The insertion of 6-aminohexanoic acid between histidine and alanine at positions 7 and 8 of glucagon-like peptide 1 (GLP-1) prevents N-terminal degradation by dipeptidyl peptidase IV and produces an effective, long-acting analog of the polypeptide, which may be useful in the treatment of type 2 diabetes mellitus. This evidence concerns the gene GCG and diabetes mellitus.