount of Mo was found, which, however, was far below the amounts to be expected from degrading wires. No abnormalities were detected for all timepoints in histological and blood analyses compared to the control group. The C-reactive protein levels were similar between all the groups, indicating no inflammation processes. These findings suggest that dissolved Mo from a degrading implant is physiologically transported and excreted. Furthermore, radiographic and µCT analyses revealed excellent radiopacity of Mo in tissues. These findings and the unique combination with its extraordinary mechanical properties make Mo an interesting alternative for established BMMs.

Mechanistic insights into the treatment of iron-deficiency anemia and arthritis in humans with dietary molybdenum

In the last few decades, there has been a resurgence in interest in the use of dietary supplements to treat diseases in humans and molybdenum has the potential to be used therapeutically. In humans, dietary molybdenum has been shown to treat iron-deficiency anemia and it may treat joint pain in arthritis. It has been proposed that the anti-anemic and tentative anti-arthritic properties of molybdenum are because it is increasing the activity of one or more mammalian molybdoenzymes. Molybdenum forms part of the active site of these enzymes. Despite this, it is unlikely that a molybdenum deficiency can develop in humans that are on an oral diet and not exposed to unsafe levels of a molybdenum antagonist. Therefore, the underlying mechanism by which dietary molybdenum treats or may treat these diseases is currently not known. This minireview examines three possible underlying mechanisms. It investigates the possibility that molybdenum: increases the quantity of active mammalian molybdoenzymes, restores or partially restores activity to malfunctioning mammalian molybdoenzymes, or blocks nuclear receptors, in cells. The examination of these mechanisms has provided an impression of the mechanism by which molybdenum treats iron-deficiency anemia and may treat arthritis; and hypothesize uses of molybdenum for other human diseases.

Urinary trace metals in association with fetal ultrasound measures during pregnancy

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Toxic metals have been associated with lower birth weight while essential metals have been associated with higher birth weight. Evidence for other metals is either inconsistent or limited in terms of number of studies. This study analyzed 17 urinary metals, individually and as a mixture, and their association with measures of fetal growth in the LIFECODES birth cohort. Ultrasound was used to measure the abdominal circumference, head circumference, and femur length and measures were used to calculate estimated fetal weight at ~26 and ~35 weeks. We calculated the z score based on gestational age at scan, and estimated fetal weight (EFW) was combined with birth weight for longitudinal analyses. Metals were measured in samples collected at ~26 weeks. We used linear mixed-effects models to examine associations between metals and repeated measures of each outcome, controlling for covariates. Principal components analysis reduced the biomarkers to predictors that may share some commonality. We found that an interquartile range increase in selenium was inversely associated with femur length z score as well as other growth outcomes. Other essential metals, however, were associated with an increase in growth. Finally, the PCA component comprised of arsenic, mercury, and tin was associated with decreased head circumference z score (−0.14 [95% CI, −0.23, −0.05]).

Transition metals and host-microbe interactions in the inflamed intestine

Host-associated microbial communities provide critical functions for their hosts. Transition metals are essential for both the mammalian host and the majority of commensal bacteria. As such, access to transition metals is an important component of host-microbe interactions in the gastrointestinal tract. In mammals, transition metal ions are often sequestered by metal binding proteins to limit microbial access under homeostatic conditions. In response to invading pathogens, the mammalian host further decreases availability of these micronutrients by regulating their trafficking or releasing high-affinity metal chelating proteins, a process termed nutritional immunity. Bacterial pathogens have evolved several mechanisms to subvert nutritional immunity. Here, we provide an overview on how metal ion availability shapes host-microbe interactions in the gut with a particular focus on intestinal inflammatory diseases.