Aziz Yazar

Serotonin transporter gene polymorphism in irritable bowel syndrome

OBJECTIVES:Serotonin is a key mediator of intestinal peristalsis, and after it is secreted, it is effectively cleansed from the neuronal gap by means of a high affinity substance called serotonin transporter (SERT), which depends on the Na+ and Cl− ions localized in the presynaptic neuronal membranes. The aim of this study was to investigate SERT polymorphism in patients with irritable bowel syndrome (IBS).METHODS:SERT gene polymorphism was assessed by polymerase chain reaction on DNA chains obtained from leukocytes in serum samples from 54 patients diagnosed with IBS and 91 healthy subjects. The polymorphism of two regions (variable number tandem repeats and the SERT gene—linked polymorphic region [5-HTTLPR]) of SERT was assessed.RESULTS:SERT polymorphisms were found to be similar in healthy subjects and IBS patients (p > 0.05). IBS patients were divided into three groups: diarrhea predominant (n = 18), constipation predominant (n = 26), and alternating diarrhea and constipation (n = 10). These groups were compared with respect to gene polymorphism, and it was found that the 5-HTTLPR allele S/S genotype occurred with greater frequency in the constipation predominant group than in the other two subgroups (p < 0.05), and L/S genotype frequency in the diarrhea predominant group was higher than those in the constipation and control groups.CONCLUSIONS:No relationship was found between IBS and SERT gene polymorphism. It is conceivable that the presence of the S/S genotype in IBS patients carries an increased risk of the constipation predominant type of IBS, whereas the presence of the 5-HTTLPR allele L/S genotype carries an increased risk of the diarrhea predominant type.

Respiratory symptoms and pulmonary functional changes in patients with irritable bowel syndrome

OBJECTIVE:Scientific evidence of functional interface between the immune and sensory motor systems of the gut and respiratory systems has been reported. In recent studies excess prevalence of bronchial hyper-responsiveness has been shown among patients with irritable bowel syndrome (IBS). The purpose of our study was to investigate the possible relationship between IBS and asthma.METHODS:One hundred thirty-three patients with IBS (108 women, 25 men) and 137 control subjects (105 women, 32 men) were included in this study. Both for IBS and the control group, the mean ages were 41.64 ± 9.45 yr and 39.94 ± 10.62 yr, respectively. Patients more than 50 yr old, with any organic GI disease, acute respiratory system infection, current or ex-smokers, and patients using drugs affecting smooth muscle and autonomic nervous system were not included in the study. Respiratory symptoms were questioned and pulmonary function tests were performed for every subject.RESULTS:There were 45 (33.8%) and eight (5.8%) subjects with respiratory symptoms in IBS and control groups, respectively (p < 0.0001). Twenty-one (15.8%) patients from the IBS group and two (1.45%) patients from the control group had the diagnosis of asthma according to history, clinical, and PFT findings. There was no statistical difference between two groups with respect to percentage of forced vital capacity and forced expiratory volume in 1 s-to-forced vital capacity. The difference between the two groups in forced expiratory volume in 1 s, flow after 50% of the vital capacity has been exhaled, peak expiratory flow rate, and maximal mid-expiratory flow rate was statistically significant (p < 0.01).Conclusion:We found that the prevalence of asthma was more common in the IBS group than in controls. Our finding supports the speculation that asthma and IBS may share common pathophysiological processes

The urinary 5-hydroxyindole acetic acid and plasma nitric oxide levels in irritable bowel syndrome: a preliminary study.

Background and Aims: Postprandial increase of 3-hydroxytryptamine (5-HT) has been implicated in irritable bowel syndrome (IBS). There is evidence that nitric oxide (NO) may act as a mediator of 5-HT-evoked secretions in the colon. Our aim is to investigate the role of urinary 5-hydroxyindole acetic acid (5-HIAA) and plasma NO levels (with diarrhoea) in IBS patients. Methods: Nineteen (with constipation) IBS patients (group 1), 22 IBS patients (group 2) and 18 healthy controls (group 3) were included in the study. The diagnosis of IBS was made according to the Rome I Criteria. The urine was collected for determination of 5-HIAA and venous blood was collected from each subject for the measurement of plasma NO levels. Results: The levels of urinary 5-HIAA mmol/day and plasma NO mmol/l of group 1 (22,4±2,2 and 29,4±2 respectively) were significantly higher than group 3(14,2 ± 2,3 and 21,3 ± 2,1 respectively) (p =0,036 and p =0,019 respectively). The NO level of group 1 was also significantly higher than group 2(21,8 ± 1,9) (p = 0,021). The 5-HIAA level of group 1 was higher than group 2 (15,2, ± 2,1) and the difference was marginally significant (p = 0,055). There was no difference between group 2 and group 3 with respect to 5-HIAA and NO levels. Conclusions: The results of this preliminary study lend support to the involvement of 5-HT in some symptomatology of diarrhoea predominant IBS. Furthermore, NO may be one of the effector mediators of the 5-HT-induced symptoms in these patients.