GCG and diabetes mellitus: Gcg-Cre rats are a valuable addition to the research toolbox for examining the structure and function of central neurons and peripheral secretory cells that express Gcg. Our discovery that Homo Gcg-Cre rats have markedly reduced Gcg mRNA and GLP1 protein levels make them a useful and novel rodent model to address research questions regarding the role of GLP1 and other Gcg-encoded protein products in food intake, metabolism, obesity, and diabetes.