Anthocyanins inhibit tumor necrosis alpha-induced loss of Caco-2 cell barrier integrity

Pigmented corn as a gluten-free source of polyphenols with anti-inflammatory and antioxidant properties in CaCo-2 cells

A high number of varieties from corn (Zea mays L.) have been consumed for long time all over the world, however pigmented varieties are recently gaining renewed attention due to their beneficial effects and polyphenolic content. The natural lack of gluten makes corn suitable for consumption by celiac population, who need to control their inflammatory state through an appropriate gluten-free diet. The biological effects of polyphenols from pigmented corn are poorly investigated in the context of celiac disease. In this work, we analyzed through HPLC-DAD the phenolic composition of two Italian purple and red varieties ("Scagliolo Rosso" and "Rostrato di Rovetta", respectively) comparing their effects in human intestinal epithelial cells (CaCo-2 cells). The possible impact of gastro-intestinal digestion following oral consumption was assessed as well. The phenolic profile showed the presence of phenolic acids in both varieties, while anthocyanins were identified in Scagliolo Rosso only. After simulated digestion, the level of polyphenols did not significantly change and paralleled with an increased scavenging activity. In CaCo-2 cells, stimulated by a proinflammatory cocktail containing gliadin-derived peptides (IL-1β, IFN-γ, digested gliadin), pigmented corn extracts inhibited the release of CXCL-10 and sICAM-1, with mechanisms partially ascribed to NF-κB impairment. At the same concentration (200 μg/mL), ROS production and catalase depletion were reverted through Nrf-2-independent mechanisms. Our data suggest that polyphenols from pigmented corns might help in controlling the inflammatory and oxidative state of people with celiac disease at intestinal level, at concentrations potentially achievable through a gluten-free diet.

Dietary Anthocyanins Mitigate High-Fat Diet-Induced Hippocampal Inflammation in Mice

BACKGROUND

Obesity and consumption of high-fat diets (HFD) are associated with intestinal permeabilization and increased paracellular transport of endotoxins, which can promote neuroinflammation. Inflammation can affect the hypothalamic pituitary adrenal (HPA) axis, which controls responses to stress and downregulates the brain-derived neurotrophic factor (BDNF), which can promote anxiety and depression, conditions frequently found in obesity. We previously showed that consumption of anthocyanins (AC) mitigate HFD-induced insulin resistance, intestinal permeability, and inflammation.

OBJECTIVES

This study investigated if a dietary supplementation with a cyanidin- and delphinidin-rich extract (CDRE) could counteract HFD/obesity-induced hippocampal inflammation in mice.

METHODS

C57BL/6J male mice were fed for 14 wk on one of the following diets: 1) a control diet containing 10% total calories from fat (C), 2) a control diet supplemented with 40 mg AC/kg body weight (BW) (CAC), 3) a HFD containing 60% total calories from fat (lard) (HF), or 4) the HFD supplemented with 2, 20, or 40 mg AC/kg BW (HFA2, HFA20, and HFA40, respectively). In plasma and in the hippocampus, parameters of neuroinflammation and the underlying cause (endotoxemia) and consequences (alterations to the HPA and BDNF downregulation) were measured.

RESULTS

Consumption of the HFD caused endotoxemia. Accordingly, hippocampal Tlr4 mRNA levels were 110% higher in the HF group, which were both prevented by CDRE supplementation. Consumption of the HFD also caused: 1) microgliosis and increased expression of genes involved in neuroinflammation, that is, Iba-1, Nox4, Tnfα, and Il-1β, 2) alterations of HPA axis regulation, that is, with low expression of mineralocorticoid (MR) and glucocorticoid (GR) receptors; and 3) decreased Bdnf expression. Supplementation of HFD-fed mice with CDRE mitigated neuroinflammation, microgliosis, and MR and BDNF decreases.

CONCLUSIONS

CDRE supplementation mitigates the negative effects associated with HFD consumption and obesity in mouse hippocampus, in part by decreasing inflammation, improving glucocorticoid metabolism, and upregulating BDNF.

Red raspberry (Rubus idaeus) preserves intestinal barrier integrity and reduces oxidative stress in Caco-2 cells exposed to a proinflammatory stimulus

Growing evidence showed the capacity of (poly)phenols to exert a protective role on intestinal health. Nevertheless, the existing findings are still heterogeneous and the underlying mechanisms remain unclear. This study investigated the potential benefits of a red raspberry (Rubus idaeus) powder on the integrity of the intestinal barrier, focusing on its ability to mitigate the effects of tumor necrosis factor-α (TNF-α)-induced intestinal permeability. Human colorectal adenocarcinoma cells (i.e., Caco-2 cells) were used as a model to assess the impact of red raspberry on intestinal permeability, tight junction expression, and oxidative stress. The Caco-2 cells were differentiated into polarized monolayers and treated with interferon-γ (IFN-γ) (10 ng mL-1) for 24 hours, followed by exposure to TNF-α (10 ng mL-1) in the presence or absence of red raspberry extract (1-5 mg mL-1). The integrity of the intestinal monolayer was evaluated using transepithelial electrical resistance (TEER) and fluorescein isothiocyanate-dextran (FITC-D) efflux assay. Markers of intestinal permeability (claudin-1, occludin, and zonula occludens-1 (ZO-1)) and oxidative stress (8-hydroxy-2-deoxyguanosine (8-OHdG) and protein carbonyl) were assessed using ELISA kits. Treatment with red raspberry resulted in a significant counteraction of TEER value loss (41%; p < 0.01) and a notable reduction in the efflux of FITC-D (-2.5 times; p < 0.01). Additionally, red raspberry attenuated the levels of 8-OHdG (-48.8%; p < 0.01), mitigating the detrimental effects induced by TNF-α. Moreover, red raspberry positively influenced the expression of the integral membrane protein claudin-1 (+18%; p < 0.01), an essential component of tight junctions. These findings contribute to the growing understanding of the beneficial effects of red raspberry in the context of the intestinal barrier. The effect of red raspberry against TNF-α-induced intestinal permeability observed in our in vitro model suggests, for the first time, its potential as a dietary strategy to promote gastrointestinal health.

An overview on the cellular mechanisms of anthocyanins in maintaining intestinal integrity and function

Structural and functional changes of the intestinal barrier, as a consequence of a number of (epi)genetic and environmental causes, have a main role in penetrations of pathogens and toxic agents, and lead to the development of inflammation-related pathological conditions, not only at the level of the GI tract but also in other extra-digestive tissues and organs. Anthocyanins (ACNs), a subclass of polyphenols belonging to the flavonoid group, are well known for their health-promoting properties and are widely distributed in the human diet. There is large evidence about the correlation between the human intake of ACN-rich products and a reduction of intestinal inflammation and dysfunction. Our review describes the more recent advances in the knowledge of cellular and molecular mechanisms through which ACNs can modulate the main mechanisms involved in intestinal dysfunction and inflammation, in particular the inhibition of the NF-κB, JNK, MAPK, STAT3, and TLR4 proinflammatory pathways, the upregulation of the Nrf2 transcription factor and the expression of tight junction proteins and mucins.

Physiologic effects of the maqui berry (Aristotelia chilensis): a focus on metabolic homeostasis

The prevalence and socioeconomic impact of metabolic diseases is rapidly growing. The limited availability of effective and affordable treatments has fuelled interest in the therapeutic potential of natural compounds as they occur in selected food sources. These compounds might help to better manage the current problems of treatment availability, affordability, and adverse effects that, in combination, limit treatment duration and efficacy at present. Specifically, berries garnered interest given a strong epidemiological link between their consumption and improved metabolic functions, making the analysis of their phytochemical composition and the identification and characterization of biologically active ingredients an emerging area of research. In this regard, the present review focuses on the South American maqui berry Aristotelia chilensis, which has been extensively used by the indigenous Mapuche population for generations to treat a variety of disease conditions. An overview of the maqui plant composition precedes a review of pre-clinical and clinical studies that investigated the effects of maqui berries and their major components on metabolic homeostasis. The final part of the review highlights possible technologies to conserve maqui berry structural and functional integrity during passage through the small intestine, ultimately aiming to augment their systemic and luminal bioavailability and biological effects. The integration of the various aspects discussed herein can assist in the development of effective maqui-based therapies to benefit the growing population of metabolically compromised patients.

Food Polyphenols as Preventive Medicine

Reactive oxygen species (ROS) are the initiators in foods and in the stomach of oxidized dietary lipids, proteins, and lipid-oxidation end-products (ALEs), inducing in humans the development of several chronic diseases and cancer. Epidemiological, human clinical and animal studies supported the role of dietary polyphenols and derivatives in prevention of development of such chronic diseases. There is much evidence that polyphenols/derivatives at the right timing and concentration, which is critical, acts mostly in the aerobic stomach and generally in the gastrointestinal tract as reducing agents, scavengers of free radicals, trappers of reactive carbonyls, modulators of enzyme activity, generators of beneficial gut microbiota and effectors of cellular signaling. In the blood system, at low concentration, they act as generators of electrophiles and low concentration of H2O2, acting mostly as cellular signaling, activating the PI3K/Akt-mediated Nrf2/eNOS pathways and inhibiting the inflammatory transcription factor NF-κB, inducing the cells, organs and organism for eustress, adaptation and surviving.

Phloretin suppresses intestinal inflammation and maintained epithelial tight junction integrity by modulating cytokines secretion in in vitro model of gut inflammation

Ulcerative colitis is a type of inflammatory bowel disease which in long run can lead to colorectal cancer (CRC). Chronic inflammation can be a key factor for the occurrence of CRC thus mitigating an inflammation can be a preventive strategy for the occurrence of CRC. In this study we have explored the anti-inflammatory potential of phloretin, in in vitro gut inflammation model, developed by co-culture of Caco2 (intestinal epithelial) cells and RAW264.7 macrophages (immune cells). Phloretin is a dihydrochalcone present in apple, pear and strawberries. An anti-inflammatory effect of phloretin in reducing LPS induced inflammation and maintenance of transepithelial electric resistance (TEER) in Caco2 cells was examined. Paracellular permeability assay was performed using Lucifer yellow dye to evaluate the effect of phloretin in inhibiting gut leakiness caused by inflammatory mediators secreted by activated macrophages. Phloretin attenuated LPS induced nitric oxide levels, oxidative stress, depolarization of mitochondrial membrane potential in Caco2 cells as evidenced by reduction in reactive oxygen species (ROS), and enhancement of MMP, and decrease in inflammatory cytokines IL8, TNFα, IL1β and IL6. It exhibited anti-inflammatory activity by inhibiting the expression of NFκB, iNOS and Cox2. Phloretin maintained the epithelial integrity by regulating the expression of tight junction proteins ZO1, occludin, Claudin1 and JAM. Phloretin reduced LPS induced levels of Cox2 along with the reduction in Src expression which further regulated an expression of tight junction protein occludin. Phloretin in combination to sodium pyruvate exhibited potential anti-inflammatory activity via targeting NFkB signaling. Our findings paved a way to position phloretin as nutraceutical in preventing the occurrence of colitis and culmination of disease into colitis associated colorectal cancer.

Wild blueberry (V. angustifolium) improves TNFα-induced cell barrier permeability through claudin-1 and oxidative stress modulation in Caco-2 cells

Increasing evidence links the impairment of intestinal permeability (IP), a feature of the intestinal barrier, to numerous dysmetabolic and dysfunctional conditions. Several host and environmental factors, including dietary factors, can negatively and/or positively affect IP. In this regard, polyphenol-rich foods including berries have been proposed as potential IP modulators. However, the exact mechanisms involved are not yet fully elucidated. The aim of the present study was to evaluate the effect of a wild blueberry (WB; V. angustifolium) powder, naturally rich in polyphenols, to affect Caco-2 cell monolayer permeability and to identify the potential mechanisms in modulating the IP process. Caco-2 cells were incubated with TNF-α (10 ng mL-1), as a pro-inflammatory stimulus, and supplemented for 24 hours with different concentrations (1 and 5 mg mL-1) of WB powder. The integrity of the intestinal cell monolayer was evaluated by measuring the transepithelial electrical resistance (TEER) and the paracellular transport of FITC-dextran. In addition, the production of the tight junction proteins, such as claudin-1 and occludin, as well as protein carbonyl and 8-hydroxy 2 deoxyguanosine, as oxidative stress markers, were quantified in the supernatant by ELISA kits. Overall, the treatment with WB powder (5 mg mL-1) mitigated the loss of Caco-2 cell barrier integrity, as documented by an increase in TEER and a reduction in FITC values. This modulation was accompanied by an upregulation of claudin-1 and a reduction of 8-OHdG. Conversely, no effect was documented for the lower concentration (1 mg mL-1) and the other IP markers, as well as oxidative stress markers analysed. In conclusion, our findings suggest a potential role of WB in the modulation of cell barrier integrity. This modulation process could be attributed to an increase in claudin-1 expression and a reduction in 8-OHdG. Further studies should be performed to corroborate the results obtained. In addition, since the effects were observed at doses of WB achievable with the diet, these findings should be substantiated also through in vivo approaches.

Exploring the Impact of Cyanidin-3-Glucoside on Inflammatory Bowel Diseases: Investigating New Mechanisms for Emerging Interventions

Cyanidin-3-O-glucoside (C3G), the most widely distributed anthocyanin (ACN) in edible fruits, has been proposed for several bioactivities, including anti-inflammatory, neuro-protective, antimicrobial, anti-viral, anti-thrombotic and epigenetic actions. However, habitual intake of ACNs and C3G may vary widely among populations, regions, and seasons, among individuals with different education and financial status. The main point of C3G absorption occurs in the small and large bowel. Therefore, it has been supposed that the treating properties of C3G might affect inflammatory bowel diseases (IBD), such as ulcerative colitis (UC) and Crohn's disease (CD). IBDs develop through complex inflammatory pathways and sometimes may be resistant to conventional treatment strategies. C3G presents antioxidative, anti-inflammatory, cytoprotective, and antimicrobial effects useful for IBD management. In particular, different studies have demonstrated that C3G inhibits NF-κB pathway activation. In addition, C3G activates the Nrf2 pathway. On the other hand, it modulates the expression of antioxidant enzymes and cytoprotective proteins, such as NAD(P)H, superoxide dismutase, heme-oxygenase (HO-1), thioredoxin, quinone reductase-oxide 1 (NQO1), catalase, glutathione S-transferase and glutathione peroxidase. Interferon I and II pathways are downregulated by C3G inhibiting interferon-mediating inflammatory cascades. Moreover, C3G reduces reactive species and pro-inflammatory cytokines, such as C reactive protein, interferon-γ, tumor necrosis factor-α, interleukin (IL)-5, IL-9, IL-10, IL-12p70, and IL-17A in UC and CD patients. Finally, C3G modulates gut microbiota by inducing an increase in beneficial gut bacteria and increasing microbial abundances, thus mitigating dysbiosis. Thus, C3G presents activities that may have potential therapeutic and protective actions against IBD. Still, in the future, clinical trials should be designed to investigate the bioavailability of C3G in IBD patients and the proper therapeutic doses through different sources, aiming to the standardization of the exact clinical outcome and efficacy of C3G.

Complexation with Polysaccharides Enhances the Stability of Isolated Anthocyanins

Isolated anthocyanins have limited colonic bioavailability due to their instability as free forms. Thus, many methods have been fabricated to increase the stability of anthocyanins. Complexation, encapsulation, and co-pigmentation with other pigments, proteins, metal ions, and carbohydrates have been reported to improve the stability and bioavailability of anthocyanins. In this study, anthocyanins extracted from purple potatoes were complexed with four different polysaccharides and their mixture. The anthocyanin-polysaccharide complexes were characterized using a zeta potential analyzer, particle size analyzer, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Complexes were subjected to simulated digestion for assessing the stability of anthocyanins. Furthermore, complexes were subjected to different pH conditions and incubated at high temperatures to monitor color changes. A Caco-2 cell monolayer was used to evaluate the colonic concentrations of anthocyanins. In addition, the bioactivity of complexes was assessed using LPS-treated Caco-2 cell monolayer. Results show that pectin had the best complexation capacity with anthocyanins. The surface morphology of the anthocyanin-pectin complex (APC) was changed after complexation. APC was more resistant to the simulated upper gastrointestinal digestion, and high pH and temperature conditions for a longer duration. Furthermore, APC restored the lipopolysaccharide (LPS)-induced high cell permeability compared to isolated anthocyanins. In conclusion, complexation with pectin increased the stability and colonic bioavailability and the activity of anthocyanins.

Grape Pomace as a Cardiometabolic Health-Promoting Ingredient: Activity in the Intestinal Environment

Grape pomace (GP) is a winemaking by-product particularly rich in (poly)phenols and dietary fiber, which are the main active compounds responsible for its health-promoting effects. These components and their metabolites generated at the intestinal level have been shown to play an important role in promoting health locally and systemically. This review focuses on the potential bioactivities of GP in the intestinal environment, which is the primary site of interaction for food components and their biological activities. These mechanisms include (i) regulation of nutrient digestion and absorption (GP has been shown to inhibit enzymes such as α-amylase and α-glucosidase, protease, and lipase, which can help to reduce blood glucose and lipid levels, and to modulate the expression of intestinal transporters, which can also help to regulate nutrient absorption); (ii) modulation of gut hormone levels and satiety (GP stimulates GLP-1, PYY, CCK, ghrelin, and GIP release, which can help to regulate appetite and satiety); (iii) reinforcement of gut morphology (including the crypt-villi structures, which can improve nutrient absorption and protect against intestinal damage); (iv) protection of intestinal barrier integrity (through tight junctions and paracellular transport); (v) modulation of inflammation and oxidative stress triggered by NF-kB and Nrf2 signaling pathways; and (vi) impact on gut microbiota composition and functionality (leading to increased production of SCFAs and decreased production of LPS). The overall effect of GP within the gut environment reinforces the intestinal function as the first line of defense against multiple disorders, including those impacting cardiometabolic health. Future research on GP's health-promoting properties should consider connections between the gut and other organs, including the gut-heart axis, gut-brain axis, gut-skin axis, and oral-gut axis. Further exploration of these connections, including more human studies, will solidify GP's role as a cardiometabolic health-promoting ingredient and contribute to the prevention and management of cardiovascular diseases.

Cyanidin-3-O-glucoside protects intestinal epithelial cells from palmitate-induced lipotoxicity

CONTEXT

Increased free fatty acids (FFAs) levels, typical in obesity condition, can contribute to systemic lipotoxicity and inflammation adversely influencing Inflammatory Bowel Disease development and progression. Anthocyanins possess health promoting properties mainly associated to the induction of Nrf2-regulated cytoprotective proteins.

OBJECTIVE

Using a novel experimental model, we evaluated the in vitro intracellular mechanisms involved in FFAs modulation of intestinal epithelial lipotoxicity and the protective effects of cyanidin-3-O-glucoside (C3G) in Caco-2 cells.

RESULTS

Caco-2 exposed to palmitic acid (PA) in the serosal (basolateral) side showed a combined state of epithelial inflammation, inducing NF-κB pathway and downstream cytokines, that was reverted by C3G apical pre-treatment. In addition, PA altered intracellular redox status and induced reactive oxygen species that were reduced by C3G via the redox-sensitive Nrf2 signalling.

DISCUSSION AND CONCLUSION

Results suggest that anti-inflammatory properties of anthocyanins, mediated by Nrf2, could represent an interesting tool for intestinal inflammatory disorders.

Blackcurrant Alleviates Dextran Sulfate Sodium (DSS)-Induced Colitis in Mice

Previous studies have reported that anthocyanin (ACN)-rich materials have beneficial effects on ulcerative colitis (UC). Blackcurrant (BC) has been known as one of the foods rich in ACN, while studies demonstrating its effect on UC are rare. This study attempted to investigate the protective effects of whole BC in mice with colitis using dextran sulfate sodium (DSS). Mice were orally given whole BC powder at a dose of 150 mg daily for four weeks, and colitis was induced by drinking 3% DSS for six days. Whole BC relieved symptoms of colitis and pathological changes in the colon. The overproduction of pro-inflammatory cytokines such as IL-1β, TNF-α, and IL-6 in serum and colon tissues was also reduced by whole BC. In addition, whole BC significantly lowered the levels of mRNA and protein of downstream targets in the NF-κB signaling pathway. Furthermore, BC administration increased the expression of genes related to barrier function: ZO-1, occludin, and mucin. Moreover, the whole BC modulated the relative abundance of gut microbiota altered with DSS. Therefore, the whole BC has demonstrated the potential to prevent colitis through attenuation of the inflammatory response and regulation of the gut microbial composition.

Anthocyanin actions at the gastrointestinal tract: Relevance to their health benefits

Anthocyanins (AC) are flavonoids abundant in the human diet, which consumption has been associated to several health benefits, including the mitigation of cardiovascular disease, type 2 diabetes, non-alcoholic fatty liver disease, and neurological disorders. It is widely recognized that the gastrointestinal (GI) tract is not only central for food digestion but actively participates in the regulation of whole body physiology. Given that AC, and their metabolites reach high concentrations in the intestinal lumen after food consumption, their biological actions at the GI tract can in part explain their proposed local and systemic health benefits. In terms of mechanisms of action, AC have been found to: i) inhibit GI luminal enzymes that participate in the absorption of lipids and carbohydrates; ii) preserve intestinal barrier integrity and prevent endotoxemia, inflammation and oxidative stress; iii) sustain goblet cell number, immunological functions, and mucus production; iv) promote a healthy microbiota; v) be metabolized by the microbiota to AC metabolites which will be absorbed and have systemic effects; and vi) modulate the metabolism of GI-generated hormones. This review will summarize and discuss the latest information on AC actions at the GI tract and their relationship to overall health benefits.

Red raspberry supplementation mitigates alcohol-induced liver injury associated with gut microbiota alteration and intestinal barrier dysfunction in mice

Alcoholic liver disease (ALD) is still a global health concern. Long-term alcohol intake alters the gut microbiota diversity and metabolic activity, and causes intestinal barrier dysfunction, leading to the development of ALD. This research explored the protective effects and underlying mechanisms of red raspberry (RR) on alcohol-related disorders in mice. Male C57BL/6J mice were fed a standard diet or a standard diet supplemented with 2%, 4%, and 8% weight/weight RR. Meanwhile, mice were administered 35% (v/v) ethanol (EtOH, 10 mL per kg body weight) intragastrically once daily for six weeks, except the control group mice. The results showed that RR supplementation decreased liver injury markers (alanine and aspartate transaminases) in the serum, reduced triglyceride level in the liver and downregulated hepatic cytochrome P450 2E1 mRNA expression in mice administered EtOH. In addition, EtOH-mediated oxidative stress in the liver was attenuated by RR supplementation through decreased hepatic malondialdehyde content and increased antioxidant (glutathione, glutathione peroxidase, and catalase) levels and activities in mice exposed to EtOH. Moreover, RR supplementation reversed EtOH-induced alteration in the cecal microbial composition at the phylum, order, genus, and species levels and improved the intestinal barrier function associated with the inhibition of the NF-κB/MLCK pathway, which was accompanied by upregulation of tight junctions (zonula occludens 1, occludin, claudin-1, and claudin-4) and E-cadherin mRNA and protein expressions. Accordingly, RR supplementation resulted in a decreased level of endotoxins in the serum and attenuation of the inflammatory response in the liver, illustrated by a significant decrease in tumor necrosis factor-alpha, interleukin (IL)-1β, and IL-6 levels. Overall, RR supplementation alleviated the adverse effects of chronic alcohol intake in C57BL/6J mice and could be a potential supplement for improving ALD.

Anti-Inflammatory Activity of an In Vitro Digested Anthocyanin-Rich Extract on Intestinal Epithelial Cells Exposed to TNF-α

Background: The consumption of foods rich in anthocyanins (ACN) have been associated with beneficial properties in chronic inflammatory disorders such as intestinal bowel diseases (IBD). These effects were attributed not only to a direct antioxidant mechanism but also to the modulation of cell redox-dependent signaling. However, ACN bioavailability is low for their poor stability in the digestive tract, so ACN gastrointestinal digestion should be considered. Methods: To have a more realistic knowledge of the effects of ACN, we performed an in vitro simulated gastrointestinal digestion of an ACN-rich purified and standardized bilberry and blackcurrant extract (BBE), followed by an evaluation of ACN composition modification (HPLC-DAD and pH differential method) and antioxidant activity (FRAP assay). Then, we studied the effects of BBE gastrointestinal extract on Caco-2 exposed to TNF-α. Results: The results confirmed the high instability of ACN in the mild alkaline environment of the small intestine (17% recovery index). However, the digested BBE maintained part of its bioactivity. Additionally, BBE gastrointestinal extract inhibited the TNF-α-induced NF-κB pathway in Caco-2 and activated the Nrf2 pathway. Conclusions: Although ACN stability is affected by gastrointestinal digestion, the anti-inflammatory and antioxidant activity of digested extracts were confirmed; thus, the loss of ACN can probably be counterweighed by their metabolites. Then, ACN introduced by diet or food supplements could represent an approach for IBD prevention.

Cyanidin and delphinidin restore colon physiology in high fat diet-fed mice: Involvement of TLR-4 and redox-regulated signaling

Consumption of high fat diets (HFD) mimics a modern or "Western style" diet pattern and can impair intestinal barrier integrity, leading to endotoxemia and associated unhealthy conditions. This study investigated if supplementation with an anthocyanin (cyanidin and delphinidin glucosides)-rich extract (CDRE) could revert or mitigate HFD-induced alterations of colonic physiology in part through the regulation of Toll-Like Receptor 4 (TLR-4)- and redox-regulated signaling. C57BL/6J male mice were fed for 4 weeks with a control or an HFD. Then, mice were divided in four groups fed either control or HFD, or these diets supplemented with CDRE for the subsequent 4 weeks. After 8 weeks on the HFD we observed in the colon: i) disruption of tight junction structure and function; ii) increased TLR-4 expression; iii) increased NADPH oxidase NOX1 expression, and iv) activation of redox-sensitive and TLR-4-triggered pathways, i.e. NF-κB, ERK1/2, JNK1/2, PI3K/Akt. All these events were prevented or reverted by CDRE supplementation. Supporting the relevance of CDRE-mediated downregulation of TLR-4 on its colon beneficial effect; in vitro (Caco-2 cell monolayers), cyanidin, delphinidin and their metabolites protocatechuic and gallic acid, mitigated lipopolysaccharide (LPS)-induced monolayer permeabilization by restoring tight junction structure and dynamics and preventing lipid/protein oxidation. The CDRE also mitigated HFD-mediated alterations in parameters of goblet cell differentiation and function, including the downregulation of markers of goblet cell differentiation (Klf4), and intestinal mucosa healing (Tff3). Results show that a short-term supplementation with cyanidin and delphinidin, protect from HFD-induced alterations in colon physiology in part through the modulation of TLR-4- and redox-regulated signaling.

Research progress of anthocyanin prebiotic activity: A review

BACKGROUND

Anthocyanins are a kind of flavonoids and natural water-soluble pigments, which endow fruits, vegetables, and plants with multiple colors. They are important source of new products with prebiotic activity. However, there is no systematic review documenting prebiotic activity of anthocyanins and their structural analogues. This study aims to fill this gap in literature.

PURPOSE

The objective of this review is to summarize and evaluate the prebiotic activity of anthocyanin's, and discuss the physical and molecular modification methods to improve their biological activities.

STUDY DESIGN AND METHODS

In this review, the databases (PubMed, Google Scholar, Web of Science, Researchgate and Elsevier) were searched profoundly with keywords (anthocyanin's, prebiotics, probiotics, physical embedding and molecular modification).

RESULTS

A total of 34 articles were considered for reviewing. These studies approved that anthocyanins play an important role in promoting the proliferation of probiotics, inhibiting the growth of harmful bacteria and improving the intestinal environment. In addition, physical embedding and molecular modification have also been proved to be effective methods to improve the prebiotic activity of anthocyanins. Anthocyanins could promote the production of short chain fatty acids, accelerate self degradation and improve microbial related enzyme activities to promote the proliferation of probiotics. They inhibited the growth of harmful bacteria by inhibiting the expression of harmful bacteria genes, interfering with the role of metabolism related enzymes and affecting respiratory metabolism. They promoted the formation of a complete intestinal barrier and regulated the intestinal environment to keep the body healthy. Physical embedding, including microencapsulation and colloidal embedding, greatly improved the stability of anthocyanins. On the other hand, molecular modification, especially enzymatic modification, significantly improved the biological activities (antioxidant, prebiotic activity and so on) of anthocyanins.

CONCLUSION

All these research results displayed by this review indicate that anthocyanins are a useful tool for developing prebiotic products. The better activities of the new anthocyanins formed by embedding and modification may make them become more effective raw materials. Our review provides a scientific basis for the future research and application of anthocyanins.

Non-Celiac Gluten Sensitivity and Protective Role of Dietary Polyphenols

Pathogenetically characterized by the absence of celiac disease and wheat allergy, non-celiac gluten sensitivity (NCGS) is a clinical entity triggered by the consumption of gluten-containing foods that relieved by a gluten-free diet. Since it is very difficult to maintain a complete gluten-free diet, there is a high interest in discovering alternative strategies aimed at reducing gluten concentration or mitigating its toxic effects. Plant-based dietary models are usually rich in bioactive compounds, such as polyphenols, recognized to prevent, delay, or even reverse chronic diseases, including intestinal disorders. However, research on the role of polyphenols in mitigating the toxicity of gluten-containing foods is currently limited. We address the metabolic fate of dietary polyphenols, both as free and bound macromolecule-linked forms, with particular reference to the gastrointestinal compartment, where the concentration of polyphenols can reach high levels. We analyze the potential targets of polyphenols including the gluten peptide bioavailability, the dysfunction of the intestinal epithelial barrier, intestinal immune response, oxidative stress and inflammation, and dysbiosis. Overall, this review provides an updated overview of the effects of polyphenols as possible dietary strategies to counteract the toxic effects of gluten, potentially resulting in the improved quality of life of patients with gluten-related disorders.

A randomized placebo-controlled cross-over study on the effects of anthocyanins on inflammatory and metabolic responses to a high-fat meal in healthy subjects

This study investigated the effects of supplementation with a cyanidin- and delphinidin-rich extract (CDRE) on the postprandial dysmetabolism, inflammation, and redox and insulin signaling, triggered by the consumption of a high fat meal (HFM) in healthy individuals. Participants (n = 25) consumed a 1026-kcal HFM simultaneously with either the CDRE providing 320.4 mg of anthocyanins (90% cyanidin and delphinidin) or placebo. Diets were randomly assigned in a double blind, placebo-controlled crossover design. Blood was collected prior to (fasted, time 0), and for 5 h after meal consumption; plasma, serum, and peripheral blood mononuclear cells (PBMC) were isolated. AC metabolites were detected in serum as early as 30 min after CDRE consumption. The CDRE mitigated HFM-induced endotoxemia, reducing increases in plasma LPS and LPS-binding protein. The CDRE also reduced other events associated with HFM-triggered postprandial dysmetabolism including: i) plasma glucose and triglyceride increases; ii) TNFα and NOX4 upregulation in PBMC; and iii) JNK1/2 activation in PBMC. The CDRE did not significantly affect HFM-mediated increases in plasma insulin, GLP-1, GLP-2, GIP, and LDL- and HDL-cholesterol, and IKK phosphorylation in PBMC. In summary, dietary AC, i.e. cyanidin and delphinidin, exerted beneficial actions against unhealthy diets by modulating the associated postprandial dysmetabolism, endotoxemia, alterations of glycemia and lipidemia, and redox and insulin signaling.

Curcumin Mitigates TNFα-Induced Caco-2 Cell Monolayer Permeabilization Through modulation of NF-κB, ERK1/2 and JNK Pathways

SCOPE

This work studied the capacity of curcumin to inhibit TNFα-induced inflammation, oxidative stress, and loss of intestinal barrier integrity, characterizing the underlying mechanisms.

METHODS AND RESULTS

Caco-2 cell monolayers were incubated with TNFα (10 ng/ml), in the absence or presence of curcumin. TNFα caused an increase in interleukin (IL)-6 and IL-8 release which was inhibited by curcumin in a dose-dependent manner (IC₅₀ = 3.4 μM for IL-6). Moreover, TNFα led to: i) increased ICAM-1 and NLRP3 expression; ii) increased cell monolayer permeability and decreased levels of tight junction proteins; iii) increased cellular and mitochondrial oxidant production; iv) decreased mitochondrial membrane potential and complex I-III activity; v) activation of redox-sensitive pathways, i.e., NF-κB, ERK1/2 and JNK; and vi) increased MLCK expression and phosphorylation levels of MLC. Curcumin (2-8 μM) inhibited all these TNFα-triggered undesirable outcomes, mostly showing dose-dependent effects.

CONCLUSION

The inhibition of NF-κB, ERK1/2 and JNK activation could be in part involved in the capacity of curcumin to mitigate intestinal inflammation, oxidant production, activation of redox-sensitive pathways, and prevention of monolayer permeabilization. These results support an action of dietary curcumin in sustaining gastrointestinal tract physiology. This article is protected by copyright. All rights reserved.

Supplementation with cyanidin and delphinidin mitigates high fat diet-induced endotoxemia and associated liver inflammation in mice

Consumption of high fat diets (HFD) and the associated metabolic endotoxemia can initiate liver inflammation and lipid deposition that with time can progress to non-alcoholic fatty liver disease (NAFLD). We previously observed that 14 weeks supplementation with the anthocyanidins cyanidin and delphinidin mitigated HFD-induced metabolic endotoxemia and liver insulin resistance, steatosis, inflammation and oxidative stress. This work investigated if a 4-week supplementation of mice with a cyanidin- and delphinidin-rich extract (CDRE) could mitigate or reverse HFD (60% calories from lard fat)-induced liver steatosis and inflammation. After a first 4-weeks period on the HFD, mice showed increased endotoxemia and activation of liver proinflammatory signaling cascades. Supplementation with CDRE between weeks 4 and 8 did not mitigate liver steatosis or the altered lipid and glucose plasma levels. However, CDRE supplementation reverted HFD-induced metabolic endotoxemia, in parallel with the mitigation of the overexpression of hepatic TLR2 and TLR4, and of the activation of: (i) NF-κB, (ii) AP-1 and upstream mitogen-activated kinases p38 and ERK1/2, and (iii) HIF-1. Thus, even a short-term consumption of cyanidin and delphinidin could help mitigate the adverse consequences, i.e. metabolic endotoxemia and associated liver inflammation, triggered by the regular consumption of diets rich in fat.

Present and Future Therapeutic Approaches to Barrier Dysfunction

There is converging and increasing evidence, but also uncertainty, for the role of abnormal intestinal epithelial barrier function in the origin and development of a growing number of human gastrointestinal and extraintestinal inflammatory disorders, and their related complaints. Despite a vast literature addressing factors and mechanisms underlying changes in intestinal permeability in humans, and its connection to the appearance and severity of clinical symptoms, the ultimate link remains to be established in many cases. Accordingly, there are no directives or clinical guidelines related to the therapeutic management of intestinal permeability disorders that allow health professionals involved in the management of these patients to carry out a consensus treatment based on clinical evidence. Instead, there are multiple pseudoscientific approaches and commercial propaganda scattered on the internet that confuse those affected and health professionals and that often lack scientific rigor. Therefore, in this review we aim to shed light on the different therapeutic options, which include, among others, dietary management, nutraceuticals and medical devices, microbiota and drugs, and epigenetic and exosomes-manipulation, through an objective evaluation of the scientific publications in this field. Advances in the knowledge and management of intestinal permeability will sure enable better options of dealing with this group of common disorders to enhance quality of life of those affected.

Effect of roasted peanut allergen Ara h 3 protein on the sensitization of Caco-2 cells

BACKGROUND

Roasted peanut is widely loved as a kind of food with rich taste. However, peanut allergy is one of the major threats to human health, which affects about 5% of children and 1.4-2% of adults in the world.

RESULTS

To evaluate the sensitization mechanism of peanut allergen Ara h 3, Caco-2 cells as the model, which has the similar structure and function to differentiated small intestinal epithelial cells. Compared with Ara h 3-raw (purified from raw peanut) group, more significant results such as the inhibited Caco-2 cell viability and proliferation, the increased secretion of reactive oxygen species (ROS) and the decreased transepithelial electrical resistance were obtained in Ara h 3-roasted (purified from roasted peanut) group. Accordingly, oxidative stress and NF-κB signaling pathway were more imbalanced, which lead to the increased of thymic stromal lymphopoietin (TSLP), interleukin 6 (IL-6), IL-8 and monocyte chemotactic protein 1 (MCP-1). Then, the gene expression of tight junction proteins ZO-1, occludin and JAM-1 were reduced, which proved that the integrity of the Caco-2 monolayer barrier is severely damaged.

CONCLUSION

These finding identify the mechanisms of the allergenicity of roasted peanut allergy proteins are probably associated with intestinal uptake and cytokine dependent allergies. The aggravated allergic reaction might be caused by the increment of TSLP, IL-6, IL-8 and MCP-1 due to the activated NF-κB signaling pathway, and the enhanced transport of Ara h 3-roasted protein by Caco-2 monolayer. © 2021 Society of Chemical Industry.

Gastrointestinal Digestion of a Grape Pomace Extract: Impact on Intestinal Barrier Permeability and Interaction with Gut Microbiome

Grape pomace (GP) is a winemaking by-product rich in polyphenols and fibre. Supplementation with GP extracts has shown potential benefits against oxidative stress- and inflammation-related pathologies. As a new nutritional target, this paper explores the impact of the ingestion of a grape pomace extract on intestinal barrier functionality. A GP extract was sequentially subjected to gastrointestinal and colonic digestion using the dynamic gastrointestinal simulator (simgi^®). This generated two simulated fluids: intestinal-digested extract (IDE) and colonic-digested extract (CDE). The effects of these two fluids on paracellular permeability and the expression of tight junction (TJ) proteins (i.e., zonula occludens-1 (ZO-1) and occludin) were assessed in Caco-2-cell monolayers grown in Transwell^® inserts. The IDE fluid significantly (p < 0.001) reduced the paracellular transport of FITC-dextran with respect to the control, whereas no significant differences (p > 0.05) were found for CDE, which could be due, at least partially, to the pro-leaky effect of the colonic digestion medium. Accordant slight increases in the mRNA levels of both ZO-1 and occludin were observed for IDE, but without statistical significance. Additionally, the colonic fermentation of the GP extract promoted the production of short-chain fatty acids (SCFA) and phenolic metabolites and led to changes in the relative abundance of some bacteria that might affect paracellular permeability. Overall, this paper reports first trends about the effects of grape pomace extracts on intestinal permeability that would require further confirmation in future experiments.

Damage to intestinal barrier integrity in piglets caused by porcine reproductive and respiratory syndrome virus infection

Porcine reproductive and respiratory syndrome (PRRS) induces respiratory disease and reproductive failure accompanied by gastroenteritis-like symptoms. The mechanism of intestinal barrier injury caused by PRRSV infection in piglets has yet to be investigated. An in vivo PRRSV-induced model was established in 30-day-old piglets by the intramuscular injection of 2 mL of 10⁴ TCID₅₀/mL PRRSV for 15 days. Observations of PRRSV replication and histology were conducted in the lungs and intestine, and goblet cell counts, relative MUC2 mRNA expression, and tight junction protein, proinflammatory cytokine, TLR4, MyD88, IκB and p-IκB expression were measured. PRRSV replicated in the lungs and small intestine, as demonstrated by absolute RT-qPCR quantification, and the PRRSV N protein was detected in the lung interstitium and jejunal mucosa. PRRSV infection induced both lung and gut injury, markedly decreased villus height and the villus to crypt ratio in the small intestine, and obviously increased the number of goblet cells and the relative expression of MUC2 mRNA in the jejunum. PRRSV infection aggravated the morphological depletion of tight junction proteins and increased IL-1β, IL-6, IL-8 and TNF-α expression by activating the NF-κB signalling pathway in the jejunum. PRRSV infection impaired intestinal integrity by damaging physical and immune barriers in the intestine by inducing inflammation, which may be related to the regulation of the gut-lung axis. This study also provides a new hypothesis regarding the pathogenesis of PRRSV-induced diarrhoea.

Flavonoids and cellular stress: a complex interplay affecting human health

Flavonoid consumption has beneficial effects on human health, however, clinical evidence remains often inconclusive due to high interindividual variability. Although this high interindividual variability has been consistently observed in flavonoid research, the potential underlying reasons are still poorly studied. Especially the knowledge on the impact of health status on flavonoid responsiveness is limited and merits more investigation. Here, we aim to highlight the bidirectional interplay between flavonoids and cellular stress. First, the state-of-the-art concerning inflammatory stress and mitochondrial dysfunction is reviewed and a comprehensive overview of recent in vitro studies investigating the impact of flavonoids on cellular stress, induced by tumor necrosis factor α, lipopolysaccharide and mitochondrial stressors, is given. Second, we critically discuss the influence of cellular stress on flavonoid uptake, accumulation, metabolism and cell responses, which has, to our knowledge, never been extensively reviewed before. Next, we advocate the innovative insight that stratification of the general population based on health status can reveal subpopulations that benefit more from flavonoid consumption. Finally, suggestions are given for the development of future cell models that simulate the physiological micro-environment, including interindividual variability, since more mechanistic research is needed to establish scientific-based personalized food recommendations for specific subpopulations.

(-)-Epicatechin and Anthocyanins Modulate GLP-1 Metabolism: Evidence from C57BL/6J Mice and GLUTag Cells

BACKGROUND

Generated in intestinal L cells through cleavage of proglucagon (Gcg), glucagon-like peptide 1 (GLP-1) is secreted and rapidly inactivated by dipeptidyl peptidase IV (DPP-IV). GLP-1 regulates insulin secretion and overall glucose homeostasis. The capacity of dietary bioactives to increase GLP-1 circulating levels, and therefore increase insulin secretion and glucose metabolism, has gained significant interest of late.

OBJECTIVES

We evaluated the effects of (-)-epicatechin (EC) and different anthocyanins (ACs) and AC metabolites on GLP-1 metabolism in mice and on GLUTag cells.

METHODS

We fed 6-week-old C57BL/6J male mice a control diet or a control diet supplemented with either 40 mg AC or 20 mg EC/kg body weight for 14 weeks (AC) or 15 weeks (EC). Intestinal mRNA levels of Gcg and Dpp-iv were measured. In vitro, GLUTag cells were incubated in the presence or absence of different ACs, the AC metabolite protocatechuic acid (PCA), and EC. GLP-1 secretion and the main pathways involved in its release were assessed.

RESULTS

Long-term supplementation with EC or AC increased mouse GLP-1 plasma concentrations (55% and 98%, respectively; P < 0.05). In mice, 1) EC and AC increased Gcg mRNA levels in the ileum (91%) and colon (41%), respectively (P < 0.05); and 2) AC lowered ileum Dpp-iv mRNA levels (35%), while EC decreased plasma DPP-IV activity (15%; P < 0.05). In GLUTag cells, 1) cyanidin, delphinidin, PCA, and EC increased GLP-1 secretion (53%, 33%, 53%, and 68%, respectively; P < 0.05); and 2) cyanidin, delphinidin, EC, and PCA increased cyclin adenosine monophosphate levels (25-50%; P < 0.05) and activated protein kinase A (PKA; 100%, 50%, 80%, and 86%, respectively; P < 0.05).

CONCLUSIONS

In mice, EC and ACs regulated different steps in GLP-1 regulation, leading to increased plasma GLP-1. Cyanidin, delphinidin, PCA, and EC promoted GLP-1 secretion from GLUTag cells by activating the PKA-dependent pathway. These findings support the beneficial actions of these flavonoids in sustaining intestinal and glucose homeostasis through the modulation of the GLP-1 metabolism.

Potential therapeutic targets and molecular details of anthocyan-treated inflammatory bowel disease: a systematic bioinformatics analysis of network pharmacology

Anthocyans, containing anthocyanins and anthocyanidins, play a crucial role in preventing and treating inflammatory bowel disease (IBD). Most anthocyanins and their basic elements, namely anthocyanidins have been recognized for the effective treatment of IBD, but the key biomarkers of anthocyan-treated IBD remain unclear. In this study, a bioinformatics analysis based on network pharmacology was performed to demonstrate the core-targets, biological functions, and signaling pathways of most common anthocyanidins that existed in anthocyans to reveal their potential or major mechanisms. The network pharmacology of the multi-target drug molecular design with specific signal nodes was selected, which was used to analyse core targets and complete the bioinformatics analysis of core targets. The network assays indicated 44 common targeted genes, 5 of which were core targets of both six most common anthocyanidins and IBD. These 44 common targets related to major signaling mechanisms of the six most common anthocyanidins in IBD may involve following processes: promotion of intracellular metabolism and proliferation, inhibition of cell necrosis, anti-inflammation and regulation of intestinal epithelial survival mainly via pathways such as, the EGFR tyrosine kinase inhibitor resistance pathway, platelet activation, microRNAs in cancer, arachidonic acid metabolism and the cGMP-PKG signaling pathway. Thus, our findings may provide other molecular details about anthocyans in the treatment of IBD and contribute towards the use of anthocyanidins, which will be meaningful shedding light on the action mechanisms of anthocyanidins in treating IBD.

Differential protection by anthocyanin-rich bilberry extract and resveratrol against lipid micelle-induced oxidative stress and monolayer permeability in Caco-2 intestinal epithelial cells

Excess dietary fat, and associated bile acids, can impair intestinal barrier integrity, produce intestinal or systemic inflammation and promote tumorigenesis.

Betulinic Acid Ameliorates the T-2 Toxin-Triggered Intestinal Impairment in Mice by Inhibiting Inflammation and Mucosal Barrier Dysfunction through the NF-κB Signaling Pathway

T-2 toxin, a trichothecene mycotoxin produced by Fusarium, is widely distributed in crops and animal feed and frequently induces intestinal damage. Betulinic acid (BA), a plant-derived pentacyclic lupane-type triterpene, possesses potential immunomodulatory, antioxidant and anti-inflammatory biological properties. The current study aimed to explore the protective effect and molecular mechanisms of BA on intestinal mucosal impairment provoked by acute exposure to T-2 toxin. Mice were intragastrically administered BA (0.25, 0.5, or 1 mg/kg) daily for 2 weeks and then injected intraperitoneally with T-2 toxin (4 mg/kg) once to induce an intestinal impairment. BA pretreatment inhibited the loss of antioxidant capacity in the intestine of T-2 toxin-treated mice by elevating the levels of CAT, GSH-PX and GSH and reducing the accumulation of MDA. In addition, BA pretreatment alleviated the T-2 toxin-triggered intestinal immune barrier dysregulation by increasing the SIgA level in the intestine at dosages of 0.5 and 1 mg/kg, increasing IgG and IgM levels in serum at dosages of 0.5 and 1 mg/kg and restoring the intestinal C3 and C4 levels at a dosage of 1 mg/kg. BA administration at a dosage of 1 mg/kg also improved the intestinal chemical barrier by decreasing the serum level of DAO. Moreover, BA pretreatment improved the intestinal physical barrier via boosting the expression of ZO-1 and Occludin mRNAs and restoring the morphology of intestinal villi that was altered by T-2 toxin. Furthermore, treatment with 1 mg/kg BA downregulated the expression of p-NF-κB and p-IκB-α proteins in the intestine, while all doses of BA suppressed the pro-inflammatory cytokines expression of IL-1β, IL-6 and TNF-α mRNAs and increased the anti-inflammatory cytokine expression of IL-10 mRNA in the intestine of T-2 toxin-exposed mice. BA was proposed to exert a protective effect on intestinal mucosal disruption in T-2 toxin-stimulated mice by enhancing the intestinal antioxidant capacity, inhibiting the secretion of inflammatory cytokines and repairing intestinal mucosal barrier functions, which may be associated with BA-mediated inhibition of the NF-κB signaling pathway activation.

Propionic Acid Targets the TLR4/NF-κB Signaling Pathway and Inhibits LPS-Induced Intestinal Barrier Dysfunction: In Vitro and In Vivo Studies

Intestinal barrier dysfunction contributes to the development of intestinal diseases. Propionic acid (PA), a metabolite generated by anaerobic fermentation of dietary fiber in the intestinal cavity, has been proved to exert anti-inflammatory effects in a variety of diseases. However, the exact role of PA in LPS-induced intestinal barrier dysfunction is still unclear. Accordingly, we examined the latent mechanism of PA and its protective role in LPS-induced intestinal barrier dysfunction by both in vitro and in vivo experiments. In vitro, we identified that PA treatment could strongly promote cell migration, inhibit activation of NLRP3 inflammasome and maintain intestinal barrier function in LPS-induced IEC-6 cells, indicating the protective effect on the intestinal barrier function of PA. Further investigation of the mechanism involved revealed that PA could suppress the activation of TLR4/NF-κB pathway. In vivo, in a LPS-induced rat model, PA-induced protective effects in intestinal barrier dysfunction could be detected. In summary, our findings clarify the role of PA in intestinal barrier dysfunction and suggest that it is promising for the treatment of LPS-related intestinal diseases.

Phytochemicals affect T helper 17 and T regulatory cells and gut integrity: implications on the gut-bone axis

The pathology of osteoporosis is multifactorial, but a growing body of evidence supports an important role of the gut-bone axis, especially in bone loss associated with menopause, rheumatoid arthritis, and periodontal disease. Aberrant T cell responses favoring an increase in the ratio of T helper 17 cells to T regulatory cells play a critical role in the underlying etiology of this bone loss. Many of the dietary phytochemicals known to have osteoprotective activity such as flavonoids, organosulfur compounds, phenolic acids, as well as the oligosaccharides also improve gut barrier function and affect T cell differentiation and activation within gut-associated lymphoid tissues and at distal sites. Here, we examine the potential of these phytochemicals to act as prebiotics and immunomodulating agents, in part targeting the gut to mediate their effects on bone.

Polysaccharide from the seeds of Plantago asiatica L. alleviates nonylphenol induced intestinal barrier injury by regulating tight junctions in human Caco-2 cell line

The intestinal epithelium is known as an important barrier to protect the body from harmful pathogens or toxic substance that may induce intestinal barrier injury. The aim of this study was to investigate the effects of polysaccharide from the seeds of Plantago asiatica L. (PLP) on nonylphenol (NP) induced intestinal barrier injury in vitro. Caco-2 cells were pretreated with PLP, or co-cultured with PLP and NP simultaneously, and cytotoxicity, LDH leakage, transepithelial electrical resistance (TEER), FITC-dextran flux and tight junction (TJ) proteins were conducted to evaluate the intestinal barrier function. The results suggested that PLP pretreatment or co-culture with NP could significantly attenuated NP induced Caco-2 cytotoxicity, suppressed LDH release, restored the TEER value and paracellular permeability of Caco-2 monolayers, which were attributed to enhancing the TJ protein expressions. In addition, PLP co-cultured with NP possessed better protective effects against NP induced cytotoxicity. This study indicated that PLP assuaged NP induced intestinal barrier injury by increasing TJ, and threw light on the development of a dietary supplementation for preventing exogenous toxic substances induced intestinal barrier injury or improving intestinal TJ barrier function.

Ellagic acid protects Caco-2 cell monolayers against inflammation-induced permeabilization

Chronic intestinal inflammation involves a cycle of oxidative stress, activation of redox sensitive transcription factors, and barrier permeabilization. The latter can lead to systemic inflammation and its associated co-morbidities. Diet can play a major role in the modulation of intestinal inflammation. Among plant bioactives, ellagic acid (EA) was reported to inhibit inflammatory bowel disease in animal models. This work investigated the mechanisms by which EA inhibits tumor necrosis factor alpha (TNFα)-induced inflammation, oxidative stress, and loss of barrier integrity. Caco-2 cells differentiated into an intestinal epithelial cell monolayer were incubated with TNFα (10 ng/ml), in the presence of different EA concentrations. TNFα triggered interleukin (IL) 6 and 8 release into the medium, which was inhibited by EA in a dose-dependent manner (IC₅₀ = 17.3 μM for IL-6). TNFα also led to: i) increased ICAM-1 and NLRP3 expression; ii) loss of epithelial barrier function; iii) increased oxidant production from NOX and mitochondrial origin; iv) NF-κB and ERK1/2 activation; and v) increased MLCK gene expression and MLC phosphorylation. EA (10-40 μM) inhibited all these adverse effects of TNFα. EA mainly acted through NF-κB and ERK1/2 inhibition, breaking the cycle of inflammation, oxidative stress, redox-sensitive pathway (e.g. NF-κB, ERK1/2) activation and intestinal permeabilization. This suggests that consumption of EA, via foods or supplements, may afford a strategy to mitigate intestinal inflammation and its associated co-morbidities.

Fermented blueberry pomace ameliorates intestinal barrier function through the NF-κB-MLCK signaling pathway in high-fat diet mice

The barrier-improving functions of fermented blueberry pomace (FBP) and its potential mechanism were investigated in this study. Polyphenols and the approximate composition of FBP were evaluated according to the National Standard of the People's Republic of China and the UPLC-MS system. Male C57BL/6 mice were fed a control diet (CD) or a high-fat diet (HFD) with or without FBP supplementation. Oxidative stress, inflammation, histological morphology and the expression of functional proteins in the small intestine of mice were evaluated using the enzyme linked immunosorbent assay (ELISA), quantitative polymerase chain reaction (qPCR) and western blotting. The content of protein, fat, soluble dietary fiber, insoluble dietary fiber and carbohydrates (non-dietary fiber) was 114.5 ± 1.5 g kg^-1, 5.0 ± 0.2 g kg^-1, 48.0 ± 0.1 g kg^-1, 360.3 ± 2.2 g kg^-1 and 423 g kg^-1 (by difference), respectively. Thirty-six polyphenols were identified in FBP. FBP improved the growth of mice and attenuated hepatic and intestinal oxidative stress. Intestinal inflammation was significantly reduced through the decrease of tumor necrosis factor-alpha (TNF-α) and myeloperoxidase (MPO) as well as an increase of interleukin-10 (IL-10). FBP supplementation significantly improved the intestinal morphology and barrier function, potentially by mediating the NF-κB-MLCK signaling pathway. The supplementation of FBP in HFD mice enhanced the intestinal barrier function. This suggested that polyphenol-rich by-products might provide a similar health effect in HFD individuals.

Isolation and Characterization of Blueberry Polyphenolic Components and Their Effects on Gut Barrier Dysfunction

Highbush blueberries contain anthocyanins and proanthocyanidins that have antimicrobial and anti-inflammatory bioactivities. We isolated and characterized three polyphenolic fractions, a total polyphenol fraction (TPF), an anthocyanin-enriched fraction (AEF), and a proanthocyanidin-enriched fraction (PEF), from freeze-dried blueberry powder and evaluated their effects on an in vitro model of gut barrier dysfunction. High-performance liquid chromatography chromatograms illustrate successful fractionation of the blueberry powder into TPF, AEF, and PEF. AEF contained 21 anthocyanins, and PEF contained proanthocyanidin oligomers of (epi)catechin with primarily B-type interflavan bonds. The model uses a strain of Escherichia coli to disrupt a Caco-2 cell monolayer on Transwell inserts. Barrier function was measured by transepithelial electrical resistance (TEER), a marker of membrane permeability. All fractions were able to restore TEER values after an E. coli challenge when compared to the control, while AEF was able to attenuate the E. coli-induced decrease in TEER in a dose-dependent manner.

Polyphenols and Intestinal Permeability: Rationale and Future Perspectives

Increasing evidence links intestinal permeability (IP), a feature of the intestinal barrier, to several pathological or dysfunctional conditions. Several host and environmental factors, including dietary factors, can affect the maintenance of normal IP. In this regard, food bioactives, such as polyphenols, have been proposed as potential IP modulators, even if the mechanisms involved are not yet fully elucidated. The aim of the present paper is to provide a short overview of the main evidence from in vitro and in vivo studies supporting the role of polyphenols in modulating IP and briefly discuss future perspectives in this research area.

Flavonoids as Anticancer Agents

Flavonoids are polyphenolic compounds subdivided into 6 groups: isoflavonoids, flavanones, flavanols, flavonols, flavones and anthocyanidins found in a variety of plants. Fruits, vegetables, plant-derived beverages such as green tea, wine and cocoa-based products are the main dietary sources of flavonoids. Flavonoids have been shown to possess a wide variety of anticancer effects: they modulate reactive oxygen species (ROS)-scavenging enzyme activities, participate in arresting the cell cycle, induce apoptosis, autophagy, and suppress cancer cell proliferation and invasiveness. Flavonoids have dual action regarding ROS homeostasis—they act as antioxidants under normal conditions and are potent pro-oxidants in cancer cells triggering the apoptotic pathways and downregulating pro-inflammatory signaling pathways. This article reviews the biochemical properties and bioavailability of flavonoids, their anticancer activity and its mechanisms of action.

The Multifunctional Benefits of Naturally Occurring Delphinidin and Its Glycosides

Delphinidin (Del) and its glycosides are water-soluble pigments, belonging to a subgroup of flavonoids. They are health-promoting candidates for pharmaceutical and nutraceutical uses, as indicated by exhibiting antioxidation, anti-inflammation, antimicroorganism, antidiabetes, antiobesity, cardiovascular protection, neuroprotection, and anticancer properties. Glycosylation modification of Del is associated with increased stability and reduced biological activity. Del and its glycosides can be the alternative inhibitors of CBRs, ERα/β, EGFR, BCRP, and SGLT-1, and virtual docking indicates that the sugar moiety may not effectively interact with the active sites of the targets. Structure-based characteristics confer the multifunctional properties of Del and its glycosides. Because of their health-promoting effects, Del and its glycosides are promising and have been developed as potential pharmaceuticals. However, more investigation on the underlying mechanisms of Del and its glycosides in mediating cellular processes with high specificity are still needed. The research progression of Del and its glycosides over the last 10 years is comprehensively reviewed in this article.

Cyanidin ameliorates the progression of osteoarthritis via the Sirt6/NF-κB axis in vitro and in vivo

Osteoarthritis (OA) is the most prevalent form of human arthritis which is characterized by the degradation of cartilage and inflammation. As a rare Sirt6 activator, cyanidin is the major component of anthocyanins commonly found in the Mediterranean diet, and increasing evidence has shown that cyanidin exhibits anti-inflammatory effects in a variety of diseases. However, the anti-inflammatory effects of cyanidin on OA have not been reported. In the present study, we identified that cyanidin treatment could strongly suppress the expression of NO, PGE2, TNF-α, IL-6, iNOs, COX-2, ADAMTS5 and MMP13, and reduce the degradation of aggrecan and collagen II in IL-1β-induced human OA chondrocytes, indicating the anti-inflammatory effect of cyanidin. Further investigation of the mechanism involved revealed that cyanidin could upregulate the Sirt6 level in a dose-dependent manner and Sirt6 silencing abolished the effect of cyanidin in IL-1β-stimulated human OA chondrocytes, indicating a stimulatory effect of cyanidin on Sirt6 activation. Meanwhile, we found that cyanidin could inhibit the NF-κB pathway in IL-1β-stimulated human OA chondrocytes and its effect may to some extent depend on Sirt6 activation, suggesting that cyanidin may exert a protective effect through regulating the Sirt6/NF-κB signaling axis. Moreover, the in vivo study also proved that cyanidin ameliorated the development of OA in surgical destabilization of the medial meniscus (DMM) mouse OA models. In conclusion, these results demonstrate that cyanidin may have therapeutic potential for the treatment of OA.

Assessing the Fate and Bioavailability of Glucosinolates in Kale (Brassica oleracea) Using Simulated Human Digestion and Caco-2 Cell Uptake Models

Glucosinolates and their hydrolysis products were characterized in fresh and in in vitro gastric and intestinal digesta of Dinosaur kale (Brassica oleracea L var. palmifolia DC). In fresh kale, glucoraphanin, sinigrin, gluconapin, gluconasturtiin, glucoerucin, glucobrasscin, and 4-methoxylglucobrassicin were identified. After 120 min of gastric digestion, the levels of glucoraphanin, sinigrin, and gluconapin decreased, and no glucoerucin or glucobrasscin was detected. However, a concomitant increase in the glucosinolate hydrolysis products allyl nitrile, 3-butenyl isothiocyanate, phenylacetonitrile, and sulforaphane was observed. This trend continued through intestinal digestion. After 120 min, the levels of allyl nitrile, 3-butenyl isothiocyanate, phenylacetonitrile, and sulforaphane were 88.19 ± 5.85, 222.15 ± 30.26, 129.17 ± 17.57, and 13.71 ± 0.62 pmol/g fresh weight, respectively. Intestinal digesta were then applied to Caco-2 cell monolayers to assess the bioavailability. After 6 h of incubation, no glucosinolates were detected and the percentage of total cellular uptake of the glucosinolate hydrolysis products ranged from 29.35% (sulforaphane) to 46.60% (allyl nitrile).

Red wine extract preserves tight junctions in intestinal epithelial cells under inflammatory conditions: implications for intestinal inflammation

The altered expression and subcellular distribution of tight junction (TJ) proteins, leading to a dysfunctional intestinal barrier, is a key mechanistic feature of inflammatory bowel disease (IBD). Therefore, increasing the integrity of the intestinal barrier by manipulating the TJ may constitute an innovative and effective therapeutic strategy in IBD. In this context, recent studies showed that dietary polyphenols are able to protect the intestinal TJ barrier integrity. Here, using a cellular model of intestinal inflammation, consisting of cytokine-stimulated HT-29 colon epithelial cells, we show that a polyphenolic extract obtained from Portuguese red wine (RWE) decreased the paracellular permeability across the cell monolayer compared with the control cells, even in the presence of pro-inflammatory cytokines. The beneficial effect of RWE was exerted at three complementary levels: (1) by promoting a significant increase of the mRNA of key barrier-forming TJ proteins, including occludin, claudin-5 and zonnula occludens (ZO)-1 above the levels observed in the control cells; (2) by preventing the decrease in the expression of these proteins under inflammatory conditions and (3) by averting the increase in claudin-2 mRNA, a channel-forming TJ protein induced by pro-inflammatory cytokines. Taken together, these results strongly suggest that polyphenols presented and consumed in red wine as a mixture can reinforce and protect the intestinal barrier against inflammatory stimulus by affecting the TJ protein expression and, thus, without the need for purifying individual compounds, might represent a readily available therapeutic intervention against IBD and intestinal inflammation.

Anthocyanins protect the gastrointestinal tract from high fat diet-induced alterations in redox signaling, barrier integrity and dysbiosis

The gastrointestinal (GI) tract can play a critical role in the development of pathologies associated with overeating, overweight and obesity. We previously observed that supplementation with anthocyanins (AC) (particularly glycosides of cyanidin and delphinidin) mitigated high fat diet (HFD)-induced development of obesity, dyslipidemia, insulin resistance and steatosis in C57BL/6J mice. This paper investigated whether these beneficial effects could be related to AC capacity to sustain intestinal monolayer integrity, prevent endotoxemia, and HFD-associated dysbiosis. The involvement of redox-related mechanisms were further investigated in Caco-2 cell monolayers. Consumption of a HFD for 14 weeks caused intestinal permeabilization and endotoxemia, which were associated with a decreased ileum expression of tight junction (TJ) proteins (occludin, ZO-1 and claudin-1), increased expression of NADPH oxidase (NOX1 and NOX4) and NOS2 and oxidative stress, and activation of redox sensitive signals (NF-κB and ERK1/2) that regulate TJ dynamics. AC supplementation mitigated all these events and increased GLP-2 levels, the intestinal hormone that upregulates TJ protein expression. AC also prevented, in vitro, tumor necrosis factor alpha-induced Caco-2 monolayer permeabilization, NOX1/4 upregulation, oxidative stress, and NF-κB and ERK activation. HFD-induced obesity in mice caused dysbiosis and affected the levels and secretion of MUC2, a mucin that participates in intestinal cell barrier protection and immune response. AC supplementation restored microbiota composition and MUC2 levels and distribution in HFD-fed mice. Thus, AC, particularly delphinidin and cyanidin, can preserve GI physiology in HFD-induced obesity in part through redox-regulated mechanisms. This can in part explain AC capacity to mitigate pathologies, i.e. insulin resistance and steatosis, associated with HFD-associated obesity.

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Anthocyanidins (AC) mitigate high fat diet (HFD)-induced intestinal permeabilization and endotoxemia.

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AC inhibit HFD-induced ileum NADPH oxidase upregulation and oxidative stress.

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AC inhibit the activation of redox sensitive signals that cause intestinal permeabilization.

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AC mitigate HFD-induced dysbiosis and improve ileum endocrine/immunological responses.

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AC's beneficial systemic effects in HFD-mice could begin at the GI tract.

Rhein protects against barrier disruption and inhibits inflammation in intestinal epithelial cells

BACKGROUND AND AIMS

Intestinal epithelial barrier and intestinal inflammation play indispensable roles in the development of intestinal diseases. The major aims of the current study were to investigate the potential of rhein, a major flavonoid compound isolated from Rheum rhabarbarum, in the treatment of intestinal diseases and its underlying mechanisms in vitro.

METHODS

The protective role of rhein on intestinal epithelial barrier was evaluated in a monolayer of IEC-6 cells stimulated by TNF-α, while the anti-inflammatory effects were investigated in an IEC-6 cell model with LPS stimulation.

RESULTS

Rhein inhibited the increase of phenol red flux and the decrease of TEER, as well as recovered the expression and distribution of ZO-1 and weakened MLC phosphorylation, MLCK expression and NF-κB activation. Meanwhile, LPS-stimulated IL-1β and IL-6 were down-regulated, expression levels of TLR4, NLRP3 and cleaved caspase1 were weakened and NF-κB was inactivated.

CONCLUSIONS

These results suggested that rhein has potential therapeutic effects against intestinal diseases by maintaining intestinal epithelial barrier and suppressing intestinal inflammation.