Low-Dose Persistent Organic Pollutants Impair Insulin Secretory Function of Pancreatic β-Cells: Human and In Vitro Evidence

CYP1A1/1A2 enzymes mediate glucose homeostasis and insulin secretion in mice in a sex-specific manner

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that controls the expression of several downstream targets including xenobiotic metabolism enzymes, cytochrome P450 1A1 and 1A2 (Cyp1a1/1a2). Besides xenobiotic metabolism, AhR also mediates responses to other stressors including high-fat diets (HFDs). Although global deletion or downregulation of AhR protects against metabolic dysfunction in HFD-fed mice, the role of Cyp1a1/1a2 in glucose homeostasis remains unclear. We demonstrated that Cyp1a1 expression is induced in mouse pancreatic islets not only by xenobiotic exposure but also by HFD feeding. Since CYP1A1/1A2 enzymes can produce reactive oxygen intermediates, we hypothesized that chronic CYP1A1/1A2 activation may contribute to HFD-induced metabolic dysfunction in mice, and thus, deleting these enzymes may be protective. We fed 29- to 31-wk-old male and female global Cyp1a1/1a2 knockout (CypKO) and wild-type (CypWT) mice a 45% HFD or standard chow for 14 wk. CypKO females were partially protected from HFD-induced glucose intolerance, and chow-fed CypKO females had lower plasma insulin and suppressed insulin secretion in isolated islets compared with CypWT females. Meanwhile, CypKO males exhibited HFD-induced hyperinsulinemia later than CypWT males. HFD feeding elevated Cyp1a1 and other stress genes in CypWT male islets but not in CypKO islets, indicating that CYP1A1 mediates islet stress responses. Liver pathology, adiposity, and adipose inflammation were primarily affected by diet, not genotype, in both sexes. Our study highlights a novel sex-dependent role for Cyp1a1/1a2 in shaping the systemic metabolic response to HFD feeding, suggesting that CYP1A1/1A2 enzymes are involved in glucose homeostasis, insulin secretion, and islet stress responses.NEW & NOTEWORTHY Cytochrome P450 (CYP)1A1/1A2 enzymes have sex-specific roles in glucose homeostasis in mice. In females, global Cyp1a1/1a2 deletion partially protects from glucose intolerance in high-fat diet (HFD)-fed mice and lowers plasma insulin in chow-fed mice. In males, Cyp1a1/1a2 deletion delays HFD-induced hyperinsulinemia in vivo and inhibits HFD-induced islet stress responses. Genotype-driven differences were only seen in islets, suggesting a novel role for islet CYP1A1/1A2 enzymes in responding to metabolic stress.

Pentachlorophenol increases diabetes risk by damaging β-cell secretion and disrupting gut microbial-related amino acids and fatty acids biosynthesis

Pentachlorophenol (PCP), a ubiquitous environmental pollutant, has been reported as a possible contributor to diabetes. However, evidence for general population is scarce while related mechanisms are largely unknown. Using a representative population-based case-control study in Beijing (n = 1796), we found a positive association between PCP exposure and diabetes risk with the odds ratio reaching 1.68 (95 % confidence interval: 1.30 to 2.18). A further rat experiment revealed that low-dose PCP mimicking real-world human exposure can significantly impair glycemic homeostasis by inducing pancreatic β-cell dysfunction, with non-linear dose-response relationships. Subsequent multi-omics analysis suggested that low-dose PCP led to notable gut microbiota dysbiosis (especially the species from genus Prevotella, such as intermedia, dentalis, ruminicola, denticola, melaninogenica, and oris), decreased serum amino acids (L-phenylalanine, L-tyrosine, and L-tryptophan) and increased serum fatty acids (oleic and palmitic acid) in rats, while strong correlations were observed among alterations of gut microbes, serum metabolites and glycemic-related biomarkers (e.g., fasting blood glucose and insulin). Collectively, these results imply PCP may increase diabetes risk by disrupting gut microbial-related amino acids and fatty acids biosynthesis. This will help guide future in-depth studies on the roles of PCP in the development of human diabetes.

Dioxin-Induced PAI-1 Expression: A Novel Pathway to Pancreatic β-Cell Failure in Type 2 Diabetes

Exposure to environment-polluting chemicals (EPCs), which are ligands of the aryl hydrocarbon receptor (AhR), is associated with the development of type 2 diabetes (T2D). This study explores the mechanisms by which AhR ligands contribute to β-cell failure in T2D. Incubation of RINm5F rat pancreatic β-cells with low-dose 2,3,7,8-tetrachlorodibenzodioxin (TCDD), the most potent AhR ligand, inhibited glucose-stimulated insulin secretion (GSIS). A single injection of TCDD in wild type mice reduced the size of Langerhans islets, but not in AhR liver knock-out mice (AhR-LKO). RNA-seq database analysis identified Serpine1, encoding for plasminogen activator inhibitor type-1 (PAI-1) as a TCDD-mediated secretory protein that is synthesized in an AhR-dependent manner in the liver. Elevated PAI-1 levels were shown to induce Caspase-3/7-dependent apoptosis in RINm5F cells, suggesting a novel pathway through which EPCs exacerbate T2D. These findings support the hypothesis that chronic exposure to AhR ligands may directly inhibit GSIS in pancreatic β-cells and indirectly induce β-cell apoptosis through increased PAI-1. This study provides new insights into the EPC-PAI-1 axis as a missing link between pancreatic β-cell failure and the progression of T2D and offers a potential target for therapeutic intervention.

Genetic predisposition to impaired beta-cell function modifies the association between serum pyrethroid levels and the risk of type 2 diabetes: A gene-environment interaction study

Previous studies suggested that pyrethroid exposure was associated with elevated type 2 diabetes (T2D) risk, while it remains uncertain whether genetic predisposition modifies this association. A nested case-control study within the prospective Dongfeng-Tongji cohort comprised 1832 T2D cases, age- (±5 years) and sex-matched controls with qualified genotyping data. Serum pyrethroids were measured by gas chromatography-tandem mass spectrometry. Overall diabetes-related genetic risk score (GRS) or pathway-specific GRS, including unweighted GRSs (uGRS) and weighted GRSs (wGRS), was developed by genetic variants identified in Asian populations. Higher overall diabetes-related GRS and GRS specific to the pathway of impaired beta cell function (Beta-cell GRS) were associated with a higher incident T2D risk. Beta-cell uGRS significantly modified the association of serum permethrin (Pinteraction=0.04) and deltamethrin (Pinteraction=0.01) with T2D. Specifically, for each doubling increase in serum deltamethrin, the odds ratios (ORs) (95 % confidence intervals [CIs]) for T2D were 1.23 (0.98-1.56) and 0.91 (0.77-1.07) in the highest and lowest Beta-cell uGRS group, as well as 1.23 (1.02-1.47) and 0.95 (0.78-1.15) for Beta-cell wGRS group, respectively. When considering jointly, those with the highest deltamethrin levels and highest Beta-cell GRS had a substantially higher T2D risk, compared with the reference group (OR for uGRS: 3.79 [95 % CI: 2.03-7.07], Pinteraction=0.03 and 3.23 [95 % CI: 1.78-5.87], Pinteraction=0.05 for wGRS). Our findings suggested that genetic susceptibility to impaired beta-cell function should be considered for T2D prevention targeting pyrethroid exposure, particularly deltamethrin.

Persistent organic pollutants disrupt the oxidant/antioxidant balance of INS-1E pancreatic β-cells causing their physiological dysfunctions

BACKGROUND

Persistent organic pollutants (POPs) have emerged as potent diabetogenic agents, but their mechanisms of action remain poorly identified.

OBJECTIVES

In this study, we aim to determine the mechanisms regulating the damaging effects of POPs in pancreatic β-cells, which have a central role in the development of diabetes.

METHODS

We treated INS-1E pancreatic β-cells with PCB-153, p,p'-DDE, PCB-126, or TCDD at doses ranging from 1 × 10-15to 5 × 10-6M. We measured insulin content and secretion, cell viability and assessed the mRNA expression of the xenobiotic nuclear receptors Nr1i2 and Nr1i3, and the aryl hydrocarbon receptor (Ahr). In addition, we evaluated the antioxidant defense and production of reactive oxygen species (ROS). Finally, we studied the ability of the antioxidant N-acetyl-L-cysteine (NAC) to counteract the effects of POPs in INS-1E cells.

RESULTS

When exposed to environmental POP levels, INS-1E cells had impaired production and secretion of insulin. These defects were observed for all tested POPs and were paralleled by reduced Ins1 and Ins2 mRNA expression. While POP treatment for 3 days did not affect INS-1E cell viability, longer treatment progressively killed the cells. Furthermore, we found that the xenobiotic detoxification machinery is poorly expressed in the INS-1E cells, as characterized by the absence of Nr1i2 and Nr1i3 and their respective downstream targets Cyp3a1/Cyp3a2 and Cyp2b1/Cyp2b3, and the weak functionality of the Ahr/Cyp1a1 signaling. Interestingly, POPs dysregulated key antioxidant enzymes such as glutathione peroxidases, peroxiredoxins, thioredoxins, and catalases. In parallel, the production of intracellular ROS, including superoxide anion (O2•-) and hydrogen peroxide (H2O2), was increased by POP exposure. Improving the oxidant scavenging capacity of INS-1E cells by NAC treatment restored the production and secretion of insulin.

CONCLUSION

By promoting oxidative stress and impairing the ability of INS-1E cells to produce and secrete insulin, this study reveals how POPs can mechanistically act as diabetogenic agents, and provides new scientific evidence supporting the concept that POPs are fueling the diabetes epidemics.

Associations of insulin sensitivity and immune inflammatory responses with child blood lead (Pb) and PM2.5 exposure at an e-waste recycling area during the COVID-19 lockdown

Fine particular matter (PM2.5) and lead (Pb) exposure can induce insulin resistance, elevating the likelihood of diabetes onset. Nonetheless, the underlying mechanism remains ambiguous. Consequently, we assessed the association of PM2.5 and Pb exposure with insulin resistance and inflammation biomarkers in children. A total of 235 children aged 3-7 years in a kindergarten in e-waste recycling areas were enrolled before and during the Corona Virus Disease 2019 (COVID-19) lockdown. Daily PM2.5 data was collected and used to calculate the individual PM2.5 daily exposure dose (DED-PM2.5). Concentrations of whole blood Pb, fasting blood glucose, serum insulin, and high mobility group box 1 (HMGB1) in serum were measured. Compared with that before COVID-19, the COVID-19 lockdown group had lower DED-PM2.5 and blood Pb, higher serum HMGB1, and lower blood glucose and homeostasis model assessment of insulin resistance (HOMA-IR) index. Decreased DED-PM2.5 and blood Pb levels were linked to decreased levels of fasting blood glucose and increased serum HMGB1 in all children. Increased serum HMGB1 levels were linked to reduced levels of blood glucose and HOMA-IR. Due to the implementation of COVID-19 prevention and control measures, e-waste dismantling activities and exposure levels of PM2.5 and Pb declined, which probably reduced the association of PM2.5 and Pb on insulin sensitivity and diabetes risk, but a high level of risk of chronic low-grade inflammation remained. Our findings add new evidence for the associations among PM2.5 and Pb exposure, systemic inflammation and insulin resistance, which could be a possible explanation for diabetes related to environmental exposure.

The Role of Endocrine Disruption Chemical-Regulated Aryl Hydrocarbon Receptor Activity in the Pathogenesis of Pancreatic Diseases and Cancer

The aryl hydrocarbon receptor (AHR) serves as a ligand-activated transcription factor crucial for regulating fundamental cellular and molecular processes, such as xenobiotic metabolism, immune responses, and cancer development. Notably, a spectrum of endocrine-disrupting chemicals (EDCs) act as agonists or antagonists of AHR, leading to the dysregulation of pivotal cellular and molecular processes and endocrine system disruption. Accumulating evidence suggests a correlation between EDC exposure and the onset of diverse pancreatic diseases, including diabetes, pancreatitis, and pancreatic cancer. Despite this association, the mechanistic role of AHR as a linchpin molecule in EDC exposure-related pathogenesis of pancreatic diseases and cancer remains unexplored. This review comprehensively examines the involvement of AHR in EDC exposure-mediated regulation of pancreatic pathogenesis, emphasizing AHR as a potential therapeutic target for the pathogenesis of pancreatic diseases and cancer.

The aryl hydrocarbon receptor in β-cells mediates the effects of TCDD on glucose homeostasis in mice

OBJECTIVE

Chronic exposure to persistent organic pollutants (POPs) is associated with increased incidence of type 2 diabetes, hyperglycemia, and poor insulin secretion in humans. Dioxins and dioxin-like compounds are a broad class of POPs that exert cellular toxicity through activation of the aryl hydrocarbon receptor (AhR). We previously showed that a single high-dose injection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, aka dioxin; 20 μg/kg) in vivo reduced fasted and glucose-stimulated plasma insulin levels for up to 6 weeks in male and female mice. TCDD-exposed male mice were also modestly hypoglycemic and had increased insulin sensitivity, whereas TCDD-exposed females were transiently glucose intolerant. Whether these effects are driven by AhR activation in β-cells requires investigation.

METHODS

We exposed female and male β-cell specific Ahr knockout (βAhrKO) mice and littermate Ins1-Cre genotype controls (βAhrWT) to a single high dose of 20 μg/kg TCDD and tracked the mice for 6 weeks.

RESULTS

Under baseline conditions, deleting AhR from β-cells caused hypoglycemia in female mice, increased insulin secretion ex vivo in female mouse islets, and promoted modest weight gain in male mice. Importantly, high-dose TCDD exposure impaired glucose homeostasis and β-cell function in βAhrWT mice, but these phenotypes were largely abolished in TCDD-exposed βAhrKO mice.

CONCLUSION

Our study demonstrates that AhR signaling in β-cells is important for regulating baseline β-cell function in female mice and energy homeostasis in male mice. We also show that β-cell AhR signaling largely mediates the effects of TCDD on glucose homeostasis in both sexes, suggesting that the effects of TCDD on β-cell function and health are driving metabolic phenotypes in peripheral tissues.

Sex-specific, non-linear and congener-specific association between mixed exposure to polychlorinated biphenyls (PCBs) and diabetes in U.S. adults

BACKGROUND

Whether and to what extent the impact of exposure to various polychlorinated biphenyls (PCBs) congeners on diabetes, as well as the important contributors, have remained unclear.

OBJECTIVE

We aimed to investigate the association patterns between PCBs mixture and diabetes, identify the critical congeners, and explore the potential modifiers.

METHODS

The present study included 5900 U.S. adults from the National Health and Nutrition Examination Survey (NHANES) conducted between 2007 and 2016. Weighted logistic regression, restricted cubic spline regression, weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR) were applied to estimate the linear and non-linear associations of single and mixed PCB exposure with diabetes. Subgroup analyses were also conducted to explore potential sex differences.

RESULTS

In the weighted logistic regression model, total PCBs were positively associated with diabetes (OR = 1.33, P < 0.025), and significant non-linear associations were observed using RCS analyses. The non-linear positive association between PCBs mixed exposure and diabetes was likewise found in the WQS and BKMR results. PCB180, PCB194, PCB196, and PCB167 were with the highest weights in the WQS, and PCB209 and PCB66 were with the highest posterior inclusion probabilities in the BKMR. Additionally, exposure to total PCBs and most of individual PCB congeners were significantly associated with elevated risk of in females (OR = 1.74; P for trend < 0.001), while fewer significant associations were observed in males.

CONCLUSION

The present study highlighted the importance of the long-term surveillance of PCBs and the need to enhance protective measures against them. Notably, these associations were non-linear, congener-specific, and significantly stronger in females than males, especially at relatively high levels of PCBs exposure. Further prospective and mechanistic studies were warranted to ascertain the causal effects between PCBs mixture and diabetes.

Circulating organochlorine pesticide levels, genetic predisposition and the risk of incident type 2 diabetes

Persistent organochlorine pesticide (OCP) has been associated with type 2 diabetes (T2D), and genetic polymorphism might modify such an association. However, prospective evidence remains scarce. We conducted a nested case-control study comprising 1006 incident diabetic cases and 1006 matched non-diabetic controls [sex and age (±5 years)] from 2008 to 2013 (mean follow-up period: ∼4.6 years) based on the Dongfeng-Tongji cohort in Shiyan City of China, determined baseline levels of nineteen OCPs, and examined the associations of circulating OCPs, both individually and collectively, with incident T2D risk. We also constructed overall genetic risk score (GRS) based on 161 T2D-associated variants and five pathway-specific cluster GRSs based on established variants derived from the Asian population. Compared with the first quartile of serum β-BHC levels, the multivariable-adjusted ORs (95% CIs) of incident T2D risk in the second, third, and fourth quartiles were 0.98 (0.70-1.39), 1.43 (0.99-2.07), and 1.75 (1.14-2.68), respectively (FDR-adjusted Ptrend = 0.03). A positive association was observed between serum OCP mixture and incident T2D risk and can be largely attributed to β-BHC. Furthermore, serum β-BHC and p,p'-DDE showed significant interactions with the GRS for lipodystrophy, a T2D-related pathway representing fat redistribution to viscera, on T2D risk (Pinteraction < 0.05). In conclusion, higher circulating OCP levels were independently associated with an increased risk of T2D, with β-BHC possibly being the major contributor. Genetic predisposition to T2D-related morbidity, such as visceral adiposity, should be considered when assessing the risk of T2D conferred by OCPs.

Targets for pollutants in rat and human pancreatic beta-cells: The effect of prolonged exposure to sub-lethal concentrations of hexachlorocyclohexane isomers on the expression of function- and survival-related proteins

Decades after most countries banned hexachlorocyclohexane, HCH isomers still pollute the environment. Many studies described HCH as a pro-diabetic factor; nevertheless, the effect of HCH isomers on pancreatic beta-cells remains unexplored. This study investigated the effects of a one-month exposure to α-HCH, β-HCH, and γ-HCH on protein expression in human (NES2Y) and rat (INS1E) pancreatic beta-cell lines. α-HCH and γ-HCH increased proinsulin and insulin levels in INS1E cells, while β-HCH showed the opposite trend. α-HCH altered the expression of PKA, ATF3, and PLIN2. β-HCH affected the expression of GLUT1, GLUT2, PKA, ATF3, p-eIF2α, ATP-CL, and PLIN2. γ-HCH altered the expression of PKA, ATF3, PLIN2, PLIN5, and IDH1. From the tested proteins, PKA, ATF3, and PLIN-2 were the most sensitive to HCH exposure and have the potential to be used as biomarkers.

The mechanism underlying pentabromoethylbenzene-induced adipogenesis and the obesogenic outcome in both cell and mouse model

Convergent evidence links traditional brominated flame retardants (BFRs) exposure to weight gain, while the obesogenic potency of new BFRs (NBFRs) remain largely unknown. Aiding by luciferase-reporter gene assay, the present study revealed only pentabromoethylbenzene (PBEB), an alternative for penta-BDEs, binds with retinoid X receptor α (RXRα) but not peroxisomeproliferator receptor γ (PPARγ) among the seven testing NBFRs. An apparent induction of adipogenesis in 3T3-L1 cells was observed at nanomolar of PBEB, much lower than penta-BFRs. Mechanistic research uncovered PBEB initiated the adipogenesis by demethylated CpG sites in the PPARγ promoter region. Specifically, activation RXRα by PBEB strengthened the activity of RXRα/PPARγ heterodimer, tightened the interaction between the heterodimer and PPAR response elements, and further enhanced adipogenesis. RNA sequencing combined with k-means clustering analysis exposed adenosine 5'-monophosphate (AMP)-activated protein kinase and phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) signaling as two predominant pathways that enriched in PBEB-induced lipogenesis. The obesogenic outcome was further corroborated in offspring mice when the maternal mice exposed to environmental relevant doses of PBEB. We found the male offspring exhibited adipocyte hypertrophy and increased weight gain in the epididymal white adipose tissue (eWAT). Consistent with in vitro findings, the reduction in protein phosphorylation of both AMPK and PI3K/AKT were observed within eWAT. Thus, we posited PBEB disrupts the pathways controlling adipogenesis and adipose tissue maintenance, supporting its potential as an environmental obesogen.

Association between tea consumption and glucose metabolism and insulin secretion in the Shanghai High-risk Diabetic Screen (SHiDS) study

INTRODUCTION

The relationship between tea consumption and glucose metabolism remains controversial. This study investigated the associations of tea consumption with impaired glucose regulation, insulin secretion and sensitivity in Shanghai High-risk Diabetic Screen project.

RESEARCH DESIGN AND METHODS

A total of 2337 Chinese subjects were enrolled in the study from 2014 to 2019. Each participant conducted a 75 g oral glucose tolerance test (OGTT) with five-point glucose and insulin level examined. They also completed a nurse-administered standard questionnaire including tea, coffee, and alcohol consumption, smoking habit, physical activity, education, sleep quality, etc. RESULTS: The result showed that tea consumption was positively associated with plasma glucose levels during OGTT after adjusting for confounder (Ps <0.05) and was associated with worsening glucose tolerance (OR 1.21, 95% CI 1.01-1.44; p=0.034). Strong tea consumption or long-term tea intake (>10 years) had an increased risk of glucose intolerance (all p<0.05). These associations did not vary in participants drinking green tea. In addition, insulin secretion indexes were decreased 7.0%-13.0% in tea consumption group. Logistic regression analysis showed that tea consumption was independently associated with lower insulin secretion (homeostasis model assessment of β-cell function (HOMA-β) (OR 0.81, 95% CI 0.68-0.97; p=0.021); Stumvoll first-phase index (OR 0.81, 95% CI 0.68-0.97; p=0.020)) in a fully adjusted model. Green tea consumption showed a negative association with insulin secretion (HOMA-β (OR 0.77, 95% CI 0.62-0.96; p=0.019)).

CONCLUSIONS

Tea intake is associated with an increased risk of glucose intolerance in a large high-risk diabetic Chinese population. Habitual tea consumption subjects might have lower pancreatic β-cell function.

Critical Overview on Endocrine Disruptors in Diabetes Mellitus

Diabetes mellitus is a major public health problem in all countries due to its high human and economic burden. Major metabolic alterations are associated with the chronic hyperglycemia that characterizes diabetes and causes devastating complications, including retinopathy, kidney failure, coronary disease and increased cardiovascular mortality. The most common form is type 2 diabetes (T2D) accounting for 90 to 95% of the cases. These chronic metabolic disorders are heterogeneous to which genetic factors contribute, but so do prenatal and postnatal life environmental factors including a sedentary lifestyle, overweight, and obesity. However, these classical risk factors alone cannot explain the rapid evolution of the prevalence of T2D and the high prevalence of type 1 diabetes in particular areas. Among environmental factors, we are in fact exposed to a growing amount of chemical molecules produced by our industries or by our way of life. In this narrative review, we aim to give a critical overview of the role of these pollutants that can interfere with our endocrine system, the so-called endocrine-disrupting chemicals (EDCs), in the pathophysiology of diabetes and metabolic disorders.

Insight into the physiological and pathological roles of the aryl hydrocarbon receptor pathway in glucose homeostasis, insulin resistance, and diabetes development

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcriptional factor that mediates the toxicities of several environmental pollutants. Decades of research have been carried out to understand the role of AhR as a novel mechanism for disease development. Its involvement in the pathogenesis of cancer, cardiovascular diseases, rheumatoid arthritis, and systemic lupus erythematosus have long been known. One of the current hot research topics is investigating the role of AhR activation by environmental pollutants on glucose homeostasis and insulin secretion, and hence the pathogenesis of diabetes mellitus. To date, epidemiological studies have suggested that persistent exposure to environmental contaminants such as dioxins, with subsequent AhR activation increases the risk of specific comorbidities such as obesity and diabetes. The importance of AhR signaling in various molecular pathways highlights that the role of this receptor is far beyond just xenobiotic metabolism. The present review aims at providing significant insight into the physiological and pathological role of AhR and its regulated enzymes, such as cytochrome P450 1A1 (CYP1A1) and CYP1B1 in both types of diabetes. It also provides a comprehensive summary of the current findings of recent research studies investigating the role of the AhR/CYP1A1 pathway in insulin secretion and glucose hemostasis in the pancreas, liver, and adipose tissues. This review further highlights the molecular mechanisms involved, such as gluconeogenesis, hypoxia-inducible factor (HIF), oxidative stress, and inflammation.

NMR-based metabolomic analysis of human plasma to examine the effect of exposure to persistent organic pollutants

Persistent organic pollutants (POPs) are lipophilic environmental toxins, and the level of chemicals accumulated in the body through the food chain has been linked to the incidence of diseases such as type 2 diabetes, cardiovascular disease, and cancer. We analyzed the concentration of POPs and circulating metabolites and investigated the associations between the concentration of plasma metabolites and the levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) to determine the effect of the accumulation of POPs in human samples. Metabolic profiling of plasma from 276 Korean participants was performed using ¹H nuclear magnetic resonance (NMR) and statistical analyses. The concentrations of PCBs and OCPs in each sample were measured. Correlation analysis and a covariate-adjusted general linear model (GLM) were used to investigate the association of the concentration of POPs with circulating metabolites in human blood samples. We found that four categories of Σ6PCBs and Σ5OCPs based on rank were significantly correlated with 4 and 5 metabolites, respectively, after adjusting for confounding factors, including age, sex, body mass index (BMI), smoking status, alcohol intake, physical activity, triglycerides, and total cholesterol. According to the GLM analyses, 3 metabolites, namely, creatinine, acetate, and formate, among the 4 correlated metabolites were associated with four categories of rank-based Σ6PCBs. On the other hand, the quartiles of the rank-based Σ5OCPs were not associated with any circulating metabolites among the 5 correlated metabolites. Our findings indicate that the metabolites related to short-chain fatty acids and creatine can be useful risk indicators for estimating the effect of PCB exposure.

Associations of polychlorinated biphenyls exposure with plasma glucose and diabetes in general Chinese population: The mediating effect of lipid peroxidation

Polychlorinated biphenyls (PCBs) exposure has been related to the abnormal glucose metabolism and the risk of diabetes. However, the joint effects of various PCBs are uncertain and the potential mechanisms remain unclear. Our objectives were to evaluate the associations of serum PCBs with fasting plasma glucose (FPG) and the risk of diabetes among a general Chinese population, and to estimate the mediating effects of oxidative stress in the above associations. Serum levels of seven indicator-PCBs (PCB-28, 52, 101, 118, 138, 153, and 180) and FPG values were determined among 4498 subjects from the Wuhan-Zhuhai cohort. Oxidative DNA damage biomarker (urinary 8-hydroxy-2'-deoxyguanosine, 8-OHdG) and lipid peroxidation biomarker (urinary 8-isoprostane, 8-iso-PGF_2α) were also measured. Positive relationships of serum PCBs with FPG values as well as the risk of diabetes were observed. With each 1% increment in the natural log-transformed values of wet weight serum PCBs, FPG levels increased a 0.125% for PCB-52, 0.168% for PCB-118, 0.221% for PCB-138, 0.273% for PCB-153, and 0.379% for ΣPCB (the sum of seven PCBs). The adjusted odds ratios of diabetes associated with wet weight PCBs were 1.186 for PCB-52, 1.373 for PCB-118, 1.635 for PCB-153, and 1.456 for ΣPCB. The seven serum PCBs showed positive overall effect on the risk of diabetes. Elevated PCB-28, PCB-52, PCB-118, PCB-138, PCB-153, and ΣPCB were associated with the increased urinary 8-iso-PGF_2α, which was positively related with FPG values. Furthermore, urinary 8-iso-PGF_2α partially mediated the positive associations between PCBs and FPG values, with the mediated proportions ranged from 3.20 to 12.93%. In conclusion, our results suggested that serum PCBs were positively related with increased oxidative stress, FPG values, and the risk of diabetes among a general Chinese population. Serum PCBs mixture had positive overall effect on the risk of diabetes. Lipid peroxidation partly mediated the FPG elevation induced by PCB exposure.

Persistent organic pollutants in foods, their interplay with gut microbiota and resultant toxicity

Persistent Organic Pollutants (POPs) have become immensely prevalent in the environment as a result of their unique chemical properties (persistent, semi-volatile and bioaccumulative nature). Their occurrence in the soil, water and subsequently in food has become a matter of concern. With food being one of the major sources of exposure, the detrimental impact of these chemicals on the gut microbiome is inevitable. The gut microbiome is considered as an important integrant for human health. It participates in various physiological, biochemical and immunological activities; thus, affects the metabolism and physiology of the host. A myriad of studies have corroborated an association between POP-induced gut microbial dysbiosis and prevalence of disorders. For instance, ingestion of polychlorinated biphenyls, polybrominated diphenyl ethers or organochlorine pesticides influenced bile acid metabolism via alteration of bile salt hydrolase activity of Lactobacillus, Clostridium or Bacteroides genus. At the same time, some chemicals such as DDE have the potential to elevate Proteobacteria and Firmicutes/Bacteriodetes ratio influencing their metabolic activity leading to enhanced short-chain fatty acid synthesis, ensuing obesity or a pre-diabetic state. This review highlights the impact of POPs exposure on the gut microbiota composition and metabolic activity, along with an account of its corresponding consequences on the host physiology. The critical role of gut microbiota in impeding the POPs excretion out of the body resulting in their prolonged exposure and consequently, enhanced degree of toxicity is also emphasized.

Associations between persistent organic pollutants and type 1 diabetes in youth

BACKGROUND

Diabetes affects millions of people worldwide with a continued increase in incidence occurring within the pediatric population. The potential contribution of persistent organic pollutants (POPs) to diabetes in youth remains poorly known, especially regarding type 1 diabetes (T1D), generally the most prevalent form of diabetes in youth.

OBJECTIVES

We investigated the associations between POPs and T1D in youth and studied the impacts of POPs on pancreatic β-cell function and viability in vitro.

METHODS

We used data and plasma samples from the SEARCH for Diabetes in Youth Case Control Study (SEARCH-CC). Participants were categorized as Controls, T1D with normal insulin sensitivity (T1D/IS), and T1D with insulin resistance (T1D/IR). We assessed plasma concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides and estimated the odds of T1D through multivariable logistic regression. In addition, we performed in vitro experiments with the INS-1E pancreatic β-cells. Cells were treated with PCB-153 or p,p'-DDE at environmentally relevant doses. We measured insulin production and secretion and assessed the mRNA expression of key regulators involved in insulin synthesis (Ins1, Ins2, Pdx1, Mafa, Pcsk1/3, and Pcsk2), glucose sensing (Slc2a2 and Gck), and insulin secretion (Abcc8, Kcnj11, Cacna1d, Cacna1b, Stx1a, Snap25, and Sytl4). Finally, we assessed the effects of PCB-153 and p,p'-DDE on β-cell viability.

RESULTS

Among 442 youths, 112 were controls, 182 were classified with T1D/IS and 148 with T1D/IR. The odds ratios (OR) of T1D/IS versus controls were statistically significant for p,p'-DDE (OR 2.0, 95% confidence interval (CI) 1.0, 3.8 and 2.4, 95% CI 1.2, 5.0 for 2nd and 3rd tertiles, respectively), trans-nonachlor (OR 2.5, 95% CI 1.3, 5.0 and OR 2.3, 95% CI 1.1, 5.1 for 2nd and 3rd tertiles, respectively), and PCB-153 (OR 2.3, 95% CI 1.1, 4.6 for 3rd tertile). However, these associations were not observed in participants with T1D/IR. At an experimental level, treatment with p,p'-DDE or PCB-153, at concentrations ranging from 1 × 10-15 M to 5 × 10-6 M, impaired the ability of pancreatic β-cells to produce and secrete insulin in response to glucose. These failures were paralleled by impaired Ins1 and Ins2 mRNA expression. In addition, among different targeted genes, PCB-153 significantly reduced Slc2a2 and Gck mRNA expression whereas p,p'-DDE mainly affected Abcc8 and Kcnj11. While treatment with PCB-153 or p,p'-DDE for 2 days did not affect β-cell viability, longer treatment progressively killed the β-cells.

CONCLUSION

These results support a potential role of POPs in T1D etiology and demonstrate a high sensitivity of pancreatic β-cells to POPs.

Persistent organic pollutants and β-cell toxicity: a comprehensive review

Persistent organic pollutants (POPs) are a diverse family of contaminants that show widespread global dispersion and bioaccumulation. Humans are continuously exposed to POPs through diet, air particles, and household and commercial products; POPs are consistently detected in human tissues, including the pancreas. Epidemiological studies show a modest but consistent correlation between exposure to POPs and increased diabetes risk. The goal of this review is to provide an overview of epidemiological evidence and an in-depth evaluation of the in vivo and in vitro evidence that POPs cause β-cell toxicity. We review evidence for six classes of POPs: dioxins, polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), flame retardants, and per- and polyfluoroalkyl substances (PFAS). The available data provide convincing evidence implicating POPs as a contributing factor driving impaired glucose homeostasis, β-cell dysfunction, and altered metabolic and oxidative stress pathways in islets. These findings support epidemiological data showing that POPs increase diabetes risk and emphasize the need to consider the endocrine pancreas in toxicity assessments. Our review also highlights significant gaps in the literature assessing islet-specific endpoints after both in vivo and in vitro POP exposure. In addition, most rodent studies do not consider the impact of biological sex or secondary metabolic stressors in mediating the effects of POPs on glucose homeostasis and β-cell function. We discuss key gaps and limitations that should be assessed in future studies.

In Vitro Assays to Identify Metabolism-Disrupting Chemicals with Diabetogenic Activity in a Human Pancreatic β-Cell Model

There is a need to develop identification tests for Metabolism Disrupting Chemicals (MDCs) with diabetogenic activity. Here we used the human EndoC-βH1 β-cell line, the rat β-cell line INS-1E and dispersed mouse islet cells to assess the effects of endocrine disruptors on cell viability and glucose-stimulated insulin secretion (GSIS). We tested six chemicals at concentrations within human exposure (from 0.1 pM to 1 µM). Bisphenol-A (BPA) and tributyltin (TBT) were used as controls while four other chemicals, namely perfluorooctanoic acid (PFOA), triphenylphosphate (TPP), triclosan (TCS) and dichlorodiphenyldichloroethylene (DDE), were used as “unknowns”. Regarding cell viability, BPA and TBT increased cell death as previously observed. Their mode of action involved the activation of estrogen receptors and PPARγ, respectively. ROS production was a consistent key event in BPA-and TBT-treated cells. None of the other MDCs tested modified viability or ROS production. Concerning GSIS, TBT increased insulin secretion while BPA produced no effects. PFOA decreased GSIS, suggesting that this chemical could be a “new” diabetogenic agent. Our results indicate that the EndoC-βH1 cell line is a suitable human β-cell model for testing diabetogenic MDCs. Optimization of the test methods proposed here could be incorporated into a set of protocols for the identification of MDCs.

Effects of Arachidonic Acid and Its Metabolites on Functional Beta-Cell Mass

Arachidonic acid (AA) is a polyunsaturated 20-carbon fatty acid present in phospholipids in the plasma membrane. The three primary pathways by which AA is metabolized are mediated by cyclooxygenase (COX) enzymes, lipoxygenase (LOX) enzymes, and cytochrome P450 (CYP) enzymes. These three pathways produce eicosanoids, lipid signaling molecules that play roles in biological processes such as inflammation, pain, and immune function. Eicosanoids have been demonstrated to play a role in inflammatory, renal, and cardiovascular diseases as well type 1 and type 2 diabetes. Alterations in AA release or AA concentrations have been shown to affect insulin secretion from the pancreatic beta cell, leading to interest in the role of AA and its metabolites in the regulation of beta-cell function and maintenance of beta-cell mass. In this review, we discuss the metabolism of AA by COX, LOX, and CYP, the roles of these enzymes and their metabolites in beta-cell mass and function, and the possibility of targeting these pathways as novel therapies for treating diabetes.

An overview of organic contaminants in indoor dust, their health impact, geographical distribution and recent extraction/analysis methods

People spend a substantial proportion of their time indoors; therefore, exposure to contaminants in indoor dust is persistent and profuse. According to the findings of recent studies, contaminants such as flame retardants (FRs), organochlorines (OCs), and phthalate esters (PAEs) are more prevalent in indoor dust. The discrepancy in the geographical distribution of these chemicals indicates country-specific applications. However, many studies have revealed that chlorophosphates, polychlorinated biphenyls (PCBs) and di-2-ethylhexyl phthalate are frequently detected in indoor dust throughout the world. Although some chemicals (e.g., OCs) were banned/severely restricted decades ago, they have still been detected in indoor dust. These organic contaminants have shown clear evidence of carcinogenic, neurotoxic, immunogenic, and estrogenic activities. Recent extraction methods have shown their advantages, such as high recoveries, less solvent consumption, less extraction time and simplicity of use. The latest separation techniques such as two-dimensional gas/liquid chromatography, latest ionization techniques (e.g., matrix-assisted laser desorption/ionization (MALDI)), and modern techniques of mass spectrometry (e.g., tandem mass spectrometry (MS/MS), time-of-flight (TOF) and high-resolution mass spectrometry (HRMS)) improve the detection limits, accuracy, reproducibility and simultaneous detection of organic contaminants. For future perspectives, it is suggested that the importance of the study of dust morphology for comprehensive risk analysis, introducing standard reference materials to strengthen the analytical methods, adopt common guidelines for comparison of research findings and the importance of dust analysis in the developing world since lack of records on the production and usage of hazardous substances. Such measures will help to evaluate the effectiveness of prevailing legislations and to set up new regulations.

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.

Mixed Exposure of Persistent Organic Pollutants Alters Oxidative Stress Markers and Mitochondrial Function in the Tail of Zebrafish Depending on Sex

Persistent organic pollutants (POPs) are lipid-soluble toxins that are not easily degraded; therefore, they accumulate in the environment and the human body. Several studies have indicated a correlation between POPs and metabolic diseases; however, their effects on mitochondria as a central organelle in cellular metabolism and the usage of mitochondria as functional markers for metabolic disease are barely understood. In this study, a zebrafish model system was exposed to two subclasses of POPs, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), under two different conditions (solitary OCPs or OCPs with PCBs (Aroclor 1254)), and changes in the oxidative stress marker levels and mitochondrial enzyme activities in the electron transport chain of the tail were measured to observe the correlation between POPs and representative biomarkers for metabolic disease. The results indicated different responses upon exposure to OCPs and OCPs with Aroclor 1254, and accelerated toxicity was observed following exposure to mixed POPs (OCPs with Aroclor 1254). Males were more sensitive to changes in the levels of oxidative stress markers induced by POP exposure, whereas females were more susceptible to the toxic effects of POPs on the levels of mitochondrial activity markers. These results demonstrate that the study reflects real environmental conditions, with low-dose and multiple-toxin exposure for a long period, and that POPs alter major mitochondrial enzymes’ functions with an imbalance of redox homeostasis in a sex-dependent manner.

Exposure to a low concentration of mixed organochlorine pesticides impairs glucose metabolism and mitochondrial function in L6 myotubes and zebrafish

More realistic effects on glucose metabolic dysfunction can be evaluated by applying organochlorine (OCP) mixtures than individual OCPs. We formulated an equal ratio mixture of five OCPs (chlordane, heptachlor, p,p'-dichlorodiphenyltrichloroethane, β-hexachlorocyclohexane, and hexachlorobenzene) and treated L6 myotubes with this OCP mixture to investigate effects on glucose uptake and the underlying mechanism. Exposure to the OCP mixture reduced 2-NBDG staining, representing glucose uptake, and stimulated the excessive production of reactive oxygen species (ROS). Reduced 2-NBDG uptake and ROS overproduction were compensated by insulin treatment. The expression of proteins such as IRβ, PI3K, and AKT was downregulated, indicating that ROS overproduction contributed to the inhibition of insulin-dependent glucose uptake. Reduction in mitochondria quantity and decreased expression levels of PGC-1α, PDH, and GLUT4 proteins were observed, suggesting that mitochondrial dysfunction played a causative role in the disruption of glucose uptake. The inhibition of glucose uptake and ROS overproduction caused by the OCP mixture were also found in zebrafish as an in vivo model. We demonstrated that exposure to the OCP mixture, even at the lowest concentration, perturbed glucose uptake, which was associated with mitochondrial dysfunction, suggesting that an OCP mixture could be a potential environmental factor in type 2 diabetes-related effects on skeletal muscles.

Prolonged Low-Dose Dioxin Exposure Impairs Metabolic Adaptability to High-Fat Diet Feeding in Female but Not Male Mice

CONTEXT

Human studies consistently show an association between exposure to persistent organic pollutants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, aka "dioxin"), and increased diabetes risk. We previously showed that a single high-dose TCDD exposure (20 µg/kg) decreased plasma insulin levels in male and female mice in vivo, but effects on glucose homeostasis were sex-dependent.

OBJECTIVE

The current study assessed whether prolonged exposure to a physiologically relevant low-dose of TCDD impacts glucose homeostasis and/or the islet phenotype in a sex-dependent manner in chow-fed or high-fat diet (HFD)-fed mice.

METHODS

Male and female mice were exposed to 20 ng/kg/d TCDD 2×/week for 12 weeks and simultaneously fed standard chow or a 45% HFD. Glucose homeostasis was assessed by glucose and insulin tolerance tests, and glucose-induced plasma insulin levels were measured in vivo. Histological analysis was performed on pancreas from male and female mice, and islets were isolated from females for TempO-Seq transcriptomic analysis.

RESULTS

Low-dose TCDD exposure did not lead to adverse metabolic consequences in chow-fed male or female mice, or in HFD-fed males. However, TCDD accelerated the onset of HFD-induced hyperglycemia and impaired glucose-induced plasma insulin levels in females. TCDD caused a modest increase in islet area in males but reduced the percent beta cell area within islets in females. TempO-Seq analysis suggested abnormal changes to endocrine and metabolic pathways in female TCDDHFD islets.

CONCLUSION

Our data suggest that prolonged low-dose TCDD exposure has minimal effects on glucose homeostasis and islet morphology in chow-fed male and female mice but promotes maladaptive metabolic responses in HFD-fed females.

Association of persistent organic pollutants with sensorimotor neuropathy in participants with and without diabetes or prediabetes: Results from the population-based KORA FF4 study

BACKGROUND

Concentrations of persistent organic pollutants (POPs) have been associated with an increased type 2 diabetes (T2D) risk. It remains unclear whether POPs are also associated with the risk of diabetes complications including neuropathy and evidence on this topic is scarce. We aimed to investigate the hypothesis that low-dose background concentrations of POPs were positively associated with distal sensorimotor polyneuropathy (DSPN).

METHODS

This cross-sectional study was based on data from the second follow-up (FF4, 2013-2014, N = 2279) of the population-based KORA S4 study (Augsburg, Germany). The study sample consisted of 200 participants, including four groups of 50 persons each with known T2D, prediabetes, newly diagnosed diabetes, and normal glucose tolerance (NGT) based on an oral glucose tolerance test. We analyzed the association of six most abundant serum concentrations of POPs, including polychlorinated biphenyls (PCBs) as well as organochlorine (OC) pesticides, with DSPN by multivariable logistic regression adjusted for age, sex, glycaemic status, body mass index, physical activity, smoking and alcohol consumption. We assessed effect modification by age, sex, glycaemic status and obesity and conducted two-pollutant models to check the robustness of the estimates.

RESULTS

For all pollutants, the main models indicated no significant association of having DSPN but pointed to rather decreased odds for DSPN. Two-pollutant models supported these findings, though only the association between the combination of PCB-138 and beta-hexachlorocyclohexane (β-HCH) (OR: 0.59; 95% CI: 0.35-0.99) with DSPN became significant. No effect modification was found by age, sex, glycaemic status and obesity.

CONCLUSION

Low-dose concentrations of POPs were not associated with increased odds of having DSPN in T2D, prediabetes and NGT.

Inulin Fermentable Fiber Ameliorates Type I Diabetes via IL22 and Short-Chain Fatty Acids in Experimental Models

BACKGROUND & AIMS

Nourishment of gut microbiota via consumption of fermentable fiber promotes gut health and guards against metabolic syndrome. In contrast, how dietary fiber impacts type 1 diabetes is less clear.

METHODS

To examine impact of dietary fibers on development of type 1 diabetes in the streptozotocin (STZ)-induced and spontaneous non-obese diabetes (NOD) models, mice were fed grain-based chow (GBC) or compositionally defined diets enriched with a fermentable fiber (inulin) or an insoluble fiber (cellulose). Spontaneous (NOD mice) or STZ-induced (wild-type mice) diabetes was monitored.

RESULTS

Relative to GBC, low-fiber diets exacerbated STZ-induced diabetes, whereas diets enriched with inulin, but not cellulose, strongly protected against or treated it. Inulin's restoration of glycemic control prevented loss of adipose depots, while reducing food and water consumption. Inulin normalized pancreatic function and markedly enhanced insulin sensitivity. Such amelioration of diabetes was associated with alterations in gut microbiota composition and was eliminated by antibiotic administration. Pharmacologic blockade of fermentation reduced inulin's beneficial impact on glycemic control, indicating a role for short-chain fatty acids (SCFA). Furthermore, inulin's microbiota-dependent anti-diabetic effect associated with SCFA-independent restoration of interleukin 22, which was necessary and sufficient to ameliorate STZ-induced diabetes. Inulin-enriched diets significantly delayed diabetes in NOD mice.

CONCLUSIONS

Fermentable fiber confers microbiota-dependent increases in SCFA and interleukin 22 that, together, may have potential to prevent and/or treat type 1 diabetes.

Exposure to persistent organic pollutants and the risk of type 2 diabetes: a case-cohort study

AIMS

To explore exposure to 22 persistent organic pollutants (POPs) and incident type 2 diabetes in a population-based, prospective cohort.

METHODS

This case-cohort study on 753 participants without type 2 diabetes at baseline, was followed-up over nine years, as part of the French D.E.S.I.R. cohort. We measured 22 POPs in fasting serum at baseline. The associations between baseline POP concentrations, pre-adjusted for lipids, BMI, age and sex, with incident type 2 diabetes, were assessed using Prentice-weighted Cox regression models (time scale: age), adjusted for traditional confounding factors. POPs were also modelled summed in functional groups: polychlorinated biphenyls (∑PCB) and organochlorines (∑OC) and also individually, after log-transformation, in adjusted Cox models.

RESULTS

There were 200 incident diabetes cases over nine years. Pre-adjusted POP concentrations were not related to diabetes risk for any of the 22 POPs examined. The fully-adjusted hazard ratios (HRs) per interquartile range of the pre-adjusted POPs, ranged from 0.87 (95% CI: 0.64,1.19) to 1.22 (0.93,1.59,). For dichlorodiphenyldichloroethylene (p, p'-DDE) and dichlorodiphenyltrichloroethane (p, p'-DDT), the HRs were 1.09 (0.83,1.43) and 0.89 (0.70,1.13), respectively. The HRs for PeCB, HCB, β-HCH, γ-HCH, oxychlordane, trans-nonachlor were 0.98 (0.85,1.13), 1.06 (0.84,1.33), 1.22 (0.93,1.59), 1.13 (0.89,1.42), 1.00 (0.76,1.31), 0.86 (0.66,1.13), respectively. HRs for ∑PCB, ∑OC and for individual log-transformed POPs did not differ significantly from one.

CONCLUSION

We did not observe any relations between exposure to POPs and diabetes in this population-based cohort. These results do not support causal inferences reported in previous studies linking serum POP concentrations and diabetes risk.

Human Pluripotent Stem Cells: A Unique Tool for Toxicity Testing in Pancreatic Progenitor and Endocrine Cells

Diabetes prevalence is increasing worldwide, and epidemiological studies report an association between diabetes incidence and environmental pollutant exposure. There are >84,000 chemicals in commerce, many of which are released into the environment without a clear understanding of potential adverse health consequences. While in vivo rodent studies remain an important tool for testing chemical toxicity systemically, we urgently need high-throughput screening platforms in biologically relevant models to efficiently prioritize chemicals for in depth toxicity analysis. Given the increasing global burden of obesity and diabetes, identifying chemicals that disrupt metabolism should be a high priority. Pancreatic endocrine cells are key regulators of systemic metabolism, yet often overlooked as a target tissue in toxicology studies. Immortalized β-cell lines and primary human, porcine, and rodent islets are widely used for studying the endocrine pancreas in vitro, but each have important limitations in terms of scalability, lifespan, and/or biological relevance. Human pluripotent stem cell (hPSC) culture is a powerful tool for in vitro toxicity testing that addresses many of the limitations with other β-cell models. Current in vitro differentiation protocols can efficiently generate glucose-responsive insulin-secreting β-like cells that are not fully mature, but still valuable for high-throughput toxicity screening in vitro. Furthermore, hPSCs can be applied as a model of developing pancreatic endocrine cells to screen for chemicals that influence endocrine cell formation during critical windows of differentiation. Given their versatility, we recommend using hPSCs to identify potential β-cell toxins, which can then be prioritized as chemicals of concern for metabolic disruption.

The insulin signaling pathway in Drosophila melanogaster: A nexus revealing an "Achilles' heel" in DDT resistance

Insecticide resistance is an ongoing challenge in agriculture and disease vector control. Here, we demonstrate a novel strategy to attenuate resistance. We used genomics tools to target fundamental energy-associated pathways and identified a potential "Achilles' heel" for resistance, a resistance-associated protein that, upon inhibition, results in a substantial loss in the resistance phenotype. Specifically, we compared the gene expression profiles and structural variations of the insulin/insulin-like growth factor signaling (IIS) pathway genes in DDT-susceptible (91-C) and -resistant (91-R) Drosophila melanogaster (Drosophila) strains. A total of eight and seven IIS transcripts were up- and down-regulated, respectively, in 91-R compared to 91-C. A total of 114 nonsynonymous mutations were observed between 91-C and 91-R, of which 51.8% were fixed. Among the differentially expressed transcripts, phosphoenolpyruvate carboxykinase (PEPCK), down-regulated in 91-R, encoded the greatest number of amino acid changes, prompting us to perform PEPCK inhibitor-pesticide exposure bioassays. The inhibitor of PEPCK, hydrazine sulfate, resulted in a 161- to 218-fold decrease in the DDT resistance phenotype (91-R) and more than a 4- to 5-fold increase in susceptibility in 91-C. A second target protein, Glycogen synthase kinase 3β (GSK3β-PO), had one amino acid difference between 91-C and 91-R, and the corresponding transcript was also down-regulated in 91-R. A GSK3β-PO inhibitor, lithium chloride, likewise reduced the resistance but to a lesser extent than did hydrazine sulfate for PEPCK. We demonstrate the potential role of IIS genes in DDT resistance and the potential discovery of an "Achilles' heel" against pesticide resistance in this pathway.

Accumulation of distinct persistent organic pollutants is associated with adipose tissue inflammation

Hydrophobic environmental chemicals bio-accumulate in adipose tissue (AT) in animals and humans, but their impact on diseases related to adipose tissue dysfunction remains unclear. Moreover, visceral rather than subcutaneous (SC) fat deposition is more closely associated with cardio-metabolic diseases such as type 2 diabetes, fatty liver and cardiovascular diseases. We therefore tested the hypotheses that environmental chemicals bio-accumulate in a fat depot specific pattern and that these patterns are related AT inflammation and obesity comorbidities. First, we developed an extraction method for detecting and quantifying a set of 9 persistent organic pollutants (POPs) in human AT. The quantified chemicals exhibit K_OW coefficients from 4 to 7. Paired abdominal omental and SC AT samples were obtained from 54 individuals (30 women, 24 men) with a wide range of body mass index (BMI, 16-70 kg/m²) during laparoscopic abdominal surgeries. Among the POPs are classical halogenated substances like Dichlorodiphenyldichloroethylene (DDE) and polychlorinated biphenyls (PCBs), but also fragrance substances. We find that AT concentrations of these chemicals are neither significantly different between visceral and SC fat depots nor between women and men. However, AT bio-accumulation of distinct POPs significantly correlates with AT macrophage infiltration, adipocyte size and parameters of glucose metabolism. In both fat depots, the strongest correlations of POPs (Ethyl- tetradecanoate, 4,4'-Diisopropylbiphenyl, 2-Phenyltetralin, 2,2',4,4',5,5'-Hexachlorobiphenyl, Hexachlorobenzene) and AT macrophage infiltration were detected in lean individuals. In men with obesity, abundance of POPs correlated with the duration of obesity. Additional significant associations between AT POPs and parameters of glycemia, insulin sensitivity, and inflammation suggest that specific environmental chemicals may contribute to AT dysfunction, adipocyte hypertrophy, impaired glucose metabolism, systemic inflammation and variation in fat distribution, but not to obesity.

Biomarkers of metabolic disorders and neurobehavioral diseases in a PCB- exposed population: What we learned and the implications for future research

Polychlorinated biphenyls (PCBs) are one of the original twelve classes of toxic chemicals covered by the Stockholm Convention on Persistent Organic Pollutants (POP), an international environmental treaty signed in 2001. PCBs are present in the environment as mixtures of multiple isomers at different degree of chlorination. These compounds are manmade and possess useful industrial properties including extreme longevity under harsh conditions, heat absorbance, and the ability to form an oily liquid at room temperature that is useful for electrical utilities and in other industrial applications. They have been widely used for a wide range of industrial purposes over the decades. Despite a ban in production in 1979 in the US and many other countries, they remain persistent and ubiquitous in environment as contaminants due to their improper disposal. Humans, independent of where they live, are therefore exposed to PCBs, which are routinely found in random surveys of human and animal tissues. The prolonged exposures to PCBs have been associated with the development of different diseases and disorders, and they are classified as endocrine disruptors. Due to its ability to interact with thyroid hormone, metabolism and function, they are thought to be implicated in the global rise of obesity diabetes, and their potential toxicity for neurodevelopment and disorders, an example of gene by environmental interaction (GxE). The current review is primarily intended to summarize the evidence for the association of PCB exposures with increased risks for metabolic dysfunctions and neurobehavioral disorders. In particular, we present evidence of gene expression alterations in PCB-exposed populations to construct the underlying pathways that may lead to those diseases and disorders in course of life. We conclude the review with future perspectives on biomarker-based research to identify susceptible individuals and populations.

Markers of acute toxicity of DDT exposure in pancreatic beta-cells determined by a proteomic approach

Many compounds have the potential to harm pancreatic beta-cells; organochlorine pollutants belong to those compounds. In this work, we aimed to find markers of acute toxicity of p,p'-DDT exposure among proteins expressed in NES2Y human pancreatic beta-cells employing 2-D electrophoresis. We exposed NES2Y cells to a high concentration (150 μM, LC96 after 72 hours) of p,p'-DDT for 24 and 30 hours and determined proteins with changed expression using 2-D electrophoresis. We have found 22 proteins that changed their expression. They included proteins involved in ER stress (GRP78, and endoplasmin), mitochondrial proteins (GRP75, ECHM, IDH3A, NDUS1, and NDUS3), proteins involved in the maintenance of the cell morphology (EFHD2, TCPA, NDRG1, and ezrin), and some other proteins (HNRPF, HNRH1, K2C8, vimentin, PBDC1, EF2, PCNA, biliverdin reductase, G3BP1, FRIL, and HSP27). The proteins we have identified may serve as indicators of p,p'-DDT toxicity in beta-cells in future studies, including long-term exposure to environmentally relevant concentrations.

Can Habitual Exercise Help Reduce Serum Concentrations of Lipophilic Chemical Mixtures? Association between Physical Activity and Persistent Organic Pollutants

BACKGROUND

Low-dose persistent organic pollutants (POPs), especially organochlorine pesticides (OCPs), have emerged as a new risk factor of many chronic diseases. As serum concentrations of POPs in humans are mainly determined by both their release from adipose tissue to circulation and their elimination from circulation, management of these internal pathways may be important in controlling the serum concentrations of POPs. As habitual physical activity can increase the elimination of POPs from circulation, we evaluated whether chronic physical activity is related to low serum POP concentrations.

METHODS

A cross-sectional study of 1,850 healthy adults (age ≥20 years) without cardio-metabolic diseases who participated in the U.S. National Health and Nutrition Examination Survey 1999 to 2004 was conducted. Information on moderate or vigorous leisure-time physical activity was obtained based on questionnaires. Serum concentrations of OCPs and polychlorinated biphenyls were investigated as typical POPs.

RESULTS

Serum concentrations of OCPs among physically active subjects were significantly lower than those among physically inactive subjects (312.8 ng/g lipid vs. 538.0 ng/g lipid, P<0.001). This difference was maintained after adjustment for potential confounders. When analyses were restricted to physically active subjects, there were small decreases in the serum concentrations of OCPs with increasing duration of physical activity, showing a curvilinear relationship over the whole range of physical activity (Pquadratic <0.001). In analyses stratified by age, sex, body mass index, and smoking status, a strong inverse association was similarly observed among all subgroups.

CONCLUSION

Physical activity may assist in decreasing serum concentrations of lipophilic chemical mixtures such as OCPs.

Cardiometabolic-Based Chronic Disease, Adiposity and Dysglycemia Drivers: JACC State-of-the-Art Review

A new cardiometabolic-based chronic disease (CMBCD) model is presented that provides a basis for early and sustainable, evidence-based therapeutic targeting to promote cardiometabolic health and mitigate the development and ravages of cardiovascular disease. In the first part of this JACC State-of-the-Art Review, a framework is presented for CMBCD, focusing on 3 primary drivers (genetics, environment, and behavior) and 2 metabolic drivers (adiposity and dysglycemia) with applications to 3 cardiovascular endpoints (coronary heart disease, heart failure, and atrial fibrillation). Specific mechanistic pathways are presented configuring early primary drivers with subsequent adiposity, insulin resistance, β-cell dysfunction, and metabolic syndrome, leading to cardiovascular disease. The context for building this CMBCD model is to expose actionable targets for prevention to achieve optimal cardiovascular outcomes. The tactical implementation of this CMBCD model is the subject of second part of this JACC State-of-the-Art Review.

Cardiometabolic-Based Chronic Disease, Adiposity and Dysglycemia Drivers: JACC State-of-the-Art Review

A new cardiometabolic-based chronic disease (CMBCD) model is presented that provides a basis for early and sustainable, evidence-based therapeutic targeting to promote cardiometabolic health and mitigate the development and ravages of cardiovascular disease. In the first part of this JACC State-of-the-Art Review, a framework is presented for CMBCD, focusing on 3 primary drivers (genetics, environment, and behavior) and 2 metabolic drivers (adiposity and dysglycemia) with applications to 3 cardiovascular endpoints (coronary heart disease, heart failure, and atrial fibrillation). Specific mechanistic pathways are presented configuring early primary drivers with subsequent adiposity, insulin resistance, β-cell dysfunction, and metabolic syndrome, leading to cardiovascular disease. The context for building this CMBCD model is to expose actionable targets for prevention to achieve optimal cardiovascular outcomes. The tactical implementation of this CMBCD model is the subject of second part of this JACC State-of-the-Art Review.

Adipose Tissue Transcriptome Is Related to Pollutant Exposure in Polar Bear Mother-Cub Pairs from Svalbard, Norway

Being at the food chain apex, polar bears (Ursus maritimus) are highly contaminated with persistent organic pollutants (POPs). Females transfer POPs to their offspring through gestation and lactation; therefore, young cubs present higher POPs concentrations than their mothers. Recent studies suggest that POPs affect the lipid metabolism in female polar bears; however, the mechanisms and impact on their offspring remain unknown. Here, we hypothesized that exposure to POPs differentially alters genome-wide gene transcription in the adipose tissue from mother polar bears and their cubs, highlighting molecular differences in response between adults and young. Adipose tissue biopsies were collected from 13 adult female polar bears and their twin cubs in Svalbard, Norway, in April 2011, 2012, and 2013. Total RNA extracted from biopsies was subjected to next-generation RNA sequencing. Plasma concentrations of summed polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers in mothers ranged from 897 to 13620 ng/g wet weight and were associated with altered adipose tissue gene expression in both mothers and cubs. In mothers, 2502 and 2586 genes in total were positively and negatively, respectively, correlated to POP exposure, whereas in cubs, 2585 positively and 1690 negatively genes. Between mothers and cubs, 743 positively and negatively genes overlapped between mothers and cubs suggesting partially shared molecular responses to ΣPOPs. ΣPOP-associated genes were involved in numerous metabolic pathways in mothers and cubs, indicating that POP exposure alters the energy metabolism, which, in turn, may be linked to metabolic dysfunction.

A Human Relevant Defined Mixture of Persistent Organic Pollutants (POPs) Affects In Vitro Secretion of Glucagon-Like Peptide 1 (GLP-1), but Does Not Affect Translocation of Its Receptor

Environmental exposure to persistent organic pollutants (POPs) has been suggested as a contributing factor for the increased rate of type 2 diabetes and obesity. A complex mixture of 29 POPs (Total mixture), based on human blood concentrations, was used to expose a glucagon-like peptide 1 (GLP-1) secreting enteroendocrine cell line (pGIP/neo: STC-1) in vitro for 3 and 24 h. Significant increases of GLP-1 occurred when cells were exposed to the Total mixture at ×500 blood levels. Six sub-mixtures representing chlorinated (Cl), brominated (Br), and perfluorinated chemicals (PFAA), and their combinations (Cl + Br, Cl + PFAA, Br + PFAA) were also tested at ×500. Secretion levels seen for these remained lower than the Total mixture, and the Br mixture had no effect. After 24 h, increased secretion was seen with all mixtures at ×1 blood levels. Cytotoxicity was present for ×100 and ×500 blood levels. When tested in a GLP-1 receptor translocation assay (U2OS-GLP1R-EGFP), neither agonistic nor antagonist effects on receptor internalization were seen for any of the mixtures. We conclude individual classes of POPs, alone or in combination, can affect GLP-1 secretion and may contribute as a molecular mechanism linking environmental toxicants and diabetes.

Pesticides-induced energy metabolic disorders

Metabolic disorders have become a heavy burden on society. Recently, through excessive use, pesticides have been found to be present in environmental matrixes and sometimes even accumulate in humans or other mammals through the food chain, which then causes health concerns. Evidence has indicated that pesticides have the potential to induce energy metabolic disorders by disturbing the physical process of energy absorption in the intestine and energy storage in the liver, adipose tissue and skeletal muscle in humans or other mammals. In addition, the homeostasis of energy regulation by the pancreas and immune cells is also affected by pesticides. These pesticide-induced disruptions ultimately cause abnormal levels of blood glucose and lipids, which in turn induce the development of related metabolic diseases, including overweight, underweight, insulin resistance and even diabetes. In this review, the results of previous studies focused on the induction of metabolic disorders by pesticides are summarized. We hope that this work will facilitate the discovery of a potential strategy for the treatment of diseases caused by pesticides.

Severe dioxin-like compound (DLC) contamination in e-waste recycling areas: An under-recognized threat to local health

Electrical and electronic waste (e-waste) burning and recycling activities have become one of the main emission sources of dioxin-like compounds (DLCs). Workers involved in e-waste recycling operations and residents living near e-waste recycling sites (EWRS) are exposed to high levels of DLCs. Epidemiological and experimental in vivo studies have reported a range of interconnected responses in multiple systems with DLC exposure. However, due to the compositional complexity of DLCs and difficulties in assessing mixture effects of the complex mixture of e-waste-related contaminants, there are few studies concerning human health outcomes related to DLC exposure at informal EWRS. In this paper, we have reviewed the environmental levels and body burdens of DLCs at EWRS and compared them with the levels reported to be associated with observable adverse effects to assess the health risks of DLC exposure at EWRS. In general, DLC concentrations at EWRS of many countries have been decreasing in recent years due to stricter regulations on e-waste recycling activities, but the contamination status is still severe. Comparison with available data from industrial sites and well-known highly DLC contaminated areas shows that high levels of DLCs derived from crude e-waste recycling processes lead to elevated body burdens. The DLC levels in human blood and breast milk at EWRS are higher than those reported in some epidemiological studies that are related to various health impacts. The estimated total daily intakes of DLCs for people in EWRS far exceed the WHO recommended total daily intake limit. It can be inferred that people living in EWRS with high DLC contamination have higher health risks. Therefore, more well-designed epidemiological studies are urgently needed to focus on the health effects of DLC pollution in EWRS. Continuous monitoring of the temporal trends of DLC levels in EWRS after actions is of highest importance.

Association between exposure to persistent organic pollutants and mercury, and glucose metabolism in two Canadian Indigenous populations

BACKGROUND

The body burden of metals and persistent organic pollutants (POPs) is particularly high in populations that rely on fish and other marine species for sustenance. This exposure has been associated with an increased risk of type 2 diabetes, but results remain contrasted.

OBJECTIVE

We studied this association in two Indigenous populations of northern Québec (Canada) with markedly different prevalences of diabetes and levels of exposure to POPs and mercury.

METHODS

As part of health surveys conducted in 2004-2009, diabetes prevalence and glucose metabolism (glucose, insulin, HOMA-IR, HOMA-B) in non-diabetic fasting adults were assessed using similar protocols in two populations: Inuit from Nunavik (n = 877) and Cree from Eeyou Istchee territory (n = 780). Blood mercury, plasma polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides/metabolites and polybrominated diphenylethers (PBDEs) levels were measured in samples collected at the time of examination. Logistic and linear regressions and restricted cubic splines analyses were conducted adjusting for sex, age, waist circumference, smoking and omega-3 fatty acid content in plasma phospholipids.

RESULTS

Diabetes prevalence was higher in Cree (20%) than in Inuit (7%), whereas environmental exposure was 2 to 3-fold greater in Inuit than in Cree participants. In the range of exposure common to the two populations, we observed similar linear increases in the risk of diabetes with increasing contaminant exposure. Among Cree participants, fasting glucose was positively associated with plasma PBDE level, and HOMA-B negatively associated with concentrations of ∑PCBs, dichlorodiphenyldichloroethylene, PBDEs and ∑OC pesticides. Among Inuit participants, a trend towards reduced insulin secretion was observed in association with most contaminants, but the relation was nonlinear (greater reduction at intermediate levels of exposure). A significant increase in fasting glucose levels was observed at elevated blood mercury levels (>16 μg/L).

CONCLUSION

The observed association between POPs exposure and diabetes risk in the two populations studied should be confirmed using prospective design. Our results suggest the need for additional research on the physiopathological process through which POPs exposure may induce type 2 diabetes in these Indigenous populations.

Endocrine disrupting chemicals: exposure, effects on human health, mechanism of action, models for testing and strategies for prevention

Endocrine Disrupting Chemicals (EDCs) are a global problem for environmental and human health. They are defined as "an exogenous chemical, or mixture of chemicals, that can interfere with any aspect of hormone action". It is estimated that there are about 1000 chemicals with endocrine-acting properties. EDCs comprise pesticides, fungicides, industrial chemicals, plasticizers, nonylphenols, metals, pharmaceutical agents and phytoestrogens. Human exposure to EDCs mainly occurs by ingestion and to some extent by inhalation and dermal uptake. Most EDCs are lipophilic and bioaccumulate in the adipose tissue, thus they have a very long half-life in the body. It is difficult to assess the full impact of human exposure to EDCs because adverse effects develop latently and manifest at later ages, and in some people do not present. Timing of exposure is of importance. Developing fetus and neonates are the most vulnerable to endocrine disruption. EDCs may interfere with synthesis, action and metabolism of sex steroid hormones that in turn cause developmental and fertility problems, infertility and hormone-sensitive cancers in women and men. Some EDCs exert obesogenic effects that result in disturbance in energy homeostasis. Interference with hypothalamo-pituitary-thyroid and adrenal axes has also been reported. In this review, potential EDCs, their effects and mechanisms of action, epidemiological studies to analyze their effects on human health, bio-detection and chemical identification methods, difficulties in extrapolating experimental findings and studying endocrine disruptors in humans and recommendations for endocrinologists, individuals and policy makers will be discussed in view of the relevant literature.

Long-term metabolic consequences of acute dioxin exposure differ between male and female mice

Epidemiological studies have consistently shown an association between exposure to environmental pollutants and diabetes risk in humans. We have previously shown that direct exposure of mouse and human islets (endocrine pancreas) to the highly persistent pollutant TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) causes reduced insulin secretion ex vivo. Furthermore, a single high-dose of TCDD (200 µg/kg) suppressed both fasting and glucose-induced plasma insulin levels and promoted beta-cell apoptosis after 7 days in male mice. The current study investigated the longer-term effects of a single high-dose TCDD injection (20 µg/kg) on glucose metabolism and beta cell function in male and female C57Bl/6 mice. TCDD-exposed males displayed modest fasting hypoglycemia for ~4 weeks post-injection, reduced fasting insulin levels for up to 6 weeks, increased insulin sensitivity, decreased beta cell area, and increased delta cell area. TCDD-exposed females also had long-term suppressed basal plasma insulin levels, and abnormal insulin secretion for up to 6 weeks. Unlike males, TCDD did not impact insulin sensitivity or islet composition in females, but did cause transient glucose intolerance 4 weeks post-exposure. Our results show that a single exposure to dioxin can suppress basal insulin levels long-term in both sexes, but effects on glucose homeostasis are sex-dependent.

Functional cytochrome P450 1A enzymes are induced in mouse and human islets following pollutant exposure

AIMS/HYPOTHESIS

Exposure to environmental pollution has been consistently linked to diabetes incidence in humans, but the potential causative mechanisms remain unclear. Given the critical role of regulated insulin secretion in maintaining glucose homeostasis, environmental chemicals that reach the endocrine pancreas and cause beta cell injury are of particular concern. We propose that cytochrome P450 (CYP) enzymes, which are involved in metabolising xenobiotics, could serve as a useful biomarker for direct exposure of islets to pollutants. Moreover, functional CYP enzymes in islets could also impact beta cell physiology. The aim of this study was to determine whether CYP1A enzymes are activated in islets following direct or systemic exposure to environmental pollutants.

METHODS

Immortalised liver (HepG2) and rodent pancreatic endocrine cell lines (MIN6, βTC-6, INS1, α-TC1, α-TC3), as well as human islets, were treated in vitro with known CYP1A inducers 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3-methylcholanthrene (3-MC). In addition, mice were injected with either a single high dose of TCDD or multiple low doses of TCDD in vivo, and islets were isolated 1, 7 or 14 days later.

RESULTS

CYP1A enzymes were not activated in any of the immortalised beta or alpha cell lines tested. However, both 3-MC and TCDD potently induced CYP1A1 gene expression and modestly increased CYP1A1 enzyme activity in human islets after 48 h. The induction of CYP1A1 in human islets by TCDD was prevented by cotreatment with a cytokine mixture. After a systemic single high-dose TCDD injection, CYP1A1 enzyme activity was induced in mouse islets ~2-fold, ~40-fold and ~80-fold compared with controls after 1, 7 and 14 days, respectively, in vivo. Multiple low-dose TCDD exposure in vivo also caused significant upregulation of Cyp1a1 in mouse islets. Direct TCDD exposure to human and mouse islets in vitro resulted in suppressed glucose-induced insulin secretion. A single high-dose TCDD injection resulted in lower plasma insulin levels, as well as a pronounced increase in beta cell death.

CONCLUSIONS/INTERPRETATION

Transient exposure to TCDD results in long-term upregulation of CYP1A1 enzyme activity in islets. This provides evidence for direct exposure of islets to lipophilic pollutants in vivo and may have implications for islet physiology.

Exposure to Persistent Organic Pollutants (POPs) and Their Relationship to Hepatic Fat and Insulin Insensitivity among Asian Indian Immigrants in the United States

Persistent organic pollutants (POPs), such as dichlorodiphenyltrichloroethane (DDT) and other organochlorine compounds, are abundant in the environment and in foodstuffs from the Indian subcontinent. These environmental contaminants have been associated with a higher risk of diabetes in numerous studies. Asian Indians are well known to have a high risk of diabetes compared with other populations, and this risk is also found in migrant populations of Asian Indians in the United States, Europe, and elsewhere. We hypothesized that high plasma concentrations of POPs in Asian Indian migrants are linked to a variety of diabetes-related pathologies and explored the mechanism for the induction of these effects. We measured 30 environmental pollutants in plasma samples obtained from 147 participants in the Metabolic syndrome and Atherosclerosis in South Asians Living in America pilot study using a gas chromatography-tandem mass spectrometry analytical method that uses less than 0.5 mL of plasma. We found that plasma levels of o,p'-DDT and p,p'-DDT were independently associated with both body mass index (BMI) and waist circumference. Doubling the levels of the sums of these DDTs was associated with insulin insensitivity (-0.38 Matsuda index, p = 0.001), increased adiposity (1.26 kg/m2 BMI and 3.58 cm waist circumference increase, p < 0.0001), circulating insulin (12.9 mIU/L, p = 0.002), hepatic fat (-0.051 HU, p = 0.001), as well as increased odds of obesity (OR = 2.17, p < 0.001, BMI-based; OR = 2.37, p = 0.001, waist-based), prediabetes (OR = 1.55, p = 0.02), diabetes (OR = 1.72, p = 0.01), and fatty liver (OR = 1.66, p = 0.01) in multivariable models accounting for confounding by age, sex, years in the US, education, and fish protein. Furthermore, levels of DDTs were associated with increased hepatic fat and circulating insulin, independent of obesity and confounders. These findings suggest that exposure to DDTs may contribute to the risk of metabolic disease among Asian Indians by affecting hepatic fat levels independent of obesity.

Upregulation of vitamin D-binding protein is associated with changes in insulin production in pancreatic beta-cells exposed to p,p'-DDT and p,p'-DDE

Persistent organochlorine pollutants (POPs) gradually accumulate in the human organism due to their presence in the environment. Some studies have described a correlation between the level of POPs in the human body and the incidence of diabetes, but we know little about the direct effect of POPs on pancreatic beta-cells. We exposed pancreatic beta-cells INS1E to non-lethal concentrations of p,p′-DDT (1,1′-(2,2,2-Trichloroethane-1,1-diyl)bis(4-chlorobenzene)) and p,p′-DDE (1,1′-(2,2-dichloroethene-1,1-diyl)bis(4-chlorobenzene)) for 1 month, and assessed changes in protein expression and the intracellular insulin level. 2-D electrophoresis revealed 6 proteins with changed expression in cells exposed to p,p′-DDT or p,p′-DDE. One of the detected proteins – vitamin D-binding protein (VDBP) – was upregulated in both cells exposed to p,p′-DDT, and cells exposed to p,p′-DDE. Both exposures to pollutants reduced the intracellular level of insulin mRNA, proinsulin, and insulin monomer; p,p′-DDT also slightly reduced the level of hexameric insulin. Overexpression of VDBP caused by the stable transfection of beta-cells with the gene for VDBP decreased both the proinsulin and hexameric insulin level in beta-cells similarly to the reduction detected in cells exposed to p,p′-DDT. Our data suggest that in the cells exposed to p,p′-DDT and p,p′-DDE, the increased VDBP protein level decreased the proinsulin expression in an unknown mechanism.

Persistent organic pollutants and the incidence of type 2 diabetes in the CARLA and KORA cohort studies

BACKGROUND

Associations between several persistent organic pollutants (POPs) and type 2 diabetes have been found in humans, but the relationship has rarely been investigated in the general population. The current nested case-control study examined internal exposure to polychlorinated biphenyls (PCB) and pesticides and the incidence of type 2 diabetes among participants of two population-based German cohort studies.

METHODS

We retrospectively selected 132 incident cases of type 2 diabetes and 264 age- and sex-matched controls from the CARdiovascular Living and Aging in Halle (CARLA) study (2002-2006, East Germany) and the Cooperative Health Research in the Region of Augsburg (KORA) study (1999-2001, South Germany) based on diabetes status at follow-up examinations in 2007-2010 and 2006-08, respectively (60% male, mean age 63 and 54 years). We assessed the association between baseline POP concentrations and incident diabetes by conditional logistic regression adjusted for cohort, BMI, cholesterol, alcohol, smoking, physical activity, and parental diabetes. Additionally, we examined effect modification by sex, obesity, parental diabetes and cohort.

RESULTS

In both cohorts, diabetes cases showed a higher BMI, a higher frequency of parental diabetes, and higher levels of POPs. We observed an increased chance for incident diabetes for PCB-138 and PCB-153 with an odds ratio (OR) of 1.50 (95%CI: 1.07-2.11) and 1.53 (1.15-2.04) per interquartile range increase in the respective POP. In addition, explorative results suggested higher OR for women and non-obese participants.

CONCLUSIONS

Our results add to the evidence on diabetogenic effects of POPs in the general population, and warrant both policies to prevent human exposure to POPs and additional research on the adverse effects of more complex chemical mixtures.