title: Cholestenoic acid, an endogenous cholesterol metabolite, is a potent γ-secretase modulator.
abstract: BACKGROUND
  Amyloid-β (Aβ) 42 has been implicated as the initiating molecule in the pathogenesis of Alzheimer's disease (AD); thus, therapeutic strategies that target Aβ42 are of great interest. γ-Secretase modulators (GSMs) are small molecules that selectively decrease Aβ42. We have previously reported that many acidic steroids are GSMs with potencies ranging in the low to mid micromolar concentration with 5β-cholanic acid being the most potent steroid identified GSM with half maximal effective concentration (EC50) of 5.7 μM.
  
  
  RESULTS
  We find that the endogenous cholesterol metabolite, 3β-hydroxy-5-cholestenoic acid (CA), is a steroid GSM with enhanced potency (EC50 of 250 nM) relative to 5β-cholanic acid. CA i) is found in human plasma at ~100-300 nM concentrations ii) has the typical acidic GSM signature of decreasing Aβ42 and increasing Aβ38 levels iii) is active in in vitro γ-secretase assay iv) is made in the brain. To test if CA acts as an endogenous GSM, we used Cyp27a1 knockout (Cyp27a1-/-) and Cyp7b1 knockout (Cyp7b1-/-) mice to investigate if manipulation of cholesterol metabolism pathways relevant to CA formation would affect brain Aβ42 levels. Our data show that Cyp27a1-/- had increased brain Aβ42, whereas Cyp7b1-/- mice had decreased brain Aβ42 levels; however, peripheral dosing of up to 100 mg/kg CA did not affect brain Aβ levels. Structure-activity relationship (SAR) studies with multiple known and novel CA analogs studies failed to reveal CA analogs with increased potency.
  
  
  CONCLUSIONS
  These data suggest that CA may act as an endogenous GSM within the brain. Although it is conceptually attractive to try and increase the levels of CA in the brain for prevention of AD, our data suggest that this will not be easily accomplished.
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. jjung@ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. jjung@ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. jjung@ufl.edu.
authors.forename: Joo In
authors.initials: JI
authors.lastname: Jung
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. ashleighp@ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. ashleighp@ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. ashleighp@ufl.edu.
authors.forename: Ashleigh R
authors.initials: AR
authors.lastname: Price
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. tomladd@mbi.ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. tomladd@mbi.ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. tomladd@mbi.ufl.edu.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Ladd
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. yran@ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. yran@ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. yran@ufl.edu.
authors.forename: Yong
authors.initials: Y
authors.lastname: Ran
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. Hyo-Jin.Park@neurology.ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. Hyo-Jin.Park@neurology.ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. Hyo-Jin.Park@neurology.ufl.edu.
authors.forename: Hyo-Jin
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. carolina.ceballos@mbi.ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. carolina.ceballos@mbi.ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. carolina.ceballos@mbi.ufl.edu.
authors.forename: Carolina
authors.initials: C
authors.lastname: Ceballos-Diaz
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. lsmithson@ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. lsmithson@ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. lsmithson@ufl.edu.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Smithson
authors.affiliation: College of Pharmacy, University of Florida, Gainesville, FL, 32610, USA. hochhaus@cop.ufl.edu.
authors.forename: Günther
authors.initials: G
authors.lastname: Hochhaus
authors.affiliation: College of Pharmacy, University of Florida, Gainesville, FL, 32610, USA. yufei@cop.ufl.edu.
authors.forename: Yufei
authors.initials: Y
authors.lastname: Tang
authors.affiliation: SAI Life Sciences Ltd., Turkapally, AP500078, India. saibd@sailife.com.
authors.forename: Rajender
authors.initials: R
authors.lastname: Akula
authors.affiliation: SAI Life Sciences Ltd., Turkapally, AP500078, India. saibd@sailife.com.
authors.forename: Saritha
authors.initials: S
authors.lastname: Ba
authors.affiliation: Department of Neuroscience, University of California, La Jolla, San Diego, CA, 92093, USA. edkoo@ucsd.edu.|Departments of Medicine and Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119077, Singapore. edkoo@ucsd.edu.
authors.forename: Edward H
authors.initials: EH
authors.lastname: Koo
authors.affiliation: Pharmore, Inc., Gainesville, FL, 32653, USA. gideon.shapiro@gmail.com.
authors.forename: Gideon
authors.initials: G
authors.lastname: Shapiro
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. kfelsenstein0@ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. kfelsenstein0@ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. kfelsenstein0@ufl.edu.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Felsenstein
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, 32610, USA. tgolde@ufl.edu.|Department of Neuroscience, University of Florida, Gainesville, FL, 32610, USA. tgolde@ufl.edu.|McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL, 32610, USA. tgolde@ufl.edu.
authors.forename: Todd E
authors.initials: TE
authors.lastname: Golde
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D016466:CHO Cells; D002478:Cells, Cultured; D053493:Cholestanetriol 26-Monooxygenase / Q000172:deficiency / Q000235:genetics; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002793:Cholic Acids / Q000494:pharmacology; D018920:Coculture Techniques; D006224:Cricetinae; D003412:Cricetulus; D000072474:Cytochrome P450 Family 7; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015394:Molecular Structure; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism*; D013250:Steroid Hydroxylases / Q000172:deficiency / Q000235:genetics; D013329:Structure-Activity Relationship
chemical_list: D016229:Amyloid beta-Peptides; D002793:Cholic Acids; D010446:Peptide Fragments; C078639:amyloid beta-protein (1-38); C075222:amyloid beta-protein (1-42); C029435:3-hydroxy-5-cholestenoic acid; D002784:Cholesterol; D013250:Steroid Hydroxylases; D000072474:Cytochrome P450 Family 7; C097207:Cyp7b1 protein, mouse; D053493:Cholestanetriol 26-Monooxygenase; C506832:Cyp27a1 protein, mouse; D053829:Amyloid Precursor Protein Secretases; C007036:cholanic acid