Cadmium and tubular dysfunction marker levels in urine of residents in non-polluted areas with natural abundance of cadmium in Japan

Current Situation and Causes Analysis of Cadmium Pollution in the Kakehashi River Basin

Cadmium (Cd) pollution is a public environmental problem worthy of attention. Long-term exposure to Cd may have adverse effects on human health. Our previous study showed that urinary concentration of Cd (U-Cd) in the residents decreased when Cd-polluted paddy soil was removed. However, from 2008 to 2014, the concentration of U-Cd increased. At the same time, the concentration of urinary β2-microglobulin (β2-MG), which is considered to be an early sign of cadmium-induced renal dysfunction, increased continuously. To find the cause of elevated urinary cadmium (U-Cd) in residents of cadmium-contaminated areas, we measured the concentration of cadmium in the blood (B-Cd) of 29 elderly residents (15 female and 14 male) and edible rice (R-Cd), and correlations between R-Cd, B-Cd, and U-Cd were analyzed in the formerly cadmium-polluted areas (the Kakehashi River basin). In 2016, we collected blood, urine, and rice samples from each participant. The analysis showed a significant correlation between age and B-Cd, U-Cd, and β2-MG. However, there was no significant correlation between R-Cd and U-Cd, B-Cd, or β2-MG concentrations. Although we found a slightly higher level of Cd in rice and urine than reported in 2008, we cannot be sure that it indicates an increased Cd contamination in the Kakehashi River basin because larger studies are required for such a conclusion. The increased urinary Cd concentrations in this area may be because Cd in tissues and organs returns to blood and urine as participants age, which leads to an increasing trend.

Associations between Urinary Excretion of Cadmium and Renal Biomarkers in Nonsmoking Females: A Cross-Sectional Study in Rural Areas of South China

OBJECTIVES

The aim of this study was to systematically evaluate the relationship between urinary excretion of cadmium (U-Cd) and biomarkers of renal dysfunction.

METHODS

One hundred eighty five non-smoking female farmers (aged from 44 to 71 years) were recruited from two rural areas with different cadmium levels of exposure in southern China. Morning spot urine samples were collected for detecting U-Cd, urinary creatinine (U-cre), β₂-microglobulin (β₂-MG), α₁-microglobulin (α₁-MG), metallothionein (MT), retinol binding protein (RBP), albumin (AB), N-acetyl-β-D-glucosaminidase (NAG), alkaline phosphatase (ALP), γ-glutamyl transpeptidase (GGT) and kidney injury molecule-1 (KIM-1). Spearman's rank correlation was carried out to assess pairwise bivariate associations between continuous variables. Three different models of multiple linear regression (the cre-corrected, un-corrected and cre-adjusted model) were used to model the dose-response relationships between U-Cd and nine urine markers.

RESULTS

Spearman's rank correlation showed that NAG, ALP, RBP, β₂-MG and MT were significantly associated with U-Cd for both cre-corrected and observed data. Generally, NAG correlated best with U-Cd among the nine biomarkers studied, followed by ALP and MT. In the un-corrected model and cre-adjusted model, the regression coefficients and R² of nine biomarkers were larger than the corresponding values in the cre-corrected model, indicating that the use of observed data was better for investigating the relationship between biomarkers and U-Cd than cre-corrected data.

CONCLUSIONS

Our results suggest that NAG, MT and ALP in urine were better biomarkers for long-term environmental cadmium exposure assessment among the nine biomarkers studied. Further, data without normalization with creatinine show better relationships between cadmium exposure and renal dysfunction.

Urine β 2-Microglobolin in the Patients with Congenital Heart Disease

BACKGROUND

This study aimed to evaluate the renal tubular function in the patients with congenital heart disease using β2-microglobulin.

METHODS

In this case-control study, based on oxymetry, the patients with congenital heart disease were divided into two groups of cyanotic (n=20) and acyanotic (n=20). Congenital heart disease was diagnosed by echocardiography. Healthy individuals within the same age and sex groups were used as controls. Na(+), β2-micro globulin, creatinine (Cr), and β2-microglobulin/Cr ratio were measured in random urine samples and the results were compared to the same parameters in the control group using Tukey, One-Way ANOVA, and X(2) tests.

RESULTS

Based on the study results, urine sodium in the patients with cyanotic heart disease was significantly different from that of the controls (P=0.023). The results also revealed a significant difference between the two groups with congenital heart disease regarding urine β2-microglobulin (P=0.045). In addition, the patients with cyanotic heart disease were significantly different from those with acyanotic heart disease and the controls regarding urine β2-micro globulin/Cr ratio (P=0.012 and P=0.026, respectively).

CONCLUSIONS

The results of this study demonstrated that renal tubular dysfunction began in the patients with congenital heart disease, especially in those with cyanotic congenital heart disease. Besides, early diagnosis before cardiac surgery leads to better control of renal tubular disease.

Association of past diseases with levels of cadmium and tubular dysfunction markers in urine of adult women in non-polluted areas in Japan

BACKGROUND AND OBJECTIVES

Whereas information has been accumulating on the association of anemia and other diseases with cadmium (Cd) burden, histories of past diseases of the examinees are often not taken in account when the results of health examination are evaluated for cadmium exposure-related health effects on general populations. The present study was initiated to examine the possible association of previous diseases with Cd exposure parameters, taking advantage of compiled data on adult women.

METHODS

Data were cited from previous publications of this research group on Cd, α1-microglobulin (α1-MG), β2-microglobulin (β2-MG), N-acetyl-β-D-glucosaminidase (NAG) and urine density makers (i.e., creatinine and specific gravity) in the urine of more than 17,000 adult women in non-polluted areas in Japan. Information on previous disease history together with age and smoking habits was obtained by self-administered questionnaires, and 13,031 never-smoking women were selected for the present analyses. To compare the cases with disease history, control cases were randomly selected after stratification by 5 years of age at a ratio of one case to three controls from those with no disease history; summation for all age strata made up the control groups for the disease group in concern. The random sampling to set up control groups was repeated three times in total. The difference between the disease group and control groups was considered valid in cases the difference was statistically significant (p ≦ 0.05), in all three cases after correction (or non-correction) for urine density, and the same results were obtained when compared with the three different control groups.

RESULTS

In the anemia group, Cd-U was higher over corresponding three control groups, although none of α1-MG-U, β2-MG-U or NAG-U showed significant changes. In the diabetes mellitus group, NAG-U was higher than in the controls, but such differences were not observed in Cd-U or β2-MG-U. The elevation in α1-MG-U was not reproducible. In the case of the hypertension group, the elevations in Cd-U, α1-MG-U, and β2-MG-U were observed, but changes in NAG-U could not be confirmed. In the analysis of dose-response relationship, the diabetes mellitus group showed increases in the slope for β2-MG-U and in the intercept for NAG-U. No changes in dose-response relationship were observed in other disease groups as compared with the corresponding control groups.

CONCLUSIONS

Care should be taken in evaluating Cd-related health examination results for those with history of diseases such as hypertension, anemia and diabetes mellitus in particular.

Variation in benchmark dose (BMD) and the 95% lower confidence limit of benchmark dose (BMDL) among general Japanese populations with no anthropogenic exposure to cadmium

BACKGROUND

The use of benchmark dose (BMD) and the 95% lower confidence limit of benchmark dose (BMDL) have been gaining popularity not only in experimental studies but also in epidemiological studies including those on toxicology of cadmium (Cd), a ubiquitous hazardous element in the environment. However, the reproducibility of BMD and BMDL values has seldom been examined.

OBJECTIVES

This study was initiated to determine whether consistent BMD and BMDL values are obtained for similar non-exposed populations, i.e., the populations with no anthropogenic exposure to Cd in a single nation of Japan.

METHODS

Cd (an exposure marker), α(1)-microglobulin (α(1)-MG), β(2)-microglobulin (β(2)-MG) and N-acetyl-β-D-glucosaminidase (NAG) (three effect markers of tubular dysfunction) levels in the urine of adult Japanese women from five previous publications of this study group were examined. Overall, data were available for 17,375 cases (in 16 prefectures) regarding Cd, α(1)-MG and β(2)-MG, and 6,409 cases (in ten prefectures) regarding NAG. The data were used to calculate BMD and BMDL values taking advantage of the hybrid approach (Budtz-Jǿrgensen et al. in Biometrics 57:698-706, 2001). It was possible to calculate BMD and BMDL values for α(1)-MG and β(2)-MG for all of the 16 prefectures with 17,375 cases, whereas the values for NAG were successfully calculated for nine prefectures with 5,843 cases.

RESULTS

The application gave BMD values of 1.92, 2.46 and 2.32 μg Cd/g cr for α(1)-MG, β(2)-MG and NAG, respectively, and BMDL values of 1.83, 2.32 and 2.09 μg Cd/g cr. Large inter-prefectural variations were observed in the BMD and BMDL; there was about fourfold difference both in BMD and in BMDL calculated for α(1)-MG and β(2)-MG in 16 prefectures, and the variation was greater (i.e., by about sevenfold) in BMD and BMDL for NAG in nine prefectures. A survey of relevant literature revealed variation in BMD and BMDL values of similar folds as observed in the present analyses in five studies of Japanese populations. Multiple regression analyses taking BMD or BMDL as a dependent variable and age, CR concentration and Cd concentration as independent variables showed both BMD and BMDL were significantly influenced by Cd concentration in cases of α(1)-MG and β(2)-MG, whereas BMD and BMDL for NAG was by CR.

CONCLUSIONS

Even when the analysis was conducted in a single nation, both BMD and BMDL for the Cd effect markers varied by ca. fourfold when examining α(1)-MG or β(2)-MG and the values varied by ca. sevenfold for NAG among Cd-non-exposed populations. The most influential factors in the study population may include urine density and Cd levels in the urine.

Low cadmium levels in urine of residents in two prefectures where cadmium levels in locally harvested brown rice are higher than in other prefectures in Japan

Recent publications in Japan suggest that Cd in river beds and locally harvested rice tend to be higher in seven prefectures in the north-eastern part on the coast of the Sea of Japan (the high-Cd zone). The present study was initiated to investigate the current level of exposure to Cd and possible health effects among local populations in the zone. Thus, levels of Cd and three tubular dysfunction markers [i.e., α(1)-MG, β(2)-MG, and N-acetyl-β-D-glucosaminidase (NAG)] were examined in urine of local residents (700 and 704 adult women, respectively) in two prefectures (prefecture 1 and prefecture 7), which were located in the north-east (prefecture 1) and south-west ends (prefecture 7) of the high-Cd zone. Urinary Cd levels [e.g., 0.99 and 0.78 μg/l as geometric mean (GM) for observed (non-corrected) values, respectively] in prefecture 1 and prefecture 7 were comparable to the levels in other parts of Japan (All Japan-A; 0.99 μg/l). Correspondingly, GM values for α(1)-MG (2.29 and 1.99 mg/l vs. 2.17 mg/l for All Japan-A) and for β(2)-MG (87 and 80 μg/l vs. 99 μg/l for All Japan-A) were not elevated, and NAG also stayed unchanged (2.89 and 2.87 units/l for prefecture 1 and prefecture 7, respectively). Evaluation in combination with the findings in other five prefectures in the zone suggests that Cd exposure is equal to the national average both in prefecture 1 and in prefecture 7, whereas Cd exposure appeared to be elevated in the central part of the zone. The observation appears to be on line with geographical location of the two prefectures that they are on the two ends of the zone of high natural Cd background.

Early biomarkers of cadmium exposure and nephrotoxicity

As the risks of cadmium (Cd)-induced kidney disease have become increasingly apparent, much attention has been focused on the development and use of sensitive biomarkers of Cd nephrotoxicity. The purpose of this review is to briefly summarize the current state of Cd biomarker research. The review includes overviews of the toxicokinetics of Cd, the mechanisms of Cd-induced proximal tubule injury, and mechanistic summaries of some of the biomarkers (N-acetyl-β-D-glucosamidase; β(2)-microglubulin, metallothionein, etc.) that have been most widely used in monitoring of human populations for Cd exposure and nephrotoxicity. In addition, several novel biomarkers (kidney injury molecule-1, α-glutathione-S-transferase and insulin) that offer the potential for improved biomonitoring of Cd-exposed populations are discussed.