Genetic polymorphism of pri-microRNA 325, targeting SLC6A4 3′-UTR, is closely associated with the risk of functional dyspepsia in Japan

Background The role of genetics in the susceptibility to functional dyspepsia (FD) remains unclear. We attempted to clarify the association between FD and polymorphisms in SLC6A4 . In addition, rs5981521 (C>T) in the pri-microRNA 325 (pri-miR-325) coding region was also investigated. Methods The study was performed in 395 subjects (172 with no upper abdominal symptoms and 223 with FD, including medication-resistant FD). We employed a polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) method to detect gene polymorphisms. Results Neither SLC6A4 −185 A>C nor *463 G>T was associated with susceptibility to FD. The number of rs5981521 T alleles was significantly correlated with an increased risk for FD (odds ratio [OR] 1.45, 95 % confidence interval [CI] 1.05–1.98; p = 0.022) and the TT homozygote was more closely associated with the risk for FD (OR 3.01, 95 % CI 1.41–6.42; p = 0.0043). The TT homozygote also had significantly increased risks for both the epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS) subtypes of FD (OR 3.04, 95 % CI 1.25–7.42; p = 0.014 and OR 3.05, 95 % CI 1.14–8.13; p = 0.026, respectively). In addition, Helicobacter pylori -negative TT homozygotes had a greater risk for FD (OR 8.37, 95 % CI 1.78–39.5; p = 0.0072). In subjects with the SLC6A4 5′-untranslated region (UTR) wild homozygote, the number of rs5981521 T alleles was significantly correlated to an increased risk for FD (OR 1.45, 95 % CI 1.03–2.04, p = 0.033). Of note, in subjects who were SLC6A4 3′-UTR mutant carriers, the number of rs5981521 T alleles was also significantly correlated with an increased risk for FD (OR 2.07, 95 % CI 1.08–3.98; p = 0.029). Conclusions Our results suggest that the genetic polymorphism pri-miR-325 is associated with FD and interacts with SLC6A4 polymorphisms in increasing susceptibility to FD in Japanese.