Inflammation, immunity, and vaccines for Helicobacter

CD177 Expression and Inflammation Grade in Helicobacter pylori-Infected Wild-Type and CD177-/- C57BL/6 Mice

This study was undertaken to further investigate the CD177 expression in Helicobacter pylori- (Hp-) infected wild-type and CD177^-/- C57BL/6 mice, which may be helpful to elucidate the relationship between CD177 and Hp-related gastritis. 20 WT mice were randomly assigned into the Hpss1 WT group (n = 10) and Hp49503 WT group (n = 10); 20 KO mice were randomly assigned into the Hpss1 KO group (n = 10) and Hp49503 KO group (n = 10). The remaining mice served as controls. Mice in the HpSS1 groups and Hp49503 groups were independently infected with corresponding strains. Results showed that the Hp colonization score was related to the grade of mucosal inflammation (P < 0.05). The inflammation grade was comparable between the HpSS1 group and Hp49503 group as well as between the WT group and KO group. In addition, the Hp colonization score was related to the CD177 expression score (P < 0.05). The CD177 expression in the Hp colonization group was higher than that in the non-Hp colonization group (P < 0.05). CD177 expression was positively related to the inflammation grade (P < 0.01). In conclusion, CD177 expression was similar between HP49503- and HPss1-infected WT C57BL/6 mice, and CD177 expression was undetectable in CD177^-/- mice. CD177 expression in the gastric mucosa increases with the elevation of inflammation grade. In Hp-infected mice, the inflammation grade had no relationship with the type of Hp strain and the CD177 expression, but the mucosal inflammation score in Hp-infected mice was higher than that in non-Hp infected mice.

The Sweeping Role of Cholesterol Depletion in the Persistence of Helicobacter pylori Infections

The ability of Helicobacter pylori to persist lifelong in the human gastric mucosa is a striking phenomenon. It is even more surprising since infection is typically associated with a vivid inflammatory response. Recent studies revealed the mechanism by which this pathogen inhibits the epithelial responses to IFN-γ and other central inflammatory cytokines in order to abolish an effective antimicrobial defense. The mechanism is based on the modification and depletion of cholesterol by the pathogen's cholesterol-α-glucosyltransferase. It abrogates the assembly of numerous cytokine receptors due to the reduction of lipid rafts. Particularly, the receptors for IFN-γ, IL-22, and IL-6 then fail to assemble properly and to activate JAK/STAT signaling. Consequently, cholesterol depletion prevents the release of antimicrobial peptides, including the highly effective β-defensin-3. Intriguingly, the inhibition is spatially restricted to heavily infected cells, while the surrounding epithelium continues to respond normally to cytokine stimulation, thus providing a platform of the intense inflammation typically observed in H. pylori infections. It appears that pathogen and host establish a homeostatic balance between tightly colonized and rather inflamed sites. This homeostasis is influenced by the levels of available cholesterol, which potentially exacerbate H. pylori-induced inflammation. The observed blockage of epithelial effector mechanisms by H. pylori constitutes a convincing explanation for the previous failures of T-cell-based vaccination against H. pylori, since infected epithelial cells remain inert upon stimulation by effector cytokines. Moreover, the mechanism provides a rationale for the carcinogenic action of this pathogen in that persistent infection and chronic inflammation represent a pro-carcinogenic environment. Thus, cholesterol-α-glucosyltransferase has been revealed as a central pathogenesis determinant of H. pylori.

Audit of Helicobacter pylori Testing in Microbiology Laboratories in England: To Inform Compliance with NICE Guidance and the Feasibility of Routine Antimicrobial Resistance Surveillance

Introduction. The National Institute for Health and Clinical Excellence (NICE) guidance recommends that dyspeptic patients are tested for Helicobacter pylori using a urea breath test, stool antigen test, or serology. Antibiotic resistance in H. pylori is globally increasing, but treatment in England is rarely guided by susceptibility testing or surveillance. Aims. To determine compliance of microbiology laboratories in England with NICE guidance and whether laboratories perform culture and antibiotic susceptibility testing (AST). Methods. In 2015, 170 accredited English microbiology laboratories were surveyed, by email. Results. 121/170 (71%) laboratories responded; 96% provided H. pylori testing (78% on site). 94% provided H. pylori diagnosis using stool antigen; only four provided serology as their noninvasive test; 3/4 of these encouraged urea breath tests in their acute trusts. Only 22/94 (23%) of the laboratories performed H. pylori cultures from gastric biopsies on site; 9/22 performed AST, but the vast majority processed less than one specimen/week. Conclusions. Only five laboratories in England do not comply with NICE guidance; these will need the guidance reinforced. National surveillance needs to be implemented; culture-based AST would need to be centralised. Moving forward, detection of resistance in H. pylori from stool specimens using molecular methods (PCR) needs to be explored.

Non-pharmacological treatment of Helicobacter pylori

Many food and plant extracts have shown in vitro anti-Helicobacter pylori (H. pylori) activity, but are less effective in vivo. The anti-H. pylori effects of these extracts are mainly permeabilitization of the membrane, anti-adhesion, inhibition of bacterial enzymes and bacterial grown. We, herein, review treatment effects of cranberry, garlic, curcumin, ginger and pistacia gum against H. pylori in both in vitro, animal studies and in vivo studies.

Functionalized graphene oxide serves as a novel vaccine nano-adjuvant for robust stimulation of cellular immunity

Benefiting from their unique physicochemical properties, graphene derivatives have attracted great attention in biomedicine. In this study, we carefully engineered graphene oxide (GO) as a vaccine adjuvant for immunotherapy using urease B (Ure B) as the model antigen. Ure B is a specific antigen for Helicobacter pylori, which is a class I carcinogen for gastric cancer. Polyethylene glycol (PEG) and various types of polyethylenimine (PEI) were used as coating polymers. Compared with single-polymer modified GOs (GO-PEG and GO-PEI), certain dual-polymer modified GOs (GO-PEG-PEI) can act as a positive modulator to promote the maturation of dendritic cells (DCs) and enhance their cytokine secretion through the activation of multiple toll-like receptor (TLR) pathways while showing low toxicity. Moreover, this GO-PEG-PEI can serve as an antigen carrier to effectively shuttle antigens into DCs. These two advantages enable GO-PEG-PEI to serve as a novel vaccine adjuvant. In the subsequent in vivo experiments, compared with free Ure B and clinically used aluminum-adjuvant-based vaccine (Alum-Ure B), GO-PEG-PEI-Ure B induces stronger cellular immunity via intradermal administration, suggesting promising applications in cancer immunotherapy. Our work not only presents a novel, highly effective GO-based vaccine nano-adjuvant, but also highlights the critical roles of surface chemistry for the rational design of nano-adjuvants.

Helicobacter pylori Infection Is Associated with Higher CD4 T Cell Counts and Lower HIV-1 Viral Loads in ART-Naïve HIV-Positive Patients in Ghana

BACKGROUND

Worldwide, there is a high co-endemicity of HIV and H. pylori infection and there is growing evidence that H. pylori co-infection is associated with parameters of HIV disease progression. The objective of this study was to investigate the prevalence of H. pylori infection, and the association with clinical, immunological and virological parameters in a large cohort of HIV-infected individuals and uninfected controls in a West African country.

METHODS

HIV-patients (n = 1,095) and HIV-negative individuals (n = 107) were recruited at a university hospital in Ghana. H. pylori status was determined using stool antigen testing. HIV-related, clinical and socio-demographic parameters were recorded and analyzed according to H. pylori status.

RESULTS

The prevalence of H. pylori infection was significantly lower in HIV-positive compared to HIV-negative individuals (51.5 vs. 88%, p<0.0001). In HIV patients, H. pylori prevalence decreased in parallel with CD4+ T cell counts. In ART-naïve HIV-infected individuals, but not in those taking ART, H. pylori infection was associated with higher CD4 cell counts (312 vs. 189 cells/μL, p<0.0001) and lower HIV-1 viral loads (4.92 vs. 5.21 log10 copies/mL, p = 0.006). The findings could not be explained by socio-demographic confounders or reported use of antibiotics. Having no access to tap water and higher CD4+ T cell counts were identified as risk factors for H. pylori infection.

CONCLUSIONS

H. pylori prevalence was inversely correlated with the degree of immunosuppression. In ART-naïve individuals, H. pylori infection is associated with favorable immunological and virological parameters. The underlying mechanisms for this association are unclear and warrant investigation.

BH3-only protein Bim is associated with the degree of Helicobacter pylori-induced gastritis and is localized to the mitochondria of inflammatory cells in the gastric mucosa

BH3-only protein, Bim, is a pro-apoptotic protein that mediates mitochondria-dependent cell death. However, the role of Bim in Helicobacter pylori-associated gastritis remains unclear. This study aimed to assess the cellular localization of Bim and its possible role in H. pylori-induced gastritis. The study was conducted on biopsy specimens obtained from 80 patients who underwent upper gastrointestinal endoscopy (H. pylori-negative: n=30, positive: n=50). Association between Bim mRNA expression and severity of gastritis was evaluated and the localization of Bim was examined by immunofluorescence. Bim mRNA expression was positively correlated with the degree of gastritis, as defined by the Sydney system. Immunohistochemical analysis confirmed increased Bim expression in H. pylori-infected gastric mucosa compared with uninfected mucosa in both humans and mice. Bim localized in myeloperoxidase- and CD138-positive cells of H. pylori-infected lamina propria and submucosa of the gastric tract, indicating that this protein is predominantly expressed in neutrophils and plasma cells. In contrast, Bim did not localize in CD20-, CD3-, or CD68-positive cells. Bim was expressed in the mitochondria, where it was partially co-localized with activated Bax and cleaved-PARP. In conclusion, Bim is expressed in neutrophils and plasma cells in H. pylori-associated gastritis, where it may participate in the termination of inflammatory response by causing mitochondria-mediated apoptosis in specific leucocytes.

Effect of anti-Helicobacter pylori treatment on early diabetic kidney disease

AIM: To assess the effect of anti-Helicobacter pylori (H. pylori) therapy on chronic kidney disease (CKD) associated with type 2 diabetes mellitus (T2DM).

METHODS: Seventy-five T2DM patients with newly diagnosed CKD and H. pylori infection were randomly divided into an anti-H. pylori therapy group (n = 39) and a control group (n = 36). All of the patients received routine treatment for three months. Patients in the anti-H. pylori group were additionally given anti-H. pylori therapy. Clinical indices including fasting blood glucose (FBG), 2-h plasma glucose (2-h PG), hemoglobin A1c (HbA1c), systolic blood pressure (SBP), diastolic blood pressure (DBP), cholesterol (TC), triglyceride (TG), urinary albumin/creatitine ratio (UAlb/Cr), C-reactive protein (CRP), tumor necrosis factor α (TNF-α), plasma endothelin 1 (ET-1), and homocysteine (HCY) were recorded before and three months after treatment.

RESULTS: No significant differences were observed in all clinical indices between the two groups before treatment (P > 0.05). The eradication rate of H. pylori in the anti-H. pylori group was significantly higher than that in the control group three months after treatment (P < 0.01). There were no differences in FBG, 2-h PG, SBP, DBP, HbA1c, TG, or TC between before and after treatment (P > 0.05). At three months after treatment, UAlb/Cr, CRP, ET-1, TNF-α and HCY decreased significantly in both groups (P < 0.05), and changes were statistically significant different between the two groups (P < 0.05).

CONCLUSION: Anti-H. pylori therapy is beneficial for T2DM patients with CKD, because it can help control UAlb/Cr, CRP, ET-1, TNF-α, and HCY and even play an important role in postponing CKD.

Gastric cancer mortality in a high incidence area: long-term follow-up of Helicobacter pylori-related precancerous lesions in the general population

BACKGROUND

Due to a lack of clear criteria for recognizing subjects at risk of progression to gastric cancer (GC), this cohort study seeks to identify predictors of GC death in a high-risk population.

METHODS

During 2000-2001, 1011 randomly selected residents of Ardabil, Iran without a history of gastrointestinal diseases, underwent upper endoscopy with targeted biopsy sampling. Until 2013, cancer mortality data were obtained using cancer and death registry data and verbal autopsy reports. Cox regression was used to estimate hazard ratios (HR).

RESULTS

A total of 3.95% of the participants [mean age: 53.1 ± 9.9 years, 49.8% males, and 88.2% Helicobacter pylori (H. pylori-positive)] died of GC. In the multivariate model, precancerous lesions at the beginning of follow-up were associated with increased GC mortality. The HR [95% confidence interval (CI)] was 7.4 (1.6-33.8) for atrophic gastritis (AG) and 23.6 (5.5-102.3) for intestinal metaplasia (IM). Age over 50 (HR = 4.4; 1.3-14.2), family history of GC (HR = 6.8; 3.3-13.8), smoking (HR = 7.4; 3.2-17.3), and endoscopically confirmed gastric ulcer (GU, HR = 6.5; 2.5-16.4) were independently associated with GC mortality. The concomitant presence of a precancerous lesion increased the HR to 46.5 (10.8-198.6) for a family history of GC, 27.6 (6.5-116.4) for smoking, and 25.1 (6.3-105.3) for age >50 years.

CONCLUSIONS

In this population with a high rate of H. pylori infection, age over 50 years, smoking, family history of GC, IM, AG, and in particular, an undiagnosed GU were significant independent risk factors for mortality due to GC. The assessment of a combination of these risk factors might identify individuals at risk of GC who could possibly benefit from regular surveillance.

Endoplasmic reticulum stress contributes to Helicobacter pylori VacA-induced apoptosis

Vacuolating cytotoxin A (VacA) is one of the important virulence factors produced by H. pylori. VacA induces apoptotic cell death, which is potentiated by ammonia. VacA also causes cell death by mitochondrial damage, via signaling pathways that are not fully defined. Our aim was to determine whether endoplasmic reticulum (ER) stress is associated with VacA-induced mitochondrial dysfunction and apoptosis. We found that C/EBP homologous protein (CHOP), a key signaling protein of ER stress-induced apoptosis, was transcriptionally up-regulated following incubation of gastric epithelial cells with VacA. The effect of VacA on CHOP induction was significantly enhanced by co-incubation with ammonium chloride. Phosphorylation of eukaryotic initiation factor 2 (eIF2)-alpha, which is known to occur downstream of the ER stress sensor PKR-like ER-localized eIF2-alpha kinase (PERK) and to regulate CHOP expression, was also observed following incubation with VacA in the presence of ammonium chloride. Knockdown of CHOP by siRNA resulted in inhibition of VacA-induced apoptosis. Further studies showed that silencing of the PERK gene with siRNA attenuated VacA-mediated phosphorylation of eIF2-alpha, CHOP induction, expression of BH3-only protein Bim and Bax activation, and cell death induced by VacA with ammonium chloride, indicating that ER stress may lead to mitochondrial dysfunction during VacA-induced toxicity. Activation of ER stress and up-regulation of BH3-only proteins were also observed in human H. pylori-infected gastric mucosa. Collectively, this study reveals a possible association between VacA-induced apoptosis in gastric epithelial cells, and activation of ER stress in H. pylori-positive gastric mucosa.

Helicobacter pylori seropositivity in diabetic patients is associated with microalbuminuria

AIM: To investigate the relationship between Helicobacter pylori (H. pylori) seropositivity and the presence of microalbuminuria.

METHODS: Between December 2003 and February 2010, asymptomatic individuals who visited the Seoul National University Healthcare System Gangnam Center for a routine check-up and underwent tests for H. pylori immunoglobulin G antibodies and urinary albumin to creatinine ratio (UACR) were included. All study subjects completed a structured questionnaire, anthropometric measurements and laboratory tests. Anti-H. pylori immunoglobulin G was identified using an enzyme-linked immunosorbent assay kit. A random single-void urine sample, collected using a clean-catch technique, was obtained to determine the UACR. The presence of microalbuminuria was defined as a UACR from 30 to 300 μg/mg. The presence of diabetes mellitus (DM) was defined as either a fasting serum glucose level greater than or equal to 126 mg/dL or taking anti-diabetic medication. Multiple logistic regression analysis was performed to identify the risk factors. The dependent variable was microalbuminuria, and the independent variables were the other study variables.

RESULTS: A total of 2716 subjects (male, 71.8%; mean age, 54.9 years) were included. Among them, 224 subjects (8.2%) had microalbuminuria and 324 subjects (11.9%) had been diagnosed with DM. Subjects with microalbuminuria had a significantly higher H. pylori seropositivity rate than subjects without microalbuminuria (60.7% vs 52.8%, P = 0.024). Multivariate analysis after adjustment for age, body mass index (BMI), waist circumference, and glucose and triglyceride levels showed that H. pylori seropositivity was significantly associated with microalbuminuria [odds ratio (OR), 1.40, 95% CI, 1.05-1.89, P = 0.024]. After the data were stratified into cohorts by glucose levels (≤ 100 mg/dL, 100 mg/dL < glucose < 126 mg/dL, and ≥ 126 mg/dL or history of DM), H. pylori seropositivity was found to be significantly associated with microalbuminuria in diabetic subjects after adjusting for age, BMI and serum creatinine level (OR, 2.21, 95% CI, 1.20-4.08, P = 0.011). In addition, the subjects were divided into five groups. Those without microalbuminuria (an UACR of < 30 μg/mg) were divided into four groups in accordance with their UACR values, and subjects with microalbuminuria comprised their own group. Notably, H. pylori seropositivity gradually increased with an increase in UACR (P = 0.001) and was highest in subjects with microalbuminuria (OR, 2.41, 95% CI, 1.14-5.11). This suggests that H. pylori seropositivity is positively associated with microalbuminuria in diabetic subjects.

CONCLUSION: H. pylori seropositivity was independently associated with microalbuminuria, and the prevalence of H. pylori seropositivity was associated with the severity of UACR in diabetic subjects.

The Helicobacter pylori virulence effector CagA abrogates human β-defensin 3 expression via inactivation of EGFR signaling

Antimicrobial peptides are constituents of the first-line innate mucosal defense system that acts as a barrier to establishment of infection. The highly successful human gastric pathogen, Helicobacter pylori, is able to persistently colonize its host despite inducing expression of several antimicrobial peptides, including human β-defensin 3 (hBD3). We find that hBD3 is highly active against H. pylori in vitro and is rapidly induced during early infection via EGFR-dependent activation of MAP kinase and JAK/STAT signaling. However, during prolonged infection, hBD3 was subsequently downregulated by the H. pylori virulence determinant CagA. Upon translocation into host cells, CagA activated the cellular tyrosine phosphatase, SHP-2, terminating EGFR activation and downstream signaling and increasing bacterial viability. Chemical inhibition and knockdown of SHP-2 expression rescued hBD3 synthesis and bactericidal activity. Thus, we reveal how cagPAI-positive H. pylori strains use CagA to evade a key innate mucosal defense pathway to support the establishment of persistent infection.

Inhibition of H. pylori colonization and prevention of gastritis in murine model

Helicobacter pylori is a Gram-negative spiral bacterium that colonizes human gastric mucosa causing infection. In this study aiming at inhibition of H. pylori infection we made an attempt to evaluate immunogenicity of the total (UreC) and C-terminal (UreCc) fragments of H. pylori urease. Total UreC and its C-terminal fragment were expressed in E. coli. Recombinant proteins were analyzed by SDS-PAGE and western blot and then purified by Ni-NTA affinity chromatography. Female C57BL6/j mice were immunized with the purified proteins (UreC and UreCc). Antibody titers from isolated sera were measured by ELISA. Immunized mice were then challenged by oral gavage with live H. pylori Sydney strain SS1. Total of 109 CFU were inoculated into stomach of immunized and unimmunized healthy mice three times each at one day interval. Eight weeks after the last inoculation, the blood sample was collected and the serum antibody titer was estimated by ELISA. Stomach tissues from control and experimental animal groups were studied histopathologically. UreC and UreCc yielded recombinant proteins of 61 and 31 kDa respectively. ELIZA confirmed establishment of immunity and the antibodies produced thereby efficiently recognized H. pylori and inhibited its colonization in vivo. Pathological analysis did not reveal established infection in immunized mice challenged with H. pylori. The results support the idea that UreC and UreCc specific antibodies contribute to protection against H. pylori infections.

Persistent Helicobacter pylori specific Th17 responses in patients with past H. pylori infection are associated with elevated gastric mucosal IL-1β

BACKGROUND

Ongoing Helicobacter pylori (HP) infection triggers a chronic active gastritis. Eradicating HP reduces gastric inflammation, but does not eliminate it. We sought to characterize this persistent gastritis, and demonstrate the persistence of HP-specific Th17 responses in individuals previously infected with HP but who no longer had evidence of ongoing infection.

METHODOLOGY/PRINCIPAL FINDINGS

Study subjects were divided into 3 groups 55 individuals had active HP infection (group A), 41 were diagnosed with previous HP infection (group P), and 59 were naïve to HP (group N). Blood and gastric tissue were obtained with written informed consent from all subjects, and immune responses were evaluated using flow cytometry, semi-quantitative real time PCR, immunofluorescent staining, ELISA, and multiplex cytometric bead array for cytokine quantification. Elevated IL-17A responses were observed in patients from group A compared to group N. Interestingly, IL-17A responses remained persistently elevated in the blood and gastric mucosa of individuals from group P, despite the absence of ongoing HP infection. Using purified CD4(+) T cells as effectors and antibodies that blocked antigen presentation by MHC Class II, we showed that these persistent IL-17A responses were mediated primarily by HP-specific Th17 cells, rather than other immune cells that have also been described to secrete IL-17A. Gastric mucosal IL-1β levels were also persistently elevated in group P, and neutralisation of IL-1β reduced the HP-specific IL-17A response of purified CD4(+) T cells to autologous HP-pulsed antigen presenting cells in vitro, suggesting a functional association between IL-1β and the persistent Th17 response in group P patients.

CONCLUSIONS/SIGNIFICANCE

Despite lack of ongoing HP infection, HP-specific Th17 cells persist in the blood and gastric mucosa of individuals with past HP infection. We speculate that this persistent inflammation might contribute to gastric mucosal pathology, for example, persistent increased gastric cancer risk despite eradication of HP.

Chronic inflammation and immunologic-based constraints in malignant disease

Acute inflammatory reactions benefit the host by supporting the effective clearance of pathogens and fostering wound healing, in addition to other self-preservative processes. However, when the inflammatory program is not resolved, becoming chronic in nature, it creates an environment conducive to cancer development and progression. Therefore, minimizing exposure to risk factors that contribute to chronic inflammation and reconditioning the host towards a state of (at least locoregional) acute inflammation would meaningfully impact cancer incidence and its treatment, respectively. Regarding cancer therapy, combinational treatments that both disrupt chronic inflammation and install specific adaptive type I immunity are predicted to enhance quality of life and extend the overall survival of patients.

Protease-activated receptor-2 (PAR2) in human gastric mucosa as mediator of proinflammatory effects in Helicobacter pylori infection

INTRODUCTION

Protease-activated receptors (PAR) are seven transmembrane receptors that are expressed throughout the gastrointestinal tract. In vitro experiments using gastric tumor cell lines, murine models and one clinical study provided evidence for a potential role of PAR2 in Helicobacter pylori-induced gastritis.

AIM

To investigate PAR2 expression in H. pylori-infected patients and correlation with proinflammatory IL-8, IL-1β as well as histologic changes of the mucosa. Furthermore, PAR2 expression was studied in context to mucosal amounts of secretory leukocyte protease inhibitor (SLPI), a putative regulator of PAR2.

METHODS

Twenty-two H. pylori-infected patients and 72 H. pylori-negative subjects underwent upper GI endoscopy. In antrum-derived mucosal biopsies, PAR2, IL-1β, IL-8, and SLPI expression was analyzed by quantitative RT-PCR, and in part by ELISA and immunohistochemistry. Histopathologic evaluation of gastritis was performed according to the updated Sydney classification.

RESULTS

IL-8 gene expression was 5-fold increased in the mucosa of H. pylori-infected patients compared with non-infected (p < .0001), whereas no differences for PAR2 and IL-1β mRNA amounts were observed between both groups. PAR2 gene expression correlated positively with transcript levels of IL-8, IL-1β as well mucosal SLPI levels in H. pylori-infected patients (r: 0.47-0.84; p < .0001), whereas no correlation was found with the degree of gastritis.

CONCLUSIONS

PAR2 represents an additive pathway of IL-8 secretion and proinflammatory effects in H. pylori-induced gastritis. Reduced SLPI levels leading to higher serine protease activities in the mucosa of infected subjects might regulate PAR2 activation.

Carcinogenesis, prevention and early detection of gastric cancer: where we are and where we should go

Helicobacter pylori is the most common cause of gastric cancer (GC), though smoking, alcohol, diet, genetics and epigenetic factors may also have a role in the occurrence of the disease. Why H. pylori cause GC in only a minority of those infected remains unknown. Although mechanisms of H. pylori-induced carcinogenesis are not yet well understood, several genotypes of H. pylori have been associated with strain virulence and disease risk. Primary prevention of GC should be addressed by avoiding exposure to factors that increase the risk and to promote factors associated with decrease risk. Vaccines against H. pylori are an ongoing promise and not yet available. Chemoprevention through vitamin supplementation has shown no benefit. Screening and eradication of H. pylori in the general population is not advised. Given that GC is a multiple-steps process, the identification of patients with preneoplastic lesions with high risk of progression, and periodic endoscopic surveillance of them represents the most effective way for early diagnosis of GC. However, clinical guidelines for surveillance are lacking and there are no clear criteria to classify patients into high or low risk of progressing to GC. No study has shown the potential usefulness of combining the information on the type of preneoplastic lesions, genetic and epigenetic, lifestyle and virulence bacterial factors in order to identify high risk patients who need more intensive surveillance. The integration of all this information, in a prediction model requires further research and could be the most important contribution for reducing the burden of GC.

The association between Helicobacter pylori infection and insulin resistance: a systematic review

BACKGROUND

Helicobacter pylori infection has been associated with diverse extradigestive morbidity, including insulin resistance (IR) syndrome. The aim of this systematic review was to summarize the epidemiologic evidence concerning the association between H. pylori infection and IR quantitative indexes.

MATERIALS AND METHODS

A computerized literature search in PubMed electronic databases and Cochrane Central Register of Controlled Trials was performed.

RESULTS

Nine studies reporting data on 2120 participants were finally eligible for this systematic review. Seven of them were cross-sectional studies and two were nonrandomized, open-label, controlled trials investigating the effect of H. pylori eradication on IR. Homeostatic model of assessment insulin resistance (HOMA-IR) was used in all studies to quantify IR. There seems to be a trend toward a positive association between H. pylori infection and HOMA-IR, strengthened by regression analysis in one study. However, there was significant heterogeneity between studies regarding the method(s) of H. pylori infection diagnosis based on and the study populations. The studies for the effect of H. pylori eradication on HOMA-IR revealed conflicting results.

CONCLUSIONS

Although data seem to indicate a potential association between H. pylori infection and IR, further studies are needed to strengthen this association and to clarify whether there is a causative link between them. If a causal link is confirmed in the future, this may have a major impact on the pathophysiology and management of IR syndrome, including type 2 diabetes mellitus and nonalcoholic fatty liver disease.