TOXICOLOGICAL SCIENCES 97(1), 189–195 (2007)
doi:10.1093/toxsci/kfm016
Advance Access publication February 14, 2007
Estimation of Benchmark Dose for Pancreatic Damage in
Cadmium-Exposed Smelters
Li-Jian Lei,* Liang Chen,* Tai-Yi Jin,*,†,1 Monica Nordberg,‡ and Xiu-Li Chang*
*Department of Occupational Health, School of Public Health, Fudan University, Shanghai 200032, China; †Environmental Medicine;
Department of Public Health and Clinical Medicine, Umeå University, SE-90187 Umeå, Sweden; and ‡Institute of Environmental Medicine,
Karolinska Institutet, SE-171 77, Stockholm, Sweden
Received November 20, 2006; accepted December 13, 2006
The aim of this study was to estimate the benchmark dose
(BMD) for pancreas dysfunction caused by cadmium (Cd) exposure in smelters. Smelter workers who had been exposed to Cd
for more than 1 year and matching nonoccupationally exposed
subjects were asked to participate in this study. Urinary cadmium
(UCd) was used as a biomarker for exposure, serum insulin and
amylase were used as biomarkers for pancreatic effects. In this
study, serum insulin and amylase were lower in the smelter
workers than in the nonoccupationally exposed subjects. A significant dose-response relationship with UCd was displayed. BMDs
in terms of urinary Cd corrected for creatinine were calculated by
use of BMDS (version 1.3.2). The benchmark dose lower limit of
a one-sided 95% confidence interval (BMDL) for 10% excess risk
was also determined. It was found that the BMDL10 for serum
insulin and serum amylase was 3.7 and 5.3 mg/g Cr, respectively.
Compared to the BMDL for renal damage caused by Cd exposure,
identified by the effect biomarkers urinary b2-microglobulin, urinary N-acetyl-b-glucosaminidase, and urinary albumin (UALB),
it was shown that BMDL10 for serum insulin is the lowest among
all values and UALB gave the highest value (5.8 mg/g Cr). This
study indicates that Cd exposure can result in pancreatic dysfunction and the effect appears at lower urinary Cd level than renal
dysfunction. The endocrine function of the pancreas was affected
at lower urinary levels of Cd, compared to the exocrine function,
which was seen at higher urinary levels of Cd than those giving
rise to renal tubular dysfunction.
Key Words: cadmium exposure; benchmark dose; pancreas;
biomarker; renal; endocrine.
Cadmium (Cd) (CAS Reg. no. 7440-43-9) is a naturally
occurring component of the earth’s crust. Its physicochemical
characteristics e.g., low melting point and malleability explain
its wide use in industry and extensive environmental dispersed
(Verougstraete et al., 2002). Cd is a toxic metal of continuing
occupational and environmental concern which causes a variety
of adverse health effects. Cd has an extremely long biological
1
To whom Correspondence should be addressed. Fax: +86-21-64178160.
E-mail: [email protected].
half-life i.e., 20–30 years in humans, that essentially make it
a cumulative toxicant (WHO, 1992). Still the only effective
treatments for chronic Cd intoxication (Waalkes, 2000) is
either to decrease or to stop exposure to Cd. In mammals, Cd
preferentially accumulates in the liver, kidney, and reproductive systems which are the major target organs of Cd toxicity
(Swiergoz-Kowalewska, 2001; WHO, 1992). Biological monitoring of renal dysfunction caused by Cd has been performed
in China both in the general and in the occupational population
(Cai et al., 1995, 1998; Jin et al., 1999b, 2002; Nordberg et al.,
1997). Long-term exposure to Cd induces excretion of protein
and glucose in the urine. It was considered that the increase of
urinary glucose was related to a change in renal concentration
of Cd as an outcome of exposure to Cd. Jin et al. (1999a)
demonstrated that diabetic rats are more susceptible to Cd
nephrotoxicity than normal rats. However, pancreatic dysfunction, such as decrease in insulin production, can also result in
increased urinary glucose levels. Impaired insulin action or
lack of insulin secretion is a well-known cause of the metabolic
derangement characteristics of diabetes mellitus (Hardikar,
2004; Schwitzgebel, 2001). In spite of the fact that Cd accumulates in the pancreas (Jerome, 1981) and that a decrease in
pancreatic function is one of the characteristics of Itai-Itai
disease, there have been few investigations of the effects of Cd
on pancreas (Ghafghazi and Mennear, 1973). The pancreas is
a unique organ because the endocrine pancreas, composed of
the hormone-producing cells, is located within the exocrine
part of the tissue (Hardikar, 2004). The endocrine part consists
of four different cell types which are organized as islets of
Langerhans with a core of beta cells surrounded by alpha, delta,
and PP cells. Insulin is the key regulator of the glucose homeostasis. The exocrine part secretes digestive enzymes which play
key role in metabolism of glucose. Animal studies have shown
that Cd can decrease both the endocrine and the exocrine
pancreatic function (Ghafghazi and Mennear, 1973; Linari
et al., 2001). In rats and mice, Cd damages pancreatic b cells,
reduces glucose tolerance, and is diabetogenic (Ghafghazi and
Mennear, 1975; Ithakissios et al., 1975). The decrease of serum
insulin was found in rats given drinking water containing 100
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190
LEI ET AL.
and 200 mg/l for 30 days, with no change of the levels of blood
glucose (Lei et al., 2005). A significant glucose intolerance was
found in rats administrated Cd sc with 1.0 and 2.0 mg/kg bw for
7 days, corresponding with the decrease of serum insulin in 2.0
mg/kg bw (Lei et al., in press). But little is known about the
effect of Cd on human pancreas and no study on biomarkers of
pancreatic damage has not been reported relative to Cd
exposure has been reported.
In the present study, we used the benchmark dose (BMD)
approach to characterize the relationship between urinary Cd
and pancreatic damage, as well as renal dysfunction. For this
purpose, serum insulin (EI Beitune et al., 2005) and serum
amylase (Moridani and Bromberg, 2003) were measured as
indicators of pancreatic function. Urinary cadmium (UCd) was
determined in all the subjects. Renal biomarkers such as urinary
N-acetyl-b-glucosaminidase (UNAG), urinary b2-microglobulin
(UB2M), and urinary albumin (UALB) were also determined.
METHODS
Study population. One hundred and three workers (85 males and 18
females; aged 23–55 years) in a smelter located in east Hunan Province, Central
China, were selected to be the exposed population and constituted the Cdexposed group. Thirty-six healthy persons (29 males and 7 females) working in
a hospital and with no exposure to Cd were selected as nonoccupationally
exposed (reference) subjects and constituted the control group (nonoccupationally exposed). Twenty-five females, 18 of occupationally exposed and 7 of
nonoccupationally exposed, were in the present study. The selection criteria of
exposure were comparable with regard to socioeconomic status, employment at
the present place of work for at least 1 year with no disease or nonoccupational
exposure related to Cd. The number of smokers in the exposed group and
nonoccupationally exposed group was 61 and 14, respectively. There were no
significant differences in the smoking habits between the two groups by
statistical analysis. A detailed questionnaire including data on age, marital
status, smoking habits, alcohol consumption, and professional and medical
history from each subject was evaluated by well-trained interviewers.
Ethical permission was given by the Ethics Committee of Fudan University
and the study was performed with permission for the local authority. Informed
consent was attained for each participant.
Collection and treatment of biological samples. Venous blood was drawn
into anticoagulant and metal-free tube after 10–12 h of fasting to determine
blood cadmium (BCd) and glucose, serum insulin, and serum amylase activity.
Glucose oxidase method (Roche Glucotrend 2) was used to measure glucose.
BCd concentrations were measured by graphite-furnace atomic absorption
spectrometry using standard addition as described by Jin et al. (2002). Serum
insulin levels were determined by radioimmunoassay. The intra- and interassay
coefficients of variation were of 8.1 and 6.8%, respectively. Serum amylase
activity was determined by an assay method measuring the starch digestive
power using the starch iodine reaction (Demeester et al., 1997).
Urine samples were collected from all participants and tested for glucose,
which is not normally present and divided into three aliquots. The first was
acidified with concentrated nitric acid and was used for assay Cd; the second
was used to measure B2M after being made alkaline; and the third was used to
determine NAG and creatinine. UCd concentrations were measured by
graphite-furnace atomic absorption spectrometry described by Jin et al.
(2002). UNAG was measured as described by Tucker et al. (1980). UB2M
and UALB were analyzed by ELISA. Creatinine was measured by the Jaffe
reaction method. All urinary parameters were adjusted for creatinine in urine
(Jin et al., 2002).
BMD method. The BMD was defined by Crump (1984) as a lower
confidence limit corresponding to a moderate increase in risk (1–10%) above
the background risk. Crump suggested that the BMD could be used to replace
the no observed adverse effect level (NOAEL) or the lowest observed adverse
effect level (LOAEL) for noncarcinogenic effects in the regulatory process for
setting acceptable daily intakes for human exposure to potentially toxic substances (Gaylor et al., 1998). The main advantage with the BMD methodology
is that it uses all dose-response data from a study (Falk et al., 2003). Gaylor
et al. (1998) redefined the BMD as the point estimate of the dose corresponding
to a specified low level of risk and suggested that the concept of BMDL (lower
confidence limit of benchmark dose) could be used as a replacement for the
NOAEL or LOAEL (Gaylor et al., 1998). The BMDL resulting from this
approach is more accurate than a NOAEL or LOAEL. The BMDL is typically
calculated using the lower 95% confidence limit on the dose-response curve to
a 1–10% level if risk above the background. A 10% benchmark response level
(BMR) is conventionally used for dichotomous end points because it is at the
low end of the observable range for many common study designs.
In the present study, UCd concentration was used as the dose parameter.
During long-term low-level exposure, there is good agreement between average
kidney Cd burden or body Cd burden and the average daily urinary Cd
excretion (Friberg et al., 1985a; WHO, 1992). We used the BMDL to estimate
the lower confidence limit of the population critical concentration of UCd.
The BMD is the dose of UCd that results in an increased probability of
abnormal test performance by a BMR in the study. The BMR considered in the
study was 10% extra risk. The median UCd concentrations of different UCd
groups (1.43, 3.04, 6.72, 15.18 lg/g Cr, respectively) were used to estimate the
values of the BMD10 and BMDL10 for different indicators of renal and pancreatic dysfunction. The BMDL was specified as the lower 95% confidence
limit on the dose corresponding to the BMR. The goodness of fit was determined through application of several dose-response models. The BMD analysis
for serum insulin was used as an example to explain the models selected.
p values 0.05 can be found in all models (Table 1), providing an initial
indicator of goodness of fit. The BMDL from the log-logistic and log-dose
probit models were lower than those of logistic and probit models (Table 1).
However, according to these results, the BMDL of insulin was 0.19 and 0.23
lg/g Cr, respectively (showed in Fig. 1). In fact, these values were too low to be
accepted as a critical exposure levels. We have used logistic models to estimate
BMDL value for Cd-induced renal dysfunction (Chen et al., 2006; Jin et al.,
2002). In order to compare with the pervious results, we chose the logistic
model for application in the present study. The probit model has been used to
calculate BMDL in this study, which gives similar results to logistic models
(data not shown). Thus, the unconstrained logistic linear regression model was
used as a model in this present study. The BMDL was specified as the lower
95% confidence limit on the dose corresponding to the BMR in the study and
the smooth option of the model was applied.
The equation of this model is
PðdÞ ¼ 1=½1 þ expðb0 b1 3dÞ;
where P(d) is the probability of an adverse effect, d is the dose (as UCd), and
b0 and b1 are coefficients derived from the data.
TABLE 1
The Parameters of Different Models for BMD and BMDL
When Serum Insulin Was Taken as an Indicator of
Pancreatic Dysfunction
Indicator
Insulin
Insulin
Insulin
Insulin
BMD
BMDL
Model
AIC
p value
5.3
5.0
1.2
1.2
3.7
3.4
0.2
0.2
Logistic
Probit
Log-logistic
Log-dose probit
134.98
134.87
133.66
133.62
0.50
0.53
0.96
0.98
191
ESTIMATION OF BMD
Logistic Model with 0.95 Confidence Level
A
Logistic
BMD Lower Bound
0.7
0.7
0.6
0.6
0.5
0.5
prevlance
prevlance
Probit Model with 0.95 Confidence Level
B
0.4
0.3
Probit
BMD Lower Bound
0.4
0.3
0.2
0.2
0.1
0.1
BMDL
0
0
2
BMD
4
6
BMDL
0
8
10
12
14
16
0
2
BMD
4
Ucd (µg/g Cr)
Log-Logistic Model with 0.95 Confidence Level
C
0.6
0.7
0.6
0.5
0.4
0.3
0.1
0
BMD
2
4
6
8
10
14
16
12
14
Probit
BMD Lower Bound
0.3
0.1
0
12
0.4
0.2
BMDL
10
0.5
0.2
0
8
Log-Probit Model with 0.95 Confidence Level
prevlance
prevlance
D
Logistic
BMD Lower Bound
0.7
6
Ucd (µg/g Cr)
16
BMDL
0
Ucd (µg/g Cr)
BMD
2
4
6
8
10
12
14
16
Ucd (µg/g Cr)
Fig. 1. Different models were used to estimate the BMD and BMDL for serum insulin. (a) The logistic model curve, (b) the probit model curve, (c) the loglogistic model curve, and (d) the log-probit model curve. The models are all good fit (p 0.05). The BMDL of serum insulin estimate by log-logistic and log-dose
probit models are lower than that of logistic and probit models. They are outliers dependent on the empirical observation and the BMDL estimated by logistic and
probit models are closely.
The BMDs from this work are not directly useful for environmental
regulation since they are given as biomarker levels, and not as ambient
exposure concentrations.
Comparison of the Serum Insulin, Amylase and Urinary
NAG, B2M, and ALB at Different UCd Levels
Statistical analysis. The data were expressed in terms of geometric means
(GM) and 95% confidence interval for GM and entered into a database using
SPSS (version 11.0) statistical analysis software. For comparisons between
more than two groups, one-way ANOVA was used. The criterion for significance was set at p < 0.05. The dichotomous dose-response models in the
United States Environmental Protection Agency BMD software (version 1.3.2)
were used in this work.
One of the biomarkers for exposure to Cd is UCd corrected
for creatinine. The degree of exposure was ranked as follows:
<2, 2-, 5-, 10-lg/g Cr (Jin et al., 2002). The levels of serum
insulin and amylase were inversely correlated with UCd (Table 4).
No significant change in blood glucose was found in the
different UCd groups. The frequency of urinary glucose in the
RESULTS
Body Burden of Cd
Data in Table 2 show the Cd body burden, which was
estimated by UCd, and BCd, in the nonoccupationally exposed
group and the smelters. The BCd and UCd in smelters were
significantly higher than in the nonoccupationally exposed
group.
Subjects were further divided according to smoking habits.
The results (Table 3) show that the average BCd and UCd
concentrations of smokers were significantly higher than those
of nonsmokers in the respective Cd exposure groups.
TABLE 2
Concentration of Cd in Blood (BCd) and in Urine (UCd) in
Nonoccupationally Exposed Group and Exposed Group
Expressed as mg/l and mg/g Cr, Respectively
Group
Nonoccupationally exposed
Exposed
n
BCd (lg/l)
UCd (lg/g Cr)
36
103
3.22 (2.31–4.47)
7.58** (6.24–9.23)
1.67 (1.26–2.22)
3.09** (2.49–3.84)
Note. UCd was adjusted for creatinine. Data are expressed as GM (and 95%
confidence intervals of GM).
*p < 0.05, **p < 0.01, significant difference from nonoccupationally
exposed group.
192
LEI ET AL.
TABLE 3
BCd and UCd Level in Smoker or Nonsmoker in Exposed and Nonoccupationally Exposed Group
Group
Number
Exposed
Smokers
Nonsmokers
Smokers
Nonsmokers
Nonoccupationally exposed
BCd (lg/l)
13.06ab
3.60
6.89a
1.98
61
42
14
22
UCd (lg/g Cr)
(10.57–16.14)
(2.88–4.51)
(4.60–10.30)
(1.36–2.88)
3.50ab
2.56
1.66
1.71
(2.55–4.79)
(1.93–3.41)
(1.12–2.65)
(1.11–2.65)
Note. Data are expressed as GM (and 95% confidence intervals of GM).
a
Compared with nonsmokers in same group, p < 0.01.
b
Compared with nonsmokers of nonoccupationally exposed group, p < 0.01.
2-lg/g Cr UCd was statistically higher than that in <2-lg/g Cr
UCd group (Table 4). Table 5 shows that with the increase of
UCd, all urinary biomarkers including UNAG, UB2M, and
UALB increase dramatically.
Because age might affect Cd accumulation and effects,
Pearson correlation was used to explore the relationship
between age and renal dysfunction. The coefficient between
UB2M, UNAG, UALB, and age was 0.087, 0.127, and 0.091
(p > 0.05) in all subjects, respectively. The relationship
between age, serum insulin, and amylase was examined as
well. The coefficient between serum insulin, serum amylase,
and age was 0.076 and 0.041 (p > 0.05) in all subjects.
Prevalence of Low Insulin, Low Amylase, HyperNAGuria,
HyperB2Muria, and HyperALBuria at Different Cd
Concentrations in Urine
We defined the normal cutoff point based on the 10th
percentile value for serum insulin (6.74 lIU/ml) and serum
amylase (77.98 U) in the nonoccupationally exposed group.
Values below the defined cutoff points were defined as
abnormal (positive) of the pancreatic function. The cutoff
point of serum insulin in this study is close to lower limit of
normal reference value of our country (7 lIU/ml). In the
nonoccupationally exposed group, a 90th percentile value was
the normal cutoff point for UNAG, UB2M, and UALB. Values
higher than the normal cutoff point were defined as the renal
abnormal function (Chen et al., 2006). The cutoff points of
UNAG, UB2M, and UALB were 10.72 U/gCr, 162.55 lg/g Cr,
and 16.79 mg/g Cr, respectively. The prevalence of low insulin,
low amylase, hyperNAGuria, hyperB2Muria, and hyperALBuria
at different concentrations of Cd in urine were calculated in all
subjects (Table 6). This finding demonstrates that there is
a significantly increased prevalence of low insulin, low
amylase, hyperNAGuria, hyperB2Muria, and hyperALBuria
with the increase of urinary Cd.
The Values of BMD and BMDL of UCd for Different
Indicators
The estimated parameters and corresponding values of
BMDL10 are presented in Table 7. The chi-square values and
p values provide a goodness-of-fit measure of the models. We
find that when serum insulin is used as an indicator of
pancreatic dysfunction, the BMDL10 is 3.7 lg/g Cr, which is
lower than the estimated values for UB2M and UNAG (3.8 and
4.1 lg/g Cr, respectively), common biomarkers of Cd-induced
renal tubular dysfunction.
DISCUSSION
Cd is a nonessential metal that accumulates in the human
pancreas. There are several studies documenting nonnegligible
concentrations of Cd in the pancreas (Ghafghazi and Mennear,
1973; Jerome, 1981). The concentrations of Cd in pancreas are
usually below 2 mg/kg wet weight in samples obtained from
humans living in the United States and Europe (Elinder et al.,
TABLE 4
Cd-Induced Variation in Serum Insulin, Serum Amylase, Blood Glucose, Positive Ratio of Urinary Glucose in Different Groups X±s
UCd (lg/g Cr)
02510-
Number
55
56
16
12
Blood glucose (mM)
4.689
4.577
4.508
4.511
±
±
±
±
0.429
0.429
0.332
0.252
*p < 0.05, **p < 0.01, significant difference from UCd < 2 lg/g Cr.
Percent with urinary
glucose (incidence)
0.00
7.14
0.00
0.00
(0)
(4)
(0)
(0)
Serum insulin (lIU/ml)
11.87
9.90
8.39
6.62
±
±
±
±
6.43
5.01
3.33*
2.14**
Serum amylase (U)
153.60
154.77
147.04
116.76
±
±
±
±
55.28
59.98
81.50
49.29*
193
ESTIMATION OF BMD
TABLE 5
Cd-Induced Variation in Biomarker of Renal Dysfunction in Population
UCd (lg/g Cr)
Number
02510-
UNAG (U/gCr)
55
56
16
12
4.75
4.64
8.26**
8.22**
UB2M (lg/g Cr)
(4.68–6.87)
(4.54–7.07)
(6.72–11.99)
(6.09–14.47)
53.18
69.04
141.03**
118.65**
UALB (mg/g Cr)
(48.26–95.17)
(69.78–125.66)
(106.92 -269.41)
(42.29–453.40)
5.90
6.15
8.82*
10.49**
(5.63–8.89)
(5.82–9.08)
(5.16–20.26)
(7.60–18.60)
Note. Values in brackets indicate 95% confidence intervals of GM.
*p < 0.05, **p < 0.01, significant difference from UCd < 2 lg/g Cr.
1976; Tipton and Cook, 1963) and 2–3 mg/kg in Japanese
(Friberg et al., 1985b).
It is well recognized that the renal damage is the mainly
adverse effect related to Cd exposed (WHO, 1992), and the
concentration of Cd in kidney gives rise to the first irreversible
damage thus rendering the kidney as the critical organ in Cd
exposure. The effects of Cd on the kidney have been of interest
for the toxicologists for many years. The increase of urinary
glucose related to Cd exposure and the accumulation of Cd in
the pancreas has so far only been of limited interest. Few
reports about the effects and/or damage of pancreas caused by
xenobiotics can be found. Intact function of the pancreas is
essential for the production of a number of hormones and
digestive enzymes, and for maintaining an even blood sugar
level. It is thus important to not underestimate the value of
intact pancreatic function.
Until now, the major concern from Cd exposure has been the
concentration of Cd in urine and its relationship to renal
dysfunction (Bernard et al., 1979; Buchet et al., 1990; Jin et al.,
1999a; Nordberg et al., 1997; WHO, 1992). UNAG and UB2M
have been suggested as sensitive biomarkers of renal tubular
dysfunction. UALB is biomarker for glomerular damage. It
suggested that Cd levels in the kidneys and in urine should be
kept below 2.5 lg/g Cr in order to avoid clinical disease (Jarup
et al., 1998).
Insulin is normally secreted by the beta cells of the pancreas
in response to an increase in blood glucose for regulation of
glucose levels. In normal conditions, the stimulus for insulin
secretion is an increase of blood glucose. In this study, the
blood glucose levels did not differ significantly with different
levels of UCd, while serum insulin did. It is indicated that the
serum insulin might be a sensitive index of pancreatic damage
caused by Cd. The release of insulin is a calcium-dependent
phenomenon. A rapid influx of calcium ions can initiate insulin
secretion. But Cd has been shown in laboratory animals to
inhibit stimulation of amylase secretion by the activity of
blocking calcium channel (Linari et al., 2001). This may lead
to speculation that Cd can influence the biosynthesis and
release of insulin.
Although amylase is present in saliva of some mammals,
including humans, the major source of amylase in all species is
pancreatic secretions. There was an excellent correlation
between pancreatic and total amylase in obese Zucker rats
(Majid and Irvin, 2003). At a lower concentration, it is a strong
inhibitor of stimulated pancreatic secretion of amylase acting
directly, and possibly indirectly, on the acinar cell (Linari et al.,
TABLE 6
Prevalence of Low Insulin, Low Amylase, HyperNAGuria, HyperB2Muria and HyperALBuria at Different Levels of
UCd Levels in all Subjects (%)
Insulin
UCd (lg/g Cr)
þ/
02510v2
p
Linear trend
v2
p
6/49
11/45
5/11
5/7
Amylase
%
12.24
19.64
31.25*
41.67**
10.854
0.013
10.759
0.001
þ/
3/52
5/51
3/13
4/8
UNAG
%
5.45
8.93
18.75
33.33**
9.216
0.027
8.129
0.004
*p < 0.05, **p < 0.01, significant difference from UCd < 2 lg/g Cr.
þ/
5/50
5/51
6/10
5/7
UB2M
%
9.09
8.93
37.50**
41.67**
16.075
0.001
11.606
0.001
þ/
4/51
9/47
6/10
5/7
UALB
%
7.27
16.07
37.50**
41.67**
13.488
0.004
12.604
0.000
þ/
%
2/53
3/53
3/13
4/8
3.64
5.36
18.75
33.33
13.861
0.003
11.365
0.001
194
LEI ET AL.
TABLE 7
BMDL Estimates of UCd (mg/g Cr) for Urinary Indicators of
Renal Dysfunction and Serum Indicators of Pancreatic
Dysfunction
Indicators
n
b0
b1
Insulin
UB2M
UNAG
Amylase
UALB
139
139
139
139
139
1.95
2.25
2.48
2.84
3.32
0.12
0.15
0.16
0.15
0.18
BMD10 BMDL10
5.3
5.2
5.5
7.4
7.8
3.7
3.8
4.1
5.3
5.8
AIC
v2
p values
134.98
123.02
112.18
92.22
76.32
1.40
3.62
3.94
0.54
1.16
0.50
0.16
0.14
0.80
0.56
Note: Model, PðdÞ ¼ 1=½1 þ expðb0 b1 3 dÞ. Excess risk at BMD is
0.10. p values were obtained from the chi-square test, with the Pearson
goodness-of-fit test; if p > 0.05, then the equation is a good fit.
BMDL for renal dysfunction. The endocrine dysfunction
develops earlier than the exocrine dysfunction. In this study,
insulin and amylase were used as biomarkers of endocrine and
exocrine effects. Further researches into the precise role of the
sensitive biomarkers and the approaches of BMD or BMDL
are warranted to increase our understanding of the effects of
cadmium toxicology.
ACKNOWLEDGMENTS
This study was supported by the National Key Research and Development
Program of China (No. 2002 CB 512905). The authors certify that all research
involving human subjects was done under full compliance with all government
policies and the Helsinki Declaration.
REFERENCES
2001). Insulin may play a major role in the control of pancreatic amylase biosynthesis. Severe insulin resistance was associated with impairment of amylase gene expression (Trimble
et al., 1986). Thus, it seems that insulin alterations may
influence pancreatic function through several machanisms.
This study documents the dose-response relationship between UCd and both serum insulin and amylase, as well as
between UCd and indicators of renal dysfunction. The BMD
procedure was used to calculate the critical concentration of
UCd from population data. The BMDL value for UB2M is
3.8 lg/g Cr. The results are in agreement with several previous
studies from Japan (Nogawa et al., 1992). Abe et al. (2001)
used path analysis and mathematically proved that the
excretion of B2M was the most sensitive urinary indicators
of the early stage of chronic Cd-induced renal dysfunction.
Surprisingly in the study it was found that if serum insulin is
taken as an indicator of pancreatic dysfunction, the BMDL
(3.7 lg/g Cr) is lower than the BMDL value for UB2M. These
results suggest that Cd-induced pancreatic dysfunction may
appear earlier or at the same time as renal damage. It suggests
that the serum insulin could be regarded as a sensitive biomarker of Cd impact. The decrease of serum amylase also
appeared in smelters after long-term and low-dose Cd exposure. The BMDL for serum amylase is higher than that for
serum insulin. It can be concluded that the exocrine dysfunction is later than the endocrine, partly because insulin can
influence the biosynthesis of amylase.
Recently, the critical concentration of Cd in urine has been
suggested to have been overestimated (Jarup et al., 1998; Jin
et al., 2004). The obtained BMDL value is lower than that in
previously reported studies. The value of BMDL lies in the
range of 3.7–5.8 lg/g Cr in the present study. This range
implied that there is an increased 10% prevalence of pancreatic
dysfunction in this occupational population.
In conclusion, this study showed that more than 1-year
exposure to Cd can decrease the serum levels of insulin and
amylase. It was also shown that BMDL of UCd related to
a decrease of the serum insulin is lower than comparable
Abe, T., Kobayashi, E., Okubo, Y., Suwazono, Y., Kido, T., Shaikh, Z. A., and
Nogawa, K. (2001). Application of path analysis to urinary findings of
cadmium-induced renal dysfunction. J. Environ. Sci. Health A Tox. Hazard.
Subst. Environ. Eng. 36, 75–87.
Bernard, A., Buchet, J. P., Roels, H., Masson, P., and Lauwerys, R. (1979).
Renal excretion of protein and enzymes in workers exposed to cadmium.
Eur. J. Clin. Invest. 9, 11–22.
Buchet, J. P., Lauwerys, R., Roels, H., Bernard, A., Bruaux, P., Claeys, F.,
Ducoffre, G., de Plaen, P., Staessen, J., Amery, A., et al. (1990). Renal effects
of cadmium body burden of the general population. Lancet 336, 699–702.
Cai, S., Yue, L., Jin, T., and Nordberg, G. (1998). Renal dysfunction from
cadmium contamination of irrigation water: Dose-response analysis in
a Chinese population. Bull. World Health Organ. 76, 153–159.
Cai, S., Yue, L., Shang, Q., and Nordberg, G. (1995). Cadmium exposure
among residents in an area contaminated by irrigation water in China. Bull.
World Health Organ. 73, 359–367.
Chen, L., Jin, T., Huang, B., Nordberg, G., and Nordberg, M. (2006). Critical
exposure level of cadmium for elevated urinary metallothionein—an
occupational population study in China. Toxicol. Appl. Pharmacol. 215,
93–99.
Crump, K. S. (1984). A new method for determining allowable daily intakes.
Fundam. Appl. Toxicol. 4, 854–871.
Demeester, J., Dekeyser, P. M., Samyn, S., Verhamme, I., Sierens, W., and
Lauwers, A. (1997). Assays. In Pharmaceutical Enzymes. (A. Lauwers and
S. Scharpé, Eds.), pp. 401. Marcel Dekker, New York.
El Beitune, P., Duarte, G., Foss, M. C., Montenegro, R. M., Jr, Quintana, S. M.,
Figueiro-Filho, E. A., and Nogueira, A. A. (2005). Effect of maternal use of
antiretroviral agents on serum insulin levels of the newborn infant. Diabetes
Care 28, 856–859.
Elinder, G.-G., Kjellstrom, T., Friberg, L., Lind, B., and Linnman, L. (1976).
Cadmium in kidney cortex, liver, and pancreas from Swedish autopsies.
Arch. Environ. Health 31, 292–302.
Filipsson, A. F., and Victorin, K. (2003). Comparison of available benchmark
dose softwares and models using trichloroethylene as a model substance.
Regul. Toxicol. Pharmacol. 37, 343–355.
Friberg, L., Elinder, C. G., Kjellstrom, T., and Nordberg, G. F. (1985).
Cadmium and Health: A Toxicological and Epidemiological Appraisal. Vol. I
Exposure, Dose, and Metabolism, CRC Press, Inc Boca Raton, FL. pp. 161.
Friberg, L., Elinder, C. G., Kjellstrom, T., and Nordberg, G. F. (1985).
Cadmium and Health: A Toxicological and Epidemiological Appraisal.
Volume I. Exposure, Dose, and Metabolism, CRC Press, Inc Boca Raton, FL.
pp. 96–97.
ESTIMATION OF BMD
195
Gaylor, D., Ryan, L., Krewski, D., and Zhu, Y. L. (1998). Procedures for
calculating benchmark doses for health risk assessment. Regul. Toxicol.
Pharmacol. 28, 150–164.
Linari, G., Nencini, P., and Nucerito, V. (2001). Cadmium inhibits stimulated
amylase secretion from isolated pancreatic lobules of the guinea-pig.
Pharmacol. Res. 43, 219–223.
Ghafghazi, T., and Mennear, J. H. (1973). Effects of acute and subacute
cadmium administration on carbohydrate metabolism in mice. Toxicol. Appl.
Pharmacol. 26, 231–240.
Majid, Y. M., and Irvin, L. B. (2003). Lipase and pancreatic amylase versus
total amylase as biomarkers of pancreatitis: An analytical investigation. Clin.
Biochem. 36, 31–33.
Ghafghazi, T., and Mennear, J. H. (1975). The inhibitory effect of cadmium on
the secretory activity of the isolated perfused rat pancreas. Toxicol. Appl.
Pharmacol. 31, 134–142.
Moridani, M. Y., and Bromberg, I. L. (2003). Lipase and pancreatic amylase
versus total amylase as biomarkers of pancreatitis: An analytical investigation. Clin. Biochem. 36, 31–33.
Hardikar, A. A. (2004). Generating new pancreas from old. Trends. Endocrinol.
Metab. 15, 198–203.
Nogawa, K., Kido, T., and Shaikh, Z. A. (1992). Dose–response relationship for
renal dysfunction in a population environmentally exposed to cadmium.
IARC Sci. Publ. 118, 311–318.
Ithakissios, D. S., Ghafghazi, T., Mennear, J. H., Kessler, W. V. (1975). Effect
of multiple doses of cadmium on glucose metabolism and insulin secretion in
the rat. Toxicol. Appl. Pharmacol. 31, 143–149 (Abstract).
Jarup, L., Berglund, M., Elinder, C. G., Nordberg, G., and Vahter M. (1998).
Health effects of cadmium exposure—a review of the literature and a risk
estimate. Scand. J. Work Environ. Health 24(Suppl. 1), 1–50.
Jin, T., Nordberg, M., Frech, W., Dumont, X., Bernard, A., Ye, T. T., Kong, Q.,
Wang, Z., Li, P., Lundstrom, N. G., et al. (2002). Cadmium biomonitoring
and renal dysfunction among a population environmentally exposed to
cadmium from smelter in China (ChinaCad). Biometals 15, 397–410.
Jin, T., Nordberg, G., Sehlin, J. O., Wallin, H., and Sandberg, S. (1999a). The
susceptibility to nephrotoxicity of streptozotocin-induced diabetic rats
subchronically exposed to cadmium chloride in drinking water. Toxicology
142, 69–75.
Jin, T., Nordberg, G., Wu, X., Ye, T., Kong, Q., Wang, Z., Zhuang, F. and
Cai, S. (1999b). Urinary NAG isoenzymes as biomarker of renal dysfunction
caused by cadmium in a general population. Environ. Res. 81,
167–173.
Jin, T., Wu, X., Tang, Y., Nordberg, M., Bernard, A., Ye, T., Kong, Q.,
Lundstrom, N. G., and Nordberg, G. F. (2004). Environment epidemiological
study and estimation of benchmark dose for renal dysfunction in a cadmiumpolluted area in China. Biometals 17, 525–530.
Nordberg, G. F., Jin, T., Kong, Q., Ye, T., Cai, S., Wang, Z., Zhuang, F. and Wu, X.
(1997). Biological monitoring of cadmium exposure and renal effects in
a population group residing in a polluted area in China. Sci. Total Environ.
199, 111–114.
Nriagu, J. O. (1981). Cadmium in the Environment. Canada Centre for Inland
Waters Burlington, Ontario, Canada, pp. 624.
Schwitzgebel, V. M. (2001). Programming of the pancreas. Mol. Cell.
Endocrinol. 20, 99–108.
Swiergoz-Kowalewska, R. (2001). Cadmium distribution and toxicity in tissues
of small rodents. Microsc. Res. Techniq. 55, 208–222.
Tipton, I. H., and Cook, M. J. (1963). Trace elements in human tissues. II.
Adults subjects from the United States. Health Phys. 9, 103–145.
Trimble, E. R., Bruzzone, R., and Belin, D. (1986). Insulin resistance is
accompanied by impairment of amylase-gene expression in the exocrine
pancreas of the obese Zucker rat. Biochem. J. 237, 807–812.
Tucker, S. M., Boyd, P. J. R., and Thompson, A. E. (1980). Automated assay of
N-acetyl-b-glucosaminidase in normal and pathological human urine. Clin.
Chim. Acta 62, 333–339.
Verougstraete, V., Lison, D., and Hotz, P. (2002). A systematic review of
cytogenetic studies conducted in human populations exposed to cadmium
compounds. Mutat. Res. 511, 15–43.
Lei, L. J., Jin, T. Y., and Zhou, Y. F. (2005). Effects of cadmium on levels of
insulin in rats. Wei Sheng Yan Jiu 34, 394–396 (In Chinese).
Waalkes, M. P. (2000). Cadmium carcinogenesis in review. J. Inorg. Biochem.
79, 241–244.
Lei, L. J., Jin, T. Y., and Zhou, Y. F. (2007). Insulin expression in rats exposed to
cadmium. Biomed. Environ. Sci. (in press).
WHO/IPCS. (1992). Environmental Health Criteria Document 134 Cadmium.
WHO, Geneva.