The modifying effect of vitamin C on the association between perfluorinated compounds and insulin resistance in the Korean elderly: a double-blind, randomized, placebo-controlled crossover trial

Associations of per- and polyfluoroalkyl substances, polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers with oxidative stress markers: A systematic review and meta-analysis

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) are intentionally produced persistent organic pollutants (POPs) that are resistant to environmental degradation. Previous in-vitro and in-vivo studies have shown that POPs can induce oxidative stress, which is linked to neurodegenerative diseases, cardiovascular diseases, and cancer. However, findings in epidemiological studies are inconsistent and an evidence synthesis study is lacking to summarize the existing literature and explore research gaps.

OBJECTIVE

We evaluated the effects of PFAS, PCBs, OCPs, and PBDEs, on oxidative stress biomarkers in epidemiological studies.

METHODS

A literature search was conducted in PubMed, Embase, and Cochrane CENTRAL to identify all published studies related to POPs and oxidative stress up to December 7th, 2022. We included human observational studies reporting at least one exposure to POPs and an oxidative stress biomarker of interest. Random-effects meta-analyses on standardized regression coefficients and effect direction plots with one-tailed sign tests were used for quantitative synthesis.

RESULTS

We identified 33 studies on OCPs, 35 on PCBs, 49 on PFAS, and 12 on PBDEs. Meta-analyses revealed significant positive associations of α-HCH with protein carbonyls (0.035 [0.017, 0.054]) and of 4'4-DDE with malondialdehyde (0.121 [0.056, 0.187]), as well as a significant negative association between 2'4-DDE and total antioxidant capacity (TAC) (-0.042 [-0.079, -0.004]), all β [95%CI]. Sign tests showed a significant positive association between PCBs and malondialdehyde (pone-tailed = 0.03). Additionally, we found significant negative associations of OCPs with acetylcholine esterase (pone-tailed = 0.02) and paraoxonase-1 (pone-tailed = 0.03). However, there were inconsistent associations of OCPs with superoxide dismutase, glutathione peroxidase, and catalase.

CONCLUSIONS

Higher levels of OCPs were associated with increased levels of oxidative stress through increased pro-oxidant biomarkers involving protein oxidation, DNA damage, and lipid peroxidation, as well as decreased TAC. These findings have the potential to reveal the underlying mechanisms of POPs toxicity.

The Hidden Threat: Endocrine Disruptors and Their Impact on Insulin Resistance

The association between Insulin resistance, a global health issue, and endocrine disruptors (EDCs), chemicals interfering with the endocrine system, has sparked concern in the scientific community. This article provides a comprehensive review of the existing literature regarding the intricate relationship between EDCs and insulin resistance. Phthalates, commonly found in consumer products, are well-established EDCs with documented effects on insulin-signaling pathways and metabolic processes. Epidemiological studies have connected phthalate exposure to an increased risk of type 2 diabetes mellitus (T2DM). Perfluoroalkyl substances (PFAS), persistent synthetic compounds, have shown inconsistent associations with T2DM in epidemiological research. However, studies suggest that PFAS may influence insulin resistance and overall metabolic health, with varying effects depending on specific PFAS molecules and study populations. Bisphenol A (BPA), found in plastics and resins, has emerged as a concern for glucose regulation and insulin resistance. Research has linked BPA exposure to T2DM, altered insulin release, obesity, and changes in the mass and function of insulin-secreting β-cells. Triclosan, an antibacterial agent in personal care products, exhibits gender-specific associations with T2DM risk. It may impact gut microbiota, thyroid hormones, obesity, and inflammation, raising concerns about its effects on metabolic health. Furthermore, environmental EDCs like polycyclic aromatic hydrocarbons, pesticides, and heavy metals have demonstrated associations with T2DM, insulin resistance, hypertension, and obesity. Occupational exposure to specific pesticides and heavy metals has been linked to metabolic abnormalities.

Association between perfluoroalkyl and polyfluoroalkyl internal exposure and serum α-Klotho levels in middle-old aged participants

Purpose

Exposure to perfluoroalkyl and polyfluoroalkyl substances causes oxidative stress, which is strongly associated with adverse health effects. Klotho protein plays an anti-aging role via antioxidation activity.

Methods

We investigated the levels of serum α-Klotho and PFAS exposure in adults who participated in the National Health and Nutrition Examination Survey from 2013 to 2016. A nationally representative subsample of 1,499 adults aged 40-79 years was analyzed for the associations of serum α-Klotho levels with serum PFAS exposures by correlation analysis and multiple general linear models. Of note, the potential confounding factors including age and gender were adjusted. Quantile-based g-computation models were used to assess the effects of mixed PFAS exposure on serum α-Klotho levels.

Results

The weighted geometric mean of serum α-Klotho was 791.38 pg/mL for the subjects during 2013-2016. After adjusting for potential confounders, serum Klotho levels showed a statistically significant downward trend with increasing quartiles of PFOA and PFNA. Multivariate adjusted general linear regression analysis showed that increased exposure to PFNA was substantially associated with lower serum levels of α-Klotho, and each 1-unit increase in PFNA concentration was accompanied by a 20.23 pg/mL decrease in α-Klotho level; while no significant association was observed between other PFAS exposures and serum α-Klotho levels. It was negatively correlated between α-Klotho and Q4 for PFNA relative to the lowest quartile (Q1) of exposure (P = 0.025). It was found that the strongest negative correlation between PFNA exposure and serum α-Klotho levels was in the middle-aged (40-59 years) female participants. Furthermore, the mixture of the four PFAS substances showed an overall inverse association with serum α-Klotho concentrations, with PFNA being the major contributor.

Conclusions

Taken together, in a representative sample of the U.S. middle-aged and elderly populations, serum concentrations of PFAS, especially PFNA, have been negatively associated with serum levels of α-Klotho, which is strongly associated with cognition and aging. It was important to note that the majority of associations were limited to middle-aged women. It will be meaningful to clarify the causal relationship and the pathogenic mechanisms of PFAS exposure and α-Klotho levels, which is helpful to aging and aging-related diseases.

Mitochondrial iron overload mediated by cooperative transfer of plasma membrane ATP5B and TFR2 to mitochondria triggers hepatic insulin resistance under PFOS exposure

In general populations, insulin resistance (IR) is related to perfluorooctane sulfonate (PFOS), a persistent organic pollutant. However, the underlying mechanism remains unclear. In this study, PFOS induced mitochondrial iron accumulation in the liver of mice and human hepatocytes L-O2. In the PFOS-treated L-O2 cells, mitochondrial iron overload preceded the occurrence of IR, and pharmacological inhibition of mitochondrial iron relieved PFOS-caused IR. Both transferrin receptor 2 (TFR2) and ATP synthase β subunit (ATP5B) were redistributed from the plasma membrane to mitochondria with PFOS treatment. Inhibiting the translocation of TFR2 to mitochondria reversed PFOS-induced mitochondrial iron overload and IR. In the PFOS-treated cells, ATP5B interacted with TFR2. Stabilizing ATP5B on the plasma membrane or knockdown of ATP5B disturbed the translocation of TFR2. PFOS inhibited the activity of plasma-membrane ATP synthase (ectopic ATP synthase, e-ATPS), and activating e-ATPS prevented the translocation of ATP5B and TFR2. Consistently, PFOS induced ATP5B/TFR2 interaction and redistribution of ATP5B and TFR2 to mitochondria in the liver of mice. Thus, our results indicated that mitochondrial iron overload induced by collaborative translocation of ATP5B and TFR2 was an up-stream and initiating event for PFOS-related hepatic IR, providing novel understandings of the biological function of e-ATPS, the regulatory mechanism for mitochondrial iron and the mechanism underlying PFOS toxicity.

Serum per- and polyfluoroalkyl substances and abnormal lipid metabolism: A nationally representative cross-sectional study

BACKGROUND

The associations of legacy per- and polyfluoroalkyl substances (PFAS) with lipid metabolism are controversial, and there is little information about the impact of emerging PFAS (6:2 Cl-PFESA) on lipid metabolism in China.

OBJECTIVES

We aimed to explore the associations of legacy and emerging PFAS with lipid profiles and dyslipidemia in Chinese adults.

METHODS

We included 10,855 Chinese participants aged 18 years and above in the China National Human Biomonitoring. The associations of 8 PFAS with 5 lipid profiles and 4 dyslipidemia were investigated using weighted multiple linear regression or weighted logistic regression, and the dose-response associations were investigated using restricted cubic spline model.

RESULTS

Among the 8 PFAS, the concentration of PFOS was the highest, with a geometric mean of 5.15 ng/mL, followed by PFOA and 6:2 Cl-PFESA, which were 4.26 and 1.63 ng/mL, respectively. Legacy (PFOA, PFOS, PFUnDA) or emerging (6:2 Cl-PFESA) PFAS were associated with lipid profiles (TC, LDL-C, HDL-C, non HDL-C) and dyslipidemia (high LDL-C, high TC, low HDL-C), and their effects on TC were most obvious. TC concentration increased by 0.595 mmol/L in the highest quartile (Q4) of PFOS when compared with the lowest quartile (Q1), (95 % CI:0.396, 0.794). Restricted cubic spline models showed that PFAS are nonlinearly associated with TC, non HDL-C, LDL-C and HDL-C, and that the lipid concentrations tend to be stable when PFOS and PFOA were > 20 ng/mL well as when the 6:2 Cl-PFESA level was > 10 ng/mL. The positive associations between PFAS mixtures and lipid profiles were also significant.

CONCLUSIONS

Single and mixed exposure to PFAS were positively associated with lipid profiles, and China's unique legacy PFAS substitutes (6:2 Cl-PFESA) contributed less to lipid profiles than legacy PFAS. In the future, cohort studies will be needed to confirm our findings.

Association between per- and polyfluoroalkyl substances exposure and risk of diabetes: a systematic review and meta-analysis

BACKGROUND

Emerging evidence suggests that per- and polyfluoroalkyl substances (PFAS) are endocrine disruptors and may contribute to the etiology of diabetes.

OBJECTIVES

This study aimed to systematically review the epidemiological evidence on the associations of PFAS with mortality and morbidity of diabetes and to quantitatively evaluate the summary effect estimates of the existing literature.

METHODS

We searched three electronic databases for epidemiological studies concerning PFAS and diabetes published before April 1, 2022. Summary odds ratio (OR), hazard ratio (HR), or β and their 95% confidence intervals (CIs) were respectively calculated to evaluate the association between PFAS and diabetes using random-effects model by the exposure type, and dose-response meta-analyses were also performed when possible. We also assessed the risk of bias of the studies included and the confidence in the body of evidence.

RESULTS

An initial literature search identified 1969 studies, of which 22 studies were eventually included. The meta-analyses indicated that the observed statistically significant PFAS-T2DM associations were consistent in cohort studies, while the associations were almost non-significant in case-control and cross-sectional studies. Dose-response meta-analysis showed a "parabolic-shaped" association between perfluorooctanoate acid (PFOA) exposure and T2DM risk. Available evidence was rated with "low" risk of bias, and the level of evidence for PFAS and incident T2DM was considered "moderate".

CONCLUSIONS

Our findings suggest that PFAS exposure may increase the risk of incident T2DM, and that PFOA may exert non-monotonic dose-response effect on T2DM risk. Considering the widespread exposure, persistence, and potential for adverse health effects of PFAS, further cohort studies with improvements in expanding the sample size, adjusting the covariates, and considering different types of PFAS exposure at various doses, are needed to elucidate the putative causal associations and potential mode of action of different PFAS on diabetes.

IMPACT STATEMENT

A growing body of evidence suggests that per- and polyfluoroalkyl substances (PFAS) are endocrine disruptors and may contribute to the development of diabetes. However, epidemiological evidence on the associations of PFAS and diabetes is inconsistent. We performed this comprehensive systematic review and meta-analysis to quantitatively synthesize the evidence. The findings of this study suggest that exposure to PFAS may increase diabetes risk among the general population. Reduced exposure to these "forever and everywhere chemicals" may be an important preventative approach to reducing the risk of diabetes across the population.

Associations of per- and polyfluoroalkyl substances (PFAS) and their mixture with oxidative stress biomarkers during pregnancy

BACKGROUND

Oxidative stress from excess reactive oxygen species (ROS) is a hypothesized contributor to preterm birth. Per- and polyfluoroalkyl substances (PFAS) exposure is reported to generate ROS in laboratory settings, and is linked to adverse birth outcomes globally. However, to our knowledge, the relationship between PFAS and oxidative stress has not been examined in the context of human pregnancy.

OBJECTIVE

To investigate the associations between prenatal PFAS exposure and oxidative stress biomarkers among pregnant people.

METHODS

Our analytic sample included 428 participants enrolled in the Illinois Kids Development Study and Chemicals In Our Bodies prospective birth cohorts between 2014 and 2019. Twelve PFAS were measured in second trimester serum. We focused on seven PFAS that were detected in >65 % of participants. Urinary levels of 8-isoprostane-prostaglandin-F_2α, prostaglandin-F_2α, 2,3-dinor-8-iso-PGF_2α, and 2,3-dinor-5,6-dihydro-8-iso-PGF_2α were measured in the second and third trimesters as biomarkers of oxidative stress. We fit linear mixed-effects models to estimate individual associations between PFAS and oxidative stress biomarkers. We used quantile g-computation and Bayesian kernel machine regression (BKMR) to assess associations between the PFAS mixture and averaged oxidative stress biomarkers.

RESULTS

Linear mixed-effects models showed that an interquartile range increase in perfluorooctane sulfonic acid (PFOS) was associated with an increase in 8-isoprostane-prostaglandin-F_2α (β = 0.10, 95 % confidence interval = 0, 0.20). In both quantile g-computation and BKMR, and across all oxidative stress biomarkers, PFOS contributed the most to the overall mixture effect. The six remaining PFAS were not significantly associated with changes in oxidative stress biomarkers.

CONCLUSIONS

Our study is the first to investigate the relationship between PFAS exposure and biomarkers of oxidative stress during human pregnancy. We found that PFOS was associated with elevated levels of oxidative stress, which is consistent with prior work in animal models and cell lines. Future research is needed to understand how prenatal PFAS exposure and maternal oxidative stress may affect fetal development.

Perfluorinated compounds in adults and their association with fasting glucose and incident diabetes: a prospective cohort study

BACKGROUND

The endocrine disruption of perfluorinated compounds is an emerging issue. We aimed to examine the association of serum perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) levels with incident diabetes and fasting serum glucose concentration.

METHODS

This prospective cohort study was based on an urban-based cohort subpopulation from the Korean Genome and Epidemiology Study. Serum samples (600 µL) were received from 100 participants in the normoglycemic baseline survey (2004-2013), and concentrations of PFOA and PFOS were measured using mass spectrometry. The incidence of diabetes was tracked in the follow-up survey (2012-2016).

RESULTS

The mean age was 56.4 years (men, 59%). The median serum PFOA and PFOS concentrations were 4.29 ng/mL and 9.44 ng/mL, respectively. PFOA and PFOS concentrations differed according to age, sex, and residential area. After 60 months, 23 patients had diabetes. Log-transformed PFOA (lnPFOA) and log-transformed PFOS (lnPFOS) were significantly higher in those who transitioned to diabetes than in those who did not (both p < 0.05). After multivariate adjustment, lnPFOA (coefficient = 6.98, 95% CI -0.04-14, p = 0.054) and lnPFOS (coefficient = 7.06, 95% CI -0.96-15.08, p = 0.088) predicted increased fasting glucose without statistical significance. In addition, lnPFOA, but not lnPFOS, significantly predicted incident diabetes (HR = 3.98, 95% CI 1.42-11.1, p < 0.01).

CONCLUSION

Exposure to PFOA and PFOS may have a potential dysglycemic effect. In particular, exposure to PFOA increased the risk of diabetes. Further research with larger sample size is warranted.

Characterization of Potential Adverse Outcome Pathways Related to Metabolic Outcomes and Exposure to Per- and Polyfluoroalkyl Substances Using Artificial Intelligence

Human exposure to per- and polyfluoroalkyl substances (PFAS) has been associated with numerous adverse health effects, depending on various factors such as the conditions of exposure (dose/concentration, duration, route of exposure, etc.) and characteristics associated with the exposed target (e.g., age, sex, ethnicity, health status, and genetic predisposition). The biological mechanisms by which PFAS might affect systems are largely unknown. To support the risk assessment process, AOP-helpFinder, a new artificial intelligence tool, was used to rapidly and systematically explore all available published information in the PubMed database. The aim was to identify existing associations between PFAS and metabolic health outcomes that may be relevant to support building adverse outcome pathways (AOPs). The collected information was manually organized to investigate linkages between PFAS exposures and metabolic health outcomes, including dyslipidemia, hypertension, insulin resistance, and obesity. Links between PFAS exposure and events from the existing metabolic-related AOPs were also retrieved. In conclusion, by analyzing dispersed information from the literature, we could identify some associations between PFAS exposure and components of existing AOPs. Additionally, we identified some linkages between PFAS exposure and metabolic outcomes for which only sparse information is available or which are not yet present in the AOP-wiki database that could be addressed in future research.

Perfluorooctane sulfonate induces mitochondrial calcium overload and early hepatic insulin resistance via autophagy/detyrosinated alpha-tubulin-regulated IP3R2-VDAC1-MICU1 interaction

Perfluorooctane sulfonate (PFOS), one kind of persistent organic pollutants, is associated with insulin resistance (IR) in general population. However, the exact mechanism is still obscure. In this study, we found that 50 μM PFOS caused IR in L-02 hepatocytes after 1 h, and induced autophagy and mitochondrial calcium (Ca²⁺) accumulation as early as 0.5 h. Inhibiting autophagy relieved mitochondrial Ca²⁺ overload and then reversed IR. Mitochondria were aggregated at cell periphery, and extracellular Ca²⁺ from IP3R2 on the plasma membrane, rather than endoplasmic reticulum Ca²⁺, was the priority source of mitochondrial Ca²⁺ uptake at early stages of PFOS exposure. Furthermore, we discovered that the linkage connecting autophagy and mitochondrial Ca²⁺ response was detyrosinated α-tubulin, which autophagy-dependently ascended, interacted with VDAC1 and enhanced the formation of IP3R2-VDAC1-MICU1 complex. Consistently, PFOS caused IR, activated autophagy, induced mitochondrial Ca²⁺ overload, increased the level of detyrosinated α-tubulin, and promoted the formation of IP3R2-VDAC1-MICU1 complex in the liver of C57BL/6J mice exposed to 2.5 mg/kg/day PFOS for 6 weeks. This study clarified that autophagy and mitochondrial Ca²⁺ accumulation were the early and triggering event that caused PFOS-related IR, also unveiled a novel mechanism regulating mitochondrial Ca²⁺ homeostasis.

Associations between both legacy and alternative per- and polyfluoroalkyl substances and glucose-homeostasis: The Isomers of C8 health project in China

BACKGROUND

Epidemiological studies on the associations of legacy per- and polyfluoroalkyl substances (PFASs) and glucose homeostasis remain discordant. Understanding of PFAS alternatives is limited, and few studies have reported joint associations of PFASs and PFAS alternatives.

OBJECTIVES

To investigate associations of novel PFAS alternatives (chlorinated perfluoroalkyl ether sulfonic acids, Cl-PFESAs and perfluorobutanoic acid, PFBA) and two legacy PFASs (Perfluorooctanoic acid, PFOA and perfluorooctane sulfonate, PFOS) with glucose-homeostasis markers and explore joint associations of 13 legacy and alternative PFASs with the selected outcomes.

METHODS

We used cross-sectional data of 1,038 adults from the Isomers of C8 Health Project in China. Associations of PFASs and PFAS alternatives with glucose-homeostasis were explored in single-pollutant models using generalized linear models with natural cubic splines for PFASs. Bayesian Kernel Machine Regression (BKMR) models were applied to assess joint associations of exposures and outcomes. Sex-specific analyses were also conducted to evaluate effect modification.

RESULTS

After adjusting for confounders, both legacy (PFOA, PFOS) and alternative (Cl-PFESAs and PFBA) PFASs were positively associated with glucose-homeostasis markers in single-pollutant models. For example, in the total study population, estimated changes with 95% confidence intervals (CI) of fasting glucose at the 95th percentile of 6:2Cl-PFESA and PFOS against the thresholds were 0.90 (95% CI: 0.59, 1.21) and 0.44 (95% CI: 0.26, 0.62). Positive joint associations were found in BKMR models with 6:2Cl-PFESA contributing most. Sex-specific associations existed in both single- and multi-pollutant models.

CONCLUSIONS

Legacy and alternative PFASs were positively associated with glucose-homeostasis markers. 6:2Cl-PFESA was the primary contributor. Sex-specific associations were also identified. These results indicate that joint associations and effect modification should be considered in risk assessment. However, further studies are recommended to strengthen our findings and to elucidate the mechanisms of action of legacy and alternative PFASs.

Exposure to per- and polyfluoroalkyl substances (PFAS) and type 2 diabetes risk

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous man-made chemicals found in consumer products including fabrics, food packaging, non-stick coatings, and aqueous film-forming foams. PFAS are stable and extremely resistant to degradation, resulting in high persistence throughout the environment as well as in human blood. PFAS consist of a large family of synthetic chemicals, with over 4000 distinct varieties having been identified and around 250 currently being manufactured at globally relevant levels. Numerous epidemiological studies have linked exposure to PFAS with adverse health effects ranging from immunotoxicity, cardiometabolic disease, developmental and reproductive effects, cancer, and recently type 2 diabetes. Several studies have demonstrated associations between serum PFAS concentrations and glycemic indicators of type 2 diabetes including glucose, insulin, and HOMA-IR in adolescent and adult cohorts. In addition, some studies have shown positive associations with incident type 2 diabetes and multiple PFAS. However, the link between PFAS exposure and the development of diabetes continues to be a disputed area of study, with conflicting data having been reported from various epidemiological studies. In this mini review we will summarize the current state of the literature linking PFAS to type 2 diabetes and discuss important future directions including the use of more complex mixtures-based statistical analyses.

Associations between Exposures to Perfluoroalkyl Substances and Diabetes, Hyperglycemia, or Insulin Resistance: A Scoping Review

Per- and polyfluoroalkyl substances (PFASs) are persistent environmental pollutants that are commonly found in the human body due to exposures via drinking water, surfactants used in consumer materials, and aqueous film-forming foams (AFFFs). PFAS exposure has been linked to adverse health effects such as low infant birth weights, cancer, and endocrine disruption, though increasingly studies have demonstrated that they may perturb metabolic processes and contribute to dysfunction. This scoping review summarizes the chemistry of PFAS exposure and the epidemiologic evidence for associations between exposure to per- and polyfluoroalkyl substances and the development of diabetes, hyperglycemia, and/or insulin resistance. We identified 11 studies on gestational diabetes mellitus, 3 studies on type 1 diabetes, 7 studies on type 2 diabetes, 6 studies on prediabetes or unspecified diabetes, and 15 studies on insulin resistance or glucose tolerance using the SCOPUS and PubMed databases. Approximately 24 reported positive associations, 9 negative associations, 2 non-linear associations, and 2 inverse associations, and 8 reported no associations found between PFAS and all diabetes search terms. Cumulatively, these data indicate the need for further studies to better assess these associations between PFAS exposure and diabetes.

Exposure to Perfluoroalkyl Chemicals and Cardiovascular Disease: Experimental and Epidemiological Evidence

Polyfluoro- and perfluoro-alkyl substances (PFAS) are organic chemicals extensively used worldwide for industry and consumer products. Due to their chemical stability, PFAS represent a major cause of environmental pollution. PFAS accumulate in animal and human blood and tissues exerting their toxicity. We performed a review of the epidemiological studies exploring the relationship between exposure to PFAS and thromboembolic cardiovascular disease. An increase in cardiovascular disease or death related to PFAS exposure has been reported from cross-sectional and longitudinal observational studies with evidence concerning the relation with early vascular lesions and atherosclerosis. Several studies indicate an alteration in lipid and glucose metabolism disorders and increased blood pressure as a possible link with cardiovascular thromboembolic events. We also examined the recent evidence indicating that legacy and new PFAS can be incorporated in platelet cell membranes giving a solid rationale to the observed increase risk of cardiovascular events in the populations exposed to PFAS by directly promoting thrombus formation. Exposure to PFAS has been related to altered plasma membrane fluidity and associated with altered calcium signal and increased platelet response to agonists, both in vitro and ex vivo in subjects exposed to PFAS. All the functional responses are increased in platelets by incorporation of PFAS: adhesion, aggregation, microvesicles release and experimental thrombus formation. These findings offer mechanistic support the hypothesis that platelet-centred mechanisms may be implicated in the increase in cardiovascular events observed in populations chronically exposed to PFAS.

Functional benefit and molecular mechanism of vitamin C against perfluorooctanesulfonate-associated leukemia

Perfluorooctanesulfonate (PFOS) is a persistent pollutant that can induce toxic effects, including leukemia, on blood cells. Vitamin C (VC), a functional nutrient, has been found to possess potent cytoprotective effects. However, there are currently no reports on its ability to treat PFOS-associated leukemia. This study used a molecular networking analysis to reveal the functional action and pharmacological mechanism of VC against PFOS-associated leukemia. The biological informatics findings revealed a total of 17 intersection targets against PFOS-associated leukemia. In addition, seven core-functional targets, including tumor protein p53 (TP53), mitogen-activated protein kinase 1 (MAPK1), estrogen receptor 1 (ESR1), sirtuin 1 (SIRT1), nitric oxide synthase 3 (NOS3), myeloid cell leukemia-1 (MCL1), and telomerase reverse transcriptase (TERT), were screened and identified. Notably, the molecular docking findings indicated that TP53, MAPK1, and ESR1 were potent pharmacological targets of VC against PFOS-associated leukemia. Moreover, the pharmacological functions including biological processes, cell components, and molecular pathways of VC against PFOS-associated leukemia were determined. According to the computational findings, we conclude that VC protects against PFOS-associated leukemia action by suppressing leukemia-associated cell proliferation and tumor growth. The validated genes of TP53, MAPK1, ESR1 may become potential biomarkers for monitoring and treating PFOS-associated leukemia.

Per- and Polyfluoroalkyl Substances and Obesity, Type 2 Diabetes and Non-alcoholic Fatty Liver Disease: A Review of Epidemiologic Findings

Per- and polyfluoroalkyl substances, a group of fluoro-surfactants widely detected in the environment, wildlife and humans, have been linked to adverse health effects. A growing body of literature has addressed their effects on obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis. This review summarizes the brief historical use and chemistry of per- and polyfluoroalkyl substances, routes of human exposure, as well as the epidemiologic evidence for associations between exposure to per- and polyfluoroalkyl substances and the development of obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis. We identified 22 studies on obesity and 32 studies on diabetes, while only 1 study was found for non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis by searching PubMed for human studies. Approximately 2/3 of studies reported positive associations between per- and polyfluoroalkyl substances exposure and the prevalence of obesity and/or type 2 diabetes. Causal links between per- and polyfluoroalkyl substances and obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis, however, require further large-scale prospective cohort studies combined with mechanistic laboratory studies to better assess these associations.

The association between total serum isomers of per- and polyfluoroalkyl substances, lipid profiles, and the DNA oxidative/nitrative stress biomarkers in middle-aged Taiwanese adults

Per- and polyfluoroalkyl substances (PFAS) have been widely used in consumer products. In vitro and animal studies have demonstrated that exposure to perfluorooctanoic acid (PFOA) and/or perfluorooctane sulfonate (PFOS) increases oxidative/nitrative stress. Recent studies have also found that isomers of PFOA/PFOS may have unique biological effects on clinical parameters. However, the correlation between PFOA/PFOS isomers and markers of oxidative/nitrative stress has never been investigated in the general population. In the current study, 597 adult subjects (ages between 22 and 63 years old) were enrolled from a control group of a case-control study entitled "Work-related risk factors and coronary heart disease". We investigated the correlation between the serum isomers of PFOA/PFOS, lipid profiles, and the urine compounds 8-hydroxy-2-deoxyguanosine (8-OHdG) and 8-nitroguanine (8-NO2Gua) in these participants. There were 519 men and 78 women with a mean age of 45.8 years. Linear PFOA levels were positively correlated with serum low density lipoprotein cholesterol (LDL-C), small dense LDL, and triglyceride, and linear PFOS levels were positively correlated with LDL-C and HDL-C in multiple linear regression analyses. After controlling for potential confounders, the mean levels of 8-OHdG and 8-NO2Gua significantly increased across the quartiles of linear PFOS in multiple linear regression analyses. When both the 8-OHdG and 8-NO2Gua levels were above the 50th percentile, the odds ratio (OR) of higher levels of LDL-C (>75th percentile) with one unit increase in ln linear PFOS level was the highest (OR 3.15 (95% CI = 1.45-6.64), P = 0.003) in logistic regression models. In conclusion, serum linear PFOA/PFOS were correlated with lipid profiles, and linear PFOS was associated with urine oxidative/nitrative stress biomarkers. The positive correlation between linear PFOS and LDL-C was more marked when concentrations of urine oxidative/nitrative stress biomarkers were elevated. Further studies are needed to elucidate the causal relationships among PFAS isomers, lipid profiles, and oxidative/nitrative stress.

Associations of Perfluoroalkyl and Polyfluoroalkyl Substances With Incident Diabetes and Microvascular Disease

OBJECTIVE

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are suspected endocrine disruptors widely detected across populations. We examine the extent to which PFASs are associated with diabetes incidence and microvascular disease. Secondarily, we tested whether a lifestyle intervention modifies associations and decreases concentrations.

RESEARCH DESIGN AND METHODS

We analyzed data from a prospective cohort of 957 participants from the Diabetes Prevention Program (DPP) trial and Diabetes Prevention Program Outcomes Study (DPPOS). At baseline, participants were randomized to an intensive lifestyle intervention of diet, physical activity, and behavior modification or a placebo medication. We quantified plasma concentrations of six PFASs at baseline and 2 years after randomization. Participants were monitored for ∼15 years, repeatedly tested for diabetes, and evaluated for microvascular disease at the end of the follow-up.

RESULTS

A doubling in baseline branched perfluorooctanoic acid concentration was associated with a 14% increase in diabetes risk for the placebo (hazard ratio [HR] 1.14, 95% CI 1.04, 1.25) but not in the lifestyle intervention group (HR 1.01, 95% CI 0.92, 1.11, P interaction = 0.11). Mean change in plasma baseline branched perfluorooctanoic acid concentration was greater for the placebo (0.96 ng/mL; 95% CI 0.71, 1.22) compared with the lifestyle intervention group (0.31 ng/mL; 95% CI 0.14, 0.48) 2 years after randomization. Each doubling in N-ethyl-perfluorooctane sulfonamido acetic acid was associated with 17% greater odds of prevalent microvascular disease (OR 1.17, 95% CI 1.05, 1.31), and a similar association was observed for perfluorodimethylhexane sulfonic acid (OR 1.18, 95% CI 1.04, 1.35), regardless of treatment.

CONCLUSIONS

Some plasma PFASs were associated with diabetes and microvascular disease. Our results suggest that exercise and diet may attenuate the diabetogenic association of PFASs.

Association of Perfluoroalkyl and Polyfluoroalkyl Substances With Adiposity

IMPORTANCE

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are ubiquitous synthetic chemicals that are suspected endocrine disruptors.

OBJECTIVES

To determine the extent to which PFASs are associated with increases in weight and body size and evaluate whether a lifestyle intervention modifies this association.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study included 957 individuals who participated in the Diabetes Prevention Program trial, conducted from July 1996 to May 2001, and the Diabetes Prevention Program Outcomes Study, conducted from September 2002 to January 2014. Statistical analysis was conducted from September 1, 2017, to May 25, 2018.

INTERVENTIONS AND EXPOSURES

The initial lifestyle intervention consisted of training in diet, physical activity, and behavior modification, with the major goals of achieving 7% weight loss with subsequent maintenance and a minimum of 150 minutes per week of physical activity. Participants randomized to placebo received standard information about diet and exercise. A total of 6 plasma PFASs were quantified at baseline and 2 years after randomization, means were calculated from baseline and year 2 concentrations, and means were summed to assess total PFAS burden.

MAIN OUTCOMES AND MEASURES

Weight, waist circumference, and hip girth were measured at baseline and at scheduled visits.

RESULTS

Of the 957 participants, 625 (65.3%) were women and 731 participants (76.4%) were between 40 and 64 years of age; 481 participants were randomized to the lifestyle intervention and 476 participants were randomized to the placebo arm. The PFAS concentrations were not different by treatment arm and were similar to concentrations reported for the US population in 1999-2000. The association of PFAS and weight change differed by treatment. Each doubling in total PFAS concentration was associated with an increase of 1.80 kg (95% CI, 0.43-3.17 kg; P = .01) from baseline to 9 years after randomization for the placebo group but not the lifestyle intervention group (-0.59 kg; 95% CI, -1.80 to 0.62 kg; P = .34). Similarly, each doubling in PFAS was associated with a 1.03-cm increase in hip girth in the Diabetes Prevention Program trial for the placebo group (95% CI, 0.18-1.88 cm; P = .02) but not the lifestyle intervention group (-0.09 cm; 95% CI, -0.82 to 0.63 cm; P = .80). No associations were observed for changes in mean waist circumference.

CONCLUSIONS AND RELEVANCE

Among adults at high risk for diabetes, higher plasma PFAS concentration was associated with increases in weight and hip girth over time, but a lifestyle intervention attenuated these associations. Diet and exercise may mitigate the obesogenic effects of environmental chemicals.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00004992 and NCT00038727.

Vitamin C deficiency aggravates tumor necrosis factor α-induced insulin resistance

Chronic low-grade inflammation plays a major role in the development of insulin resistance. The potential role and underlying mechanism of vitamin C, an antioxidant and anti-inflammatory agent, was investigated in tumor necrosis factor-α (TNF-α)-induced insulin resistance. Gulonolactone oxidase knockout (Gulo^-/-) mice genetically unable to synthesize vitamin C were used to induce insulin resistance by continuously pumping small doses of TNF-α for seven days, and human liver hepatocellular carcinoma cells (HepG2 cells) were used to induce insulin resistance by treatment with TNF-α. Vitamin C deficiency aggravated TNF-α-induced insulin resistance in Gulo^-/- mice, resulting in worse glucose tolerance test (GTT) results, higher fasting plasma insulin level, and the inactivation of the protein kinase B (AKT)/glycogen synthase kinase-3β (GSK3β) pathway in the liver. Vitamin C deficiency also worsened liver lipid accumulation and inflammation in TNF-α-treated Gulo^-/- mice. In HepG2 cells, vitamin C reversed the TNF-α-induced reduction of glucose uptake and glycogen synthesis, which were mediated by increasing GLUT2 levels and the activation of the insulin receptor substrate (IRS-1)/AKT/GSK3β pathway. Furthermore, vitamin C inhibited the TNF-α-induced activation of not only the mitogen-activated protein kinase (MAPKs), but also nuclear factor-kappa B (NF-κB) signaling. Taken together, vitamin C is essential for preventing and improving insulin resistance, and the supplementing with vitamin C may be an effective therapeutic intervention for metabolic disorders.

The role of pollutants in type 2 diabetes mellitus (T2DM) and their prospective impact on phytomedicinal treatment strategies

Type 2 diabetes mellitus (T2DM) is the most common form of diabetes and it is characterized by high blood sugar and abnormal sera lipid levels. Although the specific reasons for the development of these abnormalities are still not well understood, traditionally, genetic and lifestyle behavior have been reported as the leading causes of this disease. In the last three decades, the number of diabetic patients has drastically increased worldwide, with current statistics suggesting the number is to double in the next two decades. To combat this incurable ailment, orthodox medicines, to which economically disadvantaged patients have minimal access to, have been used. Thus, a considerable amalgamation of medicinal plants has recently been proven to possess therapeutic capabilities to manage T2DM, and this has prompted studies primarily focusing on the healing aspect of these plants, and ultimately, their commercialization. Hence, this review aims to highlight the potential threat of pollutants, i.e., polyfluoroalkyl compounds (PFCs), endocrine disrupting chemicals (EDCs) and heavy metals, to medicinal plants, and their prospective impact on the phytomedicinal therapy strategies for T2DM. It is further suggested that auxiliary research be undertaken to better comprehend the factors that influence the uptake of these compounds by these plants. This should include a comprehensive risk assessment of phytomedicinal products destined for the treatment of T2DM. Regulations that control the use of PFC-precursors in certain developing countries are also long overdue.

Association among total serum isomers of perfluorinated chemicals, glucose homeostasis, lipid profiles, serum protein and metabolic syndrome in adults: NHANES, 2013-2014

Perfluorinated chemicals (PFCs) have been used widely in consumer products manufacture. Recent in vitro as well as animal studies have found that there are different toxicity and pharmacokinetic profiles between isomers of perfluorooctanoic acid (PFOA) and/or perfluorooctane sulfonate (PFOS). However, the differential effects of linear or branched PFOA/PFOS isomers on human beings have never been reported. Herein, we examined 1871 adult subjects (age older than 18 years) from the National Health and Nutrition Examination Survey (NHANES) 2013-2014 to determine the association between the isomers of PFOA/PFOS and serum biochemistry profiles, including glucose, lipids, protein and components of metabolic syndrome (MS). The results showed that for PFOA, increased linear PFOA was associated with increases in total cholesterol, serum albumin and an enhancement of β cell function as well as a decrease in the serum globulin. Increased branched PFOA was significantly associated with increased fasting glucose. All isomers of PFOA were positively associated with high-density lipoprotein-cholesterol (HDL-C) and negatively associated with glycohemoglobin (HbA1C). The branched PFOS was positively associated with β cell function and inversely associated with serum globulin. Both linear and branched isomers of PFOS were positively associated with the total protein and albumin. The increased branched PFOA was associated with less HDL-C insufficiency defined by the National Cholesterol Education Program Third Adult Treatment Panel (NCEP-ATP III) MS criteria, whereas the increased concentrations of serum total and linear PFOS were associated with less hypertriglyceridemia by the NCEP-ATP III. In conclusion, serum isomers of PFOA and PFOS were associated with glucose homeostasis, serum protein as well as lipid profiles; they were also indicators of MS. This may suggest that there is a distinct difference in the toxicokinetics of the isomers of PFOA and PFOS. Further clinical and animal studies are warranted to clarify the putative causal relationships between isomers and biochemical alterations.

Bisphenol A induces COX-2 through the mitogen-activated protein kinase pathway and is associated with levels of inflammation-related markers in elderly populations

Bisphenol A (BPA) is a well-known endocrine-disrupting chemical, and it is one of the highest volume chemicals produced worldwide. Even though several in vivo and in vitro studies showed positive associations of BPA exposure with pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin (IL)-6, the mechanism by which BPA induces inflammation is unclear. We investigated the mechanism by which BPA induces inflammation (expression of inflammation-related genes, changes in oxidative stress, and cell proliferation and migration) and evaluated the effect of BPA exposure on inflammation-related markers in epidemiologic studies using repeat urine and serum samples from elderly subjects. BPA induced COX-2 expression via nuclear translocation of NF-κB and activation of mitogen-activated protein kinase (MAPK) by phosphorylation of ERK1/2 and enhanced the migration of lung cancer A549 and breast cancer MDAMB-231 cells. In two epidemiologic studies, we detected associations of BPA with six inflammation-related markers (WBC, CRP, IL-10, ALT, AST, and γ-GTP levels). Our findings probably suggest that BPA exposure induces inflammation and exacerbates tumorigenesis.

Perfluorooctane sulfonate-induced insulin resistance is mediated by protein kinase B pathway

Perfluorooctane sulfonate (PFOS), a persistent organic pollutant, is blamed to be associated with the incidence of insulin resistance in the general human population. In this study, we found that PFOS inhibited the phosphorylation and activation of protein kinase B (AKT), a key mediator of cellular insulin sensitivity, in human hepatoma HepG2 cells. The mRNA level of the gluconeogenic gene PEPCK, a downstream target gene of AKT, was increased in PFOS-treated cells. Due to stimulated gluconeogenesis, insulin-stimulated glucose uptake was decreased in HepG2 cells. In our previous study, we found that PFOS disturbed autophagy in HepG2 cells. We proposed that PFOS could inhibit the activation of AKT through inhibiting mTORC2, a key regulator of autophagy. In this study, we found that the levels of triglyceride were increased in HepG2 cells. PFOS-induced accumulation of hepatic lipids also contributed to the inhibition of AKT. Eventually, the inhibition of AKT led to insulin resistance in PFOS-treated cells. Our data would provide new mechanistic insights into PFOS-induced hepatic insulin resistance.