Polyamines in Gut Epithelial Renewal and Barrier Function

Posttranscriptional Regulation of Intestinal Mucosal Growth and Adaptation by Noncoding RNAs in Critical Surgical Disorders

The human intestinal epithelium has an impressive ability to respond to insults and its homeostasis is maintained by well-regulated mechanisms under various pathophysiological conditions. Nonetheless, acute injury and inhibited regeneration of the intestinal epithelium occur commonly in critically ill surgical patients, leading to the translocation of luminal toxic substances and bacteria to the bloodstream. Effective therapies for the preservation of intestinal epithelial integrity and for the prevention of mucosal hemorrhage and gut barrier dysfunction are limited, primarily because of a poor understanding of the mechanisms underlying mucosal disruption. Noncoding RNAs (ncRNAs), which include microRNAs (miRNAs), long ncRNAs (lncRNAs), circular RNAs (circRNAs), and small vault RNAs (vtRNAs), modulate a wide array of biological functions and have been identified as orchestrators of intestinal epithelial homeostasis. Here, we feature the roles of many important ncRNAs in controlling intestinal mucosal growth, barrier function, and repair after injury-particularly in the context of postoperative recovery from bowel surgery. We review recent literature surrounding the relationships between lncRNAs, microRNAs, and RNA-binding proteins and how their interactions impact cell survival, proliferation, migration, and cell-to-cell interactions in the intestinal epithelium. With advancing knowledge of ncRNA biology and growing recognition of the importance of ncRNAs in maintaining the intestinal epithelial integrity, ncRNAs provide novel therapeutic targets for treatments to preserve the gut epithelium in individuals suffering from critical surgical disorders.

The potential of EGCG in modulating the oral-gut axis microbiota for treating inflammatory bowel disease

Inflammatory bowel disease (IBD) is a recurrent chronic intestinal disorder that includes ulcerative colitis (UC) and Crohn's disease (CD). Its pathogenesis involves intricate interactions between pathogenic microorganisms, native intestinal microorganisms, and the intestinal immune system via the oral-gut axis. The strong correlation observed between oral diseases and IBD indicates the potential involvement of oral pathogenic microorganisms in IBD development. Consequently, therapeutic strategies targeting the proliferation, translocation, intestinal colonization and exacerbated intestinal inflammation of oral microorganisms within the oral-gut axis may partially alleviate IBD. Tea consumption has been identified as a contributing factor in reducing IBD, with epigallocatechin gallate (EGCG) being the primary bioactive compound used for IBD treatment. However, the precise mechanism by which EGCG mediates microbial crosstalk within the oral-gut axis remains unclear. In this review, we provide a comprehensive overview of the diverse oral microorganisms implicated in the pathogenesis of IBD and elucidate their colonization pathways and mechanisms. Subsequently, we investigated the antibacterial properties of EGCG and its potential to attenuate microbial translocation and colonization in the gut, emphasizing its role in attenuating exacerbations of IBD. We also elucidated the toxic and side effects of EGCG. Finally, we discuss current strategies for enhancing EGCG bioavailability and propose novel multi-targeted nano-delivery systems for the more efficacious management of IBD. This review elucidates the role and feasibility of EGCG-mediated modulation of the oral-gut axis microbiota in the management of IBD, contributing to a better understanding of the mechanism of action of EGCG in the treatment of IBD and the development of prospective treatment strategies.

Dietary probiotic and synbiotic supplementation starting from maternal gestation improves muscular lipid metabolism in offspring piglets by reshaping colonic microbiota and metabolites

Probiotics and synbiotics have been intensively used in animal husbandry due to their advantageous roles in animals' health. However, there is a paucity of research on probiotic and synbiotic supplementation from maternal gestation to the postnatal growing phases of offspring piglets. Thus, we assessed the effects of dietary supplementation of these two additives to sows and offspring piglets on skeletal muscle and body metabolism, colonic microbiota composition, and metabolite profiles of offspring piglets. Pregnant Bama mini-pigs and their offspring piglets (after weaning) were fed either a basal diet or a basal diet supplemented with antibiotics, probiotics, or synbiotics. At 65, 95, and 125 days old, eight pigs per group were euthanized and sampled for analyses. Probiotics increased the intramuscular fat content in the psoas major muscle (PMM) at 95 days old, polyunsaturated fatty acid (PUFA) and n-3 PUFA levels in the longissimus dorsi muscle (LDM) at 65 days old, C16:1 level in the LDM at 125 days old, and upregulated ATGL, CPT-1, and HSL expressions in the PMM at 65 days old. Synbiotics increased the plasma HDL-C level at 65 days old and TC level at 65 and 125 days old and upregulated the CPT-1 expression in the PMM at 125 days old. In addition, probiotics and synbiotics increased the plasma levels of HDL-C at 65 days old, CHE at 95 days old, and LDL-C at 125 days old, while decreasing the C18:1n9t level in the PMM at 65 days old and the plasma levels of GLU, LDH, and TG at 95 days old. Microbiome analysis showed that probiotic and synbiotic supplementation increased colonic Actinobacteria, Firmicutes, Verrucomicrobia, Faecalibacterium, Pseudobutyrivibrio, and Turicibacter abundances. However, antibiotic supplementation decreased colonic Actinobacteria, Bacteroidetes, Prevotella, and Unclassified_Lachnospiraceae abundances. Furthermore, probiotic and synbiotic supplementation was associated with alterations in 8, 7, and 10 differential metabolites at three different age stages. Both microbiome and metabolome analyses showed that the differential metabolic pathways were associated with carbohydrate, amino acid, and lipid metabolism. However, antibiotic supplementation increased the C18:1n9t level in the PMM at 65 days old and xenobiotic biodegradation and metabolism at 125 days old. In conclusion, sow-offspring's diets supplemented with these two additives showed conducive effects on meat flavor, nutritional composition of skeletal muscles, and body metabolism, which may be associated with the reshaping of colonic microbiota and metabolites. However, antibiotic supplementation has negative effects on colonic microbiota composition and fatty acid composition in the PMM.

IMPORTANCE

The integral sow-offspring probiotic and synbiotic supplementation improves the meat flavor and the fatty acid composition of the LDM to some extent. Sow-offspring probiotic and synbiotic supplementation increases the colonic beneficial bacteria (including Firmicutes, Verrucomicrobia, Actinobacteria, Faecalibacterium, Turicibacter, and Pseudobutyrivibrio) and alters the colonic metabolite profiles, such as guanidoacetic acid, beta-sitosterol, inosine, cellobiose, indole, and polyamine. Antibiotic supplementation in sow-offspring's diets decreases several beneficial bacteria (including Bacteroidetes, Actinobacteria, Unclassified_Lachnospiraceae, and Prevotella) and has a favorable effect on improving the fatty acid composition of the LDM to some extent, while presenting the opposite effect on the PMM.

The Roles of Polyamines in Intestinal Development and Function in Piglets

The gastrointestinal tract plays crucial roles in the digestion and absorption of nutrients, as well as in maintenance of a functional barrier. The development and maturation of the intestine is important for piglets to maintain optimal growth and health. Polyamines are necessary for the proliferation and growth of enterocytes, which play a key role in differentiation, migration, remodeling and integrity of the intestinal mucosa after injury. This review elaborates the development of the structure and function of the intestine of piglets during embryonic, suckling and weaning periods, the utilization and metabolism of polyamines in the intestine, as well as the role of polyamines in intestinal development and mucosal repair. The nutritional intervention to improve intestinal development and functions by modulating polyamine metabolism in piglets is also put forward. These results may help to promote the adaption to weaning in pigs and provide useful information for the development and health of piglets.

A distinct Fusobacterium nucleatum clade dominates the colorectal cancer niche

Fusobacterium nucleatum (Fn), a bacterium present in the human oral cavity and rarely found in the lower gastrointestinal tract of healthy individuals1, is enriched in human colorectal cancer (CRC) tumours2-5. High intratumoural Fn loads are associated with recurrence, metastases and poorer patient prognosis5-8. Here, to delineate Fn genetic factors facilitating tumour colonization, we generated closed genomes for 135 Fn strains; 80 oral strains from individuals without cancer and 55 unique cancer strains cultured from tumours from 51 patients with CRC. Pangenomic analyses identified 483 CRC-enriched genetic factors. Tumour-isolated strains predominantly belong to Fn subspecies animalis (Fna). However, genomic analyses reveal that Fna, considered a single subspecies, is instead composed of two distinct clades (Fna C1 and Fna C2). Of these, only Fna C2 dominates the CRC tumour niche. Inter-Fna analyses identified 195 Fna C2-associated genetic factors consistent with increased metabolic potential and colonization of the gastrointestinal tract. In support of this, Fna C2-treated mice had an increased number of intestinal adenomas and altered metabolites. Microbiome analysis of human tumour tissue from 116 patients with CRC demonstrated Fna C2 enrichment. Comparison of 62 paired specimens showed that only Fna C2 is tumour enriched compared to normal adjacent tissue. This was further supported by metagenomic analysis of stool samples from 627 patients with CRC and 619 healthy individuals. Collectively, our results identify the Fna clade bifurcation, show that specifically Fna C2 drives the reported Fn enrichment in human CRC and reveal the genetic underpinnings of pathoadaptation of Fna C2 to the CRC niche.

Border Control: The Role of the Microbiome in Regulating Epithelial Barrier Function

The gut mucosal epithelium is one of the largest organs in the body and plays a critical role in regulating the crosstalk between the resident microbiome and the host. To this effect, the tight control of what is permitted through this barrier is of high importance. There should be restricted passage of harmful microorganisms and antigens while at the same time allowing the absorption of nutrients and water. An increased gut permeability, or "leaky gut", has been associated with a variety of diseases ranging from infections, metabolic diseases, and inflammatory and autoimmune diseases to neurological conditions. Several factors can affect gut permeability, including cytokines, dietary components, and the gut microbiome. Here, we discuss how the gut microbiome impacts the permeability of the gut epithelial barrier and how this can be harnessed for therapeutic purposes.

Lycibarbarspermidine L from the fruit of Lycium barbarum L. recovers intestinal barrier damage via regulating miR-195-3p

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Lycium barbarum L. is widely employed with the traditional effect of tonic properties. According to the theory of traditional Chinese medicine, Gou Qi can be distributed in the meridian of stomach, as well as the liver and kidney, indicating its effect on the digestive system. Clinical studies found that Gou Qi enhanced gastrointestinal functions. Pharmacological research showed the extract of Lycium barbarum exhibiting a repaired effect on the intestine barrier. Lycibarbarspermidine L (LBS L), which belongs to polyamines, is separated from the fruit of Lycium barbarum. However, it is unknown whether LBS L can restore damaged intestinal barrier like other polyamines such as spermidine.

AIM OF THE STUDY

To elucidate the recovery effect of LBS L on damaged intestinal epithelium and its miRNA-related mechanism.

MATERIALS AND METHODS

IEC-6 cells were used in vitro to assess the therapeutic effect of LBS L on the injured intestine and the regulation of miR-195-3p. Spermidine (SPD) with intestinal mucosal repair effect was used as a positive control. Sprague Dawley (SD) rats were subjected to 48 h fasting to induce intestinal epithelial atrophy in vivo. To determine the therapeutic effect of LBS L on injured intestinal epithelium and explore the mechanism, the fasting model group rats were treated with LBS L (25 mg/kg) for 4 days.

RESULTS

Results in vitro showed that LBS L (10 μM) promoted cell proliferation and migration, affecting the S phase of the cell cycle. Western blot signals showed that LBS L raised the expression level of occludin. The miR-195-3p levels were decreased following LBS L treatment, which could be inversed by transfecting miR-195-3p mimic, demonstrating that LBS L inhibited miR-195-3p to improve cell growth. Results in vivo showed that LBS L could reverse the atrophic villi and inflammatory cell infiltration in the submucosa and restore miR-195-3p, occludin, and Ki67 levels in the intestine of mice in the fasting group.

CONCLUSIONS

LBS L restores injured intestinal epithelium by reducing the expression of miR-195-3p.

Stabilization of Cx43 mRNA via RNA-binding protein HuR regulated by polyamines enhances intestinal epithelial barrier function

Gut barrier dysfunction occurs commonly in patients with critical disorders, leading to the translocation of luminal toxic substances and bacteria to the bloodstream. Connexin 43 (Cx43) acts as a gap junction protein and is crucial for intercellular communication and the diffusion of nutrients. The levels of cellular Cx43 are tightly regulated by multiple factors, including polyamines, but the exact mechanism underlying the control of Cx43 expression remains largely unknown. The RNA-binding protein HuR regulates the stability and translation of target mRNAs and is involved in many aspects of intestinal epithelial pathobiology. Here we show that HuR directly bound to Cx43 mRNA via its 3'-untranslated region in intestinal epithelial cells (IECs) and this interaction enhanced Cx43 expression by stabilizing Cx43 mRNA. Depletion of cellular polyamines inhibited the [HuR/Cx43 mRNA] complex and decreased the level of Cx43 protein by destabilizing its mRNA, but these changes were prevented by ectopic overexpression of HuR. Polyamine depletion caused intestinal epithelial barrier dysfunction, which was reversed by ectopic Cx43 overexpression. Moreover, overexpression of checkpoint kinase 2 in polyamine-deficient cells increased the [HuR/Cx43 mRNA] complex, elevated Cx43 levels, and promoted barrier function. These findings indicate that Cx43 mRNA is a novel target of HuR in IECs and that polyamines regulate Cx43 mRNA stability via HuR, thus playing a critical role in the maintenance of intestinal epithelial barrier function.NEW & NOTEWORTHY The current study shows that polyamines stabilize the Cx43 mRNA via HuR, thus enhancing the function of the Cx43-mediated gap junction. These findings suggest that induced Cx43 by HuR plays a critical role in the process by which polyamines regulate intestinal epithelial barrier.

Dynamics and Crosstalk between Gut Microbiota, Metabolome, and Fecal Calprotectin in Very Preterm Infants: Insights into Feeding Intolerance

BACKGROUND

Feeding intolerance (FI) is a significant concern in the care of preterm infants, impacting their growth and development. We previously reported that FI is linked to lower fecal calprotectin (FC) levels. This study aims to explore the postnatal dynamics and interplay between microbiota, metabolic profiles, and host immunity in preterm infants with and without FI.

METHODS

Infants with gestational age <32 weeks or birth weight <1500 g were enrolled at the Children's Hospital of Fudan University between January 2018 and October 2020. Weekly fecal samples were analyzed for bacterial profiling, metabolome, and calprotectin levels, exploring their longitudinal development and interrelationships.

RESULTS

Of the 118 very preterm infants studied, 48 showed FI. These infants experienced an interrupted microbial-immune trajectory, particularly at 3-4 weeks of age, marked by a reduced bacterial abundance, alpha diversity, and FC levels. Metabolic changes in FI were pronounced between 3 and 6 weeks. Pantothenic acid and two polyamine metabolites were closely associated with bacterial abundance and FC levels and negatively correlated with the duration to attain full enteral feeding.

CONCLUSIONS

FI infants demonstrated compromised microbiome-immune interactions, potentially influenced by specific metabolites. This research underscored the importance of early microbial and metabolic development in the pathogenesis of FI in very preterm infants.

Polyamines and hypusination are important for Clostridioides difficile toxin B (TcdB)-mediated activation of group 3 innate lymphocytes (ILC3s)

Clostridioides difficile is the most common cause of nosocomial gastrointestinal tract bacterial infections. We lack fully effective reliable treatments for this pathogen, and there is a critical need to better understand how C. difficile interacts with our immune system. Group 3 innate lymphocytes (ILC3s) are rare immune cells localized within mucosal tissues that protect against bacterial infections. Upon activation, ILC3s secrete high levels of the cytokine interleukin-22 (IL-22), which is a critical regulator of tissue responses during infection. C. difficile toxin B (TcdB), the major virulence factor, directly activates ILC3s, resulting in high IL-22 levels. We previously reported that polyamines are important in the activation of ILC3s by the innate cytokine interleukin-23 (IL-23) but did not identify a specific mechanism. In this study, we examine how a pathogen impacts a metabolic pathway important for immune cell function and hypothesized that polyamines are important in TcdB-mediated ILC3 activation. We show that TcdB upregulates the polyamine biosynthesis pathway, and the inhibition of the pathway decreases TcdB-mediated ILC3 activation. Two polyamines, putrescine and spermidine, are involved. Spermidine is the key polyamine in the hypusination of eukaryotic initiation factor 5A (eIF5A), and the inhibition of eIF5A reduced ILC3 activation. Thus, there is potential to leverage polyamines in ILC3s to promote activation of ILC3s during C. difficile infection and other bacterial infections where ILC3s serve a protective role.

Shotgun Metagenomic Sequencing Revealed the Prebiotic Potential of a Fruit Juice Drink with Fermentable Fibres in Healthy Humans

Fibre-based dietary interventions are at the forefront of gut microbiome modulation research, with a wealth of 16S rRNA information to demonstrate the prebiotic effects of isolated fibres. However, there is a distinct lack of data relating to the effect of a combination of soluble and insoluble fibres in a convenient-to-consume fruit juice food matrix on gut microbiota structure, diversity, and function. Here, we aimed to determine the impact of the MOJU Prebiotic Shot, an apple, lemon, ginger, and raspberry fruit juice drink blend containing chicory inulin, baobab, golden kiwi, and green banana powders, on gut microbiota structure and function. Healthy adults (n = 20) were included in a randomised, double-blind, placebo-controlled, cross-over study, receiving 60 mL MOJU Prebiotic Shot or placebo (without the fibre mix) for 3 weeks with a 3-week washout period between interventions. Shotgun metagenomics revealed significant between-group differences in alpha and beta diversity. In addition, the relative abundance of the phyla Actinobacteria and Desulfobacteria was significantly increased as a result of the prebiotic intervention. Nine species were observed to be differentially abundant (uncorrected p-value of <0.05) as a result of the prebiotic treatment. Of these, Bifidobacterium adolescentis and CAG-81 sp900066785 (Lachnospiraceae) were present at increased abundance relative to baseline. Additionally, KEGG analysis showed an increased abundance in pathways associated with arginine biosynthesis and phenylacetate degradation during the prebiotic treatment. Our results show the effects of the daily consumption of 60 mL MOJU Prebiotic Shot for 3 weeks and provide insight into the functional potential of B. adolescentis.

Spermidine-Eugenol Supplement Preserved Inflammation-Challenged Intestinal Cells by Stimulating Autophagy

Increases in non-communicable and auto-immune diseases, with a shared etiology of defective autophagy and chronic inflammation, have motivated research both on natural products in drug discovery fields and on the interrelationship between autophagy and inflammation. Within this framework, the tolerability and protective effects of a wheat-germ spermidine (SPD) and clove eugenol (EUG) combination supplement (SUPPL) were investigated on inflammation status (after the administration of lipopolysaccharide (LPS)) and on autophagy using human Caco-2 and NCM460 cell lines. In comparison to the LPS treatment alone, the SUPPL + LPS significantly attenuated ROS levels and midkine expression in monocultures, as well as occludin expression and mucus production in reconstituted intestinal equivalents. Over a timeline of 2-4 h, the SUPPL and SUPPL + LPS treatments stimulated autophagy LC3-11 steady state expression and turnover, as well as P62 turnover. After completely blocking autophagy with dorsomorphin, inflammatory midkine was significantly reduced in the SUPPL + LPS treatment in a non-autophagy-dependent manner. After a 24 h timeline, preliminary results showed that mitophagy receptor BNIP3L expression was significantly downregulated in the SUPPL + LPS treatment compared to the LPS alone, whereas conventional autophagy protein expression was significantly higher. The SUPPL shows promise in reducing inflammation and increasing autophagy to improve intestinal health.

Polysaccharides from Panax ginseng promote intestinal epithelial cell migration through affecting the Ca2+ related regulators

Background and aim

Panax ginseng, a key herbal medicine of replenishing Qi and tonifying Spleen, is widely used in the treatment of gastrointestinal diseases in East Asia. In this study, we aim to investigate the potential effects and mechanisms of polysaccharides from P. ginseng (PGP) on intestinal mucosal restitution which is one of the crucial repair modalities during the recovery of mucosal injury controlled by the Ca²⁺ signaling.

Methods

Rat model of intestinal mucosal injury was induced by indomethacin. The fractional cell migration was carried out by immunohistochemistry staining with BrdU. The morphological observations on intestinal mucosal injury were also performed. Intestinal epithelial cell (IEC-6) migration in vitro was conducted by scratch method. Western-blot was adopted to determine the expressions of PLC-γ1, Rac1, TRPC1, RhoA and Cav-1. Immunoprecipitation was used to evaluate the levels of Rac1/PLC-γ1, RhoA/TRPC1 and Cav-1/TRPC1.

Results

The results showed that PGP effectively reduced the assessment of intestinal mucosal injury, reversed the inhibition of epithelial cell migration induced by Indomethacin, and increased the level of Ca²⁺ in intestinal mucosa in vivo. Moreover, PGP dramatically promoted IEC-6 cell migration, the expression of Ca²⁺ regulators (PLC-γ1, Rac1, TRPC1, Cav-1 and RhoA) as well as protein complexes (Rac1/PLC-γ1, Cav-1/TRPC1 and RhoA/TRPC1) in vitro.

Conclusion

PGP increases the Ca²⁺ content in intestinal mucosa partly through controlling the regulators of Ca²⁺ mobilization, subsequently promotes intestinal epithelial cell migration, and then prevents intestinal mucosal injury induced by indomethacin.

Gut Microbiota Alterations in Trace Amine-Associated Receptor 9 (TAAR9) Knockout Rats

Trace amine-associated receptors (TAAR1-TAAR9) are a family of G-protein-coupled monoaminergic receptors which might have great pharmacological potential. It has now been well established that TAAR1 plays an important role in the central nervous system. Interestingly, deletion of TAAR9 in rats leads to alterations in the periphery. Previously, we found that knockout of TAAR9 in rats (TAAR9-KO rats) decreased low-density lipoprotein cholesterol levels in the blood. TAAR9 was also identified in intestinal tissues, and it is known that it responds to polyamines. To elucidate the role of TAAR9 in the intestinal epithelium, we analyzed TAAR9-co-expressed gene clusters in public data for cecum samples. As identified by gene ontology enrichment analysis, in the intestine, TAAR9 is co-expressed with genes involved in intestinal mucosa homeostasis and function, including cell organization, differentiation, and death. Additionally, TAAR9 was co-expressed with genes implicated in dopamine signaling, which may suggest a role for this receptor in the regulation of peripheral dopaminergic transmission. To further investigate how TAAR9 might be involved in colonic mucosal homeostasis, we analyzed the fecal microbiome composition in TAAR9-KO rats and their wild-type littermates. We identified a significant difference in the number of observed taxa between the microbiome of TAAR9-KO and wild-type rats. In TAAR9-KO rats, the gut microbial community became more variable compared with the wild-type rats. Furthermore, it was found that the family Saccharimonadaceae, which is one of the top 10 most abundant families in TAAR9-KO rat feces, is almost completely absent in wild-type animal fecal samples. Taken together, these data indicate a role of TAAR9 in intestinal function.

Dysbiosis: The first hit for digestive system cancer

Gastrointestinal cancer may be associated with dysbiosis, which is characterized by an alteration of the gut microbiota. Understanding the role of gut microbiota in the development of gastrointestinal cancer is useful for cancer prevention and gut microbiota-based therapy. However, the potential role of dysbiosis in the onset of tumorigenesis is not fully understood. While accumulating evidence has demonstrated the presence of dysbiosis in the intestinal microbiota of both healthy individuals and patients with various digestive system diseases, severe dysbiosis is often present in patients with digestive system cancer. Importantly, specific bacteria have been isolated from the fecal samples of these patients. Thus, the association between dysbiosis and the development of digestive system cancer cannot be ignored. A new model describing this relationship must be established. In this review, we postulate that dysbiosis serves as the first hit for the development of digestive system cancer. Dysbiosis-induced alterations, including inflammation, aberrant immune response, bacteria-produced genotoxins, and cellular stress response associated with genetic, epigenetic, and/or neoplastic changes, are second hits that speed carcinogenesis. This review explains the mechanisms for these four pathways and discusses gut microbiota-based therapies. The content included in this review will shed light on gut microbiota-based strategies for cancer prevention and therapy.

Interaction between gut microbiota and immune checkpoint inhibitor-related colitis

Immune checkpoint inhibitors (ICIs) have become a promising therapeutic strategy for malignant tumors, improving patient prognosis, along with a spectrum of immune-related adverse events (irAEs), including gastrointestinal toxicity, ICI-related colitis (IRC), and diarrhea. The gut microbiota has been suggested as an important regulator in the pathogenesis of IRC, and microbiota modulations like probiotics and fecal microbiota transplantation have been explored to treat the disease. This review discusses the interaction between the gut microbiota and IRC, focusing on the potential pathogenic mechanisms and promising interventions.

Mouse feeding study and microbiome analysis of sourdough bread for evaluation of its health effects

Sourdough bread fermented with yeast and lactic acid bacteria (LAB) is thought to have various beneficial health effects. However, its beneficial effects were not fully evaluated with in vivo mouse model. To evaluate these effects in vivo, a mouse feeding study and microbiome analysis of white bread containing 40% sourdough (WBS) and yeast-leavened white bread (WB) were performed. Although feed consumption and body weight increased with WBS, the glycemic index was reduced, suggesting a diabetes-lowering effect, probably due to the presence of dietary fiber and short-chain fatty acids (SCFA). In addition, a mineral absorption test showed that WBS increased magnesium absorption owing to phytate degradation during fermentation. Interestingly, WBS decreased total cholesterol and triglycerides, probably due to the dietary fiber and SCFA in LAB. In addition, the ratio of low- and high-density lipoprotein was decreased in WBS, implying potential risk reduction for cardiovascular disease. An immunomodulatory assay of WBS revealed that pro-inflammatory cytokines TNF-α and IL-6 were decreased, suggesting anti-inflammatory activity. Gluten degradation by fermentation and antioxidation activity of menaquinol/ubiquinol by gut microbiota also supported the anti-inflammatory activity of sourdough bread. Furthermore, some beneficial gut bacteria, including Akkermansia, Bifidobacterium, and Lactobacillus, were increased in WBS. In particular, Akkermansia has been associated with anti-inflammatory properties. Consequently, WBS has beneficial effects on health, including decreased glycemic index and cholesterol, increased mineral availability and absorption, anti-inflammatory properties, and establishment of healthy gut microbiota.

Probiotics or synbiotics addition to sows’ diets alters colonic microbiome composition and metabolome profiles of offspring pigs

Little information exists about the effects of maternal probiotics and synbiotics addition on the gut microbiome and metabolome of offspring. The present study evaluated the effects of probiotics or synbiotics addition to sows’ diets on colonic microbiota and their metabolites in offspring using 16S rRNA gene sequencing and metabolome strategy. A total of 64 pregnant Bama mini-pigs were randomly divided into control, antibiotic, probiotics, and synbiotics groups and fed the corresponding experimental diets during pregnancy and lactation. After weaning, two piglets per litter and eight piglets per group were selected and fed a basal diet. The β-diversity analysis showed that the colonic microbiota of offspring had a clear distinction among the four groups at 65 days of age. Maternal probiotics addition increased the Actinobacteria abundance at 65 days of age and Tenericutes and Firmicutes abundances at 95 days of age of offspring compared with the other three groups, whereas maternal antibiotic addition increased Spirochaetes and Proteobacteria abundances at 95 days of age of offspring compared with the other three groups. Metabolomic analysis showed that colonic metabolites were different between the groups, regardless of the days of age. Furthermore, both PICRUSt2 and enrichment analysis of metabolic pathways showed that maternal probiotics and synbiotics addition affected metabolism of carbohydrate, amino acid, cofactors and vitamins in the colonic microbiota. Compared with the control group, the colonic concentration of indole decreased and skatole increased in the probiotics group, whereas indole increased and skatole decreased in the synbiotics group. Maternal probiotics addition increased the colonic concentrations of acetate and butyrate at 65 and 125 days of age, whereas probiotics and synbiotics addition decreased short-chain fatty acids concentrations at 95 days of age. In addition, the colonic concentrations of putrescine, cadaverine, 1,7-heptanediamine, and spermidine were increased in the antibiotic, probiotics, and synbiotics groups compared with the control group at 95 days of age. The correlation analysis showed that Gemmiger, Roseburia, and Faecalibacterium abundances were positively correlated with acetate, propionate, and butyrate concentrations; Gemmiger, Blautia, and Faecalibacterium were positively correlated with putrescine and spermidine; and Faecalibacterium, Blautia, Clostridium, and Streptococcus were positively correlated with (R)-3-hydroxybutyric acid. Collectively, these findings suggest that probiotics and synbiotics addition to sows’ diets exerts effects on offspring pigs by altering gut microbiota composition and their metabolites. The potential beneficial effect on gut health is discussed.

Microbial Metabolite Regulation of Epithelial Cell-Cell Interactions and Barrier Function

Epithelial cells that line tissues such as the intestine serve as the primary barrier to the outside world. Epithelia provide selective permeability in the presence of a large constellation of microbes, termed the microbiota. Recent studies have revealed that the symbiotic relationship between the healthy host and the microbiota includes the regulation of cell–cell interactions at the level of epithelial tight junctions. The most recent findings have identified multiple microbial-derived metabolites that influence intracellular signaling pathways which elicit activities at the epithelial apical junction complex. Here, we review recent findings that place microbiota-derived metabolites as primary regulators of epithelial cell–cell interactions and ultimately mucosal permeability in health and disease.

miR-195 Regulates Intestinal Epithelial Restitution after Wounding by altering Actin-Related Protein-2 Translation

Early gut epithelial restitution reseals superficial wounds after acute injury, but the exact mechanism underlying this rapid mucosal repair remains largely unknown. MicroRNA-195 (miR-195) is highly expressed in the gut epithelium and involved in many aspects of mucosal pathobiology. Actin-related proteins (ARPs) are key components essential for stimulation of actin polymerization and regulate cell motility. Here we reported that miR-195 modulates early intestinal epithelial restitution by altering ARP-2 expression at the translation level. MiR-195 directly interacted with the ARP-2 mRNA, and ectopically overexpressed miR-195 decreased ARP-2 protein without effect on its mRNA content. In contrast, miR-195 silencing by transfection with the anti-miR-195 increased ARP-2 protein expression. Decreased ARP-2 levels by miR-195 were associated with an inhibition of early epithelial restitution, as indicated by a decrease in cell migration over the wounded area. Elevation of cellular ARP-2 levels by transfection with its transgene restored cell migration after wounding in cells overexpressing miR-195. Polyamines were found to decrease miR-195 abundance and enhanced ARP-2 translation, thus promoting epithelial restitution after wounding. Moreover, increasing the levels of miR-195 disrupted F-actin cytoskeleton organization, which was prevented by ARP2 overexpression. These results indicate that miR-195 inhibits early epithelial restitution by decreasing ARP-2 translation and that miR-195 expression is negatively regulated by cellular polyamines.

Total ginsenosides promote the IEC-6 cell proliferation via affecting the regulatory mechanism mediated by polyamines

Epithelial cell proliferation has been demonstrated to be a critical modality for mucosal repair after gastrointestinal mucosal injury. This research aimed to investigate the effect of total ginsenosides upon the proliferation of intestinal epithelial cells (IEC-6), and elucidate its potential mechanisms through polyamine-regulated pathway including the expression of proliferation-related proteins. Total ginsenosides (PGE3) were extracted from Panax ginseng, a Chinese herbal medicine, whose chromatogram was obtained by high performance liquid chromatographic method with evaporative light scattering detection (HPLC-ELSD). The cell proliferation, cell cycle distribution and the level of c-Myc, RhoA, Cdk2 proteins were detected to determine the effects of PGE3 at 25, 50 and100 mg/l doses on IEC-6. Furthermore, rats model of intestinal mucosal injury were induced by the subcutaneous injection of indomethacin, and the effect of Panax ginseng aqueous extracts (PGE1) on intestinal mucosal injury was observed. PGE3 could promote IEC-6 cell proliferation, reduce the proportion of G0/G1 phase cells and elevate the proportion of G2/M + S phase cells, and revert the proliferation and cell cycle arrest induced by DFMO (DL-a-difluoromethylornithine, an inhibitor of polyamines synthesis). PGE3 exposure enhanced the level of c-Myc, RhoA and Cdk2 proteins, and reversed the inhibition of these proteins expression induced by DFMO. The results of gross and pathological scores showed administration of PGE1 significantly alleviated intestinal mucosal injury of rats. Our findings indicate that total ginsenosides promoted the IEC-6 proliferation presumably via its regulation on cell cycle and the expression of proliferation-related proteins regulated by polyamines, and provided a novel perspective for exploring the repair effect of Panax ginseng upon gastrointestinal mucosal injury.

Circular RNA CircHIPK3 Promotes Homeostasis of the Intestinal Epithelium by Reducing MicroRNA 29b Function

BACKGROUND & AIMS

Circular RNAs (circRNAs) are a class of endogenous noncoding RNAs that form covalently closed circles. Although circRNAs influence many biological processes, little is known about their role in intestinal epithelium homeostasis. We surveyed circRNAs required to maintain intestinal epithelial integrity and identified circular homeodomain-interacting protein kinase 3 (circHIPK3) as a major regulator of intestinal epithelial repair after acute injury.

METHODS

Intestinal mucosal tissues were collected from mice exposed to cecal ligation and puncture for 48 hours and patients with inflammatory bowel diseases and sepsis. We isolated primary enterocytes from the small intestine of mice and derived intestinal organoids. The levels of circHIPK3 were silenced in intestinal epithelial cells (IECs) by transfection with small interfering RNAs targeting the circularization junction of circHIPK3 or elevated using a plasmid vector that overexpressed circHIPK3. Intestinal epithelial repair was examined in an in vitro injury model by removing part of the monolayer. The association of circHIPK3 with microRNA 29b (miR-29b) was determined by biotinylated RNA pull-down assays.

RESULTS

Genome-wide profile analyses identified ∼300 circRNAs, including circHIPK3, differentially expressed in the intestinal mucosa of mice after cecal ligation and puncture relative to sham mice. Intestinal mucosa from patients with inflammatory bowel diseases and sepsis had reduced levels of circHIPK3. Increasing the levels of circHIPK3 enhanced intestinal epithelium repair after wounding, whereas circHIPK3 silencing repressed epithelial recovery. CircHIPK3 silencing also inhibited growth of IECs and intestinal organoids, and circHIPK3 overexpression promoted intestinal epithelium renewal in mice. Mechanistic studies revealed that circHIPK3 directly bound to miR-29b and inhibited miR-29 activity, thus increasing expression of Rac1, Cdc42, and cyclin B1 in IECs after wounding.

CONCLUSIONS

In studies of mice, IECs, and human tissues, our results indicate that circHIPK3 improves repair of the intestinal epithelium at least in part by reducing miR-29b availability.

Enteral feeding and the microbiome in critically ill children: a narrative review

OBJECTIVE

This narrative review summarizes our current knowledge on the interplay between enteral nutrition (EN) and gut microbiota in critically ill children, using examples from two commonly encountered diagnoses in the pediatric intensive care unit (PICU): severe sepsis and acute respiratory distress syndrome (ARDS). This review will also highlight potential areas of therapeutic interventions that should be explored in future studies.

BACKGROUND

Critically ill children display extreme dysbiosis in their gut microbiome. Factors within the PICU that are often associated with dysbiosis include the use of broad-spectrum antibiotics, proton-pump inhibitors (PPIs), intravenous morphine, and fasting. Dysbiosis can potentially lead to adverse clinical outcomes (e.g., nosocomial infection, and prolonged hospitalization). EN may modulate dysbiosis. The gut microbiota is involved in the breaking down of macronutrients, mainly carbohydrates and proteins. Fermentation of undigestible carbohydrate (e.g., inulin and oligosaccharides), and amino acids by large intestine microbiota produces short chain fatty acids (SCFAs). SCFAs serve as the main fuel source for enterocytes and help to maintain healthy gut lining. Changes to selected components of macronutrients can result in alterations in gut microbiome and have potentially beneficial effects in patients in the PICU.

METHODS

A comprehensive search of the MEDLINE, Cochrane Library and Google Scholar databases was conducted using appropriate MESH terms and keywords. In this narrative review, we provide a summary of current knowledge on effect of EN on gut microbiota in pediatric studies, but also describes animal- and lab-based, as well as adult studies where relevant.

CONCLUSIONS

The gut microbiome can be altered by dietary modifications and common PICU practices and treatment. Although there are strong associations in restoring eubiosis and improvement in clinical outcomes, proving causality remains challenging. Further microbiome research is needed to provide mechanistic insights into the impact of the ever changing gut microbiome. In the future, new microbiota targeted therapies could potentially be the treatment of challenging PICU conditions and restore homeostasis in these children.

3D cell culture models: Drug pharmacokinetics, safety assessment, and regulatory consideration

Nonclinical testing has served as a foundation for evaluating potential risks and effectiveness of investigational new drugs in humans. However, the current two-dimensional (2D) in vitro cell culture systems cannot accurately depict and simulate the rich environment and complex processes observed in vivo, whereas animal studies present significant drawbacks with inherited species-specific differences and low throughput for increased demands. To improve the nonclinical prediction of drug safety and efficacy, researchers continue to develop novel models to evaluate and promote the use of improved cell- and organ-based assays for more accurate representation of human susceptibility to drug response. Among others, the three-dimensional (3D) cell culture models present physiologically relevant cellular microenvironment and offer great promise for assessing drug disposition and pharmacokinetics (PKs) that influence drug safety and efficacy from an early stage of drug development. Currently, there are numerous different types of 3D culture systems, from simple spheroids to more complicated organoids and organs-on-chips, and from single-cell type static 3D models to cell co-culture 3D models equipped with microfluidic flow control as well as hybrid 3D systems that combine 2D culture with biomedical microelectromechanical systems. This article reviews the current application and challenges of 3D culture systems in drug PKs, safety, and efficacy assessment, and provides a focused discussion and regulatory perspectives on the liver-, intestine-, kidney-, and neuron-based 3D cellular models.

TRPC1-mediated Ca2+ signaling enhances intestinal epithelial restitution by increasing α4 association with PP2Ac after wounding

Gut epithelial restitution after superficial wounding is an important repair modality regulated by numerous factors including Ca²⁺ signaling and cellular polyamines. Transient receptor potential canonical-1 (TRPC1) functions as a store-operated Ca²⁺ channel in intestinal epithelial cells (IECs) and its activation increases epithelial restitution by inducing Ca²⁺ influx after acute injury. α4 is a multiple functional protein and implicated in many aspects of cell functions by modulating protein phosphatase 2A (PP2A) stability and activity. Here we show that the clonal populations of IECs stably expressing TRPC1 (IEC-TRPC1) exhibited increased levels of α4 and PP2A catalytic subunit (PP2Ac) and that TRPC1 promoted intestinal epithelial restitution by increasing α4/PP2Ac association. The levels of α4 and PP2Ac proteins increased significantly in stable IEC-TRPC1 cells and this induction in α4/PP2Ac complexes was accompanied by an increase in IEC migration after wounding. α4 silencing by transfection with siRNA targeting α4 (siα4) or PP2Ac silencing destabilized α4/PP2Ac complexes in stable IEC-TRPC1 cells and repressed cell migration over the wounded area. Increasing the levels of cellular polyamines by stable transfection with the Odc gene stimulated α4 and PP2Ac expression and enhanced their association, thus also promoting epithelial restitution after wounding. In contrast, depletion of cellular polyamines by treatment with α-difluoromethylornithine reduced α4/PP2Ac complexes and repressed cell migration. Ectopic overexpression of α4 partially rescued rapid epithelial repair in polyamine-deficient cells. These results indicate that activation of TRPC1-mediated Ca²⁺ signaling enhances cell migration primarily by increasing α4/PP2Ac associations after wounding and this pathway is tightly regulated by cellular polyamines.

MicroRNA-195 regulates Tuft cell function in the intestinal epithelium by altering translation of DCLK1

Intestinal Tuft cells sense luminal contents to influence the mucosal immune response against eukaryotic infection. Paneth cells secrete antimicrobial proteins as part of the mucosal protective barrier. Defects in Tuft and Paneth cells occur commonly in various gut mucosal disorders. MicroRNA-195 (miR-195) regulates the stability and translation of target mRNAs and is involved in many aspects of cell processes and pathologies. Here, we reported the posttranscriptional mechanisms by which miR-195 regulates Tuft and Paneth cell function in the small intestinal epithelium. Mucosal tissues from intestinal epithelial tissue-specific miR-195 transgenic (miR195-Tg) mice had reduced numbers of double cortin-like kinase 1 (DCLK1)-positive (Tuft) and lysozyme-positive (Paneth) cells, compared with tissues from control mice, but there were no effects on Goblet cells and enterocytes. Intestinal organoids expressing higher miR-195 levels from miR195-Tg mice also exhibited fewer Tuft and Paneth cells. Transgenic expression of miR-195 in mice failed to alter growth of the small intestinal mucosa but increased vulnerability of the gut barrier in response to lipopolysaccharide (LPS). Studies aimed at investigating the mechanism underlying regulation of Tuft cells revealed that miR-195 directly interacted with the Dclk1 mRNA via its 3'-untranslated region and inhibited DCLK1 translation. Interestingly, the RNA-binding protein HuR competed with miR-195 for binding Dclk1 mRNA and increased DCLK1 expression. These results indicate that miR-195 suppresses the function of Tuft and Paneth cells in the small intestinal epithelium and further demonstrate that increased miR-195 disrupts Tuft cell function by inhibiting DCLK1 translation via interaction with HuR.

RNA-binding proteins and long noncoding RNAs in intestinal epithelial autophagy and barrier function

The intestinal autophagy and barrier function are crucial for maintaining the epithelium homeostasis and tightly regulated through well-controlled mechanisms. RNA-binding proteins (RBPs) and long noncoding RNAs (lncRNAs) modulate gene expression at the posttranscription level and are intimately involved in different physiological processes and diverse human diseases. In this review, we first highlight the roles of several RBPs and lncRNAs in the regulation of intestinal epithelial autophagy and barrier function, particularly focusing on the emerging evidence of RBPs and lncRNAs in the control of mRNA stability and translation. We additionally discuss recent findings that the interactions between RBPs and lncRNAs alter the fate of their target transcripts and thus influence gut epithelium host defense in response to stressful environments. These exciting advances in understanding the posttranscriptional control of the epithelial autophagy and barrier function by RBPs and lncRNAs provide a strong rationale for developing new effective therapeutics based on targeting RBPs and/or lncRNAs to preserve the intestinal epithelial integrity in patients with critical illnesses.