An expanding body of research indicates a correlation between the gut microbiota and various diseases. Metabolites produced by the gut microbiota act as mediators between the gut microbiota and the host, interacting with multiple systems in the human body to regulate physiological or pathological functions. However, further investigation is still required to elucidate the underlying mechanisms. One such metabolite involved in choline metabolism by gut microbes is trimethylamine (TMA), which can traverse the intestinal epithelial barrier and enter the bloodstream, ultimately reaching the liver where it undergoes oxidation catalyzed by flavin-containing monooxygenase 3 (FMO3) to form trimethylamine N-oxide (TMAO). While some TMAO is eliminated through renal excretion, remaining amounts circulate in the bloodstream, leading to systemic inflammation, endoplasmic reticulum (ER) stress, mitochondrial stress, and disruption of normal physiological functions in humans. As a representative microbial metabolite originating from the gut, TMAO has significant potential both as a biomarker for monitoring disease occurrence and progression and for tailoring personalized treatment strategies for patients. This review provides an extensive overview of TMAO sources and its metabolism in human blood, as well as its impact on several major human diseases. Additionally, we explore the latest research areas related to TMAO along with future directions.

An increasing number of studies have shown that the consumption of soybeans and soybeans products is beneficial to human health, and the biological activity of soy products may be attributed to the presence of Soy Isoflavones (SI) in soybeans. In the intestinal tracts of humans and animals, certain specific bacteria can metabolize soy isoflavones into equol. Equol has a similar chemical structure to endogenous estradiol in the human body, which can bind with estrogen receptors and exert weak estrogen effects. Therefore, equol plays an important role in the occurrence and development of a variety of hormone-dependent malignancies such as breast cancer and prostate cancer. Despite the numerous health benefits of equol for humans, only 30-50% of the population can metabolize soy isoflavones into equol, with individual variation in gut microbiota being the main reason. This article provides an overview of the relevant gut microbiota involved in the synthesis of equol and its anti-tumor effects in various types of cancer. It also summarizes the molecular mechanisms underlying its anti-tumor properties, aiming to provide a more reliable theoretical basis for the rational utilization of equol in the field of cancer treatment.

Background: Prostate cancer is one of the most common malignant tumors among men worldwide, and current treatments still face many challenges. Therefore, researchers are continuously seeking new therapeutic methods to improve treatment efficacy and reduce side effects. Phenylacetylglutamine (PAGln), a common metabolite of the gut microbiota, has been reported to have anti-inflammatory and anti-tumor activities.Methods: We assessed the impact of PAGln on prostate cancer using in vitro and in vivo models. Cell proliferation, migration, and invasion capabilities were evaluated through CCK8, EdU incorporation, and colony formation assays, as well as wound healing and Transwell assays. The in vivo anti-cancer effects of PAGln were evaluated using a BALB/c nude mouse xenograft model of prostate cancer and a lung metastatic tumor model established via tail vein injection. Molecular mechanisms were investigated through qRT-PCR and Western blot analysis.Results: PAGln inhibited the proliferation, migration, and invasion of prostate cancer (PCa) cells in vitro and suppressed the growth of prostate cancer in vivo. PAGln notably increased the mRNA levels of CCNG2 in PCa cells. Importantly, the knockdown of CCNG2 weakened the effects of PAGln on PCa cells. Mechanistic studies revealed that PAGln could promote the phosphorylation of β-catenin by upregulating CCNG2, thereby inhibiting the Wnt/β-catenin signaling pathway.Conclusion: In summary, PAGln can effectively inhibit the proliferation, migration, and invasion of PCa by upregulating CCNG2 and suppressing the Wnt/β-catenin signaling pathway. These findings suggest that PAGln may serve as a promising therapeutic agent for prostate cancer.

Background: Prostate cancer was the fourth most diagnosed cancer worldwide in 2022. Radical treatments and androgen deprivation therapy benefit newly diagnosed patients but impact quality of life, often leading to castration-resistant prostate cancer. Short-term dietary changes significantly affect the gut microbiota, which differs markedly between prostate cancer patients and healthy individuals, impacting both cancer progression and treatment response. A high-choline diet increases the risk of fatal prostate cancer, potentially mediated by the conversion of choline to the trimethylamine N-oxide (TMAO) by the gut microbiota.Methods: The CCK8 assay was employed to investigate whether TMAO affects the proliferation ability of prostate cancer cells and to determine the appropriate drug concentration. Subsequently, CCK8 time gradients, colony formation assays, and EdU assays measured TMAO’s influence on cell proliferation. Wound healing and transwell migration assays evaluated TMAO’s effect on cell migration. RNA-seq analysis was performed to explore the mechanisms by which TMAO influences the proliferation and migration of prostate cancer cells. qPCR and Western blotting were utilized to validate the expression of related mRNA or proteins. Finally, we performed in vivo experiments to evaluate the effect of a high choline diet on the growth of subcutaneous tumors and lung metastases in mice.Results: Our study found that TMAO enhances the proliferation and migration of prostate cancer cells by upregulating HMOX1 via activation of the MAPK signaling pathway, specifically p38 MAPK. In mouse subcutaneous tumor and lung metastatic tumor experiments, the high-choline diet increased prostate cancer cell proliferation and migration, resulting in significantly greater tumor volume and number of metastases than controls.Conclusion: This study is the first to demonstrate the role of the gut microbiota-derived metabolite TMAO in prostate cancer. TMAO promotes the proliferation and migration of prostate cancer cells by activating the p38 pathway and increasing HMOX1 expression. Reducing choline intake through dietary intervention may delay the onset and progression of prostate cancer, presenting significant clinical application value.

Background: Kidney stones are a common urologic disease with an increasing incidence year by year, and there are similar influences between gout status and kidney stone incidence. Therefore the contribution of gout status to the incidence of kidney stones is unclear. The aim of this study was to investigate the relationship between gout status and kidney stones and to further explore the causal relationship by Mendelian randomization (MR) analysis.Method: An epidemiologic study of 49,693 participants in the 2009–2018 National Health and Nutrition Examination Survey (NHANES) was conducted to examine the association between the two. The causal relationship between gout status and kidney stones was assessed by Mendelian randomization analysis of data from the GWAS database.Result: A total of 28,742 participants were included in the NHANES analysis. We found that gout status was associated with an increased risk of kidney stones [odds ratio (OR) = 1.45 (95%CI, 1.243–1.692); p < 0.001]. In the MR analysis, we found a causal relationship between gout status and the risk of developing kidney stones (OR = 1.047, 95%CI, 1.011–1.085, p = 0.009).Conclusion: There may be an association between gout status and kidney stone risk. This finding requires further large-sample studies and adequate follow-up.