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

Enhancing the Bioavailability of the Ellagitannin, Geraniin: Formulation, Characterization, and in vivo Evaluation

Geraniin (GE), an ellagitannin (ET) renowned for its promising health advantages, faces challenges in its practical applications due to its limited bioavailability. This innovative and novel formulation of GE and soy-phosphatidylcholine (GE-PL) complex has the potential to increase oral bioavailability, exhibiting high entrapment efficiency of 100.2 ± 0.8 %, and complexation efficiency of 94.6 ± 1.1 %. The small particle size (1.04 ± 0.11 μm), low polydispersity index (0.26 ± 0.02), and adequate zeta potential (-26.1 ± 0.12 mV), indicate its uniformity and stability. Moreover, the formulation also demonstrates improved lipophilicity, reduced aqueous and buffer solubilities, and better partition coefficient. It has been validated by various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) studies. Oral bioavailability and pharmacokinetics of free GE and GE-PL complex investigated in rabbits demonstrated enhanced plasma concentration of ellagic acid (EA) compared to free GE. Significantly, GE, whether in its free form or as part of the GE-PL complex, was not found in the circulatory system. However, EA levels were observed at 0.5 h after administration, displaying two distinct peaks at 2 ± 0.03 h (T1max) and 24 ± 0.06 h (T2max). These peaks corresponded to peak plasma concentrations (C1max and C2max) of 588.82 ng/mL and 711.13 ng/mL respectively, signifying substantial 11-fold and 5-fold enhancements when compared to free GE. Additionally, it showed an increased area under the curve (AUC), the elimination half-life (t1/2, el) and the elimination rate constant (Kel). The formulation of the GE-PL complex prolonged the presence of EA in the bloodstream and improved its absorption, ultimately leading to a higher oral bioavailability. In summary, the study highlights the significance of the GE-PL complex in overcoming the bioavailability limitations of GE, paving the way for enhanced therapeutic outcomes and potential applications in drug delivery and healthcare.

Microbial-derived Urolithin A Targets GLS1 to Inhibit Glutaminolysis and Attenuate Cirrhotic Portal Hypertension

BACKGROUND & AIMS

Cirrhotic portal hypertension (CPH) is the leading cause of mortality in patients with cirrhosis. Over 50% of patients with CPH treated with current clinical pharmacotherapy still present variceal bleeding or sometimes death owing to insufficient reduction in portal pressure. Elevated intrahepatic vascular resistance (IHVR) plays a fundamental role in increasing portal pressure. Because of its potent effect in reducing portal pressure and maintaining normal portal inflow to preserve liver function, lowering the IHVR is acknowledged as an optimal anti-CPH strategy but without clinical drugs. We aimed to investigate the protective effect of microbial-derived Urolithin A (UroA) in IHVR and CPH.

METHODS

Carbon tetrachloride or bile duct ligation surgery was administered to mice to induce liver fibrosis and CPH. 16S rRNA gene sequencing was used for microbial analysis. Transcriptomics and metabolomics analyses were employed to study the host and cell responses.

RESULTS

UroA was remarkably deficient in patients with CPH and was negatively correlated with disease severity. UroA deficiency was also confirmed in CPH mice and was associated with a reduced abundance of UroA-producing bacterial strain (Lactobacillus murinus, L. murinus). Glutaminolysis of hepatic stellate cells (HSCs) was identified as a previously unrecognized target of UroA. UroA inhibited the activity of glutaminase1 to suppress glutaminolysis, which counteracted fibrogenesis and contraction of HSCs and ameliorated CPH by relieving IHVR. Supplementation with UroA or L. murinus effectively ameliorated CPH in mice.

CONCLUSIONS

We for the first time identify the deficiency of gut microbial metabolite UroA as an important cause of CPH. We demonstrate that UroA exerts an excellent anti-CPH effect by suppressing HSC glutaminolysis to lower the IHVR, which highlighted its great potential as a novel therapeutic agent for CPH.

Urolithin A improves Alzheimer's disease cognition and restores mitophagy and lysosomal functions

BACKGROUND

Compromised autophagy, including impaired mitophagy and lysosomal function, plays pivotal roles in Alzheimer's disease (AD). Urolithin A (UA) is a gut microbial metabolite of ellagic acid that stimulates mitophagy. The effects of UA's long-term treatment of AD and mechanisms of action are unknown.

METHODS

We addressed these questions in three mouse models of AD with behavioral, electrophysiological, biochemical, and bioinformatic approaches.

RESULTS

Long-term UA treatment significantly improved learning, memory, and olfactory function in different AD transgenic mice. UA also reduced amyloid beta (Aβ) and tau pathologies and enhanced long-term potentiation. UA induced mitophagy via increasing lysosomal functions. UA improved cellular lysosomal function and normalized lysosomal cathepsins, primarily cathepsin Z, to restore lysosomal function in AD, indicating the critical role of cathepsins in UA-induced therapeutic effects on AD.

CONCLUSIONS

Our study highlights the importance of lysosomal dysfunction in AD etiology and points to the high translational potential of UA.

HIGHLIGHTS

Long-term urolithin A (UA) treatment improved learning, memory, and olfactory function in Alzheimer's disease (AD) mice. UA restored lysosomal functions in part by regulating cathepsin Z (Ctsz) protein. UA modulates immune responses and AD-specific pathophysiological pathways.

Urolithin A Hijacks ERK1/2-ULK1 Cascade to Improve CD8+ T Cell Fitness for Antitumor Immunity

According to the latest evidence, the microbial metabolite Urolithin A (UA), known for its role in promoting cellular health, modulates CD8+ T cell-mediated antitumor activity. However, the direct target protein of UA and its underlying mechanism remains unclear. Here, this research identifies ERK1/2 as the specific target crucial for UA-mediated CD8+ T cell activation. Even at low doses, UA markedly enhances the persistence and effector functions of primary CD8+ cytotoxic T lymphocytes (CTLs) and human chimeric antigen receptor (CAR) T cells both in vitro and in vivo. Mechanistically, UA interacts directly with ERK1/2 kinases, enhancing their activation and subsequently facilitating T cell activation by engaging ULK1. The UA-ERK1/2-ULK1 axis promotes autophagic flux in CD8+ CTLs, enhancing cellular metabolism and maintaining reactive oxygen species (ROS) levels, as evidenced by increased oxygen consumption and extracellular acidification rates. UA-treated CD8+ CTLs also display elevated ATP levels and enhanced spare respiratory capacity. Overall, UA activates ERK1/2, inducing autophagy and metabolic adaptation, showcasing its potential in tumor immunotherapy and interventions for diseases involving ERKs.

Pomegranate (Punica granatum L.) and Its Rich Ellagitannins as Potential Inhibitors in Ulcerative Colitis

Ulcerative colitis, an immune-mediated inflammatory disease of the gastrointestinal tract, places a significant financial burden on patients and the healthcare system. Recently, reviews of the pomegranate and the abundant medicinal applications of its ellagitannins, as well as its pharmacological action, phytochemicals, metabolism, and pharmacokinetics, have been completed. However, summaries on their anti-ulcerative colitis effects are lacking. Numerous preclinical animal investigations and clinical human trial reports demonstrated the specific therapeutic effects of pomegranate and the effect of its ellagitannins against ulcerative colitis. According to the literature collected by Sci-finder and PubMed databases over the past 20 years, this is the first review that has compiled references regarding how the rich ellagitannins found in pomegranate have altered the ulcerative colitis. It was suggested that the various parts of pomegranates and their rich ellagitannins (especially their primary components, punicalagin, and ellagic acid) can inhibit oxidant and inflammatory processes, regulate the intestinal barrier and flora, and provide an anti-ulcerative colitis resource through dietary management.

Pharmacological Effects of Urolithin A and Its Role in Muscle Health and Performance: Current Knowledge and Prospects

Urolithin A (UA) is a naturally occurring compound derived from the metabolism of gut microbiota, which has attracted considerable research attention due to its pharmacological effects and potential implications in muscle health and performance. Recent studies have demonstrated that Urolithin A exhibits diverse biological activities, encompassing anti-inflammatory, antioxidant, anti-tumor, and anti-aging properties. In terms of muscle health, accumulating evidence suggests that Urolithin A may promote muscle protein synthesis and muscle growth through various pathways, offering promise in mitigating muscle atrophy. Moreover, Urolithin A exhibits the potential to enhance muscle health and performance by improving mitochondrial function and regulating autophagy. Nonetheless, further comprehensive investigations are still warranted to elucidate the underlying mechanisms of Urolithin A and to assess its feasibility and safety in human subjects, thereby advancing its potential applications in the realms of muscle health and performance.

Pomegranate: A Source of Multifunctional Bioactive Compounds Potentially Beneficial in Alzheimer's Disease

Pomegranate fruit (PF) is a fruit rich in nutraceuticals. Nonedible parts of the fruit, especially peels, contain high amounts of bioactive components that have been largely used in traditional medicine, such as the Chinese, Unani, and Ayurvedic ones, for treating several diseases. Polyphenols such as anthocyanins, tannins, flavonoids, phenolic acids, and lignans are the major bioactive molecules present in PF. Therefore, PF is considered a source of natural multifunctional agents that exert simultaneously antioxidant, anti-inflammatory, antitumor, antidiabetic, cardiovascular, and neuroprotective activities. Recently, several studies have reported that the nutraceuticals contained in PF (seed, peel, and juice) have a potential beneficial role in Alzheimer's disease (AD). Research suggests that the neuroprotective effect of PF is mostly due to its potent antioxidant and anti-inflammatory activities which contribute to attenuate the neuroinflammation associated with AD. Despite the numerous works conducted on PF, to date the mechanism by which PF acts in combatting AD is not completely known. Here, we summarize all the recent findings (in vitro and in vivo studies) related to the positive effects that PF and its bioactive components can have in the neurodegeneration processes occurring during AD. Moreover, considering the high biotransformation characteristics of the nutraceuticals present in PF, we propose to consider the chemical structure of its active metabolites as a source of inspiration to design new molecules with the same beneficial effects but less prone to be affected by the metabolic degradation process.

Urolithin A Produced by Novel Microbial Fermentation Possesses Anti-aging Effects by Improving Mitophagy and Reducing Reactive Oxygen Species in Caenorhabditis elegans

Urolithin, intestinal microbiota metabolites of ellagitannin-rich foods, exhibit anti-aging activities. However, urolithin A is significantly superior to other types of urolithin with regard to this anti-aging function. This study aimed to screen edible urolithin A-producing strains of bacteria and explore the corresponding anti-aging efficacy of fermented products produced by these strains using Caenorhabditis elegans as a model. Our results showed that the Lactobacillus plantarum strains CCFM1286, CCFM1290, and CCFM1291 converted ellagitannin to produce urolithin A; the corresponding yields of urolithin A from these strains were 15.90 ± 1.46, 24.70 ± 0.82, and 32.01 ± 0.97 μM, respectively. Furthermore, it was found that the pomegranate juice extracts fermented by the CCFM1286, CCFM1290, and CCFM1291 strains of L. plantarum could extend lifespan by 26.04 ± 0.12, 32.05 ± 0.14, and 46.33 ± 0.12%, respectively, by improving mitochondrial function and/or reducing reactive oxygen species levels. These findings highlight the potential application of this fermentation in the subsequent development of anti-aging products.

Urolithin A's Antioxidative, Anti-Inflammatory, and Antiapoptotic Activities Mitigate Doxorubicin-Induced Liver Injury in Wistar Rats

Human colon microbiota produce a metabolite called urolithin A (URO A) from ellagic acid and linked compounds, and this metabolite has been demonstrated to have antioxidant, anti-inflammatory, and antiapoptotic activities. The current work examines the various mechanisms through which URO A protects against doxorubicin (DOX)-induced liver injury in Wistar rats. In this experiment, Wistar rats were administered DOX intraperitoneally (20 mg kg^-1) on day 7 while given URO A intraperitoneally (2.5 or 5 mg kg^-1 d^-1) for 14 days. The serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma glutamyl transferase (GGT) were measured. Hematoxylin and eosin (HE) staining was used to evaluate histopathological characteristics, and then antioxidant and anti-inflammatory properties were evaluated in tissue and serum, respectively. We also looked at how active caspase 3 and cytochrome c oxidase were in the liver. The findings demonstrated that supplementary URO A therapy clearly mitigated DOX-induced liver damage. The antioxidant enzymes SOD and CAT were elevated in the liver, and the levels of inflammatory cytokines, such as TNF-α, NF-kB, and IL-6, in the tissue were significantly attenuated, all of which complemented the beneficial effects of URO A in DOX-induced liver injury. In addition, URO A was able to alter the expression of caspase 3 and cytochrome c oxidase in the livers of rats that were subjected to DOX stress. These results showed that URO A reduced DOX-induced liver injury by reducing oxidative stress, inflammation, and apoptosis.

Natural Coumarin Derivatives Activating Nrf2 Signaling Pathway as Lead Compounds for the Design and Synthesis of Intestinal Anti-Inflammatory Drugs

Nrf2 (nuclear factor erythroid 2-related factor 2) is a transcription factor related to stress response and cellular homeostasis that plays a key role in maintaining the redox system. The imbalance of the redox system is a triggering factor for the initiation and progression of non-communicable diseases (NCDs), including Inflammatory Bowel Disease (IBD). Nrf2 and its inhibitor Kelch-like ECH-associated protein 1 (Keap1) are the main regulators of oxidative stress and their activation has been recognized as a promising strategy for the treatment or prevention of several acute and chronic diseases. Moreover, activation of Nrf2/keap signaling pathway promotes inhibition of NF-κB, a transcriptional factor related to pro-inflammatory cytokines expression, synchronically promoting an anti-inflammatory response. Several natural coumarins have been reported as potent antioxidant and intestinal anti-inflammatory compounds, acting by different mechanisms, mainly as a modulator of Nrf2/keap signaling pathway. Based on in vivo and in vitro studies, this review focuses on the natural coumarins obtained from both plant products and fermentative processes of food plants by gut microbiota, which activate Nrf2/keap signaling pathway and produce intestinal anti-inflammatory activity. Although gut metabolites urolithin A and urolithin B as well as other plant-derived coumarins display intestinal anti-inflammatory activity modulating Nrf2 signaling pathway, in vitro and in vivo studies are necessary for better pharmacological characterization and evaluation of their potential as lead compounds. Esculetin, 4-methylesculetin, daphnetin, osthole, and imperatorin are the most promising coumarin derivatives as lead compounds for the design and synthesis of Nrf2 activators with intestinal anti-inflammatory activity. However, further structure-activity relationships studies with coumarin derivatives in experimental models of intestinal inflammation and subsequent clinical trials in health and disease volunteers are essential to determine the efficacy and safety in IBD patients.