The invention provides a compound or its pharmaceutically-acceptable salt of formula wherein A1 is a hydrogen, etc.; j and k are 0 or 1; is a double bond, etc.; is a double bond, etc.; one of W1 and W2 is E—O—W, etc., and the other is a hydrogen atom, etc.; E is a divalent group derived from a benzene ring, etc., by removing two hydrogen atoms therefrom; W is a group of formula (II-1): which has a histamine-H3 receptor antagonistic effect or a histamine-H3 receptor inverse-agonistic effect and is useful for prevention or remedy of metabolic system diseases, circulatory system diseases or nervous system diseases.