Anti-renal fibrosis and anti-inflammation effect of urolithin B, ellagitannin-gut microbial-derived metabolites in unilateral ureteral obstruction rats

Beneficial effects of phenolic compounds: native phenolic compounds vs metabolites and catabolites

In the human body, the positive effects of phenolic compounds are increasingly observed through their presence in tissues and organs in their native form or in the form of metabolites or catabolites formed during digestion, microbial metabolism, and host biotransformation. The full extent of these effects is still unclear. The aim of this paper is to review the current knowledge of beneficial effects of native phenolic compounds or their metabolites and catabolites focusing on their role in the health of the digestive system, including disorders of the gastrointestinal and urinary tracts and liver. Studies are mostly connecting beneficial effects in the gastrointestinal and urinary tract to the whole food rich in phenolics, or to the amount of phenolic compounds/antioxidants in food. Indeed, the bioactivity of parent phenolic compounds should not be ignored due to their presence in the digestive tract, and the impact on the gut microbiota. However, the influence of their metabolites and catabolites might be more important for the liver and urinary tract. Distinguishing between the effects of parent phenolics vs metabolites and catabolites at the site of action are important for novel areas of food industry, nutrition and medicine.

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.

The role and mechanism of gut microbiota-derived short-chain fatty in the prevention and treatment of diabetic kidney disease

Diabetic kidney disease (DKD), an emerging global health issue, is one of the most severe microvascular complications derived from diabetes and a primary pathology contributing to end-stage renal disease. The currently available treatment provides only symptomatic relief and has failed to delay the progression of DKD into chronic kidney disease. Recently, multiple studies have proposed a strong link between intestinal dysbiosis and the occurrence of DKD. The gut microbiota-derived short-chain fatty acids (SCFAs) capable of regulating inflammation, oxidative stress, fibrosis, and energy metabolism have been considered versatile players in the prevention and treatment of DKD. However, the underlying molecular mechanism of the intervention of the gut microbiota-kidney axis in the development of DKD still remains to be explored. This review provides insight into the contributory role of gut microbiota-derived SCFAs in DKD.

Glucosidase inhibitor, Nimbidiol ameliorates renal fibrosis and dysfunction in type-1 diabetes

Diabetic nephropathy is characterized by excessive accumulation of extracellular matrix (ECM) leading to renal fibrosis, progressive deterioration of renal function, and eventually to end stage renal disease. Matrix metalloproteinases (MMPs) are known to regulate synthesis and degradation of the ECM. Earlier, we demonstrated that imbalanced MMPs promote adverse ECM remodeling leading to renal fibrosis in type-1 diabetes. Moreover, elevated macrophage infiltration, pro-inflammatory cytokines and epithelial‒mesenchymal transition (EMT) are known to contribute to the renal fibrosis. Various bioactive compounds derived from the medicinal plant, Azadirachta indica (neem) are shown to regulate inflammation and ECM proteins in different diseases. Nimbidiol is a neem-derived diterpenoid that is considered as a potential anti-diabetic compound due to its glucosidase inhibitory properties. We investigated whether Nimbidiol mitigates adverse ECM accumulation and renal fibrosis to improve kidney function in type-1 diabetes and the underlying mechanism. Wild-type (C57BL/6J) and type-1 diabetic (C57BL/6-Ins2^Akita/J) mice were treated either with saline or with Nimbidiol (0.40 mg kg^-1 d^-1) for eight weeks. Diabetic kidney showed increased accumulation of M1 macrophages, elevated pro-inflammatory cytokines and EMT. In addition, upregulated MMP-9 and MMP-13, excessive collagen deposition in the glomerular and tubulointerstitial regions, and degradation of vascular elastin resulted to renal fibrosis in the Akita mice. These pathological changes in the diabetic mice were associated with functional impairments that include elevated resistive index and reduced blood flow in the renal cortex, and decreased glomerular filtration rate. Furthermore, TGF-β1, p-Smad2/3, p-P38, p-ERK1/2 and p-JNK were upregulated in diabetic kidney compared to WT mice. Treatment with Nimbidiol reversed the changes to alleviate inflammation, ECM accumulation and fibrosis and thus, improved renal function in Akita mice. Together, our results suggest that Nimbidiol attenuates inflammation and ECM accumulation and thereby, protects kidney from fibrosis and dysfunction possibly by inhibiting TGF-β/Smad and MAPK signaling pathways in type-1 diabetes.

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.

Urolithins Modulate the Viability, Autophagy, Apoptosis, and Nephrin Turnover in Podocytes Exposed to High Glucose

Urolithins are bioactive compounds generated in human and animal intestines because of the bacterial metabolism of dietary ellagitannins (and their constituent, ellagic acid). Due to their multidirectional effects, including anti-inflammatory, antioxidant, anti-cancer, neuroprotective, and antiglycative properties, urolithins are potential novel therapeutic agents. In this study, while considering the future possibility of using urolithins to improve podocyte function in diabetes, we assessed the results of exposing mouse podocytes cultured in normal (NG, 5.5 mM) and high (HG, 25 mM) glucose concentrations to urolithin A (UA) and urolithin B (UB). Podocytes metabolized UA to form glucuronides in a time-dependent manner; however, in HG conditions, the metabolism was lower than in NG conditions. In HG milieu, UA improved podocyte viability more efficiently than UB and reduced the reactive oxygen species level. Both types of urolithins showed cytotoxic activity at high (100 µM) concentration. The UA upregulated total and surface nephrin expression, which was paralleled by enhanced nephrin internalization. Regulation of nephrin turnover was independent of ambient glucose concentration. We conclude that UA affects podocytes in different metabolic and functional aspects. With respect to its pro-survival effects in HG-induced toxicity, UA could be considered as a potent therapeutic candidate against diabetic podocytopathy.

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.

Network Pharmacology and In Vivo Analysis of Dahuang-Huangqi Decoction Effectiveness in Alleviating Renal Interstitial Fibrosis

Dahuang and Huangqi are the most frequently prescribed treatment methods for chronic kidney disease in China. Our study aimed to clarify the pharmacological mechanism of action of Dahuang-Huangqi decoction (DHHQD) in renal interstitial fibrosis (RIF). The intersection of genes targeted by DHHQD active ingredients and RIF target genes was searched using network pharmacology to build a chemical ingredient and disease target network. For in vivo analysis, Sprague–Dawley rats with unilateral urethral obstruction (UUO) were administered DHHQD, and their kidney function-related indicators and pathological indices were determined. The expression of core targets was quantified using real-time polymerase chain reaction and western blotting. A total of 139 common targets for DHHQD and RIF in chronic kidney disease were detected. Compared with the untreated UUO rats, the DHHQD-treated rats showed reductions in the following: blood urea nitrogen and serum creatinine levels, kidney tubular atrophy and necrosis, interstitial fibrosis, hyperplasia and abnormal deposition of extracellular matrix, and microstructural changes in the mesangial matrix and glomerular basement membrane. DHHQD treatment significantly regulated the levels of renal core proteins, such as eNOS, IL-6, EGFR, and VEGF and reduced the mRNA and protein expression of the core targets involved in inflammation pathways, such as PI3K/AKT and TLR4/NF-κB. DHHQD treatment ameliorated the severity of RIF by potentially regulating the AKT/PI3K and TLR4/NF-κB signaling pathways. Our study findings provide insights into the mechanisms associated with DHHQD action and essential data for future research.

Urolithins: The Colon Microbiota Metabolites as Endocrine Modulators: Prospects and Perspectives

Selective estrogen receptor modulators (SERMs) have been used in hormone related disorders, and their role in clinical medicine is evolving. Tamoxifen and raloxifen are the most commonly used synthetic SERMs, and their long-term use are known to create side effects. Hence, efforts have been directed to identify molecules which could retain the beneficial effects of estrogen, at the same time produce minimal side effects. Urolithins, the products of colon microbiota from ellagitannin rich foodstuff, have immense health benefits and have been demonstrated to bind to estrogen receptors. This class of compounds holds promise as therapeutic and nutritional supplement in cardiovascular disorders, osteoporosis, muscle health, neurological disorders, and cancers of breast, endometrium, and prostate, or, in essence, most of the hormone/endocrine-dependent diseases. One of our findings from the past decade of research on SERMs and estrogen modulators, showed that pomegranate, one of the indirect but major sources of urolithins, can act as SERM. The prospect of urolithins to act as agonist, antagonist, or SERM will depend on its structure; the estrogen receptor conformational change, availability and abundance of co-activators/co-repressors in the target tissues, and also the presence of other estrogen receptor ligands. Given that, urolithins need to be carefully studied for its SERM activity considering the pleotropic action of estrogen receptors and its numerous roles in physiological systems. In this review, we unveil the possibility of urolithins as a potent SERM, which we are currently investigating, in the hormone dependent tissues.

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.

Effects of urolithins on obesity-associated gut dysbiosis in rats fed on a high-fat diet

Obesity is a global health concern associated with the dysbiosis of intestinal microbial composition. In this study, we investigated the potentials of urolithin A (Uro-A) and urolithin B (Uro-B), two gut microbiota-derived metabolites of ellagitannins, in reducing body weight gain through the modulation of the gut microbiota. We established a high-fat diet (HFD)-induced obesity model in rats that were later administered with either 2.5 mg/kg of Uro-A or Uro-B. Serum biochemical parameters were quantified, and changes in the composition of the gut microbial community were analysed using 16S rDNA gene sequencing. Our results showed that the urolithins significantly decreased the body weight in HFD-fed rats and restored serum lipid profile. The taxonomic analysis showed that both Uro-A and Uro-modulated gut microbes related to body weight, dysfunctional lipid metabolism and inflammation. Overall, our results suggest that Uro-A and Uro-B possess anti-obesity properties, which may be related to the modulation of the gut microbial composition.