Is mercury exposure causing diabetes, metabolic syndrome and insulin resistance? A systematic review of the literature

Evaluation of the cognitive, physiological, and biomarker effects of heavy metal exposure in Wistar rats

Background and Aim

Individuals exposed to heavy metals are known to experience physiological and biochemical changes, which raise questions regarding possible health effects. In our earlier research, significant concentrations of vanadium (V), mercury (Hg), cadmium (Cd), and arsenic (As) were found in food and medical packaging materials. This study aimed to evaluate the cognitive, physiological, and biomarker effects of select heavy metal exposure in Wistar rats.

Materials and Methods

Over a 13-week period, five groups of rats (six rats per group, with both males and females) were assessed to study the effects of oral exposure to V, Hg, Cd, and As. The study focused on evaluating physiological, cognitive, and biochemical markers, with the results compared to those of a control group.

Results

Comparing all groups of rats treated with heavy metals, the study revealed significant deficits in learning and spatial orientation (water maze test); rats treated with V, Cd, and Hg showed signs of depression. Rats treated with As also showed signs of hyperactivity, which may indicate a connection to attention-deficit hyperactivity disorder (rat tail suspension test). The groups exposed to different heavy metals varied in their physiological (water and food intake, urine and feces output) and biochemical responses (enzyme-linked immunosorbent assay, prostate-specific antigen, T3, T4, thyroid-stimulating hormone, carcinoembryonic antigen, and blood glucose analysis), with Hg exhibiting the strongest impacts. Rats given Hg showed signs of hypothyroidism, such as increased food intake and weight gain.

Conclusion

This study clarifies the complex relationships between exposure to heavy metals and various biological systems, shedding light on their potential health impacts. The findings provide insight into the effects of heavy metals on neural and thyroid tissues, as well as their propensity to cause cellular dedifferentiation. However, the study has certain limitations, such as the relatively short duration of exposure and the use of only a few selected biomarkers. Future research should focus on long-term exposure studies, incorporate a broader range of biomarkers, and explore the underlying mechanisms at a molecular level to better understand the full spectrum of health risks associated with heavy metal exposure.

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.

Associations between patterns of blood heavy metal exposure and health outcomes: insights from NHANES 2011-2016

BACKGROUND

Extensive research has explored the association between heavy metal exposure and various health outcomes, including malignant neoplasms, hypertension, diabetes, and heart diseases. This study aimed to investigate the relationship between patterns of exposure to a mixture of seven heavy metals and these health outcomes.

METHODS

Blood samples from 7,236 adults in the NHANES 2011-2016 studies were analyzed for levels of cadmium, manganese, lead, mercury, selenium, copper, and zinc. Cluster analysis and logistic regression identified three distinct patterns of mixed heavy metal exposure, and their associations with health outcomes were evaluated.

RESULTS

Pattern 1 exhibited higher odds ratios (ORs) for malignancy during NHANES 2011-2012 (OR = 1.33) and 2015-2016 (OR = 1.29) compared to pattern 2. Pattern 3 showed a lower OR for malignancy during NHANES 2013-2014 (OR = 0.62). For hypertension, pattern 1 displayed higher ORs than pattern 2 for NHANES 2011-2012 (OR = 1.26), 2013-2014 (OR = 1.31), and 2015-2016 (OR = 1.41). Pattern 3 had lower ORs for hypertension during NHANES 2013-2014 (OR = 0.72) and 2015-2016 (OR = 0.67). In terms of heart diseases, pattern 1 exhibited higher ORs than pattern 2 for NHANES 2011-2012 (OR = 1.34), 2013-2014 (OR = 1.76), and 2015-2016 (OR = 1.68). Pattern 3 had lower ORs for heart diseases during NHANES 2013-2014 (OR = 0.59) and 2015-2016 (OR = 0.52). However, no significant trend was observed for diabetes. All three patterns showed the strongest association with hypertension among the health outcomes studied.

CONCLUSIONS

The identified patterns of seven-metal mixtures in NHANES 2011-2016 were robust. Pattern 1 exhibited higher correlations with hypertension, heart disease, and malignancy compared to pattern 2, suggesting an interaction between these metals. Particularly, the identified patterns could offer valuable insights into the management of hypertension in healthy populations.

Environmental exposure to lead and cadmium are associated with triglyceride glucose index

The triglyceride glucose (TyG) index was suggested as a novel reliable surrogate marker for insulin resistance and related cardiovascular-metabolic diseases. We aimed to evaluate the association between the TyG index and environmental exposure to lead (Pb), mercury (Hg), and cadmium (Cd). A total of 9645 adults who enrolled in the Korea National Health and Nutrition Examination Survey in 2005, 2008-2013, and 2016 were included. Fasting plasma glucose and triglyceride levels were used to calculate the TyG index. Multivariate logistic regression model was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). We noted an increasing trend in the TyG index with increment of blood Pb and Cd concentrations. Participants in the highest quartile of blood Pb and Cd concentrations had higher TyG index values than those in the lowest quartile, with ORs (95% CIs) of 1.32 (1.07-1.63) and 1.29 (1.04-1.59) for Pb and Cd, respectively. Strong associations between blood Pb and Cd concentrations and the TyG index were found in men. Blood Hg concentrations did not show a significant association with the TyG index. Our study suggests that public health strategies for cardiovascular-metabolic disorder prevention should be directed toward individuals exposed to priority heavy metals.

The association of blood metals with latent tuberculosis infection among adults and adolescents

Objective

We aimed to investigate the relationship of metal exposure and latent tuberculosis infection (LTBI) among US adults and adolescents.

Methods

Participants from the National Health and Nutrition Examination Surveys (NHANES 2011 ~ 2012) were included. Multiple logistic regression models were used to explore the associations between metal exposure and LTBI. A total of 5,248 adults and 1,860 adolescents were included in the present analysis.

Results

For adults, we only found a positive association between total mercury and LTBI (OR: 1.411; 95% CI: 1.164 ~ 1.710) when used as a continuous variable. Compared with Q1, Q4 increased the prevalence of LTBI (2.303; 1.455 ~ 3.644) when used as a quartile. The OR of total mercury and LTBI was higher among females (1.517; 1.009 ~ 2.279), individuals aged 45 ~ 64 (1.457; 1.060 ~ 2.002), and non-Hispanic White individuals (1.773; 1.316 ~ 2.388). A relationship was observed among only participants with obesity (1.553; 1.040 ~ 2.319) or underweight (1.380; 1.076 ~ 1.771), with college or above (1.645; 1.184 ~ 2.286), with PIR > 3.0 (1.701; 1.217 ~ 2.376), reported smoking (1.535; 1.235 ~ 1.907) and drinking (1.464; 1.232 ~ 1.739). For adolescents, blood manganese was positively associated with LTBI. The OR and 95% CIs for each one-unit increase in the log-transformed level of blood manganese with LTBI were 9.954 (1.389 ~ 71.344).

Conclusion

Significant associations were observed in girls, aged ≥12 years and in the non-Hispanic white population. In conclusion, total mercury is associated with an increased prevalence of LTBI among adults and positive association between blood manganese and LTBI was observed among adolescents. Further studies should be conducted to verify the results and explore potential biological mechanisms.

Association with Combined Occupational Hazards Exposure and Risk of Metabolic Syndrome: A Workers' Health Examination Cohort 2012-2021

Background

This study aimed to evaluate the association between exposure to occupational hazards and the metabolic syndrome. A secondary objective was to analyze the additive and multiplicative effects of exposure to risk factors.

Methods

This retrospective cohort was based on 31,615 health examinees at the Pusan National University Yangsan Hospital in Republic of Korea from 2012-2021. Demographic and behavior-related risk factors were treated as confounding factors, whereas three physical factors, 19 organic solvents and aerosols, and 13 metals and dust were considered occupational risk factors. Time-dependent Cox regression analysis was used to calculate hazard ratios.

Results

The risk of metabolic syndrome was significantly higher in night shift workers (hazard ratio = 1.45: 95% confidence interval = 1.36-1.54) and workers who were exposed to noise (1.15:1.07-1.24). Exposure to some other risk factors was also significantly associated with a higher risk of metabolic syndrome. They were dimethylformamide, acetonitrile, trichloroethylene, xylene, styrene, toluene, dichloromethane, copper, antimony, lead, copper, iron, welding fume, and manganese. Among the 28 significant pairs, 19 exhibited both positive additive and multiplicative effects.

Conclusions

Exposure to single or combined occupational risk factors may increase the risk of developing metabolic syndrome. Working conditions should be monitored and improved to reduce exposure to occupational hazards and prevent the development of the metabolic syndrome.

Exposure to mercury among Spanish adolescents: Eleven years of follow-up

The toxic effects of mercury exposure on human health are a public health concern. The most important source of this exposure is the consumption of fish and marine mammals. This study aims to describe hair mercury concentrations and their evolution from birth until eleven years of age in adolescents from the INMA (Environment and Childhood) birth cohort study, and to assess the association of hair mercury concentrations at eleven years of age with sociodemographic and dietary factors. The sample comprised 338 adolescents from the sub-cohort of Valencia (in eastern Spain). Total mercury (THg) was measured in hair samples collected at 4, 9 and 11 years old and in cord blood at birth. The equivalent of hair for cord-blood THg concentrations was calculated. Fish consumption and other characteristics at 11 years old were collected through questionnaires. Multivariate linear regression models were conducted to explore the association between THg concentrations, fish consumption and covariates. The geometric mean of hair THg concentrations at 11 years of age was 0.86 μg/g (95%CI: 0.78-0.94) and 45.2% of the participants presented concentrations above the equivalent RfD proposed by the US EPA (1 μg/g). Consumption of fish such as swordfish, canned tuna and other large oily fish was associated with higher levels of hair mercury at 11 years of age. Swordfish had the highest effect with an increase of 125% in hair mercury (95%CI: 61.2-214.9%) given a 100 g/week increase in its consumption, and, taking into account the frequency of consumption, canned tuna was the main contributor to Hg exposure among our population. The hair THg concentrations at 11 years of age represented a reduction of around 69% with respect to that estimated at childbirth. Even though THg exposure shows a sustained decreasing trend, it can still be considered elevated. INMA birth cohort studies provide a longitudinal assessment of mercury exposure in a vulnerable population, its associated factors and temporal trends, and this information could be used to adjust recommendations about this issue.

Heavy Metals and Essential Elements in Association with Oxidative Stress in Women with Polycystic Ovary Syndrome-A Systematic Review

Altered levels of heavy metals and essential elements have been associated with oxidative stress (OS) and metabolic and hormonal changes in women with polycystic ovary syndrome (PCOS). We aimed to summarize the knowledge on the association of heavy metals and essential elements with OS in PCOS. An electronic literature search using PubMed for studies published between January 2008 and April 2023 was conducted. We evaluated heavy metals and essential elements in relation to OS in PCOS in 15 articles. PCOS women had increased antimonium (Sb), cadmium (Cd), lead (Pb), mercury (Hg), arsenic (As), tellurium (Te), thallium (Tl) and osmium (Os) blood levels and decreased zinc (Zn) blood levels; the results of copper (Cu) blood levels were conflicting. Some studies showed a significant correlation between heavy metals (Sb, Cd, Pb, Hg, As, Te and Tl) and essential elements (Se, Zn, Cr, Ca, Mg and Cu) and markers of OS and chronic inflammation. Heavy metals (Sb, Cd, Pb and Hg) and essential elements (Zn, Cr, Se, Ca, Mg and Cu) were associated with metabolic and hormonal characteristics in PCOS. There might be a possible benefit from supplementation therapy in reducing OS and endocrinological problems related to PCOS. Our review confirmed an association between heavy metals and essential elements with OS in PCOS women. This systematic review is registered in PROSPERO under number CRD42023418453.

Methylmercury drives lipid droplet formation and adipokine expression during the late stages of adipocyte differentiation in 3T3-L1 cells

Chronic exposure to methylmercury (MeHg) is positively associated with obesity and metabolic syndromes. However, the effect of MeHg on adipogenesis has not been thoroughly investigated. This study investigated the effects of continuous exposure to 0.5 µM MeHg on adipocyte differentiation in 3T3-L1 cells. Oil Red O staining and triglycerides (TG) assays demonstrated that MeHg enhanced the TG content in 3T3-L1 cells. MeHg enhanced the mRNA and protein expression of adipocyte differentiation markers including peroxisome proliferator-activated receptor γ, adiponectin, and fatty acid-binding protein, and their expression levels were prominent during the late stages (days 6-8) after the induction of differentiation. In addition, 0.5 µM MeHg promoted the expression of autophagy-related genes, including light chain 3 B-II and p62, after induction of differentiation. Treatment of 3T3-L1 cells with chloroquine (CQ), an autophagy inhibitor, during the early stages (days 0-2) after induction of differentiation inhibited cellular lipid accumulation in the presence of 0.5 µM MeHg. However, treatment with CQ during the late stages (days 6-8) had little effect on the MeHg-induced increase in TG content and the expression of adipocyte differentiation markers. Although the underlying mechanisms in the late stages remain to be completely elucidated, but the present data suggest that autophagy and other mechanisms play critical roles in adipogenesis during MeHg-induced differentiation. Collectively, our results suggest that continuous exposure to MeHg induces TG accumulation and expression of genes related to adipogenesis, especially during the late stages of 3T3-L1 differentiation, which may contribute to an improved understanding of MeHg-induced adipogenesis.

Epigenome-wide DNA methylation in leukocytes and toenail metals: The normative aging study

BACKGROUND

Environmental metal exposures have been associated with multiple deleterious health endpoints. DNA methylation (DNAm) may provide insight into the mechanisms underlying these relationships. Toenail metals are non-invasive biomarkers, reflecting a medium-term time exposure window.

OBJECTIVES

This study examined variation in leukocyte DNAm and toenail arsenic (As), cadmium (Cd), lead (Pb), manganese (Mn), and mercury (Hg) among elderly men in the Normative Aging Study, a longitudinal cohort.

METHODS

We repeatedly collected samples of blood and toenail clippings. We measured DNAm in leukocytes with the Illumina HumanMethylation450 K BeadChip. We first performed median regression to evaluate the effects of each individual toenail metal on DNAm at three levels: individual cytosine-phosphate-guanine (CpG) sites, regions, and pathways. Then, we applied a Bayesian kernel machine regression (BKMR) to assess the joint and individual effects of metal mixtures on DNAm. Significant CpGs were identified using a multiple testing correction based on the independent degrees of freedom approach for correlated outcomes. The approach considers the effective degrees of freedom in the DNAm data using the principal components that explain >95% variation of the data.

RESULTS

We included 564 subjects (754 visits) between 1999 and 2013. The numbers of significantly differentially methylated CpG sites, regions, and pathways varied by metals. For example, we found six significant pathways for As, three for Cd, and one for Mn. The As-associated pathways were associated with cancer (e.g., skin cancer) and cardiovascular disease, whereas the Cd-associated pathways were related to lung cancer. Metal mixtures were also associated with 47 significant CpG sites, as well as pathways, mainly related to cancer and cardiovascular disease.

CONCLUSIONS

This study provides an approach to understanding the potential epigenetic mechanisms underlying observed relations between toenail metals and adverse health endpoints.

Chemical Compounds and Ambient Factors Affecting Pancreatic Alpha-Cells Mass and Function: What Evidence?

The exposure to different substances present in the environment can affect the ability of the human body to maintain glucose homeostasis. Some review studies summarized the current evidence about the relationships between environment and insulin resistance or beta-cell dysfunction. Instead, no reviews focused on the relationships between the environment and the alpha cell, although in recent years clear indications have emerged for the pivotal role of the alpha cell in glucose regulation. Thus, the aim of this review was to analyze the studies about the effects of chemical, biological, and physical environmental factors on the alpha cell. Notably, we found studies focusing on the effects of different categories of compounds, including air pollutants, compounds of known toxicity present in common objects, pharmacological agents, and compounds possibly present in food, plus studies on the effects of physical factors (mainly heat exposure). However, the overall number of relevant studies was limited, especially when compared to studies related to the environment and insulin sensitivity or beta-cell function. In our opinion, this was likely due to the underestimation of the alpha-cell role in glucose homeostasis, but since such a role has recently emerged with increasing strength, we expect several new studies about the environment and alpha-cell in the near future.

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.

Hair methylmercury levels are inversely correlated with arterial stiffness

BACKGROUND AND AIMS

Cardiovascular diseases (CVD), including coronary heart disease, are the leading cause of death worldwide. Several studies investigating the relationship between fish intake, methylmercury exposure, and CVDs in adults have reported inconsistent results. This study aimed to determine the association between hair methylmercury levels and arterial stiffness using brachial-ankle pulse wave velocity (baPWV).

METHODS

This cross-sectional study included 891 seemingly healthy Korean adults (418 men and 473 women). The anthropometric and biochemical profiles, including methylmercury levels in the hair, were measured. Arterial stiffness was measured using baPWV, wherein high baPWV was defined as >1375 cm/s (>75th percentile). The odds ratios for high baPWVs were examined using multivariable logistic regression analysis after adjusting for potential confounders across the quintiles of hair methylmercury levels (Q1 = ≤0.6, Q2 = 0.6-0.8, Q3 = 0.8-1.1, Q4 = 1.1-1.5, and Q5=>1.5 μg/g).

RESULTS

After adjusting for multiple confounders-age, sex, height, body weight, smoking status, weekly alcohol consumption, total metabolic equivalent of task, mean arterial blood pressure, resting heart rate, triglycerides, low density lipoprotein cholesterol, fasting plasma glucose, uric acid and white blood cell count-the odds ratios (95% confidence intervals) for high baPWVs in each quintile of hair methylmercury levels were 1.00, 0.36 (0.17-0.76), 0.38 (0.20-0.76), 0.28 (0.13-0.61), and 0.49 (0.24-0.99), respectively.

CONCLUSIONS

Within non-toxic low levels, higher hair methylmercury levels are independently associated with lower arterial stiffness in seemingly healthy Korean adults regardless of classical cardiovascular risk factors.

Potential benefits of egg white hydrolysate in the prevention of Hg-induced dysfunction in adipose tissue

Aim: To investigate the effects of egg white hydrolysate (EWH) on the lipid and glycemic metabolism disruption in the white adipose tissue (WAT) dysfunction induced by mercury (Hg). Experimental: Wistar rats were treated for 60 days: control (saline, intramuscular - i.m.); hydrolysate (EWH, gavage, 1 g kg^-1 day^-1); mercury (HgCl₂, i.m., 1^st dose 4.6 μg kg^-1, subsequent doses 0.07 μg kg^-1 day^-1) and hydrolysate-mercury (EWH-HgCl₂). Hg level and histological analyses were performed in epididymal WAT (eWAT), pancreas and liver. GRP78, CHOP, PPARα, PPARγ, leptin, adiponectin, and CD11 mRNA expressions were analyzed in eWAT. The plasma lipid profile, glucose, and insulin levels were measured. Antioxidant status was also evaluated in the plasma and liver. Results: EWH intake prevented the reduced eWAT weight, adipocyte size, insulin levels, and antioxidant defenses and the increased glucose and triglyceride levels induced by Hg exposure; hepatic glutathione levels were higher in rats co-treated with EWH. The increased mRNA expression of CHOP, PPARα, and leptin induced by Hg was reduced in co-treated rats. EWH did not modify the elevated mRNA expression of GRP78, PPARγ and adiponectin in Hg-treated rats. Increased levels of Hg were found in the liver; the co-treatment did not alter this parameter. EWH prevented the morphological and metabolic disorder induced by Hg, by improving antioxidant defenses, inactivating pro-apoptotic pathways and normalizing the mRNA expression of PPARs and adipokines. Its effects enabled an increase in insulin levels and a normal balance between the fat storage and expenditure mechanisms in WAT. Conclusions: EWH may have potential benefits in the prevention and management of Hg-related metabolic disorders.

Contamination, exposure, and health risk assessment of Hg in Pakistan: A review

Mercury is a highly toxic and highly mobile heavy metal. It has been regarded as more toxic than other nonessential and toxic nonradioactive heavy metals. Moreover, it has a high tendency of bioaccumulation and biomagnification in the ecosystem. This study aimed to assess the environmental and health risks related to Hg. Seventy studies related to Hg in environmental media, aquatic biota, and food stuffs across Pakistan were reviewed, and their concentrations were used for ecological and human health risk assessments. High concentrations of Hg were reported in the environment, with maximum concentrations of 72 mg L^-1, 144 mg kg^-1, 887 mg kg^-1, and 49,807 ng m^-3 in surface water, surface soil, surface sediments, and urban atmosphere, respectively. The possible non-carcinogenic health risk (hazard quotient) of Hg was assessed in soil, water, and fish. High risks were calculated for seafood and vegetable consumption, while low risks were estimated for soils and groundwater ingestion and exposure. Overall, children showed higher risks than adults. Last, the risk quotient analysis (RQ) revealed significant risks for aquatic species. RQs showed that multiple species, especially those with smaller resilience, could face long-term detrimental impacts. High, medium, and low risks were calculated from 66.66, 16.17, and 16.17% of the reported Hg concentrations.

Methylmercury Induces Mitochondria- and Endoplasmic Reticulum Stress-Dependent Pancreatic β-Cell Apoptosis via an Oxidative Stress-Mediated JNK Signaling Pathway

Methylmercury (MeHg), a long-lasting organic pollutant, is known to induce cytotoxic effects in mammalian cells. Epidemiological studies have suggested that environmental exposure to MeHg is linked to the development of diabetes mellitus (DM). The exact molecular mechanism of MeHg-induced pancreatic β-cell cytotoxicity is still unclear. Here, we found that MeHg (1-4 μM) significantly decreased insulin secretion and cell viability in pancreatic β-cell-derived RIN-m5F cells. A concomitant elevation of mitochondrial-dependent apoptotic events was observed, including decreased mitochondrial membrane potential and increased proapoptotic (Bax, Bak, p53)/antiapoptotic (Bcl-2) mRNA ratio, cytochrome c release, annexin V-Cy3 binding, caspase-3 activity, and caspase-3/-7/-9 activation. Exposure of RIN-m5F cells to MeHg (2 μM) also induced protein expression of endoplasmic reticulum (ER) stress-related signaling molecules, including C/EBP homologous protein (CHOP), X-box binding protein (XBP-1), and caspase-12. Pretreatment with 4-phenylbutyric acid (4-PBA; an ER stress inhibitor) and specific siRNAs for CHOP and XBP-1 significantly inhibited their expression and caspase-3/-12 activation in MeHg-exposed RIN-mF cells. MeHg could also evoke c-Jun N-terminal kinase (JNK) activation and reactive oxygen species (ROS) generation. Antioxidant N-acetylcysteine (NAC; 1mM) or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox; 100 μM) markedly prevented MeH-induced ROS generation and decreased cell viability in RIN-m5F cells. Furthermore, pretreatment of cells with SP600125 (JNK inhibitor; 10 μM) or NAC (1 mM) or transfection with JNK-specific siRNA obviously attenuated the MeHg-induced JNK phosphorylation, CHOP and XBP-1 protein expression, apoptotic events, and insulin secretion dysfunction. NAC significantly inhibited MeHg-activated JNK signaling, but SP600125 could not effectively reduce MeHg-induced ROS generation. Collectively, these findings demonstrate that the induction of ROS-activated JNK signaling is a crucial mechanism underlying MeHg-induced mitochondria- and ER stress-dependent apoptosis, ultimately leading to β-cell death.

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.

Manganese Exposure and Metabolic Syndrome: A Systematic Review and Meta-Analysis

Manganese (Mn) is an essential element acting as a co-factor of superoxide dismutase, and it is potentially beneficial for cardiometabolic health by reducing oxidative stress. Although some studies have examined the relationship between Mn and metabolic syndrome (MetS), no systematic review and meta-analysis has been presented to summarize the evidence. Therefore, the present review examined the association between dietary and environmental Mn exposure, and MetS risk. A total of nine cross-sectional studies and three case-control studies were included, which assessed Mn from diet, serum, urine, and whole blood. The association of the highest Mn level from diet (three studies, odds ratio (OR): 0.83, 95% confidence interval (C.I.) = 0.57, 1.21), serum (two studies, OR: 0.87, 95% C.I. = 0.66, 1.14), urine (two studies, OR: 0.84, 95% C.I. = 0.59, 1.19), and whole blood (two studies, OR: 0.92, 95% C.I. = 0.53, 1.60) were insignificant, but some included studies have suggested a non-linear relationship of urinary and blood Mn with MetS, and higher dietary Mn may associate with a lower MetS risk in some of the included studies. While more evidence from prospective cohorts is needed, future studies should use novel statistical approaches to evaluate relative contribution of Mn on MetS risk along with other inter-related exposures.

Cellular and genetic mechanism of bacterial mercury resistance and their role in biogeochemistry and bioremediation

Mercury (Hg) is a highly toxic element that occurs at low concentrations in nature. However, various anthropogenic and natural sources contribute around 5000 to 8000 metric tons of Hg per year, rapidly deteriorating the environmental conditions. Mercury-resistant bacteria that possess the mer operon system have the potential for Hg bioremediation through volatilization from the contaminated milieus. Thus, bacterial mer operon plays a crucial role in Hg biogeochemistry and bioremediation by converting both reactive inorganic and organic forms of Hg to relatively inert, volatile, and monoatomic forms. Both the broad-spectrum and narrow-spectrum bacteria harbor many genes of mer operon with their unique definitive functions. The presence of mer genes or proteins can regulate the fate of Hg in the biogeochemical cycle in the environment. The efficiency of Hg transformation depends upon the nature and diversity of mer genes present in mercury-resistant bacteria. Additionally, the bacterial cellular mechanism of Hg resistance involves reduced Hg uptake, extracellular sequestration, and bioaccumulation. The presence of unique physiological properties in a specific group of mercury-resistant bacteria enhances their bioremediation capabilities. Many advanced biotechnological tools also can improve the bioremediation efficiency of mercury-resistant bacteria to achieve Hg bioremediation.

Mercury Exposure and Risk of Type 2 Diabetes: A Systematic Review and Meta-Analysis

METHODS

Scopus and PubMed databases were systematically searched from their inception to November 2021 to obtain pertinent studies. Standardized mean differences (SMDs) with corresponding 95% confidence intervals (CIs) were calculated to evaluate the difference in Hg levels between people with and without T2DM. The association of the Hg exposure with T2DM was assessed using a random-effects model by pooling the odds ratios (ORs) and 95% CIs.

RESULTS

A total of 17 studies, with 42,917 participants, aged ≥18 years, were analyzed. Overall, Hg levels were significantly higher in T2DM patients compared with non-T2DM controls (SMD = 1.07; 95%CI = 0.59 to 1.55, P ≤ 0.001), with significant heterogeneity across studies (I² = 96.1%; P=≤0.001). No significant association was found between Hg exposure and risk of T2DM in the overall analysis and subgroup analysis based on the source of sample and study design. However, higher exposure to Hg was related to reduced risk of T2DM in men (OR = 0.71; 95%CI = 0.57 to 0.88), but not in women. No significant evidence for publication bias was detected.

CONCLUSIONS

Although the Hg level in T2DM is significantly higher than that of nondiabetics, there was no association between Hg exposure and the overall risk of T2DM. Nevertheless, our study shows that higher exposure to Hg might reduce the risk of T2DM in men.

Cadmium exposure and risk of diabetes and prediabetes: A systematic review and dose-response meta-analysis

BACKGROUND

Cadmium exposure has been associated with increased diabetes risk in several studies, though there is still considerable debate about the magnitude and shape of the association.

OBJECTIVE

To perform a systematic review and meta-analysis of observational studies investigating the relation between cadmium exposure and risk of type 2 diabetes and prediabetes, and to summarize data on the magnitude and shape of the association.

DATA SOURCE

After conducting an online literature search through October 1, 2021, we identified 42 eligible studies investigating the association between cadmium exposure and risk of diabetes and prediabetes.

STUDY ELIGIBILITY CRITERIA

We included studies that assessed cadmium exposure through biomarker levels; examined type 2 diabetes or prediabetes among outcomes; and reported effect estimates for cadmium exposure for meta-analysis only.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies were evaluated using ROBINS-E risk of bias tool. We quantitively assessed the relation between exposure and study outcomes using one-stage dose-response meta-analysis with a random effects meta-analytical model.

RESULTS

In the meta-analysis, comparing highest-versus-lowest cadmium exposure levels, summary relative risks (RRs) for type 2 diabetes were 1.24 (95% confidence interval 0.96-1.59), 1.21 (1.00-1.45), and 1.47 (1.01-2.13) for blood, urinary, and toenail matrices, respectively. Similarly, there was an increased risk of prediabetes for cadmium concentrations in both urine (RR = 1.41, 95% CI: 1.15-1.73) and blood (RR = 1.38, 95% CI: 1.16-1.63). In the dose-response meta-analysis, we observed a consistent linear positive association between cadmium exposure and diabetes risk, with RRs of 1.25 (0.90-1.72) at 2.0 µg/g of creatinine. Conversely for blood cadmium, diabetes risk appeared to increase only above 1 µg/L. Prediabetes risk increased up to approximately 2 µg/g creatinine above which it reached a plateau with RR of 1.42 (1.12-1.76) at 2 µg/g creatinine.

LIMITATIONS AND CONCLUSIONS

This analysis provides moderate-certainty evidence for a positive association between cadmium exposure (measured in multiple matrices) and risk of both diabetes and prediabetes.

Uma revisão de escopo de revisões sistemáticas sobre exposição humana ao mercúrio

Resumo: Introdução: a promulgação da Convenção de Minamata no Brasil em 2018 incentivou o cumprimento dos seus objetivos em reduzir o uso e a poluição por mercúrio. Objetivo: caracterizar a produção científica sobre exposição humana ao mercúrio e identificar lacunas de conhecimento a fim de subsidiar a tomada de decisão em saúde. Métodos: revisão de escopo de revisões sistemáticas e metanálises, sem restrição de idioma ou data de publicação, utilizando as bases PubMed, BVS e Cochrane Library. Resultados: 71 estudos atenderam aos critérios de elegibilidade, com 40 revisões sistemáticas, 30 metanálises e 1 overview. Amálgama dentário e contaminação alimentar e ambiental por atividades que utilizam mercúrio foram as fontes de exposição mais mencionadas. Os temas mais estudados contaram com transtornos mentais e comportamentais, assim como uso de biomarcadores e testes neurocomportamentais relacionados à exposição ao mercúrio. Discussão: lacunas como a exposição ocupacional ao mercúrio, uso em práticas tradicionais e em cosméticos apontam para a necessidade de mais estudos. As revisões identificadas podem oferecer subsídios para sínteses de evidências e protocolos de atenção à saúde de populações expostas, assim como para a elaboração de políticas públicas que visem o controle do uso e da exposição ao mercúrio.

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.

Antioxidant status in relation to heavy metals induced oxidative stress in patients with polycystic ovarian syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is a global health concern for women of reproductive age, as 6.5% of women worldwide are affected by this syndrome. PCOS is marked by hyperandrogenism, anovulation, menstrual abnormalities, and polycystic ovaries. Metals such as arsenic, cadmium, lead and mercury are considered to be systemic toxicants/human carcinogens and seem to have devastating effects on humans, even at minimal exposures. One of the probable aetiological factors for PCOS has been identified as oxidative stress. In view of the probable associations among oxidative stress, metal toxicity and PCOS, the present study examined the role of heavy metals in the generation of oxidative stress among females. This prospective study included 106 women (56 women diagnosed with PCOS and 50 women who were not diagnosed with PCOS as control women). There were no significant differences in the sociodemographic characteristics between the two groups except for the irregularity of menses and the presence of acne. The serum As, Cd, Pb, and Hg levels increased and the serum glutathione (GSH) and superoxide dismutase (SOD) levels diminished significantly in the PCOS group compared to the control group at P < 0.001. The SOD levels were negatively correlated with the As and Pb levels at P < 0.05. Additionally, the PCOS group exhibited a strong negative correlation between the GSH and As levels (P < 0.01), GSH and Pb levels (P < 0.05) and GSH and Hg levels (P < 0.01). Furthermore, the As levels were positively correlated with increased levels of Cd, Pb and Hg among PCOS women. Significant positive correlations were observed between Pb and Cd and between Cd and Hg at P < 0.001. The outcome of the study provides clear insight into the role of metal-induced oxidative stress, which plays a vital role in the pathophysiology underlying PCOS and suggests the use of these markers as prognostic tools to reduce the consequences of high-risk exposure to these metals among females.

Early pregnancy essential and non-essential metal mixtures and gestational glucose concentrations in the 2nd trimester: Results from project viva

Metals are involved in glucose metabolism, and some may alter glycemic regulation. However, joint effects of essential and non-essential metals on glucose concentrations during pregnancy are unclear. This study explored the joint associations of pregnancy exposures to essential (copper, magnesium, manganese, selenium, zinc) and non-essential (arsenic, barium, cadmium, cesium, lead, mercury) metals with gestational glucose concentrations using 1,311 women enrolled 1999-2002 in Project Viva, a Boston, MA-area pregnancy cohort. The study measured erythrocyte metal concentrations from 1st trimester blood samples and used glucose concentrations measured 1 h after non-fasting 50-gram glucose challenge tests (GCT) from clinical gestational diabetes screening at 26-28 weeks gestation. Bayesian Kernel Machine Regression (BKMR) and quantile-based g-computation were applied to model the associations of metal mixtures-including their interactions-with glucose concentrations post-GCT. We tested for reproducibility of BKMR results using generalized additive models. The BKMR model showed an inverse U-shaped association for barium and a linear inverse association for mercury. Specifically, estimated mean glucose concentrations were highest around 75th percentile of barium concentrations [2.1 (95% confidence interval: -0.2, 4.4) mg/dL higher comparing to the 25th percentile], and each interquartile range increase of erythrocyte mercury was associated with 1.9 mg/dL lower mean glucose concentrations (95% credible interval: -4.2, 0.4). Quantile g-computation showed joint associations of all metals, essential-metals, and non-essential metals on gestational glucose concentrations were all null, however, we observed evidences of interaction for barium and lead. Overall, we found early pregnancy barium and mercury erythrocytic concentrations were associated with altered post-load glucose concentrations in later pregnancy, with potential interactions between barium and lead.

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.

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.

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.

Associations between blood and urinary manganese with metabolic syndrome and its components: Cross-sectional analysis of National Health and Nutrition Examination Survey 2011-2016

Manganese (Mn) may improve cardiometabolic health with its anti-oxidative ability. However, epidemiological evidence on the overall and sex-specific relationship between Mn exposure and metabolic syndrome (MetS) has been inconclusive. We evaluated the associations of urinary (n = 1713) and blood (n = 3335) Mn levels with the prevalence of MetS, its components (elevated waist circumference, impaired glucose metabolism, elevated blood pressure and dyslipidemia) and sex-dependent heterogeneities among participants in the United States National Health and Nutrition Examination Survey 2011-2016. After adjusting for multiple covariates and the levels of other metals (Arsenic, Barium, Cadmium, Mercury, Molybdenum, Tin and Uranium), urinary Mn at the third quartile associated with a lower odd of MetS (odds ratio [OR] = 0.55, 95% confidence interval [C.I.] = 0.32-0.97), elevated waist circumference (OR = 0.56, 95% C.I. = 0.36-0.86) and elevated fasting plasma glucose (OR = 0.46, 95% C.I. = 0.27-0.76) among overall participants, and lower odds of MetS (OR = 0.40, 95% C.I. = 0.16-0.99), elevated waist circumference (OR = 0.39, 95% C.I. = 0.19-0.81) and elevated fasting plasma glucose (OR = 0.44, 95% C.I. = 0.22-0.90) among men. The U-shaped dose-response relationship between urinary Mn and MetS (P non-linear = 0.008) was observed among all participants. We did not observe the significant associations of blood Mn with the prevalence of MetS. Compared with other metals, urinary Mn played a less important role in development of MetS (posterior inclusion probabilities [PIP] = 0.49 for Mn versus 0.54 to 0.91 for other metals), but the contribution of blood Mn (PIP = 0.59 versus 0.60 to 0.61) was similar to other blood metals (Cadmium, Lead, Mercury and Selenium). These findings have provided new evidence of the potential roles of Mn in cardiometabolic health, and the needs to explore how Mn interacts with multiple metals in sex-specific manner.

Methylmercury Induces Metabolic Alterations in Caenorhabditis elegans: Role for C/EBP Transcription Factor

Methylmercury (MeHg) is a well-known neurotoxicant; however, its role in metabolic diseases has been gaining wider attention. We have previously shown that MeHg causes metabolic alterations in Caenorhabditis elegans, leading to decreased nicotinamide adenine dinucleotide cofactor, mitochondrial dysfunction, and oxidative stress. We were, therefore, interested in whether MeHg also affects nutrient metabolism, particularly lipid homeostasis, which may contribute to the development of metabolic conditions such as obesity or metabolic syndrome (MS). RNA from wild-type worms exposed to MeHg was collected immediately after treatment and used for gene expression analysis by DNA microarray. MeHg differentially regulated 215 genes, 17 genes involved in lipid homeostasis, and 12 genes involved in carbohydrate homeostasis. Of particular interest was cebp-1, the worm ortholog to human C/EBP, a pro-adipogenic transcription factor implicated in MS. MeHg increased the expression of cebp-1 as well as pro-adipogenic transcription factors sbp-1 and nhr-49, triglyceride synthesis enzyme acl-6, and lipid transport proteins vit-2 and vit-6. Concurrent with the altered gene expression, MeHg increased triglyceride levels, lipid storage, and feeding behaviors. Worms expressing mutant cebp-1 were protected from MeHg-induced alterations in lipid content, feeding behaviors, and gene expression, highlighting the importance of this transcription factor in the worm's response to MeHg. Taken together, our data demonstrate that MeHg induces biochemical, metabolic, and behavioral changes in C. elegans that can lead to metabolic dysfunction.

The relationship between dietary exposure to persistent organic pollutants from fish consumption and type 2 diabetes among First Nations in Canada

OBJECTIVE

We previously examined the associations between dietary dichlorodiphenyldichloroethylene (DDE) and polychlorinated biphenyls (PCBs) intake from fish consumption and type 2 diabetes (T2D) prevalence in Ontario and Manitoba. This study aims to further explore the relationship in a regionally representative sample of First Nations adults living on-reserve across Canada.

METHODS

Dietary, health and lifestyle data collected by the cross-sectional First Nations Food, Nutrition and Environment Study (2008-2018) were analyzed. This participatory study included 6091 First Nations adult participants who answered questions on T2D. The consumption of locally caught fish was estimated with a food frequency questionnaire. A total of 551 samples from 96 fish species were collected and analyzed for the presence of DDE and PCBs. The associations between fish and dietary DDE/PCBs intake with self-reported T2D were investigated using multiple logistic regression models adjusted for confounders.

RESULTS

Dietary exposure to DDE (>2.11 ng/kg/bw) and PCBs (>1.47 ng/kg/bw) vs no exposure was positively associated with T2D with ORs of 2.33 (95% CI: 1.24-4.35) for DDE and 1.43 (95% CI: 1.01-3.59) for PCBs. The associations were stronger among females (DDE OR = 3.11 (1.41-6.88); PCBs OR = 1.76 (1.10-3.65)) and older individuals (DDE OR = 2.64 (1.12-6.20); PCBs OR = 1.44 (1.01-3.91)) as compared with males and younger participants. Also, significant dose-response relationships were found for fish consumption in females only.

CONCLUSION

This study confirms our previous findings that dietary DDE/PCBs exposure may increase the risk of T2D. The effect of DDE/PCBs from fish consumption is driven by geographical differences in DDE/PCBs concentrations in fish and by the amount of fish consumed, and is more prominent in females than in males.

Exposure to heavy metals from point pollution sources and risk of incident type 2 diabetes among women: a prospective cohort analysis

Heavy metal exposures may contribute to diabetes risk but prospective studies are uncommon. We analyzed the Australian Longitudinal Study on Women's Health (three cohorts aged 18-23, 45-50, or 70-75 at baseline in 1996, N = 34,191) merged with emissions data for 10 heavy metals (As, Be, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn) from the National Pollutant Inventory. Over 20-year follow-up, 2,584 women (7.6%) reported incident diabetes. Cox proportional hazards regression models showed that women aged 45-50 at baseline had higher diabetes risk in association with exposure to total air emissions, total water emissions, all individual metals air emissions, and six individual water emissions. After correction for false discovery rate, nine of 11 air emissions and five water emissions remained significant. Associations were not observed for land-based emissions, or for younger or older cohorts. Emissions were dominated by mining, electricity generation and other metals-related industrial processes.

Diet: A Source of Endocrine Disruptors

BACKGROUND

Food is indispensable for human life and determines the health and wellbeing of the consumer. As food is the source of energy for humans, it also emerges as one of the most important sources of exposure to deleterious chemicals both natural and synthetic. The food exposed chemicals cause a number of detrimental health effects in humans, with endocrine disruption being of serious concern amongst these effects. Such chemicals disrupting the health of endocrine system are known as endocrine-disrupting chemicals (EDCs). The food exposed EDCs need to be identified and classified to effectuate a cautious consumption of food by all and especially by vulnerable groups.

AIM

The aim of the present review was to discuss food as a source of exposure to common endocrine disruptors in humans. This review presents the occurrence and levels of some of the critical endocrine disruptors exposed through frequently consumed diets.

METHODS

The major source of data was PubMed, besides other relevant publications. The focus was laid on data from the last five years, however significant earlier data was also considered.

CONCLUSION

The food as a source of endocrine disruptors to humans cannot be neglected. It is highly imperative for the consumer to recognize food as a source of EDCs and make informed choices in the consumption of food items.

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.

Mercury in the human adrenal medulla could contribute to increased plasma noradrenaline in aging

Plasma noradrenaline levels increase with aging, and this could contribute to the sympathetic overactivity that is associated with essential hypertension and the metabolic syndrome. The underlying cause of this rise in noradrenaline is unknown, but a clue may be that mercury increases noradrenaline output from the adrenal medulla of experimental animals. We therefore determined the proportion of people from 2 to 104 years of age who had mercury in their adrenal medulla. Mercury was detected in paraffin sections of autopsied adrenal glands using two methods of elemental bioimaging, autometallography and laser ablation-inductively coupled plasma-mass spectrometry. Mercury first appeared in cells of the adrenal medulla in the 21–40 years group, where it was present in 52% of samples, and increased progressively in frequency in older age groups, until it was detected in 90% of samples from people aged over 80 years. In conclusion, the proportion of people having mercury in their adrenal medulla increases with aging. Mercury could alter the metabolism of catecholamines in the adrenal medulla that leads to the raised levels of plasma noradrenaline in aging. This retrospective autopsy study was not able to provide a definitive link between adrenal mercury, noradrenaline levels and hypertension, but future functional human and experimental studies could provide further evidence for these associations.

Temporal variation of total mercury levels in the hair of pregnant women from the Maternal-Infant Research on Environmental Chemicals (MIREC) study

Prenatal exposure to total mercury (T-Hg) comes from both natural and anthropogenic sources. T-Hg can cross the blood-brain and placental barriers, and may be associated with future neurological and physiological dysfunctions. Scalp hair is an optimal and non-invasive indicator of chronic T-Hg exposure. As part of the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, hair samples from 350 women were collected within weeks after giving birth, to determine temporal variations in T-Hg levels from preconception to delivery, and to compare these levels to corresponding levels measured in other matrices (maternal and umbilical cord blood, and infant's meconium). A maximum of 12 one-cm hair segments were cut starting at the scalp; segments closer to the scalp reflected recent exposure (within the last month). For proper comparison, the hair segments were matched with the collection dates for other matrices. GM hair T-Hg levels greatly decreased during pregnancy, from 0.26 μg g^-1 (preconception or full-length hair) to 0.18 μg g^-1 (at delivery or segments closer to the scalp). A similar decreasing trend was found for T-Hg in maternal blood: 1st trimester (0.60 μg L^-1) to 3rd trimester (0.47 μg L^-1). The median hair-to-blood ratios of T-Hg levels varied from 364 (1st trimester), to 408 (3rd trimester), to 229 (cord blood). Very low T-Hg levels were detected in meconium. Mercury levels in blood and hair correlated with consumption of large predatory fish.

Mercury exposure, cardiovascular disease, and mortality: A systematic review and dose-response meta-analysis

BACKGROUND

There is evidence that exposure to mercury (Hg) may be a risk factor for cardiovascular disease (CVD).

OBJECTIVE

To conduct a systematic review of published studies and a meta-analysis of the results to examine the associations between chronic Hg exposure and CVD outcomes.

METHODS

We searched PubMed, Embase, and TOXLINE using previously developed strategies. Studies were selected according to a priori-defined inclusion criteria, and their qualities were assessed. Study estimates were extracted, and subgroup analyses were conducted to explore potential sources of heterogeneity: 1) fatal vs. nonfatal events, 2) cohort study vs. non-cohort study, and 3) inorganic Hg vs. methyl mercury (MeHg). Dose-response meta-analyses were conducted for MeHg exposure and fatal/nonfatal ischemic heart disease (IHD), stroke, and all CVD.

RESULTS

A total of 14 studies reporting results collected from more than 34,000 participants in 17 countries were included in the meta-analysis. Hg exposure was associated with an increase in nonfatal IHD (relative risk (RR): 1.21 (0.98, 1.50)), all-cause mortality (RR: 1.21 (0.90, 1.62)), CVD mortality (RR: 1.68 (1.15, 2.45)), and mortality due to other heart diseases (RR: 1.50 (1.07, 2.11)). No association was observed between Hg exposure and stroke. A heterogeneous relationship was found between studies reporting fatal and nonfatal outcomes and between cohort and non-cohort studies. However, these differences were mainly due to differences in Hg exposure level. Occupational inorganic Hg exposure was associated with similar increases in different mortality outcomes. A J-shaped relationship between Hg exposure and different fatal/nonfatal outcomes was observed, with turning points at hair Hg concentrations of 1 μg/g for IHD and 2 μg/g for stroke and all CVD.

CONCLUSION

Chronic exposure to Hg was associated with an increased risk of all-cause mortality and fatal/nonfatal IHD. The risk of multiple cardiovascular endpoints starts to increase consistently at a hair Hg concentration of 2 μg/g.

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.

Curcumin ameliorates mercuric chloride-induced liver injury via modulating cytochrome P450 signaling and Nrf2/HO-1 pathway

Environmental mercury is a concern for coastal ecosystem health, and exerts adverse effects on human health. Despite the growing body of evidence showing the hepatoprotective roles of curcumin on mercury, the knowledge between the macroscopic descriptions and the actual mechanism(s) underlying these processes is getting larger remains elusive. Herein, mice received single injection of mercuric chloride (HgCl₂) (5 mg/kg body weight) and/or curcumin (50 mg/kg, body weight, p.o.). Firstly, the results showed curcumin could decline HgCl₂-induced up-regulated the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Additionally, we also found that curcumin could suppress inflammatory damage, unbalance of trace elements (including sodium, magnesium, kalium, calcium overload), oxidative burst induced by HgCl₂, which could be associated with cytochrome P450 (CYP450) signaling. Secondly, we found that curcumin could prevent HgCl₂-induced cell death both in vivo and in vitro. Furthermore, curcumin significantly increased the nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) and consequently upregulated the expression of heme oxygenase 1 (HO-1) under HgCl₂ treatment. Meanwhile, inhibition of HO-1 by zinc protoporphyria could abolish the cytoprotective effects of curcumin in HgCl₂-treated L02 hepatocytes. In conclusion, our data identify that curcumin could enhance Nrf2-mediated HO-1 to upregulate antioxidant ability, which might be associate with CYP450 signaling to suppress liver damage induced by HgCl₂. The present study further enriches and perfects the mechanism theory of HgCl₂ toxicity and suggest that the CYP450 signaling and Nrf2/HO-1 pathway is important in shedding light on curcumin's hepatoprotective effects in HgCl₂ toxicity.

Mercury in Pancreatic Cells of People with and without Pancreatic Cancer

Toxic metals have been implicated in the pathogenesis of pancreatic cancer. Human exposure to mercury is widespread, but it is not known how often mercury is present in the human pancreas and which cells might contain mercury. We therefore aimed to determine, in people with and without pancreatic cancer, the distribution and prevalence of mercury in pancreatic cells. Paraffin-embedded sections of normal pancreatic tissue were obtained from pancreatectomy samples of 45 people who had pancreatic adenocarcinoma, and from autopsy samples of 38 people without pancreatic cancer. Mercury was identified using two methods of elemental bio-imaging: (1) With autometallography, inorganic mercury was seen in islet cells in 14 of 30 males (47%) with pancreatic cancer compared to two of 17 males (12%) without pancreatic cancer (p = 0.024), and in 10 of 15 females (67%) with pancreatic cancer compared to four of 21 females (19%) without pancreatic cancer (p = 0.006). Autometallographic mercury was present in acinar cells in 24% and in periductal cells in 11% of people with pancreatic cancer, but not in those without pancreatic cancer. (2) Laser ablation-inductively coupled plasma-mass spectrometry confirmed the presence of mercury in islets that stained with autometallography and detected cadmium, lead, chromium, iron, nickel and aluminium in some samples. In conclusion, the genotoxic metal mercury is found in normal pancreatic cells in more people with, than without, pancreatic cancer. These findings support the hypothesis that toxic metals such as mercury contribute to the pathogenesis of pancreatic cancer.

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.

Effects of environmental metals on mitochondrial bioenergetics of the CD-1 mice pancreatic beta-cells

Environmental metals are believed to have diabetogenic effects without any clear underlying mechanisms. The study investigated the effects of metals, lead (Pb), mercury (Hg), cadmium (Cd), and molybdenum (Mo), on the bioenergetics of isolated pancreatic β-cells from CD-1 mice via different functional and structural techniques. The tested metals caused significant decrease in ATP production in concentration and exposure duration-dependent pattern; Cd was the most potent cytotoxic metal. In ATP assay estimated effective concentration 50 (EC50) (25, 40, 20, and 100 μM for Pb, Hg, Cd, and Mo, respectively), the metals also significantly inhibited the glucose-stimulated insulin secretion (GSIS), mitochondrial complexes activity, mitochondrial membranes potential, and oxygen consumption rates of the treated cells with parallel increases in their lactate production and in the mitochondrial swelling and permeation of their inner mitochondrial membranes to potassium (K⁺) and hydrogen (H⁺) ions. In addition, Cd, Pb, and Hg produced significant increases in mitochondrial membrane fluidity (MMF) with significant decreases in saturated/unsaturated fatty acid ratios. In 10 μM concentration, away from Mo, the three metals showed inhibitory effects on the mitochondrial functions to variable degrees. Only Cd showed significant effect on MMF and fatty acid ratios at a concentration of 10 μM. In conclusion, the tested metals significantly affected the bioenergetics of the pancreatic β-cells with significant effect on GSIS. Cd showed the most significant functional and structural effects on their mitochondria followed by Pb, then Hg, while Mo was almost safe up to 10 μM concentration. Hence, bioenergetic mitochondrial disruption can be considered as an underlying mechanism of the diabetogenic effects of the tested metals.

Association between exposure to persistent organic pollutants and mercury, and glucose metabolism in two Canadian Indigenous populations

BACKGROUND

The body burden of metals and persistent organic pollutants (POPs) is particularly high in populations that rely on fish and other marine species for sustenance. This exposure has been associated with an increased risk of type 2 diabetes, but results remain contrasted.

OBJECTIVE

We studied this association in two Indigenous populations of northern Québec (Canada) with markedly different prevalences of diabetes and levels of exposure to POPs and mercury.

METHODS

As part of health surveys conducted in 2004-2009, diabetes prevalence and glucose metabolism (glucose, insulin, HOMA-IR, HOMA-B) in non-diabetic fasting adults were assessed using similar protocols in two populations: Inuit from Nunavik (n = 877) and Cree from Eeyou Istchee territory (n = 780). Blood mercury, plasma polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides/metabolites and polybrominated diphenylethers (PBDEs) levels were measured in samples collected at the time of examination. Logistic and linear regressions and restricted cubic splines analyses were conducted adjusting for sex, age, waist circumference, smoking and omega-3 fatty acid content in plasma phospholipids.

RESULTS

Diabetes prevalence was higher in Cree (20%) than in Inuit (7%), whereas environmental exposure was 2 to 3-fold greater in Inuit than in Cree participants. In the range of exposure common to the two populations, we observed similar linear increases in the risk of diabetes with increasing contaminant exposure. Among Cree participants, fasting glucose was positively associated with plasma PBDE level, and HOMA-B negatively associated with concentrations of ∑PCBs, dichlorodiphenyldichloroethylene, PBDEs and ∑OC pesticides. Among Inuit participants, a trend towards reduced insulin secretion was observed in association with most contaminants, but the relation was nonlinear (greater reduction at intermediate levels of exposure). A significant increase in fasting glucose levels was observed at elevated blood mercury levels (>16 μg/L).

CONCLUSION

The observed association between POPs exposure and diabetes risk in the two populations studied should be confirmed using prospective design. Our results suggest the need for additional research on the physiopathological process through which POPs exposure may induce type 2 diabetes in these Indigenous populations.

Mercury exposure and premature mortality in the Grassy Narrows First Nation community: a retrospective longitudinal study

BACKGROUND

Little is known about the influence of toxic exposures on reduced life expectancy in First Nations people in Canada. The Grassy Narrows First Nation community have lived with the consequences of one of the worst environmental disasters in Canadian history. In the early 1960s, 10 000 kg of mercury (Hg) was released into their aquatic ecosystem. Although Hg concentration in fish, their dietary staple, decreased over time, it remains high. We aimed to examine whether elevated Hg exposure over time contributes to premature mortality (younger than 60 years) in this community.

METHODS

We did longitudinal and case-control analyses with data for individuals of the Grassy Narrows First Nation community. In 2019, the community obtained their historical Hg biomarker data from a government surveillance programme, which was then shared with the authors. A matched-pair approach allowed us to compare longitudinal hair Hg concentration between cases (individuals who died aged younger than 60 years) and controls (individuals who lived beyond 60 years). Matching criteria included year of birth (allowing 2 years either side), sex, and a minimum of four hair Hg concentration measures, of which at least two were in the same year. Analyses included change-point detection, interrupted time series, mixed models, and Cox survival models.

FINDINGS

We analysed data collected between Jan 1, 1970, and Jan 31, 1997, for 657 individuals (319 women and 338 men, born between 1884 and 1991) for whom we assembled a retrospective database of yearly measures of hair Hg concentration (n=3603). Hair Hg concentration decreased over time. A subgroup of 222 individuals (107 women and 115 men) reached or could have reached 60 years old by August, 2019. There was an increased risk of dying at a younger age among those with at least one hair Hg measure of 15 μg/g or more (adjusted hazard ratio 1·55, 95% CI 1·11-2·16; p=0·0088). Among the deceased individuals (n=154), longevity decreased by 1 year with every 6·25 μg/g (4·35-14·29) increase in hair Hg concentration. Analyses of 36 matched pairs showed that hair Hg concentration of those who died aged younger than 60 years was 4·7 times higher (3·4-5·9) than controls.

INTERPRETATION

The consistent findings between our different analyses support an association between long-term Hg exposure from freshwater fish consumption and premature mortality in this First Nation community. There is a need to do risk-benefit analyses of freshwater fish consumption in environmentally contaminated regions.

FUNDING

Canadian Institutes of Health Research.

Toxicity of mercury: Molecular evidence

Minamata disease in Japan and the large-scale poisoning by methylmercury (MeHg) in Iraq caused wide public concerns about the risk emanating from mercury for human health. Nowadays, it is widely known that all forms of mercury induce toxic effects in mammals, and increasing evidence supports the concern that environmentally relevant levels of MeHg could impact normal biological functions in wildlife. The information of mechanism involved in mercurial toxicity is growing but knowledge gaps still exist between the adverse effects and mechanisms of action, especially at the molecular level. A body of data obtained from experimental studies on mechanisms of mercurial toxicity in vivo and in vitro points to that disruption of the antioxidant system may play an important role in the mercurial toxic effects. Moreover, the accumulating evidence indicates that signaling transduction, protein or/and enzyme activity, and gene regulation are involving in mediating toxic and adaptive response to mercury exposure. We conducted here a comprehensive review of mercurial toxic effects on wildlife and human, in particular synthesized key findings of molecular pathways involved in mercurial toxicity from the cells to human. We discuss the molecular evidence related mercurial toxicity to the adverse effects, with particular emphasis on the gene regulation. The further studies relying on Omic analysis connected to adverse effects and modes of action of mercury will aid in the evaluation and validation of causative relationship between health outcomes and gene expression.

Association of Fish Consumption and Mercury Exposure During Pregnancy With Metabolic Health and Inflammatory Biomarkers in Children

Importance

The balance of mercury risk and nutritional benefit from fish intake during pregnancy for the metabolic health of offspring to date is unknown.

Objective

To assess the associations of fish intake and mercury exposure during pregnancy with metabolic syndrome in children and alterations in biomarkers of inflammation in children.

Design, Setting, and Participants

This population-based prospective birth cohort study used data from studies performed in 5 European countries (France, Greece, Norway, Spain, and the UK) between April 1, 2003, and February 26, 2016, as part of the Human Early Life Exposome (HELIX) project. Mothers and their singleton offspring were followed up until the children were aged 6 to 12 years. Data were analyzed between March 1 and August 2, 2019.

Exposures

Maternal fish intake during pregnancy (measured in times per week) was assessed using validated food frequency questionnaires, and maternal mercury concentration (measured in micrograms per liter) was assessed using maternal whole blood and cord blood samples.

Main Outcomes and Measures

An aggregate metabolic syndrome score for children was calculated using the z scores of waist circumference, systolic and diastolic blood pressures, and levels of triglyceride, high-density lipoprotein cholesterol, and insulin. A higher metabolic syndrome score (score range, -4.9 to 7.5) indicated a poorer metabolic profile. Three protein panels were used to measure several cytokines and adipokines in the plasma of children.

Results

The study included 805 mothers and their singleton children. Among mothers, the mean (SD) age at cohort inclusion or delivery of their infant was 31.3 (4.6) years. A total of 400 women (49.7%) had a high educational level, and 432 women (53.7%) were multiparous. Among children, the mean (SD) age was 8.4 (1.5) years (age range, 6-12 years). A total of 453 children (56.3%) were boys, and 734 children (91.2%) were of white race/ethnicity. Fish intake consistent with health recommendations (1 to 3 times per week) during pregnancy was associated with a 1-U decrease in metabolic syndrome score in children (β = -0.96; 95% CI, -1.49 to -0.42) compared with low fish consumption (<1 time per week) after adjusting for maternal mercury levels and other covariates. No further benefit was observed with fish intake of more than 3 times per week. A higher maternal mercury concentration was independently associated with an increase in the metabolic syndrome score of their offspring (β per 2-fold increase in mercury concentration = 0.18; 95% CI, 0.01-0.34). Compared with low fish intake, moderate and high fish intake during pregnancy were associated with reduced levels of proinflammatory cytokines and adipokines in children. An integrated analysis identified a cluster of children with increased susceptibility to metabolic disease, which was characterized by low fish consumption during pregnancy, high maternal mercury levels, decreased levels of adiponectin in children, and increased levels of leptin, tumor necrosis factor α, and the cytokines interleukin 6 and interleukin 1β in children.

Conclusions and Relevance

Results of this study suggest that moderate fish intake consistent with current health recommendations during pregnancy was associated with improvements in the metabolic health of children, while high maternal mercury exposure was associated with an unfavorable metabolic profile in children.