The half-life of cholesterol in the adult brain is between 6 months and 5 years (Andersson et al., 1990; Björkhem et al., 2006), in contrast, the half-life of plasma cholesterol is only a few days (Dietschy and Turley, 2004). The maintenance of cholesterol homeostasis is critical to prevent atherosclerosis. J Biol Chem 277:42781–42789, Patel SC, Suresh S, Kumar U, Hu CY, Cooney A, Blanchette-Mackie EJ et al (1999) Localization of Niemann-Pick C1 protein in astrocytes: implications for neuronal degeneration in Niemann- Pick type C disease. The investigation of cholesterol metabolism in the brain has a long history, but this field has gained momentum only within the last decade, probably because cholesterol is implied in neurodegenerative disease. inhibiting the Niemann-Pick C1-like 1 protein (ezetimibe). Hippocampus 19:692–705, Fox MA, Umemori H (2006) Seeking long-term relationship: axon and target communicate to organize synaptic differentiation. In this article, we review sterol metabolism and its implications for mammalian CNS function and disease, with particular emphasis on the emerging role(s) of brain oxysterols in the pathophysiology of AD. Proc Natl Acad Sci USA 76:646–649, Saher G, Brügger B, Lappe-Siefke C et al (2005) High cholesterol level is essential for myelin membrane growth. No Citations. ApoE lipoprotein particles secreted by glial cells have higher affinity for LDLR than LRP1, but CSF-isolated high-density lipoprotein (HDL) particles bind more strongly to LRP1 (Fagan et al., 1996). J Lipid Res 42:1143–1151, Koldamova RP, Lefterov IM, Ikonomovic MD, Skoko J, Lefterov PI, Isanski BA et al (2003) 22R-hydroxycholesterol and 9-cis-retinoic acid induce ATP-binding cassette transporter A1 expression and cholesterol efflux in brain cells and decrease amyloid beta secretion. Brain is the most cholesterol-rich organ, it contains about 20% of the whole body’s cholesterol (Björkhem et al., 2004). AB - Lipids and lipid metabolism are critical factors in hair follicle (HF) biology, and cholesterol has long been suspected of influencing hair growth. Cholesterol homeostasis is a highly regulated process in human body because of its several functions underlying the biology of cell membranes, the synthesis of all steroid hormones and bile acids and the need of trafficking lipids destined to cell metabolism. cholesterol gallstones is of major importance in Western healthcare systems. When cholesterol synthesis rate exceeds its acquisition rate in the brain, that is when the net excretion of cholesterol occurs. Proc Natl Acad Sci USA 103:5644–5651, Marquer C, Devauges V, Cossec JC, Liot G, Lecart S, Saudou F, Duyckaerts C, Leveque-Fort S, Potier MC (2011) Local cholesterol increase triggers amyloid precursor protein-BACE1 clustering in lipid rafts and rapid endocytosis. Cell 71:343–353, Pooler AM, Xi SC, Wurtman RJ (2006) The 3- hydroxy-3-methylglutaryl co-enzyme A reductase inhibitor pravastatin enhances neurite outgrowth in hippocampal neurons. Besides this, astrocytes also produce messenger RNAs that encode several synaptic adhesion proteins, including neurexins, neuroligins, and cadherins (Cahoy et al., 2008), that are known to be important for synapse formation and are believed function in neurons only (Fox and Umemori, 2006). 81422015, 91332111, and 31371087), the National Basic Research Program (973 Program) (No. Science 277:228–231, Christopherson KS et al (2005) Thrombospondins are astrocyte-secreted proteins that promote CNS synaptogenesis. Science 291:657–661, Valdez CM, Smith MA, Perry G, Phelix CF, Santamaria F (2010) Cholesterol homeostasis markers are localized to mouse hippocampal pyramidal and granule layers. Proc Natl Acad Sci USA 89:4471–4475, Pitas RE, Boyles JK, Lee SH, Hui D, Weisgraber KH (1987a) Lipoproteins and their receptors in the central nervous system. Cholesterol is directly released onto APOA1-containing lipoproteins that is present in CSF (Roheim et al., 1979; Pitas et al., 1987a; Koch et al., 2001), then these lipoproteins could be removed from the brain through LRP1 or scavenger receptor class B1, both of these two receptors are expressed in brain capillary endothelial cells (Panzenboeck et al., 2002; Gosselet et al., 2009). cholesterol homeostasis), may constitute novel targets for therapeutic intervention in AD and possibly other human neurodegenerations. Although there is a large body of work elucidating these cho- lesterol-related pathways, less is known about the role of Hippocampus 20:902–905, Vance JE, Pan D, Campenot RB, Bussiere M, Vance DE (1994) Evidence that the major membrane lipids, except cholesterol, are made in axons of cultured rat sympathetic neurons. Disrupting cholesterol homeostasis by depleting cells of cholesterol with β‐cyclodextrin inhibits insulin‐dependent glucose uptake. Lipoprotein related protein (LRP) level remains the same in this mouse model too, this also supports that adult neurons already express sufficient LRP to import cholesterol as apoE-containing lipoprotein particles. Proc Natl Acad Sci 107:3081–3086, Cahoy JD et al (2008) A transcriptome database for astrocytes, neurons, and oligodendrocytes: a new resource for understanding brain development and function. Cholesterol homeostasis is affected by exogenous factors (i.e. This review will discuss current knowledge of cholesterol physiology, with emphasis on cholesterol absorption, cholesterol synthesis and fecal excretion, and new (possible) therapeutic options for hypercholesterolemia. Cholesterol in neurons is primarily biosynthesized through Kandutsch-Russell pathway, whereas in astrocytes through Bloch pathway. Critical Review The Role of Signalling in Cellular Cholesterol Homeostasis Winnie Luu1 Laura J. Sharpe1,2 Ingrid C. Gelissen2 Andrew J. Brown1* 1School of Biotechnology and Biomolecular Sciences, The University of New South Wales, NSW, Australia All the evidences indicate that ABCA1 is a crucial molecule for apoE-containing lipoprotein formation in CNS. Different profiles of post-squalene precursors were observed in neurons in comparison to astrocytes (Fig. Management of blood cholesterol is a major focus of efforts to prevent cardiovascular diseases. Although many roles have been described for BAs with regard to cholesterol homeostasis and endocrine signaling in both hepatic and extrahepatic tissues, we focus this review on conversion of cholesterol to BAs and sexual dimorphisms in the activity and regulation of … J Biol Chem 278:8043–8051, Heino S, Lusa S, Somerharju P, Ehnholm C, Olkkonen VM, Ikonen E (2000) Dissecting the role of the Golgi complex and lipid rafts in biosynthetic transport of cholesterol to the cell surface. Neurobiol Dis 29:422–437, Xu PT, Gilbert JR, Qiu HL, Ervin J, Rothrock-Christian TR, Hulette C, Schmechel DE (1999) Specificregional transcription of apolipoprotein E in human brain neurons. A Review. Nat Rev Mol Cell Biol 9:125–138, Janowski BA, Grogan MJ, Jones SA, Wisely GB, Kliewer SA, Corey EJ, Mangelsdorf DJ (1999) Structural requirements of ligands for the oxysterol liver X receptors LXRalpha and LXRbeta. Biochimi et Biophys Acta 917:148–161, CAS Zhang, J., Liu, Q. Neurons need to build up a large amount of membrane surface of their axons, dendrites and synapses, including postsynaptic spines and presynaptic vesicles, where significantly high cholesterol content was detected (Goritz et al., 2005; Pfenninger, 2009; Takamori et al., 2006). Cholesterol homeostasis is among the most intensely regulated processes in biology. Defects in cholesterol metabolism lead to structural and functional central nervous system (CNS) diseases such as Niemann-Pick C disease, Huntington’s disease, Alzheimer’s disease and Parkinson’s disease (Madra and Sturley, 2010; Block et al., 2010; Di Paolo and Kim, 2011; Wang et al., 2011). Curr Opin Lipidol 20:190–196, Hirsch-Reinshagen V, Zhou S, Burgess BL, Bernier L, McIsaac SA, Chan JY et al (2004) Deficiency of ABCA1 impairs apolipoprotein E metabolism in brain. REVIEW Open Access Dual functions of Insig proteins in cholesterol homeostasis Xiao-Ying Dong1,2, Sheng-Qiu Tang2 and Jin-Ding Chen1* Abstract The molecular mechanism of how cells maintain cholesterol homeostasis has become clearer for the understanding Excess of cholesterol is prevented by intracellular esterification and storage in lipid droplets, or released as a complex with apolipoprotein-containing lipoprotein via ATP-binding cassette transporter, or converting to oxysterols then passing through BBB. J. Lipid Res 21:364–376, Jurevics H, Morell P (1995) Cholesterol for synthesis of myelin is made locally, not imported into brain. J Lipid Res 42:1007–1017, DeBose-Boyd RA, Brown MS, Li WP, Nohturfft A, Goldstein JL, Espenshade PJ (1999) Transport-dependent proteolysis of SREBP: relocation of Site-1 protease from Golgi to ER obviates the need for SREBP transport to Golgi. The brain is the most cholesterol-rich organ in the body, and dysregulation of cholesterol homeostasis may influence neurological disorders such as AD (29– 32, 41, 42). However, in situ hybridization data from the Allen Mouse Brain Atlas suggest that transcript level of many cholesterol synthesis enzymes are higher in neurons compared to these in astrocytes (Valdez et al., 2010), although higher transcript level doesn’t necessarily mean the actual protein level and enzymatic activity have the same pattern. Cholesterol Homeostasis: Methods and Protocols: Gelissen, Ingrid C., Brown, Andrew J.: Amazon.sg: Books Chapters also cover techniques for studying the regulation of cholesterol homeostasis at The understanding of cholesterol metabolism in the brain and its role in disease requires further studies. Murri”, Bari University School of Medicine, Policlinico Hospital - 70124 Bari – Italy. Helen H. Wang, Sluiten. All these evidences indicate that cholesterol synthesis in neurons is essential at early development stage. This article does not contain any studies with human or animal subjects performed by the any of the authors. prevent cholesterol gallstones in selected subjects at risk. ABCA and ABCG are the major classes in the brain, they are critical for lipid homeostasis (Dean et al., 2001; Schmitz et al., 2000; Puglielli et al., 2003). J Neurochem 75:1250–1257, Puglielli L, Tanzi RE, Kovacs DM (2003) Alzheimer’s disease: the cholesterol connection. Cholesterol homeostasis is tightly regulated by a group of endocrine hormones under physiological conditions. Prog Lipid Res 50:357–371, Piedrahita JA, Zhang SH, Hagaman JR, Oliver PM, Maeda N (1992) Generation of mice carrying a mutant apolipoprotein E gene inactivated by gene targeting in embryonic stem cells. Freeman, New York, Björkhem I (2006) Crossing the barrier: oxysterols as cholesterol transporters and metabolic modulators in the brain. Arterioscler Thromb Vasc Biol 24:806–815, Björkhem I, Heverin M, Leoni V, Meaney S, Dicz-falusy U (2006) Oxysterols and Alzheimer’s disease. J Lipid Res 45:582–591, Roheim PS, Carey M, Forte T, Vega GL (1979) Apolipoproteins in human cerebrospinal fluid. Cholesterol homeostasis in the hair follicle: identification of known mutations and knockout mouse models associated with hair disorders. On the other hand, mice lacking cellular cholesterol synthesis in adult neurons were phenotypically indistinguishable from controls, furthermore, no obivious signs of neurodegeneration or inflammation were observed (Fünfschilling et al., 2007). It was detected that adult neurons have a lower rate of sterol synthesis in comparison to glial cells. Cholesterol biosynthesis is regulated by transcription factors named steroid regulatory element-binding proteins. Disturbed cholesterol balance underlies not only cardiovascular disease but also an increasing number of other diseases such as neurodegenerative diseases and cancers. Very little is currently known about the maintenance of cholesterol homeostasis in the retina (Figs. Mol Psychiatry 8:635–638, Wollmer MA, Streffer JR, Lutjohann D, Tsolaki M, Iakovidou V, Hegi T et al (2003b) ABCA1 modulates CSF cholesterol levels and influences the age at onset of Alzheimer’s disease. As this lipid is both vital and lethal, ensuring that its levels are kept in check is important for maintaining health. Cholesterol has long been implicated in diverse aspects of human health and disease. J Biol Chem 276:18000–18006, Liang Y, Lin S, Beyer TP, Zhang Y, Wu X, Bales KR, DeMattos RB, May PC, Li SD, Jiang XC Eacho PI, Cao G, Paul SM (2004) A liver X receptor and retinoid X receptor heterodimer mediates apolipoprotein E expression secretion and cholesterol homeostasis in astrocyte. Astrocytes are the major source of apoE followed by oligodendrycytes, microglia, and ependymal layer cells (Mahley et al., 2006). Google Scholar, Björkhem I, Meaney S, Fogelman AM (2004) Brain cholesterol: long secret life behind a barrier.
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