Striking association between urinary cadmium level and albuminuria among Torres Strait Islander people with diabetes

The pathogenesis of albuminuria in cadmium nephropathy

Background

Urinary cadmium excretion (ECd) rises with renal tissue content of the metal. Whereas glomerulopathies are sometimes associated with massive albuminuria, tubular accumulation of Cd typically causes modest albuminuria. Since β2-microglobulinuria (Eβ2M) is an established marker of proximal tubular dysfunction, we hypothesized that a comparison of albuminuria (Ealb) to Eβ2M in Cd-exposed subjects would provide evidence of similar mishandling of both proteins.

Methods

To depict excretion rates per functional nephron, ECd, Ealb, and Eβ2M were normalized to creatinine clearance (Ccr), a surrogate for the glomerular filtration rate (GFR). Estimation of GFR itself (eGFR) was accomplished with CKD-EPI formulas (2009). Linear and logistic regression analyses were performed to relate Ealb/Ccr, Eβ2M/Ccr, and eGFR to several independent variables. Simple linear regressions of eGFR, Ealb/Ccr, and Eβ2M/Ccr on ECd/Ccr were examined before and after adjustment of dependent variables for age. All regressions were performed after log-transformation of ratios and standardization of all variables. Increments in Ealb/Ccr and Eβ2M/Ccr and decrements in eGFR were quantified through four quartiles of ECd/Ccr.

Results

As age or ECd/Ccr rose, Ealb/Ccr and Eβ2M/Ccr also rose, and eGFR fell. In linear regressions, slopes relating Ealb/Ccr and Eβ2M/Ccr to ECd/Ccr were similar. After adjustment of dependent variables for age, coefficients of determination (R2) for all regressions rose by a multiple, and slopes approached unity. Ealb/Ccr and Eβ2M/Ccr were similarly associated with each other. Mean Ealb/Ccr and Eβ2M/Ccr rose and mean eGFR fell in stepwise fashion through quartiles of ECd/Ccr. Whereas Eβ2M/Ccr did not vary with blood pressure, Ealb/Ccr rose in association with hypertension in two of the four quartiles.

Conclusions

Our data indicate that Cd in renal tissue affected tubular reabsorption of albumin and β2M similarly in a large cohort of exposed subjects. The results suggest that Cd reduced receptor-mediated endocytosis and subsequent lysosomal degradation of each protein by a shared mechanism.

Health risk assessment of dietary cadmium intake in children aged 2-17 years in East China

Food is the main way for people to be exposed to heavy metal cadmium (Cd), and Cd pollution will affect human health. In this paper, exposure and health risk assessment of dietary Cd intake were conducted in children aged 2, 3, 4, 5, 6-8, 9-11, 12-14 and 15-17 years in East China. The results showed that the total exposure of dietary Cd intake in children exceeded the standard limits. The total exposure of all age groups were 1.11 × 10-3, 1.15 × 10-3, 9.67 × 10-4, 8.75 × 10-4, 9.18 × 10-4, 7.75 × 10-4, 8.24 × 10-4, 7.11 × 10-4 mg kg-1 d-1, respectively, and the highest was the children aged 3 years. The hazard quotients of children aged 2 and 3 years were 1.11 and 1.15, respectively, at an unacceptable health risk level. The hazard quotients of dietary Cd intake in children of other ages were less than 1, at an acceptable health risk level. Staple foods were the most significant contributor to the dietary Cd intake in children, and the contribution ratio of non-carcinogenic risk of dietary Cd intake in all age groups were more than 35%, the proportion of non-carcinogenic risk in children aged 6-8 and 9-11 years were as high as 50%. This study provides scientific basis for the health of children in East China.

Chronic Kidney Disease Induced by Cadmium and Diabetes: A Quantitative Case-Control Study

Kidney disease associated with chronic cadmium (Cd) exposure is primarily due to proximal tubule cell damage. This results in a sustained decline in glomerular filtration rate (GFR) and tubular proteinuria. Similarly, diabetic kidney disease (DKD) is marked by albuminuria and a declining GFR and both may eventually lead to kidney failure. The progression to kidney disease in diabetics exposed to Cd has rarely been reported. Herein, we assessed Cd exposure and the severity of tubular proteinuria and albuminuria in 88 diabetics and 88 controls, matched by age, gender and locality. The overall mean blood and Cd excretion normalized to creatinine clearance (C_cr) as E_Cd/C_cr were 0.59 µg/L and 0.0084 µg/L filtrate (0.96 µg/g creatinine), respectively. Tubular dysfunction, assessed by β₂-microglobulin excretion rate normalized to C_cr(E_β2M/C_cr) was associated with both diabetes and Cd exposure. Doubling of Cd body burden, hypertension and a reduced estimated GFR (eGFR) increased the risks for a severe tubular dysfunction by 1.3-fold, 2.6-fold, and 84-fold, respectively. Albuminuria did not show a significant association with E_Cd/C_cr, but hypertension and eGFR did. Hypertension and a reduced eGFR were associated with a 3-fold and 4-fold increases in risk of albuminuria. These findings suggest that even low levels of Cd exposure exacerbate progression of kidney disease in diabetics.

Cadmium-Induced Tubular Dysfunction in Type 2 Diabetes: A Population-Based Cross-Sectional Study

The global prevalence of diabetes, and its major complication, diabetic nephropathy, have reached epidemic proportions. The toxic metal cadmium (Cd) also induces nephropathy, indicated by a sustained reduction in the estimated glomerular filtration rate (eGFR) and the excretion of β₂-microglobulin (β₂M) above 300 µg/day, which reflects kidney tubular dysfunction. However, little is known about the nephrotoxicity of Cd in the diabetic population. Here, we compared Cd exposure, eGFR, and tubular dysfunction in both diabetics (n = 81) and non-diabetics (n = 593) who were residents in low- and high-Cd exposure areas of Thailand. We normalized the Cd and β₂M excretion rates (E_Cd and E_β2M) to creatinine clearance (C_cr) as E_Cd/C_cr and E_β2M/C_cr. Tubular dysfunction and a reduced eGFR were, respectively, 8.7-fold (p < 0.001) and 3-fold (p = 0.012) more prevalent in the diabetic than the non-diabetic groups. The doubling of E_Cd/C_cr increased the prevalence odds ratios for a reduced eGFR and tubular dysfunction by 50% (p < 0.001) and 15% (p = 0.002), respectively. In a regression model analysis of diabetics from the low-exposure locality, E_β2M/C_cr was associated with E_Cd/C_cr (β = 0.375, p = 0.001) and obesity (β = 0.273, p = 0.015). In the non-diabetic group, E_β2M/C_cr was associated with age (β = 0.458, p < 0.001) and E_Cd/C_cr (β = 0.269, p < 0.001). However, after adjustment for age, and body mass index (BMI), E_β2M/C_cr was higher in the diabetics than non-diabetics of similar E_Cd/C_cr ranges. Thus, tubular dysfunction was more severe in diabetics than non-diabetics of similar age, BMI, and Cd body burden.

Estimation of health risks associated with dietary cadmium exposure

In much of the world, currently employed upper limits of tolerable intake and acceptable excretion of cadmium (Cd) (ECd/Ecr) are 0.83 µg/kg body weight/day and 5.24 µg/g creatinine, respectively. These figures were derived from a risk assessment model that interpreted β2-microglobulin (β2MG) excretion > 300 μg/g creatinine as a "critical" endpoint. However, current evidence suggests that Cd accumulation reduces glomerular filtration rate at values of ECd/Ecr much lower than 5.24 µg/g creatinine. Low ECd/Ecr has also been associated with increased risks of kidney disease, type 2 diabetes, osteoporosis, cancer, and other disorders. These associations have cast considerable doubt on conventional guidelines. The goals of this paper are to evaluate whether these guidelines are low enough to minimize associated health risks reliably, and indeed whether permissible intake of a cumulative toxin like Cd is a valid concept. We highlight sources and levels of Cd in the human diet and review absorption, distribution, kidney accumulation, and excretion of the metal. We present evidence for the following propositions: excreted Cd emanates from injured tubular epithelial cells of the kidney; Cd excretion is a manifestation of current tissue injury; reduction of present and future exposure to environmental Cd cannot mitigate injury in progress; and Cd excretion is optimally expressed as a function of creatinine clearance rather than creatinine excretion. We comprehensively review the adverse health effects of Cd and urine and blood Cd levels at which adverse effects have been observed. The cumulative nature of Cd toxicity and the susceptibility of multiple organs to toxicity at low body burdens raise serious doubt that guidelines concerning permissible intake of Cd can be meaningful.

Cadmium exposure is associated with chronic kidney disease in a superfund site lead smelter community in Dallas, Texas

Background: The study was conducted in a Dallas lead smelter community following an Environmental Protection Agency (EPA) Superfund Cleanup project. Lead smelters operated in the Dallas community since the mid-1930s.Aim: To test the hypothesis that cadmium (Cd) exposure is associated with chronic kidney disease (CKD) ≥ stage 3.Subjects and methods: Subjects were African American residents aged ≥19 to ≤ 89 years (n=835). CKD ≥ stage 3 was predicted by blood Cd concentration with covariates.Results: In logistic regression analysis, CKD ≥ stage 3 was predicted by age ≥ 50 years (OR = 4.41, p < 0.0001), Cd level (OR = 1.89, p < .05), hypertension (OR = 3.15, p < 0.03), decades living in the community (OR = 1.34, p < 0.003) and T2DM (OR = 2.51, p < 0.01). Meta-analysis of 11 studies of Cd and CKD ≥ stage 3 yielded an ORRANDOM of 1.40 (p < 0.0001). Chronic environmental Cd exposure is associated with CKD ≥ stage 3 in a Dallas lead smelter community controlling covariates.Conclusion: Public health implications include screening for heavy metals including Cd, cleanup efforts to remove Cd from the environment and treating CKD with newer renal-sparing medications (e.g., SGLT-2 inhibitors, GLP-1s).

Exploring the Link Between the Serum/Blood Levels of Heavy Metals (Pb, As, Cd, and Cu) and 2 Novel Biomarkers of Cardiovascular Stress (Growth Differentiation Factor 15 and Soluble Suppression of Tumorigenicity 2) in Copper Smelter Workers

OBJECTIVE

Studying the association between the occupational exposure to Pb, As, Cd, and Cu with the serum levels of 2 novel biomarkers of cardiovascular stress; growth differentiation factor 15 and soluble suppression of tumorigenicity 2, in some Egyptian Cu smelter workers.

METHODS

Forty-one exposed workers and 41 administrative controls were clinically evaluated. Serum/blood levels of heavy metals and biomarkers were measured for both groups.

RESULTS

The smelter workers showed significantly elevated levels of heavy metals and biomarkers compared with controls. The elevated serum levels of both biomarkers were significantly and positively correlated with each other, the levels of heavy metals, and the duration of employment of the exposed workers.

CONCLUSIONS

There was a significant association between the levels of heavy metals and both biomarkers among the smelter workers. Further prospective studies should be performed.

Associations of multiple plasma metals with chronic kidney disease in patients with diabetes

As common contaminants, metals are non-negligible risk factors for diabetes and chronic kidney disease. However, whether there is an association between multiple metals exposure and incident chronic kidney disease (CKD) risk in patients with diabetes is unclear. We conducted a prospective study to evaluate these associations. In total, 3071 diabetics with baseline estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m² from the Dongfeng-Tongji cohort were included. We measured baseline plasma concentrations of 23 metals and investigated the associations between plasma metal concentrations and CKD in diabetics using logistic regression, the least absolute shrinkage and selection operator (LASSO), and the Bayesian Kernel Machine Regression (BKMR) models. During average 4.6 years of follow-up, 457 diabetics developed CKD (14.9 %). The three models consistently found plasma levels of zinc, arsenic, and rubidium had a positive association with incident CKD risk in patients with diabetes, while titanium, cadmium, and lead had an inverse correlation. The results of BKMR showed a significant and positive overall effect of 23 metals on the risk of CKD, when all of the metals were above the 50th percentile as compared to the median value. In addition, potential interactions of zinc and arsenic, zinc and cadmium, zinc and lead, titanium and arsenic, and cadmium and lead on CKD risk were observed. In summary, we found significant associations of plasma titanium, zinc, arsenic, rubidium, cadmium, and lead with CKD in diabetes and interactions between these metals except for rubidium. Co-exposure to multiple metals was associated with increased CKD risk in diabetics.

Multiple Targets of Toxicity in Environmental Exposure to Low-Dose Cadmium

Dietary assessment reports and population surveillance programs show that chronic exposure to low levels of environmental cadmium (Cd) is inevitable for most people, and adversely impacts the health of children and adults. Based on a risk assessment model that considers an increase in the excretion of β₂-microglobulin (β₂M) above 300 μg/g creatinine to be the "critical" toxicity endpoint, the tolerable intake level of Cd was set at 0.83 µg/kg body weight/day, and a urinary Cd excretion rate of 5.24 µg/g creatinine was considered to be the toxicity threshold level. The aim of this review is to draw attention to the many other toxicity endpoints that are both clinically relevant and more appropriate to derive Cd exposure limits than a β₂M endpoint. In the present review, we focus on a reduction in the glomerular filtration rate and diminished fecundity because chronic exposure to low-dose Cd, reflected by its excretion levels as low as 0.5 µg/g creatinine, have been associated with dose-dependent increases in risk of these pathological symptoms. Some protective effects of the nutritionally essential elements selenium and zinc are highlighted. Cd-induced mitochondrial dysfunction is discussed as a potential mechanism underlying gonadal toxicities and infertility.

Effects of Environmental Exposure to Cadmium and Lead on the Risks of Diabetes and Kidney Dysfunction

Environmental exposure to cadmium (Cd) or lead (Pb) is independently associated with increased risks of type 2 diabetes, and chronic kidney disease. The aim of this study was to examine the effects of concurrent exposure to these toxic metals on the risks of diabetes and kidney functional impairment. The Cd and Pb exposure levels among study subjects were low to moderate, evident from the means for blood concentrations of Cd and Pb ([Cd]_b and [Pb]_b) of 0.59 µg/L and 4.67 µg/dL, respectively. Of 176 study subjects (mean age 60), 71 (40.3%) had abnormally high fasting plasma glucose levels. Based on their [Cd]_b and [Pb]_b, 53, 71, and 52 subjects were assigned to Cd and Pb exposure profiles 1, 2, and 3, respectively. The diagnosis of diabetes was increased by 4.2-fold in those with an exposure profile 3 (p = 0.002), and by 2.9-fold in those with the estimated glomerular filtration (eGFR) ≤ 60 mL/min/1.73 m² (p = 0.029). The prevalence odds ratio (POR) for albuminuria was increased by 5-fold in those with plasma glucose levels above kidney threshold of 180 mg/dL (p = 0.014), and by 3.1-fold in those with low eGFR) (p = 0.050). Collectively, these findings suggest that the Cd and Pb exposure profiles equally impact kidney function and diabetes risk.

Drinking water heavy metal toxicity and chronic kidney diseases: a systematic review

Heavy metals in drinking water can threat human health and may induce several diseases. The association between heavy metals exposure and chronic kidney disease (CKD) has been indicated by few epidemiological studies. We conducted a systematic review of the epidemiologic publications of the association between exposure to heavy metals through drinking water and CKD. Keywords related to heavy metals and kidney diseases on MeSH were identified and searched in PubMed, Google Scholar, Scopus, Ovid-Medline and Web of Science until July 2020. 14 publications met our inclusion criteria and included in the current review. The included articles were conducted on the association between arsenic, cadmium, lead and chromium in drinking water and CKD. Our study could not find strong evidence between heavy exposure to through drinking water and CKD, except for arsenic. The negative association was found between arsenic and lead and glomerular filtration rate (eGFR). The positive correlation was observed between cadmium exposure and urinary N-acetyl-β-d-glucosaminidase (NAG) concentrations, and also arsenic and chromium exposure and kidney injury molecule (KIM-1). Assessment of studies showed an association between arsenic, cadmium, lead and chromium and albuminuria and proteinuria, without CKD outcomes. Current systematic study showed few evidence for exposure to arsenic, cadmium, lead and chromium through drinking water and incidence of kidney problems. However, more epidemiological studies are required to confirm this association.

Reported sources of health inequities in Indigenous Peoples with chronic kidney disease: a systematic review of quantitative studies

BACKGROUND

To summarise the evidentiary basis related to causes of inequities in chronic kidney disease among Indigenous Peoples.

METHODS

We conducted a Kaupapa Māori meta-synthesis evaluating the epidemiology of chronic kidney diseases in Indigenous Peoples. Systematic searching of MEDLINE, Google Scholar, OVID Nursing, CENTRAL and Embase was conducted to 31 December 2019. Eligible studies were quantitative analyses (case series, case-control, cross-sectional or cohort study) including the following Indigenous Peoples: Māori, Aboriginal and Torres Strait Islander, Métis, First Nations Peoples of Canada, First Nations Peoples of the United States of America, Native Hawaiian and Indigenous Peoples of Taiwan. In the first cycle of coding, a descriptive synthesis of the study research aims, methods and outcomes was used to categorise findings inductively based on similarity in meaning using the David R Williams framework headings and subheadings. In the second cycle of analysis, the numbers of studies contributing to each category were summarised by frequency analysis. Completeness of reporting related to health research involving Indigenous Peoples was evaluated using the CONSIDER checklist.

RESULTS

Four thousand three hundred seventy-two unique study reports were screened and 180 studies proved eligible. The key finding was that epidemiological investigators most frequently reported biological processes of chronic kidney disease, particularly type 2 diabetes and cardiovascular disease as the principal causes of inequities in the burden of chronic kidney disease for colonised Indigenous Peoples. Social and basic causes of unequal health including the influences of economic, political and legal structures on chronic kidney disease burden were infrequently reported or absent in existing literature.

CONCLUSIONS

In this systematic review with meta-synthesis, a Kaupapa Māori methodology and the David R Williams framework was used to evaluate reported causes of health differences in chronic kidney disease in Indigenous Peoples. Current epidemiological practice is focussed on biological processes and surface causes of inequity, with limited reporting of the basic and social causes of disparities such as racism, economic and political/legal structures and socioeconomic status as sources of inequities.

Environmental pollution and diabetes mellitus

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

Pancreatic Islets Accumulate Cadmium in a Rodent Model of Cadmium-Induced Hyperglycemia

Cadmium (Cd) is an anthropogenic as well as a naturally occurring toxicant associated with prediabetes and T2DM in humans and experimental models of Cd exposure. However, relatively few studies have examined the mechanism(s) of Cd-induced hyperglycemia. The purpose of this study was to examine the role of pancreatic islets in Cd-induced hyperglycemia. Male Sprague–Dawley rats were given daily subcutaneous doses of Cd at 0.6 mg/kg over 12 weeks. There was a resulting time-dependent increase in fasting blood glucose and altered insulin release in vitro. Islets isolated from control (saline-treated) and Cd-treated animals were incubated in low (0.5 mg/mL) or high (3 mg/mL) glucose conditions. Islets from 12 week Cd-treated animals had significantly less glucose-stimulated insulin release compared to islets from saline-treated control animals. The actual Cd content of isolated islets was 5 fold higher than the whole pancreas (endocrine + exocrine) and roughly 70% of that present in the renal cortex. Interestingly, islets isolated from Cd-treated animals and incubated in high glucose conditions contained significantly less Cd and zinc than those incubated in low glucose. These results show that within whole pancreatic tissue, Cd selectively accumulates in pancreatic islets and causes altered islet function that likely contributes to dysglycemia.

Cadmium Is Associated with Type 2 Diabetes in a Superfund Site Lead Smelter Community in Dallas, Texas

OBJECTIVE

To test the hypothesis that cadmium (Cd) exposure is associated with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

A two-phase health screening (physical examination and laboratory tests) was conducted in a lead smelter community following a Superfund Cleanup. Participants were African Americans aged >19 years to <89 years. Multiple logistic regression was used to analyze T2DM regressed on blood Cd level and covariates: body mass index (BMI), heavy metals (Ar, Cd, Hg, Pb), duration of residence, age, smoking status, and sex.

RESULTS

Of 875 subjects environmentally exposed to Cd, 55 were occupationally exposed to by-products of lead smelting and 820 were community residents. In addition, 109 T2DM individuals lived in the community for an average of 21.0 years, and 766 non-T2DM individuals for 19.0 years. T2DM individuals (70.3%) were >50 years old. Blood Cd levels were higher among T2DM subjects (p < 0.006) compared to non-T2DM individuals. Logistic regression of T2DM status identified significant predictors: Cd level (OR = 1.85; 95% CI: 1.14-2.99, p < 0.01), age >50 years (OR = 3.10; 95% CI: 1.91-5.02, p < 0.0001), and BMI (OR = 1.07; CI: 1.04-1.09, 0.0001). In meta-analysis of 12 prior studies and this one, T2DM risk was OR = 1.09 (95% CI: 1.03-1.15, p < 0.004) fixed effects and 1.22 (95% CI: 1.04-1.44, p < 0.02) random effects.

DISCUSSION

Chronic environmental Cd exposure was associated with T2DM in a smelter community, controlling for covariates. T2DM onset <50 years was significantly associated with Cd exposure, but >50 years was not. Meta-analysis suggests that Cd exposure is associated with a small, but significant increased risk for T2DM. Available data suggest Cd exposure is associated with an increased propensity to increased insulin resistance.

Exogenous indole acetic acid alleviates Cd toxicity in tea (Camellia sinensis)

Cadmium (Cd), a toxic heavy metal, restrains the growth and development of plants and threatens global food safety. Many studies on the alleviation of heavy metal toxicity by exogenous phytohormones have emerged, but reports on tea (Camellia sinensis) are still scarce. In this study, the effects of indole acetic acid (IAA) (2 μM and 10 μM) on Cd uptake and on the physiological and biochemical characteristics of the 'Xiangfeicui' tea cultivar were investigated for the first time. The order of Cd accumulation in tea seedlings was root > stem > mature leaf > tender leaf. Under Cd stress (30 mg kg^-1), photosynthetic pigment levels, antioxidant enzyme activity, root vigor, root IAA content, and the levels of most metabolites (including caffeine, soluble sugar, total amino acids, some amino acid components, and most catechins) were significantly reduced, while levels of malondialdehyde, proline, epicatechin, and some amino acids increased. We therefore propose that by reducing Cd accumulation, exogenous IAA can lessen the adverse effects of Cd on the physiology and biochemistry of tea seedlings, promoting the growth of healthier tea plants.

An explanation of soil amendments to reduce cadmium phytoavailability and transfer to food chain

Cadmium contamination in soil, water and food has become a global problem since last century's industrial and agricultural revolution. It is a highly toxic metal with serious consequences on human and animal health. Different natural and anthropogenic sources are responsible for Cd release in the soil which ultimately leads to the food chain. Cd persists in soil for long durations due to its minimal microbial or chemical loss. There are various physical, chemical or biological techniques which are helpful to minimize Cd risk in food chain. Among them, in-situ immobilization with organic, inorganic or clay amendments is a cost-effective and an environment friendly strategy to remediate Cd polluted sites. Lime, biochar, organic wastes, phosphorus fertilizers, sepiolite, zeolite, hydroxyapatite and bentonite are commonly used amendments for amelioration of Cd contaminated soils. These amendments reduce Cd uptake and enhance immobilization by adsorption, complexation, and precipitation processes. This review is aimed to provide a comprehensive note on Cd toxicity in humans and environment, its immobilization by different agents through variety of processes, and comparison of technologies for Cd removal from contaminated sites.

Relation between cadmium exposure and gestational diabetes mellitus

BACKGROUND

Cadmium (Cd) has been associated with type 2 diabetes in general population. However, the role of Cd in the occurrence of Gestational diabetes mellitus (GDM) remains unclear.

OBJECTIVES

Our study was aimed at investigating whether Cd exposure during pregnancy was associated with increased risk of GDM.

METHODS

Cd concentrations were measured in urine samples from 6837 pregnant women in Wuhan, China, from 2012 to 2014. A "modified Poisson" model with a robust error variance was used to examine the association of GDM with continuous natural logarithm (ln) transformed urinary Cd or quartiles of urinary Cd levels.

RESULTS

For about 3-fold increase in Cd concentrations, there were 16% [relative risk (RR) =1.16; 95% confidence interval (CI): 1.03, 1.33] increase in risk of GDM. Compared with women in the lowest quartile of urinary Cd levels, women in the highest quartile had 1.30 higher risk of GDM [95% CI: 1.05, 1.61; p-trend <0.05]. Further analyses indicated overweight/obese women with higher urinary Cd levels had significantly higher risk of GDM, compared with women in the reference category of lowest quartile of Cd and normal pre-pregnancy body mass index [RR =2.71; 95% CI: 1.81, 4.07].

CONCLUSIONS

Our study presented a significantly positive association between urinary Cd levels and risk of GDM, supporting the hypothesis that environmental exposure to Cd may contribute to the development of GDM.

Soil contamination with cadmium, consequences and remediation using organic amendments

Cadmium (Cd) contamination of soil and food crops is a ubiquitous environmental problem that has resulted from uncontrolled industrialization, unsustainable urbanization and intensive agricultural practices. Being a toxic element, Cd poses high threats to soil quality, food safety, and human health. Land is the ultimate source of waste disposal and utilization therefore, Cd released from different sources (natural and anthropogenic), eventually reaches soil, and then subsequently bio-accumulates in food crops. The stabilization of Cd in contaminated soil using organic amendments is an environmentally friendly and cost effective technique used for remediation of moderate to high contaminated soil. Globally, substantial amounts of organic waste are generated every day that can be used as a source of nutrients, and also as conditioners to improve soil quality. This review paper focuses on the sources, generation, and use of different organic amendments to remediate Cd contaminated soil, discusses their effects on soil physical and chemical properties, Cd bioavailability, plant uptake, and human health risk. Moreover, it also provides an update of the most relevant findings about the application of organic amendments to remediate Cd contaminated soil and associated mechanisms. Finally, future research needs and directions for the remediation of Cd contaminated soil using organic amendments are discussed.

Health risk assessment of Chinese consumers to Cadmium via dietary intake

This paper investigated the concentration of Cd in foods via surveys and a literature review. The concentration of Cd in different food groups was in the decreasing order of meat > aquatic products > cereal > vegetable > bean > egg > dairy > fruit. More precisely, on average the weekly Cd intake for men, women, 2-3-year-old children and 4-17-year-old children were 0.0039, 0.0041, 0.0069 and 0.0064mgkg^-1 bw week^-1, respectively. Among all food groups, cereal was the most significant contributor to the dietary intake of Cd, followed by vegetable, aquatic products and meat. For Chinese consumers, the results of risk assessment for all groups by the deterministic method and the probabilistic method showed the mean weekly Cd intake via dietary exposure was lower than the provisional tolerable weekly intake (PTWI) proposed by WHO. However, the 95th and 97.5th percentile THQ values all exceeded 1, and the probability of dietary Cd exposure greater than the weekly intake tolerance (THQ >1) were 15.9%, 17.1%, 42.3% and 28.4% for men, women, 2-3-year-old children and 4-17-year-old children, indicating a potential risk from Cd exposure via dietary intake, especially for children. It appeared that dietary Cd exposure should deserve our attention, and positive measures must be taken to reduce the concentration of Cd in food at once.

Initial autophagic protection switches to disruption of autophagic flux by lysosomal instability during cadmium stress accrual in renal NRK-52E cells

The renal proximal tubule (PT) is the major target of cadmium (Cd2+) toxicity where Cd2+ causes stress and apoptosis. Autophagy is induced by cell stress, e.g., endoplasmic reticulum (ER) stress, and may contribute to cell survival or death. The role of autophagy in Cd2+-induced nephrotoxicity remains unsettled due to contradictory results and lack of evidence for autophagic machinery damage by Cd2+. Cd2+-induced autophagy in rat kidney PT cell line NRK-52E and its role in cell death was investigated. Increased LC3-II and decreased p62 as autophagy markers indicate rapid induction of autophagic flux by Cd2+ (5-10 µM) after 1 h, accompanied by ER stress (increased p-PERK, p-eIF2α, CHOP). Cd2+ exposure exceeding 3 h results in p62/LC3-II accumulation, but diminished effect of lysosomal inhibitors (bafilomycin A1, pepstatin A +E-64d) on p62/LC3-II levels, indicating decreased autophagic flux and cargo degradation. At 24 h exposure, Cd2+ (5-25 µM) activates intrinsic apoptotic pathways (Bax/Bcl-2, PARP-1), which is not evident earlier (≤6 h) although cell viability by MTT assay is decreased. Autophagy inducer rapamycin (100 nM) does not overcome autophagy inhibition or Cd2+-induced cell viability loss. The autophagosome-lysosome fusion inhibitor liensinine (5 μM) increases CHOP and Bax/Bcl-2-dependent apoptosis by low Cd2+ stress, but not by high Cd2+. Lysosomal instability by Cd2+ (5 μM; 6 h) is indicated by increases in cellular sphingomyelin and membrane fluidity and decreases in cathepsins and LAMP1. The data suggest dual and temporal impact of Cd2+ on autophagy: Low Cd2+ stress rapidly activates autophagy counteracting damage but Cd2+ stress accrual disrupts autophagic flux and lysosomal stability, possibly resulting in lysosomal cell death.

Metabolomics study of cadmium-induced diabetic nephropathy and protective effect of caffeic acid phenethyl ester using UPLC-Q-TOF-MS combined with pattern recognition

Diabetic nephropathy (DN) is the most severe complication of diabetes and multiple factors are involved in the pathogenesis of DN. Among them, cadmium (Cd) acts as a risk factor inducing the occurrence of DN. The present study focused on investigating the protective role of caffeic acid phenethyl ester (CAPE), an active component of propolis from honeybee hives, against Cd-induced DN in mice based on ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS)and pattern recognition. Serum and urine biochemical indexes were detected and histopathological observation has been done to evaluate the damage of Cd on animals. Moreover, the global serum profiles of different groups were distinguished by UPLC-Q-TOF-MS and principal component analysis (PCA) were applied for group differentiation and marker selection. Moreover, the influence of Cd on the oxidative status in DN mice were also evaluated by assessing the parameters of oxidative stress, proinflammatory cytokines and antioxidant competence. As shown in the scores plots, the distinct clustering among controls, DN and CAPE groups were observed, significant changes in serum levels of LysoPC(18:1(11Z)), 2,3-dinor-8-iso-PGF2a, PS(18:1(9Z)/18:1(9Z)), DG(17:0/22:4 (7Z,10Z, 13Z, 16Z)/0:0) and Arachidonic acid(AA) were noted and identified as potential biomarkers, the effect of CAPE reverted them back to near normalcy. Further, It was observed a significant improvement in lipid peroxides (LPO) and protein carbonyls (PCO) levels in Cd-induced DN kidneys along with a significant decline in superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH) levels, however, CAPE relieved these changes. In conclusion, the study suggested that the pathogenesis of DN caused by Cd probably owes to the perturbations of lipid metabolism and AA metabolism; CAPE seems to be effective agent and may be related to its potent antioxidant, anti-inflammatory properties and action as an Nrf2 activator.

Urine cadmium levels and albuminuria in a general population from Spain: A gene-environment interaction analysis

BACKGROUND

The interaction of cadmium with genes involved in oxidative stress, cadmium metabolism and transport pathways on albuminuria can provide biological insight on the relationship between cadmium and albuminuria at low exposure levels.

OBJECTIVES

We tested the hypothesis that specific genotypes in candidate genes may confer increased susceptibility to cadmium exposure.

METHODS

Cadmium exposure was estimated by inductively coupled plasma mass spectrometry (ICPMS) in urine from 1397 men and women aged 18-85years participating in the Hortega Study, a representative sample of a general population from Spain. Urine albumin was measured by automated nephelometric immunochemistry. Abnormal albuminuria was defined as urine albumin greater than or equal to 30mg/g.

RESULTS

The weighted prevalence of abnormal albuminuria was 6.3%. The median level of urine cadmium was 0.39 (IQR, 0.23-0.65) μg/g creatinine. Multivariable-adjusted geometric mean ratios of albuminuria comparing the two highest to the lowest tertile of urine cadmium were 1.62 (95% CI, 1.43-1.84) and 2.94 (95% CI, 2.58-3.35), respectively. The corresponding odds ratios of abnormal albuminuria were 1.58 (0.83, 3.02) and 4.54 (2.58, 8.00). The association between urine cadmium and albuminuria was observed across all participant subgroups evaluated including participants without hypertension, diabetes or chronic kidney disease. We observed Bonferroni-corrected statistically significant interactions between urine cadmium levels and polymorphisms in gene SLC30A7 and RAC1.

CONCLUSIONS

Increasing urine cadmium concentrations were cross-sectionally associated with increased albuminuria in a representative sample of a general population from Spain. Genetic variation in oxidative stress and cadmium metabolism and transport genes may confer differential susceptibility to potential cadmium effects.

The effect of ozone on the expression of metallothionein in tissues of rats chronically exposed to cadmium

Our aims were to evaluate the expression of metallothionein (MT) in an experimental rat model which experienced chronic exposure to cadmium (Cd) and to measure its expression after ozone therapy (OT) or oxygen (Ox) in the same model, as compared to the control group, which was exposed to neither cadmium nor ozone. Forty male Wistar rats were divided into 5 groups: control, Cd, Cd and Ox, Cd and Oz, and Oz. During our research, Cd concentration (ASA) and MT concentration (ELISA) were determined in supernatants of the kidneys, liver and pancreas. SDS-PAGE analyses and immunohistochemical localization were used to evaluate the level of MT expression in the tissue. In rats intoxicated with Cd, the highest concentration of both Cd and MT was observed in the kidneys and liver, with a significantly lower concentration measured in the pancreas. Ozone therapy reduces the accumulation of cadmium in the liver and kidneys, resulting in a reduced expression of metallothionein in those tissues.

Body burdens, sources and interrelations of selected toxic and essential elements among the nine Cree First Nations of Eeyou Istchee, James Bay region of northern Quebec, Canada

BACKGROUND

this article constitutes a report on the comprehensive Nituuchischaayihtitaau Aschii multi-community environment-and-health study conducted among the Cree peoples (Eeyouch) of northern Quebec, Canada.

OBJECTIVES

to interpret observed concentrations of a suite of chemical elements in a multi-media biological monitoring study in terms of sources and predictors.

METHODS

the concentrations of 5 essential and 6 toxic chemical elements were measured in whole blood, and/or in urine or hair by ICP-MS. Concentrations of essential elements are compared to those considered normal (i.e., required for good health) and, when toxic, deemed acceptable at specified concentrations in public health guidelines. Their dependence on age, sex, the specific community lived-in and diet were explored employing multivariate analysis of variance (MANOVA) involving new variables generated by principle component analysis (PCA) and correspondence analysis (CA).

RESULTS

the 5 most prominent PCA axes explained 67.7% of the variation, compared to 93.0% by 6 main CA factors. Concentrations of the essential elements in whole blood (WB) and iodine(i) and arsenic (As) in urine were comparable to those reported in the recent Canadian Health Measures survey and are assigned to dietary sources. By contrast, WB cadmium (Cd) was elevated even when smoking was considered. Mercury (Hg) concentrations in WB and hair were also higher in adults, although comparable to those observed for other indigenous populations living at northern latitudes. Fish consumption was identified as the prominent source. Of the 5 coastal communities, all but one had lower Hg exposures than the four inland communities, presumably reflecting the type of fish consumed. Use of firearms and smoking were correlated with WB-lead (Pb). The concentrations of both Hg and Pb increased with age and were higher in men, while WB-Cd and smoking prevalence were higher in women when considering all communities. Hg and Pb were low in children and women of reproductive age, with few exceedances of health guidelines. Although individuals with T2D had somewhat lower WB-Cd, there is some indication that Cd may potentiate renal dysfunction in this subgroup. Plots of selected CA axes grouped those elements expected to be in a normal diet and distinguished them from those with well-known unique sources (especially Hg and As in hair; and Hg, Pb and Cd in WB).

CONCLUSIONS

the use of multiple biological media in conjunction with the complementary PCA and CA approaches for constructing composite variables allowed a more detailed understanding of both the sources of the essential and toxic elements in body fluids and the dependencies of their observed concentrations on age, sex, community and diet.

Chronic Kidney Disease and Exposure to Nephrotoxic Metals

Chronic kidney disease (CKD) is a common progressive disease that is typically characterized by the permanent loss of functional nephrons. As injured nephrons become sclerotic and die, the remaining healthy nephrons undergo numerous structural, molecular, and functional changes in an attempt to compensate for the loss of diseased nephrons. These compensatory changes enable the kidney to maintain fluid and solute homeostasis until approximately 75% of nephrons are lost. As CKD continues to progress, glomerular filtration rate decreases, and remaining nephrons are unable to effectively eliminate metabolic wastes and environmental toxicants from the body. This inability may enhance mortality and/or morbidity of an individual. Environmental toxicants of particular concern are arsenic, cadmium, lead, and mercury. Since these metals are present throughout the environment and exposure to one or more of these metals is unavoidable, it is important that the way in which these metals are handled by target organs in normal and disease states is understood completely.

Blood cadmium concentrations and environmental exposure sources in newcomer South and East Asian women in the Greater Toronto Area, Canada

BACKGROUND

Immigrant women are often identified as being particularly vulnerable to environmental exposures and health effects. The availability of biomonitoring data on newcomers is limited, thus, presenting a challenge to public health practitioners in the identification of priorities for intervention.

OBJECTIVES

In fulfillment of data needs, the purpose of this study was to characterize blood concentrations of cadmium (Cd) among newcomer women of reproductive age (19-45 years of age) living in the Greater Toronto Area (GTA), Canada and to assess potential sources of environmental exposures.

METHODS

A community-based model, engaging peer researchers from the communities of interest, was used for recruitment and follow-up purposes. Blood samples were taken from a total of 211 newcomer women from South and East Asia, representing primary, regional origins of immigrants to the GTA, and environmental exposure sources were assessed via telephone survey. Metal concentrations were measured in blood samples (diluted with 0.5% (v/v) ammonium hydroxide and 0.1% (v/v) octylphenol ethoxylate) using a quadrupole ICP-MS. Survey questions addressed a wide range of environmental exposure sources, including dietary and smoking patterns and use of nutritional supplements, herbal products and cosmetics.

RESULTS

A geometric mean (GM) blood Cd concentration of 0.39µg/L (SD:±2.07µg/L) was determined for study participants (min/max: <0.045µg/L (LOD)/2.36µg/L). Several variables including low educational attainment (Relative Ratio (RR) (adjusted)=1.50; 95% CI 1.17-1.91), milk consumption (RR (adjusted)=0.86; 95% CI 0.76-0.97), and use of zinc supplements (RR (adjusted)=0.76; 95% CI 0.64-0.95) were observed to be significantly associated with blood Cd concentrations in the adjusted regression model. The variable domains socioeconomic status (R²_adj=0.11) and country of origin (R²_adj=0.236) were the strongest predictors of blood Cd.

CONCLUSION

Blood Cd concentrations fell below those generally considered to be of human health concern. However, negative health effects cannot be entirely excluded, especially for those that fall in the upper percentile range of the distribution, given the mounting evidence for negative health outcomes at low environmental exposure concentrations.

A Review of Diabetes Mellitus and Exposure to the Environmental Toxicant Cadmium with an Emphasis on Likely Mechanisms of Action

There is increasing interest in how exposure to environmental substances can contribute to the onset of Type II diabetes mellitus (T2DM). Impaired insulin release is a hallmark of type I diabetes mellitus and is involved in the progression of T2DM. Both epidemiological and experimental studies show that exposure to the environmental pollutant cadmium (Cd), is associated with hyperglycemia, T2DM and reduced serum insulin. The goal of this review is to examine likely mechanisms of action of Cd-induced dysglycemia based on experimental studies in the literature and from the most recent findings in the Edwards lab. The primary focus of this review will examine how Cd may cause islet dysfunction and subsequent impaired insulin release. Recent findings in the Edwards lab indicate that Cd causes timedependent and statistically significant changes in fasting leptin, Glucose-dependent Insulinotropic Polypeptide (GIP) and pancreas polypeptide hormone levels in a subchronic animal model of Cd-induced hyperglycemia. This review summarizes the most likely cellular mechanisms by which the ubiquitous environmental contaminant Cd disrupts glucose homeostasis. While individual cellular effects of Cd are reviewed it is likely that no one single mechanism is involved, rather multiple mechanisms exist and work synergistically resulting in islet dysfunction and ultimately dysglycemia.

Dioxins, furans and dioxin-like PCBs in human blood: causes or consequences of diabetic nephropathy?

Nephropathy, or kidney disease, is a major, potential complication of diabetes. We assessed the association of 6 chlorinated dibenzo-p-dioxins, 9 chlorinated dibenzofurans and 8 polychlorinated biphenyls (PCBs) in blood with diabetic nephropathy in the 1999-2004 National Health and Nutrition Examination Survey (unweighted N=2588, population estimate=117,658,357). Diabetes was defined as diagnosed or undiagnosed (glycohemoglobin ≥ 6.5%) and nephropathy defined as urinary albumin to creatinine ratio >30 mg/g, representing microalbuminuria or macroalbuminuria. For the 8 chemicals analyzed separately, values above the 75th percentile were considered elevated, whereas for the other 15 compounds values above the maximum limit of detection were considered elevated. Seven of 8 dioxins and dioxin-like compounds, analyzed separately, were found to be associated with diabetic nephropathy. The chemicals associated with diabetic nephropathy were: 1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin; 1,2,3,4,6,7,8,9-Octachlorodibenzo-p-dioxin; 2,3,4,7,8-Pentachlorodibenzofuran; PCB 126; PCB 169; PCB 118; and PCB 156. Three of the 8 dioxins and dioxin-like compounds; 1,2,3,4,6,7,8,9-Octachlorodibenzo-p-dioxin; 2,3,4,7,8-Pentachlorodibenzofuran and PCB 118; expressed as log-transformed continuous variables; were associated with diabetes without nephropathy. When 4 or more of the 23 chemicals were elevated the odds ratios were 7.00 (95% CI=1.80-27.20) for diabetic nephropathy and 2.13 (95% CI=0.95-4.78) for diabetes without nephropathy. Log-transformed toxic equivalency (TEQ) was associated with both diabetic nephropathy, and diabetes without nephropathy, the odds ratios were 2.35 (95% CI=1.57-3.52) for diabetic nephropathy, and 1.44 (95% CI=1.11-1.87) for diabetes without nephropathy. As the kidneys function to remove waste products from the blood, diabetic nephropathy could be either the cause or the consequence (or both) of exposure to dioxins, furans and dioxin-like PCBs.

An examination of traditional foods and cigarette smoking as cadmium sources among the nine First Nations of Eeyou Istchee, Northern Quebec, Canada

Cadmium (Cd), a nonessential toxic metal present in the environment, accumulates in the organs of herbivorous mammals which typically are consumed by Aboriginal populations. The relative contribution of this potential exposure source to concentrations of blood Cd was investigated in 1429 participants (age >7 years) residing in the nine Cree First Nations communities of Eeyou Istchee, northern Quebec, Canada. Analysis of variance identified significant Cd concentration differences between communities, sex, and age groups, although these were complicated by significant 2-way interactions. The percentage of participants with Cd concentrations within the adopted health-based guideline categories of 'acceptable', 'concern' and 'action' pertaining to kidney damage was 56.2%, 38.3%, and 5.5%, respectively. Partial correlations (controlling for age as a continuous variable) did not show a significant association between consumption of traditional foods and Cd concentrations (r = 0.014, df = 105, p = 0.883). A significant and positive partial correlation (r = 0.390, df = 105, p < 0.001) was observed between Cd concentrations and number of cigarettes smoked daily. Analysis of covariance (with mean daily organ meat consumption over the year as a covariate) confirmed that smokers had significantly higher levels of blood Cd than non-smokers (F1,1109 = 1918.2, p < 0.001), and that traditional food consumption was not a good predictor of Cd exposure. Our findings suggest that consumption of traditional foods should not be restricted in Eeyou Istchee for fear of increased Cd exposure risk. Further studies of smoking prevalence among the Cree First Nations and additional public health initiatives to reduce smoking are recommended.

Indigenous health and environmental risk factors: an Australian problem with global analogues?

Indigenous people experience poorer health than non-Indigenous people, and this well-described inequality has been observed in many countries. The contribution of different risk factors to the health ‘gap’ has understandably focussed on those factors for which there are sufficient data. However, this has precluded environmental risk factors – those present in air, water, food, and soil – due to a lack of data describing exposures and outcomes. These risk factors are demonstrably important at the global scale, as highlighted by the 2010 Global Burden of Disease study. Here, we describe how a greater focus on environmental risk factors is required in order to define their role in the Indigenous health gap. We use the Australian context as a case study of an issue we feel has global analogues and relevance. Suggestions for how and why this situation should be remedied are presented and discussed.

Cadmium exposure and its health effects: a 19-year follow-up study of a polluted area in China

BACKGROUND

Dayu County, which is located in southwestern Jiangxi Province in China, has been a cadmium (Cd)-contaminated area since the 1960s. A series of studies about Cd pollution were carried out in the 1980s. However, no further studies of the area were conducted during the following 19 years.

AIM

To observe cadmium (Cd) exposure levels and its health risks among residents living in contaminated areas that have been exposed to environmental cadmium pollution for 45 years.

METHODS

Subjects involved in the survey in 1987 were interviewed again in 2006. Rice and urine samples from surviving subjects were collected to assess the level of cadmium exposure. Urinary Cd (U-Cd), urinary β2-microglobulin (U-β2-M) and urinary N-acetyl-β-d-glucosaminidase (U-NAG) were used as biomarkers to evaluate renal function. A medical examination was also performed on all subjects to diagnose clinical symptoms of Cd-exposure.

RESULT

Of the 96 subjects of the 1987 study who were alive in 2006, a total of 76 subjects were successfully recruited to this study. The average cadmium concentration in rice from the exposed areas was 0.59 ± 0.41 mg/kg in 2006, the average concentration of U-Cd, U-β2-M and U-NAG from cadmium-exposed areas was 25.82 ± 0.20 μg/g Cr, 6525.71 ± 0.93 μg/g Cr and 13.65 ± 0.24 μmol/g Cr, respectively, in 2006. Compared with the 1987 results, the 2006 results showed that the U-β2-M level in the exposed areas increased significantly after 19 years (p<0.05). The levels of U-Cd and U-NAG did not significantly change over time.

CONCLUSION

The concentration of Cd in polluted areas in 2006 is higher than it was in 1987. Renal dysfunction has worsened after 45 years of continuous exposure. Thus, environmental protection and special procedures to remove cadmium in these areas require urgent consideration.

Cadmium induces apoptosis in pancreatic β-cells through a mitochondria-dependent pathway: the role of oxidative stress-mediated c-Jun N-terminal kinase activation

Cadmium (Cd), one of well-known highly toxic environmental and industrial pollutants, causes a number of adverse health effects and diseases in humans. The growing epidemiological studies have suggested a possible link between Cd exposure and diabetes mellitus (DM). However, the toxicological effects and underlying mechanisms of Cd-induced pancreatic β-cell injury are still unknown. In this study, we found that Cd significantly decreased cell viability, and increased sub-G1 hypodiploid cells and annexin V-Cy3 binding in pancreatic β-cell-derived RIN-m5F cells. Cd also increased intracellular reactive oxygen species (ROS) generation and malondialdehyde (MDA) production and induced mitochondrial dysfunction (the loss of mitochondrial membrane potential (MMP) and the increase of cytosolic cytochrome c release), the decreased Bcl-2 expression, increased p53 expression, poly (ADP-ribose) polymerase (PARP) cleavage, and caspase cascades, which accompanied with intracellular Cd accumulation. Pretreatment with the antioxidant N-acetylcysteine (NAC) effectively reversed these Cd-induced events. Furthermore, exposure to Cd induced the phosphorylations of c-jun N-terminal kinases (JNK), extracellular signal-regulated kinases (ERK)1/2, and p38-mitogen-activated protein kinase (MAPK), which was prevented by NAC. Additionally, the specific JNK inhibitor SP600125 or JNK-specific small interference RNA (si-RNA) transfection suppressed Cd-induced β-cell apoptosis and related signals, but not ERK1/2 and p38-MAPK inhibitors (PD98059 and SB203580) did not. However, the JNK inhibitor or JNK-specific si-RNA did not suppress ROS generation in Cd-treated cells. These results indicate that Cd induces pancreatic β-cell death via an oxidative stress downstream-mediated JNK activation-triggered mitochondria-regulated apoptotic pathway.

Developmental origins of obesity and type 2 diabetes: molecular aspects and role of chemicals

Obesity is a leading risk factor for impaired glucose tolerance and type 2 diabetes (T2D). Although the cause of the obesity epidemic is multi-factorial and not entirely clear, the recent acceleration in incidence is too rapid to be accounted for only by genetics, the wide availability of calorie-rich foods, and increasingly sedentary lifestyles. Accumulating data suggest that the important causes of the obesity epidemic may be related to developmental and early life environmental conditions. The concept of the developmental origins of health and disease (DOHaD) suggests that adverse influences early in development, particularly during intrauterine life, may result in permanent changes in the physiology and metabolism of the infant, which in turn result in an increased risk of non-communicable diseases in adulthood. For example, undernutrition during pregnancy and rapid postnatal weight gain are associated with obesity and T2D in the adult offspring. Moreover, increasing evidence suggests that early-life exposure to a wide range of chemicals has a significant impact on the causes of metabolic disorders. Although the underlying molecular mechanisms remain to be determined, these factors can affect epigenetic processes, such as DNA methylation, allowing the developmental environment to modulate gene transcription. The objective of this review article was to summarize recent progress in the biomedical implications of the DOHaD concept, focusing on the pathogenesis of obesity and T2D, and to discuss a future direction for preventive strategies from a public health perspective.

Emerging roles of cadmium and heme oxygenase in type-2 diabetes and cancer susceptibility

Many decades after an outbreak of severe cadmium poisoning, known as Itai-itai disease, cadmium continues to pose a significant threat to human health worldwide. This review provides an update on the effects of this environmental toxicant cadmium, observed in numerous populations despite modest exposure levels. In addition, it describes the current knowledge on the link between heme catabolism and glycolysis. It examines novel functions of heme oxygenase-2 (HO-2) that protect against type 2-diabetes and obesity, which have emerged from diabetic/obese phenotypes of the HO-2 knockout mouse model. Increased cancer susceptibility in type-2 diabetes has been noted in several large cohorts. This is a cause for concern, given the high prevalence of type-2 diabetes worldwide. A lifetime exposure to cadmium is associated with pre-diabetes, diabetes, and overall cancer mortality with sex-related differences in specific types of cancer. Liver and kidney are target organs for the toxic effects of cadmium. These two organs are central to the maintenance of blood glucose levels. Further, inhibition of gluconeogenesis is a known effect of heme, while cadmium has the propensity to alter heme catabolism. This raises the possibility that cadmium may mimic certain HO-2 deficiency conditions, resulting in diabetic symptoms. Intriguingly, evidence has emerged from a recent study to suggest the potential interaction and co-regulation of HO-2 with the key regulator of glycolysis: 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 4 (PFKFB4). HO-2 could thus be critical to a metabolic switch to cancer-prone cells because the enzyme PFKFB and glycolysis are metabolic requirements for cell proliferation and resistance to apoptosis.

Assessing human exposure risk to cadmium through inhalation and seafood consumption

The role of cadmium (Cd) bioaccessibility in risk assessment is less well studied. The aim of this study was to assess human health risk to Cd through inhalation and seafood consumption by incorporating bioaccessibility. The relationships between trophically available Cd and bioaccessibility were constructed based on available experimental data. We estimated Cd concentrations in human urine and blood via daily intake from seafood consumption and inhalation based on a physiologically-based pharmacokinetic (PBPK) model. A Hill-based dose-response model was used to assess human renal dysfunction and peripheral arterial disease risks for long-term Cd exposure. Here we showed that fish had higher bioaccessibility (~83.7%) than that of shellfish (~73.2%) for human ingestion. Our results indicated that glomerular and tubular damage among different genders and smokers ranged from 18.03 to 18.18%. Our analysis showed that nonsmokers had 50% probability of peripheral arterial disease level exceeding from 3.28 to 8.80%. Smoking populations had 2-3 folds higher morbidity risk of peripheral arterial disease than those of nonsmokers. Our study concluded that the adverse effects of Cd exposure are exacerbated when high seafood consumption coincides with cigarette smoking. Our work provides a framework that could more accurately address risk dose dependency of Cd hazard.

Mechanisms of cadmium-induced proximal tubule injury: new insights with implications for biomonitoring and therapeutic interventions

Cadmium is an important industrial agent and environmental pollutant that is a major cause of kidney disease. With chronic exposure, cadmium accumulates in the epithelial cells of the proximal tubule, resulting in a generalized reabsorptive dysfunction characterized by polyuria and low-molecular-weight proteinuria. The traditional view has been that as cadmium accumulates in proximal tubule cells, it produces a variety of relatively nonspecific toxic effects that result in the death of renal epithelial cells through necrotic or apoptotic mechanisms. However, a growing volume of evidence suggests that rather than merely being a consequence of cell death, the early stages of cadmium-induced proximal tubule injury may involve much more specific changes in cell-cell adhesion, cellular signaling pathways, and autophagic responses that occur well before the onset of necrosis or apoptosis. In this commentary, we summarize these recent findings, and we offer our own perspectives as to how they relate to the toxic actions of cadmium in the kidney. In addition, we highlight recent findings, suggesting that it may be possible to detect the early stages of cadmium toxicity through the use of improved biomarkers. Finally, some of the therapeutic implications of these findings will be considered. Because cadmium is, in many respects, a model cumulative nephrotoxicant, these insights may have broader implications regarding the general mechanisms through which a variety of drugs and toxic chemicals damage the kidney.

Associations between microRNA (miR-21, 126, 155 and 221), albuminuria and heavy metals in Hong Kong Chinese adolescents

BACKGROUND AND AIM

Pathogenetic mechanisms underlying albuminuria are not completely understood. Heavy metals might lead to atherosclerosis and kidney damage. miR-21, 126, 155 and 221 regulated endothelial function and might contribute to the development of albuminuria. To date, no clinical trial has explored the relationship between miRNAs, microalbuminuria and heavy metals in human. In this study, we aimed to examine the association between microalbuminuria, miRNAs and heavy metals in adolescents.

MATERIALS AND METHODS

From a cross-sectional, population-recruited study, we identified 60 school children aged 12-19 years with microalbuminuria (defined as spot urine albumin-creatinine ratio >3.5 mg/mmol). We compared the urine heavy metals (arsenic, mercury, cadmium and lead) and miRNAs levels (miR-21,126, 155 and 221) with another 60 age-and sex-matched normoalbuminuric adolescents as control.

RESULTS

Mean age of the study cohort was 15.5±2.1 years. 43% were boys. Among the four miRNAs tested, only miR-21 was associated with microalbuminuria (p=0.02). Urinary arsenic and lead levels had a negative association with both miR-21 and miR-221. No significant association was found between heavy metals examined and microalbuminuria.

CONCLUSION

The results of our study suggest an association between microalbuminuria, miR-21 and heavy metals (arsenic and lead). This might imply that miR-21 is involved in the pathogenetic mechanisms linking heavy metals exposure and albuminuria.

Gender differences for associations between circulating levels of metals and coronary risk in the elderly

Several studies have pointed out associations between various metals and cardiovascular disease. Since cardiovascular disease prevalence is different between males and females, we investigated whether circulating levels of metals related differently to coronary risk in men and women. In the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study, coronary risk was assessed by the Framingham Risk Score together with circulating blood levels of 11 different trace and heavy metals in 1016 subjects aged 70 years. Circulating levels of cadmium, copper and manganese were significantly higher in women than in men, while mercury, zinc and lead were significantly lower following adjustment for kidney function (measured by glomerular filtration rate, GFR). No significant differences between women and men were seen regarding levels of aluminium, molybdenum, cobalt, chromium and nickel. When all 11 metals were entered as independent variables together with GFR in multiple models in the Framingham Risk Score as the dependent variable, cadmium was the major determinant of the Framingham Risk Score in women (p<0.0001, followed by zinc p=0.03), while copper was the major determinant of the Framingham Risk Score in men (p<0.0001, followed by inverse relations vs. aluminium p=0.01 and nickel p=0.01). There are gender differences in levels of metals and also regarding the association between metals and coronary risk, with cadmium levels being most important for women and copper levels for men in this elderly population.

Impact of trace element changes on dehydroepiandrosterone sulfate in healthy and diabetic states among middle-age and elderly Egyptians

The aim of this study was to confirm if there is a link between the alteration in blood levels of trace elements (chromium, copper, lead, cadmium, and zinc) and dehydroepiandrosterone sulfate (DHEAS) in healthy and diabetic states. This study is the first study to test these parameters in Egyptians. The study included 150 subjects divided into the following four groups: healthy middle-aged, healthy elderly, middle-aged diabetics, and elderly diabetics. Our results revealed a statistically significant decrease in the level of DHEAS in the elderly compared to middle-aged healthy and diabetic groups (p < 0.05). There was a significant difference between the middle-aged groups with respect to zinc, copper, chromium, and cadmium levels. Zinc and copper were lower in the diabetic subjects while chromium and cadmium were higher in the same group in comparison to healthy subjects. In the elderly groups, there were significant increases in chromium and cadmium levels in diabetic subjects rather than healthy ones. There was a significant increase in the thiobarbituric acid reactive substance level in the elderly healthy and diabetic groups and a significant decrease in the glutathione level in the elderly groups. There was no correlation between the levels of trace elements and DHEAS or between the levels of DHEAS, oxidants, and antioxidants in all of the tested groups. In conclusion, only the DHEAS level was correlated with age. There was no difference between the diabetic and healthy groups with respect to the levels of trace elements, with the exception of chromium and cadmium, which suggests the effect of pollution on the pathogenesis of diabetes in Egyptians. No correlation existed between the levels of DHEAS and trace elements, oxidants, and antioxidants. Finally, we believe that there is a large regional variation in the levels of trace elements due to different environmental exposure and nutritional factors which are responsible for contradictory results regarding the pathogenesis of diseases related to alterations in the levels of trace elements.

Heavy metal poisoning and cardiovascular disease

Cardiovascular disease (CVD) is an increasing world health problem. Traditional risk factors fail to account for all deaths from CVD. It is mainly the environmental, dietary and lifestyle behavioral factors that are the control keys in the progress of this disease. The potential association between chronic heavy metal exposure, like arsenic, lead, cadmium, mercury, and CVD has been less well defined. The mechanism through which heavy metals act to increase cardiovascular risk factors may act still remains unknown, although impaired antioxidants metabolism and oxidative stress may play a role. However, the exact mechanism of CVD induced by heavy metals deserves further investigation either through animal experiments or through molecular and cellular studies. Furthermore, large-scale prospective studies with follow up on general populations using appropriate biomarkers and cardiovascular endpoints might be recommended to identify the factors that predispose to heavy metals toxicity in CVD. In this review, we will give a brief summary of heavy metals homeostasis, followed by a description of the available evidence for their link with CVD and the proposed mechanisms of action by which their toxic effects might be explained. Finally, suspected interactions between genetic, nutritional and environmental factors are discussed.

Environmental risk conditions and pathways to cardiometabolic diseases in indigenous populations

This review examines environments in relation to cardiometabolic diseases in Indigenous populations in developed countries. Environmental factors are framed in terms of context (features of places) and composition (features of populations). Indigenous peoples are seen to have endured sociopolitical marginalization and material disadvantage spanning generations. Past adverse collective experiences, modified by culture, are reflected by current heterogeneity in environmental context and composition. As risk conditions, unfavorable contextual and compositional exposures influence the expression of cardiometabolic risk for individuals. Minimal research has evaluated heterogeneity in risk conditions against heterogeneity in cardiometabolic diseases between or within Indigenous populations. Thus far, the features of populations, not of places themselves, have been implicated in relation to cardiometabolic diseases. Behavioral, psychosocial, and stress-axis pathways may explain the relationships between risk conditions and cardiometabolic diseases. Implications of environmental factors and their pathways as well as important research needs are discussed in relation to ecological prevention to reduce cardiometabolic diseases.

Chronic kidney disease of unknown aetiology in Sri Lanka: is cadmium a likely cause?

Background

The rising prevalence of chronic kidney disease (CKD) and subsequent end stage renal failure necessitating renal replacement therapy has profound consequences for affected individuals and health care resources. This community based study was conducted to identify potential predictors of microalbuminuria in a randomly selected sample of adults from the North Central Province (NCP) of Sri Lanka, where the burden of CKD is pronounced and the underlying cause still unknown.

Methods

Exposures to possible risk factors were determined in randomly recruited subjects (425 females and 461 males) from selected areas of the NCP of Sri Lanka using an interviewer administered questionnaire. Sulphosalicylic acid and the Light Dependent Resister microalbumin gel filtration method was used for initial screening for microalbuminuria and reconfirmed by the Micral strip test.

Results

Microalbumnuria was detected in 6.1% of the females and 8.5% of the males. Smoking (p < 0.001), alcohol use (p = 0.003), hypertension (p < 0.001), diabetes (p < 0.001), urinary tract infection (UTI) (p = 0.034) and consumption of water from wells in the fields (p = 0.025) were associated with microalbuminuria. In the binary logistic regression analysis, hypertension, diabetes mellitus, UTI, drinking well water in the fields, smoking and pesticide spraying were found to be significant predictors of microalbuminuria.

Conclusions

Hypertension, diabetes mellitus, UTI, and smoking are known risk factors for microalbuminuria. The association between microalbuminuria and consumption of well water suggests an environmental aetiology to CKD in NCP. The causative agent is yet to be identified. Investigations for cadmium as a potential causative agent needs to be initiated.

Chronic kidney disease of unknown aetiology in Sri Lanka: is cadmium a likely cause?

BACKGROUND

The rising prevalence of chronic kidney disease (CKD) and subsequent end stage renal failure necessitating renal replacement therapy has profound consequences for affected individuals and health care resources. This community based study was conducted to identify potential predictors of microalbuminuria in a randomly selected sample of adults from the North Central Province (NCP) of Sri Lanka, where the burden of CKD is pronounced and the underlying cause still unknown.

METHODS

Exposures to possible risk factors were determined in randomly recruited subjects (425 females and 461 males) from selected areas of the NCP of Sri Lanka using an interviewer administered questionnaire. Sulphosalicylic acid and the Light Dependent Resister microalbumin gel filtration method was used for initial screening for microalbuminuria and reconfirmed by the Micral strip test.

RESULTS

Microalbumnuria was detected in 6.1% of the females and 8.5% of the males. Smoking (p < 0.001), alcohol use (p = 0.003), hypertension (p < 0.001), diabetes (p < 0.001), urinary tract infection (UTI) (p = 0.034) and consumption of water from wells in the fields (p = 0.025) were associated with microalbuminuria. In the binary logistic regression analysis, hypertension, diabetes mellitus, UTI, drinking well water in the fields, smoking and pesticide spraying were found to be significant predictors of microalbuminuria.

CONCLUSIONS

Hypertension, diabetes mellitus, UTI, and smoking are known risk factors for microalbuminuria. The association between microalbuminuria and consumption of well water suggests an environmental aetiology to CKD in NCP. The causative agent is yet to be identified. Investigations for cadmium as a potential causative agent needs to be initiated.

Cadmium, environmental exposure, and health outcomes

We provide an update of the issues surrounding health risk assessment of exposure to cadmium in food. Bioavailability of ingested cadmium has been confirmed in studies of persons with elevated dietary exposure, and the findings have been strengthened by the substantial amounts of cadmium accumulated in kidneys, eyes, and other tissues and organs of environmentally exposed individuals. We hypothesized that such accumulation results from the efficient absorption and systemic transport of cadmium, employing multiple transporters that are used for the body's acquisition of calcium, iron, zinc, and manganese. Adverse effects of cadmium on kidney and bone have been observed in environmentally exposed populations at frequencies higher than those predicted from models of exposure. Population data raise concerns about the validity of the current safe intake level that uses the kidney as the sole target in assessing the health risk from ingested cadmium. The data also question the validity of incorporating the default 5% absorption rate in the threshold-type risk assessment model, known as the provisional tolerable weekly intake (PTWI), to derive a safe intake level for cadmium.

Cadmium exposure in the population: from health risks to strategies of prevention

We focus on the recent evidence that elucidates our understanding about the effects of cadmium (Cd) on human health and their prevention. Recently, there has been substantial progress in the exploration of the shape of the Cd concentration-response function on osteoporosis and mortality. Environmental exposure to Cd increases total mortality in a continuous fashion without evidence of a threshold, independently of kidney function and other classical factors associated with mortality including age, gender, smoking and social economic status. Pooled hazard rates of two recent environmental population based cohort studies revealed that for each doubling of urinary Cd concentration, the relative risk for mortality increases with 17% (95% CI 4.2-33.1%; P < 0.0001). Tubular kidney damage starts at urinary Cd concentrations ranging between 0.5 and 2 μg urinary Cd/g creatinine, and recent studies focusing on bone effects show increased risk of osteoporosis even at urinary Cd below 1 μg Cd/g creatinine. The non-smoking adult population has urinary Cd concentrations close to or higher than 0.5 μg Cd/g creatinine. To diminish the transfer of Cd from soil to plants for human consumption, the bioavailability of soil Cd for the plants should be reduced (external bioavailability) by maintaining agricultural and garden soils pH close to neutral (pH-H(2)O of 7.5; pH-KCL of 6.5). Reducing the systemic bioavailability of intestinal Cd can be best achieved by preserving a balanced iron status. The latter might especially be relevant in groups with a lower intake of iron, such as vegetarians, and women in reproductive phase of life. In exposed populations, house dust loaded with Cd is an additional relevant exposure route. In view of the insidious etiology of health effects associated with low dose exposure to Cd and the current European Cd intake which is close to the tolerable weekly intake, one should not underestimate the importance of the recent epidemiological evidence on Cd toxicity as to its medical and public health implications.

Heavy metal poisoning: the effects of cadmium on the kidney

The heavy metal cadmium (Cd) is known to be a widespread environmental contaminant and a potential toxin that may adversely affect human health. Exposure is largely via the respiratory or gastrointestinal tracts; important non-industrial sources of exposure are cigarette smoke and food (from contaminated soil and water). The kidney is the main organ affected by chronic Cd exposure and toxicity. Cd accumulates in the kidney as a result of its preferential uptake by receptor-mediated endocytosis of freely filtered and metallothionein bound Cd (Cd-MT) in the renal proximal tubule. Internalised Cd-MT is degraded in endosomes and lysosomes, releasing free Cd(2+) into the cytosol, where it can generate reactive oxygen species (ROS) and activate cell death pathways. An early and sensitive manifestation of chronic Cd renal toxicity, which can be useful in individual and population screening, is impaired reabsorption of low molecular weight proteins (LMWP) (also a receptor-mediated process in the proximal tubule) such as retinol binding protein (RBP). This so-called 'tubular proteinuria' is a good index of proximal tubular damage, but it is not usually detected by routine clinical dipstick testing for proteinuria. Continued and heavy Cd exposure can progress to the clinical renal Fanconi syndrome, and ultimately to renal failure. Environmental Cd exposure may be a significant contributory factor to the development of chronic kidney disease, especially in the presence of other co-morbidities such as diabetes or hypertension; therefore, the sources and environmental impact of Cd, and efforts to limit Cd exposure, justify more attention.

Environments and cardiometabolic diseases in aboriginal populations

This review establishes the relevance and frames the relationship of environmental factors to cardiometabolic risk factors and disease in Aboriginal populations. Environmental factors operate at the level of communities or populations. They include contextual measures of places and compositional measures of populations which together constitute "risk conditions" affecting individual risk factors. Environmental factors have been implicated by contrasting Aboriginal and non-Aboriginal populations in cardiometabolic risk factors and outcomes, or by geographic contrasts of Aboriginal populations in remote, rural and urban regions. It is unclear whether heterogeneity in contextual or compositional factors between and within Aboriginal populations is associated with heterogeneity in cardiometabolic risk factors and outcomes. Empirical literature that links environmental factors and cardiometabolic outcomes in Aboriginal populations is critically reviewed for three postulated pathways of influence: (1) behaviour; (2) psychosocial factors; and (3) stress response axes. These pathways, represented as interdependent, can explain how and why environments are associated with cardiometabolic outcomes. The need remains, however, to develop a robust quantitative evidence base in cardiometabolic research aimed at enhancing knowledge of the specific environmental factors related to the cardiometabolic health of Aboriginal populations as well as explicating the underlying mechanisms by which environmental risk conditions 'get under the skin'.