Association of Arsenic Methylation Capacity with Developmental Delays and Health Status in Children: A Prospective Case-Control Trial

Genetic Susceptibility to Neurotoxicity Related to Prenatal Inorganic Arsenic Exposure in Young Spanish Children

We explored the influence of child and maternal single nucleotide polymorphisms (SNPs) in genes related to neurological function and arsenic metabolism (i.e., ABCA1, ABCB1, PON1, CYP3A, BDNF, GSTP1, MT2A, and APOE as well as AS3MT) on the association between prenatal arsenic (As) exposure and methylation efficiency and neuropsychological development in 4-5-year-old children. Participants were 549 mother-child pairs from the INMA (Environment and Childhood) Spanish Project. We measured inorganic arsenic (iAs) and the metabolites monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in urine samples collected during pregnancy. Neuropsychological development was assessed at the age of 4-5 years using the McCarthy Scales of Children's Abilities (MSCA). Several SNPs were determined in maternal and child DNA; AS3MT and APOE haplotypes were inferred. The median ∑As (sum of iAs, DMA, and MMA) was 7.08 μg/g creatinine. Statistically significant interactions for children's APOE haplotype were observed. Specifically, ε4-carrier children had consistently lower MSCA scores in several scales with increasing ∑As and MMA concentrations. These results provide evidence regarding the neurotoxic effects of early life exposure to As, observing that the APOE ε4 allele could make children more vulnerable to this exposure.

Analysis of environmental pollutants using ion chromatography coupled with mass spectrometry: A review

The rise of emerging pollutants in the current environment and requirements of trace analysis in complex substrates pose challenges to modern analytical techniques. Ion chromatography coupled with mass spectrometry (IC-MS) is the preferred tool for analyzing emerging pollutants due to its excellent separation ability for polar and ionic compounds with small molecular weight and high detection sensitivity and selectivity. This paper reviews the progress of sample preparation and ion-exchange IC-MS methods in the analysis of several major categories of environmental polar and ionic pollutants including perchlorate, inorganic and organic phosphorus compounds, metalloids and heavy metals, polar pesticides, and disinfection by-products in past two decades. The comparison of various methods to reduce the influence of matrix effect and improve the accuracy and sensitivity of analysis are emphasized throughout the process from sample preparation to instrumental analysis. Furthermore, the human health risks of these pollutants in the environment with natural concentration levels in different environmental medias are also briefly discussed to raise public attention. Finally, the future challenges of IC-MS for analysis of environmental pollutants are briefly discussed.

Sex-specific neurotoxic effects of heavy metal pollutants: Epidemiological, experimental evidence and candidate mechanisms

The heavy metals lead (Pb), mercury (Hg), and cadmium (Cd) are ubiquitous environmental pollutants and are known to exert severe adverse impacts on the nervous system even at low concentrations. In contrast, the heavy metal manganese (Mn) is first and foremost an essential nutrient, but it becomes neurotoxic at high levels. Neurotoxic metals also include the less prevalent metalloid arsenic (As) which is found in excessive concentrations in drinking water and food sources in many regions of the world. Males and females often differ in how they respond to environmental exposures and adverse effects on their nervous systems are no exception. Here, we review the different types of sex-specific neurotoxic effects, such as cognitive and motor impairments, that have been attributed to Pb, Hg, Mn, Cd, and As exposure throughout the life course in epidemiological as well as in experimental toxicological studies. We also discuss differential vulnerability to these metals such as distinctions in behaviors and occupations across the sexes. Finally, we explore the different mechanisms hypothesized to account for sex-based differential susceptibility including hormonal, genetic, metabolic, anatomical, neurochemical, and epigenetic perturbations. An understanding of the sex-specific effects of environmental heavy metal neurotoxicity can aid in the development of more efficient systematic approaches in risk assessment and better exposure mitigation strategies with regard to sex-linked susceptibilities and vulnerabilities.

The level of exposure affects the arsenic urinary methylation profile of a population of children

Differences in the As methylation capacity of Argentine children, exposed to different levels of As in drinking water were evaluated, considering the gender and the presence of the As3MT T860C gene polymorphism. Inorganic As (%IAs), monomethylated As (%MMA) and dimethylated As (%DMA), primary methylation index (PMI) and secondary methylation index (SMI) were evaluated and represented the As methylation capacity. Urinary As ranged from 18 to 5106 µg/g creatinine. Comparisons were performed between lowest and highest quartiles of urinary As. The level of exposure was positively related to urinary %MMA and negatively to %DMA and to SMI. Considering the presence of the As3MT T860C polymorphism, the level of exposure increased %MMA, and decreased %DMA and the SMI in carriers of the T/T genotype. SMI OR for T/T carriers was 10.61 (95% CI: 2.16-52.16, p: 0.0036). Regarding the gender, the level of exposure increased %MMA, and decreased %DMA and the SMI in girls and boys. SMI OR for girls was 8.71 (95% CI: 1.48-51.08, p: 0.0165) and for boys, OR: 18.15 (95% CI: 2.03-162.35, p: 0.0095). It was possible to identify the level of exposure as a factor that can modify the influence that other factors have on the methylation of As.

Depletion of S-adenosylmethionine pool and promoter hypermethylation of Arsenite methyltransferase in arsenic-induced skin lesion individuals: A case-control study from West Bengal, India

Methylation of arsenic compounds in the human body occurs following a series of biochemical reactions in the presence of methyl donor S-adenosylmethionine (SAM) and catalyzed by arsenite methyltransferase (AS3MT). However, the extent and pattern of methylation differs among the arsenic exposed individuals leading to differential susceptibility. The mechanism for such inter-individual difference is enigmatic. In the present case-control study we recruited exposed individuals with and without arsenic induced skin lesion (WSL and WOSL), and an unexposed cohort, each having 120 individuals. Using ELISA, we observed a reduction in SAM levels (p < 0.05) in WSL compared to WOSL. Linear regression analysis revealed a negative correlation between urinary arsenic concentration and SAM concentration between the study groups. qRT-PCR revealed a significant down-regulation (p < 0.01) of key regulatory genes like MTHFR, MTR, MAT2A and MAT2B of SAM biogenesis pathway in WSL cohort. Methylation-specific PCR revealed significant promoter hypermethylation of AS3MT (WSL vs. WOSL: p < 0.01) which resulted in its subsequent transcriptional repression (WSL vs. WOSL: p < 0.001). Linear regression analysis also showed a negative correlation between SAM concentration and percentage of promoter methylation. Taken together, these results indicate that reduction in SAM biogenesis along with a higher utilization of SAM results in a decreased availability of methyl donor. These along with epigenetic down-regulation of AS3MT may be responsible for higher susceptibility in arsenic exposed individuals.

Effect of plasma selenium, red blood cell cadmium, total urinary arsenic levels, and eGFR on renal cell carcinoma

High total urinary arsenic concentrations and low estimated glomerular filtration rate (eGFR) increase the risk of renal cell carcinoma (RCC). This study aimed to determine whether other metals or metalloids can affect RCC. A total of 401 patients with RCC and 774 age- and sex-matched controls were recruited between November 2006 and December 2012 in Taiwan. Surgical resection or image-guided biopsy of renal tumors was performed to pathologically verify RCC. High-performance liquid chromatography linked to a hydride generator and atomic absorption spectrometer were used to measure the urinary arsenic species concentrations. Inductively coupled plasma mass spectrometry was used to determine plasma selenium and red blood cell cadmium and lead concentration. Plasma selenium levels were inversely related to RCC, whereas red blood cell cadmium levels were directly related to RCC. The odds ratio (OR) and 95% confidence interval (CI) were 0.14 (95% CI, 0.10-0.20) and 1.33 (95% CI, 1.03-1.72), respectively. A low plasma selenium level tended to interact with high total urinary arsenic levels or with high red blood cell cadmium concentration to increase the OR of RCC. In particular, low eGFR multiplicatively interacted with high red blood cell cadmium concentration to increase the OR of RCC (P_interaction=0.003). This study was the first to find a significant multiplicative interaction between eGFR and the red blood cell cadmium levels on the increased OR of RCC.

Children exposure to inorganic and organic arsenic metabolites: A cohort study in Northeast Italy

The aim of this study was to provide urinary levels of total arsenic (TAs) and As species as arsenobetaine (AsB), arsenocholine (AsC), inorganic As (i.e., [As(III)+As(V)]), methylarsonic acid (MMA) and dimethylarsinic acid (DMA) in 7 year-old-children (n = 200) enrolled in the Northern Adriatic Cohort II (NACII), a prospective cohort in a coastal area of Northeast Italy. TAs was determined by sector field-inductively coupled plasma mass spectrometry (SF-ICP-MS) and AsB, AsC, As(III), As(V), MMA and DMA by ion chromatography coupled to ICP-MS (IC-ICP-MS). The geometric mean (GM) for TAs was 12.9 μg/L and for [iAs + MMA + DMA] was 4.26 μg/L. The species AsB (GM of 5.09 μg/L) and DMA (GM of 3.20 μg/L) had the greatest percentage contribution to TAs levels; a greater percentage contribution from AsB is seen at TAs >10 μg/L and from DMA at TAs <10 μg/L. Urinary [iAs + MMA] levels were positively associated with [iAs + MMA + DMA] and DMA with AsB levels. Fish, shellfish and crustaceans consumption increased the AsB and TAs levels, while rice intake, mothers' education level and selenium (Se) concentration influenced the DMA concentration. Children have a high capacity to metabolize and detoxify the iAs because of the higher secondary methylation index (ratio DMA/MMA) with respect to primary methylation index (ratio MMA/iAs). In addition, the median level of [iAs + MMA + DMA] in the whole population of children was lower than the Biomonitoring Equivalent (BE) value for non-cancer endpoints. Also the Margin of Safety (MOS) value based on the population median was greater than 1, thus the exposure to the toxicologically relevant As species was not likely to be of concern.

Changes in urinary arsenic species and methylation capacity in original arsenic exposure cohort after water quality improvement

Water quality improvement is the most efficient way to prevent arsenic exposure. After the cessation of arsenic ingestion, arsenic methylation capacity of the exposed population can change significantly. The factors associated with these changes remain poorly understood. Therefore, arsenic methylation capacity in a study cohort was estimated before and after water quality improvement in the present study. Results indicated that urinary content of the arsenic species in the study cohort significantly decreased after water quality improvement. In addition, the proportions of inorganic arsenic (%iAs) and monomethyl arsenic acid (%MMA) were significantly decreased, while proportions of dimethyl arsenic (%DMA) increased. The primary methylation index (PMI) and secondary methylation index (SMI) increased from 0.85 to 0.92 and 0.82 to 0.84, respectively. Arsenic species urinary content and arsenic methylation index varied slightly between the study cohort after water quality improvement and the control cohort. The rate of increase in PMI was higher than that in SMI. The study group aged 31-50 years had the highest increase in PMI. Logistic regression revealed that %DMA before water quality improvement was negatively associated with the increase in PMI, while %iAs were positively related, and %MMA were positively associated with the increase in SMI. It is concluded that urinary arsenic species content and arsenic methylation capacity increased to the levels of the control cohort after water quality improvement. An increase in primary arsenic methylation capacity may be a burden on the secondary arsenic methylation capacity. The main role of arsenic methylation capacity recovery may be the cessation of arsenic exposure.

Polymorphism of nucleotide binding domain-like receptor protein 3 (NLRP3) increases susceptibility of total urinary arsenic to renal cell carcinoma

Our study showed that total urinary arsenic concentrations were positively correlated with renal cell carcinoma (RCC). Chronic inflammation is a key player in the development of RCC. This study explored the association between nucleotide-binding domain-like receptor protein 3 (NLRP3) genotypes and the development of RCC. We also investigated whether any of the NLRP3 genotypes modified the risk between arsenic and RCC. We recruited 350 RCC patients and 700 age-sex matched controls. RCC was confirmed by pathological assessment following surgical resection or image-guided biopsy of a renal tumor. Fifteen sites of NLRP3 gene polymorphisms were identified using the Agena Bioscience MassARRAY platform. The concentrations of the urinary arsenic species were determined by HPLC-HG-AAS. There was a significant dose-dependent association between arsenic and RCC. In addition, six of thirteen NLRP3 alleles, including rs12239046 C, rs10925025 G, rs1539019 C, rs10925026 A, rs10157379 T, and rs12143966 A, had increased odds ratios (ORs) for RCC than other NLRP3 alleles. Among these sites, we found the novel haplotype of five tag-SNPs (C-A-A-A-A) was significantly related to RCC, the OR and 95% confidence interval was 1.44 (1.08–1.92). Furthermore, participants with high total urinary arsenic levels and the NLRP3 rs1539019 C allele had significantly multiplicative and additive interactions for the risk of RCC (p _interaction = 0.012). This study is the first to identify the modified effects of NLRP3 risk alleles involved in the association between arsenic and RCC risk in a population with low arsenic exposure.

Developmental toxicity of arsenic: a drift from the classical dose-response relationship

Arsenic is a well-known natural environmental contaminant distributed in food, water, air, and soil. The developmental toxicity of arsenic exposure is a significant concern in large parts of the world. Unlike acute toxic exposure, the classical dose-response relationship is not adequate for estimating the possible impact of chronic low-level arsenic exposure. The real-life risk and impact assessments require the consideration of the co-exposure to multiple toxins, individual genetic and nutritional predisposition, and the particularly vulnerable stages of the neurodevelopment. This context shifts the assessment model away from the 'one-exposure-for-one-health-effect.' We underscore the need for a comprehensive risk assessment that takes into account all relevant determinants. We aim to elaborate a model that can serve as a basis for an understanding of complex interacting factors in a long-lasting and ongoing low-level arsenic exposure, to identify, protect, and support the children at risk.

Low level arsenic exposure, B-vitamins, and achievement among Uruguayan school children

OBJECTIVES

Millions of children globally, including the U.S., are exposed to low levels of arsenic from water and food. Arsenic is a known neurotoxicant at high levels but its effects at lower exposure levels are understudied. Arsenic methylation capacity, influenced by B-vitamin intake and status, potentially influences arsenic toxicity. In a cross-secitonal study of 5-8 year-old children from Montevideo, we assessed the relationship between urinary arsenic (U-As) and academic achievement, and tested for effect modification by B-vitamin intake, status, and arsenic methylation capacity.

METHODS

Broad math and reading scores were calculated based on six subtests (calculation, math facts fluency, applied problems, sentence reading fluency, letter word identification, passage comprehension) from the Woodcock-Muñoz Achievement Battery. B-vitamin intake was assessed from two non-consecutive 24-h dietary recalls, serum folate and vitamin B-12 levels were measured in a subset of participants. Arsenic methylation capacity was measured as the proportion of urinary monomethylarsonic acid (%MMA). Multiple imputation using chained equations was conducted to account for missing covariate and exposure data. Ordinal regressions assessed associations between U-As and achievement score tertiles in the complete case and imputed samples. A "B-vitamin index" was calculated using principal component analysis. Interactions by urinary %MMA and the B-vitamin index were assessed.

RESULTS

Median specific gravity adjusted U-As was 11.7 μg/L (range: 2.6, 50.1). We found no association between U-As and broad math and reading scores, nor effect modification by %MMA or B-vitamins.

CONCLUSION

At low-levels of exposure, U-As does not appear to affect children's academic achievement.

Fluoride exposure is associated with altered metabolism of arsenic in an adult Mexican population

Arsenic (As) and fluoride (F) are two common groundwater toxicants. The toxicity of As is closely related to As metabolism, and several biological and environmental factors have been associated with As modification. However, limited information about the effect of F exposure on the modification of the As metabolism profile has been described. The aim of this study was to assess the interaction effect of AsF coexposure on the As metabolism profile in an adult population environmentally exposed to low-moderate As levels. A cross-sectional study was conducted in 236 adults from three Mexican communities. F and As concentrations were quantified in water samples. The concentrations of urinary F and As species [inorganic arsenic (iAs), monomethylated arsenic (MAs) and dimethylated arsenic (DMAs)] were also determined and used as exposure biomarkers. As species percentages and methylation indices were estimated to evaluate the As methylation profile. Our results showed a relationship between the water and urine concentrations of both contaminants and, a significant correlation between the As and F concentrations in water and urine samples. A statistically significant interaction of F and As exposure on the increase in MAs% (β = 0.16, p = 0.018) and the decrease in DMAs% (β = -0.3, p = 0.034), PMI (β = -0.07, p = 0.052) and SMI (β = -0.13, p = 0.097) was observed. These findings indicate that drinking water is the main source of AsF coexposure and suggest that F exposure decreases As methylation capacity. However, additional large and prospective studies are required to confirm our findings, and to elucidate the involved mechanisms of interaction and their implications in adverse health effects.

Thyroid hormones and neurobehavioral functions among adolescents chronically exposed to groundwater with geogenic arsenic in Bangladesh

Groundwater, the major source of drinking water in Bengal Delta Plain, is contaminated with geogenic arsenic (As) enrichment affecting millions of people. Children exposed to tubewell water containing As may be associated with thyroid dysfunction, which in turn may impact neurodevelopmental outcomes. However, data to support such relationship is sparse. The purpose of this study was to examine if chronic water As (WAs) from Holocene alluvial aquifers in this region was associated with serum thyroid hormone (TH) and if TH biomarkers were related to neurobehavioral (NB) performance in a group of adolescents. A sample of 32 healthy adolescents were randomly drawn from a child cohort in the Health Effects of Arsenic Longitudinal Study (HEALS) in Araihazar, Bangladesh. Half of these participants were consistently exposed to low WAs (<10 μg/L) and the remaining half had high WAs exposure (≥10 μg/L) since birth. Measurements included serum total triiodothyronine (tT₃), free thyroxine (fT₄), thyrotropin (TSH) and thyroperoxidase antibodies (TPOAb); concurrent WAs and urinary arsenic (UAs); and adolescents' NB performance. WAs and UAs were positively and significantly correlated with TPOAb but were not correlated with TSH, tT₃ and fT₄. After accounting for covariates, both WAs and UAs demonstrated positive but non-significant relationships with TSH and TPOAb and negative but non-significant relationships with tT₃ and fT₄. TPOAb was significantly associated with reduced NB performance indicated by positive associations with latencies in simple reaction time (b = 82.58; p < 0.001) and symbol digit (b = 276.85; p = 0.005) tests. TSH was significantly and negatively associated with match-to-sample correct count (b = -0.95; p = 0.05). Overall, we did not observe significant associations between arsenic exposure and TH biomarkers although the relationships were in the expected directions. We observed TH biomarkers to be related to reduced NB performance as hypothesized. Our study indicated a possible mechanism of As-induced neurotoxicity, which requires further investigations for confirmatory findings.

Exposure to arsenic in utero is associated with various types of DNA damage and micronuclei in newborns: a birth cohort study

BACKGROUND

Growing evidence indicates that in utero arsenic exposures in humans may increase the risk of adverse health effects and development of diseases later in life. This study aimed to evaluate potential health risks of in utero arsenic exposure on genetic damage in newborns in relation to maternal arsenic exposure.

METHODS

A total of 205 pregnant women residing in arsenic-contaminated areas in Hanam province, Vietnam, were recruited. Prenatal arsenic exposure was determined by arsenic concentration in mother's toenails and urine during pregnancy and in umbilical cord blood collected at delivery. Genetic damage in newborns was assessed by various biomarkers of early genetic effects including oxidative/nitrative DNA damage (8-hydroxydeoxyguanosine, 8-OHdG, and 8-nitroguanine), DNA strand breaks and micronuclei (MN) in cord blood.

RESULTS

Maternal arsenic exposure, measured by arsenic levels in toenails and urine, was significantly increased (p <  0.05) in subjects residing in areas with high levels of arsenic contamination in drinking water. Cord blood arsenic level was significantly increased in accordance with maternal arsenic exposure (p <  0.001). Arsenic exposure in utero is associated with genotoxic effects in newborns indicated as increased levels of 8-OHdG, 8-nitroguanine, DNA strand breaks and MN frequency in cord blood with increasing levels of maternal arsenic exposure. Maternal toenail arsenic level was significantly associated with all biomarkers of early genetic effects, while cord blood arsenic levels associated with DNA strand breaks and MN frequency.

CONCLUSIONS

In utero arsenic exposure is associated with various types of genetic damage in newborns potentially contributing to the development of diseases, including cancer, later in life.

Plasma selenium influences arsenic methylation capacity and developmental delays in preschool children in Taiwan

Inefficient arsenic methylation capacity has been associated with developmental delay in preschool children. Selenium has antioxidant and anti-inflammatory properties that protect experimental animals from chemically induced neurotoxicity. The present study was designed to explore whether plasma selenium levels affects arsenic methylation capacity related to developmental delay in preschool children. A case-control study was conducted from August 2010 to March 2014. All participants were recruited from the Shin Kong Wu Ho-Su Memorial Teaching Hospital. In total, 178 children with a developmental delay and 88 children without a delay were recruited. High-performance liquid chromatography-linked hydride generator and atomic absorption spectrometry were used to determine urinary arsenic species, including arsenite (As^III), arsenate (As^V), monomethylarsonic acid (MMA^V), and dimethylarsinic acid (DMA^V). Plasma selenium levels were measured by inductively coupled plasma mass spectrometry. As results, plasma selenium concentration was significantly inversely associated with the odds ratio (OR) of developmental delay. Plasma selenium concentration was positively associated with arsenic methylation capacity [percentage of inorganic arsenic and percentage of MMA^V (MMA^V%) decreased, and percentage of DMA^V (DMA^V%) increased]. High plasma selenium concentration and high DMA% significantly and additively interacted to decrease the OR of developmental delay; the OR and 95% confidence interval were 0.40 (0.18-0.90). This is the first study to show a combined dose-response effect of plasma selenium concentration and that efficient arsenic methylation capacity decreased the OR of developmental delay in preschool children.

Serum folate levels and urinary arsenic methylation profiles in the US population: NHANES, 2003-2012

Arsenic is a prevalent environmental contaminant, and its folate-dependent methylation is important for detoxification in the body. In this study, we investigated the association between serum folate levels and methylation using data from the US National Health and Nutrition Examination Survey (NHANES) (2003-2012) (N = 11,016). Multivariate linear regression and penalized spline regression models were used to examine the association and possible upper limit of folate level regarding its impact on methylation in children (≤18 years) and adults (>18 years), respectively. Serum folate levels, methylation metabolites including urinary monomethylarsonic acid (MMA(V)) and dimethylarsinic acid (DMA(V)), and demographic variables were extracted from NHANES. Results showed that urinary percentage of DMA(V) (%DMA(V)) was positively associated with log(serum folate levels) after adjustment in children (β = 1.93, p < 0.01); urinary percentage of MMA(V) (%MMA(V)) was positively associated with log (serum folate levels) after adjustment in adults (β = 0.40, p < 0.01). No upper limit of folate level regarding its impact on arsenic methylation was identified. More than 50% of Non-Hispanic black and smokers with high total urinary arsenic levels had low serum folate levels. Our results indicate that folate promotes arsenic methylation, but the patterns are different in children versus in adults. Future interventions may be needed for the population exposed to high level of arsenic but with low serum folate to protect against the potential adverse health effects of arsenic.

Preliminary study of urinary arsenic concentration and arsenic methylation capacity effects on neurodevelopment in very low birth weight preterm children under 24 months of corrected age

The neurological prognoses of very low birth weight preterm (VLBWP) children during the first 2 years of life will influence their neurodevelopment during subsequent childhood years and adolescence. The objective of this study was to systemic investigate relationships of urinary arsenic (As) concentrations, the As methylation capability, and toenail As concentrations on cognitive, language, and motor development in VLBWP children under 24 months of corrected age.Participants (n = 60) in our study were recruited from October 2010 to April 2013. Urine and toenail samples were collected for evaluation to assess As exposure. The Bayley scales of infant development III were used to evaluate neurodevelopment at 2 years of corrected age. Concentrations of As species in urine and the As concentration in toenails were, respectively, analyzed using HPLC-HG-AAS and ICP-MS.The mean concentration of total As was 28.6 μg/g creatinine, and inorganic As was 1.01 μg/L in urine. The urine contained an average of 3% inorganic As, 2% monomethylarsonic acid, and 95% dimethylarsinic acid (DMA). The mean concentration of As in toenails was 225 ng/g. Children with a longer gestational age (≥28 weeks) and higher DMA % levels appeared to have the highest unadjusted cognitive and fine motor scores.Our study results suggest that gestational age is associated with neurodevelopment in VLBWP children. We recommend that further study simultaneously analyze multiple environmental contaminants that may have adverse effects on neurodevelopment, use biomarkers for the mother-child pair, and determine whether prenatal or postnatal As exposure has a greater influence on the neurological development of VLBWP children.

Risk of Alzheimer's disease with metal concentrations in whole blood and urine: A case-control study using propensity score matching

Environmental exposure to heavy metals is suspected to result in neuropathology damage and cognitive impairment. We aimed to explore the association of Alzheimer's disease (AD) risk with the internal dose of heavy metals by constructing a hospital-based case-control study and using propensity-score-matching methods. We investigated 170 patients with AD and 264 controls from the Department of Neurology and Family Medicine, China Medical University Hospital in Taiwan. All patients with AD received clinical neuropsychological examination and cognitive-function assessments, including the mini-mental status examination and clinical dementia rating scale. We also constructed a propensity-score-matched population of 82 patients with AD and 82 controls by matching age, gender, education, and AD-related comorbidity. Blood levels with cadmium, lead, mercury, selenium, and urinary arsenic profile were measured. Logistic regression models and 95% confidence intervals (CIs) were applied to estimate AD risk. After stratification by respective quartile cutoffs of heavy metals, the AD risk of study participants with high urinary inorganic arsenic (InAs%) or low dimethylarsinic acid (DMA%) significantly increased (p < 0.05), as similarly found in the propensity-score-matched population. In addition, people with a low median level of selenium and high median level of InAs%, or/and a low median level of DMA% had approximately two- to threefold significant AD risk. Urinary arsenic profiles may be associated with increased AD risk. Repeat measurements of heavy metals with large sample size and the surveying of potential exposure sources are recommended in future studies.

Association between arsenic metabolism gene polymorphisms and arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China

Individuals in a given environment contaminated with arsenic have different susceptibilities to disease, which may be related to arsenic metabolism, age, gender, genetics and other factors. This study recruited 850 subjects, including 331 cases and 519 controls, from populations exposed to high levels of arsenic in drinking water in northwest China. Genotypes were determined using a custom-by-design 48-Plex SNPscan^TM kit. The results indicated that subjects who carried at least one C allele for GSTO1 rs11191979 polymorphism, at least one A allele for GSTO1 rs2164624, at least one A allele for GSTO1 rs4925, the AG genotype for GSTO2 rs156697, the AG genotype or at least one G allele for GSTO2 rs2297235 or the GG genotype or at least one G allele for PNP rs3790064 had an increased risk of arsenic-related skin lesions. In addition, the haplotype CT between rs4925 and rs11191979 appeared to confer a high risk of arsenic-included skin lesions (OR = 1.377, 95% CI = 1.03–1.84), as did the haplotype GCG among rs156697, rs157077 and rs2297235 (OR = 2.197, 95% CI = 1.08–4.44). The results showed that the variants of GSTO1, GSTO2 and PNP render the susceptible toward developing arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China.