Compounds represented by the following structural formula (I), and pharmaceutically acceptable salts, solvates and hydrates thereof, wherein: n is 2, 3, or 4 and W is CH₂, CH(OH), C(O) or O; R1 is an unsubstituted or substituted aryl, heteroaryl, cycloalkyl, heterocycloalkyl, aryl-alkyl, heteroaryl-alkyl, cycloalkyl-alkyl, or t-butyl; R2 is H, alkyl, haloalkyl or phenyl; Y is an unsubstituted or substituted thiophen-2,5-diyl or phenylene; R3 is alkyl or haloalkyl; R4 is a substituted or unsubstituted phenyl, naphthyl, 1,2,3,4-tetrahydronaphthyl, quinolyl, pyridyl or benzo[1,3]dioxol-5-yl group; and R5 is H, alkyl, or aminoalkyl; are useful for modulating a peroxisome proliferator activated receptor, particularly in the treatment of diabetes mellitus. ##STR1##