Associations between urinary polycyclic aromatic hydrocarbon metabolites and serum testosterone in U.S. adult males: National Health and nutrition examination survey 2011-2012

Effects of polycyclic aromatic hydrocarbons on the gut-testis axis

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds which are comprised of two or more fused benzene rings. As a typical environmental pollutant, PAHs are widely distributed in water, soil, atmosphere and food. Despite extensive researches on the mechanisms of health damage caused by PAHs, especially their carcinogenic and mutagenic toxicity, there is still a lack of comprehensive summarization and synthesis regarding the mechanisms of PAHs on the gut-testis axis, which represents an intricate interplay between the gastrointestinal and reproductive systems. Thus, this review primarily focuses on the potential forms of interaction between PAHs and the gut microbiota and summarizes their adverse outcomes that may lead to gut microbiota dysbiosis, then compiles the possible mechanistic pathways on dysbiosis of the gut microbiota impairing the male reproductive function, in order to provide valuable insights for future research and guide further exploration into the intricate mechanisms underlying the impact of gut microbiota dysbiosis caused by PAHs on male reproductive function.

Association between exposure to polycyclic aromatic hydrocarbons and endometriosis: data from the NHANES 2001-2006

Aim

To evaluate the association between urinary polycyclic aromatic hydrocarbon (PAH) metabolites and the risk of endometriosis.

Methods

This cross-sectional study obtained data on women aged 20-54 years from the National Health and Nutrition Examination Survey (NHANES) 2001-2006. The weighted multivariate logistic regression model was established to assess the association between the eight urinary PAH metabolites and the risk of endometriosis. In this multivariate analysis, the eight urinary PAH metabolites were adjusted with urinary creatinine, and were divided into three groups according to tertiles: Tertile 1, Tertile 2 and Tertile 3. To evaluate the overall association of mixed PAH metabolites with endometriosis, the Bayesian kernel machine regression (BKMR) model was applied.

Results

Totally 1,291 women were included, of which 90 (6.97%) had endometriosis and 1,201 (93.03%) did not have endometriosis. After adjusting for age, race, smoking, age at menarche, hysterectomy, ovary removed, female hormone use, and menopause, compared with the Tertile 1 group, the Tertile 2 and Tertile 3 groups of all PAH metabolites demonstrated no significant risk of endometriosis. A positive tendency was found between mixed PAH metabolites and endometriosis when all the metabolites were at their 60th percentile levels or above compared with their median levels. When all the other metabolites were fixed at their median levels, 1-hydroxynaphthalene was positively correlated with endometriosis. Potential interactions existed between 1-hydroxynaphthalene and 2-hydroxynaphthalene and between 2-hydroxyfluorene and 3-hydroxyfluorene.

Conclusion

No significant association was found between individual PAH metabolites and endometriosis. A positive association existed between mixed PAH metabolites and the risk of endometriosis.

Associations of urinary polycyclic aromatic hydrocarbons with bone mineral density at specific body sites in U.S. adults, NHANES 2001-2004

OBJECTIVE

We aimed to analyze the association between certain types of urinary polycyclic aromatic hydrocarbons (PAHs) and bone mineral density (BMD) at specific sites of the body.

METHODS

A total of 2,978 eligible participants from the National Health and Nutrition Examination Survey (NHANES 2001-2004) were included in this study. Data of eight urinary PAHs and BMDs of three skeleton sites and the total body were analyzed. Univariate and multivariate linear regression analyses were performed to explore the association between urinary PAHs and BMDs. Subgroup analyses stratified by gender and body mass index (BMI) were also performed.

RESULTS

After adjustment for all confounders, elevated 3-fluorene [β=0.046; 95% confidence intervals (CI), 0.007-0.084] and 2-fluorene (β=0.054; 95%CI, 0.007-0.100) were associated with greater left arm BMD, while no statistical differences were observed in the relationship between other PAHs and BMDs (all P>0.05). Higher 3-fluorene and 2-fluorene levels were still associated with increased left arm BMD in males (P<0.05), while higher 2-phenanthrene was related to decreased left arm BMD [β=-0.062; 95%CI, -0.105-(-0.019)], right arm BMD [β=-0.059; 95%CI, -0.091-(-0.027)], and total BMD [β=-0.065; 95%CI, -0.119-(-0.012] in females. Similar results were also found in different BMI populations (all P<0.05).

CONCLUSION

Certain urinary PAHs are associated with BMDs at specific body sites. Future studies are needed to illustrate the mechanisms behind the association to establish a causal relationship and explain the variations in the associations.

Hydroxylated benzo[c]phenanthrene metabolites cause osteoblast apoptosis and skeletal abnormalities in fish

To study the toxicity of 3-hydroxybenzo[c]phenanthrene (3-OHBcP), a metabolite of benzo[c]phenanthrene (BcP), first we compared it with its parent compound, BcP, using an in ovo-nanoinjection method in Japanese medaka. Second, we examined the influence of 3-OHBcP on bone metabolism using goldfish. Third, the detailed mechanism of 3-OHBcP on bone metabolism was investigated using zebrafish and goldfish. The LC50s of BcP and 3-OHBcP in Japanese medaka were 5.7 nM and 0.003 nM, respectively, indicating that the metabolite was more than 1900 times as toxic as the parent compound. In addition, nanoinjected 3-OHBcP (0.001 nM) induced skeletal abnormalities. Therefore, fish scales with both osteoblasts and osteoclasts on the calcified bone matrix were examined to investigate the mechanisms of 3-OHBcP toxicity on bone metabolism. We found that scale regeneration in the BcP-injected goldfish was significantly inhibited as compared with that in control goldfish. Furthermore, 3-OHBcP was detected in the bile of BcP-injected goldfish, indicating that 3-OHBcP metabolized from BcP inhibited scale regeneration. Subsequently, the toxicity of BcP and 3-OHBcP to osteoblasts was examined using an in vitro assay with regenerating scales. The osteoblastic activity in the 3-OHBcP (10-10 to 10-7 M)-treated scales was significantly suppressed, while BcP (10-11 to 10-7 M)-treated scales did not affect osteoblastic activity. Osteoclastic activity was unchanged by either BcP or 3-OHBcP treatment at each concentration (10-11 to 10-7 M). The detailed toxicity of 3-OHBcP (10-9 M) in osteoblasts was then examined using gene expression analysis on a global scale with fish scales. Eight genes, including APAF1, CHEK2, and FOS, which are associated with apoptosis, were identified from the upregulated genes. This indicated that 3-OHBcP treatment induced apoptosis in fish scales. In situ detection of cell death by TUNEL methods was supported by gene expression analysis. This study is the first to demonstrate that 3-OHBcP, a metabolite of BcP, has greater toxicity than the parent compound, BcP.

Association of urinary organophosphate esters level with sex steroid hormones levels in adult males: A nationwide study, NHANES 2013-2014

BACKGROUND

Exposure to environmental pollution via different mechanisms is associated with multiple endocrine dysfunctions. Organophosphate esters (OPEs) are endocrine-disrupting chemicals that affect sex steroid hormones.

PURPOSE

We aimed to study the effect of OPEs and their metabolites, such as dibutyl phosphate [DPHP], bis(1,3-dichloro-2-propyl) phosphate [BDCPP], bis(2-chloroethyl) phosphate [BCEP], and dibutyl phosphate [DBUP], on sex steroid hormones in males.

DESIGN, SETTING, PARTICIPANTS, AND INTERVENTION

This cross-sectional analytical study analyzed data from the 2013-2014 National Health and Nutrition Examination Survey among 763 male participants aged ≥20 years.

MAIN OUTCOME MEASURES

The relationships between the metabolites of OPEs and total testosterone, estradiol, sex hormone-binding globulin, and the ratio of total testosterone to estradiol (a parameter derived from total testosterone and estradiol) were evaluated using multivariate linear regression models that were adjusted for potential confounders.

RESULTS

A total of 763 participants, with a mean age of 44.59 (±15.59) years, were enrolled. Of these, 65.7% participants had non-Hispanic white ancestry, 9.83% had non-Hispanic black ancestry, and 15.97% had Hispanic ancestry. Participants with higher urinary level of DPHP had a lower level of total testosterone and estradiol. Moreover, higher urinary levels of BDCPP were associated with higher estradiol.

CONCLUSION

According to our study, which is based on a representative population of US adults, exposure to OPEs was significantly associated with altered sex hormone levels (total testosterone and estradiol). Further studies focused on the underlying mechanisms regarding the association between each metabolite and sex steroid hormones are required. This article is protected by copyright. All rights reserved.

In utero exposure to phenanthrene induced islet cell dysfunction in adult mice: Sex differences in the effects and potential causes

Epidemiological studies show that the burden of polycyclic aromatic hydrocarbons in human body is associated with the occurrence of insulin resistance and diabetes. In the present study, pregnant mice were exposed to phenanthrene (Phe) at doses of 0, 60 and 600 μg/kg body weight of by gavage once every 3 days. The female F1 mice at 120 days of age showed no change in their fasting glucose levels (FGLs) but exhibited significantly decreased homeostasis model assessment (HOMA) β-cell (49% and 43%) and significantly downregulated pancreatic proinsulin gene (ins2) transcription. The downregulation of transcription factors, such as PDX1, PAX4 and FGF21, indicated impaired development and function of β-cells. The significantly reduced α-cell mass in 60 and 600 μg/kg groups, and the significantly downregulated expression of proglucagon gene gcg and ARX in the 600 μg/kg group suggested that the development and function of α-cells had been impacted. The males exhibited significantly increased FGLs (1.14- and 1.15-fold) in Phe exposed treatments and significantly elevated HOMA β-cell (3.15-fold) in the 600 μg/kg group. Upregulated ins2 transcription and FGF21 protein in male mice prenatally exposed to 600 μg/kg Phe suggested that these animals appeared compensatory enhancement in β-cell function. The reduced serum estradiol levels and downregulated pancreatic estrogen receptor α and β were responsible for the dysfunction of β-cells in the females. In the males, the significantly elevated androgen levels in the 600 μg/kg group might be related to the upregulated ins2 transcription, and the increased expression of pancreatic FGF21 further demonstrated the enhancement of β-cell potential. The results will be helpful for assessing the risk of developing diabetes in adulthood after prenatal exposure to phenanthrene.

Use of e-cigarettes associated with lower sperm counts in a cross-sectional study of young men from the general population

STUDY QUESTION

Are use of e-cigarettes and snuff associated with testicular function as previously shown for conventional cigarettes and marijuana?

SUMMARY ANSWER

Use of e-cigarettes is associated with reduced semen quality but not with higher serum testosterone level as observed for conventional cigarette use. Snuff use was not associated with markers of testicular function.

WHAT IS KNOWN ALREADY

Cigarette smoking has previously been associated with higher testosterone levels and impaired semen quality, whereas it is unresolved whether use of e-cigarettes or snuff influence the testicular function.

STUDY DESIGN, SIZE, DURATION

This cross-sectional population-based study included 2008 men with information on cigarette and marijuana use (enrolled between 2012 and 2018), among whom 1221 men also had information on e-cigarette and snuff use (enrolled between 2015 and 2018).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Men (median age 19.0 years) from the general population provided a semen and blood sample and filled out a questionnaire on lifestyle including information on smoking behaviour. Associations between different types of smoking (e-cigarettes, snuff, marijuana and cigarettes) and reproductive hormones (total and free testosterone, sex hormone-binding globulin, LH, oestradiol and ratios of inhibin B/FSH, testosterone/LH and free testosterone/LH) and semen parameters (total sperm count and sperm concentration) were examined using multiple linear regression analyses adjusted for relevant confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

Approximately half of the men (52%) were cigarette smokers, 13% used e-cigarettes, 25% used snuff and 33% used marijuana. Users of e-cigarettes and marijuana were often also cigarette smokers. Compared to non-users, daily e-cigarette users had significantly lower total sperm count (147 million vs 91 million) as did daily cigarette smokers (139 million vs 103 million), in adjusted analyses. Furthermore, significantly higher total and free testosterone levels were seen in cigarette smoking men (6.2% and 4.1% higher total testosterone and 6.2% and 6.2% higher free testosterone in daily smokers and occasional smokers, respectively, compared to non-smoking men), but not among e-cigarette users. Daily users of marijuana had 8.3% higher total testosterone levels compared to non-users. No associations were observed for snuff in relation to markers of testicular function.

LIMITATIONS, REASONS FOR CAUTION

We cannot exclude that our results can be influenced by residual confounding by behavioural factors not adjusted for. The number of daily e-cigarette users was limited and findings should be replicated in other studies.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first human study to indicate that not only cigarette smoking but also use of e-cigarettes is associated with lower sperm counts. This could be important knowledge for men trying to achieve a pregnancy, as e-cigarettes are often considered to be less harmful than conventional cigarette smoking.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was received from the Danish Ministry of Health (1-1010-308/59), the Independent Research Fund Denmark (8020-00218B), ReproUnion (20200407) and the Research Fund of the Capital Region of Denmark (A6176). The authors have nothing to disclose.

TRIAL REGISTRATION NUMBER

NA.

Urinary polycyclic aromatic hydrocarbons and sex hormones in children and adolescents: Evidence from NHANES

BACKGROUND

Evidences showed that polycyclic aromatic hydrocarbons (PAHs) do harm to human body. However, the association between PAHs and sex hormones in children and adolescents remains unclear.

OBJECTIVES

The study aims to investigate the associations between PAHs and sex hormones in the general children and adolescent population.

METHODS

967 participants aged 6-19 with complete data of PAHs exposure biomarkers, covariates and sex hormones [total testosterone (TT), estradiol (E2) and sex hormone binding globulin (SHBG)] were recruited from National Health and Nutrition Examination Survey (NHANES), 2013-2016. Free androgen index (FAI) was calculated with TT/SHBG. Multivariate linear regression models were performed in six subgroups (male children, male adolescents, male late adolescents, female children, female adolescents and female late adolescents) to estimate the associations between sex hormone alterations and PAHs exposure.

RESULTS

In male puberty adolescents, weighted multivariate linear regression indicated that negative trends for 2-Hydroxynaphthalene, 1-Hydroxyphenanthrene, 2&3-Hydroxyphenanthrene and E2 (2-Hydroxynaphthalene: β: -0.104, 95%CI: -0.180, -0.029, P < 0.01; 1-Hydroxyphenanthrene: β: -0.112, 95%CI: -0.206, -0.018, P = 0.019; 2&3-Hydroxyphenanthrene: β: -0.125, 95%CI: -0.232, -0.018, P = 0.022), while exposure to 2-Hydroxynaphthalene was related to TT reduction (β: -0.099, 95%CI: -0.177, -0.020, P = 0.014). Same pattern between 2&3-Hydroxyphenanthrene and E2 alteration (2&3-Hydroxyphenanthrene: β: -0.139, 95%CI: -0.236, -0.041, P < 0.01) was also observed in male late adolescents. In male children, we determined that 1-Hydroxyphenanthrene was negatively associated with SHBG (β: -0.121, 95%CI: -0.205, -0.037, P < 0.01), while the same patterns were observed in male puberty children. We did not observe any significant result in female subgroups. All these results above were determined to have q value < 0.05.

CONCLUSION

PAHs exposure was associated with the alterations of sex hormones in male adolescents and children. Considering the cross-sectional study design, further large-scale epidemiological study is necessary.

Polycyclic aromatic hydrocarbon exposure results in altered CRH, reproductive, and thyroid hormone concentrations during human pregnancy

Polycyclic aromatic hydrocarbons (PAHs) are byproducts of incomplete combustion reactions and are ubiquitous in the environment, leading to widespread human exposure via inhalation and ingestion pathways. PAHs have been implicated as endocrine disrupting compounds in previous animal and in vitro studies, but human studies are currently lacking. Pregnant women and their developing fetuses are particularly susceptible populations to environmental contaminants, in part because alterations in hormone physiology during gestation can have adverse consequences on the health of the pregnancy. We utilized data on 659 pregnant women from the PROTECT longitudinal birth cohort in Puerto Rico to assess associations between repeated measures of 8 urinary hydroxylated PAH (OH-PAH) metabolites and 9 serum hormones during gestation. Urine samples were collected at 3 study visits (median gestational ages of 18, 22, and 26 weeks at each visit, respectively) and serum samples were collected at the first and third study visits. Linear mixed effects models were used to ascertain longitudinal associations between OH-PAHs and hormones, and sensitivity analyses were employed to assess potential nonlinearity and differences in associations on the basis of fetal sex and timing of biomarker measurement. Among the multiple positive associations we observed between OH-PAHs and CRH, estriol, progesterone, T3, and the ratio of T3 to T4, and inverse associations with testosterone, the most notable are a 24.3% increase (95% CI: 13.0, 36.7) in CRH with an interquartile range (IQR) increase in 1-hydroxyphenanthrene and a 17.2% decrease (95% CI: 8.13, 25.4) in testosterone with an IQR increase in 1-hydroxynapthalene. Many associations observed were dependent on fetal sex, and some relationships showed evidence of nonlinearity. These findings demonstrate the importance of studying PAH exposures during pregnancy and highlight the potential complexity of their impacts on the physiology of human pregnancy.

Association between Urinary Triclosan and Serum Testosterone Levels in U.S. Adult Males from NHANES, 2011-2012

Triclosan was introduced into the market in the 1970s and has since been used as an antimicrobial agent in a diverse array of consumer and personal care products. Although it has been widely used over a number of years, there is growing concern and debate over its safety and efficacy and its potential as an endocrine disruptor. Although prior animal toxicology studies have shown an association between triclosan and decreased testosterone levels, human studies have been limited, particularly for adult men. Using the National Health and Nutrition Examination Survey data (NHANES, 2011-2012), we examined the association of urinary triclosan on testosterone levels in adult men 18-65 years of age. Multivariable linear regression analysis failed to show an association between triclosan and serum testosterone (β = 0.0003, p = 0.98, 95% CI = -0.024, 0.025). The results suggest there is no association or that triclosan concentrations are too low to cause a significant impact on testosterone levels. Additionally, longitudinal studies would provide a more comprehensive understanding of the direction of change and magnitude of causal relationships over time.

Associations of urinary polycyclic aromatic hydrocarbons with age at natural menopause in U.S. women aged 35-65, NHANES 2003-2012

Polycyclic aromatic hydrocarbons (PAHs) mediated ovarian toxicity has been demonstrated in animal experiments. However, this issue has not been assessed in humans. Based on the National Health and Nutrition Examination Survey (NHANES) 2003-2012, data analysis was restricted to 1221 general U.S. women aged 35-65 years with complete data of interest. Levels of nine PAH metabolites in spot urine specimens were measured by isotope dilution gas chromatography/tandem mass spectrometry (GC-MS/MS). Self-reported information on the menopause status and age at menopause were obtained during interview. Cox proportional hazards regression was employed to assess the associations between PAH levels and natural menopause. Compared with women in the first quartile, subjects in the highest quartile of 1-Hydroxynapthalene [hazard ratio (HR) = 1.46, 95% confidence interval (CI) = 1.06 to 2.01], 2-Hydroxynapthalene (HR = 1.51, 95% CI = 1.12 to 2.05) and 3-Hydroxyfluorene (HR = 1.51, 95% CI = 1.06 to 2.16), or in the second quartile of 9-Hydroxyfluorene (HR = 1.53, 95% CI = 1.05 to 2.22), had elevated risks of earlier onset of natural menopause. Our findings suggested positive associations between urinary PAH levels and earlier age at natural menopause in the general U.S. women. Prospective studies are warranted to confirm the causality in the future.

Associations of urinary polycyclic aromatic hydrocarbons with bone mass density and osteoporosis in U.S. adults, NHANES 2005-2010

Polycyclic aromatic hydrocarbons (PAHs) are environmental endocrine disruptors, which may modify the bone mineralization. However, epidemiological evidences on this issue were scant. We aimed to investigate the associations of PAHs with bone mass density (BMD) and osteoporosis based on a nationally-representative sample from general U.S.

POPULATION

Data utilized were extracted from the 2005-2010 National Health and Nutrition Examination Survey (NHANES). Nine urinary PAHs (U-PAHs) metabolites were measured as exposure biomarkers. Associations of specific U-PAHs with BMD and osteoporosis were estimated by multivariable adjusted linear regression models and logistic regression models, respectively. Compared with women at the first tertiles, those at the third tertiles of 1-Hydroxynapthalene, 2-Hydroxyfluorene, 3-Hydroxyphenanthrene, 2-Hydroxyphenanthrene and 9-Hydroxyfluorene had significantly decreased BMD levels [coefficient (β) = -0.023 to -0.014, p < 0.05] or increased likelihoods of osteoporosis [odds ratios (ORs) = 1.86 to 3.36, p < 0.05] at different bone sites. Whereas, elevated BMD levels (β = 0.021, p < 0.05) at trochanter and decreased likelihoods of osteoporosis (OR = 0.33, p < 0.05) at intertrochanter were observed among women at the second tertiles of 1-Hydroxypyrene and 2-Hydroxynapthalene, respectively. Similar results were found for all the population, i.e., combination of men and women. Most of the significant associations disappeared among adult men only. Furthermore, Associations between U-PAHs and BMD were stronger for postmenopausal women when compared with premenopausal group. In conclusion, associations of U-PAHs with BMD and osteoporosis varied by specific U-PAHs and bone sites, as well as menopausal status and genders in U.S. adults.