Disclosed is a method for obtaining glucose-regulated expression of active insulin in the cells of a mammalian subject. The method involves delivering into the subject a genetic construct comprising a coding sequence for a human proinsulin operably connected a promoter functional in the host cells. The construct includes a glucose responsive regulatory module having at least one glucose inducible regulatory element comprising a pair of CACGTG motifs linked by a five base nucleotide sequence, which confers glucose inducible expression of the proinsulin coding sequence. To ensure proper processing of the proinsulin to active insulin, the coding sequence was modified to direct the synthesis of a mutant proinsulin polypeptide having amino acid sequences that can be cleaved to mature insulin in suitable host cells, such as hepatocytes.