High-fat diet in mice led to increased severity of spermatogenesis impairment by lead exposure: perspective from gut microbiota and the efficacy of probiotics

Molecular Changes Associated with Inflammation and Reproduction in Cadmium-Induced Testicular Toxicity: Mitigating Effect of Lactobacillus plantarum

Cadmium (Cd) is a dangerous heavy metal that causes toxicity in humans and animals. Various protective agents are being investigated to ameliorate the toxic effect of Cd. Lactic acid bacteria are promising as a protective agent because of their ability to remove heavy metals from contaminated products. The aim of this study was to evaluate the effects of Lactobacillus plantarum on biomarkers associated with reproduction and inflammation in the testes of rats exposed to Cd. For the application, rats were randomly divided into four groups: Control group, Cd group, L. plantarum group, and combined group (Cd + L. plantarum). At the end of 21 days of oral administration, testicular tissues of the rats were removed and mRNA expression levels of genes associated with reproduction (Dazl, Amh, and Ddx4) and inflammation (Tnf-α, Il-6, Cox-2, Inos, Foxo1, Foxo3, and Nfkb) were determined. On the other hand, the amounts of NOS2/iNOS, 8-ohdg, and Tnfα were analyzed in the tissues. The mtDNA copy number was also investigated. Cd caused an increase in the expression level of inflammation-related genes, except Nfkb, and a decrease in the expression level of reproduction-related genes. It also increased the levels of TNF-α, iNOS, and 8-OHdG biomarkers and mtDNA copy number. However, L. plantarum treatment did not cause a significant change in these parameters. Moreover, L. plantarum exposure in combination with Cd attenuated the observed Cd-mediated molecular changes in testicular tissue. In conclusion, the findings suggest that L. plantarum administration may be beneficial against Cd-induced testicular toxicity and may be considered as a biological agent in the development of protective strategies against environmental pollutants with further studies.

Probiotics Combined with Metformin Improves Sperm Parameters in Obese Male Mice through Modulation of Intestinal Microbiota Equilibrium

The decline in sperm parameters among obese males has attracted significant scholarly interest. The intestinal microbiota plays a crucial role in obesity, and investigating the intestinal-reproductive axis may offer a novel molecular approach to addressing the decline in male sperm parameters caused by obesity. To clarify whether probiotics, either alone or in conjunction with metformin, can enhance sperm parameters in obese male mice and assess the underlying mechanisms involved. 6-week-old male mice were constructed as obese models. Probiotics and metformin were used as intervention conditions. Changes in inflammatory factors and ROS content were detected by ELISA, morphological changes in testicular and colon tissues were observed by H&E staining, changes in intestinal microbiota abundance were detected by 16SrRNA gene sequencing, and changes in metabolites such as blood glucose, blood lipids, and lipopolysaccharide were detected by biochemical testing to investigate the mechanism of probiotics, metformin, and their combination to ameliorate reproductive impairment in obese male mice. Our results revealed that high-fat diet would result in reduced testicular spermatogenic tubule hierarchy, decreased spermatogenic cell counts, decreased sperm concentration and motility, and altered abundance of intestinal microbiota, whereas the combination of probiotics and metformin could restore high-fat-mediated pathophysiological alterations thereby ameliorating spermatogenic disorders in mice. The combination of probiotics and metformin can attenuate inflammation and oxidative stress, while enhancing androgen production to improve testicular spermatogenic function by re-construction intestinal microbiota equilibrium in HFD mice.

High-fat diet led to testicular inflammation and ferroptosis via dysbiosis of gut microbes

The disorder of gut microbiota has negative impact on male reproductive, and testicular damage is associated with obesity. However, the detailed mechanism of gut microbiota on the obesity-induced testis injury are still unknown. Therefore, we constructed a mouse model to investigate the effects of obesity on testis injury. In this study, we found that HFD-induced obesity could disorder gut microbiota homeostasis, which increased the abundance of Brevundimonas, Desulfovibrionaceae_unclassified and Ralstonia, ultimately leading to the overproduction of lipopolysaccharides (LPS). Meanwhile, HFD-feeding promoted intestinal permeability via inhibiting expression of tight junction proteins (ZO-1, Occludin and Claudin) and reducing excretion of mucus, leading to translocation of LPS. The over-accumulation of LPS in the bloodstream triggered an inflammatory response by activating TLR4/NF-κB pathway in testis. On the other hand, the gut microbiota produced-LPS also could induce ferroptosis in testis, as reflected by enhancing iron content and lipid peroxidation (MDA), as well as decreasing ferroptosis-related proteins, including GPX4, FTH1 and SLC1A11. Moreover, inhibition of LPS ligand (TLR4) with Resatorvid (TAK-242) alleviated obesity-induced testis injury through suppression of inflammation and ferroptosis. In conclusion, this study provides novel insights into the underlying mechanisms of obesity-related testis injury induced by gut microbiota disorder via the gut-testis axis, thus offering potential targets to counteract obesity-induced male reproductive disorder.

Exploring the hypothetical links between environmental pollutants, diet, and the gut-testis axis: The potential role of microbes in male reproductive health

The gut system, commonly referred to as one of the principal organs of the human "superorganism," is a home to trillions of bacteria and serves an essential physiological function in male reproductive failures or infertility. The interaction of the endocrine-immune system and the microbiome facilitates reproduction as a multi-network system. Some recent studies that link gut microbiota to male infertility are questionable. Is the gut-testis axis (GTA) real, and does it affect male infertility? As a result, this review emphasizes the interconnected links between gut health and male reproductive function via changes in gut microbiota. However, a variety of harmful (endocrine disruptors, heavy metals, pollutants, and antibiotics) and favorable (a healthy diet, supplements, and phytoconstituents) elements promote microbiota by causing dysbiosis and symbiosis, respectively, which eventually modify the activities of male reproductive organs and their hormones. The findings of preclinical and clinical studies on the direct and indirect effects of microbiota changes on testicular functions have revealed a viable strategy for exploring the GTA-axis. Although the GTA axis is poorly understood, it may have potential ties to reproductive issues that can be used for therapeutic purposes in the future.

Bile acid metabolism is altered in learning and memory impairment induced by chronic lead exposure

Lead is a neurotoxic contaminant that exists widely in the environment. Although lead neurotoxicity has been found to be tightly linked to gut microbiota disturbance, the effect of host metabolic disorders caused by gut microbiota disturbance on lead neurotoxicity has not been investigated. In this work, the results of new object recognition tests and Morris water maze tests showed that chronic low-dose lead exposure caused learning and memory dysfunction in mice. The results of 16 S rRNA sequencing of cecal contents and fecal microbiota transplantation showed that the neurotoxicity of lead could be transmitted through gut microbiota. The results of untargeted metabolomics and bile acid targeted metabolism analysis showed that the serum bile acid metabolism profile of lead-exposed mice was significantly changed. In addition, supplementation with TUDCA or INT-777 significantly alleviated chronic lead exposure-induced learning and memory impairment, primarily through inhibition of the NLRP3 inflammasome in the hippocampus to relieve neuroinflammation. In conclusion, our findings suggested that dysregulation of host bile acid metabolism may be one of the mechanisms of lead-induced neurotoxicity, and supplementation of specific bile acids may be a possible therapeutic strategy for lead-induced neurotoxicity.

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.

Indole-3-acetamide from gut microbiota activated hepatic AhR and mediated the remission effect of Lactiplantibacillus plantarum P101 on alcoholic liver injury in mice

Alcoholic liver disease is a prevalent condition resulting from excessive alcohol consumption, characterized by hepatic lipid accumulation and inflammation. This study delved into the protective effects and mechanisms of L. plantarum P101 on alcoholic liver injury in mice. As a result, L. plantarum P101 intervention reduced ALT and AST release, indicative of hepatocyte injury alleviation, while enhancing the activity of the antioxidant enzymes SOD and CAT. A reduction in pro-inflammatory cytokine TNF-α and an increase in anti-inflammatory cytokine IL-10 levels were observed in the L. plantarum P101-intervened mouse liver, signifying reduced inflammation within the mice. Furthermore, L. plantarum P101 intervention altered the gut microbial composition, primarily marked by an increase in Bacteroidota abundance, along with significant enrichment of beneficial bacteria, including Coprostanoligenes, Blautia and Lactiplantibacillus. Correlation analysis unveiled connections between serum tryptophan metabolites and the altered gut microbiota genera, suggesting that gut microbiota-driven effects may extend to extraintestinal organs through their metabolites. Intriguingly, serum indole-3-acetamide (IAM) was elevated by L. plantarum P101-regulated gut microbiota. Subsequently, the role of IAM in ameliorating alcoholic injury was explored using HepG2 cells, where it bolstered cell viability and attenuated EtOH-induced oxidative damage. Concomitantly, IAM activated the gene and protein expression of AhR in cells. Likewise, hepatic AhR expression in mice subjected to L. plantarum P101 significantly up-regulated, possibly instigated by gut microbiota-mediated IAM. Collectively, L. plantarum P101 orchestrates a modulation of gut microbiota and its metabolites, particularly IAM, to activate AhR, thereby alleviating alcoholic liver injury.

Comparative analysis of microbial community structure in different times of Panax ginseng Rhizosphere microbiome and soil properties under larch forest

BACKGROUND

Panax ginseng cultivated under the forest is popular because its shape and effective ingredients are similar to wild ginseng. The growth of P. ginseng in the larch forest is generally better than in the broad-leaved forest, and the incidence rate of diseases is low. Therefore, the selection of forest species is one of the basic factors in the successful cropping of P. ginseng.

METHODS

Illumina HiSeq high-throughput sequencing was used to analyze the 16S rRNA/ITS gene sequence of P. ginseng rhizosphere soil under larch forest to study the rhizosphere microbiome's diversity and community composition structure.

RESULTS

The species classification and richness of rhizosphere bacterial and fungal communities in the same-aged P. ginseng were similar. Consistent with the soil system of commonly cultivated crops, Proteobacteria, Actinobacteriota, Acidobacteriota, Verrucomicrobiota, Chloroflexi, and Basidiomycota, Ascomycota were the dominant phylum of bacteria and fungi, respectively. Compared with the soil without planting P. ginseng, the diversity of microorganisms and community structure of continuous planting for 2 years, 5 years, and 18 years of P. ginseng rhizosphere soil had little change. The accumulation levels of Ilyonectria, Fusarium, Gibberella, and Cylindrocarpon were not significantly increased with planting P. ginseng and the increased age of cropping P. ginseng.

CONCLUSIONS

The results of this study showed that the soil function of the larch forest was good, which provided a theoretical basis for the land selection and soil improvement of cultivating P. ginseng under the larch forest.