They are provided gene constructs comprising a nucleotide sequence encoding the Insulin-like growth factor 1 (IGF-1) of a mammal； and target sequences of a microRNA of a tissue where the expression of IGF-1 is wanted to be prevented, wherein the sequences (a) and (b) are operationally linked to a promoter of ubiquitous expression. Also provided are expression vectors comprising the gene construct and pharmaceutical compositions comprising them. They are useful in the treatment and/or prevention of diabetes mellitus in mammals, wherein a dysfunction and/or a loss of the beta-cells of the islets of Langerhans is present.
