Yoshio Yamaoka | Oita University (original) (raw)

Papers by Yoshio Yamaoka

Helicobacter pylori lives in the human stomach and has a population structure which resembles tha... more Helicobacter pylori lives in the human stomach and has a population structure which resembles that of its host. However, H. pylori from Europe and the Middle East trace a substantially higher fraction of ancestry from modern African populations than the humans that carry them. We use a collection of Afro-Eurasian genomes to show that this African ancestry is due to at least three distinct admixture events. H. pylori from East Asia, which have undergone little admixture, have accumulated many more non-synonymous mutations than African strains. European and Middle Eastern bacteria have elevated African ancestry at the sites of these mutations compared to either non-segregating or synonymous sites. We use simulations to show demographic bottlenecks can lead to long-term segregation of deleterious mutations, despite high rates of homologous recombination, but that population fitness can be restored by migration of small numbers of bacteria from non-bottlenecked populations, leading to m...

Helicobacter, 2005

As with many infectious diseases, only a fraction of people infected with Helicobacter pylorideve... more As with many infectious diseases, only a fraction of people infected with Helicobacter pyloridevelop clinical disease, and host genetics, host immune response, and bacterial virulence factors appear to play critical roles. There has been considerable interest in putative bacterial virulence ...

Journal of digestive diseases, Jan 25, 2015

Gastric cancer is etiologically related to interactions between Helicobacter pylori infection, en... more Gastric cancer is etiologically related to interactions between Helicobacter pylori infection, environmental, and host factors. Gastric carcinoma is associated with a cascade of increasing atrophic gastric mucosal damage. Prostate stem cell antigen polymorphisms have been associated with an increased risk of gastric cancer. Here, we examined the interaction between prostate stem cell antigen polymorphisms and H. pylori in the progression of H. pylori gastritis. Prostate stem cell antigen polymorphisms (TT, TC and CC) among H. pylori infected and uninfected Bhutanese were compared with the severity of H. pylori gastritis (neutrophils, monocytes, atrophy scores, H. pylori density, and the presence and extent of intestinal metaplasia) using the updated Sydney system. Biopsies from 339 patients were included. The proportion of biopsies with intestinal metaplasia was also significantly (P<0.05) greater among those with the TT genotype than with either the CT or CC genotype. Despite no...

PloS one, 2015

The prevalence of Helicobacter pylori infection in Indonesia is still controversial and mainly in... more The prevalence of Helicobacter pylori infection in Indonesia is still controversial and mainly investigated in the largest ethnic group, Javanese. We examined the prevalence of H. pylori infection using four different tests including culture, histology confirmed by immunohistochemistry and rapid urease test. We also analyzed risk factors associated with H. pylori infection in five largest islands in Indonesia. From January 2014-February 2015 we consecutively recruited a total of 267 patients with dyspeptic symptoms in Java, Papua, Sulawesi, Borneo and Sumatera Island. Overall, the prevalence of H. pylori infection was 22.1% (59/267). Papuan, Batak and Buginese ethnics had higher risk for H. pylori infection than Javanese, Dayak and Chinese ethnics (OR = 30.57, 6.31, 4.95; OR = 28.39, 5.81, 4.61 and OR = 23.23, 4.76, 3.77, respectively, P <0.05). The sensitivity and specificity for RUT and culture were 90.2%, 92.9% and 80.5%, 98.2%, respectively. The patients aged 50-59 years grou...

Gut Pathogens, 2015

Background: It remains unclear whether the low incidence of gastric cancer in Indonesia is due to... more Background: It remains unclear whether the low incidence of gastric cancer in Indonesia is due to low infection rates only or is also related to low Helicobacter pylori pathogenicity. We collected H. pylori strains from the five largest islands in Indonesia and evaluated genetic virulence factors.

The aim of the study was to compare published H. pylori primer pairs for their ability to reliabl... more The aim of the study was to compare published H. pylori primer pairs for their ability to reliably 2 detect H. pylori in gastric biopsies and salivary samples. Detection limits of the 26 PCR primer 3 pairs previously described for detection of H. pylori DNA in clinical samples were determined. 4

PLOS ONE, 2015

Prevalence of Helicobacter pylori infection in Nepal, a low-risk country for gastric cancer, is d... more Prevalence of Helicobacter pylori infection in Nepal, a low-risk country for gastric cancer, is debatable. To our knowledge, no studies have examined H. pylori virulence factors in Nepal. We determined the prevalence of H. pylori infection by using three different tests, and the genotypes of virulence factors were determined by PCR followed by sequencing. Multilocus sequence typing was used to analyze the population structure of the Nepalese strains. The prevalence of H. pylori infection in dyspeptic patients was 38.4% (56/146), and was significantly related with source of drinking water. In total, 51 strains were isolated and all were cagA-positive. Western-type-cagA (94.1%), cagA pre-EPIYA type with no deletion (92.2%), vacA s1a (74.5%), and m1c (54.9%) were the predominant genotypes. Antral mucosal atrophy levels were significantly higher in patients infected with vacA s1 than in those infected with s2 genotypes (P = 0.03). Several Nepalese strains were H. pylori recombinants with genetic features of South Asian and East Asian genotypes. These included all East-Asian-type-cagA strains, with significantly lesser activity and inflammation in the corpus than the strains of the specific South Asian genotype (P = 0.03 and P = 0.005, respectively). Although the population structure confirmed that most Nepalese strains belonged to the hpAsia2 population, some strains shared hpEurope- and Nepalese-specific components. Nepalese patients infected with strains belonging to hpEurope showed higher inflammation in the antrum than strains from the Nepalese specific population (P = 0.05). These results support that ancestor roots of Kathmandu`s people not only connected with India alone.

BioMed Research International, 2015

The American Journal of Gastroenterology, 2005

H. pylori-infected patients were randomly assigned to undergo twice daily treatment with esomepra... more H. pylori-infected patients were randomly assigned to undergo twice daily treatment with esomeprazole 40 mg (n = 100) or pantoprazole 40 mg (n = 100) combined with clarithromycin 500 mg and amoxicillin 1 g for 1 wk (ECA and PCA groups, respectively). Follow-up endoscopy was performed at 8 wks after the end of treatment to assess the treatment response.

World journal of gastroenterology : WJG, Jan 14, 2015

To survey the detailed analyses for Helicobacter pylori (H. pylori) infection and gastric mucosal... more To survey the detailed analyses for Helicobacter pylori (H. pylori) infection and gastric mucosal status in Myanmar. A total of 252 volunteers with dyspeptic symptoms (155 female and 97 male; mean age of 43.6 ± 14.2 years) was participated in Yangon and Mandalay. The status of H. pylori infection was determined based on 5 different tests including rapid urease test, culture, histology, immunohistochemistry and serology. Histological scores were evaluated according to the update Sydney system and the Operative Link for Gastritis Assessment system. Pepsinogen (PG) I and PG II were measured using enzyme-linked immunosorbent assays. The overall prevalence of H. pylori infection was 48.0%. There was no relationship between age and infection rate. Even in young group (less than 29 years old), the H. pylori infection rate was relatively high (41.9%). The prevalence of H. pylori infection was significantly higher in Yangon than that of Mandalay. H. pylori infection was significantly associa...

Gut Pathogens, 2014

Background: Sulawesi in Indonesia has a unique geographical profile with assumed separation from ... more Background: Sulawesi in Indonesia has a unique geographical profile with assumed separation from Sundaland. Studies of Helicobacter pylori in this region are rare due to the region's rural location and lack of endoscopy equipment. Indirect methods are, therefore, the most appropriate for measuring H. pylori infection in these areas; with the disposable gastric brush test, we can obtain gastric juice as well as small gastric tissue samples for H. pylori culture. We investigated the prevalence of H. pylori infection and evaluated human migration patterns in the remote areas of North Sulawesi. Methods: We recruited a total of 251 consecutive adult volunteers and 131 elementary school children. H. pylori infection was determined by urine antibody test. A gastric brush test was used to culture H. pylori. We used next-generation and polymerase chain reaction based sequencing to determine virulence factors and multi-locus sequence typing (MLST).

Medical Clinics of North America, 2000

Helicobacter pylori infection is now recognized as a serious transmissible infectious disease. H.... more Helicobacter pylori infection is now recognized as a serious transmissible infectious disease. H. pylori is not associated with disease; it causes disease: peptic ulcers, gastric cancer, and primary B-cell gastric lymphoma. H. pylori is a curable chronic destructive bacterial infection. This article addresses the current approach to diagnosis and therapy, new considerations regarding whom to treat, and the role of putative virulence factors in disease causation.

Human pathology, 2015

The outcomes of Helicobacter pylori infection vary geographically. H pylori strains, disease pres... more The outcomes of Helicobacter pylori infection vary geographically. H pylori strains, disease presentation, and environments differ markedly in Bhutan and Dominican Republic. The aims were to compare the strains, histology, and expression of interleukin (IL) 8 and IL-10 from gastric mucosa from the 2 countries. H pylori status was assessed by the combination of rapid urease test, culture, and histology. Histology was evaluated using the updated Sydney System, and cytokines in gastric biopsies were measured using real-time polymerase chain reaction (PCR). There were 138 subjects from Bhutan and 155 from Dominican Republic. The prevalence of H pylori infection was 65% and 59%, respectively. The genotype of cagA was predominantly East Asian type in Bhutan versus Western type in Dominican Republic. Gastritis severity was significantly higher in H pylori-infected subjects from Bhutan than those from Dominican Republic. IL-8 expression by H pylori infection was 5.5-fold increased in Bhutan...

PLoS ONE, 2014

Background: A recent report has shown that the phylogenetic origin of Helicobacter pylori based o... more Background: A recent report has shown that the phylogenetic origin of Helicobacter pylori based on multi-locus sequence typing (MLST) was significantly associated with the severity of gastritis in Colombia. However, the potential relationship between phylogenetic origin and clinical outcomes was not examined in that study. If the phylogenetic origin rather than virulence factors were truly associated with clinical outcomes, identifying a population at high risk for gastric cancer in Colombia would be relatively straightforward. In this study, we examined the phylogenetic origins of strains from gastric cancer and duodenal ulcer patients living in Bogota, Colombia.

Digestive diseases and sciences, 2002

NSAID use and Helicobacter pylori both cause damage to the gastric mucosa and can cause peptic ul... more NSAID use and Helicobacter pylori both cause damage to the gastric mucosa and can cause peptic ulcers. Our aim was to test the relationship between gastric mucosal polymorphonuclear leukocyte (PMN) infiltration and the severity of NSAID-induced gastric injury. H. pylori density, mucosal interleukin-8 (IL-8), and nitrite levels were assessed after receiving placebo and again after receiving 1000 mg of naproxen daily for three days. Histology was graded using a visual analog scale (0-5). IL-8 levels were assayed by ELISA and nitrite levels by Griess reaction. Eleven healthy volunteers with H. pylori infection entered. All had normal-appearing gastric mucosa after placebo. Postnaproxen gastric damage included three with none, one with mild, three with moderate, two with severe, and three were very severe mucosal injury (including one with an ulcer >5 mm). There was an inverse correlation between endoscopic score and the pH of the gastric juice post-therapy (R = -0.77, P = 0.004). Th...

Proceedings of the National Academy of Sciences, 2000

PLoS ONE, 2011

Gastric cancer is one of the most common causes of cancer-related mortality worldwide. Expression... more Gastric cancer is one of the most common causes of cancer-related mortality worldwide. Expression of the tumor suppressor, promyelocytic leukemia (PML) protein, is reduced or abolished in gastric carcinomas, in association with an increased level of lymphatic invasion, development of higher pTNM staging, and unfavorable prognosis. Herein, we investigated the relationship between the extent of tumor-infiltrating lymphocytes and the status of PML protein expression in advanced gastric carcinoma. We observed higher numbers of infiltrating T-cells in gastric carcinoma tissues in which PML expression was reduced or abolished, compared to tissues positive for PML. The extent of T-cell migration toward culture supernatants obtained from interferon-gamma (IFN-c-stimulated gastric carcinoma cell lines was additionally affected by expression of PML in vitro. Interferon-gamma-inducible protein 10 (IP-10/CXCL10) expression was increased in gastric carcinoma tissues displaying reduced PML levels. Moreover, both Pml knockout and knockdown cells displayed enhanced IP-10 mRNA and protein expression in the presence of IFN-c. PML knockdown increased IFN-c-mediated Signal Transducer and Activator of Transcription-1 (STAT-1) binding to the IP-10 promoter, resulting in elevated transcription of the IP-10 gene. Conversely, PML IV protein expression suppressed IP-10 promoter activation. Based on these results, we propose that loss of PML protein expression in gastric cancer cells contributes to increased IP-10 transcription via enhancement of STAT-1 activity, which, in turn, promotes lymphocyte trafficking within tumor regions.

Kidney International, 2009

Journal of Gastroenterology and Hepatology, 1998

We have previously reported on laser spectroscopy as a simple alternative to mass spectrometry. T... more We have previously reported on laser spectroscopy as a simple alternative to mass spectrometry. To validate a simplified 13C-urea breath test (UBT) with laser spectroscopy for the detection of Helicobacter pylori in clinical use, we evaluated the optimal time of breath sample collection. The 13C-UBT was carried out on each of 102 infected and 70 non-infected subjects (32 without eradication and 38 after eradication therapy). Breath samples were taken at five time points within 60 min followed by 100 mg of 13C-urea administration. The ratio of 13CO2 to 12CO2 was measured using laser spectroscopy and the recovery of tracer in the exhaled breath was calculated. Results were compared with histological and culture examinations of gastric biopsies to establish the infection status. For statistical evaluation of 13C-UBT, the optimal timing of breath sample collection was examined on the basis of the kinetics of delta-13CO2. In 32 H. pylori-negative patients (without therapy), the mean +/- 2SD of delta-13CO2 was at its minimum 20 min after urea ingestion whereas in H. pylori-positive patients, the mean +/- SD delta-13CO2 was maximum at 20 min. In addition, receiver operating characteristic (ROC) curve analysis showed that the cut-off value was estimated between 2.5-3.0 per mil (%0) at 20 min before therapy. Based on the histology and culture results, the sensitivity, specificity and positive and negative predictive values were 98.0%, 100%, and 94.1%, respectively. In conclusion, 13C-UBT with laser spectroscopy is a non-invasive, simple, sensitive and specific test to determine H. pylori status. Our findings suggest that in clinical use, measurements made at 20 min after substrate administration could be recommended for most sensitive and specific 13C-UBT results.

Journal of Gastroenterology, 1997

A rare case of endescopic and histological regression of a gastric lymphoid mucosal lesion after ... more A rare case of endescopic and histological regression of a gastric lymphoid mucosal lesion after eradication of Helicobacter pylori is reported. A 72year-old man was suspected of having a low-grade Bcell gastric mucosa-associated lymphoid tissue (MALT) lymphoma by endoscopic and histological findings. Histology of biopsy specimens showed massive infiltration of atypical lymphocytes and lymphoepithelial lesions. Immunohistochemical staining revealed kappa light chain expression in the infiltrated atypical lymphocytes to be twofold that of lambda light chain. The above 9 diagnosis was thus highly suspected but not confirmed.