Bile acids are essential for solubilization and transport of dietary lipids, are the major products of cholesterol catabolism, and are physiological ligands for farnesoid X receptor (FXR), a nuclear receptor that regulates genes involved in lipid metabolism.1They are also inherently cytotoxic, as physiological imbalance contributes to increased oxidative stress.2,3Bile acid-controlled signaling pathways are promising novel targets to treat such metabolic diseases as obesity, type II diabetes, hyperlipidemia, and atherosclerosis.Guggulsterone, derived from resin of the guggul tree, is a competitive antagonist of FXR bothin vitroandin vivo.4Thecisstereoisomer of guggulsterone, (E)-guggulsterone, decreases chenodeoxycholic acid (CDCA)-induced FXR activation with an IC50value of 15 μM.5,6By inhibiting CDCA-induced transactivation of FXR, guggulsterone lowers low-density lipoprotein cholesterol and triglyceride levels in rodents fed a high cholesterol diet.4 1.Makishima, M., Okamoto, A.Y., Repa, J.J., et al.Identification of a nuclear receptor for bile acidsScience2841362-1365(1999) 2.Barbier, O., Torra, I.P., Sirvent, A., et al.FXR induces the UGT2B4 enzyme in hepatocytes: A potential mechanism of negative feedback control of FXR activityGastroenterology1241926-1940(2003) 3.Tan, K.P., Yang, M., and Ito, S.Activation of nuclear factor (erythroid-2 like) factor 2 by toxic bile acids provokes adaptive defense responses to enhance cell survival at the emergence of oxidative stressMol. Pharmacol.72(5)1380-1390(2007) 4.Urizar, N.L., Liverman, A.B., Dodds, D.T., et al.A natural product that lowers cholesterol as an anatagonist ligand for FXRScience296(5573)1703-1706(2002) 5.Cui, J., Huang, L., Zhao, A., et al.Guggulsterone is a farnesoid X receptor antagonist in coactivator association assays but acts to enhance transcription of bile salt export pumpThe Journal of Biological Chemisty278(12)10214-10220(2003) 6.Wu, J., Xia, C., Meier, J., et al.The hypolipidemic natural product guggulsterone acts as an antagonist of the bile acid receptorMolecular Endocrinology16(7)1590-1597(2002)
JTP-4819 is a potent and selective prolyl endopeptidase (PEP) inhibitor with potential for treating Alzheimer's disease. At nanomolar concentration, JTP-4819 inhibited the degradation of substance P, arginine-vasopressin, and thyrotropin-releasing hormone by PEP in supernatants of the rat cerebral cortex and hippocampus. Repeated administration of JTP-4819 reversed the aging-induced decrease in brain substance P-like and thyrotropin-releasing hormone-like immunoreactivity, suggesting that this drug may be able to improve the imbalance of peptidergic neuronal systems that develops with senescense by inhibiting PEP activity. JTP-4819 increased acetylcholine release from the frontal cortex and hippocampus, regions closely associated with memory, in both young and aged rats.