While unesterified cholesterol (C) is essential for remodeling neuronal plasma membranes, its role in certain neurodegenerative disorders remains poorly defined. Uptake of sterol from pericellular fluid requires processing that involves two lysosomal proteins, lysosomal acid lipase (LAL) that hydrolyzes C esters and NPC1. In systemic tissues, inactivation of either protein led to sterol accumulation and cell death, but in the brain, inactivation of only NPC1 caused C sequestration and neurodegeneration. When injected into the CNS of the npc1-/- mouse, HP-β-CD, a compound known to prevent this C accumulation, diffused throughout the brain and was excreted with a T½ of 6.5 h. This agent caused suppression of C synthesis, elevation of C esters, suppression of SREBP2 target genes, and activation of LXR controlled genes. These findings indicated that HP-β-CD promoted movement of the sequestered C from lysosomes to the metabolically active pool of C in the cytosolic compartment of cells in the CNS. The ED50 for this agent in the brain was ∼0.5 mg/kg, and the therapeutic effect lasted more than 7 days. Continuous infusion of HP-β-CD into the ventricular system of npc1-/- animals between 3 and 7 weeks of age normalized the biochemical abnormalities and completely prevented the expected neurodegeneration. These studies support the concept that neurons continuously acquire C from interstitial fluid to permit plasma membrane turnover and remodeling. Inactivation of NPC1 leads to lysosomal C sequestration and neurodegeneration, but this is prevented by the continuous, direct administration of HP-β-CD into the CNS.

This article is available online at http://www.jlr.org Nearly all cells in the body, including neurons of the central nervous system (CNS), take up cholesteryl ester (CE) and/or unesterifi ed cholesterol (UC) carried in various lipoproteins from the surrounding pericellular fl uid by receptor-mediated and bulk-phase endocytosis ( 1, 2 ). The sterol in these particles is processed in the late endosomal/lysosomal (E/L) compartment of cells by the sequential action of at least three proteins, lysosomal acid lipase (LAL) ( 3 ), Niemann-Pick C2 (NPC2) ( 4 ), and Niemann-Pick C1 (NPC1) ( 5 ), before being exported into the cytosolic compartment. There it joins other UC, newly synthesized from acetyl-CoA, to provide a metabolically active pool of sterol critical for normal turnover of plasma membrane cholesterol. Because UC is a hydrophobic amphipath and potentially toxic to cells, the size of this metabolically active pool is tightly monitored by two systems, the sterol regulatory element binding proteins (SREBPs) ( 6 ) and the liver X receptors (LXRs) ( 7 ), which, in turn, regulate the expression of genes controlling the uptake, synthesis, degradation, and export of UC. In this manner, the size of the metabolically active pool is kept relatively small and constant even though rates of lipoprotein uptake and sterol synthesis may vary widely.Mutations in any one of these three proteins cause accumulation of CE (LAL, Wolman disease) or UC (NPC2 or NPC1, Niemann-Pick C disease) in every tissue, which leads to cell dysfunction and death, and to a variety of clinical syndromes including disease of the liver, lungs, and Abstract Lipoprotein cholesterol taken up by cells is processed in the endosomal/lysosomal (E/L) compartment by the sequential action of lysosomal acid lipase (LAL), Niemann-Pick C2 (NPC2), and Niemann-Pick C1 (NPC1). Inactivation of NPC2 in mouse caused sequestration of unesterifi ed cholesterol (UC) and expanded the whole animal sterol pool from 2,305 to 4,337 mg/kg. However, this pool increased to 5,408 and 9,480 mg/kg, respectively, when NPC1 or LAL function was absent. The transport defect in mutants lacking NPC2 or NPC1, but not in those lacking LAL, was reversed by cyclodextrin (CD), and the ED 50 values for this reversal varied from ‫ف‬ 40 mg/kg in kidney to >20,000 mg/kg in brain in both groups. This reversal occurred only with a CD that could interact with UC. Further, a CD that could interact with, but not solubilize, UC still overcame the transport defect. These studies showed that processing and export of sterol from the late E/L compartment was quantitatively different in mice lacking LAL, NPC2, or NPC1 function. In both npc2 Ϫ / Ϫ and npc1 Ϫ / Ϫ mice, the transport defect was reversed by a CD that interacted with UC, likely at the membrane/bulk-water interface, allowing sterol to move rapidly to the export site of the E/L compartment. Press, February 2, 2011 DOI 10.1194 Abbreviations: ALT, alanine aminotransferase ; AST, aspartate aminotransferase ; bw, body weight; CD, cyclodextrin; CE, c...

Liver stiffness, as determined by transient elastography, correlates with the presence and severity of CFLD. Although APRI provided some information regarding severity of liver disease, LSM performed better than APRI in this population.

Cholesteryl ester storage disease (CESD) results from loss-of-function mutations in LIPA, the gene that encodes lysosomal acid lipase (LAL). Hepatomegaly and deposition of esterified cholesterol (EC) in multiple organs ensue. The present studies quantitated rates of synthesis, absorption, and disposition of cholesterol, and whole body cholesterol pool size in a mouse model of CESD. In 50-day-old lal(-/-) and matching lal(+/+) mice fed a low-cholesterol diet, whole animal cholesterol content equalled 210 and 50 mg, respectively, indicating that since birth the lal(-/-) mice sequestered cholesterol at an average rate of 3.2 mg·day(-1)·animal(-1). The proportion of the body sterol pool contained in the liver of the lal(-/-) mice was 64 vs. 6.3% in their lal(+/+) controls. EC concentrations in the liver, spleen, small intestine, and lungs of the lal(-/-) mice were elevated 100-, 35-, 15-, and 6-fold, respectively. In the lal(-/-) mice, whole liver cholesterol synthesis increased 10.2-fold, resulting in a 3.2-fold greater rate of whole animal sterol synthesis compared with their lal(+/+) controls. The rate of cholesterol synthesis in the lal(-/-) mice exceeded that in the lal(+/+) controls by 3.7 mg·day(-1)·animal(-1). Fractional cholesterol absorption and fecal bile acid excretion were unchanged in the lal(-/-) mice, but their rate of neutral sterol excretion was 59% higher than in their lal(+/+) controls. Thus, in this model, the continual expansion of the body sterol pool is driven by the synthesis of excess cholesterol, primarily in the liver. Despite the severity of their disease, the median life span of the lal(-/-) mice was 355 days.

N eonatal cholestasis (NC) affects 1 in 2500 term infants with varying etiologies (1). Ciliopathies constitute a group of genetic disorders associated with ciliary dysfunction leading to multiorgan involvement that can present with cholestasis (2). We report 2 siblings who presented with NC and paucity of bile ducts. They subsequently developed end-stage liver (ESLD) and renal disease (ESRD) with severe progressive cardiac dysfunction. A novel homozygous variant in the NEK8 (never in mitosis A-related kinase A) gene, associated with the multiorgan ciliopathy Nephronophthisis (NPHP) type 9, was identified in both siblings (3). INDEX PATIENTThe patient (IV-3, Supplement Fig. 1A, Supplemental Digital Content, http://links.lww.com/MPG/B726) was born male, fullterm, to healthy, consanguineous parents. He had worsening direct hyperbilirubinemia of 14 with elevated gamma-glutamyl transferase (GGT) up to 2306 units/L, within the first 2 weeks of life (Supplemental Table 1, Supplemental Digital Content, http:// links.lww.com/MPG/B726). Infectious workup was nonrevealing. Abdominal ultrasound showed normal liver echogenicity without hepatic masses or intrahepatic ductal dilatation and 2 small kidneys. An intraoperative cholangiogram excluded biliary atresia (BA). The liver biopsy demonstrated paucity of interlobular bile ducts, cholangiolar proliferation, cholestasis, and mild bridging fibrosis (Fig. 1A and B). Genetic testing for Alagille syndrome including JAG1 deletion/duplication, progressive familial intrahepatic cholestasis (PFIC) and bile acid synthesis disorders (BASD) was negative. An echocardiogram showed