Jpn J Clinand
Ecol
No.1 2014）（Vol.23
Relationship between dioxin compounds
hepatic
disorderwith obesity in Japanese adult males

49

Original Article

Relationship between dioxin compounds andhepatic disorder with obesity in Japanese adult males
Yoji Mochida1) Kenichi Sakurai2) Yoshiharu Matsuno1, 3)
Shingo Ochiai1, 3) Masahiro Watanabe3) Chisato Mori1, 3)
1) Department of Bioenvironmental Medicine, Graduate School of Medicine, Chiba University
2) Clinical Cell Biology and Medicine, Graduate School of Medicine, Chiba University
3) Center for Preventive Medical Sciences, Chiba University

Abstract
Although exposure to high levels of dioxins was reported to be related to hepatic disorders including glycolipid
metabolism abnormalities, the impact of typical low-level environmental dioxin exposure on non-alcoholic fatty
liver disease (NAFLD) remains unclear. To examine the relationship between suspected NAFLD and dioxin
exposure, we measured the blood levels of 29 dioxin congeners and isomers in 68 adult male volunteers with nohistory of viral hepatitis or alcoholism. Study participants were recruited from 2006 to 2008 and subjected to ahealth checkup and a battery of biochemical tests, including measurement of dioxin levels. The participants were
determined to be at high risk of NAFLD on the basis of high body mass index (BMI ≥ 25 kg/m2) and elevated bloodlevels of alanine aminotransferase (ALT ≥ 36 IU/ℓ). In this study, 11 participants were classified as having
NAFLD (16.2% of the total recruited number). A higher concentration of 3,3’,4,4’-tetrachlorobiphenyl (PCB77)
was detected in the blood of those with suspected NAFLD, with no other significant differences found in levels ofother dioxins, compared to the levels in participants who were considered not to be at risk of NAFLD. We used alogistic regression analysis taking into account age, smoking habit, and levels of total cholesterol, triglycerides,
high-density lipoprotein cholesterol, and hemoglobin A1c to estimate the impact of elevated blood PCB77 levels on
the risk of NAFLD. We observed an increased risk of NAFLD in participants with elevated PCB77 levels, indicatingthat even low-level exposure to PCB77 may contribute to NAFLD development.
( Jpn J Clin Ecol 23 : 49－60, 2014)《Key words》Dioxins, 3,3’,4,4’-tetrachlorobiphenyl (PCB77), non-alcoholic fatty liver disease (NAFLD)

Ⅰ．Introduction

environ­ment on human health, reflecting the

There are growing concerns about the adverse

increasing appreciation of their tendency to remain in

effects of toxic chemical compounds in thethe tissues and to accumulate over time. These toxic

Received: May 8, 2014 Accepted June 18, 2014
Reprint Requests to Chisato Mori, Department of Bioenvironmental Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba
260-8670, Japan2 ) Present affiliation: Department of Endocrinology and Metabolism, Kimitsu Chuo HospitalJpn J Clin Ecol（Vol.23 No.1 2014）

50compounds, called persistent organic pollutants

NAFLD

can

reportedly

cause

non-alcoholic(POPs), are de­tected in most humans. Dioxins, asteatohepatitis (NASH) or cirrhosis, eventuallygroup of POPs known to exhibit deleterious effects

result­ing in liver cancer. The identification of risk

on health, include polychloro-dibenzo-p-dioxin (PCDD),

factors, effective prevention, and improved early

polychloro-dibenzofrananddioxin-like

detection of this disorder is therefore a public healthpolychlorinated biphenyl (DL-PCB).

While thepriority.

(PCDF),A recent study has reported that theenvironmental levels of dioxins and PCBs have been

exposure to chemical substances is one of the risk

decreasing yearly since the implementation of a ban

factors for NAFLD .

8)

on their use in Japan in 1973, Ministry of the

The National Health and Nutrition Examination

Environment reported that dioxins were still detected

Survey (NHANES) 2003–2004 suggested that1, 2)

in the Japanese people . The ingestion of fish andexposure to some non-dioxin-like PCBs (NDL-PCBs)

other seafood contaminated with dioxins has beenor DL-PCBs may potentially cause NAFLD, based onreported as a factor underlying the results of thethe measured blood levels of these chemicals16).

survey. Dioxins tend to accumulate in the adipose

However, the relationship between NAFLD and3)tissue and liver . PCDDs and PCDFs are produced

dioxin levels in the Japanese population has not been

as byproducts of incomplete combustion of chlorine-

reported thus far.

containing ma­terials, and can be released from the

NAFLD in Japan and growing concern over thechlorine-containing waste and plastics. DL-PCBs arepotential threat of POPs to human health provide theorganic chlorine compounds that have been used inrationale for investigating the causal relationshipthe past in a number of electronic and industrial

between NAFLD and POPs, including dioxin. There­

products.

fore, in this report, we aimed to elucidate the rela­

The toxicity of these various dioxins varies amongindividual congeners and isomers. The toxic equiva­

The increasing prevalence oftionship between blood dioxin levels measured inJapanese adult male population and NAFLD.

lency factor (TEF) is often employed to present therelative toxicity of a particular dioxin, by using

Ⅱ．Subjects and Methods

2,3,7,8-tetrachloro-dibenzodioxin (TCDD) as a refer­

1． Study population

4)

The Center for Preventive Medical Sciences,ence (TEF =1) .
Short-term exposure of humans to high levels of

Chiba University, offers a dioxin medical examination

dioxins may result in skin lesions, such as chloracne,

program that aims to assess the impact of dioxins on

5－7). Recently, an increasing

health by measuring blood dioxin levels, subjecting

number of research has focused on the effects of theparticipants to a general biochemical examination,

exposure to low doses of dioxins and DL-PCBs on

and surveying the participants’ medical histories andand altered liver function

human health8－10). A number of studies have reported

an association of low-level PCB accumulation in thehuman body with obesity or diabetes

11－14).

Patients with diabetes, as well as those who are
overweight or obese, often suffer from fatty liver

lifestyle habits using a questionnaire.
The present cross-sectional study assessed therelationship between NAFLD and the blood dioxin
levels. The data collected between 2006 and 2008
were analyzed.

disease. Fatty liver disease can be categorized into

Study population comprised 106 male participants

simple fatty liver and non-alcoholic fatty liver disease

over 20 years of age who consented to undergo a(NAFLD). The prevalence of NAFLD in Japan isbiochemical examination and provide a blood sample

15)

around 14%, increasing in recent years . Further­more,

for the measurement of blood dioxin levels. Subjects

Relationship between dioxin compounds and hepatic disorder with obesity in Japanese adult males

51

reporting a history of hepatitis B or C, cirrhosis,

Total toxicity of detected dioxins is expressed as ahepatocellular carcinoma, or those with high dioxin

sum of its toxic equivalents (TEQ) using the TEF

exposure were excluded. Of the 106 subjects who

2005 index, in accordance with the method proposed

consented to participate in the survey, data wereby the World Health Organization (WHO) . Levels

collected from 68 subjects that met the inclusion andof dioxin congeners and isomers levels were

exclusion criteria. The present study was approvedex­pressed as the concentration per fat mass in bloodby the Ethical Committee of the School of Medicine,(pg dioxin/g lipid) and converted to TEQ concentration

Chiba University, and all subjects provided written

per fat mass (pg TEQ/g lipid) using the TEF. General

informed consent prior to participation (Ethics Com­biochemical testing was performed and the outcomesmittee number 907).

analyzed by SRL Inc.

2． Measurements of dioxin levels and biochemi-

3． Detection of NAFLD

cal parameters

18)

In the present study, risk of NAFLD was establishedThe levels of dioxin congeners and isomers wereon the basis of laboratory tests, the Body Mass Indexquantified by measuring the concentrations of 29(BMI), and serum alanine aminotransferase levels

isomers of 7 types of PCDDs, 10 types of PCDFs, 4(ALT), which are an index of hepatic function

15, 16, 19).

types of non-ortho PCBs, and 8 types of mono-ortho

Obesity was defined as a BMI ≥ 25 kg/m , in

PCBs. Dioxin concentrations were expressed peraccordance with the guidelines of the Japanese

fat-weight extracted from the blood samples (fatSociety for the Study of Obesity20).

mass; pg dioxin/g blood lipid). Blood samples (50 mℓhepatocellular liver injury was defined as ALT ≥ 36each) were collected from the subjects in pre-washed

IU/ℓ, according to the guidelines of the Japanese

glass vacuum blood collection tubes. The analyticalSociety of Ningen Dock21). In this study, the suspected

method used in this study conformed to the technique

NAFLD group was defined to include subjects that

described in the provisional manual in 2000 by thepresented with both BMI ≥ 25 kg/m2 and ALT ≥ 36

17)

Japanese Ministry of Health, Labour and Welfare .

IU/ℓ, with no significant history of alcohol use.

Approximately 50 g of whole blood with 13C PCDDs/

Subjects with normal BMI and ALT levels were

PCDFs/ DL-PCBs (clean-up spike; Wellington Labo­

assigned to the control group (i.e., non-NAFLD).

ratories, Canada) was hydrolyzed with 2 M KOH/

4． Questionnaire

2Presence ofethanol at room temperature. The solution containing

Drinking and smoking habits were surveyed as

dioxins was extracted with n-hexane and subjected tobackground information using a questionnaire. Drink­

purification using a multilayer silica gel column,

ing habits were classified as “drinks often” or “drinks

alumina column, and active carbon-impregnatedrarely” based on the questionnaire. Smoking habitssilica gel column. After extraction and cleanup, thewere classified as “smokes” and “has quit or never

samples were spiked with another set of C-labeledsmoked” .

compounds (syringe spike; Wellington Laboratories).

5．Statistical analysis

13

Levels of PCDDs, PCDFs, and DL-PCBs were ana­

We determined the prevalence of suspected NAFLD

lyzed using high-resolution gas chromatography(ALT ≥ 36 IU/ℓand BMI ≥ 25 kg/m2) in 68 subjects,(6890; Agilent Technologies, Santa Clara, CA, USA)/and used the Mann-Whitney U-test to detect statis­

high-resolution mass spectrometry (Autospec-Ultima;

tically significant differences in ALT levels, BMI

Micromass, Cary, NC, USA) technique (HRGC/

elevation, and biochemical parameters. The Mann-

HRMS), with the measurements performed by a

Whitney U-test was used to compare the concen­

specialized testing company (SRL Inc., Tokyo, Japan).

trations of each dioxin isomer, ALT levels, and BMI

Jpn J Clin Ecol（Vol.23 No.1 2014）52

between the two groups. The Bonferroni method wassumma­rized in Table 1. Out of the total 68 recruitedused to correct for multiple comparisons.

The

subjects, 11 subjects were at risk of NAFLD (16.2%).

Spearman correlations test was used to assess the

Signifi­cant differences between the suspected NAFLD

correlations between the concentration of each dioxin

group and the control group were observed except

congeners and ALT levels, with the significancefor the AST and GGTP levels. The blood levels of 29

threshold set at p < 0.1. Subsequently, concentra­

dioxin congeners and isomers are presented in Table

tions of blood dioxin congeners and isomers that2.

showed significant differences in the Mann-Whitney

concentration in the fat mass of the blood sample) of

U-test were categorized into quartiles. The asso­

total PCDDs, total PCDFs, total DL-PCBs, and total

ciations of ALT levels and BMI with the exposure

dioxins were as follows: total PCDDs, 125.00 (85.50

level to each dioxin congeners and isomers were

– 187.50) pg/g lipid; total PCDFs, 13.50 (8.95 – 20.00)

evaluated using adjusted odds ratios.

Potential

pg/g lipid; total non-ortho PCBs, 56.00 (36.25 – 87.25)

confounders included age, smoking habit, total

pg/g lipid; total mono-ortho PCBs: 9,600.00 (6,675.00

cholesterol levels, triglyc­eride levels, high-density– 16,000.00) pg/g lipid; and total dioxins (PCDDs +lipoprotein cholesterol levels, and hemoglobin A1c

PCDFs + non-ortho PCBs + mono-ortho PCBs),levels. p values were obtained from multiple logistic

9,900.00 (66,800.00–16,000.00) pg/g lipid.

regression analysis, with 95% confidence intervals.

median TEQ values per fat mass for each dioxin

All analyses were conducted using SPSS (version

congener and isomer were as follows: total PCDDs,

19.0; IBM). The level of significance was set at p <5.06 (3.41–7.76) pg TEQ/g lipid; total PCDFs, 2.14

0.05.

(1.48–2.98) pg TEQ/g lipid; total non-ortho PCBs,

The median blood levels (expressed as

The

3.38 (2.14–5.29) pg TEQ/g lipid; total mono-ortho

Ⅲ．Results

PCBs, 0.29 (0.20–0.49) pg TEQ/g lipid; and total

The demographics, as well as the drinking anddioxins, 11.51 (7.35–16.25) pg TEQ/g lipid. A com­smoking habits of the enrolled subjects areparison of the concentrations of individual dioxin

Table 1

Characteristics of participants
Total
n=68

Age (year)
Total cholesterol (mg/dℓ)
Triglyceride (mg/dℓ)
HDL cholesterol (mg/dℓ)
Hemoglobin A1c (%)
Gamma- glutamyl transpeptidase (IU/ℓ)
Aspartate aminotransferase (IU/ℓ)
Alanine aminotransferase (IU/ℓ)
Body mass index (kg/m²)
Definite Diabetes (%)
Definite Hypertension (%)
Smoking habits (%)

Suspected NAFLD groupn=11(16.2%)

	  44 ± 12.8 	   37 ± 8.9
195 ± 31.4
206.0 ± 41.2
111 ± 78.2
128.0 ± 82.2
	  52 ± 13.5 	  47.0 ± 10.0
5.3 ± 1.2
	   5.3 ± 1.8
	  34 ± 81.6 	  66.0 ± 93.2
	  23 ± 37.6 	  37.0 ± 89.1
	  24 ± 24
	  58.0 ± 143.2
	  23 ± 3.4
	  29.1 ± 2.2
10/68 (14.7%)
0/11 ( 0.0%)
9/68 (13.2%)
3/11 (18.2%)
35/68 (52.1%)
6/11 (54.5%)

Control
n=57 (83.8%)

p-value	   45 ± 13.1
195.0 ± 29.8
104.0 ± 78.1
	  54.0 ± 13.5
	   5.3 ± 1.1
	  28.0 ± 82.4
	  21.0 ± 9.8
	  22.0 ± 14.8
	  23.6 ± 2.9
10/57 ( 1.8%)
6/57 (10.5%)
29/57 (50.9%)

0.065
0.947
0.127
0.086
0.221
0.018
<0.001<0.001<0.001－－－

Catagorical variables shown as actual number (weighted frequency). Continuous variables shown as mean (standard deviation). Suspected
NAFLD group: subject with an BMI≥ 25 and ALT level ≥ 36IU/ℓ. Control group (non-NAFLD): subject with no noted elevation in BMI or
ALT. The mean were total cholesterol, triglyceride, and hemoglobin A1c, gamma-glutamyl transpeptidase, asparate aminotransferase, alanine
aminotransferese in the blood levels.

Total PCDFs

Total PCDDs

0.00010.00030.1
0.03
0.000030.000030.000030.000030.000030.000030.000030.00003

5
5
5
5
6
6
6
7

0.1
0.03
0.3
0.1
0.1
0.1
0.1
0.01
0.01
0.0003

1
1
0.1
0.1
0.1
0.01
0.0003

4
4
5
6

4
5
5
6
6
6
6
7
7
8

4
5
6
6
6
7
8

TEF
2005

9,900.00 6,800.00 － 16,000.00

11.51

0.00
0.00
2.60
0.80
3.38
0.03
0.01
0.15
0.00
0.07
0.02
0.02
0.01
0.29
3.65

7.31

97.25 － 210.00

0.75
0.00 － 1.78
0.94
0.65 － 1.80
26.00
14.25 － 40.50
26.50
20.25 － 45.75
56.00
36.25 － 87.25
970.00 590.00 － 1,575.00
295.00 220.00 － 530.00
4,850.00 3,050.00 － 7,275.00
77.50
47.50 － 120.00
2,200.00 1,600.00 － 4,450.00
595.00 430.00 － 1,175.00
790.00 532.50 － 1,300.00
305.00 210.00 － 545.00
9,600.00 6,675.00 － 16,000.00
9,700.00 6,675.00 － 16,000.00

140.00

0.64
2.90
0.11
1.10
0.15
0.07
0.03
5.06
0.03
0.00
1.59
0.21
0.26
0.00
0.07
0.02
0.00
0.00
2.14

0.00 － 0.88
2.00 － 4.58
0.76 － 1.50
7.90 － 17.75
1.00 － 2.30
4.95 － 10.00
62.25 － 150.00
85.50 － 187.50
0.00 － 0.63
0.00 － 0.00
3.63 － 7.28
1.30 － 2.68
1.63 － 3.30
0.00 － 0.00
0.41 － 1.08
1.40 － 3.10
0.00 － 0.00
0.00 － 0.00
8.95 － 20.00

7.35 － 16.25

0.00 － 0.00
0.00 － 0.00
1.43 － 4.05
0.61 － 1.37
2.14 － 5.29
0.02 － 0.05
0.01 － 0.02
0.09 － 0.22
0.00 － 0.00
0.05 － 0.13
0.01 － 0.04
0.02 － 0.04
0.01 － 0.02
0.20 － 0.49
2.40 － 5.61

4.97 － 10.62

0.00 － 0.88
2.00 － 4.58
0.08 － 0.15
0.79 － 1.78
0.10 － 0.23
0.05 － 0.10
0.02 － 0.05
3.41 － 7.76
0.00 － 0.06
0.00 － 0.00
1.09 － 2.18
0.13 － 0.27
0.16 － 0.33
0.00 － 0.00
0.04 － 0.11
0.01 － 0.03
0.00 － 0.00
0.00 － 0.00
1.48 － 2.98

Median (25-75%)

Median (25-75%)
0.64
2.90
1.10
11.00
1.50
7.10
99.00
125.00
0.30
0.00
5.30
2.10
2.60
0.00
0.74
2.10
0.00
0.00
13.50

Concentration(pg-TEQ/g lipid)(n=68)

Concentration(pg/g-lipid)(n=68)

87.00 － 190.00

0.54 － 0.97
1.90 － 4.30
0.85 － 1.40
8.50 － 16.00
1.20 － 2.30
5.40 － 11.00
61.00 － 140.00
76.00 － 170.00
0.00 － 0.81
0.00 － 0.80
3.60 － 6.40
1.90 － 3.00
2.20 － 3.30
0.00 － 0.00
0.57 － 1.50
1.50 － 5.90
0.00 － 0.00
0.00 － 0.00
12.00 － 24.00

9,800.00 8,600.00 － 12,000.00

1.50
0.74 － 2.80
1.30
0.85 － 2.30
30.00
20.00 － 47.00
24.00
20.00 － 32.00
59.00
47.00 － 71.00
1,100.00 710.00 － 1,400.00
300.00 240.00 － 330.00
5,100.00 3,900.00 － 6,600.00
93.00
61.00 － 120.00
1,700.00 1,500.00 － 2,400.00
510.00 390.00 － 640.00
760.00 650.00 － 870.00
220.00 160.00 － 270.00
9,500.00 8,500.00 － 12,000.00
9,600.00 8,500.00 － 12,000.00

160.00

0.62
3.00
1.10
12.00
2.10
7.50
110.00140.00
0.35
0.00
6.20
2.40
2.70
0.00
0.87
2.90
0.00
0.00
15.00

Median (25-75%)

Suspected NAFLD(pg/g-lipid)(n=11)

Concentrations of dioxin congeners and isomers

97.50 － 210.00

0.00 － 0.86
2.00 － 4.65
0.70 － 1.50
7.80 － 18.00
0.97 － 2.30
4.90 － 9.95
62.50 － 165.00
86.00 － 195.00
0.00 － 0.56
0.00 － 0.00
3.50 － 7.50
1.30 － 2.60
1.60 － 3.30
0.00 － 0.00
0.40 － 1.00
1.40 － 2.90
0.00 － 0.00
0.00 － 0.00
8.70 － 20.00

10,000.00

6,600.00 － 17,000.00

0.65
0.00 － 1.45
0.91
0.63 － 1.55
26.00
14.00 － 40.00
28.00
20.50 － 49.00
55.00
36.00 － 89.00
960.00575.00 － 1,650.00
290.00210.00 － 535.00
4,600.00 2,950.00 － 7,550.00
77.00
47.00 － 125.00
2,500.00 1,600.00 － 4,650.00
640.00435.00 － 1,250.00
800.00515.00 － 1,400.00
320.00210.00 － 565.00
9,700.00 6,500.00 － 17,000.00
9,800.00 6,550.00 － 17,000.00

130.00

0.65
2.70
1.10
11.00
1.40
7.10
94.00
120.00
0.30
0.00
5.10
1.90
2.60
0.00
0.71
2.00
0.00
0.00
13.00

Median (25-75%)

Control(pg/g-lipid)(n=57)

0.65

0.03 *
0.12
0.38
0.31
0.64
0.59
0.89
0.70
0.63
0.30
0.38
0.75
0.09 *
0.90
0.70

0.71

0.34
0.89
0.95
0.68
0.44
0.61
0.83
0.67
0.56
0.28
0.71
0.27
0.55
－
0.43
0.13
－
－
0.60

p-value

Suspected NAFLD: subject with an BMI≥ 25 and ALT level ≥ 36IU/L. Control (non－NAFLD): subject with no noted elevation in BMI or ALT. p-values were calculated by Mann－Whitney tests. *indicates statistically significant change (p<0.1).

Total dioxins(PCDDs + PCDFs + DL-PCBs)

3,3',4,4'-Tetrachlorobiphenyl (PCB77)
3,4,4',5-Tetrachlorobiphenyl (PCB81)
3,3',4,4',5-Pentachlorobiphenyl (PCB126)
3,3',4,4',5,5'-Hexachlorobiphenyl (PCB169)
Total non-ortho PCBs
2,3,3',4,4'-Pentachlorobiphenyl (PCB105)
2,3,4,4',5-Pentachlorobiphenyl (PCB114)
2,3',4,4',5-Pentachlorobiphenyl (PCB118)
2,3',4,4',5'-Pentachlorobiphenyl (PCB123)
2,3,3',4,4',5-Hexachlorobiphenyl (PCB156)
2,3,3',4,4',5'-Hexachlorobiphenyl (PCB157)
2,3',4,4',5,5'-Hexachlorobiphenyl (PCB167)
2,3,3',4,4',5,5'-Heptachlorobiphenyl (PCB189)
Total mono-ortho PCBs
Total DL-PCBs

Total (PCDDs+PCDFs)

2,3,7,8-TetraCDF
1,2,3,7,8-PentaCDF
2,3,4,7,8-PentaCDF
1,2,3,4,7,8-HexaCDF
1,2,3,6,7,8-HexaCDF
1,2,3,7,8,9-HeptaCDF
2,3,4,6,7,8-HexaCDF
1,2,3,4,6,7,8-HeptaCDF
1,2,3,4,7,8,9-HeptaCDF
OctaCDF

2,3,7,8-TetraCDD
1,2,3,7,8-PentaCDD
1,2,3,4,7,8-HexaCDD
1,2,3,6,7,8-HexaCDD
1,2,3,7,8,9-HexaCDD
1,2,3,4,6,7,8-HeptaCDD
OctaCDD

Chlorine
atoms

Table 2

Relationship between dioxin compounds and hepatic disorder with obesity in Japanese adult males
53Jpn J Clin Ecol（Vol.23 No.1 2014）54

congeners and isomers measured in the suspected189) levels (Table 2). ALT levels correlated with the

NAFLD group and in the control group revealed ablood concentration of PCB77 (Fig 1). BMI values ofsignificant difference in 3,3’,4,4’-tetrachlorobiphenyl

study participants did not correlate with the blood(PCB77) and 2,3,3’,4,4’,5,5’-heptachlorobiphenyl (PCB

concentrations of dioxin congeners and isomers (data3,3',4,4'-Tetrachlorobiphenyl (PCB77)

A

65

55
50

50
45

45

40

40

35

35

30

30
25

r=0.22p=0.07

55

ALT

ALT

60

r=0.33p<0.0160

2,3,7,8-TetraCDD*References

C

0.0

1.0

2.0

3.0

4.0

5.0

6.0

25

7.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5(pg/g lipid, pg TEQ/g lipid)(pg/g lipid)

B

3,3',4,4'-Tetrachlorobiphenyl (PCB77)*Refarences

65

D

65

r=0.30p<0.01

60

55

ALT

ALT

r=0.13p=0.28

60

55
50

50

45

45

40

40

35

35

30

30

25

Total dioxins (PCDDs+PCDFs+DL-PCBs)*References

00.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007

25

3,000

13,00023,00033,000Fig. 1

43,000(pg/g lipid)(pg TEQ/g lipid)

Correlations of dioxin congeners and ALT

Spearman correlation test. Correlations of blood level of dioxin congeners/isomers and ALT. Data are expressedin concentration per fat mass in blood (A, C, D). Data are expressed in concentration TEQ per fat mass, which is
calculated using WHO-TEF (B, C).

Table 3The prevalence of susupected NFLD and quartiles concentration of DL-PCBs
Quartile [case/total, median concentration (pg/g-lipid), range]nFirst quartile

Second quartile

Third quartile

Fourth quartile

p-value

3,3’,4,4’-Tetrachlorobiphenyl(PCB77)

68

1/28
0.00
0.00-0.59

2/11
0.74
0.60-0.97

3/12
1.20
1.10-1.70

5/17
2.80
1.80-6.40< 0.05

2,3,3’,4,4’,5,5’-Heptachlorobiphenyl(PCB189)68

4/16
140.00100.00-200.00

5/18
245.00210.00-300.00

0/17
400.00310.00-530.00

2/17
880.00550.00-1,700.00

0.10

The summary values were categorized by cutoff points of 25th, 50th, and 75th values of the sum of ranks. *p-value were calculated by chisquared test.

Relationship between dioxin compounds and hepatic disorder with obesity in Japanese adult males

Table 455

Risk of suspected NAFLD according to DL-PCBs

A
Total cholesterol
HDL cholesterol
Triglyceride
HbA1c_NGSP
3,3’,4,4’-Tetrachlorobiphenyl (PCB77)
2,3,3’,4,4’,5,5’-Heptachlorobiphenyl (PCB189)

p-value

OR

0.633
0.370
0.210
0.250
0.005
0.022

1.01
1.03
0.99
0.72
3.19
2.38

p-value

OR

0.514
0.180
0.970
0.647
0.170
0.652
0.002
0.679

1.87
1.10
1.00
1.02
0.99
0.87
4.08
0.75

95% CI
0.98
0.96
0.99
0.42
1.40
0.14

－
－
－
－
－
－

1.04
1.11
1.00
1.25
7.20
0.86

B
Smoking habit
AgeTotal cholesterol
HDL cholesterol
Triglyceride
HbA1c_NGSP
3,3’,4,4’-Tetrachlorobiphenyl (PCB77)
2,3,3’,4,4’,5,5’-Heptachlorobiphenyl (PCB189)

95% CI
0.29
0.96
0.97
0.94
0.98
0.49
1.67
0.19

－
－
－
－
－
－
－
－

12.26
1.27
1.03
1.10
1.00
1.57
9.98
3.00

A; Adjusted for total cholesterol, high-density lipoprotein cholesterol level, triglycerides, hemoglobin A1c. B; Adjusted for totalcholesterol, high-density lipoprotein cholesterol level, triglycerides, hemoglobin A1c, age and smoking. Data are adjusted odds
ratio (OR) and 95% confidence interval (95% CI).

not shown).

of NAFLD.

Concentrations of blood PCB77 and PCB189 were

The observed relationship is consistent with thecategorized into quartiles (Table 3). The multiple

findings of previous studies, suggesting that exposure

logistic regression analysis showed that higher bloodto PCBs, which have been banned since 1973,

levels of blood PCB77 and PCB189 were associatedproceeds primarily from the diet, with the compoundswith suspected NAFLD (Table 4-A). Furthermore,accumulating in the human body. No other correlation

the adjustment of results for age and smoking habit

between other concentrations of dioxin compounds

using multiple logistic regression analyses showed aand ALT levels could be found. The blood levels of

relationship between elevated blood PCB77 levels

PCB77 in the NAFLD group were significantly higher

and the risk of suspected NAFLD (Table 4-B).

in comparison to the control group, whereas no
significant difference was observed in the concen­

Ⅳ．Discussion

trations of other dioxin congeners and isomers. The

The prevalence rate of suspected NAFLD in thisrelationship between elevated PCB77 and NAFLD

study was consistent with the incidence of thisremains significant when the confounding factors,

hepatic disorder in a general Japanese population, as

including age and smoking habit, are taken into

reported from the findings of a study using medical

consideration in comparing the two groups. Although15)

examinations . Among the dioxin congeners andsome published reports have suggested a relationshipisomers measured in this study, PCB77 showed abetween combined exposure to DL-PCB (PCB126)/

correlation with ALT levels, suggesting that in­creased

NDL-PCBs (PCB153) or their increased levels in thelevels of PCB77 exposure may contribute to the risk

blood and suspected NAFLD, those studies did notJpn J Clin Ecol（Vol.23 No.1 2014）56

measure PCB77 levels. Our report is, therefore, thea relationship between the two clinical conditions33).

first to describe the relationship between the blood

Although some animal studies have reported anlevels of PCB77 and NAFLD. On the other hand, thisassociation between PCB77 and NAFLD, the relation­

study design has several potential problems whichship in the human body has not been reported. As

have to be mentioned. Firstly, the exact specify ofmentioned above, although the relationship between

ALT for hepatic disorder in this study is unknown

a number of PCBs and human NAFLD has previously

because liver biopsies were not conducted. Although,been suggested, there is no published reportelevation of hepatic transaminases in patient withdescribing the relationship with PCB77. The findings

NAFLD are characterized by predominance of ALT,of this study raise the possibility that PCB77 may berecent research indicate that patients with BMI

one of the triggers of NAFLD.

22, 23).

The most common PCBs products in Japan include

Actually, lower laboratory values of ALT have been

“Kanechlor 300” a manufactured by Kanegafuchi Co.

used in some previous studies to obtain higher

Ltd., while Monsanto Chemical Company’s “Aroclors”

below 25 often showed normal ALT levels

sensitivity

24, 25). Previous studies that described theaccounts for the largest share of PCBs worldwide

34－36).

impact of chemicals on human health included

These products contain high concentrations of DL-

patients with normal and boundary ALT levels to

PCBs, especially PCB77 and PCB12637). DL-PCBs

investigate the relationship between particular chemi­

are transferred through water, air, and soil to living

cals and biochemical parameters. This study adoptedorganisms and accumulate in their tissues29). The

the similar methodology with previous studies, andbiotransfer factor or bioaccumulation factor isthe finding indicated that subjects with lower blood

particularly high in fish and cattle, with these factors

level of PCBs showed the tendency of lower levels ofshown to be determined by the number of chlorine

For this reason, it is inferred that theatoms in the toxin molecule37, 38). The beef biotransfer

measurement of blood levels of PCBs and ALT could

factor of PCB126 was reported to be higher than thatpossibly be helpful in future diagnosing NAFLD, if

of PCB7739), while the bioaccumulation factor of

not a definitive.

PCB77 and PCB 126 in fish are reportedly of similar

ALT15, 26).

The biological half-life of DL-PCBs varies depend­

magnitudes40). The amounts of DL-PCBs accumulated

ing on the number and the binding site of chlorine

in the living body can therefore vary according to the27)

atoms in the toxin molecule . The liver and adipose

frequencies and amounts of food ingested. According

tissues may be the principal target organs for theto previous reports, annual per-capita consumption of

toxicity of DL-PCBs, since these compounds tend tobeef is higher in the United States than in Japan,

accumulate in the hepatic fatty tissues. Rats fed awhile fish consumption is higher in Japan41, 42).

diet supple­
mented with PCBs were reported toAdditionally, the biological half-life of PCB126 in. Administration ofblood is longer than that of PCB7727). Unlike one

PCB77 was reported to worsen fatty liver diseaseprevious study that detected an association withand affect the genes involved in apoptosis, inflam­

PCB126, the relationship with the pathogenesis ofmation, and oxidative stress in hepatocytes in mice30, 31).

suspected NAFLD was only seen with PCB77 in thisMiyazaki et al. reported that an increase in hydroxylated

study, likely reflecting the differences in the kinetics

metabo­lites of PCB77 decreases the levels of thyroidof PCB126 and PCB77 in the blood, or in the

exhibit increased liver weight32)

hormone in rodents .

28, 29)Furthermore, insufficientfrequency and amount of ingested food. Since theproduction of thyroid hormone was shown to be acurrent methods of measuring dioxin congeners andrisk factor of NAFLD, with some reports suggestingisomers are too expensive to be widely used inRelationship between dioxin compounds and hepatic disorder with obesity in Japanese adult males

clinical practice as an evaluation index of NAFLD, it
is difficult to conclusively determine the relationshipbetween NAFLD and dioxins. However, an approach
to measuring dioxins using packed column-electron
capture detector/gas chroma­tograph or GC/NICI-MS
requires a smaller amount of blood and can be
performed at lower cost, as compared to HRGC/
HRMS.

Since the GC/NICI-MS method uses acapillary column and therefore has strong potential
for detecting PCB77 separately, leading to growinginterest in this technique and recent efforts to43)establish its validity .

57

Acknowledgements
We thank Mr. Yusuke Tsutsumi from Tokyo University of
Science (Japan) for his great help.

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日本人の肥満成人男性における肝機能障害とダイオキシン類の関連性
要約
近年、ダイオキシン類の曝露が糖・脂質代謝異常や肝機能障害発症の一因であることが複数の報告で示唆されている。しかし、一般環境レベルの低濃度ダイオキシン類曝露と非アルコール性脂肪性肝疾患（NAFLD）の関連性は未だ不明である。我々は68名の一般成人で、ダイオキシン様ポリ塩化ビフェニルを含む29種類の血中ダイオキシン類濃度と生化学パラメータを用いて、血中ダイオキシン類濃度と NAFLD
罹患の関連性を調査した。11名の対象者が NAFLD の罹患疑いに分類された。NAFLD の罹患疑いの対象者
は、血中ダイオキシン類濃度のうち3,3’,4,4’- tetrachlorobiphenyl（PCB77）が有意に高かった。NAFLD の罹患疑いの対象者は年齢や喫煙、総コレステロール、中性脂肪、HDL コレステロール、HbA1c で補正をおこなっても、PCB77の寄与率が高かった。
本結果から、PCB77の低レベル曝露が NAFLD 発症の一因となる可能性を示唆した。
（臨床環境 23：49－60，2014）《キーワード》‌ダイオキシン類、3,3’,4,4’- テトラクロロビフェニル（PCB77）、非アルコール性脂肪性肝疾患（NAFLD）