Assessment of bone metabolism in cadmium-induced renal tubular dysfunction by measurements of biochemical markers

Cadmium-Tolerant Rhizospheric Bacteria of the C3/CAM Intermediate Semi-Halophytic Common Ice Plant (Mesembryanthemum crystallinum L.) Grown in Contaminated Soils

The common ice plant, Mesembryanthemum crystallinum L., has recently been found as a good candidate for phytoremediation of heavy-metal polluted soils. This semi-halophyte is a C₃/CAM (Crassulacean acid metabolism) intermediate plant capable of tolerating extreme levels of cadmium in the soil. The aim of the work was to obtain and characterize novel, Cd-tolerant microbial strains that populate the root zone of M. crystallinum performing different types of photosynthetic metabolism and growing in Cd-contaminated substrates. The plants exhibiting either C₃ or CAM photosynthesis were treated for 8 days with different CdCl₂ doses to obtain final Cd concentrations ranging from 0.82 to 818 mg⋅kg^-1 of soil d.w. The CAM phase was induced by highly saline conditions. After treatment, eighteen bacterial and three yeast strains were isolated from the rhizosphere and, after preliminary Cd-resistance in vitro test, five bacterial strains were selected and identified with a molecular proteomics technique. Two strains of the species Providencia rettgeri (W6 and W7) were obtained from the C₃ phase and three (one Paenibacillus glucanolyticus S7 and two Rhodococcus erythropolis strains: S4 and S10) from the CAM performing plants. The isolates were further tested for Cd-resistance (treatment with either 1 mM or 10 mM CdCl₂) and salinity tolerance (0.5 M NaCl) in model liquid cultures (incubation for 14 days). Providencia rettgeri W7 culture remained fully viable at 1 mM Cd, whereas Rh. erythropolis S4 and S10 together with P. glucanolyticus S7 were found to be resistant to 10 mM Cd in the presence of 0.5 M NaCl. It is suggested that the high tolerance of the common ice plant toward cadmium may result from the synergic action of the plant together with the Cd/salt-resistant strains occurring within rhizospheral microbiota. Moreover, the isolated bacteria appear as promising robust microorganisms for biotechnological applications in bio- and phytoremediation projects.

Probabilistic modelling techniques in dietary exposure assessment: application on the risk assessment of cadmium for Austrian adults

Probabilistic exposure and risk assessment of chemical hazards in the diet have increasingly gained ground in recent years as a pragmatic approach for the approximation of reality. This work presents the outcomes of a project which aimed at applying probabilistic techniques for basic modelling of chronic dietary exposure to food contaminants following EFSA guidance. These techniques, based on Monte Carlo Risk Assessment (MCRA) software and on the programming language R, were employed for the risk assessment of cadmium for Austrian adults, enabling the validation and the critical comparison of the two approaches. Harmonisation and optimisation of procedures, refinement of exposure assessment skills and confidence in the results were the main benefits. Data amount and validity were identified as critical parameters, influencing the precision of the results. Cadmium was selected as a case study due to its toxicological properties, its ubiquitous presence in food and the availability of Austrian occurrence data. Similar exposure and risk estimates were generated through MCRA and R in alternative optimistic and pessimistic exposure scenarios, suggesting low levels of concern, except for vegetarians, whose upper tail exposures are close to the established Tolerable Weekly Intake. However, as occurrence data gaps have been identified as the major element of uncertainty, the estimated exposure and risk levels are characterised as underestimated. Grains and grain-based products, potatoes and leafy vegetables are the main contributors to the intake. The results will contribute to risk management and to a future refinement of the assessment.

Toxicological approaches for the quantitative inhalation risk assessment of toxic metals from tobacco smoke: application on the deterministic and probabilistic inhalation risk assessment of cadmium for Austrian smokers

OBJECTIVE

The objective of this study was the assessment of risks from inhalation exposure of Austrian smokers to cadmium through established toxicological approaches with emphasis on the exposure assessment component, which is challenging regarding the actual amount of metal that is inhaled and the simulation of the smoking pattern.

MATERIALS AND METHODS

Exposure assessment comprised an estimation of the proportion of cadmium inhaled through smoking and actual occurrence data in tobacco products and survey smoking habits, which were integrated in alternative scenarios through a deterministic and a probabilistic Monte Carlo simulation method. Risks were characterized through the comparison of the exposure with health-based guidance values, as well as through the assessment of the excess lifetime cancer risk (ELCR), the non-cancer hazard quotient (NCHQ), and the margin of exposure (MOE). The strengths, the uncertainties, and the limitations of the different methodologies were discussed.

RESULTS AND DISCUSSION

Upper exposures are close or exceed the Permitted Daily Exposure. Respiratory ELCRs are unacceptable compared to the benchmark range of 1.0E-06 to 1.0E-04. Renal and respiratory NCHQs exceed the target value of 1.0 by 3- to 17-fold. MOEs are not protective enough for cancer and non-cancer effects. The amount of cadmium that reaches the lung is a key source of uncertainty.

CONCLUSION

Probabilistic estimates provide a refined capture of the actual inhalation exposure. Risk estimates and gender and age profiles are alarming, especially for young smokers. Application of toxicological approaches, combined with realistic assessment of the inhalation exposure levels, can support risk communication and management.

Environmental Cadmium Exposure and Dental Indices in Orthodontic Patients

BACKGROUND

Previous studies have shown that environmental cadmium exposure could disrupt salivary gland function and is associated with dental caries and reduced bone density. Therefore, this cross-sectional study attempted to determine whether tooth decay with tooth loss following cadmium exposure is associated with some dental or skeletal traits such as malocclusions, sagittal skeletal pattern, and tooth decay.

METHODS

Between August 2019 and June 2020, 60 orthodontic patients with no history of previous orthodontics, functional appliances, or surgical treatment were examined. The patients were stratified into two groups according to their urine cadmium concentrations: high (>1.06 µg/g creatinine, n = 28) or low (<1.06 µg/g creatinine, n = 32).

RESULTS

The patients were 25.07 ± 4.33 years old, and most were female (female/male: 51/9 or 85%). The skeletal relationship was mainly Class I (48.3%), followed by Class II (35.0%) and Class III (16.7%). Class I molar relationships were found in 46.7% of these patients, Class II molar relationships were found in 15%, and Class III molar relationships were found in 38.3%. The mean decayed, missing, and filled surface (DMFS) score was 8.05 ± 5.54, including 2.03 ± 3.11 for the decayed index, 0.58 ± 1.17 for the missing index, and 5.52 ± 3.92 for the filled index. The mean index of complexity outcome and need (ICON) score was 53.35 ± 9.01. The facial patterns of these patients were within the average low margin (26.65 ± 5.53 for Frankfort-mandibular plane angle (FMA)). There were no significant differences in the above-mentioned dental indices between patients with high urine cadmium concentrations and those with low urine cadmium concentrations. Patients were further stratified into low (<27, n = 34), average (27-34, n = 23), and high (>34, n = 3) FMA groups. There were no statistically significant differences in the urine cadmium concentration among the three groups. Nevertheless, a marginally significant p-value of 0.05 for urine cadmium concentration was noted between patients with low FMA and patients with high FMA.

CONCLUSION

This analysis found no association between environmental cadmium exposure and dental indices in our orthodontic patients.

Review of Sewage Sludge as a Soil Amendment in Relation to Current International Guidelines: A Heavy Metal Perspective

Overexploitation of resources makes the reutilization of waste a focal topic of modern society, and the question of the kind of wastes that can be used is continuously raised. Sewage sludge (SS) is derived from the wastewater treatment plants, considered important underused biomass, and can be used as a biofertilizer when properly stabilized due to the high content of inorganic matter, nitrate, and phosphorus. However, a wide range of pollutants can be present in these biosolids, limiting or prohibiting their use as biofertilizer, depending on the type and origin of industrial waste and household products. Long-term applications of these biosolids could substantially increase the concentration of contaminants, causing detrimental effects on the environment and induce hyperaccumulation or phytotoxicity in the produced crops. In this work, some critical parameters for soils and SS agronomic use, such as organic matter, nitrogen, phosphorous, and potassium (NPK), and heavy metals concentration have been reviewed. Several cases of food crop production and the accumulation of heavy metals after SS application are also discussed. SS production, usage, and legislation in EU are assessed to determine the possibility of sustainable management of this bioresource. Additionally, the World Health Organization (WHO) and Food and Agriculture Organization (FAO) guidelines are addressed. The opportunity to produce bioenergy crops, employing sewage sludge to enhance degraded land, is also considered, due to energy security. Although there are numerous advantages of sewage sludge, proper screening for heavy metals in all the variants (biosolids, soil, food products) is a must. SS application requires appropriate strict guidelines with appropriate regulatory oversight to control contamination of agricultural soils.

Changes in compact bone microstructure of rats subchronically exposed to cadmium

Background

Chronic exposure to cadmium (Cd), even at low concentrations, has an adverse impact on the skeletal system. Histologically, primary and secondary osteons as basic structural elements of compact bone can also be affected by several toxicants leading to changes in bone vascularization and mechanical properties of the bone. The current study was designed to investigate the effect of subchronic peroral exposure to Cd on femoral bone structure including histomorphometry of the osteons in adult male rats.

In our study, 20 one-month-old male Wistar rats were randomly divided into two experimental groups. In the first group, young males received a drinking water containing 30 mg of CdCl₂/L, for 90 days. Ten one-month-old males without Cd intoxication served as a control group. After 90 days of daily peroral exposure, body weight, femoral weight, femoral length, cortical bone thickness and histological structure of the femora were analysed.

Results

We found that subchronic peroral application of Cd had no significant effect on body weight, femoral length and cortical bone thickness in adult rats. On the other hand, femoral weight was significantly increased (P < 0.05) in Cd-intoxicated rats. These rats also displayed different microstructure in the middle part of the compact bone where vascular canals expanded into central area of substantia compacta and supplied primary and secondary osteons. Additionally, a few resorption lacunae which are connected with an early stage of osteoporosis were identified in these individuals. Histomorphometrical evaluations showed that all variables (area, perimeter, maximum and minimum diameter) of the primary osteons’ vascular canals, Haversian canals and secondary osteons were significantly decreased (P < 0.05) in the Cd group rats. This fact points to alterations in bone vascularization.

Conclusions

Subchronic peroral exposure to Cd significantly influences femoral weight and histological structure of compact bone in adult male rats. It induces an early stage of osteoporosis and causes reduced bone vascularization. Histomorphometrical changes of primary and secondary osteons allow for the conclusion that the bone mechanical properties could be weakened in the Cd group rats. The current study significantly expands the knowledge on damaging action of Cd on the bone.

Effects of a single intraperitoneal administration of cadmium on femoral bone structure in male rats

BACKGROUND

Exposure to cadmium (Cd) is considered a risk factor for various bone diseases in humans and experimental animals. This study investigated the acute effects of Cd on femoral bone structure of adult male rats after a single intraperitoneal administration.

METHODS

Ten 4-month-old male Wistar rats were injected intraperitoneally with a single dose of 2 mg CdCl2/kg body weight and killed 36 h after the Cd had been injected. Ten 4-month-old males served as a control group. Differences in body weight, femoral weight, femoral length and histological structure of the femur were evaluated between the two groups of rats. The unpaired Student's t-test was used for establishment of statistical significance.

RESULTS

A single intraperitoneal administration of Cd had no significant effect on the body weight, femoral weight or femoral length. On the other hand, histological changes were significant. Rats exposed to Cd had significantly higher values of area, perimeter, maximum and minimum diameters of the primary osteons' vascular canals and Haversian canals. In contrast, a significant decrease in all variables of the secondary osteons was observed in these rats.

CONCLUSIONS

The results indicate that, as expected, a single intraperitoneal administration of 2 mg CdCl2/kg body weight had no impact on macroscopic structure of rat's femora; however, it affected the size of vascular canals of primary osteons, Haversian canals, and secondary osteons.

Exposure to multiple metals from groundwater-a global crisis: geology, climate change, health effects, testing, and mitigation

This paper presents an overview of the global extent of naturally occurring toxic metals in groundwater. Adverse health effects attributed to the toxic metals most commonly found in groundwater are reviewed, as well as chemical, biochemical, and physiological interactions between these metals. Synergistic and antagonistic effects that have been reported between the toxic metals found in groundwater and the dietary trace elements are highlighted, and common behavioural, cultural, and dietary practices that are likely to significantly modify health risks due to use of metal-contaminated groundwater are reviewed. Methods for analytical testing of samples containing multiple metals are discussed, with special attention to analytical interferences between metals and reagents. An overview is presented of approaches to providing safe water when groundwater contains multiple metallic toxins.

Serial follow-up study on renal handling of calcium and phosphorus after soil replacement in Cd-polluted rice paddies estimated using a general linear mixed model

A 10-year follow-up study was conducted to investigate the effects of renal handling of calcium (Ca) and phosphorus (P) after the removal of cadmium-polluted soil in rice paddies and replacing it with nonpolluted soil. Using a general linear mixed model, serial changes of Ca and P concentrations in urine and serum (Ca-U/S, P-U/S), fractional excretion of Ca (FECa), and percent tubular reabsorption of P (%TRP) were determined in 37 persons requiring observation in the Cd-polluted Kakehashi River Basin, Japan. Ca-U and Ca-S remained within the normal range in both sexes. FECa in men returned to the normal level within 3.3 years from the completion of soil replacement. Overall, it is suggested that the renal handling of Ca showed no or only a slight change throughout the observation period in both sexes. P-U decreased gradually. P-S showed lower than normal values in the men and values at the lower end of the normal range in women, although the values recovered gradually to normal. %TRP values remained low throughout the observation period and the values did not recover in either sex. However, the results of P-U and P-S suggested that the renal handling of P may recover after the completion of soil replacement.

Effect of different doses of hexavalent chromium on mandibular growth and tooth eruption in juvenile Wistar rats

Not only workers employed at industrial plants are exposed to intoxication with the element they manipulate, the population at large is also at risk of suffering health problems caused by contaminating wastes inadequately treated for their safe disposal. As a result certain toxic substances, such as hexavalent chromium,has reached the general population including children. The present study sought to evaluate the effect of intoxication with hexavalent chromium on body and mandibular growth and tooth eruption in suckling Wistar rats. Potassium dichromate was administered by gavage in a dose of 6.25 or 12.5mg/kg body weight (b.w.) to one of the two groups of 4-day-old Wistar rats during 10 days. Our results showed that the effects of chromium are dose-dependent. Morphometric studies of body growth showed lower body weight in both experimental groups and shorter tail length in animals receiving 12.5mg/kg b.w. dose of chromium, compared with controls. All parameters of mandibular growth were lower in the experimental group receiving 12.5mg/kg b.w. of chromium. Differences in tooth eruption were observed at the level of the first molar in animals receiving 12.5mg/kg and of the second molar in those receiving 6.25mg/kg b.w. of chromium. Chromium was found to affect all the studied parameters.

Elevated Urinary Levels of Vitamin D-Binding Protein in the Inhabitants of a Cadmium Polluted Area, Jinzu River Basin, Japan

Environmental cadmium (Cd) pollution and its effects on human health are still important issues. The most severe and representative manifestation of chronic Cd intoxication is Itai-itai disease, which is a syndrome that includes renal tubular dysfunction, osteomalacia, and generalized pain due to multiple bone fractures. The whole mechanism of how renal dysfunction relates to the development of bone lesions is unresolved. Vitamin D-binding protein (DBP) binds, transports and activates vitamin D, which plays a major role in calcium homeostasis and bone turnover. In this study, we measured urinary DBP levels and investigated their relationship to the markers of renal tubular dysfunction in the inhabitants of a Cd-polluted Jinzu River basin in Toyama Prefecture, Japan (Cd group). We also investigated age-matched subjects from an area known to have lower levels of Cd pollution (reference group). Urinary DBP was measured by a fluorometric enzyme-linked immunosorbent assay (ELISA), which was established in our laboratory. Significantly higher levels of urinary DBP were observed in the Cd group compared to the reference group. We observed significant positive correlations between urinary levels of DBP and renal tubular dysfunction markers in both groups. In the Cd group, urinary levels of DBP had a negative correlation with serum phosphate value. These results indicate that excretion of urinary DBP is increased after long-term Cd exposure and that the loss of DBP in urine may be linked to renal tubular dysfunction and possibly bone lesions in the inhabitants of Cd-polluted areas.

Cadmium-induced effects on bone in a population-based study of women

High cadmium exposure is known to cause bone damage, but the association between low-level cadmium exposure and osteoporosis remains to be clarified. Using a population-based women's health survey in southern Sweden [Women's Health in the Lund Area (WHILA) ] with no known historical cadmium contamination, we investigated cadmium-related effects on bone in 820 women (53-64 years of age) . We measured cadmium in blood and urine and lead in blood, an array of markers of bone metabolism, and forearm bone mineral density (BMD) . Associations were evaluated in multiple linear regression analysis including information on the possible confounders or effect modifiers: weight, menopausal status, use of hormone replacement therapy, age at menarche, alcohol consumption, smoking history, and physical activity. Median urinary cadmium was 0.52 microg/L adjusted to density (0.67 microg/g creatinine) . After multivariate adjustment, BMD, parathyroid hormone, and urinary deoxypyridinoline (U-DPD) were adversely associated with concentrations of urinary cadmium (p < 0.05) in all subjects. These associations persisted in the group of never-smokers, which had the lowest cadmium exposure (mainly dietary) . For U-DPD, there was a significant interaction between cadmium and menopause (p = 0.022) . Our results suggest negative effects of low-level cadmium exposure on bone, possibly exerted via increased bone resorption, which seemed to be intensified after menopause. Based on the prevalence of osteoporosis and the low level of exposure, the observed effects, although slight, should be considered as early signals of potentially more adverse health effects. Key words: biochemical bone markers, bone mineral density, cadmium, lead, osteoporosis, women.

Kidney Dysfunction and Hypertension: Role for Cadmium, P450 and Heme Oxygenases?

Cadmium (Cd) is a metal toxin of continuing worldwide concern. Daily intake of Cd, albeit in small quantities, is associated with a number of adverse health effects which are attributable to distinct pathological changes in a variety of tissues and organs. In the present review, we focus on its renal tubular effects in people who have been exposed environmentally to Cd at levels below the provisional tolerable intake level set for the toxin. We highlight the data linking such low-level Cd intake with tubular injury, altered abundance of cytochromes P450 (CYPs) in the kidney and an expression of a hypertensive phenotype. We provide updated knowledge on renal and vascular effects of the eicosanoids 20-hydroxyeicosatetraenoic acid (20-HETE) and eicosatrienoic acids (EETs), which are biologically active metabolites from arachidonate metabolism mediated by certain CYPs in the kidney. We note the ability of Cd to elicit "oxidative stress" and to alter metal homeostasis notably of zinc which may lead to augmentation of the defense mechanisms involving induction of the antioxidant enzyme heme oxygenase-1 (HO-1) and the metal binding protein metallothionein (MT) in the kidney. We hypothesize that renal Cd accumulation triggers the host responses mediated by HO-1 and MT in an attempt to protect the kidney against injurious oxidative stress and to resist a rise in blood pressure levels. This hypothesis predicts that individuals with less active HO-1 (caused by the HO-1 genetic polymorphisms) are more likely to have renal injury and express a hypertensive phenotype following chronic ingestion of low-level Cd, compared with those having more active HO-1. Future analytical and molecular epidemiologic research should pave the way to the utility of induction of heme oxygenases together with dietary antioxidants in reducing the risk of kidney injury and hypertension in susceptible people.

Cadmium effects on growth and mineral nutrition of two halophytes: Sesuvium portulacastrum and Mesembryanthemum crystallinum

Growth, cadmium accumulation and potassium and calcium status were studied in two halophytes from Aizoaceae family: Sesuvium portulacastrum and Mesembryanthemum crystallinum. After multiplication, the seedlings were cultivated on nutrient solution supplemented with NaCl (100mM) and CdCl2 (0, 50, 100, 200 and 300 microM). After 1 month of treatment, plants were harvested and the dry weight, as well as the Cd, K and Ca concentrations in tissues were determined. Results showed that S. portulacastrum, a perennial halophyte with slow growth, is significantly more tolerant to Cd than M. crystallinum, an annual plant. Cd severely inhibited Mesembryanthemum growth even at the lowest Cd concentration in culture medium (50 microM), and did not modify significantly that of Sesuvium. For both halophytes, Cd accumulation was significantly higher in the roots than in the shoots. However, Cd concentration reached 350-700 microg g(-1) DM in the shoots, values characteristic of Cd hyperaccumulator plants. The addition of Cd in the culture medium led to a disturbance of Ca and especially K nutrition, suggesting the possibility to improve plant growth and Cd phytoextraction of both halophytes by increasing nutrient availability in the culture medium.

Bone as a possible target of chemical toxicity of natural uranium in drinking water

Uranium accumulates in bone, affects bone metabolism in laboratory animals, and when ingested in drinking water increases urinary excretion of calcium and phosphate, important components in the bone structure. However, little is known about bone effects of ingested natural uranium in humans. We studied 146 men and 142 women 26-83 years of age who for an average of 13 years had used drinking water originating from wells drilled in bedrock, in areas with naturally high uranium content. Biochemical indicators of bone formation were serum osteocalcin and amino-terminal propeptide of type I procollagen, and a marker for bone resorption was serum type I collagen carboxy-terminal telopeptide (CTx). The primary measure of uranium exposure was uranium concentration in drinking water, with additional information on uranium intake and uranium concentration in urine. The data were analyzed separately for men and women with robust regression (which suppresses contributions of potential influential observations) models with adjustment for age, smoking, and estrogen use. The median uranium concentration in drinking water was 27 microg/L (interquartile range, 6-116 microg/L). The median of daily uranium intake was 36 microg (7-207 microg) and of cumulative intake 0.12 g (0.02-0.66 g). There was some suggestion that elevation of CTx (p = 0.05) as well as osteocalcin (p = 0.19) could be associated with increased uranium exposure (uranium in water and intakes) in men, but no similar relationship was found in women. Accordingly, bone may be a target of chemical toxicity of uranium in humans, and more detailed evaluation of bone effects of natural uranium is warranted.

Disorders in bone metabolism of female rats chronically exposed to cadmium

The effect of cadmium (Cd) on bone metabolism during skeletal development and maturity was investigated on a rat model of human exposure. Young female Wistar rats were exposed to 1, 5, or 50 mg Cd/l in drinking water for 3, 6, 9, and 12 months. Total bone mineral density (T-BMD), bone mineral content (BMC), density (BMD), and bone area at the femur and lumbar spine (L1-L5) were measured densitometrically. Alkaline phosphatase (ALP) and osteocalcin (OC) as bone formation markers, and carboxy-terminal cross-linking telopeptides of type I collagen (CTX) in bone (trabecular and cortical) or serum as bone resorption markers were measured. Renal calcium (Ca) handling and Cd body burden were evaluated as well. At the stage of intensive skeletal development (the first 6 months of the experiment), at all exposure levels, Cd inhibited the processes of bone formation and as a result disturbed the accumulation of bone mass leading to osteopenia (- 1 > Z score/T score BMD > -2.5) and at 5 and 50 mg Cd/l even to more advanced disorders in the BMD. Continuation of the exposure up to skeletal maturity led to high bone turnover with increased resorption enhancing the prevalence of osteopenia or the BMD values having the Z score/T score < -2.5. The results allow for the conclusion that chronic, even low-level exposure to Cd disturbs bone metabolism during skeletal development and maturity by affecting bone turnover most probably through a direct influence on bone formation and resorption, and indirectly via disorders in Ca metabolism. Our findings confirm the hypothesis that environmental exposure to Cd may be a risk factor for low BMD.

Low-level lifetime exposure to cadmium decreases skeletal mineralization and enhances bone loss in aged rats

The effects of low-level lifetime exposure to cadmium (Cd) on the skeleton mineral status and the risk of bone loss in the elderly were studied in an experimental model of human environmental exposure in non-Cd-polluted areas. Young female Wistar rats were exposed to 1 mg Cd/l in drinking water for 24 months. Bone mineral content (BMC), density (BMD) and area of the lumbar spine (L1-L5) and femur, and total skeleton BMD (T-BMD) were measured densitometrically at the baseline and after 6, 12, 18, and 24 months. Prevalence of osteopenia and osteoporosis was evaluated based on the BMD T score and Z score. Osteocalcin (OC) in the serum and total alkaline phosphatase (total ALP) in the serum, cortical and trabecular bone samples as bone formation markers, and C-terminal cross-linking telopeptide of type I collagen (CTX) in the serum and urine as bone resorption markers were measured. Calcium (Ca) and Cd concentrations in the serum/blood and urine were determined as well. In the Cd-exposed females, the L1-L5 and femur BMC and BMD at all the studied time points were lower compared to control. The exposure to Cd resulted in lower accumulation of peak bone mass, accelerated osteopenia, and enhanced the prevalence of osteoporosis in aged rats. The effect of Cd was more pronounced at the L1-L5 than at the femur. CTX concentration in the urine was decreased after 6 months and next increased compared to control, whereas the urinary loss of Ca was enhanced during the exposure to Cd. After 24 months of the treatment, the serum total ALP activity and the activity of this enzyme in cortical and trabecular bone decreased and serum CTX concentration increased, whereas the concentrations of OC and Ca were unchanged. The study clearly revealed that low-level lifetime exposure to Cd diminishes the accumulation of bone mass during skeletal growth and influences bone metabolism at maturity causing osteopenia, and enhances the age-related bone loss due to high turnover rate leading in consequence to osteoporosis in aged rats. The results together with our previous findings confirm the hypothesis that environmental exposure to Cd may be a risk factor for skeletal diseases.

Low-Level Exposure to Cadmium during the Lifetime Increases the Risk of Osteoporosis and Fractures of the Lumbar Spine in the Elderly: Studies on a Rat Model of Human Environmental Exposure

In this study, based on a rat model of human environmental exposure to cadmium (Cd), it has been examined whether low-level lifetime Cd exposure increases the risk of vertebral osteoporosis and vertebrae fractures in the elderly. For this purpose, the lumbar vertebral bodies (L4 or L3) of control and Cd-exposed (1 mg Cd/l in drinking water for 24 months) female Wistar rats were assigned to densitometric, radiographic, biomechanical (compression test), and biochemical studies, as well as to assess their dimensions and chemical composition. The exposure to Cd affected the mineral status of the L4. The decreased mineral content, density (BMD) and bone mineral area of the vertebral body together with the unchanged ratio of non-organic and organic components indicate osteoporotic nature of the Cd-induced changes. The activity of alkaline phosphatase in the L3 decreased. Cd also influenced the mechanical properties of the L4. The yield load and ultimate load decreased indicating a weakness in the vertebral body compression strength. Stiffness of the L4 decreased and the displacement at ultimate increased suggesting its enhanced susceptibility to deformities. Indeed, in the Cd group vertebral deformities (in 30% of females) or even fractures (in 40% of females), including those with disruption of bone continuity were evident. Z-score values for the L4 BMD revealed vertebral osteopenia in 30% and osteoporosis in 70% of the Cd-exposed females. The results allow for the conclusion that low lifetime exposure to Cd may become an important factor increasing the risk of lumbar spine osteoporosis with vertebral deformities and fractures in the elderly.

Reduction of erythrocyte catalase and superoxide dismutase activities in male inhabitants of a cadmium-polluted area in Jinzu river basin, Japan

Cadmium (Cd) is a toxic heavy metal which causes oxidative damage in organisms. In this study, we investigated the activities of the antioxidant enzymes erythrocyte catalase and copper/zinc superoxide dismutase (Cu/Zn-SOD) in 22 male inhabitants of the Cd-polluted Jinzu River basin in Toyama Prefecture, Japan (Cd group). The reference group consisted of 21 male inhabitants from an area that was not polluted with Cd (reference group). Urinary Cd levels and two renal tubular dysfunction markers in urine, alpha1-microglobulin (alpha1-m) level and N-acetyl-beta-D-glucosaminidase (NAG) activity, were significantly elevated in the Cd group. Catalase and Cu/Zn-SOD activities were significantly reduced in the Cd group as compared to the reference group. Significant negative correlation was observed between the activities of these two antioxidant enzymes and urinary Cd levels. We also observed significant negative correlations between activities of these two antioxidant enzymes and the renal tubular dysfunction markers. Our results indicate that erythrocyte catalase and Cu/Zn-SOD activities are reduced as a result of long-term Cd exposure. This may be linked to renal tubular dysfunction in the inhabitants of the Cd-polluted area.

Adverse health effects of chronic exposure to low-level cadmium in foodstuffs and cigarette smoke

Cadmium is a cumulative nephrotoxicant that is absorbed into the body from dietary sources and cigarette smoking. The levels of Cd in organs such as liver and kidney cortex increase with age because of the lack of an active biochemical process for its elimination coupled with renal reabsorption. Recent research has provided evidence linking Cd-related kidney dysfunction and decreases in bone mineral density in nonoccupationally exposed populations who showed no signs of nutritional deficiency. This challenges the previous view that the concurrent kidney and bone damage seen in Japanese itai-itai disease patients was the result of Cd toxicity in combination with nutritional deficiencies, notably, of zinc and calcium. Further, such Cd-linked bone and kidney toxicities were observed in people whose dietary Cd intakes were well within the provisional tolerable weekly intake (PTWI) set by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives of 1 microg/kg body weight/day or 70 microg/day. This evidence points to the much-needed revision of the current PTWI for Cd. Also, evidence for the carcinogenic risk of chronic Cd exposure is accumulating and Cd effects on reproductive outcomes have begun to emerge.

Comprehensive study of the effects of age, iron deficiency, diabetes mellitus, and cadmium burden on dietary cadmium absorption in cadmium-exposed female Japanese farmers

The absorption rate of dietary cadmium (Cd) was investigated among 38 female farmers who had been exposed to Cd at levels close to the current provisional tolerable weekly intake (PTWI); these levels were much higher than those examined in previous studies. The study group composed of 7 diabetics and their 13 age-matched controls and 6 anemic subjects and their 12 controls. With their informed consent, the study participants were confined in an inn for 7 nights and 8 days to collect all feces and urine and duplicates of all food consumed. The dietary Cd absorption rate was calculated for each subject from her total Cd intake and fecal excretion. The means and 95% confidence intervals (CI) of the diabetic group and the anemic group did not differ significantly from those of their respective controls. By individual analysis using all 38 subjects, however, significant Pearson's correlation coefficients were observed between Cd absorption rate and age, serum ferritin, serum iron, and blood and urine Cd levels. Among these, multiple regression analysis revealed that only age was a significant factor contributing to Cd absorption rate. The actual Cd absorption rate in the youngest age group (20-39 years) was 44.0%, which was highly accelerated compared with the rate in the total subject group of 6.5%, while zero to negative balance was observed in the older subjects. These results demonstrate that age, rather than iron deficiency, diabetes mellitus (DM), or Cd burden, is the only independent factor affecting the Cd absorption rate, suggesting that young women are always at high risk.