Quantitation of two pathways for cholesterol excretion from the brain in normal mice and mice with neurodegeneration.
Although the pool of cholesterol in the adult central nervous system (CNS) is large and of constant size, little is known of the process(es) involved in regulation of sterol turnover in this pool. In 7-week-old mice, net excretion of cholesterol from the brain equaled 1.4 mg/day/kg body weight, and from the whole animal was 179 mg/day/kg. Deletion of cholesterol 24-hydroxylase, an enzyme highly expressed in the CNS, did not alter brain growth or myelination, but reduced sterol excretion from the CNS 64% to 0.5 mg/day/kg. In mice with a mutation in the Niemann-Pick C gene that had ongoing neurodegeneration, sterol excretion from the CNS was increased to 2.3 mg/day/kg. Deletion of cholesterol 24-hydroxylase activity in these animals reduced net excretion only 22% to 1.8 mg/day/kg. Thus, at least two different pathways promote net sterol excretion from the CNS. One uses cholesterol 24-hydroxylase and may reflect sterol turnover in large neurons in the brain. The other probably involves the movement of cholesterol or one of its metabolites across the blood-brain barrier and may more closely mirror sterol turnover in pools such as glial cell membranes and myelin.
Xie
Chonglun
C
Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-8887, USA.
Lund
Erik G
EG
Turley
Stephen D
SD
Russell
David W
DW
Dietschy
John M
JM
D000375:Aging / Q000502:physiology; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D053493:Cholestanetriol 26-Monooxygenase; D002784:Cholesterol / Q000378:metabolism*; D000072556:Cholesterol 24-Hydroxylase; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009410:Nerve Degeneration / Q000503:physiopathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012727:Sex Characteristics; D013250:Steroid Hydroxylases / Q000235:genetics
D012333:RNA, Messenger; D002784:Cholesterol; D013250:Steroid Hydroxylases; D002790:Cholesterol 7-alpha-Hydroxylase; D000072556:Cholesterol 24-Hydroxylase; D053493:Cholestanetriol 26-Monooxygenase; C506832:Cyp27a1 protein, mouse