Environmental Pollution 195 (2014) 24e30
Contents lists available at ScienceDirect
Environmental Pollution journal homepage: www.elsevier.com/locate/envpol
Dose-response relationship between polycyclic aromatic hydrocarbon metabolites and risk of diabetes in the general Chinese population Liangle Yang, Yun Zhou, Huizhen Sun, Hanpeng Lai, Chuanyao Liu, Kai Yan, Jing Yuan, Tangchun Wu, Weihong Chen*, Xiaomin Zhang* Department of Occupational and Environmental Health and Ministry of Education Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 May 2014 Received in revised form 22 July 2014 Accepted 11 August 2014 Available online 3 September 2014
The incidence of diabetes is increasing rapidly in Chinese population, and it has been postulated that environmental factors may play a role in the etiology of diabetes. Therefore, we aimed to investigate the association between PAHs exposure and risk of diabetes in a community-based population of 2824 participants with completed questionnaires, measurements of biochemical indices, and urinary PAHs metabolites. We found that elevated urinary PAHs metabolites were associated, in a dose-dependent manner, with increased risk of diabetes. Particularly, these associations were more evident in subjects who were female, less than 55 years old, nonsmokers, and normal weight. In addition, there was a modest improvement in diabetes discrimination of prediction models when incorporating certain PAHs metabolites into conventional risk factors (CRF). Overall, our data suggested that there may be a dosedependent relationship between PAHs metabolites and risk of diabetes among general Chinese population. © 2014 Elsevier Ltd. All rights reserved.
Keywords: Polycyclic aromatic hydrocarbons Diabetes Dose-response relationship
1. Introduction With rapid economic growth, marked changes in dietary patterns and lifestyle, the incidence of type 2 diabetes has increased rapidly in Chinese population in recent decades (Chan et al., 2009). Until now, the Chinese diabetes epidemic has been the largest in the world: 90 million Chinese live with diabetes and 1.3 million died in 2011 (Scully, 2012). Furthermore, the International Diabetes Federation has predicted that the number of individuals with diabetes and impaired glucose tolerance will increase to 138 million in 2025 in China, which will put a huge burden on healthcare systems and governments (IDF, 2006). Accumulating data suggest that established risk factors of type 2 diabetes in Asian populations
Abbreviations: AUC, the area under the curve; BMI, body mass index; CRF, conventional risk factors; IDI, integrated discrimination index; IFG, impaired fasting glucose; LMW, low molecular weight; NRI, net reclassification index; OHNa, hydroxynaphthalene; OHFlu, hydroxyfluorene; OHPh, hydroxyphenanthrene; 1OHP, 1-hydroxypyrene; 6-OHChr, 6-hydroxychrysene; 3-OHBaP, 3-hydroxybenzo [a]pyrene; OH-PAHs, monohydroxylated polycyclic aromatic hydrocarbons; PAHs, polycyclic aromatic hydrocarbons; ROC, receiver operating characteristic. * Corresponding authors. E-mail addresses: [email protected] (W. Chen), [email protected] (X. Zhang). http://dx.doi.org/10.1016/j.envpol.2014.08.012 0269-7491/© 2014 Elsevier Ltd. All rights reserved.
include obesity, overnutrition, sedentary lifestyles, cigarette smoking, and environmental factors such as chronic arsenic exposure and persistent organic pollutants (Chan et al., 2009; Chen et al., 2007; Lee et al., 2006; Will et al., 2001). Polycyclic aromatic hydrocarbons (PAHs) are a wide class of toxic organic compounds formed in all processes involving incomplete combustion of organic material, automobile exhaust, cigarette smoking, coal burning, home cooking, and industrial production processes (Bostrom et al., 2002). Thus, PAHs are ubiquitous contaminants in both the general environment and in certain occupational settings (Armstrong et al., 2004). The major sources of PAHs in general population were identified to be atmosphere, diet, and cigarette smoking (Suzuki and Yoshinaga, 2007). PAHs absorbed into the human body are metabolized as monohydroxylated PAHs (OH-PAHs) and excreted mainly through urine, and thus urinary PAHs metabolites can be useful biomarkers for assessing multiple routes of external exposure (Gunier et al., 2006). Numeral studies have suggested that elevated PAHs levels were associated with increased systemic inflammatory activity and oxidative stress, which may cause insulin resistance, ultimately contributing to diabetes (Ceriello and Motz, 2004; Khalil et al., 2010; Roberts and Sindhu, 2009). However, very little is known about how background, enduring environmental exposure to PAHs
L. Yang et al. / Environmental Pollution 195 (2014) 24e30
links with risk of diabetes. The latest study based on the data of National Health and Nutrition Examination Survey (NHANES) reported a positive association between urinary biomarkers of low molecular weight (LMW) PAHs and risk of diabetes in US adults 20e65 years of age (Alshaarawy et al., 2014). Therefore, we aimed to 1) verify the relationship of environmental PAHs exposure and the risk of diabetes among a community-based population in China; 2) explore whether characteristic differences associated with diabetes may become extraordinarily evident in certain individuals; and 3) examine the roles of PAHs metabolites in the discrimination of diabetes. 2. Materials and methods 2.1. Study population The study population used in the present study has been described previously (Feng et al., 2014). Briefly, 3092 volunteers >18 years of age who resided in Wuhan at least 5 years were recruited in the survey. Information on demographic variables, history of disease, medications, occupational history, educational background and lifestyle habits including smoking status, passive smoking, alcohol consumption, physical activity and diet were collected using standardized questionnaires by trained reviewers. Body mass index (BMI) was calculated as weight (kg) divided by height (m2). Individuals who had smoked less than one cigarette per day over the previous 6 months were defined as nonsmokers; otherwise, they were considered as smokers. Individuals who had drunk alcohol beverage less than once a week over the previous 6 months were defined as nondrinkers; otherwise, they were considered as drinkers. Physical activity was defined as regularly doing at least 20 min of physical activity during leisure time over the previous 6 months (yes or no). Education was categorized as less than high school graduate, high school graduate, and college or beyond. A fasting blood sample was drawn for examination of cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), and blood glucose. One morning urine sample (20 mL) was collected from each subject into sterile conical tubes, and all urine samples were divided into aliquots and stored at 20 C until laboratory analysis. The study was reviewed and approved by the Ethics and Human Subject Committee of Tongji Medical College, and all participants provided written informed consent. The exclusion criteria were participants with missing data on PAHs metabolites and fasting blood glucose or other variables included in the multivariable model. After exclusion, a total of 2824 subjects with complete data remained for analysis within the current study. No significant differences were observed regarding basic characteristics between the analytical sample and excluded subjects, except for the number of drinkers (Appendix A). 2.2. Determination of urinary PAHs metabolites We measured 12 urinary PAHs metabolites [pyrene metabolite: 1hydroxypyrene (1-OHP); naphthalene metabolites: 1-hydroxynaphthalene (1OHNa), 2-OHNa; fluorene metabolites: 2-hydroxyfluorene (2-OHFlu), 9-OHFlu; phenanthrene metabolites: 1-hydroxyphenanthrene (1-OHPh), 2-OHPh, 3-OHPh, 4OHPh, 9-OHPh; chrysene metabolite: 6-hydroxychrysene (6-OHChr); and benzo[a] pyrene metabolite: 3-hydroxybenzo[a]pyrene (3-OHBaP)] by gas chromatographyemass spectrometry (GC/MS, Agilent 6890N þ 5975B, Agilent Technologies Inc., Santa Clara, CA, USA) as previously described (Li et al., 2012). Briefly, each 3.0 mL of urine were extracted with 20 mL b-Glucuronidase/sulphatase (type H-2 from Helix pomatia; b-glucuronidase activity 85,000 units/mL and sulphatase activity 2400 U/mL, aqueous solution type, SigmaeAldrich, Milan, Italy), 20 mL pure deuterated compounds as internal standards (IS) solution containing 1-OHPYRd9 (Toronto Research Chemicals, Toronto, Canada) and 1-OHNAPd7 (C/D/N isotopes inc., Beijing, China) at a concentration of 5 mg/L and 50 mg/L in acetonitrile. The set of the standard curve was operated about every 100 samples, and about 10% of the total samples were used as quality control. The identification and quantification of urinary PAHs metabolites were based on retention time, mass-to-charge ratio, and peak area using a linear regression curve obtained from separate internal standard solutions. The limits of detection (LOD) for urinary PAHs metabolites were in the range 0.1e0.9 mg/L; default values were replaced with 50% of the LOD. Valid urinary PAHs metabolites concentrations were calibrated by levels of urinary creatinine and calculated as nmol/mmol creatinine. Because 6-OHChr and 3-OHBaP were below the limits of quantification, we only analyzed 10 metabolites of PAHs. 2.3. Definition of normoglycemia, impaired fasting glucose (IFG), and diabetes Diabetes was defined as having a fasting blood glucose 7.0 mmol/L, self reported physician-diagnosed diabetes, or taking oral hypoglycemic medication or insulin. IFG was defined as fasting glucose 5.6e6.9 mmol/l, absence of previously diagnosed diabetes, and absence of glycemic control medications. Normoglycemia was defined as individuals with a negative self-report of diabetes, fasting glucose
Contents lists available at ScienceDirect
Environmental Pollution journal homepage: www.elsevier.com/locate/envpol
Dose-response relationship between polycyclic aromatic hydrocarbon metabolites and risk of diabetes in the general Chinese population Liangle Yang, Yun Zhou, Huizhen Sun, Hanpeng Lai, Chuanyao Liu, Kai Yan, Jing Yuan, Tangchun Wu, Weihong Chen*, Xiaomin Zhang* Department of Occupational and Environmental Health and Ministry of Education Key Lab for Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 May 2014 Received in revised form 22 July 2014 Accepted 11 August 2014 Available online 3 September 2014
The incidence of diabetes is increasing rapidly in Chinese population, and it has been postulated that environmental factors may play a role in the etiology of diabetes. Therefore, we aimed to investigate the association between PAHs exposure and risk of diabetes in a community-based population of 2824 participants with completed questionnaires, measurements of biochemical indices, and urinary PAHs metabolites. We found that elevated urinary PAHs metabolites were associated, in a dose-dependent manner, with increased risk of diabetes. Particularly, these associations were more evident in subjects who were female, less than 55 years old, nonsmokers, and normal weight. In addition, there was a modest improvement in diabetes discrimination of prediction models when incorporating certain PAHs metabolites into conventional risk factors (CRF). Overall, our data suggested that there may be a dosedependent relationship between PAHs metabolites and risk of diabetes among general Chinese population. © 2014 Elsevier Ltd. All rights reserved.
Keywords: Polycyclic aromatic hydrocarbons Diabetes Dose-response relationship
1. Introduction With rapid economic growth, marked changes in dietary patterns and lifestyle, the incidence of type 2 diabetes has increased rapidly in Chinese population in recent decades (Chan et al., 2009). Until now, the Chinese diabetes epidemic has been the largest in the world: 90 million Chinese live with diabetes and 1.3 million died in 2011 (Scully, 2012). Furthermore, the International Diabetes Federation has predicted that the number of individuals with diabetes and impaired glucose tolerance will increase to 138 million in 2025 in China, which will put a huge burden on healthcare systems and governments (IDF, 2006). Accumulating data suggest that established risk factors of type 2 diabetes in Asian populations
Abbreviations: AUC, the area under the curve; BMI, body mass index; CRF, conventional risk factors; IDI, integrated discrimination index; IFG, impaired fasting glucose; LMW, low molecular weight; NRI, net reclassification index; OHNa, hydroxynaphthalene; OHFlu, hydroxyfluorene; OHPh, hydroxyphenanthrene; 1OHP, 1-hydroxypyrene; 6-OHChr, 6-hydroxychrysene; 3-OHBaP, 3-hydroxybenzo [a]pyrene; OH-PAHs, monohydroxylated polycyclic aromatic hydrocarbons; PAHs, polycyclic aromatic hydrocarbons; ROC, receiver operating characteristic. * Corresponding authors. E-mail addresses: [email protected] (W. Chen), [email protected] (X. Zhang). http://dx.doi.org/10.1016/j.envpol.2014.08.012 0269-7491/© 2014 Elsevier Ltd. All rights reserved.
include obesity, overnutrition, sedentary lifestyles, cigarette smoking, and environmental factors such as chronic arsenic exposure and persistent organic pollutants (Chan et al., 2009; Chen et al., 2007; Lee et al., 2006; Will et al., 2001). Polycyclic aromatic hydrocarbons (PAHs) are a wide class of toxic organic compounds formed in all processes involving incomplete combustion of organic material, automobile exhaust, cigarette smoking, coal burning, home cooking, and industrial production processes (Bostrom et al., 2002). Thus, PAHs are ubiquitous contaminants in both the general environment and in certain occupational settings (Armstrong et al., 2004). The major sources of PAHs in general population were identified to be atmosphere, diet, and cigarette smoking (Suzuki and Yoshinaga, 2007). PAHs absorbed into the human body are metabolized as monohydroxylated PAHs (OH-PAHs) and excreted mainly through urine, and thus urinary PAHs metabolites can be useful biomarkers for assessing multiple routes of external exposure (Gunier et al., 2006). Numeral studies have suggested that elevated PAHs levels were associated with increased systemic inflammatory activity and oxidative stress, which may cause insulin resistance, ultimately contributing to diabetes (Ceriello and Motz, 2004; Khalil et al., 2010; Roberts and Sindhu, 2009). However, very little is known about how background, enduring environmental exposure to PAHs
L. Yang et al. / Environmental Pollution 195 (2014) 24e30
links with risk of diabetes. The latest study based on the data of National Health and Nutrition Examination Survey (NHANES) reported a positive association between urinary biomarkers of low molecular weight (LMW) PAHs and risk of diabetes in US adults 20e65 years of age (Alshaarawy et al., 2014). Therefore, we aimed to 1) verify the relationship of environmental PAHs exposure and the risk of diabetes among a community-based population in China; 2) explore whether characteristic differences associated with diabetes may become extraordinarily evident in certain individuals; and 3) examine the roles of PAHs metabolites in the discrimination of diabetes. 2. Materials and methods 2.1. Study population The study population used in the present study has been described previously (Feng et al., 2014). Briefly, 3092 volunteers >18 years of age who resided in Wuhan at least 5 years were recruited in the survey. Information on demographic variables, history of disease, medications, occupational history, educational background and lifestyle habits including smoking status, passive smoking, alcohol consumption, physical activity and diet were collected using standardized questionnaires by trained reviewers. Body mass index (BMI) was calculated as weight (kg) divided by height (m2). Individuals who had smoked less than one cigarette per day over the previous 6 months were defined as nonsmokers; otherwise, they were considered as smokers. Individuals who had drunk alcohol beverage less than once a week over the previous 6 months were defined as nondrinkers; otherwise, they were considered as drinkers. Physical activity was defined as regularly doing at least 20 min of physical activity during leisure time over the previous 6 months (yes or no). Education was categorized as less than high school graduate, high school graduate, and college or beyond. A fasting blood sample was drawn for examination of cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), and blood glucose. One morning urine sample (20 mL) was collected from each subject into sterile conical tubes, and all urine samples were divided into aliquots and stored at 20 C until laboratory analysis. The study was reviewed and approved by the Ethics and Human Subject Committee of Tongji Medical College, and all participants provided written informed consent. The exclusion criteria were participants with missing data on PAHs metabolites and fasting blood glucose or other variables included in the multivariable model. After exclusion, a total of 2824 subjects with complete data remained for analysis within the current study. No significant differences were observed regarding basic characteristics between the analytical sample and excluded subjects, except for the number of drinkers (Appendix A). 2.2. Determination of urinary PAHs metabolites We measured 12 urinary PAHs metabolites [pyrene metabolite: 1hydroxypyrene (1-OHP); naphthalene metabolites: 1-hydroxynaphthalene (1OHNa), 2-OHNa; fluorene metabolites: 2-hydroxyfluorene (2-OHFlu), 9-OHFlu; phenanthrene metabolites: 1-hydroxyphenanthrene (1-OHPh), 2-OHPh, 3-OHPh, 4OHPh, 9-OHPh; chrysene metabolite: 6-hydroxychrysene (6-OHChr); and benzo[a] pyrene metabolite: 3-hydroxybenzo[a]pyrene (3-OHBaP)] by gas chromatographyemass spectrometry (GC/MS, Agilent 6890N þ 5975B, Agilent Technologies Inc., Santa Clara, CA, USA) as previously described (Li et al., 2012). Briefly, each 3.0 mL of urine were extracted with 20 mL b-Glucuronidase/sulphatase (type H-2 from Helix pomatia; b-glucuronidase activity 85,000 units/mL and sulphatase activity 2400 U/mL, aqueous solution type, SigmaeAldrich, Milan, Italy), 20 mL pure deuterated compounds as internal standards (IS) solution containing 1-OHPYRd9 (Toronto Research Chemicals, Toronto, Canada) and 1-OHNAPd7 (C/D/N isotopes inc., Beijing, China) at a concentration of 5 mg/L and 50 mg/L in acetonitrile. The set of the standard curve was operated about every 100 samples, and about 10% of the total samples were used as quality control. The identification and quantification of urinary PAHs metabolites were based on retention time, mass-to-charge ratio, and peak area using a linear regression curve obtained from separate internal standard solutions. The limits of detection (LOD) for urinary PAHs metabolites were in the range 0.1e0.9 mg/L; default values were replaced with 50% of the LOD. Valid urinary PAHs metabolites concentrations were calibrated by levels of urinary creatinine and calculated as nmol/mmol creatinine. Because 6-OHChr and 3-OHBaP were below the limits of quantification, we only analyzed 10 metabolites of PAHs. 2.3. Definition of normoglycemia, impaired fasting glucose (IFG), and diabetes Diabetes was defined as having a fasting blood glucose 7.0 mmol/L, self reported physician-diagnosed diabetes, or taking oral hypoglycemic medication or insulin. IFG was defined as fasting glucose 5.6e6.9 mmol/l, absence of previously diagnosed diabetes, and absence of glycemic control medications. Normoglycemia was defined as individuals with a negative self-report of diabetes, fasting glucose
