GLP1R and type 1 diabetes mellitus: PGLP-1-VP can increase islet β-cell mass in STZ-induced hyperglycemia and NOD mice through activating GLP-1R, and reduce NOD mice morbidity, mortality, and pancreatic inflammation through anti-inflammation and immune regulation effects, which, as a dual-functional peptide, can improve glycemic control, reduce insulin usage, and avoid other serious complications in the prevention and treatment of type 1 diabetes.