Helicobacter pylori infection and low dietary iron alter behavior, induce iron deficiency anemia, and modulate hippocampal gene expression in female C57BL/6 mice

Dual role of hepcidin in response to pathogens

Hepcidin is the primary regulator of vertebrate iron homeostasis. Its production is stimulated by systemic iron levels and inflammatory signals. Although the role of hepcidin in iron homeostasis is well characterized, its response to pathogenic agents is complex and diverse. In this review, we examine studies that investigate the role of hepcidin in response to infectious agents. Interleukin-6 (IL-6) is a key factor responsible for the induction of hepcidin expression. During infection, hepcidin-mediated depletion of extracellular iron serves as a protective mechanism against a variety of pathogens. However, accumulation of iron in macrophages through hepcidin-mediated pathways may increase susceptibility to intracellular pathogens such as Mycobacterium tuberculosis. Prolonged elevation of hepcidin production can lead to anemia due to reduced iron availability for erythropoiesis, a condition referred to as anemia of inflammation. In addition, we highlight the role of hepcidin upregulation in several infectious contexts, including HIV-associated anemia, iron deficiency anemia in Helicobacter pylori infection, and post-malarial anemia in pediatric patients. In addition, we show that certain infectious agents, such as hepatitis C virus (HCV), can suppress hepcidin production during both the acute and chronic phases of infection, while hepatitis B virus (HBV) exhibits similar suppression during the chronic phase.

Research progress on the relationship between Helicobacter pylori infection and iron deficiency anemia

Helicobacter pylori (H. pylori) infection affects around half of the global population and is a globally highly prevalent pathogen that is closely linked not only to gastrointestinal diseases such as chronic atrophic gastritis, functional dyspepsia and peptic ulcer but also to the development and progression of a variety of extra-gastrointestinal diseases. Numerous studies have shown the correlation between H. pylori infection and iron-deficiency anemia (IDA). The prevalence of H. pylori infection is higher in individuals with IDA, and the hemoglobin level of patients with IDA can be increased to different degrees or even returned to normal following active H. pylori eradication. However, this conclusion is still controversial. In this paper, a comprehensive literature search was conducted using the PubMed/MEDLINE/Web of Science database, combining the following terms: "Helicobacter pylori," "Helicobacter pylori infection," "iron deficiency anemia," "iron deficiency," "iron absorption," "iron malabsorption," "serum iron," "hemoglobin," "pathogenesis," "mechanism," and "eradication therapy." Through extensive literature searches, the correlation between H. pylori infection and IDA, its potential mechanism, and the efficacy of H. pylori eradication therapy in IDA patients have been comprehensively discussed. We conclude that the majority of existing studies have confirmed the correlation between H. pylori infection and IDA, indicating that patients with H. pylori infection are more likely to develop IDA and that the prevalence of H. pylori infection is higher in individuals with IDA. Compared with iron supplementation alone, combining H. pylori eradication with iron supplementation is more effective in treating IDA, particularly in unexplained or refractory IDA cases. These findings provide valuable insights for clinicians managing patients with unexplained or refractory IDA.

The causal effect of iron status on risk of anxiety disorders: A two-sample Mendelian randomization study

OBJECTIVES

Observational studies had investigated the association of iron metabolism with anxiety disorders. The conclusions were inconsistent and not available to reveal the causal or reverse-causal association due to the confounding. In this study we estimated the potential causal effect of iron homeostasis markers on anxiety disorders using two-sample Mendelian randomization (MR) analysis.

METHODS

Summary data of single nucleotide polymorphisms (SNPs) associated with four iron-related biomarkers were extracted from a recent report about analysis of three genome-wide association study (GWAS), the sample size of which ranged from 131471 to 246139 individuals. The corresponding data for anxiety disorders were from Finngen database (20992 cases and 197800 controls). The analyses were mainly based on inverse variance weighted (IVW) method. In addition, the heterogeneity and pleiotropy of the results were assessed by Cochran's Q test and MR-Egger regression.

RESULTS

Basing on IVW method, genetically predicted serum iron level, ferritin and transferrin had negative effects on anxiety disorders. The odd ratios (OR) of anxiety disorders per 1 standard deviation (SD) unit increment in iron status biomarkers were 0.922 (95% confidence interval (CI) 0.862-0.986; p = 0.018) for serum iron level, 0.873 (95% CI 0.790-0.964; p = 0.008) for log-transformed ferritin and 0.917 (95% CI 0.867-0.969; p = 0.002) for transferrin saturation. But no statical significance was found in the association of 1 SD unit increased total iron-binding capacity (TIBC) with anxiety disorders (OR 1.080; 95% CI 0.988-1.180; p = 0.091). The analyses were supported by pleiotropy test which suggested no pleiotropic bias.

CONCLUSION

Our results indicated that genetically determined iron status biomarkers causally linked to the risk of anxiety disorders, providing valuable insights into the genetic research and clinical intervention of anxiety disorders.

Gastric coinfection with thiopeptide-positive Cutibacterium acnes decreases FOXM1 and pro-inflammatory biomarker expression in a murine model of Helicobacter pylori-induced gastric cancer

IMPORTANCE

H. pylori infects half of the world population and is the leading cause of gastric cancer. We previously demonstrated that gastric cancer risk is associated with gastric microbiota. Specifically, gastric urease-positive Staphylococcus epidermidis and Streptococcus salivarius had contrasting effects on H. pylori-associated gastric pathology and immune responses in germ-free INS-GAS mice. As gastritis progresses to gastric cancer, the oncogenic transcription factor Foxm1 becomes increasingly expressed. In this study, we evaluated the gastric commensal C. acnes, certain strains of which produce thiopeptides that directly inhibit FOXM1. Thiopeptide-positive C. acnes was isolated from Nicaraguan patient gastric biopsies and inoculated into germ-free INS-GAS mice with H. pylori. We, therefore, asked whether coinfection with C. acnes expressing thiopeptide and H. pylori would decrease gastric Foxm1 expression and pro-inflammatory cytokine mRNA and protein levels. Our study supports the growing literature that specific non-H. pylori gastric bacteria affect inflammatory and cancer biomarkers in H. pylori pathogenesis.

Effects of chronic Helicobacter pylori strain PMSS1 infection on whole brain and gastric iron homeostasis in male INS-GAS mice

Iron deficiency, the most common micronutrient deficiency in humans, is associated with long-term deficits in cognition and memory if left untreated. Infection with the gastric pathogen Helicobacter pylori has been linked to iron deficiency anemia (IDA). The H. pylori virulence factor cytotoxin-associated gene A (cagA) is proposed to be especially pertinent in iron deficiency. Male INS-GAS/FVB mice were infected with the CagA⁺ strain pre-murine Sydney strain 1 (PMSS1) for 12-13 or 27-29 weeks to investigate the role of chronic H. pylori infection in iron deficiency and neurological sequelae. Mice at both timepoints demonstrated significantly elevated gastric histopathology scores and inflammatory cytokines compared to sham-dosed controls. However, only mice at 27-29 weeks post infection had changes in hematological parameters, with significantly decreased erythrocyte count, hematocrit, serum hemoglobin, and increased serum total iron binding capacity. Gastric transcription of iron-regulatory genes Hamp and Bmp4 were significantly downregulated at both timepoints. In the brain, iron-dependent myelingergic and synaptic markers were significantly downregulated at 27-29 weeks. These results indicated that long-term infection of the CagA ⁺ PMSS1 strain of H. pylori in this study caused anemia, altered gastric iron homeostasis, and neurological changes similar to those reported in other rodent H. pylori CagA^- strain infection models.

Epstein-Barr Virus Infection Is Associated with Elevated Hepcidin Levels

EBV and Helicobacter pylori (H. pylori) cause highly prevalent persistent infections as early as in childhood. Both pathogens are associated with gastric carcinogenesis. H. pylori interferes with iron metabolism, enhancing the synthesis of acute-phase proteins hepcidin, C-reactive protein (CRP), and α-1 glycoprotein (AGP), but we do not know whether EBV does the same. In this study, we correlated the EBV antibody levels and the serum levels of hepcidin, CRP, and AGP in 145 children from boarding schools in Mexico City. We found that children IgG positive to EBV antigens (VCA, EBNA1, and EA) presented hepcidin, AGP, and CRP levels higher than uninfected children. Hepcidin and AGP remained high in children solely infected with EBV, while CRP was only significantly high in coinfected children. We observed positive correlations between hepcidin and EBV IgG antibodies (p < 0.5). Using the TCGA gastric cancer database, we also observed an association between EBV and hepcidin upregulation. The TCGA database also allowed us to analyze the two important pathways controlling hepcidin expression, BMP−SMAD and IL-1β/IL-6. We observed only the IL-1β/IL-6-dependent inflammatory pathway being significantly associated with EBV infection. We showed here for the first time an association between EBV and enhanced levels of hepcidin. Further studies should consider EBV when evaluating iron metabolism and anemia, and whether in the long run this is an important mechanism of undernourishment and EBV gastric carcinogenesis.

Gastrointestinal Changes and Alzheimer's Disease

BACKGROUND

There is a well-described mechanism of communication between the brain and gastrointestinal system in which both organs influence the function of the other. This bi-directional communication suggests that disease in either organ may affect function in the other.

OBJECTIVE

To assess whether the evidence supports gastrointestinal system inflammatory or degenerative pathophysiology as a characteristic of Alzheimer's disease (AD).

METHODS

A review of both rodent and human studies implicating gastrointestinal changes in AD was performed.

RESULTS

Numerous studies indicate that AD changes are not unique to the brain but also occur at various levels of the gastrointestinal tract involving both immune and neuronal changes. In addition, it appears that numerous conditions and diseases affecting regions of the tract may communicate to the brain to influence disease.

CONCLUSION

Gastrointestinal changes represent an overlooked aspect of AD, representing a more system influence of this disease.

Iron Deficiency-Induced Changes in the Hippocampus, Corpus Striatum, and Monoamines Levels That Lead to Anxiety, Depression, Sleep Disorders, and Psychotic Disorders

Iron deficiency anemia caused by severe iron deficiency in infancy is associated with poor health and severe neurological impairment such as mental, motor, social, emotional, neurophysiological, and neurocognitive dysfunction. The behavioral effects of iron deficiency can present themselves in infancy, but they are also found in adulthood. Some behaviors can start in childhood but persist throughout adulthood.

The behaviors that are particularly often seen in infants and children include wariness and hesitance, lack of positive affect, and diminished social engagement. The affected behaviors in adults include anxiety, depression, higher complex cogitative tasks, and other psychological disorders.

The mechanisms of how iron deficiency affects behavior include affecting the hippocampus, the corpus striatum, and certain neurotransmitters. The hippocampus is a brain region that is essential for memory, learning, and other purposes. The hippocampus is very sensitive to lack of Iron during early development. The corpus striatum dispatches dopamine-rich projects to the prefrontal cortex, and it is involved in controlling executive activities such as planning, inhibitory control, sustained attention, working memory, regulation of emotion, memory storage and retrieval, motivation, and reward. Iron deficiency has been known to cause changes in behavioral and developmental aspects by affecting neurotransmitters such as serotonin, noradrenaline, and dopamine.

Iron deficiency causes behavior changes that can present in infancy and, even if corrected postnatally, it can have long-lasting effects well into adulthood.

Red Cell Distribution Width, Anemia, and Brain Volumetric Outcomes Among Middle-Aged Adults

BACKGROUND

Anemia and red cell distribution width (RDW) have been linked to poor cognitive performance, pending studies of underlying mechanisms.

OBJECTIVE

We examined cross-sectional relationships of initial RDW status (v1), RDW change (δ), and anemia with brain structural magnetic resonance imaging (sMRI) markers, including global and cortical brain and hippocampal and white matter lesion (WML) volumes, 5-6 years later.

METHODS

Data were used from three prospective visits within the Healthy Aging in Neighborhoods of Diversity Across the Life Span (HANDLS) study with complete v1 (2004-2009) and v2 (2009-2013) exposures and ancillary sMRI data at vscan (2011-2015, n = 213, mean v1 to vscan time: 5.7 years). Multivariable-adjusted linear regression models were conducted, overall, by sex, by race, and within non-anemics, correcting for multiple testing with q-values.

RESULTS

In minimally adjusted models (socio-demographics and follow-up time), anemiav1 and RDWv1 were consistently associated with smaller bilateral hippocampal volumes overall, and among females (q < 0.05), without significant sex differences. RDWv1 was related to smaller select regional cortical brain gray and white matter volumes in hematological measure-adjusted models; anemiav1 was associated with larger WML volumes only among whites.

CONCLUSION

In summary, baseline anemia and RDW were consistently associated with smaller bilateral hippocampal volumes, particularly among females, while anemia was linked to larger WML volume among Whites. In hematological measure-adjusted models, baseline RDW was linked to smaller regional gray and white matter volumes. Pending studies with sMRI repeats, randomized controlled trials are needed, demonstrating associations of anemia and elevated RDW with reduced brain volumes and cognitive dysfunction.

The Associations of Dietary Iron Intake and the Transferrin Receptor (TFRC) rs9846149 Polymorphism with the Risk of Gastric Cancer: A Case-Control Study Conducted in Korea

Background: A positive association between a high iron intake and colorectal cancer has been identified; however, the effect of dietary iron on gastric cancer (GC) remains unclear. Here, we investigate whether dietary iron is related to GC risk and whether the transferrin receptor (TFRC) rs9846149 polymorphism modifies this association. Methods: A case–control study was designed to assess this association among 374 GC patients and 754 healthy controls. A self-administered questionnaire was used to collect information on demographics, medical history and lifestyle. Dietary iron intake was assessed using a semi-quantitative food frequency questionnaire. TFRC rs9846149 was genetically analyzed using the Affymetrix Axiom Exom 319 Array platform. Results: A higher total dietary iron was significantly associated with decreased GC risk [OR = 0.65 (0.45–0.94), p for trend = 0.018]. A similar association was observed with nonheme iron [OR = 0.64 (0.44–0.92), p for trend = 0.018]. Individuals with a major allele of TFRC rs9846149 (CC/GC) and higher intake of total iron had a significantly lower GC risk than those with a lower intake [OR = 0.60 (0.41–0.88), p interaction = 0.035]. Conclusion: Our findings show the protective effects of total dietary iron, especially nonheme iron, against GC risk, and this association can be modified by TFRC rs9846149.

Evaluation of Helicobacter pylori Infection, Neutrophil–Lymphocyte Ratio and Platelet–Lymphocyte Ratio in Dyspeptic Patients

Recent studies have shown a correlation between Helicobacter pylori (H. Pylori) infection and the neutrophil/lymphocyte ratio (NLR) and platelet/lymphocyte ratio (PLR). The aim of this study was to investigate the relationship between H. Pylori infection and hematimetric indices in patients with dyspepsia symptoms. Overall, 448 patients who underwent gastroscopy were analyzed retrospectively. Histopathological evaluation of biopsies according to H. pylori presence was classified as H. Pylori positive and negative groups, which are analyzed in relation with hematimetric indices. NLR and PLR measurements did not show a statistically significant difference between H. pylori negative and positive groups (p > 0.05). NLR revealed a negative correlation between hemoglobin (HGB), iron, and ferritin measurements in the correlation analysis of the H. Pylori positive group (r = −0.133, p = 0.031; r = −0.270, p = 0.002; r = −0.162, p = 0.032). Again, with PLR, there was a negative correlation between HGB, mean corpuscular volume (MCV), iron, and ferritin measurements (r = −0.310, p = 0.001, r = −0.187, p = 0.002, r = −0.335, p = 0.001; r = −0.290; p = 0.001). The results of our study do not reveal an association between H. pylori presence and inflammatory response, which is evaluated by NLR and PLR measurements in patients with dyspepsia. However, low serum iron and ferritin values of H. pylori-positive patients suggest the effect of H. pylori on iron metabolism.