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Background: Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by altered bowel habits and abdominal pain in the absence of a recognizable structural anomaly. The pathogenesis of IBS has been associated with inflammation and the expression of pro-inflammatory chemokines, such as CCL2 and CCL16. Our study aimed to investigate the relationship between the serum levels of CCL2 and CCL16 and IBS. Additionally, we examined how serum levels of these chemokines relate to IBS subtypes. Methods: Patients with IBS diagnosed according to the Rome III criteria participated in this study (n= 96). Healthy individuals with no history of allergic, autoimmune, chronic or active gastrointestinal infectious diseases were used as controls (n= 44). The serum levels of CCL2 and CCL16 was measured via enzymelinked immunosorbent assay (ELISA). Results: A significant decrease in the serum levels of CCL16 and CCL2 was observed in the patients with IBS. Additionally, the serum levels of CCL16 in IBS patients with diarrhea (D-IBS) was significantly higher than those with the mixed IBS (M-IBS) subtype. Conclusions: The significant increase in the serum levels of CCL-16 in patients with D-IBS compared to patients with M-IBS suggests that CCL-16 may be used as an immunological biomarker to differentiate between these two subtypes. [ABSTRACT FROM AUTHOR]

BACKGROUND Irritable bowel syndrome (IBS) is a digestive system disorder with an unknown etiology. Serotonin has a key role in the secretion and motility of the intestine. Polymorphism in serotonin re-uptake transporter (SERT or SLC6A4) gene may have a functional role in the gut of patients with IBS. The aims of the present study were to investigate the association between SLC6A4 gene polymorphism and IBS and to detect the correlation between rectal serotonin levels and IBS sub-types. METHODS SLC6A4 gene polymorphism in 131 patients with IBS and 211 healthy controls were analysed using the quantitative polymerase chain reaction high-resolution melting (qPCR-HRM) curve technique. Serotonin was measured in rectal biopsies of patients with IBS using the enzyme-linked immunosorbent assay (ELISA) method. RESULTS The patients were categorized into three groups: IBS with diarrhoea (IBS-D): 70 patients, IBS with constipation (IBS-C): 18 patients, and IBS with mixed symptoms (IBS-M): 43 patients. The frequency of SLC6A4 s/s and l/s genotypes was significantly higher in IBS-C than IBS-D, IBS-M, and controls (p=0.036). Serotonin levels were similar in IBS sub-types. CONCLUSION SLC6A4 polymorphism is a possible candidate gene associated with the pathogenesis of IBS-C. Although serotonin levels did not differ in rectal biopsies of IBS sub-types, further investigation is recommended. [ABSTRACT FROM AUTHOR]