Using gene therapy strategy, we have demonstrated that a single intramuscular injection resulted in a persistent expression of GLP-1/IgG-Fc fusion protein in mice, which, as a results, improved insulin production and normalized glucose tolerance in T2D db/db mice [13] and reduced diabetes incidence in streptozotocin (STZ)-induced beta-cell injury T1D mouse model [12]. This evidence concerns the gene GCG and type 2 diabetes mellitus.