Per- and polyfluoroalkyl substances exposure and its influence on the intestinal barrier: An overview on the advances

Ultra-processed foods and food additives in gut health and disease

Ultra-processed foods (UPFs) and food additives have become ubiquitous components of the modern human diet. There is increasing evidence of an association between diets rich in UPFs and gut disease, including inflammatory bowel disease, colorectal cancer and irritable bowel syndrome. Food additives are added to many UPFs and have themselves been shown to affect gut health. For example, evidence shows that some emulsifiers, sweeteners, colours, and microparticles and nanoparticles have effects on a range of outcomes, including the gut microbiome, intestinal permeability and intestinal inflammation. Broadly speaking, evidence for the effect of UPFs on gut disease comes from observational epidemiological studies, whereas, by contrast, evidence for the effect of food additives comes largely from preclinical studies conducted in vitro or in animal models. Fewer studies have investigated the effect of UPFs or food additives on gut health and disease in human intervention studies. Hence, the aim of this article is to critically review the evidence for the effects of UPF and food additives on gut health and disease and to discuss the clinical application of these findings.

Insights into PFAS environmental fate through computational chemistry: A review

Per- and polyfluoroalkyl substances (PFAS) are widely used chemicals that exhibit exceptional chemical and thermal stability. However, their resistance to degradation has led to their widespread environmental contamination. PFAS also negatively affect the environment and other organisms, highlighting the need for effective remediation methods to mitigate their presence and prevent further contamination. Computational chemistry methods, such as Density Functional Theory (DFT) and Molecular Dynamics (MD) offer valuable tools for studying PFAS and simulating their interactions with other molecules. This review explores how computational chemistry methods contribute to understanding and tackling PFAS in the environment. PFAS have been extensively studied using DFT and MD, each method offering unique advantages and computational limitations. MD simulates large macromolecules systems however it lacks the ability model chemical reactions, while DFT provides molecular insights however at a high computational cost. The integration of DFT with MD shows promise in predicting PFAS behavior in different environments. This work summarizes reported studies on PFAS compounds, focusing on adsorption, destruction, and bioaccumulation, highlighting contributions of computational methods while discussing the need for continued research. The findings emphasize the importance of computational chemistry in addressing PFAS contamination, guiding risk assessments, and informing future research and innovations in this field.

Poly- and perfluoroalkyl substances (PFASs) in amphibians and reptiles - exposure and health effects

Poly- and perfluoroalkyl substances (PFASs) are commonly used in various industries and everyday products, including clothing, electronics, furniture, paints, and many others. PFASs are primarily found in aquatic environments, but also present in soil, air and plants, making them one of the most important and dangerous pollutants of the natural environment. PFASs bioaccumulate in living organisms and are especially dangerous to aquatic and semi-aquatic animals. As endocrine disruptors, PFASs affect many internal organs and systems, including reproductive, endocrine, nervous, cardiovascular, and immune systems. This manuscript represents the first comprehensive review exclusively focusing on PFASs in amphibians and reptiles. Both groups of animals are highly vulnerable to PFASs in the natural habitats. Amphibians and reptiles, renowned for their sensitivity to environmental changes, are often used as crucial bioindicators to monitor ecosystem health and environmental pollution levels. Furthermore, the decline in amphibian and reptile populations worldwide may be related to increasing environmental pollution. Therefore, studies investigating the exposure of amphibians and reptiles to PFASs, as well as their impacts on these organisms are essential in modern toxicology. Summarizing the current knowledge on PFASs in amphibians and reptiles in a single manuscript will facilitate the exploration of new research topics in this field. Such a comprehensive review will aid researchers in understanding the implications of PFASs exposure on amphibians and reptiles, guiding future investigations to mitigate their adverse effects of these vital components of ecosystems.

Association of per- and polyfluoroalkyl substances with constipation: The National Health and Nutrition Examination Survey (2005-2010)

BACKGROUND

The impact of per- and polyfluoroalkyl substances (PFAS) on constipation, as mediated through gastrointestinal absorption and perturbations to the intestinal microecology, remains poorly understood.

OBJECTIVE

This study seeks to explain the relationship between PFAS and constipation.

METHODS

A total of 2945 adults from the National Health and Nutrition Examination Survey (NHANES) 2005-2010 were included in this study. Constipation was defined using the Bristol Stool Form Scale (BSFS) based on stool consistency. The relationship between PFAS and constipation was evaluated using weighted logistic regression and restricted cubic spline (RCS) analysis, while adjusting for confounding variables.

RESULTS

The weighted median concentration of total PFAS (ΣPFAS) was significantly lower in individuals with constipation (19.01 μg/L) compared to those without constipation (23.30 μg/L) (p < 0.0001). Subgroup analysis revealed that the cumulative effect of PFAS was more pronounced in the elderly, men, individuals with obesity, high school education or equivalent, and high-income individuals (p < 0.05). After adjusting for confounding factors, multivariable analysis demonstrated an inverse association between PFOA [OR (95% CI), 0.666(0.486,0.914)] and PFHxS [OR (95% CI), 0.699(0.482,1.015)], and constipation. None of the personal and lifestyle factors showed a significant correlation with this negative association, as confirmed by subgroup analysis and interaction testing (p for interaction > 0.05). The RCS analysis demonstrated a linear inverse relationship between PFAS levels and constipation.

CONCLUSION

The findings of this study provide evidence of a significant inverse correlation between serum concentrations of PFAS, particularly PFOA and PFHxS, and constipation.

Lacticaseibacillus paracasei CCFM1222 Ameliorated the Intestinal Barrier and Regulated Gut Microbiota in Mice with Dextran Sulfate Sodium-Induced Colitis

Lacticaseibacillus paracasei has been regarded as a probiotic bacterium because of its role in anti-inflammatory properties and maintenance of intestinal barrier permeability. Here, we explored the anticolitic effects and mechanism of L. paracasei CCFM1222. The results showed that L. paracasei CCFM1222 supplementation could suppress the disease activity index (DAI) and colon length shortening in colitis mice, accompanied by a moderate increase in colonic tight junction proteins (ZO-1, occludin and claudin-1). L. paracasei CCFM1222 intervention significantly suppressed the levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6) and significantly elevated the activities of antioxidant enzymes (including SOD, GSH-Px, and CAT) in the colon by regulating the TLR4/MyD88/NF-κB and Nrf2 signaling pathways in colitis mice. In addition, L. paracasei CCFM1222 significantly shifted the gut microbiota, including elevating the abundance of Catabacter, Ruminiclostridium 9, Alistipes, and Faecalibaculum, as well as reducing the abundance of Mucispirillum, Escherichia-Shigella, and Salmonella, which was associated with the improvement of colonic barrier damage. Overall, these results suggest that L. paracasei CCFM1222 is a good candidate for probiotic of improving colonic barrier damage and associated diseases.

Dietary exposure to per- and polyfluoroalkyl substances: Potential health impacts on human liver

Per- and polyfluoroalkyl substances (PFAS), dubbed "forever chemicals", are widely present in the environment. Environmental contamination and food contact substances are the main sources of PFAS in food, increasing the risk of human dietary exposure. Numerous epidemiological studies have established the link between dietary exposure to PFAS and liver disease. Correspondingly, PFAS induced-hepatotoxicity (e.g., hepatomegaly, cell viability, inflammation, oxidative stress, bile acid metabolism dysregulation and glycolipid metabolism disorder) observed from in vitro models and in vivo rodent studies have been extensively reported. In this review, the pertinent literature of the last 5 years from the Web of Science database was researched. This study summarized the source and fate of PFAS, and reviewed the occurrence of PFAS in food system (natural and processed food). Subsequently, the characteristics of human dietary exposure PFAS (population characteristics, distribution trend, absorption and distribution) were mentioned. Additionally, epidemiologic evidence linking PFAS exposure and liver disease was alluded, and the PFAS-induced hepatotoxicity observed from in vitro models and in vivo rodent studies was comprehensively reviewed. Lastly, we highlighted several critical knowledge gaps and proposed future research directions. This review aims to raise public awareness about food PFAS contamination and its potential risks to human liver health.

Interaction between Per- and Polyfluorinated Substances (PFAS) and Acetaminophen in Disease Exacerbation-Focusing on Autism and the Gut-Liver-Brain Axis

This review presents a new perspective on the exacerbation of autism spectrum disorder (ASD) by per- and polyfluoroalkyl substances (PFAS) through the gut-liver-brain axis. We have summarized evidence reported on the involvement of the gut microbiome and liver inflammation that led to the onset and exacerbation of ASD symptoms. As PFAS are toxicants that particularly target liver, this review has comprehensively explored the possible interaction between PFAS and acetaminophen, another liver toxicant, as the chemicals of interest for future toxicology research. Our hypothesis is that, at acute dosages, acetaminophen has the ability to aggravate the impaired conditions of the PFAS-exposed liver, which would further exacerbate neurological symptoms such as lack of social communication and interest, and repetitive behaviors using mechanisms related to the gut-liver-brain axis. This review discusses their potential interactions in terms of the gut-liver-brain axis and signaling pathways that may contribute to neurological diseases.

Changing epidemiology of colorectal cancer - birth cohort effects and emerging risk factors

Incidence and mortality of colorectal cancer (CRC) are increasing worldwide, suggesting broad changes in the epidemiology of CRC. In this Review, we discuss the changes that are becoming evident, including trends in CRC incidence and mortality by age and birth cohort, and consider the contributions of early-life exposures and emerging risk factors to these changes. Importantly, incidence of CRC has increased among people born since the early 1950s in nearly all regions of the world. These so-called birth cohort effects imply the involvement of factors that influence the earliest stages of carcinogenesis and have effects across the life course. Accumulating evidence supports the idea that early-life exposures are important risk factors for CRC, including exposures during fetal development, childhood, adolescence and young adulthood. Environmental chemicals could also have a role because the introduction of many in the 1950s and 1960s coincides with increasing incidence of CRC among people born during those years. To reverse the expected increases in the global burden of CRC, participation in average-risk screening programmes needs to be increased by scaling up and implementing evidence-based screening strategies, and emerging risk factors responsible for these increases need to be identified.

Tracing the Bioaccessibility of Per- and Polyfluoroalkyl Substances in Fish during Cooking Treatment

The effect of cooking on the contents of per- and polyfluoroalkyl substances (PFAS) in foods has been widely studied, but whether cooking-induced structural and chemical modifications in foods affect the oral bioaccessibility of PFAS remains largely unknown. In this study, three kinds of fishes with different fat contents were selected, and the bioaccessibility of PFAS during cooking treatment (steaming and frying) was evaluated using in vitro gastrointestinal simulation with gastric lipase addition. The results showed that related to their molecular structures, the bioaccessibility of an individual PFAS varied greatly, ranging from 26.0 to 108.1%. Cooking can reduce the bioaccessibility of PFAS, and steaming is more effective than oil-frying; one of the possible reasons for this result is that the PFAS is trapped in protein aggregates after heat treatment. Fish lipids and cooking oil ingested with meals exert different effects on the bioaccessibility of PFAS, which may be related to the state of the ingested lipid/oil and the degree of unsaturation of fatty acids. Gastric lipase boosted the release of long-chain PFAS during in vitro digestion, indicating that the degree of lipolysis considerably influences the bioaccessibility of hydrophobic PFAS. Estimated weekly PFAS intakes were recalibrated using bioaccessibility data, enabling more accurate and reliable dietary exposure assessments.

Perfluorooctanoic acid-induced metabolic disorder via enhancing metabolism of glutamine and fatty acids in human intestinal cells

Intestinal cell metabolism plays an important role in intestine health. Perfluorooctanoic acid (PFOA) exposure could disorder intestinal cell metabolism. However, the mechanisms regarding how the three carbon sources interact under PFOA stress remined to be understood. The present study aimed to dissect the interconnections of glucose, glutamine, and fatty acids in PFOA-treated human colorectal cancer (DLD-1) cells using 13C metabolic flux analysis. The abundance of glycolysis and tricarboxylic acid (TCA) cycle metabolites was decreased in PFOA-treated cells except for succinate, whereas most of amino acids were more abundant. Beside serine and glycine, the levels of metabolites derived from 13C glucose were reduced in PFOA-treated cells, and the pentose phosphate pathway flux was 1.4-fold higher in PFOA-treated cells than in the controls. In reductive glutamine pathway, higher labeled enrichment of citrate, malate, fumarate, and succinate was observed for PFOA-treated cells. The contribution of glucose to fatty acid synthesis in PFOA-treated cells decreased while the contribution of glutamine to fatty acid synthesis increased. Additionally, synthesis of TCA intermediates from fatty acid β-oxidation was promoted in PFOA-treated cells. All results suggested that metabolic remodeling could happen in intestinal cells exposed to PFOA, which was potentially related to PFOA toxicity relevant with the loss of glucose in biomass synthesis and energy metabolism.

Influence of dietary bioactive compounds on the bioavailability and excretion of PFOA and its alternative HFPO-TA: Mechanism exploration

Oral ingestion is considered an important route of human exposure to perfluorooctanoic acid (PFOA) and its alternative hexafluoropropylene oxide trimer acid (HFPO-TA). Bioactive compounds are widely used as dietary supplements and food additives. However, little is known about the influence of dietary bioactive compounds on the bioavailability of PFOA and HFPO-TA. Here, three dietary bioactive compounds, β-carotene, quercetin and curcumin, were selected to study their influence on the relative bioavailability (RBA) of PFOA and HFPO-TA in soil using a mouse model. Compared to the control group (68.7 ± 6.27 %), quercetin and curcumin at medium and high doses (20 and 100 mg/kg/d) significantly (p < 0.05) decreased PFOA RBA to 55.2 ± 4.85-56.4 ± 4.57 % and 48.3 ± 5.49-48.6 ± 5.44 %, respectively. Mechanism study showed that medium- and high-dose quercetin as well as high-dose curcumin increased urinary excretion of PFOA by 33.6-35.6 % and 32.2 % through upregulating renal expression of multidrug resistance protein 2 (Mrp2) (1.52-1.63 folds) and Mrp4 (1.26-1.53 folds), thereby reducing PFOA accumulation. In PFOA-treated groups, quercetin at medium and high doses dramatically downregulated the hepatic expression of organic anion transport polypeptides (Oatp1a6, Oatp1b2), organic anion transport proteins (Oat1, Oat2), and fatty acid binding proteins (FABP4, FABP12), while curcumin at medium and high doses inhibited the hepatic expression of Oatp1a6, Oat1 and Oat2. These downregulated genes may reduce the transport of PFOA from blood to liver, and in turn decrease the PFOA RBA. However, β-carotene, quercetin and curcumin exhibited no significant effect on RBA and excretion of HFPO-TA (p > 0.05). This indicated the different absorption mechanisms between PFOA and HFPO-TA, and further research is warranted. This study provided a novel perspective for establishing environmentally friendly ways to reduce health hazards from per- and polyfluoroalkyl substances (PFASs).

Mediating effect of endocrine hormones on association between per- and polyfluoroalkyl substances exposure and birth size: Findings from sheyang mini birth cohort study

BACKGROUND

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) has been reported to affect fetus growth, but current results were inconsistent and their mechanism remained unclear.

OBJECTIVES

We aimed to evaluate the associations of prenatal exposure to single and/or multiple PFAS with birth size and to elucidate whether thyroid hormones and reproductive hormones mediate these associations.

METHODS

A total of 1087 mother-newborn pairs from Sheyang Mini Birth Cohort Study were included in the present cross-sectional analysis. 12 PFAS, 5 thyroid hormones and 2 reproductive hormones were measured in cord serum. Multiple linear regression models and Bayesian kernel machine regression (BKMR) models were used to examine the associations of PFAS with either birth size or endocrine hormones. One-at-a-time pairwise mediating effect analysis was applied to estimate the mediating effect of single hormone in the association between individual chemical and birth size. High-dimensional mediation approach including elastic net regularization and Bayesian shrinkage estimation were further performed to reduce exposure dimension and figure out the global mediation effects of joint endocrine hormones.

RESULTS

Perfluorononanoic acid (PFNA) exposure was positively associated to weight for length z score [WLZ, per log10-unit: regression coefficient (β) = 0.26, 95% confidence intervals (CI): 0.04, 0.47] and ponderal index (PI, β = 0.56, 95% CI: 0.09, 1.02), and PFAS mixture results fit by BKMR model showed consistent consequences. High-dimensional mediating analyses revealed that thyroid stimulating hormone (TSH) explained 6.7% of the positive association between PFAS mixtures exposure and PI [Total effect (TE) = 1.499 (0.565, 2.405); Indirect effect (IE) = 0.105 (0.015, 0.231)]. Besides, 7.3% of the PI variance was indirectly explained by 7 endocrine hormones jointly [TE = 0.810 (0.802, 0.819); IE = 0.040 (0.038, 0.041)].

CONCLUSIONS

Prenatal PFAS mixtures exposure, especially PFNA, was positively associated to birth size. Such associations were partly mediated by cord serum TSH.

Contribution of air-water interface in removing PFAS from drinking water: Adsorption, stability, interaction and machine learning studies

As a class of synthetic persistent organic pollutants, contamination of Per-and poly-fluoroalkyl substances (PFAS) in drinking water has attracted widespread concern. Aeration has been confirmed to enhance the removal of PFAS in drinking water by activated carbon (AC). However, the contribution of the air-water interface in removing PFAS is not yet to be fully understood at the molecular level. In this work, molecular dynamics (MD) simulations were employed to investigate the role of nanobubble in removing PFAS in the aqueous environment. The result suggests that the free energies of the air-water interface are about 3-7 kcal mol^-1 lower than that of the bulk water region, indicating that the transformation of PFAS from the water phase into the air-water interface is favorable from the viewpoint of thermodynamics. The interface-water partition coefficients (P_sur/wat) of PFAS are in the order of PFOS > PFOA > PFHxS > PFBS. On the air-water-AC three-phase interface, PFBS can not only move along the interface region but also leave the interface region into water phase, while PFOS tended to move along the interface region until it was captured by AC. Finally, the ΔG_{water-interface} quantitative structure-activity relationships (QSAR) models were developed to predict the removal efficiencies of PFAS enhanced by aeration in aquatic systems. The proposed mechanism promotes the understanding of the contribution of air-water interface in removing PFAS from drinking water by activated carbon.