Postnatal intestinal mucosa and gut microbial composition develop hand in hand: A mouse study

Perturbed maternal microbiota shapes offspring microbiota during early colonization period in mice

Recent studies have highlighted the impact of disrupted maternal gut microbiota on the colonization of offspring gut microbiota, with implications for offspring developmental trajectories. The extent to which offspring inherit the characteristics of altered maternal gut microbiota remains elusive. In this study, we employed a mouse model where maternal gut microbiota disruption was induced using non-absorbable antibiotics. Systematic chronological analyses of dam fecal samples, offspring luminal content, and offspring gut tissue samples revealed a notable congruence between offspring gut microbiota profiles and those of the perturbed maternal gut microbiota, highlighting the profound influence of maternal microbiota on early-life colonization of offspring gut microbiota. Nonetheless, certain dominant bacterial genera in maternal microbiota did not transfer to the offspring, indicating a bacterial taxonomy-dependent mechanism in the inheritance of maternal gut microbiota. Our results embody the vertical transmission dynamics of disrupted maternal gut microbiota in an animal model, where the gut microbiota of an offspring closely mirrors the gut microbiota of its mother.

Effect of Lifelong Exposure to Dietary Plant and Marine Sources of n-3 Polyunsaturated Fatty Acids on Morphologic and Gene Expression Biomarkers of Intestinal Health in Early Life

Altered intestinal health is also associated with the incidence and severity of many chronic inflammatory conditions, which could be attenuated via dietary n-3 PUFA interventions. However, little is known about the effect of lifelong exposure to n-3 PUFA from plant and marine sources (beginning in utero via the maternal diet) on early life biomarkers of intestinal health. Harems of C57Bl/6 mice were randomly assigned to one of three isocaloric AIN-93G modified diets differing in their fat sources consisting of the following: (i) 10% safflower oil (SO, enriched in n-6 PUFA), (ii) 3% flaxseed oil + 7% safflower oil (FX, plant-based n-3 PUFA-enriched diet), or (iii) 3% menhaden fish oil + 7% safflower oil (MO, marine-based n-3 PUFA-enriched diet). Mothers remained on these diets throughout pregnancy and offspring (n = 14/diet) continued on the same parental diet until termination at 3 weeks of age. In ileum, villi:crypt length ratios were increased in both the FX and MO dietary groups compared to SO (p < 0.05). Ileum mRNA expression of critical intestinal health biomarkers was increased by both n-3 PUFA-enriched diets including Relmβ and REG3γ compared to SO (p < 0.05), whereas only the FX diet increased mRNA expression of TFF3 and Muc2 (p < 0.05) and only the MO diet increased mRNA expression of ZO-1 (p < 0.05). In the proximal colon, both the FX and MO diets increased crypt lengths compared to SO (p < 0.05), whereas only the MO diet increased goblet cell numbers compared to SO (p < 0.05). Further, the MO diet increased proximal colon mRNA expression of Relmβ and REG3γ (p < 0.05) and both MO and FX increased mRNA expression of Muc2 compared to SO (p < 0.05). Collectively, these results demonstrate that lifelong exposure to dietary n-3 PUFA, beginning in utero, from both plant and marine sources, can support intestinal health development in early life. The differential effects between plant and marine sources warrants further investigation for optimizing health.

Transepithelial Barrier Dysfunction Drives Microbiota Dysbiosis to Initiate Epithelial Clock-driven Inflammation

BACKGROUND

Factors that contribute to inflammatory bowel disease [IBD] pathogenesis include genetic polymorphisms, barrier loss, and microbial dysbiosis. A major knowledge gap exists in the origins of the colitogenic microbiome and its relationship with barrier impairment. Epithelial myosin light chain kinase [MLCK] is a critical regulator of the paracellular barrier, but the effects of MLCK activation on the intraepithelial bacteria [IEB] and dysbiosis are incompletely understood. We hypothesise that MLCK-dependent bacterial endocytosis promotes pathobiont conversion and shapes a colitogenic microbiome.

METHODS

To explore this, transgenic [Tg] mice with barrier loss induced by intestinal epithelium-specific expression of a constitutively active MLCK were compared with wild-type [WT] mice.

RESULTS

When progeny of homozygous MLCK-Tg mice were separated after weaning by genotype [Tg/Tg, Tg/WT, WT/WT], increased IEB numbers associated with dysbiosis and more severe colitis were present in Tg/Tg and Tg/WT mice, relative to WT/WT mice. Cohousing with MLCK-Tg mice induced dysbiosis, increased IEB abundance, and exacerbated colitis in WT mice. Conversely, MLCK-Tg mice colonised with WT microbiota at birth displayed increased Escherichia abundance and greater colitis severity by 6 weeks of age. Microarray analysis revealed circadian rhythm disruption in WT mice co-housed with MLCK-Tg mice relative to WT mice housed only with WT mice. This circadian disruption required Rac1/STAT3-dependent microbial invasion but not MLCK activity, and resulted in increased proinflammatory cytokines and glucocorticoid downregulation.

CONCLUSIONS

The data demonstrate that barrier dysfunction induces dysbiosis and expansion of invasive microbes that lead to circadian disruption and mucosal inflammation. These results suggest that barrier-protective or bacterium-targeted precision medicine approaches may be of benefit to IBD patients.

Low-dose perinatal supplementation with Enterococcus faecalis increases concentrations of short-chain fatty acids in the offspring but does not protect against allergic asthma

Childhood allergic asthma is associated with a dysbiotic gut microbiome in early life, and maternal perinatal treatment with probiotics is a potential way alter the infant microbiome, which may improve asthma outcomes. This study used a mouse model to examine the effect of maternal supplementation with the probiotic Enterococcus faecalis on faecal short-chain fatty acid (SCFA) concentrations and asthma risk in the offspring. Pregnant/lactating mice were treated daily, from gestation day 6 to postnatal day 21, with an oral suspension of 106, 107 or 108 colony-forming units of a live preparation of the probiotic E. faecalis (Symbioflor®1). At weaning, offspring were subjected to an ovalbumin-induced experimental asthma protocol. Faeces were collected from the mothers and offspring at several different time points to determine SCFA concentrations. It was found that maternal supplementation with E. faecalis did not alter litter size, sex ratio or offspring weight, and was associated with an increase in SCFAs in offspring faeces at weaning and after allergy induction. However, allergic offspring from E. faecalis supplemented mothers showed no difference in asthma severity when compared with allergic offspring from control mothers. In conclusion, although maternal perinatal supplementation with low-dose E. faecalis was associated with increased faecal SCFAs in the offspring, it did not protect against offspring asthma. This is may be because SCFA concentrations were not increased to an immunoprotective level. We recommend that future studies concentrate on probiotic supplementation in high-risk cases, for instance, to repair gut dysbiosis resulting from antibiotic use in pregnant mothers or their infants.

White adipose tissue undergoes browning during preweaning period in association with microbiota formation in mice

Beige adipocytes are transiently induced during early postnatal period in mice. Previous studies have suggested that, unlike in adults, the induction is independent of the sympathetic nerve activity; however, the mechanism is yet unknown. Here, we showed that beige adipocytes are induced during the preweaning period in association with the formation of microbiota in mice. Alteration of gut microbiota composition in preweaning mice by maternal treatment with antibiotics or high-fat diet feeding substantially suppressed WAT browning. The suppression was also found in pups transplanted cecal microbiota from pups of high-fat diet-fed dams. These treatments reduced the hepatic expression of genes involved in bile acid synthesis and the serum bile acids level. The abundance of Porphyromonadaceae and Ruminococcaceae in microbiota showed a positive and negative correlation with the induction of beige adipocytes, respectively. This finding may provide comprehensive understanding of the association between gut microbiota and adipose tissue development in the neonatal period.

Prebiotic Supplementation during Lactation Affects Microbial Colonization in Postnatal-Growth-Restricted Mice

BACKGROUND

An inadequate perinatal nutritional environment can alter the maturation of the intestinal barrier and promote long-term pathologies such as metabolic syndrome or chronic intestinal diseases. The intestinal microbiota seems to play a determining role in the development of the intestinal barrier. In the present study, we investigated the impact of consuming an early postnatal prebiotic fiber (PF) on growth, intestinal morphology and the microbiota at weaning in postnatal-growth-restricted mice (PNGR).

METHODS

Large litters (15 pups/mother) were generated from FVB/NRj mice to induce PNGR at postnatal day 4 (PN4) and compared to control litters (CTRL, 8 pups/mother). PF (a resistant dextrin) or water was orally administered once daily to the pups from PN8 to PN20 (3.5 g/kg/day). Intestinal morphology was evaluated at weaning (PN21) using the ileum and colon. Microbial colonization and short-chain fatty acid (SCFA) production were investigated using fecal and cecal contents.

RESULTS

At weaning, the PNGR mice showed decreased body weight and ileal crypt depth compared to the CTRL. The PNGR microbiota was associated with decreased proportions of the Lachnospiraceae and Oscillospiraceae families and the presence of the Akkermansia family and Enterococcus genus compared to the CTRL pups. The propionate concentrations were also increased with PNGR. While PF supplementation did not impact intestinal morphology in the PNGR pups, the proportions of the Bacteroides and Parabacteroides genera were enriched, but the proportion of the Proteobacteria phylum was reduced. In the CTRL pups, the Akkermansia genus (Verrucomicrobiota phylum) was present in the PF-supplemented CTRL pups compared to the water-supplemented ones.

CONCLUSIONS

PNGR alters intestinal crypt maturation in the ileum at weaning and gut microbiota colonization. Our data support the notion that PF supplementation might improve gut microbiota establishment during the early postnatal period.

Postnatal 14D is the Key Window for Mice Intestinal Development- An Insight from Age-Dependent Antibiotic-Mediated Gut Microbial Dysbiosis Study

The postnatal period is one of the critical windows for the structure-function development of the gastrointestinal tract and associated mucosal immunity. Along with other constituent members, recent studies suggest the contribution of gut microbiota in maintaining host health, immunity, and development. Although the gut microbiota's role in maintaining barrier integrity is known, its function in early life development still needs to be better understood. To understand the details of gut microbiota's effects on intestinal integrity, epithelium development, and immune profile, the route of antibiotic-mediated perturbation is taken. Mice on days 7(P7D), 14(P14D), 21(P21D) and 28(P28D) are sacrificed and 16S rRNA metagenomic analysis is performed. The barrier integrity, tight junction proteins (TJPs) expression, intestinal epithelial cell (IEC) markers, and inflammatory cytokines are analyzed. Results reveal a postnatal age-related impact of gut microbiota perturbation, with a gradual increase in the relative abundance of Proteobacteria and a reduction in Bacteroidetes and Firmicutes. Significant barrier integrity disruption, reduced TJPs and IECs marker expression, and increased systemic inflammation at P14D of AVNM-treated mice are found. Moreover, the microbiota transplantation shows recolonization of Verrucomicrobia, proving a causal role in barrier functions. The investigation reveals P14D as a critical period for neonatal intestinal development, regulated by specific microbiota composition.

Delayed Microbial Maturation Durably Exacerbates Th17-driven Asthma in Mice

Microbial maturation disrupted by early-life dysbiosis has been linked with increased asthma risk and severity; however, the immunological mechanisms underpinning this connection are poorly understood. We sought to understand how delaying microbial maturation drives worsened asthma outcomes later in life and its long-term durability. Drinking water was supplemented with antibiotics on Postnatal Days 10-20. To assess the immediate and long-term effects of delaying microbial maturation on experimental asthma, we initiated house dust mite exposure when bacterial diversity was either at a minimum or had recovered. Airway hyperresponsiveness, histology, pulmonary leukocyte recruitment, flow cytometric analysis of cytokine-producing lymphocytes, and assessment of serum IgG1 (Immunoglobulin G1) and IgE (Immunoglobulin E) concentrations were performed. RT-PCR was used to measure IL-13 (Interleukin 13)-induced gene expression in sequentially sorted mesenchymal, epithelial, endothelial, and leukocyte cell populations from the lung. Delayed microbial maturation increased allergen-driven airway hyperresponsiveness and Th17 frequency compared with allergen-exposed control mice, even when allergen exposure began after bacterial diversity recovered. Blockade of IL-17A (Interleukin 17A) reversed the airway hyperresponsiveness phenotype. In addition, allergen exposure in animals that experienced delayed microbial maturation showed signs of synergistic signaling between IL-13 and IL-17A in the pulmonary mesenchymal compartment. Delaying microbial maturation in neonates promotes the development of more severe asthma by increasing Th17 frequency, even if allergen exposure is initiated weeks after microbial diversity is normalized. In addition, IL-17A-aggravated asthma is associated with increased expression of IL-13-induced genes in mesenchymal, but not epithelial cells.

When it doesn't run in the blood(vessels) - events involved in vascular disorders

In the current issue of the Biomedical Journal the underlying pathology of hemodynamic compromise in acute small subcortical infarction are elucidated. A follow-up study in patients with childhood Kawasaki disease is presented, as well as an insight into the gradually decreasing antigen expression in cases of acute myeloid leukemia. Furthermore this issue provides an exciting update concerning COVID-19 and the use of CRISPR-Cas, a review about computational approaches in the research of kidney stone formation, factors connected to central precocious puberty, and why a rock star of paleogenetics recently received a Nobel Prize. Additionally, this issue contains an article proposing the repurposing of the lung cancer drug Capmatinib, a study of how the gut microbiome develops in neonates, an impulse about the role of the transmembrane protein TMED3 in esophageal carcinoma, and the revelation about how competing endogenous RNA influences ischemic stroke. Lastly, genetic reasons for male infertility are discussed, as well as the relation between non-alcoholic fatty liver disease and chronic kidney disease.

Recent Trends on Mitigative Effect of Probiotics on Oxidative-Stress-Induced Gut Dysfunction in Broilers under Necrotic Enteritis Challenge: A Review

Gut health includes normal intestinal physiology, complete intestinal epithelial barrier, efficient immune response, sustained inflammatory balance, healthy microbiota, high nutrient absorption efficiency, nutrient metabolism, and energy balance. One of the diseases that causes severe economic losses to farmers is necrotic enteritis, which occurs primarily in the gut and is associated with high mortality rate. Necrotic enteritis (NE) primarily damages the intestinal mucosa, thereby inducing intestinal inflammation and high immune response which diverts nutrients and energy needed for growth to response mediated effects. In the era of antibiotic ban, dietary interventions like microbial therapy (probiotics) to reduce inflammation, paracellular permeability, and promote gut homeostasis may be the best way to reduce broiler production losses. The current review highlights the severity effects of NE; intestinal inflammation, gut lesions, alteration of gut microbiota balance, cell apoptosis, reduced growth performance, and death. These negative effects are consequences of; disrupted intestinal barrier function and villi development, altered expression of tight junction proteins and protein structure, increased translocation of endotoxins and excessive stimulation of proinflammatory cytokines. We further explored the mechanisms by which probiotics mitigate NE challenge and restore the gut integrity of birds under disease stress; synthesis of metabolites and bacteriocins, competitive exclusion of pathogens, upregulation of tight junction proteins and adhesion molecules, increased secretion of intestinal secretory immunoglobulins and enzymes, reduction in pro-inflammatory cytokines and immune response and the increased production of anti-inflammatory cytokines and immune boost via the modulation of the TLR/NF-ĸ pathway. Furthermore, increased beneficial microbes in the gut microbiome improve nutrient utilization, host immunity, and energy metabolism. Probiotics along with biosecurity measures could mitigate the adverse effects of NE in broiler production.

A snapshot of gut microbiota data from murine models of Autism Spectrum Disorder: Still a blurred picture

Autism Spectrum Disorder (ASD) is a heterogeneous neurodevelopmental disorder characterized by deficits in social communication and interaction and repetitive/stereotyped behaviors. In recent years, the role of microbiota-gut-brain axis in ASD pathogenesis received growing attention, appearing as an attractive therapeutic target. We provide a comprehensive overview of changes in microbiota composition in ASD murine models so far identified, and summarize the therapeutic approaches targeting the microbiota on ASD-like neurobehavioral profile. Although alterations in microbiota composition have been observed in both genetic and environmental murine models of ASD, a clear microbiota profile shared by different ASD murine models has not been identified. We documented substantial discrepancies among studies (often within the same model), likely due to several confounding factors (from sex and age of animals to housing conditions). Despite these limitations, ASD animal models (under standardized conditions) remain a useful tool to evaluate (i) the beneficial effects of manipulations of gut microbiota on behavioral abnormalities; (ii) underlying neurobiological mechanisms related to gut-brain axis; and (iii) to identify optimal time windows for therapeutic interventions.

Programmed and environmental determinants driving neonatal mucosal immune development

The mucosal immune system of neonates goes through successive, non-redundant phases that support the developmental needs of the infant and ultimately establish immune homeostasis. These phases are informed by environmental cues, including dietary and microbial stimuli, but also evolutionary developmental programming that functions independently of external stimuli. The immune response to exogenous stimuli is tightly regulated during early life; thresholds are set within this neonatal "window of opportunity" that govern how the immune system will respond to diet, the microbiota, and pathogenic microorganisms in the future. Thus, changes in early-life exposure, such as breastfeeding or environmental and microbial stimuli, influence immunological and metabolic homeostasis and the risk of developing diseases such as asthma/allergy and obesity.

Neonatal development of intestinal neuroimmune interactions

Interactions between the enteric nervous system (ENS), immune system, and gut microbiota regulate intestinal homeostasis in adults, but their development and role(s) in early life are relatively underexplored. In early life, these interactions are dynamic, because the mucosal immune system, microbiota, and the ENS are developing and influencing each other. Moreover, disrupting gut microbiota and gut immune system development, and potentially ENS development, by early-life antibiotic exposure increases the risk of diseases affecting the gut. Here, we review the development of the ENS and immune/epithelial cells, and identify potential critical periods for their interactions and development. We also highlight knowledge gaps that, when addressed, may help promote intestinal homeostasis, including in the settings of early-life antibiotic exposure.

Intestinal epithelium in early life

Rapid development of the fetal and neonatal intestine is required to meet the growth requirements of early life and form a protective barrier against external insults encountered by the intestinal mucosa. The fetus receives nutrition via the placenta and is protected from harmful pathogens in utero, which leads to intestinal development in a relatively quiescent environment. Upon delivery, the intestinal mucosa is suddenly tasked with providing host defense and meeting nutritional demands. To serve these functions, an array of specialized epithelial cells develop from intestinal stem cells starting in utero and continuing postnatally. Intestinal disease results when these homeostatic processes are interrupted. For preterm neonates, the most common pathology resulting from epithelial barrier dysfunction is necrotizing enterocolitis (NEC). In this review, we discuss the normal development and function of the intestinal epithelium in early life as well as how disruption of these processes can lead to NEC.