Novel heterocyclic compound, salt thereof and pharmaceutical use thereof

A heterocyclic compound of the formula [I], wherein R1 is hydrogen atom or lower alkyl, R2 is hydrogen atom, alkyl optionally having a substituent and the like, R3 is hydrogen atom, lower alkyl and the like, A is a single bond or > N-R5 wherein R5 is hydrogen atom or lower alkyl, B is lower alkylene, and Y is aryl optionally having a substituent and the like, and a pharmaceutically acceptable salt thereof show a hypoglycemic action, a blood hypolipidemic action, an insulin resistance-improving action and a PPAR activating action, and are useful as a pharmaceutical composition, such as a hypoglycemic agent, a hypolipidemic agent, an insulin resistance improver, a therapeutic agent of diabetes, a therapeutic agent of diabetic complication, a glucose tolerance improver, an anti-atherosclerosis agent, an anti-obesity agent, an antiinflammatory agent, an agent for the prophylaxis and treatment of PPAR-mediated disease and an agent for the prophylaxis and treatment of syndrome X.