To Örebro University

Background: Irritable bowel syndrome (IBS) affects 5%- 15% of adults in the general population, and is characterized by chronic recurrent abdominal pain and discomfort and associated with altered bowel habits. The pathophysiology of IBS is complex and not fully under-stood. Hence, treatment is often based on symptomatology rather than underlying physiological aberrancies.

Objective: To compare the expression of membrane transporters in mucosal biopsies of healthy subjects, IBS patients and post- infectious (PI)- IBS patients.

Methods: Mucosal biopsies were obtained from the unprepared sigmoid colon in 18 IBS patients, 9 PI- IBS patients and 10 healthy subjects. Total RNA was isolated and prepared for gene expression analyses using quantitative reverse- transcription polymerase chain reaction (qRT- PCR). We compared the expression of genes encoding membrane- spanning transporters, using GAPDH as a reference gene, and by using the comparative 2- ΔΔCt method.

Results: Colonic expression of SCL7A5 and SLC3A2 (together com-prising the amino acid transporter LAT1+4F2hc) was significantly lower in IBS patients, but not in PI- IBS patients, compared to healthy controls (P<.001). The expression of SLC7A8 (LAT2) tended to be lower in IBS patients compared to controls (P=.06). Mucosal gene ex-pression of the short chain fatty acid transporter SMCT1 (SLC5A8) was lower in both IBS- patients and PI- IBS patients compared to healthy subjects (P<.01).

Conclusions: The amino acid transporters LAT1 and LAT2 appeared to be affected in IBS patients, but not in PI- IBS patients, compared to healthy subjects, suggesting a possible alteration in amino acids transport in this patient group. Furthermore, our results suggest a lower uptake of short chain fatty acids in both IBS- and PI- IBS pa-tients. Altered expression of these transporters may be involved in the pathophysiology of IBS as well as being a potential biomarker of this aberration, and therefore deserves further study in IBS.