The present invention relates to methods for treating or preventing a disorder of lipid metabolism, pain, diabetes, a vascular condition, demyelination or nonalcoholic fatty liver disease, comprising administering a compound having the formula or a pharmaceutically acceptable salt, solvate, ester, prodrug or stereoisomer thereof, wherein: R.sup.1 and R.sup.2 are defined in Tables 1-6 herein, and R.sub.3 is -phenyl, -4-chlorophenyl, -2-pyridyl, or -3-pyridyl.