Molecular epidemiologic evidence for diabetogenic effects of dioxin exposure in U.S. Air force veterans of the Vietnam war

Rekindling Hope for Remission: Current Impact of Diabetes for Our World's Future Health and Economy

The individual and societal burdens of living with a chronic disease are a global issue. Diabetes directly increases health care costs to manage the disease and the associated complications and indirectly increases the economic burden through long-term complications that hinder the productivity of humans worldwide. Thus, it is crucial to have accurate information on diabetes-related costs and the geographic and global economic impact when planning interventions and future strategies. Health care systems must work with government agencies to plan national-level pre diabetes and diabetes strategies and policies. Public health services must focus on diabetes screening prevention and remission.

U.S. Blue Water Navy Veterans of the Vietnam War: Comparisons from the Vietnam Era Health Retrospective Observational Study (VE-HEROeS)

Background

US Vietnam War Blue Water Navy veterans (BWN) conducted military operations on Vietnam's offshore waters and likely experienced various war-related exposures. The overall health of the BWN has never been systematically studied.

Purpose

Describe and compare BWN's health with other servicemembers and non-veterans of the Vietnam era.

Materials and methods

Survey of 45 067 randomly selected US Vietnam War theatre and non-theatre veterans and 6885 non-veterans.

Results

For 22 646 male respondents, self-reported health was contrasted by veteran status defined as BWN (n=985), theatre veterans (n=6717), non-theatre veterans (n=10 698) and non-veterans (n=4246). Exposure was service in the Vietnam War theatre. Collected were demographics, military service characteristics, lifestyle factors and health conditions. Adjusted odds ratios (aOR) were calculated using multivariable logistic regression. Controlling for cigarette smoking and other covariates, respiratory cancer risk was highest in BWN vs other veterans (theatre: aOR 1.65; 95% CI 1.09, 2.50; non-theatre: aOR 1.77; 1.13, 2.77) and to non-veterans (aOR 1.78; 1.15, 2.74). Other findings showed BWN's health risks between theatre and non-theatre veterans.

Conclusion

There was a higher risk for respiratory cancers in BWN. Other risks were less than theatre veterans but greater than non-theatre or non-veterans, indicating a potential role of military exposures in BWN's health.

Health risk assessment of exposure to organochlorine pesticides in the general population in Seoul, Korea over 12 years: A cross-sectional epidemiological study

This study evaluated the 12-year trends in serum levels of 28 organochlorine pesticides (OCPs) in 880 adults living in Seoul, Korea. The OCP levels decreased from 2006 to 2017, and p,p'-dichlorodiphenyldichloroethylene was a predominant compound. OCP levels were higher in females than in males, and showed positive associations with BMI and age. The OCP concentrations had inverted U-shaped associations with low-density lipoprotein cholesterol and total cholesterol. Concentrations of β-hexachlorocyclohexane were significantly higher in patients with hypertension than in participants that were normotensive. OCP levels showed positive associations with uric acid, creatinine, and thyroid-stimulating hormone, but negative associations with free thyroxine. Participants with diabetes had significantly higher OCP levels than those without it. Principal component analysis suggested possible differences in disease manifestation depending on the composition of OCPs. These results suggest that OCPs might disturb renal transport and thyroid homeostasis. To our knowledge, the inverted U-shaped associations of heptachlor epoxide and endosulfan with cholesterol, the epidemiological associations of trans-nonachlor and endosulfan with thyroid hormones, and the association of p,p'-DDE with hyperuricemia have not been previously reported in general population. This is the first long-term study to show trends of 28 OCPs in serum and associations with various health indicators in Korea.

Environmental Factors as Diabetic Mediators: A Mechanistic Approach

Despite substantial investment in research and treatment options, diabetes mellitus remains a pressing public health concern with potential epidemic proportions globally. There are reports that by the end of 2040, 642 million people will be suffering from diabetes. Also, according to an estimation, 1.6 million deaths were caused directly by diabetes in 2016. Diabetes is a metabolic disorder characterized by impaired glucose regulation in the body due to the destruction of pancreatic β-cells or insulin resistance. Genetic propensity, unhealthy and imbalanced diet, obesity and increasing urbanization are the common risk factors for diabetes. Besides this, it has been reported that environmental pollutants like organic pesticides, heavy metals, and air pollutants act as strong predisposing factors for diabetes owing to their highly bio-accumulative nature. These pollutants disturb glucose homeostasis either by up-regulating or down-regulating the expression of diabetic marker genes like insulin (INS) and glucokinase (GCK). Unfortunately, the molecular mechanism of the role of pollutants in causing diabetes is not very clear. This mechanistic review provides evidence of different environmental determinants, including persistent organic pollutants (POPs), air pollutants, toxic metals, etc., in inducing diabetes and proposes a framework for the possible mechanisms involved. It also illuminates the current status and future challenges, which will not only broaden our understanding but can also be a reasonable platform for further investigation.

Increased AHR Transcripts Correlate With Pro-inflammatory T-Helper Lymphocytes Polarization in Both Metabolically Healthy Obesity and Type 2 Diabetic Patients

Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor whose transcription activity is regulated by small compounds provided by diet, xenobiotics, and metabolism. It has been proven to be involved in energy homeostasis and inflammation in most recent years. Epidemiologically, exposure to xenobiotic AHR ligands contributes to obesity and type 2 diabetes (T2D). AHR is also the critical transcription factor determining the lineage commitment of pro-inflammatory Th17 and Th22 cells from naïve CD4+ T lymphocytes. It has been well-illustrated in animal models that IL-22, the major effector cytokine of Th17 and Th22 cells, played a major role in the interaction of metabolism and gut microbiota. But there were still missing links between gut microbiota, IL-22, and metabolism in humans. Our previous findings indicated that elevated circulating levels of IL-22 and frequencies of Th22 cells were associated with insulin resistance in both patients with obesity and T2D. Additionally, the hyperactive Th17 and Th22 cells phenotype also correlate with islets β-cell dysfunction in T2D. In this study, we made efforts to determine AHR expressions in peripheral blood mononuclear cells (PBMCs) from patients with T2D and metabolically healthy obesity (MHO). Correlation analyses were conducted to assess the possible link between AHR and the metabolic and inflammatory context. We revealed that mRNA expression of AHR was up-regulated and correlated with the percentage of Th17, Th22 as well as Th1 cells. Elevated plasma levels of IL-22 and IL-17 also correlated with increased AHR transcripts in PBMCs from both MHO and T2D patients. The transcription factor AHR may thus have a plausible role in the interaction between metabolism and pro-inflammatory status of patients in the development of obesity and T2D.

Long-Term Effects of Chemical Warfare on Post-traumatic Stress Disorder, Depression, and Chronic Medical Conditions in Veterans

We investigated the association between exposure to chemical warfare and chronic mental/physical conditions. This was a secondary analysis of data from a case-control study on Iranian male veterans. Participants with neuropsychiatric disorders other than depressive/anxiety disorders, anatomical defects, or malignancies were excluded. Compared to non-exposed veterans, exposed veterans demonstrated significantly higher odds of PTSD [OR (95% CI) = 5.23 (1.98-13.85)], hypertension [OR (95% CI) = 5.57 (1.68-18.48)], coronary heart disease [OR (95% CI) = 6.8 (1.62-28.49)], and diabetes [OR (95% CI) = 3.88 (1.35-11.16)], and marginally higher odds of moderate to severe depressive symptoms [OR (95% CI) = 2.21 (0.93-5.28)]. This study provides preliminary evidence on association of exposure to chemical warfare with long-term mental disorders as well as chronic medical conditions.

Negative association between serum aryl hydrocarbon receptor concentrations and β-cell function in patients with no history of diabetes undergoing coronary angiography

BACKGROUND

The aim of the present study was to investigate the association between serum aryl hydrocarbon receptor (AhR) levels and insulin resistance and β-cell function in patients undergoing coronary angiography with no history of diabetes.

METHODS

Patients with no history of diabetes who had undergone coronary angiography underwent an oral glucose tolerance test (OGTT) 2-4 weeks after discharge from hospital; blood samples were collected for measurements of glucose, insulin, and AhR. Patients' glucose regulation status was determined on the basis of the OGTT. Insulin resistance was assessed using the homeostasis model assessment of insulin resistance (HOMA-IR). β-Cell function was assessed using the insulinogenic index (IGI).

RESULTS

The study included 473 patients (mean (±SD) age 61 ±12 years, 81.8% male, mean body mass index 26.1 ±3.6 kg/m² ). Overall, mean serum AhR concentrations were 25.1 ±12.2 pg/mL. Patients with normal glucose tolerance had a lower serum AhR concentrations than patients with prediabetes or newly diagnosed diabetes (23.4 ±10.8 vs 26.2 ±13.2 and 26.9 ±12.3 pg/mL, respectively; P = 0.029). Linear regression analysis revealed that serum AhR concentrations were not associated with HOMA-IR, but were negatively associated with IGI after adjustment for several confounders, including HOMA-IR (β = -0.162; 95% confidence interval - 0.302, -0.022; P = 0.023).

CONCLUSIONS

In patients with no history of diabetes, serum AhR concentrations were negatively associated with β-cell function, independent of several confounders, including insulin resistance.

Transcriptomic and methylomic analysis reveal the toxicological effect of 2,3,7,8-Tetrachlorodibenzodioxin on human embryonic stem cell

Cumulating epidemiological studies demonstrated that environmental exposure to endocrine disrupting chemicals (EDCs) during the early stages of fetal development is associated with the increase in disease susceptibility in later life. The fetal developmental plasticity is considered as a protective mechanism against an undesirable prenatal environment. Dioxin is one of the environmental contaminants and is considered a diabetogenic factor. Experimental animal and human epidemiological studies have revealed that dioxin exposure was associated with insulin resistance and altered beta cell function. But the effect of dioxin exposure in early stage of fetal development is still largely unknown. In this report, we used the human embryonic stem cell (hESC) line, VAL-3, as a model, together with Methyl-CpG Binding Domain (MBD) protein-enriched genome sequencing and transcriptome sequencing (RNA-seq), in order to determine the dynamic changes of the epigenetic landscape and transcriptional dysregulation in hESC upon dioxin exposure. The bioinformatics analyses including the Database for Annotation, Visualization and Integrated Discovery (DAVID) analysis and Ingenuity Pathway Analysis (IPA) highlighted the predisposed neural, hepatic, cardiac and metabolic toxicological effects of dioxin during the fetal development.

Morbidity in New Zealand pesticide producers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

OBJECTIVES

To conduct a cross-sectional morbidity survey among 245 former employees of a pesticide production plant exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in New Zealand.

METHODS

Demographic factors and health information were collected in face-to-face interviews. TCDD, lipids, thyroid hormones, glucose and immunoglobulin G (IgG) were determined in non-fasting blood. For 111 participants, a neurological examination was conducted. Associations between health outcomes and working in a TCDD exposed job (prevalence 49%) and serum TCDD concentration≥10pg/g lipid (18%) were assessed using logistic regression whilst controlling for age, gender, smoking, body mass index and ethnicity.

RESULTS

Diabetes was more common in those who had worked in TCDD exposed jobs (OR 4.0, 95%CI 1.0-15.4) and in those with serum TCDD ≥10pg/g (OR 3.1, 95%CI 0.9-10.7). Non-fasting glucose levels >6.6mmol/l were more common in those with TCDD exposed jobs (OR 3.6, 95%CI 1.0-12.9), as were serum free thyroxine 4<12.8pmol/l (OR 4.5, 95%CI 1.4-14.4), triglycerides >1.7mmol/l (OR 2.5, 95%CI 1.1-5.7) and high density lipoprotein cholesterol (HDL) <1mmol/l (OR 4.0, 95%CI 1.2-13.2). IgG was negatively associated with TCDD (linear regression p=0.05). The neurological examination revealed a higher frequency of abnormal reflexes in those with serum TCDD ≥10pg/g (OR 4.8, 95%CI 1.1-21.0).

CONCLUSIONS

In this occupationally exposed population, TCDD was associated with an increased risk of diabetes and a range of subclinical responses in multiple systems (peripheral nervous system, immune system, thyroid hormones and lipid metabolism), several decades after last exposure. These results need to be interpreted with caution due to the small study size and the cross-sectional nature of the study.

Tetrabromobisphenol A induces cellular damages in pancreatic β-cells in vitro

Tetrabromobisphenol A (TBBPA) is a well-known organobrominated flame retardant. TBBPA has been detected in the environment. The roles played by environmental pollutants in increasing the prevalence of metabolic syndrome are attracting increasing concern. In the present work, we investigated the effects of TBBPA on rat pancreatic β-cells (the RIN-m5F cell line). RIN-m5F cells were incubated with different concentrations of TBBPA for 48 h, and cell viability and the extent of apoptosis were determined. We also measured the levels of inflammatory cytokines, reactive oxygen species (ROS), mitochondrial adenosine triphosphate (ATP), and cardiolipin, as well as the extent of cytochrome c release from mitochondria. TBBPA reduced the ATP level, induced cardiolipin peroxidation and cytochrome c release, and triggered apoptotic cell death. Moreover, TBBPA increased the levels of inflammatory cytokines (TNF-α and IL-1β), nitric oxide, intracellular ROS, and mitochondrial superoxide. Together, our results indicate that TBBPA damages pancreatic β-cells by triggering mitochondrial dysfunction and inducing apoptosis.

Role of Aryl Hydrocarbon Receptor in Circadian Clock Disruption and Metabolic Dysfunction

The prevalence of metabolic syndrome, a clustering of three or more risk factors that include abdominal obesity, increased blood pressure, and high levels of glucose, triglycerides, and high-density lipoproteins, has reached dangerous and costly levels worldwide. Increases in morbidity and mortality result from a combination of factors that promote altered glucose metabolism, insulin resistance, and metabolic dysfunction. Although diet and exercise are commonly touted as important determinants in the development of metabolic dysfunction, other environmental factors, including circadian clock disruption and activation of the aryl hydrocarbon receptor (AhR) by dietary or other environmental sources, must also be considered. AhR binds a range of ligands, which prompts protein-protein interactions with other Per-Arnt-Sim (PAS)-domain-containing proteins and subsequent transcriptional activity. This review focuses on the reciprocal crosstalk between the activated AhR and the molecular circadian clock. AhR exhibits a rhythmic expression and time-dependent sensitivity to activation by AhR agonists. Conversely, AhR activation influences the amplitude and phase of expression of circadian clock genes, hormones, and the behavioral responses of the clock system to changes in environmental illumination. Both the clock and AhR status and activation play significant and underappreciated roles in metabolic homeostasis. This review highlights the state of knowledge regarding how AhR may act together with the circadian clock to influence energy metabolism. Understanding the variety of AhR-dependent mechanisms, including its interactions with the circadian timing system that promote metabolic dysfunction, reveals new targets of interest for maintenance of healthy metabolism.

Occupational chemical exposure and diabetes mellitus risk

Diabetes mellitus (DM) is a group of metabolic diseases that may originate from an interaction between genetic and lifestyle risk factors. However, the possible role of occupational chemical exposures in the disease development and progression remains unclear. Therefore, this review aimed to provide a comprehensive evaluation of the relationship between occupational exposure to specific chemical substances or industrial activities and DM morbidity and mortality outcomes. Although some positive findings may support the diabetogenic role of certain pesticides and dioxins in different workplaces, the variable conditions of exposure, the lack of quantitative environmental or biological monitoring data and the different outcomes evaluated do not allow defining a specific exposure-disease causality. Therefore, further epidemiological studies will be necessary to adequately assess modes of action for different substances, dose–response relationships as well as individual susceptibility factors potentially affecting the exposure-disease continuum. Overall, this appears important to adequately assess, communicate and manage risks in occupational chemical exposure settings with the aim to protect workers and build healthier job conditions for diabetic employees.

Transgenic Overexpression of Aryl Hydrocarbon Receptor Repressor (AhRR) and AhR-Mediated Induction of CYP1A1, Cytokines, and Acute Toxicity

BACKGROUND

The aryl hydrocarbon receptor repressor (AhRR) is known to repress aryl hydrocarbon receptor (AhR) signaling, but very little is known regarding the role of the AhRR in vivo.

OBJECTIVE

This study tested the role of AhRR in vivo in AhRR overexpressing mice on molecular and toxic end points mediated through a prototypical AhR ligand.

METHODS

We generated AhRR-transgenic mice (AhRR Tg) based on the genetic background of C57BL/6J wild type (wt) mice. We tested the effect of the prototypical AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the expression of cytochrome P450 (CYP)1A1 and cytokines in various tissues of mice. We next analyzed the infiltration of immune cells in adipose tissue of mice after treatment with TCDD using flow cytometry.

RESULTS

AhRR Tg mice express significantly higher levels of AhRR compared to wt mice. Activation of AhR by TCDD caused a significant increase of the inflammatory cytokines Interleukin (IL)-1β, IL-6 and IL-10, and CXCL chemokines in white epididymal adipose tissue from both wt and AhRR Tg mice. However, the expression of IL-1β, CXCL2 and CXCL3 were significantly lower in AhRR Tg versus wt mice following TCDD treatment. Exposure to TCDD caused a rapid accumulation of neutrophils and macrophages in white adipose tissue of wt and AhRR Tg mice. Furthermore we found that male AhRR Tg mice were protected from high-dose TCDD-induced lethality associated with a reduced inflammatory response and liver damage as indicated by lower levels of TCDD-induced alanine aminotransferase and hepatic triglycerides. Females from both wt and AhRR Tg mice were less sensitive than male mice to acute toxicity induced by TCDD.

CONCLUSION

In conclusion, the current study identifies AhRR as a previously uncharacterized regulator of specific inflammatory cytokines, which may protect from acute toxicity induced by TCDD.

CITATION

Vogel CF, Chang WL, Kado S, McCulloh K, Vogel H, Wu D, Haarmann-Stemmann T, Yang GX, Leung PS, Matsumura F, Gershwin ME. 2016. Transgenic overexpression of aryl hydrocarbon receptor repressor (AhRR) and AhR-mediated induction of CYP1A1, cytokines, and acute toxicity. Environ Health Perspect 124:1071-1083; http://dx.doi.org/10.1289/ehp.1510194.

PCDDs, PCDFs and PCBs in farmed fish produced in Greece: Levels and human population exposure assessment

Fish is among the essential components of Mediterranean diet and has beneficial effects on human health. Farmed fish is an affordable alternative to wild fish and a significant food export product for Greece. Published studies worldwide have reported significant levels of environmental pollutants in fish tissues. Especially for PCDDs/Fs and PCBs, the studies suggest that the most important contribution to human dietary intake is from fish and seafood. In the present study, we investigate the levels of PCDDs/Fs, dioxin-like and non dioxin-like PCBs in the most common farmed fish species produced in Greece i.e. sea bass, sea bream and rainbow trout. These species are widely consumed in Greece and are also exported to many countries worldwide. The mean levels found were WHO-PCDD/F-TEQ: 0.22 pg g(-1) wet weight (w.w.), WHO-PCDD/F-PCB-TEQ: 0.88 pg g(-1) w.w. for sea bream, WHO-PCDD/F-TEQ: 0.13 pg g(-1) w.w., WHO-PCDD/F-PCB-TEQ: 0.68 pg g(-1) w.w. for sea bass and WHO-PCDD/F-TEQ: 0.10 pg g(-1) w.w., WHO-PCDD/F-PCB-TEQ: 0.43 pg g(-1) w.w. for rainbow trout. For non dioxin-like PCBs, mean sum values found were 8.02 ng g(-1) w.w. for sea bream, 5.24 ng g(-1) w.w. for sea bass and 2.90 ng g(-1) w.w. for rainbow trout. All concentrations found were far below maximum levels set by the European Union and in the same range as wild-caught fish also presented for comparison. Daily intake from the consumption of farmed fish species examined is calculated at 1.3 pg WHO-TEQ kg(-1) b.w., which is at the lowest end of TDI values proposed by the WHO.

Health status of male steel workers at an electric arc furnace (EAF) in Trentino, Italy

Background

The aim of this retrospective cohort study was to determine if the workers of an Electric Arc Furnace (EAF), which recycles scrap, had higher mortality and morbidity due to possible exposure to pollutants at work. EAFs do not run on coke ovens. In EAFs 40 % of the particulate matter (PM) is made up of PM _2.5. The foundry dust contained iron, aluminum, zinc, manganese, lead, chromium, nickel, cadmium, mercury, arsenic, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls and dioxins.

Methods

Mortality study: a cohort of 331 exposed workers (6731 person-years) was studied from 19/03/1979 to 31/12/2009 (mean follow up 20.7 years). The group of exposed workers was compared to the general population and to a small control group of 32 workers from the same company.

Morbidity study: rates of exemption from health fee for the seven major diseases of 235 exposed workers were compared to the rates of exemption in the Province of Trento.

Results

Mortality study: an excess mortality was found in the exposed workers as compared to the general population (SMR 1.13; 95 % CI: 0.76–1.62; 29 deaths) and to the internal group (RR 2.34; 95 % CI: 0.39–95.7). The mortality rate was increased for all tumours (SMR 1.36; 95 % CI: 0.75–2.29; 14 cases), for lung cancer (SMR 3.35; 95 % CI 1.45–6.60; 8 cases), for ischemic heart disease (SMR 1.27; 95 % CI: 0.35–3.26; 4 cases), for chronic liver disease (SMR 1.16; 95 % CI: 0.14–4.20; 2 cases) and for injury and poisoning (SMR 1.32; 95 % CI: 0.48–2.88; 6 cases).

Morbidity study: there was a statistically significant increase of diabetes, rheumatoid arthritis, hypertension and cardiovascular diseases in exposed workers.

Conclusions

With the limitations of this relatively small cohort, we found a statistically significant increase of diabetes, cardiovascular diseases and deaths due to lung cancer in exposed workers. These findings cannot be explained by PAH exposure alone; metal particulates are the most important pollutants in the working area of EAFs. A reliable method for measuring metal PM in tissues is urgently needed for exposure assessment. This study underlines the necessity to maximize the standards of security toward foundry dusts/diffuse emission. Further studies on EAF’s are needed to confirm our findings and to increase statistical power.

Adverse health consequences of the Vietnam War

The 40th anniversary of the end of the Vietnam War is a useful time to review the adverse health consequences of that war and to identify and address serious problems related to armed conflict, such as the protection of noncombatant civilians. More than 58,000 U.S. servicemembers died during the war and more than 150,000 were wounded. Many suffered from posttraumatic stress disorders and other mental disorders and from the long-term consequences of physical injuries. However, morbidity and mortality, although difficult to determine precisely, was substantially higher among the Vietnamese people, with at least two million of them dying during the course of the war. In addition, more than one million Vietnamese were forced to migrate during the war and its aftermath, including many "boat people" who died at sea during attempts to flee. Wars continue to kill and injure large numbers of noncombatant civilians and continue to damage the health-supporting infrastructure of society, expose civilians to toxic chemicals, forcibly displace many people, and divert resources away from services to benefit noncombatant civilians. Health professionals can play important roles in promoting the protection of noncombatant civilians during war and helping to prevent war and create a culture of peace.

Impaired glucose and lipid metabolism in ageing aryl hydrocarbon receptor deficient mice

Disturbed homeostasis of glucose and lipid metabolism are dominant features of the so-called metabolic syndrome (MetS) and can increase the risk for the development of type 2 diabetes (T2D), a severe metabolic disease. T2D prevalence increases with age. The aryl hydrocarbon receptor (AHR) is a sensor of small molecules including dietary components. AHR has been identified as potential regulator of glucose homeostasis and lipid metabolism. Epidemiologically, exposure to xenobiotic AHR ligands such as polycyclic aromatic hydrocarbons is linked to T2D. We assess here the potential role of the AHR in disturbances of glucose and lipid metabolism in young (age 2-5 months) and old (age > 1,5 years) AHR-deficient (AHR KO) mice. Fasted young wildtype (WT) and AHR-KO mice displayed similar blood glucose kinetics after challenge with intra-peritoneal glucose injection. However, old AHR-KO mice showed lower tolerance than WT to i.p. administered glucose, i.e. glucose levels rose higher and returned more slowly to normal levels. Old mice had overall higher insulin levels than young mice, and old AHR-KO had a somewhat disturbed insulin kinetic in the serum after glucose challenge. Surprisingly, young AHR-KO mice had significantly lower triglycerides, cholesterol, high density lipoprotein values than WT, i.e., a dyslipidemic profile. With ageing, AHR-KO and WT mice did not differ in these lipid levels, except for slightly reduced levels of triglycerides and cholesterol. In conclusion, our findings in AHR KO mice suggest that AHR expression is relevant for the maintenance of glucose and lipid homeostasis in old mice.

Persistent organic pollutants and biomarkers of diabetes risk in a cohort of Great Lakes sport caught fish consumers

BACKGROUND

Exposure to persistent organic pollutants (POPs) is associated with increased diabetes risk, although the mechanism of action is not well delineated.

METHODS

We investigated established diabetes biomarkers that could implicate potential mechanistic pathways, including C-reactive protein (CRP), a marker of systemic inflammation; gamma glutamyl transferase (GGT), a liver enzyme associated with oxidative stress; and adiponectin, an adipokine modulating glucose regulation and fatty acid oxidation. These biomarkers as well as hemoglobin A1c (HA1c), and POPs [polychlorinated biphenyls (PCBs), p,p-dichlorodiphenyldichloroethylene (DDE) and polybrominated diphenyl ethers (PBDEs)] were measured in a cohort of Great Lakes sport caught fish (GLSCF) consumers. We examined associations of POPs and fish consumption with HA1c and incident diabetes, and evaluated mediation and moderation by the diabetes biomarkers.

RESULTS

Odds of incident diabetes were elevated with exposure to DDE and PCBs. DDE and PCB 118 were positively, and fish meals were inversely, associated with HA1c. CRP was inversely associated with saltwater and total fish meals, particularly in persons with higher adiposity, but did not mediate the associations of fish meals with HA1c. There were few associations of POPs with adiponectin, CRP and GGT, with the exception of positive associations of PCB 118 with GGT, PBDEs with GGT in older persons, and PBDEs with adiponectin. Adiponectin, CRP and GGT did not mediate associations of DDE and PCBs with HA1c or incident diabetes. However, the association of DDE with HA1c was stronger in persons with higher CRP, GGT and BMI, and lower adiponectin, while the association of PCB 118 with HA1c was stronger in persons with higher GGT.

CONCLUSIONS

These findings suggest that adiponectin, CRP and GGT did not mediate effects of POPs on diabetes or HA1c. However, POPs may have stronger effects on blood glucose in persons at higher risk for diabetes.

Aryl hydrocarbon receptor deficiency protects mice from diet-induced adiposity and metabolic disorders through increased energy expenditure

BACKGROUND/OBJECTIVES

Epidemics of obesity and diabetes are escalating. High-calorie/high-fat food is a major cause for these global health issues, but molecular mechanisms underlying high-fat, diet-induced obesity are still not well understood. The aryl hydrocarbon receptor (AhR), a transcription factor that acts as a xenobiotic sensor, mediates environmental toxicant-induced obesity, insulin resistance and development of diabetes. AhR also influences lipid metabolism and diet-induced obesity. The effects of AhR deficiency on diet-induced obesity, hepatic steatosis and insulin resistance were examined.

METHODS

Male wild-type (WT), AhR null (AhR(-/-)) and AhR heterozygote (AhR(+/-)) mice were fed a normal chow diet (NCD, 10% kcal from fat) or a high-fat diet (HFD, 60% kcal from fat) for up to 14 weeks. Adiposity, adipose and liver morphology, insulin signaling, metabolic parameters and gene profiles were assessed.

RESULTS

AhR deficiency protected against HFD-induced obesity, hepatic steatosis, insulin resistance and inflammation. Moreover, AhR deficiency preserved insulin signaling in major metabolic tissues. These protective effects result from a higher energy expenditure in AhR-deficient mice compared with WT. Levels of transcript for both the thermogenic gene, uncoupling protein 1 (Ucp1), in brown adipose tissue and mitochondrial β-oxidation genes in muscle were significantly higher in AhR(-/-) and AhR(+/-) mice compared with WT.

CONCLUSIONS

This work documents a physiologically relevant function for AhR in regulation of body weight, hepatic fat deposition, insulin sensitivity and energy expenditure under HFD exposure, suggesting that AhR signaling may be developed as a potential therapeutic target for treatment of obesity and metabolic disorders.

Chlorinated persistent organic pollutants, obesity, and type 2 diabetes

Persistent organic pollutants (POPs) are lipophilic compounds that travel with lipids and accumulate mainly in adipose tissue. Recent human evidence links low-dose POPs to an increased risk of type 2 diabetes (T2D). Because humans are contaminated by POP mixtures and POPs possibly have nonmonotonic dose-response relations with T2D, critical methodological issues arise in evaluating human findings. This review summarizes epidemiological results on chlorinated POPs and T2D, and relevant experimental evidence. It also discusses how features of POPs can affect inferences in humans. The evidence as a whole suggests that, rather than a few individual POPs, background exposure to POP mixtures-including organochlorine pesticides and polychlorinated biphenyls-can increase T2D risk in humans. Inconsistent statistical significance for individual POPs may arise due to distributional differences in POP mixtures among populations. Differences in the observed shape of the dose-response curves among human studies may reflect an inverted U-shaped association secondary to mitochondrial dysfunction or endocrine disruption. Finally, we examine the relationship between POPs and obesity. There is evidence in animal studies that low-dose POP mixtures are obesogenic. However, relationships between POPs and obesity in humans have been inconsistent. Adipose tissue plays a dual role of promoting T2D and providing a relatively safe place to store POPs. Large prospective studies with serial measurements of a broad range of POPs, adiposity, and clinically relevant biomarkers are needed to disentangle the interrelationships among POPs, obesity, and the development of T2D. Also needed are laboratory experiments that more closely mimic real-world POP doses, mixtures, and exposure duration in humans.

Chlorinated persistent organic pollutants, obesity, and type 2 diabetes

Persistent organic pollutants (POPs) are lipophilic compounds that travel with lipids and accumulate mainly in adipose tissue. Recent human evidence links low-dose POPs to an increased risk of type 2 diabetes (T2D). Because humans are contaminated by POP mixtures and POPs possibly have nonmonotonic dose-response relations with T2D, critical methodological issues arise in evaluating human findings. This review summarizes epidemiological results on chlorinated POPs and T2D, and relevant experimental evidence. It also discusses how features of POPs can affect inferences in humans. The evidence as a whole suggests that, rather than a few individual POPs, background exposure to POP mixtures-including organochlorine pesticides and polychlorinated biphenyls-can increase T2D risk in humans. Inconsistent statistical significance for individual POPs may arise due to distributional differences in POP mixtures among populations. Differences in the observed shape of the dose-response curves among human studies may reflect an inverted U-shaped association secondary to mitochondrial dysfunction or endocrine disruption. Finally, we examine the relationship between POPs and obesity. There is evidence in animal studies that low-dose POP mixtures are obesogenic. However, relationships between POPs and obesity in humans have been inconsistent. Adipose tissue plays a dual role of promoting T2D and providing a relatively safe place to store POPs. Large prospective studies with serial measurements of a broad range of POPs, adiposity, and clinically relevant biomarkers are needed to disentangle the interrelationships among POPs, obesity, and the development of T2D. Also needed are laboratory experiments that more closely mimic real-world POP doses, mixtures, and exposure duration in humans.

Association of dioxin and other persistent organic pollutants (POPs) with diabetes: epidemiological evidence and new mechanisms of beta cell dysfunction

The worldwide explosion of the rates of diabetes and other metabolic diseases in the last few decades cannot be fully explained only by changes in the prevalence of classical lifestyle-related risk factors, such as physical inactivity and poor diet. For this reason, it has been recently proposed that other "nontraditional" risk factors could contribute to the diabetes epidemics. In particular, an increasing number of reports indicate that chronic exposure to and accumulation of a low concentration of environmental pollutants (especially the so-called persistent organic pollutants (POPs)) within the body might be associated with diabetogenesis. In this review, the epidemiological evidence suggesting a relationship between dioxin and other POPs exposure and diabetes incidence will be summarized, and some recent developments on the possible underlying mechanisms, with particular reference to dioxin, will be presented and discussed.

The aryl hydrocarbon receptor is important for proper seminiferous tubule architecture and sperm development in mice

The aryl hydrocarbon receptor (AHR) is known for its roles in xenobiotic metabolism and essential physiologic processes such as cell growth, death, and differentiation. AHR is also an important regulator of male reproductive processes. However, no studies have characterized the consequences of loss of AHR in spermatogenesis. We used Ahr knockout (Ahr(-/-)) mice to assess the effects of loss of AHR on the architecture and gene expression of the seminiferous epithelium and functional sperm outcomes. The histopathological defects of the Ahr(-/-)seminiferous epithelium included vacuoles, multinucleated giant cells, hypocellularity with widened intercellular spaces, apical sloughing, and an excess number of retained elongated spermatids. Quantitative real-time PCR revealed significant down-regulation of Testin and Magea4, indicating Sertoli cell and spermatogenic dysregulation. Moreover, the reduced expression of Hspa2, Prm1, and Prm2 as well as decreased expression of Nrf2, Sod2, and Ucp2 suggested poorly remodeled germ cells with increased vulnerability to oxidative stress. In wild-type sperm, AHR protein was localized to the acrosome and the principal piece of the mature sperm flagellum. The in vitro fertilization rate was significantly lower with Ahr(-/-) sperm as compared to wild-type sperm, and there were morphologic abnormalities of the Ahr(-/-) sperm head and tail. Taken together, our data indicate that AHR plays an important role in normal sperm development.

Diabetes and its comorbidities--where East meets West

Fetal programming associated with in utero exposure to maternal stress is thought to alter gene expression, resulting in phenotypes that promote survival in a pathogen-rich and nutrient-poor environment but substantially increase the risk of cardiovascular, metabolic and renal disorders (such as diabetes mellitus) in adults with obesity. These (epi)genetic phenomena are modified by environmental and socioeconomic factors, resulting in multiple subphenotypes and clinical consequences. In individuals from areas undergoing rapid economic development, which is associated with a transition from communicable to noncommunicable diseases, an efficient innate immune response can exaggerate obesity-associated inflammation. By contrast, in individuals with a genetic predisposition to autoimmune or monogenic diabetes mellitus, obesity can lead to atypical presentation of diabetes mellitus, termed 'double diabetes mellitus'. The increasingly young age at diagnosis of diabetes mellitus in developing countries results in prolonged exposure to glucolipotoxicity, low-grade inflammation and increased oxidative stress, which put enormous strain on pancreatic β cells and renal function. These conditions create a metabolic milieu conducive to cancer growth. This Review discusses how rapid changes in technology and human behaviour have brought on the global epidemic of metabolic diseases, and suggests that solutions will be based on using system change, technology and behavioural strategies to combat this societal-turned-medical problem.

Diabetes, metabolic syndrome, and obesity in relation to serum dioxin concentrations: the Seveso women's health study

BACKGROUND

In animal studies, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters glucose transport and increases serum lipid levels and blood pressure. Epidemiologic evidence suggests an association between TCDD and metabolic disease.

OBJECTIVES

On 10 July 1976, a chemical explosion in Seveso, Italy, resulted in the highest known residential exposure to TCDD. Using data from the Seveso Women's Health Study (SWHS), a cohort study of the health of the women, we examined the relation of serum TCDD to diabetes, metabolic syndrome, and obesity > 30 years later.

METHODS

In 1996, we enrolled 981 women who were newborn to 40 years of age in 1976 and resided in the most contaminated areas. Individual TCDD concentration was measured in archived serum that had been collected soon after the explosion. In 2008, 833 women participated in a follow-up study. Diabetes was classified based on self-report or fasting serum glucose and glycated hemoglobin levels. Metabolic syndrome was defined by International Diabetes Federation criteria. Obesity was defined as body mass index ≥ 30 kg/m2.

RESULTS

A 10-fold increase in serum TCDD (log10TCDD) was not associated with diabetes (adjusted hazard ratio = 0.76; 95% CI: 0.45, 1.28) or obesity [adjusted odds ratio (OR) = 0.80; 95% CI: 0.58, 1.10]. Log10TCDD was associated with metabolic syndrome, but only among women who were ≤ 12 years of age at the time of the explosion (adjusted OR = 2.03; 95% CI: 1.25, 3.29; pinteraction = 0.01).

CONCLUSIONS

We found an increased prevalence of metabolic syndrome associated with TCDD, but only among women who were the youngest at the time of the explosion. Continued follow-up of the SWHS cohort will be informative.

In utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin modulates dysregulation of the lipid metabolism in mouse offspring fed a high-calorie diet

Exposure to environmental chemicals, including dioxins, is a risk factor for type 2 diabetes mellitus in humans. This study explored the hypothesis that in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic congener among dioxins, aggravates this disease state later in adulthood. Pregnant C57Bl/6 J mice were administered either a single oral dose of TCDD (3.0 µg kg(-1) body weight) or corn oil on gestational day 12.5. The male pups born to these two groups of dams were given either a regular diet or a high-calorie diet, after postnatal day (PND) 28. The four groups of investigated offspring were thus termed T-R (TCDD regular diet), T-H (TCDD high-calorie diet), V-R (vehicle regular diet), and V-H (vehicle high-calorie diet). The mice were regularly monitored for body weight, blood pressure and glucose, until they reached 26 weeks of age. Mice in the V-H group were significantly obese at weeks 15 and 26, but they exhibited no diabetes-associated signs of insulin resistance or hypertension. However, metabolic syndrome-related alterations with marginal signs of liver damage were found at week 26. Pronounced signs of dysregulated lipid metabolism with altered gene expression and liver inflammation were already present at week 15, whereas such alterations were suppressed in the T-H group. Although the mechanism is unclear, this study showed that in utero and lactational exposure to low-dose TCDD does not aggravate obesity-induced disease states, such as adult-onset diabetes, but instead attenuates the dysregulation of lipid metabolism brought on by a high-calorie diet.

Polychlorinated Biphenyls, Glycaemia and Diabetes in a Population Living in a Highly Polychlorinated Biphenyls-Polluted Area in Northern Italy: a Cross-sectional and Cohort Study

Conflicts of interests: the authors declare no potential conflict of interests.

IL-22 mRNA expression in blood samples as a useful biomarker for assessing the adverse health effects of PCBs on allergic children

To facilitate the assessment of adverse effects of very low concentrations of air pollutants on general populations, we planned to establish a reliable biomarker that is also useful in identifying vulnerable populations. For this purpose we monitored several inflammation markers in blood samples from 2 year old Japanese children (N = 30), and found that those children living close to major highways (<50 m) show higher levels of mRNA expression IL-22 in their blood samples than those living further away (+50 m). This tendency was more pronounced among subjects showing positive IgE against egg and milk. We further examined association between IL-22 mRNA expression and PCB residues and found a number of significant positive correlations between each individual PCB congener and IL-22 expression. To identify the most vulnerable population among those children we selected asthma as a typical allergy-related disease, and could show that there are significant differences in the levels of IL-22 mRNA expression between IgE negative non-asthmatic subject and asthmatic children showing positive IgE reaction toward egg or milk, again. These observations support our main conclusion that IL-22 expression is a sensitive biomarker which is useful in identifying sub-populations of children who are especially vulnerable to air pollution.

Polychlorinated biphenyl exposure, diabetes and endogenous hormones: a cross-sectional study in men previously employed at a capacitor manufacturing plant

BACKGROUND

Studies have shown associations of diabetes and endogenous hormones with exposure to a wide variety of organochlorines. We have previously reported positive associations of polychlorinated biphenyls (PCBs) and inverse associations of selected steroid hormones with diabetes in postmenopausal women previously employed in a capacitor manufacturing plant.

METHODS

This paper examines associations of PCBs with diabetes and endogenous hormones in 63 men previously employed at the same plant who in 1996 underwent surveys of their exposure and medical history and collection of bloods and urine for measurements of PCBs, lipids, liver function, hematologic markers and endogenous hormones.

RESULTS

PCB exposure was positively associated with diabetes and age and inversely associated with thyroid stimulating hormone and triiodothyronine-uptake. History of diabetes was significantly related to total PCBs and all PCB functional groupings, but not to quarters worked and job score, after control for potential confounders. None of the exposures were related to insulin resistance (HOMA-IR) in non-diabetic men.

CONCLUSIONS

Associations of PCBs with specific endogenous hormones differ in some respects from previous findings in postmenopausal women employed at the capacitor plant. Results from this study, however, do confirm previous reports relating PCB exposure to diabetes and suggest that these associations are not mediated by measured endogenous hormones.

Association of serum levels of polychlorinated biphenyls with IL-8 mRNA expression in blood samples from asthmatic and non-asthmatic Japanese children

BACKGROUND

One of the suggested health outcomes of PCB exposure is childhood asthma.

OBJECTIVES

This study was conducted to find health relevant biomarkers providing the molecular epidemiological evidence for the positive relationship between exposure to PCBs and childhood asthma.

METHODS

Blood samples from fifteen asthmatic children as well as an equal number of non-asthmatic children (average 2 year old) were collected, and were analyzed for PCBs and their select marker expression by using qRT-PCR.

RESULTS

Among biomarkers examined IL-8 expression was significantly correlated to serum levels of PCB #163+164 (P=0.022), #170 (P=0.046), #177 (P=0.022), #178 (P=0.022) and #180+193 (P=0.046) in a dose-dependent manner, which was found only among asthmatic children. In contrast, COX-2 correlations to individual congener levels were recognized only among control subjects, not among asthmatic subjects.

CONCLUSION

Serum concentrations of PCB#163+164, #170, #177, #178 and #180+193 correlate significantly with IL-8 mRNA expressions among asthmatic children.

Aryl hydrocarbon receptor deficiency enhances insulin sensitivity and reduces PPAR-α pathway activity in mice

BACKGROUND

Numerous man-made pollutants activate the aryl hydrocarbon receptor (AhR) and are risk factors for type 2 diabetes. AhR signaling also affects molecular clock genes to influence glucose metabolism.

OBJECTIVE

We investigated mechanisms by which AhR activation affects glucose metabolism.

METHODS

Glucose tolerance, insulin resistance, and expression of peroxisome proliferator-activated receptor-α (PPAR-α) and genes affecting glucose metabolism or fatty acid oxidation and clock gene rhythms were investigated in wild-type (WT) and AhR-deficient [knockout (KO)] mice. AhR agonists and small interfering RNA (siRNA) were used to examine the effect of AhR on PPAR-α expression and glycolysis in the liver cell line Hepa-1c1c7 (c7) and its c12 and c4 derivatives. Brain, muscle ARNT-like protein 1 (Bmal1) siRNA and Ahr or Bmal1 expression plasmids were used to analyze the effect of BMAL1 on PPAR-α expression in c7 cells.

RESULTS

KO mice displayed enhanced insulin sensitivity and improved glucose tolerance, accompanied by decreased PPAR-α and key gluconeogenic and fatty acid oxidation enzymes. AhR agonists increased PPAR-α expression in c7 cells. Both Ahr and Bmal1 siRNA reduced PPAR-α and metabolism genes. Moreover, rhythms of BMAL1 and blood glucose were altered in KO mice.

CONCLUSIONS

These results indicate a link between AhR signaling, circadian rhythms, and glucose metabolism. Furthermore, hepatic activation of the PPAR-α pathway provides a mechanism underlying AhR-mediated insulin resistance.

The OBELIX project: early life exposure to endocrine disruptors and obesity

The hypothesis of whether early life exposure (both pre- and early postnatal) to endocrine-disrupting chemicals (EDCs) may be a risk factor for obesity and related metabolic diseases later in life will be tested in the European research project OBELIX (OBesogenic Endocrine disrupting chemicals: LInking prenatal eXposure to the development of obesity later in life). OBELIX is a 4-y project that started in May 2009 and which has the following 5 main objectives: 1) to assess early life exposure in humans to major classes of EDCs identified as potential inducers of obesity (ie, dioxin-like compounds, non-dioxin-like polychlorinated biphenyls, organochlorine pesticides, brominated flame retardants, phthalates, and perfluorinated compounds) by using mother-child cohorts from 4 European regions with different food-contaminant exposure patterns; 2) to relate early life exposure to EDCs with clinical markers, novel biomarkers, and health-effect data related to obesity; 3) to perform hazard characterization of early life exposure to EDCs for the development of obesity later in life by using a mouse model; 4) to determine mechanisms of action of obesogenic EDCs on developmental programming with in vivo and in vitro genomics and epigenetic analyses; and 5) to perform risk assessments of prenatal exposure to obesogenic EDCs in food by integrating maternal exposure through food-contaminant exposure and health-effect data in children and hazard data in animal studies.

Associations of polychlorinated biphenyl exposure and endogenous hormones with diabetes in post-menopausal women previously employed at a capacitor manufacturing plant

There is an increasing body of literature showing associations of organochlorine exposure with risk of diabetes and insulin resistance. Some studies suggest that associations differ by gender and that diabetes risk, in turn, may be affected by endogenous steroid hormones. This report examines the relationships of serum PCBs and endogenous hormones with history of diabetes in a cohort of persons previously employed at a capacitor manufacturing plant. A total of 118 women were post-menopausal with complete data, of whom 93 were not using steroid hormones in 1996, at the time of examination, which included a survey of exposure and medical history, height, weight and collection of blood and urine for measurements of lipids, liver function, hematologic markers and endogenous hormones. This analysis examines relationships of serum polychlorinated biphenyls (PCBs), work exposure and endogenous hormones with self-reported history of diabetes after control for potential confounders. All PCB exposure groups were significantly related to history of diabetes, but not to insulin resistance as measured by the homeostatic model assessment of insulin resistance (HOMA-IR) in non-diabetics. Diabetes was also independently and inversely associated with follicle stimulating hormone (FSH), dehydroepiandrosterone sulfate (DHEAS) and triiodothyronine (T3) uptake. HOMA-IR was positively associated with body mass index (BMI) and C-reactive protein (CRP) and inversely associated with sex hormone binding globulin (SHBG) and T3 uptake after control for PCB exposure. Possible biologic mechanisms are discussed. This study confirms previous reports relating PCB exposure to diabetes and suggests possible hormonal pathways deserving further exploration.

Metabolomic analysis of liver and skeletal muscle tissues in C57BL/6J and DBA/2J mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been demonstrated to have the adverse effects on human health. In this study, we applied a metabolomic approach in conjunction with unsupervised and supervised machine learning methods to investigate the toxic effects of TCDD. By using liquid chromatography/quadrupole time-of-flight mass spectrometry, non-targeted metabolomic analysis revealed the metabolic signatures of the toxicity in aryl hydrocarbon receptor (AhR)-high affinity C57BL/6J (C6) mice as well as low affinity strain-DBA/2J (D2) mice. Lysophospholipids and long chain fatty acids were strikingly elevated in the C6 mice exposed to TCDD in both liver and skeletal muscle tissues. Meanwhile, the level of palmitoylcarnitine, which is one of the important indicators in fatty acid β-oxidation, increased significantly. Moreover, several nucleosides and amino acids decreased markedly. On the other hand, much less differentiating metabolites were highlighted in another strain-D2 mouse model. Taking liver and skeletal muscle tissues together, the levels of inosine, valine and glutamine decreased significantly. One lysophospholipid and two fatty acids were found to be enhanced. The principal components analysis and support vector machine clustering results also exhibited discriminations in the liver and skeletal muscle tissues of the mice. The obtained results indicated that TCDD could disrupt several metabolic pathways, including fatty acid biosynthesis and amino acid metabolism in both C6 and D2 mice. The increased rate of fatty acid beta-oxidation, however, was only observed in the liver and skeletal muscle tissues of C6 mice. The perturbation of the tricarboxylic acid (TCA) cycle was testified in two strains but the change was much slighter in D2 mice. It was of particular interest to note that the succinate level was enhanced in the liver tissues of both strains, and particularly, the change was up to 11.49-fold in the liver of C6 mice treated with TCDD. Collectively, the discrimination of D2 mice was not as distinct as that of C6 mice when exposed to the same dosage. Furthermore, D2 was confirmed to be less-sensitive rather than resistant to a high dose of TCDD.

Increase in metabolic syndrome-related hospitalizations in relation to environmental sources of persistent organic pollutants

Evidence from cell studies indicates that persistent organic pollutants (POP) can induce insulin resistance, an essential component of the metabolic syndrome (MetS). We hypothesized that residential proximity to environmental sources of POP would be associated with the MetS in the population. The present study examined the association between residency in a zip code containing or abutting environmental sources of POP and MetS-related hospitalization rates. Hospitalization data were obtained from the New York Statewide Planning and Research Cooperative System. Relative risks (RR) were calculated as hospitalization rate ratios. Adjusted RR and their 95% confidence intervals (CI) were estimated by multivariable Poisson regression. A higher proportion of African Americans resided in POP zip codes compared to Caucasians (25.9% and 24.3%, respectively, p < 0.01). Residence in POP zip codes was associated with a statistically significant 39.2% increase in MetS-related hospitalization rates, adjusted for race, gender, and age (adjusted RR = 1.392, 95% CI: 1.032-1.879, p = 0.030). Increase in age was independently associated with higher MetS-related hospitalization rates (p for trend < 0.001). Our findings contribute to the body of evidence supporting the hypothesis of POP constituting an environmental risk factor for the MetS. Further studies investigating exposure to POP and insulin resistance are warranted.

Exposure to an organometal compound stimulates adipokine and cytokine expression in white adipose tissue

OBJECTIVE

White adipose tissue (WAT) is now considered a defined tissue capable of interactions with other organ systems. WAT role in elevating the level of systemic chronic inflammation suggests that alterations in this tissue as the result of disease or environmental factors may influence the development and progression of various obesity-related pathologies. This study investigated WAT cell-specific responses to an organometal compound, trimethyltin (TMT), to determine possible contribution to induced inflammation.

METHODS

Human primary mature adipocytes and macrophage differentiated THP-1 cells were cultured in TMT presence and relative toxicities and different adipokine levels were determined. The inflammatory response was examined in TMT presence for primary cells from obese ob/ob mice WAT, and after TMT injection in ob/ob mice.

RESULTS

Both adipocytes and macrophages were resistant to cell death induced by TMT. However, adipocytes cultured in TMT presence showed increased expression of TNFα and IL-6, and modified leptin levels. In macrophage cultures, TMT also increased TNFα and IL-6, while MCP-1 and MIP-1α were decreased. In vivo, a single injection of TMT in ob/ob mice, elevated TNFα, MIP-1α and adiponectin in WAT.

CONCLUSIONS

Elevation of the inflammatory related products can be induced by chemical exposure in adipocytes and macrophages, as well as murine WAT. These data suggest that numerous factors, including a systemic chemical exposure, can induce an inflammatory response from the WAT. Furthermore, when characterizing both chemical-induced toxicity and the progression of the chronic inflammation associated with elevated WAT content, such responses in this target tissue should be taken into consideration.

Exposure to bioaccumulative organochlorine compounds alters adipogenesis, fatty acid uptake, and adipokine production in NIH3T3-L1 cells

Exposure to the organochlorine compounds p,p'-dichlorodiphenyldichloroethylene (DDE) and oxychlordane have been associated with an increased prevalence of diabetes. Although the exact etiology of diabetes, especially type 2 diabetes, is not known, it is thought that adipose dysfunction plays a vital role in the progression of this disease. Thus, the present study examined whether exposure to these bioaccumulative compounds promotes adipocyte dysfunction including alterations in adipogenesis, fatty acid storage, and adipokine production within the adipocyte. We employed the NIH3T3-L1 cell line as a model for adipogenesis and mature adipocyte function. Exposure to DDE or oxychlordane prior to and throughout differentiation did not affect adipogenesis. In mature NIH3T3-L1 adipocytes, exposure to oxychlordane, DDE, or dieldrin had no effect on insulin-stimulated fatty acid uptake but did increase basal fatty acid uptake over a 24 h period. There was no observed effect of exposure to these compounds on lipolysis. Exposure to DDE significantly increased the release of leptin, resistin, and adiponectin from mature adipocytes with corresponding increases in expression of resistin and adiponectin. Taken together, the current data suggest that exposure to these compounds, especially DDE, may promote some aspects of adipocyte dysfunction that are commonly associated with obesity and type 2 diabetes.

Childhood obesity and environmental chemicals

Childhood and adolescent rates of obesity and overweight are continuing to increase in much of the world. Risk factors such as diet composition, excess caloric intake, decreased exercise, genetics, and the built environment are active areas of etiologic research. The obesogen hypothesis, which postulates that prenatal and perinatal chemical exposure can contribute to risk of childhood and adolescent obesity, remains relatively underexamined. This review surveys numerous classes of chemicals for which this hypothesis has been explored. We focus on human data where they exist and also discuss the findings of rodent and cell culture studies. Organochlorine chemicals as well as several classes of chemicals that are peroxisome proliferator-activated receptor agonists are identified as possible risk factors for obesity. Recommendations for future epidemiologic and experimental research on the chemical origins of obesity are also given.

Relationship of polychlorinated biphenyls with type 2 diabetes and hypertension

Diabetes and hypertension are important contributors to morbidity and mortality worldwide. Both of these conditions are caused by some combination of genetic and environmental factors which may include exposure to persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs). Studies have shown an association between elevated serum PCBs and the metabolic syndrome, insulin sensitivity and insulin secretion. Cross-sectional studies have shown associations between diabetes or hypertension and certain PCB congeners or classes, while those same studies show no association between diabetes or hypertension and several other PCB congeners. In animal and human cell studies, various PCBs and dioxins appear to alter glucose and insulin metabolism. These studies specifically show effects on the glucose transporter (GLUT-4) gene and protein; insulin-like growth factor binding protein-1 (IGFBP-1); nuclear transcription factor kappa B (NFκB); tumor necrosis factor alpha (TNF-α); and insulin production. There are a few longitudinal studies examining the association of diabetes or hypertension and PCBs with no consensus conclusion. Some longitudinal studies have found there to be an association, others have not and a gender difference has also been noted. Prospective studies are needed to determine if PCBs and other POPs contribute to development of diabetes and hypertension.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on adipogenic differentiation and insulin-induced glucose uptake in 3T3-L1 cells

Dioxin exposure has been positively associated with human type II diabetes. Because lipophilic dioxins accumulate mainly in adipose tissue, this study aimed to determine if dioxins induce metabolic dysfunction in fat cells. Using 3T3-L1 cells as an in vitro model, we analyzed the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a model dioxin, on adipogenic differentiation, glucose uptake, and lipolysis. TCDD inhibited adipogenic differentiation, as determined by using oil droplet formation and adipogenic marker gene expression, including PPARgamma (peroxisome proliferator-activated receptor gamma), C/EBPalpha (CCAAT/enhancer-binding protein alpha), and Glut4 (glucose transporter type 4). Effects of TCDD on glucose uptake were evaluated using fully differentiated 3T3-L1 adipocytes, revealing that TCDD significantly attenuated insulin-induced glucose uptake dose dependently. Inhibition of aryl hydrocarbon receptor (AhR) by alpha-naphthoflavone (alpha-NF), an AhR inhibitor, did not prevent the inhibitory effect of TCDD on glucose uptake, suggesting that TCDD attenuates insulin-induced glucose uptake in an AhR-independent manner. Effects of TCDD on lipolysis were determined using glycerol release assay. We found that TCDD had no marked effect on isoproterenol-induced glycerol release in fully differentiated 3T3-L1 adipocytes. These results provide in vitro evidence of TCDD's effects on fat cell metabolism, suggesting dioxin exposure in development of insulin resistance and type II diabetes.

The impacts of organochlorines and other persistent pollutants on thyroid and metabolic health

High prevalence of thyroid and metabolic disorders has been repeatedly observed in the population living in the area of eastern Slovakia highly polluted by a mixture of PCBs, DDE and HCB since about 50 years ago. Among thyroid disorders, increase of thyroid volume as measured by ultrasound volumetry may be suggested as one of notable findings which appeared possibly related to increased OCs levels and to autoimmunity signs (e.g. positive thyroperoxidase antibodies in blood and/or hypoechogenicity image obtained by ultrasound), while some participation of individual susceptibility and also of immunogenic effect of OCs and iodine in this iodine replete country cannot be excluded. Another notable finding has been the increase of blood FT4 and TT3 positively related to high PCBs level. Such increased FT4 level has been found associated with TSH level in hyperthyroid range in about 2% of examined population from polluted area. High prevalence of thyroid autoimmune disorders strongly supported the assumption on impaired immune system and thus also on presumably increased prevalence of other autoimmune disorders in highly exposed population. In addition, markedly increased prevalence of prediabetes and diabetes significantly related to major OCs (PCBs, DDE and HCB) levels and accompanied by increasing level of cholesterol and triglycerides has been observed. The observations also suggested a role of prenatal exposure to OCs in the development of several adverse health signs (e.g. increased prevalence of thyroid antibodies, impaired fasting glucose level, increased thyroid volume, decreased thymus volume, decreased neurobehavioral performance, increased hearing and dental disorders) in young generation born to highly exposed mothers in polluted area.

Increased hospitalizations for ischemic stroke with comorbid diabetes and residential proximity to sources of organic pollutants: a 12-year population-based study

BACKGROUND

Evidence is emerging that exposure to persistent organic pollutants (POP) is a risk factor for atherosclerosis-related diseases and for diabetes mellitus (DM). We hypothesized that residential proximity to sources of POP will be associated with an increase in hospitalization rates for ischemic stroke (IS) with comorbid DM (IS-DM).

METHODS

We examined IS-DM hospitalization rates in the New York State (exclusive of New York City) during a 12-year period. POP exposure status was assessed based on residency in a zip code containing or abutting environmental sources of POP. Adjusted relative risks (RR) of IS-DM hospitalization were estimated by multivariate Poisson regression.

RESULTS

A statistically significant 10% increase in IS-DM hospitalization rates was observed in populations environmentally exposed to POP (adjusted RR 1.10, 95% confidence interval, CI, 1.01-1.20; p = 0.031). IS-DM hospitalization rates were also higher in males (adjusted RR 1.34, 95% CI 1.30-1.39; p < 0.001), in blacks (adjusted RR 4.54, 95% CI 4.16-4.94; p < 0.001) and in older age groups (p for trend <0.001).

CONCLUSIONS

Residential proximity to sources of POP is associated with an increase in RR of IS-DM hospitalization. Our findings support the hypothesis of POP being a risk factor for IS. Further studies are warranted.

Effects of environmental pollutants on the reproduction and welfare of ruminants

Anthropogenic pollutants comprise a wide range of synthetic organic compounds and heavy metals, which are dispersed throughout the environment, usually at low concentrations. Exposure of ruminants, as for all other animals, is unavoidable and while the levels of exposure to most chemicals are usually too low to induce any physiological effects, combinations of pollutants can act additively or synergistically to perturb multiple physiological systems at all ages but particularly in the developing foetus. In sheep, organs affected by pollutant exposure include the ovary, testis, hypothalamus and pituitary gland and bone. Reported effects of exposure include changes in organ weight and gross structure, histology and gene and protein expression but these changes are not reflected in changes in reproductive performance under the conditions tested. These results illustrate the complexity of the effects of endocrine disrupting compounds on the reproductive axis, which make it difficult to extrapolate between, or even within, species. Effects of pollutant exposure on the thyroid gland, immune, cardiovascular and obesogenic systems have not been shown explicitly, in ruminants, but work on other species suggests that these systems can also be perturbed. It is concluded that exposure to a mixture of anthropogenic pollutants has significant effects on a wide variety of physiological systems, including the reproductive system. Although this physiological insult has not yet been shown to lead to a reduction in ruminant gross performance, there are already reports indicating that anthropogenic pollutant exposure can compromise several physiological systems and may pose a significant threat to both reproductive performance and welfare in the longer term. At present, many potential mechanisms of action for individual chemicals have been identified but knowledge of factors affecting the rate of tissue exposure and of the effects of combinations of chemicals on physiological systems is poor. Nevertheless, both are vital for the identification of risks to animal productivity and welfare.

Residential proximity to environmental sources of persistent organic pollutants and first-time hospitalizations for myocardial infarction with comorbid diabetes mellitus: a 12-year population-based study

OBJECTIVES

Environmental exposure to persistent organic pollutants (POPs) has been associated with an increased risk of both acute myocardial infarction (AMI) and diabetes mellitus (DM). A study of first-time hospitalizations for AMI with DM as a comorbidity in populations presumed to be exposed or not exposed on the basis of residence near POPs sites was conducted to investigate whether exposure to POPs increases the environmental burden of disease.

MATERIALS AND METHODS

We examined the association between residential proximity to environmental sources of POPs and hospitalization rates for first-time AMI with comorbid DM in 31,428 patients aged 25-74 years, using the New York Statewide Planning and Research Cooperative System data for a 12-year period (1993-2004). Environmental exposure status was assessed based on the zip code of residence. Adjusted relative risks (RR) of AMI hospitalization were estimated by multivariate Poisson regression.

RESULTS

Hospitalization rates for first-time AMI with comorbid DM were significantly greater in populations living near POPs sites (adjusted RR = 1.169, 95% CI: 1.014-1.347, p < 0.05). These rates were also significantly higher in African Americans than in Caucasians (adjusted RR = 1.902, 95% CI: 1.659-2.180, p < 0.001), in males (adjusted RR = 1.767, 95% CI: 1.695-1.843, p < 0.001), and for older ages (p for trend < 0.001). These findings, consistent with established non-modifiable risk factors, support the plausibility of our model.

CONCLUSIONS

Residential proximity to environmental sources of POPs is associated with a significant increase in hospitalization rates for first-time AMI with comorbid DM, compared to respective rates in populations not exposed to POPs.