Effects of fluoride on the histology, lipid metabolism, and bile acid secretion in liver of Bufo gargarizans larvae

Zirconium‑cerium modified polyvinyl alcohol/NaCMC biocomposite film: Synthesis of films through high-speed shear assisted technique and removal fluoride from water

A new zirconium and cerium-modified polyvinyl alcohol (PVA) sodium carboxymethyl cellulose (NaCMC) film (PVA/CMC-Zr-Ce) was synthesized thru a high-speed shear-assisted method and its adsorption for the removal of fluoride was studied, in which the NaCMC provided -COONa for ion exchange between Na and Zr-Ce, thus the loading amount of Zr-Ce on films was accordingly increased. The morphology and structure of PVA/CMC-Zr-Ce were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Besides, the mechanical properties, water contact angle, and swelling ratio of film were also evaluated. The addition of high-speed shear improved the dispersion of the emulsion system, and PVA/CMC-Zr-Ce film with good adsorption performance and film stability was prepared. While, it was found that the adsorption capacity could reach 67.25 mg/g and equilibrium time could reach 20 min. The adsorption mechanism of PVA/CMC-Zr-Ce revealed that ion exchange between hydroxide and fluoride, electrostatic interactions and complexation were the dominating influencing factors. Based on these findings, it can be concluded that PVA/CMC-Zr-Ce film- synthesized with high-speed shear assistance technique is a promising adsorbent for fluoride removal from water.

Fluoride induces hepatointestinal damage and vitamin B2 mitigation by regulating IL-17A and Bifidobacterium in ileum

INTRODUCTION

Fluorosis is a global public health disease affecting more than 50 countries and 500 million people. Excessive fluoride damages the liver and intestines, yet the mechanisms and therapeutic approaches remain unclear.

OBJECTIVES

To explore the mechanisms by which fluoride-induced intestinal-hepatic damage and vitamin B2 alleviation.

METHODS

Fluoride and/or vitamin B2-treated IL-17A knockout and wild-type mouse models were established, the morphological and functional changes of liver and gut, total bile acid biosynthesis, metabolism, transport, and regulation of FXR-FGF15 signaling pathways were evaluated, the ileal microbiome was further analyzed by 16S rDNA sequence. Finally, Bifidobacterium supplementation mouse model was designed and re-examined the above indicators.

RESULTS

The results demonstrated that fluoride induced hepatointestinal injury and enterohepatic circulation disorder by altering the synthesis, transporters, and FXR-FGF15 pathway regulation of total bile acid. Importantly, the ileum was found to be the most sensitive and fluoride changed ileal microbiome particularly by reducing abundance of Bifidobacterium. While vitamin B2 supplementation attenuated fluoride-induced enterohepatic circulation dysfunction through IL-17A and ileal microbiome, Bifidobacterium supplementation also reversed fluoride-induced hepatointestinal injury.

CONCLUSION

Fluoride induces morphological and functional impairment of liver and gut tissues, as well as enterohepatic circulation disorder by altering total bile acid (TBA) synthesis, transporters, and FXR-FGF15 signaling regulation. Vitamin B2 attenuated fluoride-induced enterohepatic circulation disorder through IL-17A knockout and ileal microbiome regulation. The ileum was found to be the most sensitive to fluoride, leading to changes in ileal microbiome, particularly the reduction of Bifidobacterium. Furthermore, Bifidobacterium supplementation reversed fluoride-induced hepatointestinal injury. This study not only elucidates a novel mechanism by which fluoride causes hepatointestinal toxicity, but also provides a new physiological function of vitamin B2, which will be useful in the therapy of fluorosis and other hepatoenterological diseases.

Cytochrome P450 enzymes in the black-spotted frog (Pelophylax nigromaculatus): molecular characterization and upregulation of expression by sulfamethoxazole

Cytochrome P450 (CYP) enzymes are crucial for the detoxification of xenobiotics, cellular metabolism, and homeostasis. This study investigated the molecular characterization of CYP enzymes in the black-spotted frog, Pelophylax nigromaculatus, and examined the regulation of CYP expression in response to chronic exposure to the antibiotic sulfamethoxazole (SMX) at various environmental concentrations (0, 1, 10, and 100 μg/L). The full-length cDNA of Pn-CYP26B1 was identified. The sequence included open reading frames of 1,536 bp, encoding proteins comprising 511 amino acids. The signature motif, FxxGxxxCxG, was highly conserved when compared with a number of selected animal species. SMX significantly upregulated the expression of the protein CYP26B1 in frog livers at concentrations of 1 and 10 μg/L. SMX showed an affinity for CYP26B1 of -7.6 kcal/mol, indicating a potential mechanism for SMX detoxification or adaptation of the frog. These findings contributed to our understanding of the environmental impact of antibiotics on amphibian species and underscored the importance of CYP enzymes in maintaining biochemical homeostasis under exposure to xenobiotic stress.

Bifidobacterium Relieved Fluoride-Induced Hepatic and Ileal Toxicity via Inflammatory Response and Bile Acid Transporters in Mice

Fluoride is a pervasive environmental contaminant. Prolonged excessive fluoride intake can inflict severe damage on the liver and intestines. Previous 16S rDNA sequencing revealed a decrease in ileal Bifidobacterium abundance during fluoride-induced hepatointestinal injury. Hence, this work aimed to investigate the possible mitigating function of Bifidobacterium on hepatointestinal injury caused by fluoride. Thirty-six 6-week-old C57BL/6J mice (equally divided between males and females) were allotted randomly to three groups: Ctrl group (distilled water), NaF group, and NaF + Ba group (100 mg/L NaF distilled water). After 10 weeks, the mice were given 1 × 109 CFU/mL Bifidobacterium solution (0.2 mL/day) intragastrically in the NaF + Ba group for 8 weeks, and the mice in other groups were given the same amount of distilled water. Dental damage, bone fluoride content, blood routine, liver and intestinal microstructure and function, inflammatory factors, and regulatory cholic acid transporters were examined. Our results showed that fluoride increased glutamic-oxalacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT) activities, and the levels of lipopolysaccharide (LPS), IL-1β, IL-6, TNF-α, and IL-10 levels in serum, liver, and ileum. However, Bifidobacterium intervention alleviated fluoride-induced changes in the above indicators. In addition, Bifidobacterium reduced the mRNA expression levels of bile acid transporters ASBT, IBABP, OST-α, and OST-β in the ileum. In summary, Bifidobacterium supplementation relieved fluoride-induced hepatic and ileal toxicity via an inflammatory response and bile acid transporters in the liver and ileum of mice.

Flunitrazepam and its metabolites exposure disturb the zebrafish gut-liver axis: Combined microbiome and metabolomic analysis

Due to clinical treatment and illegal use, psychoactive substances have been widely detected in the aquatic environment. In this study, we investigated the effects of the benzodiazepine drug flunitrazepam (FLZ) and its metabolite 7-aminoflunitrazepam (7-FLZ) on the gut-liver axis of zebrafish. Zebrafish were exposed to two concentrations of FLZ and 7-FLZ (0.05 and 1 μg/L) for 30 days. Results showed that both FLZ and 7-FLZ exposure altered the relative abundance of Proteobacteria at the phylum level, with significant differences observed at the genus level for pathogenic bacteria such as Paracoccus, Shewanella, and Aeromonas. Metabolomics results showed both exposures significantly interfered with nucleotide and amino acid metabolism. The imbalance of gut microbiota and metabolic disorder increased the level of malondialdehyde, which in turn heightened the permeability of the gut mucosal barrier. FLZ and 7-FLZ induced oxidative stress in the liver via the gut-liver axis, leading to decreased levels of glucose, total cholesterol, and triglyceride, as well as the down-regulation of glycolipid metabolism-related genes (PPARα, PPARγ, FABP2, Fabp11, PFKFB3, and LDHA). Metabolomics results revealed that FLZ and 7-FLZ significantly affected the biosynthesis of amino acids and arginine, and other metabolic pathways such as nucleotide, nicotinate and nicotinamide, and purine in the liver. Our results unveiled the mechanisms behind the toxicological effects of psychoactive substances on the gut-liver axis, providing valuable data for ecological and environmental risk assessments.

Comparative Genomic Analysis of the Thiolase Family and Functional Characterization of the Acetyl-Coenzyme A Acyltransferase-1 Gene for Milk Biosynthesis and Production of Buffalo and Cattle

Cattle and buffalo served as the first and second largest dairy animals, respectively, providing 96% milk products worldwide. Understanding the mechanisms underlying milk synthesis is critical to develop the technique to improve milk production. Thiolases, also known as acetyl-coenzyme A acetyltransferases (ACAT), are an enzyme family that plays vital roles in lipid metabolism, including ACAT1, ACAT2, ACAA1, ACAA2, and HADHB. Our present study showed that these five members were orthologous in six livestock species including buffalo and cattle. Transcriptomic data analyses derived from different lactations stages showed that ACAA1 displayed different expression patterns between buffalo and cattle. Immunohistochemistry staining revealed that ACAA1 were dominantly located in the mammary epithelial cells of these two dairy animals. Knockdown of ACAA1 inhibited mammary epithelial cell proliferation and triglyceride and β-casein secretion by regulating related gene expressions in cattle and buffalo. In contrast, ACAA1 overexpression promoted cell proliferation and triglyceride secretion. Finally, three novel SNPs (g.-681A>T, g.-23117C>T, and g.-24348G>T) were detected and showed significant association with milk production traits of Mediterranean buffaloes. In addition, g.-681A>T mutation located in the promoter region changed transcriptional activity significantly. Our findings suggested that ACAA1 play a key role in regulating buffalo and cattle milk synthesis and provided basic information to further understand the dairy animal lactation physiology.

Comparison of the characteristics of gut microbiota response to lead in Bufo gargarizans tadpole at different developmental stages

In amphibians, lead (Pb) exposure could alter the composition and structure of gut microbiota, but changes involving microbiota of several successive phases following Pb exposure have been less studied. In the present study, we compared the effects of Pb exposure on morphological parameters and gut microbiota of Bufo gargarizans at Gosner stage (Gs) 33, Gs36, and Gs42. Our results showed that total length (TL), snout-vent length (SVL), and body wet weight (TW) of B. gargarizans at Gs33, as well as TL and SVL at Gs42, were significantly increased after Pb exposure. In addition, high-throughput sequencing analysis indicated that gut microbiota has distinct responses to Pb exposure at different developmental stages. The diversity of gut microbiota was significantly reduced under Pb exposure at Gs33, while it was significantly increased at Gs42. In terms of community composition, Spirochaetota, Armatimonadota, and Patescibacteria appeared in the control groups at Gs42, but not after Pb treatment. Furthermore, functional prediction indicated that the relative abundance of metabolism pathway was significantly decreased at Gs33 and Gs36, and significantly increased at Gs42. Our results fill an important knowledge gap and provide comparative information on the gut microbiota of tadpoles at different developmental stages following Pb exposure.

α-Lipoic Acid Alleviated Fluoride-Induced Hepatocyte Injury via Inhibiting Ferroptosis

Fluoride is widely used in agricultural production and food packaging. Excessive fluoride in water and food is a serious threat to liver health. α-Lipoic acid, a natural free radical scavenger, has hepatoprotective properties. However, the protective effect of α-lipoic acid on fluorohepatotoxicity is uncertain. The aim of this study was to investigate the mechanism of ferroptosis in α-lipoic acid preventing fluoride-induced hepatotoxicity. Five-week-old ICR mice were treated with sodium fluoride (100 mg/L) and/or α-lipoic acid (200 mg/kg) for 9 weeks. The results showed that α-lipoic acid attenuated fluoride-induced damage to liver morphology and ultrastructure. Moreover, α-lipoic acid alleviated fluoride-induced iron accumulation, increased oxidative stress, and elevated lipid peroxidation in the liver. In addition, the mechanism study found that α-lipoic acid prevented fluoride-induced ferroptosis through the System Xc^-/GPX4 axis, lipid peroxidation axis, and iron metabolism axis, but it was interestingly not regulated by mitochondrial free radical axis in the hepatocytes. Altogether, this study indicated that α-lipoic acid prevents fluoride-induced liver injury by inhibiting ferroptosis, which has potential implications for the prevention and treatment of fluoride-induced liver injury.

Multiomics Analysis Revealed the Molecular Mechanism of miRNAs in Fluoride-Induced Hepatic Glucose and Lipid Metabolism Disorders

Fluoride-induced liver injury seriously endangers human and animal health and animal food safety, but the underlying mechanism remains unclear. This study aims to explore the mechanism of miRNAs in fluoride-induced hepatic glycolipid metabolism disorders. C57 male mice were used to establish the fluorosis model (22.62 mg/L F^-, 12 weeks). The results indicated that fluoride increased fluoride levels, impaired the structure and function, and disrupted the glycolipid metabolism in the liver. Furthermore, the sequencing results showed that fluoride exposure resulted in the differential expression of 35 miRNAs and 480 mRNAs, of which 23 miRNAs were related to glycolipid metabolism. miRNA-mRNA network analyses and RT-PCR revealed that miRNAs mediated fluoride-induced disturbances in the hepatic glycolipid metabolism. Its possible mechanism was to regulate the insulin pathway, PPAR pathway, and FOXO pathway, which in turn affected the bile secretion, the metabolic processes of glucose, the decomposition of lipids, and the synthesis of unsaturated fatty acids in the liver. This study provides a theoretical basis for miRNAs as diagnostic indicators and target drugs for the treatment of fluoride-induced liver injury.

Differential regulation of mRNAs and lncRNAs related to lipid metabolism in Duolang and Small Tail Han sheep

The function of long non-coding RNA (lncRNA) can be achieved through the regulation of target genes, and the deposition of fat is regulated by lncRNA. Fat has an important effect on meat quality. However, there are relatively few studies on lncRNAs in the subcutaneous adipose tissue of Duolang sheep and Small Tail Han sheep. In this study, RNA-Seq technology and bioinformatics methods were used to identify and analyze the lncRNA and mRNA in the subcutaneous adipose tissue of the two breeds of sheep. The results showed that 107 lnRNAs and 1329 mRNAs were differentially expressed. The differentially expressed genes and lncRNA target genes were significantly enriched in the biosynthesis of unsaturated fatty acids signaling pathway, fatty acid metabolism, adipocyte differentiation and other processes related to fat deposition. Among them, LOC105616076, LOC114118103, LOC105607837, LOC101116622, and LOC105603235 target FADS1, SCD, ELOVL6, HSD17B12 and HACD2, respectively. They play a key regulatory role in the biosynthesis of unsaturated fatty acids. This study lays a foundation for the study of the molecular mechanism of lncRNA on fat development, and has reference value for studying the differences in fat deposition between Duolang sheep and Small Tail Han sheep.

Challenges of fluoride pollution in environment: Mechanisms and pathological significance of toxicity - A review

Fluoride is an important trace element in the living body. A suitable amount of fluoride has a beneficial effect on the body, but disproportionate fluoride entering the body will affect various organs and systems, especially the liver, kidneys, nervous system, endocrine system, reproductive system, bone, and intestinal system. In recent years, with the rapid development of agriculture and industry, fluoride pollution has become one of the important factors of environmental pollution, and fluoride pollution in any form is becoming a serious problem. Although countries around the world have made great breakthroughs in controlling fluoride pollution, however fluorosis still exists. A large amount of fluoride accumulated in animals will not only produce the toxic effects, but it also causes cell damage and affect the normal physiological activities of the body. There is no systematic description of the damage mechanism of fluoride. Therefore, the study on the toxicity mechanism of fluoride is still in progress. This review summarizes the existing information of several molecular mechanisms of the fluoride toxicity comprehensively, aiming to clarify the toxic mechanism of fluoride on various body systems. We have also summerized the pathological changes of those organ systems after fluoride poisoning in order to provide some ideas and solutions to the reader for the prevention and control of modern fluoride pollution.

Pseudomonas sp. Strain 273 Incorporates Organofluorine into the Lipid Bilayer during Growth with Fluorinated Alkanes

Anthropogenic organofluorine compounds are recalcitrant, globally distributed, and a human health concern. Although rare, natural processes synthesize fluorinated compounds, and some bacteria have evolved mechanisms to metabolize organofluorine compounds. Pseudomonas sp. strain 273 grows with 1-fluorodecane (FD) and 1,10-difluorodecane (DFD) as carbon sources, but inorganic fluoride release was not stoichiometric. Metabolome studies revealed that this bacterium produces fluorinated anabolites and phospholipids. Mass spectrometric fatty acid profiling detected fluorinated long-chain (i.e., C₁₂-C₁₉) fatty acids in strain 273 cells grown with FD or DFD, and lipidomic profiling determined that 7.5 ± 0.2 and 82.0 ± 1.0% of the total phospholipids in strain 273 grown with FD or DFD, respectively, were fluorinated. The detection of the fluorinated metabolites and macromolecules represents a heretofore unrecognized sink for organofluorine, an observation with consequences for the environmental fate and transport of fluorinated aliphatic compounds.

Lotus seed resistant starch ameliorates high-fat diet induced hyperlipidemia by fatty acid degradation and glycerolipid metabolism pathways in mouse liver

We investigated the potential efficacy and underlying mechanisms of Lotus seed Resistant Starch (LRS) for regulating hyperlipidemia in mice fed a High-fat Diet (HFD). Mouse were fed a normal diet (Normal Control group, NC group), HFD alone (MC group), HFD plus lovastatin (PC group), or HFD with low/medium/high LRS (LLRS, MLRS, and HLRS groups, respectively) for 4 weeks. LRS supplementation significantly decreased body weight and significantly reduced serum levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, and high-density lipopro-tein cholesterol compared with the MC group. LRS also significantly alleviated hepatic steatosis, especially in the MLRS group, which also showed a significantly reduced visceral fat index. LLRS supplementation significantly regulated genes associated with glycerolipid metabolism and steroid hormone biosynthesis (Lpin1 and Ugt2b38), MLRS significantly regulated genes related to fatty acid degradation, fatty acid elongation, and glycerolipid metabolism (Lpin1, Hadha, Aldh3a2, and Acox1), whereas HLRS significantly regulated genes related to fatty acid elongation and glycerolipid metabolism (Lpin1, Elovl3, Elovol5, and Agpat3). The fatty acid-degradation pathway regulated by MLRS thus exerts better control of serum lipid levels, body weight, visceral fat index, and liver steatosis in mice compared with LLRS- and HLRS-regulated pathways.

Estrogen Deficiency Aggravates Fluoride-Induced Liver Damage and Lipid Metabolism Disorder in Rats

Estrogen exerts essential role in liver metabolism, and its deficiency is frequently accompanied by a series of metabolic disorder diseases. To investigate the role of estrogen deficiency in fluorine ions (F^-) induced liver injury, the ovariectomy (OVX) rat models were performed by surgically removing the ovaries, and the rats from OVX and non-OVX models were exposed to differential dose of F^- (0, 25, 50 and 100 mg/L) in drinking water for 90 days. The liver morphological structure was evaluated by hematoxylin-eosin staining. Proliferation ability of hepatocytes was evaluated by 5-bromo-2-deoxyuridine (BrdU) assay. And distribution of lipid droplets in liver tissue was observed via oil red O staining. In addition, the liver function and lipid metabolism parameters in serum were detected by commercial kits. Results showed that F^- induced hepatocytes morphological damage and inhibited the proliferation ability of hepatocytes; estrogen deficiency exacerbated these changes. The deposition of lipid droplets in the liver tissue was multiplicative with increased F^- dose, especially after estrogen deficiency. In addition, F^- exposure increased (P < 0.05 or P < 0.01) serum aminotransferase (ALT), aminotransferase (AST), alkaline phosphatase (ALP), and γ-glutamyl transpeptidase (γ-GT) activities and total bilirubin (T-bil) level; meanwhile, serum triglyceride (TG) and cholesterol (TC) levels were also elevated (P < 0.05 or P < 0.01). F^--induced liver function and lipid metabolism indexes were further increased (P < 0.05 or P < 0.01) in the state of estrogen deficiency. In conclusion, estrogen deficiency aggravated F^--induced liver damage and lipid metabolism disorder.

Fluoride exposure induces mitochondrial damage and mitophagy via activation of the IL-17A pathway in hepatocytes

As an environmental toxicant, the damage of fluoride to the body has attracted global attention. Because liver is an essential organ for fluoride accumulation and damage. Our previous studies revealed fluoride-induced hepatic injury through interleukin 17A (IL-17A) pathway, but the underlying cellular mechanism remains unclear. Hence, this research explored the mechanism of IL-17A pathway and mitophagy in fluoride-induced liver injury through the use of the mice fluorosis model, IL-17A addition fluorosis cell model, IL-17A gene knockout mice fluorosis model, flow cytometry, immunohistochemistry, fluorescence double staining, ELISA, western blotting, and other techniques. The results showed that fluoride reduced the bodyweight and liver coefficient, increased the bone fluoride content, the aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutamate dehydrogenase (GDH) levels, caspase 8 and caspase 9 activities, and induced liver morphology and ultrastructure damage. Furthermore, the protein expression levels of IL-17A pathway key proteins, IL-17A, IL-17R, and Act1 were increased, but IκB was decreased after fluoride exposure. In addition, fluoride exposure elevated the mitochondrial depolarization percent, the mitochondria damage, the fluorescent spots of mitophagy, and the LC3II/LC3I protein relative expression level. To further verify the role of the IL-17A pathway in fluoride-induced hepatocyte mitochondrial damage and mitophagy disorder, the IL-17A was added and knocked out in cells of animals. The results showed that the addition of IL-17A aggravated fluoride-induced liver morphology and functional damage, activation of the IL-17A pathway, mitochondrial injury, and mitophagy, but the IL-17A knockout mitigated fluoride-induced changes. These results suggested that fluoride exposure induced mitochondrial damage and mitophagy through the IL-17A pathway in hepatocytes.

Inhibition of Metamorphosis, Thyroid Gland, and Skeletal Ossification Induced by Hexavalent Chromium in Bufo gargarizans Larvae

Hexavalent chromium (Cr [VI]) is one of the major detrimental heavy metal pollutants. In the present study, Bufo gargarizans were exposed to 0, 52, 104, 208, and 416 μg/L Cr (VI) from Gosner stage 2 until metamorphosis; and growth, development, and histological characteristics of the thyroid gland and skeletal ossification were examined. The results demonstrated that the survival rate of larvae exposed to Cr (VI) was not different from that measured in animals from the control group. However, high levels of Cr (VI) (104, 208, and 416 μg/L) were associated with significantly delayed growth and development. The suppression of skeletal ossification was observed at high Cr (VI) levels. Besides, histological alterations of the thyroid gland, such as follicular cell hyperplasia, colloid depletion, and peripheral colloid vacuolation, were found in 52 to 416 μg/L Cr (VI) treatments. The results of the present study highlight reductions in growth and development as well as percent metamorphosis and skeletal ossification due to histological alteration of the thyroid gland during exposure to Cr (VI) in B. gargarizans larvae. The present investigation could provide a basis for understanding the detrimental effects of Cr (VI) in amphibian larvae. Environ Toxicol Chem 2021;40:2474-2483. © 2021 SETAC.

A metabolomic-based study on disturbance of bile acids metabolism induced by intratracheal instillation of nickel oxide nanoparticles in rats

Nickel oxide nanoparticles (Nano NiO) evoke hepatotoxicity, while whether it affects the hepatic metabolism remains unclear. The aim of this study was to explore the differential metabolites and their metabolic pathways in rat serum and to further verify the potential mechanism of bile acids' (BAs) metabolism dysregulation after Nano NiO exposure. Sixteen male Wistar rats were intratracheally instilled with Nano NiO (0.24 mg/kg body weight) twice a week for 9 weeks. Liquid chromatography/mass spectrometry was applied to filter the differentially expressed metabolites in rat serum. Western blot was employed to detect the protein contents. Twenty-one differential metabolites that associated with BAs, lipid and phospholipid metabolism pathways were identified in rat serum after Nano NiO exposure. Decreased cholic acid and deoxycholic acid implied that the BAs metabolism was disturbed. The nickel content increased in liver after Nano NiO exposure. The protein expression of cholesterol 7α-hydroxylase (CYP7A1) was down-regulated, and the bile salt export pump was up-regulated after Nano NiO administration in rat liver. Moreover, dehydroepiandrosterone sulphotransferase (SULT2A1) and cytochrome P450 (CYP) 3A4 were elevated in the exposure group. In conclusion, Nano NiO might trigger the disturbances of BAs, lipid and phospholipid metabolism pathways in rats. The diminished serum BAs induced by Nano NiO might be related to the down-regulation of synthetase and to the overexpression of transmembrane protein and detoxification enzymes in BAs metabolism.

The beneficial or detrimental fluoride to gut microbiota depends on its dosages

Fluoride, widely presented in drinking water and tea, may be detrimental or beneficial to the human health, depending on its dosages ingested. However, the relationship of different dosages of fluoride and gut microbiota is still unclear. In this work, the fermentation model using fecal samples provided by four volunteers was used to evaluate the effects of different dosages of fluoride (1, 2, 10 and 15 mg/L) on the gut microbiota in vitro. The result showed low dosages of fluoride (1 and 2 mg/L) had limited effect on the structure and functional Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway of gut microbiota. Furthermore, the low dosage of fluoride could promote the growth of beneficial gut microbiota, including Faecalibacterium and Lactobacillus. Whereas, the high dosage of fluoride (10 and 15 mg/L) significantly changed the composition and functional KEGG pathway of gut microbiota. Moreover, the high dosage of fluoride could also reduce the beneficial gut microbiota, including Faecalibacterium and Phascolarctobacterium, and increase the harmful bacterium including Proteobacteria and Enterobacteriaceae. Both low and high dosages of fluoride showed limited effect on the productions of short-chain fatty acids (SCFAs). Thus, the beneficial or detrimental fluoride to gut microbiota depends on its dosages. The fluoride is expected to serve as a food additive in suitable dosage to improve human health through modulation of the gut microbiota. Moreover, more attention should be paid to toxicity of fluoride with high dosage to gut microbiota.

Exposure to low concentration of trifluoromethanesulfonic acid induces the disorders of liver lipid metabolism and gut microbiota in mice

Trifluoromethanesulfonic acid (TFMS) is the shortest chain perfluorinated compound. Recently, it has been identified as a persistent and mobile organic chemical with a maximum concentration of 1 μg/L in the environment. However, its toxicological mechanism remains unclear. In this study, to evaluate the liver and intestinal toxicity of TFMS in mammals, male mice were orally exposed to 0, 1, 10 and 100 μg/kg for 12 weeks. Our results showed that TFMS exposure reduced the epididymal fat weight in mice, caused the decrease of serum and liver triglyceride (TG) level and the increase of serum low density lipoprotein (LDL) level. Also, we observed the inflammatory cell infiltration in the liver of mice exposed to 10 μg/kg and 100 μg/kg TFMS, which was coupled with the increased mRNA expression levels of inflammatory factors such as COX2, TNF-α, IL-1β in the liver. In addition, the mRNA expression levels of lipid metabolism-related genes (PPAR-α, ACOX, SCD1, PPAR-γ, etc.) were significantly decreased in the liver of mice after exposure to both doses of TFMS. We also found TFMS exposure caused the imbalance of cecal gut microbiota and change of cecal microbiota diversity. KEGG pathway predictions showed that the exposure of 100 μg/kg TFMS changed the synthesis and degradation of ketone bodies, benzoate degradation and several other metabolic pathways. Our findings indicated that TFMS exposure disturbed the liver lipid metabolism possibly via altering the gut microbiota.

Comparison of the characteristics of intestinal microbiota response in Bufo gargarizans tadpoles: Exposure to the different environmental chemicals (Cu, Cr, Cd and NO3-N)

Environmental pollutants could change the intestinal microbiota communities, while data concerning the dynamics of the intestinal microbiota in response to different environmental chemicals in amphibian are lacking. We compared the effects of Cu, Cd, Cr and NO₃-N on intestinal microbiota of B. gargarizans tadpoles by using high-throughput 16S rRNA sequencing technology. Our results revealed that responses of intestinal microbiota to three metals and NO₃-N showed different characteristics. At the phylum level, the most 100 OTUs were predominantly colonized by Proteobacteria, and meanwhile, expansion of Proteobacteria was observed in Cu 64 μg/L, Cd (100 μg/L and 200 μg/L) and NO₃-N100 mg/L treatment groups. In addition, the abundance of Bacteroidetes significantly increased in the gut administrate with Cu, Cd, Cr, NO₃-N 20 mg/L exposures, while declined abundance of Fusobacteria was observed in Cu64 μg/L Cd100 μg/L Cd200μg/L-exposed groups. At the genus level, several genera exhibited increased prevalence of abundance such as Shewanella, Azospira and Flavobacterium. The functional prediction revealed that exposures of three metals and NO₃-N increase the risks of metabolic disorders and diseases. Our research could be an important step toward an assessment of the ecological risks of different chemicals to aquatic organisms using intestinal microbiota.