Increased serum concentrations of persistent organic pollutants among prediabetic individuals: potential role of altered substrate oxidation patterns

Per- and polyfluoroalkyl substances, polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers and dysregulation of MicroRNA expression in humans and animals-A systematic review

BACKGROUND

Persistent organic pollutants (POPs) are chemicals characterized by their environmental persistence. Evidence suggests that exposure to POPs, which is ubiquitous, is associated with microRNA (miRNA) dysregulation. miRNA are key regulators in many physiological processes. It is thus of public health concern to understand the relationships between POPs and miRNA as related to health outcomes.

OBJECTIVES

This systematic review evaluated the relationship between widely recognized, intentionally manufactured, POPs, including per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (dichlorodiphenyltrichloroethane [DDT], dichlorodiphenyldichloroethylene [DDE], hexachlorobenzene [HCB]), with miRNA expression in both human and animal studies.

METHODS

We used PubMed and Embase to systematically search the literature up to September 29th, 2023. Search results for human and animal studies were included if they incorporated at least one POP of interest in relation to at least one miRNA. Data were synthesized to determine the direction and significance of associations between POPs and miRNA. We utilized ingenuity pathway analysis to review disease pathways for miRNA that were associated with POPs.

RESULTS

Our search identified 38 eligible studies: 9 in humans and 29 in model organisms. PFAS were associated with decreased expression of miR-19, miR-193b, and miR-92b, as well as increased expression of miR-128, miR-199a-3p, and miR-26b across species. PCBs were associated with increased expression of miR-15a, miR-1537, miR-21, miR-22-3p, miR-223, miR-30b, and miR-34a, as well as decreased expression of miR-130a and let-7b in both humans and animals. Pathway analysis for POP-associated miRNA identified pathways related to carcinogenesis.

DISCUSSION

This is the first systematic review of the association of POPs with miRNA in humans and model organisms. Large-scale prospective human studies are warranted to examine the role of miRNA as mediators between POPs and health outcomes.

The diabetogenic effects of pesticides: Evidence based on epidemiological and toxicological studies

While the use of pesticides has improved grain productivity and controlled vector-borne diseases, the widespread use of pesticides has resulted in ubiquitous environmental residues that pose health risks to humans. A number of studies have linked pesticide exposure to diabetes and glucose dyshomeostasis. This article reviews the occurrence of pesticides in the environment and human exposure, the associations between pesticide exposures and diabetes based on epidemiological investigations, as well as the diabetogenic effects of pesticides based on the data from in vivo and in vitro studies. The potential mechanisms by which pesticides disrupt glucose homeostasis include induction of lipotoxicity, oxidative stress, inflammation, acetylcholine accumulation, and gut microbiota dysbiosis. The gaps between laboratory toxicology research and epidemiological studies lead to an urgent research need on the diabetogenic effects of herbicides and current-use insecticides, low-dose pesticide exposure research, the diabetogenic effects of pesticides in children, and assessment of toxicity and risks of combined exposure to multiple pesticides with other chemicals.

Assessing the risk of diabetes in participants with DDT DDE exposure- A systematic review and meta-analysis

We have performed a systematic review and meta-analysis of the association between DDT/DDE and diabetes, searching PubMed, Embase, and Cochrane for relevant articles published up to August 30, 2021, and eventually including 43 publications. Our researchers evaluate included studies' quality and risk of bias via the recommended tool. This study uses meta-analyses of random effects of each exposure and outcome to estimate combined odds ratios (ORs) and 95% confidence intervals (CIs). Our research identified 43 cross-sectional, case-control, and cohort studies, including 40,141 individuals in America, Europe, Asia, and Africa. The summary ORs (95% CIs) of incident diabetes were 1.61 (1.10-2.39) for DDT, 1.67 (1.41-1.98) for DDE. The subgroup analysis indicated that the association is significantly higher in the region of Asia for both DDT (OR = 2.73) and DDE (OR = 2.62). Besides, we also tried various types of stratification to identify the more influential confounding factors, among which regional factors have a significant influence. Study evidence suggests that exposure to DDT and its breakdown product, DDE, might be associated with the risk of incident diabetes. Among Asian patients, DDT/DDE concentrations are more closely associated with diabetes. Further studies in specific regions will be considered in the future.

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.

Endocrine Disruptors and the Induction of Insulin Resistance

INTRODUCTION

The incidence of insulin resistance syndrome and type 2 diabetes mellitus has increased at an alarming rate worldwide and constitutes a serious challenge to public health care in the 21st century. Endocrine disrupting chemicals are defined as "substances or mixtures of substances that alter the endocrine system functions and, hence, adversely affect organisms, their progeny, or sub populations" and may be associated with this increase in prevalence.

OBJECTIVE

This study aimed to assess the role of endocrine disrupting chemicals in insulin resistance and the importance of approaching the subject during anamnesis.

METHODS

A full review of the literature regarding insulin resistance, type-2 diabetes and endocrine disruptors were conducted.

CONCLUSION

Large-scale production and distribution of endocrine disrupting chemicals coincide with the increase in the prevalence of insulin resistance globally. In recent years, studies have shown that endocrine disrupting chemicals are positively associated with insulin resistance syndrome, evidenced by worse prognoses among individuals with higher levels of exposure. Health professionals should recognize the forms of exposure, most susceptible people, and lifestyle habits that can worsen patients' prognoses.

Longitudinal association of biomarkers of pesticide exposure with cardiovascular disease risk factors in youth with diabetes

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of death among individuals with diabetes, but little is known about the role of exposures to environmental chemicals such as pesticides in the early development of CVD risk in this population.

OBJECTIVES

To describe changes over time in concentrations of pesticide biomarkers among youth with diabetes in the United States and to estimate the longitudinal association between these concentrations and established risk factors for CVD.

METHODS

Pesticide biomarkers were quantified in urine and serum samples from 87 youth with diabetes participating in the multi-center SEARCH cohort study. Samples were obtained around the time of diagnosis (baseline visit, between 2006 and 2010) and, on average, 5.4 years later (follow-up visit, between 2012 and 2015). We calculated geometric mean (95% CI) pesticide biomarker concentrations. Eight CVD risk factors were measured at these two time points: body mass index (BMI) z-score, HbA1c, insulin sensitivity, fasting C-peptide (FCP), LDL cholesterol, HDL cholesterol, total cholesterol, and triglycerides. Linear regression models were used to estimate the associations between each pesticide biomarker at baseline and each CVD risk factor at follow-up, adjusting for baseline health outcome, elapsed time between baseline and follow up, sex, age, race/ethnicity, and diabetes type.

RESULTS

Participants were, on average, 14.2 years old at their baseline visit, and most were diagnosed with type 1 diabetes (57.5%). 4-nitrophenol, 3-phenoxybenzoic acid, 2,4-dichlorophenoxyacetic acid (2,4-D), 3,5,6-trichloro-2-pyridinol, 2,2-bis(4-chlorophenyl)-1,1-dichloroethene, and hexachlorobenzene were detected in a majority of participants at both time points. Participants in the highest quartile of 2,4-D and 4-nitrophenol at baseline had HbA1c levels at follow-up that were 1.05 percentage points (95% CI: -0.40, 2.51) and 1.27 percentage points (0.22, 2.75) higher, respectively, than participants in the lowest quartile of these pesticide biomarkers at baseline. These participants also had lower log FCP levels (indicating reduced beta-cell function) compared to participants in the lowest quartile at baseline: beta (95% CI) for log FCP of -0.64 (-1.17, -0.11) for 2,4-D and -0.39 (-0.96, 0.18) for 4-nitrophenol. In other words, participants in the highest quartile of 2,4-D had a 47.3% lower FCP level compared to participants in the lowest quartile, and those in the highest quartile of 4-nitrophenol had a 32.3% lower FCP level than those in the lowest quartile. Participants with trans-nonachlor concentrations in the highest quartile at baseline had HbA1c levels that were 1.45 percentage points (-0.11, 3.01) higher and log FCP levels that were -0.28 (-0.84, 0.28) lower than participants in the lowest quartile at baseline, that is to say, participants in the highest quartile of trans-nonachlor had a 24.4% lower FCP level than those in the lowest quartile. While not all of these results were statistically significant, potentially due to the small same size, clinically, there appears to be quantitative differences. No associations were observed between any pesticide biomarker at baseline with BMI z-score or insulin sensitivity at follow-up.

CONCLUSIONS

Exposure to select pesticides may be associated with impaired beta-cell function and poorer glycemic control among youth with diabetes.

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.

Persistent Organic Pollutants in Food: Contamination Sources, Health Effects and Detection Methods

Persistent organic pollutants (POPs) present in foods have been a major concern for food safety due to their persistence and toxic effects. To ensure food safety and protect human health from POPs, it is critical to achieve a better understanding of POP pathways into food and develop strategies to reduce human exposure. POPs could present in food in the raw stages, transferred from the environment or artificially introduced during food preparation steps. Exposure to these pollutants may cause various health problems such as endocrine disruption, cardiovascular diseases, cancers, diabetes, birth defects, and dysfunctional immune and reproductive systems. This review describes potential sources of POP food contamination, analytical approaches to measure POP levels in food and efforts to control food contamination with POPs.

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.

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

Low-dose persistent organic pollutants (POPs), especially organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), have emerged as a new risk factor for type 2 diabetes. We evaluated whether chronic exposure to low-dose POPs affects insulin secretory function of β-cells in humans and in vitro cells. Serum concentrations of OCPs and PCBs were measured in 200 adults without diabetes. Mathematical model-based insulin secretion indices were estimated by using a 2-h seven-sample oral glucose tolerance test. Insulin secretion by INS-1E β-cells was measured after 48 h of treatment with three OCPs or one PCB mixture. Static second-phase insulin secretion significantly decreased with increasing serum concentrations of OCPs. Adjusted means were 63.2, 39.3, 44.1, 39.3, 39.7, and 22.3 across six categories of a summary measure of OCPs (P_trend = 0.02). Dynamic first-phase insulin secretion remarkably decreased with increasing concentrations of OCPs among only insulin-sensitive individuals (P_trend = 0.02); the insulin levels among individuals with high OCPs were ∼30% of those with low OCPs. Compared with OCPs, PCBs showed weaker associations. The decreased insulin secretion by INS-1E β-cells was observed for even 1 pmol/L OCP. The data from human and in vitro cell experiments suggest that chronic exposure to low-dose POPs, especially OCPs, can induce pancreatic β-cell dysfunction.

Potential contribution of insecticide exposure and development of obesity and type 2 diabetes

The introduction of insecticides has greatly improved agricultural productivity and human nutrition; however, the wide use of insecticides has also sparked growing concern over their health impacts. Increased rate of cancers, neurodegenerative disorders, reproductive dysfunction, birth defects, respiratory diseases, cardiovascular diseases and aging have been linked with insecticide exposure. Meanwhile, a growing body of evidence is suggesting that exposure to insecticides can also potentiate the risk of obesity and type 2 diabetes. This review summarizes the relationship between insecticide exposure and development of obesity and type 2 diabetes using epidemiological and rodent animal studies, including potential mechanisms. The evidence as a whole suggests that exposure to insecticides is linked to increased risk of obesity and type 2 diabetes.

Increased blood levels of persistent organic pollutants (POP) in obese individuals after weight loss-A review

Lipophilic persistent organic pollutants (POP) are stored in adipose tissue. Following rapid weight loss such as when induced by bariatric surgery, an increased release of potential harmful lipophilic compounds into the blood circulation may occur. Weight reduction is recommended for overweight and obese individuals in order to decrease risk of weight-related health problems. However, in cases of significant weight reduction POP become mobilized chemicals and consequently may adversely affect health, including endocrine disruption. The objective of the present investigation was to estimate quantitatively the level of mobilization of POP following weight loss over time. According to literature search criteria, 17 studies were identified with 2061 participants. Data from 5 of the studies with 270 participants were used to assess the change in blood levels of POP in percent per kilogram weight loss. Weight loss in the included studies varied from 4.4 to 64.8 kg. In all studies, the majority of POP concentrations in blood were found to rise following weight reduction. Blood concentrations following weight reduction were elevated by 2-4% per kilogram weight loss for most POP examined. The increased POP levels were still elevated 12 mo after intervention. Most research in this field, including animal studies, is carried out on a single compound or group of selected compounds, not taking the "cocktail effect" into consideration. This does not reflect the true range of POP to which humans are actually exposed. Few chronic investigations have been published and, in particular, few studies were available that compared the increase in POP concentrations with clinical consequences as individuals lost weight. These limitations call for caution in interpreting results. The benefits of losing weight still far outweigh the potential adverse health risks. However, further studies are recommended to determine the clinical significance of increased blood levels of POPs following rapid and excessive weight loss, particularly for women attending weight reduction treatment before pregnancy.

The effect of a vegetarian versus conventional hypocaloric diet on serum concentrations of persistent organic pollutants in patients with type 2 diabetes

BACKGROUND AND AIMS

The aim of this study was to explore the effect of a vegetarian versus conventional diet on the serum levels of persistent organic pollutants (POPs) in patients with T2D after 12 weeks of dietary intervention and to assess their relationships with metabolic parameters.

METHODS AND RESULTS

Men and women with T2D were randomly assigned to follow either a vegetarian diet without fish or meat (n = 37) or an isocaloric conventional antidiabetic diet (n = 37). Both diets were energy restricted (minus 500 kcal/day). All foods were provided to the participants. At randomization (week 0) and 12 weeks, the meal test was performed to assess the β-cell function and serum levels of 24 POPs. Dioxins and dioxin-like POPs were analyzed by isotope dilution high-resolution gas chromatography (HRGC) and mass spectrometry after cleanup of the silica and carbon columns. Non-dioxin-like POPs were analyzed by gas chromatography with an electron capture detector (GC-ECD). Statistical analyses used were repeated-measures analysis of variance (ANOVA), a multivariate regression model, and Pearson's correlations. We observed a statistically nonsignificant trend toward increases in the serum levels of most POPs in response to both hypocaloric diets with no differences between groups. In the groups combined, the change in serum concentrations of total POPs was correlated to changes in HbA1c (r = +0.34; p < 0.01), fasting plasma glucose (r = +0.41; p < 0.01) levels, and β-cell function measured as insulin secretion at a reference glucose level (r = -0.37; p < 0.01), independent of the changes in body weight and volume of visceral fat.

CONCLUSION

Short-term hypocaloric vegetarian and conventional diets did not reduce the POP levels, possibly due to mobilization of fat stores. Our findings support the relationship between POPs and diabetes, especially β-cell function.

TRIAL REGISTRATION

ClinicalTrials.gov number, NCT00883038, completed.

Polychlorinated biphenyl 126 exposure in L6 myotubes alters glucose metabolism: a pilot study

Polychlorinated biphenyls (PCBs) are increasingly recognized as metabolic disruptors. Due to its mass, skeletal muscle is the major site of glucose disposal. While muscle mitochondrial dysfunction and oxidative stress have been shown to play a central role in metabolic disease development, no studies to date have investigated the effect of PCB exposure on muscle energy metabolism and oxidative stress. In this pilot study, we tested the effect of exposure to PCB126 in L6 myotubes (from 1 to 2500 nM for 24 h) on mitochondrial function, glucose metabolism, and oxidative stress. Exposure to PCB126 had no apparent effect on resting, maximal, and proton leak-dependent oxygen consumption rate in intact L6 myotubes. However, basal glucose uptake and glycolysis were inhibited by 20-30 % in L6 myotubes exposed to PCB126. Exposure to PCB126 did not appear to alter skeletal muscle anti-oxidant defense or oxidative stress. In conclusion, our study shows for the first time that exposure to a dioxin-like PCB adversely affects skeletal muscle glucose metabolism. Given the importance of skeletal muscle in the maintenance of glucose homeostasis, PCB126 could play an important role in the development of metabolic disorders.

Persistent Organic Pollutants and Concern Over the Link with Insulin Resistance Related Metabolic Diseases

Persistent organic pollutants (POPs) are mostly halogenated compounds tending to persist in the environment, enter into the food chain, and accumulate in fat mass of mammals due to their high lipophilicity. They include some organochlorine pesticides, polychlorinated biphenyls, brominated flame retardants and polycyclic aromatic hydrocarbons. Some of these chemicals were widely used in the past so that their residues can be detected in the human body, though their usage has been banned for years. POPs have been shown to perturb the health of biological systems in different ways evidenced by carcinogenicity and disrupting effects on endocrine, immune, and reproductive systems. There are many epidemiologic and experimental studies on the association of exposure to POPs with insulin resistance and related metabolic disorders like obesity, diabetes, and metabolic syndrome. Inflammation as a known mechanism accompanying insulin resistance has also been shown to arise in insulin target tissues exposed to POPs. This review addresses the breast milk concentration of POPs in different regions of the world, synthesizes the current information on the association of POPs with insulin resistance related metabolic disorders, and discusses the inflammation as an involved mechanism. Considering high prevalence of insulin resistance related metabolic diseases and their relation with POPs, much need is felt regarding international and regional programs to not only limit their production and usage but eliminate these persistent pollutants from the environment.

Effect of prolonged exposure to sublethal concentrations of DDT and DDE on protein expression in human pancreatic beta cells

Pollution of the environment represents one of less explored potential reasons for the worldwide epidemic of type 2 diabetes. One of the most prevalent organochlorine pollutants remains the pesticide DDT and its degradation product DDE. Despite some epidemiologic correlations between levels of DDT and DDE in human organism and the prevalence of diabetes, there is almost no information about the exact targets of these compounds inside pancreatic beta cells. To detect functional areas of pancreatic beta cells that could be affected by exposure to DDT and DDE, we analyzed changes in protein expression in the NES2Y human pancreatic beta cell line exposed to three sublethal concentrations (0.1 μM, 1 μM, 10 μM) of DDT and DDE for 1 month. Protein separation and identification was achieved using high-resolution 2D-electrophoresis, computer analysis and mass spectrometry. With these techniques, four proteins were found downregulated after exposure to 10 μM DDT: three cytoskeletal proteins (cytokeratin 8, cytokeratin 18 and actin) and one protein involved in glycolysis (alpha-enolase). Two proteins were downregulated after exposure to 10 μM DDE: cytokeratin 18 and heterogenous nuclear ribonucleoprotein H1 (HNRH1). These changes correlate with previously described effects of other stress conditions (e.g. exposure to palmitate, hyperglycemia, imidazoline derivative, and cytokines) on protein expression in pancreatic beta cells. We conclude that cytoskeletal proteins and their processing, glucose metabolism, and mRNA processing may represent targets affected by exposure to conditions hostile to pancreatic beta cells, including exposure to DDT and DDE.

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.

Transcriptional profiling and biological pathway analysis of human equivalence PCB exposure in vitro: indicator of disease and disorder development in humans

BACKGROUND AND AIMS

Our earlier gene-expression studies with a Slovak PCBs-exposed population have revealed possible disease and disorder development in accordance with epidemiological studies. The present investigation aimed to develop an in vitro model system that can provide an indication of disrupted biological pathways associated with developing future diseases, well in advance of the clinical manifestations that may take years to appear in the actual human exposure scenario.

METHODS

We used human Primary Blood Mononuclear Cells (PBMC) and exposed them to a mixture of human equivalence levels of PCBs (PCB-118, -138, -153, -170, -180) as found in the PCBs-exposed Slovak population. The microarray studies of global gene expression were conducted on the Affymetrix platform using Human Genome U133 Plus 2.0 Array along with Ingenuity Pathway Analysis (IPA) to associate the affected genes with their mechanistic pathways. High-throughput qRT-PCR Taqman Low Density Array (TLDA) was done to further validate the selected 6 differentially expressed genes of our interest, viz., ARNT, CYP2D6, LEPR, LRP12, RRAD, TP53, with a small population validation sample (n=71).

RESULTS

Overall, we revealed a discreet gene expression profile in the experimental model that resembled the diseases and disorders observed in PCBs-exposed population studies. The disease pathways included endocrine system disorders, genetic disorders, metabolic diseases, developmental disorders, and cancers, strongly consistent with the evidence from epidemiological studies.

INTERPRETATION

These gene finger prints could lead to the identification of populations and subgroups at high risk for disease, and can pose as early disease biomarkers well ahead of time, before the actual disease becomes visible.

Dietary exposure to the endocrine disruptor tolylfluanid promotes global metabolic dysfunction in male mice

Environmental endocrine disruptors are implicated as putative contributors to the burgeoning metabolic disease epidemic. Tolylfluanid (TF) is a commonly detected fungicide in Europe, and previous in vitro and ex vivo work has identified it as a potent endocrine disruptor with the capacity to promote adipocyte differentiation and induce adipocytic insulin resistance, effects likely resulting from activation of glucocorticoid receptor signaling. The present study extends these findings to an in vivo mouse model of dietary TF exposure. After 12 weeks of consumption of a normal chow diet supplemented with 100 parts per million TF, mice exhibited increased body weight gain and an increase in total fat mass, with a specific augmentation in visceral adipose depots. This increased adipose accumulation is proposed to occur through a reduction in lipolytic and fatty acid oxidation gene expression. Dietary TF exposure induced glucose intolerance, insulin resistance, and metabolic inflexibility, while also disrupting diurnal rhythms of energy expenditure and food consumption. Adipose tissue endocrine function was also impaired with a reduction in serum adiponectin levels. Moreover, adipocytes from TF-exposed mice exhibited reduced insulin sensitivity, an effect likely mediated through a specific down-regulation of insulin receptor substrate-1 expression, mirroring effects of ex vivo TF exposure. Finally, gene set enrichment analysis revealed an increase in adipose glucocorticoid receptor signaling with TF treatment. Taken together, these findings identify TF as a novel in vivo endocrine disruptor and obesogen in mice, with dietary exposure leading to alterations in energy homeostasis that recapitulate many features of the metabolic syndrome.

Relationship between serum concentrations of persistent organic pollutants and markers of insulin resistance in a cohort of women with a history of gestational diabetes mellitus

The aim of the present study was to assess the relationship between serum concentrations of several persistent organic pollutants and insulin resistance markers in a cohort of women with a history of gestational diabetes mellitus. ∑POPs was computed as the sum of individual serum POP concentrations. No statistically significant associations were found between levels of any POP and fasting glucose. However, polychlorinated biphenyl (PCB) congeners 138 and 180 were positively associated with 2-h glucose levels and PCB 180 also with fasting immunoreactive insulin (IRI). We also found a positive association of p,p'- dichlorodiphenyldichloroethylene (p,p'- DDE), PCBs (138, 153, and 180), hexachlorobenzene, and ∑POPs with 2-h IRI. Serum concentrations of PCBs (138, 153, and 180), hexachlorobenzene, and ∑POPs were also positively associated with homeostasis model assessment (HOMA2-IR) levels. Moreover, p,p'- DDE, PCBs (138, 153 and 180), hexachlorobenzene, and ∑POPs were negatively associated with Insulin Sensitivity Index (ISI-gly) levels. No significant association was found between glycated hemoglobin and the concentrations of any POP. The removal of women under blood glucose lowering treatment from the models strengthened most of the associations previously found for the whole population. Our findings suggest that exposure to certain POPs is a modifiable risk factor contributing to insulin resistance.

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.

Persistent organic pollutants distribution in lipoprotein fractions in relation to cardiovascular disease and cancer

Persistent organic pollutants (POPs) are lipophilic environmental toxins that have been associated with cardiovascular disease (CVD) and cancer. The aim of this study was to investigate the concentrations of POPs in human high and low/very low-density lipoproteins (HDL and LDL/VLDL) and the possible association with CVD and cancer occurrence in individuals living in a contaminated area. Lipoproteins from 28 individuals (7 healthy controls, 8 subjects with cancer, 13 subjects with CVD) were isolated and the fraction-specific concentration of 20 different POPs was analyzed by high resolution gas chromatography/high resolution mass spectrometry. The activity of Paraoxonase 1 (PON1), an anti-oxidant in HDL, was determined in plasma of these 28 subjects and additional 50 subjects from the same area excluding diseases other than cancer or CVD. Fourteen polychlorinated biphenyls (PCBs) and three organochlorine pesticides were detected, and especially highly chlorinated PCBs were enriched in lipoproteins. Significantly higher concentrations of POPs were found among individuals with CVD or cancer compared to controls. Principal component analyses showed that POP concentrations in HDL were more associated with CVD, while POP concentrations in LDL/VLDL were more associated with cancer. PON1 activity was negatively correlated to sumPCB and a co-variation between decreased arylesterase-activity, increased PCB concentrations and CVD was found. This study shows that POPs are present in lipoproteins and were more abundant in individuals with CVD or cancer compared to healthy controls. The results also indicate that PCB exposure is accompanied by reduced PON1 activity that could impair the HDL function to protect against oxidation.

Insulin resistance and environmental pollutants: experimental evidence and future perspectives

BACKGROUND

The metabolic disruptor hypothesis postulates that environmental pollutants may be risk factors for metabolic diseases. Because insulin resistance is involved in most metabolic diseases and current health care prevention programs predominantly target insulin resistance or risk factors thereof, a critical analysis of the role of pollutants in insulin resistance might be important for future management of metabolic diseases.

OBJECTIVES

We aimed to critically review the available information linking pollutant exposure to insulin resistance and to open the discussion on future perspectives for metabolic disruptor identification and prioritization strategies.

METHODS

We searched PubMed and Web of Science for experimental studies reporting on linkages between environmental pollutants and insulin resistance and identified a total of 23 studies as the prime literature.

DISCUSSION

Recent studies specifically designed to investigate the effect of pollutants on insulin sensitivity show a potential causation of insulin resistance. Based on these studies, a summary of viable test systems and end points can be composed, allowing insight into what is missing and what is needed to create a standardized insulin resistance toxicity testing strategy.

CONCLUSIONS

It is clear that current research predominantly relies on top-down identification of insulin resistance-inducing metabolic disruptors and that the development of dedicated in vitro or ex vivo screens to allow animal sparing and time- and cost-effective bottom-up screening is a major future research need.

Adipose tissue concentrations of persistent organic pollutants and prevalence of type 2 diabetes in adults from Southern Spain

There is increasing evidence that environmental factors play an important role in the development of type 2 diabetes. Several persistent organic pollutants are suspected to contribute to the increasing prevalence and risk of type 2 diabetes. The aim of this study was to investigate the association of the body burden of three organochlorine pesticides and three polychlorinated biphenyls and the overall estrogenic activity with the risk of type 2 diabetes in a sample of adults from Southern Spain. Samples of adipose tissue and serum were obtained from 386 subjects undergoing non-cancer-related surgery and were extracted using validated methodologies. Residues of persistent organic pollutants were analyzed by means of high-resolution gas chromatography with a mass spectrometry detector in tandem mode. The overall estrogenicity of the adipose tissue extracts was measured by using the total effective xenoestrogen burden (TEXB) biomarker. Data on lifestyle, dietary habits, and health status were gathered from face-to-face interviews and clinical records. Statistical analyses were performed with unconditional logistic regression and different adjustment levels. In the models adjusted for adipose tissue origin, sex, age, and body mass index, the 2nd and 3rd tertiles of adipose tissue concentrations of p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) were positively associated with the risk of diabetes [odds ratios (95% confidence interval)=3.6 (0.8-17.3) and 4.4 (1.0-21.0), respectively]. A positive association with β-hexachlorocyclohexane was also found when body mass index and adipose tissue origin were removed from the models, with odds ratios (95% confidence interval) of 3.3 (1.0-10.4) and 5.5 (1.7-17.3), for the 2nd and 3rd tertiles of exposure, respectively. In addition, a statistically significant interaction was observed between p,p'-DDE and body mass index, such that the risk of diabetes increased with tertiles of exposure in a linear manner in non-obese subjects but not in the obese, in whom an inverted U-shape pattern was observed.