(+)-Sesamin, a sesame lignan, is a potent inhibitor of gut bacterial tryptophan indole-lyase that is a key enzyme in chronic kidney disease pathogenesis

Cellular and Molecular Mechanisms of Phytochemicals Against Inflammation-Associated Diseases and Viral Infection

Inflammation-associated diseases have become widespread and pose a significant threat to human health, and the therapeutic methods for diverse diseases are inadequate due to the undesirable effects of synthetic ingredients. Recently, more and more evidence indicated that phytochemicals, plant secondary metabolites, have numerous therapeutic functions against human diseases via affecting a variety of mechanisms with their distinct advantages of high efficiency and low toxicity. Here, we highlight the mechanisms of phytochemicals to hinder inflammation-associated diseases (including Inflammatory diseases, cardiovascular diseases, metabolic syndrome, neurological disorders, skin diseases, respiratory diseases, kidney diseases, gastrointestinal diseases, retinal diseases, viral infections) by regulating the crosstalk among various signal cascades (including MicroRNAs, SIRT1, DNMTs, NF-κB, NLRP3, TGF-β, the Gasdermin-mediated pyroptosis pathway), which can be considered as a novel and potential therapeutic strategy. Furthermore, phytochemicals could prevent virus infection by disturbing different targets in the virus replication cycle. However, natural plants have shown limited bioavailability due to their low water solubility, the use of adjuvants such as liposomal phytochemicals, phytochemical nanoparticles and phytochemicals-phospholipid complex promote their bioavailability to exhibit beneficial effects against various diseases. The purpose of this review is to explore the molecular mechanisms and promising applications of phytochemicals in the fields of inflammation-associated diseases and virus infection to provide some direction.

Suppression of fecal phenol production by oral supplementation of sesamol: inhibition of tyrosine phenol-lyase by sesamol

Phenol is produced from dietary L-tyrosine by the action of tyrosine phenol-lyase (TPL) of gut bacteria and contributes to various physiological disorders, including skin diseases, certain cancers, and kidney dysfunction. We found that oral supplementation of sesamol (36 or 180 μg mL-1) ad libitum for 14 days in mice significantly suppressed fecal phenol production. Fecal microbiota structure analysis in sesamol-supplemented and control groups revealed that their overall microbiota structures were indistinguishable. To explain the sesamol-induced suppression of fecal phenol production, we characterized inhibition of bacterial TPL by sesamol in vitro. Sesamol specifically inhibited bacterial TPL in a mixed-type fashion (Ki, 135 μM), which was rationalized by computational docking studies using the crystal structure of Pantoea agglomerans TPL that was determined at 1.3 Å resolution. Sesamol was detected at 0-0.295 μmol g-1 feces in the sesamol-supplemented group. Given the Ki value of sesamol for TPL inhibition, these levels may not have been sufficient to fully inhibit TPL and suppress fecal phenol production. Therefore, the observed suppression of fecal phenol production upon oral sesamol supplementation arose not solely from the inhibition of TPL by sesamol, but also potentially from the effects of metabolites derived from sesamol and the antioxidant activities of sesamol and related metabolites. Nevertheless, these findings highlight the potential for using sesamol to prevent physiological disorders associated with phenol production by the gut microbiota.

3,5-Dihydroxybenzoic Acid as a Potent Inhibitor of Tyrosine Phenol-Lyase Decreases Fecal Phenol Levels in Mice

Phenol is produced by β-elimination of l-tyrosine (Tyr) catalyzed by tyrosine phenol-lyase (TPL) during intestinal bacterial metabolism. Phenol and its conjugate, phenyl sulfate (PhS), are protein-bound uremic toxins (PBUTs). Elevated levels of phenol and PhS are strongly implicated in the etiology and outcomes of uremia. Because hemodialysis is insufficient in removing phenol and PhS, novel methods are necessary for inhibiting phenol production during bacterial metabolism. We explored TPL inhibitors and found that dietary polyphenols, particularly gallic acid (GA), strongly inhibited TPL-catalyzed phenol production. A GA derivative, 3,5-dihydroxybenzoic acid (3,5DHBA), competitively inhibited TPL and significantly decreased phenol levels in TPL-expressing bacteria (Morganella morganii and Citrobacter koseri) and Tyr-rich-diet-fed C57BL/6J mouse feces. Our findings suggested that 3,5DHBA was the most promising polyphenol in decreasing phenol levels. Therefore, dietary intake of 3,5DHBA or its phenolic precursors may be useful in minimizing PBUT levels by targeting intestinal bacteria.

Phytoestrogens: Pharmacological Potential and Therapeutic Insights for Urinary Tract Infections

Urinary tract infections (UTIs) are exceptionally common in postmenopausal female or patients with diabetes mellitus or nephrolithiasis, carrying substantial burden on patients and healthcare system. Increasing proportion and ongoing spread of antibiotic-resistant pathogens have further debilitated the condition in battlefield against the UTIs. Lack of estrogen may contribute to high inclination of UTIs after menopause and hormone replacement therapy can mitigate symptoms of hot flashes, vaginal dryness and UTIs, rationalizing the usage of estrogen and analogues in treatment and prophylaxis of UTIs. Phytoestrogens which comprise flavonoids, coumerins, stilbenes, and lignans, are natural botanical compounds with estrogen structural similarity and biochemical features. Phytoestrogens have emerged as adjuvant remedy and prophylaxis for uropathogenic bacteria even for multidrug-resistant ones, with the multifaceted mechanisms such as inhibition of adhesion and invading ability of bacteria, destruction of biofilms, synergistically enhancement of antibiotics activity. It is plausible to propose phytoestrogens as potential agents or combination with other strategies to ameliorate the challenge of multi-drug resistance in UTIs.

CKD patients comorbid with hypertension are associated with imbalanced gut microbiome

Intestinal flora has been linked to chronic kidney disease (CKD) and hypertension, respectively. This study aimed to investigate the microbial community among 54 individuals without CKD, 46 hypertensive CKD patients (CKD_HTN), and 48 non-hypertensive CKD patients. Variations in microbial diversity were detected in CKD. The Prevotella-dominated type progressively increased from CKD to CKD_HTN. Based on the variation patterns, we identified six distinct clusters. Klebsiella, Turicibacter, and Enterobacter were enriched in CKD, whereas Escherichia and Mogibacterium were elevated, and Blautia and Clostridium were reduced in CKD_HTN. Enhanced phenylalanine metabolism and siderophore group nonribosomal peptides biosynthesis from non-CKD to CKD were observed, particularly in CKD with hypertension. The connections between genera and KEGG pathways suggest an impact of microbial dysbiosis on metabolism. Our findings demonstrate that imbalances in gut microorganisms and functions are associated with increased susceptibility to hypertension in CKD patients and could be targeted for improving kidney function in CKD.

Renal Health Through Medicine-Food Homology: A Comprehensive Review of Botanical Micronutrients and Their Mechanisms

BACKGROUND

As an ancient concept and practice, "food as medicine" or "medicine-food homology" is receiving more and more attention these days. It is a tradition in many regions to intake medicinal herbal food for potential health benefits to various organs and systems including the kidney. Kidney diseases usually lack targeted therapy and face irreversible loss of function, leading to dialysis dependence. As the most important organ for endogenous metabolite and exogenous nutrient excretion, the status of the kidney could be closely related to daily diet. Therefore, medicinal herbal food rich in antioxidative, anti-inflammation micronutrients are ideal supplements for kidney protection. Recent studies have also discovered its impact on the "gut-kidney" axis.

METHODS

Here, we review and highlight the kidney-protective effects of botanicals with medicine-food homology including the most frequently used Astragalus membranaceus and Angelica sinensis (Oliv.) Diels, concerning their micronutrients and mechanism, offering a basis and perspective for utilizing and exploring the key substances in medicinal herbal food to protect the kidney.

RESULTS

The index for medicine-food homology in China contains mostly botanicals while many of them are also consumed by people in other regions. Micronutrients including flavonoids, polysaccharides and others present powerful activities towards renal diseases.

CONCLUSIONS

Botanicals with medicine-food homology are widely speeded over multiple regions and incorporating these natural compounds into dietary habits or as supplements shows promising future for renal health.

Tyrosine phenol-lyase inhibitor quercetin reduces fecal phenol levels in mice

Tyrosine phenol-lyase (TPL), which is expressed in intestinal bacteria, catalyzes the formation of phenol from the substrate L-Tyr. Bacterial metabolite phenol and the sulfate conjugate (phenyl sulfate) are known as a type of uremic toxins, some of which exert cytotoxicity. Therefore, pathologically elevated phenol and phenyl sulfate levels are strongly implicated in the etiology and outcome of uremia. In this study, we explored the inhibitory effects of dietary polyphenols on TPL-catalyzed phenol production using a TPL activity assay. Quercetin, one of the most popular polyphenols, exhibited the strongest inhibitory activity (Ki = 19.9 µM). Quercetin competitively inhibited TPL, and its activity was stronger than that of a known TPL inhibitor (Tyr analog; 2-aza-Tyr, Ki = 42.0 µM). Additionally, quercetin significantly inhibited phenol production in TPL-expressing bacterial cultures (Morganella morganii and Citrobacter koseri) and Tyr-rich (5%) diet-fed C57BL/6J mouse feces. Our findings suggest that quercetin is the most promising polyphenol for reducing phenol levels. Because quercetin has a low gastrointestinal absorption rate, TPL inhibition in the intestinal tract by quercetin may be an effective strategy for treating uremia.

Sesame Seeds: A Nutrient-Rich Superfood

Sesame seeds (Sesamum indicum L.) have been cultivated for thousands of years and have long been celebrated for their culinary versatility. Beyond their delightful nutty flavor and crunchy texture, sesame seeds have also gained recognition for their remarkable health benefits. This article provides an in-depth exploration of the numerous ways in which sesame seeds contribute to overall well-being. Sesame seeds are a powerhouse of phytochemicals, including lignans derivatives, tocopherol isomers, phytosterols, and phytates, which have been associated with various health benefits, including the preservation of cardiovascular health and the prevention of cancer, neurodegenerative disorders, and brain dysfunction. These compounds have also been substantiated for their efficacy in cholesterol management. Their potential as a natural source of beneficial plant compounds is presented in detail. The article further explores the positive impact of sesame seeds on reducing the risk of chronic diseases thanks to their rich polyunsaturated fatty acids content. Nevertheless, it is crucial to remember the significance of maintaining a well-rounded diet to achieve the proper balance of n-3 and n-6 polyunsaturated fatty acids, a balance lacking in sesame seed oil. The significance of bioactive polypeptides derived from sesame seeds is also discussed, shedding light on their applications as nutritional supplements, nutraceuticals, and functional ingredients. Recognizing the pivotal role of processing methods on sesame seeds, this review discusses how these methods can influence bioactive compounds. While roasting the seeds enhances the antioxidant properties of the oil extract, certain processing techniques may reduce phenolic compounds.

Mechanism-based inhibition of gut microbial tryptophanases reduces serum indoxyl sulfate

Indoxyl sulfate is a microbially derived uremic toxin that accumulates in late-stage chronic kidney disease and contributes to both renal and cardiovascular toxicity. Indoxyl sulfate is generated by the metabolism of indole, a compound created solely by gut microbial tryptophanases. Here, we characterize the landscape of tryptophanase enzymes in the human gut microbiome and find remarkable structural and functional similarities across diverse taxa. We leverage this homology through a medicinal chemistry campaign to create a potent pan-inhibitor, (3S) ALG-05, and validate its action as a transition-state analog. (3S) ALG-05 successfully reduces indole production in microbial culture and displays minimal toxicity against microbial and mammalian cells. Mice treated with (3S) ALG-05 show reduced cecal indole and serum indoxyl sulfate levels with minimal changes in other tryptophan-metabolizing pathways. These studies present a non-bactericidal pan-inhibitor of gut microbial tryptophanases with potential promise for reducing indoxyl sulfate in chronic kidney disease.

Dietary Phenolic Compounds: Their Health Benefits and Association with the Gut Microbiota

Oxidative stress causes various diseases, such as type II diabetes and dyslipidemia, while antioxidants in foods may prevent a number of diseases and delay aging by exerting their effects in vivo. Phenolic compounds are phytochemicals such as flavonoids which consist of flavonols, flavones, flavanonols, flavanones, anthocyanidins, isoflavones, lignans, stilbenoids, curcuminoids, phenolic acids, and tannins. They have phenolic hydroxyl groups in their molecular structures. These compounds are present in most plants, are abundant in nature, and contribute to the bitterness and color of various foods. Dietary phenolic compounds, such as quercetin in onions and sesamin in sesame, exhibit antioxidant activity and help prevent cell aging and diseases. In addition, other kinds of compounds, such as tannins, have larger molecular weights, and many unexplained aspects still exist. The antioxidant activities of phenolic compounds may be beneficial for human health. On the other hand, metabolism by intestinal bacteria changes the structures of these compounds with antioxidant properties, and the resulting metabolites exert their effects in vivo. In recent years, it has become possible to analyze the composition of the intestinal microbiota. The augmentation of the intestinal microbiota by the intake of phenolic compounds has been implicated in disease prevention and symptom recovery. Furthermore, the “brain–gut axis”, which is a communication system between the gut microbiome and brain, is attracting increasing attention, and research has revealed that the gut microbiota and dietary phenolic compounds affect brain homeostasis. In this review, we discuss the usefulness of dietary phenolic compounds with antioxidant activities against some diseases, their biotransformation by the gut microbiota, the augmentation of the intestinal microflora, and their effects on the brain–gut axis.

Food-Derived Uremic Toxins in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) have a higher cardiovascular risk compared to the average population, and this is partially due to the plasma accumulation of solutes known as uremic toxins. The binding of some solutes to plasma proteins complicates their removal via conventional therapies, e.g., hemodialysis. Protein-bound uremic toxins originate either from endogenous production, diet, microbial metabolism, or the environment. Although the impact of diet on uremic toxicity in CKD is difficult to quantify, nutrient intake plays an important role. Indeed, most uremic toxins are gut-derived compounds. They include Maillard reaction products, hippurates, indoles, phenols, and polyamines, among others. In this review, we summarize the findings concerning foods and dietary components as sources of uremic toxins or their precursors. We then discuss their endogenous metabolism via human enzyme reactions or gut microbial fermentation. Lastly, we present potential dietary strategies found to be efficacious or promising in lowering uremic toxins plasma levels. Aligned with current nutritional guidelines for CKD, a low-protein diet with increased fiber consumption and limited processed foods seems to be an effective treatment against uremic toxins accumulation.

The Microbiome and Uremic Solutes

Uremic retention solutes, especially the protein-bound compounds, are toxic metabolites, difficult to eliminate with progressive renal functional decline. They are of particular interest because these uremic solutes are responsible for the pathogenesis of cardiovascular and chronic kidney diseases. Evidence suggests that the relation between uremic toxins, the microbiome, and its host is altered in patients with chronic kidney disease, with the colon’s motility, epithelial integrity, and absorptive properties also playing an important role. Studies found an alteration of the microbiota composition with differences in species proportion, diversity, and function. Since uremic toxins precursors are generated by the microbiota, multiple therapeutic options are currently being explored to address dysbiosis. While an oral adsorbent can decrease the transport of bacterial metabolites from the intestinal lumen to the blood, dietary measures, supplements (prebiotics, probiotics, and synbiotics), and antibiotics aim to target directly the gut microbiota composition. Innovative approaches, such as the modulation of bacterial enzymes, open new perspectives to decrease the plasma level of uremic toxins.