A possible relation of the Helicobacter pylori pfr gene to iron deficiency anemia?

Helicobacter pylori-Associated Iron Deficiency Anemia in Childhood and Adolescence-Pathogenesis and Clinical Management Strategy

Many epidemiological studies and meta-analyses show that persistent Helicobacter pylori infection in the gastric mucosa can lead to iron deficiency or iron deficiency anemia (IDA), particularly in certain populations of children and adolescents. Moreover, it has been demonstrated that H. pylori infection can lead to and be closely associated with recurrent and/or refractory iron deficiency and IDA. However, the pathogenesis and specific risk factors leading to this clinical outcome in H. pylori-infected children remain poorly understood. In general, most of pediatric patients with H. pylori-associated IDA do not show evidence of overt blood loss due to gastrointestinal hemorrhagic lesions. In adult populations, H. pylori atrophic gastritis is reported to cause impaired iron absorption due to impaired gastric acid secretion, which, subsequently, results in IDA. However, significant gastric atrophy, and the resultant substantial reduction in gastric acid secretion, has not been shown in H. pylori-infected children. Recently, it has been hypothesized that competition between H. pylori and humans for iron availability in the upper gastrointestinal tract could lead to IDA. Many genes, including those encoding major outer membrane proteins (OMPs), are known to be involved in iron-uptake mechanisms in H. pylori. Recent studies have been published that describe H. pylori virulence factors, including specific OMP genes that may be associated with the pathogenesis of IDA. Daily iron demand substantively increases in children as they begin pubertal development starting with the associated growth spurt, and this important physiological mechanism may play a synergistic role for the microorganisms as a host pathogenetic factor of IDA. Like in the most recent pediatric guidelines, a test-and-treat strategy in H. pylori infection should be considered, especially for children and adolescents in whom IDA is recurrent or refractory to iron supplementation and other definitive causes have not been identified. This review will focus on providing the evidence that supports a clear biological plausibility for H. pylori infection and iron deficiency, as well as IDA.

Helicobacter pylori sabA gene is associated with iron deficiency anemia in childhood and adolescence

Background

Gastric Helicobacter pylori colonization leads to iron deficiency anemia (IDA), especially in children and adolescents. However the pathogenesis is poorly understood.

Objective

We sought to identify specific H. pylori genes involved in IDA development, by comparing bacterial genome-wide expression profiling in patients affected or not.

Methods

H. pylori were isolated from four children with IDA and four from matched controls without IDA. Based on these isolates, cDNA microarrays under iron-replete or depleted conditions were systematically performed to compare gene expression profiles at the whole genome level. Real-time reverse-transcription (RT-) PCR and protein assays were performed for further assessing the profile differentiation of the identified H. pylori IDA-associated genes.

Results

We identified 29 and 11 genes with significantly higher or lower expression in the IDA isolates compared to non-IDA isolates, respectively. Especially notable were higher expression of sabA gene encoding sialic acid-binding adhesin in the IDA isolates, which was confirmed by real-time RT-PCR study. Moreover, iron-depletion in vitro led to up-regulation of fecA1 and frpB1 genes and down-regulation of pfr, as predicted. Known iron-regulated genes such as fur, pfr, fecA, and feoB did not significantly differ between both groups. The IDA isolates had significantly higher expression of vacuolating cytotoxin gene vacA than non-IDA isolates, consistent with the results of VacA protein assays. There were no significant differences in bacterial growth value between IDA and non-IDA isolates.

Conclusions

It is likely that H. pylori carrying high expression of sabA causes IDA, especially in children and adolescents who have increased daily iron demand. In addition, it is possible that several host-interactive genes, including vacA, may play a synergistic role for sabA in IDA development.

The ferric uptake regulator of Helicobacter pylori: a critical player in the battle for iron and colonization of the stomach

Helicobacter pylori is arguably one of the most successful pathogens; it colonizes the stomachs of more than half of the human population. Colonization and persistence in such an inhospitable niche requires the presence of exquisite adaptive mechanisms. One of the proteins that contributes significantly to the remarkable adaptability of H. pylori is the ferric uptake regulator (Fur), which functions as a master regulator of gene expression. In addition to genes directly related to iron homeostasis, Fur controls expression of several enzymes that play a central role in metabolism and energy production. The absence of Fur leads to severe H. pylori colonization defects and, accordingly, several Fur-regulated genes have been shown to be essential for colonization. Moreover, proteins encoded by Fur-regulated genes have a strong impact on redox homeostasis in the stomach and are major determinants of inflammation. In this review, we discuss the main roles of Fur in the biology of H. pylori and highlight the importance of this regulatory protein in the infectious process.

Unintended consequences of Helicobacter pylori infection in children in developing countries: iron deficiency, diarrhea, and growth retardation

Helicobacter pylori infection is predominantly acquired early in life. The prevalence of the infection in childhood is low in developed countries, whereas in developing countries most children are infected by 10 y of age. In poor resource settings, where malnutrition, parasitic/enteropathogen and H. pylori infection co-exist in young children, H. pylori might have potentially more diverse clinical outcomes. This paper reviews the impact of childhood H. pylori infection in developing countries that should now be the urgent focus of future research. The extra-gastric manifestations in early H. pylori infection in infants in poor resource settings might be a consequence of the infection associated initial hypochlorhydria. The potential role of H. pylori infection on iron deficiency, growth impairment, diarrheal disease, malabsorption and cognitive function is discussed in this review.

Positive relationship between a polymorphism in Helicobacter pylori neutrophil-activating protein a gene and iron-deficiency anemia

BACKGROUND

Numerous studies have suggested a link between iron-deficiency anemia (IDA) and Helicobacter pylori infection. Previously, we found that strains isolated from IDA patients showed higher levels of Fe ion uptake and Fe-ion-dependent rapid proliferation than those of strains derived from patients without IDA.

MATERIALS AND METHODS

Twenty-four H. pylori strains from IDA patients (IDA strains) and 25 strains from patients who had H. pylori gastritis without anemia (non-IDA strains) were examined. Their nucleotide sequences of napA, fur, and feoB, which contribute to Fe ion uptake, were determined.

RESULTS

Numerous polymorphisms of the three genes were found in both strains. Frequency of neutrophil-activating protein A (NapA), which encoded by napA, with threonine at amino acid residue No. 70 (Thr70-type NapA) was significantly higher in IDA strains than in non-IDA strains. Strains with Thr70-type NapA showed significantly higher levels of Fe(3+) and Fe(2+) uptake than did strains with other types, Ser70-type of NapA, which is found in standard strains. Other significantly different occurrences of polymorphisms between IDA and non-IDA groups were not observed in these genes.

CONCLUSION

The results suggest that H. pylori strains with Thr70-type NapA have enhanced Fe ion uptake ability and are associated with the pathogenesis of IDA.

Identification of Proteins Related to Nickel Homeostasis in Helicobater pylori by Immobilized Metal Affinity Chromatography and Two-Dimensional Gel Electrophoresis

Helicobacter pylori (H. pylori) is a widespread human pathogen causing peptic ulcers and chronic gastritis. Maintaining nickel homeostasis is crucial for the establishment of H. pylori infection in humans. We used immobilized-nickel affinity chromatography to isolate Ni-related proteins from H. pylori cell extracts. Two-dimensional gel electrophoresis and mass spectrometry were employed to separate and identify twenty two Ni-interacting proteins in H. pylori. These Ni-interacting proteins can be classified into several general functional categories, including cellular processes (HspA, HspB, TsaA, and NapA), enzymes (Urease, Fumarase, GuaB, Cad, PPase, and DmpI), membrane-associated proteins (OM jhp1427 and HpaA), iron storage protein (Pfr), and hypothetical proteins (HP0271, HP jhp0216, HP jhp0301, HP0721, HP0614, and HP jhp0118). The implication of these proteins in nickel homeostasis is discussed.

[Role of Helicobacter pylori infection in iron deficiency anemia]

Anemia induced by digestive diseases refers to anemia due to iron deficiency. Conventional gastrointestinal diagnostic workup fails to establish the cause of iron deficiency in about one third of patients. Abnormal iron absorption is increasingly recognized as an important cause of unexplained iron deficiency. The importance of coeliac disease as a possible cause of iron deficiency anemia refractory to oral iron treatment, without other manifestations of malabsorption syndrome, is increasingly being recognized. In addition, Helicobacter pylori (HP) has been implicated in several recent studies as a cause of iron deficiency anemia (IDA) refractory to oral iron treatment. Cure of previously refractory IDA by HP eradication provides strong evidence supporting a cause-and-effect relationship. In order to establish a cause-and-effect relationship between HP gastritis and IDA, prospective randomized studies comparing the effects of iron administration with or without H. pylorieradication are highly recommended.

Identification of clinical and simple laboratory variables predicting responsible gastrointestinal lesions in patients with iron deficiency anemia

Iron deficiency anemia (IDA) is a frequent disorder. Also, it may be a sign of underlying serious diseases. Iron deficiency points to an occult or frank bleeding lesion when occurred in men or postmenopausal women. In this study, we aimed to evaluate the diagnostic yield of endoscopy in patients with IDA and to define predictive factors of gastrointestinal (GI) lesions causing IDA. Ninety-one patients (77 women, 14 men; mean age: 43 years) who were decided to have esophago-duodenoscopy and/or colonoscopy for iron deficiency anemia were interviewed and responded to a questionnaire that included clinical and biochemical variables. The endoscopic findings were recorded as GI lesions causing IDA or not causing IDA. Endoscopy revealed a source of IDA in 18.6 % of cases. The risk factors for finding GI lesions causing IDA were as follows: male gender (p= 0.004), advanced age (> 50 years) (p= 0.010), weight loss (over 20% of total body weight lost in last 6 month) (p= 0.020), chronic diarrhea (p= 0.006), change of bowel habits (p= 0.043), epigastric tenderness (p= 0.037), raised carcinoembryonic antigen (CEA) level (normal range: 0-7 ng/mL) (p= 0.039), < 10 gr/dl hemoglobin (Hb) level (p=0.054). None of these risk factors had been present in 21 (23%) women younger than 51 years. In this group, no patient had any GI lesion likely to cause IDA (negative predictive value= 100%). In multivariate analysis, advanced age (p=0.017), male gender (p< 0.01) and weight lost (p=0.012) found that associated with GI lesions in all patients. It may be an appropriate clinical approach to consider these risk factors when deciding for gastrointestinal endoscopic evaluation in iron deficiency anemia.

A short review of malabsorption and anemia

Anemia is a frequent finding in most diseases which cause malabsorption. The most frequent etiology is the combination of iron and vitamin B12 deficiency. Celiac disease is frequently diagnosed in patients referred for evaluation of iron deficiency anemia (IDA), being reported in 1.8%-14.6% of patients. Therefore, duodenal biopsies should be taken during endoscopy if no obvious cause of iron deficiency (ID) can be found. Cobalamin deficiency occurs frequently among elderly patients, but it is often unrecognized because the clinical manifestations are subtle; it is caused primarily by food-cobalamin malabsorption and pernicious anemia. The classic treatment of cobalamin deficiency has been parenteral administration of the vitamin. Recent data suggest that alternative routes of cobalamin administration (oral and nasal) may be useful in some cases. Anemia is a frequent complication of gastrectomy, and has been often described after bariatric surgery. It has been shown that banding procedures which maintain digestive continuity with the antrum and duodenum are associated with low rates of ID. Helicobacter pylori (H pylori) infection may be considered as a risk factor for IDA, mainly in groups with high demands for iron, such as some children and adolescents. Further controlled trials are needed before making solid recommendations about H pylori eradication in these cases.

Controlled, household-randomized, open-label trial of the effect of treatment of Helicobacter pylori infection on iron deficiency among children in rural Alaska: results at 40 months

BACKGROUND

Helicobacter pylori infection treatment was found not to reduce the prevalence of iron deficiency or anemia among Alaska Native children at 14 months after treatment initiation. We hypothesized that 14 months was to early to resolve H. pylori-induced gastric damage. Consequently, we conducted a 40-month follow-up.

METHODS

We enrolled 219 children 7-11 years old who had H. pylori infection (as diagnosed by (13)C-labeled urea breath test) and iron deficiency (serum ferritin level, <22.47 pmol/L) in a controlled, household-randomized trial of the effect of treatment of H. pylori on iron deficiency and anemia (hemoglobin level, <115 g/L). At 40 months, 176 children were evaluated.

RESULTS

Forty-four (52%) of 85 children in the intervention group and 53 (58%) of 91 in the control group had iron deficiency (adjusted relative risk [ARR], 0.92 [95% confidence interval {CI}, 0.68-1.26]), versus 4 (5%) and 17(19%), respectively, with both iron deficiency and anemia (ARR, 0.25 [95% CI, 0.09-0.73]). Reinfection occurred among 33 (52%) of 64 children who had cleared their infection. H. pylori-negative children had lower prevalences of iron deficiency (ARR, 0.62 [95% CI, 0.38-1.01]) and iron deficiency and anemia (ARR, 0.22 [95% CI, 0.03-1.50]), compared with H. pylori -positive children.

CONCLUSIONS

The resolution of H. pylori infection for >14 months modestly reduced the prevalence of iron deficiency and substantially reduced the prevalence of iron deficiency and anemia. H. pylori likely plays a casual role in hematological outcomes for some children.

Severe iron-deficiency anaemia in adolescents: consider Helicobacter pylori infection

AIM

This article describes the association of severe iron-deficiency anaemia with Helicobacter pylori gastritis.

RESULTS

We report three children who had symptomatic iron-deficiency anaemia with no obvious clinical cause and refractory to iron replacement therapy. All three underwent a diagnostic endoscopy and were found to have H. pylori gastritis. Histopathology confirmed inflammatory changes consisting of dense bands of clusters of plasma cells within the lamina propria and two of the three adolescents were noted to have numerous H. pylori in gastric crypts and glands. Two of the three cases had a urease positive test. Iron deficiency was successfully corrected following antibiotic eradication of H. pylori infection.

CONCLUSIONS

This case series highlights the importance of considering H. pylori infection as a cause of refractory iron-deficiency anaemia in adolescents, even in the absence of gastrointestinal symptoms.

Helicobacter pylori infection and iron stores: a systematic review and meta-analysis

BACKGROUND AND AIMS

We carried out a systematic literature review and meta-analysis to evaluate the existing evidence on the association between Helicobacter pylori infection and iron stores.

METHODS

Twelve case reports and case series, 19 observational epidemiologic studies and six intervention trials were included in the review.

RESULTS

Although only few studies controlled for multiple potential confounders, most studies reported a positive association, linking between H. pylori and decreased body iron stores in symptomatic and asymptomatic H. pylori-infected subjects. H. pylori infection may be regarded as a risk factor for reduction in body iron stores and also for iron deficiency or iron deficiency anemia, especially in high-risk groups. The results of the meta-analysis of thoroughly designed and analyzed studies revealed an increased risk for iron deficiency anemia; pooled odds ratio (OR) 2.8 (95% confidence interval (CI) 1.9, 4.2) and also for iron deficiency; pooled OR 1.38 (95%CI 1.16-1.65) among H. pylori-infected subjects. The biologic mechanism by which H. pylori induces the alteration in the iron stores is not fully understood, but it seems to involve several pathways, including gastrointestinal blood loss, decrease in the absorption of dietary iron, and enhanced uptake of the iron by the bacterium.

CONCLUSIONS

H. pylori is associated with reduced iron stores. Future research is needed to determine whether this relationship is a causal association and to better understand its biologic mechanism. The impact of anti-H. pylori therapy on improvement of iron stores needs to be further evaluated in large and well-controlled trials.

The paradox of anemia with high meat intake: a review of the multifactorial etiology of anemia in the Inuit of North America

Anemia is a serious concern among indigenous populations in North America, and it appears to be widespread among the Inuit despite abundant intakes of heme iron. It is therefore hypothesized that anemia for the Inuit involves other dietary factors not usually associated with animal foods, such as low intakes of vitamin A and/or folate, riboflavin, and vitamin C. Also, Helicobacter pylori infection and/or parasitosis may result in gastrointestinal blood loss and/or functional iron deficiency. This review aims to describe factors that may cause anemia in Inuit populations despite high meat intakes, abundant bioavailable iron, and other important hematological nutrients.

Comparative proteomic analysis ofHelicobacter pylori strains associated with iron deficiency anemia

Helicobacter pylori is known to cause chronic gastritis, peptic ulcer, and gastric cancer, and has also been linked to iron deficiency anemia (IDA). To determine whether H. pylori clinical isolates correlate with the prevalence of H. pylori-associated IDA, we compared the proteomic profiles of H. pylori strains isolated from antral biopsy specimens of H. pylori-positive patients with or without IDA. Fifteen strains, including eight non-IDA and seven IDA strains, were cultured under iron-rich and iron-depleted conditions and then analyzed for protein expression profiles by 2-DE. The distances between two H. pylori strains were determined on the basis of similarities between their expression patterns of 189 protein spots, and a phylogenetic tree was constructed. The results revealed that the IDA strains formed a cluster separate from that of six non-IDA strains, with two non-IDA strains between the clusters. H. pylori strain 26695 was located in the non-IDA cluster. Protein spots displaying similar expression patterns were clustered, and 18 spots predominantly expressed in IDA strains were identified by MALDI-TOF analysis. These data indicate that the non-IDA and IDA strains can be distinguished by their protein expression profiles, suggesting that the polymorphism of H. pylori strains may be one of the factors determining the occurrence of H. pylori-associated IDA.

Polymorphism of the Helicobacter pylori feoB gene in Korea: a possible relation with iron-deficiency anemia?

BACKGROUND

Helicobacter pylori is a causative agent of gastritis, and H. pylori infection is thought to be correlated with iron-deficiency anemia (IDA) at puberty. The H. pylori feoB gene product, a high-affinity ferrous iron transporter, plays a central role in iron acquisition and virulence. This study was undertaken to analyze H. pylori feoB status according to clinical data, including antral gastritis with or without IDA.

METHODS

Fourteen H. pylori-positive patients aged from 10 to 18 years were categorized into subgroups based on the presence or absence of IDA. Eight patients were diagnosed as having IDA; the other six showed normal hematological findings. Genomic DNA was isolated from H. pylori cultured from each gastric biopsy specimen. Five sets of primers were used for the PCR amplification of the feoB gene. Linking and sequencing of PCR products generated the feoB region, which was 1.93 kb in size. The feoB gene sequences of H. pylori J99 and 26695 were compared with the clinical strains, and the sequences of feoB regions in the IDA (+) and (-) groups were compared.

RESULTS

Sequence analysis of the complete coding region of the feoB gene revealed 16 sites of polymorphism or mutation. Among these, three polymorphisms (E/T254A, I263V, and K511Q) were indigenous to the Korean clinical strains. Although statistically significant differences were observed at four sites (K127T, A273S/P, I438V and I441T) between IDA (+) and (-), the number of specimens was too low to assess the significance of the differences.

CONCLUSION

The four polymorphisms of the feoB gene observed appear to be related to the clinical phenotype of IDA, but the relation is unclear because of the small number of strains studied. Further studies are required to confirm a correlation between IDA and H. pylori infection.

Helicobacter pylori impairs iron absorption in infected individuals

BACKGROUND

Infection with Helicobacter pylori is recognised as a major risk factor for chronic gastritis, peptic ulcer disease and gastric cancer. The association between H. pylori infection and iron deficiency anaemia has been established. Multiple mechanisms have been advocated to explain the relationship between H. pylori and iron status and their association might reduce iron deposit.

AIM

Aim of this study was to investigate whether H. pylori infection affects iron absorption.

METHODS

The study was designed on a prospective basis. Fifty-five subjects underwent upper gastrointestinal endoscopy and biopsy to investigate the presence of H. pylori and, when this was positive, also search of serum anti-CagA was performed. Tests included an oral iron absorption test with the administration of 1 mg/kg of Fe2+. Iron levels were measured before and 2 h after iron administration (delta iron). H. pylori-positive subjects were administered antibiotic therapy for 1 week and, 2 months later, the oral iron absorption test was repeated and urea-breath test was first performed.

RESULTS

H. pylori-positive subjects had lower serum level of ferritin and lower delta iron compared to H. pylori-negative subjects. That difference is significant in anaemic women and is independent of the presence of serum anti-CagA antibodies. After H. pylori eradication iron absorption test was similar to those of non-infected subjects.

CONCLUSION

H. pylori infection impairs iron uptake. That mechanism, together with others, may contribute to the depletion of iron in infected patients.

Iron Deficiency Anemia as the Only Sign of Infection withHelicobacter pylori: A Report of 9 Pediatric Cases

Recently, an association between Helicobacter pylori (HP) and iron deficiency anemia (IDA) was proposed. We describe 9 pediatric patients with a history of long-standing IDA and HP infection. After HP test results were confirmed to be positive, anti-HP therapy consisting of omeprazole, clarithromycin, and amoxicillin was administered for 2 weeks. The hematologic profile and iron status were assessed before and periodically after the end of the eradication regimen. The eradication of HP was associated with stable normalization of iron stores. HP infection may be involved in cases of IDA of unknown origin, and the eradication of HP is associated with the resolution of anemia.

Consequences of Helicobacter pylori infection on the absorption of micronutrients

Recent studies have suggested a relationship between Helicobacter pylori infection and various important micronutrients, including iron and vitamin B12, suggesting likely biological factors in the association between Helicobacter pylori and microcytic or macrocytic anaemia. There is some evidence that direct or indirect consequences of Helicobacter pylori gastritis on acid secretion account for the role of the bacterium in the absorption process of iron and Vitamin B12. The plasma, intragastric and mucosal concentration of different antioxidant compounds such as ascorbic acid, a-tocopherol and beta-carotene is also affected by Helicobacter pylori gastritis supporting the possible role of Helicobacter pylori in the multistep cascade leading to gastric carcinogenesis. The relationship between Helicobacter pylori infection and micronutrients is, therefore, a promising and, until now, poorly investigated field of research.

Essential role of ferritin Pfr in Helicobacter pylori iron metabolism and gastric colonization

The reactivity of the essential element iron necessitates a concerted expression of ferritins, which mediate iron storage in a nonreactive state. Here we have further established the role of the Helicobacter pylori ferritin Pfr in iron metabolism and gastric colonization. Iron stored in Pfr enabled H. pylori to multiply under severe iron starvation and protected the bacteria from acid-amplified iron toxicity, as inactivation of the pfr gene restricted growth of H. pylori under these conditions. The lowered total iron content in the pfr mutant, which is probably caused by decreased iron uptake rates, was also reflected by an increased resistance to superoxide stress. Iron induction of Pfr synthesis was clearly diminished in an H. pylori feoB mutant, which lacked high-affinity ferrous iron transport, confirming that Pfr expression is mediated by changes in the cytoplasmic iron pool and not by extracellular iron. This is well in agreement with the recent discovery that iron induces Pfr synthesis by abolishing Fur-mediated repression of pfr transcription, which was further confirmed here by the observation that iron inhibited the in vitro binding of recombinant H. pylori Fur to the pfr promoter region. The functions of H. pylori Pfr in iron metabolism are essential for survival in the gastric mucosa, as the pfr mutant was unable to colonize in a Mongolian gerbil-based animal model. In summary, the pfr phenotypes observed give new insights into prokaryotic ferritin functions and indicate that iron storage and homeostasis are of extraordinary importance for H. pylori to survive in its hostile natural environment.

Helicobacter pylori-related iron deficiency anemia: a review

Several clinical reports have demonstrated that Helicobacter pylori gastric infection has emerged as a new cause of refractory iron deficiency anemia, unresponsive to iron therapy, and not attributable to usual causes such as intestinal losses or poor intake, malabsorption or diversion of iron in the reticulo-endothelial system. Although the interaction between infection and iron metabolism is now well consolidated, our understanding of the pathogenetic mechanism underlying the anemia is still wanting. Microbiological and ferrokinetic studies seem to suggest that Helicobacter pylori infected antrum could act as a sequestering focus for serum iron by means of outer membrane receptors of the bacterium, that in vitro are able to capture and utilize for growth iron from human lactoferrin. The proposed hypothesis does not answer why this complication is such a rare disease outcome in a common human infection but it may be used as a template for further controlled studies to determine the mechanisms of this atypical, medically important putative sequelae of H. pylori infection.