The fecal arsenic excretion, tissue arsenic accumulation, and metabolomics analysis in sub-chronic arsenic-exposed mice after in situ arsenic-induced fecal microbiota transplantation

Host-microbiota interplay in arsenic metabolism: Implications on host glucose homeostasis

Arsenic (As), a naturally occurring element with unique properties, has been recognized as the largest mass poisoning in the world by the World Health Organization (WHO). Approximately 200 million people worldwide are exposed to toxic levels of arsenic due to natural and anthropogenic activities. This widespread exposure necessitates a deeper understanding of microbe-arsenic interactions and their potential influence on host exposure and health risks. It is a major causative factor for metabolic diseases, including diabetes. Arsenic exposure has been linked to dysfunction in various cell types and tissues, notably affecting pancreatic islet cells. Numerous mechanisms have been identified to be responsible for arsenic exposure under both in vitro and in vivo conditions. These mechanisms contribute to the regulation of processes underlying diabetes etiology, such as glucose-stimulated insulin secretion from pancreatic beta cells. Unlike other toxic elements, arsenic undergoes metabolism by living organisms, including microbes, plants, and animals. Other toxic elements like Lead (Pb) and mercury (Hg) are generally not metabolized in the same way as Arsenic in microbes, plants and animals. In this review, we strive to initiate a dialogue by reviewing known aspects of microbe-arsenic interactions and placing it in the context of the potential for influencing host exposure and health risks. This review provides an up-to-date insight into arsenic metabolism by the human body and its associated microbiota, as well as the deciphered molecular pathways linking the different species of arsenic in the etiology of diabetes. Additionally, the future perspectives of mitigation and detoxification of arsenic in translational medicine and limitations in current scenarios are discussed. The comprehensive review presented here underscores the importance of exploring the complex interplay between arsenic metabolism, host-microbiota interactions, and their implications on glucose homeostasis and metabolic diseases. It emphasizes the need for continued research to develop effective strategies for mitigating arsenic-related health risks and fostering better translational medicine approaches.

Helicobacter pylori promotes intestinal flora imbalance and hepatic metabolic disorders under arsenic stress

Environmental arsenic contamination is a serious issue that cannot be ignored, since arsenic levels in drinking water frequently exceed safety standards, and there is an increased prevalence of Helicobacter pylori (H. pylori) infection. This results in an increasing population at risk of simultaneous exposure to both harmful agents, yet whether a synergistic interaction exists between them remains unclear. Therefore, this study aims to investigate the combined effects and underlying pathogenic mechanisms of concurrent exposure to these two hazardous factors by establishing a mouse model that is infected with H. pylori and exposed to inorganic arsenic through drinking water. Analysis of intestinal flora revealed significant alterations in the composition, relative abundance (Akkermansia, Faecalibaculum, Ilieibacterium, etc.), and metabolic potential of the intestinal microflora (amino acid metabolism and energy metabolism) in the combinatory exposure group. Non-targeted metabolomics analysis identified that the combinatory exposure group exhibited greater fluctuations in metabolite content, particularly in triacylglycerol, fatty-acid, peptide and amino acid. Moreover, H. pylori infection and arsenic exposure had increased levels of metabolites associated with the intestinal microbiota in their livers (4-Ethylphenyl sulfate and Phenylacetylglycine). Further analysis revealed significant correlations between changes in the intestinal flora and alterations in liver metabolic profiles. Herein, we hypothesize that H. pylori infection may exacerbate the intestinal flora imbalance and hepatic metabolic disturbances caused by arsenic exposure, which may disrupt enterohepatic homeostasis and potentially increase biological susceptibility to heavy metal toxicity.

Residues of veterinary drugs and heavy metal contamination in livestock and poultry meat from Hunan Province, China

Livestock and poultry meat consumption play an important role in the dietary structure of Chinese residents. However, the extent of residues of veterinary drugs and heavy metal contamination in livestock and poultry meat and their by-products within Hunan province is not extensively studied. This survey aimed to fill this gap by assessing the presence of 76 veterinary drug residues in Hunan province. Additionally, heavy metals in pork and pig liver were also assessed. The obtained findings suggest that residues of veterinary drugs are still present in livestock and poultry meat, as well as their by-products, within Hunan province. However, the contamination of heavy metals remained within the food safety limits. These results underscore the significance of establishing more refined criteria for assessing human exposure, taking into account factors such as consumption patterns, product varieties and chemical compounds of interest.

Modulation of gut microbiota with probiotics as a strategy to counteract endogenous and exogenous neurotoxicity

The existing data demonstrate that probiotic supplementation affords protective effects against neurotoxicity of exogenous (e.g., metals, ethanol, propionic acid, aflatoxin B1, organic pollutants) and endogenous (e.g., LPS, glucose, Aβ, phospho-tau, α-synuclein) agents. Although the protective mechanisms of probiotic treatments differ between various neurotoxic agents, several key mechanisms at both the intestinal and brain levels seem inherent to all of them. Specifically, probiotic-induced improvement in gut microbiota diversity and taxonomic characteristics results in modulation of gut-derived metabolite production with increased secretion of SFCA. Moreover, modulation of gut microbiota results in inhibition of intestinal absorption of neurotoxic agents and their deposition in brain. Probiotics also maintain gut wall integrity and inhibit intestinal inflammation, thus reducing systemic levels of LPS. Centrally, probiotics ameliorate neurotoxin-induced neuroinflammation by decreasing LPS-induced TLR4/MyD88/NF-κB signaling and prevention of microglia activation. Neuroprotective mechanisms of probiotics also include inhibition of apoptosis and oxidative stress, at least partially by up-regulation of SIRT1 signaling. Moreover, probiotics reduce inhibitory effect of neurotoxic agents on BDNF expression, on neurogenesis, and on synaptic function. They can also reverse altered neurotransmitter metabolism and exert an antiamyloidogenic effect. The latter may be due to up-regulation of ADAM10 activity and down-regulation of presenilin 1 expression. Therefore, in view of the multiple mechanisms invoked for the neuroprotective effect of probiotics, as well as their high tolerance and safety, the use of probiotics should be considered as a therapeutic strategy for ameliorating adverse brain effects of various endogenous and exogenous agents.

Could the gut microbiota be capable of making individuals more or less susceptible to environmental toxicants?

Environmental toxicants are chemical substances capable to impair environmental quality and exert adverse effects on humans and other animals. The main routes of exposure to these pollutants are through the respiratory tract, skin, and oral ingestion. When ingested orally, they will encounter trillions of microorganisms that live in a community - the gut microbiota (GM). While pollutants can disrupt the GM balance, GM plays an essential role in the metabolism and bioavailability of these chemical compounds. Under physiological conditions, strategies used by the GM for metabolism and/or excretion of xenobiotics include reductive and hydrolytic transformations, lyase and functional group transfer reactions, and enzyme-mediated functional transformations. Simultaneously, the host performs metabolic processes based mainly on conjugation, oxidation, and hydrolysis reactions. Thus, due to the broad variety of bacterial enzymes present in GM, the repertoire of microbial transformations of chemicals is considered a key component of the machinery involved in the metabolism of pollutants in humans and other mammals. Among pollutants, metals deserve special attention once contamination by metals is a worldwide problem, and their adverse effects can be observed even at very low concentrations due to their toxic properties. In this review, bidirectional interaction between lead, arsenic, cadmium, and mercury and the host organism and its GM will be discussed given the most recent literature, presenting an analysis of the ability of GM to alter the host organism's susceptibility to the toxic effects of heavy metals, as well as evaluating the extent to which interventions targeting the microbiota could be potential initiatives to mitigate the adverse effects resulting from poisoning by heavy metals. This study is the first to highlight the overlap between some of the bacteria found to be altered by metal exposure and the bacteria that also aid the host organism in the metabolism of these metals. This could be a key factor to determine the beneficial species able to minimize the toxicity of metals in future therapeutic approaches.

Effects of Intestinal Microbiota on the Biological Transformation of Arsenic in Zebrafish: Contribution and Mechanism

Both the gut microbiome and their host participate in arsenic (As) biotransformation, while their exact roles and mechanisms in vivo remain unclear and unquantified. In this study, as3mt-/- zebrafish were treated with tetracycline (TET, 100 mg/L) and arsenite (iAsIII) exposure for 30 days and treated with probiotic Lactobacillus rhamnosus GG (LGG, 1 × 108 cfu/g) and iAsIII exposure for 15 days, respectively. Structural equation modeling analysis revealed that the contribution rates of the intestinal microbiome to the total arsenic (tAs) and inorganic As (iAs) metabolism approached 44.0 and 18.4%, respectively. Compared with wild-type, in as3mt-/- zebrafish, microbial richness and structure were more significantly correlated with tAs and iAs, and more differential microbes and microbial metabolic pathways significantly correlated with arsenic metabolites (P < 0.05). LGG supplement influenced the microbial communities, significantly up-regulated the expressions of genes related to As biotransformation (gss and gst) in the liver, down-regulated the expressions of oxidative stress genes (sod1, sod2, and cat) in the intestine, and increased arsenobetaine concentration (P < 0.05). Therefore, gut microbiome promotes As transformation and relieves As accumulation, playing more active roles under iAs stress when the host lacks key arsenic detoxification enzymes. LGG can promote As biotransformation and relieve oxidative stress under As exposure.