Is Arsenic Exposure a Risk Factor for Metabolic Syndrome? A Review of the Potential Mechanisms

As, Cd, Hg, and Pb Biological Concentrations and Anthropometry in Slovak Adolescents

Anthropometry provides a non-invasive technique for evaluating growth and obesity and serves as an indicator of health status. This cross-sectional study aims to investigate the association of internal arsenic (As), cadmium (Cd), total mercury (THg), methylmercury (MeHg), and lead (Pb) exposure with anthropometric parameters, including obesity, in adolescents. Participants (N = 320) were children aged 10-14 years (mean 11.8 years) from eastern Slovakia, at an early stage of adolescence characterized by growth acceleration. Metal concentrations in blood and urine were measured by ICP-MS (for As, Cd, and Pb), GC/ICP-MS (for MeHg) and amalgamation technique AAS (for THg). Median concentrations of the studied elements in whole blood (Cd: 0.16, Pb: 10.6, THg: 0.25, MeHg: 0.11 µg/L) and urine (Cd: 0.25, Pb: 0.73, As: 3.38 µg/g creatinine) were relatively low in our study group. The results showed that blood Cd and Pb concentrations were inversely associated with several anthropometric parameters (body weight, BMI, body fat percentage, chest circumference, and waist circumference) in both boys and girls. Conversely, blood THg concentration was positively associated with these parameters in boys. A positive relationship was also observed between blood MeHg concentration and height in boys, while negative associations between blood Cd and Pb concentrations and height were significant only in girls. No associations were found between metal concentrations (As, Cd, Pb) in urine and parameters of physical growth or obesity. This study demonstrates that even low-level exposure to Cd, Pb, and Hg can influence growth and obesity indicators in adolescents, with distinct sex-specific patterns, highlighting the need for ongoing monitoring and protection against environmental metal exposure.

Polystyrene bead ingestion promotes atherosclerosis plaque progression via BMP signaling in mice

Microplastics have emerged as persistent organic pollutants, generating significant concerns regarding their potential toxicity. Nevertheless, the impact of microplastics (MPs) on atherosclerosis in mammals remains uncertain. The present study investigated the deleterious effects of polystyrene microplastics (PS-MPs) on the cardiovascular system of mice. A total of thirty-six male ApoE-/- mice were divided into three groups: a control group and two experimental groups. The experimental groups were subjected to the exposure of 5 μm PS-MPs at concentrations of 1 μg/ml and 10 μg/ml, respectively, for twelve weeks. In parallel, HUVECs were treated with the same concentrations of PS-MPs to assess cellular responses. Our results indicate that PS-MPs exposure increased mouse body weight, disrupted lipid metabolism, and exacerbated atherosclerosis. Additionally, both in vivo and in vitro studies indicate that PS-MPs can induce oxidative stress and promote EndMT through the BMP signaling pathway. These findings suggest that PS-MPs may trigcger atherosclerosis and cardiovascular toxicity by activating the BMP pathway and driving EndMT via oxidative stress. In summary, this study elucidates the cardiovascular deleterious effects induced by PS-MPs in mice, providing new insights into the toxicity of PS-MPs in mammalian organisms.

Arsenic and metabolic diseases: New insights from mesenchymal stem cells

Arsenic is a common toxic metal contaminant in the environment. Humans are exposed to arsenic through drinking water, air, food, and medical treatment. Chronic exposure to arsenic is a well-documented risk factor of type 2 diabetes and a potential risk factor of osteoporosis and obesity. Mesenchymal stem cells (MSCs) are adult stem cells with multiple differentiation potential and immunomodulatory capacity. These cells have shown therapeutic potential in experimental studies of metabolic diseases by differentiating into parenchymal cells of damaged tissues, such as islet-like cells and osteoblasts, and resisting chronic inflammation. Meanwhile, when key functional genes were suppressed in MSCs, experimental animals showed metabolic disease-related changes, such as insulin resistance and obesity. Arsenic exposure inhibits the differentiation capacity of MSCs, leads to changes in the synthesis and secretion of immunomodulatory factors, and induces cellular senescence and apoptosis. Therefore, dysfunction and death of MSCs may be important pathogenesis of arsenic-related metabolic diseases. Future studies on the functional changes of MSCs in arsenic-related metabolic diseases and the role of MSCs in arsenic pathogenesis are worthwhile. In addition, the mechanism of arsenic-induced dysfunction in MSCs needs to be explored in depth.

Heavy metal exposures in aerodigestive clinic cohort of infants with reflux or dysphagia

Infant cereals (rice/oatmeal), purees, and anti-reflux formulas are often first line treatments for thickening in infants with reflux and oropharyngeal dysphagia. However, there has been growing concern about heavy metal contamination, especially arsenic, in these commonly used thickeners. This is a particular concern in infants who may be more susceptible to heavy metal neurotoxicity. The study aimed to assess whether there are differences in heavy metal levels, particularly arsenic, in infants with reflux or oropharyngeal dysphagia while on different thickeners. We performed a single center study in infants (< 1 year of age) with diagnosis of reflux or oropharyngeal dysphagia who were seen between December 2021-2023. Participants submitted urine samples and completed dietary questionnaires to assess their elemental exposures. The primary outcome of interest was urinary arsenic concentrations, though other elements were also measured. Of the 56 infants, 27 were on gelmix® or purees, 19 were on Enfamil AR and 10 were on infant oatmeal/rice cereal as a thickener. The median total urinary arsenic concentration did not differ between groups (p = 0.086) and levels between groups were well below the Agency for Toxic Substances and Disease Registry (ATSDR)'s toxicity limits. Infants with higher number of servings of alternative arsenic sources via their solid food were more likely to have higher urinary arsenic level (p = 0.001), suggesting a potential need for the FDA to implement stricter food supply regulations. Only molybdenum had significant difference in levels between thickeners (p = 0.0012). Even in high-risk patients, urinary arsenic concentrations did not differ between thickener groups.

Effect of Adopting a Gluten-Free Diet on Exposure to Arsenic and Other Heavy Metals in Children With Celiac Disease: A Prospective Cohort Study

INTRODUCTION

Lifelong adherence to a gluten-free diet (GFD) is the primary treatment of celiac disease (CeD), a gluten-driven enteropathy. Concerns have been raised about increased exposure to arsenic from a GFD because rice, which naturally bioaccumulates arsenic, is commonly used as a substitute for gluten-containing grains such as wheat. We hypothesize that arsenic exposure increases in newly diagnosed children with CeD after they adopt a GFD.

METHODS

This is a single-center prospective longitudinal cohort study of children (age 2-18 years) with elevated celiac serology who underwent a diagnostic endoscopy before initiation of a GFD between January and May 2022. The primary outcome was change in urinary arsenic concentration between endoscopy and after 6 months on a GFD.

RESULTS

Of the 67 recruited participants, 50 had a biopsy diagnostic of CeD and were invited to continue the study. Thirty-five participants completed sample collection. Participants were from a middle-class, well-educated population that was predominantly White with presenting symptoms of abdominal pain (51%) and diarrhea (29%). After 6 months on a GFD, there was a significant increase in the median urinary arsenic concentration (3.3 µg/L vs 13.6 µg/L, P = 0.000004). In regression models, family history of CeD and Hispanic ethnicity were associated with having a higher urinary arsenic concentration after 6 months on a GFD.

DISCUSSION

Children with newly diagnosed CeD have increased arsenic exposure shortly after transitioning to a GFD. While the arsenic levels were well below acutely toxic concentrations, the clinical impact of chronic exposure to mildly elevated arsenic levels is unknown.

Ameliorating arsenic toxicity in young goats: assessing vitamin E and Saccharomyces cerevisiae on feed intake, carcass quality, mineral profiles in tissues and impending health risks to humans

This study aimed to assess the efficacy of vitamin E, yeast culture (Saccharomyces cerevisiae), and a combined supplement of both in alleviating the impacts of arsenic exposure on young goats. Alongside, we investigated feed consumption, carcass traits, arsenic levels in blood and organs, mineral distribution in different tissues, and potential human health risks from consuming meat from arsenic-exposed goats. Thirty healthy male Black Bengal goat weaned kids, averaging 6.15 ± 0.32 kg and 142.87 ± 9.28 days old, were involved in the trial. They were divided into five equal treatment groups. The diet consisted of chopped sorghum sudan grass as roughage and a concentrate mixture for growth and maintenance of young goats. Arsenic was administered through the concentrate as sodium arsenite, with T0 as the control (no arsenic). To prevent stress-related issues, kids under T1-T4 groups received gradually increasing arsenic doses over a three-week adaptation period, followed by a consistent 50 ppm dose for 17 weeks. Vitamin E and yeast culture were introduced concurrently with arsenic exposure, with DL-α-Tocopherol added to the concentrate at 250 IU/kg of feed dry matter for T2 and T4, and T3 and T4 received 4 × 109 colony forming units of yeast culture (Saccharomyces cerevisiae) daily. High arsenic levels led to reduced feed dry matter intake (g/kg body weight) (p = 0.01) and crude protein consumption (g/kg body weight) (p < 0.001) in arsenic-challenged goats. However, supplementation with vitamin E, yeast culture, or both mitigated these effects and decreased blood arsenic levels (p < 0.001). Interestingly, neither arsenic exposure nor the mitigation strategies significantly impacted the levels of Ca, P, Mg, Cu, Mn, Zn and Fe in various organs and carcass components except for liver copper levels, which showed a negative correlation (p < 0.008) with arsenic concentration. Organs such as the liver, kidneys and testes accumulated higher (p < 0.001) arsenic levels compared to other body parts. Vitamin E, alone or with yeast culture, significantly reduced (p < 0.001) arsenic deposition in carcass components, while yeast culture alone showed no additional benefit. Despite supplementation, arsenic levels in meat and carcass parts from exposed goats (T1, T2, T3 and T4) remained higher (p < 0.001) than in the control group, posing a cancer risk exceeding acceptable thresholds value (1 × 10-6). Vitamin E supplementation, alone or combined with S. cerevisiae, partially mitigated arsenic deposition in various organs and body parts, offering a promising solution to the issue.

Arsenic exposure accelerates type 1 diabetes mellitus progression via pyroptosis pathway in mice

The relationship between arsenic exposure and the development of diabetes mellitus has garnered significant interest in recent years. However, current experimental studies have not definitively established the role of arsenic in the onset of diabetes mellitus. To investigate this relationship specifically concerning type 1 diabetes mellitus, Streptozocin (STZ) was utilized as an inducer to initiate the fundamental pathological changes associated with the disease. A high dose of STZ (50 mg/kg) served as the positive control, while a low dose of STZ (20 mg/kg) was administered in combination with arsenic at varying doses. The objective was to determine whether arsenic enhances the effects of STZ, thereby leading to an expedited onset and progression of type 1 diabetes mellitus. The preliminary investigation into the impact of arsenic exposure on experimental type 1 diabetic mice focused on the NLRP3/Caspase-1/GSDMD mediated pyroptosis pathway. The results showed that fasting blood glucose (FBG) was increased, glucose tolerance was impaired, insulin sensitivity was decreased, fasting serum insulin and the homeostatic model assessment-β (HOMA-β) were significantly reduced, hair arsenic content was increased, reactive oxygen species(ROS), interleukin (IL)-1β and IL-18 contents were increased, and the pathological morphology of pancreas was more serious in the combined group. Moreover, the expression levels of proteins associated with the NLRP3/Caspase-1/GSDMD-mediated pyroptosis pathway were elevated in the combined group. This study illustrates that exposure to arsenic, combined with low-dose STZ, not only leads to pancreatic injury in mice, impacting insulin secretion and causing elevated blood glucose levels, thereby hastening the progression of type 1 diabetes, but also induces pyroptosis in pancreatic tissues by influencing the NLRP3/Caspase-1/GSDMD signaling pathway, further facilitating the development of type 1 diabetes.

Integrating New Approach Methodologies to Address Environmental Pancreatic Toxicity and Metabolic Disorders

Advancing our understanding of pancreatic toxicity and metabolic disorders caused by environmental exposures requires innovative approaches. The pancreas, a vital organ for glucose regulation, is increasingly recognized as a target of harm from environmental chemicals and dietary factors. Traditional toxicological methods, while foundational, often fail to address the mechanistic complexities of pancreatic dysfunction, particularly under real-world conditions involving multiple exposures. New Approach Methodologies (NAMs)-including high-throughput screening (HTS), OMICS technologies, computational modeling, and advanced in vitro systems-offer transformative tools to tackle these challenges. NAMs enable the identification of mechanistic pathways, improve testing efficiency, and reduce reliance on animal testing. This commentary explores the integration of NAMs into pancreatic toxicity screening, addresses critical gaps in evaluating the cumulative risks of chemical and dietary exposures, and proposes solutions for integrating the pancreas into toxicity screening through NAMs. By highlighting recent advancements and emphasizing their adoption in environmental toxicity assessment frameworks, this work demonstrates the potential of NAMs to revolutionize environmental health research, inspire interdisciplinary collaboration, and protect public health.

Roles of serum uric acid on the association between arsenic exposure and incident metabolic syndrome in an older Chinese population

Growing evidences showed that heavy metals exposure may be associated with metabolic diseases. Nevertheless, the mechanism underlying arsenic (As) exposure and metabolic syndrome (MetS) risk has not been fully elucidated. So we aimed to prospectively investigate the role of serum uric acid (SUA) on the association between blood As exposure and incident MetS. A sample of 1045 older participants in a community in China was analyzed. We determined As at baseline and SUA concentration at follow-up in the Yiwu Elderly Cohort. MetS events were defined according to the criteria of the International Diabetes Federation (IDF). Generalized linear model with log-binominal regression model was applied to estimate the association of As with incident MetS. To investigate the role of SUA in the association between As and MetS, a mediation analysis was conducted. In the fully adjusted log-binominal model, per interquartile range increment of As, the risk of MetS increased 1.25-fold. Compared with the lowest quartile of As, the adjusted relative risk (RR) of MetS in the highest quartile was 1.42 (95% confidence interval, CI: 1.03, 2.00). Additionally, blood As was positively associated with SUA, while SUA had significant association with MetS risk. Further mediation analysis demonstrated that the association of As and MetS risk was mediated by SUA, with the proportion of 15.7%. Our study found higher As was remarkably associated with the elevated risk of MetS in the Chinese older adults population. Mediation analysis indicated that SUA might be a mediator in the association between As exposure and MetS.

Zingerone effects on arsenic-induced glucose intolerance and hepatotoxicity in mice via suppression of oxidative stress-mediated hepatic inflammation and apoptosis

BACKGROUND

Arsenic (As), a poisonous metalloid, is widely distributed in air, water, and soil and has been associated with the occurrence of diabetes and liver toxicity. Zingerone (ZNG), one of the active compounds in ginger, has several pharmacological benefits such as antioxidant and anti-inflammatory characteristics. The objective of this research was to assess the protective role of ZNG against arsenic (As)-induced glucose intolerance (GI) and hepatotoxicity in mice.

METHODS

Male NMRI mice were treated with ZNG (25, 50, and 100 mg/kg, oral gavage for 29 days) before As administration (10 mg/kg, oral gavage for 29 days). On the 29th day, fasting blood glucose (FBG) and glucose tolerance test were measured. The animals were euthanized (day 30), and samples from blood and tissue (liver and pancreas) were gathered for further evaluations.

RESULTS

Administration of ZNG inhibited As-induced elevation of FBG and GI. Moreover, hepatic tissue damage and decreased Langerhans islets' diameter caused by As administration were improved by ZNG treatment. Pretreatment with ZNG attenuated the elevation of serum liver enzymes induced by As (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase). Also, the reduction in total thiol content, as well as the decline in antioxidant enzyme activities (catalase, superoxide dismutase, and glutathione peroxidase) and the increase in lipid peroxidation marker (thiobarbituric acid reactive substances) in the liver tissue of As-exposed mice were reversed in ZNG-treated mice. Furthermore, ZNG prevented the increase of hepatic inflammatory markers (nitric oxide and tumor necrosis factor-alpha levels, and protein expression of nuclear factor-kappa B) and apoptosis-related marker (caspase-3 protein expression) in As-treated mice.

CONCLUSIONS

This study has provided evidence indicating that ZNG can act as a beneficial agent in preventing As-induced hepatotoxicity and diabetes.

Metabolomics reveals the metabolic disturbance caused by arsenic in the mouse model of inflammatory bowel disease

Arsenic exposure has long been a significant global health concern due to its association with various human diseases. The adverse health effects of arsenic can be influenced by multiple factors, resulting in considerable individual variability. Individuals with inflammatory bowel disease (IBD) are particularly vulnerable to the effects of toxin exposure, yet the specific impact of arsenic in the context of IBD remains unclear. In this study, we employed a non-targeted metabolomics approach to investigate how arsenic exposure affects metabolic homeostasis in an IBD model using Helicobacter trogontum-infected interleukin-10 deficient mice. Our results demonstrated that arsenic exposure disrupted the balance of various metabolites, including tryptophan, polyunsaturated fatty acids, purine and pyrimidine metabolites, and branched-chain amino acids, in mice with colitis but not in those without colitis. Notably, several crucial metabolites involved in anti-inflammatory responses, oxidative stress, and energy metabolism were significantly altered in mice with colitis. These results indicate that arsenic exposure in an IBD context can lead to extensive metabolic disturbances, potentially exacerbating disease severity and impacting overall health. This study underscores the necessity of evaluating arsenic toxicity in relation to IBD to better understand and mitigate associated health risks.

Exposure to drinking water pollutants and non-syndromic birth defects: a systematic review and meta-analysis synthesis

OBJECTIVES

To evaluate the association between drinking water pollutants and non-syndromic birth defects.

DESIGN

Systematic review and meta-analysis synthesis.

DATA SOURCES

A search of MEDLINE, EMBASE and Google Scholar was performed to review relevant citations reporting on birth defects in pregnancies exposed to water pollutants between January 1962 and April 2023.

ELIGIBILITY CRITERIA

Prospective or retrospective cohort, population studies and case-control studies that provided data on exposure to drinking water pollutants around conception or during pregnancy and non-syndromic birth defects. We included studies published in the English language after the Minamata Bay disaster to reflect on contemporary concerns about the effect of environmental pollution and obstetric outcomes.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently read the retrieved articles for content, data extraction and analysis. The methodological quality of studies was assessed using the Newcastle-Ottawa Scale. Included studies were assessed for comparability when considered for meta-analysis.

RESULTS

32 studies met inclusion criteria including 17 cohorts (6 389 097 participants) and 15 case-control studies (47 914 cases and 685 712 controls). The most common pollutants investigated were trihalomethanes (11 studies), arsenic (5 studies) and nitrates (4 studies). The studies varied in design with different estimates of exposure, different stages of gestation age and different durations of exposure to pollutants. 21 articles reported data on any birth defects in their population or study groups and the others on specific birth defects including congenital heart defects, neural tube defects, orofacial defects and hypospadias. An increased risk or higher incidence of overall birth defects was reported by 9 studies and for specific birth defects by 14 studies. Eight studies compared the risk or incidence of birth defects with exposure to different concentrations of the pollutants. The analysis showed an association between higher levels of trihalomethanes (TTMs) and arsenic increase in major birth defects (lower vs higher exposure (OR 0.76, 95% CI 0.65 to 0.89; p<0.001 and OR 0.56, 95% CI 0.39 to 0.82; p<0.005, respectively).

CONCLUSION

The evidence of an association between exposure to average levels of common drinking water chemical pollutants during pregnancy and an increased risk or incidence of birth defects is uncertain. Available evidence indicates that some common chemical pollutants currently found in drinking water may have a direct teratogenic effect at high maternal exposure, however, wide variation in methodology limits the interpretation of the results. Future prospective studies using standardised protocols comparing maternal levels during all three trimesters of pregnancy and cord blood levels at birth are needed to better understand the placental transfer of water pollutants and accurately evaluate individual fetal exposure to drinking water pollutants.

PROSPERO REGISTRATION NUMBER

CRD42018112524.

Long-term arsenic exposure decreases mice body weight and liver lipid droplets

Arsenic (As) is a widespread global pollutant, and there is significant controversy surrounding its complex relationship with obesity, primarily focused on short-term exposure. Recognizing the prolonged nature of dietary arsenic exposure, this study involved feeding mice with arsenic-contained food for 14 months. The results showed that mice exposed to arsenic developed a non-alcoholic fatty liver condition, characterized by a light-yellow hue on the liver surface and various pathological alterations in the liver cells, including enlarged nuclei, cellular necrosis, inflammatory infiltration, dysfunctional mitochondria, and endoplasmic reticulum disorganization. There were also disruptions in biochemistry indices, with a significant increase in total cholesterol (TC) level and a decrease in high-density lipoprotein (HDL) level. However, some contradictory observations occurred, such as a significant decrease in body weight, triglyceride (TG) level, and the numbers of lipid droplets. Several genes related to lipid metabolism were tested, and a model was used to explain these discrepancies. Besides, examinations of the colon revealed compromised intestinal barrier function and signs of inflammation. Fecal 16S rRNA sequencing and pseudo-targeted metabolomics revealed disruptions in internal homeostasis, such as modules, nodes, connections, and lipid-related KEGG pathways. Fecal targeted metabolomics analyses of short-chain fatty acids (SCFAs) and bile acids (BAs) demonstrated a significant upregulation in three primary bile acids (CA, CDCA, TCDCA), four secondary bile acids (TUDCA, DCA, LCA, GUDCA), and total SCFAs level. Oxidative stress and inflammation were also evident. Additionally, based on correlation analysis and mediation analysis, it was assumed that changes in the microbiota (e.g., Dubosiella) can impact the liver metabolites (e.g., TGs) through alterations in fecal metabolites (e.g., LPCs). These findings provide a theoretical reference for the long-term effect of arsenic exposure on liver lipid metabolism.

Unveiling the link between arsenic toxicity and diabetes: an in silico exploration into the role of transcription factors

Arsenic-induced diabetes, despite being a relatively newer finding, is now a growing area of interest, owing to its multifaceted nature of development and the diversity of metabolic conditions that result from it, on top of the already complicated manifestation of arsenic toxicity. Identification and characterization of the common and differentially affected cellular metabolic pathways and their regulatory components among various arsenic and diabetes-associated complications may aid in understanding the core molecular mechanism of arsenic-induced diabetes. This study, therefore, explores the effects of arsenic on human cell lines through 14 transcriptomic datasets containing 160 individual samples using in silico tools to take a systematic, deeper look into the pathways and genes that are being altered. Among these, we especially focused on the role of transcription factors due to their diverse and multifaceted roles in biological processes, aiming to comprehensively investigate the underlying mechanism of arsenic-induced diabetes as well as associated health risks. We present a potential mechanism heavily implying the involvement of the TGF-β/SMAD3 signaling pathway leading to cell cycle alterations and the NF-κB/TNF-α, MAPK, and Ca2+ signaling pathways underlying the pathogenesis of arsenic-induced diabetes. This study also presents novel findings by suggesting potential associations of four transcription factors (NCOA3, PHF20, TFDP1, and TFDP2) with both arsenic toxicity and diabetes; five transcription factors (E2F5, ETS2, EGR1, JDP2, and TFE3) with arsenic toxicity; and one transcription factor (GATA2) with diabetes. The novel association of the transcription factors and proposed mechanism in this study may serve as a take-off point for more experimental evidence needed to understand the in vivo cellular-level diabetogenic effects of arsenic.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-024-00255-y.

Association between urinary fluoride concentrations and the prevalence of metabolic syndrome in adult individuals from the Central Region of Mexico

Emerging scientific studies have supported the hypothesis that exposure to environmental chemicals increases the incidence of diverse human metabolic disorders. Therefore, this study aimed to evaluate the association between fluoride exposure and metabolic syndrome (MetS) prevalence in people from the Central Region of Mexico. This research included 575 adult individuals. Urinary fluoride concentrations were determined using a potentiometric method. Anthropometric measurements and blood pressure were also acquired. Serum fasting glucose and lipid levels were quantified. For the MetS screening, we used the International Diabetes Federation (IDF) and National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria. The mean urinary fluoride levels were 3.50 ± 2.50 mg/L. The prevalence of MetS was approximately 27 and 25% according to NCEP ATP III and IDF criteria, respectively. A multivariate logistic regression analysis showed significant associations (p < 0.05) between urinary fluoride concentrations and MetS occurrence using NCEP ATP III criteria (OR = 1.60; 95% CI 1.05-2.10) and IDF criteria (OR = 1.35; 95% CI 0.95-1.45). These findings emphasize the need to discover the underlying mechanisms that fluoride exposure has on MetS pathogenesis.

Down-regulation of O-GlcNAcylation alleviates insulin signaling pathway impairment following arsenic exposure via suppressing the AMPK/mTOR-autophagy pathway

Impairment of the insulin signaling pathway is a key contributor to insulin resistance under arsenic exposure. Specifically, O-GlcNAcylation, an important post-translational modification, plays a crucial role in insulin resistance. Nevertheless, the concrete effect and mechanism of O-GlcNAcylation in arsenic-induced impairment of the insulin signaling pathway remain elusive. Herein, C57BL/6 mice were continuously fed arsenic-containing food, with a total arsenic concentration of 30 mg/kg. We observed that the IRS/Akt/GSK-3β insulin signaling pathway was impaired, and autophagy was activated in mouse livers and HepG2 cells exposed to arsenic. Additionally, O-GlcNAcylation expression in mouse livers and HepG2 cells was elevated, and the key O-GlcNAcylation homeostasis enzyme, O-GlcNAc transferase (OGT), was upregulated. In vitro, non-targeted metabolomic analysis showed that metabolic disorder was induced, and inhibition of O-GlcNAcylation restored the metabolic profile of HepG2 cells exposed to arsenic. In addition, we found that the compromised insulin signaling pathway was dependent on AMPK activation. Inhibition of AMPK mitigated autophagy activation and impairment of insulin signaling pathway under arsenic exposure. Furthermore, down-regulation of O-GlcNAcylation inhibited AMPK activation, thereby suppressing autophagy activation, and improving the impaired insulin signaling pathway. Collectively, our findings indicate that arsenic can impair the insulin signaling pathway by regulating O-GlcNAcylation homeostasis. Importantly, O-GlcNAcylation inhibition alleviated the impaired insulin signaling pathway by suppressing the AMPK/mTOR-autophagy pathway. This indicates that regulating O-GlcNAcylation may be a potential intervention for the impaired insulin signaling pathway induced by arsenic.

Metabolic Derangement by Arsenic: a Review of the Mechanisms

Studies have implicated arsenic exposure in various pathological conditions, including metabolic disorders, which have become a global phenomenon, affecting developed, developing, and under-developed nations. Despite the huge risks associated with arsenic exposure, humans remain constantly exposed to it, especially through the consumption of contaminated water and food. This present study provides an in-depth insight into the mechanistic pathways involved in the metabolic derangement by arsenic. Compelling pieces of evidence demonstrate that arsenic induces metabolic disorders via multiple pathways. Apart from the initiation of oxidative stress and inflammation, arsenic prevents the phosphorylation of Akt at Ser473 and Thr308, leading to the inhibition of PDK-1/Akt insulin signaling, thereby reducing GLUT4 translocation through the activation of Nrf2. Also, arsenic downregulates mitochondrial deacetylase Sirt3, decreasing the ability of its associated transcription factor, FOXO3a, to bind to the agents that support the genes for manganese superoxide dismutase and PPARg co-activator (PGC)-1a. In addition, arsenic activates MAPKs, modulates p53/ Bcl-2 signaling, suppresses Mdm-2 and PARP, activates NLRP3 inflammasome and caspase-mediated apoptosis, and induces ER stress, and ox-mtDNA-dependent mitophagy and autophagy. More so, arsenic alters lipid metabolism by decreasing the presence of 3-hydroxy-e-methylglutaryl-CoA synthase 1 and carnitine O-octanoyl transferase (Crot) and increasing the presence of fatty acid-binding protein-3 mRNA. Furthermore, arsenic promotes atherosclerosis by inducing endothelial damage. This cascade of pathophysiological events promotes metabolic derangement. Although the pieces of evidence provided by this study are convincing, future studies evaluating the involvement of other likely mechanisms are important. Also, epidemiological studies might be necessary for the translation of most of the findings in animal models to humans.

Association Between Arsenic Toxicity, AS3MT Gene Polymorphism and Onset of Type 2 Diabetes

Arsenic (As) exposure in drinking water has become a serious public health issue. AS3MT gene is involved in the metabolism of arsenic, so a single nucleotide polymorphism in this gene may lead to the development of type 2 diabetes in arsenic-exposed areas. This study aimed to evaluate the association of the AS3MT gene with the development of type 2 diabetes in highly arsenic-exposed areas of Punjab, Pakistan. Total 200 samples equal in number from high arsenic exposed-areas of Lahore (Nishtar) and Kasur (Mustafa Abad) were collected. rs11191439 was utilized as an influential variable to evaluate the association between arsenic metabolism and diabetes status to find a single nucleotide polymorphism in the AS3MT gene. We observed the arsenic level in drinking water of the arsenic-exposed selected areas 115.54 ± 1.23 µg/L and 96.88 ± 0.48 µg/L, respectively. The As level in the urine of diabetics (98.54 ± 2.63 µg/L and 56.38 ± 12.66 µg/L) was higher as compared to non-diabetics (77.58 ± 1.8 µg/L and 46.9 ± 8.95 µg/L) of both affected areas, respectively. Correspondingly, the As level in the blood of diabetics (6.48 ± 0.08 µg/L and 5.49 ± 1.43 µg/L) and non-diabetics (6.22 ± 0.12 µg/L and 5.26 ± 0.24 µg/L) in the affected areas. Genotyping showed significant differences in the frequencies of alleles among cases and controls. Nevertheless, notable disparities in genotype distribution were observed in SNPs rs11191439 (T/C) (P < 0.05) and when comparing T2D patients and non-diabetic control subjects. The AS3MT gene and clinical parameters show a significant association with the affected people with diabetes living in arsenic-exposed areas.

Arsenic and adipose tissue: an unexplored pathway for toxicity and metabolic dysfunction

Arsenic-contaminated drinking water can induce various disorders by disrupting lipid and glucose metabolism in adipose tissue, leading to insulin resistance. It inhibits adipocyte development and exacerbates insulin resistance, though the precise impact on lipid synthesis and lipolysis remains unclear. This review aims to explore the processes and pathways involved in adipogenesis and lipolysis within adipose tissue concerning arsenic-induced diabetes. Although arsenic exposure is linked to type 2 diabetes, the specific role of adipose tissue in its pathogenesis remains uncertain. The review delves into arsenic's effects on adipose tissue and related signaling pathways, such as SIRT3-FOXO3a, Ras-MAP-AP-1, PI(3)-K-Akt, endoplasmic reticulum stress proteins, CHOP10, and GPCR pathways, emphasizing the role of adipokines. This analysis relies on existing literature, striving to offer a comprehensive understanding of different adipokine categories contributing to arsenic-induced diabetes. The findings reveal that arsenic detrimentally impacts white adipose tissue (WAT) by reducing adipogenesis and promoting lipolysis. Epidemiological studies have hinted at a potential link between arsenic exposure and obesity development, with limited research suggesting a connection to lipodystrophy. Further investigations are needed to elucidate the mechanistic association between arsenic exposure and impaired adipose tissue function, ultimately leading to insulin resistance.

Molecular and Metabolic Analysis of Arsenic-Exposed Humanized AS3MT Mice

BACKGROUND

Chronic exposure to inorganic arsenic (iAs) has been associated with type 2 diabetes (T2D). However, potential sex divergence and the underlying mechanisms remain understudied. iAs is not metabolized uniformly across species, which is a limitation of typical exposure studies in rodent models. The development of a new "humanized" mouse model overcomes this limitation. In this study, we leveraged this model to study sex differences in the context of iAs exposure.

OBJECTIVES

The aim of this study was to determine if males and females exhibit different liver and adipose molecular profiles and metabolic phenotypes in the context of iAs exposure.

METHODS

Our study was performed on wild-type (WT) 129S6/SvEvTac and humanized arsenic + 3 methyl transferase (human AS3MT) 129S6/SvEvTac mice treated with 400   ppb of iAs via drinking water ad libitum. After 1 month, mice were sacrificed and the liver and gonadal adipose depots were harvested for iAs quantification and sequencing-based microRNA and gene expression analysis. Serum blood was collected for fasting blood glucose, fasting plasma insulin, and homeostatic model assessment for insulin resistance (HOMA-IR).

RESULTS

We detected sex divergence in liver and adipose markers of diabetes (e.g., miR-34a, insulin signaling pathways, fasting blood glucose, fasting plasma insulin, and HOMA-IR) only in humanized (not WT) mice. In humanized female mice, numerous genes that promote insulin sensitivity and glucose tolerance in both the liver and adipose are elevated compared to humanized male mice. We also identified Klf11 as a putative master regulator of the sex divergence in gene expression in humanized mice.

DISCUSSION

Our study underscored the importance of future studies leveraging the humanized mouse model to study iAs-associated metabolic disease. The findings suggested that humanized males are at increased risk for metabolic dysfunction relative to humanized females in the context of iAs exposure. Future investigations should focus on the detailed mechanisms that underlie the sex divergence. https://doi.org/10.1289/EHP12785.

Associations between area-level arsenic exposure and adverse birth outcomes: An Echo-wide cohort analysis

BACKGROUND

Drinking water is a common source of exposure to inorganic arsenic. In the US, the Safe Drinking Water Act (SDWA) was enacted to protect consumers from exposure to contaminants, including arsenic, in public water systems (PWS). The reproductive effects of preconception and prenatal arsenic exposure in regions with low to moderate arsenic concentrations are not well understood.

OBJECTIVES

This study examined associations between preconception and prenatal exposure to arsenic violations in water, measured via residence in a county with an arsenic violation in a regulated PWS during pregnancy, and five birth outcomes: birth weight, gestational age at birth, preterm birth, small for gestational age (SGA), and large for gestational age (LGA).

METHODS

Data for arsenic violations in PWS, defined as concentrations exceeding 10 parts per billion, were obtained from the Safe Drinking Water Information System. Participants of the Environmental influences on Child Health Outcomes Cohort Study were matched to arsenic violations by time and location based on residential history data. Multivariable, mixed effects regression models were used to assess the relationship between preconception and prenatal exposure to arsenic violations in drinking water and birth outcomes.

RESULTS

Compared to unexposed infants, continuous exposure to arsenic from three months prior to conception through birth was associated with 88.8 g higher mean birth weight (95% CI: 8.2, 169.5), after adjusting for individual-level confounders. No statistically significant associations were observed between any preconception or prenatal violations exposure and gestational age at birth, preterm birth, SGA, or LGA.

CONCLUSIONS

Our study did not identify associations between preconception and prenatal arsenic exposure, defined by drinking water exceedances, and adverse birth outcomes. Exposure to arsenic violations in drinking water was associated with higher birth weight. Future studies would benefit from more precise geodata of water system service areas, direct household drinking water measurements, and exposure biomarkers.

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.

Association between Heavy Metals, Metalloids and Metabolic Syndrome: New Insights and Approaches

Metabolic syndrome (MetS) is an important public health issue that affects millions of people around the world and is growing to pandemic-like proportions. This syndrome is defined by the World Health Organization (WHO) as a pathologic condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. Moreover, the etiology of MetS is multifactorial, involving many environmental factors, including toxicant exposures. Several studies have associated MetS with heavy metals exposure, which is the focus of this review. Environmental and/or occupational exposure to heavy metals are a major risk, contributing to the development of chronic diseases. Of particular note, toxic metals such as mercury, lead, and cadmium may contribute to the development of MetS by altering oxidative stress, IL-6 signaling, apoptosis, altered lipoprotein metabolism, fluid shear stress and atherosclerosis, and other mechanisms. In this review, we discuss the known and potential roles of heavy metals in MetS etiology as well as potential targeted pathways that are associated with MetS. Furthermore, we describe how new approaches involving proteomic and transcriptome analysis, as well as bioinformatic tools, may help bring about an understanding of the involvement of heavy metals and metalloids in MetS.

Arsenic exposure and pruritus: Evidence from observational, interventional, and mendelian randomization studies

BACKGROUND

Pruritus is identified as an adverse drug reaction to arsenic trioxide, but the association of arsenic exposure with pruritus has not been investigated.

METHODS

A cross-sectional study was conducted in Shimen, China. A Mendelian randomization analysis was conducted to confirm the causal relationship between genetically predicted percentages of monomethylated arsenic (MMA%) and dimethylated arsenic (DMA%) in urine with chronic pruritus in UK Biobank. A case-control study was then conducted to determine the biomarker for pruritus. Arsenite-treated mice were used to confirm the biomarker, and von Frey test was used to induce scratching bouts. Last, a randomized, double-blind, placebo-controlled trial was conducted to test the efficacy of naloxone in arsenic-exposed patients with pruritus in Shimen.

RESULTS

Hair arsenic (μg/g) showed a dose-response relationship with the intensity of itch in 1079 participants, with odds ratios (OR) of 1.11 for moderate-to-severe itch (p = 0.012). The Mendelian randomization analysis confirmed the causal relationship, with ORs of 1.043 for MMA% (p = 0.029) and 0.904 for DMA% (p = 0.077) above versus under median. Serum β-endorphin was identified as a significant biomarker for the intensity of itch (p < 0.001). Consistently, treatment with arsenite upregulated the level of β-endorphin (p = 0.002) and induced scratching bouts (p < 0.001) in mice. The randomized controlled trial in 126 participants showed that treatment with sublingual naloxone significantly relieved the intensity of itch in arsenic-exposed participants in 2 weeks (β = -0.98, p = 0.04).

CONCLUSION

Arsenic exposure is associated with pruritus, and β-endorphin serves as a biomarker of pruritus. Naloxone relieves pruritus in patients with arseniasis.

The effects of sucrose and arsenic on muscular insulin signaling pathways differ between the gastrocnemius and quadriceps muscles

Introduction

Insulin resistance in muscle can originate from a sedentary lifestyle, hypercaloric diets, or exposure to endocrine-disrupting pollutants such as arsenic. In skeletal muscle, insulin stimulates glucose uptake by translocating GLUT4 to the sarcolemma. This study aimed to evaluate the alterations induced by sucrose and arsenic exposure in vivo on the pathways involved in insulinstimulated GLUT4 translocation in the quadriceps and gastrocnemius muscles.

Methods

Male Wistar rats were treated with 20% sucrose (S), 50 ppm sodium arsenite (A), or both (A+S) in drinking water for 8 weeks. We conducted an intraperitoneal insulin tolerance (ITT) test on the seventh week of treatment. The quadriceps and gastrocnemius muscles were obtained after overnight fasting or 30 min after intraperitoneal insulin injection. We assessed changes in GLUT4 translocation to the sarcolemma by cell fractionation and abundance of the proteins involved in GLUT4 translocation by Western blot.

Results

Male rats consuming S and A+S gained more weight than control and Atreated animals. Rats consuming S, A, and A+S developed insulin resistance assessed through ITT. Neither treatments nor insulin stimulation in the quadriceps produced changes in GLUT4 levels in the sarcolemma and Akt phosphorylation. Conversely, A and A+S decreased protein expression of Tether containing UBX domain for GLUT4 (TUG), and A alone increased calpain-10 expression. All treatments reduced this muscle's protein levels of VAMP2. Conversely, S and A treatment increased basal GLUT4 levels in the sarcolemma of the gastrocnemius, while all treatments inhibited insulin-induced GLUT4 translocation. These effects correlated with lower basal levels of TUG and impaired insulin-stimulated TUG proteolysis. Moreover, animals treated with S had reduced calpain-10 protein levels in this muscle, while A and A+S inhibited insulin-induced Akt phosphorylation.

Conclusion

Arsenic and sucrose induce systemic insulin resistance due to defects in GLUT4 translocation induced by insulin. These defects depend on which muscle is being analyzed, in the quadriceps there were defects in GLUT4 retention and docking while in the gastrocnemius the Akt pathway was impacted by arsenic and the proteolytic pathway was impaired by arsenic and sucrose.

Inherited Epigenetic Hallmarks of Childhood Obesity Derived from Prenatal Exposure to Obesogens

Childhood obesity has reached epidemic levels in developed countries and is becoming a major cause for concern in the developing world. The causes of childhood obesity are complex and multifactorial, involving the interaction between individual genetics and environmental and developmental factors. Among the environmental factors, there is a growing interest in understanding the possible relationship between the so-called environmental obesogens and the development of obesity in children. Exposure to these obesogens such as phthalates, bisphenol A, or parabens, has been identified as a promoter of obesity through different mechanisms such as the alteration of adipocyte development from mesenchymal progenitors, the interference with hormone receptors, and induced inflammation. However, less attention has been paid to the inheritance of epigenetic modifications due to maternal exposure to these compounds during pregnancy. Thus, the aim of this review is to summarize the current knowledge of epigenetic modifications due to maternal exposure to those obesogens during pregnancy as well as their potential implication on long-term obesity development in the offspring and transgenerational inheritance of epiphenotypes.

Linking the Low-Density Lipoprotein-Cholesterol (LDL) Level to Arsenic Acid, Dimethylarsinic, and Monomethylarsonic: Results from a National Population-Based Study from the NHANES, 2003–2020

Arsenic (As) contamination is a global public health problem. Elevated total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) are risk factors for cardiovascular diseases, but data on the association of urinary arsenic species’ level and LDL-C are limited. We performed an association analysis based on urinary arsenic species and blood TC and LDL-C in US adults. Methods: Urinary arsenic, arsenic acid (AA), dimethylarsinic (DMA), monomethylarsonic (MMA), TC, LDL-C, and other key covariates were obtained from the available National Health and Nutrition Examination Survey (NHANES) data from 2003 to 2020. Multiple linear regression analysis and generalized linear model are used to analyze linear and nonlinear relationships, respectively. Results: In total, 6633 adults aged 20 years were enrolled into the analysis. The median total urinary arsenic level was 7.86 µg/L. A positive association of urinary arsenic concentration quartiles was observed with TC (β: 2.42 95% CI 1.48, 3.36). The OR for TC of participants in the 80th versus 20th percentiles of urinary total arsenic was 1.34 (95% CI 1.13, 1.59). The OR for LDL-C of participants in the 80th versus 20th percentiles of urinary total arsenic was 1.36 (95% CI 1.15, 1.62). For speciated arsenics analysis, the OR for arsenic acid and TC was 1.35 (95% CI 1.02, 1.79), whereas the OR for DMA and LDL-L was 1.20 (95% CI 1.03, 1.41), and the OR for MMA and LDL-L was 1.30 (95% CI 1.11, 1.52). Conclusions: Urinary arsenic and arsenic species were positively associated with increased LDL-C concentration. Prevention of exposure to arsenic and arsenic species maybe helpful for the control of TC and LDL-C level in adults.