Nutritional iron turned inside out: intestinal stress from a gut microbial perspective

Candida albicans and Candida glabrata: global priority pathogens

SUMMARYA significant increase in the incidence of Candida-mediated infections has been observed in the last decade, mainly due to rising numbers of susceptible individuals. Recently, the World Health Organization published its first fungal pathogen priority list, with Candida species listed in medium, high, and critical priority categories. This review is a synthesis of information and recent advances in our understanding of two of these species-Candida albicans and Candida glabrata. Of these, C. albicans is the most common cause of candidemia around the world and is categorized as a critical priority pathogen. C. glabrata is considered a high-priority pathogen and has become an increasingly important cause of candidemia in recent years. It is now the second most common causative agent of candidemia in many geographical regions. Despite their differences and phylogenetic divergence, they are successful as pathogens and commensals of humans. Both species can cause a broad variety of infections, ranging from superficial to potentially lethal systemic infections. While they share similarities in certain infection strategies, including tissue adhesion and invasion, they differ significantly in key aspects of their biology, interaction with immune cells, host damage strategies, and metabolic adaptations. Here we provide insights on key aspects of their biology, epidemiology, commensal and pathogenic lifestyles, interactions with the immune system, and antifungal resistance.

Superparamagnetic iron oxide nanoparticle regulates microbiota-gut-inner ear axis for hearing protection

Noise-induced hearing loss (NIHL) is a highly prevalent form of sensorineural hearing damage that has significant negative effects on individuals of all ages and there are no effective drugs approved by the US Food and Drug Administration. In this study, we unveil the potential of superparamagnetic iron oxide nanoparticle assembly (SPIOCA) to reshape the dysbiosis of gut microbiota for treating NIHL. This modulation inhibits intestinal inflammation and oxidative stress responses, protecting the integrity of the intestinal barrier. Consequently, it reduces the transportation of pathogens and inflammatory factors from the bloodstream to the cochlea. Additionally, gut microbiota-modulated SPIOCA-induced metabolic reprogramming in the gut-inner ear axis mainly depends on the regulation of the sphingolipid metabolic pathway, which further contributes to the restoration of hearing function. Our study confirms the role of the microbiota-gut-inner ear axis in NIHL and provides a novel alternative for the treatment of NIHL and other microbiota dysbiosis-related diseases.

The Hog1 MAPK substrate governs Candida glabrata-epithelial cell adhesion via the histone H2A variant

CgHog1, terminal kinase of the high-osmolarity glycerol signalling pathway, orchestrates cellular response to multiple external stimuli including surplus-environmental iron in the human fungal pathogen Candida glabrata (Cg). However, CgHog1 substrates remain unidentified. Here, we show that CgHog1 adversely affects Cg adherence to host stomach and kidney epithelial cells in vitro, but promotes Cg survival in the iron-rich gastrointestinal tract niche. Further, CgHog1 interactome and in vitro phosphorylation analysis revealed CgSub2 (putative RNA helicase) to be a CgHog1 substrate, with CgSub2 also governing iron homeostasis and host adhesion. CgSub2 positively regulated EPA1 (encodes a major adhesin) expression and host adherence via its interactor CgHtz1 (histone H2A variant). Notably, both CgHog1 and surplus environmental iron had a negative impact on CgSub2-CgHtz1 interaction, with CgHTZ1 or CgSUB2 deletion reversing the elevated adherence of Cghog1Δ to epithelial cells. Finally, the surplus-extracellular iron led to CgHog1 activation, increased CgSub2 phosphorylation, elevated CgSub2-CgHta (canonical histone H2A) interaction, and EPA1 transcriptional activation, thereby underscoring the iron-responsive, CgHog1-induced exchange of histone partners of CgSub2. Altogether, our work mechanistically defines how CgHog1 couples Epa1 adhesin expression with iron abundance, and point towards specific chromatin composition modification programs that probably aid fungal pathogens align their adherence to iron-rich (gut) and iron-poor (blood) host niches.

Discovery of a Gut Bacterial Metabolic Pathway that Drives α-Synuclein Aggregation

Parkinson's disease (PD) etiology is associated with aggregation and accumulation of α-synuclein (α-syn) proteins in midbrain dopaminergic neurons. Emerging evidence suggests that in certain subtypes of PD, α-syn aggregates originate in the gut and subsequently spread to the brain. However, mechanisms that instigate α-syn aggregation in the gut have remained elusive. In the brain, the aggregation of α-syn is induced by oxidized dopamine. Such a mechanism has not been explored in the context of the gastrointestinal tract, a niche harboring 46% of the body's dopamine reservoirs. Here, we report that Enterobacteriaceae, a bacterial family prevalent in human gut microbiotas, induce α-syn aggregation. More specifically, our in vitro data indicate that respiration of nitrate by Escherichia coli K-12, which results in production of nitrite that mediates oxidation of Fe2+ to Fe3+, creates an oxidizing redox potential. These oxidizing conditions enabled the formation of dopamine-derived quinones and α-syn aggregates. Exposing nitrite, but not nitrate, to enteroendocrine STC-1 cells induced aggregation of α-syn that is natively expressed in these cells, which line the intestinal tract. Taken together, our findings indicate that bacterial nitrate reduction may be critical for initiating intestinal α-syn aggregation.

Diagnosis and management of anemia in pediatric inflammatory bowel diseases: Clinical practice guidelines on behalf of the SIGENP IBD Working group

Anemia is one of the most frequent extra-intestinal manifestations of inflammatory bowel disease. Insidious onset, variability of symptoms and lack of standardized screening practices may increase the risk of underestimating its burden in children with IBD. Despite its relevance and peculiarity in everyday clinical practice, this topic is only dealt with in a few documents specifically for the pediatric field. The aim of the current guidelines is therefore to provide pediatric gastroenterologists with a practical update to support the clinical and therapeutic management of children with IBD and anemia. A panel of 19 pediatric gastroenterologists and 1 pediatric hematologist with experience in the field of pediatric IBD was agreed by IBD Working group of the Italian Society of Gastroenterology, Hepatology and Nutrition (SIGENP) to produce the present article outlining practical clinical approaches to the pediatric patient with IBD and anemia. The levels of evidence and recommendations have been defined for each part of the statement according to the GRADE system.

L-Citrulline Ameliorates Iron Metabolism and Mitochondrial Quality Control via Activating AMPK Pathway in Intestine and Improves Microbiota in Mice with Iron Overload

SCOPE

Oxidative stress caused by iron overload tends to result in intestinal mucosal barrier dysfunction and intestinal microbiota imbalance. As a neutral and nonprotein amino acid, L-Citrulline (L-cit) has been implicated in antioxidant and mitochondrial amelioration properties. This study investigates whether L-cit can alleviate iron overload-induced intestinal injury and explores the underlying mechanisms.

METHODS AND RESULTS

C57BL/6J mice are intraperitoneally injected with iron dextran, then gavaged with different dose of L-cit for 2 weeks. L-cit treatment significantly alleviates intestine pathological injury, oxidative stress, ATP level, and mitochondrial respiratory chain complex activities, accompanied by ameliorating mitochondrial quality control. L-cit-mediated protection is associated with the upregulation of Glutathione Peroxidase 4 (GPX4) expression, inhibition Nuclear Receptor Coactivator 4 (NCOA4)-mediated ferritinophagy and ferroptosis, and improvement of gut microbiota. To investigate the underlying molecular mechanisms, Intestinal Porcine Epithelial Cell line-J2 (IPEC-J2) cells are treated with L-cit or AMP-activated Protein Kinase (AMPK) inhibitor. AMPK signaling has been activated by L-cit. Notably, Compound C abolishes L-cit's protection on intestinal barrier, mitochondrial function, and antioxidative capacity in IPEC-J2 cells.

CONCLUSION

L-cit may restrain ferritinophagy and ferroptosis to regulate iron metabolism, and induce AMPK pathway activation, which contributes to exert antioxidation, ameliorate iron metabolism and mitochondrial quality control, and improve intestinal microbiota. L-cit is a promising therapeutic strategy for iron overload-induced intestinal injury.

Ironing out the details of ferroptosis

Ferroptosis, spurred by excess labile iron and lipid peroxidation, is implicated in various diseases. Advances have been made in comprehending the lipid-peroxidation side of ferroptosis, but the exact role of iron in driving ferroptosis remains unknown. Although iron overload is characterized in multiple disease states, the potential role of ferroptosis within them remains undefined. This overview focuses on the 'ferro' side of ferroptosis, highlighting iron dysregulation in human diseases and potential therapeutic strategies targeting iron regulation and metabolism.

Intestinal microbiota composition and efficacy of iron supplementation in Peruvian children

OBJECTIVE

Despite repeated public health interventions, anemia prevalence among children remains a concern. We use an evolutionary medicine perspective to examine the intestinal microbiome as a pathway underlying the efficacy of iron-sulfate treatment. This study explores whether gut microbiota composition differs between anemic children who respond and do not respond to treatment at baseline and posttreatment and if specific microbiota taxa remain associated with response to iron supplementation after controlling for relevant inflammatory and pathogenic variables.

METHODS

Data come from 49 pre-school-aged anemic children living in San Juan de Lurigancho, Lima, Peru. We tested for differences in alpha and beta diversity using QIIME 2 and performed differential abundance testing in DESeq2 in R. We ran multivariate regression models to assess associations between abundance of specific taxa and response while controlling for relevant variables in Stata 17.

RESULTS

While we found no evidence for gut microbiota diversity associated with child response to iron treatment, we observed several differential abundance patterns between responders and non-responders at both timepoints. Additionally, we present support for a nonzero relationship between lower relative abundance of Barnesiellaceae and response to iron supplementation in samples collected before and after treatment.

CONCLUSION

While larger studies and more specific approaches are needed to understand the relationship between microbes and anemia in an epidemiological context, this study suggests that investigating nutritional status and pathogen exposure is key to better understanding the gut microbiome and impact of iron fortification.

Potential effects of nutrition-induced alteration of gut microbiota on inflammatory bowel disease: A review

Inflammatory bowel disease (IBD), mainly comprising ulcerative colitis and Crohn's disease, is a group of gradually progressive diseases bringing significant mental anguish and imposes serious economic burdens. Interplay of genetic, environmental, and immunological factors have been implicated in its pathogenesis. Nutrients, as crucial environmental determinants, mainly encompassing carbohydrates, fats, proteins, and micronutrients, are closely related to the pathogenesis and development of IBD. Nutrition is essential for maintaining the dynamic balance of intestinal eco-environments to ensure intestinal barrier and immune homeostasis, while this balance can be disrupted easily by maladjusted nutrition. Research has firmly established that nutrition has the potential to shape the composition and function of gut microbiota to affect the disease course. Unhealthy diet and eating disorders lead to gut microbiota dysbiosis and further destroy the function of intestinal barrier such as the disruption of membrane integrity and increased permeability, thereby triggering intestinal inflammation. Notably, appropriate nutritional interventions, such as the Mediterranean diet, can positively modulate intestinal microecology, which may provide a promising strategy for future IBD prevention. In this review, we provide insights into the interplay between nutrition and gut microbiota and its effects on IBD and present some previously overlooked lines of evidence regarding the role of derived metabolites in IBD processes, such as trimethylamine N-oxide and imidazole propionate. Furthermore, we provide some insights into reducing the risk of onset and exacerbation of IBD by modifying nutrition and discuss several outstanding challenges and opportunities for future study.

Prebiotics increase iron absorption and reduce the adverse effects of iron on the gut microbiome and inflammation: a randomized controlled trial using iron stable isotopes in Kenyan infants

BACKGROUND

Iron fortificants tend to be poorly absorbed and may adversely affect the gut, especially in African children.

OBJECTIVE

We assessed the effects of prebiotic galacto-oligosaccharides/fructo-oligosaccharides (GOS/FOS) on iron absorption and gut health when added to iron-fortified infant cereal.

METHODS

We randomly assigned Kenyan infants (n = 191) to receive daily for 3 wk a cereal containing iron and 7.5 g GOS/FOS (7.5 g+iron group), 3 g (3-g+iron group) GOS/FOS, or no prebiotics (iron group). A subset of infants in the 2 prebiotic+iron groups (n = 66) consumed 4 stable iron isotope-labeled test meals without and with prebiotics, both before and after the intervention. Primary outcome was fractional iron absorption (FIA) from the cereal with or without prebiotics regardless of dose, before and after 3 wk of consumption. Secondary outcomes included fecal gut microbiota, iron and inflammation status, and effects of prebiotic dose.

RESULTS

Median (25th-75th percentiles) FIAs from meals before intervention were as follows: 16.3% (8.0%-27.6%) without prebiotics compared with 20.5% (10.4%-33.4%) with prebiotics (Cohen d = 0.53; P < 0.001). FIA from the meal consumed without prebiotics after intervention was 22.9% (8.5%-32.4%), 41% higher than from the meal without prebiotics before intervention (Cohen d = 0.36; P = 0.002). FIA from the meal consumed with prebiotics after intervention was 26.0% (12.2%-36.1%), 60% higher than from the meal without prebiotics before intervention (Cohen d = 0.45; P = 0.007). After 3 wk, compared with the iron group, the following results were observed: 1) Lactobacillus sp. abundances were higher in both prebiotic+iron groups (P < 0.05); 2) Enterobacteriaceae sp. abundances (P = 0.022) and the sum of pathogens (P < 0.001) were lower in the 7.5-g+iron group; 3) the abundance of bacterial toxin-encoding genes was lower in the 3-g+iron group (false discovery rate < 0.05); 4) fecal pH (P < 0.001) and calprotectin (P = 0.033) were lower in the 7.5-g+iron group.

CONCLUSIONS

Adding prebiotics to iron-fortified infant cereal increases iron absorption and reduces the adverse effects of iron on the gut microbiome and inflammation in Kenyan infants. This trial was registered at clinicaltrials.gov as NCT03894358.

Efficacy of polysaccharide iron complex in IDA rats: A comparative study with iron protein succinylate and ferrous succinate

Iron deficiency anemia (IDA) is the most common nutrient-related health problem in the world. There is still a lack of comprehensive comparative study on the efficacies of commonly used iron supplements such as polysaccharide iron complex (PIC), iron protein succinylate (IPS) and ferrous succinate (FS) for IDA. In this study, we compared the PIC, IPS and FS efficacies in IDA rats via intragastric administration. The results showed that the three iron supplements had similar efficacies. PIC/IPS/FS at a dose of 15 mg Fe/kg/d for 10 d increased the hematological and serum biochemical parameters to 2.15/2.12/2.18 (Hb), 1.71/1.67/1.69 (RBC), 2.10/2.11/2.12 (HCT), 1.26/1.22/1.22 (MCV), all 1.34 (MCH), 1.15/1.15/1.14 (MCHC), 1.94/1.82/1.91 (SF), 9.75/9.67/9.53 (SI), and 23.30/22.68/21.64 (TS) times, and reduced TIBC to 0.42/0.43/0.44 times, compared to untreated IDA rats. PIC performed slightly better than IPS and FS in restoring MCV level. Meanwhile, the heart, spleen and kidney coefficients reduced to 67%/74%/65% (heart), all 59% (spleen) and 87%/88%/88% (kidney), and the liver coefficient increased to 116%/115%/116%, compared to untreated IDA rats. The liver iron content was found to be more affected by IDA than the spleen iron content. PIC/IPS/FS at 15 mg Fe/kg/d increased organ iron contents to 4.20/3.97/4.03 times (liver) and 1.36/1.24/1.41 times (spleen) within 10 d compared to untreated IDA rats, and PIC-H and FS were slightly better than IPS in restoring spleen iron content. The results of this study can provide useful data information for the comparison of three iron supplements, PIC, IPS and FS.

Impact on oxidative stress of oral, high-dose, iron supplementation for management of iron deficiency after bariatric surgery, a preliminary study

OBJECTIVES

High-dose oral iron supplementation for patients who develop iron deficiency after bariatric surgery may induce oxidative stress in the gastrointestine. The study's objective was to test this hypothesis by determining the impact of high-dose oral iron on systemic oxidative stress.

METHODS

We used archived plasma samples from a randomized controlled clinical trial (NCT02404012) comparing FeSO4 (195 mg/day, NatureMade®, West Hills, CA) with a heme iron polypeptide (HIP, 60.4 mg/day, Proferrin®, Colorado Biolabs, Lafayette, CO) for 8 weeks. Systemic oxidative stress was measured using malondialdehyde and total antioxidant capacity (MDA, Abcam, ab238537 and TAC, Abcam, ab65329 Cambridge, UK) assays. Data was log-transformed and presented as means and standard deviations; a mixed model was used to determine the effects of time (0, 2, 4, and 8 weeks) and treatment (FeSO4 versus HIP) on oxidative stress.

RESULTS

The FeSO4 (N = 8) and HIP (N = 5) participants were balanced in body mass index (35.0 ± 5.5 kg/m2), race (93 % White), time post-surgery (7.3 ± 3.3 years), as well as serum concentrations of iron (P > 0.05). The FeSO4 group tended to be older (44.3 ± 4.5 years) and they had lower concentrations of serum ferritin (6.5 ± 2.7 µg/mL) than the HIP (38.2 ± 9.3 years, and 12.9 ± 16.8 µg/mL) group (P = 0.080, and P = 0.017 respectively). We observed a larger increase in serum iron in the FeSO4 group during the 8 weeks of Fe supplementation, compared to that in the HIP group (p = 0.004). We observed a decreasing trend in MDA over the 8 weeks (p = 0.080) in the FeSO4 treatment group. There were no significant differences in TAC between and within FeSO4 and HIP groups over the 8 week supplementation period.

CONCLUSIONS

This preliminary study suggests that high-dose oral iron supplementation for iron deficiency does not adversely impact systemic oxidative stress in patients undergoing bariatric surgery.

Association of iron therapy with incidence of chronic kidney disease

OBJECTIVE

We investigated the association of oral iron replacement with the incidence of chronic kidney disease (CKD) in a population with normal kidney function to study the effects of iron replacement on the development of new onset CKD.

METHODS

In a national cohort of US Veterans with no pre-existing CKD, we identified 33 894 incident new users of oral iron replacement and a comparable group of 112 780 patients who did not receive any iron replacement during 2004-2018. We examined the association of oral iron replacement versus no iron replacement with the incidence of eGFR <60 mL/min/1.73 m2 and the incidence of urine albumin creatinine ratio (UACR) ≥30 mg/g in competing risk regressions and in Cox models. We used propensity score weighing to account for differences in key baseline characteristics associated with the use of oral iron replacement.

RESULTS

In the cohort of 146 674 patients, a total of 18 547 (13%) patients experienced incident eGFR <60 mL/min/1.73 m2 , and 16 117 patients (11%) experienced new onset UACR ≥30 mg/g. Oral iron replacement was associated with significantly higher risk of incident eGFR <60 mL/min/1.73 m2 (subhazard ratio, 95% confidence interval [CI]: 1.3 [1.22-1.38], p < .001) and incident albuminuria (subhazard ratio, 95% CI: 1.14 [1.07-1.22], p < .001).

CONCLUSION

Oral iron replacement is associated with higher risk of new onset CKD. The long-term kidney safety of oral iron replacement should be tested in clinical trials.

The effect of iron therapy on oxidative stress and intestinal microbiota in inflammatory bowel diseases: A review on the conundrum

One in five patients with Inflammatory Bowel Disease (IBD) suffers from anemia, most frequently caused by iron deficiency. Anemia and iron deficiency are associated with worse disease outcomes, reduced quality of life, decreased economic participation, and increased healthcare costs. International guidelines and consensus-based recommendations have emphasized the importance of treating anemia and iron deficiency. In this review, we draw attention to the rarely discussed effects of iron deficiency and iron therapy on the redox status, the intestinal microbiota, and the potential interplay between them, focusing on the clinical implications for patients with IBD. Current data are scarce, inconsistent, and do not provide definitive answers. Nevertheless, it is imperative to rule out infections and discern iron deficiency anemia from other types of anemia to prevent untargeted oral or intravenous iron supplementation and potential side effects, including oxidative stress. Further research is necessary to establish the clinical significance of changes in the redox status and the intestinal microbiota following iron supplementation.

Enhancing the antibacterial function of probiotic Escherichia coli Nissle: when less is more

Probiotic bacteria confer multiple health benefits, including preventing the growth, colonization, or carriage of harmful bacteria in the gut. Bacteriocins are antibacterial peptides produced by diverse bacteria, and their production is tightly regulated and coordinated at the transcriptional level. A popular strategy for enhancing the antibacterial properties of probiotic bacteria is to retrofit them with the ability to overproduce heterologous bacteriocins. This is often achieved from non-native constitutive promoters or in response to host or pathogen signal from synthetic promoters. How the dysregulated overproduction of heterologous bacteriocins affects the fitness and antibacterial efficacy of the retrofitted probiotic bacteria is often overlooked. We have conferred the prototypical probiotic Escherichia coli strain Nissle (EcN) the ability to produce microcin C (McC) from the wild-type promoter and two mutant promoters that allow, relative to the wild-type promoter, high and low amounts of McC production. This was done by introducing specific changes to the sequence of the wild-type promoter driving transcription of the McC operon while ensuring that the modified promoters respond to native regulation. By studying the transcriptomic responses and antibacterial efficacy of the retrofitted EcN bacteria in a Galleria mellonella infection model of enterohemorrhagic E. coli, we show that EcN bacteria that produce the lowest amount of McC display the highest antibacterial efficacy with little-to-none undesired collateral impact on their fitness. The results highlight considerations researchers may take into account when retrofitting probiotic bacteria with heterogenous gene products for therapeutic, prophylactic, or diagnostic applications. Bacteria that resist killing by antibiotics are a major risk to modern medicine. The use of beneficial "probiotic" bacteria to make antibiotic-like compounds at the site of infection in the body is emerging as a popular alternative to the use of conventional antibiotics. A potential drawback of engineering probiotic bacteria in this way is that producing antibiotic-like compounds could impart undesired side effects on the performance of such bacteria, thereby compromising their intended use. This study highlights considerations researchers may take into account when engineering probiotic bacteria for therapeutic, prophylactic, or diagnostic applications.

Multi-site microbiota alteration is a hallmark of kidney stone formation

BACKGROUND

Inquiry of microbiota involvement in kidney stone disease (KSD) has largely focussed on potential oxalate handling abilities by gut bacteria and the increased association with antibiotic exposure. By systematically comparing the gut, urinary, and oral microbiota of 83 stone formers (SF) and 30 healthy controls (HC), we provide a unified assessment of the bacterial contribution to KSD.

RESULTS

Amplicon and shotgun metagenomic sequencing approaches were consistent in identifying multi-site microbiota disturbances in SF relative to HC. Biomarker taxa, reduced taxonomic and functional diversity, functional replacement of core bioenergetic pathways with virulence-associated gene markers, and community network collapse defined SF, but differences between cohorts did not extend to oxalate metabolism.

CONCLUSIONS

We conclude that multi-site microbiota alteration is a hallmark of SF, and KSD treatment should consider microbial functional restoration and the avoidance of aberrant modulators such as poor diet and antibiotics where applicable to prevent stone recurrence. Video Abstract.

Mothers' Breast Milk Composition and Their Respective Infant's Gut Microbiota Differ between Five Distinct Rural and Urban Regions in Vietnam

Microbiota colonization and development in early life is impacted by various host intrinsic (genetic) factors, but also diet, lifestyle, as well as environmental and residential factors upon and after birth. To characterize the impact of maternal nutrition and environmental factors on vaginally born infant gut microbiota composition, we performed an observational study in five distinct geographical areas in Vietnam. Fecal samples of infants (around 39 days old) and fecal and breast milk samples of their mothers (around 28 years) were collected. The microbiota composition of all samples was analyzed by 16S rRNA gene Illumina sequencing and a bioinformatics workflow based on QIIME. In addition, various breast milk components were determined. Strong associations between the geographically determined maternal diet and breast milk composition as well as infant fecal microbiota were revealed. Most notable was the association of urban Ha Noi with relatively high abundances of taxa considered pathobionts, such as Klebsiella and Citrobacter, at the expense of Bifidobacterium. Breast milk composition was most distinct in rural Ha Long Bay, characterized by higher concentrations of, e.g., docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), selenium, and vitamin B12, while it was characterized by, e.g., iron, zinc, and α-linolenic acid (ALA) in Ha Noi. Breast milk iron levels were positively associated with infant fecal Klebsiella and negatively with Bifidobacterium, while the EPA and DHA levels were positively associated with Bifidobacterium. In conclusion, differences between five regions in Vietnam with respect to both maternal breast milk and infant gut microbiota composition were revealed, most likely in part due to maternal nutrition. Thus, there could be opportunities to beneficially steer infant microbiota development in a more desired (rural instead of urban) direction through the mother's diet.

Association of oral iron replacement therapy with kidney failure and mortality in CKD patients

Background

Oral iron is the predominant route of iron replacement (IRT) but its benefits and safety are unclear in patients with chronic kidney disease (CKD).

Methods

We examined the association of oral IRT vs no IRT with end-stage kidney disease (ESKD) and mortality in a national cohort of US Veterans. We identified 17 413 incident new users of oral IRT with estimated glomerular filtration rates <60 mL/min/1.73 m2 and 32 530 controls who did not receive any IRT during 2004-18. We used propensity score-overlap weighting to account for differences in key baseline characteristics associated with the use of oral IRT. We examined associations using competing risk regression and Cox models.

Results

In the cohort of 49 943 patients, 1616 (3.2%) patients experienced ESKD and 28 711 (57%) patients died during a median follow-up of 1.9 years. Oral IRT was not associated with ESKD [subhazard ratio (HR) (95% confidence interval, CI) 1.00 (0.84-1.19), P = .9] and was associated with higher risk of all-cause mortality [HR (95% CI) 1.06 (1.01-1.11), P = .01]. There was significant heterogeneity of treatment effect for mortality, with oral IRT associated with higher mortality in the subgroups of patients without congestive heart failure (CHF), anemia or iron deficiency. In patient with blood hemoglobin <10 g/dL oral IRT was associated with significantly lower mortality.

Conclusion

Oral IRT was associated with lower mortality only in patients with anemia. In patients without anemia, iron deficiency or CHF, the risk-benefit ratio of oral IRT should be further examined.

Robbing the thief

Salmonella employs an arsenal of different tools to obtain iron. In this issue of Cell Host & Microbe, Spiga et al. add to these mechanisms, revealing that commensal Bacteroides species use a specialized lipoprotein to acquire catecholate siderophores from Enterobacteriaceae, only to have them reacquired by Salmonella.

Dietary iron regulates intestinal goblet cell function and alleviates Salmonella typhimurium invasion in mice

Iron is an important micronutrient that plays a vital role in host defenses and bacterial pathogenicity. As iron treatments increase the risk of infection by stimulating the growth and virulence of bacterial pathogens, their roles in anti-infection immunity have frequently been underestimated. To estimate whether adequate dietary iron intake would help defend against pathogenic bacterial infection, mice were fed iron-deficient (2 mg kg-1 feed), iron-sufficient (35 mg kg-1 feed), or iron-enriched diet (350 mg kg-1 feed) for 12 weeks, followed by oral infection with Salmonella typhimurium. Our results revealed that dietary iron intake improved mucus layer function and decelerated the invasion of the pathogenic bacteria, Salmonella typhimurium. Positive correlations between serum iron and the number of goblet cells and mucin2 were found in response to total iron intake in mice. Unabsorbed iron in the intestinal tract affected the gut microbiota composition, and the abundance of Bacteroidales, family Muribaculaceae, was positively correlated with their mucin2 expression. However, the results from antibiotic-treated mice showed that the dietary iron-regulated mucin layer function was not microbial-dependent. Furthermore, in vitro studies revealed that ferric citrate directly induced mucin2 expression and promoted the proliferation of goblet cells in both ileal and colonic organoids. Thus, dietary iron intake improves serum iron levels, regulates goblet cell regeneration and mucin layer function, and plays a positive role in the prevention of pathogenic bacteria.

Is a Lower Dose of More Bioavailable Iron (18-mg Ferrous Bisglycinate) Noninferior to 60-mg Ferrous Sulfate in Increasing Ferritin Concentrations While Reducing Gut Inflammation and Enteropathogen Detection in Cambodian Women? A Randomized Controlled Noninferiority Trial

BACKGROUND

Global guidelines recommend untargeted iron supplementation for women in regions of anemia prevalence ≥40%, such as Cambodia. However, the potential harms of untargeted iron on the gut have not been rigorously studied in women and likely vary depending on iron dose and form.

OBJECTIVES

We investigated if a lower dose of a highly bioavailable iron amino acid chelate was as effective as the standard dose of iron salts in increasing ferritin concentrations and whether any differences were observed in gut inflammation or enteropathogen detection.

METHODS

A double-blind, randomized placebo-controlled noninferiority trial was conducted in Cambodia. Nonpregnant women (n = 480, 18-45 y) were randomly assigned to 60-mg ferrous sulfate, 18-mg ferrous bisglycinate, or placebo for 12 wk. Nonfasting blood and stool specimens were collected at baseline and 12 wk. Ferritin and fecal calprotectin were measured with an ELISA. A molecular assay was used to detect 11 enteropathogens in a random subset of n = 100 women. Generalized linear mixed-effects models were used to estimate the adjusted mean difference in ferritin concentrations at 12 wk (primary outcome), as compared with our 'a priori' noninferiority margin of 20 μg/L.

RESULTS

Baseline anemia and iron deficiency prevalence was low (17% and 6%, respectively). The adjusted mean difference in ferritin concentrations between the iron groups was 14.6 (95% confidence interval [CI]: 7.6, 21.6) μg/L. Mean ferritin concentration at 12 wk was higher in the ferrous sulfate (99 [95% CI: 95, 103] μg/L, P < 0.001) than in ferrous bisglycinate (84 [95% CI: 80, 88] μg/L) and placebo groups (78 [95% CI: 74, 82] μg/L). No differences in fecal calprotectin concentrations or enteropathogen detection were observed across groups at 12 wk.

CONCLUSIONS

Ferrous bisglycinate (18-mg) was not as effective as ferrous sulfate (60-mg) in increasing ferritin concentrations and did not differentially influence biomarkers of gut health in this predominantly iron-replete population of Cambodian women. This trial was registered at clinicaltrials.gov registry as NCT04017598.

Saliva as Biomarker for Oral and Chronic Degenerative Non-Communicable Diseases

Saliva is a very complex fluid and it is essential to maintain several physiological processes and functions, including oral health, taste, digestion and immunological defenses. Saliva composition and the oral microbiome can be influenced by several factors, like diet and smoking habits, and their alteration can represent an important access point for pathogens and, thus, for systemic illness onset. In this review, we explore the potentiality of saliva as a new tool for the early detection of some pathological conditions, such as oral diseases, chronic degenerative non-communicable diseases, among these chronic kidney disease (CKD). We also examined the possible correlation between oral and systemic diseases and oral and gut microbiota dysbiosis. In particular, we deeply analyzed the relationship between oral diseases and CKD. In this context, some salivary parameters can represent a new device to detect either oral or systemic pathologies. Moreover, the positive modulation of oral and gut microbiota induced by prebiotics, postbiotics, or symbiotics could represent a new possible adjuvant therapy in the clinical management of oral diseases and CKD.

Bacteria from the gut influence the host micronutrient status

Micronutrient deficiencies or "hidden hunger" remains a serious public health problem in most low- and middle-income countries, with severe consequences for child development. Traditional methods of treatment and prevention, such as supplementation and fortification, have not always proven to be effective and may have undesirable side-effects (i.e., digestive troubles with iron supplementation). Commensal bacteria in the gut may increase bioavailability of specific micronutrients (i.e., minerals), notably by removing anti-nutritional compounds, such as phytates and polyphenols, or by the synthesis of vitamins. Together with the gastrointestinal mucosa, gut microbiota is also the first line of protection against pathogens. It contributes to the reinforcement of the integrity of the intestinal epithelium and to a better absorption of micronutrients. However, its role in micronutrient malnutrition is still poorly understood. Moreover, the bacterial metabolism is also dependent of micronutrients acquired from the gut environment and resident bacteria may compete or collaborate to maintain micronutrient homeostasis. Gut microbiota composition can therefore be modulated by micronutrient availability. This review brings together current knowledge on this two-way relationship between micronutrients and gut microbiota bacteria, with a focus on iron, zinc, vitamin A and folate (vitamin B9), as these deficiencies are public health concerns in a global context.

A Diet Enriched with Lacticaseibacillus rhamnosus HN001 and Milk Fat Globule Membrane Alters the Gut Microbiota and Decreases Amygdala GABA a Receptor Expression in Stress-Sensitive Rats

Brain signalling pathways involved in subclinical anxiety and depressed mood can be modulated via the gut brain axis (GBA), providing the potential for diet and dietary components to affect mood. We investigated behavioural, physiological and gut microbiome responses to the Lacticaseibacillus rhamnosus strain HN001 (LactoB HN001™), which has been shown to reduce postpartum anxiety and depression, and a milk fat globule membrane-enriched product, Lipid 70 (Surestart^TM MFGM Lipid 70), which has been implicated in memory in stress-susceptible Wistar Kyoto rats. We examined behaviour in the open field, elevated plus maze and novel object recognition tests in conjunction with the expression of host genes in neuro-signalling pathways, and we also assessed brain lipidomics. Treatment-induced alterations in the caecal microbiome and short-chain fatty acid (SCFA) profiles were also assessed. Neither ingredient induced behavioural changes or altered the brain lipidome (separately or when combined). However, with regard to brain gene expression, the L. rhamnosus HN001 + Lipid 70 combination produced a synergistic effect, reducing GABAA subunit expression in the amygdala (Gabre, Gat3, Gabrg1) and hippocampus (Gabrd). Treatment with L. rhamnosus HN001 alone altered expression of the metabotropic glutamate receptor (Grm4) in the amygdala but produced only minor changes in gut microbiota composition. In contrast, Lipid 70 alone did not alter brain gene expression but produced a significant shift in the gut microbiota profile. Under the conditions used, there was no observed effect on rat behaviour for the ingredient combination. However, the enhancement of brain gene expression by L. rhamnosus HN001 + Lipid 70 implicates synergistic actions on region-specific neural pathways associated with fear, anxiety, depression and memory. A significant shift in the gut microbiota profile also occurred that was mainly attributable to Lipid 70.

Effectiveness of low-dose iron treatment in non-anaemic iron-deficient women: a prospective open-label single-arm trial

BACKGROUND

Iron deficiency without anaemia is highly prevalent and is particularly associated with fatigue, cognitive impairment, or poor physical endurance. Standard oral iron therapy often results in intestinal irritation with associated side effects and premature discontinuation of therapy, therefore, optimal oral iron therapy with sufficient iron absorption and minimal side effects is desirable.

METHODS

Thirty-six iron-deficient non-anaemic premenopausal women (serum ferritin ≤30 ng/ml, haemoglobin ≥117 g/l) with normal body mass index (BMI) and no hypermenorrhea received 6 mg of elemental oral iron (corresponding to 18.6 mg ferrous sulphate) twice daily for 8 weeks.

RESULTS

Participants treated with low-dose iron had an average age of 28 years and a BMI of 21 kg/m2. Their serum ferritin and haemoglobin increased significantly from 18 ng/ml to 33 ng/ml (p <0.001) and from 135 g/l to 138 g/l (p = 0.014), respectively. Systolic blood pressure increased from 114 mmHg to 120 mmHg (p = 0.003). Self-reported health status improved after 8 weeks (p <0.001) and only one woman reported gastrointestinal side effects (3%).

CONCLUSION

This prospective open-label single-arm trial shows that oral iron treatment of 6 mg of elemental iron twice daily over 8 weeks is effective in iron-deficient non-anaemic women. Due to the negligible side effects, low-dose iron treatment is a valuable therapeutic option for iron-deficient non-anaemic women with normal BMI and menstruation. Further placebo-controlled studies with a larger number of participants are needed to confirm these results.

CLINICALTRIALS

gov NCT04636060.

Gut microbiota interspecies interactions shape the response of Clostridioides difficile to clinically relevant antibiotics

In the human gut, the growth of the pathogen Clostridioides difficile is impacted by a complex web of interspecies interactions with members of human gut microbiota. We investigate the contribution of interspecies interactions on the antibiotic response of C. difficile to clinically relevant antibiotics using bottom-up assembly of human gut communities. We identify 2 classes of microbial interactions that alter C. difficile's antibiotic susceptibility: interactions resulting in increased ability of C. difficile to grow at high antibiotic concentrations (rare) and interactions resulting in C. difficile growth enhancement at low antibiotic concentrations (common). Based on genome-wide transcriptional profiling data, we demonstrate that metal sequestration due to hydrogen sulfide production by the prevalent gut species Desulfovibrio piger increases the minimum inhibitory concentration (MIC) of metronidazole for C. difficile. Competition with species that display higher sensitivity to the antibiotic than C. difficile leads to enhanced growth of C. difficile at low antibiotic concentrations due to competitive release. A dynamic computational model identifies the ecological principles driving this effect. Our results provide a deeper understanding of ecological and molecular principles shaping C. difficile's response to antibiotics, which could inform therapeutic interventions.

Gut Microbiota in Anxiety and Depression: Unveiling the Relationships and Management Options

The gut microbiota is critical for maintaining human health and the immunological system. Several neuroscientific studies have shown the significance of microbiota in developing brain systems. The gut microbiota and the brain are interconnected in a bidirectional relationship, as research on the microbiome-gut-brain axis shows. Significant evidence links anxiety and depression disorders to the community of microbes that live in the gastrointestinal system. Modified diet, fish and omega-3 fatty acid intake, macro- and micro-nutrient intake, prebiotics, probiotics, synbiotics, postbiotics, fecal microbiota transplantation, and 5-HTP regulation may all be utilized to alter the gut microbiota as a treatment approach. There are few preclinical and clinical research studies on the effectiveness and reliability of various therapeutic approaches for depression and anxiety. This article highlights relevant research on the association of gut microbiota with depression and anxiety and the different therapeutic possibilities of gut microbiota modification.

Development and Characterization of Pullulan-Based Orodispersible Films of Iron

Iron deficiency is the principal cause of nutritional anemia and it constitutes a major health problem, especially during pregnancy. Despite the availability of various non-invasive traditional oral dosage forms such as tablets, capsules, and liquid preparations of iron, they are hard to consume for special populations such as pregnant women, pediatric, and geriatric patients with dysphagia and vomiting tendency. The objective of the present study was to develop and characterize pullulan-based iron-loaded orodispersible films (i-ODFs). Microparticles of iron were formulated by a microencapsulation technique, to mask the bitter taste of iron, and ODFs were fabricated by a modified solvent casting method. Morphological characteristics of the microparticles were identified by optical microscopy and the percentage of iron loading was evaluated by inductively coupled plasma optical emission spectroscopy (ICP-OES). The fabricated i-ODFs were evaluated for their morphology by scanning electron microscopy. Other parameters including thickness, folding endurance, tensile strength, weight variation, disintegration time, percentage moisture loss, surface pH, and in vivo animal safety were evaluated. Lastly, stability studies were carried out at a temperature of 25 °C/60% RH. The results of the study confirmed that pullulan-based i-ODFs had good physicochemical properties, excellent disintegration time, and optimal stability at specified storage conditions. Most importantly, the i-ODFs were free from irritation when administered to the tongue as confirmed by the hamster cheek pouch model and surface pH determination. Collectively, the present study suggests that the film-forming agent, pullulan, could be successfully employed on a lab scale to formulate orodispersible films of iron. In addition, i-ODFs can be processed easily on a large scale for commercial use.

Effect of Intravenous Ferric Carboxymaltose on Exercise Capacity After Kidney Transplantation (EFFECT-KTx): rationale and study protocol for a double-blind, randomised, placebo-controlled trial

INTRODUCTION

Iron deficiency (ID) is common and has been associated with an excess mortality risk in kidney transplant recipients (KTRs). In patients with chronic heart failure and ID, intravenous iron improves exercise capacity and quality of life. Whether these beneficial effects also occur in KTRs is unknown. The main objective of this trial is to address whether intravenous iron improves exercise tolerance in iron-deficient KTRs.

METHODS AND ANALYSIS

The Effect of Ferric Carboxymaltose on Exercise Capacity after Kidney Transplantation study is a multicentre, double-blind, randomised, placebo-controlled clinical trial that will include 158 iron-deficient KTRs. ID is defined as plasma ferritin <100 µg/L or plasma ferritin 100-299 µg/L with transferrin saturation <20%. Patients are randomised to receive 10 mL of ferric carboxymaltose (50 mg Fe³⁺/mL, intravenously) or placebo (0.9% sodium chloride solution) every 6 weeks, four dosages in total. The primary endpoint is change in exercise capacity, as quantified by the 6 min walk test, between the first study visit and the end of follow-up, 24 weeks later. Secondary endpoints include changes in haemoglobin levels and iron status, quality of life, systolic and diastolic heart function, skeletal muscle strength, bone and mineral parameters, neurocognitive function and safety endpoints. Tertiary (explorative) outcomes are changes in gut microbiota and lymphocyte proliferation and function.

ETHICS AND DISSEMINATION

The protocol of this study has been approved by the medical ethical committee of the University Medical Centre Groningen (METc 2018/482;) and is being conducted in accordance with the principles of the Declaration of Helsinki, the Standard Protocol Items: Recommendations for Interventional Trials checklist and the Good Clinical Practice guidelines provided by the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use. Study results will be disseminated through publications in peer-reviewed journals and conference presentations.

TRIAL REGISTRATION NUMBER

NCT03769441.

The Chelating Ability of Plant Polyphenols Can Affect Iron Homeostasis and Gut Microbiota

In the past decades, many studies have widely examined the effects of dietary polyphenols on human health. Polyphenols are well known for their antioxidant properties and for their chelating abilities, by which they can be potentially employed in cases of pathological conditions, such as iron overload. In this review, we have highlighted the chelating abilities of polyphenols, which are due to their structural specific sites, and the differences for each class of polyphenols. We have also explored how the dietary polyphenols and their iron-binding abilities can be important in inflammatory/immunomodulatory responses, with a special focus on the involvement of macrophages and dendritic cells, and how they might contribute to reshape the gut microbiota into a healthy profile. This review also provides evidence that the axes “polyphenol–iron metabolism–inflammatory responses” and “polyphenol–iron availability–gut microbiota” have not been very well explored so far, and the need for further investigation to exploit such a potential to prevent or counteract pathological conditions.

The Prevention of Inflammation and the Maintenance of Iron and Hepcidin Homeostasis in the Gut, Liver, and Brain Pathologies

The human gut microbiome consists of a variety of microorganisms that inhabit the intestinal tract. This flora has recently been shown to play an important role in human disease. The crosstalk between the gut and brain axis has been investigated through hepcidin, derived from both hepatocytes and dendritic cells. Hepcidin could potentially play an anti-inflammatory role in the process of gut dysbiosis through a means of either a localized approach of nutritional immunity, or a systemic approach. Like hepcidin, mBDNF and IL-6 are part of the gut-brain axis: gut microbiota affects their levels of expression, and this relationship is thought to play a role in cognitive function and decline, which could ultimately lead to a number of neurodegenerative diseases such as Alzheimer's disease. This review will focus on the interplay between gut dysbiosis and the crosstalk between the gut, liver, and brain and how this is mediated by hepcidin through different mechanisms including the vagus nerve and several different biomolecules. This overview will also focus on the gut microbiota-induced dysbiotic state on a systemic level, and how gut dysbiosis can contribute to beginnings and the progression of Alzheimer's disease and neuroinflammation.

Siderophore-Linked Ruthenium Catalysts for Targeted Allyl Ester Prodrug Activation within Bacterial Cells

Due to rising resistance, new antibacterial strategies are needed, including methods for targeted antibiotic release. As targeting vectors, chelating molecules called siderophores that are released by bacteria to acquire iron have been investigated for conjugation to antibacterials, leading to the clinically approved drug cefiderocol. The use of small-molecule catalysts for prodrug activation within cells has shown promise in recent years, and here we investigate siderophore-linked ruthenium catalysts for the activation of antibacterial prodrugs within cells. Moxifloxacin-based prodrugs were synthesised, and their catalyst-mediated activation was demonstrated under anaerobic, biologically relevant conditions. In the absence of catalyst, decreased antibacterial activities were observed compared to moxifloxacin versus Escherichia coli K12 (BW25113). A series of siderophore-linked ruthenium catalysts were investigated for prodrug activation, all of which displayed a combinative antibacterial effect with the prodrug, whereas a representative example displayed little toxicity against mammalian cell lines. By employing complementary bacterial growth assays, conjugates containing siderophore units based on catechol and azotochelin were found to be most promising for intracellular prodrug activation.

The role of oral iron in the treatment of adults with iron deficiency

Iron deficiency is the most common nutrient deficiency in the world, affecting over 20% of premenopausal women worldwide. Oral iron supplementation is often the first-line treatment for the acute and chronic management of iron deficiency due to its ease and accessibility. However, there is no consensus on the optimal formulation or dosing strategy, or which patients should be preferentially treated with intravenous iron. Management of iron deficiency is complicated by the hepcidin-ferroportin iron regulatory pathway, which has evolved to prevent iron overload and thereby creates an inherent limit on gastrointestinal iron uptake and efficacy of oral iron. Unabsorbed iron propagates many of the side effects that complicate oral iron use including dyspepsia and constipation, all of which can thus be exacerbated by excessive oral iron doses. Daily low dose and every other day dosing protocols have attempted to bypass this physiologic bottleneck to allow for effective absorption and limit side effects; however, this approach has still resulted in low fractional iron absorption. In the following manuscript, we review the pathophysiology of iron absorption and current evidence for various preparations of oral iron. Lastly, we highlight opportunities for further study to advance the care of individuals affected by iron deficiency.

nZVI-induced iron poisoning aggravated the toxicity of TCEP to earthworm in soil

Tris (2-chloroethyl) phosphate (TCEP) is a newly developed organophosphorus flame retardant that has been increasingly detected in soil as a contaminant. Nanoremediation is a potential solution for the control of TCEP, while the effectiveness and ecological risks are poorly understood. Here, we investigated the physicochemical interactions and joint toxicity of nano zero-valent iron (nZVI) (50-5000 mg/kg) and TCEP (50-5000 μg/kg) at environmental relevant concentrations to earthworms (Eisenia fetida) in soil. During a 28-d exposure, TCEP in soil was neither self-degraded nor removed by nZVI, and the individual toxicity of TCEP on the physiology of earthworms was significantly higher than that of nZVI. Notably, nZVI was found to synergize the toxicity of TCEP to earthworms without showing the classical "Trojan horse effect". Mechanically, TCEP mainly induced a typical neurotoxicity, and indirectly inhibited the food ingestion and growth performance of earthworms; nZVI induced iron poisoning aggravated the intestinal damage and directly inhibited the energy metabolism, therefore exacerbated the TCEP-induced malnutrition. Our findings provide new insights into the toxic mechanisms of nZVI-TCEP co-exposure to soil organisms, and emphasize the necessity of risk assessment and cautious usage of nanoremediation in newly emerged contaminations.

Ferric citrate-induced colonic mucosal damage associated with oxidative stress, inflammation responses, apoptosis, and the changes of gut microbial composition

Ferric citrate (FC) has been used as an iron fortifier and nutritional supplement, which is reported to induce colitis in rats, however the underlying mechanism remains to be elucidated. We performed a 16-week study of FC in male healthy C57BL/6 mice (nine-month-old) with oral administration of Ctr (0.9 % NaCl), 1.25 % FC (71 mg/kg/bw), 2.5 % FC (143 mg/kg/bw) and 5 % FC (286 mg/kg/bw). FC-exposure resulted in colon iron accumulation, histological alteration and reduce antioxidant enzyme activities, such as glutathione (GSH), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and total antioxidant capacity (T-AOC), together with enhanced lipid peroxidation level, including malondialdehyde (MDA) level and 4-Hydroxynonenal (4-HNE) protein expression. Exposure to FC was associated with upregulated levels of the interleukin (IL)- 6, IL-1β, IL-18, IL-8 and tumor necrosis factor α (TNF-α), while down-regulated levels of IL-4 and IL-10. Exposure to FC was positively associated with the mRNA and protein expressions of cysteine-aspartic proteases (Caspase)- 9, Caspase-3, Bcl-2-associated X protein (Bax), while negatively associated with B-cell lymphoma 2 (Bcl2) in mitochondrial apoptosis signaling pathway. FC-exposure changed the diversity and composition of gut microbes. Additionally, the serum lipopolysaccharide (LPS) contents increased in FC-exposed groups when compared with the control group, while the expression of colonic tight junction proteins (TJPs), such as Claudin-1 and Occludin were decreased. These findings indicate that the colonic mucosal injury induced by FC-exposure are associated with oxidative stress generation, inflammation response and cell apoptosis, as well as the changes in gut microbes diversity and composition.

Iron in infectious diseases friend or foe?: The role of gut microbiota

Iron is a trace element involved in metabolic functions for all organisms, from microorganisms to mammalians. Iron deficiency is a prevalent health problem that affects billions of people worldwide, and iron overload could have some hazardous effect. The complex microbial community in the human body, also called microbiota, influences the host immune defence against infections. An imbalance in gut microbiota, dysbiosis, changes the host's susceptibility to infections by regulating the immune system. In recent years, the number of studies on the relationship between infectious diseases and microbiota has increased. Gut microbiota is affected by different parameters, including mode of delivery, hygiene habits, diet, drugs, and plasma iron levels during the lifetime. Gut microbiota may influence iron levels in the body, and iron overload and deficiency can also affect gut microbiota composition. Novel researches on microbiota shed light on the fact that the bidirectional interactions between gut microbiota and iron play a role in the pathogenesis of many diseases, especially infections. A better understanding of these interactions may help us to comprehend the pathogenesis of many infectious and metabolic diseases affecting people worldwide and following the development of more effective preventive and/or therapeutic strategies. In this review, we aimed to present the iron-mediated host-gut microbiota interactions, susceptibility to bacterial infections, and iron-targeted therapy approaches for infections.

Intestinal iron bio-accessibility changes by Lignin and the subsequent impact on cell metabolism and intestinal microbiome communities

Lignin chelates iron within the gastrointestinal lumen, altering bio-accessibility and leading to modulated enterocyte iron metabolism and changes in intestinal bacteria.

Metallobiology of Lactobacillaceae in the gut microbiome

Lactobacillaceae are a diverse family of lactic acid bacteria found in the gut microbiota of humans and many animals. These bacteria exhibit beneficial effects on intestinal health, including modulating the immune system and providing protection against pathogens, and many species are frequently used as probiotics. Gut bacteria acquire essential metal ions, like iron, zinc, and manganese, through the host diet and changes to the levels of these metals are often linked to alterations in microbial community composition, susceptibility to infection, and gastrointestinal diseases. Lactobacillaceae are frequently among the organisms increased or decreased in abundance due to changes in metal availability, yet many of the molecular mechanisms underlying these changes have yet to be defined. Metal requirements and metallotransporters have been studied in some species of Lactobacillaceae, but few of the mechanisms used by these bacteria to respond to metal limitation or excess have been investigated. This review provides a current overview of these mechanisms and covers how iron, zinc, and manganese impact Lactobacillaceae in the gut microbiota with an emphasis on their biochemical roles, requirements, and homeostatic mechanisms in several species.

Ferric Carboxymaltose Versus Ferrous Fumarate in Anemic Children with Inflammatory Bowel Disease: The POPEYE Randomized Controlled Clinical Trial

OBJECTIVE

To determine whether intravenous (IV) or oral iron suppletion is superior in improving physical fitness in anemic children with inflammatory bowel disease (IBD).

STUDY DESIGN

We conducted a clinical trial at 11 centers. Children aged 8-18 with IBD and anemia (defined as hemoglobin [Hb] z-score < -2) were randomly assigned to a single IV dose of ferric carboxymaltose or 12 weeks of oral ferrous fumarate. Primary end point was the change in 6-minute walking distance (6MWD) from baseline, expressed as z-score. Secondary outcome was a change in Hb z-score from baseline.

RESULTS

We randomized 64 patients (33 IV iron and 31 oral iron) and followed them for 6 months. One month after the start of iron therapy, the 6MWD z-score of patients in the IV group had increased by 0.71 compared with -0.11 in the oral group (P = .01). At 3- and 6-month follow-ups, no significant differences in 6MWD z-scores were observed. Hb z-scores gradually increased in both groups and the rate of increase was not different between groups at 1, 3, and 6 months after initiation of iron therapy (overall P = .97).

CONCLUSION

In this trial involving anemic children with IBD, a single dose of IV ferric carboxymaltose was superior to oral ferrous fumarate with respect to quick improvement of physical fitness. At 3 and 6 months after initiation of therapy, no differences were discovered between oral and IV therapies. The increase of Hb over time was comparable in both treatment groups.

TRIAL REGISTRATION

NTR4487 [Netherlands Trial Registry].

Overview of lunar dust toxicity risk

Lunar dust (LD), the component of lunar regolith with particle sizes less than 20 μm, covers the surface of the Moon. Due to its fineness, jagged edges, and electrostatic charge, LD adheres to and coats almost any surface it contacts. As a result, LD poses known risks to the proper functioning of electronic and mechanical equipment on the lunar surface. However, its mechanical irritancy and chemical reactivity may also pose serious health risks to humans by a number of mechanisms. While Apollo astronauts reported mild short-lived respiratory symptoms, the spectrum of health effects associated with high-dose acute exposure or chronic low-dose exposure are not yet well-understood. This paper explores known and potential human risks of exposure to LD which are thought to be important in planning upcoming lunar missions and planetary surface work.

The role of iron in host-microbiota crosstalk and its effects on systemic glucose metabolism

Iron is critical for the appearance and maintenance of life on Earth. Almost all organisms compete or cooperate for iron acquisition, demonstrating the importance of this essential element for the biological and physiological processes that are key for the preservation of metabolic homeostasis. In humans and other mammals, the bidirectional interactions between the bacterial component of the gut microbiota and the host for iron acquisition shape both host and microbiota metabolism. Bacterial functions influence host iron absorption, whereas the intake of iron, iron deficiency and iron excess in the host affect bacterial biodiversity, taxonomy and function, resulting in changes in bacterial virulence. These consequences of the host-microbial crosstalk affect systemic levels of iron, its storage in different tissues and host glucose metabolism. At the interface between the host and the microbiota, alterations in the host innate immune system and in circulating soluble factors that regulate iron (that is, hepcidin, lipocalin 2 and lactoferrin) are associated with metabolic disease. In fact, patients with obesity-associated metabolic dysfunction and insulin resistance exhibit dysregulation in iron homeostasis and alterations in their gut microbiota profile. From an evolutionary point of view, the pursuit of two important nutrients - glucose and iron - has probably driven human evolution towards the most efficient pathways and genes for human survival and health.

Ligand-Promoted Surface Solubilization of TiO2 Nanoparticles by the Enterobactin Siderophore in Biological Medium

Titanium dioxide nanoparticles (TiO2-NPs) are increasingly used in consumer products for their particular properties. Even though TiO2 is considered chemically stable and insoluble, studying their behavior in biological environments is of great importance to figure their potential dissolution and transformation. The interaction between TiO2-NPs with different sizes and crystallographic forms (anatase and rutile) and the strong chelating enterobactin (ent) siderophore was investigated to look at a possible dissolution. For the first time, direct evidence of anatase TiO2-NP surface dissolution or solubilization (i.e., the removal of Ti atoms located at the surface) in a biological medium by this siderophore was shown and the progressive formation of a hexacoordinated titanium-enterobactin (Ti-ent) complex observed. This complex was characterized by UV-visible and Fourier transform infrared (FTIR) spectroscopy (both supported by Density Functional Theory calculations) as well as electrospray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS). A maximum of ca. 6.3% of Ti surface atoms were found to be solubilized after 24 h of incubation, releasing Ti-ent complexes in the micromolar range that could then be taken up by bacteria in an iron-depleted medium. From a health and environmental point of view, the effects associated to the solubilization of the E171 TiO2 food additive in the presence of enterobactin and the entrance of the Ti-enterobactin complex in bacteria were questioned.

Fecal Iron Measurement in Studies of the Human Intestinal Microbiome

Iron is an essential micronutrient for humans and their intestinal microbiota. Host intestinal cells and iron-dependent bacteria compete for intraluminal iron, so the composition and functions of the gut microbiota may influence iron availability. Studies of the effects of the microbiota or probiotic interventions on host iron absorption may be particularly relevant to settings with high burdens of iron deficiency and gastrointestinal infections, since inflammation reduces iron bioavailability and unabsorbed intraluminal iron may modify the composition of the microbiota. The quantification of stool iron content may serve as an indicator of the amount of intraluminal iron to which the intestinal microbiota is exposed, which is particularly relevant for studies of the effect of iron on the intestinal microbiome, where fecal samples collected for purposes of microbiome characterization can be leveraged for stool iron analysis. However, few studies are available to guide researchers in the selection and implementation of stool iron assays, particularly because cross-comparison of available methods is limited in literature. This review aims to describe the available stool iron quantification methods and highlight their potential application in studies of iron-microbiome relationships, with a focus on pediatric research. MS-based methods offer high sensitivity and precision, but the need for expensive equipment and the high per-sample and maintenance costs may limit their widespread use. Conversely, colorimetric assays offer lower cost, ease of use, and rapid turnaround times but have thus far been optimized primarily for blood-derived matrices rather than stool. Further research efforts are needed to validate and standardize methods for stool iron assessment and to determine if the incorporation of such analyses in human microbiome studies 1) yields insights into the interactions between intestinal microbiota and iron and 2) contributes to the development of interventions that mitigate iron deficiency and promote a healthy microbiome.

Regulation of a High-Iron Diet on Lipid Metabolism and Gut Microbiota in Mice

Iron homeostasis disorder is associated with the imbalance of lipid metabolism, while the specific interaction remains unclear. In the present study, we investigated the effect of a high-iron diet on lipid metabolism in mice. The C57BL/6 mice were fed with a normal diet (WT) or a high-iron diet (WT + Fe) for 12 weeks. We found that mice in the WT + Fe group showed a significant decrease in body weight gain, body fat and lipid accumulation of liver when compared with mice in the WT group. Accordingly, serum total cholesterol and triglyceride levels were both reduced in mice with a high-iron diet. Moreover, mice in the WT + Fe group exhibited a significant decrease in expression of genes regulating adipogenesis and adipocyte differentiation, and a significant increase in expression of fat hydrolysis enzyme genes in both liver and adipose tissues, which was consistent with their dramatic reduction in adipocyte cell size. In addition, a high-iron diet decreased the relative abundance of beneficial bacteria (Akkermansia, Bifidobacterium and Lactobacillus) and increased the relative abundance of pathogenic bacteria (Romboutsia and Erysipelatoclostridium). Thus, our research revealed that a high-iron diet reduced lipid deposition by inhibiting adipogenesis and promoting lipolysis. Altered gut microbial composition induced by a high-iron diet may not play a critical role in regulating lipid metabolism, but might cause unwanted side effects such as intestinal inflammation and damaged villi morphology at the intestinal host–microbe interface. These findings provide new insights into the relationship among iron, lipid metabolism and gut microbiota.

Fluctuating selection on bacterial iron regulation in the mammalian gut

Iron is critical in host-microbe interactions, and its availability is tightly regulated in the mammalian gut. Antibiotics and inflammation can perturb iron availability in the gut, which could alter host-microbe interactions. Here, we show that an adaptive allele of iscR, a major regulator of iron homeostasis of Escherichia coli, is under fluctuating selection in the mouse gut. In vivo competitions in immune-competent, immune-compromised, and germ-free mice reveal that the selective pressure on an iscR mutant E. coli is modulated by the presence of antibiotics, the microbiota, and the immune system. In vitro assays show that iron availability is an important mediator of the iscR allele fitness benefits or costs. We identify Lipocalin-2, a host's immune protein that prevents bacterial iron acquisition, as a major host mechanism underlying fluctuating selection of iscR. Our results provide a remarkable example of strong fluctuating selection acting on bacterial iron regulation in the mammalian gut.

Dietary High Dose of Iron Aggravates the Intestinal Injury but Promotes Intestinal Regeneration by Regulating Intestinal Stem Cells Activity in Adult Mice With Dextran Sodium Sulfate-Induced Colitis

The effects of excessive dietary iron intake on the body have been an important topic. The purpose of this study was to investigate the effects of high-dose iron on intestinal damage and regeneration in dextran sodium sulfate (DSS)-induced colitis model mice. A total of 72 8-week-old adult C57BL/6 mice were randomly divided into two dietary treatment groups: the basal diet supplemented with 45 (control) and 450 mg/kg iron (high-iron) from ferrous sulfate. The mice were fed different diets for 2 weeks, and then 2.5% DSS was orally administered to all mice for 7 days. Samples of different tissues were collected on days 0, 3, and 7 post administration (DPA). High-iron treatment significantly decreased the relative weight of the large intestine at 7 DPA but not at 0 DPA or 3 DPA. High dietary iron increased the jejunal villus width at 0 DPA, decreased the villus width and the crypt depth of the jejunum at 3 DPA, and decreased the number of colonic crypts at 7 DPA. Meanwhile, high dietary iron decreased the number of goblet cells in the jejunal villi and the Paneth cells in the jejunal crypts at 0 DPA, increased the number of goblet cells per crypt of the colon at 3 DPA, and the number of Paneth cells in the jejunal crypts, the goblet cells in the colon, the Ki67-positive proliferating cells in the colon, and the Sex-determining region Y-box transcription factor 9⁺ (SOX9) cells in the jejunum crypts and colon at 7 DPA. The organoid formation rate was increased by high-iron treatments at 3 DPA and 7 DPA. High dietary iron treatment decreased the mRNA level of jejunal jagged canonical Notch ligand 2 (Jag-2) at 0 DPA and bone morphogenetic protein 4 (Bmp4) and neural precursor cell-expressed developmentally downregulated 8 (Nedd8) in the jejunum and colon at 7 DPA, whereas it increased the mRNA expression of the serum/glucocorticoid-regulated kinase 1 (Sgk1) in the colon at 3 DPA. The results suggested that a high dose of iron aggravated intestinal injury but promoted intestinal repair by regulating intestinal epithelial cell renewal and intestinal stem cell activity in adult mice with colitis.

Impact of sucroferric oxyhydroxide on the oral and intestinal microbiome in hemodialysis patients

Hyperphosphatemia is a consequence of chronic kidney disease associated with mineral/bone impairment, increased cardiovascular events and mortality. Therapeutically, most dialysis patients have to take phosphate binders. Here, we investigated effects of the Fe(3+)-based phosphate binder sucroferric oxyhydroxide (SFOH) on the oral and gastrointestinal microbiome of 11 hemodialysis patients. Saliva, dental plaque and stool were collected at baseline, one and four weeks of SFOH intake and subjected to 16S rRNA gene (V3-V4 region) directed Illumina MiSeq-based analysis. Total Fe, Fe(2+) and Fe(3+) were determined in stool and saliva. Overall, the microbiome did not change significantly. However, some patient-, sample- and taxon-specific differences were noted, which allowed patients to be divided into those with a shift in their microbiome (6/11) and those without a shift (5/11). Total Fe and Fe(2+) were highest after one week of SFOH, particularly in patients who exhibited a shift in microbiome composition. Eight bacterial taxa showed significant unidirectional changes during treatment. In-depth microbiome analysis revealed that taxa that significantly benefited from iron plethora had no iron-binding siderophores or alternatives, which was in contrast to taxa that significantly declined under iron plethora. Patients with microbiome-shift were significantly younger and had higher serum phosphate concentrations. In conclusion, this study sheds light on the impact of iron on the microbiome of hemodialysis patients.

Proteomes of Uropathogenic Escherichia coli Growing in Human Urine and in J82 Urinary Bladder Cells

Uropathogenic Escherichia coli (UPEC) are the most common cause of urinary tract infection (UTI). UPEC normally reside in the intestine, and during establishment of UTI, they undergo metabolic adaptations, first to urine and then upon tissue invasion to the bladder cell interior. To understand these adaptations, we used quantitative proteomic profiling to characterize protein expression of the UPEC strain UTI89 growing in human urine and when inside J82 bladder cells. In order to facilitate detection of UPEC proteins over the excess amount of eukaryotic proteins in bladder cells, we developed a method where proteins from UTI89 grown in MOPS and urine was spiked-in to enhance detection of bacterial proteins. More than 2000 E. coli proteins were detected. During growth in urine, proteins associated with iron acquisition and several amino acid uptake and biosynthesis systems, most prominently arginine metabolism, were significantly upregulated. During growth in J82 cells, proteins related to iron uptake and arginine metabolisms were likewise upregulated together with proteins involved in sulfur compound turnover. Ribosomal proteins were downregulated relative to growth in MOPS in this environment. There was no direct correlation between upregulated proteins and proteins reported to be essential for infections, showing that upregulation during growth does not signify that the proteins are essential for growth under a condition.

Iron Supplementation at the Crossroads of Nutrition and Gut Microbiota: The State of the Art

Gut microbiota has received significant attention owing to its decisive role in human health and disease. Diet exerts a significant influence on the variety and number of bacteria residing in the intestinal epithelium. On the other hand, as iron is a key micronutrient for blood formation and oxygen supply, its deficiency is highly prevalent worldwide. In fact, it is the most common cause of anemia and thus, iron supplementation is widespread. However, there is concern due to some potential risks linked to iron supplementation. Therefore, we have reviewed the available evidence of the effects that iron supplementation exerts on the gut microbiota as well as its potential benefits and risks. The compiled information suggests that iron supplementation is potentially harmful for gut microbiota. Therefore, it should be performed with caution, and by principle, recommended only to individuals with proven iron deficiency or iron-deficiency anemia to avoid potential adverse effects. In any case, large and long-term population studies are urgently needed to confirm or refute these results, mainly focused on vulnerable populations.

Ferrous Bisglycinate Supplementation Modulates Intestinal Antioxidant Capacity via the AMPK/FOXO Pathway and Reconstitutes Gut Microbiota and Bile Acid Profiles in Pigs

Multi-omics were applied to compare the risks and benefits of ferrous sulfate (FeSO₄) and ferrous bisglycinate (FebisGly) in pigs in the current study. The FebisGly group showed reduced triglyceride (TG) and triglyceride/total cholesterol (TG/CHOL) values in the serum and reduced malondialdehyde (MDA) and increased glutathione (GSH) levels in the duodenum. Transcriptome analysis revealed that differentially expressed genes in the duodenum were enriched in oxidative phosphorylation, AMPK, and FOXO signaling pathways between FeSO₄ and FebisGly groups. AMPK phosphorylation and FOXO3 protein expressions were significantly increased in the FebisGly group. Bacterial 16S rRNA gene sequence analysis revealed significantly reduced alpha diversity in the FeSO₄ group and increased Firmicutes, reduced Bacteroidetes, and Proteobacteria abundances in the FebisGly group. Targeted metabolome revealed notably increased lithocholic acid (LCA), glycolithocholic acid (GLCA), hyodeoxycholic acid (HDCA), ursodeoxycholic acid (UDCA), and glycoursodeoxycholic acid (GUDCA) in the FebisGly group. RDA analysis indicated that Fusobacteria was positively correlated with TG and TG/high-density lipoprotein in the FeSO₄ group while Christensenellaceae_R-7_group, Ruminococcaceae_UCG-002, and Ruminococcaceae_UCG-005 were positively correlated with UDCA and GLCA in the FebisGly group. According to the current study, FebisGly improves serum lipid metabolism, modulates intestinal antioxidant capacity via the AMPK/FOXO pathway, and reconstitutes gut microbiota and bile acid profiles in pigs.