The novel synonymous variant in LIPA gene affects splicing and causes lysosomal acid lipase deficiency.

Lysosomal acid lipase deficiency (LALD; MIM#278000) is a continuum of autosomal recessive diseases caused by defects in the gene LIPA and historically divided into two phenotypes: severe infantile-onset form called Wolman disease (WD) and childhood/adult-onset form known as cholesteryl ester storage disease (CESD). We report a novel synonymous homozygous variant c.600G > A in LIPA of a patient with LALD. Functional analysis of the patient cDNA and minigene assay revealed this variant as the cause of exonic cryptic splice site activation and 63 b.p. deletion in exon 6. To investigate the impact of this in-frame deletion on protein function, we performed 3D modeling of the human lysosomal acid lipase and showed the alteration of highly conservative region in close proximity to protein active site, which may completely eliminate the enzymatic activity. Using transcript specific real-time quantitative PCR method, we evaluated the relative ratio of the patient's wild type transcript isoform which is significantly reduced and correlates with severe childhood-onset variant of LALD.

Wolman's disease and cholesteryl ester storage disorder: the phenotypic spectrum of lysosomal acid lipase deficiency.

Lysosomal acid lipase deficiency is a rare, autosomal recessive condition caused by mutations in the gene encoding lysosomal acid lipase (LIPA) that result in reduced or absent activity of this essential enzyme. The severity of the resulting disease depends on the nature of the underlying mutation and magnitude of its effect on enzymatic function. Wolman's disease is a severe disorder that presents during infancy, resulting in failure to thrive, hepatomegaly, and hepatic failure, and an average life expectancy of less than 4 months. Cholesteryl ester storage disorder arises later in life and is less severe, although the two diseases share many common features, including dyslipidaemia and transaminitis. The prevalence of these diseases has been estimated at one in 40 000 to 300 000, but many cases are undiagnosed and unreported, and awareness among clinicians is low. Lysosomal acid lipase deficiency-which can be diagnosed using dry blood spot testing-is often misdiagnosed as non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), hereditary dyslipidaemia, or cryptogenic cirrhosis. There are no formal guidelines for treatment of these patients, and treatment options are limited. In this Review we appraise the existing literature on Wolman's disease and cholesteryl ester storage disease, and discuss available treatments, including enzyme replacement therapy, oral lipid-lowering therapy, stem-cell transplantation, and liver transplantation.

Lysosomal acid lipase deficiency: a form of non-obese fatty liver disease (NOFLD).

INTRODUCTION: With the growing obesity epidemic, nonalcoholic fatty liver disease (NAFLD) is rapidly becoming one of the leading causes of liver disease worldwide. Although obesity is a main risk factor for the development of NAFLD, it can also develop in lean subjects and can be encountered in different clinical setting and in association with an array of genetic, metabolic, nutritional, infectious and drug-induced disorders. Areas covered: This article discusses causes of fatty liver in non-obese subjects focusing on Lysosomal acid lipase deficiency (LAL-D), a commonly overlooked disorder reviewing its prevalence, genetics, pathogenesis, clinical features, diagnosis and treatment. It will also review other causes of non-alcoholic fatty liver disease, which can be encountered in the absence of obesity and metabolic syndrome. Expert commentary: Although the prevalence of LAL-D has been estimated in the range of 1 in 40,000 and 1 in 300,000, this estimate is much more than the identified cases reported in the literature, which suggests that that the disease may be considerably under-diagnosed. There is a pressing need to educate clinicians about the disease, especially with the development of new promising therapeutic modalities.

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.

The role of mannosylated enzyme and the mannose receptor in enzyme replacement therapy.

Lysosomal acid lipase (LAL) is the critical enzyme for the hydrolysis of triglycerides (TGs) and cholesteryl esters (CEs) in lysosomes. LAL defects cause Wolman disease (WD) and CE storage disease (CESD). An LAL null (lal-/-) mouse model closely mimics human WD/CESD, with hepatocellular, Kupffer cell and other macrophage, and adrenal cortical storage of CEs and TGs. The effect on the cellular targeting of high-mannose and complex oligosaccharide-type oligosaccharide chains was tested with human LAL expressed in Pichia pastoris (phLAL) and CHO cells (chLAL), respectively. Only chLAL was internalized by cultured fibroblasts, whereas both chLAL and phLAL were taken up by macrophage mannose receptor (MMR)-positive J774E cells. After intraperitoneal injection into lal-/- mice, phLAL and chLAL distributed to macrophages and macrophage-derived cells of various organs. chLAL was also detected in hepatocytes. Ten injections of either enzyme over 30 d into 2- and 2.5-mo-old lal-/- mice produced normalization of hepatic color, decreased liver weight (50%-58%), and diminished hepatic cholesterol and TG storage. Lipid accumulations in macrophages were diminished with either enzyme. Only chLAL cleared lipids in hepatocytes. Mice double homozygous for the LAL and MMR deficiences (lal-/-;MMR-/-) showed phLAL uptake into Kupffer cells and hepatocytes, reversal of macrophage histopathology and lipid storage in all tissues, and clearance of hepatocytes. These results implicate MMR-independent and mannose 6-phosphate receptor-independent pathways in phLAL uptake and delivery to lysosomes in vivo. In addition, these studies show specific cellular targeting and physiologic effects of differentially oligosaccharide-modified human LALs mediated by MMR and that lysosomal targeting of mannose-terminated glycoproteins occurs and storage can be eliminated effectively without MMR.

A new mutation in the gene for lysosomal acid lipase leads to Wolman disease in an African kindred.

Cholesteryl ester storage disease (CESD) and Wolman disease (WD) are both autosomal recessive disorders associated with reduced activity and genetic defects of lysosomal acid lipase (LAL). The strikingly more severe course of WD is caused by genetic defects of LAL that leave no residual enzymatic activity. Mutations at the exon 8/intron 8 transition of the LAL gene have been identified in several CESD and WD patients and are responsible for the manifestation of the disease. We have determined the genetic defect in a 3-month-old boy of African origin affected by WD. No enzymatic activity of the lysosomal acid lipase was detectable in white blood cells and cultured fibroblasts. Analysis of his LAL cDNA and genomic DNA revealed that he was homozygous for a mutation at position -3 of the exon 8 splice donor site. A C-->T transition leads to a nonsense codon and to a premature termination of the LAL protein at amino acid 277. Due to this mutation, a shorter LAL mRNA species was also generated that lacked exon 8 and was deficient of the nonsense codon. As a consequence, the protein synthesis proceeded to the natural termination codon, but the enzyme generated had an internal deletion of 24 amino acids (254-277) and was also inactive. These findings, together with our previous observations when analyzing the mutations in WD and CESD patients lead to the conclusion that the more severe WD is due to mutations that absolutely abolish lysosomal acid lipase (LAL) enzyme activity and the cholesteryl ester storage disease phenotype is due to mutations that allow some residual LAL activity to be manifested.

[Acid lipase deficiency: Wolman disease and cholesteryl ester storage disease].

Wolman disease and cholesteryl ester storage disease (CESD) are caused by a deficiency of lysosomal acid lipase activity, resulting in massive accumulation of cholesteryl ester and triglycerides. Wolman disease occurs in infancy, with hepatosplenomegaly, steatorrhea and adrenal calcification. It is fatal before the age of 1 year. In CESD, hepatomegaly may be the only clinical abnormality, although lipid deposition is widespread. Lysosomal acid lipase hydrolyzes both triaclyglycerols and cholesteryl esters, and the enzyme plays an important role in the cellular processing of plasma lipoproteins, and contributes to homeostatic control of lipoprotein levels in blood and prevention of cellular lipid overloading. The gene encoding lysosomal acid lipase was cloned and characterized in 1994, and two mutations of acid lipase gene were found in a patient with Wolman disease, as a compound heterozygote. It is suggested that structural gene defects are also present in CESD cells. However, the reason (s) for the clinical difference between Wolman disease and CESD remain (s) to be studied.

New pathogenetic hypothesis for Wolman disease: possible role of oxidized low-density lipoproteins in adrenal necrosis and calcification.

Wolman disease in an inherited metabolic disease, characterized by a severe deficiency of the acid lipase and a massive lysosomal storage of triacylglycerols and cholesteryl esters, associated with hepatosplenomegaly, adrenal calcification and nearly always fatal in the first year of life. Cultured human lymphoblastoid cells and human adrenal cells are able to promote the formation of mildly oxidized low-density lipoproteins (LDL), which in turn exhibit a non-negligible cytotoxic effect on these cells. In contrast, fibroblasts induce only very low levels of LDL oxidation. Comparative experiments have shown that the cytotoxic effect of oxidized LDL was higher to Wolman-disease cells than to controls. The oxidative ability of Wolman cells was similar to that of normal ones. The over-cytotoxicity of mildly oxidized LDL to Wolman cells resulted from the higher uptake of mildly oxidized LDL through the LDL-receptor pathway, which is only poorly down-regulated in Wolman cells subsequently to the block of the lysosomal degradation of LDL-cholesteryl esters. In cultured adrenal cells, oxidized LDL induced a sustained rise in intracellular [Ca2+] which is directly involved in the cellular damage and cell death induced by oxidized LDL [Nègre-Salvayre and Salvayre (1992) Biochim. Biophys. Acta 1123, 207-215]. This Ca2+ peak is followed by a dramatic deposition of calcium in damaged or/and dead cultured adrenal cells, quite similar to that observed in Wolman-disease adrenal cortex. The cell-induced LDL oxidation and the subsequent cytotoxic effect can be prevented, at least in part, by antioxidants such as alpha-tocopherol and nordihydroguaiaretic acid. These findings support the hypothesis that the Wolman-disease adrenal damage (necrosis and calcification) could result from the association of the following events: mild oxidation of LDL by adrenal cells, over-uptake of mildly oxidized LDL by Wolman cells (resulting from the block of the lysosomal degradation of cholesteryl esters in Wolman cells), and cytotoxicity related to the amount of mildly oxidized LDL internalized by cells. The reported data also suggest that LDL oxidation induced by adrenal cells and their subsequent cytotoxicity can be prevented (in part) by antioxidants, and the potential therapeutic use of antioxidants in Wolman disease is discussed.