Urolithin B suppresses tumor growth in hepatocellular carcinoma through inducing the inactivation of Wnt/β-catenin signaling

Urolithin B inhibits the differentiation of M1 macrophages and relieves the inflammation around the implants under osteoporosis via down-regulating the phosphorylation of VEGFR2

The inflammation causes the destroyed osseointegration at the implant-bone interface, significantly increasing the probability of implant loosening in osteoporotic patients. Currently, inhibiting the differentiation of M1 macrophages and the inflammatory response could be a solution to stabilize the microenvironment of implants. Interestingly, some natural products have anti-inflammatory and anti-polarization effects, which could be a promising candidate for stabilizing the implants' microenvironment in osteoporotic patients. This research aims to explore the inhibitory effect of Urolithin B(UB) on macrophage M1 polarization, which ameliorates inflammation, thus alleviating implant instability. We established an osteoporosis mouse model of implant loosening. The mouse tissues were taken out for morphological analysis, staining analysis, and bone metabolic index analysis. In in vitro experiments, RAW264.7 cells were polarized to M1 macrophages using lipopolysaccharide (LPS) and analyzed by immunofluorescence (IF) staining, Western blot (WB), and flow cytometry. The CSP100 plus chip experiments were used to explore the potential mechanisms behind the inhibiting effects of UB. Through observation of these experiments, UB can improve the osseointegration between the implants and femurs in osteoporotic mice and enhance the stability of implants. The UB can inhibit the differentiation of M1 macrophages and local inflammation via inhibiting the phosphorylation of VEGFR2, which can be further proved by the weakened inhibited effects of UB in macrophages with lentivirus-induced overexpression of VEGFR2. Overall, UB can specifically inhibit the activation of VEGFR2, alleviate local inflammation, and improve the stability of implants in osteoporotic mice.

Urolithin C suppresses colorectal cancer progression via the AKT/mTOR pathway

Urolithin families are gut-microbial metabolites of ellagic acid (EA). Although urolithin A (UA) and urolithin B (UB) were reported to have antiproliferative activities in cancer cells, the role and related mechanisms of urolithin C (UC) in colorectal cancer (CRC) have not yet been clarified. In this study, we assess the antitumor activities of UC in vitro and in vivo and further explore the underlying mechanisms in CRC cell lines. We found that UC inhibited the proliferation and migration of CRC cells, induced apoptosis, and arrested the cell cycle at the G2/M phase in vitro, and UC inhibited tumor growth in a subcutaneous transplantation tumor model in vivo. Mechanically, UC blocked the activation of the AKT/mTOR signaling pathway by decreasing the expression of Y-box binding protein 1(YBX1). The AKT agonist SC79 could reverse the suppression of cell proliferation in UC-treated CRC cells. In conclusion, our research revealed that UC could prevent the progression of CRC by blocking AKT/mTOR signaling, suggesting that it may have potential therapeutic values.

Multi-omics-based investigation of Bifidobacterium's inhibitory effect on glioma: regulation of tumor and gut microbiota, and MEK/ERK cascade

Glioma, the most prevalent primary tumor of the central nervous system, is characterized by a poor prognosis and a high recurrence rate. The interplay between microbes, such as gut and tumor microbiota, and the host has underscored the significant impact of microorganisms on disease progression. Bifidobacterium, a beneficial bacterial strain found in the human and animal intestines, exhibits inhibitory effects against various diseases. However, the existing body of evidence pertaining to the influence of Bifidobacterium on glioma remains insufficient. Here, we found that Bifidobacterium reduces tumor volume and prolongs survival time in an orthotopic mouse model of glioma. Experiments elucidated that Bifidobacterium suppresses the MEK/ERK cascade. Additionally, we noted an increase in the α-diversity of the tumor microbiota, along with an augmented relative abundance of Bifidobacterium in the gut microbiota. This rise in Bifidobacterium levels within the intestine may be attributed to a concurrent increase in Bifidobacterium within the glioma. Additionally, Bifidobacterium induced alterations in serum metabolites, particularly those comprised of organonitrogen compounds. Thus, our findings showed that Bifidobacterium can suppress glioma growth by inhibiting the MEK/ERK cascade and regulating tumor, and gut microbiota, and serum metabolites in mice, indicating the promising therapeutic prospects of Bifidobacterium against glioma.

The Gut Connection: Exploring the Possibility of Implementing Gut Microbial Metabolites in Lymphoma Treatment

Recent research has implicated the gut microbiota in the development of lymphoma. Dysbiosis of the gut microbial community can disrupt the production of gut microbial metabolites, thereby impacting host physiology and potentially contributing to lymphoma. Dysbiosis-driven release of gut microbial metabolites such as lipopolysaccharides can promote chronic inflammation, potentially elevating the risk of lymphoma. In contrast, gut microbial metabolites, such as short-chain fatty acids, have shown promise in preclinical studies by promoting regulatory T-cell function, suppressing inflammation, and potentially preventing lymphoma. Another metabolite, urolithin A, exhibited immunomodulatory and antiproliferative properties against lymphoma cell lines in vitro. While research on the role of gut microbial metabolites in lymphoma is limited, this article emphasizes the need to comprehend their significance, including therapeutic applications, molecular mechanisms of action, and interactions with standard chemotherapies. The article also suggests promising directions for future research in this emerging field of connection between lymphoma and gut microbiome.

Gallic acid promotes ferroptosis in hepatocellular carcinoma via inactivating Wnt/β-catenin signaling pathway

Hepatocellular carcinoma (HCC) has high morbidity and mortality, and effective therapies are lacking. Gallic acid (GA), a natural phenolic compound derived from plants, has been reported to prevent the onset and progression of various cancers. However, there is limited elaboration on the potential mechanisms and anticancer effects of GA on hepatocellular carcinoma. Inducing ferroptosis of tumor cells has become one of the most promising ways to eradicate tumor cells. However, the effect of GA on HCC ferroptosis remains unknown. We evaluated the impact of GA on cell viability, migration, and mitochondrial morphology in HepG2 cells. Our study identified a critical role of GA in inducing ferroptosis in HepG2 cells. Mechanistically, we found that GA could inhibit the expression of a ferroptosis-related protein SLC7A11 and GPX4 in HepG2, by blocking β-catenin transport from nuclear to the cytoplasm, thus inducing the inactivation of the Wnt/β-catenin pathway. Our study has confirmed that GA is a novel ferroptosis inducer of HC, suggesting GA could be a promising candidate for the clinical treatment of HCC.

Urolithin B protects PC12 cells against glutamate-induced toxicity

BACKGROUND

The involvement of malfunctioning glutamate systems in various central nervous system (CNS) disorders is widely acknowledged. Urolithin B, known for its neuroprotective and antioxidant properties, has shown potential as a therapeutic agent for these disorders. However, little is known about its protective effects against glutamate-induced toxicity in PC12 cells. Therefore, in this study, for the first time we aimed to investigate the ability of Urolithin B to reduce the cytotoxic effects of glutamate on PC12 cells.

METHODS

Different non-toxic concentrations of urolithin B were applied to PC12 cells for 24 h before exposure to glutamate (10 mM). The cells were then analyzed for cell viability, intracellular reactive oxygen species (ROS), cell cycle arrest, apoptosis, and the expression of Bax and Bcl-2 genes.

RESULTS

The results of MTT assay showed that glutamate at a concentration of 10 mM and urolithin B at a concentration of 114 μM can reduce PC12 cell viability by 50%. However, urolithin B at non-toxic concentrations of 4 and 8 μM significantly reduced glutamate-induced cytotoxicity (p < 0.01). Interestingly, treatment with glutamate significantly enhanced the intracellular ROS levels and apoptosis rate in PC12 cells, while pre-treatment with non-toxic concentrations of urolithin B significantly reduced these cytotoxic effects. The results also showed that pre-treatment with urolithin B can decrease the Bax (p < 0.05) and increase the Bcl-2 (p < 0.01) gene expression, which was dysregulated by glutamate.

CONCLUSIONS

Taken together, urolithin B may play a protective role through reducing oxidative stress and apoptosis against glutamate-induced toxicity in PC12 cells, which merits further investigations.

Urolithin B alleviates Helicobacter pylori-induced inflammation and oxidative stress in mice

BACKGROUND

Helicobacter pylori is one of the most common chronic bacterial infections. Active eradication of H. pylori infection is rare due to the fact that most infected patients are asymptomatic and the use of large amounts of antibiotics in eradication therapy leads to severe side effects. Urolithin B (UB) is an additional major intestinal metabolite of ellagic acid (EA), which has been shown to possess anti-inflammatory, antioxidant, and antiapoptotic biological activities. Preventing the incidence of H. pylori-related gastric disease and reducing the damage to the host by H. pylori is a current approach to control H. pylori infection. In this study, we explored the effect of UB on H. pylori infection.

MATERIALS AND METHODS

The effects of UB on inflammation and oxidative stress induced by H. pylori in vivo and in vitro were investigated by qPCR, ELISA, HE staining, IHC staining, etc. RESULTS: UB reduced the adhesion and colonization of H. pylori and improved H. pylori-induced inflammation and oxidative stress in vivo and in vitro. Moreover, UB had better anti-inflammatory and antioxidant effects than clarithromycin (CLR) and metronidazole (MET). In addition to inhibiting the secretion of CagA, UB reduced tissue damage by H. pylori infection.

CONCLUSIONS

UB was effective in improving damage caused by H. pylori.

Urolithin B inhibits proliferation and migration and promotes apoptosis and necrosis by inducing G2/M arrest and targeting MMP-2/-9 expression in osteosarcoma cells

Osteosarcoma (OS) is the most prevalent primary bone cancer, with a high morbidity and mortality rate. Over the past decades, therapeutic approaches have not considerably improved patients' survival rates, and further research is required to find efficient treatments for OS. Data from several studies have shown that urolithin B (UB), the intestinal metabolite of polyphenolic ellagitannins, is emerging as a new class of anticancer compounds, yet its effect on OS cancer cells remains elusive. Herein, we investigated UB's antimetastatic, antiproliferative, and apoptotic effects on the MG-63 OS cell line. Cell viability assay, annexin V/propidium iodide staining, cell cycle arrest analysis, determination of the gene expression of MMP-2, MMP-9, Bax, Bcl-2, and p53 messenger RNA (mRNA), evaluation of reactive oxygen species (ROS) generation and migration, and MMP-2 and MMP-9 protein expression assessments were performed. UB caused late apoptosis, necrosis, G2/M arrest, and ROS generation in MG-63 cells. It increased the mRNA expression of the p53 tumor suppressor and Bax proapoptotic genes. UB also inhibited the migration and metastatic behavior of MG-63 OS cells by downregulating mRNA and MMP-2 and MMP-9 protein expression. In general, although further in vivo investigations are warranted, the current results showed that UB might be utilized as a potential novel natural compound for OS therapy due to its nontoxic, antiproliferative, and antimetastatic nature.

Inhibitory Effects of Urolithins, Bioactive Gut Metabolites from Natural Polyphenols, against Glioblastoma Progression

We previously reported that proinflammatory cytokines, particularly tumor necrosis factor (TNF)-α, promoted tumor migration, invasion, and proliferation, thus worsening the prognosis of glioblastoma (GBM). Urolithins, the potent metabolites produced by the gut from pomegranate polyphenols, have anticancer properties. To develop an effective therapy for GBM, this study aimed to study the effects of urolithins against GBM. Urolithin A and B significantly reduced GBM migration, reduced epithelial-mesenchymal transition, and inhibited tumor growth. Moreover, urolithin A and B inhibited TNF-α-induced vascular cell adhesion molecule (VCAM)-1 and programmed death ligand 1 (PD-L1) expression, thereby reducing human monocyte (HM) binding to GBM cells. Aryl hydrocarbon receptor (AhR) level had higher expression in patients with glioma than in healthy individuals. Urolithins are considered pharmacological antagonists of AhR. We demonstrated that the inhibition of AhR reduced TNF-α-stimulated VCAM-1 and PD-L1 expression. Furthermore, human macrophage condition medium enhanced expression of PD-L1 in human GBM cells. Administration of the AhR antagonist attenuated the enhancement of PD-L1, indicating the AhR modulation in GBM progression. The modulatory effects of urolithins in GBM involve inhibiting the Akt and epidermal growth factor receptor pathways. The present study suggests that urolithins can inhibit GBM progression and provide valuable information for anti-GBM strategy.

Urolithins: A Prospective Alternative against Brain Aging

The impact of host-microbiome interactions on cognitive health and disease has received increasing attention. Microbial-derived metabolites produced in the gut are one of crucial mechanisms of the gut-brain axis interaction, showing attractive perspectives. Urolithins (Uros) are gut microbial-derived metabolites of ellagitannins and ellagic acid, whose biotransformation varies considerably between individuals and decreases greatly with age. Recently, accumulating evidence has suggested that Uros may have specific advantages in preventing brain aging including favorable blood-brain barrier permeability, selective brain distribution, and increasingly supporting data from preclinical and clinical studies. However, the usability of Uros in diagnosis, prevention, and treatment of neurodegenerative diseases remains elusive. In this review, we aim to present the comprehensive achievements of Uros in age-related brain dysfunctions and neurodegenerative diseases and discuss their prospects and knowledge gaps as functional food, drugs, or biomarkers against brain aging.

Urolithin B loaded in cerium oxide nanoparticles enhances the anti-glioblastoma effects of free urolithin B in vitro

Glioblastoma multiforme (GBM) is the most aggressive kind of malignant primary brain tumor in humans. Given the limitation of Conventional therapeutic strategy, the development of nanotechnology and natural product therapy seems to be an effective method enhancing the prognosis of GBM patients. In this research, cell viability, mRNA expressions of various apoptosis-related genes apoptosis, and generation of reactive oxygen species (ROS) in human U-87 malignant GBM cell line (U87) treated with Urolithin B (UB) and CeO₂-UB. Unlike CeO₂-NPs, both UB and CeO₂-UB caused a dose-dependent decrease in the viability of U87 cells. The half-maximal inhibitory concentration values of UB and CeO₂-UB were 315 and 250 μM after 24 h, respectively. Moreover, CeO₂-UB exerted significantly higher effects on U87 viability, P53 expression, and ROS generation. Furthermore, UB and CeO2-UB increased the accumulation of U87 cells in the SUB-G1 population, decreased the expression of cyclin D1, and increased the Bax/Bcl2 ratio expression. Collectively, these data indicate that CeO₂-UB exhibited more substantial anti-GBM effects than UB. Although further in vivo investigations are needed, these results proposed that CeO₂-NPs could be utilized as a potential novel anti-GBM agent after further studies.

A Review of Gut Microbiota-Derived Metabolites in Tumor Progression and Cancer Therapy

Gut microbiota-derived metabolites are key hubs connecting the gut microbiome and cancer progression, primarily by remodeling the tumor microenvironment and regulating key signaling pathways in cancer cells and multiple immune cells. The use of microbial metabolites in radiotherapy and chemotherapy mitigates the severe side effects from treatment and improves the efficacy of treatment. Immunotherapy combined with microbial metabolites effectively activates the immune system to kill tumors and overcomes drug resistance. Consequently, various novel strategies have been developed to modulate microbial metabolites. Manipulation of genes involved in microbial metabolism using synthetic biology approaches directly affects levels of microbial metabolites, while fecal microbial transplantation and phage strategies affect levels of microbial metabolites by altering the composition of the microbiome. However, some microbial metabolites harbor paradoxical functions depending on the context (e.g., type of cancer). Furthermore, the metabolic effects of microorganisms on certain anticancer drugs such as irinotecan and gemcitabine, render the drugs ineffective or exacerbate their adverse effects. Therefore, a personalized and comprehensive consideration of the patient's condition is required when employing microbial metabolites to treat cancer. The purpose of this review is to summarize the correlation between gut microbiota-derived metabolites and cancer, and to provide fresh ideas for future scientific research.

The Gut Microbiota Metabolite Urolithin B Prevents Colorectal Carcinogenesis by Remodeling Microbiota and PD-L1/HLA-B

Colorectal cancer has risen to the third occurring cancer in the world. Fluorouracil (5-Fu), oxaliplatin, and cisplatin are the most effective chemotherapeutic agents for clinical chemotherapy. Nevertheless, due to chemotherapeutic drug resistance, the survival rate of patients with CRC remains very low. In this study, we used the inflammation-induced or mutation-family-inherited murine CRC models to study the anticancer and immunotherapy effects of urolithin B (UB), the final metabolite of polyphenols in the gastrointestinal tract. The label-free proteomics analysis and the gene ontology (GO) classifications were used to test and analyze the proteins affected by UB. And 16S rDNA sequencing and flow cytometry were utilized to uncover gut microbiome composition and immune defense improved by UB administration. The results indicated that urolithin B prevents colorectal carcinogenesis by remodeling gut microbial and tumor immune microenvironments, such as HLA-B, NK cells, regulatory T cells, and γδ TCR cells, and decreasing the PD-L1. The combination of urolithin B with first-line therapeutic drugs improved the colorectal intestinal hematochezia by shaping gut microbiota, providing a strategy for the treatment of immunotherapy treatment for CRC treatments. UB combined with anti-PD-1 antibody could inhibit the growth of colon cancer. Urolithin B may thus contribute to anticancer treatments and provide a high immune response microenvironment for CRC patients' further immunotherapy.

Berberine inhibits tumour growth in vivo and in vitro through suppressing the lincROR-Wnt/β-catenin regulatory axis in colorectal cancer

BACKGROUND

Berberine, a non-prescription medicine clinically applied for diarrhoea and gastroenteritis. Recent studies have demonstrated that it possesses anti-tumour properties in colorectal cancer, but the exact molecular mechanism remains obscure.

OBJECTIVES

To elucidate the underly molecular mechanisms of berberine in colorectal cancer from a perspective of epigenetics, and tried to explore the role of lincROR-Wnt/β-catenin molecular axis in the berberine induced the anti-tumour activity in colorectal cancer.

METHODS

The effects of berberine on cell growth, cell cycle and apoptosis were examined in CRC cells. The in vivo effect of berberine on tumour growth was investigated using a xenograft mice model. Moreover, lincROR and Wnt/β-catenin signalling were detected by luciferase activity, qRT-PCR and western blotting assays.

KEY FINDINGS

Berberine suppressed cell growth in vitro via inducing cell cycle arrest and apoptosis in CRC cell, and inhibited tumourigenesis in vivo. LincROR was significantly down-regulated by berberine, inducing the inactivation of the canonical Wnt/β-catenin signalling, meanwhile, the overexpression of lincROR partially reversed the suppressive effects on tumour growth and Wnt/β-catenin signalling induced by berberine.

CONCLUSIONS

Berberine inhibits tumour growth partially via regulating the lincROR-Wnt/β-catenin regulatory axis, which provides a strategy for the design of anti-tumour drugs for CRC patients after our advanced validation.

The Impact of Ellagitannins and Their Metabolites through Gut Microbiome on the Gut Health and Brain Wellness within the Gut-Brain Axis

Ellagitannins (ETs) are a large group of bioactive compounds found in plant-source foods, such as pomegranates, berries, and nuts. The consumption of ETs has often been associated with positive effects on many pathologies, including cardiovascular diseases, neurodegenerative syndromes, and cancer. Although multiple biological activities (antioxidant, anti-inflammatory, chemopreventive) have been discussed for ETs, their limited bioavailability prevents reaching significant concentrations in systemic circulation. Instead, urolithins, ET gut microbiota-derived metabolites, are better absorbed and could be the bioactive molecules responsible for the antioxidant and anti-inflammatory activities or anti-tumor cell progression. In this review, we examined the dietary sources, metabolism, and bioavailability of ETs, and analyzed the last recent findings on ETs, ellagic acid, and urolithins, their intestinal and brain activities, the potential mechanisms of action, and the connection between the ET microbiota metabolism and the consequences detected on the gut-brain axis. The current in vitro, in vivo, and clinical studies indicate that ET-rich foods, individual gut microbiomes, or urolithin types could modulate signaling pathways and promote beneficial health effects. A better understanding of the role of these metabolites in disease pathogenesis may assist in the prevention or treatment of pathologies targeting the gut-brain axis.

The Synthesis of Urolithins and their Derivatives and the Modes of Antitumor Action

Urolithins are microbial metabolites derived from berries and pomegranate fruits, which display anti-inflammatory, anti-oxidative, and anti-aging activities. There are eight natural urolithins (urolithin A-E, M5, M6 and M7), which have been isolated by now. Structurally, urolithins are phenolic compounds and belong to 6H-dibenzo [b,d] pyran-6-one. They have drawn considerable attention because of their vast range of biological activities and health benefits. Recent studies also suggest that they possess anti-SARS-CoV-2 and anticancer effects. In this article, the recent advances in the synthesis of urolithins and their derivatives from 2015 to 2021 are reviewed. To improve or overcome the solubility and metabolism stability issues, the modifications of urolithins are mainly centered on the hydroxy group and lactone group, and some compounds have been found to display promising results and the potential for further study. The possible modes of antitumor action of urolithin are also discussed. Several signaling pathways, including PI3K-Akt, Wnt/β-catenin pathways, and multiple receptors (aryl hydrocarbon receptor, estrogen and androgen receptors) and enzymes (tyrosinase and lactate dehydrogenase) are involved in the antitumor activity of urolithins.

Urolithins: a Comprehensive Update on their Metabolism, Bioactivity, and Associated Gut Microbiota

Urolithins, metabolites produced by the gut microbiota from the polyphenols ellagitannins and ellagic acid, are discovered by the research group in humans almost 20 years ago. Pioneering research suggests urolithins as pleiotropic bioactive contributors to explain the health benefits after consuming ellagitannin-rich sources (pomegranates, walnuts, strawberries, etc.). Here, this study comprehensively updates the knowledge on urolithins, emphasizing the review of the literature published during the last 5 years. To date, 13 urolithins and their corresponding conjugated metabolites (glucuronides, sulfates, etc.) have been described and, depending on the urolithin, detected in different human fluids and tissues (urine, blood, feces, breastmilk, prostate, colon, and breast tissues). There has been a substantial advance in the research on microorganisms involved in urolithin production, along with the compositional and functional characterization of the gut microbiota associated with urolithins metabolism that gives rise to the so-called urolithin metabotypes (UM-A, UM-B, and UM-0), relevant in human health. The design of in vitro studies using physiologically relevant assay conditions (molecular forms and concentrations) is still a pending subject, making some reported urolithin activities questionable. In contrast, remarkable progress has been made in the research on the safety, bioactivity, and associated mechanisms of urolithin A, including the first human interventions.

Inhibition of glioblastoma proliferation, invasion, and migration by Urolithin B through inducing G0/G1 arrest and targeting MMP-2/-9 expression and activity

One kind of brain cancer with a dismal prognosis is called glioblastoma multiforme (GBM) due to its high growth rate and widespread tumor cell invasion into various areas of the brain. To improve therapeutic approaches, the objective of this research investigates the cytotoxic, anti-metastatic, and apoptotic effect of urolithin-B (UB) as a bioactive metabolite of ellagitannins (ETs) on GBM U87 cells. The malignant GBM cell line (U87) was examined for apoptosis rate, cell cycle analysis, cell viability, mRNA expressions of several apoptotic and metastasis-associated genes, production of reactive oxygen species (ROS), MMP-2, and MMP-9 activity and protein expression, and migration ability. The findings revealed that UB decreased U87 GBM viability in a dose-dependent manner and NIH/3T3 normal cells with the IC₅₀ value of 30 and 55 μM after 24 h, respectively. UB also induces necrosis and G0/G1 cell cycle arrest in U87 cells. UB also increases ROS production and caused down-regulation of Bcl2 and up-regulation of Bax apoptotic genes. Additionally, treatment of UB reduced the migration of U87 cells. The protein levels, mRNA expression, and the MMP-2 and MMP-9 enzyme activities also decreased concentration-dependently. So, due to the non-toxic nature of UB and its ability to induce apoptosis and reduce the U87 GBM cell invasion and migration, after more research, it can be regarded as a promising new anti-GBM compound.

Synthesis of 7-hydroxydibenzopyran-6-ones via benzannulation of coumarins

We have successfully demonstrated a facile synthesis of a variety of 7-hydroxydibenzopyran-6-ones via a two-step protocol from 3-acylcoumarins having a latent Nazarov dienone functionality. Condensation of 3-acylcoumarins and ethyl cyanoacetate under basic (wet K₂CO₃) and microwave irradiation conditions followed by decarboethoxylative aromatization with Br₂ or DDQ furnished dibenzopyran-6-ones in high yields. The formation of ring C of the dibenzopyran-6-one motif critically depended on an active methylene compound and C7 substitution on coumarins. The Ar-Br or ArOTf substitution in dibenzopyran-6-ones was leveraged for the palladium-catalysed Suzuki coupling with diverse aryl boronic acids to increase the structural diversity. Reductive decyanation of C10 cyano dibenzopyran-6-ones furnished some of the isomers of urolithin A.

The Therapeutic Relevance of Urolithins, Intestinal Metabolites of Ellagitannin-Rich Food: A Systematic Review of In Vivo Studies

The therapeutic effects of food rich in ellagitannins have been established to stem from its microbial metabolite, urolithin. Over the past decade, there has been a growing trend in urolithin research pertaining to its pharmacological properties. The purpose of this systematic review is to collate and synthesise all available data on urolithin’s therapeutic ability, to highlight its potential as a pharmaceutical agent, and prospective direction on future research. Methods: This systematic review was written based on the PRISMA guideline and was conducted across Ovid via Embase, Ovid MEDLINE, Cochrane Central Register for Controlled Trials, and Web of Science Core Collection. Results: A total of 41 animal studies were included in this systematic review based on the appropriate keyword. The included studies highlighted the neuroprotective, anti-metabolic disorder activity, nephroprotective, myocardial protective, anti-inflammatory, and musculoskeletal protection of urolithin A, B, and its synthetic analogue methylated urolithin A. The Sirt1, AMPK, and PI3K/AKT/mTOR signalling pathways were reported to be involved in the initiation of autophagy and mitochondrial biogenesis by urolithin A. Conclusions: This review methodically discusses the therapeutic prospects of urolithins and provides scientific justification for the potential development of urolithin A as a potent natural mitophagy inducer for anti-ageing purposes.

Health functions and related molecular mechanisms of ellagitannin-derived urolithins

Ellagitannins are vital bioactive polyphenols that are widely distributed in a variety of plant-based foods. The main metabolites of ellagitannins are urolithins, and current research suggests that urolithins provide a variety of health benefits. This review focused on the role of the gut bacteria in the conversion of ellagitannins to urolithins. Based on the results of in vitro and in vivo studies, the health benefits of urolithins, including antioxidant, anti-inflammatory, anti-cancer, anti-obesity, anti-diabetic, anti-aging, cardiovascular protective, neuroprotective, kidney protective, and muscle mass protective effects, were thoroughly outlined, with a focus on their associated molecular mechanisms. Finally, we briefly commented on urolithins' safety. Overall, urolithins' diverse health benefits indicate the potential utilization of ellagitannins and urolithins in the creation of functional foods and nutraceuticals to treat and prevent some chronic diseases.

Urolithin B suppresses osteoclastogenesis via inhibiting RANKL-induced signalling pathways and attenuating ROS activities

Osteoporosis (OP) has severely affected human health, which is characterized by abnormal differentiation of osteoclasts. Urolithin B (UB), as a potential natural drug, has been reported to exhibit numerous biological activities including antioxidant and anti‐inflammatory but its effects on OP, especially on RANKL‐stimulated osteoclast formation and activation, are still understood. In our study, we have demonstrated for the first time that UB inhibits RANKL‐induced osteoclast differentiation and explored its potential mechanisms of action. The RAW264.7 cells were cultured and induced with RANKL followed by UB treatment. Then, the effects of UB on mature osteoclast differentiation were evaluated by counting tartrate‐resistant acid phosphatase (TRAP)‐positive multinucleated cells and F‐actin ring analysis. Moreover, the effects of UB on RANKL‐induced reactive oxygen species (ROS) were measured by 2′, 7′‐dichlorodihydrofluorescein diacetate (DCFH‐DA) staining. Further, we explored the potential mechanisms of these downregulation effects by performing Western blotting and quantitative RT‐PCR examination. We found that UB represses osteoclastogenesis, F‐actin belts formation, osteoclast‐specific gene expressions and ROS activity in a time‐ and concentration‐dependent manner. Mechanistically, UB attenuates intracellular ROS levels by upregulation of Nrf2 and other ROS scavenging enzymes activation. Furthermore, UB also inhibited RANKL‐induced NF‐κB, MAPK and Akt signalling pathway and suppressed expression of c‐Fos and nuclear factor of activated T cells 1 (NFATc1), which is the master transcription factor of osteoclast differentiation. Taken together, our findings confirm that UB is a polyphenolic compound that can be a potential therapeutic treatment for osteoclast‐related bone diseases such as osteoporosis.

Recent Advances and Perspectives on the Health Benefits of Urolithin B, A Bioactive Natural Product Derived From Ellagitannins

Urolithin (Uro) B is a natural compound produced by gut bacteria from ingested ellagitannins (ETs) and ellagic acid (EA), complex polyphenols abundant in foods such as pomegranates, raspberries, blueberries and chestnuts. Uro B has recently garnered considerable attention owing to its wide range of nutraceutical effects and relatively high potency. According to several studies, Uro B prevents the development of hyperlipidemia, cardiovascular disease (CVD) and tumors due to its strong antioxidant and anti-inflammatory properties. Many reviews have systematically summarized the health benefits and pharmacological activities of ETs, EA and urolithins (especially Uro A) while available reviews or detailed summaries on the positive impact of Uro B are rarer. Here, we sought to review the pharmacological activity, mechanism of action, regulation of immune function and its associated diseases and preventive potential of Uro B to elucidate its function as a nutritional agent in humans.

Urolithin B suppressed osteoclast activation and reduced bone loss of osteoporosis via inhibiting ERK/NF-κB pathway

Objectives

The main target of current drugs for alleviating bone loss is osteoclasts. However, the long‐term application of such drugs will also cause side effects. Therefore, it is of great need to develop new and safer therapeutics for osteoporosis. In recent years, drug development based on gut microbiota has gradually attracted attention. This manuscript investigates the inhibitory effect of urolithin B (UB) on osteoclastogenesis and differentiation in vitro and in ovariectomized (OVX) mice.

Materials and Methods

CCK‐8 was used to analyse the cytotoxicity of UB; BMMs cells were differentiated into osteoclasts by RANKL, and respectively treated with 1, 5, and 25 μmol/L UB during this process. After one week of intervention, tartrate‐resistant acid phosphatase (TRAP) staining was used to analyse the number and average area of osteoclasts. F‐actin staining and immunofluorescence staining were conducted to evaluate the morphology and function of osteoclasts. Bone resorption function of osteoclasts was detected by Pit Formation Assay. The expression of osteoclast‐related protein genes in RAW264.7 cells were investigated via western blot and RT‐PCR assays. Western blot analysis of RANKL‐mediated activation of MAPK/NF‐κB pathway after 0, 5, 15, 30, 60 min of intervention. For in vivo experiments, OVX mice received intraperitoneal injection of 10, 50 mg/kg every two days, 8 weeks later, the femurs of mice were taken for morphological analysis, and the serum content of CTX‐1, a bone metabolism index, was analysed.

Results

UB could inhibit the osteoclast differentiation of rankl‐induced bone marrow macrophages (BMMs) and RAW264.7 cells in vitro, suppress the uptake activity of hydroxyapatite and expression of osteoclast‐related gene MMP9, CTSK, NFATc1 and c‐fos. Furthermore, UB repressed the rankl‐induced phosphorylation and degradation of IκB and the phosphorylation of P65 in the NF‐κB pathway of RAW264.7 cells, and also down‐regulated the phosphorylation level of ERK in the MAPK pathway. For in vivo studies, UB‐treated OVX mice showed more significant improved various parameters of distal femur compared with the control group, with fewer NFATc1, MMP9 and TRAP‐positive osteoclasts in bone tissues, and less serum content of CTX‐1.

Conclusion

Urolithin B attenuated bone loss in OVX mice by inhibiting the formation and activation of osteoclasts via down‐regulation of the ERK/NF‐κB signalling pathway.

The role of key gut microbial metabolites in the development and treatment of cancer

In recent years, the role of gut microbial metabolites on the inhibition and progression of cancer has gained significant interest in anticancer research. It has been established that the gut microbiome plays a pivotal role in the development, treatment and prognosis of different cancer types which is often mediated through the gut microbial metabolites. For instance, gut microbial metabolites including bacteriocins, short-chain fatty acids and phenylpropanoid-derived metabolites have displayed direct and indirect anticancer activities through different molecular mechanisms. Despite the reported anticancer activity, some gut microbial metabolites including secondary bile acids have exhibited pro-carcinogenic properties. This review draws a critical summary and assessment of the current studies demonstrating the carcinogenic and anticancer activity of gut microbial metabolites and emphasises the need to further investigate the interactions of these metabolites with the immune system as well as the tumour microenvironment in molecular mechanistic and clinical studies.

Wnt/β-Catenin Signaling as a Driver of Hepatocellular Carcinoma Progression: An Emphasis on Molecular Pathways

Liver cancers cause a high rate of death worldwide and hepatocellular carcinoma (HCC) is considered as the most common primary liver cancer. HCC remains a challenging disease to treat. Wnt/β-catenin signaling pathway is considered a tumor-promoting factor in various cancers; hence, the present review focused on the role of Wnt signaling in HCC, and its association with progression and therapy response based on pre-clinical and clinical evidence. The nuclear translocation of β-catenin enhances expression level of genes such as c-Myc and MMPs in increasing cancer progression. The mutation of CTNNB1 gene encoding β-catenin and its overexpression can lead to HCC progression. β-catenin signaling enhances cancer stem cell features of HCC and promotes their growth rate. Furthermore, β-catenin prevents apoptosis in HCC cells and increases their migration via triggering EMT and upregulating MMP levels. It is suggested that β-catenin signaling participates in mediating drug resistance and immuno-resistance in HCC. Upstream mediators including ncRNAs can regulate β-catenin signaling in HCC. Anti-cancer agents inhibit β-catenin signaling and mediate its proteasomal degradation in HCC therapy. Furthermore, clinical studies have revealed the role of β-catenin and its gene mutation (CTNBB1) in HCC progression. Based on these subjects, future experiments can focus on developing novel therapeutics targeting Wnt/β-catenin signaling in HCC therapy.

Gallic Acid Suppressed Tumorigenesis by an LncRNA MALAT1-Wnt/β-Catenin Axis in Hepatocellular Carcinoma

Gallic acid (3,4,5-trihydroxybenzoic acid; GA), a natural phenolic acid, is abundantly found in numerous natural products. Increasing evidence have demonstrated that GA plays anti-cancer roles in multiple cancers. However, its anti-tumor effects on hepatocellular carcinoma (HCC) and the underlying mechanism remain obscure. In the present study, we found that GA suppressed the in vitro cell viability and metastasis and inhibited the in vivo tumor growth of HCC cells. The underlying mechanism was further to investigate and it was showed that GA suppressed the expression of β-catenin and led to the functional inactivation of Wnt/β-catenin signaling. As a kind of significant regulators, the long noncoding RNA molecules (lncRNAs) have attracted widespread attentions for their critical roles in diverse biological process and human diseases. To further identify which lncRNA participated this GA-mediated process, several lncRNAs related to Wnt/β-catenin signaling were chosen for examination of their expression profiling in the GA-treated HCC cells. Of which, Metastasis-Associated Lung Adenocarcinoma Transcript 1 (MALAT1) was the most promising candidate. And moreover, MALAT1 was significantly down-regulated by GA. Its overexpression partially reversed the GA-induced the inhibitory effects on cell proliferation and metastasis; and successfully abolished the suppressive effect of GA on Wnt/β-catenin signaling. In conclusion, our results indicated that GA suppressed tumorigenesis in vitro and in vivo by the MALAT1-Wnt/β-catenin signaling axis, suggesting that GA has great potential to be developed as a chemo-prevention and chemotherapy agent for HCC patients.

A mechanistic insight into the biological activities of urolithins as gut microbial metabolites of ellagitannins

Urolithins are the gut metabolites produced from ellagitannin-rich foods such as pomegranates, tea, walnuts, as well as strawberries, raspberries, blackberries, and cloudberries. Urolithins are of growing interest due to their various biological activities including cardiovascular protection, anti-inflammatory activity, anticancer properties, antidiabetic activity, and antiaging properties. Several studies mostly based on in vitro and in vivo experiments have investigated the potential mechanisms of urolithins which support the beneficial effects of urolithins in the treatment of several diseases such as Alzheimer's disease, type 2 diabetes mellitus, liver disease, cardiovascular disease, and various cancers. It is now obvious that urolithins can involve several cellular mechanisms including inhibition of MDM2-p53 interaction, modulation of mitogen-activated protein kinase pathway, and suppressing nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activity. Antiaging activity is the most appealing and probably the most important property of urolithin A that has been investigated in depth in recent studies, owing to its unique effects on activation of mitophagy and mitochondrial biogenesis. A recent clinical trial showed that urolithin A is safe up to 2,500 mg/day and can improve mitochondrial biomarkers in elderly patients. Regarding the importance of mitochondria in the pathophysiology of many diseases, urolithins merit further research especially in clinical trials to unravel more aspects of their clinical significance. Besides the nutritional value of urolithins, recent studies proved that urolithins can be used as pharmacological agents to prevent or cure several diseases. Here, we comprehensively review the potential role of urolithins as new therapeutic agents with a special focus on the molecular pathways that have been involved in their biological effects. The pharmacokinetics of urolithins is also included.

Microbiome Assisted Tumor Microenvironment: Emerging Target of Breast Cancer

The microbiome assisted tumor microenvironment (TME) supports the tumors by modulating multiple mechanisms. Recent studies reported that microbiome dysbiosis is the main culprit of immune suppressive phenotypes of TME. Further, it has been documented that immune suppressive stimulate metastatic phenotype in TME via modulating signaling pathways, cell differentiation, and innate immune response. This review aims at providing comprehensive developments in microbiome and breast TME interface. The combination of microbiome and breast cancer, breast TME and microbiome or microbial dysbiosis, microbiome and risk of breast cancer, microbiome and phytochemicals or anticancer drugs were as used keywords to retrieve literature from PubMed, Google scholar, Scopus, Web of Science from 2015 onwards. Based on the literature, we presented the impact of TME assisted microbiome dysbiosis and estrobolome in breast cancer risk, drug resistance, and antitumor immunity. We have discussed the influence of antibiotics on the breast microbiome. we also presented the possible dietary phytochemicals that target microbiome dysbiosis to restore the tumor suppression immune environment in breast TME. We presented the microbiome as a possible marker for breast cancer diagnosis. This study will help in the identification of microbiome as a novel target and diagnostic markers and phytochemicals and microbiome metabolites for breast cancer treatment.

Targeting molecular signal transduction pathways in hepatocellular carcinoma and its implications for cancer therapy

Hepatocellular carcinoma is a substantial health concern. It is currently the third dominating cause of mortality associated with cancer worldwide. The development of hepatocellular carcinoma is an intricate process that encompasses the impairment of genetic, epigenetic, and signal transduction mechanisms contributing to an aberrant metabolic system, enabling tumorigenesis. Throughout the past decade, research has led to the revelation of molecular pathways implicated in the progression of this notorious disorder. The altered signal transduction pathways, such as the mitogen-activated protein kinase pathway, phosphoinositol 3-kinase/protein kinase B/mammalian target of rapamycin pathway, WNT/β-catenin pathway, hepatocyte growth factor/c-MET pathway, and just another kinase/signal transducers and activators of transcription signaling pathway is of much therapeutic significance, as targeting them may avail to revert, retard or avert hepatocarcinogenesis. The present review article sums up the contemporary knowledge of such signaling mechanisms, including their therapeutic targets and betokens that novel and efficacious therapies can be developed only by the keen understanding of their character in hepatocarcinogenesis. In additament, we address the role of consequential therapeutic agents and preclinical nondrug therapies known for combating hepatocarcinogenesis.

Hydroxysafflor yellow A promotes osteogenesis and bone development via epigenetically regulating β-catenin and prevents ovariectomy-induced bone loss

In clinical treatment, there is increasingly prevalent that traditional Chinese medicine treats common bone diseases including osteoporosis. Hydroxysafflor yellow A (HSYA), one of the essential compounds of Safflower, has been used as the therapy for thrombus, myocardial ischemia, and inflammation, but its effect on osteogenesis through epigenetic control and ovariectomy-induced bone loss in vivo has not been explored. Therefore, the study aimed to explore the function and mechanism of HSYA on bone formation and development. We found HSYA could enhance the cell viability and promote osteogenesis of hBMSCs in vitro. Mechanistically, HSYA could increase the expression of β-catenin leading to its accumulation in the nucleus and activation of downstream targets to promote osteogenesis. Besides, RNA-seq and quantitative RT-PCR and western blot showed KDM7A was significantly increased by HSYA. The occupancy of H3K27me2 on β-catenin promoter was significantly decreased by HSYA, which could be reversed by silencing endogenous KDM7A. More importantly, HSYA promoted bone development in chick embryos and prevented ovariectomy (OVX)-induced bone loss in SD rats. Taken together, our study has shown convincing evidence that HSYA could promote osteogenesis and bone development via epigenetically regulating β-catenin and prevent ovariectomy-induced bone loss.

Urolithins: The Gut Based Polyphenol Metabolites of Ellagitannins in Cancer Prevention, a Review

Cancer as a disease continues to ravage the world population without regard to sex, age, and race. Due to the growing number of cases worldwide, cancer exerts a significant negative impact on global health and the economy. Interestingly, chemotherapy has been used over the years as a therapeutic intervention against cancer. However, high cost, resistance, and toxic by-effects to treatment have overshadowed some of its benefits. In recent times, efforts have been ongoing in searching for anticancer therapeutics of plant origin, focusing on polyphenols. Urolithins are secondary polyphenol metabolites derived from the gut microbial action on ellagitannins and ellagic acid-rich foods such as pomegranate, berries, and nuts. Urolithins are emerging as a new class of anticancer compounds that can mediate their cancer-preventive activities through cell cycle arrest, aromatase inhibition, induction of apoptosis, tumor suppression, promotion of autophagy, and senescence, transcriptional regulation of oncogenes, and growth factor receptors. In this review, we discussed the growing shreds of evidence supporting these secondary phenolic metabolites' anticancer properties. Furthermore, we have pointed out some of the future directions needed to establish urolithins as anticancer agents.

Urolithin A and B Alter Cellular Metabolism and Induce Metabolites Associated with Apoptosis in Leukemic Cells

Leukemia is persistently a significant cause of illness and mortality worldwide. Urolithins, metabolites of ellagic acid and ellagitannins produced by gut microbiota, showed better bioactive compounds liable for the health benefits exerted by ellagic acid and ellagitannins containing pomegranate and walnuts. Here, we assessed the potential antileukemic activities of both urolithin A and urolithin B. Results showed that both urolithin A and B significantly inhibited the proliferation of leukemic cell lines Jurkat and K562, among which urolithin A showed the more prominent antiproliferative capability. Further, urolithin treatment alters leukemic cell metabolism, as evidenced by increased metabolic rate and notable changes in glutamine metabolism, one-carbon metabolism, and lipid metabolism. Next, we evidenced that both urolithins equally promoted apoptosis in leukemic cell lines. Based on these observations, we concluded that both urolithin A and B alter leukemic cell metabolome, resulting in a halt of proliferation, followed by apoptosis. The data can be used for designing new combinational therapies to eradicate leukemic cells.

Apigenin promotes osteogenic differentiation of mesenchymal stem cells and accelerates bone fracture healing via activating Wnt/β-catenin signaling

Apigenin (API), a natural plant flavone, is abundantly found in common fruits and vegetables. As a bioactive flavonoid, API exhibits several activities including antiproliferation and anti-inflammation. A recent study showed that API could retard osteoporosis progress, indicating its role in the skeletal system. However, the detailed function and mechanism remain obscure. In the present study, API was found to promote osteogenic differentiation of mesenchymal stem cells (MSCs). And further investigation showed that API could enhance the expression of the critical transcription factor β-catenin and several downstream target genes of Wnt signaling, thus activated Wnt/β-catenin signaling. Using a rat femoral fracture model, API was found to improve new bone formation and accelerate fracture healing in vivo. In conclusion, our data demonstrated that API could promote osteogenesis in vitro and facilitate the fracture healing in vivo via activating Wnt/β-catenin signaling, indicating that API may be a promising therapeutic candidate for bone fracture repair.NEW & NOTEWORTHY1) API promoted osteogenic differentiation of human MSCs in vitro; 2) API facilitated bone formation and accelerated fracture healing in vivo; 3) API stimulated Wnt/β-catenin signaling during osteogenesis of human MSCs.

H19-Wnt/β-catenin regulatory axis mediates the suppressive effects of apigenin on tumor growth in hepatocellular carcinoma

Hepatocellular Carcinoma (HCC) is one of the leading causes of cancer-related deaths in the world. However, the effective pharmacological approaches remain scanty in clinical practice. As a bioactive flavonoid, apigenin (API) is enriched in common fruits and vegetables. Although pharmacological activities of API have been widely investigated, its biological function in HCC remains obscure. In the present study, we found that API strongly suppressed cell growth and induced apoptosis in HCC cells. Using a xenograft mice model, API was demonstrated to inhibit the in vivo tumor growth. It is known that the long non-coding RNA H19, which is frequently elevated in HCC, plays a vital role in mediating tumorigenesis and cancer progression. Our results demonstrated that H19 was down-regulated by API, and thereby induced the inactivation of the canonical Wnt/β-catenin signaling. In conclusion, our results demonstrated that API was able to suppress tumor growth of HCC through H19-mediated Wnt/β-catenin signaling regulatory axis, suggesting that API may be a promising candidate for developing novel therapeutic approaches against liver cancer.

Stem Cell Therapy for Hepatocellular Carcinoma: Future Perspectives

Hepatocellular carcinoma (HCC) is one of the most common types of cancer and results in a high mortality rate worldwide. Unfortunately, most cases of HCC are diagnosed in an advanced stage, resulting in a poor prognosis and ineffective treatment. HCC is often resistant to both radiotherapy and chemotherapy, resulting in a high recurrence rate. Although the use of stem cells is evolving into a potentially effective approach for the treatment of cancer, few studies on stem cell therapy in HCC have been published. The administration of stem cells from bone marrow, adipose tissue, the amnion, and the umbilical cord to experimental animal models of HCC has not yielded consistent responses. However, it is possible to induce the apoptosis of cancer cells, repress angiogenesis, and cause tumor regression by administration of genetically modified stem cells. New alternative approaches to cancer therapy, such as the use of stem cell derivatives, exosomes or stem cell extracts, have been proposed. In this review, we highlight these experimental approaches for the use of stem cells as a vehicle for local drug delivery.

Gut microbiota: A new piece in understanding hepatocarcinogenesis

The gut microbiota forms a symbiotic relationship with the host and benefits the body in many critical aspects of life. However, immune system defects, alterations in the gut microbiota and environmental changes can destroy this symbiotic relationship and may lead to diseases, including cancer. Due to the anatomic and functional connection of the gut and liver, increasing studies show the important role of the gut microbiota in the carcinogenesis of hepatocellular carcinoma (HCC). In this manuscript, we review the available evidence and analyze some potential mechanisms of the gut microbiota, including bacterial dysbiosis, lipopolysaccharide (LPS), and genotoxins, in the progression and promotion of HCC. Furthermore, we discuss the possible therapeutic applications of probiotics, chemotherapy modulation, immunotherapy, targeted drugs and fecal microbiota transplantation (FMT) in targeting the gut microbiota.