Screening for a glucokinase-activating substance among rare sugars and providing a composition for treating disordered conditions in association with glucokinase activity, the composition containing the glucokinase-activating substance as the active ingredient. A promoting agent of glucokinase transfer from nucleus to cytoplasm, the promoting agent containing D-psicose and/or D-tagatose as the active ingredient, or a composition for preventing the onset of disordered conditions in association with glucokinase activity or for therapeutically treating the disordered conditions, which is in a form selected from a group consisting of food additives, food materials, drinks and foods, health drinks and foods, pharmaceutical product and feeds in blend with D-psicose and/or D-tagatose as the active ingredient for use in preventing the onset of disordered conditions in association with glucokinase activity or for therapeutically treating the disordered conditions. The disordered conditions in association with glucokinase activity are selected from impaired glucose tolerance, type 2 diabetes mellitus, insulin resistance, abnormal lipidemia, the metabolic syndrome and obesity. The composition is in a pharmaceutical form, and contains D-psicose and/or D-tagatose together with one or more pharmaceutically acceptable carriers.