Various embodiments of this invention are directed to pharmaceutical compositions and methods for treating diseases, including focal segmental glomerulosclerosis or pulmonary arterial hypertension. The compositions of such embodiments include activated fatty acids such as alkyl substituted fatty acids, keto fatty acids and nitro fatty acids. The methods of various embodiments include administering an effective amount of 10-nitro-9(E)-octadec-9-enoic acid to treat such diseases.