Exposure to ambient particulate matter induces a NASH-like phenotype and impairs hepatic glucose metabolism in an animal model

Associations between long-term exposure to air pollution, glycosylated hemoglobin, fasting blood glucose and diabetes mellitus in northern France

INTRODUCTION

A growing body of evidence suggests that long-term exposure to air pollutants like nitrogen oxides (NO_x) and particulate matter (PM) is associated with the prevalence and incidence of type 2 diabetes mellitus. Serum glucose and glycosylated hemoglobin (HbA1c) levels are biomarkers of glucose homeostasis. Data on the association between glucose homeostasis biomarkers and air pollution are scarce. HbA1c and fasting blood glucose (FBG) concentrations have been linked to PM and NO₂ exposure in Taiwan, where mean pollution levels are 3 to 7 times higher than the guideline maximum annual mean values of 40 μg/m³ (for NO₂) and 20 μg/m³ (for PM10) set by the World Health Organization (WHO). However, this association is not consistently reported at lower levels of pollution. The objective of the present study was to investigate the relationships between long-term exposure to air pollution at the place of residence, diabetes biomarkers, and prevalent diabetes in two cities with relatively low level of pollution.

METHODS

Data were recorded for 2895 adults (aged 40 to 65) having participated in the 2011-2013 ELISABET cross-sectional survey of the Lille and Dunkirk urban areas in northern France. Using multiple logistic and generalized linear regression models, we analyzed the associations between individual exposure to pollution on one hand and HbA1c, FBG and prevalent diabetes mellitus (DM) on the other. An atmospheric dispersion modelling system was used to assess annual exposure at the place of residence to coarse particulate matter (PM10), NO₂, and sulfur dioxide (SO₂).

RESULTS

The median pollutant levels were 21.96 μg/m³ for NO₂, 26.75 μg/m³ for PM10, and 3.07 μg/m³ for SO₂. A 2 μg/m³ increment in PM10 was associated with an HbA1c increment [95% confidence interval] of 0.044% [0.021; 0.067]. This association was still statistically significant after adjustment for the neighborhood's characteristics. A 5 μg/m³ increment in NO₂ was associated with an HbA1c increment of 0.031% [0.010; 0.053]. Associations between DM or FBG and air pollution did not achieve statistical significance.

CONCLUSION

Our study of a middle-aged, urban population evidenced an association between elevated HbA1c levels and long-term exposure to PM10 and NO₂ pollution levels that were relatively low but close to the WHO's guideline maximum values.

Hepatoprotective Effect of Loquat Leaf Flavonoids in PM2.5-Induced Non-Alcoholic Fatty Liver Disease via Regulation of IRs-1/Akt and CYP2E1/JNK Pathways

Ambient air particulate matter (PM) represents a class of heterogeneous substances present in polluted air, which contains many harmful components. Exposure to ambient particulate matter in fine rages (PM_2.5) is associated with non-alcoholic fatty liver disease (NAFLD). Loquat Leaf possesses pharmacological actions on NAFLD. As the main biological active ingredients, the potential therapeutic role of total flavonoids (TF) isolated from Loquat Leaf in PM_2.5-induced NAFLD model remains unclear. The present study was designed to explore the hepatoprotective effect of TF in PM_2.5-induced NAFLD mice with its related mechanisms of action. Mice were exposed to PM_2.5 to induce NAFLD, and body weight, the ratio of liver to body weight, and blood lipids increased significantly compared with the control group. It was found that TF significantly reduced the above parameters in PM_2.5-induced NAFLD mice. TF treatment alleviated oxidative stress by preventing the accumulation of oxidative product malondialdehyde (MDA) and by strengthening the anti-oxidative capacity of superoxide dismutase (SOD). TF was also found to reduce the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity in the PM_2.5 group. In addition, TF repaired the PM_2.5-induced decline of insulin receptor substrate-1 (IRs-1) and protein kinase B (Akt) phosphorylation. Meanwhile, the data showed TF suppressed the expression of cytochrome P450 2E1(CYP2E1) and the phosphorylation of c-jun N-terminal kinase (JNK) in PM_2.5-induced NAFLD. Taken together, these findings show that TF alleviate PM_2.5-induced NAFLD via regulation of IRs-1/Akt and CYP2E1/JNK pathways, which may have potential for further development as novel therapeutic agents for NAFLD.

Exposure to environmental level phenanthrene induces a NASH-like phenotype in new born rat

More and more evidence indicates that persistent organic pollutants (POPs) are a risk factor for non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Phenanthrene (Phe) is a kind of POP which existed extensively in the environment, but whose toxicity on mammals has so far received less focus. Subcutaneously injection of Phe (0.5, 5, 50 μg/kg) for 21 days induced significant NAFLD/NASH symptoms in new born rats. Exposure to environmental levels of Phe decreased body weight and liver-somatic index; impaired histology of liver; influenced the peroxisome proliferator-activated receptor gamma (PPARγ) signaling and lipid metabolism in liver; stimulated oxidative stress in the rats' liver; induced the variation of NFκB pathway and liver inflammatory response; and caused liver fibrosis via transforming growth factor β1 (tgfβ1). We speculated that the subcutaneously injected Phe was transferred to the liver through blood circulation, which may have induced the elevation of PPARγ directly or indirectly, leading to liver steatosis. Excess lipid, acting as the first hit, stimulated the second hit factors - oxidative stress, inflammatory response and lipid peroxidation, and finally resulted in steatohepatitis and liver fibrosis.

Central IKK2 Inhibition Ameliorates Air Pollution-Mediated Hepatic Glucose and Lipid Metabolism Dysfunction in Mice With Type II Diabetes

Previous studies supported a role of hypothalamic inflammation in fine ambient particulate matter (PM2.5) exposure-mediated diabetes development. We therefore investigated the effects of PM2.5 exposure on insulin resistance and the disorders of hepatic glucose and lipid metabolism via hypothalamic inflammation. KKAy mice, a genetically susceptible model of type II diabetes mellitus, were administered intra-cerebroventricularly with IKK2 inhibitor (IMD-0354) and were exposed to either concentrated PM2.5 or filtered air (FA) for 4 weeks simultaneously via a versatile aerosol concentration exposure system. At the end of the exposure, fasting blood glucose and serum insulin were evaluated before epididymal adipose tissue and liver were collected, flow cytometry, quantitative PCR and Western blot were performed at euthanasia. We observed that intracerebroventricular administration of IMD-0354 attenuated insulin resistance, inhibited macrophage polarization to M1 phenotype in epididymal adipose tissue in response to PM2.5 exposure. Although the treatment did not affect hepatic inflammation or endoplasmic reticulum stress, it inhibited the expression of the enzymes for gluconeogenesis and lipogenesis in the liver. Therefore, our current finding indicates an important role of hypothalamic inflammation in PM2.5 exposure-mediated hepatic glucose and lipid metabolism disorder.

Effects of particulate matter on allergic respiratory diseases

The health impact of airborne particulate matter (PM) has long been a concern to clinicians, biologists, and the general public. With many epidemiological studies confirming the association of PM with allergic respiratory diseases, an increasing number of follow-up empirical studies are being conducted to investigate the mechanisms underlying the toxic effects of PM on asthma and allergic rhinitis. In this review, we have briefly introduced the characteristics of PM and discussed its effects on public health. Subsequently, we have focused on recent studies to elucidate the association between PM and the allergic symptoms of human respiratory diseases. Specifically, we have discussed the mechanism of action of PM in allergic respiratory diseases according to different subtypes: coarse PM (PM2.5-10), fine PM (PM2.5), and ultrafine PM.

Changes in Metabolites Present in Lung-Lining Fluid Following Exposure of Humans to Ozone

Controlled human exposure to the oxidant air pollutant ozone causes decrements in lung function and increased inflammation as evidenced by neutrophil influx into the lung and increased levels of proinflammatory cytokines in the airways. Here we describe a targeted metabolomics evaluation of human bronchoalveolar lavage fluid (BALF) following controlled in vivo exposure to ozone to gain greater insight into its pulmonary effects. In a 2-arm cross-over study, each healthy adult human volunteer was randomly exposed to filtered air (FA) and to 0.3 ppm ozone for 2 h while undergoing intermittent exercise with a minimum of 4 weeks between exposures. Bronchoscopy was performed and BALF obtained at 1 (n = 9) or 24 (n = 23) h postexposure. Metabolites were detected using ultrahigh performance liquid chromatography-tandem mass spectroscopy. At 1-h postexposure, a total of 28 metabolites were differentially expressed (DE) (p < .05) following ozone exposure compared with FA-exposure. These changes were associated with increased glycolysis and antioxidant responses, suggesting rapid increased energy utilization as part of the cellular response to oxidative stress. At 24-h postexposure, 41 metabolites were DE. Many of the changes were in amino acids and linked with enhanced proteolysis. Changes associated with increased lipid membrane turnover were also observed. These later-stage changes were consistent with ongoing repair of airway tissues. There were 1.37 times as many metabolites were differentially expressed at 24 h compared with 1-h postexposure. The changes at 1 h reflect responses to oxidative stress while the changes at 24 h indicate a broader set of responses consistent with tissue repair. These results illustrate the ability of metabolomic analysis to identify mechanistic features of ozone toxicity and aspects of the subsequent tissue response.

Traffic-related air pollution associations with cytokeratin-18, a marker of hepatocellular apoptosis, in an overweight and obese paediatric population

INTRODUCTION

Traffic-related air pollution causes fatty liver, inflammation and fibrosis in animal models, but there have been few studies in humans.

OBJECTIVES

To test the hypothesis that traffic-related air pollution causes non-alcoholic fatty liver disease (NAFLD) and increased markers for non-alcoholic steatohepatitis (NASH); and that NAFLD increases liver susceptibility to increased NASH risk.

METHODS

Data collected prospectively from 74 overweight or obese children were obtained from the Yale Pediatric Obesity Clinic. Traffic-related air pollution was characterized as vehicle traffic volume on major roads within a 1 km residential buffer, and as residential nitrogen dioxide (NO₂ ) exposure. Outcomes were hepatic fat fraction (HFF) measured by magnetic resonance imaging, liver enzymes using standard assays and plasma cytokeratin-18 (CK-18) by immunosorbent assays.

RESULTS

Significant non-linear relationships with air pollution and CK-18 were found. Plasma CK-18 at follow-up increased from approximately 150 U/L to almost 200 U/L as residential traffic volume increased from 220 000 vehicle-km to 330 000 vehicle-km, after adjustment for baseline CK-18, age and gender. Among patients with NAFLD at baseline, CK-18 increased from 140 U/L to 200 U/L (a 1.5 standard deviation increase in CK-18) as NO₂ increased from 8 to 10 ppb.

CONCLUSIONS

Traffic-related air pollution was associated with CK-18. Effects were larger in children with pre-existing NAFLD at study entry.

Combination effects of airborne particulate matter exposure and high-fat diet on hepatic fibrosis through regulating the ROS-endoplasmic reticulum stress-TGFβ/SMADs axis in mice

BACKGROUND

Hepatic fibrosis, characterized by an excessive accumulation of extracellular matrix, is associated with toxic substance exposure, chronic infections, mechanical injury, airborne fine particulate matter (PM_2.5) exposure and metabolic disease. This study aimed to investigate the effect and mechanism of long-term, real-world airborne particulate matter (PM) exposure on hepatic fibrosis and further explored whether combination treatment of PM exposure and high-fat diet (HFD) aggravate the adverse effects in mice.

METHODS AND RESULTS

Six-week-old male C57BL/6J mice fed with either a standard chow diet (STD) or an HFD were treated with either filtered air (FA) or PM for 18 weeks. Metabolic parameters, histological examination, gene expression analysis, and Western blot analysis were utilized to measure the effect and mechanism of PM exposure on hepatic fibrosis and to further analyze the synergistic effect of HFD. Subchronic airborne PM exposure induces hepatic fibrosis in mice, and combination treatment of PM exposure and HFD accelerate the adverse effect. Meanwhile, subchronic exposure to real-world PM increased the level of hepatic ROS, and the expression of endoplasmic reticulum (ER) stress markers (GRP78 and CHOP), p-SMAD2 and p-SMAD3, as well as up-regulated TGFβ and collagen 1 in liver tissues. Furthermore, PM exposure and HFD displayed the synergistic effects on these changes in liver.

CONCLUSION

Our findings indicate that airborne PM exposure aggravates HFD -induced hepatic fibrosis. The ROS-ER stress-TGFβ/SMADs regulatory axis mediates the effects of airborne PM exposure on accelerating hepatic fibrosis.

Air pollution and occurrence of type 2 diabetes in a large cohort study

The few cohort studies that have investigated the association between exposure to air pollution and occurrence of diabetes have reported conflicting results. We aimed to evaluate the association of long-term exposure to particulate matter (PM), nitrogen oxides (NO_x) and ozone (O₃), with baseline prevalence and incidence of type 2 diabetes in a large administrative cohort in Rome, Italy. A total of 1,425,580 subjects aged 35+years (January 1st, 2008) were assessed and followed for six years. We estimated PM₁₀, PM_2.5-10, PM_2.5, NO₂, and NO_x exposures at residence using land use regression models, and summer O₃ exposure using dispersion modeling. To estimate the association between air pollutant exposures and prevalence and incidence of diabetes, we used logistic and Cox regression models, considering individual, environmental (noise and green areas), and contextual characteristics. We identified 106,387 prevalent cases at baseline and 65,955 incident cases during the follow-up period. We found positive associations between nitrogen oxides exposures and prevalence of diabetes with odds ratios (ORs) up to 1.010 (95% CI: 1.002, 1.017) and 1.015 (1.009, 1.021) for NO₂ and NOx, respectively, per fixed increases (per 10μg/m³ and 20μg/m³, respectively). We also found some evidence of an association between NOx and O₃ and incidence of diabetes, with hazard ratios (HRs) of 1.011 (95%CI: 1.003-1.019) and 1.015 (1.002-1.027) per 20 and 10μg/m³ increases, respectively. The association with O₃ with incident diabetes was stronger in women than in men and among those aged <50years. In sum, long-term exposure to nitrogen oxides was associated with prevalent diabetes while NOx and O₃ exposures were associated with incident diabetes.

Prenatal Exposure to Endocrine Disruptors and Reprogramming of Adipogenesis: An Early-Life Risk Factor for Childhood Obesity

Obesity is a global health problem. It is characterized by excess adipose tissue that results from either increase in the number of adipocytes or increase in adipocytes size. Adipocyte differentiation is a highly regulated process that involves the activation of several transcription factors culminating in the removal of adipocytes from the cell cycle and induction of highly specific proteins. Several other factors, including hormones, genes, and epigenetics, are among the most important triggers of the differentiation process. Although the main contributing factors to obesity are high caloric intake, a sedentary lifestyle, and genetic predisposition, strong evidence supports a role for life exposure to environmental pollutants. Endocrine-disrupting chemicals are exogenous, both natural and man-made, chemicals that disrupt the body signaling processes, thus interfering with the endocrine system. Several studies have shown that prenatal exposure to endocrine disruptors modulates the mechanisms, by which multipotent mesenchymal stem cells differentiate into adipocytes. This review discusses adipocytes differentiation and highlights the possible mechanisms of prenatal exposure to endocrine disruptors in reprogramming of adipogenesis and induction of obesity later in life. Therefore, this review provides knowledge that reduction of early life exposure to these chemicals could open the door for new strategies in the prevention of obesity, especially during childhood.

Effects of air pollution exposure on glucose metabolism in Los Angeles minority children

OBJECTIVES

Growing evidence indicates that ambient (AAP: NO₂ , PM_2.5 and O₃ ) and traffic-related air pollutants (TRAP) contribute to metabolic disease risk in adults; however, few studies have examined these relationships in children.

METHODS

Metabolic profiling was performed in 429 overweight and obese African-American and Latino youth living in urban Los Angeles, California. This cross-sectional study estimated individual residential air pollution exposure and used linear regression to examine relationships between air pollution and metabolic outcomes.

RESULTS

AAP and TRAP exposure were associated with adverse effects on glucose metabolism independent of body fat percent. PM_2.5 was associated with 25.0% higher fasting insulin (p < 0.001), 8.3% lower insulin sensitivity (p < 0.001), 14.7% higher acute insulin response to glucose (p = 0.001) and 1.7% higher fasting glucose (p < 0.001). Similar associations were observed for increased NO₂ exposure. TRAP from non-freeway roads was associated with 12.1% higher insulin (p < 0.001), 6.9% lower insulin sensitivity (p = 0.02), 10.8% higher acute insulin response to glucose (p = 0.003) and 0.7% higher fasting glucose (p = 0.047).

CONCLUSIONS

Elevated air pollution exposure was associated with a metabolic profile that is characteristic of increased risk for type 2 diabetes. These results indicate that increased prior year exposure to air pollution may adversely affect type 2 diabetes-related pathophysiology in overweight and obese minority children.

Particulate air pollution: major research methods and applications in animal models

Ambient air pollution is composed of a heterogeneous mixture of gaseous and solid particle compounds in which primary particles are emitted directly into the atmosphere, such as diesel soot, while secondary particles are created through physicochemical transformation. Particulate matter (PM), especially fine and ultrafine particles, can be inhaled and deposited in the alveolar cavities and penetrate into circulation. An association between high levels of air pollutants and human disease has been known for more than half a century and increasing evidences demonstrate a strong link between exposure on PM and the development of systemic diseases, such as cardiovascular and neurological disorders. Experimental animal models have been extensively used to study the underlying mechanism caused by environmental exposure to ambient PM. Due to their availability, quality, cost, and genetically modified strains, rodent models have been widely used. Some common exposure approaches include intranasal instillation, intratracheal instillation, nose-only inhalation, whole-body inhalation, and intravenous injection have been reviewed with brief summary of its performance, merit, limitation, and application. We hope this would provide useful reference in advancing experimental researches about air pollution human health and disease development.

Inhalation Exposure to PM2.5 Counteracts Hepatic Steatosis in Mice Fed High-fat Diet by Stimulating Hepatic Autophagy

Air pollution is associated with the increased risk of metabolic syndrome. In this study, we performed inhalation exposure of mice fed normal chow or a high-fat diet to airborne fine particulate matters (PM_2.5), and then investigated the complex effects and mechanisms of inhalation exposure to PM_2.5 on hepatic steatosis, a precursor or manifestation of metabolic syndrome. Our studies demonstrated that inhalation exposure of mice fed normal chow to concentrated ambient PM_2.5 repressed hepatic transcriptional regulators involved in fatty acid oxidation and lipolysis, and thus promoted hepatic steatosis. However, PM_2.5 exposure relieved hepatic steatosis in high-fat diet-induced obese mice. Further investigation revealed that inhalation exposure to PM_2.5 induced hepatic autophagy in mouse livers in a manner depending on the MyD88-mediated inflammatory pathway. The counteractive effect of PM_2.5 exposure on high-fat diet-induced hepatic steatosis was mediated through PM_2.5-induced hepatic autophagy. The findings from this study not only defined the effects and mechanisms of PM_2.5 exposure in metabolic disorders, but also revealed the pleotrophic acts of an environmental stressor in a complex stress system relevant to public health.

Portable detection of trace metals in airborne particulates and sediments via μPADs and smartphone

Particulate matter (PM), a key indicator of air pollution by natural and anthropogenic activities, contributes to a wide spectrum of diseases that lead to a shortening of life expectancy. It has been recognized that trace metals in airborne PM are highly toxic and can be correlated with lesion in respiratory, gastrointestinal, immunological, and hematological systems. Traditional methods for trace metal assay require sophisticated instrumentations and highly trained operators in centralized laboratories. In this work, by integrating the technologies of microfluidic paper-based analytical devices, additive manufacturing, smartphone, and colorimetric sensing, we developed the first smartphone based paper microfluidic platform for portable, disposable, and quantitative measurements of cobalt (Co), copper (Cu), and iron (Fe) in ambient air and street sediments. On a single A4-sized paper, 48 devices were fabricated in under 30 s with a total cost of ∼$1.9. On each device, 12 reaction units were patterned and used for colorimetric tests. Particulate samples from urban ambient air and street sediments were collected, processed, and analyzed. Signals of the on-chip complexation product were recorded using a smartphone camera and processed by a self-developed app on an iOS system. For precisely controlling the object distance, chip position, and luminance, a hand-held 3D cellphone housing was designed and printed. The detection limits of Co, Cu, and Fe were determined to be 8.2, 45.8, and 186.0 ng, while the linear dynamic ranges were calculated to be 8.2-81.6, 45.8-4.58 × 10², and 1.86 × 10²-1.86 × 10³ ng, representing a practically relevant device performance with a significant reduction in the detection cost and time consumption. Trace metals in ambient air and sediments of two cities in China have been quantified portably, thus demonstrating the utility of our system in improving strategies for air pollution control in low-resource settings.

Polluted Pathways: Mechanisms of Metabolic Disruption by Endocrine Disrupting Chemicals

PURPOSE OF REVIEW

Environmental toxicants are increasingly implicated in the global decline in metabolic health. Focusing on diabetes, herein, the molecular and cellular mechanisms by which metabolism disrupting chemicals (MDCs) impair energy homeostasis are discussed.

RECENT FINDINGS

Emerging data implicate MDC perturbations in a variety of pathways as contributors to metabolic disease pathogenesis, with effects in diverse tissues regulating fuel utilization. Potentiation of traditional metabolic risk factors, such as caloric excess, and emerging threats to metabolism, such as disruptions in circadian rhythms, are important areas of current and future MDC research. Increasing evidence also implicates deleterious effects of MDCs on metabolic programming that occur during vulnerable developmental windows, such as in utero and early post-natal life as well as pregnancy. Recent insights into the mechanisms by which MDCs alter energy homeostasis will advance the field's ability to predict interactions with classical metabolic disease risk factors and empower studies utilizing targeted therapeutics to treat MDC-mediated diabetes.

Gestational diabetes mellitus was related to ambient air pollutant nitric oxide during early gestation

BACKGROUND

Ambient air pollution has been linked to the risk of gestational diabetes mellitus (GDM). However, evidence of this association is limited, and no study has examined the effects of nitric oxide (NO).

OBJECTIVE

This study investigated the association between air pollution exposure during gestation and GDM.

METHODS

The Taiwan Birth Cohort Study database was used to examine the association between the risk of GDM and all routinely monitored air pollutants among 21,248 women who were pregnant during 2004-2005. We further employed a two-pollutant model for confirming the effect of each pollutant on GDM.

RESULTS

After the exclusion criteria were applied, 19,606 women were included in the final analysis. Among them, 378 (1.9%) had been diagnosed as having GDM. These women were older and had higher BMIs than the women without GDM. The risks of GDM onset were significantly associated with NO exposure during the first [adjusted OR (aOR): 1.05, 95% confidence interval (CI): 1.02-1.08] and second (aOR: 1.05, 95%CI: 1.02-1.08) trimesters. Under the two-pollutant model, the effect of NO exposure was also significant during the first (aOR: 1.05, 95%CI: 1.02-1.08) and second (aOR: 1.05, 95%CI: 1.02-1.09) trimesters.

CONCLUSION

The results indicated that exposure to higher NO levels during pregnancy increases the risk of GDM.

Residential Proximity to Major Roadways, Fine Particulate Matter, and Hepatic Steatosis: The Framingham Heart Study

We examined associations between ambient air pollution and hepatic steatosis among 2,513 participants from the Framingham (Massachusetts) Offspring Study and Third Generation Cohort who underwent a computed tomography scan (2002-2005), after excluding men who reported >21 drinks/week and women who reported >14 drinks/week. We calculated each participant's residential-based distance to a major roadway and used a spatiotemporal model to estimate the annual mean concentrations of fine particulate matter. Liver attenuation was measured by computed tomography, and liver-to-phantom ratio (LPR) was calculated. Lower values of LPR represent more liver fat. We estimated differences in continuous LPR using linear regression models and prevalence ratios for presence of hepatic steatosis (LPR ≤ 0.33) using generalized linear models, adjusting for demographics, individual and area-level measures of socioeconomic position, and clinical and lifestyle factors. Participants who lived 58 m (25th percentile) from major roadways had lower LPR (β = -0.003, 95% confidence interval: -0.006, -0.001) and higher prevalence of hepatic steatosis (prevalence ratio = 1.16, 95% confidence interval: 1.05, 1.28) than those who lived 416 m (75th percentile) away. The 2003 annual average fine particulate matter concentration was not associated with liver-fat measurements. Our findings suggest that living closer to major roadways was associated with more liver fat.

iRhom2 deficiency relieves TNF-α associated hepatic dyslipidemia in long-term PM2.5-exposed mice

Accumulating researches reported that particulate matter (PM2.5) is a risk factor for developing various diseases, including metabolic syndrome. Recently, inactive rhomboid protein 2 (iRhom2) was considered as a necessary modulator for shedding of tumor necrosis factor-α (TNF-α) in immune cells. TNF-α, a major pro-inflammatory cytokine, was linked to various pathogenesis of diseases, including dyslipidemia. Here, wild type (WT) and iRhom2-knockout (iRhom2^-/-) mice were used to investigate the effects of iRhom2 on PM2.5-induced hepatic dyslipidemia. The hepatic histology, inflammatory response, glucose tolerance, serum parameters and gene expressions were analyzed. We found that long-term inhalation of PM2.5 resulted in hepatic steatosis. And a significant up-regulation of iRhom2 in liver tissues was observed, accompanied with elevated TNF-α, TNF-α converting enzyme (TACE), TNFα receptor (TNFR)2 and various inflammatory cytokines expressions. Additionally, PM2.5 treatment caused TG and TC accumulation in serum and liver, probably attributed to changes of genes modulating lipid metabolism. Intriguingly, hepatic injury and dyslipidemia were attenuated by iRhom2^-/- in mice with PM2.5 challenge. In vitro, iRhom2-knockdwon reduced TNF-α expressions and its associated inflammatory cytokines in Kupffer cells, implying that liver-resident macrophages played an important role in regulating hepatic inflammation and lipid metabolism in cells treated with PM2.5. The findings indicated that long-term PM2.5 exposure caused hepatic steatosis and dyslipidemia through triggering inflammation, which was, at least partly, dependent on iRhom2/TNF-α pathway in liver-resident macrophages.

Multi-organ toxicity induced by fine particulate matter PM2.5 in zebrafish (Danio rerio) model

The fine particulate matter (PM_2.5) in air pollution is a major public health concern and now known to contribute to severe diseases, therefore, a comprehensive understanding of PM_2.5-induced adverse effects in living organisms is needed urgently. This study was aimed to evaluate the toxicity of PM_2.5 on multi-organ systems in a zebrafish (Danio rerio) model. The embryonic toxicity induced by PM_2.5 was demonstrated by an increase in mortality and inhibition of hatching rate, in a dose- and time-dependent manner. PM_2.5 caused the pericardial edema, as well as reducing heart rate and cardiac output. The area of sub-intestinal vessels (SIVs) was significant reduced in Tg(fli-1:EGFP) transgenic zebrafish lines. Morphological defects and yolk sac retention were associated with hepatocyte injury. In addition, PM_2.5 disrupted the axonal integrity, altering of axon length and pattern in Tg(NBT:EGFP) transgenic lines. Genes involved in cardiac function (spaw, supt6h, cmlc1), angiogenesis (vegfr2a, vegfr2b), and neural function (gabrd, chrna3, npy8br) were markedly down-regulated; while genes linked to hepatic metabolism (cyp1a, cyp1b1, cyp1c1) were significantly up-regulated by PM_2.5. In summary, our data showed that PM_2.5 induced the cardiovascular toxicity, hepatotoxicity and neurotoxicity in zebrafish, suggested that PM_2.5 could cause multi-organ toxicity in aquatic organism.

Cord plasma insulin and in utero exposure to ambient air pollution

INTRODUCTION

Cardio-metabolic risk factors including insulin levels are at young age barely perceived as harmful, but over time these risk factors may track and lead to higher risk of metabolic syndrome. Studies showed that exposure to air pollution is associated with an increased risk of insulin resistance in childhood. We determined whether the origin of type 2 diabetes can be found in the early childhood by examining the levels of insulin in the neonatal cord blood and whether this can be considered as a disease marker for later life.

METHODS

In the ENVIRONAGE (ENVIRonmental influence ON early AGEing) birth cohort, we recruited 620 mother-infant pairs between February 2nd 2010 until August 12th 2014 at the East-Limburg Hospital in Genk, Belgium. We investigated in 590 newborns the association between cord plasma insulin levels and exposure to particulate matter (PM_2.5 and PM₁₀) and nitrogen dioxide (NO₂) in various exposure windows during pregnancy. Trimester-specific air pollutant exposure levels were estimated for each mother's home address using a spatiotemporal model.

RESULTS

Cord plasma insulin levels averaged 33.1pmol/L (25-75th percentile: 20.1-53.5), while PM_2.5 exposure during pregnancy averaged (SD) 13.7μg/m³ (2.4). Independent of maternal age, newborn's sex, birth weight, gestational age, parity, early-pregnancy BMI, ethnicity, smoking status, time of the day, maternal education, time of delivery, and season of delivery, cord plasma insulin levels increased with 15.8% (95% CI 7.8 to 24.4, p<0.0001) for each SD increment in PM_2.5 levels during the entire pregnancy and was most pronounced in the 2nd trimester (13.1%, 95% CI 3.4 to 23.7, p=0.007) of pregnancy. The results for PM₁₀ exposure were similar with those of PM_2.5 exposure but we did not observe an association between cord blood insulin levels and NO₂ exposure.

CONCLUSIONS

Exposure to particulate air pollution during pregnancy is associated with increased levels of cord plasma insulin at birth. The public health relevance of this association is demonstrated by the fact that a 2.4μg/m³ (SD) increase in PM_2.5 during pregnancy on cord plasma insulin levels corresponds to the effect-size of a 9kg/m² higher early-pregnancy BMI on cord plasma. Particulate air pollution induced changes in cord plasma insulin levels during early life and might be a risk factor in the development of metabolic disease, such as glucose intolerance or type 2 diabetes, later in life.

Airborne PM2.5-Induced Hepatic Insulin Resistance by Nrf2/JNK-Mediated Signaling Pathway

Animal and epidemiological studies have suggested that exposure to airborne particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM_2.5) is associated with the risk of developing type 2 diabetes. However, the mechanism underlying this risk is poorly understood. In the present study, we investigated the effects of PM_2.5 exposure on glucose homeostasis and related signaling pathways in mice. Wild-type and nuclear factor erythroid 2-related factor 2 (Nrf2) knockout (Nrf2^−/−) C57BL/6 male mice were exposed to either ambient concentrated PM_2.5 or filtered air (FA) for 12 weeks through a whole-body PM exposure system. At the end of the exposure, we assessed liver damage, and performed metabolic studies, gene expressions, as well as molecular signal transductions to determine the signaling pathways involving oxidative responses, insulin signaling, and glucose metabolism. Our results indicated that PM_2.5 exposure for 12 weeks caused significant liver damage as evidenced by elevated levels of aminotransferase (AST) and alanine aminotransferase (ALT). Furthermore, PM_2.5 exposure induced impaired glucose tolerance and inhibited glycogen synthesis, leading to hepatic insulin resistance indicated by higher glucose levels, higher area under the curve (AUC), and homeostasis model assessment of insulin resistance (HOMA-IR) values. We further found that PM_2.5 exposure significantly increased the expressions of Nrf2 and Nrf2-regulated antioxidant genes. Moreover, PM_2.5 exposure activated the c-Jun N-terminal kinase (JNK) signaling pathway and increased insulin receptor substrate-1 (IRS-1) phosphorylation at Ser³⁰⁷, but reduced protein kinase B phosphorylation at Ser⁴⁷³. Taken together, our study demonstrated PM_2.5 exposure triggered Nrf2-mediated oxidative responses and activated the JNK-mediated inhibitory signaling pathway, resulting in hepatic insulin resistance.

Comprehensive understanding of PM2.5 on gene and microRNA expression patterns in zebrafish (Danio rerio) model

PM_2.5 is a major public health concern and some severe diseases have been attributed to exposure to PM_2.5. However, a comprehensive understanding of gene and microRNA expression patterns induced by PM_2.5 is missing. The objective of this study was to evaluate the toxicity of PM_2.5 via genome-wide transcriptional analysis in the model teleost fish, zebrafish (Danio rerio). Gene ontology analysis revealed that the most impact gene functional categories induced by PM_2.5 included oxidation-reduction process, transport, response to xenobiotic stimulus, response to chemical stimulus and metabolic process. Pathway and Signal-net analysis showed that the critical pathway involved in the response to exposure to PM_2.5 was the metabolism of xenobiotics by cytochrome P450. Results from verification experiments also demonstrated that the key genes with degree higher than 10 induced by PM_2.5 were related to metabolism of xenobiotics by cytochrome P450, including cyp3a65, mgst2, gstp1, gsto2, gsto1, cyp1a, ehx1, gstal and aldh3b1. The differential expression of 8 microRNAs corresponding to those in the human genome, revealed that PM_2.5 could up-regulate let-7b, miR-153b-3p, miR-122, miR-24 and down-regulate let-7i, miR-19a-3p, miR-19b-3p and miR-7a, which suggested PM_2.5 had multiple means through which it induced toxicity in living organisms, such as suppression of adaptive immune responses, autophagy, deregulation of metabolism, impaired vasorelaxation, progression of cancers, as well as hypertension, atherosclerosis and myocardial infarction.

Association of Long-Term Near-Highway Exposure to Ultrafine Particles with Cardiovascular Diseases, Diabetes and Hypertension

Ultrafine particle (UFP) concentrations are elevated near busy roadways, however, their effects on prevalence of cardiovascular diseases, diabetes, and hypertension are not well understood. To investigate these associations, data on demographics, diseases, medication use, and time of activities were collected by in-home surveys for 704 participants in three pairs of near-highway and urban background neighborhoods in and near Boston (MA, USA). Body mass index (BMI) was measured for a subset of 435 participants. Particle number concentration (PNC, a measure of UFP) was collected by mobile monitoring in each area. Intra-neighborhood spatial-temporal regression models (approximately 20 m resolution) were used to estimate hourly ambient PNC at the residences of participants. We used participant time activity information to adjust annual average residential PNC values and assign individualized time activity adjusted annual average PNC exposures (TAA-PNC). Using multivariate logistic regression models, we found an odds ratio (OR) of 1.35 (95% CI: 0.83, 2.22) of TAA-PNC with stroke and ischemic heart diseases (S/IHD), an OR of 1.14 (95% CI: 0.81, 1.62) with hypertension, and an OR of 0.71 (95% CI: 0.46, 1.10) for diabetes. A subset analysis controlling for BMI produced slightly stronger associations for S/IHD (OR = 1.61, 95% CI: 0.88, 2.92) and hypertension (OR = 1.28, 95% CI: 0.81, 2.02), and no association with diabetes (OR = 1.09, 95% CI = 0.61, 1.96). Further research is needed with larger sample sizes and longitudinal follow-up.

Ambient air pollution and primary liver cancer incidence in four European cohorts within the ESCAPE project

BACKGROUND

Tobacco smoke exposure increases the risk of cancer in the liver, but little is known about the possible risk associated with exposure to ambient air pollution.

OBJECTIVES

We evaluated the association between residential exposure to air pollution and primary liver cancer incidence.

METHODS

We obtained data from four cohorts with enrolment during 1985-2005 in Denmark, Austria and Italy. Exposure to nitrogen oxides (NO₂ and NO_X), particulate matter (PM) with diameter of less than 10µm (PM₁₀), less than 2.5µm (PM_2.5), between 2.5 and 10µm (PM_2.5-10) and PM_{2.5 absorbance} (soot) at baseline home addresses were estimated using land-use regression models from the ESCAPE project. We also investigated traffic density on the nearest road. We used Cox proportional-hazards models with adjustment for potential confounders for cohort-specific analyses and random-effects meta-analyses to estimate summary hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Out of 174,770 included participants, 279 liver cancer cases were diagnosed during a mean follow-up of 17 years. In each cohort, HRs above one were observed for all exposures with exception of PM_{2.5 absorbance} and traffic density. In the meta-analysis, all exposures were associated with elevated HRs, but none of the associations reached statistical significance. The summary HR associated with a 10-μg/m³ increase in NO₂ was 1.10 (95% confidence interval (CI): 0.93, 1.30) and 1.34 (95% CI: 0.76, 2.35) for a 5-μg/m³ increase in PM_2.5.

CONCLUSIONS

The results provide suggestive evidence that ambient air pollution may increase the risk of liver cancer. Confidence intervals for associations with NO₂ and NO_X were narrower than for the other exposures.

Particulate Air pollution mediated effects on insulin resistance in mice are independent of CCR2

Background

Chronic exposure to fine ambient particulate matter (PM_2.5) induces insulin resistance. CC-chemokine receptor 2 (CCR2) appears to be essential in diet-induced insulin resistance implicating an important role for systemic cellular inflammation in the process. We have previously suggested that CCR2 is important in PM_2.5 exposure-mediated inflammation leading to insulin resistance under high fat diet situation. The present study assessed the importance of CCR2 in PM_2.5 exposure-induced insulin resistance in the context of normal diet.

Methods and Results

C57BL/6 and CCR2^-/- mice were subjected to exposure to concentrated ambient PM_2.5 or filtered air for 6 months. In C57BL/6 mice, concentrated ambient PM_2.5 exposure induced whole-body insulin resistance, macrophage infiltration into the adipose tissue, and upregulation of phosphoenolpyruvate carboxykinase (PEPCK) in the liver. While CCR2 deficiency reduced adipose macrophage content in the PM_2.5-exposed animals, it did not improve systemic insulin resistance. This lack of improvement in insulin resistance was paralleled by increased hepatic expression of genes in PEPCK and inflammation.

Conclusion

CCR2 deletion failed to attenuate PM_2.5 exposure-induced insulin resistance in mice fed on normal diet. The present study indicates that PM_2.5 may dysregulate glucose metabolism directly without exerting proinflammatory effects.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-017-0187-3) contains supplementary material, which is available to authorized users.

Metabolism disrupting chemicals and metabolic disorders

The recent epidemics of metabolic diseases, obesity, type 2 diabetes(T2D), liver lipid disorders and metabolic syndrome have largely been attributed to genetic background and changes in diet, exercise and aging. However, there is now considerable evidence that other environmental factors may contribute to the rapid increase in the incidence of these metabolic diseases. This review will examine changes to the incidence of obesity, T2D and non-alcoholic fatty liver disease (NAFLD), the contribution of genetics to these disorders and describe the role of the endocrine system in these metabolic disorders. It will then specifically focus on the role of endocrine disrupting chemicals (EDCs) in the etiology of obesity, T2D and NAFLD while finally integrating the information on EDCs on multiple metabolic disorders that could lead to metabolic syndrome. We will specifically examine evidence linking EDC exposures during critical periods of development with metabolic diseases that manifest later in life and across generations.

Association between soil heavy metals and fatty liver disease in men in Taiwan: a cross sectional study

OBJECTIVES

Metabolic factors are major risk factors for non-alcoholic fatty liver disease although other factors may also contribute to development of fatty liver disease. We explored the association between exposure to soil heavy metals and prevalence of fatty liver disease.

METHODS

We retrospectively analysed data from patients diagnosed with fatty liver disease in 2014 at the Health Evaluation Centre of Chang-Hua Christian Hospital (n=1137). We used residency data provided in the records of the Health Evaluation Centre and data for soil metal concentrations from a nationwide survey conducted by the Environmental Protection Administration of Taiwan. We studied the correlations between the severity of fatty liver disease and concentrations of soil heavy metals (arsenic, mercury, cadmium, chromium, copper, nickel, lead and zinc).

RESULTS

The prevalence of moderate to severe fatty liver disease in our study was 26.5%. Using univariate and multivariate analysis, we demonstrated that the presence of soil heavy metals was a significant risk factor for fatty liver disease in men (OR 1.83, 95% CI 1.161 to 2.899, p=0.009). With stratification by body mass index (BMI) and gender, lean men with a BMI <24 kg/m² were the most susceptible to soil heavy metals (OR 5.059, 95% CI 1.628 to 15.728, p<0.05).

CONCLUSIONS

Our study suggested a significant association between exposure to soil heavy metals and fatty liver disease in lean men.

The Associations Between Air Pollution and Adverse Pregnancy Outcomes in China

Research on the potential impact of air pollution on the human's health has increased rapidly in recent years. Several studies have suggested that exposure to air pollutants during period of pregnancy which is a crucial time point of mother-fetus development may have long-term and serious impact on adverse pregnancy outcomes. There is lack of review to evaluate the existed epidemiologic evidence on the associations between air pollutants and adverse pregnancy outcomes in China, so we conducted a review to explore the current epidemiological evidence on the effects of air pollutants to pregnancy outcomes and possible mechanisms during the pregnancy process. We used keywords to systematically search all the English and Chinese literatures on studies that were conducted in China. Exposure to air pollutants during pregnancy had shown there were harmful effects for different birth outcomes: preterm birth, low birth weight, stillbirth, birth defects, infertility, and macrosomia fetus. Results on the effects of air pollutants on adverse pregnancy outcomes are small and inconsistent because they vary in their design and methodology. The existed available evidence is compatible with either a small negative effect of air pollutants on pregnancy outcomes or with no effect; therefore, further studies are needed to confirm and quantify the possible associations and potential biologic mechanisms between air pollutants and pregnancy outcomes.

Macrophage-Mediated Effects of Airborne Fine Particulate Matter (PM2.5) on Hepatocyte Insulin Resistance in Vitro

Fine particulate matter (PM_2.5) pollution poses significant health risks worldwide, including metabolic syndrome-related diseases with the characteristic feature of insulin resistance. However, the mechanism and influencing factors of this effect are poorly understood. In this serial in vitro study, we aimed at testing the hypothesis that macrophage-mediated effects of PM_2.5 on hepatic insulin resistance depend on its chemical composition. Mouse macrophages were exposed to PM_2.5 that had been collected during summer or winter in Beijing, which represented different compositions of PM_2.5. Thereafter, hepatocytes were treated with macrophage-conditioned medium (CM). PM_2.5 induced interleukin-6, tumor necrosis factor-α, and monocyte chemoattractant protein-1 expression and secretion in macrophages, particularly after winter PM_2.5 exposure. Correspondingly, winter CM weakened hepatocellular insulin-stimulated glucose consumption. Further investigation revealed that the normal insulin pathway was suppressed in winter CM-treated hepatocytes, with increased phosphorylation of insulin receptor substrate 1 at serine residue 307 (Ser307) and decreased phosphorylation of protein kinase B (PKB/AKT) and forkhead box transcription factor O1 (FoxO1). Moreover, c-Jun N-terminal kinase, a key moderator of the sensitivity response to insulin stimulation, was activated in hepatocytes treated with winter CM. Although further studies are warranted, this preliminary study suggested an association between PM composition and insulin resistance, thus contributing to our understanding of the systemic toxicity of PM_2.5.

Plasma selenium levels and nonalcoholic fatty liver disease in Chinese adults: a cross-sectional analysis

Selenium exposure can induce liver insulin resistance and increased liver triglyceride concentrations in animals, which may link to an increased risk of nonalcoholic fatty liver disease (NAFLD). However, epidemiological studies investigating the association between elevated plasma selenium levels and NAFLD were not available. We aimed to investigate the association of selenium levels with the prevalence of NAFLD in Chinese adults. This was a cross-sectional study of 8550 Chinese adults aged 40 yr or older in Shanghai, China. A questionnaire, anthropometric measurements, and laboratory tests were conducted. NAFLD was diagnosed by hepatic ultrasound after the exclusion of alcohol abuse and other liver diseases. Plasma selenium concentration was assessed by inductively coupled plasma mass spectroscopy. The median concentration of plasma selenium was 213.0 μg/L. Elevated plasma selenium levels were associated with higher triglycerides, LDL-cholesterol, fasting plasma glucose, post-loading plasma glucose, A1c, HOMA-IR, as well as ALT, AST and γ-GT (all P < 0.05). The odds ratios were substantially higher for NAFLD (OR = 1.54, 95% CI 1.13–2.18) in the highest selenium quartile compared with those in the lowest quartile, after adjustment for potential cofounder. The results of this study provided epidemiological evidence that increased plasma selenium level is associated with elevated prevalence of NAFLD.

Repeated ozone exposure exacerbates insulin resistance and activates innate immune response in genetically susceptible mice

BACKGROUND

Inhaled ozone (O3) has been demonstrated as a harmful pollutant and associated with chronic inflammatory diseases such as diabetes and vascular disorders. However, the underlying mechanisms by which O3 mediates harmful effects are poorly understood.

OBJECTIVES

To investigate the effect of O3 exposure on glucose intolerance, immune activation and underlying mechanisms in a genetically susceptible mouse model.

METHODS

Diabetes-prone KK mice were exposed to filtered air (FA), or O3 (0.5 ppm) for 13 consecutive weekdays (4 h/day). Insulin tolerance test (ITT) was performed following the last exposure. Plasma insulin, adiponectin, and leptin were measured by ELISA. Pathologic changes were examined by H&E and Oil-Red-O staining. Inflammatory responses were detected using flow cytometry and real-time PCR.

RESULTS

KK mice exposed to O3 displayed an impaired insulin response. Plasma insulin and leptin levels were reduced in O3-exposed mice. Three-week exposure to O3 induced lung inflammation and increased monocytes/macrophages in both blood and visceral adipose tissue. Inflammatory monocytes/macrophages increased both systemically and locally. CD4 + T cell activation was also enhanced by the exposure of O3 although the relative percentage of CD4 + T cell decreased in blood and adipose tissue. Multiple inflammatory genes including CXCL-11, IFN-γ, TNFα, IL-12, and iNOS were up-regulated in visceral adipose tissue. Furthermore, the expression of oxidative stress-related genes such as Cox4, Cox5a, Scd1, Nrf1, and Nrf2, increased in visceral adipose tissue of O3-exposed mice.

CONCLUSIONS

Repeated O3 inhalation induces oxidative stress, adipose inflammation and insulin resistance.

Sparstolonin B attenuates early liver inflammation in experimental NASH by modulating TLR4 trafficking in lipid rafts via NADPH oxidase activation

Although significant research data exist on the pathophysiology of nonalcoholic steatohepatitis (NASH), finding an efficient treatment regimen for it remains elusive. The present study used sparstolonin B (SsnB), a novel TLR4 antagonist derived from the Chinese herb Sparganium stoloniferum, as a possible drug to mitigate early inflammation in NASH. This study used an early steatohepatitic injury model in high-fat-fed mice with CYP2E1-mediated oxidative stress as a second hit. SsnB was administered for 1 wk along with bromodichloromethane (BDCM), an inducer of CYP2E1-mediated oxidative stress. Results showed that SsnB administration attenuated inflammatory morphology and decreased elevation of the liver enzyme alanine aminotransferase (ALT). Mice administered SsnB also showed decreased mRNA expression of proinflammatory cytokines TNF-α, IFN-γ, IL-1β, and IL-23, while protein levels of both TNF-α and IL-1β were significantly decreased. SsnB significantly decreased Kupffer cell activation as evidenced by reduction in CD68 and monocyte chemoattractant protein-1 (MCP1) mRNA and protein levels with concomitant inhibition of macrophage infiltration in the injured liver. Mechanistically, SsnB decreased TLR4 trafficking to the lipid rafts, a phenomenon described by the colocalization of TLR4 and lipid raft marker flotillin in tissues and immortalized Kupffer cells. Since we have shown previously that NADPH oxidase drives TLR4 trafficking in NASH, we studied the role of SsnB in modulating this pathway. SsnB prevented NADPH oxidase activation in vivo and in vitro as indicated by decreased peroxynitrite formation. In summary, the present study reports a novel use of the TLR4 antagonist SsnB in mitigating inflammation in NASH and in parallel shows a unique molecular mechanism of decreasing nitrative stress.

Ambient Air Pollutants Have Adverse Effects on Insulin and Glucose Homeostasis in Mexican Americans

OBJECTIVE

Recent studies suggest that air pollution plays a role in type 2 diabetes (T2D) incidence and mortality. The underlying physiological mechanisms have yet to be established. We hypothesized that air pollution adversely affects insulin sensitivity and secretion and serum lipid levels.

RESEARCH DESIGN AND METHODS

Participants were selected from BetaGene (n = 1,023), a study of insulin resistance and pancreatic β-cell function in Mexican Americans. All participants underwent DXA and oral and intravenous glucose tolerance tests and completed dietary and physical activity questionnaires. Ambient air pollutant concentrations (NO2, O3, and PM2.5) for short- and long-term periods were assigned by spatial interpolation (maximum interpolation radius of 50 km) of data from air quality monitors. Traffic-related air pollution from freeways (TRAP) was estimated using the dispersion model as NOx. Variance component models were used to analyze individual and multiple air pollutant associations with metabolic traits.

RESULTS

Short-term (up to 58 days cumulative lagged averages) exposure to PM2.5 was associated with lower insulin sensitivity and HDL-to-LDL cholesterol ratio and higher fasting glucose and insulin, HOMA-IR, total cholesterol, and LDL cholesterol (LDL-C) (all P ≤ 0.036). Annual average PM2.5 was associated with higher fasting glucose, HOMA-IR, and LDL-C (P ≤ 0.043). The effects of short-term PM2.5 exposure on insulin sensitivity were largest among obese participants. No statistically significant associations were found between TRAP and metabolic outcomes.

CONCLUSIONS

Exposure to ambient air pollutants adversely affects glucose tolerance, insulin sensitivity, and blood lipid concentrations. Our findings suggest that ambient air pollutants may contribute to the pathophysiology in the development of T2D and related sequelae.

Influencing Factors of Thermogenic Adipose Tissue Activity

Obesity is an escalating public health challenge and contributes tremendously to the disease burden globally. New therapeutic strategies are required to alleviate the health impact of obesity-related metabolic dysfunction. Brown adipose tissue (BAT) is specialized for dissipating chemical energy for thermogenesis as a defense against cold environment. Intriguingly, the brown-fat like adipocytes that dispersed throughout white adipose tissue (WAT) in rodents and humans, called "brite" or "beige" adipocytes, share similar thermogenic characteristics to brown adipocytes. Recently, researchers have focused on cognition of these thermogenic adipose tissues. Some factors have been identified to regulate the development and function of thermogenic adipose tissues. Cold exposure, pharmacological conditions, and lifestyle can enhance non-shivering thermogenesis and metabolism via some mechanisms. However, environmental pollutants, such as ambient fine particulates and ozone, may impair the function of these thermogenic adipose tissues and thereby induce metabolic dysfunction. In this review, the origin, function and influencing factors of thermogenic adipose tissues were summarized and it will provide insights into identifying new therapeutic strategies for the treatment of obesity and obesity-related diseases.

Exposure to fine airborne particulate matters induces hepatic fibrosis in murine models

BACKGROUND & AIMS

Hepatic fibrosis, featured by the accumulation of excessive extracellular matrix in liver tissue, is associated with metabolic disease and cancer. Inhalation exposure to airborne particulate matter in fine ranges (PM2.5) correlates with pulmonary dysfunction, cardiovascular disease, and metabolic syndrome. In this study, we investigated the effect and mechanism of PM2.5 exposure on hepatic fibrogenesis.

METHODS

Both inhalation exposure of mice and in vitro exposure of specialized cells to PM2.5 were performed to elucidate the effect of PM2.5 exposure on hepatic fibrosis. Histological examinations, gene expression analyses, and genetic animal models were utilized to determine the effect and mechanism by which PM2.5 exposure promotes hepatic fibrosis.

RESULTS

Inhalation exposure to concentrated ambient PM2.5 induces hepatic fibrosis in mice under the normal chow or high-fat diet. Mice after PM2.5 exposure displayed increased expression of collagens in liver tissues. Exposure to PM2.5 led to activation of the transforming growth factor β-SMAD3 signaling, suppression of peroxisome proliferator-activated receptor γ, and expression of collagens in hepatic stellate cells. NADPH oxidase plays a critical role in PM2.5-induced liver fibrogenesis.

CONCLUSIONS

Exposure to PM2.5 exerts discernible effects on promoting hepatic fibrogenesis. NADPH oxidase mediates the effects of PM2.5 exposure on promoting hepatic fibrosis.

Extreme Air Pollution Conditions Adversely Affect Blood Pressure and Insulin Resistance: The Air Pollution and Cardiometabolic Disease Study

Mounting evidence supports that fine particulate matter adversely affects cardiometabolic diseases particularly in susceptible individuals; however, health effects induced by the extreme concentrations within megacities in Asia are not well described. We enrolled 65 nonsmoking adults with metabolic syndrome and insulin resistance in the Beijing metropolitan area into a panel study of 4 repeated visits across 4 seasons since 2012. Daily ambient fine particulate matter and personal black carbon levels ranged from 9.0 to 552.5 µg/m(3) and 0.2 to 24.5 µg/m(3), respectively, with extreme levels observed during January 2013. Cumulative fine particulate matter exposure windows across the prior 1 to 7 days were significantly associated with systolic blood pressure elevations ranging from 2.0 (95% confidence interval, 0.3-3.7) to 2.7 (0.6-4.8) mm Hg per SD increase (67.2 µg/m(3)), whereas cumulative black carbon exposure during the previous 2 to 5 days were significantly associated with ranges in elevations in diastolic blood pressure from 1.3 (0.0-2.5) to 1.7 (0.3-3.2) mm Hg per SD increase (3.6 µg/m(3)). Both black carbon and fine particulate matter were significantly associated with worsening insulin resistance (0.18 [0.01-0.36] and 0.22 [0.04-0.39] unit increase per SD increase of personal-level black carbon and 0.18 [0.02-0.34] and 0.22 [0.08-0.36] unit increase per SD increase of ambient fine particulate matter on lag days 4 and 5). These results provide important global public health warnings that air pollution may pose a risk to cardiometabolic health even at the extremely high concentrations faced by billions of people in the developing world today.

Endocrine disruptors and obesity

The increasing incidence of obesity is a serious global public health challenge. Although the obesity epidemic is largely fueled by poor nutrition and lack of exercise, certain chemicals have been shown to potentially have a role in its aetiology. A substantial body of evidence suggests that a subclass of endocrine-disrupting chemicals (EDCs), which interfere with endocrine signalling, can disrupt hormonally regulated metabolic processes, especially if exposure occurs during early development. These chemicals, so-called 'obesogens' might predispose some individuals to gain weight despite their efforts to limit caloric intake and increase levels of physical activity. This Review discusses the role of EDCs in the obesity epidemic, the latest research on the obesogen concept, epidemiological and experimental findings on obesogens, and their modes of action. The research reviewed here provides knowledge that health scientists can use to inform their research and decision-making processes.

Air pollution as a risk factor for type 2 diabetes

Recent studies in both humans and animals suggest that air pollution is an important risk factor for type 2 diabetes mellitus (T2DM). However, the mechanism by which air pollution mediates propensity to diabetes is not fully understood. While a number of epidemiologic studies have shown a positive association between ambient air pollution exposure and risk for T2DM, some studies have not found such a relationship. Experimental studies in susceptible disease models do support this association and suggest the involvement of tissues involved in the pathogenesis of T2DM such as the immune system, adipose, liver, and central nervous system. This review summarizes the epidemiologic and experimental evidence between ambient outdoor air pollution and T2DM.

Association of Roadway Proximity with Fasting Plasma Glucose and Metabolic Risk Factors for Cardiovascular Disease in a Cross-Sectional Study of Cardiac Catheterization Patients

BACKGROUND

The relationship between traffic-related air pollution (TRAP) and risk factors for cardiovascular disease needs to be better understood in order to address the adverse impact of air pollution on human health.

OBJECTIVE

We examined associations between roadway proximity and traffic exposure zones, as markers of TRAP exposure, and metabolic biomarkers for cardiovascular disease risk in a cohort of patients undergoing cardiac catheterization.

METHODS

We performed a cross-sectional study of 2,124 individuals residing in North Carolina (USA). Roadway proximity was assessed via distance to primary and secondary roadways, and we used residence in traffic exposure zones (TEZs) as a proxy for TRAP. Two categories of metabolic outcomes were studied: measures associated with glucose control, and measures associated with lipid metabolism. Statistical models were adjusted for race, sex, smoking, body mass index, and socioeconomic status (SES).

RESULTS

An interquartile-range (990 m) decrease in distance to roadways was associated with higher fasting plasma glucose (β = 2.17 mg/dL; 95% CI: -0.24, 4.59), and the association appeared to be limited to women (β = 5.16 mg/dL; 95% CI: 1.48, 8.84 compared with β = 0.14 mg/dL; 95% CI: -3.04, 3.33 in men). Residence in TEZ 5 (high-speed traffic) and TEZ 6 (stop-and-go traffic), the two traffic zones assumed to have the highest levels of TRAP, was positively associated with high-density lipoprotein cholesterol (HDL-C; β = 8.36; 95% CI: -0.15, 16.9 and β = 5.98; 95% CI: -3.96, 15.9, for TEZ 5 and 6, respectively).

CONCLUSION

Proxy measures of TRAP exposure were associated with intermediate metabolic traits associated with cardiovascular disease, including fasting plasma glucose and possibly HDL-C.

Air Pollution and Serum Glucose Levels: A Population-Based Study

Recent studies demonstrated an adverse effect of chronic exposure to air pollution (AP) on metabolic syndrome and its components. In a population-based study, we investigated the association between exposure to ambient AP and serum glucose (SG), among subjects with normal glucose, impaired fasting glucose (IFG), and diabetes mellitus (DM).We included 1,063,887 SG tests performed in 131,882 subjects (years 2001-2012). Exposure data included daily levels of SO2, NO2 and other pollutants of industrial, traffic, and nonanthropogenic sources. Demographical, clinical, and medications purchase data were assessed. Log-transformed SG levels were analyzed by linear mixed models adjusted for seasonal variables and personal characteristics.SG increases (%increase [95% CI]), among subjects with normal glucose, IFG, and DM, respectively, were associated with 6.36 ppb increase of NO2 measured 24 to 72 hours before the test (0.40% [0.31%; 0.50%], 0.56% [0.40%; 0.71%], and 1.08% [0.86%; 1.29%]); and with 1.17 ppb increase of SO2 measured 24 hours before the test (0.29% [0.22%; 0.36%], 0.20% [0.10%; 0.31%], and 0.33% [0.14%; 0.52%]). Among DM population, weakest association was observed among patients treated with Metformin (0.56% increase in SG [0.18%; 0.95%]).In conclusion, NO2 and SO2 exposure is associated with small but significantly increased levels of SG. Although DM patients were found to be more susceptible to the AP induced SG variations, Metformin treatment seem to have a protective effect. Given the chronic lifetime exposure to AP and the broad coverage of the population, even small associations such as those found in our study can be associated with detrimental health effects and may have profound public health implications.

Ambient air pollution: an emerging risk factor for diabetes mellitus

Growing evidence supports that air pollution has become an important risk factor for developing diabetes mellitus. Understanding the contributing effect of air pollution in population studies, elucidating the potential mechanisms involved, and identifying the most responsible pollutants are all required in order to promulgate successful changes in policy and to help formulate preventive measures in an effort to reduce the risk for diabetes. This review summarizes recent findings from epidemiologic studies and mechanistic insights that provide links between exposure to air pollution and a heightened risk for diabetes.

Petroleum coke in the urban environment: a review of potential health effects

Petroleum coke, or petcoke, is a granular coal-like industrial by-product that is separated during the refinement of heavy crude oil. Recently, the processing of material from Canadian oil sands in U.S. refineries has led to the appearance of large petcoke piles adjacent to urban communities in Detroit and Chicago. The purpose of this literature review is to assess what is known about the effects of petcoke exposure on human health. Toxicological studies in animals indicate that dermal or inhalation petcoke exposure does not lead to a significant risk for cancer development or reproductive and developmental effects. However, pulmonary inflammation was observed in long-term inhalation exposure studies. Epidemiological studies in coke oven workers have shown increased risk for cancer and chronic obstructive pulmonary diseases, but these studies are confounded by multiple industrial exposures, most notably to polycyclic aromatic hydrocarbons that are generated during petcoke production. The main threat to urban populations in the vicinity of petcoke piles is most likely fugitive dust emissions in the form of fine particulate matter. More research is required to determine whether petcoke fine particulate matter causes or exacerbates disease, either alone or in conjunction with other environmental contaminants.

Inhaled ozone (O3)-induces changes in serum metabolomic and liver transcriptomic profiles in rats

Air pollution has been linked to increased incidence of diabetes. Recently, we showed that ozone (O3) induces glucose intolerance, and increases serum leptin and epinephrine in Brown Norway rats. In this study, we hypothesized that O3 exposure will cause systemic changes in metabolic homeostasis and that serum metabolomic and liver transcriptomic profiling will provide mechanistic insights. In the first experiment, male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or O3 at 0.25, 0.50, or 1.0ppm, 6h/day for two days to establish concentration-related effects on glucose tolerance and lung injury. In a second experiment, rats were exposed to FA or 1.0ppm O3, 6h/day for either one or two consecutive days, and systemic metabolic responses were determined immediately after or 18h post-exposure. O3 increased serum glucose and leptin on day 1. Glucose intolerance persisted through two days of exposure but reversed 18h-post second exposure. O3 increased circulating metabolites of glycolysis, long-chain free fatty acids, branched-chain amino acids and cholesterol, while 1,5-anhydroglucitol, bile acids and metabolites of TCA cycle were decreased, indicating impaired glycemic control, proteolysis and lipolysis. Liver gene expression increased for markers of glycolysis, TCA cycle and gluconeogenesis, and decreased for markers of steroid and fat biosynthesis. Genes involved in apoptosis and mitochondrial function were also impacted by O3. In conclusion, short-term O3 exposure induces global metabolic derangement involving glucose, lipid, and amino acid metabolism, typical of a stress-response. It remains to be examined if these alterations contribute to insulin resistance upon chronic exposure.

Ozone exposure triggers insulin resistance through muscle c-Jun N-terminal kinase activation

A growing body of evidence suggests that exposure to traffic-related air pollution is a risk factor for type 2 diabetes. Ozone, a major photochemical pollutant in urban areas, is negatively associated with fasting glucose and insulin levels, but most aspects of this association remain to be elucidated. Using an environmentally realistic concentration (0.8 parts per million), we demonstrated that exposure of rats to ozone induced whole-body insulin resistance and oxidative stress, with associated endoplasmic reticulum (ER) stress, c-Jun N-terminal kinase (JNK) activation, and disruption of insulin signaling in skeletal muscle. Bronchoalveolar lavage fluids from ozone-treated rats reproduced this effect in C2C12 myotubes, suggesting that toxic lung mediators were responsible for the phenotype. Pretreatment with the chemical chaperone 4-phenylbutyric acid, the JNK inhibitor SP600125, or the antioxidant N-acetylcysteine alleviated insulin resistance, demonstrating that ozone sequentially triggered oxidative stress, ER stress, and JNK activation to impair insulin signaling in muscle. This study is the first to report that ozone plays a causative role in the development of insulin resistance, suggesting that it could boost the development of diabetes. We therefore provide a potential mechanism linking pollutant exposure and the increased incidence of metabolic diseases.

In Vivo Exposures to Particulate Matter Collected from Saudi Arabia or Nickel Chloride Display Similar Dysregulation of Metabolic Syndrome Genes

Particulate matter (PM) exposures have been linked to mortality, low birth weights, hospital admissions, and diseases associated with metabolic syndrome, including diabetes mellitus, cardiovascular disease, and obesity. In a previous in vitro and in vivo study, data demonstrated that PM(10μm) collected from Jeddah, Saudi Arabia (PMSA), altered expression of genes involved in lipid and cholesterol metabolism, as well as many other genes associated with metabolic disorders. PMSA contains a relatively high concentration of nickel (Ni), known to be linked to several metabolic disorders. In order to evaluate whether Ni and PM exposures induce similar gene expression profiles, mice were exposed to 100 μg/50 μl PM(SA) (PM-100), 50 μg/50 μl nickel chloride (Ni-50), or 100 μg/50 μl nickel chloride (Ni-100) twice per week for 4 wk and hepatic gene expression changes were determined. Ultimately, 55 of the same genes were altered in all 3 exposures. However, where the two Ni groups differed markedly was in the regulation (up or down) of these genes. Ni-100 and PM-100 groups displayed similar regulations, whereby 104 of the 107 genes were similarly modulated. Many of the 107 genes are involved in metabolic syndrome and include ALDH4A1, BCO2, CYP1A, CYP2U, TOP2A. In addition, the top affected pathways, such as fatty acid α-oxidation, and lipid and carbohydrate metabolism, are involved in metabolic diseases. Most notably, the top diseased outcome affected by these changes in gene expression was cardiovascular disease. Given these data, it appears that Ni and PM(SA) exposures display similar gene expression profiles, modulating the expression of genes involved in metabolic disorders.

The association between air pollutants and morbidity for diabetes and liver diseases modified by sexes, ages, and seasons in Tianjin, China

With the generalized linear model and natural splines (ns), we examined the association between outdoor air pollutants and daily morbidity for diabetes and liver disease stratified by sexes and ages based on 4 years of daily data (2008-2011) in Tianjin, China. Season effects of air pollutants including particulate matter (PM), sulfur dioxide (SO2), and nitrogen dioxide (NO2) were also investigated. An increase of 10 μg/m(3) in a 2-day average concentrations of particulate matter with diameters of 10 μm or less (PM10), SO2, and NO2 corresponds to increases in diabetes morbidity of 0.39 % (95 % confidence interval (CI), -0.42-1.12), 0.15 % (95 % CI, -0.25-0.54), and 1.22 % (95 % CI, 0.51-2.96), respectively. As for liver morbidity, the increases were -0.84 % (95 % CI, -2.33-0.62), 0.90 % (95 % CI, 0.50-1.74), and 1.10 % (95 % CI, -2.58-4.78), respectively. The effects were stronger in the cool season than those in the warm season; females and the elderly were generally more vulnerable to outdoor air pollution. This study possesses scientific implications and instructional significance for local environmental standards and medical policymaking.

Air pollution and risk of type 2 diabetes mellitus: a systematic review and meta-analysis

AIM

Whether exposure to relatively high levels of air pollution is associated with diabetes occurrence remains unclear. We sought to assess and quantify the association between exposure to major air pollutants and risk of type 2 diabetes.

METHODS

PubMed and EMBASE databases (through September 2013) were searched using a combination of terms related to exposure to gaseous (NO2 and NOx) or particulate matter pollutants (PM2.5, PM10 and PM10-2.5) and type 2 diabetes. Descriptive and quantitative information were extracted from selected studies. We used random-effects models meta-analysis to derive overall risk estimates per type of pollutant.

RESULTS

We included ten studies (five cross-sectional and five prospective), assessing the effects of air pollutants on the occurrence of diabetes. In prospective investigations, the overall effect on diabetes occurrence was significant for both NO2 (adjusted hazard ratio [HR], 1.13; 95% confidence interval [95%CI], 1.01-1.22; p < 0.001; I(2) = 36.4%, pheterogeneity = 0.208) and PM2.5 (HR, 1.11; 95%CI, 1.03-1.20; p < 0.001; I(2) = 0.0%, pheterogeneity = 0.827). Odds ratios were reported by two cross-sectional studies which revealed similar associations between both NO2 and PM2.5 with type 2 diabetes. Across studies, risk estimates were generally adjusted for age, gender, body mass index and cigarette smoking.

CONCLUSIONS

Available evidence supports a prospective association of main air pollutants with an increased risk for type 2 diabetes. This finding may have implications for population-based strategies to reduce diabetes risk.

Central IKKβ inhibition prevents air pollution mediated peripheral inflammation and exaggeration of type II diabetes

Background

Prior experimental and epidemiologic data support a link between exposure to fine ambient particulate matter (<2.5 μm in aerodynamic diameter, PM_2.5) and development of insulin resistance/Type II diabetes mellitus (Type II DM). We investigated the role of hypothalamic inflammation in PM_2.5-mediated diabetes development.

Methods

KKay mice, a genetically susceptible model of Type II DM, were assigned to either concentrated PM_2.5 or filtered air (FA) for 4–8 weeks via a versatile aerosol concentrator and exposure system, or administered intra-cerebroventricular with either IKKβ inhibitor (IMD-0354) or TNFα antibody (infliximab) for 4–5 weeks simultaneously with PM_2.5 exposure. Glucose tolerance, insulin sensitivity, oxygen consumption and heat production were evaluated. At euthanasia, blood, spleen, visceral adipose tissue and hypothalamus were collected to measure inflammatory cells using flow cytometry. Standard immunohistochemical methods and quantitative PCR were used to assess targets of interest.

Results

PM_2.5 exposure led to hyperglycemia and insulin resistance, which was accompanied by increased hypothalamic IL-6, TNFα, and IKKβ mRNA expression and microglial/astrocyte reactivity. Targeting the NFκB pathway with intra-cerebroventricular administration of an IKKβ inhibitor [IMD-0354, n = 8 for each group)], but not TNFα blockade with infliximab [(n = 6 for each group], improved glucose tolerance, insulin sensitivity, rectified energy homeostasis (O₂ consumption, CO₂ production, respiratory exchange ratio and heat generation) and reduced peripheral inflammation in response to PM_2.5.

Conclusions

Central inhibition of IKKβ prevents PM_2.5 mediated peripheral inflammation and exaggeration of type II diabetes. These results provide novel insights into how air pollution may mediate susceptibility to insulin resistance and Type II DM.