Lysosomal Acid Lipase Deficiency: Genetics, Screening, and Preclinical Study.

Lysosomal acid lipase (LAL) is a lysosomal enzyme essential for the degradation of cholesteryl esters through the endocytic pathway. Deficiency of the LAL enzyme encoded by the LIPA gene leads to LAL deficiency (LAL-D) (OMIM 278000), one of the lysosomal storage disorders involving 50-60 genes. Among the two disease subtypes, the severe disease subtype of LAL-D is known as Wolman disease, with typical manifestations involving hepatomegaly, splenomegaly, vomiting, diarrhea, and hematopoietic abnormalities, such as anemia. In contrast, the mild disease subtype of this disorder is known as cholesteryl ester storage disease, with hypercholesterolemia, hypertriglyceridemia, and high-density lipoprotein disappearance. The prevalence of LAL-D is rare, but several treatment options, including enzyme replacement therapy, are available. Accordingly, a number of screening methodologies have been developed for this disorder. This review summarizes the current discussion on LAL-D, covering genetics, screening, and the tertiary structure of human LAL enzyme and preclinical study for the future development of a novel therapy.

Screening for lysosomal acid lipase deficiency: A retrospective data mining study and evaluation of screening criteria.

BACKGROUND AND AIMS: Lysosomal acid lipase deficiency (LAL-D) is a lysosomal storage disorder. In severe cases, it can cause life-threatening organ failure due to lipid substrates accumulation. However, mild phenotypes of this disorder are increasingly recognized. The aim of this study is to determine the number of missed LAL-D patients in a large pediatric hospital population. METHODS: In a retrospective data mining study, the medical files of children, who visited the outpatient clinic at a university hospital between 2000 and 2016, with high plasma low density lipoprotein cholesterol (LDL-C) levels, were evaluated. Previously developed LAL-D screening criteria, with lipid and alanine aminotransferase (ALT) values adjusted for children, were used to analyze which children are suspect for LAL-D. For suspicion of LAL-D, at least 3 out of 5 screening criteria had to be met. Subsequently data on presentation and follow-up were collected to determine if the clinical picture was compatible with LAL-D. RESULTS: We identified 2037 children with high LDL-C levels. Of those, 36 children complied with ≥3 screening criteria. Thirty-one of those had an underlying disorder other than LAL-D that explained the abnormalities and, in the 5 remaining children, ALT and lipid levels normalized spontaneously, thus excluding LAL-D. CONCLUSIONS: This study shows that retrospective data mining is unlikely to yield a significant number of LAL-D cases in children. The screening algorithm adjusted for children seems useful and accurate in the selection of children for further testing, suggesting it can be applied prospectively, although further validation is warranted.

Hypercholesterolaemia and hepatosplenomegaly: two manifestations of cholesteryl ester storage disease.

Cholesteryl ester storage disease (CESD) is a rare autosomal recessive disease caused by mutations in LIPA. Here we describe two different clinical presentations of this disease: one case with a clear phenotype of familial hypercholesterolaemia and one case with hepatosplenomegaly from childhood onwards. These two cases exemplify the diversity of clinical phenotypes of patients with CESD. Knowledge on the phenotypic variability of the disease is of clinical relevance in light of enzyme replacement therapy (sebelipase alpha) for patients with mutations in LIPA, which is currently under development.

Deletion of sterol O-acyltransferase 2 (SOAT2) function in mice deficient in lysosomal acid lipase (LAL) dramatically reduces esterified cholesterol sequestration in the small intestine and liver.

Sterol O-acyltransferase 2 (SOAT2), also known as ACAT2, is the major cholesterol esterifying enzyme in the liver and small intestine (SI). Esterified cholesterol (EC) carried in certain classes of plasma lipoproteins is hydrolyzed by lysosomal acid lipase (LAL) when they are cleared from the circulation. Loss-of-function mutations in LIPA, the gene that encodes LAL, result in Wolman disease (WD) or cholesteryl ester storage disease (CESD). Hepatomegaly and a massive increase in tissue EC levels are hallmark features of both disorders. While these conditions can be corrected with enzyme replacement therapy, the question arose as to what effect the loss of SOAT2 function might have on tissue EC sequestration in LAL-deficient mice. When weaned at 21 days, Lal(-)(/)(-):Soat2(+)(/)(+) mice had a whole liver cholesterol content (mg/organ) of 24.7 mg vs 1.9mg in Lal(+/+):Soat2(+/+) littermates, with almost all the excess sterol being esterified. Over the next 31 days, liver cholesterol content in the Lal(-)(/)(-):Soat2(+)(/)(+) mice increased to 145 ± 2 mg but to only 29 ± 2 mg in their Lal(-)(/)(-):Soat2(-)(/)(-) littermates. The level of EC accumulation in the SI of the Lal(-)(/)(-):Soat2(-)(/)(-) mice was also much less than in their Lal(-)(/)(-):Soat2(+)(/)(+) littermates. In addition, there was a >70% reduction in plasma transaminase activities in the Lal(-)(/)(-):Soat2(-)(/)(-) mice. These studies illustrate how the severity of disease in a mouse model for CESD can be substantially ameliorated by elimination of SOAT2 function.

Hepatic entrapment of esterified cholesterol drives continual expansion of whole body sterol pool in lysosomal acid lipase-deficient mice.

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.

Lysosomal acid lipase deficiency: wolman disease and cholesteryl ester storage disease.

Cholesteryl ester storage disease (CESD, OMIM #278000) and Wolman disease (OMIM #278000) are autosomal recessive lysosomal storage disorders caused by a deficient activity of lysosomal acid lipase (cholesteryl ester hydrolase, LAL). Human lysosomal acid lipase is essential for the metabolism of cholesteryl esters and triglycerides. In Wolman disease, LAL activity is usually absent, whereas CESD usually presents some residual LAL activity. In infants, poor weight gain, massive hepatosplenomegaly, calcified adrenal glands (present about 2/3 of the time), vomiting, diarrhea and failure to thrive are indicative of Wolman disease. The clinical picture is more variable in CESD. Hepatomegaly and/or elevation of liver transaminases are almost always present. Hepatic steatosis often leads to fibrosis and cirrhosis. Other signs often include splenomegaly, high total cholesterol and LDL-cholesterol, elevated triglycerides, and low HDL-cholesterol. The diagnosis of LAL deficiency requires clinical experience and specialized laboratory tests. The diagnosis is based on finding deficient activity of acid lipase and/or molecular tests. Pilot screening projects using dried blood spot testing in 1) children with atypical fatty liver disease in the absence of overweight, 2) patients with dyslipidaemia and presence of hepatomegaly and/or elevated transaminases, 3) newborns/neonates with hepatomegaly and abdominal distension/failure to thrive/elevated transaminases are currently underway. Early diagnosis is particularly important for the enzyme replacement therapy. Human trials with recombinant LAL are currently ongoing, raising the prospect for specific correction of LAL deficiency in this progressive and often debilitating disorder.

Cholesteryl ester storage disease: protean presentations of lysosomal acid lipase deficiency.

OBJECTIVE: LIPA gene mutations result in deficiency of lysosomal acid lipase and present phenotypically as Wolman disease or cholesteryl ester storage disease (CESD) depending on the level of deficiency. Patients with CESD may often be misdiagnosed because symptoms may be nonspecific. Symptoms may present in infancy if there is complete loss of lysosomal acid lipase or in early childhood or adulthood when there is partial loss. The purpose of the present study is to review the literature for pediatric cases of CESD to better understand the phenotype of CESD. METHODS: A PubMed search of all English-language publications from 1966 through June 2012 for pediatric CESD case reports using the following key words CESD, fatty liver, and NAFLD was performed. All of the cases were reviewed and information regarding age, sex, presenting symptoms, and pertinent laboratory tests were recorded. RESULTS: Seventy-one cases were culled from 39 published case reports. Nearly two-thirds of these patients presented with their first symptoms when they were younger than 5 years. Hepatomegaly and splenomegaly were common features. Serum transaminases and lipids were often elevated. Gastrointestinal symptoms were noted in approximately one-third of cases. Two-thirds of patients had liver fibrosis. CONCLUSIONS: CESD has an estimated incidence as high as 1 in 40,000, which means that it is presently underdiagnosed. Education about common symptoms of CESD as well as a higher level of suspicion for screening for CESD will lead to earlier diagnosis. New treatments for CESD including possible enzyme replacement therapy make early diagnosis especially important.

Distinctive histopathological features that support a diagnosis of cholesterol ester storage disease in liver biopsy specimens.

AIMS: To identify reliable criteria with which to improve the diagnosis of lysosomal acid lipase (LAL) deficiency of the cholesterol ester storage disease (CESD) type in liver biopsies. METHODS AND RESULTS: We analysed a series of 16 liver biopsies of LAL deficiency of the CESD type confirmed by enzyme testing and DNA sequencing. The biopsy appearances were compared with those of biopsies of other causes of fatty liver. A predominantly microvesicular steatosis in CESD patients could not be reliably distinguished from other causes of fatty liver with cytosolic lipid accumulation in fixed paraffin-embedded tissues routinely stained with haematoxylin and eosin. The presence of luminal (cathepsin D) and membrane lysosomal markers [lysosomal-associated membrane protein (LAMP)1, LAMP2, and lysosomal integral membrane protein 2] around the lipid vacuoles facilitated the diagnosis of CESD in fixed paraffin-embedded material. Additional diagnostic clues included autofluorescent detection of ceroid induction in storage macrophages and the absence of lipopigment in hepatocytes. Stored liquid crystals of cholesteryl esters, which are associated with Maltese cross-type birefringence, were best appreciated in unfixed biopsy samples. CONCLUSIONS: The pathological diagnosis of CESD requires a high index of suspicion, and can be rapidly and effectively appreciated at the light microscopy level, even in routine fixed paraffin-embedded liver samples with immuohistochemical staining for lysosomal markers.

Structural bases of Wolman disease and cholesteryl ester storage disease.

To elucidate the bases of Wolman disease (WD) and cholesteryl ester storage disease (CESD) from the viewpoint of enzyme structure, we constructed a structural model of human lysosomal acid lipase (LAL) using molecular modeling software Modeller. The results revealed that the residues responsible for WD/CESD tend to be less solvent-accessible than others. Then, we examined the structural changes in the LAL protein caused by the WD/CESD mutations, using molecular modeling software TINKER. The results indicated that conformational changes of the functionally important residues and/or large conformational changes tend to cause the severe clinical phenotype (WD), whereas small conformational changes tend to cause the mild clinical phenotype (CESD), although there have been several exceptions. Further structural analysis is required to clarify the relationship between the three-dimensional structural changes and clinical phenotypes.

Lysosomal acid lipase deficiency impairs regulation of ABCA1 gene and formation of high density lipoproteins in cholesteryl ester storage disease.

ATP-binding cassette transporter A1 (ABCA1) mediates the rate-limiting step in high density lipoprotein (HDL) particle formation, and its expression is regulated primarily by oxysterol-dependent activation of liver X receptors. We previously reported that ABCA1 expression and HDL formation are impaired in the lysosomal cholesterol storage disorder Niemann-Pick disease type C1 and that plasma HDL-C is low in the majority of Niemann-Pick disease type C patients. Here, we show that ABCA1 regulation and activity are also impaired in cholesteryl ester storage disease (CESD), caused by mutations in the LIPA gene that result in less than 5% of normal lysosomal acid lipase (LAL) activity. Fibroblasts from patients with CESD showed impaired up-regulation of ABCA1 in response to low density lipoprotein (LDL) loading, reduced phospholipid and cholesterol efflux to apolipoprotein A-I, and reduced α-HDL particle formation. Treatment of normal fibroblasts with chloroquine to inhibit LAL activity reduced ABCA1 expression and activity, similar to that of CESD cells. Liver X receptor agonist treatment of CESD cells corrected ABCA1 expression but failed to correct LDL cholesteryl ester hydrolysis and cholesterol efflux to apoA-I. LDL-induced production of 27-hydroxycholesterol was reduced in CESD compared with normal fibroblasts. Treatment with conditioned medium containing LAL from normal fibroblasts or with recombinant human LAL rescued ABCA1 expression, apoA-I-mediated cholesterol efflux, HDL particle formation, and production of 27-hydroxycholesterol by CESD cells. These results provide further evidence that the rate of release of cholesterol from late endosomes/lysosomes is a critical regulator of ABCA1 expression and activity, and an explanation for the hypoalphalipoproteinemia seen in CESD patients.

Cholesteryl Ester Storage Disease (CESD) due to novel mutations in the LIPA gene.

Cholesteryl Ester Storage Disease (CESD) is a rare recessive disorder due to mutations in LIPA gene encoding the lysosomal acidic lipase (LAL). CESD patients have liver disease associated with mixed hyperlipidemia and low plasma levels of high-density lipoproteins (HDL). The aim of this study was the molecular characterization of three patients with CESD. LAL activity was measured in blood leukocytes. In two patients (twin sisters) the clinical diagnosis of CESD was made at 9 years of age, following the fortuitous discovery of elevated serum liver enzymes in apparently healthy children. They had mixed hyperlipidemia, hepatosplenomegaly, reduced LAL activity (approximately 5% of control) and heteroalleic mutations in LIPA gene coding sequence: (i) the common c.894 G>A mutation and (ii) a novel nonsense mutation c.652 C>T (p.R218X). The other patient was an 80 year-old female who for several years had been treated with simvastatin because of severe hyperlipidemia associated with low plasma HDL. In this patient the sequence of major candidate genes for monogenic hypercholesterolemia and hypoalphalipoproteinemia was negative. She was found to be a compound heterozygote for two LIPA gene mutations resulting in 5% LAL activity: (i) c.894 G>A and (ii) a novel complex insertion/deletion leading to a premature termination codon at position 82. These findings suggest that, in view of the variable severity of its phenotypic expression, CESD may sometimes be difficult to diagnose, but it should be considered in patients with severe type IIb hyperlipidemia associated with low HDL, mildly elevated serum liver enzymes and hepatomegaly.

Lysosomal acid lipase-deficient mice: depletion of white and brown fat, severe hepatosplenomegaly, and shortened life span.

Lysosomal acid lipase (LAL) is essential for the hydrolysis of triglycerides (TG) and cholesteryl esters (CE) in lysosomes. A mouse model created by gene targeting produces no LAL mRNA, protein, or enzyme activity. The lal-/- mice appear normal at birth, survive into adulthood, and are fertile. Massive storage of TG and CE is observed in adult liver, adrenal glands, and small intestine. The age-dependent tissue and gross progression in this mouse model are detailed here. Although lal-/- mice can be bred to give homozygous litters, they die at ages of 7 to 8 months. The lal-/- mice develop enlargement of a single mesenteric lymph node that is full of stored lipids. At 6;-8 months of age, the lal-/- mice have completely absent inguinal, interscapular, and retroperitoneal white adipose tissue. In addition, brown adipose tissue is progressively lost. The plasma free fatty acid levels are significantly higher in lal-/- mice than age-matched lal+/+ mice, and plasma insulin levels were more elevated upon glucose challenge. Energy intake was also higher in lal-/- male mice, although age-matched body weights were not significantly altered from age-matched lal+/+ mice. Early in the disease course, hepatocytes are the main storage cell in the liver; by 3;-8 months, the lipid-stored Kupffer cells progressively fill the liver. The involvement of macrophages throughout the body of lal-/- mice provide evidence for a critical nonappreciated role of LAL in cellular cholesterol and fatty acid metabolism, adipocyte differentiation, and fat mobilization.

Accumulated lipids, aberrant fatty acid composition and defective cholesterol ester hydrolase activity in cholesterol ester storage disease.

We confirmed accumulation of glycogen and lipids, particularly cholesterol esters, in the liver of a patient with cholesterol ester storage disease (CESD). Hepatic cholesterol ester concentration was 100-200 times that found in normal livers. Analysis of the fatty acid composition indicated a higher proportion (41%) of cholesterol linoleate (C18-2), a slightly lower proportion (33%) of cholesterol oleate (C18-1) and normal proportions (14%) of cholesterol palmitate (C16-0) in the CESD patient compared with the control. This fatty acid composition of cholesterol esters and the fatty acid composition of other classes of lipids in the patient's liver resembled that of LDL. We also found that acid cholesterol ester hydrolase activity in the CESD liver was reduced to 5% of that in the control liver, while neutral cholesterol ester hydrolase activity remained at the control level. These results suggest that accumulated cholesterol esters were derived mainly from serum LDL and that the accumulation resulted from lack of acid cholesterol ester hydrolase.

Testis - a novel storage site in human cholesteryl ester storage disease. Autopsy report of an adult case with a long-standing subclinical course complicated by accelerated atherosclerosis and liver carcinoma.

A case of long-standing subclinical cholesteryl ester storage disease (CESD) manifesting as hyperlipoproteinaemia type IIb without any hepatomegaly is described. The patient underwent surgical vascular interventions because of accelerated atherosclerosis, which dominated his middle age. CESD was an incidental finding when a liver biopsy specimen was taken because liver malignancy was suspected; the patient's condition proved to be due to a cholangiocarcinoma, which led to his death at the of age 52. The autopsy showed moderate-intensity storage in the set of cells characterized by constitutional high-level receptor-mediated LDL endocytosis (hepatocytes, adrenal cortical cells) and also revealed storage in the Leydig cells. The severity with which histiocytes were affected varied regionally, ranging from minimal detectable storage or none at all (gut, lymph nodes, spleen) to extreme lysosomal expansion by cholesteryl ester liquid crystals (bone marrow) or by ceroid (lung, testicular stroma), or by both (liver). The density of the histiocytic population did not correlate with the degree to which parenchymal cells were affected except in the testicular stroma, where it was prominent. The patient was a mixed heterozygote for the G934A and DeltaC(673-5) mutations.

Clinical, biochemical and histological analysis of seven patients with cholesteryl ester storage disease.

Lysosomal acid lipase (LAL) deficiency leads to two phenotypically different diseases: cholesteryl ester storage disease (CESD) and Wolman's disease. Lysosomal acid lipase hydrolyzes cholesteryl esters and triglycerides. Deficiency of LAL results in intralysosomal storage of cholesteryl esters and triglycerides. CESD has a chronic and benign course and is characterized by hepatomegaly and mild hypercholesterolemia. It leads to fibrosis (cirrhosis) and early atherosclerosis. This report presents the clinical, biochemical and microscopic data of seven patients with CESD followed up over 10 years. The physical development of all the study children remained within the normal range; 7 patients had hepatomegaly and 6 also had splenomegaly. Three patients had normal cholesterol, triglycerides and transaminases values; the other four had slightly elevated levels for these parameters. The activity of LAL in all patients was reduced to below 30% of the lower normal value. Histologically, cholesteryl crystals and lipid storage vacuoles in Kupffer cells were present in all examined patients except one. Accumulation of cholesteryl esters was visible on thin-layer chromatography of lipid extracts obtained from liver biopsies.

Cholesteryl ester storage disease: complex molecular effects of chronic lovastatin therapy.

To better characterize the in vivo effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibition on human lipid metabolism, an adolescent male with cholesteryl ester storage disease (CESD) was treated chronically with lovastatin. Therapy was associated with decreased liver-spleen size, improved but not normal serum lipids, a 26% decrease in hepatic cholesteryl ester, a 12% decrease in unesterified hepatic cholesterol, and a fourfold increase in hepatic low density lipoprotein (LDL) receptor protein. Hepatic mRNA levels for the LDL receptor and apolipoprotein (apo) B standardized to levels of hepatic gamma actin mRNA were unchanged with therapy. Kinetic studies revealed no change in the LDL fractional catabolic rate and a decrease in the LDL production rate. Size exclusion chromatography showed striking reductions in plasma very low density lipoprotein (VLDL) cholesterol and intermediate density lipoprotein (LDL) cholesterol but not LDL cholesterol with therapy. Mean LDL particle size and the LDL particle size range were increased by treatment. However, there was no difference in the ability of pretreatment or treatment LDL to bind to the LDL receptor on cultured cells consistent with previous studies in animals, indicating that lovastatin may alter LDL particles to impair interaction with the LDL receptor in vivo but not in vitro. Lovastatin therapy in CESD appears to be clinically beneficial and has complex effects on lipid metabolism that may include a dominant inhibitory effect on hepatic lipoprotein production, posttranscriptionally mediated induction of the LDL receptor, and alterations of LDL particles that interfere with their clearance by the LDL receptor in vivo.

[Cholesterol ester storage disease in two siblings]. / Enfermedad de depósito de ésteres de colesterol en dos hermanos.

Two children, male y and female brothers, with a cholesterol ester storage disease are presented. Some pathogenic, clinical biochemical and histopathological aspects are commented. The ultrastructural hepatic finding of microcrystallized cholesterol in the Von Kupffer's cells was the determinant diagnostic parameter in both cases. The clinical expression and evolution was different, with a biggest functional impairement in the male, which was submitted to hepatic transplantation.