Early-Life Arsenic Exposure, Nutritional Status, and Adult Diabetes Risk

Recent developments in speciation and determination of arsenic in marine organisms using different analytical techniques. A review

Marine organisms play a vital role as the main providers of essential and functional food. Yet they also constitute the primary pathway through which humans are exposed to total arsenic (As) in their diets. Since it is well known that the toxicity of this metalloid ultimately depends on its chemical forms, speciation in As is an important issue. Most relevant articles about arsenic speciation have been investigated. This extended not only from general knowledge about As but also the toxicity and health related issues resulting from exposure to these As species from the food ecosystem. There can be enormous side effects originating from exposure to As species that must be measured quantitatively. Therefore, various convenient approaches have been developed to identify different species of As in marine samples. Different extraction strategies have been utilized based on the As species of interest including water, methanol and mixtures of both, and many other extraction agents have been explained in this article. Furthermore, details of hyphenated techniques which are available for detecting these As species have been documented, especially the most versatile and applied technique including inductively coupled plasma mass spectrometry.

Intrauterine arsenic exposure induces glucose metabolism disorders in adult offspring by targeting TET2-mediated DNA hydroxymethylation reprogramming of HNF4α in developing livers, an effect alleviated by ascorbic acid

Exposure to arsenic during gestation has lasting health-related effects on the developing fetus, including an increase in the risk of metabolic disease later in life. Epigenetics is a potential mechanism involved in this process. Ten-eleven translocation 2 (TET2) has been widely considered as a transferase of 5-hydroxymethylcytosine (5hmC). Here, mice were exposed, via drinking water, to arsenic or arsenic combined with ascorbic acid (AA) during gestation. For adult offspring, intrauterine arsenic exposure exhibited disorders of glucose metabolism, which are associated with DNA hydroxymethylation reprogramming of hepatic nuclear factor 4 alpha (HNF4α). Further molecular structure analysis, by SEC-UV-DAD, SEC-ICP-MS, verified that arsenic binds to the cysteine domain of TET2. Mechanistically, arsenic reduces the stability of TET2 by binding to it, resulting in the decrease of 5hmC levels in Hnf4α and subsequently inhibiting its expression. This leads to the disorders of expression of its downstream key glucose metabolism genes. Supplementation with AA blocked the reduction of TET2 and normalized the 5hmC levels of Hnf4α, thus alleviating the glucose metabolism disorders. Our study provides targets and methods for the prevention of offspring glucose metabolism abnormalities caused by intrauterine arsenic exposure.

Effects of Inorganic Arsenic on Type 2 Diabetes Mellitus In Vivo: the Roles and Mechanisms of miRNAs

Accumulating studies have shown that chronic exposure to iAs correlates with an increased incidence of diabetes. In recent years, miRNA dysfunction has emerged both as a response to iAs exposure and independently as candidate drivers of metabolic phenotypes such as T2DM. However, few miRNAs have been profiled during the progression of diabetes after iAs exposure in vivo. In the present study, high iAs (10 mg/L NaAsO2) exposure mice models of C57BKS/Leprdb (db/db) and C57BLKS/J (WT) were established through the drinking water, the exposure duration was 14 weeks. The results showed that high iAs exposure induced no significant changes in FBG levels in either db/db or WT mice. FBI levels, C-peptide content, and HOMA-IR levels were significantly increased, and glycogen levels in the livers were significantly lower in arsenic-exposed db/db mice. HOMA-β% was decreased significantly in WT mice exposed to high iAs. In addition, more different metabolites were found in the arsenic-exposed group than the control group in db/db mice, mainly involved in the lipid metabolism pathway. Highly expressed glucose, insulin, and lipid metabolism-related miRNAs were selected, including miR-29a-3p, miR-143-3p, miR-181a-3p, miR-122-3p, miR-22-3p, and miR-16-3p. And a series of target genes were chosen for analysis, such as ptp1b, irs1, irs2, sirt1, g6pase, pepck and glut4. The results showed that, the axles of miR-181a-3p-irs2, miR-181a-3p-sirt1, miR-22-3p-sirt1, and miR-122-3p-ptp1b in db/db mice, and miR-22-3p-sirt1, miR-16-3p-glut4 in WT mice could be considered promising targets to explore the mechanisms and therapeutic aspects of T2DM after exposure to high iAs.

Metformin alleviates sodium arsenite-induced hepatotoxicity and glucose intolerance in mice by suppressing oxidative stress, inflammation, and apoptosis

BACKGROUND

Epidemiological studies have shown that exposure to sodium arsenite (NaAsO2) causes diabetes and hepatotoxicity. Metformin (MET), an oral hypoglycemic agent, has long been used in diabetes therapy. In addition, MET has been shown to have hepatoprotective effects. In this study, we investigated the effects of MET on NaAsO2-induced hepatotoxicity and glucose intolerance in mice.

METHODS

Mice were divided into four groups: Groups I and II received distilled water and NaAsO2 (10 mg/kg, p.o.) for five weeks, respectively. Groups III and IV were treated with NaAsO2 (10 mg/kg, p.o.) for three weeks, followed by MET (125 and 250 mg/kg, p.o.) for the last two weeks before NaAsO2. A glucose tolerance test was performed on day 35. The serum and tissue parameters were also evaluated.

RESULTS

Histopathological examination revealed NaAsO2-induced liver and pancreatic damage. NaAsO2 caused hyperglycemia, glucose intolerance, and a significant increase in liver function enzymes. Administration of NaAsO2 significantly reduced hepatic superoxide dismutase, catalase, glutathione peroxidase, and total thiol levels and increased the content of reactive thiobarbituric acid substances. In addition, it led to an increase in liver nitric oxide levels and protein expression of tumor necrosis factor-α, nuclear factor kappa B, and cysteine-aspartic proteases-3. In contrast, treatment with MET (250 mg/kg) significantly improved NaAsO2-induced biochemical and histopathological changes.

CONCLUSION

Our findings suggest that the significant effects of MET against NaAsO2-induced hepatotoxicity and glucose intolerance may be exerted via the regulation of oxidative stress, followed by suppression of inflammation and apoptosis.

Anthropometric measures and arsenic methylation among pregnant women in rural northern Bangladesh

INTRODUCTION

Arsenic methylation converts inorganic arsenic (iAs) to monomethyl (MMA) and dimethyl (DMA) arsenic compounds. Body mass index (BMI) has been positively associated with arsenic methylation efficiency (higher DMA%) in adults, but evidence in pregnancy is inconsistent. We estimated associations between anthropometric measures and arsenic methylation among pregnant women in rural northern Bangladesh.

METHODS

We enrolled pregnant women (n = 784) (median [IQR] gestational week: 14 [13, 15]) in Gaibandha District, Bangladesh from 2018 to 2019. Anthropometric measures were BMI, subscapular and triceps skinfold thicknesses, and mid-upper arm circumference (MUAC), fat area (MUAFA), and muscle area (MUAMA). Arsenic methylation measures were urinary iAs, MMA, and DMA divided by their sum and multiplied by 100 (iAs%, MMA%, and DMA%), primary methylation index (MMA/iAs; PMI), and secondary methylation index (DMA/MMA; SMI). In complete cases (n = 765 [97.6%]), we fitted linear, beta, and Dirichlet regression models to estimate cross-sectional differences in iAs%, MMA%, DMA%, PMI, and SMI per IQR-unit difference in each anthropometric measure, adjusting for drinking water arsenic, age, gestational age, education, living standards index, and plasma folate, vitamin B12, and homocysteine.

RESULTS

Median (IQR) BMI, subscapular skinfold thickness, triceps skinfold thickness, MUAC, MUAFA, and MUAMA were 21.5 (19.4, 23.8) kg/m2, 17.9 (13.2, 24.2) mm, 14.2 (10.2, 18.7) mm, 25.9 (23.8, 28.0) cm, 15.3 (10.5, 20.3) cm2, and 29.9 (25.6, 34.2) cm2, respectively. Median (IQR) iAs%, MMA%, DMA%, PMI, and SMI were 12.0 (9.3, 15.2)%, 6.6 (5.3, 8.3)%, 81.0 (77.1, 84.6)%, 0.6 (0.4, 0.7), and 12.2 (9.3, 15.7), respectively. In both unadjusted and adjusted linear models, all anthropometric measures were negatively associated with iAs%, MMA%, and PMI and positively associated with DMA% and SMI. For example, fully adjusted mean differences (95% CI) in DMA% per IQR-unit difference in BMI, subscapular skinfolds thickness, triceps skinfold thickness, MUAC, MUAFA, and MUAMA were 1.72 (1.16, 2.28), 1.58 (0.95, 2.21), 1.74 (1.11, 2.37), 1.45 (0.85, 2.06), 1.70 (1.08, 2.31), and 0.70 (0.13, 1.27) pp, respectively.

CONCLUSIONS

Anthropometric measures were positively associated with arsenic methylation efficiency among pregnant women in the early second trimester.

The association of arsenic exposure with mortality due to cancer, diabetes, Alzheimer's and congenital anomalies using Poisson regression

The present study aims to determine the relationship between the concentration of arsenic in the groundwater of Hamadan province and the mortality rate due to various types of malignancies, congenital anomalies, diabetes mellitus and Alzheimer's. Mortality data due to various causes of death in Hamadan province were collected for five years (2016-2020). Sampling of drinking water was determined in the reference laboratory using polarography method. Poisson regression was used to investigate the relationship between arsenic level and the death rate due to various types of disease, at a significant level (p value < 0.05). According to the results of Poisson regression, among the various causes of death (N = 8042), Alzheimer's 5.94 (3.67-9.61), diabetes mellitus 4.05 (3.5-5.37), congenital malformations 2.98 (1.88-4.72), breast cancer 2.72 (1.56-4.71), leukemia 1.90 (1.24-2.92), stomach cancer 1.64 (1.28-2.10), Liver cancer 1.58 (1.58-2.30), other digestive organs 5.86 (3.38-10.16), meninges and brain cancer 1.57 (1.02-2.41) showed the highest relationship with arsenic contamination. The results of this study could be evidence for a positive and significant relationship between arsenic concentrations and mortality rates due to cancers, diabetes mellitus, Alzheimer disease, and congenital malformations. Therefore, it's necessary to use appropriate water treatment methods to remove arsenic at the source in contaminated areas.

Sex differences in paternal arsenic-induced intergenerational metabolic effects are mediated by estrogen

BACKGROUND

Gene-environment interactions contribute to metabolic disorders such as diabetes and dyslipidemia. In addition to affecting metabolic homeostasis directly, drugs and environmental chemicals can cause persistent alterations in metabolic portfolios across generations in a sex-specific manner. Here, we use inorganic arsenic (iAs) as a prototype drug and chemical to dissect such sex differences.

METHODS

After weaning, C57BL/6 WT male mice were treated with 250 ppb iAs in drinking water (iAsF0) or normal water (conF0) for 6 weeks and then bred with 15-week-old, non-exposed females for 3 days in cages with only normal water (without iAs), to generate iAsF1 or conF1 mice, respectively. F0 females and all F1 mice drank normal water without iAs all the time.

RESULTS

We find that exposure of male mice to 250 ppb iAs leads to glucose intolerance and insulin resistance in F1 female offspring (iAsF1-F), with almost no change in blood lipid profiles. In contrast, F1 males (iAsF1-M) show lower liver and blood triglyceride levels than non-exposed control, with improved glucose tolerance and insulin sensitivity. The liver of F1 offspring shows sex-specific transcriptomic changes, with hepatocyte-autonomous alternations of metabolic fluxes in line with the sex-specific phenotypes. The iAsF1-F mice show altered levels of circulating estrogen and follicle-stimulating hormone. Ovariectomy or liver-specific knockout of estrogen receptor α/β made F1 females resemble F1 males in their metabolic responses to paternal iAs exposure.

CONCLUSIONS

These results demonstrate that disrupted reproductive hormone secretion in alliance with hepatic estrogen signaling accounts for the sex-specific intergenerational effects of paternal iAs exposure, which shed light on the sex disparities in long-term gene-environment interactions.

Long-term effects of prenatal arsenic exposure from gestational day 9 to birth on lung, heart, and immune outcomes in the C57BL/6 mouse model

Prenatal arsenic exposure is a major public health concern, associated with altered birth outcomes and increased respiratory disease risk. However, characterization of the long-term effects of mid-pregnancy (second trimester) arsenic exposure on multiple organ systems is scant. This study aimed to characterize the long-term impact of mid-pregnancy inorganic arsenic exposure on the lung, heart, and immune system, including infectious disease response using the C57BL/6 mouse model. Mice were exposed from gestational day 9 till birth to either 0 or 1000 µg/L sodium (meta)arsenite in drinking water. Male and female offspring assessed at adulthood (10-12 weeks of age) did not show significant effects on recovery outcomes after ischemia reperfusion injury but did exhibit increased airway hyperresponsiveness compared to controls. Flow cytometric analysis revealed significantly greater total numbers of cells in arsenic-exposed lungs, lower MHCII expression in natural killer cells, and increased percentages of dendritic cell populations. Activated interstitial (IMs) and alveolar macrophages (AMs) isolated from arsenic-exposed male mice produced significantly less IFN-γ than controls. Conversely, activated AMs from arsenic-exposed females produced significantly more IFN-γ than controls. Although systemic cytokine levels were higher upon Mycobacterium tuberculosis (Mtb) infection in prenatally arsenic-exposed offspring there was no difference in lung Mtb burden compared to controls. This study highlights significant long-term impacts of prenatal arsenic exposure on lung and immune cell function. These effects may contribute to the elevated risk of respiratory diseases associated with prenatal arsenic exposure in epidemiology studies and point to the need for more research into mechanisms driving these maintained responses.

Metabolomic changes associated with chronic arsenic exposure in a Bangladeshi population

Chronic exposure to arsenic (As) remains a global public health concern and our understanding of the biological mechanisms underlying the adverse effects of As exposure remains incomplete. Here, we used a high-resolution metabolomics approach to examine how As affects metabolic pathways in humans. We selected 60 non-smoking adults from the Folic Acid and Creatine Trial (FACT). Inorganic (AsIII, AsV) and organic (monomethylarsonous acid [MMAs], dimethylarsinous Acid [DMAs]) As species were measured in blood and urine collected at baseline and at 12 weeks. Plasma metabolome profiles were measured using untargeted high-resolution mass spectrometry. Associations of blood and urinary As with 170 confirmed metabolites and >26,000 untargeted spectral features were modeled using a metabolome-wide association study (MWAS) approach. Models were adjusted for age, sex, visit, and BMI and corrected for false discovery rate (FDR). In the MWAS screening of confirmed metabolites, 17 were associated with ≥1 blood As species (FDR<0.05), including fatty acids, neurotransmitter metabolites, and amino acids. These results were consistent across blood As species and between blood and urine As. Untargeted MWAS identified 423 spectral features associated with ≥1 blood As species. Unlike the confirmed metabolites, untargeted model results were not consistent across As species, with AsV and DMAs showing distinct association patterns. Mummichog pathway analysis revealed 12 enriched metabolic pathways that overlapped with the 17 identified metabolites, including one carbon metabolism, tricarboxylic acid cycle, fatty acid metabolism, and purine metabolism. Exposure to As may affect numerous essential pathways that underlie the well-characterized associations of As with multiple chronic diseases.

Maternal DNA methylation signatures of arsenic exposure is associated with adult offspring insulin resistance in the Strong Heart Study

Exposure to low to moderate arsenic (As) levels has been associated with type 2 diabetes (T2D) and other chronic diseases in American Indian communities. Prenatal exposure to As may also increase the risk for T2D in adulthood, and maternal As has been associated with adult offspring metabolic health measurements. We hypothesized that T2D-related outcomes in adult offspring born to women exposed to low to moderate As can be evaluated utilizing a maternally-derived molecular biosignature of As exposure. Herein, we evaluated the association of maternal DNA methylation with incident T2D and insulin resistance (Homeostatic model assessment of insulin resistance [HOMA2-IR]) in adult offspring. For DNA methylation, we used 20 differentially methylated cytosine-guanine dinucleotides (CpG) previously associated with the sum of inorganic and methylated As species (ΣAs) in urine in the Strong Heart Study (SHS). Of these 20 CpGs, we found six CpGs nominally associated (p < 0.05) with HOMA2-IR in a fully adjusted model that included clinically relevant covariates and offspring adiposity measurements; a similar model that adjusted instead for maternal adiposity measurements found three CpGs nominally associated with HOMA2-IR, two of which overlapped the offspring adiposity model. After adjusting for multiple comparisons, cg03036214 remained associated with HOMA2-IR (q < 0.10) in the offspring adiposity model. The odds ratio of incident T2D increased with an increase in maternal DNA methylation at one HOMA2-IR associated CpG in the model adjusting for offspring adiposity, cg12116137, whereas adjusting for maternal adiposity had a minimal effect on the association. Our data suggests offspring adiposity, rather than maternal adiposity, potentially influences the effects of maternal DNAm signatures on offspring metabolic health parameters. Here, we have presented evidence supporting a role for epigenetic biosignatures of maternal As exposure as a potential biomarker for evaluating risk of T2D-related outcomes in offspring later in life.

Intergenerational arsenic exposure on the mouse epigenome and metabolic physiology

Inorganic arsenic (iAs) is one of the largest toxic exposures to impact humanity worldwide. Exposure to iAs during pregnancy may disrupt the proper remodeling of the epigenome of F1 developing offspring and potentially their F2 grand-offspring via disruption of fetal primordial germ cells (PGCs). There is a limited understanding between the correlation of disease phenotype and methylation profile within offspring of both generations and whether it persists to adulthood. Our study aims to understand the intergenerational effects of in utero iAs exposure on the epigenetic profile and onset of disease phenotypes within F1 and F2 adult offspring, despite the lifelong absence of direct arsenic exposure within these generations. We exposed F0 female mice (C57BL6/J) to the following doses of iAs in drinking water 2 weeks before pregnancy until the birth of the F1 offspring: 1, 10, 245, and 2300 ppb. We found sex- and dose-specific changes in weight and body composition that persist from early time to adulthood within both generations. Fasting blood glucose challenge suggests iAs exposure causes dysregulation of glucose metabolism, revealing generational, exposure, and sex-specific differences. Toward understanding the mechanism, genome-wide DNA methylation data highlights exposure-specific patterns in liver, finding dysregulation within genes associated with cancer, T2D, and obesity. We also identified regions containing persistently differentially methylated CpG sites between F1 and F2 generations. Our results indicate the F1 developing embryos and their PGCs, which will result in F2 progeny, retain epigenetic damage established during the prenatal period and are associated with adult metabolic dysfunction.

The Pregnancy, Arsenic, and Immune Response (PAIR) Study in rural northern Bangladesh

BACKGROUND

Arsenic exposure and micronutrient deficiencies may alter immune reactivity to influenza vaccination in pregnant women, transplacental transfer of maternal antibodies to the foetus, and maternal and infant acute morbidity.

OBJECTIVES

The Pregnancy, Arsenic, and Immune Response (PAIR) Study was designed to assess whether arsenic exposure and micronutrient deficiencies alter maternal and newborn immunity and acute morbidity following maternal seasonal influenza vaccination during pregnancy.

POPULATION

The PAIR Study recruited pregnant women across a large rural study area in Gaibandha District, northern Bangladesh, 2018-2019.

DESIGN

Prospective, longitudinal pregnancy and birth cohort.

METHODS

We conducted home visits to enrol pregnant women in the late first or early second trimester (11-17 weeks of gestational age). Women received a quadrivalent seasonal inactivated influenza vaccine at enrolment. Follow-up included up to 13 visits between enrolment and 3 months postpartum. Arsenic was measured in drinking water and maternal urine. Micronutrient deficiencies were assessed using plasma biomarkers. Vaccine-specific antibody titres were measured in maternal and infant serum. Weekly telephone surveillance ascertained acute morbidity symptoms in women and infants.

PRELIMINARY RESULTS

We enrolled 784 pregnant women between October 2018 and March 2019. Of 784 women who enrolled, 736 (93.9%) delivered live births and 551 (70.3%) completed follow-up visits to 3 months postpartum. Arsenic was detected (≥0.02 μg/L) in 99.7% of water specimens collected from participants at enrolment. The medians (interquartile ranges) of water and urinary arsenic at enrolment were 5.1 (0.5, 25.1) μg/L and 33.1 (19.6, 56.5) μg/L, respectively. Water and urinary arsenic were strongly correlated (Spearman's ⍴ = 0.72) among women with water arsenic ≥ median but weakly correlated (⍴ = 0.17) among women with water arsenic < median.

CONCLUSIONS

The PAIR Study is well positioned to examine the effects of low-moderate arsenic exposure and micronutrient deficiencies on immune outcomes in women and infants.

REGISTRATION

NCT03930017.

Removal of Arsenate From Groundwater by Cathode of Bioelectrochemical System Through Microbial Electrosorption, Reduction, and Sulfuration

Arsenate [As(V)] is a toxic metalloid and has been observed at high concentrations in groundwater globally. In this study, a bioelectrochemical system (BES) was used to efficiently remove As(V) from groundwater, and the mechanisms involved were systematically investigated. Our results showed that As(V) can be efficiently removed in the BES cathode chamber. When a constant cell current of 30 mA (I_cell, volume current density = 66.7 A/m³) was applied, 90 ± 3% of total As was removed at neutral pH (7.20–7.50). However, when I_cell was absent, the total As in the effluent, mainly As(V), had increased approximately 2–3 times of the As(V) in influent. In the abiotic control reactor, under the same condition, no significant total As or As(V) removal was observed. These results suggest that As(V) removal was mainly ascribed to microbial electrosorption of As(V) in sludge. Moreover, part of As(V) was bioelectrochemically reduced to As(III), and sulfate was also reduced to sulfides [S(–II)] in sludge. The XANES results revealed that the produced As(III) reacted with S(–II) to form As₂S₃, and the residual As(III) was microbially electroadsorbed in sludge. This BES-based technology requires no organic or chemical additive and has a high As(V) removal efficiency, making it an environment-friendly technique for the remediation of As-contaminated groundwater.

Polymorphisms of the AS3MT gene are associated with arsenic methylation capacity and damage to the P21 gene in arsenic trioxide plant workers

Epidemiological evidence suggests that the metabolic profiles of each individual exposed to arsenic (As) are related to the risk of cancer, coronary heart disease, and diabetes. The arsenite methyltransferase (AS3MT) gene plays a key role in As metabolism. Several single nucleotide polymorphisms in the AS3MT gene may affect both enzyme activity and gene transcription. AS3MT polymorphisms are associated with the proportions of monomethylarsenic acid (MMA) and dimethylarsenic acid (DMA) in urine as well as the incidence of cancer. P21 protein is a cyclin-dependent kinase inhibitor. Mutations of the P21 gene have been found in cancer patients. In our study, we investigate whether polymorphisms of the AS3MT gene alter As methylation capacity and adversely affect the P21 gene in arsenic trioxide plant workers. The DNA damage was examined by the quantitative polymerase chain reaction. Restriction fragment length polymorphism was used to analyze the genotype of the AS3MT gene. The results showed that DNA damage in P21 gene fragments was greater in those individuals exposed to high levels of As. There was a strong positive correlation between the DNA damage to P21 gene fragments and the percentage of MMA in urine. However, DNA damage in P21 gene fragments was negatively associated with the percentage of DMA in urine (%uDMA), primary methylation index (PMI), and secondary methylation index. We found that subjects with the rs7085104 GG or GA allele were associated with higher %uDMA and PMI and less DNA damage. The subjects with the rs11191454 GG+GA or GA allele were also associated with higher %uDMA and PMI and less DNA damage. Our results suggest that rs1191454 and rs7085104 in the AS3MT gene affect the As-induced DNA damage by altering individual metabolic efficiency.

Health Effects Associated With Pre- and Perinatal Exposure to Arsenic

Inorganic arsenic is a well-established human carcinogen, able to induce genetic and epigenetic alterations. More than 200 million people worldwide are exposed to arsenic concentrations in drinking water exceeding the recommended WHO threshold (10μg/l). Additionally, chronic exposure to levels below this threshold is known to result in long-term health effects in humans. The arsenic-related health effects in humans are associated with its biotransformation process, whereby the resulting metabolites can induce molecular damage that accumulates over time. The effects derived from these alterations include genomic instability associated with oxidative damage, alteration of gene expression (including coding and non-coding RNAs), global and localized epigenetic reprogramming, and histone posttranslational modifications. These alterations directly affect molecular pathways involved in the onset and progression of many conditions that can arise even decades after the exposure occurs. Importantly, arsenic metabolites generated during its biotransformation can also pass through the placental barrier, resulting in fetal exposure to this carcinogen at similar levels to those of the mother. As such, more immediate effects of the arsenic-induced molecular damage can be observed as detrimental effects on fetal development, pregnancy, and birth outcomes. In this review, we focus on the genetic and epigenetic damage associated with exposure to low levels of arsenic, particularly those affecting early developmental stages. We also present how these alterations occurring during early life can impact the development of certain diseases in adult life.

Arsenic Secondary Methylation Capacity Is Inversely Associated with Arsenic Exposure-Related Muscle Mass Reduction

Skeletal muscle mass reduction has been implicated in insulin resistance (IR) that promotes cardiometabolic diseases. We have previously reported that arsenic exposure increases IR concomitantly with the reduction of skeletal muscle mass among individuals exposed to arsenic. The arsenic methylation capacity is linked to the susceptibility to some arsenic exposure-related diseases. However, it remains unknown whether the arsenic methylation capacity affects the arsenic-induced reduction of muscle mass and elevation of IR. Therefore, this study examined the associations between the arsenic methylation status and skeletal muscle mass measures with regard to IR by recruiting 437 participants from low- and high-arsenic exposure areas in Bangladesh. The subjects' skeletal muscle mass was estimated by their lean body mass (LBM) and serum creatinine levels. Subjects' drinking water arsenic concentrations were positively associated with total urinary arsenic concentrations and the percentages of MMA, as well as inversely associated with the percentages of DMA and the secondary methylation index (SMI). Subjects' LBM and serum creatinine levels were positively associated with the percentage of DMA and SMI, as well as inversely associated with the percentage of MMA. HOMA-IR showed an inverse association with SMI, with a confounding effect of sex. Our results suggest that reduced secondary methylation capacity is involved in the arsenic-induced skeletal muscle loss that may be implicated in arsenic-induced IR and cardiometabolic diseases.

Nutrition, one-carbon metabolism and arsenic methylation

Exposure to arsenic (As) is a major public health concern globally. Inorganic As (InAs) undergoes hepatic methylation to form monomethyl (MMAs)- and dimethyl (DMAs)-arsenical species, facilitating urinary As elimination. MMAsIII is considerably more toxic than either InAsIII or DMAsV, and a higher proportion of MMAs in urine has been associated with risk for a wide range of adverse health outcomes. Efficiency of As methylation differs substantially between species, between individuals, and across populations. One-carbon metabolism (OCM) is a biochemical pathway that provides methyl groups for the methylation of As, and is influenced by folate and other micronutrients, such as vitamin B12, choline, betaine and creatine. A growing body of evidence has demonstrated that OCM-related micronutrients play a critical role in As methylation. This review will summarize observational epidemiological studies, interventions, and relevant experimental evidence examining the role that OCM-related micronutrients have on As methylation, toxicity of As, and risk for associated adverse health-related outcomes. There is fairly robust evidence supporting the impact of folate on As methylation, and some evidence from case-control studies indicating that folate nutritional status influences risk for As-induced skin lesions and bladder cancer. However, the potential for folate to be protective for other As-related health outcomes, and the potential beneficial effects of other OCM-related micronutrients on As methylation and risk for health outcomes are less well studied and warrant additional research.

Sex-Specific Effects of Prenatal and Early Life Inorganic and Methylated Arsenic Exposure on Atherosclerotic Plaque Development and Composition in Adult ApoE-/- Mice

BACKGROUND

Epidemiologic studies indicate that early life arsenic exposures are linked to an increased risk of cardiovascular diseases. Different oxidation and methylation states of arsenic exist in the environment and are formed in vivo via the action of arsenic (+3 oxidation state) methyltransferase (As3MT). Methylated arsenicals are pro-atherogenic postnatally, but pre- and perinatal effects are unclear. This is particularly important because methylated arsenicals are known to cross the placenta.

OBJECTIVES

We tested the effects of early life exposure to inorganic and methylated arsenicals on atherosclerotic plaque formation and its composition in apolipoprotein E knock-out (apoE-/-) mice and evaluated whether apoE-/- mice lacking As3MT expression were susceptible to this effect.

METHODS

We exposed apoE-/- or apoE-/-/As3MT-/- mice to 200 ppb inorganic or methylated arsenic in the drinking water from conception to weaning and assessed atherosclerotic plaques in the offspring at 18 wk of age. Mixed regression models were used to estimate the mean difference in each outcome relative to controls, adjusting for sex and including a random effects term to account for within-litter clustering.

RESULTS

Early life exposure to inorganic arsenic, and more profoundly methylated arsenicals, resulted in significantly larger plaques in the aortic arch and sinus in both sexes. Lipid levels in these plaques were higher without a substantial difference in macrophage numbers. Smooth muscle cell content was not altered, but collagen content was lower. Importantly, there were sex-specific differences in these observations, where males had higher lipids and lower collagen in the plaque, but females did not. In mice lacking As3MT, arsenic did not alter the plaque size, although the size was highly variable. In addition, control apoE-/-/As3MT-/- mice had significantly larger plaque size compared with control apoE-/-.

CONCLUSION

This study shows that early life exposure to inorganic and methylated arsenicals is pro-atherogenic with sex-specific differences in plaque composition and a potential role for As3MT in mice. https://doi.org/10.1289/EHP8171.

Cooperation between NRF2-mediated transcription and MDIG-dependent epigenetic modifications in arsenic-induced carcinogenesis and cancer stem cells

Environmental exposure to arsenic, a well-established carcinogen linked to a number of human cancers, is a public health concern in many areas of the world. Despite extensive studies on the molecular mechanisms of arsenic-induced carcinogenesis, how initial cellular responses, such as activation of stress kinases and the generation of reactive oxygen species, converge to affect the transcriptional and/or epigenetic reprogramming required for the malignant transformation of normal cells or normal stem cells remains to be elucidated. In this review, we discuss some recent discoveries showing how the transcription factor NRF2 and an epigenetic regulator, MDIG, contribute to the arsenic-induced generation of cancer stem-like cells (CSCs) as determined by applying CRISPR-Cas9 gene editing and chromosome immunoprecipitation followed by DNA sequencing (ChIP-seq).

Inter- and Transgenerational Effects of Paternal Exposure to Inorganic Arsenic

The rise of metabolic disorders in modern times is mainly attributed to the environment. However, heritable effects of environmental chemicals on mammalian offsprings' metabolic health are unclear. Inorganic arsenic (iAs) is the top chemical on the Agency for Toxic Substances and Disease Registry priority list of hazardous substances. Here, we assess cross-generational effects of iAs in an exclusive male-lineage transmission paradigm. The exposure of male mice to 250 ppb iAs causes glucose intolerance and hepatic insulin resistance in F1 females, but not males, without affecting body weight. Hepatic expression of glucose metabolic genes, glucose output, and insulin signaling are disrupted in F1 females. Inhibition of the glucose 6-phosphatase complex masks the intergenerational effect of iAs, demonstrating a causative role of hepatic glucose production. F2 offspring from grandpaternal iAs exposure show temporary growth retardation at an early age, which diminishes in adults. However, reduced adiposity persists into middle age and is associated with altered gut microbiome and increased brown adipose thermogenesis. In contrast, F3 offspring of the male-lineage iAs exposure show increased adiposity, especially on a high-calorie diet. These findings have unveiled sex- and generation-specific heritable effects of iAs on metabolic physiology, which has broad implications in understanding gene-environment interactions.

Maternal and paternal histories differentially influence risks for diabetes, insulin secretion and insulin resistance in a Chinese population

Aims/Introduction

To investigate the differential effects of maternal versus paternal history of diabetes on the risks for diabetes and prediabetes, as well as on insulin secretion and resistance in Chinese individuals.

Materials and Methods

From the 2007 to 2008 China National Diabetes and Metabolism Disorders Study, 39,244 participants were included and divided into four categories: negative parental history, paternal history only (PH), maternal history only (MH), and both paternal and maternal history.

Results

The age‐ and sex‐standardized prevalence rates of diabetes in the negative parental history, PH, MH, and both paternal and maternal history groups were 8.59, 12.56, 15.86 and 29.81%, respectively. The prevalence rates of impaired glucose metabolism were 24.13, 25.41, 31.13 and 50.80%, with the prevalence in the MH group being significantly higher than that in the PH group. Compared with that in the FH0 group, the risks of diabetes in the PH, MH, and both paternal and maternal history groups were 2.01‐, 2.67‐ and 6.37‐fold greater, and the risks of impaired glucose metabolism were 1.28‐, 1.65‐ and 3.45‐fold greater. In addition, MH had a significantly greater impact on impaired glucose metabolism than PH (P_MHvsPH = 0.0292). Regression analyses suggested MH was associated with homeostatic model assessment for β‐cell function (β[SE] = −0.0910[0.0334], P = 0.0065), insulinogenic index (−0.1866[0.0550], P = 0.0007), homeostatic model assessment for insulin resistance (0.0662[0.0227], P = 0.0036) and Matsuda Index [−0.0716(0.0203), P = 0.0004]. PH was specifically associated with homeostatic model assessment for insulin resistance (0.1343[0.0267], P < 0.0001) and Matsuda Index (−0.1566[0.0243], P < 0.0001), but the effects were stronger than those of MH (P_MHvsPH = 0.0431, 0.0054).

Conclusions

MH and PH differentially influence the risks for diabetes, insulin secretion, and insulin resistance in the Chinese population, suggesting they participate in the pathogenesis of diabetes through different mechanisms.

Research into the intervention effect of folic acid on arsenic-induced heart abnormalities in fetal rats during the periconception period

BACKGROUND

The incidence of CHD is the highest among birth defects and is increasing year to year. CHD seriously harms the health of infants and young children and presents a large economic burden to families and society. The pathogenesis of CHD and preventive measures are the focus of current research. Our research aimed to explore the intervention effect of folic acid on heart abnormalities resulting from sodium arsenic (NaAsO2) exposure during the periconception period.

METHODS

Sixty 35-day-old female SD rats were randomly divided into 5 groups with 12 rats in each group. Group A was the control group. The rats were given distilled water and ordinary chow. The rats in group B were given distilled water containing 75 mg/L NaAsO2 and ordinary chow. The rats in groups C, D, and E were given distilled water containing 75 mg/L NaAsO2 and chow containing 0.53 mg/kg, 5.3 mg/kg, and 10.6 mg/kg folic acid, respectively. The general condition of the embryos and the histopathology of the embryonic hearts were examined. The acetylation levels of histone H3K9 in heart tissues and the expression levels of Mef2C (which is related to heart development) were observed.

RESULTS

The embryo weight and placental weight of groups B-E were significantly lower than those of group A (P < 0.05). The heart malformation rate of the fetal rats in groups B-E was significantly higher than that of the fetal rats in group A (P < 0.05). We found that the level of H3K9 acetylation in fetal rat cardiomyocytes in groups B-E was significantly higher than that in group A (P < 0.05) and that the level of H3K9 acetylation in groups C-E was lower than that in group B (P < 0.05). The mRNA level of Mef2C in fetal rat cardiomyocytes in group B-E was significantly higher than that in group A (P < 0.05), and the mRNA level of Mef2C in groups C-E was significantly lower than that in group B (P < 0.05).

CONCLUSION

Supplementation with folic acid during the periconception period can interfere with the toxic effects of arsenic on the heart. The mechanism may be that lowering the acetylation levels of histone H3K9 in heart tissues leads to decreased expression levels of Mef2C, which may play a protective role in heart development in fetal rats.