Exposure to bisphenol-A and reproductive hormones among male adults

BACKGROUND

Bisphenol A (BPA) is a suspected human endocrine disruptor which is widely used.

METHODS

In order to determine whether urine BPA level is associated with serum reproductive hormone levels among male adults, we carried out a cross-sectional study in China. We recruited 592 male workers and collected their urine samples for BPA measurement. We also collected blood samples and examined serum reproductive hormones. We used multiple linear regression and log-binomial model to examine associations between urine BPA level and hormone levels after controlling for age and smoking status.

RESULTS

An increased urine BPA level was associated with increased prolactin (p<0.001), estradiol (p<0.001), sex hormone-binding globulin level (p=0.001), and a reduced androstenedione (p<0.001) and free androgen index level (p=0.021). Males, whose urine BPA level was in the 2nd, 3rd and highest quartiles, had respectively 1.58, 1.33 and 3.09-fold increased prevalence of having a high prolactin level (>P75 level). The highest quartile of BPA level was associated with 1.63 and 1.50-fold increased prevalence of having a high estradiol and elevated sex hormone-binding globulin level. Males with higher quartile of BPA level had a lower inhibin B level.

CONCLUSION

High BPA exposure is associated with increased prolactin, estradiol and sex hormone-binding globulin level in males, and may contribute to male infertility.

Another functional frame-shift polymorphism of DEFB126 (rs11467497) associated with male infertility

DEFB126 rs140685149 mutation was shown to cause sperm dysfunction and subfertility. Indel rs11467497 is another 4-nucleotide frame-shift mutation (151bp upstream of rs140685149) that leads to the premature termination of translation and the expression of peptide truncated at the carboxyl terminus. In the present study, we performed a comprehensive association study to check the contribution of rs140685149 and rs11467497 to male infertility. Our results confirmed the previous findings that there was no association between rs140685149 and sperm motility. In contrast, we found a significant association of another indel rs11467497 with male infertility. Moreover, rs11467497 was shown to be associated with higher number of round cells in the infertile males with low sperm motility. Surprisingly, the two mutations commonly existed in the sperm donors (n = 672), suggesting a potential application of the two indels in the screening for eligible sperm donors. Western blotting assays showed the sperms with rs140685149 2-nt deletion tended to have unstable DEFB126 protein in contrast of no DEFB126 protein expressed in the sperms with rs11467497 4-nt deletion, suggesting a more severe consequence caused by rs11467497 mutation. In conclusion, our study presented a significant contribution of another functional frame-shift polymorphism of DEFB126 (rs11467497) to male infertility.

Association between body fat distribution and androgen deficiency in middle-aged and elderly men in China

The objective of the present study was to examine the association between body fat distribution and total testosterone (TT) and free testosterone (FT) levels among middle-aged and elderly men. A total of 922 male residents aged 40-70 years from a community in Shanghai, China, participated in the study. Their waist circumference (WC), waist-height ratio (WHtR), body mass index (BMI), and TT and FT concentrations were measured. Logistic regression models were used to estimate testosterone deficiency risk on the basis of anthropometric indices. BMI, WC and WHtR were all associated with TT deficiency. The participants in the highest quartiles of above-mentioned anthropometric indices had the highest risk of TT deficiency (BMI: odds ratio (OR)=4.40, 95% confidence interval (CI)=2.69-7.19; WC: OR=3.47, 95% CI=2.14-5.60; WHtR: OR=2.89, 95% CI=1.76-4.76). WC and WHtR were associated with FT deficiency. The participants in the highest quartiles had the highest risk of FT deficiency (WC: OR=1.87, 95% CI=1.18-2.97; WHtR: OR=1.67, 95% CI=1.04-2.66). The association between BMI and FT deficiency was not statistically significant (OR=1.21 for the highest quartile, 95% CI=0.78-1.87). Our study demonstrated that both general and abdominal obesity were associated with TT deficiency, whereas only abdominal obesity was found to be associated with FT deficiency.

LINE-1 hypomethylation in spermatozoa is associated with Bisphenol A exposure

Bisphenol A (BPA) is an endocrine disruptor with potentially harmful effects on humans. However, epigenetic mechanisms that modulate the effects of BPA remain unclear. Methylation of long interspersed nucleotide elements (LINE-1) is a marker of genome-wide methylation status. This study aims to examine whether BPA exposure was associated with LINE-1 methylation changes in men. Male factory workers in Hunan, China (N = 149) were studied, 77 with BPA exposure in workplace (BPA-exposed group) and 72 without BPA exposure in workplace (control group). Pre-shift and post-shift urine samples were collected from the BPA-exposed group and spot urine samples were collected from the control group. Urine samples were assessed for BPA. In addition, blood and semen samples were collected from both groups for LINE-1 methylation analysis. In multivariate analysis adjusted for age, education, smoking habits and alcohol consumption, sperm LINE-1 methylation level was significantly lower in BPA exposed workers (p < 0.001) compared to that in the unexposed workers. Linear regression analysis also showed that log-transformed urine BPA levels were inversely associated with sperm LINE-1 methylation (p < 0.0001), but not peripheral blood cell LINE-1 methylation. Moreover, the association between urine BPA level and semen quality was not attenuated after adjustments for LINE-1 level. In summary, the observed independent relationship between BPA exposure and LINE-1 methylation may have public health implications on reproductive health in men because of ubiquitous exposure to BPA.

In utero exposure to bisphenol-A and its effect on birth weight of offspring

To examine the effect of in utero BPA exposure on the birth weight of offspring, a total of 587 children from families in which parent(s) did or did not have occupational exposure to BPA were examined. Their birth weights were obtained by an in-person interview of the mother. Parental BPA exposure level during the index pregnancy was determined through personal air sampling measurements and exposure history. After controlling for potential confounders, parental exposure to BPA in the workplace during pregnancy was associated with decreased birth weight. The association was stronger for maternal exposure which is statistically significant (P=0.02). A dose-response relationship was observed with increased BPA exposure levels in pregnancy associated with greater magnitude of decrease of birth weight in offspring (P=0.003). Our findings provide the new epidemiologic evidence suggesting that in utero exposure to BPA during pregnancy may be associated with decreased birth weight in offspring.

The Presence of Hepatitis B Surface Antigen in the Ova of Pregnant Women and Its Relationship with Intra-Uterine Infection by Hepatitis B Virus

Vertical transmission of hepatitis B virus (HBV) has been proposed to play an important role in mother-to-child transmission, although the extent to which vertical transmission via oocytes contributes to neonatal HBV infection remains unknown. Ovarian biopsies were collected during caesarean sections in 68 clinically asymptomatic pregnant women who were carriers of HBV. The presence of hepatitis B surface antigen (HBsAg) in the ova of pregnant women was determined by immunohistochemistry. Serum markers of HBV infection in pregnant women and their neonates were analysed. It was found that, of 68 women, the ova were positive for HBsAg in only one woman and her neonate was negative for any serum HBV markers 3 days after birth. Of 68 neonates, one was positive for serum HBV markers 3 days after birth and his mother's ova were negative for HBsAg. These findings indicate that vertical transmission via oocytes may not be the major route of HBV intra-uterine infection.

Bisphenol A levels in blood and urine in a Chinese population and the personal factors affecting the levels

The objective of the study was to describe the background bisphenol A (BPA) levels in urine and serum of a Chinese population without occupational exposure and to examine the personal characteristics influencing these levels. Workers from 10 factories and their family members were recruited and their peripheral blood and spot urine samples were collected. The conjugated and free BPA of the samples was assayed with high-performance liquid chromatography. The exposure levels were checked with 2-independent-samples test, and the potential personal factors influencing exposure levels were analyzed using nonlinear correlation. Of the total of 952 subjects participating in the study, urine and blood samples were taken from 97% and 93% of them, respectively. The detectable rates were 50% for urine samples and 17% for serum samples, given the detection limit of 0.31 microg/L for urine and 0.39 microg/L for serum. The arithmetic mean (AM) and geometric mean (GM) of non-creatinine-adjusted urinary BPA level were 10.45 and 0.87 microg/L, which became 24.93 and 0.38 microg/g Cr after the creatinine level was adjusted; serum BPA levels were 2.84 microg/L (AM) and 0.18 microg/L (GM). Males and those with smoking habit had higher biological burden of BPA. The results indicated that half of the study subjects had detectable BPA in their urine samples. BPA levels were influenced by gender and smoking status. The sources of non-occupational BPA exposures should be explored.

Differential expression of two tropoelastin genes in zebrafish

Elastin is the extracellular matrix protein responsible for properties of extensibility and elastic recoil in large blood vessels, lung and skin of most vertebrates. Elastin is synthesized as a monomer, tropoelastin, but is rapidly transformed into its final polymeric form in the extracellular matrix. Until recently information on sequence and developmental expression of tropoelastins was limited to mammalian and avian species. We have recently identified and characterized two expressed tropoelastin genes in zebrafish. This was the first example of a species with multiple tropoelastin genes, raising the possibility of differential expression and function of these tropoelastins in elastic tissues of the zebrafish. Here we have investigated the temporal expression and tissue distribution of the two tropoelastin genes in developing and adult zebrafish. Expression was detected early in skeletal cartilage structures of the head, in the developing outflow tract of the heart, including the bulbus arteriosus and the ventral aorta, and in the wall of the swim bladder. While the temporal pattern of expression was similar for both genes, the upregulation of eln2 was much stronger than that of eln1. In general, both genes were expressed and their gene products deposited in most of the elastic tissues examined, with the notable exception of the bulbus arteriosus in which eln2 expression and its gene product was predominant. This finding may represent a sub-specialization of eln2 to provide the unique architecture of elastin and the specific mechanical properties required by this organ.

Monodithiolene molybdenum(V, VI) complexes: a structural analogue of the oxidized active site of the sulfite oxidase enzyme family

The active sites of the xanthine oxidase and sulfite oxidase enzyme families contain one pterin-dithiolene cofactor ligand bound to a molybdenum atom. Consequently, monodithiolene molybdenum complexes have been sought by exploratory synthesis for structural and reactivity studies. Reaction of [MoO(S(2)C(2)Me(2))(2)](1-) or [MoO(bdt)(2)](1-) with PhSeCl results in removal of one dithiolate ligand and formation of [MoOCl(2)(S(2)C(2)Me(2))](1-) (1) or [MoOCl(2)(bdt)](1-) (2), which undergoes ligand substitution reactions to form other monodithiolene complexes [MoO(2-AdS)(2)(S(2)C(2)Me(2))](1-) (3), [MoO(SR)(2)(bdt)](1-) (R = 2-Ad (4), 2,4,6-Pr(i)(3)C(6)H(2) (5)), and [MoOCl(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt)](1-) (6) (Ad = 2-adamantyl, bdt = benzene-1,2-dithiolate). These complexes have square pyramidal structures with apical oxo ligands, exhibit rhombic EPR spectra, and 3-5 are electrochemically reducible to Mo(IV)O species. Complexes 1-6 constitute the first examples of five-coordinate monodithiolene Mo(V)O complexes; 6 approaches the proposed structure of the high-pH form of sulfite oxidase. Treatment of [MoO(2)(OSiPh(3))(2)] with Li(2)(bdt) in THF affords [MoO(2)(OSiPh(3))(bdt)](1-) (8). Reaction of 8 with 2,4,6-Pr(i)(3)C(6)H(2)SH in acetonitrile gives [MoO(2)(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt)](1-) (9, 55%). Complexes 8 and 9 are square pyramidal with apical and basal oxo ligands. With one dithiolene and one thiolate ligand of a square pyramidal Mo(VI)O(2)S(3) coordination unit, 9 closely resembles the oxidized sites in sulfite oxidase and assimilatory nitrate reductase as deduced from crystallography (sulfite oxidase) and Mo EXAFS. The complex is the first structural analogue of the active sites in fully oxidized members of the sulfite oxidase family. This work provides a starting point for the development of both structural and reactivity analogues of members of this family.

[Trace elements and extracellular matrix]

OBJECTIVE

To investigate the effects of trace elements on the metabolism of extracellular matrix and explore the physiological and pathological mechanism of trauma.

METHODS

Based on the experimental and clinical data, it was studied that the action of trace elements in the metabolism of extracellular matrix in trauma repairing.

RESULTS

During wound healing, the trace elements were the components of many kinds of enzymes, carriers and proteins. They took part in the synthesis of hormones and vitamins as well as the transmission of information system. They activated many different kinds of enzymes and regulate the levels of free radicals. The trace elements had the complicated effects on the synthesis, decompose, deposition and reconstruction of collagen and other extracellular matrix.

CONCLUSION

The trace elements play an important role in regulating the metabolism of extracellular matrix.