Interaction between cadmium (Cd), selenium (Se) and oxidative stress biomarkers in healthy mothers and its impact on birth anthropometric measures.

To our knowledge, this study may be the first to examine the antagonistic role of selenium (Se) on oxidative stress induced by cadmium (Cd) and its impact on birth measures. Cd and Se levels were measured in umbilical-cord blood and the placentas of a subsample of 250 healthy mothers who participated between 2005 and 2006 in the project "Prenatal Exposure to Pollutants". The median Cd levels in cord and maternal blood and placental tissue were 0.78µg/l, 0.976µg/l and 0.037µg/g dry wt., respectively. The median levels of Se in cord serum and placental tissue were 65.68µg/l and 1.052µg/g dry wt., respectively. Se was more than 100-fold in molar excess over Cd in both cord serum and placental tissue. The median molar Cd/Se ratios in cord serum and placental tissue were 0.008 and 0.024, respectively, which were much lower than unity. This study suggests that both Cd and Se play a role in the mechanism of oxidative stress, but, the process underlying this mechanism remains unclear. Nevertheless, three biomarkers of oxidative stress had inconsistent relationships with Cd and/or Se in various matrices, perhaps due to potential untested confounders. Our results generally support an association between low in utero exposure to Cd and the anthropometric development of the fetus. Adjusted regression models indicated a negative association of cord blood Cd levels ≥0.78µg/l with Apgar 5-min scores and birth height. Maternal Cd levels ≥0.976µg/l were associated with a 5.94-fold increased risk of small-for-gestational-age births, which increased to 7.48-fold after excluding preterm births. Placenta weight decreased with increasing placental Cd levels ≥0.037µg/g dry wt. (p=0.045), an association that became stronger after excluding preterm births or adjusting for birth weight. Cord Se levels ≥65.68µg/l were positively associated with placenta weight (p=0.041) and thickness (p=0.031), an association that remained unchanged after excluding preterm births. Cord Se levels, however, were negatively associated with cephalization index, but only after excluding preterm births (p=0.017). Each birth measure was again modeled as a function of the Cd/Se ratios in cord blood and placenta tissue. Interestingly cord ratios ≥0.008 were negatively associated with Apgar-5min score (p=0.047), birth weight (p=0.034) and placenta thickness (p=0.022). After excluding preterm births, only the association with placenta thickness remained significant (p=0.021), while birth weight (p=0.053) was marginally significant. In contrast, cephalization index increased with Cd/Se ratios ≥0.008 (p=0.033), an association that became marginally significant after excluding preterm births (p=0.058). For placental Cd/Se ratios ≥0.024, only placenta weight was reduced with (p=0.037) and without (p=0.009) the inclusion of preterm births. These findings do not support an antagonistic mechanism between Cd and Se. The role of oxidative mechanisms either induced by Cd exposure or alleviated by Se on these birth anthropometric measures was examined by principal component analysis. Se did not have a clear protective role against Cd-induced adverse effects despite its substantial excess over Cd, and its role in alleviating oxidative stress by reducing malondialdehyde levels. The results may suggest that the extent of the Se beneficial effects is not governed only by its concentration but also by the chemical forms of Se that interact with various proteins. Consequently, the speciation of Se in such studies is essential for understanding and predicting Se availability for absorption.

Mercury (Hg) and oxidative stress status in healthy mothers and its effect on birth anthropometric measures.

This study was conducted to: (a) investigate the antagonistic interaction between selenium (Se) and mercury (Hg) in mothers and their newborns, (b) delineate the role of oxidative mechanisms induced by Hg exposure and (c) examine the protective effect of Se on Hg-induced oxidative stress and birth outcomes. Levels of Hg and Se were measured in umbilical cord blood and the placentas of 250 healthy mothers who participated in a study between 2006 and 2006 assessing prenatal exposure various pollutants. Levels of malondialdehyde (MDA) in cord and maternal blood and of 8-hydroxy-2-deoxyguanosine in urine were measured for assessing oxidative stress. Tail moment (TM) in the comet assay, as a biomarker of DNA damage was measured in samples of cord and maternal blood. The mean Se levels in umbilical cord blood (67.618±12.897µg/l) were lower than those reported in many countries, but none of the newborns had Se levels <20µg/l (the threshold limit of Keshan disease). More than 80% of the newborns, though, had Se levels below the 80µg/l needed for maximum glutathione peroxidase activity. Even though 18.6% of the newborns had levels of Hg ≥5.8µg/l (the reference dose of the Environmental Protection Agency), no relationship was observed with the biomarkers of oxidative stress. The mean placental Hg levels (0.056±0.075µg/g dry wt.) were higher than those reported for newborns with abnormal fetal development. Our study also documented significant placental transfer of Hg and Se to the fetus. The Hg/Se molar ratio in both cord blood and placental tissue was well below 1. The average amount of Se in both matrices was approximately 50-fold in molar excess over Hg. The molar excess of Se in the umbilical cord (0.843µmol/l), however, was lower than in placental tissues (13.098µmol/kg dry wt.). In further support of the relationships of Hg and Se on oxidative stress, we observed significantly lower levels of maternal MDA associated with Se levels in both cord blood and placental tissues and significantly higher TM levels associated with placental Hg in both newborns and their mothers. In contrast, Se/Hg molar ratios in placental tissues were positively associated with MDA and negatively with TM. The disproportion between Hg and Se might be influenced by the length of Hg exposure that in turn might affect Se bioavailability. Each birth anthropometric outcome was modeled as a function of Hg, Se and their interactions. After an adjustment for confounding variables, Hg in cord blood had a significantly positive rather than the expected negative association with crown-heel length. Placental Hg was associated with reduced birth height. Both associations were independent of prematurity. The status of Se in newborns was positively associated with crown-heel length and placental weight, with and without preterm births, and with birth weight, but only without preterm births. In contrast, a lower cephalization index was correlated with Se levels in cord blood, which may be an indicator of a detrimental effect on health. Our study, however, revealed associations between significantly lower levels of placental Se and several birth anthropometric measures (head circumference, birth weight and birth height) but the significance disappeared after excluding preterm births. Regression analyses generally indicated either significant or marginally significant Hg-Se antagonistic interactions that may have moderated the toxic effect of Hg on head circumference and birth weight. This finding may be due to chance or residual confounding and so may not be clinically relevant, but it may also suggest that Hg, Se and Hg-Se interactions are important factors for understanding Hg-induced adverse birth outcomes. Additional research will be necessary to evaluate the biological impact of combined metals in the assessment of fetal growth and development.

Polycyclic aromatic hydrocarbons (PAHs) as determinants of various anthropometric measures of birth outcome.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants that are known to induce oxidative stress. There have been several reports about the link between PAH exposure and complications in pregnancy. This cross-sectional study was conducted to: (1) measure the levels of benzo(a)anthracene (BaA), chrysene (Ch), benzo(b)fluoranthene (BbF), benzo(a)pyrene (BaP), and dibenzo(a,h)anthracene (DBahA) in placentas and maternal and -umbilical cord blood obtained at delivery from 1578 women between June 2005 and 2006 in the area of Al-Kharj, Saudi Arabia; (2) assess their influence on various anthropometric measures of birth outcome taking into consideration the carcinogenic properties of these PAHs; and (3) determine the degree of PAH-related oxidative DNA damage and birth outcome. Among the five tested PAHs, only BaP was carcinogenic; therefore, the levels of the other four probable or possible carcinogenic PAHs (BaA, Ch, BaF, and DBahA) were summed as ∑4-PAHs. Levels of 1-hydroxypyrene (1-HP) were determined in maternal urine samples as a biomarker of PAH internal dose. Urinary cotinine (COT) was measured as an index of smoking. The following markers of oxidative stress were selected: malondialdehyde (MDA) in cord (C-MDA) and maternal (M-MDA) serum and 8-hydroxy-2-deoxyguanosine (8-OHdG) in maternal urine. None of the tested PAHs was found in maternal or cord blood. However, all five PAH compounds were detected in placentas; Ch was the highest (6.582 µg/kg dry wt.), and BaA was the lowest (0.236 µg/kg dry wt.). The mean concentration of urinary 1-HP found in this study was 0.216 ± 0.856 µg/g Cr. After adjusting for gestational age and other confounding variables, regression models revealed an inverse relationship between placental weight, cord length and placental BaP. A similar trend was observed between cord length and ∑4-PAHs in placental tissues. Urinary 1-HP, though, cannot be used as an unequivocal biomarker of PAH exposure, but it can be an appropriate indicator of exposure to environmental tobacco smoke (ETS). The data demonstrate that ETS exposure (as measured by urinary COT) may adversely affect birth outcome as shown by reduced head circumference, birth weight, and birth length, as well as increased cephalization index. The positive relationship between 8-OHdG levels and 1-HP in urine provides evidence of an oxidative stress mechanism. Although this study provides no direct evidence of an association between PAH exposure and DNA damage, increased oxidative stress in the form of lipid peroxidation significantly affected various birth measures. Therefore, there is a need for studies regarding PAH exposure and its associated biological effects to determine the extent of potential fetal damage as well as possible long-term effects, such as cancer.

Outcome of in-vitro fertilization treatment and DDT levels in serum and follicular fluid.

BACKGROUND: Although p,p'-dichlorodiphenyltrichloroethane (DDT) is banned for agricultural purpose in Saudi Arabia, it is occasionally used to control vector-borne diseases in certain regions of the country. MATERIAL/METHODS: A case-control study was designed to investigate the possible effects of DDT and its metabolites on pregnancy and fertilization rate outcome. The study population was composed of 619 Saudi women (age 19-50 years) who sought in-vitro fertilization (IVF) treatment between 2002 and 2003. RESULTS: p,p'-DDE, the main metabolite of DDT, was the most frequently detected residue in serum or follicular fluid, with mean values of 1.646 microg/L and 0.407 microg/L, respectively. After controlling for many potential confounding variables, multiple logistic regression analysis revealed no association between pregnancy outcome or fertilization rate and p,p'-DDE levels in serum or follicular fluid. CONCLUSIONS: The inability to identify an effect may be related to the comparatively low concentrations of DDE in our population. But because p,p'-DDE was detected in the serum of 77.7% our participants, it should be considered as a matter of public heath concern. Currently there is no active source of DDT in our region; therefore, further studies are needed to identify sources in order to develop preventive measures because we can not exclude its potential reproductive toxicity.

Role of Nigella sativa and a number of its antioxidant constituents towards azoxymethane-induced genotoxic effects and colon cancer in rats.

This study examined the chemopreventive effect of Nigella sativa and some of its antioxidant constituents on a number of colon cancer biomarkers in rats induced with azoxymethane (AOM). Sixty male Sprague-Dawley rats were randomly assigned into ten subgroups: vehicle (1-5) and experimental (6-10). The rats in each group were fed one of the following diets: basal diet, (200 mg/kg) Nigella sativa, (0.2 mg/kg) selenium, (1.2 mg/kg) all-trans-retinol plus (100 mg/kg) DL-alpha-tocopherol and (10 mg/kg) thymoquinone, respectively. Only rats in subgroups 6-10 were injected with AOM (15 mg/kg) once per week for 2 weeks. Both groups were fed their respective diets for 5 weeks. Then they were killed and examined for colonic aberrant crypt foci (ACF). Our result showed that only vitamin supplementation was effective on ACF. Nigella sativa revealed inhibitory effects only on DNA damage (day 34) in the AOM-treated rat group. Alternatively, selenium, thymoquinone and vitamins inhibited the MDA content in the liver. Although the exact mechanisms involved in the protective role of Nigella sativa against the initiation of colon carcinogenesis are not clearly understood, the results suggest that its inhibitory effects might depend on the combined competitive inhibition of various antioxidant constituents of this plant.

Exposure to heavy metals (lead, cadmium and mercury) and its effect on the outcome of in-vitro fertilization treatment.

We investigated the effect of lead, cadmium and mercury exposure on pregnancy and fertilization rate outcome among 619 Saudi women (age 19-50 years) who sought in-vitro fertilization (IVF) treatment between 2002 and 2003. The concentrations of lead, cadmium and mercury were measured in both blood and follicular fluids. At levels well below the current US occupational exposure limit guidelines (40microg/dL) and even less than the current Centers for Disease Control and Prevention level of concern for preventing lead poisoning in children (10microg/dL), blood lead level was negatively associated with fertilization outcome in both adjusted and unadjusted logistic regression models. We found that among various demographic, socioeconomic and environmental factors, fish consumption was positively associated with blood lead levels. These results support the hypothesis that a raised blood lead level affects infertility and intervention to reduce the lead exposure might be needed for women of reproductive age. The present results also revealed unexpected finding - the positive relationship between follicular cadmium levels and fertilization outcome, which points to the necessity for further investigation. Though adverse effect of mercury on pregnancy outcome or fertilization rate was not evident in this study, mercury5.8microg/L (EPA safety limit) was found in the blood and follicular fluid of 18.7% and 8.3% of the women, respectively. Concerns about its possible adverse effects on the physiology of reproduction or fetal development cannot be ruled out. It should be noted that skin-lightening creams and dental amalgam were important contributors to mercury exposure. Such finding is alarming and priority for further studies are, urgently, needed.

Age and gender-related reference values for serum dl-alpha-tocopherol and all-trans-retinol levels in Saudi population.

We established a reference range for dl-alpha-tocopherol and all-trans-retinol in a Saudi population previously selected for a cross-sectional study evaluating selenium and vitamin status. Concentrations of dl-alpha-tocopherol and all-trans-retinol were 0.999 +/- 0.31 mg/dL (n=994, range 0.11-3.42 mg/dL) and 49.14 +/- 24.15 micro/dL (n=1000, range 11.20-400.85 microg/dL), respectively. The levels of dl-alpha-tocopherol and all-trans-retinol in serum were determined by high-pressure liquid chromatography (HPLC) equipped with a UV detector. We took the influence of age and gender into account. Both had significant effect on the levels of all-trans-retinol in serum, except in the case of dl-alpha-tocopherol, where no gender related effect was found. We used the 5th and 95th percentiles as reference limits. Based on these criteria, it was found that these reference limits differed between genders for all-trans-retinol. Our lower and upper limits for dl-alpha-tocopherol classified by three age groups were very close to the normal range of 0.5-1.6 mg/dL, as found in previous studies. The 5th percentile of all-trans-retinol in both males and females, stratified by age, was close to a level of <20 microg/dL, which could be regarded as a mild vitamin A deficiency according to WHO criteria. But the value corresponding to the 95th percentile was higher than the upper limit of vitamin A's normal range of 70 microg/dL, suggesting a potentially harmful high dietary intake of vitamin A. The reference intervals elaborated here may help in the assessment of the vitamin status and in detecting subjects at risk of developing pathologies associated with either excess intake or deficiency.

Status of selenium, vitamin E, and vitamin A among Saudi adults: potential links with common endemic diseases.

This study was designed to determine the status of selenium, dl-alpha-tocopherol, and all-trans-retinol in adults living in Al-Kharj district using serum and toenail samples, and to look for possible association between these parameters and the etiology of endemic diseases in the same area. For this purpose, we examined a cross section of samples of 743 healthy Saudi adults on routine visits to the Primary Health Care Unites (PHCUs) for different common health problems. The arithmetic mean for selenium, dl-alpha-tocopherol, and all-trans-retinol in serum and toenail selenium levels were 107.045 +/- 23.045 microg/l (n = 743, range 52.600-210.120 microg/l), 1.053 +/- 0.324 mg/dl (n = 737, range 0.29-3.42 mg/dl), 52.561 +/- 25.671 microg/dl (n = 743, range 11.20-400.85 microg/dl), and 0.634 +/- 0.221 microg/g (n = 691, range < DL - 1.797 microg/g), respectively. The average serum selenium concentration seems to be satisfactory and compares favourably with high selenium intake countries. Although none of our participants exhibited serum selenium deficiency (< 45 microg/l), 41% of our participants had toenail selenium < 0.56 microg/g reported low levels in the previous study. The mean serum dl-alpha-tocopherol concentrations fall within the upper limit of the normal range of > 0.698-1.981 mg/dl for alpha-tocopherol as found in previous studies. On the other hand, the mean serum all-trans-retinol is higher than the normal range (20-30 microg/dl). None had exhausted retinol stores trans-retinol and MDA levels in the serum was found as a sign of peroxidative lipid damage, confirming the role of vitamin A in reducing oxidative stress. Our data also revealed a link between the status of selenium, dl-alpha-tocopherol and all-trans-retinol and a number of health problems. However, these observations need larger epidemiological studies for further confirmation.

Selenium and vitamins status in Saudi children.

BACKGROUND: Selenium is an essential element, and a cofactor required to maintain glutathione peroxidase activity. Its deficiency may induce modification in the cellular antioxidative status and the appearance of different diseases. Previous studies in Al-Kharj reported low selenium levels in the soil and the milk of lactating mothers living in that area. METHODS: A cross-sectional study was carried out to determine the status of selenium, dl-alpha-tocopherol, and all-trans-retinol in 513 Saudi children living in Al-Kharj district using serum and toenail samples. RESULTS: The prevalence of children with serum selenium below the threshold limit of clinical importance in coronary and cardiovascular diseases (45 microg/l) was only 1.4%, while 53.4% of the tested children had toenail selenium >0.56 microg/g, which is considered a low level as indicated in a previous study. DL-alpha-tocopherol deficiency (<0.5 mg/dl) was found only in 3.1%. However, none of the children in this study had a severe all-trans-retinol deficiency (<10 microg/dl) and the percentage of children with marginal deficiency <20 microg/dl was 5.5%. CONCLUSION: It seems that the geographical location of primary health care units (PHCUs) is the most important factor in influencing the selenium status of these children. This implies variations in food habits. Serum and toenail selenium concentrations were significantly related which can both reflect dietary selenium intake. Although our results suggest an adequate vitamin A status, we found interestingly that 10.9% of the children had retinol >50 microg/dl. This suggests that a high dietary intake of vitamin A might have a harmful effect. Further work is necessary to determine whether the hypervitaminosis A in children reflects an excessive dietary intake of retinol. A significant negative association was also found between dl-alpha-tocopherol and all-trans-retinol and malonaldehyde (MDA) levels in the serum of children population. This confirms their role in reducing oxidative stress.

Comparison of mercury levels in various tissues of albino and pigmented mice treated with two different brands of mercury skin-lightening creams.

The use of mercury containing skin-lightening creams are becoming increasingly popular among dark-skinned women. The long-term use of certain brands may cause serious health effects over the years. In the present study, we investigated the dermal absorption of mercury and its accumulation in the tissues of albino and pigmented mice treated with two brands of mercury containing skin-lightening creams for a period of one months at different intervals. The mean +/- SD of mercury in the selected brands were: (1) Fair & Lovely (0.304 +/- 0.316 microg/g); and (2) Rose (77513.0 +/- 71063.0 microg/g). Mercury levels were measured in a total of 133 and 144 liver, kidney and brain tissue samples of albino and pigmented mice respectively by the Atomic Absorption Spectrophotometer coupled to Vapour Generator Accessory. In both strains, we found that the mercury concentration in the tissues of mice treated with Rose skin-lightening cream samples was significantly higher than those treated with Fair & Lovely skin lightening cream. Looking at the mercury concentration in the tissue samples with respect to the application of skin lightening creams at different intervals, the highest mercury concentrations were found in the tissues of albino and pigmented mice treated three times a day. On the other hand, the lowest mercury concentrations were found in the tissues of mice treated once a week. Despite the brand of skin-lightening cream that was applied, the study indicated that mercury was readily absorbed through the skin of both albino and pigmented mice as evidenced with its accumulation in the brain, kidney and liver tissues where the kidney had the highest mercury content and brain had the lowest (it P < 0.0001). Significant differences in the mercury levels were observed between the albino and pigmented mice. This emphasizes the protective role of melanin against mercury toxicity. Results of this study stresses the potential harm of these mercury containing skin-lightening creams regardless of their mercury contents especially for women who apply these creams frequently or for extended periods. Permanent nephrological or/and neurological deficits may occur if the damage is severe and diagnosis and treatment are delayed.