An improvement in exercise capacity assessed by a 6 min walk test was found after 5 weeks of GLP-1 infusion in patients with heart failure [8], but could not be confirmed in a randomized study where cardiopulmonary exercise testing was performed after 48 h GLP-1 infusion [18] or after 12 weeks of albiglutide treatment [19]. This evidence concerns the gene GLP1R and heart failure.