Disclosed herein are cells that secrete insulin in a glucose-dependent manner. The cell line comprises insulin-secreting cells that have been transfected with a minigene construct comprising a nucleotide sequence encoding for glucagon-like peptide-1 (GLP-1). In preferred embodiments, the minigene construct is operatively associated with a promoter. The cell line may be used to treat diabetes or other conditions in which delivering insulin in a glucose-dependent manner would be advantageous, to investigate the function and development of pancreatic cells, and to test the efficacy of drugs that stimulate insulin secretion. The cells may be implanted in a mammal, or may be included in a device that resides exterior to the mammal, yet which delivers insulin to the mammal in response to the glucose level of a body fluid in contact therewith. The minigene construct may also be implemented in conjunction with an in vivo gene transfer approach.