Determinants of AhR-mediated transcriptional activity induced by plasma extracts from Nunavik Inuit adults

Maternal serum dioxin-like activity and gestational age at birth and indices of foetal growth: The Aarhus birth cohort

Human exposure to lipophilic persistent organic pollutants (lipPOP) is ubiquitous and life-long, beginning during foetal development. Exposure to lipPOP elicits a number of species and tissue specific responses including dioxin-like activity which involve the activation of aryl hydrocarbon receptor (AhR). This study aims i) to describe the combined dioxin-like activity in serum from Danish pregnant women collected during 2011-2013; ii) to assess the association between maternal serum dioxin-like activity, gestational age at birth and foetal growth indices. The serum lipPOP fraction was extracted using Solid Phase Extraction and cleaned-up on Supelco multi-layer silica and florisil columns. The combined dioxin-like activity of the extract was determined using the AhR reporter gene bioassay, expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent (TEQ) [AhR-TEQ (pg/g lipid)]. The associations of AhR-TEQ and foetal growth indices (birth weight, birth length and head circumference) and gestational age were assessed by linear regression models. We detected AhR-TEQ in 93.9 % of maternal first trimester serum samples, with a median level of 185 pg/g lipid. Each ln-unit increase in AhR-TEQ was associated with an increase in birth weight of 36 g (95 % CI: 5; 68), birth length of 0.2 cm (95 % CI: 0.01; 0.3) and pregnancy duration of 1 day (95 % CI: 0; 1.5). In women who never smoked, higher AhR-TEQ values were associated with higher birth weight and longer duration of gestation, while in smokers the association was the opposite. Mediation analyses suggested that gestational age may mediate the association of AhR-TEQ with foetal growth indices. We conclude that AhR activating substances are present in the bloodstream of almost all pregnant women in Denmark and the AhR-TEQ level was around four times higher than previously reported. The AhR-TEQ was associated with slightly longer gestational duration and thereby higher birth weight and birth length.

Dioxin-like Activity in Pregnant Women and Indices of Fetal Growth: The ACCEPT Birth Cohort

Exposure to lipophilic persistent organic pollutants (lipPOPs) elicits a number of species- and tissue-specific toxic responses, many of which involve the aryl hydrocarbon receptor (AhR). This study aims to measure the combined serum dioxin-like activity of lipPOPs in Greenlandic Inuit pregnant women and the associations with fetal growth indices. The combined dioxin-like activity of serum lipPOPs extracts was determined using the AhR reporter gene bioassay and expressed as pico-gram (pg) TCDD equivalent (TEQ) per gram serum lipid [AhR-TEQ (pg/g lipid)]. Significant AhR-TEQ was found in >87% of serum samples with the median level of 86.2 pg TEQ/g lipid. The AhR-TEQ level positively correlated with the marine food intake biomarker n-3/n-6 polyunsaturated fatty acids ratio, while negatively correlated with body mass index and parity. Women giving birth to infants with low birth weight (<2500 g) and length (<50 cm) had higher AhR-TEQ level compared to those with normal weight and length infants. For previous smokers, we found significant inverse associations between maternal AhR-TEQ level and fetal growth indices. In conclusion, exposure of Greenlandic Inuit pregnant women to dioxin-like compounds through traditional marine food can adversely influence the fetal growth via induced AhR activity. Smoking might have modifying effects.

Exposure to Aroclor 1254 persistently suppresses the functions of pancreatic β-cells and deteriorates glucose homeostasis in male mice

Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants that have been shown to be related to the occurrence of type 2 diabetes mellitus (T2DM). Nevertheless, it is necessary to further explore the development of T2DM caused by PCBs and its underlying mechanisms. In the present study, 21-day-old C57BL/6 male mice were orally treated with Aroclor 1254 (0.5, 5, 50 or 500 μg kg^-1) once every three days. After exposure for 66 d, the mice showed impaired glucose tolerance, 13% and 14% increased fasting serum insulin levels (FSIL), and 63% and 69% increases of the pancreatic β-cell mass in the 50 and 500 μg kg^-1 groups, respectively. After stopping exposure for 90 d, treated mice returned to normoglycemia and normal FSIL. After re-exposure of these recovered mice to Aroclor 1254 for 30 d, fasting plasma glucose showed 15%, 28% and 16% increase in the 5, 50 and 500 μg kg^-1 treatments, FSIL exhibited 35%, 27%, 30% and 32% decrease in the 0.5, 5, 50 or 500 μg kg^-1 groups respectively, and there was no change in pancreatic β-cell mass. Transcription of the pancreatic insulin gene (Ins2) was significantly down-regulated in the 50 and 500 μg kg^-1 groups, while DNA-methylation levels were simultaneously increased in the Ins2 promoter during the course of exposure, recovery and re-exposure. Reduced insulin levels were initially rescued by a compensative increase in β-cell mass. However, β-cell mass eventually failed to make sufficient levels of insulin, resulting in significant increases in fasting blood glucose, and indicating the development of T2DM.

A veterinary perspective on One Health in the Arctic

Exposure to long-range transported industrial chemicals, climate change and diseases is posing a risk to the overall health and populations of Arctic wildlife. Since local communities are relying on the same marine food web as marine mammals in the Arctic, it requires a One Health approach to understand the holistic ecosystem health including that of humans. Here we collect and identify gaps in the current knowledge of health in the Arctic and present the veterinary perspective of One Health and ecosystem dynamics. The review shows that exposure to persistent organic pollutants (POPs) is having multiple organ-system effects across taxa, including impacts on neuroendocrine disruption, immune suppression and decreased bone density among others. Furthermore, the warming Arctic climate is suspected to influence abiotic and biotic long-range transport and exposure pathways of contaminants to the Arctic resulting in increases in POP exposure of both wildlife and human populations. Exposure to vector-borne diseases and zoonoses may increase as well through range expansion and introduction of invasive species. It will be important in the future to investigate the effects of these multiple stressors on wildlife and local people to better predict the individual-level health risks. It is within this framework that One Health approaches offer promising opportunities to survey and pinpoint environmental changes that have effects on wildlife and human health.

Overview of ongoing cohort and dietary studies in the Arctic

This article gives an overview of the ongoing cohort and dietary studies underlying the assessment of population health in the Arctic. The emphasis here is on a description of the material, methods and results or preliminary results for each study. Detailed exposure information is available in an article in this journal, whereas another paper describes the effects associated with contaminant exposure in the Arctic. The cohort descriptions have been arranged geographically, beginning in Norway and moving east to Finland, Sweden, Russia and the other Arctic countries and ultimately to the Faroe Islands. No cohort studies have been reported for Alaska or Iceland.

Health effects associated with measured levels of contaminants in the Arctic

The Human Health Assessment Group has over the past decade recommended that effect studies be conducted in the circumpolar area. Such studies examine the association between contaminant exposure in the Arctic populations and health effects. Because foetuses and young children are the most vulnerable, effect studies are often prospective child cohort studies. The emphasis in this article is on a description of the effects associated with contaminant exposure in the Arctic. The main topics addressed are neurobehavioural, immunological, reproductive, cardiovascular, endocrine and carcinogenic effect. For each topic, the association between exposure and effects is described, and some results are reported for similar studies outside the Arctic.

Aroclor 1254 causes atrophy of exocrine pancreas in mice and the mechanism involved

Polychlorinated biphenyls (PCBs) are a class of organic pollutants that have been linked to pancreatic disease. However, their role in affecting the exocrine function of pancreas and the underlying mechanism remains elusive. In the present study, male C57 mice were treated with Aroclor 1254, a commercially available PCBs mixture, at a dosage of 0.5, 5, 50, or 500 μg kg(-1) every 3 days by oral gavage. Decrease in pancreas/soma index and acinar atrophy were observed in the mice after exposure for 50 days. Aroclor 1254 exposure significantly decreased the PCNA-positive cells in the pancreatic acini in a dose-dependent manner. In addition, western blot analysis showed that PCNA expression was decreased in pancreas in the presence of Aroclor 1254, which suggests that Aroclor 1254 suppresses cell proliferation. TUNEL-positive apoptotic cells as well as the expression of Bcl2, BclXL, BAX, and Bad of exocrine pancreas did not show significant changes in the treated mice, indicating that Aroclor 1254 has no effect on apoptosis. We also found that phosphorylation of ERK1/2, P90RSK1 and Bad was increased in the treated groups; this compensatory activation of phosphorylation in ERK1/2-P90RSK1-Bad signaling cascade could protect cell from apoptosis to maintain the cell numbers and function of exocrine pancreas. Moreover, we found that the expression of Kras and TNFα was increased in the pancreas, indicating that Aroclor 1254 exposure could result in increased risk of inflammation and carcinoma. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 671-678, 2016.

Prenatal exposure to persistent organic pollutants and polybrominated diphenyl ethers in 10 Caribbean countries

Prenatal exposures to legacy persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and dioxin-like compounds (DLC), as well as polybrominated diphenyl ethers (PBDE), were analyzed in pregnant women from 10 Caribbean countries. A total of 438 samples were collected and descriptive statistics calculated and compared to comparable Canadian Health Measure Survey (CHMS) and U.S. National Health and Nutritional Examination Survey (NHANES) datasets. Maternal POPs blood concentrations were found to be generally relatively low in the Caribbean samples compared with the U.S. and Canada datasets. Evidence of exposure to DLC and PBDE was established. DLC levels ranged from a geometric mean low of 3.96 pg/g lipids in Antigua and Barbuda to a high of 11.4 pg/g lipids in St. Lucia. Several of the PBDEs (15, 17, 25, 28, 33, 100) were detected in less than 60% of the country' samples. For PBDE-47, significantly higher levels were found in Bermuda, while Jamaica recorded a significantly low level. The overall calculated concentration of PBDE-47 for the Caribbean (5.33 μg/kg lipids) was significantly lower than the concentrations measured for the U.S. (10.83 μg/kg lipids) and Canada (23.90 μg/kg lipids). This study confirms that prenatal expose to multiple environmental chemicals is taking place in the Caribbean and highlights the need to implement surveillance programs that continuously monitor, intervene, and evaluate the levels of these toxic environmental contaminants to ensure that they are reduced as much as possible and that the health risk to humans, in particular the unborn child, are minimized.

Saturated and monounsaturated fatty acid status is associated with bone strength estimated by calcaneal ultrasonography in Inuit women from Nunavik (Canada): a cross-sectional study

OBJECTIVE

The aim of this study is to examine the relationship between the status in selected saturated (SFAs) and monounsaturated (MUFAs) fatty acids and the Stiffness Index (SI) in Inuit women from Nunavik (Northern Quebec, Canada).

DESIGN

Cross-sectional descriptive study.

SETTING

Inuit population from 14 communities who participated to Qanuippitaa? How are we? Nunavik Inuit Health Survey in 2004.

PARTICIPANTS

187 Inuit women aged 35-72 years.

MEASUREMENTS

SI was determined by ultrasonography (Achilles InSight device) at the right calcaneus of participants. SFAs and MUFAs contents of erythrocyte membrane phospholipids were measured after transmethylation by gas chromatography coupled with a flame ionization detector. Several factors known to be associated with bone strength were concomitantly recorded. Multiple linear regression was used to investigate relations between selected SFAs, MUFAs and SI, taking into consideration several potential confounders and covariates.

RESULTS

Total SFAs, in particular behenic acid, and cis-vaccenic acid among MUFAs were negatively associated with SI (β = -0.028, SE = 0.011, p = 0.0084; β = -0.060, SE = 0.023, p = 0.0093 and β = -0.087, SE = 0.019, p <0.0001, respectively), whereas total cis-MUFAs and specifically oleic acid were positively associated with SI (β = 0.036, SE = 0.011, p = 0.0008; β = 0.037, SE = 0.011, p = 0.0014, respectively) after adjustment for several covariates.

CONCLUSION

Saturated and monounsaturated fatty acid status is associated with bone strength estimated by calcaneal SI values in Inuit women from Nunavik.

Dioxin-like compounds and bone quality in Cree women of Eastern James Bay (Canada): a cross-sectional study

BACKGROUND

Aboriginal populations living in Canada's northern regions are exposed to a number of persistent organic pollutants through their traditional diet which includes substantial amounts of predator fish species. Exposure to dioxin-like compounds (DLCs) can cause a variety of toxic effects including adverse effects on bone tissue. This descriptive cross-sectional study was conducted to investigate the relationship between plasma concentrations of DLCs and bone quality parameters in Cree women of Eastern James Bay (Canada).

METHODS

Two hundred and forty-nine Cree women from seven communities in Eastern James Bay (Canada), aged 35 to 74 years old, participated in the study. In order to determine the total DLC concentration in plasma samples of participants, we measured the aryl hydrocarbon receptor-mediated transcriptional activity elicited by plasma sample extracts using a luciferase reporter gene assay. Plasma concentrations of mono-ortho-substituted dioxin-like polychlorinated biphenyls (DL-PCBs) 105, 118 and 156 were measured by gas chromatography-mass spectrometry. Bone quality parameters (speed of sound, m/s; broadband ultrasound attenuation, dB/MHz; stiffness index, %) were assessed by quantitative ultrasound at the right calcaneus with the Achilles InSight system. Several factors known to be associated with osteoporosis were documented by questionnaire. Multiple linear regression models were constructed for the three ultrasound parameters.

RESULTS

DL-PCBs 105 and 118 concentrations, but not the global DLC concentration, were inversely associated with the stiffness index, even after adjusting for several confounding factors. The stiffness index (log) decreased by -0.22% (p=0.0414) and -0.04% (p=0.0483) with an increase of one μg/L in plasma concentrations of DL-PCB 105 and DL-PCB 118, respectively. Other factors, including age, height, smoking status, menopausal status and the percentage of omega-6 polyunsaturated fatty acids (PUFAs) in erythrocyte membranes were negatively associated with one of the ultrasound parameters, while the percentage of omega-3 PUFAs in these membranes and levels of physical activity and education were positively associated with them.

CONCLUSIONS

Our results show that an increase in plasma concentrations of DL-PCBs 105 and 118 was negatively associated with stiffness index, a measure of bone quality/strength, in women of this population. In addition to environmental contaminants, future studies should also consider PUFA intake as a factor influencing bone quality.

Novel cell-based assay reveals associations of circulating serum AhR-ligands with metabolic syndrome and mitochondrial dysfunction

Serum concentrations of environmental pollutants have been positively correlated with diabetes and metabolic syndrome in epidemiologic studies. In turn, abnormal mitochondrial function has been associated with the diseases. The relationships between these variables, however, have not been studied. We developed novel cell-based aryl hydrocarbon receptor (AhR) agonist bioassay system without solvent extraction process and analyzed whether low-dose circulating AhR ligands in human serum are associated with parameters of metabolic syndrome and mitochondrial function. Serum AhR ligand activities were measured as serum 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent (sTCDDeq) in pM using 10 μL human sera from 97 Korean participants (47 with glucose intolerance and 50 matched controls, average age of 46.6 ± 9.9 years, 53 male and 45 female). sTCDDeq were higher in participants with glucose intolerance than normal controls and were positively associated (P < 0.01) with obesity, blood pressure, serum triglyceride, and fasting glucose, but not with HDL-cholesterol. Body mass index was in a positive linear relationship with serum AhR ligands in healthy participants. When myoblast cells were incubated with human sera, ATP generating power of mitochondria became impaired in an AhR ligand concentration-dependent manner. Our results support that circulating AhR ligands may directly reduce mitochondrial function in tissues, leading to weight gain, glucose intolerance, and metabolic syndrome. Our rapid cell-based assay using minute volume of human serum may provide one of the best monitoring systems for circulating AhR ligands, good clinical biomarkers for the progress of disease and therapeutic efficacy.

Dioxin-like compounds are not associated with bone strength measured by ultrasonography in Inuit women from Nunavik (Canada): results of a cross-sectional study

BACKGROUND

Bone strength in Inuit people appears lower than that of non-Aboriginals. Inuit are exposed to persistent organic pollutants including dioxin-like compounds (DLCs) through their traditional diet that comprises predatory fish and marine mammal fat. Results from experimental and population studies suggest that some DLCs can alter bone metabolism and increase bone fragility.

OBJECTIVE

This cross-sectional descriptive study was conducted to examine the relationship between the stiffness index (SI) and plasma concentrations of total DLCs or specific dioxin-like polychlorinated biphenyls (DL-PCBs) in Inuit women of Nunavik (Northern Quebec, Canada).

METHODS

SI was determined by ultrasonography at the right calcaneus of 194 Inuit women aged 35-72 years who participated to Qanuippitaa? How Are We? Nunavik Inuit Health Survey in 2004. Plasma total DLC levels were quantified by measuring the aryl hydrocarbon receptor-mediated transcriptional activity elicited by plasma sample extracts in a cell-based reporter gene assay. Plasma concentrations of DL-PCBs nos. 105, 118, 156, 157, 167 and 189 were measured by gas chromatography-mass spectrometry. We used multiple linear regression analyses to investigate relations between total DLCs or specific DL-PCBs and SI, taking into consideration several potential confounders.

RESULTS

Neither total plasma DLCs nor specific DL-PCBs were associated with SI after adjustment for several confounders and covariates.

CONCLUSION

Our results do not support a relation between exposure to DLCs and bone strength measured by ultrasonography in Inuit women of Nunavik.

Polychlorinated biphenyls and organochlorine pesticides in plasma of older Canadians

No nationwide study has ever measured polychlorinated biphenyl (PCB) and organochlorine pesticide (OCP) body burden in Canadians aged 65 years and over. The objective of this study was to determine plasma concentrations of PCB congeners and OCPs in participants from a sub-cohort of the Canadian Study of Health and Aging and to examine the effects of socio-demographic, anthropometric and lifestyle characteristics on selected organochlorine concentrations. Archived plasma samples collected from 2023 subjects were analyzed by gas chromatography-mass spectrometry using negative chemical ionization for 15 PCB congeners and 11 OCPs. Descriptive statistics were used to report PCB congeners and OCP plasma concentrations. Multivariate models were used to study whether age at blood collection, sex, education, body mass index, rural residence, geographic region, smoking status and alcohol intake influences PCB 153, the most abundant congener, and the major OCP (beta-hexachlorocyclohexane, hexachlorobenzene, trans-nonachlor, p,p'-DDE) plasma concentrations. Statistical analyses were restricted to 1979 subjects and 17 organochlorine compounds for which at least 50% of the samples had concentrations above the limit of detection. Of these, 775 were men (mean age: 82.2 years) and 1204 were women (mean age: 84.6 years). The median concentrations (ng/g lipid) of PCB 153 in the plasma of men and women were 70.9 and 75.4, respectively. The levels of the sum of PCBs and the sum of dioxin-like PCBs were 276 and 31.3 for men, and 300 and 45.5 for women, respectively. The median concentrations (ng/g lipid) of p,p'-DDE, the most abundant OCP, were 565 for men and 828 for women. All compounds were positively and significantly intercorrelated (rs=0.39-0.99; p<0.001). Except for trans-nonachlor, the multivariate models revealed that age and male sex were the determining characteristics that showed, respectively, strongly positive and negative associations with selected organochlorine concentrations. These plasma concentrations from a large population based study can be considered as baseline data for body burdens of older Canadians.

Perfluorinated compounds are related to breast cancer risk in Greenlandic Inuit: a case control study

BACKGROUND

Breast cancer (BC) is the most common cancer for women in the western world. From very few cases an extraordinary increase in BC was observed in the Inuit population of Greenland and Canada although still lower than in western populations. Previous data suggest that exposure to persistent organic pollutants (POPs) might contribute to the risk of BC. Rat studies showed that perfluorinated compounds (PFCs) cause significantly increase in mammary fibroadenomas. This study aimed at evaluating the association between serum levels of POPs/PFCs in Greenlandic Inuit BC cases and their controls, and whether the combined POP related effect on nuclear hormone receptors affect BC risk.

METHODS

Thirty-one BC cases and 115 controls were sampled during 2000-2003 from various Greenlandic districts. The serum levels of POPs, PFCs, some metals and the combined serum POP related effect on estrogen- (ER), androgen- (AR) and Ah-receptor (AhR) transactivity were determined. Independent student t-test was used to compare the differences and the odds ratios were estimated by unconditional logistic regression models.

RESULTS

We observed for the very first time a significant association between serum PFC levels and the risk of BC. The BC cases also showed a significantly higher concentration of polychlorinated biphenyls at the highest quartile. Also for the combined serum POP induced agonistic AR transactivity significant association to BC risk was found, and cases elicited a higher frequency of samples with significant POP related hormone-like agonistic ER transactivity. The AhR toxic equivalent was lowest in cases.

CONCLUSIONS

The level of serum POPs, particularly PFCs, might be risk factors in the development of BC in Inuit. Hormone disruption by the combined serum POP related xenoestrogenic and xenoandrogenic activities may contribute to the risk of developing breast cancer in Inuit. Further investigations are needed to document these study conclusions.