Long-term exposure to phenanthrene at environmental-level induces intestinal dysbiosis and disrupted hepatic lipid metabolism in mice

Gut microbes in metabolic disturbances. Promising role for therapeutic manipulations?

The prevalence of overweight, obesity, type 2 diabetes, metabolic syndrome and steatotic liver disease is rapidly increasing worldwide with a huge economic burden in terms of morbidity and mortality. Several genetic and environmental factors are involved in the onset and development of metabolic disorders and related complications. A critical role also exists for the gut microbiota, a complex polymicrobial ecology at the interface of the internal and external environment. The gut microbiota contributes to food digestion and transformation, caloric intake, and immune response of the host, keeping the homeostatic control in health. Mechanisms of disease include enhanced energy extraction from the non-digestible dietary carbohydrates, increased gut permeability and translocation of bacterial metabolites which activate a chronic low-grade systemic inflammation and insulin resistance, as precursors of tangible metabolic disorders involving glucose and lipid homeostasis. The ultimate causative role of gut microbiota in this respect remains to be elucidated, as well as the therapeutic value of manipulating the gut microbiota by diet, pre- and pro- synbiotics, or fecal microbial transplantation.

Melatonin alleviates lead-induced fatty liver in the common carps (Cyprinus carpio) via gut-liver axis

As a widespread aquatic environmental contaminant, Lead (Pb) can provoke hepatic injury in various animals. Melatonin (MT) plays a crucial role in the regulation of inflammatory response. Accumulating evidence elucidates exogenous toxins can elicit hepatic lipid metabolic disorders by influencing the gut microbiome. Nevertheless, the effects of Pb on gut microbiota and hepatic lipid metabolism of the common carps, and whether MT can prevent and cure Pb-induced toxicity via regulating microbiome remains unknown. Here, metagenomic and transcriptomic analysis were subsequently implemented to identify the Pb exposure-triggered prominent alternation of gut-liver signal. In the present study the severe intestinal injury and fatty liver formation caused by Pb in common carp were preliminarily determined. Metagenomic analysis confirmed that the gut microbiome dominant phyla, family and genus of the common carps were Fusobacteria, Fusobacteriaceae and Cetobacterium. Meanwhile, lipopolysaccharide (LPS) biosynthesis pathway was regarded as one of the main responsible for Pb exposure. Subsequently, LPS was demonstrated as the Pb-triggered microbial-derived signal of the common carps by ELISA analysis, and involves in the hepatic metabolic disorders via deteriorating the intestinal barrier. Additionally, it confirmed that hepatocytes ferroptosis associated with Pb-evoked fatty liver of the common carps, and the aggravation of lysosomal dyshomeostasis as well as inhibition of AMPK phosphorylation were referred to lipid metabolic disorders. The results of the present study demonstrated microbial-derived signal induced by aquatic Pb contaminant cause fatty liver formation in the common carps, and the protective effects of MT on Pb toxicity were performed by receding LPS over-synthesis, restraining microbiota-sourced LPS transport, along with attenuation of hepatocytes ferroptosis.

Exposure to phenanthrene affects oocyte meiosis by inducing mitochondrial dysfunction and endoplasmic reticulum stress

OBJECTIVES

Phenanthrene (PHE) is one of the most abundant polycyclic aromatic hydrocarbons (PAHs), which is a widespread environmental contaminant. Various studies showed that PHE has adverse impacts on animals and human health. It has been shown that PHE exposure induced follicular atresia and endocrine dyscrasia in female mice. However, the potential mechanism regarding how PHE affects female reproductive system especially the oocyte quality has not been elucidated.

METHODS AND RESULTS

In this study, we set up PHE exposure model and found that PHE exposure compromised oocytes maturation competence by inhibiting spindle assembly and chromosomes alignment. Moreover, PHE exposure induced mitochondrial dysfunction and endoplasmic reticulum (ER) stress, leading to increased reactive oxygen species (ROS) and aberrant calcium levels in cytoplasm, eventually induced oxidative stress and DNA damage in oocytes. Furthermore, we found that oral administration of PHE caused the occurrence of oxidative stress and apoptosis in female ovary. In addition, the oocyte exhibited aberrant spindle morphology and failure of actin cap formation in metaphase II oocytes.

CONCLUSIONS

Taken together, our study demonstrated that mitochondrial dysfunction and ER stress-induced oxidative stress and DNA damage are the major cause of poor oocyte quality after PHE exposure.

Persistent organic pollutants in foods, their interplay with gut microbiota and resultant toxicity

Persistent Organic Pollutants (POPs) have become immensely prevalent in the environment as a result of their unique chemical properties (persistent, semi-volatile and bioaccumulative nature). Their occurrence in the soil, water and subsequently in food has become a matter of concern. With food being one of the major sources of exposure, the detrimental impact of these chemicals on the gut microbiome is inevitable. The gut microbiome is considered as an important integrant for human health. It participates in various physiological, biochemical and immunological activities; thus, affects the metabolism and physiology of the host. A myriad of studies have corroborated an association between POP-induced gut microbial dysbiosis and prevalence of disorders. For instance, ingestion of polychlorinated biphenyls, polybrominated diphenyl ethers or organochlorine pesticides influenced bile acid metabolism via alteration of bile salt hydrolase activity of Lactobacillus, Clostridium or Bacteroides genus. At the same time, some chemicals such as DDE have the potential to elevate Proteobacteria and Firmicutes/Bacteriodetes ratio influencing their metabolic activity leading to enhanced short-chain fatty acid synthesis, ensuing obesity or a pre-diabetic state. This review highlights the impact of POPs exposure on the gut microbiota composition and metabolic activity, along with an account of its corresponding consequences on the host physiology. The critical role of gut microbiota in impeding the POPs excretion out of the body resulting in their prolonged exposure and consequently, enhanced degree of toxicity is also emphasized.

The role of microbiota in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most frequent liver disease worldwide. Gut microbiota can play a role in the pathogenesis of NAFLD since dysbiosis is associated with reduced bacterial diversity, altered Firmicutes/Bacteroidetes ratio, a relative abundance of alcohol-producing bacteria, or other specific genera. Changes can promote disrupted intestinal barrier and hyperpermeability, filtration of bacterial products, activation of the immune system, and pro-inflammatory changes in the intestine, in the liver, and at a systemic level. Microbiota-derived molecules can contribute to the steatogenic effects. The link between gut dysbiosis and NAFLD, however, is confused by several factors which include age, BMI, comorbidities, dietary components, and lifestyle. The role of toxic chemicals in food and water requires further studies in both gut dysbiosis and NAFLD. We can anticipate that gut microbiota manipulation will represent a potential therapeutic tool to delay or reverse the progression of NAFLD, paving the way to primary prevention measures.

Gut microbiota disturbance exaggerates battery wastewater-induced hepatotoxicity through a gut-liver axis

As the primary source of electricity for various devices, batteries are important contributors to the overall electronic waste generated; and are widely considered a source of highly ecotoxic pollutants. Material leakage in battery manufacturing has not been completely solved, and the elucidation of the toxic mechanisms of battery wastewater exposure is needed. We demonstrated that battery waste exposure disrupted the intestinal flora and aggravated hepatotoxicity via the gut-liver axis. Under battery waste exposure, colon epithelium suffered physiological damage, and gene and protein expression levels related to gut barrier function (ZO-1, claudin-1, and Occludin) were significantly downregulated. Meanwhile, battery waste reduced the richness and diversity of the flora, causing metabolites produced by intestinal microbes to enter the gut-liver axis. Gut microbial dysbiosis impaired mitochondrial respiratory function in liver tissue cells, and mitophagy, apoptosis, and the disorder of glycolipids and amino acid metabolism were induced in hosts exposed to battery toxins. Altogether, these results provided novel insights into the underlying mechanisms of battery wastewater-related hepatotoxicity induced by gut microbiota via the gut-liver axis, which has public health implications where humans and animals are exposed to industrial toxins generated by uncontained battery disposal.

Tartrazine exposure results in histological damage, oxidative stress, immune disorders and gut microbiota dysbiosis in juvenile crucian carp (Carassius carassius)

Tartrazine (TZ) is an azo dye widely used in foods, cosmetics, beverages, textile, and leather. In recent years, there are reports on detecting azo dyes in the aquatic environment, so the impact of these compounds on aquatic organisms could not be ignored. In this study, we aimed to evaluate the adverse effects of TZ exposure on teleosts' embryo development and juvenile's health by using crucian carp (Carassius carassius) as the experimental fish. The results showed that embryos exposed to TZ (0.19, 0.76 and 1.5 mM) exhibited a deformity, delayed egg resorption and decreased fertilization and hatching rate. When the juvenile fish were exposed to TZ at a level higher than those present in water for 30 days caused severe histopathological damages of the gill, intestine, kidney and liver. Antioxidant enzymes (CAT, SOD and GSH-Px) activities in the gill, intestine and liver, exhibited a decreasing trend after TZ exposure, while MDA contents elevated. TZ exposure also resulted in the upregulation of pro-inflammatory cytokines (il1 and il6), lysozymes (lyz), complement component 3 (c3), and β-defensin 3 (defb3). In addition, TZ exposure also affected the intestinal microbiota structure. In summary, the data in the present study indicated that TZ exposure  reduce the embryo fertilization and hatching rate; cause histopathological damage of tissues, trigger oxidative stress, innate immune disorders and dysbiosis of gut microbiota in juvenile crucian carp. Therefore, it is necessary to be informed about the hazards of TZ exposure and the discharge of the dye into waters should be strictly administrated to prevent environmental pollution.