Characterization of the Interindividual Variability Associated with the Microbial Metabolism of (-)-Epicatechin

The effects of Mitragyna speciosa extracts on intestinal microbiota and their metabolites in vitro fecal fermentation

BACKGROUND

Kratom (Mitragyna speciosa) has a long history of traditional use. It contains various alkaloids and polyphenols. The properties of kratom's alkaloids have been well-documented. However, the property of kratom's polyphenols in water-soluble phase have been less frequently reported. This study assessed the effects of water-soluble Mitragyna speciosa (kratom) extract (MSE) on gut microbiota and their metabolite production in fecal batch culture.

RESULTS

The water-soluble kratom extract (MSE0) and the water-soluble kratom extract after partial sugar removal (MSE50) both contained polyphenols, with total phenolic levels of 2037.91 ± 51.13 and 3997.95 ± 27.90 mg GAE/g extract, respectively and total flavonoids of 81.10 ± 1.00 and 84.60 ± 1.43 mg CEQ/g extract. The gut microbiota in fecal batch culture was identified by 16S rRNA gene sequencing at 0 and 24 h of fermentation. After fermentation, MSE50 stimulated the growth of Bifidobacterium more than MSE0. MSE0 gave the highest total fatty acids level among the treatments. The phenolic metabolites produced by some intestinal microbiota during fecal fermentation at 24 h were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The major metabolite of biotransformation of both water-soluble MSEs by intestinal microbiota was pyrocatechol (9.85-11.53%).

CONCLUSION

The water-soluble MSEs and their produced metabolites could potentially be used as ingredients for functional and medicinal food production that supports specific gut microbiota. © 2024 Society of Chemical Industry.

Lactiplantibacillus plantarum Interstrain Variability in the Production of Bioactive Phenolic Metabolites from Flavan-3-ols

Flavan-3-ols intake is associated with numerous health benefits, but these are influenced by their conversion into smaller phenolic metabolites by the gut microbiota. Thus, the identification of bacteria that metabolize flavan-3-ols could lead to targeted interventions to enhance their benefits. To this end, we screened 47 Lactiplantibacillus plantarum strains for their ability to metabolize (+)-catechin, a flavan-3-ol. Then, we assessed these strains for their capacity to convert various flavan-3-ol structures. Out of the 47 isolates, 12 released 3-(3',4'-dihydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)-propan-2-ol (a form of diphenylpropan-2-ol) from (+)-catechin. All strains metabolized (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, but only a subset transformed (-)-gallocatechin. Among these simple flavan-3-ol structures, (-)-epicatechin was metabolized the most. A hierarchical cluster analysis identified two groups of flavan-3-ol-metabolizing strains categorized as having "high" and "low" production of diphenylpropan-2-ols. Notably, the strains that produced higher levels of diphenylpropan-2-ol from (+)-gallocatechin and (+)-catechin also performed better with a camu-camu extract, which was studied as a complex source of flavan-3-ols and predominantly contained these two flavan-3-ols. These results demonstrate the interstrain variability in L. plantarum metabolism, which may be useful for developing tailored formulations to enhance the production of flavan-3-ols bioactive metabolites.

(-)-Epicatechin ameliorates type 2 diabetes mellitus by reshaping the gut microbiota and Gut-Liver axis in GK rats

As one of the most abundant plant polyphenols in the human diet, (-)-epicatechin (EC) can improve insulin sensitivity and regulate glucose homeostasis. However, the primary mechanisms involved in EC anti-T2DM benefits remain unclear. The present study explored the effects of EC on the gut microbiota and liver transcriptome in type 2 diabetes mellitus (T2DM) Goto-Kakizaki rats for the first time. The findings showed that EC protected glucose homeostasis, alleviated systemic oxidative stress, relieved liver damage, and increased serum insulin. Further investigation showed that EC reshaped gut microbiota structure, including inhibiting the proliferation of lipopolysaccharide (LPS)-producing bacteria and reducing serum LPS. In addition, transcriptome analysis revealed that the insulin signaling pathway may be the core pathway of the EC anti-T2DM effect. Therefore, EC may modulate the gut microbiota and liver insulin signaling pathways by the gut-liver axis to alleviate T2DM. As a diet supplement, EC has promising potential in T2DM prevention and treatment.

Short term supplementation with cranberry extract modulates gut microbiota in human and displays a bifidogenic effect

Cranberry is associated with multiple health benefits, which are mostly attributed to its high content of (poly)phenols, particularly flavan-3-ols. However, clinical trials attempting to demonstrate these positive effects have yielded heterogeneous results, partly due to the high inter-individual variability associated with gut microbiota interaction with these molecules. In fact, several studies have demonstrated the ability of these molecules to modulate the gut microbiota in animal and in vitro models, but there is a scarcity of information in human subjects. In addition, it has been recently reported that cranberry also contains high concentrations of oligosaccharides, which could contribute to its bioactivity. Hence, the aim of this study was to fully characterize the (poly)phenolic and oligosaccharidic contents of a commercially available cranberry extract and evaluate its capacity to positively modulate the gut microbiota of 28 human subjects. After only four days, the (poly)phenols and oligosaccharides-rich cranberry extract, induced a strong bifidogenic effect, along with an increase in the abundance of several butyrate-producing bacteria, such as Clostridium and Anaerobutyricum. Plasmatic and fecal short-chain fatty acids profiles were also altered by the cranberry extract with a decrease in acetate ratio and an increase in butyrate ratio. Finally, to characterize the inter-individual variability, we stratified the participants according to the alterations observed in the fecal microbiota following supplementation. Interestingly, individuals having a microbiota characterized by the presence of Prevotella benefited from an increase in Faecalibacterium with the cranberry extract supplementation.

Assessing the Gut Microbiota's Ability to Metabolize Oligomeric and Polymeric Flavan-3-ols from Aronia and Cranberry

Clinical trials investigating the health effects of flavan-3-ols yield heterogeneous results due to interindividual variability in the gut microbiota metabolism. In fact, different groups in the population have similar metabolic profiles following (-)-epicatechin and (+)-catechin gut microbial metabolism and can be regrouped into so-called metabotypes. In this study, the capacity of 34 donors to metabolize polymeric B-type flavan-3-ols from aronia and oligomeric A-type flavan-3-ols from cranberry is investigated by in vitro fecal batch fermentations. Less than 1% of the flavan-3-ols from both sources are converted into microbial metabolites, such as phenyl-γ-valerolactones (PVLs). To further confirm this result, gut microbial metabolites from flavan-3-ols are quantified in urine samples collected from participants, before and after a 4-day supplementation of cranberry extract providing 82.3 mg of flavan-3-ols per day. No significant difference is observed in the urinary excretion of flavan-3-ols microbial metabolites. Hence, it demonstrates by both in vitro and in vivo approaches that flavan-3-ols from aronia and cranberry are poorly degraded by the gut microbiota. The beneficial health impacts of these molecules likely stem from their capacity to affect gut microbiota and their interactions with the gut epithelium, rather than from their breakdown into smaller metabolites.

Unraveling the parahormetic mechanism underlying the health-protecting effects of grapeseed procyanidins

Proanthocyanidins (PACs), the predominant constituents within Grape Seed Extract (GSE), are intricate compounds composed of interconnected flavan-3-ol units. Renowned for their health-affirming properties, PACs offer a shield against a spectrum of inflammation associated diseases, such as diabetes, obesity, degenerations and possibly cancer. While monomeric and dimeric PACs undergo some absorption within the gastrointestinal tract, their larger oligomeric and polymeric counterparts are not bioavailable. However, higher molecular weight PACs engage with the colonic microbiota, fostering the production of bioavailable metabolites that undergo metabolic processes, culminating in the emergence of bioactive agents capable of modulating physiological processes. Within this investigation, a GSE enriched with polymeric PACs was employed to explore in detail their impact. Through comprehensive analysis, the present study unequivocally verified the gastrointestinal-mediated transformation of medium to high molecular weight polymeric PACs, thereby establishing the bioaccessibility of a principal catabolite termed 5-(3',4'-dihydroxyphenyl)-γ-valerolactone (VL). Notably, our findings, encompassing cell biology, chemistry and proteomics, converge to the proposal of the notion of the capacity of VL to activate, upon oxidation to the corresponding quinone, the nuclear factor E2-related factor 2 (Nrf2) pathway-an intricate process that incites cellular defenses and mitigates stress-induced responses, such as a challenge brought by TNFα. This mechanistic paradigm seamlessly aligns with the concept of para-hormesis, ultimately orchestrating the resilience to stress and the preservation of cellular redox equilibrium and homeostasis as benchmarks of health.