The present invention provides a composition (a bloodglucose increase inhibitor) that has an effect of lowering bloodglucose level in a hyperglycemic patient and that is thereforeused to reduce blood glucose level in the patient. The presentinvention further provides a composition that is used to preventor treat diseases caused by hyperglycemia, in particular,diabetes and diabetic complications (a composition for preventingor treating diseases caused by hyperglycemia, an antidiabetic),based on the above-mentioned effect. A feature of the presentinvention is using a peptide consisting of the amino acidsequence of Leu-Ser-Glu-Leu as an active ingredient.
