Researchers from Kumamoto University, Japan have found that DNP peptide, a small intestine-permeable cyclic peptide originally used as an insulin additive to improve absorption into the small intestinal, lowers blood glucose levels in mice. They also found that insulin can be administered orally by simply adding D-form DNP peptide (D-DNP) peptide to injectable insulin used in clinical practice. This study is expected to provide a basis for the development of oral insulin using DNP peptides.