Arsenic induces diabetic effects through beta-cell dysfunction and increased gluconeogenesis in mice. Sci Rep. 2014;4:6894. [PMID: 25367288 PMCID: PMC4219158 DOI: 10.1038/srep06894]

Environmental Heavy Metal Exposure and Associated Cardiovascular Diseases in Light of the Triglyceride Glucose Index

Cardiovascular diseases (CVD), primarily ischemic heart disease and stroke, remain leading global health burdens. Environmental risk factors have a major role in the development of CVD, particularly exposure to heavy metals. The Triglyceride Glucose Index (TyG), a measure of insulin resistance and CVD risk, is the primary focus of this study, which summarizes the most recent findings on the effects of lead (Pb), arsenic (As), and cadmium (Cd) on CVD risk. A higher risk of CVD is correlated with an elevated TyG index, which has been linked to insulin resistance. Exposure to Cd is associated with disturbance of lipid metabolism and oxidative stress, which increases the risk of CVD and TyG. Exposure reduces insulin secretion and signaling, which raises the TyG index and causes dyslipidemia. Pb exposure increases the risk of CVD and TyG index via causing oxidative stress and pancreatic β-cell destruction. These results highlight the need of reducing heavy metal exposure by lifestyle and environmental modifications in order to lower the risk of CVD. To comprehend the mechanisms and create practical management plans for health hazards associated with heavy metals, more study is required.

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.

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 of exposure to multiple heavy metals during pregnancy with the risk of gestational diabetes mellitus and insulin secretion phase after glucose stimulation

BACKGROUND

Epidemiological evidence for the association between heavy metals exposure during pregnancy and gestational diabetes mellitus (GDM) is still inconsistent. Additionally, that is poorly understood about the potential cause behind the association, for instance, whether heavy metal exposure is related to the change of insulin secretion phase is unknown.

OBJECTIVES

We aimed to explore the relationships of blood levels of arsenic (As), lead (Pb), thallium (Tl), nickel (Ni), cadmium (Cd), cobalt (Co), barium (Ba), chromium (Cr), mercury (Hg) and copper (Cu) during early pregnancy with the odds of GDM, either as an individual or a mixture, as well as the association of the metals with insulin secretion phase after glucose stimulation.

METHODS

We performed a nested case-control study consisting of 302 pregnant women with GDM and 302 controls at the First Affiliated Hospital of Anhui Medical University in Hefei, China. Around the 12th week of pregnancy, blood samples of pregnant women were collected and levels of As, Pb, Tl, Ni, Cd, Co, Ba, Cr, Hg and Cu in blood were measured. An oral glucose tolerance test (OGTT) was done in each pregnant woman during the 24-28th week of pregnancy to diagnose GDM and C-peptide (CP) levels during OGTT were measured simultaneously. The four metals (As, Pb, Tl and Ni) with the highest effect on odds of GDM were selected for the subsequent analyses via the random forest model. Conditional logistic regression models were performed to analyze the relationships of blood As, Pb, Tl and Ni levels with the odds of GDM. The weighted quantile sum (WQS) regression and bayesian kernel machine regression (BKMR) were used to assess the joint effects of levels of As, Pb, Tl and Ni on the odds of GDM as well as to evaluate which metal level contributed most to the association. Latent profile analysis (LPA) was conducted to identify profiles of glycemic and C-peptide levels at different time points. Multiple linear regression models were employed to explore the relationships of metals with glycaemia-related indices (fasting blood glucose (FBG), 1-hour blood glucose (1h BG), 2-hour blood glucose (2h BG), fasting C-peptide (FCP), 1-hour C-peptide (1h CP), 2-hour C-peptide (2h CP), FCP/FBG, 1h CP/1h BG, 2h CP/2h BG, area under the curve of C-peptide (AUCP), area under the curve of glucose (AUCG), AUCP/AUCG and profiles of BGs and CPs, respectively. Mixed-effects models with repeated measures data were used to explore the relationship between As (the ultimately selected metal) level and glucose-stimulated insulin secretion phase. The mediation effects of AUCP and AUCG on the association of As exposure with odds of GDM were investigated using mediation models.

RESULTS

The odds of GDM in pregnant women increased with every ln unit increase in blood As concentration (odds ratio (OR) = 1.46, 95% confidence interval (CI) = 1.04-2.05). The joint effects of As, Pb, Tl and Ni levels on the odds of GDM was statistically significant when blood levels of four metals were exceeded their 50th percentile, with As level being a major contributor. Blood As level was positively associated with AUCG and the category of glucose latent profile, the values of AUCG were much higher in GDM group than those in non-GDM group, which suggested that As exposure associated with the odds of GDM may be due to that As exposure was related to the impairment of glucose tolerance among pregnant women. The significant and positive relationships of As level with AUCP, CP latent profile category, 2h CP and 2h CP/2h BG were observed, respectively; and the values of 1h CP/1h BG and AUCP/AUCG were much lower in GDM group than those in non-GDM group, which suggested that As exposure may not relate to the impairment of insulin secretion (pancreatic β-cell function) among pregnant women. The relationships between As level and 2h CP as well as 2h CP/2h BG were positive and significant; additionally, the values of 2h CP/2h BG in GDM group were comparable with those in non-GDM group; the peak value of CP occurred at 2h in GDM group, as well as the values of 2h CP/2h BG in high As exposure group were much higher than those in low As exposure group, which suggested that As exposure associated with the increased odds of GDM may be due to that As exposure was related to the change of insulin secretion phase (delayment of the peak of insulin secretion) among pregnant women. In addition, AUCP mediated 11% (p < 0.05) and AUCG mediated 43% (p < 0.05) of the association between As exposure and the odds of GDM.

CONCLUSION

Our results suggested that joint exposure to As, Pb, Tl and Ni during early pregnancy was positively associated with the odds of GDM, As was a major contributor; and the association of environmental As exposure with the increased odds of GDM may be due to that As exposure was related to the impairment of glucose tolerance and change of insulin secretion phase after glucose stimulation (delayment of the peak of insulin secretion) among pregnant women.

Multilevel Regulation of Membrane Proteins in Response to Metal and Metalloid Stress: A Lesson from Yeast

In the face of flourishing industrialization and global trade, heavy metal and metalloid contamination of the environment is a growing concern throughout the world. The widespread presence of highly toxic compounds of arsenic, antimony, and cadmium in nature poses a particular threat to human health. Prolonged exposure to these toxins has been associated with severe human diseases, including cancer, diabetes, and neurodegenerative disorders. These toxins are known to induce analogous cellular stresses, such as DNA damage, disturbance of redox homeostasis, and proteotoxicity. To overcome these threats and improve or devise treatment methods, it is crucial to understand the mechanisms of cellular detoxification in metal and metalloid stress. Membrane proteins are key cellular components involved in the uptake, vacuolar/lysosomal sequestration, and efflux of these compounds; thus, deciphering the multilevel regulation of these proteins is of the utmost importance. In this review, we summarize data on the mechanisms of arsenic, antimony, and cadmium detoxification in the context of membrane proteome. We used yeast Saccharomyces cerevisiae as a eukaryotic model to elucidate the complex mechanisms of the production, regulation, and degradation of selected membrane transporters under metal(loid)-induced stress conditions. Additionally, we present data on orthologues membrane proteins involved in metal(loid)-associated diseases in humans.

Glycemic Changes Related to Arsenic Exposure: An Overview of Animal and Human Studies

BACKGROUND

Arsenic (As) is a risk factor associated with glycemic alterations. However, the mechanisms of action and metabolic aspects associated with changes in glycemic profiles have not yet been completely elucidated. Therefore, in this review, we aimed to investigate the metabolic aspects of As and its mechanism of action associated with glycemic changes.

METHODS

We searched the PubMed (MEDLINE) and Google Scholar databases for relevant articles published in English. A combination of free text and medical subject heading keywords and search terms was used to construct search equations. The search yielded 466 articles; however, only 50 were included in the review.

RESULTS

We observed that the relationship between As exposure and glycemic alterations in humans may be associated with sex, smoking status, body mass index, age, occupation, and genetic factors. The main mechanisms of action associated with changes induced by exposure to As in the glycemic profile identified in animals are increased oxidative stress, reduced expression of glucose transporter type 4, induction of inflammatory factor expression and dysfunction of pancreatic β cells.

CONCLUSIONS

Therefore, As exposure may be associated with glycemic alterations according to inter-individual differences.

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.

Urinary metal profiles in mother-offspring pairs and their association with early dysglycemia in the International Hyperglycemia and Adverse Pregnancy Outcome Follow Up Study (HAPO-FUS)

BACKGROUND

Variations in dietary intake and environmental exposure patterns of essential and non-essential trace metals influence many aspects of human health throughout the life span.

OBJECTIVE

To examine the relationship between urine profiles of essential and non-essential metals in mother-offspring pairs and their association with early dysglycemia.

METHODS

Herein, we report findings from an ancillary study to the international Hyperglycemia and Adverse Pregnancy Outcome Follow-Up Study (HAPO-FUS) that examined urinary essential and non-essential metal profiles from mothers and offspring ages 10-14 years (1012 mothers, 1013 offspring, 968 matched pairs) from 10 international sites.

RESULTS

Our analysis demonstrated a diverse exposure pattern across participating sites. In multiple regression modelling, a positive association between markers of early dysglycemia and urinary zinc was found in both mothers and offspring after adjustment for common risk factors for diabetes. The analysis showed weaker, positive, and negative associations of the 2-h glucose value with urinary selenium and arsenic respectively. A positive association between 2-h glucose values and cadmium was found only in mothers in the fully adjusted model when participants with established diabetes were excluded. There was a high degree of concordance between mother and offspring urinary metal profiles. Mother-to-offspring urinary metal ratios were unique for each metal, providing insights into changes in their homeostasis across the lifespan.

SIGNIFICANCE

Urinary levels of essential and non-essential metals are closely correlated between mothers and their offspring in an international cohort. Urinary levels of zinc, selenium, arsenic, and cadmium showed varying degrees of association with early dysglycemia in a comparatively healthy cohort with a low rate of preexisting diabetes.

IMPACT STATEMENT

Our data provides novel evidence for a strong correlation between mother and offspring urinary metal patterns with a unique mother-to-offspring ratio for each metal. The study also provides new evidence for a strong positive association between early dysglycemia and urinary zinc, both in mothers and offspring. Weaker positive associations with urinary selenium and cadmium and negative associations with arsenic were also found. The low rate of preexisting diabetes in this population provides the unique advantage of minimizing the confounding effect of preexisting, diabetes related renal changes that would alter the relationship between dysglycemia and renal metal excretion.

Sex-specific transgenerational effects of preconception exposure to arsenite: metabolic phenotypes of C57BL/6 offspring

Chronic exposure to inorganic arsenic (iAs) has been linked to diabetes in both humans and mice, but the role of iAs exposure prior to conception and its transgenerational effects are understudied. The present study investigated transgenerational effects of preconception iAs exposure in C57BL/6J mice, focusing on metabolic phenotypes of G1 and G2 offspring. Body composition and diabetes indicators, including fasting blood glucose, fasting plasma insulin, glucose tolerance, and indicators of insulin resistance and beta cell function, were examined in both generations. The results suggest that the preconception iAs exposure in the parental (G0) generation induced diabetic phenotypes in G1 and G2 offspring in a sex-dependent manner. G1 females from iAs-exposed parents developed insulin resistance while no significant effects were found in G1 males. In the G2 generation, insulin resistance was observed only in males from iAs-exposed grandparents and was associated with higher bodyweights and adiposity. Similar trends were observed in G2 females from iAs-exposed grandparents, but these did not reach statistical significance. Thus, preconception iAs exposure altered metabolic phenotype across two generations of mouse offspring. Future research will investigate the molecular mechanisms underlying these transgenerational effects, including epigenomic and transcriptomic profiles of germ cells and tissues from G0, G1 and G2 generations.

The Role of the Nuclear Receptor FXR in Arsenic-Induced Glucose Intolerance in Mice

Inorganic arsenic in drinking water is prioritized as a top environmental contaminant by the World Health Organization, with over 230 million people potentially being exposed. Arsenic toxicity has been well documented and is associated with a plethora of human diseases, including diabetes, as established in numerous animal and epidemiological studies. Our previous study revealed that arsenic exposure leads to the inhibition of nuclear receptors, including LXR/RXR. To this end, FXR is a nuclear receptor central to glucose and lipid metabolism. However, limited studies are available for understanding arsenic exposure-FXR interactions. Herein, we report that FXR knockout mice developed more profound glucose intolerance than wild-type mice upon arsenic exposure, supporting the regulatory role of FXR in arsenic-induced glucose intolerance. We further exposed mice to arsenic and tested if GW4064, a FXR agonist, could improve glucose intolerance and dysregulation of hepatic proteins and serum metabolites. Our data showed arsenic-induced glucose intolerance was remarkably diminished by GW4064, accompanied by a significant ratio of alleviation of dysregulation in hepatic proteins (83%) and annotated serum metabolites (58%). In particular, hepatic proteins "rescued" from arsenic toxicity by GW4064 featured members of glucose and lipid utilization. For instance, the expression of PCK1, a candidate gene for diabetes and obesity that facilitates gluconeogenesis, was repressed under arsenic exposure in the liver, but revived with the GW4064 supplement. Together, our comprehensive dataset indicates FXR plays a key role and may serve as a potential therapeutic for arsenic-induced metabolic disorders.

The associations of non-essential metal mixture with fasting plasma glucose among Chinese older adults without diabetes

The evidence about the effect of non-essential metal mixture on fasting plasma glucose (FPG) levels among older adults without diabetes is limited. This study aims to estimate the individual and joint relationship between five non-essential metals and FPG levels in Chinese older adults without diabetes. This study included 2362 older adults without diabetes. Urinary concentrations of five non-essential metals, i.e., cesium (Cs), aluminum (Al), thallium (Tl), cadmium (Cd), and arsenic (As), were detected by inductively coupled plasma mass spectrometry (ICP-MS). The associations of single metals and the metal mixture with FPG levels were assessed using linear regression and Bayesian kernel machine regression (BKMR) models, respectively. Adjusted single-metal linear regression models showed positive associations of urinary Al (β = 0.016, 95%CI: 0.001-0.030) and Cs (β = 0.018, 95%CI: 0.006-0.031) with FPG levels. When comparing the 2th, 3th, and 4th quartiles of urine Cs to its 1th quartile, the significant associations between Cs and FPG levels were found and presented as an "inverted U" trend (βQ2 vs. Q1: 0.034; βQ3 vs. Q1:0.054; βQ4 vs. Q1: 0.040; all P<0.05). BKMR analyses showed urinary level of Cs exhibited an "inverted U" shape association with FPG levels. Moreover, the FPG levels increased linearly with the raised levels of the non-essential metal mixture, and the posterior inclusion probability (PIP) of Cs was the highest (0.92). Potential positive interaction of As and Cs on FPG levels was found in BKMR model. Stratified analysis displayed significant interactions of hyperlipidemia and urine Cs or Tl on FPG levels. An inverse U-shaped association between Cs and FPG was found, individually and as mixture. The FPG levels increased with the raised levels of the non-essential metal mixture, and Cs was the most contributor to FPG levels. Further research is required to confirm the correlation between non-essential metals and FPG levels and to clarify the underlying mechanisms.

Arsenic metabolism, diabetes prevalence, and insulin resistance among Mexican Americans: A mendelian randomization approach

Background

Differences in arsenic metabolism capacity may influence risk for type 2 diabetes, but the mechanistic drivers are unclear. We evaluated the associations between arsenic metabolism with overall diabetes prevalence and with static and dynamic measures of insulin resistance among Mexican Americans living in Starr County, Texas.

Methods

We utilized data from cross-sectional studies conducted in Starr County, Texas, from 2010-2014. A Mendelian randomization approach was utilized to evaluate the associations between arsenic metabolism and type 2 diabetes prevalence using the intronic variant in the arsenic methylating gene, rs9527, as the instrumental variable for arsenic metabolism. To further assess mechanisms for diabetes pathogenesis, proportions of the urinary arsenic metabolites were employed to assess the association between arsenic metabolism and insulin resistance among participants without diabetes. Urinary biomarkers of arsenic metabolites were modeled as individual proportions of the total. Arsenic metabolism was evaluated both with a static outcome of insulin resistance, homeostatic measure of assessment (HOMA-IR), and a dynamic measure of insulin sensitivity, Matsuda Index.

Results

Among 475 Mexican American participants from Starr County, higher metabolism capacity for arsenic is associated with higher diabetes prevalence driven by worse insulin resistance. Presence of the minor T allele of rs9527 is independently associated with an increase in the proportion of monomethylated arsenic (MMA%) and is associated with an odds ratio of 0.50 (95% CI: 0.24, 0.90) for type 2 diabetes. This association was conserved after potential covariate adjustment. Furthermore, among participants without type 2 diabetes, the highest quartile of MMA% was associated with 22% (95% CI: -33.5%, -9.07%) lower HOMA-IR and 56% (95% CI: 28.3%, 91.3%) higher Matsuda Index for insulin sensitivity.

Conclusions

Arsenic metabolism capacity, indicated by a lower proportion of monomethylated arsenic, is associated with increased diabetes prevalence driven by an insulin resistant phenotype among Mexican Americans living in Starr County, Texas.

Environmental Pollution and the Risk of Developing Metabolic Disorders: Obesity and Diabetes

To meet the increased need for food and energy because of the economic shift brought about by the Industrial Revolution in the 19th century, there has been an increase in persistent organic pollutants (POPs), atmospheric emissions and metals in the environment. Several studies have reported a relationship between these pollutants and obesity, and diabetes (type 1, type 2 and gestational). All of the major pollutants are considered to be endocrine disruptors because of their interactions with various transcription factors, receptors and tissues that result in alterations of metabolic function. POPs impact adipogenesis, thereby increasing the prevalence of obesity in exposed individuals. Metals impact glucose regulation by disrupting pancreatic β-cells, causing hyperglycemia and impaired insulin signaling. Additionally, a positive association has been observed between the concentration of endocrine disrupting chemicals (EDCs) in the 12 weeks prior to conception and fasting glucose levels. Here, we evaluate what is currently known regarding the link between environmental pollutants and metabolic disorders. In addition, we indicate where further research is required to improve our understanding of the specific effects of pollutants on these metabolic disorders which would enable implementation of changes to enable their prevention.

Arsenic in Drinking Water and Diabetes

Arsenic is ubiquitous in soil and water environments and is consistently at the top of the Agency for Toxic Substances Disease Registry (ATSDR) substance priority list. It has been shown to induce toxicity even at low levels of exposure. One of the major routes of exposure to arsenic is through drinking water. This review presents current information related to the distribution of arsenic in the environment, the resultant impacts on human health, especially related to diabetes, which is one of the most prevalent chronic diseases, regulation of arsenic in drinking water, and approaches for treatment of arsenic in drinking water for both public utilities and private wells. Taken together, this information points out the existing challenges to understanding both the complex health impacts of arsenic and to implementing the treatment strategies needed to effectively reduce arsenic exposure at different scales.

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.

Relationships Between Urinary Metals and Diabetes Traits Among Mexican Americans in Starr County, Texas, USA

Hispanics/Latinos have higher rates of type 2 diabetes (T2D), and the origins of these disparities are poorly understood. Environmental endocrine-disrupting chemicals (EDCs), including some metals and metalloids, are implicated as diabetes risk factors. Data indicate that Hispanics/Latinos may be disproportionately exposed to EDCs, yet they remain understudied with respect to environmental exposures and diabetes. The objective of this study is to determine how metal exposures contribute to T2D progression by evaluating the associations between 8 urinary metals and measures of glycemic status in 414 normoglycemic or prediabetic adults living in Starr County, Texas, a Hispanic/Latino community with high rates of diabetes and diabetes-associated mortality. We used multivariable linear regression to quantify the differences in homeostatic model assessments for pancreatic β-cell function, insulin resistance, and insulin sensitivity (HOMA-β, HOMA-IR, HOMA-S, respectively), plasma insulin, plasma glucose, and hemoglobin A1c (HbA1c) associated with increasing urinary metal concentrations. Quantile-based g-computation was utilized to assess mixture effects. After multivariable adjustment, urinary arsenic and molybdenum were associated with lower HOMA-β, HOMA-IR, and plasma insulin levels and higher HOMA-S. Additionally, higher urinary copper levels were associated with a reduced HOMA-β. Lastly, a higher concentration of the 8 metal mixtures was associated with lower HOMA-β, HOMA-IR, and plasma insulin levels as well as higher HOMA-S. Our data indicate that arsenic, molybdenum, copper, and this metal mixture are associated with alterations in measures of glucose homeostasis among non-diabetics in Starr County. This study is one of the first to comprehensively evaluate associations of urinary metals with glycemic measures in a high-risk Mexican American population.

Arsenic and Diabetes Mellitus: A Putative Role for the Immune System

Diabetes mellitus (DM) is an enormous public health issue worldwide. Recent data suggest that chronic arsenic exposure is linked to the risk of developing type 1 and type 2 DM, albeit the underlying mechanisms are unclear. This review discusses the role of the immune system as a link to possibly explain some of the mechanisms of developing T1DM or T2DM associated with arsenic exposure in humans, animal models, and in vitro studies. The rationale for the hypothesis includes: (1) Arsenic is a well-recognized modulator of the immune system; (2) arsenic exposures are associated with increased risk of DM; and (3) dysregulation of the immune system is one of the hallmarks in the pathogenesis of both T1DM and T2DM. A better understanding of DM in association with immune dysregulation and arsenic exposures may help to understand how environmental exposures modulate the immune system and how these effects may impact the manifestation of disease.

SOX2 modulated astrocytic process plasticity is involved in arsenic-induced metabolic disorders

Metabolic disorders induced by arsenic exposure have attracted great public concern. However, it remains unclear whether hypothalamus-based central regulation mechanisms are involved in this process. Here, we exposed mice to 100 μg/L arsenic in drinking water and established a chronic arsenic exposure model. Our study revealed that chronic arsenic exposure caused metabolic disorders in mice including impaired glucose metabolism and decreased energy expenditure. Arsenic exposure also impaired glucose sensing and the activation of proopiomelanocortin (POMC) neurons in the hypothalamus. In particular, arsenic exposure damaged the plasticity of hypothalamic astrocytic process. Further research revealed that arsenic exposure inhibited the expression of sex-determining region Y-Box 2 (SOX2), which decreased the expression level of insulin receptors (INSRs) and the phosphorylation of AKT. The conditional deletion of astrocytic SOX2 exacerbated arsenic-induced effects on metabolic disorders, the impairment of hypothalamic astrocytic processes, and the inhibition of INSR/AKT signaling. Furthermore, the arsenic-induced impairment of astrocytic processes and inhibitory effects on INSR/AKT signaling were reversed by SOX2 overexpression in primary hypothalamic astrocytes. Together, we demonstrated here that chronic arsenic exposure caused metabolic disorders by impairing SOX2-modulated hypothalamic astrocytic process plasticity in mice. Our study provides evidence of novel central regulatory mechanisms underlying arsenic-induced metabolic disorders and emphasizes the crucial role of SOX2 in regulating the process plasticity of adult astrocytes.

In vitro toxic interaction of arsenic and hyperglycemia in mitochondria: an important implication of increased vulnerability in pre-diabetics

Environmental pollutants and lifestyle both contribute to the rapidly increasing prevalence of type 2 diabetes mellitus (T2DM) worldwide. Evidence suggests that exposure to environmental contaminants such as arsenic is associated with impaired glucose metabolism and insulin signaling. In the present study, isolated rat liver mitochondria (1 mg/ml) were co-exposed to low concentration of arsenic trioxide (ATO) ( IC₂₅ = 40 µM) and hyperglycemic condition (20, 40, 80, 160 mM glucose or 20, 40, 80, 160 mM pyruvate (PYR)). Mitochondrial dehydrogenase activity (complex II), glutathione content (GSH), reactive oxygen species (ROS), lipid peroxidation, mitochondrial membrane potential (ΔΨ), and mitochondrial swelling were then evaluated in the presence of ATO 40 µM and PYR 40 mM. Unexpectedly, glucose alone (20, 40, 80, 160 mM) had no toxic effect on mitochondria, even at very high concentrations and even when combined with ATO. Interestingly, PYR at low concentrations (≤ 10 mM) has a protective effect on mitochondria, but at higher concentrations (≥ 40 mM) with ATO, it decreased the complex II activity and increased mitochondrial ROS production, lipid peroxidation, GSH depletion, mitochondrial membrane damage, and swelling (p < 0.05). In conclusion, PYR but not glucose increased ATO mitochondrial toxicity even at low concentrations. These results suggest that pre-diabetics with non-clinical hyperglycemia, who are inevitably exposed to low concentrations of arsenic through food and water, may develop mitochondrial dysfunction that accelerates their progression to diabetes over time.

Arsenic exposure during pregnancy and postpartum maternal glucose tolerance: evidence from Bangladesh

BACKGROUND

Arsenic exposure has been associated with gestational diabetes mellitus. However, the extent to which arsenic exposure during pregnancy is associated with postpartum glucose intolerance is unknown.

METHODS

We studied 323 women in Bangladesh. We assessed arsenic exposure in early pregnancy via toenail and water samples. We measured fasting glucose and insulin in serum at a mean (SD) of 4.0 (3.5) weeks post-delivery. We ran covariate-adjusted, linear regression models to examine associations of arsenic concentrations with HOMA-IR, a marker of insulin resistance, and HOMA-β, a marker of beta cell function.

RESULTS

Median (IQR) arsenic concentration was 0.45 (0.67) μg/g in toenails and 2.0 (6.5) μg/L in drinking water. Arsenic concentrations during pregnancy were not associated with insulin resistance or beta cell function postpartum. HOMA-IR was 0.07% (- 3.13, 3.37) higher and HOMA-β was 0.96% (- 3.83, 1.99) lower per IQR increment in toenail arsenic, but effect estimates were small and confidence intervals crossed the null.

CONCLUSIONS

Although arsenic exposure during pregnancy has been consistently associated with gestational diabetes mellitus, we found no clear evidence for an adverse effect on postpartum insulin resistance or beta cell function.

Metabolic reprogramming in the arsenic carcinogenesis

Chronic exposure to arsenic has been associated with a variety of cancers with the mechanisms undefined. Arsenic exposure causes alterations in metabolites in bio-samples. Recent research progress on cancer biology suggests that metabolic reprogramming contributes to tumorigenesis. Therefore, metabolic reprogramming provides a new clue for the mechanisms of arsenic carcinogenesis. In the present manuscript, we review the latest findings in reprogramming of glucose, lipids, and amino acids in response to arsenic exposure. Most studies focused on glucose reprogramming and found that arsenic exposure enhanced glycolysis. However, in vivo studies observed "reverse Warburg effect" in some cases due to the complexity of the disease evolution and microenvironment. Arsenic exposure has been reported to disturb lipid deposition by inhibiting lipolysis, and induce serine-glycine one-carbon pathway. As a dominant mechanism for arsenic toxicity, oxidative stress is considered to link with metabolism reprogramming. Few studies analyzed the causal relationship between metabolic reprogramming and arsenic-induced cancers. Metabolic alterations may vary with exposure doses and periods. Identifying metabolic alterations common among humans and experiment models with human-relevant exposure characteristics may guide future investigations.

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

Exposure to arsenic in drinking water is a worldwide health problem. This pollutant is associated with increased risk of developing chronic diseases, including metabolic diseases. Metabolic syndrome (MS) is a complex pathology that results from the interaction between environmental and genetic factors. This condition increases the risk of developing type 2 diabetes, cardiovascular diseases, and cancer. The MS includes at least three of the following signs, central obesity, impaired fasting glucose, insulin resistance, dyslipidemias, and hypertension. Here, we summarize the existing evidence of the multiple mechanisms triggered by arsenic to developing the cardinal signs of MS, showing that this pollutant could contribute to the multifactorial origin of this pathology.

Ubiquitinated gasdermin D mediates arsenic-induced pyroptosis and hepatic insulin resistance in rat liver

As an environmental toxicant, arsenic exposure may cause insulin resistance (IR). Previous studies have shown that pyroptosis plays an important role in the occurrence and development of IR. Although gasdermin D (GSDMD) functions as an executor of pyroptosis, the relationship between GSDMD-mediated pyroptosis and hepatic IR remains unclear. Here, we observed that sodium arsenite (NaAsO₂) activated NOD-like receptors containing pyrin domain 3 (NLRP3) inflammasomes, promoted GSDMD activation, induced pyroptosis and hepatic IR, while GSDMD knockdown attenuated pyroptosis and hepatic IR caused by NaAsO₂. However, GSDMD interference did not affect NLRP3 activation. Ubiquitination modification is widely involved in protein regulation and intracellular signal transduction, and whether it regulates GSDMD and affects its degradation, and exerts effects on arsenic-induced pyroptosis remain unclear. We observed that NaAsO₂ reduced the K48- and K63-linked ubiquitination of GSDMD, thereby inhibiting its degradation through the ubiquitin-proteasome system (UPS) and the autophagy-lysosome pathway (ALP), causing GSDMD to accumulate and lyse into GSDMD-N, which promoted pyroptosis. In summary, we demonstrated that GSDMD participated in arsenic-induced hepatic IR. Moreover, NaAsO₂ reduced GSDMD ubiquitination and decreased its intracellular degradation, aggravating pyroptosis and hepatic IR. We have revealed the molecular mechanism underpinning arsenic-induced IR, and we provide potential solutions for the prevention and treatment of type 2 diabetes (T2D).

Environmental arsenic exposure and its contribution to human diseases, toxicity mechanism and management

Arsenic is a well-recognized environmental contaminant that occurs naturally through geogenic processes in the aquifer. More than 200 million people around the world are potentially exposed to the elevated level of arsenic mostly from Asia and Latin America. Many adverse health effects including skin diseases (i.e., arsenicosis, hyperkeratosis, pigmentation changes), carcinogenesis, and neurological diseases have been reported due to arsenic exposure. In addition, arsenic has recently been shown to contribute to the onset of non-communicable diseases, such as diabetes mellitus and cardiovascular diseases. The mechanisms involved in arsenic-induced diabetes are pancreatic β-cell dysfunction and death, impaired insulin secretion, insulin resistance and reduced cellular glucose transport. Whereas, the most proposed mechanisms of arsenic-induced hypertension are oxidative stress, disruption of nitric oxide signaling, altered vascular response to neurotransmitters and impaired vascular muscle calcium (Ca²⁺) signaling, damage of renal, and interference with the renin-angiotensin system (RAS). However, the contributions of arsenic exposure to non-communicable diseases are complex and multifaceted, and little information is available about the molecular mechanisms involved in arsenic-induced non-communicable diseases and also no suitable therapeutic target identified yet. Therefore, in the future, more basic research is necessary to identify the appropriate therapeutic target for the treatment and management of arsenic-induced non-communicable diseases. Several reports demonstrated that a daily balanced diet with proper nutrient supplements (vitamins, micronutrients, natural antioxidants) has shown effective to reduce the damages caused by arsenic exposure. Arsenic detoxication through natural compounds or nutraceuticals is considered a cost-effective treatment/management and researchers should focus on these alternative options. This review paper explores the scenarios of arsenic contamination in groundwater with an emphasis on public health concerns. It also demonstrated arsenic sources, biogeochemistry, toxicity mechanisms with therapeutic targets, arsenic exposure-related human diseases, and onsets of cardiovascular diseases as well as feasible management options for arsenic toxicity.

Correlation between urinary contents of some metals and fasting plasma glucose levels: A cross-sectional study in China

Many metals are involved in the pathogenesis of diabetes, but most of existing studies focused on single metals. The study of mixtures represents real-life exposure scenarios and deserves attention. This study aimed to explore the potential relationship of urinary copper (Cu), zinc (Zn), arsenic (As), selenium (Se), and strontium (Sr) contents with fasting plasma glucose (FPG) levels in 2766 participants. The levels of metals in urine were determined by inductively coupled plasma-mass spectrometry. We used linear regression models and the Bayesian kernel machine regression (BKMR) to evaluate the association between metals and FPG levels. In the multiple metals linear regression, Zn (β = 0.434), Se (β = 0.172), and Sr (β = -0.143) showed significant association with FPG levels (all P < 0.05). The BKMR model analysis showed that the results of single metal association were consistent with the multiple metals linear regression. The mixture of five metals had a positive over-all effect on FPG levels, and Zn (PIP = 1.000) contributed the most to the FPG levels. Cu and As were negatively correlated with FPG levels in women. The potential interaction effect between Cu and Sr was observed in participants aged ≥ 60 years old (Pinteraction = 0.035). In summary, our results suggested that multiple metals in urine are associated with FPG levels. Further studies are needed to confirm these findings and clarify the underlying mechanisms.

Dietary Selenium Deficiency Partially Mimics the Metabolic Effects of Arsenic

Chronic arsenic exposure via drinking water is associated with diabetes in human pop-ulations throughout the world. Arsenic is believed to exert its diabetogenic effects via multiple mechanisms, including alterations to insulin secretion and insulin sensitivity. In the past, acute arsenicosis has been thought to be partially treatable with selenium supplementation, though a potential interaction between selenium and arsenic had not been evaluated under longer-term exposure models. The purpose of the present study was to explore whether selenium status may augment arsenic's effects during chronic arsenic exposure. To test this possibility, mice were exposed to arsenic in their drinking water and provided ad libitum access to either a diet replete with selenium (Control) or deficient in selenium (SelD). Arsenic significantly improved glucose tolerance and decreased insulin secretion and β-cell function in vivo. Dietary selenium deficiency resulted in similar effects on glucose tolerance and insulin secretion, with significant interactions between arsenic and dietary conditions in select insulin-related parameters. The findings of this study highlight the complexity of arsenic's metabolic effects and suggest that selenium deficiency may interact with arsenic exposure on β-cell-related physiological parameters.

Prepubertal arsenic exposure alters phosphoproteins profile, quality, and fertility of epididymal spermatozoa in sexually mature rats

Arsenic intoxication affects male reproductive parameters of prepubertal rats. Besides, morphological and functional alterations in their testis and epididymis may remain after withdrawal of arsenic insult, causing potential impairment in male fertility during adulthood. In this study, we aimed at analyzing the effect of prepubertal arsenic exposure on the fecundity of epididymal sperm from sexually mature Wistar rats, assessing fertility indexes, sperm parameters, and sperm phosphoproteins content. Male pups on postnatal day (PND) 21 received filtered water (controls, n = 10) and 10 mg L^-1 arsenite (n = 10) daily for 30 days. From PND52 to PND81, rats from both groups received filtered water. During this period, the males mated with non-exposed females between PND72 and PND75. Our results showed that sexually mature rats presented low sperm production, epididymal sperm count, motility, and quality after prepubertal arsenic exposure. These findings possibly contributed to the low fertility potential and high preimplantation loss. Epididymal sperm proteome detected 268 proteins, which 170 were found in animals from both control and arsenic groups, 27 proteins were detected only in control animals and 71 proteins only in arsenic-exposed rats. In these animals, SPATA 18 and other five proteins were upregulated, whereas keratin type II cytoskeletal 1 was downregulated (q < 0.1). The results of KEGG pathway analysis demonstrated an enrichment of pathways related to dopaminergic response, adrenergic signaling, protein degradation, and oocyte meiosis in arsenic-exposed animals. Moreover, 26 proteins were identified by phosphoproteomic with different phosphorylation pattern in animals from both groups, but SPATA18 was phosphorylated only in arsenic-exposed animals. We concluded that prepubertal exposure to arsenic is deleterious to sperm quality and male fertility, altering the sperm phosphoproteins profile.

Environmental pollution and diabetes mellitus

Diabetes mellitus (DM) is a chromic metabolic disease that affects a large segment of the population worldwide. Physical inactivity, poor nutrition, and genetic predisposition are main risk factors for disease development. In the last decade, it was clear to the scientific community that DM development is linked to a novel disease inducer that was later defined as diabetogenic factors of pollution and endocrine disrupting agents. Environmental pollution is exponentially increasing in uncontrolled manner in several countries. Environmental pollutants are of diverse nature and toxicities, including polyaromatic hydrocarbons (PAHs), pesticides, and heavy metals. In the current review, we shed light on the impact of each class of these pollutants and the underlined molecular mechanism of diabetes induction and biological toxicities. Finally, a brief overview about the connection between coronavirus disease 2019 and diabetes pandemics is presented.

Arsenic disrupts neuronal insulin signaling through increasing free PI3K-p85 and decreasing PI3K activity

Previously, we reported that prolonged arsenic exposure impaired neuronal insulin signaling. Here we have further identified novel molecular mechanisms underlying neuronal insulin signaling impairment by arsenic. Arsenic treatment altered insulin dose-response curve and reduced maximum insulin response in differentiated human neuroblastoma SH-SY5Y cells, suggesting that arsenic hindered neuronal insulin signaling in a non-competitive like manner. Mechanistically, arsenic suppressed insulin receptor (IR) kinase activity, as witnessed by a decreased insulin-activated autophosphorylation of IR at Y1150/1151. Arsenic decreased the level of insulin receptor substrate 1 (IRS1) but increased the protein ratio between PI3K regulatory subunit, p85, and PI3K catalytic subunit, p110. Interestingly, co-immunoprecipitation demonstrated that arsenic did not alter a level of PI3K-p110/PI3K-p85 complex while increased PI3K-p85 levels in a PI3K-p110 depletion supernatant resulted from PI3K-p110 immunoprecipitation. These results indicated that arsenic increased PI3K-p85 which was free from PI3K-p110 binding. In addition, arsenic significantly increased interaction between IRS1 and PI3K-p85 but not PI3K-p110, suggesting that there may be a fraction of free PI3K-p85 interacting with IRS1. In vitro PI3K activity demonstrated that arsenic lowered PI3K activity in both basal and insulin-stimulated conditions. These results suggested that the increase in free PI3K-p85 by arsenic might compete with PI3K heterodimer for the same IRS1 binding site, in turn blocking the activation of its catalytic subunit, PI3K-p110. Taken together, our results provide additional insights into mechanisms underlying the impairment of neuronal insulin signaling by arsenic through the reduction of IR autophosphorylation, the increase in free PI3K-p85, and the impeding of PI3K activity.

In utero exposure to phenanthrene induced islet cell dysfunction in adult mice: Sex differences in the effects and potential causes

Epidemiological studies show that the burden of polycyclic aromatic hydrocarbons in human body is associated with the occurrence of insulin resistance and diabetes. In the present study, pregnant mice were exposed to phenanthrene (Phe) at doses of 0, 60 and 600 μg/kg body weight of by gavage once every 3 days. The female F1 mice at 120 days of age showed no change in their fasting glucose levels (FGLs) but exhibited significantly decreased homeostasis model assessment (HOMA) β-cell (49% and 43%) and significantly downregulated pancreatic proinsulin gene (ins2) transcription. The downregulation of transcription factors, such as PDX1, PAX4 and FGF21, indicated impaired development and function of β-cells. The significantly reduced α-cell mass in 60 and 600 μg/kg groups, and the significantly downregulated expression of proglucagon gene gcg and ARX in the 600 μg/kg group suggested that the development and function of α-cells had been impacted. The males exhibited significantly increased FGLs (1.14- and 1.15-fold) in Phe exposed treatments and significantly elevated HOMA β-cell (3.15-fold) in the 600 μg/kg group. Upregulated ins2 transcription and FGF21 protein in male mice prenatally exposed to 600 μg/kg Phe suggested that these animals appeared compensatory enhancement in β-cell function. The reduced serum estradiol levels and downregulated pancreatic estrogen receptor α and β were responsible for the dysfunction of β-cells in the females. In the males, the significantly elevated androgen levels in the 600 μg/kg group might be related to the upregulated ins2 transcription, and the increased expression of pancreatic FGF21 further demonstrated the enhancement of β-cell potential. The results will be helpful for assessing the risk of developing diabetes in adulthood after prenatal exposure to phenanthrene.

Combined effects of arsenic and palmitic acid on oxidative stress and lipid metabolism disorder in human hepatoma HepG2 cells

The toxicity of arsenic (As) can be influenced by many nutrients in food. However, the combined effects and underlying mechanisms of As and palmitic acid (PA) are still unclear. Here, cell viability, oxidative stress, lipids accumulation, gene expression profiles, and metabolome profiles of human hepatoma HepG2 cells exposed to As, PA, and As + PA were analyzed and compared. Results showed that co-exposure of 100 μM PA and 2 μM As induced lower cell viability, higher intracellular reactive oxygen species level, more lipid droplet accumulation, and more intracellular triglyceride contents than As alone or PA alone exposure. High-throughput quantitative PCR and ¹H NMR-based metabolomics analysis showed that co-exposure of As and PA caused all toxic effects on gene expression and metabolome profiles induced by As alone or PA alone exposure, and showed higher toxicities. Gene expression profiles in the As + PA group had higher similarity with those in the As group than the PA group. However, PA played a more important role in metabolism disorder than As in their interactive effects. Oxidative stress and lipid metabolism disorder were found to be the main toxic effects in the As + PA group. Several differentially expressed genes (such as OXR1, OXSR1, INSR, and PPARA) and changed metabolites (such as pyruvate, acetate, and L-phenylalanine) were involved in the combined toxicity of As and PA. This study provides basic information on the interactive effects of As and PA, which is useful for the health risk assessment of As and FFA.

Diverse genetic backgrounds play a prominent role in the metabolic phenotype of CC021/Unc and CC027/GeniUNC mice exposed to inorganic arsenic

Arsenic methyltransferase (AS3MT) is the key enzyme in the pathway for the methylation of inorganic arsenic (iAs), a potent human carcinogen and diabetogen. AS3MT converts iAs to mono- and dimethylated arsenic species (MAs, DMAs) that are excreted mainly in urine. Polymorphisms in AS3MT is a key genetic factor affecting iAs metabolism and toxicity. The present study examined the role of As3mt polymorphisms in the susceptibility to the diabetogenic effects of iAs exposure using two Collaborative Cross mouse strains, CC021/Unc and CC027/GeniUnc, carrying different As3mt haplotypes. Male mice from the two strains were exposed to iAs in drinking water (0, 0.1 or 50 ppm) for 11 weeks. Blood glucose and plasma insulin levels were measured after 6-h fasting and 15 min after i.p. injection of glucose. Body composition was determined using magnetic resonance imaging. To asses iAs metabolism, the concentrations of iAs, MAs and DMAs were measured in urine. The results show that CC021 mice, both iAs-exposed and controls, had higher body fat percentage, lower fasting blood glucose, higher fasting plasma insulin, and were more insulin resistant than their CC027 counterparts. iAs exposure had a minor effect on diabetes indicators and only in CC027 mice. Blood glucose levels 15 min after glucose injection were significantly higher in CC027 mice exposed to 0.1 ppm iAs than in control mice. No significant differences were found in the concentrations or proportions of arsenic species in urine of CC021 and CC027 mice at the same exposure level. These results suggest that the differences in As3mt haplotypes did not affect the profiles of iAs or its metabolites in mouse urine. The major differences in diabetes indicators were associated with the genetic backgrounds of CC021 and CC027 mice. The effects of iAs exposure, while minor, were genotype- and dose-dependent.

Sex-dependent effects of preconception exposure to arsenite on gene transcription in parental germ cells and on transcriptomic profiles and diabetic phenotype of offspring

Chronic exposure to inorganic arsenic (iAs) has been linked to diabetic phenotypes in both humans and mice. However, diabetogenic effects of iAs exposure during specific developmental windows have never been systematically studied. We have previously shown that in mice, combined preconception and in utero exposures to iAs resulted in impaired glucose homeostasis in male offspring. The goal of the present study was to determine if preconception exposure alone can contribute to this outcome. We have examined metabolic phenotypes in male and female offspring from dams and sires that were exposed to iAs in drinking water (0 or 200 μg As/L) for 10 weeks prior to mating. The effects of iAs exposure on gene expression profiles in parental germ cells, and pancreatic islets and livers from offspring were assessed using RNA sequencing. We found that iAs exposure significantly altered transcript levels of genes, including diabetes-related genes, in the sperm of sires. Notably, some of the same gene transcripts and the associated pathways were also altered in the liver of the offspring. The exposure had a more subtle effect on gene expression in maternal oocytes and in pancreatic islets of the offspring. In female offspring, the preconception exposure was associated with increased adiposity, but lower blood glucose after fasting and after glucose challenge. HOMA-IR, the indicator of insulin resistance, was also lower. In contrast, the preconception exposure had no effects on blood glucose measures in male offspring. However, males from parents exposed to iAs had higher plasma insulin after glucose challenge and higher insulinogenic index than control offspring, indicating a greater requirement for insulin to maintain glucose homeostasis. Our results suggest that preconception exposure may contribute to the development of diabetic phenotype in male offspring, possibly mediated through germ cell-associated inheritance. Future research can investigate role of epigenetics in this phenomenon. The paradoxical outcomes in female offspring, suggesting a protective effect of the preconception exposure, warrant further investigation.

Arsenic exposure-related hyperglycemia is linked to insulin resistance with concomitant reduction of skeletal muscle mass

BACKGROUND

Alargebodyof evidence has shown a link between arsenic exposure and diabetes, but the underlying mechanisms have not yet been clarified.

OBJECTIVE

We explored the association between arsenic exposure and the reduction of skeletal muscle mass as a potential mechanism of insulin resistance for developing arsenic-related hyperglycemia.

METHODS

A total of 581 subjects were recruited from arsenic-endemic and non-endemic areas in Bangladesh and their fasting blood glucose (FBG), serum insulin, and serum creatinine levels were determined. Subjects' arsenic exposure levels were assessed by arsenic concentrations in water, hair, and nails. HOMA-IR and HOMA-β were used to calculate insulin resistance and β-cell dysfunction, respectively. Serum creatinine levels and lean body mass (LBM) were used as muscle mass indicators.

RESULTS

Water, hair and nail arsenic concentrations showed significant positive associations with FBG, serum insulin and HOMA-IR and inverse associations with serum creatinine and LBM in a dose-dependent manner both in males and females. Water, hair and nail arsenic showed significant inverse associations with HOMA-β in females but not in males. FBG and HOMA-IR were increased with the decreasing levels of serum creatinine and LBM. Odds ratios (ORs)of hyperglycemia were significantly increased with the increasing concentrations of arsenic in water, hair and nails and with the decreasing levels of serum creatinine and LBM. Females' HOMA-IR showed greater susceptibility to the reduction of serum creatinine and LBM, possibly causing the greater risk of hyperglycemia in females than males. Path analysis revealed the mediating effect of serum creatinine level on the relationship of arsenic exposure with HOMA-IR and hyperglycemia.

CONCLUSION

Arsenic exposure elevates FBG levels and the risk of hyperglycemia through increasing insulin resistance with greater susceptibility in females than males. Additionally, arsenic exposure-related reduction of skeletal muscle mass may be a mechanism underlying the development of insulin resistance and hyperglycemia.

Endocrine disruption and obesity: A current review on environmental obesogens

Obesity represents an important public health concern because it substantially increases the risk of multiple chronic diseases and thereby contributing to a decline in both quality of life and life expectancy. Besides unhealthy diet, physical inactivity and genetic susceptibility, environmental pollutants also contribute to the rising prevalence of obesity epidemic. An environmental obesogen is defined as a chemical that can alter lipid homeostasis to promote adipogenesis and lipid accumulation whereas an endocrine disrupting chemical (EDC) is defined as a synthetic chemical that can interfere with the endocrine function and cause adverse health effects. Many obesogens are EDCs that interfere with normal endocrine regulation of metabolism, adipose tissue development and maintenance, appetite, weight and energy balance. An expanding body of scientific evidence from animal and epidemiological studies has begun to provide links between exposure to EDCs and obesity. Despite the significance of environmental obesogens in the pathogenesis of metabolic diseases, the contribution of synthetic chemical exposure to obesity epidemic remains largely unrecognised. Hence, the purpose of this review is to provide a current update on the evidences from animal and human studies on the role of fourteen environmental obesogens in obesity, a comprehensive view of the mechanisms of action of these obesogens and current green and sustainable chemistry strategies to overcome chemical exposure to prevent obesity. Designing of safer version of obesogens through green chemistry approaches requires a collaborative undertaking to evaluate the toxicity of endocrine disruptors using appropriate experimental methods, which will help in developing a new generation of inherently safer chemicals.

•

Many environmental obesogens are endocrine disrupting chemicals that interfere with normal endocrine regulation of metabolism.

•

Understanding the role of environmental obesogens in the epidemics of obesity is in an infant stage.

•

Green chemistry approach aims to design a safer version of these chemicals by understanding their hazardous effects.

•

Further studies are necessary to fully establish the hazardous effects of obesogens and their association to human obesity.

Effect of low- and high-level groundwater arsenic on peripheral blood and lung function of exposed rural women

The World Health Organization (WHO) recommended maximum contaminant level (MCL) of arsenic (As) in drinking water at 10 μg/L. Many Asian countries still have their MCL for As at 50 μg/L. The current cross sectional study was conducted on asymptomatic females (without As related skin lesions) selected from rural areas of West Bengal, Baruipur and Dhamakhali [low As 11-50 μg/L; N,93]; Kamardanga & Sibhati [high As>50 μg/L; N,70] and Boria [Control; As<10 μg/L N,118] of West Bengal, India. The study was designed to compare the status of peripheral blood and lung function due to prolonged As exposure. The lung function parameters were considered according to Miller's prediction quadrant - FVC less than 80% indicated restrictive lung, FEV1/FVC less than 70% showed obstructive lung and both FVC and FEV1/FVC less than predicted percentage exhibited combined lung function decrement. The study showed that groundwater As concentration [22.5 ± 19.2 (low), 67.8 ± 26.9 (high) and 1.02 ± 2.3 μg/L (control)] was correlated with nail As content of the enrolled women. Linear regression depicted that nail As content influenced reduction of haemoglobin (β: 0.43; 95%CI: 0.02 to -0.006; p = 0.0001) and CD56⁺ NK cells (β: 0.53; 95%CI: 0.07 to -0.03; p = 0.0001) per 1 μg/g increase in As in nails. Multivariate logistic regression exhibited that nail As content was associated with reduction of lung function parameters [FEV1 (Exp B:1.04; 95%CI: 1.022 to 1.055; p = 0.0001) and FVC (Exp B:1.05; 95%CI: 1.03 to 1.07; p = 0.0001) per 1 μg/g increase in As in nails. Hence the study may be indicative of the fact that even in asymptomatic women, increase in chronic As exposure may weaken immune surveillance and provoke respiratory ailments.

Arsenic Exposure Decreases Adiposity During High-Fat Feeding

OBJECTIVE

Arsenic is an endocrine-disrupting chemical associated with diabetes risk. Increased adiposity is a significant risk factor for diabetes and its comorbidities. Here, the impact of chronic arsenic exposure on adiposity and metabolic health was assessed in mice.

METHODS

Male C57BL/6J mice were provided ad libitum access to a normal or high-fat diet and water +/- 50 mg/L of sodium arsenite. Changes in body weight, body composition, insulin sensitivity, energy expenditure, and locomotor activity were measured. Measures of adiposity were compared with accumulated arsenic in the liver.

RESULTS

Despite uniform arsenic exposure, internal arsenic levels varied significantly among arsenic-exposed mice. Hepatic arsenic levels in exposed mice negatively correlated with overall weight gain, individual adipose depot masses, and hepatic triglyceride accumulation. No effects were observed in mice on a normal diet. For mice on a high-fat diet, arsenic exposure reduced fasting insulin levels, homeostatic model assessment of insulin resistance and β-cell function, and systemic insulin resistance. Arsenic exposure did not alter energy expenditure or activity.

CONCLUSIONS

Collectively, these data indicate that arsenic is antiobesogenic and that concentration at the source poorly predicts arsenic accumulation and phenotypic outcomes. In future studies, investigators should consider internal accumulation of arsenic rather than source concentration when assessing the outcomes of arsenic exposure.

Environmental heavy metals and cardiovascular diseases: Status and future direction

Cardiovascular disease (CVD) and environmental degradation are leading global health problems of our time. Recent studies have linked exposure to heavy metals to the risks of CVD and diabetes, particularly in populations from low- and middle-income countries, where concomitant rapid development occurs. In this review, we 1) assessed the totality, quantity, and consistency of the available epidemiological studies, linking heavy metal exposures to the risk of CVD (including stroke and coronary heart disease); 2) discussed the potential biological mechanisms underlying some tantalizing observations in humans; and 3) identified gaps in our knowledge base that must be investigated in future work. An accumulating body of evidence from both experimental and observational studies implicates exposure to heavy metals, in a dose-response manner, in the increased risk of CVD. The limitations of most existing studies include insufficient statistical power, lack of comprehensive assessment of exposure, and cross-sectional design. Given the widespread exposure to heavy metals, an urgent need has emerged to investigate these putative associations of environmental exposures, either independently or jointly, with incident CVD outcomes prospectively in well-characterized cohorts of diverse populations, and to determine potential strategies to prevent and control the impacts of heavy metal exposure on the cardiometabolic health outcomes of individuals and populations.

Molecular Mechanisms of Arsenic-Induced Disruption of DNA Repair

Exposure to arsenic in contaminated drinking water is an emerging public health problem that impacts more than 200 million people worldwide. Accumulating lines of evidence from epidemiological studies revealed that chronic exposure to arsenic can result in various human diseases including cancer, type 2 diabetes, and neurodegenerative disorders. Arsenic is also classified as a Group I human carcinogen. In this review, we survey extensively different modes of action for arsenic-induced carcinogenesis, with focus being placed on arsenic-mediated impairment of DNA repair pathways. Inorganic arsenic can be bioactivated by methylation, and the ensuing products are highly genotoxic. Bioactivation of arsenicals also elicits the production of reactive oxygen and nitrogen species (ROS and RNS), which can directly damage DNA and modify cysteine residues in proteins. Results from recent studies suggest zinc finger proteins as crucial molecular targets for direct binding to As3+ or for modifications by arsenic-induced ROS/RNS, which may constitute a common mechanism underlying arsenic-induced perturbations of DNA repair.

Arsenic induces pancreatic dysfunction and ferroptosis via mitochondrial ROS-autophagy-lysosomal pathway

Chronic arsenic exposure is a significantly risk factor for pancreatic dysfunction and type 2 diabetes (T2D). Ferroptosis is a newly identified iron-dependent form of oxidative cell death that relies on lipid peroxidation. Previous data have indicated that ferroptosis is involved in various diseases, including cancers, neurodegenerative diseases, and T2D. However, the concrete effect and mechanism of ferroptosis on pancreatic dysfunction triggered by arsenic remains unknown. In this study, we verified that ferroptosis occurred in animal models of arsenic-induced pancreatic dysfunction through assessing proferroptotic markers and morphological changes in mitochondria. In vitro, arsenic caused execution of ferroptosis in a dose-dependent manner, which could be significantly reduced by ferrostatin-1. Additionally, arsenic damaged mitochondria manifested as diminishing of mitochondrial membrane potential, reduced cytochrome c level and production of mitochondrial reactive oxygen species (MtROS) in MIN6 cells. Using the Mito-TEMPO, we found the autophagy level and subsequent ferroptotic cell death induced by arsenic were both alleviated. With autophagy inhibitor chloroquine, we further revealed that ferritin regulated ferroptosis through the MtROS-autophagy pathway. Collectively, NaAsO₂-induced ferroptotic cell death is relied on the MtROS-dependent autophagy by regulating the iron homeostasis. Ferroptosis is involved in pancreatic dysfunction triggered by arsenic, and arsenic-induced ferroptosis involves MtROS, autophagy, ferritin.

A State-of-the-Science Review of Arsenic's Effects on Glucose Homeostasis in Experimental Models

BACKGROUND

The prevalence of type 2 diabetes (T2D) has more than doubled since 1980. Poor nutrition, sedentary lifestyle, and obesity are among the primary risk factors. While an estimated 70% of cases are attributed to excess adiposity, there is an increased interest in understanding the contribution of environmental agents to diabetes causation and severity. Arsenic is one of these environmental chemicals, with multiple epidemiology studies supporting its association with T2D. Despite extensive research, the molecular mechanism by which arsenic exerts its diabetogenic effects remains unclear.

OBJECTIVES

We conducted a literature search focused on arsenite exposure in vivo and in vitro, using relevant end points to elucidate potential mechanisms of oral arsenic exposure and diabetes development.

METHODS

We explored experimental results for potential mechanisms and elucidated the distinct effects that occur at high vs. low exposure. We also performed network analyses relying on publicly available data, which supported our key findings.

RESULTS

While several mechanisms may be involved, our findings support that arsenite has effects on whole-body glucose homeostasis, insulin-stimulated glucose uptake, glucose-stimulated insulin secretion, hepatic glucose metabolism, and both adipose and pancreatic β -cell dysfunction.

DISCUSSION

This review applies state-of-the-science approaches to identify the current knowledge gaps in our understanding of arsenite on diabetes development. https://doi.org/10.1289/EHP4517.

Arsenic is more potent than cadmium or manganese in disrupting the INS-1 beta cell microRNA landscape

Diabetes is a metabolic disorder characterized by fasting hyperglycemia and impaired glucose tolerance. Laboratory and population studies have shown that inorganic arsenic (iAs) can impair these pathways. Other metals including cadmium (Cd) and manganese (Mn) have also been linked to diabetes phenotypes. MicroRNAs, short non-coding RNAs that regulate gene expression, have emerged as potential drivers of metabolic dysfunction. MicroRNAs responsive to metal exposures in vitro have also been reported in independent studies to regulate insulin secretion in vivo. We hypothesize that microRNA dysregulation may associate with and possibly contribute to insulin secretion impairment upon exposure to iAs, Cd, or Mn. We exposed insulin secreting rat insulinoma cells to non-cytotoxic concentrations of iAs (1 µM), Cd (5 µM), and Mn (25 µM) for 24 h followed by small RNA sequencing to identify dysregulated microRNAs. RNA sequencing was then performed to further investigate changes in gene expression caused by iAs exposure. While all three metals significantly inhibited glucose-stimulated insulin secretion, high-throughput sequencing revealed distinct microRNA profiles specific to each exposure. One of the most significantly upregulated microRNAs post-iAs treatment is miR-146a (~ + 2-fold), which is known to be activated by nuclear factor κB (NF-κB) signaling. Accordingly, we found by RNA-seq analysis that genes upregulated by iAs exposure are enriched in the NF-κB signaling pathway and genes down-regulated by iAs exposure are enriched in miR-146a binding sites and are involved in regulating beta cell function. Notably, iAs exposure caused a significant decrease in the expression of Camk2a, a calcium-dependent protein kinase that regulates insulin secretion, has been implicated in type 2 diabetes, and is a likely target of miR-146a. Further studies are needed to elucidate potential interactions among NF-kB, miR-146a, and Camk2a in the context of iAs exposure.

Zinc deficiency alters the susceptibility of pancreatic beta cells (INS-1) to arsenic exposure

Pancreatic beta cells produce and release insulin, a hormone that regulates blood glucose levels, and their dysfunction contributes to the development of diabetes mellitus. Zinc deficiency and inorganic arsenic exposure both independently associate with the development of diabetes, although the effects of their combination on pancreatic beta cell health and function remain unknown. We hypothesized zinc deficiency increases the toxicity associated with arsenic exposure, causing an increased susceptibility to DNA damage and disruption of insulin production. Zinc deficiency decreased cell proliferation by 30% in pancreatic INS-1 rat insulinoma cells. Arsenic exposure (0, 50 or 500 ppb exposures) significantly decreased cell proliferation, and increased mRNA levels of genes involved in stress response (Mt1, Mt2, Hmox1) and DNA damage (p53, Ogg1). When co-exposed to both zinc deficiency and arsenic, zinc deficiency attenuated this response to arsenic, decreasing the expression of Mt1, Hmox1, and Ogg1, and significantly increasing DNA double-strand breaks 2.9-fold. Arsenic exposure decreased insulin expression, but co-exposure did not decrease insulin levels beyond the arsenic alone condition, but did result in a further 33% decline in cell proliferation at the 500 ppb arsenic dose, and a significant increase in beta cell apoptosis. These results suggest zinc deficiency and arsenic, both independently and in combination, adversely affect pancreatic beta cell health and both factors should be considered in the evaluation of health outcomes for susceptible populations.

Biochemical investigation of association of arsenic exposure with risk factors of diabetes mellitus in Pakistani population and its validation in animal model

Arsenic is one of the naturally occurring heavy metal that has been reported to cause damaging effects on different body organs. This study was aimed to determine the arsenic level in different water sources and investigate the effect of arsenic exposure on risk factors of diabetes mellitus (DM) in human participants and experimental animals. We recruited 150 participants to investigate the arsenic exposure in their urine and from drinking water. We found that males contained significantly higher (P < 0.001) concentrations of urinary arsenic as compared with that of their female counterparts. Similarly, urinary arsenic concentration was high and showed significant association in the age of ≥ 60 years (P < 0.05), illiterate (P < 0.001), smokers (P < 0.0001), and diabetic (P < 0.0001) participants. Moreover, urinary arsenic exposure was also associated with higher levels of fasting (P < 0.001) and random blood glucose (P < 0.001), HbA1c (P < 0.001), AST, ALT, MDA, IL-6, CRP, blood urea nitrogen, and creatinine in arsenic-exposed diabetics as compared with that of unexposed diabetics. Further, we also exposed the white albino rats with arsenic in drinking water for 30 days and their blood glucose was measured at 15th and 30th days of treatment that was significantly higher (P < 0.001) in arsenic-exposed animals as compared with that of unexposed animals. Similarly, arsenic-exposed animals failed to tolerate exogenously administered glucose (P < 0.001) as compared with that of unexposed animals. Likewise, insulin and glutathione concentrations were also significantly decreased (P < 0.001) in arsenic-exposed animals as compared with that of unexposed animals. The alterations in normal values of glucose, insulin, and glutathione exhibited the damaging effects of arsenic exposure in experimental rats. This study showed that arsenic exposed to human beings and animals through drinking water resulted in the disruption of pancreatic β-cell functioning that provoked the risk factor for development of DM. This study also suggested that long-term arsenic exposure induces hyperglycemia, inflammation, and oxidative stress that may lead to the onset of development of DM.

Non-monotonic dose-response effects of arsenic on glucose metabolism

BACKGROUND

Inorganic arsenic (iAs) is a widespread environmental toxin. In addition to being a human carcinogen, its effect on diabetes has started to gain recognition recently. Insulin is the key hormone regulating systemic glucose metabolism. The in vivo effect of iAs on insulin sensitivity has not been directly addressed.

OBJECTIVES

Here we use mouse models to dissect the dose-dependent effects of iAs on glucose metabolism in vivo.

METHODS

We performed hyperinsulinemic-euglycemic clamp, the gold standard analysis of systemic insulin sensitivity. We also performed dynamic metabolic testings and RNA-seq analysis.

RESULTS

We found that a low-dose exposure (0.25 ppm iAs in drinking water) caused glucose intolerance in adult male C57BL/6 mice, likely by disrupting glucose-induced insulin secretion without affecting peripheral insulin sensitivity. However, a higher-dose exposure (2.5 ppm iAs) had diminished effects on glucose tolerance despite disrupted pancreatic insulin secretion. Insulin Clamp analysis showed that 2.5 ppm iAs actually enhanced systemic insulin sensitivity by simultaneously enhancing insulin-stimulated glucose uptake in skeletal muscles and improved insulin-mediated suppression of endogenous glucose production. RNA-seq analysis of skeletal muscles revealed that 2.5 ppm iAs regulated expression of many genes involved in the metabolism of fatty acids, pyruvate, and amino acids.

CONCLUSION

These findings suggest that iAs has opposite glycemic effects on distinct metabolic tissues at different dose thresholds. Such non-monotonic dose-response effects of iAs on glucose tolerance shed light on the complex interactions between iAs and the systemic glucose metabolism, which could potentially help reconcile some of the conflicting results in human epidemiological studies.

Arsenic exposure intensifies glycogen nephrosis in diabetic rats

It is known that either arsenic exposure or diabetes can impact renal function. However, it is unclear how these combined factors may influence kidney functions. Therefore, we evaluated morphological, functional, and oxidative parameters in the kidney of diabetic rats exposed to arsenic. Healthy male Wistar rats and streptozotocin-induced diabetic rats were exposed to 0 and 10 mg/L arsenate through drinking water for 40 days. Renal tissue was assessed using morphometry, mitosis and apoptosis markers, mineral proportion, oxidative stress markers, as well as the activity of antioxidant enzymes and membrane-bound adenosine triphosphatases. Arsenate intake altered glucose levels in healthy animals, but it did not reach hyperglycemic conditions. In diabetic animals, arsenate led to a remarkable increase of glycogen nephrosis in distal tubules. In these animals, additionally, the activity of catalase and glutathione S-transferase, besides the proportion of Fe, Cu, and K in renal tissue, was altered. Nevertheless, arsenate did not accumulate in the kidney and did not impact on other parameters previously altered by diabetes, including levels of malondialdehyde, Na, urea, creatinine, and apoptosis and mitosis markers. In conclusion, besides the intensification of glycogen nephrosis, the kidney was able to handle arsenate toxicity at this point, preventing arsenic deposition in the exposed groups and the impairment of renal function.

Role of cadmium and arsenic as endocrine disruptors in the metabolism of carbohydrates: Inserting the association into perspectives

Endocrine disrupting chemicals (EDCs) have widespread environmental distribution originated from both natural and anthropogenic sources. From the last few decades, their contamination has been raised dramatically owing to continuous discharge in sewage and untreated industrial effluents. They have rapidly gained a considerable attention due to their critical role in the development of multiple endocrine-related disorders notably diabetes mellitus (DM). Cadmium and arsenic, among the most hazardous EDCs, are not only widely spread in our environment, but they are also found to be associated with wide range of health hazards. After entering into the human body, they are preferably accumulated in the liver, kidney and pancreas where they exhibit deleterious effects on carbohydrate metabolism pathways notably glycolysis, glucogenesis and gluconeogenesis through the modification and impairment of relevant key enzymes activity. Impairment of hepatic glucose homeostasis plays a crucial role in the pathogenesis of DM. Along with compromised function of pancreas and muscles, diminished liver and kidney functions also contribute considerably to increase the blood glucose level. These metals have potential to bring conformational changes in these enzymes and make them inactive. Additionally, these metals also disturb the hormonal balance, such as insulin, glucocorticoids and catecholamines; by damaging pancreas and adrenal gland, respectively. Moreover, these metals also enhance the production of reactive oxygen species and depress the anti-oxidative defense mechanism with subsequent disruption of multiple organs. In this article, we have briefly highlighted the impact of arsenic and cadmium on the metabolism of carbohydrates and the enzymes that are involved in carbohydrate metabolism and glucose homeostasis.