Significance of elevated urinary human intestinal alkaline phosphatase in Japanese people exposed to environmental cadmium

A systematic review of adverse health effects associated with oral cadmium exposure

Scientific data characterizing the adverse health effects associated with dietary cadmium (Cd) exposure were identified in order to make informed decisions about the most appropriate toxicological reference value (TRV) for use in assessing dietary Cd exposure. Several TRVs are available for Cd and regulatory organizations have used epidemiologic studies to derive these reference values; however, risk of bias (RoB) evaluations were not included in the assessments. We performed a systematic review by conducting a thorough literature search (through January 4, 2020). There were 1714 references identified by the search strings and 328 studies identified in regulatory assessments. After applying the specific inclusion and exclusion criteria, 208 studies (Human: 105, Animal: 103) were considered eligible for further review and data extraction. For the epidemiologic and animal studies, the critical effects identified for oral Cd exposure from the eligible studies were a decrease in bone mineral density (BMD) and renal tubular degeneration. A RoB analysis was completed for 49 studies (30 epidemiological and 19 animal) investigating these endpoints. The studies identified through the SR that were considered high quality and low RoB (2 human and 5 animal) can be used to characterize dose-response relationships and inform the derivation of a Cd TRV.

A 28-year observational study of urinary cadmium and β2 -microglobulin concentrations in inhabitants in cadmium-polluted areas in Japan

The biological half-life of cadmium (Cd) is as long as 10-30 years. Exposure to this element induces renal tubular dysfunction, which is considered irreversible. β₂ -microglobulin (β₂ -MG) is a low-molecular-weight protein, and urinary β₂ -MG is one of the most useful and critical indicators for the early detection of renal tubular dysfunction. However, very little research has been published concerning the long-term observation of Cd-induced adverse health effects. As such, this follow-up study was conducted for 28 years to clarify the relationship between the concentration of Cd and β₂ -MG in the urine of 28 inhabitants (14 male and 14 female) living in the Kakehashi River basin, Ishikawa prefecture (Japan), previously one of the most highly Cd-polluted regions in this country. All subjects were over 60 years old in 2014 and participated in all six health examinations conducted over 28 years (1986-2014). Urine was collected at the appropriate time and kept frozen to analyze urinary Cd and β₂ -MG concentrations. The urinary Cd concentration was found to decrease by nearly half between 1986 and 2008 in both male and female subjects, whereas it increased significantly from 2008 to 2014 in males. In contrast, urinary β₂ -MG concentrations tended to increase over the 28-year study period in both sexes. Urinary Cd and β₂ -MG concentrations in females were significantly higher than those in males in this Cd-polluted region. Age is more strongly associated with urinary β₂ -MG concentration than recent Cd body burden. Copyright © 2016 John Wiley & Sons, Ltd.

Co-exposure to lead increases the renal response to low levels of cadmium in metallurgy workers

PURPOSE

Research on the effect of co-exposure to Cd and Pb on the kidney is scarce. The objective of the present study was to assess the effect of co-exposure to these metals on biomarkers of early renal effect.

METHODS

Cd in blood (Cd-B), Cd in urine (Cd-U), Pb in blood (Pb-B) and urinary renal biomarkers, i.e., microalbumin (μ-Alb), beta-2-microglobulin (β₂-MG), retinol binding protein (RBP), N-acetyl-β-d-glucosaminidase (NAG), intestinal alkaline phosphatase (IAP) were measured in 122 metallurgic refinery workers examined in a cross-sectional survey.

RESULTS AND CONCLUSIONS

The median Cd-B, Cd-U, Pb-B were: 0.8 μg/l (IQR = 0.5, 1.2), 0.5 μg/g creatinine (IQR = 0.3, 0.8) and 158.5 μg/l (IQR = 111.0, 219.3), respectively. The impact of Cd-B on the urinary excretion of NAG and IAP was only evident among workers with Pb-B concentrations ≥ 75th percentile. The association between Cd-U and the renal markers NAG and RBP was also evidenced when Pb-B ≥ 75th percentile. No statistically significant interaction terms were observed for the associations between Cd-B or Cd-U and the other renal markers under study (i.e., μ-Alb and β2-MG). Our findings indicate that Pb increases the impact of Cd exposure on early renal biomarkers.

The relationship between the bone mineral density and urinary cadmium concentration of residents in an industrial complex

BACKGROUND

An association between cadmium exposure and bone mineral density (BMD) has been demonstrated in elderly women, but has not been well studied in youths and men. Some studies report either no or a weak association between cadmium exposure and bone damage.

OBJECTIVES

This study was designed to investigate the relationship between the urinary cadmium (U-Cd) levels and BMD of females and males of all ages.

METHODS

A total of 804 residents near an industrial complex were surveyed in 2007. U-Cd and BMD on the heel (non-dominant calcaneus) were analyzed with AAS-GTA and Dual-Energy X-ray absorptiometry, respectively. Demographic characteristics were collected by structured questionnaires. Osteoporosis and osteopenia were defined by BMD cut-off values and T-scores set by the WHO; T score>-1, normal; -2.5<T score <-1, osteopenia; and T score <-2.5, osteoporosis. Logistic and multiple linear regressions were applied to estimate the association between U-Cd levels and BMD.

RESULTS

The U-Cd levels in females (0.64 μg/g creatinine) were higher than those in males (0.48 μg/g creatinine) (p<0.001). With the logistic regression model, osteopenia was associated with high U-Cd levels (≥ 1.0 μg/g creatinine) in females (OR=2.92; 95% CI, 1.51-5.64) and in males (OR=3.37; 95% CI, 1.09-10.38). With the multiple linear regression model, the BMD of the adult group was negatively associated with U-Cd (<0.05), gender (female, p<0.001) and age (p<0.001). The BMD of participants who were ≤ 19 years of age was negatively associated with gender (female, p<0.01), whereas it was positively associated with age and BMI (p<0.001). BMD was not associated with exercise, smoking habits, alcohol consumption, job or parental education.

CONCLUSION

Results suggested that U-Cd might be associated with osteopenia as well as osteoporosis in both male and female adults. Age and female gender were negatively associated with BMD in the adult group, whereas age was positively associated with BMD in the youth group. Cadmium exposure may be a potential risk factor for lower-BMD and osteopenia symptoms as well as for osteoporosis symptoms.

Biochemical changes in urine and plasma of rats in food chain-mediated cadmium toxicity

The present study sets out to assess the toxicity of cadmium (Cd) administered via the food chain. The food chain was mimicked by exposing rats to diet containing milled Cd-exposed catfish as the source of protein. The toxicity of Cd was monitored by the determination of indices of oxidative stress and kidney dysfunction in plasma and urine of the rats after 1- and 3-month exposure periods. The results obtained indicate that Cd exposure in the rats was followed by marked accumulation of the metal in the liver and kidney with time. However, the kidney accumulated more Cd relative to the liver after both exposure periods. The levels of glucose, creatinine and lipid peroxidation were significantly (p < 0.05) increased in both plasma and urine of the rats after 1 month of exposure. Conversely, rats fed the test diet for 3 months had significantly (p < 0.05) decreased level of lipid peroxidation in the plasma and urine. However, the plasma and urine glucose concentrations were restored to levels not significantly (p > 0.05) different from control in rats fed the test diet for 3 months. Similarly, after 3 months, the creatinine level in the plasma was also restored to a level not significantly (p > 0.05) different from that of the control but was significantly (p < 0.05) elevated in the urine. A significant increase in urine protein concentration was demonstrated after 1-month exposure to Cd, but no significant change occurred in the plasma. Rats fed diet containing the Cd-incorporated fish for 3 months also had no significant (p > 0.05) change in plasma and urine protein concentrations. These results suggest that this route of exposure caused kidney impairment, oxidative stress as well as alteration in glucose metabolism after 1 month but not after 3 months, possibly due to adaptation occasioned by the antioxidative defense armory of the rats.

Urban population exposure to lead and cadmium in east and south-east Asia

Information is still scarce for many Asian countries on general population exposure to two potentially toxic heavy metals of lead (Pb) and cadmium (Cd). The present review on publications from this study group is intended to provide an overview of the non-occupational exposure to Pb and Cd among general populations in east and south-east Asia. During the period of 1991-1998, surveys were conducted in four cities in south-east Asia, five cities in mainland China, and two cities each in Japan and Korea. Peripheral blood, morning spot urine and 24-h food duplicate samples were collected from 20-50 non-smoking adult women in each survey site. The samples were digested by heating in the presence of mineral acids, and then analyzed by inductively-coupled plasma mass spectrometry for the metals in blood (Pb-B and Cd-B), in urine (Pb-U and Cd-U), and in food duplicate (Pb-F and Cd-F). Measures were subjected to statistical analysis with an assumption of log-normal distribution. Pb-B, Pb-U and Pb-F levels varied substantially among the 11 urban sites; GM distributed in ranges of 32-65 microg/l for Pb-B, 2.1-7.5 microg/g cr (creatinine) for Pb-U, and 7-32 microg/day for Pb-F. The same was also the case for Cd exposure parameters, the distribution ranges being 0.5-1.8 microg/l for Cd-B, 1.2-3.1 microg/g cr for Cd-U, and 5-32 microg/day for Cd-F. It appeared that the exposure to Pb and Cd was highest in Kuala Lumpur, and Tokyo + Kyoto, respectively, and lowest in Tokyo + Kyoto and in Manila. Additional surveys in Japan showed that Pb exposure was even lower in rural areas than in Tokyo + Kyoto. When compared with the values reported in the literature, Pb exposure levels among Asian populations appear to be similar to the levels in Europe and in the United States, whereas Cd exposure seems to be higher in Asia than in Europe. The contribution of the dietary route in Pb absorption was variable and was inversely related to the extent of air pollution, whereas Cd uptake was almost exclusively via the dietary route with little contribution of the respiratory route.

Time course of chronic oral cadmium nephrotoxicity in Wistar rats: excretion of urinary enzymes

Twelve male and female Wistar rats each received cadmium (as CdCl2) in their diet at concentrations of 0, 10, 50, and 250 ppm for 72 weeks. After 1, 4, 8, 13, 18, 26, 32, 45, 57, and 68 weeks a total of 8 enzymes from different cellular compartments of the nephron were measured. At the end of the study period, the kidneys were examined histopathologically. Concentrations up to and including 50 ppm did not induce any adverse effect. At 250 ppm, growth of male and female animals was markedly retarded. Significantly increased activities of the cytosolic phosphohexose isomerase were excreted by males and females receiving 250 ppm at all timepoints from week 13. The values of the mitochondrial glutamate dehydrogenase were mostly elevated from week 1 to 57, however, due to a wide scatter range, were only occasionally significantly different from control values. The brush border enzymes (gamma-glutamyl transferase, alkaline phosphatase and leucine arylamidase) were not changed in a relevant manner in female rats, while in 250 ppm males the excreted activity of ALP and LAP from week 1 to week 18, and that of GGT during the entire study period were significantly lower than the control values. Excretion of the lysosomal enzymes aryl sulfatase A, beta-galactosidase, and beta-N-acetyl-D-glucosaminidase was at no time influenced in a noteworthy manner. Histopathology after 72 weeks revealed chronic but also acute degenerative changes in the kidneys of 250 ppm males and females. A comparison of published data on persons having undergone high cadmium exposure with the results presented here shows remarkable differences.