Urinary Cadmium Threshold to Prevent Kidney Disease Development

Urinary cadmium concentration is associated with the severity and clinical outcomes of COVID-19: a bicenter observational cohort study

BACKGROUND

Cadmium and nickel exposure can cause oxidative stress, induce inflammation, inhibit immune function, and therefore has significant impacts on the pathogenesis and severity of many diseases. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can also provoke oxidative stress and the dysregulation of inflammatory and immune responses. This study aimed to assess the potential associations of cadmium and nickel exposure with the severity and clinical outcomes of patients with coronavirus disease 2019 (COVID-19).

METHODS

We performed a retrospective, observational, bicenter cohort analysis of patients with SARS-CoV-2 infection in Taiwan between June 2022 and July 2023. Cadmium and nickel concentrations in blood and urine were measured within 3 days of the diagnosis of acute SARS-CoV-2 infection, and the severity and clinical outcomes of patients with COVID-19 were analyzed.

RESULTS

A total of 574 patients were analyzed and divided into a severe COVID-19 group (hospitalized patients) (n = 252; 43.9%), and non-severe COVID-19 group (n = 322; 56.1%). The overall in-hospital mortality rate was 11.8% (n = 68). The severe COVID-19 patients were older, had significantly more comorbidities, and significantly higher neutrophil/lymphocyte ratio, C-reactive protein, and interleukin-6 than the non-severe COVID-19 patients (all p < 0.05). Blood and urine cadmium and urine nickel concentrations were significantly higher in the severe COVID-19 patients than in the non-severe COVID-19 patients. Among the severe COVID-19 patients, those in higher urine cadmium/creatinine quartiles had a significantly higher risk of organ failure (i.e., higher APACHE II and SOFA scores), higher neutrophil/lymphocyte ratio, lower PaO2/FiO2 requiring higher invasive mechanical ventilation support, higher risk of acute respiratory distress syndrome, and higher 60-, 90-day, and all-cause hospital mortality (all p < 0.05). Multivariable logistic regression models revealed that urine cadmium/creatinine was independently associated with severe COVID-19 (adjusted OR 1.643 [95% CI 1.060-2.547], p = 0.026), and that a urine cadmium/creatinine value > 2.05 μg/g had the highest predictive value (adjusted OR 5.349, [95% CI 1.118-25.580], p = 0.036).

CONCLUSIONS

Urine cadmium concentration in the early course of COVID-19 could predict the severity and clinical outcomes of patients and was independently associated with the risk of severe COVID-19.

Cadmium-associated protein changes in residents of contaminated areas: Abandoned mine and smelter

Cadmium (Cd), a serious environmental contaminant, is associated with adverse health effects. However, the specific changes that the human body experiences in response to exposure to varying concentrations of cadmium remain unknown. The high levels of heavy metal contamination, especially Cd, in abandoned mines and smelter sites make them ideal locations to investigate the physiological manifestations of Cd exposure. This study found that individuals inhabiting abandoned mine and smelter areas had higher concentrations of Cd in their urine and blood compared to those living outside these areas (i.e., the controls). Furthermore, proteomic profiling of blood samples from all study groups was performed to identify proteomic biomarkers associated with chronic and severe Cd exposure. This analysis showed statistically significant correlations between urine Cd levels and sixteen proteins. Among these proteins, seven exhibited significantly altered expressions in samples from contaminated areas compared with those from control areas. Therefore, these proteins were selected as potential markers representing Cd-related protein alterations. Multiple reaction monitoring analysis was performed to validate the expression patterns of the proteins and four proteins were found to exhibit consistent trends. The findings show that Cd exposure significantly affects the expression of certain proteins in the human body. Understanding the underlying mechanisms and diseases associated with Cd-induced protein alterations can aid in the development of effective preventive and therapeutic strategies for individuals exposed to Cd-linked pollution.

In situ localization of lipids on mouse kidney tissues with acute cadmium toxicity using atmospheric pressure-MALDI mass spectrometry imaging

Cadmium-induced nephrotoxicity has been one of the major concerns for public health over the past century. Lipid peroxidation is a principal mechanism in its pathological process. Atmospheric pressure-MALDI mass spectrometry imaging (AP-MALDI MSI) enables direct mapping of lipids in the biological tissue sections. Considering the spatial visualization of lipids on mouse kidney tissues with acute cadmium toxicity is lacking, this study dedicates to filling the gap by using AP-MALDI MSI. Of the tested matrices, the optimized matrix for labeling lipids was 2,5-dihydroxyacetophenone (DHAP). A set of lipids including phosphatidylcholines (PC), phosphatidylglycerol (PG), lysophosphatidylcholine (LPC), sphingomyelin (SM), phosphatidic acid (PA), triglyceride (TG), phosphatidylethanolamine (PE) and phosphatidylinositol (PI), etc. were identified and visualized. Accordingly, PC, PG, LPC, SM, PA and TG were down-regulated while PE and PI were up-regulated in the renal cortex or medulla regions in kidney tissues of the mouse with acute cadmium toxicity. Such in situ locations of lipids on mouse kidney tissues with acute cadmium toxicity could help discover tissue-specific nephrotoxic biomarkers and provide new insights into its renal toxicological mechanism.

Biomarkers of cadmium exposure and renal function in estuarine adult villagers

OBJECTIVE

Assess cadmium (Cd) exposure of adults living in two estuarine communities in Aratu bay, Bahia, Brazil and its association with effects on renal function.

METHODS

This cross-sectional study included 88 volunteers aged 17-55 years, living in the following two communities: Santa Luzia (SL) located more intimately in the bay and Cotegipe (CT), a bit further and closer to a ferro-manganese alloy plant. Cd in blood (CdB) and urine (CdU), along with blood lead (PbB) levels were determined by graphite furnace atomic absorption spectrometry. Renal function was evaluated by the estimated glomerular filtration rate (eGFR) and tubular cell biomarkers: retinol binding protein (RBP), β2-microglobulin (β2M), and N-acetyl-β-D-glucosaminidase (NAG).

RESULTS

The median CdU levels in villagers of the two communities were 0.20 and 0.44 µg/g creat. and SL vs CT, respectively. Age range (> 35 years), cigarette smoking and lower family income were significantly associated with more elevated CdU levels. Multiple linear regression analysis demonstrated a significant association between LnCdU and LnRBP levels (β = 0.200, 95%CI 0.074-0.365) after adjusted for sex, urinary creatinine and blood lead levels.

CONCLUSION

These data show consistent evidences of association between Cd exposure and elevated tubular cell biomarker excretion in estuarine villagers living close to an industrial site.

Epidermal Growth Factor Receptor (EGFR) Gene Polymorphism May be a Modifier for Cadmium Kidney Toxicity

The results of many studies indicate that cadmium (Cd) exposure is harmful to humans, with the proximal tubule of the kidney being the main target of Cd accumulation and toxicity. Studies have also shown that Cd has the effect of activating the pathway of epidermal growth factor receptor (EGFR) signaling and cell growth. The EGFR is a family of transmembrane receptors, which are widely expressed in the human kidney. The aim of this study was to investigate the kidney function estimated glomerular filtration rate (eGFR), and its relationship with plasma Cd level and EGFR gene polymorphism. Using data from Academia Sinica Taiwan biobank, 489 subjects aged 30-70 years were analyzed. The demographic characteristics was determined from questionnaires, and biological sampling of urine and blood was determined from physical examination. Kidney function was assessed by the eGFR with CKD-EPI formula. Plasma Cd (ug/L) was measured by inductively coupled plasma mass spectrometry. A total of 97 single-nucleotide polymorphisms (SNPs) were identified in the EGFR on the Taiwan biobank chip, however 4 SNPs did not pass the quality control. Multiple regression analyses were performed to achieve the study aim. The mean (±SD) plasma Cd level of the study subjects was 0.02 (±0.008) ug/L. After adjusting for confounding variables, rs13244925 AA, rs6948867 AA, rs35891645 TT and rs6593214 AA types had higher eGFR (4.89 mL/min/1.73 m² (p = 0.035), 5.54 mL/min/1.73 m² (p = 0.03), 4.96 mL/min/1.73 m² (p = 0.048) and 5.16 mL/min/1.73 m² (p = 0.048), respectively). Plasma cadmium and rs845555 had an interactive effect on eGFR. In conclusion, EGFR polymorphisms could be modifiers of Cd kidney toxicity, in which rs13244925 AA, rs6948867 AA, rs35891645 TT and rs6593214 AA may be protective, and Cd interacting with rs845555 may affect kidney function.

Quercetin alleviates cadmium chloride-induced renal damage in rats by suppressing endoplasmic reticulum stress through SIRT1-dependent deacetylation of Xbp-1s and eIF2α

Endoplasmic reticulum (ER) stress plays a key role in cadmium chloride (CdCl2)-induced nephrotoxicity. Sirtuin-1 (SIRT1) is a potent inhibitor of ER stress. In this study, we examined whether the protective effect of quercetin (QUR) against CdCl₂-induced nephrotoxicity in rats involved modulation of SIRT1 and/or ER stress. Adult male rats were divided into five groups (n = 8, each) and treated for eight weeks as follows: control, control + QUR, CdCl₂, CdCl₂ + QUR, and CdCl₂ + QUR + EX-527 (a SIRT1 inhibitor). Treatment of rats with QUR preserved the glomerulus and tubule structure, attenuated interstitial fibrosis, increased creatinine excretion, and reduced urinary levels of albumin, N-acetyl-β-D-glucosaminidase, and β2-microglobulin in CdCl₂-treated rats. Concomitantly, QUR increased renal levels of Bcl-2, reduced mRNA levels of CHOP, and protein levels of Bax, caspase-3, and cleaved caspase-3, but failed to reduce the mRNA levels of GRP78, PERK, eIf2α, ATF-6, and xbp-1. QUR also reduced the renal levels of reactive oxygen species, tumour necrosis factor, and interleukin-6 and the nuclear activity of NF-κB in the control and CdCl₂-treated rats but increased the nuclear activity of Nrf2 and levels of glutathione and manganese superoxide dismutase. Additionally, QUR increased the total levels and nuclear activity of SIRT1 and reduced the acetylation of eIf2α and xbp-1. The nephroprotective effects of QUR were abrogated by treatment with EX-527. Thus, QUR ameliorated CdCl₂-induced nephrotoxicity through antioxidant and anti-inflammatory effects and suppressed ER stress mediated by the upregulation or activation of SIRT1-induced deacetylation of Nrf2, NF-κB p65, eIF2α, and xbp-1.

"Metalloestrogenic" effects of cadmium downstream of G protein-coupled estrogen receptor and mitogen-activated protein kinase pathways in human uterine fibroid cells

Cadmium (Cd) is a toxic metal reported to act as an estrogen "mimic" in the rat uterus and in vitro. We have reported that Cd stimulates proliferation of estrogen-responsive human uterine leiomyoma (ht-UtLM; fibroid) cells through nongenomic signaling involving the G protein-coupled estrogen receptor (GPER), with activation of epidermal growth factor receptor (EGFR) and mitogen-activated protein kinase (pMAPK44/42). In this study, we explored Cd-induced mechanisms downstream of MAPK and whether Cd could stimulate phosphorylation of Histone H3 at serine 10 (H3Ser10ph) through activated Aurora B kinase (pAurora B), a kinase important in activation of histone H3 at serine 10 during mitosis, and if this occurs via Fork head box M1 (FOXM1) and cyclin D1 immediately downstream of MAPK. We found that Cd increased proliferating cell nuclear antigen (PCNA) and H3Ser10ph expression by immunofluorescence, and that H3ser10ph and pAurora B were coexpressed along the metaphase plate in ht-UtLM cells. In addition, Cd-exposed cells showed higher expression of pMAPK44/42, FOXM1, pAurora B, H3ser10ph, and Cyclin D1 by western blotting. Immunoprecipitation and proximity ligation assays further indicated an association between FOXM1 and Cyclin D1 in Cd-exposed cells. These effects were attenuated by MAPK kinase (MEK1/2) inhibitor. In summary, Cd-induced proliferation of ht-UtLM cells occurred through activation of Histone H3 and Aurora B via FOXM1/Cyclin D1 interactions downstream of MAPK. This provides a molecular mechanism of how Cd acts as an "estrogen mimic" resulting in mitosis in hormonally responsive cells.

Environmental cadmium exposure induces kidney tubular and glomerular dysfunction in the Myanmar adults

Cadmium is an environmental toxic metal and its exposure has become a worldwide public health threat. We aimed to evaluate the exposure assessment of cadmium in people living in Ta Zin Yae Kyaw village of Nyaung Don Township in Ayeyarwady Division, Myanmar and adverse effects of cadmium on the kidneys. Subjects (18-40 years) residing in this village were selected as the exposed group (n = 65) and those living in Kamayut Township in Yangon Division, Myanmar as the control group (n = 65). Spot urine samples were taken for determination of urinary cadmium concentration using graphite-furnace atomic absorption spectrometry (GFAAS) method and adjusted to the concentration of creatinine in urine. To assess the kidney function, urinary β₂-microglobulin level was determined by ELISA, serum creatinine was measured by colorimetric Jaffe method and estimated glomerular filtration rate (eGFR) was calculated by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Urine cadmium concentrations were significantly higher in the exposed group (median (Interquartile range): 0.96 (0.19-1.77) μg/g Creatinine) compared to the control (p = 0.036). Urinary β₂-microglobulin levels were significantly higher (p = 0.000) and eGFR was significantly lower in the exposed group (p = 0.013) compared to the control. In addition, urine cadmium level showed significant positive correlation with urinary β₂-microglobulin in all study population (p < 0.01). Positive correlation becomes stronger (p < 0.01) in the exposed group only. For eGFR, significant negative correlation was found in all study population (p < 0.01) and exposed group (p < 0.01). Our findings suggested that environmental cadmium exposure can induce renal dysfunction in both tubular and glomerular functions in apparently healthy human adults.

Cadmium and Lead Exposure, Nephrotoxicity, and Mortality

The present review aims to provide an update on health risks associated with the low-to-moderate levels of environmental cadmium (Cd) and lead (Pb) to which most populations are exposed. Epidemiological studies examining the adverse effects of coexposure to Cd and Pb have shown that Pb may enhance the nephrotoxicity of Cd and vice versa. Herein, the existing tolerable intake levels of Cd and Pb are discussed together with the conventional urinary Cd threshold limit of 5.24 μg/g creatinine. Dietary sources of Cd and Pb and the intake levels reported for average consumers in the U.S., Spain, Korea, Germany and China are summarized. The utility of urine, whole blood, plasma/serum, and erythrocytes to quantify exposure levels of Cd and Pb are discussed. Epidemiological studies that linked one of these measurements to risks of chronic kidney disease (CKD) and mortality from common ailments are reviewed. A Cd intake level of 23.2 μg/day, which is less than half the safe intake stated by the guidelines, may increase the risk of CKD by 73%, and urinary Cd levels one-tenth of the threshold limit, defined by excessive ß₂-microglobulin excretion, were associated with increased risk of CKD, mortality from heart disease, cancer of any site and Alzheimer's disease. These findings indicate that the current tolerable intake of Cd and the conventional urinary Cd threshold limit do not provide adequate health protection. Any excessive Cd excretion is probably indicative of tubular injury. In light of the evolving realization of the interaction between Cd and Pb, actions to minimize environmental exposure to these toxic metals are imperative.

An assessment of sensitivity biomarkers for urinary cadmium burden

BACKGROUND

Excess cadmium (Cd) intake poses a general risk to health and to the kidneys in particular. Among indices of renal dysfunction under Cd burden measures are the urinary N-acetyl-β-D-glucosidase (UNAG) and urinary β2-microglobulin (Uβ2-MG) enzymes. However, the end-pointed values and the Cd burden threshold remain controversial because the scopes fluctuate widely.

METHODS

To ascertain the clinical benchmark dose of urinary Cd (UCd) burden for renal dysfunction, 1595 residents near a Cd site were surveyed. Urine was sampled and assayed. A benchmark dose low (BMDL) was obtained by fitting UCd levels and index levels.

RESULTS

We found that over 50% of the subjects were suffering from Cd exposure as their UCd levels far exceeded the national standard threshold of 5.000 μg/g creatinine (cr). Further analysis indicated that Uβ2-MG was more sensitive than UNAG for renal dysfunction. The BMDL for UCd was estimated as 3.486 U/g cr (male, where U is unit of enzyme) and 2.998 U/g cr (female) for UNAG. The BMDL for Uβ2-MG, which is released into urine from glomerulus after Cd exposure, was found to be 2.506 μg/g cr (male, where μg is the unit of microglobulin) and 2.236 μg/g cr (female).

CONCLUSIONS

Uβ2-MG is recommended as the sensitivity index for renal dysfunction, with 2.2 μg/g cr as the threshold for clinical diagnosis. Our findings suggest that Uβ2-MG is the better biomarker for exposure to Cd.

Emerging Links between Cadmium Exposure and Insulin Resistance: Human, Animal, and Cell Study Data

Recent research has helped clarify the role of cadmium (Cd) in various pathological states. We have demonstrated Cd involvement in pancreatic cancer, as well as the bioaccumulation of Cd in the pancreas. Bioaccumulation and increased toxicity suggest that Cd may also be involved in other pancreas-mediated diseases, like diabetes. Cd falls into the category of "hyperglycemic" metals, i.e., metals that increase blood glucose levels, which could be due to increased gluconeogenesis, damage to β-cells leading to reduced insulin production, or insulin resistance at target tissue resulting in a lack of glucose uptake. This review addresses the current evidence for the role of Cd, leading to insulin resistance from human, animal, and in vitro studies. Available data have shown that Cd may affect normal insulin function through multiple pathways. There is evidence that Cd exposure results in the perturbation of the enzymes and modulatory proteins involved in insulin signal transduction at the target tissue and mutations of the insulin receptor. Cd, through well-described mechanisms of oxidative stress, inflammation, and mitochondrial damage, may also alter insulin production in β-cells. More work is necessary to elucidate the mechanisms associated with Cd-mediated insulin resistance.

A Comparison of the Nephrotoxicity of Low Doses of Cadmium and Lead

Environmental exposure to moderate-to-high levels of cadmium (Cd) and lead (Pb) is associated with nephrotoxicity. In comparison, the health impacts of chronic low-level exposure to Cd and Pb remain controversial. The aim of this study was to therefore evaluate kidney dysfunction associated with chronic low-level exposure to Cd and Pb in a population of residents in Bangkok, Thailand. The mean age and the estimated glomerular filtration rate (eGFR) for 392 participants (195 men and 197 women) were 34.9 years and 104 mL/min/1.73 m², respectively, while the geometric mean concentrations of urinary Cd and Pb were 0.25 μg/L (0.45 μg/g of creatinine) and 0.89 μg/L (1.52 μg/g of creatinine), respectively. In a multivariable regression analysis, the eGFR varied inversely with blood urea nitrogen in both men (β = −0.125, p = 0.044) and women (β = −0.170, p = 0.008), while inverse associations of the eGFR with urinary Cd (β = −0.132, p = 0.043) and urinary Pb (β = −0.130, p = 0.044) were seen only in women. An increased urinary level of Cd to the median level of 0.38 μg/L (0.44 μg/g of creatinine) was associated with a decrease in the eGFR by 4.94 mL/min/1.73 m² (p = 0.011). The prevalence odds of a reduced eGFR rose 2.5-, 2.9- and 2.3-fold in the urinary Cd quartile 3 (p = 0.013), the urinary Cd quartile 4 (p = 0.008), and the urinary Pb quartile 4 (p = 0.039), respectively. This study suggests that chronic exposure to low-level Cd is associated with a decline in kidney function and that women may be more susceptible than men to nephrotoxicity due to an elevated intake of Cd and Pb.

The inverse association of glomerular function and urinary β2-MG excretion and its implications for cadmium health risk assessment

Urinary β2-microgroblin (β2-MG) excretion levels above 300 μg/g creatinine are used to indicate defective tubular reabsorption. Arguably, increased urinary β2-MG excretion could also reflect glomerular filtration rate decline. Thus, we investigated an association between urinary β2-MG and estimated glomerular filtration rate (eGFR). We studied 527 subjects, aged 30-87 years (mean 51.2), who lived in a rural area of Thailand polluted with cadmium (Cd). Of this cohort, 10.3% had urinary Cd levels <2 μg/g creatinine and 53.5% had urinary Cd levels ≥5 μg/g creatinine. Half (53.1%) of the participants had urinary β2-MG levels ≥ 300 μg/g creatinine, and 11.6% had low GFR, defined as eGFR <60 mL/min/1.73 m². Lower eGFR values were associated with older age (β = -0.568, P < 0.001), higher urinary β2-MG (β = -0.170, P < 0.001), higher urinary Cd (β = -0.103, P = 0.005) and diabetes (β = 0.074, P = 0.032). An inverse association between eGFR and urinary β2-MG was evident in subjects with low GFR (β = -0.332, P = 0.033), but not in those with GFR >90 mL/min/1.73 m² (β = -0.008, P = 0.896). These findings suggested Cd-induced nephron loss and reduced tubular reabsorption in low eGFR subjects. Urinary β2-MG levels <300 μg/g creatinine were associated with 4.66 (95% CI: 1.92, 11.32) fold increase in the POR for low GFR, compared with urinary β2-MG levels <100 μg/g creatinine. Findings in the present study cast doubt on a cut-off value for urinary β2-MG, while lending support to the notion that elevated urinary β2-MG excretion could indicate a fall of GFR.

Chronic exposure to cadmium is associated with a marked reduction in glomerular filtration rate

Background

Urinary 20-hydroxyeicosatetraenoic acid (20-HETE) has been associated with hypertension in women with elevated urinary cadmium (Cd) excretion rates. The present study investigates the urinary Cd and 20-HETE levels in relation to the estimated glomerular filtration rate (eGFR) and albumin excretion in men and women.

Methods

A population-based, cross-sectional study, which included 225 women and 84 men aged 33–55 years, was conducted in a rural area known to be polluted with Cd.

Results

In all subjects, lower eGFR values were associated with higher urinary Cd excretion (P = 0.030), and tubulopathy markers N-acetyl-β-d-glucosaminidase (P < 0.001) and β2-microglobulin (β2-MG) (P < 0.001). On average, the hypertensive subjects with the highest quartile of urinary Cd had eGFR values of 12 and 17 mL/min/1.73 m² lower than that in the hypertensive (P = 0.009) and normotensive subjects (P < 0.001) with the lowest quartile of urinary Cd, respectively. In men, urinary albumin was inversely associated with 20-HETE (β = −0.384, P < 0.001), while showing a moderately positive association with systolic blood pressure (SBP) (β = 0.302, P = 0.037). In women, urinary albumin was not associated with 20-HETE (P = 0.776), but was associated with tubulopathy, reflected by elevated urinary excretion of β2-MG (β = 0.231, P = 0.002).

Conclusions

Tubulopathy is a determinant of albumin excretion in women, while 20-HETE and SBP are determinants of urinary albumin excretion in men. Associations of chronic exposure to Cd with marked eGFR decline and renal tubular injury seen in both Cd-exposed men and women add to mounting research data that links Cd to the risk of developing chronic kidney disease.