Congener-specific polychlorinated biphenyls and the prevalence of diabetes in the Saku Control Obesity Program (SCOP)

Polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, pesticides, and diabetes in the Anniston Community Health Survey follow-up (ACHS II): single exposure and mixture analysis approaches

Dioxins and dioxin-like compounds measurements were added to polychlorinated biphenyls (PCBs) and organochlorine pesticides to expand the exposure profile in a follow-up to the Anniston Community Health Survey (ACHS II, 2014) and to study diabetes associations. Participants of ACHS I (2005-2007) still living within the study area were eligible to participate in ACHS II. Diabetes status (type-2) was determined by a doctor's diagnosis, fasting glucose ≥125 mg/dL, or being on any glycemic control medication. Incident diabetes cases were identified in ACHS II among those who did not have diabetes in ACHS I, using the same criteria. Thirty-five ortho-substituted PCBs, 6 pesticides, 7 polychlorinated dibenzo-p-dioxins (PCDD), 10 furans (PCDF), and 3 non-ortho PCBs were measured in 338 ACHS II participants. Dioxin toxic equivalents (TEQs) were calculated for all dioxin-like compounds. Main analyses used logistic regression models to calculate odds ratios (OR) and 95 % confidence intervals (CI). In models adjusted for age, race, sex, BMI, total lipids, family history of diabetes, and taking lipid lowering medication, the highest ORs for diabetes were observed for PCDD TEQ: 3.61 (95 % CI: 1.04, 12.46), dichloro-diphenyl dichloroethylene (p,p'-DDE): 2.07 (95 % CI 1.08, 3.97), and trans-Nonachlor: 2.55 (95 % CI 0.93, 7.02). The OR for sum 35 PCBs was 1.22 (95 % CI: 0.58-2.57). To complement the main analyses, we used BKMR and g-computation models to evaluate 12 mixture components including 4 TEQs, 2 PCB subsets and 6 pesticides; suggestive positive associations for the joint effect of the mixture analyses resulted in ORs of 1.40 (95% CI: -1.13, 3.93) for BKMR and 1.32 (95% CI: -1.12, 3.76) for g-computation. The mixture analyses provide further support to previously observed associations of trans-Nonachlor, p,p'- DDE, PCDD TEQ and some PCB groups with diabetes.

Exposure to PCB126 during the nursing period reversibly impacts early-life glucose tolerance

Polychlorinated biphenyls (PCBs) are persistent environmental organic pollutants known to have detrimental health effects. Using a mouse model, we previously demonstrated that PCB126 exposure before and during pregnancy and throughout the perinatal period adversely affected offspring glucose tolerance and/or body composition profiles. The purpose of this study was to investigate the glucose tolerance and body composition of offspring born to dams exposed to PCB126 during the nursing period only. Female ICR mice were bred, and half of the dams were exposed to either vehicle (safflower oil) or 1 µmole PCB126 per kg of body weight via oral gavage on postnatal days (PND) 3, 10, and 17 (n = 9 per group). Offspring body weight, lean and fat mass, and glucose tolerance were recorded every three weeks. PCB126 treatment did not alter dam nor offspring body weight (p > 0.05). PCB126-exposed male and female offspring displayed normal body composition (p > 0.05) relative to vehicle-exposed offspring. However, both male and female offspring that were exposed to PCB126 during the nursing period had significantly impaired glucose tolerance at 3 and 9 weeks of age (p < 0.05). At 6 and 12 weeks of age, no impairments in glucose tolerance existed in offspring (p > 0.05). Our current study demonstrates that exposure to PCB126 through the mother's milk does not affect short- or long-term body composition but impairs glucose tolerance in the short-term.

Sex-specific Associations Between Type 2 Diabetes Incidence and Exposure to Dioxin and Dioxin-like Pollutants: A Meta-analysis

The potential for persistent organic pollutants (POPs), including dioxins and dioxin-like polychlorinated biphenyls (DL-PCBs), to increase the risk of incident diabetes in adults has been extensively studied. However, there is substantial variability in the reported associations both between and within studies. Emerging data from rodent studies suggest that dioxin disrupts glucose homeostasis in a sex-specific manner. Thus, we performed a review and meta-analysis of relevant epidemiological studies to investigate sex differences in associations between dioxin or DL-PCB exposure and type 2 diabetes incidence. Articles that met our selection criteria (n = 81) were organized into the following subcategories: data stratified by sex (n = 13), unstratified data (n = 45), and data from only 1 sex (n = 13 male, n = 10 female). We also considered whether exposure occurred either abruptly at high concentrations through a contamination event (“disaster exposure”) or chronically at low concentrations (“non-disaster exposure”). There were 8 studies that compared associations between dioxin/DL-PCB exposure and diabetes risk in males versus females within the same population. When all sex-stratified or single-sex studies were considered in the meta-analysis (n = 18), the summary relative risk (RR) for incident diabetes among those exposed relative to reference populations was 1.78 (95% CI = 1.37–2.31) and 1.95 (95% CI = 1.56–2.43) for female and males, respectively. However, when we restricted the meta-analysis to disaster-exposed populations, the RR was higher in females than males (2.86 versus 1.59, respectively). In contrast, in non-disaster exposed populations the RR for females was lower than males (1.40 and 2.02, respectively). Our meta-analysis suggests that there are sex differences in the associations between dioxin/DL-PCBs exposure and incident diabetes, and that the mode of exposure modifies these differences.

Lack of Offspring Nrf2 Does Not Exacerbate the Detrimental Metabolic Outcomes Caused by In Utero PCB126 Exposure

Human environmental exposures to toxicants, such as polychlorinated biphenyls (PCBs), increase oxidative stress and disease susceptibility. Such exposures during pregnancy and/or nursing have been demonstrated to adversely affect offspring health outcomes. Nuclear factor erythroid-2-related factor 2 (Nrf2) regulates the antioxidant response and is involved in the detoxification of coplanar PCBs, like PCB126. The purpose of this study was to investigate glucose tolerance and body composition in PCB-exposed offspring expressing or lacking Nrf2. We hypothesized that offspring lacking Nrf2 expression would be more susceptible to the long-term health detriments associated with perinatal PCB exposure. During gestation, whole-body Nrf2 heterozygous (Het) and whole-body Nrf2 knockout (KO) mice were exposed to vehicle or PCB126. Shortly after birth, litters were cross-fostered to unexposed dams to prevent PCB exposure during nursing. Offspring were weaned, and their body weight, body composition, and glucose tolerance were recorded. At two months of age, PCB exposure resulted in a significant reduction in the average body weight of offspring born to Nrf2 Het dams (p < 0.001) that primarily arose from the decrease in average lean body mass in offspring (p < 0.001). There were no differences in average body weight of PCB-exposed offspring born to Nrf2 KO dams (p > 0.05), and this was because offspring of Nrf2 KO dams exposed to PCB126 during pregnancy experienced a significant elevation in fat mass (p = 0.002) that offset the significant reduction in average lean mass (p < 0.001). Regardless, the lack of Nrf2 expression in the offspring themselves did not enhance the differences observed. After an oral glucose challenge, PCB-exposed offspring exhibited significant impairments in glucose disposal and uptake (p < 0.05). Offspring born to Nrf2 Het dams exhibited these impairments at 30 min and 120 min, while offspring born to Nrf2 KO dams exhibited these impairments at zero, 15, 30, 60 and 120 min after the glucose challenge. Again, the interactions between offspring genotype and PCB exposure were not significant. These findings were largely consistent as the offspring reached four months of age and demonstrate that the lack of offspring Nrf2 expression does not worsen the metabolic derangements caused by in utero PCB exposure as we expected. Future directions will focus on understanding how the observed maternal Nrf2 genotypic differences can influence offspring metabolic responses to in utero PCB exposure.

Association of plasma levels of lipid and polychlorinated biphenyls in Iranian adult

Background

Exposure to Polychlorinated biphenyls (PCBs) continues over the world through seafood consumption and indoor exposure to building materials containing PCB. This study aimed to assess the relationship between plasma level of PCB congeners and lipid profile and Body Mass Index (BMI) as well.

Methods

The study population consisted of 181 Iranian adults. Data on BMI, plasma concentration of PCB congeners and serum level of lipid profile including Triglyceride, low-density lipoproteins and high-density lipoproteins, recruited from database of a project entitled “Occupational and environmental exposure to PCBs in Iran”. Multiple linear regression analysis of associations between different quartiles of PCB congeners and various lipid fractions and BMI have been conducted.

Results

A linear increase in average serum Triglyceride and low-density lipoproteins (LDL) levels of participants in first, second, third and fourth quartiles of some PCB congeners was obtained. Following adjustment for age, gender, diet and other variables, only the association between different quartiles of PCB 138, PCB 153, PCB 118 and PCB sum and TG remained statistically significant.

Conclusion

The study showed a significant positive relation between plasma PCBs concentrations and serum level of TG in the study population with normal PCBs levels.

Chlorinated persistent organic pollutants and type 2 diabetes - A population-based study with pre- and post- diagnostic plasma samples

BACKGROUND

Persistent organic pollutants (POPs) have been associated with type 2 diabetes (T2D), but causality is uncertain.

OBJECTIVE

Within longitudinal population-based data from northern Sweden, we assessed how POPs associated with T2D prospectively and cross-sectionally, and further investigated factors related to individual changes in POP concentrations.

METHODS

For 129 case-controls pairs matched by age, sex and date of sampling, plasma concentrations of hexachlorobenzene (HCB), dichlorodiphenyl-dichloroethylene (p,p'-DDE), dioxin-like (DL) polychlorinated biphenyl congeners (PCB-118 and PCB-156), and non-dioxin like (NDL-PCB: PCB-74, -99, -138 -153, -170, -180, -183 and PCB-187) were analyzed twice (baseline and follow-up, 9-20 years apart). The cases received their T2D diagnose between baseline and follow-up. Prospective (using baseline data) and cross-sectional (using follow-up data) odds ratios (ORs) for T2D on lipid standardized POPs (HCB, p,p'-DDE, ∑DL-PCBs, ∑NDL-PCBs) were estimated using conditional logistic regression, adjusting for body mass index (BMI) and plasma lipids. The influence of BMI, weight-change, and plasma lipids on longitudinal changes in POP concentrations were evaluated among non-diabetic individuals (n = 306).

RESULTS

POPs were associated with T2D in both the prospective and cross-sectional assessments. Of a standard deviation increase in POPs, prospective ORs ranged 1.42 (95% CI: 0.99, 2.06) for ∑NDL-PCBs to 1.55 (95% CI: 1.01, 2.38) for HCB (p < 0.05 only for HCB), and cross-sectional ORs ranged 1.62 (95% CI: 1.13; 2.32) for p,p'-DDE to 2.06 (95% CI: 1.29, 3.28) for ∑DL-PCBs (p < 0.05 for all POPs). In analyses of non-diabetic individuals, higher baseline BMI, decreased weight and decreased plasma lipid concentrations were associated with a slower decrease of POPs. Cases had, besides a higher BMI, reduced cholesterol and weight gain at follow-up compared to controls, which can explain the higher ORs in the cross-sectional assessments.

DISCUSSION

The association between POPs and T2D was confirmed, but an indication that individuals body fat history might influence POP-T2D associations weakens the epidemiological support for a causal association. It also warrants studies based on other exposure metrics than biomonitoring. In addition, we note that a cross-sectional design overestimates the ORs if T2D cases have successfully intervened on weight and/or blood lipids, as changes in these factors cause changes in POPs.

Endocrine-Mediated Mechanisms of Metabolic Disruption and New Approaches to Examine the Public Health Threat

Obesity and metabolic disorders are of great societal concern and generate substantial human health care costs globally. Interventions have resulted in only minimal impacts on disrupting this worsening health trend, increasing attention on putative environmental contributors. Exposure to numerous environmental contaminants have, over decades, been demonstrated to result in increased metabolic dysfunction and/or weight gain in cell and animal models, and in some cases, even in humans. There are numerous mechanisms through which environmental contaminants may contribute to metabolic dysfunction, though certain mechanisms, such as activation of the peroxisome proliferator activated receptor gamma or the retinoid x receptor, have received considerably more attention than less-studied mechanisms such as antagonism of the thyroid receptor, androgen receptor, or mitochondrial toxicity. As such, research on putative metabolic disruptors is growing rapidly, as is our understanding of molecular mechanisms underlying these effects. Concurrent with these advances, new research has evaluated current models of adipogenesis, and new models have been proposed. Only in the last several years have studies really begun to address complex mixtures of contaminants and how these mixtures may disrupt metabolic health in environmentally relevant exposure scenarios. Several studies have begun to assess environmental mixtures from various environments and study the mechanisms underlying their putative metabolic dysfunction; these studies hold real promise in highlighting crucial mechanisms driving observed organismal effects. In addition, high-throughput toxicity databases (ToxCast, etc.) may provide future benefits in prioritizing chemicals for in vivo testing, particularly once the causative molecular mechanisms promoting dysfunction are better understood and expert critiques are used to hone the databases. In this review, we will review the available literature linking metabolic disruption to endocrine-mediated molecular mechanisms, discuss the novel application of environmental mixtures and implications for in vivo metabolic health, and discuss the putative utility of applying high-throughput toxicity databases to answering complex organismal health outcome questions.

Association of plasma PCB levels and HbA1c concentration in Iran

Background

The rapid increase in prevalence of diabetes mellitus over the last decades warrants more attention to the effects of environmental and occupational exposures on glucose metabolism. Our study aimed to assess the association between the plasma levels of various congeners of polychlorinated biphenyls (PCBs) and the serum concentration of glycated haemoglobin (HbA1c).

Methods

Our study population consisted of 140 Iranian adults from seven different occupational groups and a group of non-occupationally exposed female participants. The plasma concentration of PCBs were determined at the laboratory of occupational toxicology at RWTH Aachen University, Germany. We considered an HbA1c concentration of 5.7% and more as indicating a disturbed glucose metabolism. Logistic regression was used to assess the association between quartiles of concentrations of PCB congeners and serum HbA1c.

Results

Participants with an increased HbA1c value had higher plasma levels of PCB 138, 153, 180 and the PCB sum, although this association was statistically not significant. There was no significant difference between the levels of PCB 138, 153, 180, the sum of these congeners, and PCB 118 in their quartiles when comparing with HbA1c concentrations.

Conclusions

For our cohort, we could not demonstrate a significant association between PCB and HbA1c concentrations indicating a disturbance of glucose metabolism.

Electronic supplementary material

The online version of this article (10.1186/s12995-018-0199-4) contains supplementary material, which is available to authorized users.

Persistent Organic Pollutants as Risk Factors for Obesity and Diabetes

PURPOSE OF REVIEW

The rising prevalence of obesity and diabetes cannot be fully explained by known risk factors, such as unhealthy diet, a sedentary lifestyle, and family history. This review summarizes the available studies linking persistent organic pollutants (POPs) to obesity and diabetes and discusses plausible underlying mechanisms.

RECENT FINDINGS

Increasing evidence suggest that POPs may act as obesogens and diabetogens to promote the development of obesity and diabetes and induce metabolic dysfunction. POPs are synthesized chemicals and are used widely in our daily life. These chemicals are resistant to degradation in chemical or biological processes, which enable them to exist in the environment persistently and to be bio-accumulated in animal and human tissue through the food chain. Increasingly, epidemiologic studies suggest a positive association between POPs and risk of developing diabetes. Understanding the relationship of POPs with obesity and diabetes may shed light on preventive strategies for obesity and diabetes.

Diabetes Prevalence in Relation to Serum Concentrations of Polychlorinated Biphenyl (PCB) Congener Groups and Three Chlorinated Pesticides in a Native American Population

BACKGROUND

Exposure to persistent organic pollutants (POPs) is known to increase risk of diabetes.

OBJECTIVE

To determine which POPs are most associated with prevalence of diabetes in 601 Akwesasne Native Americans.

METHODS

Multiple logistic regression analysis was used to assess associations between quartiles of concentrations of 101 polychlorinated biphenyl (PCBs) congeners, congener groups and three chlorinated pesticides [dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB) and mirex] with diabetes. In Model 1, the relationship between quartiles of exposure and diabetes were adjusted only for sex, age, body mass index (BMI), and total serum lipids. Model 2 included additional adjustment for either total PCBs or total pesticides.

RESULTS

Total serum PCB and pesticide concentrations were each significantly associated with prevalence of diabetes when adjusted only for covariates (Model 1), but neither showed a significant OR for highest to lowest quartiles after additional adjustment for the other (Model 2). When applying Model 2 to PCB congener groups and individual pesticides, there were significant omnibus differences between the four quartiles (all ps < 0.042) for most groups, with the exception of penta- and hexachlorobiphenyls, DDE and mirex. However, when comparing highest to lowest quartiles only non- and mono-ortho PCBs [OR = 4.55 (95% CI: 1.48, 13.95)], tri- and tetrachloro PCBs [OR = 3.66 (95% CI: 1.37, -9.78)] and HCB [OR = 2.64 (95% CI: 1.05, 6.61)] showed significant associations with diabetes. Among the non- and mono-ortho congeners, highest to lowest quartile of dioxin TEQs was not significant [OR = 1.82 (95% CI: 0.61, 5.40)] but the OR for the non-dioxin-like congeners was [OR = 5.01 (95% CI: 1.76, 14.24)].

CONCLUSION

The associations with diabetes after adjustment for other POPs were strongest with the more volatile, non-dioxin-like, low-chlorinated PCB congeners and HCB. Because low-chlorinated congeners are more volatile, these observations suggest that inhalation of vapor-phase PCBs is an important route of exposure.

CITATION

Aminov Z, Haase R, Rej R, Schymura MJ, Santiago-Rivera A, Morse G, DeCaprio A, Carpenter DO, and the Akwesasne Task Force on the Environment. 2016. Diabetes prevalence in relation to serum concentrations of polychlorinated biphenyl (PCB) congener groups and three chlorinated pesticides in a Native American population. Environ Health Perspect 124:1376-1383; http://dx.doi.org/10.1289/ehp.1509902.

Pre-pregnancy maternal exposure to polybrominated and polychlorinated biphenyls and gestational diabetes: a prospective cohort study

BACKGROUND

While several studies have shown an association between environmental pollutants and diabetes among non-pregnant adults, few studies have prospectively assessed the association among pregnant women. We estimated the association between maternal pre-pregnancy levels of a polybrominated biphenyl (PBB 153) and 36 polychlorinated biphenyls (PCBs) with gestational diabetes (GDM).

METHODS

Data are from women (18-40 years) participating in a prospective cohort who achieved pregnancy lasting ≥24 weeks gestation and completed monthly pregnancy journals (n = 258). Women were recruited between 2005 and 2007 from 16 counties in Michigan and Texas. Women who ever reported a physician diagnosis of high blood glucose in monthly pregnancy journals were categorized as having gestational diabetes (n = 28; 10.9 %). Multivariable binary logistic regression was used to estimate odds ratios (OR) and 95 % confidence intervals (CIs).

RESULTS

There was no association between PBB 153 and GDM or any of the PCB congeners and GDM in unadjusted models. All associations remained non-significant with stepwise adjustment for age and waist-to-height ratio. Only with further adjustment for total serum lipids did the associations become significant, with lower levels of nine PCB congeners associated with GDM: 138, 153, 156, 167, 170, 172, 178, 180, and 194. The adjusted ORs for PCBs 170 and 180 were the strongest: 0.40 (0.18, 0.88) and 0.41 (0.19, 0.87), respectively.

CONCLUSIONS

Pre-pregnancy levels of PCBs were not consistently associated with development of GDM in this prospective cohort of U.S. women. Interestingly, we found that although women with GDM had higher mean pre-pregnancy circulating lipid levels compared to women without GDM, they had lower wet weight circulating levels of many PCBs. More research is needed to understand the dynamic fluctuations of PCBs and other persistent organic pollutants between lipid compartments in women preparing to conceive and throughout pregnancy.

Persistent organic pollutants as risk factors for type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a major and fast growing public health problem. Although obesity is considered to be the main driver of the pandemic of T2DM, a possible contribution of some environmental contaminants, of which persistent organic pollutants (POPs) form a particular class, has been suggested. POPs are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes which enable them to persist in the environment, to be capable of long-range transport, bio accumulate in human and animal tissue, bio accumulate in food chains, and to have potential significant impacts on human health and the environment. Several epidemiological studies have reported an association between persistent organic pollutants and diabetes risk. These findings have been replicated in experimental studies both in human (in-vitro) and animals (in-vivo and in-vitro), and patho-physiological derangements through which these pollutants exercise their harmful effect on diabetes risk postulated. This review summarizes available studies, emphasises on limitations so as to enable subsequent studies to be centralized on possible pathways and bring out clearly the role of POPs on diabetes risk.

Association of persistent organic pollutants and non-persistent pesticides with diabetes and diabetes-related health outcomes in Asia: A systematic review

BACKGROUND

Over half of the people with diabetes in the world live in Asia. Emerging scientific evidence suggests that diabetes is associated with environmental pollutants, exposures that are also abundant in Asia.

OBJECTIVE

To systematically review the literature concerning the association of persistent organic pollutants (POPs) and non-persistent pesticides with diabetes and diabetes-related health outcomes in Asia.

METHODS

PubMed and Embase were searched to identify studies published up to November 2014. A secondary reference review of all extracted articles and the National Toxicology Program Workshop on the association of POPs with diabetes was also conducted. A total of 19 articles met the inclusion criteria and were evaluated in this review.

RESULTS

To date, the evidence relating POPs and non-persistent pesticides with diabetes in Asian populations is equivocal. Positive associations were reported between serum concentrations of polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and several organochlorine pesticides (DDT, DDE, oxychlordane, trans-nonachlor, hexachlorobenzene, hexachlorocyclohexane) with diabetes. PCDD/Fs were also associated with blood glucose and insulin resistance, but not beta-cell function. There were substantial limitations of the literature including: most studies were cross-sectional, few studies addressed selection bias and confounding, and most effect estimates had exceptionally wide confidence intervals. Few studies evaluated the effects of organophosphates.

CONCLUSIONS

Well-conducted research is urgently needed on these pervasive exposures to inform policies to mitigate the diabetes epidemic in Asia.

Internal exposure to organochlorine pollutants and cadmium and self-reported health status: a prospective study

In this paper, based on the Flemish biomonitoring programs, we describe the associations between internal exposure to organochlorine pollutants and to cadmium (measured in 2004-2005 for adults aged 50-65 years) and self-reported health status obtained through a questionnaire in November 2011. Dioxin-like activity in serum showed a significant positive association with risk of cancer for women. After adjustment for confounders and covariates, the odds ratio for an exposure equal to the 90th percentile was 2.4 times higher than for an exposure equal to the 10th percentile. For both men and women dioxin-like activity and serum hexachlorobenzene (HCB) showed a significant positive association with risk of diabetes and of hypertension. Detailed analysis suggested that an increase in BMI might be part of the mechanism through which HCB contributes to diabetes and hypertension. Serum dichlorodiphenyldichloroethylene (p,p'-DDE) concentration showed a significant positive association with diabetes and hypertension in men, but not in women. Serum polychlorinated biphenyl (PCB) 118 showed a significant positive association with diabetes in both men and women, and after adjustment for correlated exposures, also with hypertension in men. Urinary cadmium concentrations showed a significant positive association with hypertension. Urinary cadmium concentrations were (in 2004-2005) significantly higher in persons who felt in less than good health (in 2011) than in persons who felt in very good health. After adjustment for correlated exposures (to HCB, p,p'-DDE and PCB118) marker PCBs showed a significant negative association with diabetes and hypertension. Serum p,p'-DDE showed in men a significant negative association with risk of diseases based on atheromata. Our findings suggest that exposure to pollutants can lead to an important increase in the risk of diseases such as cancer, diabetes and hypertension. Some pollutants may possibly also decrease the risk of some health problems, although this requires confirmation by other approaches.

Polychlorinated biphenyl exposure and glucose metabolism in 9-year-old Danish children

CONTEXT

Human exposure to polychlorinated biphenyls (PCBs) has been associated to type 2 diabetes in adults.

OBJECTIVE

We aimed to determine whether concurrent plasma PCB concentration was associated with markers of glucose metabolism in healthy children.

SETTING AND DESIGN

Cross-sectional study of 771 healthy Danish third grade school children ages 8-10 years in the municipality of Odense were recruited in 1997 through a two-stage cluster sampling from 25 schools stratified according to location and socioeconomic character; 509 (9.7 ± 0.8 y, 53% girls) had adequate amounts available for PCB analyses.

OUTCOME MEASURES

Fasting serum glucose and insulin were measured and a homeostasis assessment model of insulin resistance (HOMA-IR) and β-cell function (HOMA-B) calculated. Plasma PCB congeners and other persistent compounds were measured and ΣPCB calculated.

RESULTS

PCBs were present in plasma at low concentrations, median, 0.19 μg/g lipid (interquartile range, 0.12-0.31). After adjustment for putative confounding factors, the second, third, fourth, and fifth quintiles of total PCB were significantly inversely associated with serum insulin (-14.6%, -21.7%, -18.9%, -23.1%, P trend < .01), compared with the first quintile, but not with serum glucose (P = .45). HOMA-IR and HOMA-B were affected in the same direction due to the declining insulin levels with increasing PCB exposure. Similar results were found for individual PCB congeners, for βHCB (hexachlorobenzen) and pp-DDE (dichlorodiphenyldichloroethylene).

CONCLUSIONS

A strong inverse association between serum insulin and PCB exposure was found while fasting glucose remained within the expected narrow range. Our findings suggest that PCB may not exert effect through decreased peripheral insulin sensitivity, as seen in obese and low-fit children, but rather through a toxicity to β-cells. It remains to be demonstrated whether lower HOMA-B is caused by destruction of β-cell-reducing peripheral insulin resistance and thereby increase fasting glucose as previously found.

Exposure to organochlorine pollutants and type 2 diabetes: a systematic review and meta-analysis

Objective

Though exposure to organochlorine pollutants (OCPs) is considered a risk factor for type 2 diabetes (T2DM), epidemiological evidence for the association remains controversial. A systematic review and meta-analysis was applied to quantitatively evaluate the association between exposure to OCPs and incidence of T2DM and pool the inconsistent evidence.

Design and Methods

Publications in English were searched in MEDLINE and WEB OF SCIENCE databases and related reference lists up to August 2013. Quantitative estimates and information regarding study characteristics were extracted from 23 original studies. Quality assessments of external validity, bias, exposure measurement and confounding were performed, and subgroup analyses were conducted to examine the heterogeneity sources.

Results

We retrieved 23 eligible articles to conduct this meta-analysis. OR (odds ratio) or RR (risk ratio) estimates in each subgroup were discussed, and the strong associations were observed in PCB-153 (OR, 1.52; 95% CI, 1.19–1.94), PCBs (OR, 2.14; 95% CI, 1.53–2.99), and p,p′-DDE (OR, 1.33; 95% CI, 1.15–1.54) based on a random-effects model.

Conclusions

This meta-analysis provides quantitative evidence supporting the conclusion that exposure to organochlorine pollutants is associated with an increased risk of incidence of T2DM.

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.

Dioxins, furans and dioxin-like PCBs in human blood: causes or consequences of diabetic nephropathy?

Nephropathy, or kidney disease, is a major, potential complication of diabetes. We assessed the association of 6 chlorinated dibenzo-p-dioxins, 9 chlorinated dibenzofurans and 8 polychlorinated biphenyls (PCBs) in blood with diabetic nephropathy in the 1999-2004 National Health and Nutrition Examination Survey (unweighted N=2588, population estimate=117,658,357). Diabetes was defined as diagnosed or undiagnosed (glycohemoglobin ≥ 6.5%) and nephropathy defined as urinary albumin to creatinine ratio >30 mg/g, representing microalbuminuria or macroalbuminuria. For the 8 chemicals analyzed separately, values above the 75th percentile were considered elevated, whereas for the other 15 compounds values above the maximum limit of detection were considered elevated. Seven of 8 dioxins and dioxin-like compounds, analyzed separately, were found to be associated with diabetic nephropathy. The chemicals associated with diabetic nephropathy were: 1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin; 1,2,3,4,6,7,8,9-Octachlorodibenzo-p-dioxin; 2,3,4,7,8-Pentachlorodibenzofuran; PCB 126; PCB 169; PCB 118; and PCB 156. Three of the 8 dioxins and dioxin-like compounds; 1,2,3,4,6,7,8,9-Octachlorodibenzo-p-dioxin; 2,3,4,7,8-Pentachlorodibenzofuran and PCB 118; expressed as log-transformed continuous variables; were associated with diabetes without nephropathy. When 4 or more of the 23 chemicals were elevated the odds ratios were 7.00 (95% CI=1.80-27.20) for diabetic nephropathy and 2.13 (95% CI=0.95-4.78) for diabetes without nephropathy. Log-transformed toxic equivalency (TEQ) was associated with both diabetic nephropathy, and diabetes without nephropathy, the odds ratios were 2.35 (95% CI=1.57-3.52) for diabetic nephropathy, and 1.44 (95% CI=1.11-1.87) for diabetes without nephropathy. As the kidneys function to remove waste products from the blood, diabetic nephropathy could be either the cause or the consequence (or both) of exposure to dioxins, furans and dioxin-like PCBs.

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.

Adverse effects in adulthood resulting from low-level dioxin exposure in juvenile zebrafish

There is strong evidence indicating that disease in adult humans stems from a combination of genetic and environmental factors. A problem in identifying environmental factors is that subacute exposures during early life are often unnoticed, or exposures are variable among a diverse population. This leads to a confusing pattern in adulthood. An additional problem in following exposure effects in humans is the length of time needed to study outcomes spanning a human generation. We have recently developed a zebrafish model for studying the effects of sublethal juvenile exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin). Although the initial exposure produces no effect at the time, we find skeletal and reproductive defects in adulthood and into subsequent generations. The short generation time of zebrafish along with the ability to maintain large cohorts of exposed individuals and their offspring allows us to overcome variation in exposure and genetic background. Here we describe progress in studying TCDD as an endocrine and developmental disruptor, and our results showing adult consequences of early exposure.

Environmental chemicals and type 2 diabetes: an updated systematic review of the epidemiologic evidence

The burden of diabetes is increasing globally. Identifying novel preventable risk factors is an urgent need. In 2011, the U.S. National Toxicological Program (NTP) conducted a workshop to evaluate the epidemiologic and experimental evidence on the relationship of environmental chemicals with obesity, diabetes, and metabolic syndrome. Although the evidence was insufficient to establish causality, the NTP workshop review identified an overall positive association between some environmental chemicals and diabetes. In the present systematic review, our objective was to summarize the epidemiological research published since the NTP workshop. We identified a total of 29 articles (7 on arsenic, 3 on cadmium, 2 on mercury, 11 on persistent organic pollutants, 3 on phthalates, and 4 on bisphenol A), including 7 prospective studies. Considering consistency, temporality, strength, dose-response relationship, and biological plausibility (confounding), we concluded that the evidence is suggestive but not sufficient for a relationship between arsenic and persistent organic pollutants and is insufficient for mercury, phthalates, and bisphenol A. For cadmium, the epidemiologic evidence does not seem to suggest an association with diabetes. Important research questions include the need for additional prospective studies and the evaluation of the dose-response relationship, the role of joint exposures, and effect modification with other comorbidities and genetic variants.

Simultaneous determination of polybrominated diphenyl ethers and polychlorinated biphenyls by gas chromatography-tandem mass spectrometry in human serum and plasma

Sensitive and reliable methods for simultaneous determination of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in limited volumes of human serum or plasma need to be further documented especially when they accumulate at low levels that are still capable of disrupting endocrine and immune functions, and affecting neurodevelopment and reproduction. The objective of this study was to develop and validate a sensitive and quantitative method that simultaneously quantifies PBDEs and PCBs in 0.5 ml of human serum or plasma. We optimized a solid-phase extraction (SPE) method and used silica particle purification for the extraction of PBDEs and PCBs. Two multiple reactions monitoring (MRM) transitions were optimized for each congener. The sum of the transitions was used for quantification, and their abundance ratios were used for identification. The combined method optimization techniques resulted in limits of detection from 3 to 145 pg/ml for 10 PBDEs and 1-12 pg/ml for 15 PCBs. Method was solidly validated by analyzing serum fortified with a certified PBDE and PCB standard mixture from the National Institute of Standards and Technology (NIST). The accuracy was 88-118% and day-to-day precision was within 19%. The method was successfully applied to quantify native concentrations of PBDE and PCB in commercially available human serum. The sensitivity and selectivity of the GC/EI-MS/MS analysis enables it to be the method of choice for investigations of exposures to PBDE and PCB congeners, especially when sample volume is limited.

Reduction in adiposity, β-cell function, insulin sensitivity, and cardiovascular risk factors: a prospective study among Japanese with obesity

Background

A reduction in adiposity may be associated with an improvement in insulin sensitivity and β-cell function as well as cardiovascular disease (CVD) risk factors; however, few studies have investigated these associations in a longitudinal setting.

Methods

To investigate these associations over a 1-year period, we conducted an observational analysis of 196 Japanese subjects with obesity in the Saku Control Obesity Program. We investigated the relations between changes in adiposity (body mass index [BMI], waist circumference, subcutaneous fat area [SFAT], and visceral fat area [VFAT]) and changes in HbA1c, fasting plasma glucose (FPG), insulin sensitivity index (ISI), the homeostasis model assessment β cell function (HOMA-β), lipids, and blood pressure.

Results

All adiposity changes were positively associated with HbA1c and FPG changes. Reductions in BMI and VFAT were associated with HOMA-β reduction. Reductions in all adiposity measures were associated with an improvement in the ISI. Changes in most adiposity measures were positively associated with changes in blood pressure and lipid levels, except for LDL.

Conclusion

The present findings provide additional supportive evidence indicating that a reduction in adiposity may lead to an improvement in insulin sensitivity and the reduction of CVD risk factors in obese individuals.

Causal effects of synthetic chemicals on mitochondrial deficits and diabetes pandemic

It is generally accepted that mitochondrial deficits cause many common age-associated diseases including type 2 diabetes. However, it has not been understood what causes mitochondrial damages and how to interrupt the development of the diseases in patients. Recent epidemiologic studies demonstrated a positive correlation between serum concentrations of environmental pollutants and insulin resistance/diabetes. Emerging data strongly suggest that some synthetic pollutants disturb the signaling pathway critical for energy homeostasis and insulin action. The synthetic chemicals are possibly involved in pathogenesis of insulin resistance and diabetes as mitochondria-disturbing agents. In this review, we present a molecular scheme to address the contribution of environmental synthetic chemicals to this metabolic catastrophe. Efforts to identify synthetic chemicals with mitochondria-damaging activities may open a new era to develop effective therapeutic interventions against the worldwide-spreading metabolic disorder.

Dietary glycemic index and glycemic load in relation to HbA1c in Japanese obese adults: a cross-sectional analysis of the Saku Control Obesity Program

BACKGROUND

Dietary glycemic index or load is thought to play an important role in glucose metabolism. However, few studies have investigated the relation between glycemic index (GI) or load (GL) and glycemia in Asian populations. In this cross-sectional analysis of a randomized controlled trial, the Saku Control Obesity Program, we examined the relation between the baseline GI or GL and glycemia (HbA1c and fasting plasma glucose [FPG] levels), insulin resistance (HOMA-IR), β-cell function (HOMA-β), and other metabolic risk factors (lipid levels, diastolic and systolic blood pressure, and adiposity measures).

METHODS

The participants were 227 obese Japanese women and men. We used multiple linear regression models and logistic regression models to adjust for potential confounding factors such as age, sex, visceral fat area, total energy intake, and physical activity levels.

RESULTS

After adjustments for potential confounding factors, GI was not associated with HbA1c, but GL was positively associated with HbA1c. For increasing quartiles of GI, the adjusted mean HbA1c were 6.3%, 6.7%, 6.4%, and 6.4% (P for trend = 0.991). For increasing quartiles of GL, the adjusted mean HbA1c were 6.2%, 6.2%, 6.6%, and 6.5% (P for trend = 0.044). In addition, among participants with HbA1c ≥ 7.0%, 20 out of 28 (71%) had a high GL (≥ median); the adjusted odds ratio for HbA1c ≥ 7.0% among participants with higher GL was 3.1 (95% confidence interval [CI] = 1.2 to 8.1) compared to the participants with a lower GL (

CONCLUSIONS

Our findings suggest that participants with poor glycemic control tend to have a higher GL in an obese Japanese population.

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Affiliation(s)

Maki Goto Department of Diabetes Research, Diabetes Research Center, National Center for Global Health and Medicine, Tokyo, Japan.
Akemi Morita
Atsushi Goto
Satoshi Sasaki
Naomi Aiba
Takuro Shimbo
Yasuo Terauchi
Motohiko Miyachi
Mitsuhiko Noda
Shaw Watanabe

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Re-analysis of Ranch Hand study supports reverse causation hypothesis between dioxin and diabetes

A dose-response relationship between serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) and adult diabetes risk has been reported among U.S. Vietnam veterans in the Ranch Hand (RH) cohort. We examine the hypothesis that diabetes progression leads to higher serum dioxin (reverse causation) rather than higher serum dioxin leading to diabetes (causation) across the longitudinal medical monitoring data on these airmen. Lipid-adjusted serum dioxin levels and clinical parameters relating to diabetes progression were examined. Potential confounding due to age, race, diabetes family history, serum total lipid, and body mass index (BMI) was accounted for. The similar incidence of diabetes in RH and Comparison veterans, along with generally similar incidence trends with dioxin decile and lipid decile despite the large differential in serum dioxin, is evidence consistent with reverse causation. Of 135 RH diabetics with at least two dioxin measurements, 32.6% had a temporary serum dioxin increase more than a decade after Vietnam tour and another 22.2% had an interval of unusually slow half-life (>15.5 years); these diabetes-related changes shifted more diabetics into the higher dioxin deciles. Further, the increased diabetes odds ratio among the generally younger RH veterans in the highest dioxin decile is associated with a higher incidence of adult obesity in this RH subgroup, both at tour of duty and decades later. Change in serum dioxin levels is likely due to diabetes progression or poor control and is not independently related to serum dioxin concentrations. In summary, the data from the Ranch Hand studies does not indicate that dioxin increases adult diabetes risk.

Hormones and endocrine-disrupting chemicals: low-dose effects and nonmonotonic dose responses

For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of "the dose makes the poison," because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from the cell culture, animal, and epidemiology literature. We illustrate that nonmonotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs. Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.

Polychlorinated biphenyl (PCB) exposure and diabetes: results from the Anniston Community Health Survey

BACKGROUND

Polychlorinated biphenyls (PCBs) manufactured in Anniston, Alabama, from 1929 to 1971 caused significant environmental contamination. The Anniston population remains one of the most highly exposed in the world.

OBJECTIVES

Reports of increased diabetes in PCB-exposed populations led us to examine possible associations in Anniston residents.

METHODS

Volunteers (n = 774) from a cross-sectional study of randomly selected households and adults who completed the Anniston Community Health Survey also underwent measurements of height, weight, fasting glucose, lipid, and PCB congener levels and verification of medications. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the relationships between PCBs and diabetes, adjusting for diabetes risk factors. Participants with prediabetes were excluded from the logistic regression analyses.

RESULTS

Participants were 47% African American, 70% female, with a mean age of 54.8 years. The prevalence of diabetes was 27% in the study population, corresponding to an estimated prevalence of 16% for Anniston overall; the PCB body burden of 35 major congeners ranged from 0.11 to 170.42 ppb, wet weight. The adjusted OR comparing the prevalence of diabetes in the fifth versus first quintile of serum PCB was 2.78 (95% CI: 1.00, 7.73), with similar associations estimated for second through fourth quintiles. In participants < 55 years of age, the adjusted OR for diabetes for the highest versus lowest quintile was 4.78 (95% CI: 1.11, 20.6), whereas in those ≥ 55 years of age, we observed no significant associations with PCBs. Elevated diabetes prevalence was observed with a 1 SD increase in log PCB levels in women (OR = 1.52; 95% CI: 1.01, 2.28); a decreased prevalence was observed in men (OR = 0.68; 95% CI: 0.33, 1.41).

CONCLUSIONS

We observed significant associations between elevated PCB levels and diabetes mostly due to associations in women and in individuals < 55 years of age.