Responses of Intestinal Microbiota and Immunity to Increasing Dietary Levels of Iron Using a Piglet Model

The Effect of Oral Iron Supplementation/Fortification on the Gut Microbiota in Infancy: A Systematic Review and Meta-Analysis

(1) Background: Iron is an essential metal for the proper growth and neurodevelopment of infants. To prevent and treat iron deficiency, iron supplementation or fortification is often required. It has been shown, though, that it affects the synthesis of gut microbiota. (2) Methods: This paper is a systematic review and meta-analysis of the effect of oral iron supplementation/fortification on the gut microbiota in infancy. Studies in healthy neonates and infants who received per os iron with existing data on gut microbiota were included. Three databases were searched: PUBMED, Scopus, and Google Scholar. Randomized controlled trials (RCTs) were included. Quality appraisal was assessed using the ROB2Tool. (3) Results: A total of six RCTs met inclusion criteria for a systematic review, and four of them were included in the meta-analysis using both the fixed and random effects methods. Our results showed that there is very good heterogeneity in the iron group (I2 = 62%), and excellent heterogeneity in the non-iron group (I2 = 98%). According to the meta-analysis outcomes, there is a 10.3% (95% CI: -15.0--5.55%) reduction in the bifidobacteria population in the iron group and a -2.96% reduction for the non-iron group. There is a confirmed difference (p = 0.02) in the aggregated outcomes between iron and non-iron supplement, indicative that the bifidobacteria population is reduced when iron supplementation is given (total reduction 6.37%, 95%CI: 10.16-25.8%). (4) Conclusions: The abundance of bifidobacteria decreases when iron supplementation or fortification is given to infants.

Perturbations in lipid metabolism and gut microbiota composition precede cardiac dysfunction in a mouse model of thalassemia

Cardiomyopathy is a major complication of thalassemia, yet the precise underlying molecular mechanisms remain unclear. We examined whether altered lipid metabolism is an early driving factor in the development of cardiomyopathy using the Th3/+ mouse model of thalassemia. At age 20 weeks, male and female Th3/+ mice manifested anemia and iron overload; however, only males displayed metabolic defects and altered cardiac function. Untargeted lipidomics indicated that the circulating levels of 35 lipid species were significantly altered in Th3/+ mice compared to wild-type controls: triglycerides (TGs) with saturated fatty acids (FAs; TG42:0 and TG44:0) were elevated, while TGs with unsaturated FAs (TG(18:2_20:5_18:2 and TG54:8)) were reduced. Similarly, phosphatidylcholines (PCs) with long chain FAs (palmitic (16:0) or oleic (18:1)) were increased, while PCs with polyunsaturated FAs decreased. Circulating PC(16:0_14:0), GlcCer(d18:1/24:0) correlated significantly with iron overload and cardiac hypertrophy. 16S rRNA gene profiling revealed alterations in the intestinal microbiota of Th3/+ mice. Differentially abundant bacterial genera correlated with PC(39:6), PC(18:1_22:6), GlcCer(d18:1/24:1) and CE(14:0). These results provide new knowledge on perturbations in lipid metabolism and the gut microbiota of Th3/+ mice and identify specific factors which may represent early biomarkers or therapeutic targets to prevent development of cardiomyopathy in β-thalassemia.

Effect of replacing inorganic iron with iron-rich microbial preparations on growth performance, serum parameters and iron metabolism of weaned piglets

This study aimed to investigate the effects of replacing of dietary inorganic iron with iron-rich Lactobacillus plantarum and iron-rich Candida utilis on the growth performance, serum parameters, immune function and iron metabolism of weaned piglets. Fifty-four 28-day-old healthy Duroc × Landrace × Yorkshire castrated male weanling piglets of similar body weight were randomly and equally divided into three groups. The piglets were kept in three pens per group, with six pigs in each pen. The dietary treatments were (1) a basal diet + ferrous sulfate preparation containing 120 mg/kg iron (CON); (2) a basal diet + iron-rich Candida utilis preparation containing 120 mg/kg iron (CUI); and (3) a basal diet + iron-rich Lactobacillus plantarum preparation containing 120 mg/kg iron (LPI). The entire feeding trial lasted for 28 days, after which blood, viscera, and intestinal mucosa were collected. The results showed no significant difference in growth parameters and organ indices of the heart, liver, spleen, lung, and kidney of weaned piglets when treated with CUI and LPI compared with the CON group (P > 0.05). However, CUI and LPI significantly reduced the serum contents of AST, ALP, and LDH (P < 0.05). Serum ALT content was significantly lower in the LPI treatment compared to the CON group (P < 0.05). Compared to CON, CUI significantly increased the contents of serum IgG and IL-4 (P < 0.05), and CUI significantly decreased the content of IL-2. LPI significantly increased the contents of serum IgA, IgG, IgM and IL-4 (P < 0.05), while LPI significant decreased the levels of IL-1β, IL-2, IL-6, IL-8, and TNF-α compared to CON (P < 0.05). CUI led to a significant increase in ceruloplasmin activity and TIBC (P < 0.05). LPI significantly increased the contents of serum Fe and ferritin, and increased the serum ceruloplasmin activity and TIBC compared to CON (P < 0.05). Furthermore, CUI resulted in a significant increase in the relative mRNA expression of FPN1 and DMT1 in the jejunal mucosa (P < 0.05). LPI significantly increased the relative mRNA expression of TF, FPN1, and DMT1 in the jejunal mucosa (P < 0.05). Based on these results, the replacement of dietary inorganic iron with an iron-rich microbial supplement could improve immune function, iron absorption and storage in piglets.

Excess iron intake induced liver injury: The role of gut-liver axis and therapeutic potential

Excessive iron intake is detrimental to human health, especially to the liver, which is the main organ for iron storage. Excessive iron intake can lead to liver injury. The gut-liver axis (GLA) refers to the bidirectional relationship between the gut and its microbiota and the liver, which is a combination of signals generated by dietary, genetic and environmental factors. Excessive iron intake disrupts the GLA at multiple interconnected levels, including the gut microbiota, gut barrier function, and the liver's innate immune system. Excessive iron intake induces gut microbiota dysbiosis, destroys gut barriers, promotes liver exposure to gut microbiota and its derived metabolites, and increases the pro-inflammatory environment of the liver. There is increasing evidence that excess iron intake alters the levels of gut microbiota-derived metabolites such as secondary bile acids (BAs), short-chain fatty acids, indoles, and trimethylamine N-oxide, which play an important role in maintaining homeostasis of the GLA. In addition to iron chelators, antioxidants, and anti-inflammatory agents currently used in iron overload therapy, gut barrier intervention may be a potential target for iron overload therapy. In this paper, we review the relationship between excess iron intake and chronic liver diseases, the regulation of iron homeostasis by the GLA, and focus on the effects of excess iron intake on the GLA. It has been suggested that probiotics, fecal microbiota transfer, farnesoid X receptor agonists, and microRNA may be potential therapeutic targets for iron overload-induced liver injury by protecting gut barrier function.

Mechanism of iron on the intestinal epithelium development in suckling piglets

This study aimed to investigate the mechanism of iron on intestinal epithelium development of suckling piglets. Compared with newborn piglets, 7-day-old and 21-day-old piglets showed changes in the morphology of the jejunum, increased proliferation, differentiated epithelial cells, and expanded enteroids. Intestinal epithelium maturation markers and iron metabolism genes were significantly changed. These results suggest that lactation is a critical stage in intestinal epithelial development, accompanied by changes in iron metabolism. In addition, deferoxamine (DFO) treatment inhibited the activity of intestinal organoids at passage 4 (P4) of 0-day-old piglets, but no significant difference was observed in epithelial maturation markers at passage 1 (P1) and P4, and only argininosuccinate synthetase 1 (Ass1) and β-galactosidase (Gleb) were up-regulated at passage 7 (P7). These results in vitro show that iron deficiency may not directly affect intestinal epithelium development through intestinal stem cells (ISCs). The iron supplementation significantly down-regulated the mRNA expression of interleukin-22 receptor subunit alpha-2 (IL-22RA2) in the jejunum of piglets. Furthermore, the mRNA expression of IL-22 in 7-day-old piglets was significantly higher than that in 0-day-old piglets. Adult epithelial markers were significantly up-regulated in organoids treated with recombinant murine cytokine IL-22. Thus, IL-22 may play a key role in iron-affecting intestinal epithelium development.

Plasma non-transferrin-bound iron uptake by the small intestine leads to intestinal injury and intestinal flora dysbiosis in an iron overload mouse model and Caco-2 cells

Iron overload often occurs during blood transfusion and iron supplementation, resulting in the presence of non-transferrin-bound iron (NTBI) in host plasma and damage to multiple organs, but effects on the intestine have rarely been reported. In this study, an iron overload mouse model with plasma NTBI was established by intraperitoneal injection of iron dextran. We found that plasma NTBI damaged intestinal morphology, caused intestinal oxidative stress injury and reactive oxygen species (ROS) accumulation, and induced intestinal epithelial cell apoptosis. In addition, plasma NTBI increased the relative abundance of Ileibacterium and Desulfovibrio in the cecum, while the relative abundance of Faecalibaculum and Romboutsia was reduced. Ileibacterium may be a potential microbial biomarker of plasma NTBI. Based on the function prediction analysis, plasma NTBI led to the weakening of intestinal microbiota function, significantly reducing the function of the extracellular structure. Further investigation into the mechanism of injury showed that iron absorption in the small intestine significantly increased in the iron group. Caco-2 cell monolayers were used as a model of the intestinal epithelium to study the mechanism of iron transport. By adding ferric ammonium citrate (FAC, plasma NTBI in physiological form) to the basolateral side, the apparent permeability coefficient (Papp) values from the basolateral to the apical side were greater than 3×10-6 cm s-1. Intracellular ferritin level and apical iron concentration significantly increased, and SLC39A8 (ZIP8) and SLC39A14 (ZIP14) were highly expressed in the FAC group. Short hairpin RNA (shRNA) was used to knock down ZIP8 and ZIP14 in Caco-2 cells. Transfection with ZIP14-specific shRNA decreased intracellular ferritin level and inhibited iron uptake. These results revealed that plasma NTBI may cause intestinal injury and intestinal flora dysbiosis due to the uptake of plasma NTBI from the basolateral side into the small intestine, which is probably mediated by ZIP14.

Effect of dietary iron supplementation on the equine fecal microbiome

Iron is an essential element for all living organisms, including bacteria, as several virulence factors and replication components are influenced by iron concentration. The objective of this study was to determine whether the composition and diversity of the fecal microbiota of adult horses are affected by supplemental dietary iron. Ten clinically healthy horses were randomly divided into a control and an iron-supplemented group (n = 5). The treated group was supplemented with oral ferrous sulphate monohydrate (720 ppm of iron), whereas the control group received 320 ppm of iron daily for 15 d. Fecal samples were collected before and 5, 10, 15, and 30 d after supplementation and frozen at -80°C. DNA was sequenced using an Illumina MiSeq platform and data were analyzed using the software Mothur and linear discriminant analysis (LDA) effect size (LEfSe). Iron supplementation caused no change in the overall composition of the fecal microbiota, but some minor changes were observed in the low-abundant bacteria, as well as an increased alpha diversity after 15 d of supplementation. Significant differences in community composition of the fecal microbiota over time were observed in both groups, highlighting the importance of a control group, as there are variables that cannot be controlled in microbiome studies.

The microbiome as a major function of the gastrointestinal tract and its implication in micronutrient metabolism and chronic diseases

The composition and function of microbes harbored in the human gastrointestinal lumen have been underestimated for centuries because of the underdevelopment of nucleotide sequencing techniques and the lack of humanized gnotobiotic models. Now, we appreciate that the gut microbiome is an integral part of the human body and exerts considerable roles in host health and diseases. Dietary factors can induce changes in the microbial community composition, metabolism, and function, thereby altering the host immune response, and consequently, may influence disease risks. An imbalance of gut microbiome homeostasis (i.e., dysbiosis) has been linked to several chronic diseases, such as inflammatory bowel diseases, obesity, and diabetes. Remarkable progress has recently been made in better understanding the extent to which the influence of the diet-microbiota interaction on host health outcomes in both animal models and human participants. However, the exact causality of the gut microbiome on the development of diseases is still controversial. In this review, we will briefly describe the general structure and function of the intestine and the process of nutrient absorption in humans. This is followed by a summarization of the recent updates on interactions between gut microbiota and individual micronutrients, including carotenoids, vitamin A, vitamin D, vitamin C, folate, iron, and zinc. In the opinion of the authors, these nutrients were identified as representative of vitamins and minerals with sufficient research on their roles in the microbiome. The host responses to the gut microbiome will also be discussed. Future direction in microbiome research, for example, precision microbiome, will be proposed.

Effects of Dietary Supplementation with Iron in Breeding Pigeons on the Blood Iron Status, Tissue Iron Content, and Full Expression of Iron-Containing Enzymes of Squabs

This study was aimed at investigating the effects of diet iron levels on the blood iron status, tissue iron content, mRNA levels, and the activity of iron-containing enzymes in different tissues of squabs. A total of 120 pairs of healthy Silver Feather King parental pigeons with similar average body weight and egg production were randomly divided into 5 groups with 8 replicates and 3 pairs of pigeons per replicate. The five groups of breeding pigeons were fed an iron-unsupplemented basal diet and basal diet supplemented with 75, 150, 300, and 600 mg iron/kg, respectively. The diets were fed in the form of granular feed based on corn, soybean meal, wheat, and sorghum. A broken line model was used for regression analysis. The results showed that plasma iron (PI), serum ferritin, iron contents in crop milk and liver, liver catalase (CAT) activity, and heart succinate dehydrogenase (SDH) activity were affected by iron levels (P < 0.05). And PI, serum ferritin, iron content in crop milk, and heart SDH activity increased quadratically (P < 0.05), but the iron content and CAT activity in the liver decreased quadratically (P < 0.005) as dietary iron level increased. According to the broken-line model of serum ferritin fitting (P < 0.002), the optimal dietary iron level of breeding pigeons was estimated to be 193 mg/kg. In conclusion, serum ferritin is a sensitive index to evaluate the iron requirement of the breeding pigeon with two squabs, and the recommended iron supplemental level is 193 mg/kg.

Association between iron supplementation and the presence of diarrhoea in Peruvian children aged 6-59 months: analysis of the database of the Demographic and Family Health Survey in Peru (DHS, Peru), years 2009-2019

INTRODUCTION

According to the WHO, anaemia is a severe public health problem when the prevalence is ≥ 40 %. In 2019, in Peru, 40·1 % of children (aged 6 to 35 months) are diagnosed as anaemic. This is a concern since, despite the efforts of the governments to reduce the prevalence, the problem has stagnated since 2011. The treatment applied to deal with anaemia is Fe supplementation. Although Fe is essential for cell function, an excess can produce adverse responses, such as gut inflammation affecting microbiota and resulting in diarrhoeic episodes.

OBJECTIVE

To determine the association between diarrhoea and Fe supplementation in children with and without anaemia, controlling for different socio-demographic variables.

DESIGN

We conducted via logistic regression to obtain diarrhoea prevalence ratios (PR), adjusted by age, sex, geographic region, water and sanitation service, and rurality. The survey asked for recent episodes of diarrhoea during the last 7 d; similarly, after the consumption of Fe supplements during the last 12 months before the survey.

SETTING

Peru.

PARTICIPANTS

The Demographic and Family Health Survey (DHS) is conducted annually at home among 14 202 children on average (2009-2019).

RESULTS

Fe supplementation in the last 7 d (PR = 1·09) or the last 12 months (PR = 1·19) (P < 0·0001) was associated with an increased risk of diarrhoea. The same association was observed between Fe supplementation and the presence of anaemia.

CONCLUSIONS

Fe supplementation is associated with diarrhoea and overuse in children should be avoided.

Juglone Suppresses Inflammation and Oxidative Stress in Colitis Mice

Juglone (JUG), a natural product found in walnut trees and other plants, shows potent antioxidant, antimicrobial, and immunoregulatory activities. However, it remains unknown whether JUG can alleviate ulcerative colitis. This study aims to explore the effect of JUG on dextran sulfate sodium (DSS)-induced colitis in mice. The mice were randomly assigned into three groups: the vehicle group, the DSS group, and the JUG group. The experiments lasted for 17 days; during the experiment, all mice received dimethyl sulfoxide (DMSO, 0.03% v/v)-containing water, while the mice in the JUG group received DMSO-containing water supplemented with JUG (0.04 w/v). Colitis was induced by administering DSS (3% w/v) orally for 10 consecutive days. The results showed that the JUG treatment significantly ameliorated body weight loss and disease activity index and improved the survival probability, colon length, and tissue damage. JUG reversed the DSS-induced up-regulation of proinflammatory cytokines, including interleukin (IL)-6, 12, 21, and 23, and tumor necrosis factor-alpha, and anti-inflammatory cytokines, such as IL-10 and transforming growth factor-beta, in the serum of the colitis mice. Additionally, the activation of mitochondrial uncoupling protein 2 and phospho-Nuclear Factor-kappa B p65 and the inhibition of the kelch-like ECH-associated protein 1 and NF-E2-related factor 2 induced by DSS were also reversed under JUG administration. Although the JUG group possessed a similar microbial community structure as the DSS group, JUG enriched potential beneficial microbes such as Lachnospiraceae_NK4A136_group but not pathogens such as Escherichia Shigella, which was dominative in DSS group, at the genus level. In conclusion, our results demonstrated that JUG could be a promising agent for UC prevention to regulate inflammatory cytokines and oxidative stress.