GCG and type 2 diabetes mellitus: GPR119 expression in pancreatic β-cells and intestinal L-cells makes it as an attractive therapeutic target in type 2 diabetes; stimulation of glucose-dependent insulin secretion from β-cell by increased plasma GLP-1 released by L-cells provides new avenues for diabetes treatment using GLP-1 analogs and dipeptidyl peptidase 4 inhibitors.