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

Potential role of serum copeptin among smoker T2DM patients with emphasis to ACE I/D gene polymorphism predicting DN

Diabetic nephropathy represents one of the main long-term complications in T2DM patients. Cigarette smoking represents one of modifiable renal risk factors to kidney damage due to lead (Pb) exposure in these patients. Our goal is to investigate serum copeptin and Kidney injury molecule-1 (KIM-1) and urinary lead (UPb) in type 2 diabetes mellitus (T2DM) patients even smokers and non-smokers groups and compared to corresponding health controls and assess its associations with Angiotensin-Converting enzyme Insertion/Deletion polymorphism [ACE (I/D)] polymorphism in diabetic nephropathy progression in those patients. In present study, 106 T2DM patients and 102 healthy control individuals were enrolled. Serum glucose, copeptin, KIM-1, total cholesterol (TChol), triglycerides (TG), estimated glomerular filtration rate (eGFR) and UPb levels and ACE (I/D) polymorphisms were assessed in both groups. Results mentioned to significant variations in all parameters compared to in T2DM group compared to control group. Serum copeptin and UPb demonstrated significant difference in diabetic smokers (DS) and diabetic non-smokers (DNS) groups while KIM-1 exhibited significant change between DNS and healthy control non-smokers (CNS) groups. Positive relation was recorded between serum glucose and KIM-1 while negative one was found between serum copeptin and TChol. D allele was associated with significant variation in most parameters in T2DM, especially insertion/deletion (ID) polymorphism. ROC curve analysis (AUC) for serum copeptin was 0.8, p < 0.044 and for Kim-1 was 0.54, p = 0.13 while for uPb was 0.71, p < 0.033. Serum copeptin and UPb might be a prognostic biomarker for renal function decline in smoker T2DM patients while KIM-1 was potent marker in non-smoker T2DM with association with D allele of ACE I/D gene polymorphism.

Conversion of char from pyrolysis of plastic wastes into alternative activated carbons for heavy metal removal

The valorization of post-consumer mixed plastics in pyrolysis processes represents an abundant reservoir of carbon that can be effectively converted into useful chars. This process not only holds appeal in terms of improving plastic waste concerns but also contributes to the reduction of greenhouse gas emissions, thus aligning with the principles of a circular economy paradigm. In this study, the char produced from the pyrolysis of post-consumer mixed plastic waste has been activated with Na2CO3, KOH, NaOH, and K2CO3 to improve the textural, structural, and composition characteristics, leading to improved adsorption capability. These characteristics were studied by N2 adsorption-desorption isotherms, scanning electron microscopy, elemental and immediate analysis, and X-ray photoelectron spectroscopy. The developed surface area (SBET) was 573, 939, 704 and 592 m2 g-1 for Na2CO3, KOH, NaOH and K2CO3 activated carbons, respectively. These activated chars (ACs) were tested for the adsorption of heavy metals in both synthetic waters containing Pb, Cd, and Cu and industrial wastewater collected at an agrochemical production plant. Na2CO3-AC was the best performing material. The metal uptake in synthetic waters using a batch set-up was 40, 13 and 12 mg g-1 for Pb, Cd and Cu. Experiments in a column set-up using Na2CO3-AC resulted in a saturation time of 290, 16, and 80 min for Pb, Cd, and Cu synthetic waters, respectively, and metal uptakes of 26.8, 4.1, and 7.9 mg g-1, respectively. The agrochemical effluents, containing mainly Cr, Cu, Mn, and Zn were tested in a plug-flow column. The metal uptake notably decreased compared to synthetic water due to a competition effect for active sites.

Associations of metals and metal mixtures with glucose homeostasis: A combined bibliometric and epidemiological study

This study employs a combination of bibliometric and epidemiological methodologies to investigate the relationship between metal exposure and glucose homeostasis. The bibliometric analysis quantitatively assessed this field, focusing on study design, predominant metals, analytical techniques, and citation trends. Furthermore, we analyzed cross-sectional data from Beijing, examining the associations between 14 blood metals and 6 glucose homeostasis markers using generalized linear models (GLM). Key metals were identified using LASSO-PIPs criteria, and Bayesian kernel machine regression (BKMR) was applied to assess metal mixtures, introducing an "Overall Positive/Negative Effect" concept for deeper analysis. Our findings reveal an increasing research interest, particularly in selenium, zinc, cadmium, lead, and manganese. Urine (27.6%), serum (19.0%), and whole blood (19.0%) were the primary sample types, with cross-sectional studies (49.5%) as the dominant design. Epidemiologically, significant associations were found between 9 metals-cobalt, copper, lithium, manganese, nickel, lead, selenium, vanadium, zinc-and glucose homeostasis. Notably, positive-metal mixtures exhibited a significant overall positive effect on insulin levels, and notable interactions involving nickel were identified. These finding not only map the knowledge landscape of research in this domain but also introduces a novel perspective on the analysis strategies for metal mixtures.

Association between blood metals mixture and chronic kidney disease in adults: NHANES 2013-2016

BACKGROUND

The association between single metal exposure and chronic kidney disease (CKD) has been established. However, there is limited research on the effects of multi-metal mixtures and their potential age-specific associations with kidney injury. This study aimed to examine the relationship between metal mixtures and kidney function in adults, while also exploring the modifying effects of age.

METHODS

We included a subset (n = 4250) of a nationally representative adult population in the National Health and Nutrition Examination Survey (NHANES) 2013-2016. Kidney function was assessed using the glomerular filtration rate (eGFR) and creatinine albumin ratio (ACR). The individual and combined effects of lead (Pb), cadmium (Cd), mercury, and manganese on kidney injury and the risk of CKD were evaluated.

RESULTS

Pb and Cd were found to be positively associated with decreased kidney function. For a one Ln-unit increase in lead and cadmium, the adjusted ORs of CKD were 1.60 (95% CI: 1.35, 1.90) and 1.41 (95% CI:1.12, 1.77), respectively. We also observed an interaction between lead and cadmium for ACR. We also observed the joint effect between Pb and Cd on eGFR, ACR and CKD. Stratified analysis found a higher risk of decreased kidney function among older individuals. The quantile-g calculation model further showed that metal mixture was associated with decreased kidney function and the risk of CKD (OR = 1.53, 95% CI: 1.22, 1.90). And lead and cadmium were the main contributors. And Pb and Cd were the major components that increased the risk of CKD.

CONCLUSION

Co-exposure to metal mixture were associated with reduced kidney function in adults, especially in older. Our findings support co-exposure to lead and cadmium as risk factors of CKD in adults.

An automatic and smart platform for rapid detection of cadmium and lead simultaneously in rice using triple-amplified chemiluminescence immunoassay

Rapid detection of trace ions is urgently needed for large-scale screening to ensure food safety. This study developed an innovative and automatic strategy, based on a smart-designed platform for rapid detection of cadmium and lead in rice. As bridge antibody, the antigen was conjugated with goat anti-mouse immunoglobulin G labeled alkaline phosphatase. Meanwhile, a biotin-streptavidin system was introduced to micromagnetic particles, thus providing a triple-amplified chemiluminescence immunoassay with high sensitivity, accuracy and specificity. The limits of detection for cadmium and lead were 0.06 and 1.00 ng mL-1, respectively, within 30 min. The recoveries ranged from 89.81 to 114.92 %, with relative standard deviations less than 9.2 %. The results obtained agreed with those of inductively coupled plasma-mass spectrometry and certified reference materials. Additionally, the auto-operation avoided human errors as well as being convenient, fast, automatic and high-throughput. Therefore, this smart platform can be applied for large-scale Cd2+ and Pb2+ screening.

U-shaped relationship between fasting blood glucose and urinary albumin-to-creatinine ratio in the general United States population

Objective

The current controversy surrounding the association between fasting blood glucose (FBG) and albuminuria necessitates further investigation. Hence, the primary objective of this study was to examine the relationship between FBG and urinary albumin-to-creatinine ratio (UACR).

Methods

A cohort of complete data from National Health and Nutrition Examination Survey (NHANES) participants (1999-2020) was analyzed. Linear regression analyses and a generalized additive model explored the association between FBG and UACR. Furthermore, the stability of this relationship across different populations was assessed.

Results

The study involved a total of 20,264 participants who were identified as U.S. citizens. By employing linear regression analysis, a statistically significant relationship was observed between elevated FBG levels and an increase in UACR (P<0.0001). Additionally, using a generalized additive model analysis, a U-shaped correlation between FBG and UACR was identified. Further examination using threshold effect analysis indicated a turning point for FBG at 5.44 mmol/L. A noteworthy finding in multiple populations is the consistent U-shaped association between FBG and UACR, except for individuals with serum uric acid levels ≥420 μmol/L and those who refrain from alcohol consumption.

Conclusion

The general U.S. population has a U-shaped nonlinear relationship between FBG and UACR.

Plant-Based Diet and Glycemic Control in Type 2 Diabetes: Evidence from a Thai Health-Promoting Hospital

The prevalence of type 2 diabetes (T2DM) is associated with diet. While consumption of plant-based foods may reduce blood sugar levels, the impact of consuming plant-based foods on fasting blood sugar levels has not been well defined. This cross-sectional study was conducted at the Health-Promoting Hospital in Pak Phun Municipality, Thailand. It included 61 patients with T2DM and 74 controls matched for age and gender. Dietary intake levels among T2DM and controls were assessed by a validated food-frequency questionnaire from which plant-based-food scores were calculated. This study found significant differences between specific plant foods and fasting blood sugar levels in patients with T2DM. Adherence to a plant-based diet appeared to influence fasting blood sugar levels. Patients who consumed higher amounts of certain vegetables and fruits showed lower fasting blood sugar levels. Diabetic patients consumed more legumes than controls, but the consumption of cereals and nuts/seeds in the two groups were similar. Consumption of nuts and seeds was also associated with a 76.3% reduction in the risk of a T2DM diagnosis. These findings suggest the potential efficacy of glycemic control in T2DM patients. More work is required to explore strategies for preventing and treating metabolic disorders through dietary modification.

Is Environmental Cadmium Exposure Causally Related to Diabetes and Obesity?

Cadmium (Cd) is a pervasive toxic metal, present in most food types, cigarette smoke, and air. Most cells in the body will assimilate Cd, as its charge and ionic radius are similar to the essential metals, iron, zinc, and calcium (Fe, Zn, and Ca). Cd preferentially accumulates in the proximal tubular epithelium of the kidney, and is excreted in urine when these cells die. Thus, excretion of Cd reflects renal accumulation (body burden) and the current toxicity of Cd. The kidney is the only organ other than liver that produces and releases glucose into the circulation. Also, the kidney is responsible for filtration and the re-absorption of glucose. Cd is the least recognized diabetogenic substance although research performed in the 1980s demonstrated the diabetogenic effects of chronic oral Cd administration in neonatal rats. Approximately 10% of the global population are now living with diabetes and over 80% of these are overweight or obese. This association has fueled an intense search for any exogenous chemicals and lifestyle factors that could induce excessive weight gain. However, whilst epidemiological studies have clearly linked diabetes to Cd exposure, this appears to be independent of adiposity. This review highlights Cd exposure sources and levels associated with diabetes type 2 and the mechanisms by which Cd disrupts glucose metabolism. Special emphasis is on roles of the liver and kidney, and cellular stress responses and defenses, involving heme oxygenase-1 and -2 (HO-1 and HO-2). From heme degradation, both HO-1 and HO-2 release Fe, carbon monoxide, and a precursor substrate for producing a potent antioxidant, bilirubin. HO-2 appears to have also anti-diabetic and anti-obese actions. In old age, HO-2 deficient mice display a symptomatic spectrum of human diabetes, including hyperglycemia, insulin resistance, increased fat deposition, and hypertension.

Estimation of the Cadmium Nephrotoxicity Threshold from Loss of Glomerular Filtration Rate and Albuminuria

Cadmium (Cd) is a pervasive, toxic environmental pollutant that preferentially accumulates in the tubular epithelium of the kidney. Current evidence suggests that the cumulative burden of Cd here leads to the progressive loss of the glomerular filtration rate (GFR). In this study, we have quantified changes in estimated GFR (eGFR) and albumin excretion (Ealb) according to the levels of blood Cd ([Cd]b) and excretion of Cd (ECd) after adjustment for confounders. ECd and Ealb were normalized to creatinine clearance (Ccr) as ECd/Ccr and Ealb/Ccr. Among 482 residents of Cd-polluted and non-polluted regions of Thailand, 8.1% had low eGFR and 16.9% had albuminuria (Ealb/Ccr) × 100 ≥ 20 mg/L filtrate. In the low Cd burden group, (ECd/Ccr) × 100 < 1.44 µg/L filtrate, eGFR did not correlate with ECd/Ccr (β = 0.007) while an inverse association with ECd/Ccr was found in the medium (β = -0.230) and high burden groups (β = -0.349). Prevalence odds ratios (POR) for low eGFR were increased in the medium (POR 8.26) and high Cd burden groups (POR 3.64). Also, eGFR explained a significant proportion of Ealb/Ccr variation among those with middle (η2 0.093) and high [Cd]b tertiles (η2 0.132) but did not with low tertiles (η2 0.001). With an adjustment of eGFR, age and BMI, the POR values for albuminuria were increased in the middle (POR 2.36) and high [Cd]b tertiles (POR 2.74) and those with diabetes (POR 6.02) and hypertension (2.05). These data indicate that (ECd/Ccr) × 100 of 1.44 µg/L filtrate (0.01-0.02 µg/g creatinine) may serve as a Cd threshold level based on which protective exposure guidelines should be formulated.

Gender Differences in the Severity of Cadmium Nephropathy

The excretion of β₂-microglobulin (β₂M) above 300 µg/g creatinine, termed tubulopathy, was regarded as the critical effect of chronic exposure to the metal pollutant cadmium (Cd). However, current evidence suggests that Cd may induce nephron atrophy, resulting in a reduction in the estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73 m². Herein, these pathologies were investigated in relation to Cd exposure, smoking, diabetes, and hypertension. The data were collected from 448 residents of Cd-polluted and non-polluted regions of Thailand. The body burden of Cd, indicated by the mean Cd excretion (E_Cd), normalized to creatinine clearance (C_cr) as (E_Cd/C_cr) × 100 in women and men did not differ (3.21 vs. 3.12 µg/L filtrate). After adjustment of the confounding factors, the prevalence odds ratio (POR) for tubulopathy and a reduced eGFR were increased by 1.9-fold and 3.2-fold for every 10-fold rise in the Cd body burden. In women only, a dose-effect relationship was seen between β₂M excretion (E_β2M/C_cr) and E_Cd/C_cr (F = 3.431, η² 0.021). In men, E_β2M/C_cr was associated with diabetes (β = 0.279). In both genders, the eGFR was inversely associated with E_β2M/C_cr. The respective covariate-adjusted mean eGFR values were 16.5 and 12.3 mL/min/1.73 m² lower in women and men who had severe tubulopathy ((E_β2M/C_cr) × 100 ≥ 1000 µg/L filtrate). These findings indicate that women were particularly susceptible to the nephrotoxicity of Cd, and that the increment of E_β2M/C_cr could be attributable mostly to Cd-induced impairment in the tubular reabsorption of the protein together with Cd-induced nephron loss, which is evident from an inverse relationship between E_β2M/C_cr and the eGFR.

Patterns of global burden of 13 diseases attributable to lead exposure, 1990-2019

OBJECTIVES

Understanding the spatio-temporal patterns of the global burden of various diseases resulting from lead exposure is critical for controlling lead pollution and disease prevention.

METHODS

Based on the 2019 Global Burden of Disease (GBD) framework and methodology, the global, regional, and national burden of 13 level-three diseases attributable to lead exposure were analyzed by disease type, patient age and sex, and year of occurrence. Population attributable fraction (PAF), deaths and disability-adjusted life years (DALYs), age-standardized mortality rate (ASMR) and age-standardized DALYs rate (ASDR) obtained from the GBD 2019 database were used as descriptive indicators, and the average annual percentage change (AAPC) was estimated by a log-linear regression model to reflect the time trend.

RESULTS AND CONCLUSIONS

From 1990 to 2019, the number of deaths and DALYs resulting from lead exposure increased by 70.19% and 35.26%, respectively; however, the ASMR and ASDR decreased by 20.66% and 29.23%, respectively. Ischemic heart disease (IHD), stroke, and hypertensive heart disease (HHD) showed the highest increases in deaths; IHD, stroke, and diabetes and kidney disease (DKD) had the fastest-growing DALYs. The fastest decline in ASMR and ASDR was seen in stroke, with AAPCs of -1.25 (95% CI [95% confidence interval]: -1.36, -1.14) and -1.66 (95% CI: -1.76, -1.57), respectively. High PAFs occurred mainly in South Asia, East Asia, the Middle East, and North Africa. Age-specific PAFs of DKD resulting from lead exposure were positively correlated with age, whereas the opposite was true for mental disorders (MD), with the burden of lead-induced MD concentrated in children aged 0-6 years. The AAPCs of ASMR and ASDR showed a strong negative correlation with the socio-demographic index. Our findings showed that the global impact of lead exposure and its burden increased from 1990 to 2019 and varied significantly according to age, sex, region, and resulting disease. Effective public health measures and policies should be adopted to prevent and control lead exposure.

Vitamin D and calcium co-therapy mitigates pre-established cadmium nephropathy by regulating renal calcium homeostatic molecules and improving anti-oxidative and anti-inflammatory activities in rat

BACKGROUND

Cadmium (Cd) is a major environmental pollutant and chronic toxicity could induce nephropathy by increasing renal oxidative stress and inflammation. Although vitamin D (VD) and calcium (Ca) prophylactic treatments attenuated Cd-induced cell injury, none of the prior studies measure their renoprotective effects against pre-established Cd-nephropathy.

AIMS

To measure the alleviating effects of VD and/or Ca single and dual therapies against pre-established nephrotoxicity induced by chronic Cd toxicity prior to treatment initiation.

METHODS

Forty male adult rats were allocated into: negative controls (NC), positive controls (PC), Ca, VD and VC groups. The study lasted for eight weeks and all animals, except the NC, received CdCl₂ in drinking water (44 mg/L) throughout the study. Ca (100 mg/kg) and/or VD (350 IU/kg) were given (five times/week) during the last four weeks to the designated groups. Subsequently, the expression of transforming growth factor-β (TGF-β1), inducible nitric oxide synthase (iNOS), neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), VD synthesising (Cyp27b1) and catabolizing (Cyp24a1) enzymes with VD receptor (VDR) and binding protein (VDBP) was measured in renal tissues. Similarly, renal expression of Ca voltage-dependent channels (Ca_V1.1/Ca_V3.1), store-operated channels (RyR1/ITPR1), and binding proteins (CAM/CAMKIIA/S100A1/S100B) were measured. Serum markers of renal function alongside several markers of oxidative stress (MDA/H₂O₂/GSH/GPx/CAT) and inflammation (IL-6/TNF-α/IL-10) together with renal cell apoptosis and expression of caspase-3 were also measured.

RESULTS

The PC group exhibited hypovitaminosis D, hypocalcaemia, hypercalciuria, proteinuria, reduced creatinine clearance, and increased renal apoptosis/necrosis with higher caspase-3 expression. Markers of renal tissue damage (TGF-β1/iNOS/NGAL/KIM-1), oxidative stress (MDA/H₂O₂), and inflammation (TNF-α/IL-1β/IL-6) increased, whilst the antioxidants (GSH/GPx/CAT) and IL-10 decreased, in the PC group. The PC renal tissues also showed abnormal expression of Cyp27b1, Cyp24a1, VDR, and VDBP, alongside Ca-membranous (Ca_V1.1/Ca_V3.1) and store-operated channels (RyR1/ITPR1) and cytosolic Ca-binding proteins (CAM/CAMKIIA/S100A1/S100B). Although VD was superior to Ca monotherapy, their combination revealed the best mitigation effects by attenuating serum and renal tissue Cd concentrations, inflammation and oxidative stress, alongside modulating the expression of VD/Ca-molecules.

CONCLUSIONS

This study is the first to show improved alleviations against Cd-nephropathy by co-supplementing VD and Ca, possibly by better regulation of Ca-dependent anti-oxidative and anti-inflammatory actions.

Carcinogenic and human health risk assessment of children's and adults' exposure to toxic metal(oid)s from air PM10 in critical sites of the Republic of Serbia

With global urbanization and industrialization, air pollution has become an inevitable problem. Among air pollutants, toxic metals bound to particulate matter (PM) have a high hazardous potential, contributing to the development of several diseases, including various types of cancer. Due to PM pollution, Serbia is considered to be among the most polluted countries in Europe. Therefore, the objective of the study was to assess and characterize the non-carcinogenic and carcinogenic risks of children's and adults' exposure to metal(oid)s (Pb, Cd, Ni, and As) bound to PM₁₀ in five of the most polluted areas in the Republic of Serbia (Subotica, Smederevo, Bor, Valjevo, and Kraljevo). Non-carcinogenic (HQ and HI) and carcinogenic risk (CR) were calculated using USEPA methodology. Our results show that PM₁₀ concentrations exceeded the annual limit of 40 μg/m³ at four out of five monitoring sites (ranging from 44.33 to 63.25 μg/m³). Results obtained from Bor monitoring station show that safe limits were exceeded for both children and adults, indicating an unacceptable risk (> 1) obtained for inhalation exposure to the As (HQ = 6.14) and Cd (HQ = 1.17), while total HI was 7.43, which characterized the risk as unacceptable. For the same station, the CR value was 1.44E^-04 (> 1 × 10^-4). In other sites, the risks were acceptable. The characterized risk from exposure to the toxic elements via PM₁₀ in critical locations in Serbia contributes to improving air quality by requiring regulatory organs to take new actions and adopt new measures to reduce air pollution.

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.

Health Risk in a Geographic Area of Thailand with Endemic Cadmium Contamination: Focus on Albuminuria

An increased level of cadmium (Cd) in food crops, especially rice is concerning because rice is a staple food for over half of the world’s population. In some regions, rice contributes to more than 50% of the total Cd intake. Low environmental exposure to Cd has been linked to an increase in albumin excretion to 30 mg/g creatinine, termed albuminuria, and a progressive reduction in the estimated glomerular filtration rate (eGFR) to below 60 mL/min/1.73 m2, termed reduced eGFR. However, research into albuminuria in high exposure conditions is limited. Here, we applied benchmark dose (BMD) analysis to the relevant data recorded for the residents of a Cd contamination area and a low-exposure control area. We normalized the excretion rates of Cd (ECd) and albumin (Ealb) to creatinine clearance (Ccr) as ECd/Ccr and Ealb/Ccr to correct for differences among subjects in the number of surviving nephrons. For the first time, we defined the excretion levels of Cd associated with clinically relevant adverse kidney health outcomes. Ealb/Ccr varied directly with ECd/Ccr (β = 0.239, p < 0.001), and age (β = 0.203, p < 0.001), while normotension was associated with lower Ealb/Ccr (β = −0.106, p = 0.009). ECd/Ccr values between 16.5 and 35.5 ng/L of the filtrate were associated with a 10% prevalence of albuminuria, while the ECd/Ccr value of 59 ng/L of the filtrate was associated with a 10% prevalence of reduced eGFR. Thus, increased albumin excretion and eGFR reduction appeared to occur at low body burdens, and they should form toxicity endpoints suitable for the calculation of health risk due to the Cd contamination of food chains.

Automated and Rapid Easy-to-Use Magnetic Solid-Phase Extraction System for Five Heavy Metals in Cereals and Feeds

A rapid, accurate, and ecofriendly pretreatment plays an extremely important role prior to ICP-MS for heavy metal analysis. In order to improve the pretreatment efficiency, a high-throughput and automatic magnetic solid-phase extraction of five heavy metals (Cd, Pb, Mn, Cu, and Zn) was carried out by a magnet-controlled pretreatment system with an ecofriendly diluted acid as an extracting agent and carboxyl-functionalized magnetic beads as a pretreatment material. Key conditions, including the pH, adsorption time, and eluent solution, were optimized. The time for purification and enrichment was only 8 min. The adsorption capacities of the carboxyl-functionalized magnetic beads were in the range of 152~426 mg g^-1. The preconcentration factor of Cu was 40, and others were 200. In the optimal conditions, the limits of detection for Mn, Zn, Cd, Cu, and Pb by ICP-MS were 3.84, 2.71, 0.16, 11.54, and 6.01 ng L^-1, respectively. The percentage recoveries were in the range of 80~110%, and the relative standard deviations were less than 3%. The developed method was in good agreement with traditional standard microwave digestion. Additionally, the designed system could simultaneously process up to 24 samples within 22 min, reducing the time to less than 1 min/sample. Thus, the proposed auto-MSPE-ICP-MS method was successfully applied to analyze five heavy metals in cereals and feeds with a simple operation and high precision, safety, and reliability.

Sirtuin-1 attenuates cadmium-induced renal cell senescence through p53 deacetylation

Cadmium (Cd), the common environmental pollutant, primarily targets at renal proximal tubules and induces nephrotoxicity. Cellular senescence, a phenomenon of cell growth arrest and a characteristics of maladaptive cell self-repair, is associated with renal disease progression. However, whether and how Cd induces renal tubular cells premature senescence is unknown. In our study, we found that Cd induced kidney damage and dysfunctions, which correlated with exacerbated tubular cell senescence, evidenced by increased senescence-associated β-galactosidase activity, the upregulated protein expression of p53 and p21^Waf1/Cip1 proteins, and elevated expression and secretion of cytokines in human proximal tubular epithelial HK-2 cells in vitro and in Cd-treated mice in vivo. Moreover, a S-phase arrest and decrease in Edu positive rate were found in Cd-treated HK-2 cells. Mechanistically, Cd suppressed the expression and activity of Sirtuin-1 (SIRT1), an anti-senescence deacetylase, resulting in the accumulation of acetylated p53 and upregulation of p21^Waf1/Cip1. Activation of SIRT1 significantly abolished Cd-induced premature senescence and S-phase arrest. Finally, silencing p21^Waf1/Cip1 efficiently delayed premature senescence and recovered cell cycle progression. These findings indicate that Cd promotes tubular cells senescence and impairs tubular cells regeneration, resulting in kidney dysfunctions, which could be ameliorated by SIRT1 activation.

The NOAEL Equivalent of Environmental Cadmium Exposure Associated with GFR Reduction and Chronic Kidney Disease

Cadmium (Cd) is a highly toxic metal pollutant present in virtually all food types. Health guidance values were established to safeguard against excessive dietary Cd exposure. The derivation of such health guidance figures has been shifted from the no-observed-adverse-effect level (NOAEL) to the lower 95% confidence bound of the benchmark dose (BMD), termed BMDL. Here, we used the PROAST software to calculate the BMDL figures for Cd excretion (E_Cd) associated with a reduction in the estimated glomerular filtration rate (eGFR), and an increased prevalence of chronic kidney disease (CKD), defined as eGFR ≤ 60 mL/min/1.73 m². Data were from 1189 Thai subjects (493 males and 696 females) mean age of 43.2 years. The overall percentages of smokers, hypertension and CKD were 33.6%, 29.4% and 6.2%, respectively. The overall mean E_Cd normalized to the excretion of creatinine (E_cr) as E_Cd/E_cr was 0.64 µg/g creatinine. E_Cd/E_cr, age and body mass index (BMI) were independently associated with increased prevalence odds ratios (POR) for CKD. BMI figures ≥24 kg/m² were associated with an increase in POR for CKD by 2.81-fold (p = 0.028). E_Cd/E_cr values of 0.38-2.49 µg/g creatinine were associated with an increase in POR for CKD risk by 6.2-fold (p = 0.001). The NOAEL equivalent figures of E_Cd/E_cr based on eGFR reduction in males, females and all subjects were 0.839, 0.849 and 0.828 µg/g creatinine, respectively. The BMDL/BMDU values of E_Cd/E_cr associated with a 10% increase in CKD prevalence were 2.77/5.06 µg/g creatinine. These data indicate that Cd-induced eGFR reduction occurs at relatively low body burdens and that the population health risk associated with E_Cd/E_cr of 2.77-5.06 µg/g creatinine was not negligible.

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.

Harnessing the Full Potential of Multi-Omic Analyses to Advance the Study and Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) was the 12th leading cause of death globally in 2017 with the prevalence of CKD estimated at ~9%. Early detection and intervention for CKD may improve patient outcomes, but standard testing approaches even in developed countries do not facilitate identification of patients at high risk of developing CKD, nor those progressing to end-stage kidney disease (ESKD). Recent advances in CKD research are moving towards a more personalised approach for CKD. Heritability for CKD ranges from 30% to 75%, yet identified genetic risk factors account for only a small proportion of the inherited contribution to CKD. More in depth analysis of genomic sequencing data in large cohorts is revealing new genetic risk factors for common diagnoses of CKD and providing novel diagnoses for rare forms of CKD. Multi-omic approaches are now being harnessed to improve our understanding of CKD and explain some of the so-called 'missing heritability'. The most common omic analyses employed for CKD are genomics, epigenomics, transcriptomics, metabolomics, proteomics and phenomics. While each of these omics have been reviewed individually, considering integrated multi-omic analysis offers considerable scope to improve our understanding and treatment of CKD. This narrative review summarises current understanding of multi-omic research alongside recent experimental and analytical approaches, discusses current challenges and future perspectives, and offers new insights for CKD.