Mercury and metabolic syndrome: a review of experimental and clinical observations

Exposure to a contaminated environment and its relationship with human health: Mercury effect on loss of functionality and increased oxidative stress of blood cells

Recent findings indicate elevated levels of total Hg in the waters of the Lagoa Mundaú-Manguaba Estuarine Complex (CELMM, Maceió-AL, Brazil) and the biological fluids of fishermen that live near CELMM. This study assessed Hg levels in whole blood and the functionality, structure, morphology, and oxidative stress of blood cells from fishermen (n = 60) compared with control volunteers (n = 65). A systematic assessment was performed, and our results revealed increased Hg concentration in fishermen's blood. Erythrocyte functionality showed a 39 % decrease in O2 uptake. For peripheral blood mononuclear cells (PBMCs), ROS generation demonstrated an 87 and 116 % increase in O2•- and H2O2 production, respectively, confirmed by fluorescence microscopy. Scanning electron microscopy showed increased roughness in the PBMCs membrane. Secondary oxidative stress markers revealed a reduction in the GSH/GSSG ratio and thiol content. MDA production increased by 89 %, while antioxidant enzyme activities showed a 159 and 22 % increase in SOD and CAT, respectively; otherwise, a depletion of 33 % in GPx. The metabolomic profile exhibited changes in essential amino acids for GSH formation, and energy pathways were modified. Finally, our data indicates that exposure to a polluted environment alters redox status, leading to compromised function and structure of blood cells.

Association of heavy metals and bio-elements blood level with metabolic syndrome: a systematic review and meta-analysis of observational studies

Background and objectives

The literature has reported heavy metals might alter the physiological and biochemical functions of body organs and cause several health problems. So, the present systematic review and meta-analysis aimed to investigate the association of blood levels of essential or non-essential metals with metabolic syndrome (MetS).

Methods

In this systematic review, some international databases including PubMed, Embase, Scopus, and Web of Science were searched up to February 2024. All observational studies which assessed the association of three heavy metals (cadmium, mercury, lead) and bio-elements (chromium, iron, manganese, and magnesium, copper) with the risk of MetS were included. There was no limitation in the time of publication and language. A random-effects meta-analysis was performed to estimate the pooled effect sizes. Possible sources of heterogeneity were explored by meta-regression analysis.

Results

Totally, 29 studies were eligible for meta-analysis. Our results showed that increased level of cadmium (pooled OR: 1.24, 95% CI: 1.05, 1.46) and mercury (pooled OR: 1.22, 95% CI: 1.08, 1.38) significantly increased the risk of MetS. In contrast, increased level of chromium significantly reduced the risk of developing MetS (pooled OR: 0.68, 95% CI: 0.56, 0.83). Moreover, association between lead, iron, copper, magnesium, and manganese with MetS was not statistically significant (P > 0.05). However, elevated lead levels in men increased the odds of MetS.

Conclusion

Our results show a significant association between blood levels of some heavy metals, including cadmium, mercury, and lead, with increased odds of MetS. On the other hand, chromium as a biometal decreased the odds of MetS.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01500-9.

The Association Between Blood Mercury and Lipid Biomarkers in US Hypertensive Adults

Mercury (Hg) is detrimental to human health, but its impact on lipid biomarkers remains a subject of controversy. This study sought to delineate a clear link between blood Hg and lipid biomarkers correlated with cardiovascular disease (CVD), including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG), in hypertensive adults in the USA.

METHODS

This cross-sectional research gathered data from a total of 4415 participants sourced from the National Health and Nutrition Examination Survey (NHANES). The Holm-Bonferroni stepdown procedure was utilized to control the type I error rate in multiple comparisons. We employed multivariable linear regression models to assess the correlation between blood Hg and lipid biomarkers. Subsequently, subgroup analyses were conducted, categorized by both gender and race. Additionally, we used smooth curve fittings and generalized additive models to confirm the presence of non-linear relationships. When non-linearity was detected, we applied a recursive algorithm to calculate the inflection points. Finally, we established a weighted two-piecewise linear regression model to illustrate the associations on either side of the inflection point.

RESULTS

In our multivariable linear regression models, clear associations emerged. Specifically, positive correlations were observed between blood mercury and TC (β = 0.025; 95% CI 0.009 to 0.041; corrected P = 0.011), LDL-C (β = 0.022; 95% CI 0.007 to 0.036; corrected P = 0.012), and HDL-C (β = 0.007; 95% CI 0.001 to 0.013; corrected P = 0.058). However, there was no significant correlation with TG (β =  - 0.007; 95% CI - 0.018 to 0.004; corrected P = 0.526). Notably, it has been demonstrated that distinct inverted U-shaped and U-shaped curves exist when stratified by gender in our analysis.

CONCLUSIONS

Blood Hg exhibited a positive correlation with TC, LDL-C, and HDL-C in hypertensive adults in the USA. Nonetheless, no significant association was observed with TG.

Investigation of the impact of exposure to trace elements on health and disease from the ToxiLaus study

The ToxiLaus study aims at evaluating the impact of environmental toxic species on health and diseases' onset and development. Specifically, the ubiquitous presence of trace elements (TEs) in the environment urges for a better characterization of their influence on human organism. In its primary phase, the ToxiLaus study focused on measuring the urinary concentrations of 23 TEs in the baseline samples from the CoLaus|PsyCoLaus population-based cohort, using inductively coupled plasma mass spectrometry (ICP-MS). Statistical analyses were carried out on 5866 participants, investigating links between TEs concentrations and smoking status, metabolic syndrome and body mass index (BMI). Smoking status was associated with Cd, Zn, Pb, Mo and Hg (respectively OR = 3.64, 1.42, 1.20, 0.69 and 0.58) while metabolic syndrome was associated with Zn and Cd (OR = 1.81 and 1.24 respectively). Concentrations of Zn, Hg, Co, Ni, Cu, Mo, As, Sn, Tl, Fe where significantly different (p < 0.0001) between BMI groups (Normal, Overweight, Obese). Finally, this study provides an overview of the distribution of trace elements in a cohort large sample of the general population, as well as their main associations with cardiovascular risk factors. Theses relations will be further analysed in subsequent phases of the study.

Mercury-induced toxicity: Mechanisms, molecular pathways, and gene regulation

Mercury is a well-known neurotoxicant for humans and wildlife. The epidemic of mercury poisoning in Japan has clearly demonstrated that chronic exposure to methylmercury (MeHg) results in serious neurological damage to the cerebral and cerebellar cortex, leading to the dysfunction of the central nervous system (CNS), especially in infants exposed to MeHg in utero. The occurrences of poisoning have caused a wide public concern regarding the health risk emanating from MeHg exposure; particularly those eating large amounts of fish may experience the low-level and long-term exposure. There is growing evidence that MeHg at environmentally relevant concentrations can affect the health of biota in the ecosystem. Although extensive in vivo and in vitro studies have demonstrated that the disruption of redox homeostasis and microtube assembly is mainly responsible for mercurial toxicity leading to adverse health outcomes, it is still unclear whether we could quantitively determine the occurrence of interaction between mercurial and thiols and/or selenols groups of proteins linked directly to outcomes, especially at very low levels of exposure. Furthermore, intracellular calcium homeostasis, cytoskeleton, mitochondrial function, oxidative stress, neurotransmitter release, and DNA methylation may be the targets of mercury compounds; however, the primary targets associated with the adverse outcomes remain to be elucidated. Considering these knowledge gaps, in this article, we conducted a comprehensive review of mercurial toxicity, focusing mainly on the mechanism, and genes/proteins expression. We speculated that comprehensive analyses of transcriptomics, proteomics, and metabolomics could enhance interpretation of "omics" profiles, which may reveal specific biomarkers obviously correlated with specific pathways that mediate selective neurotoxicity.

The association between heavy metal exposure and obesity: A systematic review and meta-analysis

Background

Obesity and metabolic syndrome are global health concerns associated with development of different types of diseases and serious health threats in the long term. Their metabolic imbalance can be attributable to inherited and environmental factors. As a considerable environmental agent, heavy metals exposure can predispose individuals to diseases like obesity. This systematic review and meta-analysis aimed to evaluate the association between heavy metals exposure and the risk of obesity.

Methods

PubMed/MEDLINE, EMBASE and Web of Science were systematically searched until December 17, 2022. Only observational studies that evaluated heavy metals exposure and obesity were included. Studies were excluded if they assessed maternal or prenatal exposure, the mixture of heavy metals and other chemicals, reported the association with overweight or other diseases, and undesirable study designs. The Joanna Briggs Institute checklist was used for quality assessment. The pooled adjusted odds ratio (aOR) and the pooled standardized mean difference (SMD) with their 95% confidence intervals (CIs) were calculated, respectively. The publication bias was evaluated using Egger's and Begg's tests.

Results

Twenty studies (n = 127755), four case-control and sixteen analytical cross-sectional studies, were included. Lead exposure was significantly associated with a lower risk of obesity (aOR: 0.705, 95% CI: 0.498-0.997), while mercury (aOR: 1.458, 95% CI: 1.048-2.031) and barium (aOR: 1.439, 95% CI: 1.142-1.813) exposure increased the risk of obesity. No significant publication bias was found and the studies had a low risk of bias.

Conclusion

Overall, lead exposure reduced obesity risk, while mercury and barium exposure raised it. Further large-scale observational studies are recommended to determine the roles of heavy metals in obesity.Study registration ID: CRD42023394865.

Supplementary information

The online version contains supplementary material available at 10.1007/s40200-023-01307-0.

Prenatal Exposure to Chemical Mixtures and Metabolic Syndrome Risk in Children

Importance

Prenatal exposure to ubiquitous endocrine-disrupting chemicals (EDCs) may increase the risk of metabolic syndrome (MetS) in children, but few studies have studied chemical mixtures or explored underlying protein and metabolic signatures.

Objective

To investigate associations of prenatal exposure to EDC mixtures with MetS risk score in children and identify associated proteins and metabolites.

Design, Setting, and Participants

This population-based, birth cohort study used data collected between April 1, 2003, and February 26, 2016, from the Human Early Life Exposome cohort based in France, Greece, Lithuania, Norway, Spain, and the UK. Eligible participants included mother-child pairs with measured prenatal EDC exposures and complete data on childhood MetS risk factors, proteins, and metabolites. Data were analyzed between October 2022 and July 2023.

Exposures

Nine metals, 3 organochlorine pesticides, 5 polychlorinated biphenyls, 2 polybrominated diphenyl ethers (PBDEs), 5 perfluoroalkyl substances (PFAS), 10 phthalate metabolites, 3 phenols, 4 parabens, and 4 organophosphate pesticide metabolites measured in urine and blood samples collected during pregnancy.

Main Outcomes and Measures

At 6 to 11 years of age, a composite MetS risk score was constructed using z scores of waist circumference, systolic and diastolic blood pressures, triglycerides, high-density lipoprotein cholesterol, and insulin levels. Childhood levels of 44 urinary metabolites, 177 serum metabolites, and 35 plasma proteins were quantified using targeted methods. Associations were assessed using bayesian weighted quantile sum regressions applied to mixtures for each chemical group.

Results

The study included 1134 mothers (mean [SD] age at birth, 30.7 [4.9] years) and their children (mean [SD] age, 7.8 [1.5] years; 617 male children [54.4%] and 517 female children [45.6%]; mean [SD] MetS risk score, -0.1 [2.3]). MetS score increased per 1-quartile increase of the mixture for metals (β = 0.44; 95% credible interval [CrI], 0.30 to 0.59), organochlorine pesticides (β = 0.22; 95% CrI, 0.15 to 0.29), PBDEs (β = 0.17; 95% CrI, 0.06 to 0.27), and PFAS (β = 0.19; 95% CrI, 0.14 to 0.24). High-molecular weight phthalate mixtures (β = -0.07; 95% CrI, -0.10 to -0.04) and low-molecular weight phthalate mixtures (β = -0.13; 95% CrI, -0.18 to -0.08) were associated with a decreased MetS score. Most EDC mixtures were associated with elevated proinflammatory proteins, amino acids, and altered glycerophospholipids, which in turn were associated with increased MetS score.

Conclusions and Relevance

This cohort study suggests that prenatal exposure to EDC mixtures may be associated with adverse metabolic health in children. Given the pervasive nature of EDCs and the increase in MetS, these findings hold substantial public health implications.

A rapid and specific fluorescent probe based on aggregation-induced emission enhancement for mercury ion detection in living systems

Mercury is a harmful heavy metal that seriously threatens the environment and organisms. In this study, we combined the aggregation-induced emission mechanism and the advantages of peptides to design a novel tetraphenylene (TPE)-based peptide fluorescent probe, TPE-Cys-Pro-Gly-His (TPE-CPGH), in which the sulfhydryl group of Cys in the peptide chain and the imidazolium nitrogen provided by His were used to mimic the Hg2+ binding site of metalloproteins. The β-fold formed by Pro-Gly was used to promote the spatial coordination of the probe with Hg2+ and the formation of the coordination complex aggregates, these changes led to the "turn on" response to Hg2+. The detection of Hg2+ by TPE-CPGH not only showed high specificity and sensitivity (LOD=46.2 nM), but also had the advantages of fast response and applicability for detection over a wide pH range. Additionally, TPE-CPGH effectively detected Hg2+ in environmental samples, living cells and organisms due to its low cytotoxicity, high water solubility and cell membrane permeability. More interestingly, TPE-CPGH was also mitigated Hg2+ exposure-induced oxidative stress toxicity in vitro and in vivo.

Chronic exposure to mercury increases arrhythmia and mortality post-acute myocardial infarction in rats

Introduction: Mercury (Hg) is a heavy metal that causes a variety of toxic effects in eukaryotic cells. Previous studies have reported detrimental effects of mercury toxicity in the cardiovascular system. Given the importance of understanding the relationship between Hg and cardiovascular disease, we sought to investigate if the Hg could worsen the myocardial repercussions following ischemic injury. We demonstrated that once mercury toxicity is established, it can influence the outcome of myocardial infarction (MI). Methods: Male Wistar rats received intramuscular injections of either saline (NaCl 0.9%) or mercuric chloride (HgCl2, first dose of 4.6 μg/kg, and subsequent doses of 0.07 μg/kg/day) for 4 weeks. Three weeks post-exposure, we induced transmural infarction in the left ventricle free wall through coronary artery occlusion surgery. Results: ECG recordings obtained from MI groups demonstrated alterations in the rhythm of the heartbeat/heart electrical activity, as expected, including ventricular extrasystoles and ventricular tachycardia. However, the MI group exposed to Hg (MI-Hg) exhibited augmented ventricular extrasystoles and ventricular tachycardia compared to the MI group. Also, Basckó coefficient revealed that the arrhythmic events-after MI-were aggravated by Hg exposure. Discussion: Our results indicate that the significantly increased mortality in MI-Hg groups when compared to MI (21%, MI vs 32%, MI-Hg) is correlated with greater occurrence of arrhythmias. In conclusion, this study further supports the idea that exposure to mercury (Hg) should be recognized as a significant risk factor that exacerbates the impact of cardiac ischemic injury, potentially leading to an increased mortality rate among patients experiencing acute MI.

Trimester-specific associations of maternal dietary patterns with preterm birth: China Medical University birth cohort study

The trimester-specific associations of maternal dietary patterns with preterm birth (PTB) are unclear. In a prospective prebirth cohort study, we aimed to examine the critical time window of maternal prenatal dietary patterns and the risk of PTB. We assessed prenatal dietary intake among 1500 pregnant women with validated food frequency questionnaires during the 1st, 2nd and 3rd trimester, respectively. We used logistic regression models and generalized estimating equation models to examine the trimester-specific associations and longitudinal associations between maternal dietary patterns in relation to risk of PTB and PTB subtypes. The incidence rate of PTB was 11.9% (179 out of 1500 pregnant women) in the present study. We observed that maternal adherence to a fish-seafood pattern in the 1st trimester was associated with higher risk of PTB [tertile 3 (T3) vs. tertile 1 (T1): OR = 2.29, 95% CI: 1.32-3.96] and iatrogenic preterm birth (IPTB) (T3 vs. T1: OR = 2.26, 95% CI: 1.21-4.20), while a fish-seafood pattern in the 2nd trimester was associated with lower risk of PTB (T3 vs. T1: OR = 0.49, 95% CI: 0.25-0.93). Maternal adherence to a dairy-egg pattern in the 2nd or 3rd trimester was associated with higher risks of PTB and IPTB. No dietary patterns were associated with spontaneous preterm birth. Our findings provide new evidence that specific dietary patterns during different trimesters may have different and even inverse health effects on pregnant women. This supports the necessity of guiding the maternal diet according to different periods of pregnancy to prevent PTB.

Interaction of mercury species with proteins: towards possible mechanism of mercurial toxicology

The nature of the binding of mercurials (organic and inorganic) and their subsequent transformations in biological systems is a matter of great debate as several different hypotheses have been proposed and none of them has been conclusively proven to explain the characteristics of Hg binding with the proteins. Thus, the chemical nature of Hg-protein binding through the possible transportation mechanism in living tissues is critically reviewed herein. Emphasis is given to the process of transportation, and binding of Hg species with selenol-containing biomolecules that are appealing for toxicological studies as well as the advancement of environmental and biological research.

Disease-associated metabolic pathways affected by heavy metals and metalloid

Increased exposure to environmental heavy metals and metalloids and their associated toxicities has become a major threat to human health. Hence, the association of these metals and metalloids with chronic, age-related metabolic disorders has gained much interest. The underlying molecular mechanisms that mediate these effects are often complex and incompletely understood. In this review, we summarize the currently known disease-associated metabolic and signaling pathways that are altered following different heavy metals and metalloids exposure, alongside a brief summary of the mechanisms of their impacts. The main focus of this study is to explore how these affected pathways are associated with chronic multifactorial diseases including diabetes, cardiovascular diseases, cancer, neurodegeneration, inflammation, and allergic responses upon exposure to arsenic (As), cadmium (Cd), chromium (Cr), iron (Fe), mercury (Hg), nickel (Ni), and vanadium (V). Although there is considerable overlap among the different heavy metals and metalloids-affected cellular pathways, these affect distinct metabolic pathways as well. The common pathways may be explored further to find common targets for treatment of the associated pathologic conditions.

Methylmercury effects on avian brains

Methylmercury (MeHg) is a concerning contaminant due to its ubiquity and harmful effects on organisms. Although birds are important models in the neurobiology of vocal learning and adult neuroplasticity, the neurotoxic effects of MeHg are less understood in birds than mammals. We surveyed the literature on MeHg effects on biochemical changes in the avian brain. Publication rates of papers related to neurology and/or birds and/or MeHg increased with time and can be linked with historical events, regulations, and increased understanding of MeHg cycling in the environment. However, publications on MeHg effects on the avian brain remain relatively low across time. The neural effects measured to evaluate MeHg neurotoxicity in birds changed with time and researcher interest. The measures most consistently affected by MeHg exposure in birds were markers of oxidative stress. NMDA, acetylcholinesterase, and Purkinje cells also seem sensitive to some extent. MeHg exposure has the potential to affect most neurotransmitter systems but more studies are needed for validation in birds. We also review the main mechanisms of MeHg-induced neurotoxicity in mammals and compare it to what is known in birds. The literature on MeHg effects on the avian brain is limited, preventing full construction of an adverse outcome pathway. We identify research gaps for taxonomic groups such as songbirds, and age- and life-stage groups such as immature fledgling stage and adult non-reproductive life stage. In addition, results are often inconsistent between experimental and field studies. We conclude that future neurotoxicological studies of MeHg impacts on birds need to better connect the numerous aspects of exposure from molecular physiological effects to behavioural outcomes that would be ecologically or biologically relevant for birds, especially under challenging conditions.

Association Between Serum Trace Heavy Metals and Liver Function Among Adolescents

BACKGROUND

Exposure to metals has been associated with liver-related disease. Few studies have explored the effect of sex stratification on adolescent liver function.

METHOD

From the National Health and Nutrition Examination Survey (2011-2016), 1143 subjects aged 12-19 years were selected for analysis. The outcome variables were the levels of alanine aminotransferase (ALT), aspartate aminotransferase, and gamma-glutamyl transpeptidase.

RESULTS

The results showed a positive association between serum zinc and ALT in boys (odds ratio [OR], 2.37; 95% confidence interval [CI], 1.11-5.06). Serum mercury was associated with an increase in ALT level in girls (OR, 2.73; 95% CI, 1.14-6.57). Mechanistically, the efficacy mediated by total cholesterol accounted for 24.38% and 6.19% of the association between serum zinc and ALT.

CONCLUSIONS

The results imply that serum heavy metals were associated with the risk of liver injury, possibly mediated by serum cholesterol, in adolescents.

Associations of Prenatal First Trimester Essential and Nonessential Metal Mixtures with Body Size and Adiposity in Childhood

BACKGROUND

Prenatal nonessential metals may contribute to postnatal adiposity, whereas essential metals may have metabolic benefits. We evaluated joint and individual associations between prenatal metals and childhood adiposity.

METHODS

We measured concentrations of six nonessential (arsenic, barium, cadmium, cesium, lead, and mercury) and four essential (magnesium, manganese, selenium, and zinc) metals in first trimester maternal blood from a prebirth cohort. We collected anthropometric measures in early childhood, mid-childhood, and early adolescence including subscapular+tricep skinfold thickness (mm) (N = 715-859), waist circumference (cm) (N = 717-882), and body mass index (BMI) (z-score) (N = 716-875). We measured adiposity in mid-childhood and early adolescence using bone densitometry total- and trunk- fat mass index (kg/m 2 ) (N = 511-599). We estimated associations using adjusted quantile g-computation and linear regression.

RESULTS

The nonessential metal mixture was associated with higher total (β = 0.07, 95% CI = 0.01, 0.12) and trunk fat mass index (β = 0.12, CI = 0.02, 0.22), waist circumference (β = 0.01, CI = 0.00, 0.01), and BMI (β = 0.24, CI = 0.07, 0.41) in mid-childhood, and total fat mass index (β = 0.07, CI = 0.01, 0.14), and BMI (β = 0.19, CI = 0.02, 0.37) in early adolescence. The essential metal mixture was associated with lower early adolescence total-(β = -0.11, CI = -0.17, -0.04) and trunk- fat mass index (β = -0.13, CI = -0.21, -0.05), subscapular+tricep skinfold thickness (β = -0.02, CI = -0.03, -0.00), waist circumference (β = -0.003, CI = -0.01, -0.00), and BMI (β = -0.16, CI = -0.28, -0.04). Cadmium and cesium were individually associated with childhood adiposity at different timepoints.

CONCLUSIONS

Prenatal first-trimester essential metals were associated with lower childhood adiposity, whereas nonessential metals were associated with higher adiposity into adolescence.

Associations of metal mixtures with metabolic-associated fatty liver disease and non-alcoholic fatty liver disease: NHANES 2003-2018

Objective

The hepatotoxicity of exposure to a single heavy metal has been examined in previous studies. However, there is limited evidence on the association between heavy metals mixture and non-alcoholic fatty liver disease (NAFLD) and metabolic-associated fatty liver disease (MAFLD). This study aims to investigate the associations of 13 urinary metals, individually and jointly, with NAFLD, MAFLD, and MAFLD components.

Methods

This study included 5,548 adults from the National Health and Nutrition Examination Survey (NHANES) 2003-2018. Binary logistic regression was used to explore the associations between individual metal exposures and MAFLD, NAFLD, and MAFLD components. Bayesian kernel machine regression (BKMR) and Quantile-based g-computation (QGC) were used to investigate the association of metal mixture exposure with these outcomes.

Results

In single metal analysis, increased levels of arsenic [OR 1.09 (95%CI 1.03-1.16)], dimethylarsinic acid [1.17 (95%CI 1.07-1.27)], barium [1.22 (95%CI 1.14-1.30)], cobalt [1.22 (95%CI 1.11-1.34)], cesium [1.35 (95%CI 1.18-1.54)], molybdenum [1.45 (95%CI 1.30-1.62)], antimony [1.18 (95%CI 1.08-1.29)], thallium [1.49 (95%CI 1.33-1.67)], and tungsten [1.23 (95%CI 1.15-1.32)] were significantly associated with MAFLD risk after adjusting for potential covariates. The results for NAFLD were similar to those for MAFLD, except for arsenic, which was insignificantly associated with NAFLD. In mixture analysis, the overall metal mixture was positively associated with MAFLD, NAFLD, and MAFLD components, including obesity/overweight, diabetes, and metabolic dysfunction. In both BKMR and QGC models, thallium, molybdenum, tungsten, and barium mainly contributed to the positive association with MAFLD.

Conclusion

Our study indicated that exposure to heavy metals, individually or cumulatively, was positively associated with NAFLD, MAFLD, and MAFLD components, including obesity/overweight, diabetes, and metabolic dysfunction. Additional research is needed to validate these findings in longitudinal settings.

Selenium Status: Its Interactions with Dietary Mercury Exposure and Implications in Human Health

Selenium is an essential trace element in humans and animals and its role in selenoprotein and enzyme antioxidant activity is well documented. Food is the principal source of selenium, and it is important that selenium status in the body is adequately maintained for physiological functions. There has been increasing attention on the role of selenium in mitigating the toxic effects of mercury exposure from dietary intake in humans. In contrast, mercury is a neurotoxin, and its continuous exposure can cause adverse health effects in humans. The interactions of selenium and mercury are multi-factorial and involve complex binding mechanisms between these elements at a molecular level. Further insights and understanding in this area may help to evaluate the health implications of dietary mercury exposure and selenium status. This review aims to summarise current information on the interplay of the interactions between selenium and mercury in the body and the protective effect of selenium on at-risk groups in a population who may experience long-term mercury exposure.

Relationship Between Serum Levels of Arsenic, Cadmium, and Mercury and Body Mass Index and Fasting Plasma Glucose in a Mexican Adult Population

In Mexico, few studies have analyzed the associations between toxic elements and metabolic diseases. In the present study, we analyzed the associations between serum arsenic (As), cadmium (Cd), and mercury (Hg) levels and body mass index (BMI) and fasting plasma glucose (FPG) in a Mexican adult population. Anthropometric data corresponding to 86 Mexican healthy adults (59 females and 27 men) were analyzed. FPG was analyzed by an enzymatic colorimetric method, and serum As, Cd, and Hg levels were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS). The data show that the median serum As, Cd, and Hg levels were relatively higher in females (As = 1.78 ng mL^-1, Cd = 1.00 ng mL^-1, Hg = 0.96 ng mL^-1) than those in males (As = 1.22 ng mL^-1, Cd = 0.91 ng mL^-1, Hg = 0.95 ng mL^-1). However, these differences were not statistically significant (p ≥ 0.097). We also found that the median level of As significantly increased with an increase in the body weight categories (normal weight = 1.08; overweight = 1.50; obesity = 2.75; p < 0.001). In addition, a positive association between serum As levels and FPG before and after adjustment for BMI was demonstrated (Rho_Unadjusted = 0.012; (RhoA_djusted = 0.243, p = 0.032). Serum As levels are positively associated with BMI and FPG in the adult population of Mexico. Nevertheless, these results need to be replicated and confirmed with a larger sample size.

Combinatorial pathway disruption is a powerful approach to delineate metabolic impacts of endocrine disruptors

The prevalence of metabolic diseases, such as obesity, diabetes, metabolic syndrome and chronic liver diseases among others, has been rising for several years. Epidemiology and mechanistic (in vivo, in vitro and in silico) toxicology have recently provided compelling evidence implicating the chemical environment in the pathogenesis of these diseases. In this review, we will describe the biological processes that contribute to the development of metabolic diseases targeted by metabolic disruptors, and will propose an integrated pathophysiological vision of their effects on several organs. With regard to these pathomechanisms, we will discuss the needs, and the stakes of evolving the testing and assessment of endocrine disruptors to improve the prevention and management of metabolic diseases that have become a global epidemic since the end of last century.

Associations of Diet Quality and Heavy Metals with Obesity in Adults: A Cross-Sectional Study from National Health and Nutrition Examination Survey (NHANES)

A poor diet cannot fully explain the prevalence of obesity. Other environmental factors (e.g., heavy metals) have been reported to be associated with obesity. However, limited evidence is available for the combined effect of these factors on obesity. Therefore, we conducted a cross-sectional study and used the data from the National Health and Examination Survey (2007−2018) to explore the associations between diet quality and heavy metals and obesity. Diet quality was evaluated by the Healthy Eating Index-2015 (HEI-2015) score. Heavy metals included serum cadmium (Cd), lead (Pb), and mercury (Hg). We included 15,959 adults, with 5799 of obesity (body mass index ≥ 30 kg/m2). After adjustment for covariates, every interquartile range increase in HEI-2015 scores, Pb, Cd and Hg was associated with a 35% (odds ratios [OR] = 0.65, 95% confidence interval [CI]: 0.60, 0.70), 11% (OR = 0.89, 95% CI: 0.82, 0.98), 9% (OR = 0.91, 95% CI: 0.87, 0.96), 5% (OR = 0.85, 95% CI: 0.82, 0.89) reduction in risk of peripheral obesity, respectively. In addition, the association between the HEI-2015 scores and peripheral obesity was attenuated by higher levels of heavy metals (All p interaction < 0.05). Results remained similar for abdominal obesity. Our study reveals the distinct effects of a high-quality diet and heavy metals on obesity prevalence, and the beneficial effect of a high-quality diet could be weakened by higher levels of heavy metals.

IL17F Expression as an Early Sign of Oxidative Stress-Induced Cytotoxicity/Apoptosis

Interleukin 17F (IL17F) has been found to be involved in various inflammatory pathologies and has recently become a target for therapeutic purposes. In contrast to IL17F secreted by immune cells, the focus of this study is to describe the triggers of IL17F release in non-immune cells with a particular focus on IL17F-induced fibrosis. IL17F induction was examined in human lung epithelial (BEAS-2B) and myeloid cell lines as well as in peripheral blood mononuclear cells after in vitro exposure to aqueous cigarette smoke extract (CSE), inorganic mercury, cadmium or the apoptosis inducer brefeldin A. Fibrosis was examined in vitro, evaluating the transition of human primary dermal fibroblasts to myofibroblasts. We observed that all stressors were able to induce IL17F gene expression regardless of cell type. Interestingly, its induction was associated with cytotoxic/apoptotic signs. Inhibiting oxidative stress by N-acetylcysteine abrogated CSE-induced cytotoxic and IL17F-inducing effects. The induction of IL17F was accompanied by IL17F protein expression. The transition of fibroblasts into myofibroblasts was not influenced by either recombinant IL17F or supernatants of CSE-exposed BEAS-2B. In addition to IL17F secretion by specialized or activated immune cells, we underscored the cell type-independent induction of IL17F by mechanisms of inhibitable oxidative stress-induced cytotoxicity. However, IL17F was not involved in dermal fibrosis under the conditions used in this study.

Blood and Urinary Biomarkers of Antipsychotic-Induced Metabolic Syndrome

Metabolic syndrome (MetS) is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Antipsychotic (AP)-induced MetS (AIMetS) is the most common adverse drug reaction (ADR) of psychiatric pharmacotherapy. Herein, we review the results of studies of blood (serum and plasma) and urinary biomarkers as predictors of AIMetS in patients with schizophrenia (Sch). We reviewed 1440 studies examining 38 blood and 19 urinary metabolic biomarkers, including urinary indicators involved in the development of AIMetS. Among the results, only positive associations were revealed. However, at present, it should be recognized that there is no consensus on the role of any particular urinary biomarker of AIMetS. Evaluation of urinary biomarkers of the development of MetS and AIMetS, as one of the most common concomitant pathological conditions in the treatment of patients with psychiatric disorders, may provide a key to the development of strategies for personalized prevention and treatment of the condition, which is considered a complication of AP therapy for Sch in clinical practice.

Aberrant Gene Expression of Selenoproteins in Chicken Spleen Lymphocytes Induced by Mercuric Chloride

Mercury (Hg) is a heavy metal widely distributed in ecological environment, poisoning the immune system of humans and animals. Selenium (Se) is an essential microelement and selenoproteins involved in the procedure of Se antagonizing organ toxicity induced by heavy metals. The aim of this research was to investigate the changes of gene expression profile of selenoproteins induced by mercuric chloride (HgCl₂) in chicken spleen lymphocytes. We established cytotoxicity model of chicken spleen lymphocytes by HgCl₂ exposure, the messenger RNA (mRNA) expression levels of 25 selenoproteins in spleen lymphocytes were analyzed by real-time quantitative PCR (qPCR), and the gene expression pattern of selenoproteins was revealed by principal component analysis (PCA). The results showed that the mRNA expression levels of 13 selenoproteins (GPX3, GPX4, TXNRD2, TXNRD3, DIO2, SELENOS, SELENON, SELENOT, SELENOO, SELENOP, SELENOP2, MSRB1, and SEPHS2) were decreased in HgCl₂ treatment group, and there was strong positive correlation between these selenoproteins and component 1 as well as component 2 of the PCA. At the same time, the protein expression levels of GPX4, TXNRD1, TXNRD2, SELENOM, SELENOS, and SELENON were detected by Western blotting, which were consistent with the changes of gene expression. The results showed that the expression levels of selenoproteins were aberrant in response to HgCl₂ toxicity. The information presented in this study provided clues for further research on the interaction between HgCl₂ and selenoproteins, and the possible mechanism of immune organ toxicity induced by HgCl₂.

Lead, mercury, and cadmium exposures are associated with obesity but not with diabetes mellitus: Korean National Environmental Health Survey (KoNEHS) 2015-2017

BACKGROUND

Associations of heavy metal exposures with obesity and obesity-related traits have been suggested, while those with nonalcoholic fatty liver disease (NAFLD) and diabetes mellitus (DM) are often inconsistent.

METHODS

This study included 3787 adults aged ≥19 years who participated in the Korean National Environmental Health Survey 2015-2017, and investigated the association of toxic heavy metals with metabolic diseases. Lead (Pb), mercury (Hg), and cadmium (Cd) were measured either in urine (uHg, uCd) or total blood (bPb, bHg). Body mass index (BMI) was calculated, and DM cases were identified through a self-answered medication history. Hepatic Steatosis Index (HSI) as a surrogating index of NAFLD, was calculated using hepatic enzyme measurements, including aspartate aminotransferase (AST) and alanine aminotransferase (ALT).

RESULTS

Adults in the highest quartile of bPb, bHg, and uHg showed significantly elevated odds of obesity (BMI ≥25 kg/m²), compared to the lowest quartile (OR 1.58 for bPb, 1.92 for bHg, and 1.81 for uHg). HSI was positively correlated with bHg, uHg, and uCd concentrations. The odds of NAFLD (HSI ≥36) were also increased with increasing quartile of bHg, uHg, and uCd concentrations. For DM, bPb showed a significant negative association, while bHg and uCd exhibited non-monotonic and inconclusive associations.

CONCLUSIONS

Among the general adult population of Korea, both Pb and Hg exposures were associated with an increased risk of obesity. In addition, both Hg and Cd exposures were associated with increased odds of NAFLD. These metals, however, were not associated with an increased risk of DM.

Metabolic Syndrome and Endocrine Disrupting Chemicals: An Overview of Exposure and Health Effects

Increasing prevalence of metabolic syndrome (MetS) is causing a significant health burden among the European population. Current knowledge supports the notion that endocrine-disrupting chemicals (EDCs) interfere with human metabolism and hormonal balance, contributing to the conventionally recognized lifestyle-related MetS risk factors. This review aims to identify epidemiological studies focusing on the association between MetS or its individual components (e.g., obesity, insulin resistance, diabetes, dyslipidemia and hypertension) and eight HBM4EU priority substances (bisphenol A (BPA), per- and polyfluoroalkyl substances (PFASs), phthalates, polycyclic aromatic hydrocarbons (PAHs), pesticides and heavy metals (cadmium, arsenic and mercury)). Thus far, human biomonitoring (HBM) studies have presented evidence supporting the role of EDC exposures on the development of individual MetS components. The strength of the association varies between the components and EDCs. Current evidence on metabolic disturbances and EDCs is still limited and heterogeneous, and mainly represent studies from North America and Asia, highlighting the need for well-conducted and harmonized HBM programmes among the European population. Rigorous and ongoing HBM in combination with health monitoring can help to identify the most concerning EDC exposures, to guide future risk assessment and policy actions.

Salivary parameters alterations after early exposure to environmental methylmercury: A preclinical study in offspring rats

BACKGROUND

Methylmercury (MeHg) is still considered a global pollutant of major concern; thus, it becomes relevant to investigate and validate alternative diagnostic methods to track early-life human exposure. This study aimed to evaluate the salivary parameters and to characterize potential mechanisms of oxidative damage on the salivary glands (SG) of offspring rats after pre- and postnatal environmental-experimental MeHg exposure.

METHODS

Pregnant Wistar rats were daily exposed to 40 μg/kg MeHg during both gestational and lactation periods. Then, the saliva of offspring rats was analyzed in terms of flow rate, amylase activity, and total protein concentration. The SG of the offspring rats were dissected to perform the oxidative biochemistry analyses of antioxidant capacity against peroxyl radicals (ACAP), lipid peroxidation (LPO), and nitrite levels.

RESULTS

Exposure to MeHg significantly decreased the ACAP, increased LPO and nitrite levels, decreased salivary flow rate, amylase activity, and total protein concentration.

CONCLUSION

Saliva analyses can predict damages induced by early-life MeHg exposure and may be used as an auxiliary diagnostic method.

Association of Blood Mercury Levels with the Risks of Overweight and High Waist-to-Height Ratio in Children and Adolescents: Data from the Korean National Health and Nutrition Examination Survey

A previous study in adults demonstrated the substantial role of mercury exposure in the development of overweight and obesity. Although children and adolescents are more susceptible to the toxic effects of mercury than adults, studies on the association of overweight and obesity with mercury exposure is limited. This study aimed to investigate the association of blood mercury levels with the body mass index (BMI) and waist-to-height ratio (WHtR) as obesity indices in Korean children and adolescents. The analyzed cross-sectional data were obtained from 1327 participants (age: 10–18 years; 672 male and 655 female) who completed the Korean National Health and Nutrition Examination Survey 2010–2013. The covariates included sociodemographic factors (age, sex, and household income), dietary factors (fish, shellfish, and seaweed consumption), lifestyle factors (alcohol consumption, smoking status, and exercise), and blood hematocrit levels. The adjusted geometric mean blood mercury level was 2.19 µg/L, and the level of mercury was significantly higher in the overweight (BMI ≥ 85th gender and age-specific percentiles) and high WHtR (cutoff: ≥0.5) groups than in the normal group. In all the participants, the blood mercury levels were significantly positively associated with the BMI and WHtR after adjusting for all covariates (p < 0.05). All the participants in the highest blood mercury level quartile were at a higher risk for overweight and a high WHtR than those in the lowest quartile after adjusting for all covariates (p < 0.05). Our study suggests a significant association between mercury exposure and the risks of overweight and high WHtR in Korean children and adolescents.

Association between Blood Mercury Concentration and Prevalence of Borderline Hypercholesterolemia among Adolescents: The Korea National Health and Nutrition Examination Survey (KNHANES) 2010-2013 and 2016

There is limited evidence on the association between blood mercury (Hg) concentration and the risk of borderline dyslipidemia in adolescents. Here, we investigated the association between blood Hg concentration and the prevalence of borderline dyslipidemia among Korean adolescents. A total of 1559 participants (806 boys and 753 girls) aged 10–18 years who cross-sectionally enrolled in the Korea National Health and Nutrition Examination Survey (KNHANES) 2010–2013 and 2016 were included in this study. Hg concentrations (µg/L) in whole blood samples were measured. The geometric mean (GM) of the blood Hg concentration was 1.88 µg/L. It showed a 63% higher prevalence of borderline hypercholesterolemia (total cholesterol (TC) 170–199 mg/dL) per unit of natural log-transformed blood Hg concentration in boys (95% CI = 1.10–2.41), but not in girls. When a categorical model was applied, the positive association with the prevalence of borderline hypercholesterolemia was also persistant in boys (OR (95% CI) for 2nd and 3rd tertiles (Hg concentration 1.532–11.761 µg/L) vs. 1st tertile (Hg concentration 0.192–1.531 µg/L): 1.92 (1.19–3.10)), but not in girls. This finding suggests that blood Hg concentration might result in a higher prevalence of borderline hypercholesterolemia among adolescents and more stringent public health actions should be taken for the reduction of Hg exposure to prevent dyslipidemia from early-childhood, despite the need of further study to evaluate a causal relationship between blood Hg concentration and the risk of dyslipidemia.

Effects of Elemental Mercury Vapor Inhalation on Arterial Blood Gases, Lung Histology, and Interleukin-1 Expression in Pulmonary Tissues of Rats

We investigated the effects of elemental mercury vapor inhalation on arterial blood gases (ABGs), lung histology, and interleukin-1 (IL-1) expression in pulmonary tissues in rats. A total of 42 Sprague Dawley rats were divided randomly into three groups. Rats in the first group were used as the control (CG). A short-term group (STG) and a long-term group (LTG) were exposed to 500 μg/m3 of mercury vapor 2 hrs/day for 21 days and 65 days, respectively. After exposure periods were completed, arterial blood samples were obtained, and ABGs were measured. Lung tissue sections were prepared for histology evaluation and immune-stained to detect IL-1 expression. There was a significant decrease in body weight in both STG (15%) and LTG (22%) compared with the CG. In the LTG, six out of 14 (43%) rats died, including two males and four females, while none of the rats in the STG died during the experiment. In both STG and LTG, a significant acid-base imbalance was characterized by a significant decrease in blood pH values and a significant increase in PCO2 values. Both PO2 and SpO2 blood values were significantly decreased in the STG and LTG, while no changes were observed in HCO3 values in all groups. Histological evaluation of lung tissues revealed severe lesions characterized by pulmonary emphysema and inflammatory cellular infiltrate. IL-1 expression in lung tissues was not significantly different between exposed rats and control subjects. These results indicate significant alterations in blood acid-base status characterized by severe respiratory acidosis with hypoxemia and no evidence of compensatory alkalosis in rats after exposure to short- and long-term elementary mercury vapor.

Relationship between gestational diabetes and serum trace element levels in pregnant women from Eastern Iran: a multivariate approach

The prevalence of gestational diabetes mellitus (GDM) has increased over the recent decades. Exposure to environmental contaminants may be a risk factor for the development of GDM, but this is heavily dependent on particular circumstances. Studies on various areas linking various factors are therefore needed. We examined the associations between serum trace element levels and incidents of GDM among 102 pregnant women (diabetic n = 60 and healthy n = 42) living in Birjand (Iran). Blood serum samples were analyzed for concentrations of elements linked to particulate matter air pollution such as As, Cd, Cu, Hg, Mn, Ni, V, and Zn. Concentrations of As (8.58 vs. 3.15 μg/L), Cd (6.74 vs. 0.52 μg/L), and Hg (2.60 vs. 0.90 μg/L) were significantly higher in women with GDM. Risk difference (RD) estimation showed that As, 0.516 (0.355, 0.677); Cd, 0.719 (0.534, 0.904); and Hg, 0.505 (0.276, 0.735) increase GDM probability, while V lower that risk, -0.139 (-0.237, -0.042). With the principal component analysis, we were able to separate subjects according to their GDM status based on element levels. Such classification revealed very high efficiency with a true positive rate of 93%, according to linear discriminant analysis. GDM subjects presented higher levels of As, Cd, and Hg, indicating that these elements may disturb insulin metabolism and promote the development of GDM. Therefore, we conclude that systematic monitoring of trace elements followed by multivariate modeling in women planning pregnancy should be carried out to prevent the development of GDM.

Hair Lead, Aluminum, and Other Toxic Metals in Normal-Weight and Obese Patients with Coronary Heart Disease

The objective of the present study was to evaluate hair toxic metal levels in patients with obesity and/or coronary heart disease (CHD). Following a 2 × 2 factorial design, subjects without CHD were grouped into normal weight control (n = 123) and obese groups (n = 140). Patients suffering from CHD were divided into normal weight (n = 180) and obese CHD subjects (n = 240). Hair Al, As, Cd, Hg, Ni, and Pb levels were evaluated using inductively-coupled plasma mass-spectrometry. The data demonstrate that hair Al and Hg levels were higher in obese subjects as compared to normal weight controls. Normal weight CHD patients were characterized by significantly higher hair Al, As, Cd, and Pb levels when compared to healthy subjects. The highest hair Al, As, and Pb levels were observed in obese CHD patients, significantly exceeding the respective values in other groups. Factorial analysis revealed significant influence of factorial interaction (CHD*obesity) only for hair Pb content. Given the role of obesity as a risk factor for CHD, it is proposed that increased toxic metal accumulation in obesity may promote further development of cardiovascular diseases.

Relationship Between Elevated Hair Mercury Levels, Essential Element Status, and Metabolic Profile in Overweight and Obese Adults

The objective of the present study was to evaluate hair essential and trace element levels and metabolic risk markers in overweight and obese subjects in relation to body mercury burden. According to 2 × 2 factorial design a total of 440 adults were distributed to four groups: (i) low-Hg normal-weight subjects (n = 114); (ii) high-Hg normal weight subjects (n = 113); (iii) low-Hg overweight (BMI > 25) subjects (n = 110); (iv) high-Hg overweight (BMI > 25) subjects (n = 110). Hg-exposed groups consisted of subjects characterized by frequent seafood consumption (> 4 times/week) subsequently evaluated by hair analysis (> 0.58 μg/g). Dietary-exposed subjects were characterized by a more than 3-fold higher hair Hg content irrespectively of body weight values. Both low-Hg and high-Hg overweight subjects were characterized by significantly higher ALT activity, as well as elevated serum glucose, LDL, and triglyceride levels as compared to the respective groups of normal weight subjects. High Hg body burden had a more significant effect on metabolic parameters in overweight and obese adults. Particularly, high-Hg overweight subjects were characterized by significantly higher serum creatinine and uric acid levels, as well as increased GGT and CK activity as compared to low-Hg overweight counterparts. In addition, hair Mg, Mn, and Sr content in high-Hg overweight subjects was significantly lower than that in low-Hg normal weight and overweight examinees. In turn, high Hg levels in overweight subjects were associated with significantly higher hair Se and Zn levels when compared to unexposed overweight adults. Generally, the obtained data demonstrate that increased hair Hg levels in overweight and obese subjects is associated with adverse metabolic profile. It is proposed that observed metabolic alterations may be at least partially mediated by Hg-associated disturbances in essential trace element and mineral metabolism.

Relationship between urinary heavy metals with metabolic syndrome and its components in population from Hoveyzeh cohort study: A case-control study in Iran

BACKGROUND

The incidence of Metabolic Syndrome (MetS) has been growing rapidly and is rising to pandemic proportions. Although obesity is a primary risk factor for the enhancement of these conditions, not all obese individuals develop metabolic syndrome, indicating that the risk for developing MetS is impacted by other genetic and/or environmental factors such as heavy metals. Therefore, the present study focused on the association between exposures to heavy metal and MetS.

METHODS

Urine samples were collected from 150 participants (75 patients with MetS and 75 healthy participants), which were used from Hoveyzeh Cohort center. To make a quantitative comparison between the two groups, Man-Whitney nonparametric test was used. The logistic regression was performed adjusted for age, demographic, lifestyle factor, physical activity, occupational history and urine creatinine.

RESULTS

The results of logistic regression showed that OR and 95 % CI for Cd, Pb, Sr, As and Fe concentration were still significant after adjusting for urine creatinine. Moreover, there was a relationship between Cd and Pb levels and waist circumstance (WC). After adjusting for urine creatinine, age, sex, occupation, smoking status, education and place of residence, only Pb concentration was showed a significant association with systolic blood pressure (SBP). The subjects with high urine level of Cd had the high odds (OR: 6.273; 95 % Cl: 1.783-22.070) of MetS and low high-density lipoprotein (HDL-C). The relationship between As concentration and high fasting blood sugars confirmed the previous evidence suggesting that high As level can cause diabetes.

CONCLUSION

These results indicated that outbreak of MetS and its component are associated with heavy metal concentrations in urine.

Association between Blood Mercury Levels and Non-Alcoholic Fatty Liver Disease in Non-Obese Populations: The Korean National Environmental Health Survey (KoNEHS) 2012-2014

Mercury is widely distributed in the environment, and a plausible association between mercury exposure and hepatic damage has been reported. Non-alcoholic fatty liver disease (NAFLD), which comprises a spectrum of liver diseases, has recently been recognized in non-obese subjects. However, there have been no studies on the relationship between internal mercury levels and NAFLD in non-obese individuals. Therefore, we investigated the association between blood mercury levels and NAFLD in non-obese subjects. Cross-sectional data (n = 5919) were obtained from the Korean National Environmental Health Survey (2012–2014). NAFLD was defined using the hepatic steatosis index (HSI). Blood mercury levels were log-transformed and divided into quartiles based on a weighted sample distribution. The association between blood mercury levels and NAFLD was analyzed using a multivariate logistic analysis after body mass index stratification. The geometric mean of blood mercury in the overweight group was significantly higher than that of the non-obese group (p < 0.001). The weighted frequencies of patients with NAFLD based on the HSI were 3.0–7.2% for the non-obese subjects and 52.3–63.2% for the overweight subjects. In the multivariate analysis, blood mercury levels were positively associated with NAFLD for both the overweight and non-obese groups (all p for trend < 0.001). Increased blood mercury levels are closely associated with NAFLD. In particular, mercury could be a risk factor for NAFLD in the non-obese population.

Molecular mechanism of heavy metals (Lead, Chromium, Arsenic, Mercury, Nickel and Cadmium) - induced hepatotoxicity - A review

Heavy metals pose a serious threat if they go beyond permissible limits in our bodies. Much heavy metal's viz. Lead, Chromium, Arsenic, Mercury, Nickel, and Cadmium pose a serious threat when they go beyond permissible limits and cause hepatotoxicity. They cause the generation of ROS which in turn causes numerous injuries and undesirable changes in the liver. Epidemiological studies have shown an increase in the levels of such heavy metals in the environment posing a serious threat to human health. Epigenetic alterations have been seen in the event of exposure to such heavy metals. Apoptosis, caspase activation as well as ultrastructural changes in the hepatocytes have also been seen due to heavy metals. Inflammation involving TNF-alpha, pro-inflammatory cytokines, MAPK, ERK pathways have been seen in the event of heavy metal hepatotoxicity. All these have shown that these heavy metals pose a serious threat to human health in particular and the environment as a whole.

The Relationship Between Heavy Metal Exposure, Trace Element Level, and Monocyte to HDL Cholesterol Ratio with Gestational Diabetes Mellitus

The objective of this study is to assess the levels of heavy metals (cadmium, lead, antimony, mercury, and arsenic), which are also called endocrine-disrupting chemicals, and trace elements (chromium-III, chromium-VI, zinc, copper, and selenium) vs. monocyte to HDL ratio among pregnant women with gestational diabetes mellitus (GDM). A total of 112 pregnant women (60 with GDM and 52 healthy women) were included in this case-control study. Analysis of heavy metals and trace elements were performed in inductively coupled plasma mass spectrometer. Heavy metals (cadmium, lead, antimony, mercury, and arsenic), trace elements (chromium-III, chromium-VI, zinc, copper, and selenium), and metabolic parameters were assessed in both groups. It was determined that the levels of cadmium, lead, antimony, and copper were higher (p < 0.05) and levels of chromium-III, zinc, and selenium were lower (p < 0.05) among the GDM group compared to the control group, whereas there was a statistically insignificant difference between the two groups, regarding the levels of copper, mercury, and arsenic (p > 0.05). Moreover, the monocyte to HDL ratio was higher in the GDM group (p < 0.05), and the insulin resistance was significantly higher as well (p < 0.05). The results of our study demonstrated that environmental factors could be effective in the etiology of GDM. Toxic heavy metals, through inducing Cu, OS, and chronic inflammation, and other trace elements, either directly by impacting insulin secretion or through weakening the body's antioxidant defense system, could play a role in the occurrence of GDM.

Toenail mercury levels positively correlate with obesity and abdominal obesity among Korean adults

BACKGROUND

Although previous studies have shown that short-term exposure to mercury is associated with obesity, it should be noted that mercury is not easily released and that it constantly accumulates in the body. However, few studies have explored the association between chronic mercury exposure and obesity. This study aimed to examine the association between chronic mercury exposure and obesity in Korean adults.

METHODS

The study used baseline data from the Trace Element Study of Korean Adults in Yeungnam area. A total of 495 participants aged 40-69 years who provided the required information (demographic, diet, lifestyle, toenail mercury levels, and health examination results) were included. Toenail mercury levels were measured using neutron-activation analysis. Body mass index and waist circumference were obtained from medical examination. Multivariable-adjusted logistic regression and restricted cubic spline regression were used in the analysis.

RESULTS

In the fully adjusted logistic regression models, participants with the highest toenail mercury levels had a higher prevalence of obesity (odds ratio [OR]: 3.26, 95 % confidence interval [CI]: 1.79-5.93) and abdominal obesity (OR: 2.30, 95 % CI: 1.15-4.59). In the cubic spline regression model, linear relationships were confirmed between increased toenail mercury levels and higher prevalence of obesity and abdominal obesity (all p > 0.05 for nonlinearity).

CONCLUSIONS

In summary, chronic mercury exposure was associated with higher prevalence of obesity and abdominal obesity in Korean adults. Therefore, the development of public health interventions against environmental exposure of foods is required to manage and prevent obesity.

Endothelial Dysfunction Induced by Cadmium and Mercury and its Relationship to Hypertension

Hypertension is an important public health concern that affects millions globally, leading to a large number of morbidities and fatalities. The etiology of hypertension is complex and multifactorial, and it involves environmental factors, including heavy metals. Cadmium and mercury are toxic elements commonly found in the environment, contributing to hypertension. We aimed to assess the role of cadmium and mercury-induced endothelial dysfunction in the development of hypertension. A narrative review was carried out through database searches. In this review, we discussed the critical roles of cadmium and mercury in the etiology of hypertension and provided new insights into potential mechanisms of their effect, focusing primarily on endothelial dysfunction. Although the mechanisms by which cadmium and mercury induce hypertension have yet to be completely elucidated, evidence for both implicates impaired nitric oxide signaling in their hypertensive etiology.

Associations between metabolic syndrome and four heavy metals: A systematic review and meta-analysis

Four most concerned heavy metal pollutants, arsenic, cadmium, lead, and mercury may share common mechanisms to induce metabolic syndrome (MetS). However, recent studies exploring the relationships between MetS and metal exposure presented inconsistent findings. We aimed to clarify the relationship between heavy metal exposure biomarkers and MetS using a meta-analysis and systematic review approach. Literature search was conducted in international and the Chinese national databases up to June 2020. Of selected studies, we extracted the relevant data and evaluated the quality of each study's methodology. We then calculated the pooled effect sizes (ESs), standardized mean differences (SMDs), and their 95% confidence intervals (CIs) using a random-effect meta-analysis approach followed by stratification analyses for control of potential confounders. Involving 55,536 participants, the included 22 articles covered 52 observational studies reporting ESs and/or metal concentrations on specific metal and gender. Our results show that participants with MetS had significantly higher levels of heavy metal exposure [pooled ES = 1.16, 95% CI: 1.09, 1.23; n = 42, heterogeneity I2 = 75.6%; and SMD = 0.22, 95% CI: 0.15, 0.29; n = 32, I2 = 94.2%] than those without MetS. Pooled ESs in the subgroups stratified by arsenic, cadmium, lead, and mercury were 1.04 (95% CI: 0.97, 1.10; n = 8, I2 = 61.0%), 1.10 (0.95, 1.27; 11, 45.0%), 1.21 (1.00, 1.48; 12, 82.9%), and 1.26 (1.06, 1.48; 11, 67.7%), respectively. Pooled ESs in the subgroups stratified by blood, urine, and the other specimen were 1.22 (95% CI: 1.08, 1.38; n = 26, I2 = 75.8%), 1.06 (1.00, 1.13; 14, 58.1%), and 2.41 (1.30, 4.43; 2, 0.0%), respectively. In conclusion, heavy metal exposure was positively associated with MetS. Further studies are warranted to examine the effects of individual metals and their interaction on the relationship between MetS and heavy metals.

Plasma titanium level is positively associated with metabolic syndrome: A survey in China's heavy metal polluted regions

OBJECTIVE

Several heavy metals have been reported to be associated with metabolic syndrome(MetS) in general population, while effects of multiple metals exposure on MetS in residents living in heavy metal polluted regions have not been investigated. We aimed to assess the association of 23 metal levels and MetS among population living in China's heavy metal polluted regions.

METHODS

From August 2016 to July 2017, a total of 2109 eligible participants were consecutively enrolled in our study in Hunan province, China. The levels of plasma and urine metals were measured by inductively coupled plasma mass spectrometer (ICP-MS). MetS was defined by the criteria of the International Diabetes Federation. Multivariable regression models were applied to analysis the potential relationship.

RESULTS

In the overall population, crude model showed positive relationship of plasma titanium (Ti) with MetS and negative association of urine vanadium, iron, and selenium with MetS. After adjusted for potential confounders, only plasma Ti was positive associated with MetS (adjusted OR for Q4 versus Q1: 1.46; 95% CI: 1.06-1.99), and this positive correlation was explained by abdominal obesity (OR = 1.84, 95% CI: 1.41-2.39) and high triglycerides (OR = 2.23, 95% CI: 1.68-2.96). Further linear regression analysis revealed significant association of plasma Ti levels with waist circumference (β = 0.0056, 95% CI: 0.0004-0.0109, P = 0.036) and triglycerides (β = 0.0012, 95% CI: 0.0006-0.0019, P < 0.001), respectively.

CONCLUSION

High plasma Ti level was associated with increased risk of MetS via increasing waist circumference and triglycerides in people under high metal exposure.

Potential obesogenic effect of a complex contaminant mixture on Cree First Nations adults of Northern Québec, Canada

BACKGROUND

Obesity incidence and prevalence is of increasing concern in First Nations communities around Canada. In addition to diet and physical activity, environmental pollutants have been suggested as a potential contributory factor to obesity associated morbidity. Owing to the exposure of Cree First Nations people to various persistent organic pollutants (POPs) and toxic metals, it is important to examine the association between obesity in these communities, and contaminant body burdens.

OBJECTIVE

To determine whether selected morphometry measures (body mass index [BMI], waist circumference [WC] and body fat percentage) are associated with body burdens of 10 POPs and toxic metals.

METHODS

Using data from the Nituuchischaayihtitaau Aschii Multi-community Environment-and-Health study in the eastern James Bay (Eeyou Istchee) Cree communities, this cross-sectional study examined morphometric and contaminant measures of 695 eligible participants. Sex stratified principal component analysis was conducted on blood plasma concentrations of 10 POPs and toxic metals. BMI, WC, body fat percent, and resultant contaminant components were used to create generalized linear models, and adjusted for covariates (age, total lipids, smoking, and n-3 fatty acids).

RESULTS

Two principal components (PCs; PC-1 and PC-2) were extracted for both males and females. For females, PC-1 explained 73.3% and PC-2 explained 10.5%, and for males, PC-1 explained 71.6% and PC-2 explained 11.2% of the variance in contaminant burden. For both sexes, PC-1 loaded highly for polychlorinated biphenyl (PCB) congeners, organochlorine pesticides and, to a lesser extent, mercury and lead. PC-2 loaded highly for cadmium for females, and cadmium and lead for males. After adjusting for covariates, the generalized linear model showed that PC-2 was significantly and negatively associated with BMI, body fat percent, and WC in males and females.

CONCLUSIONS

Our cross-sectional analysis indicates a negative association between cadmium with various obesity measures in both males and females. Null associations were found between PCBs and organochlorine pesticides and morphometry.

Toxic metal exposure as a possible risk factor for COVID-19 and other respiratory infectious diseases

Multiple medical, lifestyle, and environmental conditions, including smoking and particulate pollution, have been considered as risk factors for COronaVIrus Disease 2019 (COVID-19) susceptibility and severity. Taking into account the high level of toxic metals in both particulate matter (PM2.5) and tobacco smoke, the objective of this review is to discuss recent data on the role of heavy metal exposure in development of respiratory dysfunction, immunotoxicity, and severity of viral diseases in epidemiological and experimental studies, as to demonstrate the potential crossroads between heavy metal exposure and COVID-19 severity risk. The existing data demonstrate that As, Cd, Hg, and Pb exposure is associated with respiratory dysfunction and respiratory diseases (COPD, bronchitis). These observations corroborate laboratory findings on the role of heavy metal exposure in impaired mucociliary clearance, reduced barrier function, airway inflammation, oxidative stress, and apoptosis. The association between heavy metal exposure and severity of viral diseases, including influenza and respiratory syncytial virus has been also demonstrated. The latter may be considered a consequence of adverse effects of metal exposure on adaptive immunity. Therefore, reduction of toxic metal exposure may be considered as a potential tool for reducing susceptibility and severity of viral diseases affecting the respiratory system, including COVID-19.

The threat of global mercury pollution to bird migration: potential mechanisms and current evidence

Mercury is a global pollutant that has been widely shown to adversely affect reproduction and other endpoints related to fitness and health in birds, but almost nothing is known about its effects on migration relative to other life cycle processes. Here I consider the physiological and histological effects that mercury is known to have on non-migrating birds and non-avian vertebrates to identify potential mechanisms by which mercury might hinder migration performance. I posit that the broad ability of mercury to inactivate enzymes and compromise the function of other proteins is a single mechanism by which mercury has strong potential to disrupt many of the physiological processes that make long-distance migration possible. In just this way alone, there is reason to expect mercury to interfere with navigation, flight endurance, oxidative balance, and stopover refueling. Navigation and flight could be further affected by neurotoxic effects of mercury on the brain regions that process geomagnetic information from the visual system and control biomechanics, respectively. Interference with photochemical reactions in the retina and decreases in scotopic vision sensitivity caused by mercury also have the potential to disrupt visual-based magnetic navigation. Finally, migration performance and possibly survival might be limited by the immunosuppressive effects of mercury on birds at a time when exposure to novel pathogens and parasites is great. I conclude that mercury pollution is likely to be further challenging what is already often the most difficult and perilous phase of a migratory bird's annual cycle, potentially contributing to global declines in migratory bird populations.

Sulfhydryl groups as targets of mercury toxicity

The present study addresses existing data on the affinity and conjugation of sulfhydryl (thiol; -SH) groups of low- and high-molecular-weight biological ligands with mercury (Hg). The consequences of these interactions with special emphasis on pathways of Hg toxicity are highlighted. Cysteine (Cys) is considered the primary target of Hg, and link its sensitivity with thiol groups and cellular damage. In vivo, Hg complexes play a key role in Hg metabolism. Due to the increased affinity of Hg to SH groups in Cys residues, glutathione (GSH) is reactive. The geometry of Hg(II) glutathionates is less understood than that with Cys. Both Cys and GSH Hg-conjugates are important in Hg transport. The binding of Hg to Cys mediates multiple toxic effects of Hg, especially inhibitory effects on enzymes and other proteins that contain free Cys residues. In blood plasma, albumin is the main Hg-binding (Hg2+, CH3Hg+, C2H5Hg+, C6H5Hg+) protein. At the Cys34 residue, Hg2+ binds to albumin, whereas other metals likely are bound at the N-terminal site and multi-metal binding sites. In addition to albumin, Hg binds to multiple Cys-containing enzymes (including manganese-superoxide dismutase (Mn-SOD), arginase I, sorbitol dehydrogenase, and δ-aminolevulinate dehydratase, etc.) involved in multiple processes. The affinity of Hg for thiol groups may also underlie the pathways of Hg toxicity. In particular, Hg-SH may contribute to apoptosis modulation by interfering with Akt/CREB, Keap1/Nrf2, NF-κB, and mitochondrial pathways. Mercury-induced oxidative stress may ensue from Cys-Hg binding and inhibition of Mn-SOD (Cys196), thioredoxin reductase (TrxR) (Cys497) activity, as well as limiting GSH (GS-HgCH3) and Trx (Cys32, 35, 62, 65, 73) availability. Moreover, Hg-thiol interaction also is crucial in the neurotoxicity of Hg by modulating the cytoskeleton and neuronal receptors, to name a few. However, existing data on the role of Hg-SH binding in the Hg toxicity remains poorly defined. Therefore, more research is needed to understand better the role of Hg-thiol binding in the molecular pathways of Hg toxicology and the critical role of thiols to counteract negative effects of Hg overload.

Novel Insights into Mercury Effects on Hemoglobin and Membrane Proteins in Human Erythrocytes

Mercury (Hg) is a global environmental pollutant that affects human and ecosystem health. With the aim of exploring the Hg-induced protein modifications, intact human erythrocytes were exposed to HgCl₂ (1-60 µM) and cytosolic and membrane proteins were analyzed by SDS-PAGE and AU-PAGE. A spectrofluorimetric assay for quantification of Reactive Oxygen Species (ROS) generation was also performed. Hg²⁺ exposure induces alterations in the electrophoretic profile of cytosolic proteins with a significant decrease in the intensity of the hemoglobin monomer, associated with the appearance of a 64 kDa band, identified as a mercurized tetrameric form. This protein decreases with increasing HgCl₂ concentrations and Hg-induced ROS formation. Moreover, it appears resistant to urea denaturation and it is only partially dissociated by exposure to dithiothreitol, likely due to additional protein-Hg interactions involved in aggregate formation. In addition, specific membrane proteins, including band 3 and cytoskeletal proteins 4.1 and 4.2, are affected by Hg²⁺-treatment. The findings reported provide new insights into the Hg-induced possible detrimental effects on erythrocyte physiology, mainly related to alterations in the oxygen binding capacity of hemoglobin as well as decreases in band 3-mediated anion exchange. Finally, modifications of cytoskeletal proteins 4.1 and 4.2 could contribute to the previously reported alteration in cell morphology.

Molecular genetic and geochemical assays reveal severe contamination of drinking water reservoirs at the ancient Maya city of Tikal

Understanding civilizations of the past and how they emerge and eventually falter is a primary research focus of archaeological investigations because these provocative data sets offer critical insights into long-term human behavior patterns, especially in regard to land use practices and sustainable environmental interactions. The ancient Maya serve as an intriguing example of this research focus, yet the details of their spectacular emergence in a tropical forest environment followed by their eventual demise have remained enigmatic. Tikal, one of the foremost of the ancient Maya cities, plays a central role in this discussion because of its sharp population decline followed by abandonment during the late 9th century CE. Our results, based on geochemical and molecular genetic assays on sediments from four of the main reservoirs, reveal that two of the largest reservoirs at Tikal, essential for the survival of the city during the dry seasons, were contaminated with high levels of mercury, phosphate and cyanobacteria known to produce deadly toxins. Our observations demonstrate severe pollution problems at a time when episodes of climatic aridity were prevalent. This combination of catastrophic events clearly threatened the sustainability of the city and likely contributed to its abandonment.