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Keywords:

  • functional dyspepsia;
  • gastric motility;
  • GNβ3;
  • polymorphism;
  • postprandial distress syndrome

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. References

Background  G-protein dysfunction related alteration of intracellular signal transduction might be linked to various abnormalities of functional gastrointestinal (GI) disorders. Serotonin (5-hydroxytryptamine; 5-HT) as well as G-protein is also key signaling molecule sensorimotor functions in the GI tract. Thus, this study aims to evaluate the correlation between gastric emptying and GNβ3 and 5-HTs polymorphisms in functional dyspepsia (FD) as defined by Rome III classification.

Methods  Seventy-four patients presenting with typical symptoms of FD (epigastric pain syndrome: EPS, = 24; postprandial distress syndrome: PDS, = 51) and sixty-four healthy volunteers were enrolled. Gastric motility was evaluated with the Tmax value using the 13C-acetate breath test. We used Rome III criteria to evaluate upper abdominal symptoms and SRQ-D scores to determine depression status. GNβ3-C825T, 5-HT1A-C1019G, 5-HT2A-G1438A, 5-HT3A-C42T, and 5-HT4A-G353 + 6A polymorphisms were analyzed in DNA from blood samples of enrolled subjects. Genotyping was performed by polymerase chain reaction.

Key Results  There was a significant relationship (= 0.045) between GNβ3 825CC genotype and PDS patients without gastro-esophageal reflux symptoms with impaired gastric emptying. In Japanese, GNβ3 825CC genotype in FD patients was significantly associated (= 0.0485) with the feeling of hunger compared with GNβ3 825CT and TT genotypes.

Conclusions & Inferences  Our results suggest that the GNβ3 825CC genotype is significantly associated with PDS patients without gastro-esophageal reflux with impairments of gastric emptying and also with the feeling of hunger in patients with FD. Further studies are needed to clarify whether the GNβ3 825CC genotype is linked to disturbances of gastric emptying via altered signal transduction responses.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. References

Recently, Functional dyspepsia (FD) has been subclassified into two new disease categories under the Rome III classification, epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS).1 Although Rome III criteria exclude gastro-esophageal reflux symptoms from the clinical symptoms of FD patients, some degree of overlap between the symptoms of non-erosive reflux disease (NERD) and FD is inevitable. Impairment of gastric motility such as gastric emptying is strongly associated with the pathophysiology of FD, one of the most common gastrointestinal (GI) disorders.2 Disturbances of physiological gastric emptying occur with a variety of symptoms ranging from premature saturation, fullness, nausea, vomiting, epigastric pain, and acid reflux in patients with delayed emptying in FD patients. We have previously reported that Tmax value as a marker of gastric emptying in PDS patients was significantly greater compared with that of healthy volunteers.3 We have reported that prokinetics such as mosapride citrate improve clinical symptoms through affecting Tmax value in proton pump inhibitor (PPI)-resistant NERD patients with impaired gastric emptying.4 These results suggest that Tmax value is one of the useful marker for considering the management of FD and NERD patients.

G-protein is composed of different α, β, and γ subunit isoforms, the βγ subunit forming a functional monomer. On receptor activation, both α and βγ subunits dissociate from the receptor and in turn modulate a large variety of intracellular effector system. Accordingly, G-protein dysfunction potentially could block intracellular signal transduction. The GNβ3 gene encodes the Gβ3 subunit of heterotrimeric G proteins, which are key components of intracellular signal transduction that are widely present in cells of the body.5 Thus, G-protein dysfunction related alteration of intracellular signal transduction might be linked to various abnormalities of functional GI disorders including disturbed gut sensory or motor function,6–8 dysfunction of the autonomic nervous system,9 and underlying psychiatric disturbances.10 A common C825T polymorphism has been described in the gene GNβ3 that encodes the β3 subunit of heterotrimeric G-proteins. Homozygous 825C allele carriers (CC genotype) form only minute amounts of the β3 splice variant and, thus, are characterized by diminished signal transduction responses.11 In recent studies, clinical symptoms such as unexplained abdominal symptoms and meal-unrelated dyspepsia in FD have also been associated with the various polymorphism including GNβ3 polymorphism.12,13 Moreover, familial clustering of FD has been reported, suggesting that a genetic factor may also play a significant role in developing FD.14

In addition, serotonin (5-hydroxytryptamine; 5-HT) as well as G-protein is key signaling molecule sensorimotor functions in the GI tract. 5-HT1A receptor agonists with anxiolytic properties delays gastric emptying15 and relaxes the proximal stomach in human.16 5-HT2A receptor has been reported to be involved in the modulation of enteric neuronal activity.17 5-HT3 receptor agonist, MKC-733 has also delayed gastric emptying in association with relaxation of the proximal stomach. 5-HT4 receptor as well as 5-HT3 play an important role in GI sensory and motor functions.18 Lelyveld et al. have studied whether there was a significant relationship among three genotypes including 5-HT3 and clinical symptoms in FD patients based on Rome II classification in Austria.19

In this study, we aimed to clarify whether GNβ3 genotype as well as genotypes of 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A could be associated with clinical symptoms and gastric emptying via impairment of receptor dysfunction, reduction of serotonin levels, and the response for serotonin in FD patients based on Rome III classification.

Material and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. References

Patients

Seventy-four consecutive patients presenting with typical symptoms of FD (EPS, = 24; PDS, = 51) and sixty-four healthy volunteers were enrolled after upper GI endoscopy and abdominal ultrasonography. Patients were diagnosed according to Rome III criteria.20 Healthy volunteers were also recruited from the volunteers among Japanese medical staffs of Nippon Medical School, who have no clinical history of gastroduodenal disease including clinical symptom of FD symptoms. Exclusion criteria included severe heart disease, renal or pulmonary failure, liver cirrhosis, severe systemic illness, and history of malignant disease. Patients with previous gastroduodenal surgery, duodenal ulcer scar, diabetes mellitus, and recent use of NSAIDs, PPIs or anticoagulants at endoscopy were also excluded. Helicobacter pylori infection was determined by both the 13C-urea breath test and by histological identification. Written informed consent was obtained from all subjects prior to undergoing upper GI endoscopy and abdominal ultra-sonography for evaluation of their dyspeptic symptoms. The study protocol was approved by the Ethics Review Committee of Nippon Medical School Hospital.

Clinical symptoms

Clinical symptoms of FD were evaluated according to Rome III criteria20 and must have included at least one of the following: bothersome postprandial fullness, early satiation, epigastric pain, or epigastric burning. Diagnostic criteria for PDS included bothersome postprandial fullness occurring after ordinary-sized meals and/or early satiation that prevented finishing a regular meal, with either symptom occurring at least several times a week. Diagnostic criteria for EPS included all of the following: pain or burning that is intermittent, localized to the epigastrium, and of at least moderate severity at least once per week. Diagnostic criteria for PDS and EPS were fulfilled with symptoms occurring for the last 3 months and the onset of symptoms occurring at least 6 months prior to diagnosis. Abdominal symptoms including the feeling of hunger were assessed by using the modified questionnaire that has been applied in previous studies.1,21,22 We assessed abdominal symptoms including the feeling of hunger using the modified Glasgow dyspepsia severity score,23 which consist of frequency (never; score 0, on only 1 or 2 days; score 1, on approximately 1 day per week; score 3, on approximately 50% of days; score; score 4, on most days; score 5), duration of symptoms (maximal score 5) and intensity of symptoms (maximal score 3). Status of depression was evaluated by SRQ-D (Self-Rating Questionnaire For Depression) score.24

Measurement of gastric motility

Sodium acetate (water soluble) for emptying of liquids was used as tracer (Cambridge Isotope Laboratories; MA, USA). Probes were analyzed by non-dispersive infrared spectroscopy (IRIS, Wagner Analyzentechnik; Bremen, Germany). The subject’s own production of 300 mmol CO2 per m2 body surface and per hour were set as default. We used an Integrated Software Solutions program to calculate the half gastric emptying time (T1/2) and the lag phase (Tmax; min) as the point of maximum gastric emptying according to Hellmig et al.25Tmax value greater than 60 min, representing the mean Tmax in healthy volunteers plus SD, was defined to represent relative disturbances in gastric emptying according to the diagnostic criteria of the Japan Society of Smooth Muscle Research and our study.3,26

Study protocol for gastric emptying of liquids

The liquid test meal consisted of 100 mg of 13C-acetate dissolved in 200 mL of liquid meal (Racol, 1 mL kcal−1; Otsuka Pharmacia Company, Tokyo, Japan). Breath samples were collected 0, 10 s, 5 min, 10 min, 15 min, 20 min, 30 min, 40 min, 50 min, 60 min, 75 min, and 90 min after ingestion of the test meal at 10:00 a.m. Patients were instructed not to drink, eat, or smoke during the test.

Genotyping

We have developed or optimized the following assays for genetic variation. Genotypes were confirmed or selectively assessed for GNβ3, 5-HT1A, 5-HT2A and 5-HT3A, 5-HT4A genotypes by direct sequencing using an ABI 7500 Fast. Gene polymorphisms were determined by methods in the literature. Real-time polymerase chain reaction using TaqMan chemistries (Applied Biosystems, Foster City, CA, USA) was used to determine alleles present in each sample. Real-time polymerase chain reactions were performed in an Applied Biosystems 7500 Fast machine (Applied Biosystems). TaqMan primer-probe assays for GNβ3 SNPs C825T (rs:5443; C-2184734-10), 5-HT1A SNPs C1019G (rs:6296; C-11904666-10), 5-HT2A SNPs G1438A (rs:6311; C-7488465-10), and 5-HT3A SNPs C42T (rs:1062613; C-2184734-10), 5-HT4A SNPs G353 + 6A (rs:2278392; C-15965377-10) were purchased from Applied Biosystems. In briefly, each reaction volume was 10 μl and consisted of 5 μl of a TaqMan Genotyping Master Mix (Applied Biosystems), 0.25 μl of a 40 × primer probe assay mix (Applied Biosystems), H2O 3.75 μl and 1 μl (10 ng) genomic DNA. Amplification conditions consisted of 95 °C, 10 min; 40 cycles of: 95 °C, 15 s; 60 °C, 60 s; followed by 50 °C, 2 min. And then analyzed using automated software (SDS 2.1; Applied Biosystems) to determine the genotype of each sample.

Measurement of plasma ghrelin levels in FD patients

We measured plasma ghrelin levels to evaluate their association with polymorphism of GNβ3 825CT. Blood samples were obtained after an overnight fast of > 12 h, immediately transferred to chilled polypropylene tubes containing Na2EDTA and aprotinin, then centrifuged at 4 °C. One tenth of the volume of 1N HCl was immediately added to the separated plasma. The acylated and des-acylated forms of ghrelin were measured using commercially available ELISA kits according to the manufacturer’s instructions (Active Ghrelin ELISA Kit and Desacly-Ghrelin ELISA Kit, Mitsubishi Kagaku Iatron Inc., Tokyo, Japan). The intra- and inter-assay coefficients of variation (CV) were 6.5% and 9.8% for acylated ghrelin, and 3.7% and 8.1% for des-acylated ghrelin.

Statistical analysis

For statistical evaluation of group data, Students’t-test for paired data and analysis of variance (anova) for multiple comparisons were followed by Scheffe’s F test. Mann–Whitney U test was used for analysis of categorical data. To determine factors that associated with the disturbance of gastric emptying, multiple logistic regression analysis was used at 95% confidence intervals and associated P values. A P value < 0.05 was statistically significant.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. References

Characteristics of FD patients and healthy volunteers

The age, sex, and BMI in FD and healthy volunteers were not statistically different (Table 1). SRQ-D score in FD patients was also significantly higher (< 0.001) compared with that of healthy volunteers. Both of T1/2 and Tmax values in FD patients were significantly (< 0.001, < 0.001) higher compared with those of healthy volunteers. The proportion of disturbed gastric emptying in FD patients (43.2%) was significantly (< 0.01) higher compared with that of healthy volunteers (4.7%) (Table 1).

Table 1.   Characteristics of the patients
 FDHealthy volunteer
  1. FD, functional dyspepsia.

Subjects (n)7464
Age59.2 ± 14.237.2 ± 9.13
Sex (M/F)36/3857/7
BMI22.2 ± 2.5722.9 ± 2.63
SRQ-D9.94 ± 0.716.14 ± 0.49
T1/294.5 ± 3.5472.8 ± 1.62
Tmax59.2 ± 1.7446.7 ± 0.95
Disturbed gastric emptying (%)43.24.7

GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A genotypes in FD patients

GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A genotypes distribution in FD were 14CC (18.9%), 44CT (59.5%), 16TT (21.6%); 44GG (59.5%), 28GC (37.8%), 2CC (2.7%); 17CC (23.0%), 35CT (47.3%), 22TT (29.7%); 58CC (78.4%), 16CT (21.6%); 7AA (9.4%), 29GA (39.2%), 38GG (51.4%), respectively. Meanwhile, in the healthy controls, GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A genotypes distribution were 17CC (26.6%), 28CT (43.7%), 19TT (29.7%); 33GG (51.6%), 28GC (43.7%), 3CC (4.7%); 18CC (28.1%), 30CT (46.9%), 16TT (25%); 49CC (76.5%), 14CT (21.9%), 1TT (1.6%); 7AA (10.9%), 22GA (34.4%), 35GG (54.7%), respectively. Each genotype distribution was not significantly different in FD patients and healthy volunteers (Table 2).

Table 2.   GNβ3, 5-HT1A, 5-HT2A, 5-HT3A and 5-HT4A genotypes in FD patients
Variables n (%)GenotypeOR CC vs othersP value
CCCTTT
GNβ3-G825C polymorphism and FD
 Healthy volunteers (= 64)17 (26.6)28 (43.7)19 (29.7)Reference 
 FD (= 74)14 (18.9)44 (59.5)16 (21.6)0.6450.283
Variables n (%)GenotypeOR GG vs othersP value
GGGCCC
5-HT1A-C1019G polymorphism and FD
 Healthy volunteers (n = 64)33 (51.6)28 (43.7)3 (4.7)Reference 
 FD (n = 74)44 (59.5)28 (37.8)2 (2.7)1.380.316
Variables n (%)GenotypeOR CC vs othersP value
CCCTTT
5-HT2A-G1438A polymorphism and FD
 Healthy volunteers (n = 64)18 (28.1)30 (46.9)16 (25.0)Reference 
 FD (n = 74)17 (23.0)35 (47.3)22 (29.7)0.7620.488
Variables n (%)GenotypeOR CC vs othersP value
CCCTTT
5-HT3A-G42T polymorphism and FD
 Healthy volunteers (n = 64)49 (76.5)14 (21.9)1 (1.6)Reference 
 FD (n = 74)58 (78.4)16 (21.6)0 (0)1.110.798
Variables n (%)GenotypeOR AA vs othersP value
AAGAGG
5-HT4A-G353 + 6A polymorphism and FD
 Healthy volunteers (n = 64)7 (10.9)22 (34.4)35 (54.7)Reference 
 FD (n = 74)7 (9.4)29 (39.2)38 (51.4)1.350.825

Multiple logistic analysis for Tmax value in FD patients

As various clinical symptoms in FD patients are partly involved in the disturbance of gastric motility, we tried to clarify whether these parameters including age, BMI, sex, SRQ-D score, FD symptoms, H. pylori infection, and five genotypes are linked to Tmax value as a marker of gastric emptying. Multiple logistic regression analysis revealed that there was no significant relationship between these parameters and Tmax value in FD patients (Table 3).

Table 3.   Multiple logistic analysis for impaired Tmax value in FD patients (n = 74)
FactorOdds ratio (95% CI)P value
  1. FD, functional dyspepsia; PDS, postprandial distress syndrome; EPS, epigastric pain syndrome.

  2. *Most bothersome symptom based on physician interview was early satiety.

  3. Most bothersome symptom based on physician interview was upper abdominal pain.

Age1.034 (0.998–1.071)0.061
BMI1.032 (0.857–1.242)0.742
SEX1.100 (0.438–2.761)0.839
SRQ-D0.993 (0.919–1.074)0.897
Heartburn0.955 (0.899–1.016)0.146
PDS-like*1.957 (0.639–5.992)0.239
EPS-like0.796 (0.208–3.046)0.739
H. pylori1.821 (0.273–3.787)0.271
GNβ3 (CC; CT/TT)1.400 (0.436–4.496)0.577
5-HT1A (GG; GC/CC)0.791 (0.310–2.017)0.624
5-HT2A (CC; CT/TT)1.957 (0.639–5.992)0.239
5-HT3A (CC; CT/TT)1.916 (0.591–6.214)0.280
5-HT4A (AA; GA/GG)2.027 (0.206–4.928)0.418

GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A genotypes in PDS patients with or without impaired gastric emptying

We then compared five genotypes (GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A) in FD patients with or without disturbance of gastric emptying. We divided FD patients into two groups which are disturbed with gastric emptying (Tmax value > 60 min) and normal gastric emptying (Tmax value < 60 min). We could not find a significant correlation (= 0.620; = 0.760; = 0.365; = 0.570; = 0.691) between Tmax value and genotype of GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A in seventy-four FD patients, respectively. The proportion of GNβ3 825C/C in FD patients with disturbed gastric emptying was relatively greater (= 0.06) compared with that of healthy volunteers (data not shown).

To investigate whether there is any significant difference in five genotypes and Tmax value as a marker of gastric emptying in PDS patients, we compared genotypes with PDS patients with or without disturbed gastric emptying. We found that there was no significant relationship (= 0.501; = 0.131; = 0.924; = 0.490; = 0.390) between five genotypes and PDS patients with impaired gastric emptying, respectively (Table 4).

Table 4.   Association between GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A polymorphism and gastric emptying in PDS patients
GenotypesTmax > 60 minTmax < 60 minOR (95% CI)P value
  1. PDS, postprandial distress syndrome.

GNβ3 CC652.00 (0.519–7.7703)0.501
CT/TT1525
5-HT1A GG17173.25 (0.879–12.00)0.131
GC/CC413
5-HT2A CC671.31 (0.368–4.663)0.924
TT/CT1523
5-HT3A CC18222.18 (0.503–9.442)0.490
CT/TT38
5-HT4A AA240.37 (0.061–2.232)0.390
GA/GG2619

GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A genotypes in PDS patients without gastro-esophageal reflux symptom

Moreover, to investigate whether there is any significant relationship between five genotypes and Tmax value in PDS patients without gastro-esophageal reflux symptom, we compared five genotypes with PDS patients without gastro-esophageal reflux symptom with or without impaired gastric emptying in similar way. We confirmed that there was a significant relationship (= 0.045) between GNβ3 825CC genotype and PDS patients without gastro-esophageal reflux symptom accompanying impaired gastric emptying (Table 5). In contrast, there were no significant relationship between 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A genotypes and PDS patients without gastro-esophageal reflux symptom accompanying with impaired gastric emptying (= 0.953; = 0.690; = 0.213; = 0.625) (Table 5).

Table 5.   Association between GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A polymorphism and gastric emptying in PDS patients without reflux
GenotypesTmax > 60 minTmax < 60 minOR (95% CI)P value
  1. PDS, postprandial distress syndrome.

GNβ3 CC635.71 (1.117–2.918)0.045
CT/TT720
5-HT1A GG8131.6 (0.399–6.414)0.953
GC/CC510
5-HT2A CC560.63 (0.147–2.697)0.690
TT/CT817
5-HT3A CC12165.25 (0.567–48.58)0.213
CT/TT17
5-HT4A AA130.43 (0.040–4.593)0.625
GA/GG14I8

Association between GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A genotypes and clinical symptoms in FD patients

As GNβ3 genotype has been previously reported to be linked to clinical symptoms in FD patients, we also determined whether five genotypes including GNβ3 are associated with several clinical symptoms in Japanese FD patients based on Rome III classification. In our FD populations, GNβ3 825CC genotype in FD patients is significantly (= 0.0485) associated with the feeling of hunger compared with GNβ3 825CT and TT genotypes (Fig. 1).

image

Figure 1.  Association between GNβ3, 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A genotypes and gastrointestinal symptoms in FD patients. There was no significant relationship between 5-HT1A, 5-HT2A, 5-HT3A, 5-HT4A, and various clinical symptoms. In Japanese, GNβ3 825CC genotype in FD patients is significantly (= 0.0485) associated with the feeling of hunger compared with GNβ3 825CT and TT genotypes. GNβ3: 14CC, 60CT/TT; 5-HT1A: 44GG, 30GC/CC; 5-HT2A: 17CC, 57CT/TT; 5-HT3A: 58CC, 16CT/TT; 5-HT4A: 7AA, 67GA/GG. *vs GNβ3 825CT/TT genotypes. FD, functional dyspepsia.

Download figure to PowerPoint

As ghrelin levels have been reported to be associated with appetite, we tried to determine whether plasma ghrelin levels are linked to GNβ3 825CC genotype in FD patients. We measured both plasma acylated ghrelin (7.08 ± 0.63 fmol mL−1) and des-acylated ghrelin levels (74.7 ± 6.22 fmol mL−1) in FD patients. There was no significant difference (= 0.269) in acylated ghrelin levels in GNβ3 825CC and GNβ3 825CT/TT genotypes.

In contrast, there are not significant differences between 5-HT1A GG, 5-HT2A CC, 5-HT3A CC, and 5-HT4A AA genotypes and clinical symptoms compared with other genotypes, respectively (Fig. 1).

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. References

The major findings of this study are (i) There was a significant relationship between GNβ3 825CC genotype and PDS patients without gastro-esophageal reflux symptoms with impaired gastric emptying, (ii) GNβ3 825CC genotype in FD patients was significantly associated with the feeling of hunger symptom compared with GNβ3 825CT and TT genotypes.

There is increasing evidence that susceptibility to functional GI disorders is also influenced by hereditary factors.27–29 In this study, we have first reported that GNβ3 CC variant was significantly associated with disturbance of gastric emptying in PDS patients without gastro-esophageal reflux symptoms. Previous studies have reported that there is reasonable evidence that the GNβ3 status is associated with depression,30 increased immune cell activation,11 and altered activation of α2-adrenoreceptors.31 In addition, Holtmann et al. have reported that the homozygous GNβ3 825CC was associated with upper abdominal symptoms unrelated to meals in Germany,12 while previous studies have shown that the homozygous GNβ3 825CC or 825TT was also associated with meal-unrelated dyspepsia in people randomly selected from the US community and EPS patients in Japan.13,32 Recent study has reported that there was no significant relationship between gastric emptying and GNβ3 genotype in Rome II-based FD patients.33 In this study, we investigated the relationship between gastric emptying and the GNβ3 subunit 825 genotype among FD, PDS, and healthy volunteers based on Rome III classification. We have previously reported that the Tmax value as a marker of gastric emptying in PDS patients was significantly greater compared with that of healthy volunteers.3 Therefore, in our study, we focused on the GNβ3 genotype in PDS patients with or without impaired gastric emptying and found a significant relationship between GNβ3 825CC genotype and impaired gastric emptying in PDS patients without gastro-esophageal reflux symptoms. In addition, because of small number of subjects of Rome III subgroups, type II error could not be excluded. Thus, our result should be treated carefully with caution until replicated.

The age of onset of gastro-esophageal reflux disease (GERD) is variable and many individuals develop the disease during childhood. Gastro-esophageal reflux disease is the most common esophageal disorder of children, affecting about 11% of all infants during their first year of life.34 Epidemiological data justify theory formation about a genetic component in the pathophysiology of GERD. The disease etiology is further complicated by a substantial genetic contribution as shown by familial clustering,35 autosomal dominant familial transmission of disease36,37 as well as twin studies.38 As Vries et al. have reported that GERD is associated with the GNβ3 825CT genotype,39 we investigated whether the GNβ3 825CC variant were associated with disturbance of gastric emptying in PDS patients without gastro-esophageal reflux symptoms in this study. Further studies are needed to clarify whether the reduction of threshold of 5-HTs receptors is associated with reflux symptom through protein kinase-mediated signaling pathways induced by impairment of G-protein-coupled receptors (GPCRs) via GNβ3 825CT variant in these patients.

Considering that there were the discrepancy about clinical symptoms and gastric motility for GNβ3 825 alleles of FD patients in several countries,12,13,19,32,33 it seems to be a very important factor that Japanese patients with H. pylori-infected gastritis have low levels of acid secretion compared with Europeans and Americans.40 It is very critical issue about the relationship between gastric acidity and gastric motility because Lee et al. and Schwartz et al. have reported that intraduodenally administrated acid affects gastroduodenal motility as well as visceral hypersensitivity.41,42 Considering these previous studies, high prevalence of H. pylori infection may be considered to play an important role in the etiology of certain FD patients in Japan.43 Saito et al. have reported that acceleration of gastric emptying was observed in H. pylori-infected animal model.44 In our study, the proportion of H. pylori-infected PDS patients was 37%. In our previous study, H. pylori infection reduced ghrelin-producing cell numbers which are linked to gastric emptying.45 Therefore, in the future study, we should investigate whether GNβ3 825 genotype may be linked to gastric emptying among H. pylori-negative subjects. Our findings thus needed to be replicated in different populations and other races. On the other hand, the allele distribution in controls was very similar to allele distributions that have been observed in previous studies of Japanese.32,46 Oshima et al. and Tahara et al. have reported GNβ3 825TT genotype is associated with EPS-like dyspepsia or dyspepsia, respectively. 32,46 This discrepancy between these reports and our results may have occurred in sample selection, such as patient’s age, psychological condition (SRQ-D score is high), Rome III-categorized patients, and visiting care centers. The novel 5-HT1A agonist R137696 has been reported to affect the proximal gastric function16 as well as previous studies.47,48 5-HT3A receptors also seem to be involved both in the transmission of the sensation that arises from the stomach and in the process of gastric emptying and accommodation.49 However, we have first compared genotypes of 5-HTs with gastric emptying in Rome III-based FD patients. We could not find any significant relationship between genotypes of 5-HTs such as 5-HT1A, 5-HT2A, 5-HT3A, and 5-HT4A and gastric emptying in these FD patients.

In the present data, there was a significant relationship between the feeling of hunger and GNβ3 825CC genotype in Rome III-based FD patients. In contrast, in Japanese patients, Tahara et al. have reported that the homozygous 825T allele of the GNβ3 protein influences the susceptibility of Japanese to dyspepsia.47 In our data, we could not find any significant relationship between the GNβ3 825CC genotype and Rome III-based symptoms, such as abdominal distention, epigastralgia, and abdominal discomfort. However, we investigated that there was a significant relationship between the feeling of hunger and the GNβ3 825CC genotype in FD patients. We could not find a significant relationship between disturbed Tmax value and the feeling of hunger (= 0.608) or early satiety (= 0.239) in FD patients using multiple logistic analysis. In contrast, Stanghellini et al. have reported that disturbed gastric emptying is associated with satiation and impaired food intake.7 We have previously reported that there was a significant relationship between low level of acylated ghrelin linked to appetite and Tmax value.3 However, in our data, the score for feeling of hunger was not significantly (= 0.473) associated with acylated-ghrelin levels. In addition, there was also no significant difference (= 0.269) in acylated ghrelin levels in GNβ3 825CC and GNβ3 825CT/TT genotypes. Further studies are needed to clarify the mechanism by which the GNβ3 825CC genotype is associated with the feeling of hunger in H. pylori-negative FD patients.

Taken together, in this study, we determined that there was a significant relationship between impairment of gastric emptying and the GNβ3 825CC genotype in Rome III-based PDS patients without gastro-esophageal reflux symptoms. Further studies are needed to clarify whether the GNβ3 825CC genotype are linked to disturbance of gastric emptying and feeling of hunger via diminished transduction responses.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. References
  • 1
    Tack J, Talley NJ, Camilleri M et al. Functional gastroduodenal disorders. Gastroenterology 2006; 130: 146679.
  • 2
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