Polymorphisms of 5-HTT LPR and GNβ3 825C>T and Response to Antidepressant Treatment in Functional Dyspepsia: A Study from The Functional Dyspepsia Treatment Trial

OBJECTIVES: The Functional Dyspepsia Treatment Trial reported that amitriptyline (AMI) was associated with adequate relief of functional dyspepsia (FD) symptoms, but the pharmacogenetics of antidepressant response in FD are not known. GNβ3 825C>T CC genotype has been previously linked to FD and TT genotype to antidepressant response in depression. The ss genotype of the 5-HTT LPR variant of the serotonin transporter gene (SLC6A4) has been linked to selective serotonin reuptake inhibitor (SSRI) response. We aimed to examine whether GNβ3 825C>T and 5-HTT LPR polymorphisms result in differential treatment effects in FD patients receiving antidepressant therapy. METHODS: Participants were randomized to receive placebo, 50 mg AMI, or 10 mg escitalopram (ESC). The primary end point was adequate relief for ≥5 weeks of the last 10 weeks. Genotyping of GNβ3 825C>T and 5-HTT LPR was performed utilizing PCR-based methods. RESULTS: GNβ3 825C>T and 5-HTT LPR genotype data were available for 256 (88%) and 246 (84%) patients, respectively. Both polymorphisms were in Hardy-Weinberg equilibrium. In tests for differential treatment, neither 5-HTT LPR nor GNβ3 825C>T genotype influenced response to therapy (P=0.89 and P=0.54, respectively). Although there was a tendency for a more favorable response to ESC in the SS/LS genotype compared to the LL genotype groups (40% vs. 31% reporting adequate relief of FD symptoms) among those in the ESC treatment arm, this was not significant (P=0.43). CONCLUSIONS: GNβ3 825C>T and 5-HTT LPR genetic variants do not alter treatment response to tricyclic and SSRI antidepressants in FD.