Effects of a GLP-1 Receptor Polymorphism on Responses to Liraglutide

The rs6923761 (Gly168Ser) missense variant in the glucagon-like peptide-1 receptor (GLP-1R) has been associated with favorable anthropometric and metabolic parameters in individuals with obesity but decreased responsiveness to incretin-based therapies. Here we performed a pre-specified analysis of a randomized controlled trial in individuals with obesity and pre-diabetes comparing treatment with the GLP-1R agonist liraglutide, the dipeptidyl peptidase 4 inhibitor sitagliptin or hypocaloric diet, and evaluated the effects of the rs6923761 variant on outcomes. We found significantly greater weight loss to liraglutide with each copy of the variant allele present, indicating a gene dose effect. In addition, individuals with the variant allele exhibited a significant reduction in the pro-thrombotic and pro-inflammatory factor plasminogen activator inhibitor-1 after liraglutide treatment. There was no effect of genotype on fasting glucose after liraglutide treatment, yet individuals with the variant allele exhibited decreased responsiveness to liraglutide and hypocaloric diet in measurements of fasting insulin, C-peptide, glucagon, as well as in HOMA-IR. In conclusion, we found that the GLP-1R rs6923761 variant exerts a dual impact on liraglutide efficacy -- enhancing weight loss while diminishing metabolic benefits. The observed associations could be consistent with constitutive activation of the GLP-1R in the presence of this variant with reduced activation/signaling in response to pharmacologic agents, a pattern that has been observed with the rs10305492 variant in animal models. Future studies are needed to investigate the molecular mechanisms of associations with the rs6923761 variant.