Defective Lysosomal Lipolysis Causes Prenatal Lipid Accumulation and Exacerbates Immediately after Birth.

Cholesterol and fatty acids are essential lipids that are critical for membrane biosynthesis and fetal organ development. Cholesteryl esters (CE) are degraded by hormone-sensitive lipase (HSL) in the cytosol and by lysosomal acid lipase (LAL) in the lysosome. Impaired LAL or HSL activity causes rare pathologies in humans, with HSL deficiency presenting less severe clinical manifestations. The infantile form of LAL deficiency, a lysosomal lipid storage disorder, leads to premature death. However, the importance of defective lysosomal CE degradation and its consequences during early life are incompletely understood. We therefore investigated how defective CE catabolism affects fetus and infant maturation using Lal and Hsl knockout (-/-) mouse models. This study demonstrates that defective lysosomal but not neutral lipolysis alters placental and fetal cholesterol homeostasis and exhibits an initial disease pathology already in utero as Lal-/- fetuses accumulate hepatic lysosomal lipids. Immediately after birth, LAL deficiency exacerbates with massive hepatic lysosomal lipid accumulation, which continues to worsen into young adulthood. Our data highlight the crucial role of LAL during early development, with the first weeks after birth being critical for aggravating LAL deficiency.

Advanced lipodystrophy reverses fatty liver in mice lacking adipocyte hormone-sensitive lipase.

Modulation of adipocyte lipolysis represents an attractive approach to treat metabolic diseases. Lipolysis mainly depends on two enzymes: adipose triglyceride lipase and hormone-sensitive lipase (HSL). Here, we investigated the short- and long-term impact of adipocyte HSL on energy homeostasis using adipocyte-specific HSL knockout (AHKO) mice. AHKO mice fed high-fat-diet (HFD) progressively developed lipodystrophy accompanied by excessive hepatic lipid accumulation. The increased hepatic triglyceride deposition was due to induced de novo lipogenesis driven by increased fatty acid release from adipose tissue during refeeding related to defective insulin signaling in adipose tissue. Remarkably, the fatty liver of HFD-fed AHKO mice reversed with advanced age. The reversal of fatty liver coincided with a pronounced lipodystrophic phenotype leading to blunted lipolytic activity in adipose tissue. Overall, we demonstrate that impaired adipocyte HSL-mediated lipolysis affects systemic energy homeostasis in AHKO mice, whereby with older age, these mice reverse their fatty liver despite advanced lipodystrophy.

Deficiencia de lipasa ácida lisosomal: una causa poco reconocida de dislipemia y disfunción hepática / Lysosomal acid lipase deficiency: A rarely recognised cause of dyslipidaemia and liver dysfunction

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Lysosomal lipoprotein processing in endothelial cells stimulates adipose tissue thermogenic adaptation.

In response to cold exposure, thermogenic adipocytes internalize large amounts of fatty acids after lipoprotein lipase-mediated hydrolysis of triglyceride-rich lipoproteins (TRL) in the capillary lumen of brown adipose tissue (BAT) and white adipose tissue (WAT). Here, we show that in cold-exposed mice, vascular endothelial cells in adipose tissues endocytose substantial amounts of entire TRL particles. These lipoproteins subsequently follow the endosomal-lysosomal pathway, where they undergo lysosomal acid lipase (LAL)-mediated processing. Endothelial cell-specific LAL deficiency results in impaired thermogenic capacity as a consequence of reduced recruitment of brown and brite/beige adipocytes. Mechanistically, TRL processing by LAL induces proliferation of endothelial cells and adipocyte precursors via beta-oxidation-dependent production of reactive oxygen species, which in turn stimulates hypoxia-inducible factor-1α-dependent proliferative responses. In conclusion, this study demonstrates a physiological role for TRL particle uptake into BAT and WAT and establishes endothelial lipoprotein processing as an important determinant of adipose tissue remodeling during thermogenic adaptation.

Lysosomal Acid Lipase Deficiency Controls T- and B-Regulatory Cell Homeostasis in the Lymph Nodes of Mice with Human Cancer Xenotransplants.

Utilization of proper preclinical models accelerates development of immunotherapeutics and the study of the interplay between human malignant cells and immune cells. Lysosomal acid lipase (LAL) is a critical lipid hydrolase that generates free fatty acids and cholesterol. Ablation of LAL suppresses immune rejection and allows growth of human lung cancer cells in lal-/- mice. In the lal-/- lymph nodes, the percentages of both T- and B-regulatory cells (Tregs and Bregs, respectively) are increased, with elevated expression of programmed death-ligand 1 and IL-10, and decreased expression of interferon-γ. Levels of enzymes in the glucose and glutamine metabolic pathways are elevated in Tregs and Bregs of the lal-/- lymph nodes. Pharmacologic inhibitor of pyruvate dehydrogenase, which controls the transition from glycolysis to the citric acid cycle, effectively reduces Treg and Breg elevation in the lal-/- lymph nodes. Blocking the mammalian target of rapamycin or reactivating peroxisome proliferator-activated receptor γ, an LAL downstream effector, reduces lal-/- Treg and Breg elevation and PD-L1 expression in lal-/- Tregs and Bregs, and improves human cancer cell rejection. Treatment with PD-L1 antibody also reduces Treg and Breg elevation in the lal-/- lymph nodes and improves human cancer cell rejection. These observations conclude that LAL-regulated lipid metabolism is essential to maintain antitumor immunity.

Reduced lysosomal acid lipase activity: A new marker of liver disease severity across the clinical continuum of non-alcoholic fatty liver disease?

Lysosomal acid lipase (LAL) plays a key role in intracellular lipid metabolism. Reduced LAL activity promotes increased multi-organ lysosomal cholesterol ester storage, as observed in two recessive autosomal genetic diseases, Wolman disease and Cholesterol ester storage disease. Severe liver steatosis and accelerated liver fibrosis are common features in patients with genetic LAL deficiency. By contrast, few reliable data are available on the modulation of LAL activity in vivo and on the epigenetic and metabolic factors capable of regulating its activity in subjects without homozygous mutations of the Lipase A gene. In the last few years, a less severe and non-genetic reduction of LAL activity was reported in children and adults with non-alcoholic fatty liver disease (NAFLD), suggesting a possible role of LAL reduction in the pathogenesis and progression of the disease. Patients with NAFLD show a significant, progressive reduction of LAL activity from simple steatosis to non-alcoholic steatohepatitis and cryptogenic cirrhosis. Among cirrhosis of different etiologies, those with cryptogenic cirrhosis show the most significant reductions of LAL activity. These findings suggest that the modulation of LAL activity may become a possible new therapeutic target for patients with more advanced forms of NAFLD. Moreover, the measurement of LAL activity may represent a possible new marker of disease severity in this clinical setting.

Hepatocyte-specific deletion of lysosomal acid lipase leads to cholesteryl ester but not triglyceride or retinyl ester accumulation.

Lysosomal acid lipase (LAL) hydrolyzes cholesteryl ester (CE) and retinyl ester (RE) and triglyceride (TG). Mice globally lacking LAL accumulate CE most prominently in the liver. The severity of the CE accumulation phenotype progresses with age and is accompanied by hepatomegaly and hepatic cholesterol crystal deposition. In contrast, hepatic TG accumulation is much less pronounced in these mice, and hepatic RE levels are even decreased. To dissect the functional role of LAL for neutral lipid ester mobilization in the liver, we generated mice specifically lacking LAL in hepatocytes (hep-LAL-ko). On a standard chow diet, hep-LAL-ko mice exhibited increased hepatic CE accumulation but unaltered TG and RE levels. Feeding the hep-LAL-ko mice a vitamin A excess/high-fat diet (VitA/HFD) further increased hepatic cholesterol levels, but hepatic TG and RE levels in these mice were lower than in control mice. Performing in vitro activity assays with lysosome-enriched fractions from livers of mice globally lacking LAL, we detected residual acid hydrolytic activities against TG and RE. Interestingly, this non-LAL acid TG hydrolytic activity was elevated in lysosome-enriched fractions from livers of hep-LAL-ko mice upon VitA/HFD feeding. In conclusion, the neutral lipid ester phenotype in livers from hep-LAL-ko mice indicates that LAL is limiting for CE turnover, but not for TG and RE turnovers. Furthermore, in vitro hydrolase activity assays revealed the existence of non-LAL acid hydrolytic activities for TG and RE. The corresponding acid lipase(s) catalyzing these reactions remains to be identified.

Hepatocyte-specific lysosomal acid lipase deficiency protects mice from diet-induced obesity but promotes hepatic inflammation.

Lysosomal acid lipase (LAL) hydrolyzes cholesteryl esters (CE) and triglycerides (TG) to generate fatty acids (FA) and cholesterol. LAL deficiency (LAL-D) in both humans and mice leads to hepatomegaly, hypercholesterolemia, and shortened life span. Despite its essential role in lysosomal neutral lipid catabolism, the cell type-specific contribution of LAL to disease progression is still elusive. To investigate the role of LAL in the liver in more detail and to exclude the contribution of LAL in macrophages, we generated hepatocyte-specific LAL-deficient mice (Liv-Lipa-/-) and fed them either chow or high fat/high cholesterol diets (HF/HCD). Comparable to systemic LAL-D, Liv-Lipa-/- mice were resistant to diet-induced obesity independent of food intake, movement, and energy expenditure. Reduced body weight gain was mainly due to reduced white adipose tissue depots. Furthermore, Liv-Lipa-/- mice exhibited improved glucose clearance during glucose and insulin tolerance tests compared to control mice. Analysis of hepatic lipid content revealed a massive reduction of TG, whereas CE concentrations were markedly increased, leading to CE crystal formation in the livers of Liv-Lipa-/- mice. Elevated plasma transaminase activities, increased pro-inflammatory cytokines and chemokines as well as hepatic macrophage infiltration indicated liver inflammation. Our data provide evidence that hepatocyte-specific LAL deficiency is sufficient to alter whole-body lipid and energy homeostasis in mice. We conclude that hepatic LAL plays a pivotal role by preventing liver damage and maintaining lipid and energy homeostasis, especially during high lipid availability.

Deficiency in hormone-sensitive lipase accelerates the development of pancreatic cancer in conditional KrasG12D mice.

BACKGROUND: Hormone sensitive lipase (HSL) is a neutral lipase that preferentially catalyzes the hydrolysis of diacylglycerol contributing to triacylglycerol breakdown in the adipose tissue. HSL has been implicated to play a role in tumor cachexia, a debilitating syndrome characterized by progressive loss of adipose tissue. Consequently, pharmacological inhibitors of HSL have been proposed for the treatment of cancer-associated cachexia. In the present study we used the conditional KrasG12D (KC) mouse model of pancreatic ductal adenocarcinoma (PDAC) with a deficiency in HSL to determine the impact of HSL suppression on the development of PDAC. METHODS: KC;Hsl+/+ and KC;Hsl-/- mice were fed standard rodent chow for 20 weeks. At sacrifice, the incidence of PDAC was determined and inflammation in the mesenteric adipose tissue and pancreas was assessed histologically and by immunofluorescence. To determine statistical significance, ANOVA and two-tailed Student's t-tests were performed. To compare PDAC incidence, a two-sided Fisher's exact test was used. RESULTS: Compared to KC;Hsl+/+ mice, KC;Hsl-/- mice gained similar weight and displayed adipose tissue and pancreatic inflammation. In addition, KC;Hsl-/- mice had reduced levels of plasma insulin and leptin. Importantly, the increased adipose tissue and pancreatic inflammation was associated with a significant increase in PDAC incidence in KC;Hsl-/- mice. CONCLUSIONS: HSL deficiency is associated with adipose tissue and pancreatic inflammation and accelerates PDAC development in the KC mouse model.

Lysosomal Acid Lipase Deficiency, a Rare Pathology: The First Pediatric Patient Reported in Colombia.

BACKGROUND Lysosomal acid lipase deficiency is a rare genetic metabolic lipid storage disease, with a high morbidity, and mortality, in children and adults. It is characterized by a mutation in the LIPA gene that causes an alteration of lipid metabolism, resulting in deposits of cholesterol esters and triglycerides in organs such as the liver, blood vessels, and gastrointestinal tract. Lysosomal acid lipase deficiency is predominantly caused by the mutation c.894G>A, seen in approximately 50-70% of patients. Our objective is to report the first pediatric case of lysosomal acid lipase deficiency in a pediatric patient in Colombia. CASE REPORT The patient is a 14-year-old boy with isolated hepatomegaly since 6 years of age without a family history of dyslipidemia. In the pediatric control, laboratory exams revealed dyslipidemia, and a hepatic biopsy was performed, revealing severe fibrosis with septation and grade 3 microvesicular steatosis (>75%). He was referred to our center and was suspected to have lysosomal acid lipase deficiency. Enzymatic activity was measured, showing absent activity. Confirmatory diagnosis with genetic sequencing showed a pathological homozygous mutation of c.894G>A. CONCLUSIONS Lysosomal acid lipase deficiency can manifest as early- or late-onset, with variable and severe signs and symptoms. The late-onset form has a broad spectrum of manifestations with mild symptoms, leading to under-diagnosis, which increases the actual disease burden. Early diagnosis is essential to initiate enzyme replacement therapy, since the natural disease course can be changed. More studies should be conducted in Latin America to evaluate the prevalence of the disease.

LAL (Lysosomal Acid Lipase) Promotes Reverse Cholesterol Transport In Vitro and In Vivo.

OBJECTIVE: To explore the role of LAL (lysosomal acid lipase) in macrophage cholesterol efflux and whole-body reverse cholesterol transport. APPROACH AND RESULTS: Immortalized peritoneal macrophages from lal-/- mice showed reduced expression of ABCA1 (ATP-binding cassette transporter A1) and ABCG1 (ATP-binding cassette transporter G1), reduced production of the regulatory oxysterol 27-hydroxycholesterol, and impaired suppression of cholesterol synthesis on exposure to acetylated low-density lipoprotein when compared with lal+/+ macrophages. LAL-deficient mice also showed reduced hepatic ABCG5 (ATP-binding cassette transporter G5) and ABCG8 (ATP-binding cassette transporter G8) expression compared with lal+/+ mice. LAL-deficient macrophages loaded with [3H]-cholesteryl oleate-labeled acetylated low-density lipoprotein showed impaired efflux of released [3H]-cholesterol to apoA-I (apolipoprotein A-I), with normalization of [3H]-cholesteryl ester levels and partial correction of ABCA1 expression and cholesterol efflux to apoA-I when treated with exogenous rhLAL (recombinant human LAL protein). LAL-deficient mice injected intraperitoneally with lal-/- macrophages cholesterol loaded and labeled in the same way exhibited only 1.55±0.35% total injected [3H]-cholesterol counts appearing in the feces for 48 h (n=30), compared with 5.38±0.92% in lal+/+ mice injected with labeled lal+/+ macrophages (n=27), P<0.001. To mimic the therapeutic condition of delivery of supplemental LAL in vivo, injection of labeled lal-/- macrophages into lal+/+ mice resulted in a significant increase in reverse cholesterol transport (2.60±0.46% of 3H-cholesterol counts in feces at 48 hours [n=19]; P<0.001 when compared with injection into lal-/- mice). CONCLUSIONS: These results indicate a critical role for LAL in promoting both macrophage and whole-body reverse cholesterol transport and the ability of supplemental LAL to be taken up and correct reverse cholesterol transport in vivo.

Lysosomal acid lipase regulates fatty acid channeling in brown adipose tissue to maintain thermogenesis.

Lysosomal acid lipase (LAL) is the only known enzyme, which hydrolyzes cholesteryl esters and triacylglycerols in lysosomes of multiple cells and tissues. Here, we explored the role of LAL in brown adipose tissue (BAT). LAL-deficient (Lal-/-) mice exhibit markedly reduced UCP1 expression in BAT, modified BAT morphology with accumulation of lysosomes, and mitochondrial dysfunction, consequently leading to regular hypothermic events in mice kept at room temperature. Cold exposure resulted in reduced lipid uptake into BAT, thereby aggravating dyslipidemia and causing life threatening hypothermia in Lal-/- mice. Linking LAL as a potential regulator of lipoprotein lipase activity, we found Angptl4 mRNA expression upregulated in BAT. Our data demonstrate that LAL is critical for shuttling fatty acids derived from circulating lipoproteins to BAT during cold exposure. We conclude that inhibited lysosomal lipid hydrolysis in BAT leads to impaired thermogenesis in Lal-/- mice.

Identification of rare diseases by screening a population selected on the basis of routine pathology results-the PATHFINDER project: lysosomal acid lipase/cholesteryl ester storage disease substudy.

AIMS: Lysosomal acid lipase deficiency (LALD) is an autosomal recessive disorder of cholesterol ester storage associated with hepatic disease, cirrhosis and accelerated atherosclerosis. Its prevalence in the general population, patients with dyslipidaemia and raised transaminases is unclear. This study attempted to identify the prevalence of LALD from patients with abnormal results in laboratory databases. METHODS: Electronic laboratory databases were interrogated to identify from clinical biochemistry records patients with a phenotype of low high-density lipoprotein-cholesterol (≤0.85 mmol/L; 33 mg/dL) and with elevated alanine or aspartate transaminases (≥60 IU/L) on one occasion or more over a 3-year time interval. Patients were recalled, and a dried blood spot sample was collected for lysosomal acid lipase determination by a fluorimetric enzyme assay. Histopathology databases of liver biopsies were interrogated for patients with features of 'microvesicular cirrhosis' or 'cryptogenic cirrhosis' in the report. Histological blocks were sampled, and samples were analysed by next-generation sequencing for the presence of mutations in the LAL gene. RESULTS: Samples were obtained from 1825 patients with dyslipidaemia and elevated transaminases. No cases of LALD were identified. Liver biopsies were obtained from six patients. DNA extraction was successful from four patients. Two patients were homozygous for the LAL c.46A>C;p.Thr16Pro unclassified variant in exon 2. CONCLUSIONS: Pathology databases hold routine information that can be used to identify patients with specific patterns of results or those who had biopsies to allow targeted testing for possible causes of disease. Biochemical screening suggests that the gene frequency of LAL deficiency in adults is less than 1 in 100.

Adipose tissue deficiency of hormone-sensitive lipase causes fatty liver in mice.

Fatty liver is a major health problem worldwide. People with hereditary deficiency of hormone-sensitive lipase (HSL) are reported to develop fatty liver. In this study, systemic and tissue-specific HSL-deficient mice were used as models to explore the underlying mechanism of this association. We found that systemic HSL deficient mice developed fatty liver in an age-dependent fashion between 3 and 8 months of age. To further explore the mechanism of fatty liver in HSL deficiency, liver-specific HSL knockout mice were created. Surprisingly, liver HSL deficiency did not influence liver fat content, suggesting that fatty liver in HSL deficiency is not liver autonomous. Given the importance of adipose tissue in systemic triglyceride metabolism, we created adipose-specific HSL knockout mice and found that adipose HSL deficiency, to a similar extent as systemic HSL deficiency, causes age-dependent fatty liver in mice. Mechanistic study revealed that deficiency of HSL in adipose tissue caused inflammatory macrophage infiltrates, progressive lipodystrophy, abnormal adipokine secretion and systemic insulin resistance. These changes in adipose tissue were associated with a constellation of changes in liver: low levels of fatty acid oxidation, of very low density lipoprotein secretion and of triglyceride hydrolase activity, each favoring the development of hepatic steatosis. In conclusion, HSL-deficient mice revealed a complex interorgan interaction between adipose tissue and liver: the role of HSL in the liver is minimal but adipose tissue deficiency of HSL can cause age-dependent hepatic steatosis. Adipose tissue is a potential target for treating the hepatic steatosis of HSL deficiency.

Molecular and clinical characterization of a series of patients with childhood-onset lysosomal acid lipase deficiency. Retrospective investigations, follow-up and detection of two novel LIPA pathogenic variants.

BACKGROUND AND AIMS: Childhood/Adult-onset Lysosomal Acid Lipase Deficiency (LAL-D) is a recessive disorder due to loss of function variants of LAL, the enzyme which hydrolyses cholesteryl esters, derived from internalized apoB containing lipoproteins. The disease is characterized by multi-organ involvement including the liver, spleen, intestine and cardiovascular system. The aim of this study was the clinical and molecular characterization of 14 (13 unrelated) previously unreported patients with childhood-onset LAL-D. METHODS: Data collected included clinical and laboratory investigations, liver imaging, liver biopsy and LIPA gene analysis. The response to lipid-lowering medications, liver transplantation and enzyme replacement therapy (ERT) was reported for some patients. RESULTS: LAL-D was suspected at 4.4 ± 3.3 years of age for the presence of hepatomegaly, elevated serum transaminases and hypercholesterolemia, and was confirmed by liver biopsy/imaging and LAL assay. The follow up period ranged from 3 to 40 years (mean 7.8 ± 4.0 years in 13 cases). Patients treated with statins with or without ezetimibe showed 28% reduction of plasma LDL-cholesterol without a tangible effect on liver enzymes; some patients receiving ERT showed normalized lipoprotein profile and transaminase levels. The common c.894G > A variant was observed in homozygosity or compound heterozygosity in 10 patients. We found seven previously reported variants: p.(Trp140*), p.(Arg218*), p.(Gly266*), p.(Thr288Ile), p.(Leu294Ser), p.(His295Tyr) and p.(Gly342Arg) and two novel variants: p.(Asp345Asn), affecting the LAL catalytic triad, and c.229+3A > C, affecting splicing. Homozygosity for p.(Thr288Ile) or c.229+3A > C was associated with a severe phenotype. CONCLUSIONS: This study provides additional data on the features of childhood-onset LAL-D and describes two novel pathogenic variants of the LIPA gene.

Spleen dimensions are inversely associated with lysosomal acid lipase activity in patients with non-alcoholic fatty liver disease.

Fatty liver and splenomegaly are typical features of genetic lysosomal acid lipase (LAL) deficiency. No data in adult patients with non-genetic reduction of LAL activity are available. We investigate the association between spleen dimensions and LAL activity in non-alcoholic fatty liver disease (NAFLD) patients, in whom a reduced LAL activity has been reported. We include 425 consecutive patients who underwent abdominal ultrasound to evaluate hepatic steatosis and spleen dimensions. LAL activity was measured with dried blood spot method (Lalistat2). NAFLD was present in 74.1% of screened patients. Higher median spleen longitudinal diameter (10.6 vs. 9.9 cm; p < 0.001) and spleen area (SA) (32.7 vs. 27.7 cm2; p < 0.001), together with a higher and proportion of splenomegaly (17.8 vs. 5.5%, p = 0.001), are present in patients with NAFLD compared to those without. In NAFLD patients, median LAL activity is 0.9 nmol/spot/h. LAL activity is lower in 56 patients with splenomegaly, as compared to those without (p = 0.009). At multivariable logistic regression analysis, age (above median, OR 0.344; p = 0.003), LAL activity (below median, OR 2.206, p = 0.028), and platelets (OR 0.101, p = 0.002) are significantly associated with splenomegaly. NAFLD patients disclose a relatively high prevalence of spleen enlargement and splenomegaly, which are significantly associated with a reduced LAL activity, suggesting that LAL may contribute to spleen enlargement in this setting.

Lysosome-mediated degradation of a distinct pool of lipid droplets during hepatic stellate cell activation.

Activation of hepatic stellate cells (HSCs) is a critical step in the development of liver fibrosis. During activation, HSCs lose their lipid droplets (LDs) containing triacylglycerols (TAGs), cholesteryl esters, and retinyl esters (REs). We previously provided evidence for the presence of two distinct LD pools, a preexisting and a dynamic LD pool. Here we investigate the mechanisms of neutral lipid metabolism in the preexisting LD pool. To investigate the involvement of lysosomal degradation of neutral lipids, we studied the effect of lalistat, a specific lysosomal acid lipase (LAL/Lipa) inhibitor on LD degradation in HSCs during activation in vitro The LAL inhibitor increased the levels of TAG, cholesteryl ester, and RE in both rat and mouse HSCs. Lalistat was less potent in inhibiting the degradation of newly synthesized TAG species as compared with a more general lipase inhibitor orlistat. Lalistat also induced the presence of RE-containing LDs in an acidic compartment. However, targeted deletion of the Lipa gene in mice decreased the liver levels of RE, most likely as the result of a gradual disappearance of HSCs in livers of Lipa-/- mice. Lalistat partially inhibited the induction of activation marker α-smooth muscle actin (α-SMA) in rat and mouse HSCs. Our data suggest that LAL/Lipa is involved in the degradation of a specific preexisting pool of LDs and that inhibition of this pathway attenuates HSC activation.

Quantitation of the rates of hepatic and intestinal cholesterol synthesis in lysosomal acid lipase-deficient mice before and during treatment with ezetimibe.

Esterified cholesterol (EC) and triglycerides, contained within lipoproteins taken up by cells, are hydrolysed by lysosomal acid lipase (LAL) in the late endosomal/lysosomal (E/L) compartment. The resulting unesterified cholesterol (UC) is transported via Niemann-Pick type C2 and C1 into the cytosolic compartment where it enters a putative pool of metabolically active cholesterol that is utilized in accordance with cellular needs. Loss-of-function mutations in LIPA, the gene encoding LAL, result in dramatic increases in tissue concentrations of EC, a hallmark feature of Wolman disease and cholesteryl ester storage disease (CESD). The lysosomal sequestration of EC causes cells to respond to a perceived deficit of sterol by increasing their rate of cholesterol synthesis, particularly in the liver. A similar compensatory response occurs with treatments that disrupt the enterohepatic movement of cholesterol or bile acids. Here we measured rates of cholesterol synthesis in vivo in the liver and small intestine of a mouse model for CESD given the cholesterol absorption inhibitor ezetimibe from weaning until early adulthood. Consistent with previous findings, this treatment significantly reduced the amount of EC sequestered in the liver (from 132.43±7.35 to 70.07±6.04mg/organ) and small intestine (from 2.78±0.21 to 1.34±0.09mg/organ) in the LAL-deficient mice even though their rates of hepatic and intestinal cholesterol synthesis were either comparable to, or exceeded those in matching untreated Lal-/- mice. These data reveal the role of intestinal cholesterol absorption in driving the expansion of tissue EC content and disease progression in LAL deficiency.

Managing Cardiovascular Risk in Lysosomal Acid Lipase Deficiency.

Lysosomal acid lipase deficiency (LAL-D) is a rare, life-threatening, autosomal recessive, lysosomal storage disease caused by mutations in the LIPA gene, which encodes for lysosomal acid lipase (LAL). This enzyme is necessary for the hydrolysis of cholesteryl ester and triglyceride in lysosomes. Deficient LAL activity causes accumulation of these lipids in lysosomes and a marked decrease in the cytoplasmic free cholesterol concentration, leading to dysfunctional cholesterol homeostasis. The accumulation of neutral lipid occurs predominantly in liver, spleen, and macrophages throughout the body, and the aberrant cholesterol homeostasis causes a marked dyslipidemia. LAL-D is characterized by accelerated atherosclerotic cardiovascular disease (ASCVD) and hepatic microvesicular or mixed steatosis, leading to inflammation, fibrosis, cirrhosis and liver failure. LAL-D presents as a clinical continuum with two phenotypes: the infantile-onset phenotype, formally referred to as Wolman disease, and the later-onset phenotype, formerly referred to as cholesteryl ester storage disease. Infants with LAL-D present within the first few weeks of life with vomiting, diarrhea, hepatosplenomegaly, failure to thrive and rapid progression to liver failure and death by 6-12 months of age. Children and young adults with LAL-D generally present with marked dyslipidemia, hepatic enzyme elevation, hepatomegaly and mixed steatosis by liver biopsy. The average age of the initial signs and symptoms of the later-onset phenotype is about 5 years old. The typical dyslipidemia is a significantly elevated low-density lipoprotein cholesterol (LDL-C) concentration and a low high-density lipoprotein cholesterol (HDL-C) concentration, placing these individuals at heightened risk for premature ASCVD. Diagnosis of the later-onset phenotype of LAL-D requires a heightened awareness of the disease because the dyslipidemia and hepatic transaminase elevation combination are common and overlap with other metabolic disorders. LAL-D should be considered in the differential diagnosis of healthy weight children and young adults with unexplained hepatic transaminase elevation accompanied by an elevated LDL-C level (>160 mg/dL) and low HDL-C level (<35 mg/dL) that is not caused by monogenic and polygenic lipid disorders or secondary factors. Treatment of LAL-D with sebelipase alfa (LAL replacement enzyme) should be considered as the standard of treatment in all individuals diagnosed with LAL-D. Other ASCVD risk factors that may be present (hypertension, tobacco use, diabetes mellitus, etc.) should be managed appropriately, consistent with secondary prevention goals.

Hormone-sensitive lipase deficiency alters gene expression and cholesterol content of mouse testis.

Hormone-sensitive lipase-knockout (HSL-/-) mice exhibit azoospermia for unclear reasons. To explore the basis of sterility, we performed the following three experiments. First, HSL protein distribution in the testis was determined. Next, transcriptome analyses were performed on the testes of three experimental groups. Finally, the fatty acid and cholesterol levels in the testes with three different genotypes studied were determined. We found that the HSL protein was present from spermatocyte cells to mature sperm acrosomes in wild-type (HSL+/+) testes. Spermiogenesis ceased at the elongation phase of HSL-/- testes. Transcriptome analysis indicated that genes involved in lipid metabolism, cell membrane, reproduction and inflammation-related processes were disordered in HSL-/- testes. The cholesterol content was significantly higher in HSL-/- than that in HSL+/+ testis. Therefore, gene expression and cholesterol ester content differed in HSL-/- testes compared to other testes, which may explain the sterility of male HSL-/- mice.