Enrichment of Food With Tannin Extracts Promotes Healthy Changes in the Human Gut Microbiota

Effects of pomegranate (Punica granatum L.) peel on the growth performance and intestinal microbiota of broilers challenged with Escherichia coli

The effects of pomegranate peel on the growth performance, intestinal morphology, and the cecal microbial community were investigated in broilers challenged with avian pathogenic Escherichia coli (APEC) O78. A total of 240 one-day-old chicks (120 males and 120 females) were randomly and evenly allotted into 4 treatment groups (each with 6 biological replicates each of 10 chicks), i.e., negative control (NC), positive control (PC), and 2 experimental groups treated with 0.2% fermented pomegranate peel (FP) and 0.2% unfermented pomegranate peel (UFP), respectively, with PC, FP, and UFP groups challenged with APEC O78 (5 × 108 CFU) on day 14. Results showed that the challenge of APEC O78 decreased the body weight (BW) and average daily gain (ADG) of broilers from 1 to 28 d (P < 0.01). These broilers exhibited more pathological conditions in the heart and liver and higher mortality rates in 28 d compared to the NC group. Diet supplemented with pomegranate peel (either fermented or unfermented) significantly increased BW, ADG, and the villus height/crypt depth ratio (VCR) of small intestine in 28 d compared to the NC group (P < 0.05). Results of the taxonomic structure of the gut microbiota showed that compared to the NC group, the APEC challenge significantly decreased the relative abundance of Bacteroidetes and increased the relative abundance of Firmicutes (P < 0.01). Compared to the PC group, the relative abundance of Ruminococcus_torques_group in FP group was increased, while the relative abundance of Alistipes was decreased. In summary, our study showed that the dietary supplementation of pomegranate peel could maintain the intestinal microbiota at a state favorable to the host, effectively reduce the abnormal changes in the taxonomic structure of the intestinal microbiota, and improve the growth performance in broilers treated with APEC.

Concentration-dependent effect of plant secondary metabolites on bacterial and fungal microbiomes in caterpillar guts

IMPORTANCE

The caterpillar gut is an excellent model system for studying host-microbiome interactions, as it represents an extreme environment for microbial life that usually has low diversity and considerable variability in community composition. Our study design combines feeding caterpillars on a natural and artificial diet with controlled levels of plant secondary metabolites and uses metabarcoding and quantitative PCR to simultaneously profile bacterial and fungal assemblages, which has never been performed. Moreover, we focus on multiple caterpillar species and consider diet breadth. Contrary to many previous studies, our study suggested the functional importance of certain microbial taxa, especially bacteria, and confirmed the previously proposed lower importance of fungi for caterpillar holobiont. Our study revealed the lack of differences between monophagous and polyphagous species in the responses of microbial assemblages to plant secondary metabolites, suggesting the limited role of the microbiome in the plasticity of the herbivore diet.

The Antioxidant Activity of Wild-Growing Plants Containing Phenolic Compounds in Latvia

Ethnobotanical reports from Latvia show that Tanacetum vulgare, Calluna vulgaris, Quercus robur, Artemisa absinthium, and Artemisia vulgaris contain phenolic compounds that have antioxidant properties, which can be beneficial in the treatment and prophylaxis of many diseases. The aim of this study was to characterize the phenolic compounds and antioxidant properties of these plants. Plant extracts were prepared using ethanol or acetone and then freeze-dried. Their total phenolic content (TPC), total flavonoid content (TFC), and total tannin content (TTC) were determined and characterized by HPLC. Their antioxidant properties were determined using a DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. C. vulgaris herb and T. vulgare leaf extracts contained the highest amounts of flavonoids, but the bark of Q. robur had mostly tannins and phenolic acids. A. absinthium and A. vulgaris had the lowest amounts of polyphenols. When compared using extraction solvents, all acetone extracts had more TPC, more TFC, and better antioxidant activity. All plants contained chlorogenic acid, which contributes to antioxidant properties. The analysed plant extracts could be used in future studies to develop medicinal products with antioxidant properties.

Why is it important to understand the nature and chemistry of tannins to exploit their potential as nutraceuticals?

Tannins comprise a large group of polyphenols that can differ widely in chemical composition and molecular weight. The use of tannins dates back to antiquity, but it is only in recent years that their potential use as nutraceuticals associated with the human diet is beginning to be exploited. Although the biological effects of these phytocomplexes have been studied for many years, there are still several open questions regarding their chemistry and biotransformation. The vastness of the molecules that make up the class of tannins has made their characterisation, as well as their nomenclature and classification, a daunting task. This review has been written with the aim of bringing order to the chemistry of tannins by including aspects that are sometimes still overlooked or should be updated with new research in order to understand the potential of these phytocomplexes as active ingredients or technological components for nutraceutical products. Future trends in tannin research should address many questions that are still open, such as determining the exact biosynthetic pathways of all classes of tannins, the actual biological effects determined by the interaction of tannins with other molecules, their metabolization, and the best extraction methods, but with a view to market requirements.

Evaluation of Tannin-Delivery Approaches for Gut Microbiota Modulation: Comparison of Pectin-Based Microcapsules and Unencapsulated Extracts

The aim of this study was to investigate the impact of tannins on gut microbiota composition and activity, and to evaluate the use of pectin-microencapsulation of tannins as a potential mode of tannin delivery. Thus, pectin-tannin microcapsules and unencapsulated tannin extracts were in vitro digested and fermented, and polyphenol content, antioxidant capacity, microbiota modulation, and short-chain fatty acid (SCFA) production were analyzed. Pectin microcapsules were not able to release their tannin content, keeping it trapped after the digestive process, and are therefore not recommended for tannin delivery. Unencapsulated tannin extracts were found to exert a positive effect on the human gut microbiota. The digestion step resulted to be a fundamental requirement in order to maximize tannin bioactive effects, especially with regard to condensed tannins, as the antioxidant capacity exerted and the SCFAs produced were greater when tannins were submitted to digestion prior to fermentation. Moreover, tannins interacted differently with the intestinal microbiota depending on whether they underwent prior digestion or not. Polyphenol content and antioxidant capacity correlated with SCFA production and with the abundance of several bacterial taxa.

The synergistic ramification of insoluble dietary fiber and associated non-extractable polyphenols on gut microbial population escorting alleviation of lifestyle diseases

Most of the pertinent research which aims at exploring the therapeutic effects of polyphenols usually misapprehends a large fraction of non-extractable polyphenols due to their poor aqueous-organic solvent extractability. These polymeric polyphenols (i.e., proanthocyanins, hydrolysable tannins and phenolic acids) possess a unique property to adhere to the food matrix polysaccharides and protein sowing to their structural complexity with high glycosylation, degree of polymerization, and plenty of hydroxyl groups. Surprisingly resistance to intestinal absorption does not hinder its bioactivity but accelerates its functionality manifolds due to the colonic microbial catabolism in the gastrointestinal tract, thereby protecting the body from local and systemic inflammatory diseases. This review highlights not only the chemistry, digestion, colonic metabolism of non-extractable polyphenols (NEPP) but also summarises the synergistic effect of matrix-bound NEPP exerting local as well as systemic health benefits.

Effects of Food Factors and Processing on Protein Digestibility and Gut Microbiota

Protein is an essential macronutrient. The nutritional needs of dietary proteins are met by digestion and absorption in the small intestine. Indigestible proteins are further metabolized in the gut and produce metabolites via protein fermentation. Thus, protein indigestibility exerts a wide range of effects on gut microbiota composition and function. This review aims to discuss protein digestibility, the effects of food factors, such as protein sources, intake level, and amino acid composition, and making meat analogues. Besides, it provides an inventory of antinutritional factors and processing techniques that influence protein digestibility and, consequently, the diversity and composition of intestinal microbiota. Future studies are warranted to understand the implication of plant-based analogues on protein digestibility and gut microbiota and to elucidate the mechanisms concerning protein digestibility to host gut microbiota using various omics techniques.

Gastrointestinal worms and bacteria: From association to intervention

A plethora of studies, both experimental and epidemiological, have indicated the occurrence of associations between infections by gastrointestinal (GI) helminths and the composition and function of the host gut microbiota. Given the worldwide risk and spread of anthelmintic resistance, particularly for GI parasites of livestock, a better understanding of the mechanisms underpinning the relationships between GI helminths and the gut microbiome, and between the latter and host health, may assist the development of novel microbiome-targeting and other bacteria-based strategies for parasite control. In this article, we review current and prospective methods to manipulate the host gut microbiome, and/or to exploit the immune stimulatory and modulatory properties of gut bacteria (and their products) to counteract the negative impact of GI worm infections; we also discuss the potential applications of these intervention strategies in programmes aimed to aid the fight against helminth diseases of humans and livestock.

Sorghum tannin extract impedes in vitro digestibility and fermentability of nutrients in the simulated porcine gastrointestinal tract

The site and extent of digestion of sorghum nutrients affected by tannins in the intestine are not clarified. Porcine small intestine digestion and large intestine fermentation were simulated in vitro to determine the effects of sorghum tannin extract on the digestion and fermentation characteristics of nutrients in the mimicked porcine gastrointestinal tract. In experiment 1, low-tannin sorghum grain without or with 30 mg/g sorghum tannin extract were digested by porcine pepsin and pancreatin to measure in vitro digestibility of nutrients. In experiment 2, the lyophilized porcine ileal digesta from 3 barrows (Duroc × Landrace × Yorkshire, 27.75 ± 1.46 kg) fed the low-tannin sorghum grain without or with 30 mg/g sorghum tannin extract and the undigested residues from experiment 1 were, individually, incubated with fresh pig cecal digesta as inoculums for 48 h to simulate the porcine hindgut fermentation. The results revealed that sorghum tannin extract decreased in vitro digestibility of nutrients both by pepsin hydrolysis or pepsin-pancreatin hydrolysis (P < 0.05). Although enzymatically unhydrolyzed residues provided more energy (P = 0.09) and nitrogen (P < 0.05) as fermentation substrates, the microbial degradation of nutrients from unhydrolyzed residues and porcine ileal digesta were both decreased by sorghum tannin extract (P < 0.05). Regardless of unhydrolyzed residues or ileal digesta as fermentation substrates, microbial metabolites including the accumulative gas production excluding the first 6 h, total short-chain fatty acid and microbial protein content in the fermented solutions were decreased (P < 0.05). The relative abundances of Lachnospiraceae AC2044 and NK4A136 and Ruminococcus_1 was decreased by sorghum tannin extract (P < 0.05). In conclusion, sorghum tannin extract not only directly decreased the chemical enzymatic digestion of nutrients in the simulated anterior intestine, but also directly inhibited the microbial fermentation including microbial diversities and metabolites in the simulated posterior intestine of pigs. The experiment implies that the decreased abundances of Lachnospiraceae and Ruminococcaceae by tannins in the hindgut may weaken the fermentation capacity of microflora and thus impair the nutrient digestion in the hindgut, and ultimately reduce the total tract digestibility of nutrients in pigs fed high tannin sorghum.

Anti-diabetic prospects of dietary bio-actives of millets and the significance of the gut microbiota: A case of finger millet

Finger millet (Eleusine coracana) is a staple food in several parts of the world because of its high nutritional value. In addition to its high nutrient content, finger millet contains numerous bioactive compounds, including polyphenol (10.2 mg/g TAE), flavonoid (5.54 mg/g CE), phytic acid (0.48%), and dietary fiber (15-20%). Polyphenols are known for their anti-oxidant and anti-diabetic role. Phytic acid, previously considered an anti-nutritive substance, is now regarded as a nutraceutical as it reduces carbohydrate digestibility and thus controls post-prandial glucose levels and obesity. Thus, finger millet is an attractive diet for patients with diabetes. Recent findings have revealed that the anti-oxidant activity and bio-accessibility of finger millet polyphenols increased significantly (P < 0.05) in the colon, confirming the role of the gut microbiota. The prebiotic content of finger millet was also utilized by the gut microbiota, such as Faecalibacterium, Eubacterium, and Roseburia, to generate colonic short-chain fatty acids (SCFAs), and probiotic Bifidobacterium and Lactobacillus, which are known to be anti-diabetic in nature. Notably, finger millet-induced mucus-degrading Akkermansia muciniphila can also help in alleviate diabetes by releasing propionate and Amuc_1100 protein. Various millet bio-actives effectively controlled pathogenic gut microbiota, such as Shigella and Clostridium histolyticum, to lower gut inflammation and, thus, the risk of diabetes in the host. In the current review, we have meticulously examined the role of gut microbiota in the bio-accessibility of millet compounds and their impact on diabetes.

Randomized placebo-controlled trial of oral tannin supplementation on COVID-19 symptoms, gut dysbiosis and cytokine response

The clinical study aim was to investigate whether a tannin-based dietary supplementation could improve the efficacy of standard-of-care treatment of hospitalized COVID-19 patients by restoring gut microbiota function. Adverse events and immunomodulation post-tannin supplementation were also investigated. A total of 124 patients receiving standard-of-care treatment were randomized to oral tannin-based supplement or placebo for a total of 14 days. Longitudinal blood and stool samples were collected for cytokine and 16S rDNA microbiome profiling, and results were compared with 53 healthy controls. Although oral tannin supplementation did not result in clinical improvement or significant gut microbiome shifts after 14-days, a reduction in the inflammatory state was evident and significantly correlated with microbiota modulation. Among cytokines measured, MIP-1α was significantly decreased with tannin treatment (p = 0.03) where it correlated positively with IL-1β and TNF- α, and negatively with stool Bifidobacterium abundance.

Genetic analysis of seed traits in Sorghum bicolor that affect the human gut microbiome

Prebiotic fibers, polyphenols and other molecular components of food crops significantly affect the composition and function of the human gut microbiome and human health. The abundance of these, frequently uncharacterized, microbiome-active components vary within individual crop species. Here, we employ high throughput in vitro fermentations of pre-digested grain using a human microbiome to identify segregating genetic loci in a food crop, sorghum, that alter the composition and function of human gut microbes. Evaluating grain produced by 294 sorghum recombinant inbreds identifies 10 loci in the sorghum genome associated with variation in the abundance of microbial taxa and/or microbial metabolites. Two loci co-localize with sorghum genes regulating the biosynthesis of condensed tannins. We validate that condensed tannins stimulate the growth of microbes associated with these two loci. Our work illustrates the potential for genetic analysis to systematically discover and characterize molecular components of food crops that influence the human gut microbiome.

Diet affects the human gut microbiome, but studies linking crop genetics to seed traits that influence the human gut microbiome are lacking. Here, the authors develop an in vitro microbiome screening method and reveal the association between sorghum genes regulating condensed tannin biosynthesis and human gut microbiome.

Polyphenol and Tannin Nutraceuticals and Their Metabolites: How the Human Gut Microbiota Influences Their Properties

Nutraceuticals have been receiving increasing attention in the last few years due to their potential role as adjuvants against non-communicable chronic diseases (cardiovascular disease, diabetes, cancer, etc.). However, a limited number of studies have been performed to evaluate the bioavailability of such compounds, and it is generally reported that a substantial elevation of their plasma concentration can only be achieved when they are consumed at pharmacological levels. Even so, positive effects have been reported associated with an average dietary consumption of several nutraceutical classes, meaning that the primary compound might not be solely responsible for all the biological effects. The in vivo activities of such biomolecules might be carried out by metabolites derived from gut microbiota fermentative transformation. This review discusses the structure and properties of phenolic nutraceuticals (i.e., polyphenols and tannins) and the putative role of the human gut microbiota in influencing the beneficial effects of such compounds.

The Stance4Health Project: Evaluating a Smart Personalised Nutrition Service for Gut Microbiota Modulation in Normal- and Overweight Adults and Children with Obesity, Gluten-Related Disorders or Allergy/Intolerance to Cow’s Milk

Unhealthy diets represent a major risk for the pathogenesis of metabolic and chronic inflammatory diseases. Improving the quality of diet is important to prevent chronic diseases, and diet-induced modifications of the gut microbiota (GM) community likely play an important role. The EU-funded Stance4Health project aims at performing a randomized clinical trial based on a nutritional intervention program in the context of normal weight and overweight adults as well as children with obesity and gluten-related disorders or allergy/intolerance to cow’s milk. The trial will evaluate the efficacy of a Smart Personalised Nutrition (SPN) service in modifying GM composition and metabolic function and improving consumer empowerment through technology adoption.

Evaluation of the Effects of a Short Supplementation With Tannins on the Gut Microbiota of Healthy Subjects

Western diet, high in fats and sugars and low in greens, contributes to dysbiosis of the gut microbiota, which can lead to a variety of chronic diseases related with inflammation. Supplementation with bioactive compounds can help to maintain a healthy eubiotic state. Thus, we performed a 4-weeks nutritional intervention on healthy volunteers to investigate whether a blend of natural tannin extracts could induce healthy changes in the microbial intestinal ecosystem. Changes in the composition and functionality of the microbiota could be observed from the first two weeks onward. 16S rRNA amplicon next-generation sequencing (NGS) revealed a significant increase in microbial diversity at the end of the intervention, as well as trends toward increases in the relative abundances of several beneficial taxa, such as Ruminococcus bicirculans, Faecalibacterium prausnitzii, Lachnospiraceae UCG 010, Lachnospiraceae NK4A136, Bacteroides thetaiotaomicron and B. uniformis. Remarkably, some of the identified taxa were also identified as responsible for an increase in the production of short-chain fatty acids (SCFAs), microbial metabolites that contribute to the modulation of the immune system and have various other anti-inflammatory functions in the gut. Taken together, these results suggest that the tannin supplementation could exert a prebiotic effect by selectively stimulating the growth and the activity of bacteria that are advantageous for the host.

Wood Waste from Fruit Trees: Biomolecules and Their Applications in Agri-Food Industry

In the European Union (EU), a total of 11,301,345 hectares are dedicated to the cultivation of fruit trees, mainly olive orchards, grapevines, nut trees (almond, walnut, chestnut, hazelnut, and pistachio), apple and pear trees, stone fruit trees (peach, nectarine, apricot, cherry, and plum), and citrus fruit trees (orange, clementine, satsuma, mandarin, lemon, grapefruit, and pomelo). Pruning these trees, together with plantation removal to a lesser extent, produces a huge amount of wood waste. A theoretical calculation of the wood waste in the European Union estimates approximately 2 and 25 million tons from wood plantation removal and pruning, respectively, per year. This wood waste is usually destroyed by in-field burning or crushing into the soil, which result in no direct economic benefits. However, wood from tree pruning, which is enriched in high added-value molecules, offers a wide spectrum of possibilities for its valorization. This review focuses on the contribution of wood waste to both sustainability and the circular economy, considering its use not only as biomass but also as a potential source of bioactive compounds. The main bioactive compounds found in wood are polyphenols, terpenes, polysaccharides, organic compounds, fatty acids, and alkaloids. Polyphenols are the most ubiquitous compounds in wood. Large amounts of hydroxytyrosol (up to 25 g/kg dw), resveratrol (up to 66 g/kg dw), protocatechuic acid (up to 16.4 g/kg), and proanthocyanins (8.5 g/kg dw) have been found in the wood from olive trees, grapevines, almond trees and plum trees, respectively. The bioactivity of these compounds has been demonstrated at lower concentrations, mainly in vitro studies. Bioactive compounds present antioxidant, antimicrobial, antifungal, biostimulant, anti-inflammatory, cardioprotective, and anticarcinogenic properties, among others. Therefore, wood extracts might have several applications in agriculture, medicine, and the food, pharmaceutical, nutraceutical, and cosmetics industries. For example, olive tree wood extract reduced thrombin-induced platelet aggregation in vitro; grapevine tree wood extract acts a preservative in wine, replacing SO₂; chestnut tree wood extract has antifungal properties on postharvest pathogens in vitro; and stone tree wood extracts are used for aging both wines and brandies. Moreover, the use of wood waste contributes to the move towards both a more sustainable development and a circular economy.

A Bayesian Negative Binomial Hierarchical Model for Identifying Diet-Gut Microbiome Associations

The human gut microbiota composition plays an important role in human health. Long-term diet intervention may shape human gut microbiome. Therefore, many studies focus on discovering links between long-term diets and gut microbiota composition. This study aimed to incorporate the phylogenetic relationships between the operational taxonomic units (OTUs) into the diet-microbe association analysis, using a Bayesian hierarchical negative binomial (NB) model. We regularized the dispersion parameter of the negative binomial distribution by assuming a mean-dispersion association. A simulation study showed that, if over-dispersion is present in the microbiome data, our approach performed better in terms of mean squared error (MSE) of the slope-estimates compared to the standard NB regression model or a Bayesian hierarchical NB model without including the phylogenetic relationships. Data of the Healthy Life in an Urban Setting (HELIUS) study showed that for some phylogenetic families the (posterior) variances of the slope-estimates were decreasing when including the phylogenetic relationships into the analyses. In contrast, when OTUs of the same family were not similarly affected by the food item, some bias was introduced, leading to larger (posterior) variances of the slope-estimates. Overall, the Bayesian hierarchical NB model, with a dependency between the mean and dispersion parameters, proved to be a robust method for analyzing diet-microbe associations.

Red Wine High-Molecular-Weight Polyphenolic Complex: An Emerging Modulator of Human Metabolic Disease Risk and Gut Microbiota

Moderate red wine consumption has been linked to reduced chronic disease risk. Thus far, little has been known about the physicochemical properties and potential biological effects of high-molecular-weight polyphenolic complexes (HPPCs), a major fraction of red wine polyphenols. In this work, the stability and biochemical properties of HPPCs under simulated gastrointestinal conditions in vitro were studied. The results showed that HPPCs were resistant to simulated gastric digestion (SGD) and simulated intestinal digestion (SID). They exhibited significant inhibitory activity against key metabolic syndrome-associated digestive enzymes, achieving 17.1-90.9% inhibition of pancreatic α-amylase, lipase, and cholesterol esterase at 0.02-0.45 mg/mL. HPPCs were metabolized by gut microbiota (GM), leading to significantly enhanced antioxidant capacity when compared with the original, SGD, and SID samples. Furthermore, they favorably modulated GM profiles, which was accompanied by significantly increased short-chain fatty acid generation during the early colonic fermentation phase. These findings suggest that HPPCs are a promising modulator of human metabolic disease risk.