Abstract: Provided herein are methods for the treatment of type I diabetes, Type II diabetes, metabolic syndrome, or obesity, or of appetite suppression, or for mitigating insulin resistance, or for reducing an undesirably high fasting serum glucose level, or for reducing an undesirably high peak serum glucose level, or for reducing an undesirably high peak serum insulin level, or for reducing an undesirably large response to a glucose tolerance test in synergistic combination with metformin. Treatment is effected with a combination therapy of metformin and a peptide with a sequence selected from SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 19, SEQ ID NO: 20, SEQ ID NO: 21, SEQ ID NO: 22, SEQ ID NO: 23, and SEQ ID NO: 24 administered to a patient.