Effect of Occupational Cadmium Exposure on Parathyroid Gland

Association and mediation analyses among multiple metal exposure, mineralocorticoid levels, and serum ion balance in residents of northwest China

Toxic metals are vital risk factors affecting serum ion balance; however, the effect of their co-exposure on serum ions and the underlying mechanism remain unclear. We assessed the correlations of single metal and mixed metals with serum ion levels, and the mediating effects of mineralocorticoids by investigating toxic metal concentrations in the blood, as well as the levels of representative mineralocorticoids, such as deoxycorticosterone (DOC), and serum ions in 471 participants from the Dongdagou-Xinglong cohort. In the single-exposure model, sodium and chloride levels were positively correlated with arsenic, selenium, cadmium, and lead levels and negatively correlated with zinc levels, whereas potassium and iron levels and the anion gap were positively correlated with zinc levels and negatively correlated with selenium, cadmium and lead levels (all P < 0.05). Similar results were obtained in the mixed exposure models considering all metals, and the major contributions of cadmium, lead, arsenic, and selenium were highlighted. Significant dose-response relationships were detected between levels of serum DOC and toxic metals and serum ions. Mediation analysis showed that serum DOC partially mediated the relationship of metals (especially mixed metals) with serum iron and anion gap by 8.3% and 8.6%, respectively. These findings suggest that single and mixed metal exposure interferes with the homeostasis of serum mineralocorticoids, which is also related to altered serum ion levels. Furthermore, serum DOC may remarkably affect toxic metal-related serum ion disturbances, providing clues for further study of health risks associated with these toxic metals.

The Association Between Environmental Cadmium Exposure and Parathyroid Hormone Levels

Cadmium exposure is associated with renal dysfunction and bone damage. Chronic kidney disease and bone loss are also related to parathyroid hormone (PTH). However, whether cadmium exposure affect PTH level is not completely understood. In this study, we observed the association between environmental cadmium exposure and PTH levels in a Chinese population. A ChinaCd study was performed in China in 1990s which included 790 subjects living in heavily, moderately and low cadmium polluted area. 354 of them (121 men and 233 women) also had the data of serum PTH. The cadmium levels in blood (BCd) and urine (UCd) were determined by flame atomic absorption spectrometry. Serum PTH was detected by immunoradiometric assay. Renal function was assessed based on urinary N-acetyl-β-d-glucosaminidase (UNAG), β2-microglobulin (UBMG) and urinary albumin (UALB). The median BCd and UCd levels were 4.69 μg/L and 5.50 μg/g creatinine. The BCd, UCd, UNAG, UBMG and UALB levels in subjects with low PTH (< 5.0 ng/L) were significantly higher than those with PTH ≥ 5.0 ng/L (p < 0.05 or p < 0.01). Spearman correlation analysis also showed that UCd level was negatively correlated to PTH levels (r = -0.17, p = 0.008) in women. A weak correlation was also observed between PTH level and BCd in women (r = -0.11, p = 0.09) and UBMG in total population (r = -0.114, p = 0.07). Univariable and mutivariable logistic regression analysis both demonstrated that high BCd (> 10 μg/L) (odds ratio (OR) = 2.26, 95% confidence interval (CI):1.10-4.63; OR = 2.36, 95%CI: 1.11-5.05) and UCd level (> 20 μg/g cr) (OR = 2.84, 95% CI:1.32-6.10; OR = 2.97, 95%CI: 1.25-7.05) were associated with high risk of low PTH. Our data showed that environmental cadmium exposure was associated with low PTH level.

Nutraceuticals as Alternative Approach against Cadmium-Induced Kidney Damage: A Narrative Review

Cadmium (Cd) represents a public health risk due to its non-biodegradability and long biological half-life. The main target of Cd is the kidney, where it accumulates. In the present narrative review, we assessed experimental and clinical data dealing with the mechanisms of kidney morphological and functional damage caused by Cd and the state of the art about possible therapeutic managements. Intriguingly, skeleton fragility related to Cd exposure has been demonstrated to be induced both by a direct Cd toxic effect on bone mineralization and by renal failure. Our team and other research groups studied the possible pathophysiological molecular pathways induced by Cd, such as lipid peroxidation, inflammation, programmed cell death, and hormonal kidney discrepancy, that, through further molecular crosstalk, trigger serious glomerular and tubular injury, leading to chronic kidney disease (CKD). Moreover, CKD is associated with the presence of dysbiosis, and the results of recent studies have confirmed the altered composition and functions of the gut microbial communities in CKD. Therefore, as recent knowledge demonstrates a strong connection between diet, food components, and CKD management, and also taking into account that gut microbiota are very sensitive to these biological factors and environmental pollutants, nutraceuticals, mainly present in foods typical of the Mediterranean diet, can be considered a safe therapeutic strategy in Cd-induced kidney damage and, accordingly, could help in the prevention and treatment of CKD.

Developmental cadmium exposure disrupts zebrafish vestibular calcium channels interfering with otolith formation and inner ear function

Dizziness or balance problems are estimated to affect approximately 3.3 million children aged three to 17 years. These disorders develop from a breakdown in the balance control system and can be caused by anything that affects the inner ear or the brain, including exposure to environmental toxicants. One potential environmental toxicant linked to balance disorders is cadmium, an extremely toxic metal that occurs naturally in the earth's crust and is released as a byproduct of industrial processes. Cadmium is associated with balance and vestibular dysfunction in adults exposed occupationally, but little is known about the developmental effects of low-concentration cadmium exposure. Our findings indicate that zebrafish exposed to 10-60 parts per billion (ppb) cadmium from four hours post-fertilization (hpf) to seven days post-fertilization (dpf) exhibit abnormal behaviors, including pronounced increases in auditory sensitivity and circling behavior, both of which are linked to reductions in otolith growth and are rescued by the addition of calcium to the media. Pharmacological intervention shows that agonist-induced activation of the P2X calcium ion channel in the presence of cadmium restores otolith size. In conclusion, cadmium-induced ototoxicity is linked to vestibular-based behavioral abnormalities and auditory sensitivity following developmental exposure, and calcium ion channel function is associated with these defects.

Parathyroid hormones in relation to serum cadmium and lead: the NHANES 2003-2006

The toxic effects of cadmium and lead exposure on parathyroid function have been investigated extensively while the results were conflicting. We aimed to investigate the association of blood cadmium and lead with serum parathyroid hormone (PTH) based on the general population. We analyzed a sample of 9400 adults aged 18 years or older from the US National Health and Nutrition Examination Survey 2003-2004 to 2005-2006. We estimated the association using multivariable linear regression analysis by taking cadmium and lead as a continuous or quartile variable. Restricted cubic splines were utilized to explore the non-linear relationship between cadmium or lead and PTH. The median blood cadmium and lead levels were 0.34 µg/L and 1.43 µg/dL, respectively. Cadmium was significantly associated with PTH when taken as a continuous variable [Odds ratio (OR): 0.97; 95% confidence interval (95% CI): 0.95-0.99] or a quartile variable (fourth vs first quartile, OR: 0.94; 95% CI: 0.91-0.97). Lead was significantly associated with PTH when taken as a continuous variable (OR: 1.04; 95% CI: 1.02-1.07) or a quartile variable (fourth vs first quartile, OR: 1.06; 95% CI: 1.01-1.10). P values for non-linearity were all less than 0.05. The association between cadmium and PTH was not significant in females. Cadmium was negatively associated with PTH, and lead was positively associated with PTH both in a non-linear manner among the general population. However, there was a gender difference in the relationship between cadmium and PTH.

Concentration of Selected Macronutrients and Toxic Elements in the Blood in Relation to Pain Severity and Hydrogen Magnetic Resonance Spectroscopy in People with Osteoarthritis of the Spine

Macronutrients and toxic elements may play an important role in the pathogenesis of osteoarthritis of the spine. The objective of this study was to evaluate the relationship between the concentrations of Ca, Mg, Pb, Cd and Hg in blood with the results of hydrogen magnetic resonance spectroscopy and the severity of pain. Patients with osteoarthritis of the spine (n = 90) and control subjects (n = 40) were studied. The concentrations of mineral components in blood were determined by atomic absorption spectrometry (ASA). Spinal pain severity was assessed using the Visual Analog Scale (VAS). Hydrogen magnetic resonance spectroscopy (¹H-MRS) was used to determine the fat/water ratio in the bodies of L1, L5 and the L4/5 intervertebral disc. The median concentration of Mg in the serum of subjects with spinal degenerative disease was significantly lower (p < 0.001) than that in healthy subjects. The median concentration of Cd in the blood of subjects with osteoarthritis of the spine was significantly higher (p < 0.05) than that in the control group. Significantly lower (p < 0.05) median molar ratios of Ca to Cd and Pb as well as Mg to Pb and Cd were observed among patients with osteoarthritis of the spine. Significant differences (p < 0.05) were observed in the value of the fat/water ratio in selected spinal structures, depending on normal or abnormal serum Ca and Mg concentrations. The study showed some abnormal macronutrient concentrations, as well as disturbed ratios of beneficial elements to toxic elements in the blood of people with osteoarthritis of the spine.

Environmental Factors That Affect Parathyroid Hormone and Calcitonin Levels

Calciotropic hormones, parathyroid hormone (PTH) and calcitonin are involved in the regulation of bone mineral metabolism and maintenance of calcium and phosphate homeostasis in the body. Therefore, an understanding of environmental and genetic factors influencing PTH and calcitonin levels is crucial. Genetic factors are estimated to account for 60% of variations in PTH levels, while the genetic background of interindividual calcitonin variations has not yet been studied. In this review, we analyzed the literature discussing the influence of environmental factors (lifestyle factors and pollutants) on PTH and calcitonin levels. Among lifestyle factors, smoking, body mass index (BMI), diet, alcohol, and exercise were analyzed; among pollutants, heavy metals and chemicals were analyzed. Lifestyle factors that showed the clearest association with PTH levels were smoking, BMI, exercise, and micronutrients taken from the diet (vitamin D and calcium). Smoking, vitamin D, and calcium intake led to a decrease in PTH levels, while higher BMI and exercise led to an increase in PTH levels. In terms of pollutants, exposure to cadmium led to a decrease in PTH levels, while exposure to lead increased PTH levels. Several studies have investigated the effect of chemicals on PTH levels in humans. Compared to PTH studies, a smaller number of studies analyzed the influence of environmental factors on calcitonin levels, which gives great variability in results. Only a few studies have analyzed the influence of pollutants on calcitonin levels in humans. The lifestyle factor with the clearest relationship with calcitonin was smoking (smokers had increased calcitonin levels). Given the importance of PTH and calcitonin in maintaining calcium and phosphate homeostasis and bone mineral metabolism, additional studies on the influence of environmental factors that could affect PTH and calcitonin levels are crucial.

The endocrine disruptor cadmium: a new player in the pathophysiology of metabolic diseases

Cadmium (Cd), a highly toxic heavy metal, is found in soil, environment and contaminated water and food. Moreover, Cd is used in various industrial activities, such as electroplating, batteries production, fertilizers, while an important non-occupational source is represented by cigarette smoking, as Cd deposits in tobacco leaves. Since many years it is clear a strong correlation between Cd body accumulation and incidence of many diseases. Indeed, acute exposure to Cd can cause inflammation and affect many organs such as kidneys and liver. Furthermore, the attention has focused on its activity as environmental pollutant and endocrine disruptor able to interfere with metabolic and energy balance of living beings. Both in vitro and in vivo experiments have demonstrated that the Cd-exposure is related to metabolic diseases such as obesity, diabetes and osteoporosis even if human studies are still controversial. Recent data show that Cd-exposure is associated with atherosclerosis, hypertension and endothelial damage that are responsible for cardiovascular diseases. Due to the large environmental diffusion of Cd, in this review, we summarize the current knowledge concerning the role of Cd in the incidence of metabolic and cardiovascular diseases.

Arsenic, cadmium, and selenium exposures and bone mineral density-related endpoints: The HORTEGA study

BACKGROUND AND OBJECTIVES

Experimental data suggest that trace elements, such as arsenic (As), cadmium (Cd), and selenium (Se) can influence the bone remodeling process. We evaluated the cross-sectional association between As, Cd, and Se biomarkers with bone mineral density (BMD) measured at the calcaneus, in a representative sample of a general population from Spain. As secondary analyses we evaluated the associations of interest in subgroups defined by well-established BMD determinants, and also conducted prospective analysis of osteoporosis-related incident bone fractures restricted to participants older than 50 years-old.

METHODS

In N = 1365 Hortega Study participants >20 years-old, urine As and Cd were measured by inductively coupled-plasma mass spectrometry (ICPMS); plasma Se was measured by atomic absorption spectrometry (AAS) with graphite furnace; and BMD at the calcaneus was measured using the Peripheral Instaneuous X-ray Imaging system (PIXI). As levels were corrected for arsenobetaine (Asb) to account for inorganic As exposure.

RESULTS

The median of total urine As, Asb-corrected urine As, urine Cd, and plasma Se was 61.3, 6.53 and 0.39 μg/g creatinine, and 84.9 μg/L, respectively. In cross-sectional analysis, urine As and Cd were not associated with reduced BMD (T-score < -1 SD). We observed a non-linear dose-response of Se and reduced BMD, showing an inverse association below ~105 μg/L, which became increasingly positive above ~105 μg/L. The evaluated subgroups did not show differential associations. In prospective analysis, while we also observed a U-shape dose-response of Se with the incidence of osteoporosis-related bone fractures, the positive association above ~105 μg/L was markedly stronger, compared to the cross-sectional analysis.

CONCLUSIONS

Our results support that Se, but not As and Cd, was associated to BMD-related disease. The association of Se and BMD-related disease was non-linear, including a strong positive association with osteoporosis-related bone fractures risk at the higher Se exposure range. Considering the substantial burden of bone loss in elderly populations, additional large prospective studies are needed to confirm the relevance of our findings to bone loss prevention in the population depending on Se exposure levels.

Smoking and other determinants of bone turnover

The balance between bone resorption and formation may be assessed by measurement of bone turnover markers (BTMs), like carboxyl-terminal cross-linked telopeptide of type 1 collagen (CTX-1) and procollagen type 1 amino-terminal propeptide (P1NP). Smoking has been shown to influence bone turnover and to reduce bone mass density (BMD), the exact mechanism for this is, however, not settled. In this post-hoc study including 406 subjects (mean age 51.9 years), we aimed to study the impact of smoking on bone turnover. Moreover, we wanted to assess the inter-correlation between substances regulating bone metabolism and BTMs, as well as tracking over time. BMD measurements and serum analyses of CTX-1, P1NP, osteoprotegerin (OPG), receptor activator of nuclear factor ĸB ligand (RANKL), Dickkopf-1 (DKK1), sclerostin, tumor necrosis factor-α (TNF-α), and leptin were performed. Repeated serum measurements were made in 195 subjects after four months. Adjustments were made for sex, age, body mass index (BMI), smoking status, insulin resistance, serum calcium, parathyroid hormone, 25-hydroxyvitamin D and creatinine. Smokers had higher levels of DKK1 and OPG, and lower levels of RANKL, as reflected in lower BTMs and BMD compared to non-smokers. There were strong and predominantly positive inter-correlations between BTMs and the other substances, and there was a high degree of tracking with Spearman’s rho from 0.72 to 0.92 (P < 0.001) between measurements four months apart. In conclusion, smokers exhibited higher levels of DKK1 and OPG and a lower bone turnover than did non-smokers. The strong inter-correlations between the serum parameters illustrate the coupling between bone resorption and formation and crosstalk between cells.