The object of this invention is to elucidate the factors involved in the regulation of AGE (advanced glycation endproducts, which are produced in a living body accompanied with diabetes and aging) and RAGE (the receptor for AGE), in order to facilitate investigation on the biological activities, physiological phenomenon and diseases related to AGE and RAGE. Plural molecular species are known to exist for RAGE, and among such molecular species, soluble RAGE exhibits the activity to modulate interaction between AGE and transmembrane-type RAGE. Using this soluble RAGE or a nucleic acid encoding it, the soluble RAGE can be measured, in addition, investigation on various physiological phenomenon, biological activities, and diseases related to interaction between AGE and RAGE can be performed to facilitate development a medicine having further efficacy.