Cross-sectional and prospective associations of early childhood circulating metals with early and mid-childhood cognition in the Project Viva cohort

BACKGROUND

Relatively little is known about the immediate and prospective neurodevelopmental impacts of joint exposure to multiple metals (i.e., metal mixtures) in early childhood.

OBJECTIVES

To estimate associations of early childhood (∼3 years of age) blood metal concentrations with cognitive test scores at early and mid-childhood (∼8 years of age).

METHODS

We studied children from the Project Viva cohort. We measured erythrocyte concentrations of seven essential (Co, Cu, Mg, Mn, Mo, Se, and Zn) and eight non-essential metals (As, Ba, Cd, Cs, Hg, Pb, Sn, and Sr) in early childhood blood samples. Trained research assistants administered cognitive tests assessing vocabulary, visual-motor ability, memory, and general intelligence (standard deviations: ∼10 points), in early and mid-childhood. We employed multivariable linear regression to examine associations of individual metals with test scores adjusting for confounders, other concurrently measured metals, and first-trimester maternal blood metals. We also estimated joint associations and explored interaction between metals in mixture analyses.

RESULTS

We analyzed 349 children (median whole blood Pb ∼1 μg/dL). In cross-sectional analyses, each doubling of Pb was associated with lower visual-motor function (mean difference: -2.43 points, 95% confidence interval (CI): -4.01, -0.86) and receptive vocabulary, i.e., words understood (-1.45 points, 95% CI: -3.26, 0.36). Associations of Pb with mid-childhood cognition were weaker and less precise by comparison. Mg was positively associated with cognition in cross-sectional but not prospective analyses, and cross-sectional associations were attenuated in a sensitivity analysis removing adjustment for concurrent metals. We did not observe joint associations nor interactions.

DISCUSSION

In this cohort with low blood Pb levels, increased blood Pb was robustly associated with lower cognitive ability in cross-sectional analyses, even after adjustment for prenatal Pb exposure, and regardless of adjustment for metal co-exposures. However, associations with mid-childhood cognition were attenuated and imprecise, suggesting some buffering of Pb neurotoxicity in early life.

WHAT THIS STUDY ADDS

Relatively few studies have comprehensively separated the effects of neurotoxic metals such as lead (Pb) from pre- and postnatal co-occurring metals, nor examined persistence of associations across childhood. In a cohort of middle-class children, we found higher early childhood (∼3 y) blood Pb was associated with lower scores on cognitive tests, independent of other metals and prenatal blood Pb. However, early childhood Pb was only weakly associated with cognition in mid-childhood (∼8 y). Our results suggest the effects of low-level Pb exposure may attenuate over time in some populations, implying the presence of factors that may buffer Pb neurotoxicity in early life.

Metal mixtures and oral health among children and adolescents in the National Health and Nutrition Examination Survey (NHANES), 2017-2020

INTRODUCTION

Dental caries is the most common non-communicable human disease, yet little is known about the role of environmental metals, despite teeth consisting of a hard matrix of trace elements. We conducted a cross-sectional study of associations between environmental metals and objective assessment of dental caries and subjective assessments of oral health among a representative sample of U.S. children and adolescents.

METHODS

Data were from the 2017-March 2020 pre-pandemic data file of the National Health and Nutrition Examination Survey (NHANES). To account for metal mixtures, we used weighted quantile sum (WQS) regression to estimate the joint impact of multiple trace elements assessed in blood and urine with oral disease outcomes.

RESULTS

The blood metal mixture index was associated with a 32% (95% CI: 1.11, 1.56) increased risk of decayed surfaces while the urine metal mixture index was associated with a 106%, RR (95% CI = 2.06 (1.58, 2.70) increased caries risk. For both blood and urine, Mercury (Hg) had the largest contribution to the mixture index followed by Lead (Pb). The WQS blood metal mixture index was also significantly associated with poorer self-rated oral health, although the magnitude of the association was not as strong as for the objective oral disease measures, RR (95% CI) = 1.04 (1.02, 1.07).

DISCUSSION

Increased exposure to a metal mixture was significantly related to poorer objective and subjective oral health outcomes among U.S. children and adolescents. These are among the first findings showing that metal mixtures are a significant contributor to poor oral health.

Selenium Speciation in Paired Whole Blood and Serum Samples From Pregnant Bangladeshi Women

Objectives

We aimed to characterize the relative concentrations of selected major selenium (Se) species in paired whole blood (WB) and serum samples collected from pregnant women at delivery in Dhaka, Bangladesh. Speciation analysis enabled differentiation of organic and inorganic Se, and quantification of the nutritionally bioactive reduced selenometabolite, selenoneine, which has been previously observed in WB from populations with high levels of fish consumption.

Methods

Paired WB and serum specimens (n = 515) were collected at delivery among participants of the Maternal Vitamin D for Infant Growth trial. Quantification of total serum Se and total WBSe was conducted using inductively coupled plasma mass spectrometry (ICP-MS) at the Centers for Disease Control and Prevention (CDC). Speciation analyses were conducted in a subset of pairs (n = 20) to quantify selenometabolites using liquid chromatography coupled to ICP-MS at the University of Cincinnati. Concentrations of inorganic Se (IV), selenoneine, selenocysteine (SeCys), selenomethioneine (SeMet) were expressed as % of total Se. We assessed concordance between results generated across laboratories using paired t-tests.

Results

Overall (n = 515), mean (SD) serum Se and WBSe concentrations (μg/L) were 70 (14) and 135 (18), respectively, such that average Serum Se as a proportion of WBSe was 52%. Findings were similar in the speciation subset (n = 20) [total Serum Se: 82 (19); total WBSe: 138 (18), with a ratio of serum Se to WBSe: 60%]. Sums of quantified species accounted for most of the total serum Se (72 (10); 88% of total) and WBSe (135 (16); 98%). Organic forms were predominant in both serum and WB: SeCys: 15 (2) and 20 (3); and SeMet: 54 (9) and 92 (13), respectively. Selenoneine was detected in WBSe at mean concentrations of 24 (5) μg/L. Together, SeMet and selenoneine accounted for 85% of the additional WBSe not present in serum. Inorganic Se was not detected in WB but comprised 5% of serum.

Conclusions

Approximately half of the Se in whole blood is in the cellular fraction. SeMet was enriched in WB and the most abundant form, relative to selenoneine which was not found in serum. Small amounts of inorganic serum Se may be artifactual due to freeze-thaw related degradation. These findings require confirmation in other settings but suggest that serum Se may not be a suitable biomarker of population status.

Funding Sources

BMGF.

Provision of Small-Quantity Lipid-Based Nutrient Supplements Increases Plasma Selenium Concentration in Pregnant Women in Malawi: A Secondary Outcome of a Randomized Controlled Trial

Background

Pregnant women in Malawi are at risk of selenium deficiency, which can have adverse effects on pregnancy outcomes. Interventions for improving selenium status are needed.

Objectives

To assess the effect of provision of small-quantity lipid-based nutrient supplements (SQ-LNSs) to Malawian women during pregnancy on their plasma selenium concentrations at 36 wk of gestation.

Methods

Pregnant women (≤20 wk of gestation) were randomly assigned to receive daily either: 1) iron and folic acid (IFA); 2) multiple micronutrients (MMN; 130 µg selenium per capsule); or 3) SQ-LNS (130 µg selenium/20 g). Plasma selenium concentrations were measured by inductively coupled plasma mass spectrometry at baseline and after ≥16 wk of intervention (at 36 wk of gestation) and compared by intervention group.

Results

At 36 wk of gestation, median (quartile 1, quartile 3) plasma selenium concentrations (micromoles per liter) were 0.96 (0.73, 1.23), 0.94 (0.78, 1.18), and 1.01 (0.85, 1.28) in the IFA, MMN, and SQ-LNS groups, respectively. Geometric mean (GM) plasma selenium concentration was 5.4% (95% CI: 1.8%, 9.0%) higher in the SQ-LNS group than in the MMN group and tended to be higher than in the IFA group (+4.2%; 95% CI: 1.0%, 7.8%). The prevalence of adjusted plasma selenium concentrations <1 µmol/L was 55.1%, 57.8%, and 47.3% in the IFA, MMN, and SQ-LNS groups, respectively; it was lower in the SQ-LNS group than in the MMN group, OR = 0.44 (95% CI: 0.24, 0.83), and tended to be lower than in the IFA group, OR = 0.54 (95% CI: 0.29, 1.03). There was a significant interaction between baseline plasma selenium concentration and intervention group (P = 0.003). In the lowest tertile of baseline selenium concentrations, GM plasma selenium concentration was higher, and the prevalence of low values was lower in the SQ-LNS group compared with the MMN and IFA groups at 36 wk of gestation (P ≤ 0.007).

Conclusions

Provision of SQ-LNS containing selenium to pregnant women can be an effective strategy for improving their selenium status.This trial was registered at clinicaltrials.gov (identifier: NCT01239693).

Maternal selenium levels and whole genome screen in recurrent spontaneous preterm birth population: A nested case control study

OBJECTIVE

To establish if low maternal selenium (Se) was associated with sPTB in women with recurrent sPTB and identify genetic link with maternal Se levels.

DESIGN

Nested case-control study.

SETTING

Tertiary Maternity Hospital.

POPULATION

Plasma and whole blood from pregnant women with history of early sPTB/PPROM < 34⁺⁰ and European ancestry were obtained at 20 weeks (range 15-24 weeks). 'Cases' were recurrent PTB/PPROM < 34⁺⁰ weeks and term (≥37⁺⁰) deliveries were classified as 'high-risk controls.' Women with previous term births and index birth ≥ 39 weeks were 'low-risk controls'.

METHODS

Maternal plasma Se measured by ICP-MS was used as a continuous phenotype in a GWAS analysis. Se was added to a logistic regression model using PTB predictor variables.

MAIN OUTCOME MEASURES

Maternal Se concentration, recurrent early sPTB/PPROM.

RESULTS

53/177 high-risk women had a recurrent sPTB/PPROM < 34⁺⁰weeks and were 2.7 times more likely to have a Se level < 83.3 ppm at 20weeks of pregnancy compared with low-risk term controls (n = 179), (RR 2.7, 95%CI 1.5-4.8; p = .001). One SNP from a non-coding region (FOXN3 intron variant, rs55793422) reached genome-wide significance level (p = 3.73E^-08). Targeted analysis of Se gene variant did not show difference between preterm and term births. (χ² test, OR = 0.95; 95%CI = 0.59-1.56; p = 0.82). When Se levels were added to a clinical prediction model, only an additional 5% of cases (n = 3) and 0.6% (n = 1) of controls were correctly identified.

CONCLUSIONS

Low plasma Se is associated with sPTB risk but is not sufficiently predictive at individual patient level. We did not find a genetic association between maternal Se levels and Se-related genes.

182 The effects of pure benzoic acid, an acid blend product, or their combination in nursery pig diets on post-weaning growth performance

A total of 1,325 pigs (Camborough × line 800, PIC Canada) were weaned (20 d of age, 5.5 kg BW) and used to compare the effects of 5 diet acidification strategies on growth performance from d 0 to 41 post-weaning. Feed acidification strategies were fed over 3 dietary phases; d 0 to 13 (P1), d 13 to 20 (P2), and d 20 to 41 (P3). The 5 strategies consisted of 1) NC, commercial diet without any acidifier; 2) P+, NC with recommended 0.1% of an acidifier and flavoring blend (fumaric, sorbic, malic, citric acids with thymol, vanillin, eugenol) in P1, 0.05% in P2, and nothing added in P3; 3) VH, NC with 0.5% pure benzoic acid (VevoVitall®; DSM Nutritional Products) in P1, P2, and P3; 4) VL, NC with 0.25% pure benzoic acid in P1, P2, and P3; and 5) P+V, P+ with 0.5% pure benzoic acid in P1, 0.25% pure benzoic acid in P2, and nothing added in P3. Experimental additives were substituted for wheat in the basal diets. There were 10 pens of 26-27 pigs allotted to each acidification strategy in a RCBD based on initial BW. During P1, ADG, F/G, and d 13 BW were improved (P&lt; 0.05) for pigs fed VH or P+V. In P2, ADG and d 20 BW were improved (P&lt; 0.05) for pigs fed VH or P+V, and there was a tendency (P=0.06) for pigs fed acids (P+, VH, VL, or P+V) to have greater ADFI; however, there were no differences in F/G. There were no differences in growth performance during P3 or overall (d 0 to 41). Nevertheless, performance differences during P1 and P2 resulted in pigs fed an acidification strategy using pure benzoic acid (VH, VL, or P+V) having numerically greater BW (+0.5 kg) and income-over-feed-cost (+CA $0.44/pig) on d 41 when compared to pigs fed NC or P+.

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The metabolic effects of mercury during the biological cycle of vines (Vitis vinifera)

Mercury (Hg) is a major environmental pollutant that can be disposed to the environment by human activities, reaching crops like vineyards during irrigation with contaminated waters. A 2-year study was performed to monitor Hg variations during reproductive and vegetative stages of vines after Hg supplementation. Variations were focused on total Hg concentration, the molecular weight of Hg fractions and Hg-proteins associations in roots, stems and leaves. Total Hg concentrations increased during reproductive stages and decreased during vegetative stages. Variations in length of these stages were observed, according to an extension of the vegetative period. Six months post Hg administration, in roots, stems and leaves, initial Hg proteic fractions of 200 kDa were catabolized to 66 kDa fractions according to a transition from reproductive to vegetative stages. However, 24 months after Hg supplementation, the 66 kDa Hg proteic fraction was continuously determined in a prolonged senescence. Accordingly, the identified proteins associated to Hg show catabolic functions such as endopeptidases, hydrolases, glucosidases and nucleosidases. Stress associated proteins, like peroxidase and chitinase were also found associated to Hg. During the reproductive periods of vines, Hg was associated to membrane proteins, such as ATPases and lipid transfer proteins, especially in roots where Hg is absorbed.

Evaluation of selenium in dietary supplements using elemental speciation

Selenium-enriched dietary supplements containing various selenium compounds are readily available to consumers. To ensure proper selenium intake and consumer confidence, these dietary supplements must be safe and have accurate label claims. Varying properties among selenium species requires information beyond total selenium concentration to fully evaluate health risk/benefits A LC-ICP-MS method was developed and multiple extraction methods were implemented for targeted analysis of common "seleno-amino acids" and related oxidation products, selenate, selenite, and other species relatable to the quality and/or accuracy of the labeled selenium ingredients. Ultimately, a heated water extraction was applied to recover selenium species from non-selenized yeast supplements in capsule, tablet, and liquid forms. For selenized yeast supplements, inorganic selenium was monitored as a means of assessing selenium yeast quality. A variety of commercially available selenium supplements were evaluated and discrepancies between labeled ingredients and detected species were noted.

Lead, mercury, and cadmium exposure and attention deficit hyperactivity disorder in children

BACKGROUND

There is limited research examining the relationship between lead (Pb) exposure and medically diagnosed attention deficit hyperactivity disorder (ADHD) in children. The role of mercury (Hg) and cadmium (Cd) exposures in ADHD development is even less clear.

OBJECTIVES

To examine the relationship between Pb, Hg, and Cd and ADHD in children living inside and outside a Lead Investigation Area (LIA) of a former lead refinery in Omaha, NE.

METHODS

We carried out a case-control study with 71 currently medically diagnosed ADHD cases and 58 controls from a psychiatric clinic and a pediatric clinic inside and outside of the LIA. The participants were matched on age group (5-8, 9-12 years), sex, race (African American or Caucasians and others), and location (inside or outside LIA). We measured whole blood Pb, total Hg, and Cd using inductively coupled plasma mass spectrometry.

RESULTS

Inside the LIA, the 27 cases had blood Pb geometric mean (GM) 1.89 µg/dL and the 41 controls had 1.51 µg/dL. Outside the LIA, the 44 cases had blood Pb GM 1.02 µg/dL while the 17 controls had 0.97 µg/dL. After adjustment for matching variables and maternal smoking, socioeconomic status, and environmental tobacco exposure, each natural log unit blood Pb had an odds ratio of 2.52 with 95% confidence interval of 1.07-5.92. Stratification by the LIA indicated similar point estimate but wider CIs. No associations were observed for Hg or Cd.

CONCLUSIONS

Postnatal Pb exposure may be associated with higher risk of clinical ADHD, but not the postnatal exposure to Hg or Cd.

Coupling transmission electron microscopy with synchrotron radiation X-ray fluorescence microscopy to image vascular copper

Recently, using synchrotron radiation X-ray fluorescence microscopy (SRXRF), the copper accumulation in rat aortic elastin and copper topography in human THP-1 cell monolayer have been described. However, it is necessary to locate more accurately cellular copper in the vascular cells and tissues. In the current study, SRXRF coupling with transmission electron microscopy (TEM) was used to image copper in sections of human THP-1 cells and mouse aorta. The results showed that sections of 1 µm thickness are required for SRXRF producing a correlative image with TEM between copper topography and cellular ultrastructure. As compared with SRXRF alone, coupling TEM with SRXRF can clearly identify the location of copper in the nucleus and nucleolus in non-dividing THP-1 cell sections, and can differentiate the copper location at elastic laminae from collagen in mouse aortic sections. Thus, these results revealed new information about the copper topography in vascular cells and tissues and highlighted the potential of TEM-SRXRF to investigate the role of copper in macrophage and aortic homeostasis.

Multiple liquid chromatography separations and nanoESI-ion trap detection of plasma proteins in search of stroke biomarkers: A pilot study

Stroke is the most common cause of morbidity and death in the Western world, following ischemic heart disease and cancer. Stroke can be of two types, ischemic or hemorrhagic, with ischemic stroke accounting for approximately 85% of the total number of strokes. Well-recognized environmental risk factors for stroke include hypertension, smoking, diabetes mellitus, atrial fibrillation, and atherosclerosis. Computed tomography (CT) scanning is used to diagnose hemorrhagic stroke but is relatively ineffective and may remain normal in patients with mild ischemic strokes. Magnetic Resonance Imaging (MRI) is more sensitive in detecting ischemia than CT, especially in the diagnosis of mild stroke but it is still not 100% sensitive or precise. A simple and low-cost, rapid blood test to confirm a clinical and imaging diagnosis of ischemic stroke would be extremely useful. Based on this, the central idea of this paper is to develop a method that would be applicable to a statistically viable sample set to provide candidate biomarkers for distinguishing stroke types. In search of these candidate biomarkers, different analytical separation techniques have been used to screen for major differences in the proteomes of patients plasma samples with proteomics for identification.

A transgenic Drosophila model for arsenic methylation suggests a metabolic rationale for differential dose-dependent toxicity endpoints

The mechanisms by which exposure to arsenic induces its myriad pathological effects are undoubtedly complex, while individual susceptibility to their type and severity is likely to be strongly influenced by genetic factors. Human metabolism of arsenic into methylated derivatives, once presumed to result in detoxification, may actually produce species with significantly greater pathological potential. We introduce a transgenic Drosophila model of arsenic methylation, allowing its consequences to be studied in a higher eukaryote exhibiting conservation of many genes and pathways with those of human cells while providing an important opportunity to uncover mechanistic details via the sophisticated genetic analysis for which the system is particularly well suited. The gene for the human enzyme, arsenic (+3 oxidation state) methyltransferase, was introduced into nonmethylating Drosophila under inducible control. Transgenic flies were characterized for enzyme inducibility, production of methylated arsenic species, and the dose-dependent consequences for chromosomal integrity and organismal longevity. Upon enzyme induction, transgenic flies processed arsenite into mono and dimethylated derivatives identical to those found in human urine. When induced flies were exposed to 9 ppm arsenite, chromosomal stability was clearly reduced, whereas at much higher doses, adult life span was significantly increased, a seemingly paradoxical pair of outcomes. Measurement of arsenic body burden in the presence or absence of methylation suggested that enhanced clearance of methylated species might explain this greater longevity under acutely toxic conditions. Our study clearly demonstrates both the hazards and the benefits of arsenic methylation in vivo and suggests a resolution based on evolutionary grounds.