Serum Cadmium Levels and Risk of Metabolic Syndrome: A Cross-Sectional Study

MSC-derived exosomes mitigate cadmium-induced male reproductive injury by ameliorating DNA damage and autophagic flux

Cadmium, an environmental toxicant, severely impairs male reproductive functions and currently lacks effective clinical treatments. Mesenchymal stem cell-derived exosomes (MSC-Exos) are increasingly recognized as a potential alternative to whole-cell therapy for tissue injury and regeneration. This study aims to investigate the protective effects of MSC-Exos against cadmium toxicity on male reproduction. Our findings reveal that MSC-Exos treatment significantly promotes spermatogenesis, improves sperm quality, and reduces germ cell apoptosis in cadmium-exposed mice. Mechanistically, MSC-Exos dramatically mitigate cadmium-induced cell apoptosis in a spermatogonia cell line (GC-1 spg) in vitro by reducing DNA damage and promoting autophagic flux. These results suggest that MSC-Exos have a protective effect on cadmium-induced germ cell apoptosis by ameliorating DNA damage and autophagy flux, demonstrating the therapeutic potential of MSC-Exos for cadmium toxicity on male reproduction.

Cadmium exposure causes transcriptomic dysregulation in adipose tissue and associated shifts in serum metabolites

Cadmium (Cd) is a toxic heavy metal found in natural and industrial environments. Exposure to Cd can lead to various metabolic disturbances, notably disrupting glucose and lipid homeostasis. Despite this recognition, the direct impact of Cd exposure on lipid metabolism within adipose tissue, and the mechanisms underlying these effects, have not been fully elucidated. In this study, we found that Cd accumulates in adipose tissues of mice subjected to Cd exposure. Intriguingly, Cd exposure in itself did not induce significant alterations in the adipose tissue under normal conditions. However, when subjected to cold stimulation, several notable changes were observed in the mice exposed to Cd, including a reduction in the drop of body temperature, a decrease in the size of inguinal white adipose tissue (WAT), and an increase in the expression of thermogenic genes UCP1 and PRDM16. These results indicate that Cd exposure might enhance the responsiveness of adipose tissue to external stimuli and increase the energy expenditure of the tissue. RNA-seq analysis further revealed that Cd exposure altered gene expression profiles, particularly affecting peroxisome proliferator-activated receptor (PPAR)-mediated metabolic pathways, promoting metabolic remodeling in adipose tissue and resulting in the depletion of lipids stored in adipose tissue for energy. Non-targeted metabolomic analysis of mouse serum showed that Cd exposure significantly disrupted metabolites and significantly increased serum fatty acid and triglyceride levels. Correspondingly, population-level data confirmed an association between Cd exposure and elevated levels of serum total cholesterol, total triglycerides, and low-density lipoprotein cholesterol. In summary, we provide substantial evidence of the molecular events induced by Cd that are relevant to the regulation of lipid metabolism in adipose tissue. Our findings suggest that the toxic effects of Cd can impact adipocyte functionality, positioning adipose tissue as a critical target for metabolic diseases resulting from Cd exposure.

Associations of cadmium exposure with risk of metabolic syndrome and its individual components: a meta-analysis

Data directly associating cadmium (Cd) with metabolic syndrome (MetS) are sparse and inconsistent. We aimed to quantitatively assess the association of Cd exposure with risk of MetS and its individual components. Literature searching was performed in PubMed, EMBASE, and MEDLINE-OVID through September, 2021. Weighted odds ratios (ORs) for MetS and its components were pooled by comparing the highest to the lowest category of Cd exposure using random-effects models. Eleven (10 from Asia and 1 from the US) cross-sectional studies (33,887 participants and 7176 cases) were identified. Overall, Cd exposure was not associated with risk of MetS [OR: 1.08, 95% confidence interval (CI): 0.92, 1.28]. However, the association became significant when pooling Asian studies (OR: 1.18, 95% CI: 1.02, 1.35), and it was more pronounced with Cd measured in blood (OR: 1.24, 95% CI: 1.05, 1.45). Additionally, Cd exposure was significantly associated with reduced HDL-cholesterol (OR: 1.27, 95% CI: 1.05, 1.54) and elevated triglyceride (OR: 1.17, 95% CI: 1.05, 1.30), but not other components. This meta-analysis indicates that Cd exposure is associated with risk of MetS among Asian populations, which is mainly explained by Cd's association with dyslipidemia. Further studies are needed to better understand the mechanism of action.

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.

The mediating role of telomere length in multi-pollutant exposure associated with metabolic syndrome in adults

Metabolic syndrome is a chronic and complex disease characterized by environmental and genetic factors. However, the underlying mechanisms remain unclear. This study assessed the relationship between exposure to a mixture of environmental chemicals and metabolic syndrome (MetS) and further examined whether telomere length (TL) moderated these relationships. A total of 1265 adults aged > 20 years participated in the study. Data on multiple pollutants (polycyclic aromatic hydrocarbons, phthalates, and metals), MetS, leukocyte telomere length (LTL), and confounders were provided in the 2001-2002 National Health and Nutrition Examination Survey. The correlations between multi-pollutant exposure, TL, and MetS in the males and females were separately assessed using principal component analysis (PCA), logistic and extended linear regression models, Bayesian kernel machine regression (BKMR), and mediation analysis. Four factors were generated in PCA that accounted for 76.2% and 77.5% of the total environmental pollutants in males and females, respectively. The highest quantiles of PC2 and PC4 were associated with the risk of TL shortening (P < 0.05). We observed that the relationship between PC2, PC4, and MetS risk was significant in the participants with median TL levels (P for trend = 0.04 for PC2, and P for trend = 0.01 for PC4). Furthermore, mediation analysis revealed that TL could explain 26.1% and 17.1% of the effects of PC2 and PC4 associated with MetS in males, respectively. The results of BKMR model revealed that these associations were mainly driven by 1-PYE (cPIP = 0.65) and Cd (cPIP = 0.29) in PC2. Meanwhile, TL could explain 17.7% of the mediation effects of PC2 associated with MetS in the females. However, the relationships between pollutants and MetS were sparse and inconsistent in the females. Our findings suggest that the effects of the risk of MetS associated with mixed exposure to multiple pollutants are mediated by TL, and this mediating effect in the males is more pronounced than that in the females.

Association of blood cadmium and metabolic syndrome: a cross-sectional analysis of National Health and Nutrition Examination Survey 2017-2020

Previous findings have reported the role of different types of heavy metals in cardiometabolic diseases. In the present research, we aim to evaluate the association between blood cadmium levels and Metabolic Syndrome (MetS) based on the large-sample NHANES data. Public availably data from NHANES 2017-2020 cycle was obtained. Participants were divided into MetS and non-MetS groups according to waist circumference (WC), triglyceride (TG), high-density lipoprotein (HDL), blood pressure (BP) and fasting plasma glucose (FPG) levels based on the National Cholesterol Education Program (NCEP) criteria. Student's t test, Mann-Whitney U test, and Chi-square test were performed for univariate analysis. Multivariate logistic analysis was performed to explore the relationship between blood cadmium and MetS and research findings were presented in forest plot. We also investigated the association of blood cadmium and MetS in subgroups stratified by age, gender and race. Population with MetS had significantly higher levels of blood [0.30 (0.18-0.54) vs. 0.24 (0.15-0.46) ug/L, p < 0.001] and urinary cadmium levels [0.29 (0.17-0.52) vs. 0.20 (0.09-0.42) ug/L, p < 0.001] compared with those without MetS. Higher blood cadmium concentrations were also observed in participants with elevated WC (0.28 vs. 023 ug/L, p < 0.001], TG (0.28 vs. 0.26 ug/L, p = 0.029), BP (0.33 vs. 0.23 ug/L, p < 0.001) and FPG (0.29 vs. 0.24 ug/L, p < 0.001) compared with those with normal metabolic parameters. Multivariate logistic regression showed that one-unit increasement of blood cadmium was associated with 1.25 times higher prevalence ratios for MetS after adjusting potential confounders (95% CI: 1.06-1.48, p = 0.0083). The associations between serum cadmium concentrations and MetS components were then evaluated, and the results showed higher blood cadmium levels were associated with higher risk for elevated TG, low HDL and elevated BP when treated as continuous variable. When treated as categorical variable, only BP was found positively associated with blood cadmium. Stratified multiple logistic regression analysis indicated that the positive association between blood cadmium and MetS remained significant in subjects less than 60 years old and female subgroup. In conclusion, the cross-sectional survey suggested the positive association between blood cadmium levels and risk for MetS, prospective research need to be conducted for further evaluation of the causal relationship between blood cadmium and MetS.

Recent advances in the application of ionomics in metabolic diseases

Trace elements and minerals play a significant role in human health and diseases. In recent years, ionomics has been rapidly and widely applied to explore the distribution, regulation, and crosstalk of different elements in various physiological and pathological processes. On the basis of multi-elemental analytical techniques and bioinformatics methods, it is possible to elucidate the relationship between the metabolism and homeostasis of diverse elements and common diseases. The current review aims to provide an overview of recent advances in the application of ionomics in metabolic disease research. We mainly focuses on the studies about ionomic or multi-elemental profiling of different biological samples for several major types of metabolic diseases, such as diabetes mellitus, obesity, and metabolic syndrome, which reveal distinct and dynamic patterns of ion contents and their potential benefits in the detection and prognosis of these illnesses. Accumulation of copper, selenium, and environmental toxic metals as well as deficiency of zinc and magnesium appear to be the most significant risk factors for the majority of metabolic diseases, suggesting that imbalance of these elements may be involved in the pathogenesis of these diseases. Moreover, each type of metabolic diseases has shown a relatively unique distribution of ions in biofluids and hair/nails from patients, which might serve as potential indicators for the respective disease. Overall, ionomics not only improves our understanding of the association between elemental dyshomeostasis and the development of metabolic disease but also assists in the identification of new potential diagnostic and prognostic markers in translational medicine.

Association Between Essential and Non-essential Metals, Body Composition, and Metabolic Syndrome in Adults

Growing evidence indicates that metal exposure is associated with metabolic syndrome (MetS); however, mixed results have been reported. The aim of this study was to clarify associations of exposure to essential and non-essential metals with body composition and risks of obesity and MetS. Anthropometry and blood biochemistry of metabolic parameters were obtained from 150 middle-aged Taiwanese adults. Plasma metals were assessed using inductively coupled plasma mass spectrometry, and body compositions were measured by a bioelectrical impedance analysis (BIA). The essential metals of copper (Cu), manganese (Mn), and chromium (Cr) were positively correlated with the body fat mass but inversely correlated with the skeletal muscle mass (all p < 0.05). An adjusted logistic regression showed that Mn [odds ratio (OR) = 1.624 (95% confidence interval 1.072, 2.462), p = 0.02] and, to a lesser extent, Cu [OR = 1.501 (0.985, 2.292), p = 0.059] predicted abdominal obesity, while plasma Cu [OR = 2.211 (1.146, 4.266), p = 0.02] and zinc (Zn) [OR = 2.228 (1.048, 4.736) p = 0.04] predicted MetS. Significant correlations between dyslipidemia and lithium [OR = 1.716 (1.080, 2.726)], Cu [OR = 2.210 (1.415, 3.454)], Mn [OR = 2.200 (1.320, 3.666)], molybdenum [OR = 1.853 (1.160, 2.958)], and Zn [OR = 1.993 (1.186, 3.349)], and between boron [OR = 2.583 (1.137, 5.868)] and hyperglycemia were observed (all p < 0.05). Exposure to essential metals may affect the body composition and metabolic profiles, exacerbating the risk of MetS.

Carcinogenic effects of heavy metals by inducing dysregulation of microRNAs: A review

Heavy metal exposure has soared due to the twentieth century's industrial activity. The most common heavy metals that lead to human poisoning are mercury, cadmium, and arsenic. Acute or chronic poisoning may develop following exposure to water, air, or food, so the bioaccumulation of these heavy metals causes harmful consequences in various human tissues and organs. Heavy metals interfere with biological functions such as growth, proliferation, differentiation, damage repair, and apoptosis. The mechanisms of action for these metals to cause toxicity are similar, including forming reactive oxygen species (ROS), weakening antioxidant defenses, enzyme inactivation, and oxidative stress. Heavy metal exposure is mainly associated with skin, liver, prostate, lung, urinary bladder, thyroid, and kidney cancers, as well as causing gastrointestinal malignancies. Several microRNAs (miRNAs or miRs) have been involved in various human cancers due to the dysregulation of miRNA function. Recent investigations have confirmed that microRNA dysregulation plays a role in the carcinogenesis of many tissues. This review presents the data concerning arsenic, cadmium, and mercury metals and their contamination sources, human exposure, toxicity, and inducing malignant transformations such as carcinogenicity in in-vitro or in-vivo specimens or dysregulated expression of microRNAs.

Oral Subacute Exposure to Cadmium LOAEL Dose Induces Insulin Resistance and Impairment of the Hormonal and Metabolic Liver-Adipose Axis in Wistar Rats

Cadmium is a nonessential transition metal considered one of the more hazardous environmental contaminants. The population is chronically exposed to this metal at low concentrations, designated as the LOAEL (lowest observable adverse effect level) dose. We aimed to investigate whether oral subacute exposure to cadmium LOAEL disrupts hormonal and metabolic effects of the liver-adipose axis in Wistar rats. Fifty male Wistar rats were separated into two groups: control (standard normocalorie diet + water free of cadmium) and cadmium (standard normocalorie diet + drinking water with 32.5 ppm CdCl₂). After 1 month, zoometry, a serum lipid panel, adipokines, and proinflammatory cytokines were evaluated. Tests of glucose and insulin tolerance (ITT) and insulin resistance were performed. Histological studies on structure, triglyceride distribution, and protein expression of the insulin pathway were performed in the liver and retroperitoneal adipose tissue. In both tissues, the cadmium, triglyceride, glycogen, and proinflammatory cytokine contents were also quantified. The cadmium group developed dyslipidemia, glucose intolerance, hyperinsulinemia, hyperleptinemia, inflammation, and selective insulin resistance in the liver and adipose tissue. In the liver, glycogen synthesis was diminished, while de novo lipogenesis increased, which was associated with low GSK3β-pS9 and strong expression of SREBP-1c. Dysfunctional adipose tissue was observed with hypertrophy and lipolysis, without changes in SREBP-1c expression and low glycogen synthesis. Both tissues accumulated cadmium and developed inflammation. In conclusion, oral subacute cadmium LOAEL dose exposure induces inflammation, insulin signaling modifications, an early insulin resistance stage (insensibility), and impairment of the hormonal and metabolic liver-adipose axis in Wistar rats.

Metals and risk of incident metabolic syndrome in a prospective cohort of midlife women in the United States

Exposure to metals may contribute to the development of metabolic syndrome (MetS); however, evidence from midlife women who are at greater risk of cardiometabolic disease is limited. We assessed the associations of 15 urinary metal concentrations with incident MetS in a prospective cohort of midlife women in the United States. The study population included 947 White, Black, Chinese and Japanese women, aged 45-56 years, free of MetS at baseline (1999-2000), who participated in the Study of Women's Health Across the Nation Multi-Pollutant Study. Fifteen metals were detected in almost all participants urine samples using inductively coupled plasma mass spectrometry at the baseline. Incident MetS was identified annually through 2017 as having at least three of the following five components: high blood pressure, impaired fasting glucose, abdominal obesity, high triglycerides, and poor high-density lipoprotein cholesterol. We used the Cox proportional hazards models to investigate the associations between individual metals and MetS incidence. The adjusted hazard ratios (HR) (95% CI) for MetS in associations with each doubling of urinary metal concentration were 1.14 (1.08, 1.23) for arsenic, 1.14 (1.01, 1.29) for cobalt, and 1.20 (1.06, 1.37) for zinc. We further evaluated the associations between metal mixtures and MetS using the elastic net penalized Cox model and summarized the results into the environmental risk score (ERS). Arsenic, barium, cobalt, copper, nickel, antimony, thallium, and zinc had positive weights, and cadmium, cesium, mercury, molybdenum, lead, and tin had negative weights in the construction of the ERS. The adjusted HR of MetS comparing 75th vs. 25th percentiles of the ERS was 1.45 (1.13, 1.87). These findings support the view that arsenic, cobalt, zinc, as well as metal mixtures, might influence the risks of incident MetS in midlife women.