Perigestational low-dose BDE-47 exposure alters maternal serum metabolome and results in sex-specific weight gain in adult offspring

2,2',4,4',5,5'-Hexabromophenyl ether (BDE-153) causes abnormal insulin secretion and disorders of glucose and lipid metabolism in mice

BACKGROUND

Environmental polybrominated diphenyl ether (PBDE) exposure may be associated with diabetes and obesity. 2,2',4,4',5,5'-Hexabromodiphenyl ether (BDE-153) is one of the most abundant and widely distributed homologs of PBDEs detected in humans. This study investigated the effects of BDE-153 on the expression of adipokines and glucose and lipid metabolism.

METHODS

Adult male C57BL/6 mice were divided into five BDE-153 groups and one control group. After BDE-153 exposure for 4 weeks, the levels of biochemical indexes and the mRNA and protein expression levels of leptin, adiponectin, peroxisome proliferators activated receptors gamma (PPARγ), and AMPKα were measured. The histomorphological changes of liver and pancreas tissues were observed.

RESULTS

After BDE-153 exposure, the weight of mice in the medium-high-dose group at different exposure times was lower than that in the control group ( p all <0.05), and the body weight decreased slightly with the increase of the dose of BDE-153. BDE-153 caused the disorder of glucose and lipid metabolism in mice, the weight of liver and pancreas increased, lipid droplets accumulated in liver cells, and the positive rate of insulin staining increased in a dose-dependent manner. BDE-153 also interfered with the expression of PPARγ, AMPKα, and adipokines. The results of restrictive cubic splines (RCS) showed that there were a nonlinear dose-response relationship between the exposure dose of BDE-153 and the expression levels of PPARγ, AMPKα, and adipokines.

CONCLUSION

Our results suggest that BDE-153 may interfere with the expression of adipokines and the secretion of insulin by affecting the expression of PPARγ and AMPKα, which play a key role in glucose and lipid metabolism, leading to the occurrence of glucose and lipid metabolism disorder.

Associations between prenatal exposure to polybrominated diphenyl ethers and physical growth in a seven year cohort study

Although evidence suggests that prenatal exposure to polybrominated diphenyl ethers (PBDEs) alter offspring's physical growth, most studies rely upon physical growth at a single timepoint, and little is known regarding their longitudinal effects over time. In the current study, we determined the associations between prenatal PBDEs exposure and child physical growth by following up 207 mother-child pairs from the Laizhou Wan Birth Cohort (LWBC) from pregnancy until the children were seven years old. Child physical growth including weight, height, and body mass index (BMI) was assessed at birth, and at one, two and seven years of age. Prenatal exposure to PBDEs was quantified by measuring eight PBDE congeners (BDE-28, BDE-47, BDE-85, BDE-99, BDE-100, BDE-153, BDE-154, and BDE-183) in maternal serum samples collected upon hospital admission for delivery. Linear mixed models were applied to examine the associations between prenatal PBDEs exposure and repeated measures of child physical growth, and to determine whether these associations were modified by child's sex. Our findings indicated that BDE-28, BDE-85, BDE-153, BDE-183, and Σ₇PBDEs were positively associated with child weight z-score; and that BDE-28, BDE-47, BDE-85, BDE-99, BDE-153, and Σ₇PBDEs were positively associated with child height z-score. In addition, these associations were modified by the child's sex as reflected by pronounced positive associations among boys, while negative associations were noted among girls. In conclusion, our findings indicated the sex-specific associations between prenatal PBDE exposures and child physical growth during the first seven years of life.

Perinatal exposure to low-level PBDE-47 programs gut microbiota, host metabolism and neurobehavior in adult rats: An integrated analysis

Polybrominated diphenyl ethers (PBDEs), a major class of flame retardants, have been extensively applied in plastics, electrical equipment, textile fabrics, and so on. Early-life exposure to PBDEs is correlated to neurobehavioral deficits in adulthood, yet the underlying mechanism has not been fully understood. Increasing evidence has demonstrated that gut microbiota dysbiosis and serum metabolites alterations play a role in behavioral abnormalities. However, whether their perturbation is implicated in PBDEs-induced neurotoxicity remains unclear. Here, we sought to explore the effects of developmental exposure to environmentally relevant levels of 2, 2', 4, 4'-tetrabromodiphenyl ether (PBDE-47), a major congener in human samples, on gut microbiota and serum metabolic profile as well as their link to neurobehavioral parameters in adult rats. The open field test showed that gestational and lactational exposure to PBDE-47 caused hyperactivity and anxiety-like behavior. Moreover, 16S rRNA sequencing of fecal samples identified a distinct community composition in gut microbiota following PBDE-47 exposure, manifested as decreased genera Ruminococcaceae and Moraxella, increased families Streptococcaceae and Deferribacteraceae as well as genera Escherichia-Shigella, Pseudomonas and Peptococcus. Additionally, the metabolomics of the blood samples based on liquid chromatography-mass spectrometry revealed a significant shift after PBDE-47 treatment. Notably, these differential serum metabolites were mainly involved in amino acid, carbohydrate, nucleotide, xenobiotics, and lipid metabolisms, which were further validated by pathway analysis. Importantly, the disturbed gut microbiota and the altered serum metabolites were associated with each other and with neurobehavioral disorders, respectively. Collectively, these results suggest that gut microbiota dysbiosis and serum metabolites alterations potentially mediated early-life low-dose PBDE-47 exposure-induced neurobehavioral impairments, which provides a novel perspective on understanding the mechanisms of PBDE-47 neurotoxicity.

Obesity II: Establishing causal links between chemical exposures and obesity

Obesity is a multifactorial disease with both genetic and environmental components. The prevailing view is that obesity results from an imbalance between energy intake and expenditure caused by overeating and insufficient exercise. We describe another environmental element that can alter the balance between energy intake and energy expenditure: obesogens. Obesogens are a subset of environmental chemicals that act as endocrine disruptors affecting metabolic endpoints. The obesogen hypothesis posits that exposure to endocrine disruptors and other chemicals can alter the development and function of the adipose tissue, liver, pancreas, gastrointestinal tract, and brain, thus changing the set point for control of metabolism. Obesogens can determine how much food is needed to maintain homeostasis and thereby increase the susceptibility to obesity. The most sensitive time for obesogen action is in utero and early childhood, in part via epigenetic programming that can be transmitted to future generations. This review explores the evidence supporting the obesogen hypothesis and highlights knowledge gaps that have prevented widespread acceptance as a contributor to the obesity pandemic. Critically, the obesogen hypothesis changes the narrative from curing obesity to preventing obesity.

Dynamics of defatted rice bran in physicochemical characteristics, microbiota and metabolic functions during two-stage co-fermentation

Defatted rice bran (DFRB) is an inexpensive and easily available agricultural byproduct. Existence of anti-nutritional factors (ANFs), high fiber and low protein content, susceptible to oxidation and rancidity make DFRB currently underutilized. In this study, Bacillus subtilis with high enzyme activities, Saccharomyces cerevisiae with high single-cell proteins concentration and Lactiplantibacillus plantarum with excellent acid secreting capacity were screened to co-fermented DFRB with phytase, and multiple physicochemical analyses combined with high-throughput sequencing were applied to provide insights into the dynamics of the physicochemical characteristics and the complex microbiome during the two-stage co-fermentation of DFRB. The results showed that co-fermentation effectively improved the nutritional value by degrading ANFs (trypsin inhibitors and phytic acid), fiber (acid detergent fiber and neutral detergent fiber) and allergenic protein, and increasing the trichloroacetic acid soluble protein, amino acids and organic acid. In addition, co-fermentation prevented lipid oxidation by enhancing antioxidant activity and reducing the activity of lipase and lipoxygenase. High-throughput sequencing results suggested that co-fermentation optimized microbial community of DFRB by increasing desirable Lactobacillus, Pediococcus, Saccharomyces and Talaromyces and reducing undesirable bacteria (Enterobacter and Pseudomonas) and animal and plant-pathogenic fungi (Blumeria, Alternaria, Fusarium, etc.). Furthermore, high-throughput sequencing and gas chromatography-mass spectrometry (GC-MS) were adopted to predict microbial metabolic functions and metabolic pathways during whole DFRB co-fermentation.

Impacts of PBDE-47 exposure before, during and after pregnancy on the maternal gut microbiome and its association with host metabolism

Maternal gut microbiota play an important role in the modulation of offspring disease susceptibility and gut microbiota dysbiosis has been proposed as a mechanism through which toxic environmental chemicals exert their adverse impacts on health. The brominated flame retardants polybrominated diphenyl ethers (PBDEs) are developmental toxicants and induce dysbiotic gut microbiota in offspring. Yet, whether and how PBDEs impact the maternal gut microbiota remain unclear. Here, we sought to investigate the effect of 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) exposure from preconception through lactation cessation on maternal gut microbiota and its link to host serum metabolic consequences. Female Sprague-Dawley rats were daily exposed to 10 mg/kg PBDE-47 via oral gavage from ten days before conception until offspring were weaned on postnatal day 21, then maternal fecal and blood samples were collected for microbiome and metabolome analyses by using 16S ribosomal RNA gene sequencing and gas chromatography-mass spectrometry, respectively. Maternal exposure to PBDE-47 showed a distinct profile in gut microbiota compared to control dams, as evidenced by increased Actinobacteria phylum and genera Blautia, Gemella and Phascolarctobacterium, and decreased genera AF12 and Oscillospira. Additionally, global metabolomics analysis identified 26 differential serum metabolites to distinguish PBDE-47 from controls, which were mainly involved in amino acid, lipid, carbohydrate and energy metabolism, further confirmed by pathway analysis. Importantly, the differential serum metabolites are closely correlated with the disturbed gut microbiota in response to PBDE-47. Collectively, our results suggest that maternal gut microbial dysbiosis may serve as a potential mechanism underlying PBDE-47-elicited health hazards to mothers or even offspring.

Perinatal exposure to a human relevant mixture of persistent organic pollutants: Effects on mammary gland development, ovarian folliculogenesis and liver in CD-1 mice

The ability of persistent organic pollutants (POPs) with endocrine disrupting properties to interfere with the developing reproductive system is of increasing concern. POPs are transferred from dams to offspring and the high sensitivity of neonates to endocrine disturbances may be caused by underdeveloped systems of metabolism and excretion. The present study aimed to characterize the effect of in utero and lactational exposure to a human relevant mixture of POPs on the female mammary gland, ovarian folliculogenesis and liver function in CD-1 offspring mice. Dams were exposed to the mixture through the diet at Control, Low or High doses (representing 0x, 5000x and 100 000x human estimated daily intake levels, respectively) from weaning and throughout mating, gestation, and lactation. Perinatally exposed female offspring exhibited altered mammary gland development and a suppressed ovarian follicle maturation. Increased hepatic cytochrome P450 enzymatic activities indirectly indicated activation of nuclear receptors and potential generation of reactive products. Hepatocellular hypertrophy was observed from weaning until 30 weeks of age and could potentially lead to hepatotoxicity. Further studies should investigate the effects of human relevant mixtures of POPs on several hormones combined with female reproductive ability and liver function.

Effects of Decabrominated Diphenyl Ether Exposure on Growth, Meat Characteristics and Blood Profiles in Broilers

Decabrominated diphenyl ether (BDE-209) is widely used as a flame retardant and is detected at high levels in the environment. Its toxicities have been reported and have attracted attention. In the present study, broilers were used to determine the response in growth performance, carcass traits, meat quality, blood profiles and antioxidant system to BDE-209 exposure at doses of 0, 0.02, 0.4 and 4 mg/kg. The results showed that BDE-209 exposure at levels of 0.02 or 0.4 mg/kg increased feed intake and decreased feed efficiency. BDE-209 altered the blood profiles, such as reducing the numbers of white blood cells, lymphocytes and neutrophilic granulocytes. As compared with the control, BDE-209 exposure significantly increased abdominal fat percentages of broilers at 64.9-159.5% and adversely affected the selected biochemical indicators, including alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine (CRE), which indicated its toxicity to liver and kidney functions. Moreover, BDE-209 exposure significantly increased plasma malondialdehyde (MDA) concentrations and decreased the activities of glutathione peroxidase (GSH-px) and superoxide dismutase (SOD), which implied aggravating oxidant stress and decline of antioxidant capacity in broilers. In conclusion, our data demonstrated that the environmental pollutant BDE-209 adversely influenced growth performance, increased the deposition of abdominal fat, impaired antioxidant capacity and the immune system and had potential toxicity to the liver and kidney of broilers.

Intrauterine Hyperglycemia Alters the Metabolomic Profile in Fetal Mouse Pancreas in a Gender-Specific Manner

Mounting evidence has shown that intrauterine hyperglycemia exposure during critical stages of development may be contributing to the increasing prevalence of diabetes. However, little is known about the mechanisms responsible for offspring metabolic disorder. In this present study, we explored intrauterine hyperglycemia exposure on fetal pancreatic metabolome, and its potential link to impaired glucose tolerance in adult offspring. Here, using a GDM mouse model, we found the metabolome profiling of pancreas from male and female fetus showing altered metabolites in several important pathways, including 5-methylcytosine, α-KG, branched-chain amino acids, and cystine, which are associated with epigenetic modification, insulin secretion, and intracellular redox status, respectively. This finding suggests that intrauterine exposure to hyperglycemia could cause altered metabolome in pancreas, which might be a metabolism-mediated mechanism for GDM-induced intergenerational diabetes predisposition.

Ecological and toxicological assessments of anthropogenic contaminants based on environmental metabolomics

There has long been a great concern with growing anthropogenic contaminants and their ecological and toxicological effects on living organisms and the surrounding environment for decades. Metabolomics, a functional readout of cellular activity, can capture organismal responses to various contaminant-related stressors, acquiring direct signatures to illustrate the environmental behaviours of anthropogenic contaminants better. This review entails the application of metabolomics to profile metabolic responses of environmental organisms, e.g. animals (rodents, fish, crustacean and earthworms) and microorganisms (bacteria, yeast and microalgae) to different anthropogenic contaminants, including heavy metals, nanomaterials, pesticides, pharmaceutical and personal products, persistent organic pollutants, and assesses their ecotoxicological impacts with regard to literature published in the recent five years. Contaminant-induced metabolism alteration and up/down-regulation of metabolic pathways are revealed in typical organisms. The obtained insights of variations in global metabolism provide a distinct understanding of how anthropogenic contaminants exert influences on specific metabolic pathways on living organisms. Thus with a novel ecotechnique of environmental metabolomics, risk assessments of anthropogenic contaminants are profoundly demonstrated.

A rapid GC method coupled with quadrupole or time of flight mass spectrometry for metabolomics analysis

Gas chromatography-mass spectrometry (GC-MS) is an ideal tool for analyzing the intermediates of tricarboxylic acid cycle and glycolysis, sugars, organic acids and amino acids, etc. High-throughput metabolomics methods are required by large-scale clinical researches, and time of flight mass spectrometry (TOF MS) having fast scanning rate is preferable for rapid GC. Quadrupole MS (qMS) instruments have 95% market share, and their potential in rapid metabolomics is worth being studied. In this work, a within 15-min GC program was established and matched by qMS scanning for plasma metabolome analysis after N-methyl-N-(trimethylsilyl)-trifluoroacetamide derivatization. Compared to the longer-time program GC-qMS method, the rapid GC-qMS method had nearly no metabolome information loss, and it had excellent profile performance in repeatability, intra-day and inter-day precision, sampling range, linearity and extraction recovery. Compared to TOF MS, qMS achieved similar results in investigating lung cancer serum metabolic disruptions. Partial least squares-discriminant analysis revealed that the two datasets acquired by qMS and TOF MS had very similar model parameters, and most of top ranked differential metabolites were the same. This study provides a rapid and economical GC-qMS metabolomics method for researchers. Still, MS having faster scanning rate and higher sensitivity are recommended, if possible, to detect more small peaks and some co-eluted peaks.