Genome-wide RNAi ionomics screen reveals new genes and regulation of human trace element metabolism

Phenanthroline and Schiff Base associated Cu(II)-coordinated compounds containing N, O as donor atoms for potent anticancer activity

As an inherent metal ion, copper has been the subject of investigation for developing a novel antitumoral compound that exhibits fewer adverse effects. Copper serves as a cofactor in multiple enzymes, generates reactive oxygen species (ROS), facilitates tumour evolution, metastasis and angiogenesis and has been detected at elevated concentrations in the serum and tissues of various human cancer types. In the given setting, utilising two methodologies in developing novel Copper-based pharmaceuticals for anti-cancer applications is standard practice. These approaches involve either the sequestration of unbound Copper ions or the synthesis of Copper complexes that induce cellular apoptosis. In the past four decades, the latter system has been used, leading to numerous reviews that have examined the anticancer characteristics of a wide range of Copper complexes. These analyses have consistently demonstrated that multiple factors frequently influence the efficacy of these compounds. This review examines the possible anticancer properties of copper and Cu(II) complexes that incorporate Schiff base ligands containing 1,10-phenanthroline. The present study will comprehensively analyse the examined cell lines and mechanistic research associated with each complex.

The stability and function of human cochaperone Hsp40/DNAJA1 are affected by zinc removal and partially restored by copper

The imbalance in metal homeostasis can be associated with several human diseases, and exposure to increasing concentrations of metals promotes cell stress and toxicity. Therefore, understanding the cytotoxic effect of metal imbalance is important to unravel the biochemical mechanism of homeostasis and the action of potential protective proteins against metal toxicity. Several studies, including gene deletion in yeast, provide evidence indicating the possible indirect involvement of cochaperones from the Hsp40/DNAJA family in metal homeostasis, possibly through modulating the activity of Hsp 70.This work first investigated the effect of zinc and copper on the conformation and function of the human Hsp40 cochaperone DNAJA1, a zinc-binding protein. DNAJA1 was capable to complement the phenotype of a yeast strain deleted of the ydj1 gene, which was more sensitive to the presence of zinc and copper than the wild-type strain. To gain further insight about the role of the DNAJA family in metal binding, the recombinant human DNAJA1 protein was studied. Zinc removal from DNAJA1 affected both its stability and ability to act as a chaperone, i.e., to protect other proteins from aggregation. The reintroduction of zinc restored the native properties of DNAJA1 and, surprisingly, the addition of copper partially restored the native properties.

High-Throughput Single-Cell Analysis of Nanoparticle-Cell Interactions

Understanding nanoparticle-cell interactions at single-nanoparticle and single-cell resolutions is crucial to improving the design of next-generation nanoparticles for safer, more effective, and more efficient applications in nanomedicine. This review focuses on recent advances in the continuous high-throughput analysis of nanoparticle-cell interactions at the single-cell level. We highlight and discuss the current trends in continual flow high-throughput methods for analyzing single cells, such as advanced flow cytometry techniques and inductively coupled plasma mass spectrometry methods, as well as their intersection in the form of mass cytometry. This review further discusses the challenges and opportunities with current single-cell analysis approaches and provides proposed directions for innovation in the high-throughput analysis of nanoparticle-cell interactions.

Toxicological mechanism of cadmium in the clam Ruditapes philippinarum using combined ionomic, metabolomic and transcriptomic analyses

Cadmium (Cd) contamination in marine environment poses great risks to the organisms due to its potential adverse effects. In the present study, the toxicological effects and mechanisms of Cd at environmentally relevant concentrations (5 and 50 μg/L) on clam Ruditapes philippinarum after 21 days were investigated by combined ionomic, metabolomic, and transcriptomic analyses. Results showed that the uptake of Cd significantly decreased the concentrations of Cu, Zn, Sr, Se, and Mo in the whole soft tissue from 50 μg/L Cd-treated clams. Significantly negative correlations were observed between Cd and essential elements (Zn, Sr, Se, and Mo). Altered essential elements homeostasis was associated with the gene regulation of transport and detoxification, including ATP-binding cassette protein subfamily B member 1 (ABCB1) and metallothioneins (MT). The crucial contribution of Se to Cd detoxification was also found in clams. Additionally, gene set enrichment analysis showed that Cd could interfere with proteolysis by peptidases and decrease the translation efficiency at 50 μg/L. Cd inhibited lipid metabolism in clams and increased energy demand by up-regulating glycolysis and TCA cycle. Osmotic pressure was regulated by free amino acids, including alanine, glutamate, taurine, and homarine. Meanwhile, significant alterations of some differentially expressed genes, such as dopamine-β-hydroxylase (DBH), neuroligin (NLGN), NOTCH 1, and chondroitin sulfate proteoglycan 1 (CSPG1) were observed in clams, which implied potential interference with synaptic transmission. Overall, through integrating multiple omics, this study provided new insights into the toxicological mechanisms of Cd, particularly in those mediated by dysregulation of essential element homeostasis.

Recent advances in the application of ionomics in metabolic diseases

Trace elements and minerals play a significant role in human health and diseases. In recent years, ionomics has been rapidly and widely applied to explore the distribution, regulation, and crosstalk of different elements in various physiological and pathological processes. On the basis of multi-elemental analytical techniques and bioinformatics methods, it is possible to elucidate the relationship between the metabolism and homeostasis of diverse elements and common diseases. The current review aims to provide an overview of recent advances in the application of ionomics in metabolic disease research. We mainly focuses on the studies about ionomic or multi-elemental profiling of different biological samples for several major types of metabolic diseases, such as diabetes mellitus, obesity, and metabolic syndrome, which reveal distinct and dynamic patterns of ion contents and their potential benefits in the detection and prognosis of these illnesses. Accumulation of copper, selenium, and environmental toxic metals as well as deficiency of zinc and magnesium appear to be the most significant risk factors for the majority of metabolic diseases, suggesting that imbalance of these elements may be involved in the pathogenesis of these diseases. Moreover, each type of metabolic diseases has shown a relatively unique distribution of ions in biofluids and hair/nails from patients, which might serve as potential indicators for the respective disease. Overall, ionomics not only improves our understanding of the association between elemental dyshomeostasis and the development of metabolic disease but also assists in the identification of new potential diagnostic and prognostic markers in translational medicine.

Metal ion availability and homeostasis as drivers of metabolic evolution and enzyme function

Metal ions are potent catalysts and have been available for cellular biochemistry at all stages of evolution. Growing evidence suggests that metal catalysis was critical for the origin of the very first metabolic reactions. With approximately 80% of modern metabolic pathways being dependent on metal ions, metallocatalysis and homeostasis continue to be essential for intracellular metabolic networks and physiology. However, the genetic network that controls metal ion homeostasis and the impact of metal availability on metabolism is poorly understood. Here, we review recent work on gene and protein evolution relevant for better understanding metal ion biology and its role in metabolism. We highlight the importance of analysing the origin and evolution of enzyme catalysis in the context of catalytically relevant metal ions, summarise unanswered questions essential for developing a comprehensive understanding of metal ion homeostasis and advocate for the consideration of metal ion properties and availability in the design and directed evolution of novel enzymes and pathways.

Coordination of metal center biogenesis in human cytochrome c oxidase

Mitochondrial cytochrome c oxidase (CcO) or respiratory chain complex IV is a heme aa₃-copper oxygen reductase containing metal centers essential for holo-complex biogenesis and enzymatic function that are assembled by subunit-specific metallochaperones. The enzyme has two copper sites located in the catalytic core subunits. The COX1 subunit harbors the Cu_B site that tightly associates with heme a₃ while the COX2 subunit contains the binuclear Cu_A site. Here, we report that in human cells the CcO copper chaperones form macromolecular assemblies and cooperate with several twin CX₉C proteins to control heme a biosynthesis and coordinate copper transfer sequentially to the Cu_A and Cu_B sites. These data on CcO illustrate a mechanism that regulates the biogenesis of macromolecular enzymatic assemblies with several catalytic metal redox centers and prevents the accumulation of cytotoxic reactive assembly intermediates.

Recent advances in the application of metallomics in diagnosis and prognosis of human cancer

Metals play a critical role in human health and diseases. In recent years, metallomics has been introduced and extensively applied to investigate the distribution, regulation, function, and crosstalk of metal(loid) ions in various physiological and pathological processes. Based on high-throughput multielemental analytical techniques and bioinformatics methods, it is possible to elucidate the correlation between the metabolism and homeostasis of diverse metals and complex diseases, in particular for cancer. This review aims to provide an overview of recent progress made in the application of metallomics in cancer research. We mainly focuses on the studies about metallomic profiling of different human biological samples for several major types of cancer, which reveal distinct and dynamic patterns of metal ion contents and the potential benefits of using such information in the detection and prognosis of these malignancies. Elevated levels of copper appear to be a significant risk factor for various cancers, and each type of cancer has a unique distribution of metals in biofluids, hair/nails, and tumor-affected tissues. Furthermore, associations between genetic variations in representative metalloprotein genes and cancer susceptibility have also been demonstrated. Overall, metallomics not only offers a better understanding of the relationship between metal dyshomeostasis and the development of cancer but also facilitates the discovery of new diagnostic and prognostic markers for cancer translational medicine.

The mouse metallomic landscape of aging and metabolism

Organic elements make up 99% of an organism but without the remaining inorganic bioessential elements, termed the metallome, no life could be possible. The metallome is involved in all aspects of life, including charge balance and electrolytic activity, structure and conformation, signaling, acid-base buffering, electron and chemical group transfer, redox catalysis energy storage and biomineralization. Here, we report the evolution with age of the metallome and copper and zinc isotope compositions in five mouse organs. The aging metallome shows a conserved and reproducible fingerprint. By analyzing the metallome in tandem with the phenome, metabolome and proteome, we show networks of interactions that are organ-specific, age-dependent, isotopically-typified and that are associated with a wealth of clinical and molecular traits. We report that the copper isotope composition in liver is age-dependent, extending the existence of aging isotopic clocks beyond bulk organic elements. Furthermore, iron concentration and copper isotope composition relate to predictors of metabolic health, such as body fat percentage and maximum running capacity at the physiological level, and adipogenesis and OXPHOS at the biochemical level. Our results shed light on the metallome as an overlooked omic layer and open perspectives for potentially modulating cellular processes using careful and selective metallome manipulation.

The metallome is crucial for normal cell functioning but remains largely overlooked in mammals. Here the authors analyze the metallome and copper and zinc isotope compositions in aging mice and show networks of interactions that are organ-specific, age-dependent, isotopically-typified and associated with a wealth of clinical and molecular traits.

Heterogeneous nuclear ribonucleoprotein hnRNPA2/B1 regulates the abundance of the copper-transporter ATP7A in an isoform-dependent manner

Copper (Cu) is an essential micronutrient with a critical role in mammalian growth and development. Imbalance of Cu causes severe diseases in humans; therefore, cellular Cu levels are tightly regulated. Major Cu-transport proteins and their cellular behavior have been characterized in detail, whereas their regulation at the mRNA level and associated factors are not well-understood. We show that the heterogeneous nuclear ribonucleoprotein hnRNPA2/B1 regulates Cu homeostasis by modulating the abundance of Cu(I)-transporter ATP7A. Downregulation of hnRNPA2/B1 in HeLa cells increases the ATP7A mRNA and protein levels and significantly decreases cellular Cu; this regulation involves the 3' UTR of ATP7A transcript. Downregulation of B1 and B1b isoforms of hnRNPA2/B1 is sufficient to elevate ATP7A, whereas overexpression of either hnRNPA2 or hnRNPB1 isoforms decreases the ATP7A mRNA levels. Concurrent decrease in hnRNPA2/B1, increase in ATP7A, and a decrease in Cu levels was observed in neuroblastoma SH-SY5Y cells during retinoic acid-induced differentiation; this effect was reversed by overexpression of B1/B1b isoforms. We conclude that hnRNPA2/B1 is a new isoform-specific negative regulator of ATP7A abundance.

IonFlow: a galaxy tool for the analysis of ionomics data sets

INTRODUCTION

Inductively coupled plasma mass spectrometry (ICP-MS) experiments generate complex multi-dimensional data sets that require specialist data analysis tools.

OBJECTIVE

Here we describe tools to facilitate analysis of the ionome composed of high-throughput elemental profiling data.

METHODS

IonFlow is a Galaxy tool written in R for ionomics data analysis and is freely accessible at https://github.com/wanchanglin/ionflow . It is designed as a pipeline that can process raw data to enable exploration and interpretation using multivariate statistical techniques and network-based algorithms, including principal components analysis, hierarchical clustering, relevance network extraction and analysis, and gene set enrichment analysis.

RESULTS AND CONCLUSION

The pipeline is described and tested on two benchmark data sets of the haploid S. Cerevisiae ionome and of the human HeLa cell ionome.

An Overview of Cell-Based Assay Platforms for the Solute Carrier Family of Transporters

The solute carrier (SLC) superfamily represents the biggest family of transporters with important roles in health and disease. Despite being attractive and druggable targets, the majority of SLCs remains understudied. One major hurdle in research on SLCs is the lack of tools, such as cell-based assays to investigate their biological role and for drug discovery. Another challenge is the disperse and anecdotal information on assay strategies that are suitable for SLCs. This review provides a comprehensive overview of state-of-the-art cellular assay technologies for SLC research and discusses relevant SLC characteristics enabling the choice of an optimal assay technology. The Innovative Medicines Initiative consortium RESOLUTE intends to accelerate research on SLCs by providing the scientific community with high-quality reagents, assay technologies and data sets, and to ultimately unlock SLCs for drug discovery.

Growth and ionomic responses of a freshwater cyanobacterium to supplies of nitrogen and iron

Cyanobacterial harmful algal blooms (HABs) are increasing in frequency and magnitude worldwide. A number of parameters are thought to underlie HABs, including the ratio at which two key elements, nitrogen (N) and phosphorus (P) are supplied, although a predictive understanding eludes us. While the physiological importance of iron (Fe) in electron transport and N-fixation is well known, relatively little is known about its impacts on the growth of freshwater cyanobacteria. Moreover, there is growing appreciation for correlated changes in the quotas of multiple elements encompassing an organism (i.e. the ionome) when the supply of one element changes, indicating that growth differences arise from complex biochemical adjustments rather than limitation of a key anabolic process by a single element. In this study, the effects of supply N:P and Fe on the growth and ionome of Dolichospermum, a nitrogen-fixing cyanobacterium found in freshwater ecosystems, were examined. Changes in both supply N:P and Fe had significant effects on yield. Consistent with prior observations, cyanobacterial growth was higher at N:P = 20, compared to N:P = 5, and quotas of all elements decreased with growth. Yield was negatively related with the degree of imbalance between dissolved supply and intracellular concentrations of not only N and Fe, but also multiple other elements. Changes in Fe supply had a significant effect on yield in N-limited conditions (N:P = 5). Again, ionome-wide imbalances decreased yield. Together, these results indicate that attention to multiple elements encompassing the ionome of a HAB-forming taxon, and the supplies of such elements may help improve the ability to forecast blooms. Such elemental interactions may be critical as limnologists begin to appreciate the staggering variation in the supplies of such elements among lakes, and anthropogenic activities continue to alter global biogeochemical cycles.

1,135 ionomes reveal the global pattern of leaf and seed mineral nutrient and trace element diversity in Arabidopsis thaliana

Soil is a heterogeneous reservoir of essential elements needed for plant growth and development. Plants have evolved mechanisms to balance their nutritional needs based on availability of nutrients. This has led to genetically based variation in the elemental composition, the 'ionome', of plants, both within and between species. We explore this natural variation using a panel of wild-collected, geographically widespread Arabidopsis thaliana accessions from the 1001 Genomes Project including over 1,135 accessions, and the 19 parental accessions of the Multi-parent Advanced Generation Inter-Cross (MAGIC) panel, all with full-genome sequences available. We present an experimental design pipeline for high-throughput ionomic screenings and analyses with improved normalisation procedures to account for errors and variability in conditions often encountered in large-scale, high-throughput data collection. We report quantification of the complete leaf and seed ionome of the entire collection using this pipeline and a digital tool, Ion Explorer, to interact with the dataset. We describe the pattern of natural ionomic variation across the A. thaliana species and identify several accessions with extreme ionomic profiles. It forms a valuable resource for exploratory genetic mapping studies to identify genes underlying natural variation in leaf and seed ionome and genetic adaptation of plants to soil conditions.

DIAPH3 promotes pancreatic cancer progression by activating selenoprotein TrxR1-mediated antioxidant effects

Pancreatic cancer is a highly malignant tumour of the digestive tract which is difficult to diagnose and treat. Approximately 90% of cases arise from ductal adenocarcinoma of the glandular epithelium. The morbidity and mortality of the disease have increased significantly in recent years. Its 5‐year survival rate is <1% and has one of the worst prognoses amongst malignant tumours. Pancreatic cancer has a low rate of early‐stage diagnosis, high surgical mortality and low cure rate. Selenium compounds produced by selenoamino acid metabolism may promote a large amount of oxidative stress and subsequent unfolded reactions and endoplasmic reticulum stress by consuming the NADPH in cells, and eventually lead to apoptosis, necrosis or necrotic cell death. In this study, we first identified DIAPH3 as a highly expressed protein in the tissues of patients with pancreatic cancer, and confirmed that DIAPH3 promoted the proliferation, anchorage‐independent growth and invasion of pancreatic cancer cells using overexpression and interference experiments. Secondly, bioinformatics data mining showed that the potential proteins interacted with DIAPH3 were involved in selenoamino acid metabolism regulation. Selenium may be incorporated into selenoprotein synthesis such as TrxR1 and GPX4, which direct reduction of hydroperoxides or resist ferroptosis, respectively. Our following validation confirmed that DIAPH3 promoted selenium content and interacted with the selenoprotein RPL6, a ribosome protein subunit involved in selenoamino acid metabolism. In addition, we verified that DIAPH3 could down‐regulate cellular ROS level via up‐regulating TrxR1 expression. Finally, nude mice xenograft model experimental results demonstrate DIAPH3 knock down could decrease tumour growth and TrxR1 expression and ROS levels in vivo. Collectively, our observations indicate DIAPH3 could promote pancreatic cancer progression by activating selenoprotein TrxR1‐mediated antioxidant effects.

Stoichiometric variation within and between a terrestrial herbivorous and a semi-aquatic carnivorous mammal

BACKGROUND

The elemental composition of the mammalian body is widely believed to be more or less constant within and among species, yet reliable comparisons of elemental content are lacking. Here, we examine the elemental composition of two mammal species with different diet and provenance: terrestrial herbivorous Fallow deer (Dama dama) - collected from a single area - and semi-aquatic carnivorous Eurasian otter (Lutra lutra) - collected from different areas.

METHODS

We compared twelve elemental contents for twelve different body tissues and organs, for four tissue samples per species. Homogeneous samples were tested for twelve elemental contents using ICP-OES.

RESULTS

We found evidence for differences in elemental composition between species, between tissues, and between individuals. Herbivorous Fallow deer seemed more variable in its elemental composition compared to carnivorous Eurasian otter. The absolute concentration of some elements, e.g. Mn and Cu, showed differences between the species as well.

CONCLUSION

Since we found stoichiometric variation among the species, these findings question the widely held assumption that mammals are under relative tight stoichiometrically homeostatic control.

Disease Ionomics: Understanding the Role of Ions in Complex Disease

Ionomics is a novel multidisciplinary field that uses advanced techniques to investigate the composition and distribution of all minerals and trace elements in a living organism and their variations under diverse physiological and pathological conditions. It involves both high-throughput elemental profiling technologies and bioinformatic methods, providing opportunities to study the molecular mechanism underlying the metabolism, homeostasis, and cross-talk of these elements. While much effort has been made in exploring the ionomic traits relating to plant physiology and nutrition, the use of ionomics in the research of serious diseases is still in progress. In recent years, a number of ionomic studies have been carried out for a variety of complex diseases, which offer theoretical and practical insights into the etiology, early diagnosis, prognosis, and therapy of them. This review aims to give an overview of recent applications of ionomics in the study of complex diseases and discuss the latest advances and future trends in this area. Overall, disease ionomics may provide substantial information for systematic understanding of the properties of the elements and the dynamic network of elements involved in the onset and development of diseases.

The molecular mechanisms of copper metabolism and its roles in human diseases

Copper is an essential element in cells; it can act as either a recipient or a donor of electrons, participating in various reactions. However, an excess of copper ions in cells is detrimental as these copper ions can generate free radicals and increase oxidative stress. In multicellular organisms, copper metabolism involves uptake, distribution, sequestration, and excretion, at both the cellular and systemic levels. Mammalian enterocytes take in bioavailable copper ions from the diet in a Ctr1-dependent manner. After incorporation, cuprous ions are delivered to ATP7A, which pumps Cu⁺ from enterocytes into the blood. Copper ions arrive at the liver through the portal vein and are incorporated into hepatocytes by Ctr1. Then, Cu⁺ can be secreted into the bile or the blood via the Atox1/ATP7B/ceruloplasmin route. In the bloodstream, this micronutrient can reach peripheral tissues and is again incorporated by Ctr1. In peripheral tissue cells, cuprous ions are either sequestrated by molecules such as metallothioneins or targeted to utilization pathways by chaperons such as Atox1, Cox17, and CCS. Copper metabolism must be tightly controlled in order to achieve homeostasis and avoid disorders. A hereditary or acquired copper unbalance, including deficiency, overload, or misdistribution, may cause or aggravate certain diseases such as Menkes disease, Wilson disease, neurodegenerative diseases, anemia, metabolic syndrome, cardiovascular diseases, and cancer. A full understanding of copper metabolism and its roles in diseases underlies the identification of novel effective therapies for such diseases.

Elemental metabolomics in human cord blood: Method validation and trace element quantification

BACKGROUND

Trace elements are an essential requirement for human health and development and changes in trace element status have been associated with pregnancy complications such as gestational diabetes mellitus (GDM), pre-eclampsia (PE), fetal growth restriction (FGR), and preterm birth. Elemental metabolomics, which involves the simultaneous quantification and characterisation of multiple elements, could provide important insights into these gestational disorders.

METHODS

This study used an Agilent 7900 inductively coupled plasma mass spectrometer (ICP-MS) to simultaneously measure 68 elements, in 166 placental cord blood samples collected from women with various pregnancy complications (control, hypertensive, PE, GDM, FGR, pre-term, and post-term birth).

RESULTS

There were single element differences across gestational outcomes for elements Mg, P, Cr, Ni, Sr, Mo, I, Au, Pb, and U. Hypertensive and post-term pregnancies were significantly higher in Ni concentrations when compared to controls (control = 2.74 μg/L, hypertensive = 6.72 μg/L, post-term = 7.93 μg/L, p < 0.05), iodine concentration was significantly higher in post-term pregnancies (p < 0.05), and Pb concentrations were the lowest in pre-term pregnancies (pre-term = 2.79 μg/L, control = 4.68 μg/L, PE = 5.32 μg/L, GDM = 8.27 μg/L, p < 0.01). Further analysis was conducted using receiver operating characteristic (ROC) curves for differentiating pregnancy groups. The ratio of Sn/Pb showed the best diagnostic power in discriminating between control and pre-term birth with area under the curve (AUC) 0.86. When comparing control and post-term birth, Mg/Cr (AUC = 0.84), and Cr (AUC = 0.83) had the best diagnostic powers. In pre-term and post-term comparisons Ba was the best single element (81.5%), and P/Cu provided the best ratio (91.7%).

CONCLUSIONS

This study has shown that analysis of multiple elements can enable differentiation between fetal cord blood samples from control, hypertensive, PE, GDM, FGR, pre and post-term pregnancies. This data highlights the power of elemental metabolomics and provides a basis for future gestational studies.

Towards single-cell ionomics: a novel micro-scaled method for multi-element analysis of nanogram-sized biological samples

BACKGROUND

To understand processes regulating nutrient homeostasis at the single-cell level there is a need for new methods that allow multi-element profiling of biological samples ultimately only available as isolated tissues or cells, typically in nanogram-sized samples. Apart from tissue isolation, the main challenges for such analyses are to obtain a complete and homogeneous digestion of each sample, to keep sample dilution at a minimum and to produce accurate and reproducible results. In particular, determining the weight of small samples becomes increasingly challenging when the sample amount decreases.

RESULTS

We developed a novel method for sampling, digestion and multi-element analysis of nanogram-sized plant tissue, along with strategies to quantify element concentrations in samples too small to be weighed. The method is based on tissue isolation by laser capture microdissection (LCM), followed by pressurized micro-digestion and ICP-MS analysis, the latter utilizing a stable µL min^-1 sample aspiration system. The method allowed for isolation, digestion and analysis of micro-dissected tissues from barley roots with an estimated sample weight of only ~ 400 ng. In the collection and analysis steps, a number of contamination sources were identified. Following elimination of these sources, several elements, including magnesium (Mg), phosphorus (P), potassium (K) and manganese (Mn), could be quantified. By measuring the exact area and thickness of each of the micro-dissected tissues, their volume was calculated. Combined with an estimated sample density, the sample weights could subsequently be calculated and the fact that these samples were too small to be weighed could thereby be circumvented. The method was further documented by analysis of Arabidopsis seeds (~ 20 µg) as well as tissue fractions of such seeds (~ 10 µg).

CONCLUSIONS

The presented method enables collection and multi-element analysis of small-sized biological samples, ranging down to the nanogram level. As such, the method paves the road for single cell and tissue-specific quantitative ionomics, which allow for future transcriptional, proteomic and metabolomic data to be correlated with ionomic profiles. Such analyses will deepen our understanding of how the elemental composition of plants is regulated, e.g. by transporter proteins and physical barriers (i.e. the Casparian strip and suberin lamellae in the root endodermis).

Systems Biology of Selenium and Complex Disease

Selenium is an essential trace element for maintenance of overall health, whose deficiency and dyshomeostasis have been linked to a variety of diseases and disorders. The majority of previous researches focused on characterization of genes encoding selenoproteins or proteins involved in selenium metabolism as well as their functions. Many studies in humans also investigated the relationship between selenium and complex diseases, but their results have been inconsistent. In recent years, systems biology and "-omics" approaches have been widely used to study complex and global variations of selenium metabolism and function in physiological and different pathological conditions. The present paper reviews recent progress in large-scale and systematic analyses of the relationship between selenium status or selenoproteins and several complex diseases, mainly including population-based cohort studies and meta-analyses, genetic association studies, and some other omics-based studies. Advances in ionomics and its application in studying the interaction between selenium and other trace elements in human health and diseases are also discussed.

ANKRD9 is a metabolically-controlled regulator of IMPDH2 abundance and macro-assembly

Members of a large family of Ankyrin Repeat Domain (ANKRD) proteins regulate numerous cellular processes by binding to specific protein targets and modulating their activity, stability, and other properties. The same ANKRD protein may interact with different targets and regulate distinct cellular pathways. The mechanisms responsible for switches in the ANKRDs' behavior are often unknown. We show that cells' metabolic state can markedly alter interactions of an ANKRD protein with its target and the functional outcomes of this interaction. ANKRD9 facilitates degradation of inosine monophosphate dehydrogenase 2 (IMPDH2), the rate-limiting enzyme in GTP biosynthesis. Under basal conditions ANKRD9 is largely segregated from the cytosolic IMPDH2 in vesicle-like structures. Upon nutrient limitation, ANKRD9 loses its vesicular pattern and assembles with IMPDH2 into rodlike filaments, in which IMPDH2 is stable. Inhibition of IMPDH2 activity with ribavirin favors ANKRD9 binding to IMPDH2 rods. The formation of ANKRD9/IMPDH2 rods is reversed by guanosine, which restores ANKRD9 associations with the vesicle-like structures. The conserved Cys¹⁰⁹Cys¹¹⁰ motif in ANKRD9 is required for the vesicle-to-rods transition as well as binding and regulation of IMPDH2. Oppositely to overexpression, ANKRD9 knockdown increases IMPDH2 levels and prevents formation of IMPDH2 rods upon nutrient limitation. Taken together, the results suggest that a guanosine-dependent metabolic switch determines the mode of ANKRD9 action toward IMPDH2.

Copper Transport and Disease: What Can We Learn from Organoids?

Many metals have biological functions and play important roles in human health. Copper (Cu) is an essential metal that supports normal cellular physiology. Significant research efforts have focused on identifying the molecules and pathways involved in dietary Cu uptake in the digestive tract. The lack of an adequate in vitro model for assessing Cu transport processes in the gut has led to contradictory data and gaps in our understanding of the mechanisms involved in dietary Cu acquisition. The recent development of organoid technology has provided a tractable model system for assessing the detailed mechanistic processes involved in Cu utilization and transport in the context of nutrition. Enteroid (intestinal epithelial organoid)-based studies have identified new links between intestinal Cu metabolism and dietary fat processing. Evidence for a metabolic coupling between the dietary uptake of Cu and uptake of fat (which were previously thought to be independent) is a new and exciting finding that highlights the utility of these three-dimensional primary culture systems. This review has three goals: (a) to critically discuss the roles of key Cu transport enzymes in dietary Cu uptake; (b) to assess the use, utility, and limitations of organoid technology in research into nutritional Cu transport and Cu-based diseases; and (c) to highlight emerging connections between nutritional Cu homeostasis and fat metabolism.

Trafficking mechanisms of P-type ATPase copper transporters

Copper is an essential micronutrient required for oxygen-dependent enzymes, yet excess of the metal is a toxicant. The tug-of-war between these copper activities is balanced by chaperones and membrane transporters, which control copper distribution and availability. The P-type ATPase transporters, ATP7A and ATP7B, regulate cytoplasmic copper by pumping copper out of cells or into the endomembrane system. Mutations in ATP7A and ATP7B cause diseases that share neuropsychiatric phenotypes, which are similar to phenotypes observed in mutations affecting cytoplasmic trafficking complexes required for ATP7A/B dynamics. Here, we discuss evidence indicating that phenotypes associated to genetic defects in trafficking complexes, such as retromer and the adaptor complex AP-1, result in part from copper dyshomeostasis due to mislocalized ATP7A and ATP7B.

Association of urinary ionomic profiles and acute kidney injury and mortality in patients after cardiac surgery

OBJECTIVE

The rarity of sensitive biomarkers for acute kidney injury (AKI) has impeded the timely therapy of AKI. Emerging evidence suggests that ion homeostasis may play pertinent roles in AKI. We aimed to screen out representative urinary ions and build a cardiac surgery-associated AKI indication model.

METHODS

We performed urinary ionomic analysis from patients undergoing cardiac surgeries in Zhongshan Hospital, Fudan University, Shanghai, China (N = 261). By bioinformatics analysis, we identified differentially changed elements and established the AKI indication model we named the urinary ion index (UII). Follow-ups were performed to evaluate 30-day survival.

RESULTS

The concentrations of most ions dynamically changed whether a patient developed AKI or not. A significant number of differentially changed elements between AKI and non-AKI groups were detected, especially at 2 hours after cardiac surgery, based on which we generated UII, with the area under the curve of 0.815 ± 0.006 and a cut-off value of 1.24. UII was associated with need for renal replacement therapy, with an area under the curve of 0.83 at a cutoff value of 1.62. Kaplan-Meier and log-rank methods, as well as Cox proportional hazards model, reflected that patients in the UII > 1.24 group had significantly higher risk of mortality within 30 days after surgery (hazard ratio, 5.15; P = .0097 and hazard ratio, 3.56; P = .033) than the UII ≤ 1.24 group.

CONCLUSIONS

Our data demonstrate that UII appears to be a novel and valid index of early cardiac surgery-associated AKI. UII > 1.24 at 2 hours after surgery indicates high risk of AKI and less 30-day survival.

Elemental Metabolomics and Pregnancy Outcomes

Trace elements are important for human health and development. The body requires specific micronutrients to function, with aberrant changes associated with a variety of negative health outcomes. Despite this evidence, the status and function of micronutrients during pregnancy are relatively unknown and more information is required to ensure that women receive optimal intakes for foetal development. Changes in trace element status have been associated with pregnancy complications such as gestational diabetes mellitus (GDM), pre-eclampsia (PE), intrauterine growth restriction (IUGR), and preterm birth. Measuring micronutrients with methodologies such as elemental metabolomics, which involves the simultaneous quantification and characterisation of multiple elements, could provide insight into gestational disorders. Identifying unique and subtle micronutrient changes may highlight associated proteins that are affected underpinning the pathophysiology of these complications, leading to new means of disease diagnosis. This review will provide a comprehensive summary of micronutrient status during pregnancy, and their associations with gestational disorders. Furthermore, it will also comment on the potential use of elemental metabolomics as a technique for disease characterisation and prediction.

Bioimaging predictors of rilpivirine biodistribution and antiretroviral activities

Antiretroviral therapy (ART) has changed the outcome of human immunodeficiency virus type one (HIV-1) infection from certain death to a life free of disease co-morbidities. However, infected people must remain on life-long daily ART. ART reduces but fails to eliminate the viral reservoir. In order to improve upon current treatment regimens, our laboratory created long acting slow effective release (LASER) ART nanoformulated prodrugs from native medicines. LASER ART enables antiretroviral drugs (ARVs) to better reach target sites of HIV-1 infection while, at the same time, improve ART's half-life and potency. However, novel ARV design has been slowed by prolonged pharmacokinetic testing requirements. To such ends, tri-modal theranostic nanoparticles were created with single-photon emission computed tomography (SPECT/CT), magnetic resonance imaging (MRI) and fluorescence capabilities to predict LASER ART biodistribution. The created theranostic ARV probes were then employed to monitor drug tissue distribution and potency. Intrinsically 111Indium (111In) radiolabeled, europium doped cobalt-ferrite particles and rilpivirine were encased in a polycaprolactone core surrounded by a lipid shell (111InEuCF-RPV). Particle cell and tissue distribution, and antiretroviral activities were sustained in macrophage tissue depots. 111InEuCF-PCL/RPV particles injected into mice demonstrated co-registration of MRI and SPECT/CT tissue signals with RPV and cobalt. Cell and animal particle biodistribution paralleled ARV activities. We posit that particle selection can predict RPV distribution and potency facilitated by multifunctional theranostic nanoparticles.

Copper signalling: causes and consequences

Copper-containing enzymes perform fundamental functions by activating dioxygen (O2) and therefore allowing chemical energy-transfer for aerobic metabolism. The copper-dependence of O2 transport, metabolism and production of signalling molecules are supported by molecular systems that regulate and preserve tightly-bound static and weakly-bound dynamic cellular copper pools. Disruption of the reducing intracellular environment, characterized by glutathione shortage and ambient Cu(II) abundance drives oxidative stress and interferes with the bidirectional, copper-dependent communication between neurons and astrocytes, eventually leading to various brain disease forms. A deeper understanding of of the regulatory effects of copper on neuro-glia coupling via polyamine metabolism may reveal novel copper signalling functions and new directions for therapeutic intervention in brain disorders associated with aberrant copper metabolism.

ANKRD9 is associated with tumor suppression as a substrate receptor subunit of ubiquitin ligase

BACKGROUND

Human ANKRD9 (ankyrin repeat domain 9) expression is altered in some cancers.

METHODS

We tested genetic association of ANKRD9 with gastric cancer susceptibility and examined functional association of ANKRD9 with altered proliferation of MKN45 gastric cancer cells. We then identified ANKRD9-binding partners in HEK 293 embryonic kidney cells using quantitative proteomics, western blotting and complex reconstitution assays. We finally demonstrated ANKRD9's role of recognizing substrates for ubiquitination using in vitro ubiquitylation assay.

RESULTS

ANKRD9 is associated with cancer susceptibility in a comparison of single-nucleotide polymorphisms between 1092 gastric cancer patients and 1206 healthy controls. ANKRD9 depletion accelerates tumor progression by increasing cellular proliferation, piling up, and anchorage-independent growth of MKN45 cells. We discovered that ANKRD9 is a ubiquitin ligase substrate receptor subunit and has an anti-proliferative activity. ANKRD9 associates with CUL5 (not CUL2), ELOB, ELOC, and presumably RNF7 subunits, which together assemble into a cullin-RING superfamily E3 ligase complex. ANKRD9 belongs to the ASB family of proteins, which are characterized by the presence of ankyrin repeats and a SOCS box. In addition to its interactions with the other E3 ligase subunits, ANKRD9 interacts with two isoforms of inosine monophosphate dehydrogenase (IMPDH). These IMPDH isoforms are cognate substrates of the ANKRD9-containing E3 enzyme, which ubiquitinates them for proteasomal degradation. Their ubiquitination and turnover require the presence of ANKRD9.

CONCLUSION

ANKRD9, a previously unidentified E3 substrate receptor subunit, functions in tumor suppression by recognizing the oncoprotein IMPDH isoforms for E3 ubiquitination and proteasomal degradation.

Downregulation of hepatic multi-drug resistance protein 1 (MDR1) after copper exposure

Copper homeostasis is strictly regulated in mammalian cells. We investigated the adaptation of hepatocytes after long-term copper exposure. Copper-resistant hepatoma HepG2 cell lines lacking ATP7B were generated. Growth, copper accumulation, gene expression, and transport were determined. Hepatocyte-like cells derived from a Wilson disease (WD) patient and the liver of a WD animal model were also studied. The rapidly gained copper resistance was found to be stable, as subculturing of cells in the absence of added copper (weaning) did not restore copper sensitivity. Intracellular copper levels and the expression of MT1 and HSP70 were increased, whereas the expression of CTR1 was reduced. However, the values normalized after weaning. In contrast, downregulation of multi-drug resistance protein 1 (MDR1), encoding P-glycoprotein (P-gp), was shown to be permanent. Calcein assays confirmed the downregulation of MDR1 in the resistant cell lines. MDR1 knockdown by siRNA resulted in increased copper resistance and decreased intracellular copper. Treatment of the resistant cells with verapamil, a known inducer of MDR1, was followed by increased copper-induced toxicity. Downregulation of MDR1 was also observed in hepatocyte-like cells derived from a WD patient after copper exposure. In addition, MDR1 was downregulated in Long-Evans Cinnamon rats when the liver copper was elevated. The results indicate that downregulation of MDR1 is an adaptation of hepatic cells after sustained copper exposure when ATP7B is non-functional. Our data add to the versatile functions of MDR1 in the hepatocyte and may have an impact on the treatment of copper-related diseases, prominently WD.

Trace Elements and Healthcare: A Bioinformatics Perspective

Biological trace elements are essential for human health. Imbalance in trace element metabolism and homeostasis may play an important role in a variety of diseases and disorders. While the majority of previous researches focused on experimental verification of genes involved in trace element metabolism and those encoding trace element-dependent proteins, bioinformatics study on trace elements is relatively rare and still at the starting stage. This chapter offers an overview of recent progress in bioinformatics analyses of trace element utilization, metabolism, and function, especially comparative genomics of several important metals. The relationship between individual elements and several diseases based on recent large-scale systematic studies such as genome-wide association studies and case-control studies is discussed. Lastly, developments of ionomics and its recent application in human health are also introduced.

Ecological Stoichiometry beyond Redfield: An Ionomic Perspective on Elemental Homeostasis

Elemental homeostasis has been largely characterized using three important elements that were part of the Redfield ratio (i.e., carbon: nitrogen: phosphorus). These efforts have revealed substantial diversity in homeostasis among taxonomic groups and even within populations. Understanding the evolutionary basis, and ecological consequences of such diversity is a central challenge. Here, we propose that a more complete understanding of homeostasis necessitates the consideration of other elements beyond C, N, and P. Specifically, we posit that physiological complexity underlying maintenance of elemental homeostasis along a single elemental axis impacts processing of other elements, thus altering elemental homeostasis along other axes. Indeed, transcriptomic studies in a wide variety of organisms have found that individuals differentially express significant proportions of the genome in response to variability in supply stoichiometry in order to maintain varying levels of homeostasis. We review the literature from the emergent field of ionomics that has established the consequences of such physiological trade-offs on the content of the entire suite of elements in an individual. Further, we present experimental data on bacteria exhibiting divergent phosphorus homeostasis phenotypes demonstrating the fundamental interconnectedness among elemental quotas. These observations suggest that physiological adjustments can lead to unexpected patterns in biomass stoichiometry, such as correlated changes among suites of non-limiting microelements in response to limitation by macroelements. Including the entire suite of elements that comprise biomass will foster improved quantitative understanding of the links between chemical cycles and the physiology of organisms.

ICP-MS/MS-Based Ionomics: A Validated Methodology to Investigate the Biological Variability of the Human Ionome

We here describe the development, validation and application of a quantitative methodology for the simultaneous determination of 29 elements in human serum using state-of-the-art inductively coupled plasma triple quadrupole mass spectrometry (ICP-MS/MS). This new methodology offers high-throughput elemental profiling using simple dilution of minimal quantity of serum samples. We report the outcomes of the validation procedure including limits of detection/quantification, linearity of calibration curves, precision, recovery and measurement uncertainty. ICP-MS/MS-based ionomics was used to analyze human serum of 120 older adults. Following a metabolomic data mining approach, the generated ionome profiles were subjected to principal component analysis revealing gender and age-specific differences. The ionome of female individuals was marked by higher levels of calcium, phosphorus, copper and copper to zinc ratio, while iron concentration was lower with respect to male subjects. Age was associated with lower concentrations of zinc. These findings were complemented with additional readouts to interpret micronutrient status including ceruloplasmin, ferritin and inorganic phosphate. Our data supports a gender-specific compartmentalization of the ionome that may reflect different bone remodelling in female individuals. Our ICP-MS/MS methodology enriches the panel of validated "Omics" approaches to study molecular relationships between the exposome and the ionome in relation with nutrition and health.

The role of subcutaneous adipose tissue in supporting the copper balance in rats with a chronic deficiency in holo-ceruloplasmin

We have previously shown that (1) an acute deficiency in blood serum holo-ceruloplasmin (Cp) developed in rats that were fed fodder containing silver ions (Ag-fodder) for one month and (2) the deficiency in holo-Cp was compensated by non-hepatic holo-Cp synthesis in rats that were chronically fed Ag-fodder for 6 months (Ag-rats). The purpose of the present study is to identify the organ(s) that compensate for the hepatic holo-Cp deficiency in the circulation. This study was performed on rats that were fed Ag-fodder (40 mg Ag·kg^-1 body mass daily) for 6 months. The relative expression levels of the genes responsible for copper status were measured by RT-PCR. The in vitro synthesis and secretion of [¹⁴C]Cp were analyzed using a metabolic labeling approach. Oxidase activity was determined using a gel assay with o-dianisidine. Copper status and some hematological indexes were measured. Differential centrifugation, immunoblotting, immunoelectrophoresis, and atomic absorption spectrometry were included in the investigation. In the Ag-rats, silver accumulation was tissue-specific. Skeletal muscles and internal (IAT) and subcutaneous (SAT) adipose tissues did not accumulate silver significantly. In SAT, the mRNAs for the soluble and glycosylphosphatidylinositol-anchored ceruloplasmin isoforms were expressed, and their relative levels were increased two-fold in the Ag-rats. In parallel, the levels of the genes responsible for Cp metallation (Ctr1 and Atp7a/b) increased correspondingly. In the SAT of the Ag-rats, Cp oxidase activity was observed in the Golgi complex and plasma membrane. Moreover, full-length [¹⁴C]Cp polypeptides were released into the medium by slices of SAT. The possibilities that SAT is part of a system that controls the copper balance in mammals, and it plays a significant role in supporting copper homeostasis throughout the body are discussed.

The interactome of the copper transporter ATP7A belongs to a network of neurodevelopmental and neurodegeneration factors

Genetic and environmental factors, such as metals, interact to determine neurological traits. We reasoned that interactomes of molecules handling metals in neurons should include novel metal homeostasis pathways. We focused on copper and its transporter ATP7A because ATP7A null mutations cause neurodegeneration. We performed ATP7A immunoaffinity chromatography and identified 541 proteins co-isolating with ATP7A. The ATP7A interactome concentrated gene products implicated in neurodegeneration and neurodevelopmental disorders, including subunits of the Golgi-localized conserved oligomeric Golgi (COG) complex. COG null cells possess altered content and subcellular localization of ATP7A and CTR1 (SLC31A1), the transporter required for copper uptake, as well as decreased total cellular copper, and impaired copper-dependent metabolic responses. Changes in the expression of ATP7A and COG subunits in Drosophila neurons altered synapse development in larvae and copper-induced mortality of adult flies. We conclude that the ATP7A interactome encompasses a novel COG-dependent mechanism to specify neuronal development and survival.

Sodium selenate regulates the brain ionome in a transgenic mouse model of Alzheimer's disease

Many studies have shown that imbalance of mineral metabolism may play an important role in Alzheimer's disease (AD) progression. It was recently reported that selenium could reverse memory deficits in AD mouse model. We carried out multi-time-point ionome analysis to investigate the interactions among 15 elements in the brain by using a triple-transgenic mouse model of AD with/without high-dose sodium selenate supplementation. Except selenium, the majority of significantly changed elements showed a reduced level after 6-month selenate supplementation, especially iron whose levels were completely reversed to normal state at almost all examined time points. We then built the elemental correlation network for each time point. Significant and specific elemental correlations and correlation changes were identified, implying a highly complex and dynamic crosstalk between selenium and other elements during long-term supplementation with selenate. Finally, we measured the activities of two important anti-oxidative selenoenzymes, glutathione peroxidase and thioredoxin reductase, and found that they were remarkably increased in the cerebrum of selenate-treated mice, suggesting that selenoenzyme-mediated protection against oxidative stress might also be involved in the therapeutic effect of selenate in AD. Overall, this study should contribute to our understanding of the mechanism related to the potential use of selenate in AD treatment.

Copper trafficking to the secretory pathway

Copper (Cu) is indispensible for growth and development of human organisms. It is required for such fundamental and ubiquitous processes as respiration and protection against reactive oxygen species. Cu also enables catalytic activity of enzymes that critically contribute to the functional identity of many cells and tissues. Pigmentation, production of norepinephrine by the adrenal gland, the key steps in the formation of connective tissue, neuroendocrine signaling, wound healing - all these processes require Cu and depend on Cu entering the secretory pathway. To reach the Cu-dependent enzymes in a lumen of the trans-Golgi network and various vesicular compartments, Cu undertakes a complex journey crossing the extracellular and intracellular membranes and staying firmly on course while traveling in a cytosol. The proteins that assist Cu in this journey by mediating its entry, distribution, and export, have been identified. The accumulating data also indicate that the current model of cellular Cu homeostasis is still a "skeleton" that has to be fleshed out with many new details. This review summarizes recent data on the mechanisms responsible for Cu transfer to the secretory pathway. The emerging new concepts and gaps in our knowledge are discussed.

Copper, zinc and calcium: imaging and quantification in anterior pituitary secretory granules

The anterior pituitary is specialized for the synthesis, storage and release of peptide hormones. The activation of inactive peptide hormone precursors requires a specific set of proteases and other post-translational processing enzymes. High levels of peptidylglycine α-amidating monooxygenase (PAM), an essential peptide processing enzyme, occur in the anterior pituitary. PAM, which converts glycine-extended peptides into amidated products, requires copper and zinc to support its two catalytic activities and calcium for structure. We used X-ray fluorescence microscopy on rat pituitary sections and inductively coupled plasma mass spectrometry on subcellular fractions prepared from rat anterior pituitary to localize and quantify copper, zinc and calcium. X-ray fluorescence microscopy indicated that the calcium concentration in pituitary tissue was about 2.5 mM, 10-times more than zinc and 50-times more than copper. Although no higher than cytosolic levels, secretory granule levels of copper exceeded PAM levels by a factor of 10. Atp7a, which transports copper into the lumen of the secretory pathway, was enriched in endosomes and Golgi, not in secretory granules. If Atp7a transfers copper directly to PAM, this pH-dependent process is likely to occur in Golgi and endosomes.

Plant Ionomics: From Elemental Profiling to Environmental Adaptation

Ionomics is a high-throughput elemental profiling approach to study the molecular mechanistic basis underlying mineral nutrient and trace element composition (also known as the ionome) of living organisms. Since the concept of ionomics was first introduced more than 10 years ago, significant progress has been made in the identification of genes and gene networks that control the ionome. In this update, we summarize the progress made in using the ionomics approach over the last decade, including the identification of genes by forward genetics and the study of natural ionomic variation. We further discuss the potential application of ionomics to the investigation of the ecological functions of ionomic alleles in adaptation to the environment.

Signatures of Evolutionary Adaptation in Quantitative Trait Loci Influencing Trace Element Homeostasis in Liver

Essential trace elements possess vital functions at molecular, cellular, and physiological levels in health and disease, and they are tightly regulated in the human body. In order to assess variability and potential adaptive evolution of trace element homeostasis, we quantified 18 trace elements in 150 liver samples, together with the expression levels of 90 genes and abundances of 40 proteins involved in their homeostasis. Additionally, we genotyped 169 single nucleotide polymorphism (SNPs) in the same sample set. We detected significant associations for 8 protein quantitative trait loci (pQTL), 10 expression quantitative trait loci (eQTLs), and 15 micronutrient quantitative trait loci (nutriQTL). Six of these exceeded the false discovery rate cutoff and were related to essential trace elements: 1) one pQTL for GPX2 (rs10133290); 2) two previously described eQTLs for HFE (rs12346) and SELO (rs4838862) expression; and 3) three nutriQTLs: The pathogenic C282Y mutation at HFE affecting iron (rs1800562), and two SNPs within several clustered metallothionein genes determining selenium concentration (rs1811322 and rs904773). Within the complete set of significant QTLs (which involved 30 SNPs and 20 gene regions), we identified 12 SNPs with extreme patterns of population differentiation (FST values in the top 5% percentile in at least one HapMap population pair) and significant evidence for selective sweeps involving QTLs at GPX1, SELENBP1, GPX3, SLC30A9, and SLC39A8. Overall, this detailed study of various molecular phenotypes illustrates the role of regulatory variants in explaining differences in trace element homeostasis among populations and in the human adaptive response to environmental pressures related to micronutrients.

Neuronal differentiation is associated with a redox-regulated increase of copper flow to the secretory pathway

Brain development requires a fine-tuned copper homoeostasis. Copper deficiency or excess results in severe neuro-pathologies. We demonstrate that upon neuronal differentiation, cellular demand for copper increases, especially within the secretory pathway. Copper flow to this compartment is facilitated through transcriptional and metabolic regulation. Quantitative real-time imaging revealed a gradual change in the oxidation state of cytosolic glutathione upon neuronal differentiation. Transition from a broad range of redox states to a uniformly reducing cytosol facilitates reduction of the copper chaperone Atox1, liberating its metal-binding site. Concomitantly, expression of Atox1 and its partner, a copper transporter ATP7A, is upregulated. These events produce a higher flux of copper through the secretory pathway that balances copper in the cytosol and increases supply of the cofactor to copper-dependent enzymes, expression of which is elevated in differentiated neurons. Direct link between glutathione oxidation and copper compartmentalization allows for rapid metabolic adjustments essential for normal neuronal function.

Organization of the Mammalian Ionome According to Organ Origin, Lineage Specialization, and Longevity

Trace elements are essential to all mammals, but their distribution and utilization across species and organs remains unclear. Here, we examined 18 elements in the brain, heart, kidney, and liver of 26 mammalian species and report the elemental composition of these organs, the patterns of utilization across the species, and their correlation with body mass and longevity. Across the organs, we observed distinct distribution patterns for abundant elements, transition metals, and toxic elements. Some elements showed lineage-specific patterns, including reduced selenium utilization in African mole rats, and positive correlation between the number of selenocysteine residues in selenoprotein P and the selenium levels in liver and kidney across mammals. Body mass was linked positively to zinc levels, whereas species lifespan correlated positively with cadmium and negatively with selenium. This study provides insights into the variation of mammalian ionome by organ physiology, lineage specialization, body mass, and longevity.

Inductively coupled mass spectrometry analysis of biometals in conditional Hamp1 and Hamp1 and Hamp2 transgenic mouse models

Hepcidin, a circulatory antimicrobial peptide, is involved in iron homeostasis, inflammation, infection and metabolic signals. Humans express one hepcidin gene, HAMP but mice express two hepcidin genes, Hamp1 and Hamp2. Consecutive gene targeting events were performed to produce transgenic mice expressing conditional alleles of either Hamp1 or both Hamp1 and Hamp2 (Hamp1/2). The deletion of Hamp1 alleles elevated Hamp2 expression, particularly in males, which was reduced by endotoxin treatment. The tissue levels of iron and other biometals were quantified by inductively coupled mass spectrometry. The ubiquitous or liver-specific deletion of Hamp1 alleles yielded similar quantitative changes in iron levels in the liver, duodenum, spleen, kidney, heart and brain. The introduction of Hamp2 null allele did not exacerbate the iron-related phenotype of Hamp1 null allele. Besides iron, Hamp1 null allele significantly elevated the levels of selenium in the liver, manganese in the liver and duodenum, and copper in the brain. Mice with conditional Hamp alleles will be useful to determine the tissue-specific regulation and functions of Hamp1 and Hamp2 in biometal homeostasis and other biological processes.

Should we treat the ionome as a combination of individual elements, or should we be deriving novel combined traits?

It has been more than 10 years since the concept of the ionome, all of the mineral nutrients in a cell tissue or organism, was introduced. In the intervening years, ionomics, high throughput elemental profiling, has been used to analyse over 400,000 samples from at least 10 different organisms. There are now multiple published examples where an ionomics approach has been used to find genes of novel function, find lines or environments that produce foods with altered nutritional profiles, or define gene by environmental effects on elemental accumulation. In almost all of these studies, the ionome has been treated as a collection of independent elements, with the analysis repeated on each measured element. However, many elements share chemical properties, are known to interact with each other, or have been shown to have similar interactions with biological molecules. Accordingly, there is strong evidence from ionomic studies that the elements of the ionome do not behave independently and that combinations of elements should be treated as the phenotypes of interest. In this review, I will consider the evidence that we have for the interdependence of the ionome, some of its causes, methods for incorporating this interdependence into analyses and the benefits, drawbacks, and challenges of taking these approaches.