Effects of methyl mercury on the activity and gene expression of mouse Langerhans islets and glucose metabolism

Vitamin C Alleviates the Risk of Gestational Diabetes Mellitus Associated With Exposure to Metals

Background: Exposure to heavy metals has been suggested to increase the risk of gestational diabetes mellitus (GDM) through the oxidative stress pathway. The study is aimed at examining whether vitamin C could modify the association between exposure to heavy metals and risk of GDM. Methods: We conducted a case-control study in Taiyuan, China, with 776 GDM cases and 776 controls. Data on vitamin C intake from diet and supplements were collected through questionnaires. Concentrations of metals in participants' blood were measured using inductively coupled plasma-mass spectrometry (ICP-MS). Unconditional logistic regression models were applied to estimate effect modification of vitamin C on the association between heavy metals and GDM. Results: Women with higher blood levels of mercury (Hg) (odds ratio (OR) = 2.36, 95% confidence interval (CI): 1.43, 3.92 and 2.04, 95% CI: 1.20, 3.46 for the second and third vs. the first tertile) and arsenic (As) (OR = 2.46, 95% CI: 1.37, 4.43 and 2.16, 95% CI: 1.12, 4.17 for the second and third vs. the first tertile) exposure were associated with increased risk of GDM among women without vitamin C supplement use and having dietary vitamin C intake < 85 mg/day. We found no significant association with metals among women who took vitamin C supplements and/or dietary vitamin C ≥ 85 mg/day. Significant interactions were observed between vitamin C and exposures to metals (i.e., Hg and As) on the risk of GDM (P interaction = 0.048 and 0.045, respectively). Conclusions: Our study, for the first time, suggests that vitamin C supplement use or higher dietary vitamin C intake during preconception and early pregnancy could alleviate the risk of GDM associated with exposure to As and Hg. The results warrant further investigation.

Metalloestrogens exposure and risk of gestational diabetes mellitus: Evidence emerging from the systematic review and meta-analysis

BACKGROUND

Metalloestrogens are metals and metalloid elements with estrogenic activity found everywhere. Their impact on human health is becoming more apparent as human activities increase.

OBJECTIVE

Our aim is to conduct a comprehensive systematic review and meta-analysis of observational studies exploring the correlation between metalloestrogens (specifically As, Sb, Cr, Cd, Cu, Se, Hg) and Gestational Diabetes Mellitus (GDM).

METHODS

PubMed, Web of Science, and Embase were searched to examine the link between metalloestrogens (As, Sb, Cr, Cd, Cu, Se, and Hg) and GDM until December 2023. Risk estimates were derived using random effects models. Subgroup analyses were conducted based on study countries, exposure sample, exposure assessment method, and detection methods. Sensitivity analyses and adjustments for publication bias were carried out to assess the strength of the findings.

RESULTS

Out of the 389 articles identified initially, 350 met our criteria and 33 were included in the meta-analysis, involving 141,175 subjects (9450 cases, 131,725 controls). Arsenic, antimony, and copper exposure exhibited a potential increase in GDM risk to some extent (As: OR = 1.28, 95 % CI [1.08, 1.52]; Sb: OR = 1.73, 95 % CI [1.13, 2.65]; Cu: OR = 1.29, 95 % CI [1.02, 1.63]), although there is a high degree of heterogeneity (As: Q = 52.93, p < 0.05, I2 = 64.1 %; Sb: Q = 31.40, p < 0.05, I2 = 80.9 %; Cu: Q = 21.14, p < 0.05, I2 = 71.6 %). Conversely, selenium, cadmium, chromium, and mercury exposure did not exhibit any association with the risk of GDM in our study.

DISCUSSION

Our research indicates that the existence of harmful metalloestrogens in the surroundings has a notable effect on the likelihood of GDM. Hence, we stress the significance of environmental elements in the development of GDM and the pressing need for relevant policies and measures.

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

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

Association of Blood Total Mercury with Dyslipidemia in a sample of U.S. Adolescents: Results from the National Health and Nutrition Examination Survey Database, 2011-2018

Background

Abnormal lipid profiles in adolescents predict metabolic and cardiovascular diseases in adulthood. While seafood consumption is the primary source of mercury exposure, it also provides beneficial nutrients such as omega-3 fatty acids (O3FA). Prior studies indicate that blood total mercury (TBHg) has endocrine disrupting effects and may be associated with abnormal lipid profiles in adolescents. However, the impact of beneficial nutrients on this relationship has not been examined. Our study investigated the relationship of TBHg with dyslipidemia and lipid profiles and potential confounding and modification of these relationships by sex, body mass index (BMI), selenium and O3FA from seafood consumption.

Methods

We examined 1,390 National Health and Nutrition Examination Survey participants 12-19 years of age from the 2011-2018 cycles. Using logistic and linear regression adjusted for survey design variables and stratified by sex a priori, we estimated the associations of TBHg and methylmercury with dyslipidemia, and with total cholesterol (TC), high (HDL-C) and low-density lipoprotein cholesterol (LDL-C) and triglycerides.

Results

The geometric mean of TBHg in this adolescent population was 0.44 μg/L. After controlling for socio-demographic covariates, BMI, serum selenium, age at menarche (females only) and average daily intake of O3FA; TBHg was significantly associated with higher TC levels (β=3.34, 95% CI: 0.19, 6.50; p<0.05) in females but not males. Methyl Hg was also associated with increased TC, as well as decreased HDL-C in females but not males. We did not find significant associations of Hg exposure with dyslipidemia, LDL-C or triglycerides levels in either male or female adolescents. However, we observed evidence of effect modification by BMI and serum selenium for associations of TBHg with TC levels in male and female adolescents, respectively.

Conclusion

Our findings of elevated TC levels in females but not males necessitates further research to better understand the underlying mechanisms driving these sex-specific associations.

Effects of mercury exposure on fetal body burden and its association with infant growth

Several studies have been conducted among South Korean to investigate effects of high blood mercury (Hg) levels. In this study fetal body burden of Hg in 344 pregnant women were estimated using a physiologically-based pharmacokinetic model (PBPK) and its associative effects on the growth of infants were analyzed. The association between cord blood Hg and growth variables at birth was analyzed based on parameters such as the sex of the newborn, living area, maternal age group, gestation day, maternal body mass index . We investigated the effects of Hg on infant growth through follow-ups, using a non-linear mixed model. The mean Hg levels in maternal and cord blood were 4.47 μg/L and 7.35 μg/L, respectively. Among the subjects, the corresponding fetal body burden for Methylmercury ranged between 26.3-86.9 mg. Cord blood Hg levels positively correlated with length at birth. Furthermore, the high cord blood group showed greater growth rates compared to the low cord blood group. Therefore, we suggest that pregnant women should make efforts to mitigate exposures to Hg, specifically from diet. Further research is suggested to investigate the relationship between the follow-up growth of the infants and Hg levels, considering fish consumption, diet information, and other environmental pollutants.

Association between whole blood metallic elements concentrations and gestational diabetes mellitus in Japanese women: The Japan environment and Children's study

BACKGROUND

Exposure to several metallic elements has been suggested as a risk factor for gestational diabetes mellitus (GDM), but inconsistent findings have been reported. This study aimed to examine the association between the maternal whole blood concentration of metallic elements (Hg, Pb, Cd, Mn, and Se) and GDM using the dataset of the Japan Environment and Children's Study (JECS), a nationwide birth cohort study, which was designed to examine the adverse effects of pre/post-natal exposure to hazardous environment.

METHODS

The data of 78,964 pregnant women who were participants of JECS were used. Blood samples were collected from the pregnant women at second/third trimester of gestation. We employed logistic regression analysis, quantile g-computation (QGC) and a distributed lag nonlinear model (DLNM) to examine the association between the blood concentration of metallic elements and the risk of GDM.

RESULTS

The prevalence of GDM was 2.1%. In the logistic regression analyses, maternal blood Hg was associated with an increased risk of GDM. In QGC analysis, although metallic elements mixtures were not related to an increased risk of GDM, Hg (52.6%) may be the main contributor. According to the results of DLNM, for maternal exposure to Hg, 4.99 ng/g was identified as its susceptible minimum window for elevated risk of GDM.

CONCLUSIONS

Our findings highlighted an association between Hg exposure and an increased risk of GDM. Studies of the underlying mechanisms and potential contributing factors, including fish intake, of this association are warranted.

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.

Contribution of trace element exposure to gestational diabetes mellitus through disturbing the gut microbiome

BACKGROUND

A healthy gut microbiome is critical for glucose metabolism during pregnancy. In vivo studies indicate that trace element affects the composition and function of the gut microbiome and potentially leads to metabolic disorders but their relationships are largely unknown. We aimed to investigate whether the gut microbiome plays a role in the relationship between trace element exposure and gestational diabetes mellitus (GDM).

METHODS

In a prospective cohort study, serum levels of 22 trace elements and the fecal gut microbiome composition were assessed in 837 pregnant women in the second trimester between 22 and 24 weeks of pregnancy prior to GDM diagnosis. Regression and mediation analysis were used to explore the link between element exposure, the gut microbiome, and GDM.

RESULTS

128 pregnant women (15.3%) were diagnosed with GDM. No individual trace elements were found significantly associated with GDM. In contrast, the composition of the gut microbiome was dramatically altered in women later diagnosed with GDM and characterized by lower alpha diversity and lower abundance of co-abundance groups (CAGs) composed of genera belonging to Ruminococcaceae, Coriobacteriales, and Lachnospiraceae. Rubidium (Rb) was positively associated with alpha diversity indices while mercury (Hg) and vanadium (V) showed negative associations. Elements including rubidium (Rb), thallium (Tl), arsenic (As), and antimony (Sb) were significantly correlated with GDM-related CAGs and mediation analysis revealed that Rb and Sb were inversely related to GDM risk by altering abundance levels of CAGs enriched for Lachnospiraceae, Coriobacteriales, and Ruminococcaceae.

CONCLUSION

Our study indicates that trace element exposure is associated with specific gut microbiome features that may contribute to GDM development, which could provide a new avenue for intervening in environmental exposure-related GDM.

Vinpocetine Effect on the Juncture of Diabetes and Aging: An in-vitro study

BACKGROUND

The rapid-growing population of diabetic patients and the elderly are among the direst challenges that the science of medicine is facing today. Targeting these two challenges can shed light on new means to control and ideally reverse this trend. In this experiment, Vinpocetine's effect on aged pancreatic beta-cell functions in correlation with oxidative stress was studied.

METHODS

Islet cells were isolated from the pancreas of aged rats and exposed to Vinpocetine, dissolved in acetone and RPMI, for 48 h. Then, senescence-associated molecular parameters, including P16 and P38 gene expressions and β-galactosidase activity, were investigated along with diabetic and inflammation markers.

RESULTS

Experimental results showed that Vinpocetine could significantly increase aged islets insulin secretion and also make a meaningful reduction in oxidative stress markers. This drug can also decrease expression levels of P16 and P38, the primary genes responsible for the aging pathway. TNF-α, IL-6, and NF-κB expressions were also reduced noticeably after treatment with Vinpocetine.

CONCLUSION

The current study showed that Vinpocetine, a derivative of the secondary plant metabolite called Vincamine, could break this vicious cycle of oxidative stress and aging by reducing oxidative stress and inflammation, thus inhibiting cellular aging.

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.

Roles of oxidative stress, apoptosis, and inflammation in metal-induced dysfunction of beta pancreatic cells isolated from CD1 mice

The diabetogenic effects of metals including lead (Pb), mercury (Hg), cadmium (Cd), and molybdenum (Mo) have been reported with poorly identified underlying mechanisms. The current study assessed the effect of metals on the roles of oxidative stress, apoptosis, and inflammation in beta pancreatic cells isolated from CD-1 mice, via different biochemical assays. Data showed that the tested metals were cytotoxic to the isolated cells with impaired glucose stimulated insulin secretion (GSIS). This was associated with increased reactive oxygen species (ROS) production, lipid peroxidation, antioxidant enzymes activities, active proapoptotic caspase-3 (cas-3), inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) levels in the intoxicated cells. Furthermore, antioxidant-reduced glutathione (GSH-R), cas-3 inhibitor z-VAD-FMK, IL-6 inhibitor bazedoxifene (BZ), and TNF-α inhibitor etanercept (ET) were found to significantly decrease metal-induced cytotoxicity with improved GSIS in metals' intoxicated cells. In conclusion, oxidative stress, apoptosis, and inflammation can play roles in metals-induced diabetogenic effect.

Ecological and toxicological assessments of anthropogenic contaminants based on environmental metabolomics

There has long been a great concern with growing anthropogenic contaminants and their ecological and toxicological effects on living organisms and the surrounding environment for decades. Metabolomics, a functional readout of cellular activity, can capture organismal responses to various contaminant-related stressors, acquiring direct signatures to illustrate the environmental behaviours of anthropogenic contaminants better. This review entails the application of metabolomics to profile metabolic responses of environmental organisms, e.g. animals (rodents, fish, crustacean and earthworms) and microorganisms (bacteria, yeast and microalgae) to different anthropogenic contaminants, including heavy metals, nanomaterials, pesticides, pharmaceutical and personal products, persistent organic pollutants, and assesses their ecotoxicological impacts with regard to literature published in the recent five years. Contaminant-induced metabolism alteration and up/down-regulation of metabolic pathways are revealed in typical organisms. The obtained insights of variations in global metabolism provide a distinct understanding of how anthropogenic contaminants exert influences on specific metabolic pathways on living organisms. Thus with a novel ecotechnique of environmental metabolomics, risk assessments of anthropogenic contaminants are profoundly demonstrated.

The role of taurine on chemotherapy-induced cardiotoxicity: A systematic review of non-clinical study

AIMS

Although chemotherapeutic agents have highly beneficial effects against cancer, they disturb the body's normal homeostasis. One of the critical side effects of chemotherapeutic agents is their deleterious effect on the cardiac system, which causes limitations of their clinical usage. Taurine constitutes more than 50% of the amino acids in the heart. The use of taurine might prevent chemotherapy-induced cardiotoxicity. This systematic study aims to evaluate the protective role of taurine against cardiotoxicity induced by chemotherapy.

METHODS

A systematic search was performed in databases up to November 2020, and the review is designed on PRISMA guidelines. The search keywords were selected based on our study target and were searched in the title and abstract. After the consecutive screening, out of a whole of 94 articles, 8 articles were included according to our inclusion and exclusion criteria.

KEY FINDINGS

According to the study results, chemotherapy decreases body and heart weight and increases mortality. Also, it induces some biochemical and histological changes compared to the control group. By co-administration of taurine with chemotherapy, alterations returned near to the average level. These protective effects of taurine are mediated through anti-oxidant, anti-inflammatory, and anti-apoptotic properties.

SIGNIFICANCE

Based on evaluated non-clinical studies, taurine ameliorates chemotherapy-induced cardiotoxicity, but its possible interaction with the efficacy of anti-cancer medicines that mostly act through induction of oxidants remains to be elucidated in the future. This needs conducting well-designed studies to assess the effectiveness and safety of this combination simultaneously.

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.

Mercury Exposure and Associations with Hyperlipidemia and Elevated Liver Enzymes: A Nationwide Cross-Sectional Survey

Mercury (Hg) has obesogenic properties. However, the associated health outcomes of population-level mercury exposure were unclear. This study investigated the relationships between blood mercury levels and obesity-related outcomes such as hyperlipidemia and elevated liver enzymes. Using the second cycle of the Korean National Environmental Health Survey (n = 6454), we performed logistic regression to examine the effects of Hg on hyperlipidemia and elevated liver enzymes. The blood mercury levels were significantly higher in the hyperlipidemia group (n = 3699, male: 4.03 μg/L, female: 2.83 μg/L) compared to the non-hyperlipidemia group (n = 2755, male: 3.48 μg/L, female: 2.69 μg/L), and high blood mercury levels were associated with an 11% higher risk of hyperlipidemia. The elevated liver enzymes group had higher mean blood mercury levels (n = 1189, male: 4.38 μg/L, female: 3.25 μg/L) than the normal group (n = 5265, male: 3.64 μg/L, female: 2.70 μg/L), and elevated blood mercury was associated with a 35% higher risk of elevated liver enzymes. Moreover, the effect was constant after adjusting for personal medications. These results indicate that mercury exposure is significantly associated with hyperlipidemia and elevated liver enzymes.

The Association Between Thyroid Injury and Apoptosis, and Alterations of Bax, Bcl-2, and Caspase-3 mRNA/Protein Expression Induced by Nickel Sulfate in Wistar Rats

To study the toxicity induced by Nickel sulfate (NiSO₄) on thyroid tissue, and investigate the role of apoptosis as the possible mechanism, thirty-two male Wistar rats were randomly divided into control group (normal saline, ip), low dose group (2.5 mg/kg day NiSO₄, ip), middle dose group (5 mg/kg day NiSO₄, ip), high dose group (10 mg/kg day NiSO₄, ip). After 40 consecutive days of treatment, there were obvious pathological changes in the thyroids of high dose group. Free T₄ (FT₄) and thyroid-stimulating hormone (TSH) were significantly lower in the NiSO₄-treated groups than those in the control group (F = 4.992, p = 0.016; F = 4.524, p = 0.012). The mRNA expression of Caspase-3 was significantly higher (F = 10.259, p = 0.014) in all NiSO₄-treated groups, and the mRNA expression of Bcl-2 was significantly lower (F = 9.225, p = 0.018) only in the high dose group. Both control group and the NiSO₄-treated groups showed no changes in the mRNA expression of Bax gene. The ratio of Bcl-2/Bax decreased with the increase in exposure dose of NiSO₄ (F = 13.382, p = 0.015). The mRNA expression of Fas went up in high dose group (F = 66.632, p < 0.001). The Caspase-3, Fas, and the Bax protein expressions measured by immunohistochemistry were consistent with the mRNA expression. The expression of Bcl-2 protein was significantly lower in the test groups than in the control group (F = 3.873, p = 0.025). NiSO₄ as an Endocrine Disrupting Chemical may induce the thyroid injury through apoptosis and lead to hypothyroidism. Also, apoptosis in thyroid tissues was closely related to the alternations of Caspase-3, Bcl-2, and Fas mRNA and protein expression.

Multiple metal concentrations and gestational diabetes mellitus in Taiyuan, China

BACKGROUND

The association between multiple metal concentrations and gestational diabetes mellitus (GDM) is poorly understood.

METHODS

A total of 776 women with GDM and an equal number of controls were included in the study. Concentrations of metals in participants' blood (nickel (Ni), arsenic (As), cadmium (Cd), antimony (Sb), thallium (Tl), mercury (Hg), lead (Pb)) were measured using inductively coupled plasma-mass. We used unconditional logistical regression models to estimate the associations between metals and GDM. We also employed weighted quantile sum (WQS) regression and principal components analysis (PCA) to examine metal mixtures in relation to GDM.

RESULTS

An increased risk of GDM was associated with As (OR = 1.49, 95% CI: 1.11, 2.01 for the 2nd tertile vs. the 1st tertile) and Hg (OR = 1.43, 95% CI: 1.09, 1.88 for the 3rd tertile vs. the 1st tertile). In WQS analysis, the WQS index was significantly associated with GDM (OR = 1.20, 95% CI: 1.02, 1.41). The major contributor to the metal mixture index was Hg (69.2%), followed by Pb (12.8%), and As (11.3%). Based on PCA, the second principal component, which was characterized by Hg, Ni, and Pb, was associated with an increased risk of GDM (OR = 1.46, 95% CI: 1.02, 2.08 for the highest quartile vs. the lowest quartile).

CONCLUSIONS

Our study results suggest that high metal levels are associated with an increased risk of GDM, and this increased risk is mainly driven by Hg and, to a lesser extent, by Ni, Pb, and As.

Biochemical evidence on the potential role of methyl mercury in hepatic glucose metabolism through inflammatory signaling and free radical pathways

Methylmercury (MeHg) is an extremely important environmental toxicant posing serious health risks to human health and a big source of environmental pollutant. Numerous evidence available showing a link between nervous system toxicity and MeHg exposure. Other forms of mercury are reason of metabolic toxic effects and alteration of DNA in the human body. The sources of exposure could be occupational or other environmental settings. In the present study MeHg was orally gavaged to mice, at doses of 2.5, 5, and 10 mg/kg for 4 weeks. Fasting hyperglycemia, activity of hepatic phoshphoenolpyruvate carboxykinase and glucose 6-phoshphate were reported high as compared to control group. Inflammatory markers like, tumor necrosis factor α, the actual end product of inflammatory mediators' cascade pathway was also raised in comparison to control group. Hyperinsulinemia observed in serum showed clear understanding of mercury induced insulin resistance. Moreover, tissue damage due to increased oxidative stress markers like, hepatic lipid peroxidation, 8-deoxygunosine, reactive oxygen species, and carbonyl groups was significantly higher as compared to control group. MeHg caused a significant reduction in antioxidant markers like ferric reducing antioxidant power and total thiol molecules. The present study highlighted that activity of key enzymes involved in glucose metabolism is changed, owing to MeHg induced toxicity in the liver. Induction of similar toxic effects assumed to be stimulated by the production of high quantity free radicals.

Chronic mercury at low doses impairs white adipose tissue plasticity

INTRODUCTION

The toxic effects of mercury (Hg) are involved in homeostasis of energy systems such as lipid and glucose metabolism, and white adipose tissue dysfunction is considered as a central mechanism leading to metabolic disorders.

OBJECTIVE

The aim of this study was to determine the effects of chronic inorganic Hg exposure at low doses on the lipid and glycemic metabolism.

METHODS

Male Wistar rats were divided into two groups and treated for 60 days with: saline solution, i.m. (Untreated) and mercury chloride, i.m. - 1^st dose 4.6 μg/kg, subsequent doses 0.07 μg/kg/day - (Mercury). Histological analyses, Hg levels measurement and GRP78, CHOP, PPARα, PPARγ, leptin, adiponectin and CD11 mRNA expressions were performed in epididymal white adipose tissue (eWAT). Glucose, triglycerides, total cholesterol and insulin plasma levels were also measured.

RESULTS

Hg exposure reduced the absolute and relative eWAT weights, adipocyte size, plasma insulin levels, glucose tolerance, antioxidant defenses and increased plasma glucose and triglyceride levels. In addition, CHOP, GRP78, PPARα, PPARγ, leptin and adiponectin mRNA expressions were increased in Hg-treated animals. No differences in Hg concentration were found in eWAT between the untreated and Hg groups. These results suggest that the reduction in adipocyte size is related to the impaired antioxidant defenses, endoplasmic reticulum (ER) stress, the disrupted PPARs and adipokines mRNA expression induced by the metal in eWAT. These disturbances possibly induced a decrease in circulating insulin levels, an imbalance between lipolysis and lipogenesis mechanisms in eWAT, with an increase in fatty acids mobilization, a reduction in glucose uptake and an activation of pro-apoptotic pathways, leading to hyperglycemia and hyperlipidemia.

CONCLUSIONS

Hg is a powerful environmental WAT disruptor that influences signaling events and impairs metabolic activity and hormonal balance of adipocytes.

NMR-based metabolic toxicity of low-level Hg exposure to earthworms

Mercury is a globally distributed toxicant to aquatic animals and mammals. However, the potential risks of environmental relevant mercury in terrestrial systems remain largely unclear. The metabolic profiles of the earthworm Eisenia fetida after exposure to soil contaminated with mercury at 0.77 ± 0.09 mg/kg for 2 weeks were investigated using a two-dimensional nuclear magnetic resonance-based (¹H-¹³C NMR) metabolomics approach. The results revealed that traditional endpoints (e.g., mortality and weight loss) did not differ significantly after exposure. Although histological examination showed sub-lethal toxicity in the intestine as a result of soil ingestion, the underlying mechanisms were unclear. Metabolite profiles revealed significant decreases in glutamine and 2-hexyl-5-ethyl-3-furansulfonate in the exposed group and remarkable increases in glycine, alanine, glutamate, scyllo-inositol, t-methylhistidine and myo-inositol. More importantly, metabolic network analysis revealed that low mercury in the soil disrupted osmoregulation, amino acid and energy metabolisms in earthworms. A metabolic net link and schematic diagram of mercury-induced responses were proposed to predict earthworm responses after exposure to mercury at environmental relevant concentrations. These results improved the current understanding of the potential toxicity of low mercury in terrestrial systems.

Redox stress and signaling during vertebrate embryonic development: Regulation and responses

Vertebrate embryonic development requires specific signaling events that regulate cell proliferation and differentiation to occur at the correct place and the correct time in order to build a healthy embryo. Signaling pathways are sensitive to perturbations of the endogenous redox state, and are also susceptible to modulation by reactive species and antioxidant defenses, contributing to a spectrum of passive vs. active effects that can affect redox signaling and redox stress. Here we take a multi-level, integrative approach to discuss the importance of redox status for vertebrate developmental signaling pathways and cell fate decisions, with a focus on glutathione/glutathione disulfide, thioredoxin, and cysteine/cystine redox potentials and the implications for protein function in development. We present a tissue-specific example of the important role that reactive species play in pancreatic development and metabolic regulation. We discuss NFE2L2 (also known as NRF2) and related proteins, their roles in redox signaling, and their regulation of glutathione during development. Finally, we provide examples of xenobiotic compounds that disrupt redox signaling in the context of vertebrate embryonic development. Collectively, this review provides a systems-level perspective on the innate and inducible antioxidant defenses, as well as their roles in maintaining redox balance during chemical exposures that occur in critical windows of development.

Regulation of aging and oxidative stress pathways in aged pancreatic islets using alpha-lipoic acid

Oxidative stress has been involved in the aging process and the pathogenesis of type-2 diabetes, which is a serious health problem worldwide. This study investigates the anti-aging, anti-apoptotic, and antioxidant properties of alpha-lipoic acid (ALA), aiming to improve aged rat pancreatic cells. In this regard, half maximal effective concentration (EC₅₀) of ALA based on the survival of aged pancreatic islet cells was determined as 100 µM. Following this, p38 and p53 genes expression as key factors in aging, oxidative stress biomarkers, insulin secretion, and Pdx1 protein expression were evaluated using real-time PCR, ELISA reader, and fluorescence microscope. It was revealed that ALA reduces and controls the effects of aging on beta cells mainly by suppressing p38 and p53 at the gene level (P < 0.001 and P < 0.01), respectively, reducing reactive oxygen species (P < 0.001) and enhancing levels of thiols (P < 0.05) compared with the aged islets. Furthermore, both qualitative and quantitative investigations of insulin secretion have shown that ALA can improve aged cells' function and increase insulin secretion specially in the stimulating concentration of glucose. Also, the expression of Pdx1 was considerably increased by ALA in comparison to the aged pancreatic islets (P < 0.001). As far as the authors of the present study are concerned, this is the first study, which evaluated aging associated with p38 and p53 pathways, oxidative stress parameters, and the expression of insulin in beta cells of an aged rat and reaffirmed the fact that ALA has a significant antioxidant role in reducing the aging process.

Associations between total mercury and methyl mercury exposure and cardiovascular risk factors in US adolescents

Low levels of chronic heavy metal exposure are associated with a range of adverse health effects. However, whether total blood mercury (Hg) and methyl mercury (MeHg) exposure affect risk factors for cardiovascular disease (CVD) in adolescents remains unclear. The associations between CVD risk factors and total blood Hg and MeHg in adolescents were evaluated using data from the National Health and Nutrition Examination Survey (NHANES), 2011-2012. Data for 1129 adolescents (age 12-19 years) who participated in the US NHANES 2011-2012 were analyzed. A multivariate linear regression was performed to investigate the associations between CVD risk factors and blood Hg and MeHg concentrations. We identified a strong positive association between blood Hg and MeHg and total cholesterol in adolescents in adjusted model. No associations with other CVD risk factors were found in the overall population. In the gender-stratified generalized linear models, girls with the highest MeHg levels demonstrated a 4.22% (95% CI 0.80%, 7.76%) greater increase in serum total cholesterol (P for trend = 0.029) when compared with girls with the lowest MeHg levels. Our findings suggest that blood MeHg may be positively associated with total cholesterol in adolescent girls. More research is needed to verify this association and to elucidate its underlying mechanisms.

Alteration of hepatocellular antioxidant gene expression pattern and biomarkers of oxidative damage in diazinon-induced acute toxicity in Wistar rat: A time-course mechanistic study

In the present survey, the plasma level of diazinon after acute exposure was measured by HPLC method at a time-course manner. In addition, the impact of diazinon on the expression of the key genes responsible for hepatocellular antioxidative defense, including PON1, GPx and CAT were investigated. The increase in oxidative damages in treated rats was determined by measuring LPO, protein carbonyl content and total antioxidant power in plasma. After administration of 85 mg/kg diazinon in ten groups of male Wistar rats at different time points between 0-24 hours, the activity of AChE enzyme was inhibited to about 77.94 %. Significant increases in carbonyl groups and LPO after 0.75 and 1 hours were also observed while the plasma antioxidant power was significantly decreased. Despite the dramatic reduction of GP_X and PON1 gene expression, CAT gene was significantly upregulated in mRNA level by 1.1 fold after 4 hours and 1.5-fold after 24 hours due to diazinon exposure, compared to control group. Furthermore, no significant changes in diazinon plasma levels were found after 4 hours in the treated rats. The limits of detection and quantification were 137.42 and 416.52 ng/mL, respectively. The average percentage recoveries from plasma were between 90.62 % and 95.72 %. In conclusion, acute exposure to diazinon increased oxidative stress markers in a time-dependent manner and the changes were consistent with effects on hepatic antioxidant gene expression pattern. The effect of diazinon even as a non-lethal dose was induced on the gene expression of antioxidant enzymes. The change in antioxidant defense system occurs prior to diazinon plasma peak time. These results provide biochemical and molecular evidence supporting potential acute toxicity of diazinon and is beneficial in the evaluation of acute toxicity of other organophosphorus pesticides as well.

Molecular mechanisms of action of styrene toxicity in blood plasma and liver

Styrene is an aromatic colorless hydrocarbon available in liquid form and highly volatile. In its pure form, it gives a sweet smell. The primary source of exposure in the environment is from plastic materials, rubber industries, packaging materials, insulations, and fiber glass and carpet industry. Natural sources of styrene include: few metabolites in plants which are transferred through food chain. The current study was designed to evaluate styrene toxicity, including: superoxide dismutase (SOD) and protein carbonyl, oxidative stress, glucose-6-phosphatase (G6Pase), glycogen phosphorylase (GP), and phosphoenolpyruvate carboxykinase (PEPCK) activities, adenosine triphosphate (ATP) to adenosine diphosphate (ADP) ratio, and changes in gene expressions such as glutamate dehydrogenase 1 (GLUD1), glucose transporter 2 (GLUT2), and glucokinase (GCK) in the rat liver tissue. For this purpose, styrene was dissolved in corn oil and was administered via gavage, at doses 250, 500, 1000, 1500, 2000, mg/kg/day per mL and control (corn oil) to each rat with one day off in a week, for 42 days. Plasma SOD and protein carbonyl of plasma were significantly up-regulated in 1000, 1500, and 2000 mg/kg/day styrene administrated groups (P < .001). In addition, styrene caused an increase in lipid peroxidation (LPO) and reactive oxygen species (ROS) in the dose-dependent manners in liver tissue (P < .001). Furthermore, the ferrous reducing antioxidant power (FRAP) and total thiol molecules (TTM) in styrene-treated groups were significantly decreased in liver tissue (P < .001) with increasing doses. In treated rats, styrene significantly increased G6Pase activity (P < .001) and down-regulated GP activity (P < .001) as compared to the control group. The PEPCK activity was significantly raised in a dose-dependent manner (P < .001). The ATP/ADP ratio of live cells was significantly raised by increasing the dose (P < .001). There was significantly an up-regulation of GLUD1 and GCK at 2000 mg/kg group (P < .01) and a down-regulation for GLUT2 at the same dose. While in the rest of group, GLUT2 showed up-regulation of relative fold change. By targeting genes such as GLUD1, GLUT2, and GCK, disruption of hepatic gluconeogenesis, glycogenolysis, and insulin secretory functions are obvious. The present study illustrates that induction of oxidative stress followed by changes in G6Pase, GP, and PEPCK activities and the genes responsible for glucose metabolism are the mechanisms of styrene's action in the liver.

Effect of styrene exposure on plasma parameters, molecular mechanisms and gene expression in rat model islet cells

Styrene is an aromatic hydrocarbon compound present in the environment and have primary exposure through plastic industry. The current study was designed to evaluate styrene-induced toxicity parameters in rat plasma fasting blood glucose (FBG) level, oral glucose tolerance, insulin secretion, oxidative stress, and inflammatory cytokines in cellular and molecular levels. Styrene was dissolved in corn oil and administered at different doses (250, 500, 1000, 1500, 2000mg/kg/day and control) to each rat, for 42days. In treated groups, styrene significantly increased fasting blood glucose, plasma insulin (p<0.001) and glucose tolerance. Glucose tolerance, insulin resistance and hyperglycemia were found to be the main consequences correlating gene expression of islet cells. Styrene caused a significant enhancement of oxidative stress markers (p<0.001) and inflammatory cytokines in a dose and concentration-dependent manner in plasma (p<0.001). Moreover, the activities of caspase-3 and -9 of the islet cells were significantly up-regulated by this compound at 1500 and 2000mg/kg/day styrene administrated groups (p<0.001). The relative fold change of GLUD1 was downregulated (p<0.05) and upregulated at 1500 and 2000mg/kg, respectively (p<0.01). The relative fold changes of GLUT2 were down regulated at 250 and 1000mg/kg and up regulated in 500, 1500 and 2000mg/kg doses of styrene (p<0.01). The expression level of GCK indicated a significant upregulation at 250mg/kg and downregulation of relative fold changes in the remaining doses of styrene, except for no change at 2000mg/kg of styrene for GCK. Targeting genes (GLUD1, GLUT2 and GCK) of the pancreatic islet cells in styrene exposed groups, disrupted gluconeogenesis, glycogenolysis pathways and insulin secretory functions. The present study illustrated that fasting blood glucose, insulin pathway, oxidative balance, inflammatory cytokines, cell viability and responsible genes of glucose metabolism are susceptible to styrene, which consequently lead to other abnormalities in various organs.

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

INTRODUCTION

Several populations are exposed to mercury (Hg) via their environment, occupation or diet. It is hypothesized that Hg exposure can lead to the development of diabetes mellitus (DM). Metabolic syndrome (MS) is also a possible outcome as its symptoms are closely linked to those of DM.

METHOD

We conducted a systematic review of the literature by screening Web of Science, MEDLINE, SciFinder and Embase and we included original studies pertaining to the relationship of total Hg exposure (elemental, inorganic or organic) to DM, MS or insulin resistance. The studies were selected based on the PICOS (patients, intervention, comparator, outcomes and study design) criteria and their quality assessed using a nine-point scale. Study characteristics and results were extracted and presented in structured tables. We also extracted covariates entered as confounding factors to evaluate possible biases in selected studies. Finally, a weight of evidence approach was used to assess the causality of the relationship.

RESULTS

A total of 34 studies were included in the present review. Epidemiological data assessment suggests a possible association between total Hg concentrations in different biological matrices and incidence of DM or MS, but the relationship is not consistent. In vivo and in vitro studies support the biological plausibility of the relation between Hg exposure and DM or MS. Five out of nine of Bradford Hill's criteria were fulfilled: strength, temporality, plausibility, coherence and analogy.

CONCLUSION

Increased total Hg exposure may augment the risk of DM and MS, but the lack of consistency of the epidemiological evidence prevents inference of a causal relationship. Additional prospective cohort studies and careful consideration of confounding variables and interactions are required to conclude on the causal relationship of total Hg exposure on the development of DM or MS.

Immunotoxicity of mercury: Pathological and toxicological effects

Mercury (Hg) is toxic and hazardous metal that causes natural disasters in the earth's crust. Exposure to Hg occurs via various routes; like oral (fish), inhalation, dental amalgams, and skin from cosmetics. In this review, we have discussed the sources of Hg and its potential for causing toxicity in humans. In addition, we also review its bio-chemical cycling in the environment; its systemic, immunotoxic, genotoxic/carcinogenic, and teratogenic health effects; and the dietary influences; as well as the important considerations in risk assessment and management of Hg poisoning have been discussed in detail. Many harmful outcomes have been reported, which will provide more awareness.