This study confirmed that IG-1 has insulin-mimicking bioactivities and improves glucose tolerance in several mice models of diabetes with or without obesity, such as male C57BL/6 mice fed normal diets (normal model), mice fed high fat diets (model of diabetes with mild obesity), db/db mice (genetic model of diabetes with severe obesity), ob/ob mice (genetic model of severe obesity), STZ-diabetic mice (model of lean insulin-deficient diabetes), respectively. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.