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

Wolman's disease presenting with secondary hemophagocytic lymphohistiocytosis: a case report from Saudi Arabia and literature review

Background

Hemophagocytic lymphohistiocytosis (HLH) is a rare and potentially fatal syndrome that is characterized by strong activation of the immune system from hyperinflammatory cytokines. Symptoms of HLH patients include fever, hepatosplenomegaly, cytopenia, and hyperferritinemia. Inherited HLH is classified as primary, whereas secondary HLH (sHLH) occurs when acquired from non-inherited reasons that include severe infection, immune deficiency syndrome, autoimmune disorder, neoplasm, and metabolic disorder. Wolman’s disease (WD) is a rare and fatal infantile metabolic disorder caused by lysosomal acid lipase deficiency, that exhibits similar clinical signs and symptoms as HLH. This paper reports the case of an infant diagnosed with WD and who presented with sHLH.

Case presentation

A 4-month-old infant presenting with hepatosplenomegaly, failure to thrive, and other abnormalities. WD diagnosis was confirmed by the presence of the LIPA gene homozygous deletion c.(428 + 1_967-1)_(*1_?)del. The infant also met the HLH-2004 diagnostic criteria.

Conclusions

Metabolic disorder such as WD should be investigated in infants fulfilling the HLH criteria to diagnose the underlying condition. More studies are needed to understand the link between WD and sHLH and to identify appropriate therapies.

Organoids to model liver disease

The organoid model represents a major breakthrough in cell biology that has revolutionised biomedical research. Organoids are 3D physiological in vitro structures that recapitulate morphological and functional features of in vivo tissues and offer significant advantages over traditional cell culture methods. Liver organoids are of particular interest because of the pleiotropy of functions exerted by the human liver, their utility to model different liver diseases, and their potential application as cell-based therapies in regenerative medicine. Moreover, because they can be derived from patient tissues, organoid models offer new perspectives in personalised medicine and drug discovery. In this review, we discuss the current liver organoid models for the study of liver disease.

An overview of deregulated lipid metabolism in nonalcoholic fatty liver disease with special focus on lysosomal acid lipase

Obesity and type 2 diabetes are frequently complicated by excess fat accumulation in the liver, which is known as nonalcoholic fatty liver disease (NAFLD). In this context, liver steatosis develops as a result of the deregulation of pathways controlling de novo lipogenesis and fat catabolism. Recent evidences suggest the clinical relevance of a reduction in the activity of lysosomal acid lipase (LAL), which is a key enzyme for intracellular fat disposal, in patients with NAFLD. In this review, we provided a comprehensive overview of the critical steps in hepatic fat metabolism and alterations in these pathways in NAFLD, with a special focus on lipophagy and LAL activity. During NAFLD, hepatic fat metabolism is impaired at several levels, which is significantly contributed to by impaired lipophagy, in which reduced LAL activity may play an important role. For further research and intervention in NAFLD, targeting LAL activity may provide interesting perspectives.

Lipophagy and Lipolysis Status in Lipid Storage and Lipid Metabolism Diseases

This review discusses how lipophagy and cytosolic lipolysis degrade cellular lipids, as well as how these pathway ys communicate, how they affect lipid metabolism and energy homeostasis in cells and how their dysfunction affects the pathogenesis of lipid storage and lipid metabolism diseases. Answers to these questions will likely uncover novel strategies for the treatment of aforementioned human diseases, but, above all, will avoid destructive effects of high concentrations of lipids-referred to as lipotoxicity-resulting in cellular dysfunction and cell death.

Genetic Pathways in Nonalcoholic Fatty Liver Disease: Insights From Systems Biology

Nonalcoholic fatty liver disease (NAFLD) represents a burgeoning worldwide epidemic whose etiology reflects multiple interactions between environmental and genetic factors. Here, we review the major pathways and dominant genetic modifiers known to be relevant players in human NAFLD and which may determine key components of the heritability of distinctive disease traits including steatosis and fibrosis. In addition, we have employed general assumptions which are based on known genetic factors in NAFLD to build a systems biology prediction model that includes functional enrichment. This prediction model highlights additional complementary pathways that represent plausible intersecting signaling networks that we define here as an NAFLD-Reactome. We review the evidence connecting variants in each of the major known genetic modifiers (variants in patatin-like phospholipase domain containing 3, transmembrane 6 superfamily member 2, membrane-bound O-acyltransferase domain containing 7, glucokinase regulator, and hydroxysteroid 17-beta dehydrogenase 13) to NAFLD and expand the associated underlying mechanisms using functional enrichment predictions, based on both preclinical and cell-based experimental findings. These major candidate gene variants function in distinct pathways, including substrate delivery for de novo lipogenesis; mitochondrial energy use; lipid droplet assembly, lipolytic catabolism, and fatty acid compartmentalization; and very low-density lipoprotein assembly and secretion. The NAFLD-Reactome model expands these pathways and allows for hypothesis testing, as well as serving as a discovery platform for druggable targets across multiple pathways that promote NAFLD development and influence several progressive outcomes. In conclusion, we summarize the strengths and weaknesses of studies implicating selected variants in the pathophysiology of NAFLD and highlight opportunities for future clinical research and pharmacologic intervention, as well as the implications for clinical practice.

Update on NAFLD genetics: From new variants to the clinic

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of liver diseases in high-income countries and the burden of NAFLD is increasing at an alarming rate. The risk of developing NAFLD and related complications is highly variable among individuals and is determined by environmental and genetic factors. Genome-wide association studies have uncovered robust and reproducible associations between variations in genes such as PNPLA3, TM6SF2, MBOAT7, GCKR, HSD17B13 and the natural history of NAFLD. These findings have provided compelling new insights into the biology of NAFLD and highlighted potentially attractive pharmaceutical targets. More recently the development of polygenic risk scores, which have shown promising results for the clinical risk prediction of other complex traits (such as cardiovascular disease and breast cancer), have provided new impetus for the clinical validation of genetic variants in NAFLD risk stratification. Herein, we review current knowledge on the genetic architecture of NAFLD, including gene-environment interactions, and discuss the implications for disease pathobiology, drug discovery and risk prediction. We particularly focus on the potential clinical translation of recent genetic advances, discussing methodological hurdles that must be overcome before these discoveries can be implemented in everyday practice.

Cholesteryl ester storage disease of clinical and genetic characterisation: A case report and review of literature

BACKGROUND

Cholesteryl ester storage disease (CESD) is a rare genetic disease. Its symptoms and severity are highly variable. CESD is a systemic disease that can lead to the accumulation of fat and inflammation in the liver, as well as gastrointestinal and cardiovascular disease. The majority of patients require liver transplantation due to decompensated cirrhosis. Enzyme replacement therapy has been approved based on a randomized trial. Our study aims to clinically and genetically evaluate two siblings with CESD who underwent liver transplantation, as well as their first-degree family members.

CASE SUMMARY

The siblings were compound heterozygous for the missense variant in LIPA exon 8, c.894G>A, (p.Gln298Gln) and a single base pair deletion, c.482del (p.Asn161Ilefs*19). Analyses of single nucleotide polymorphisms showed variants with an increased risk of fatty liver disease and fibrosis for both patients. Clinically, both patients show signs of recurrence of CESD in the liver after transplantation and additional gastrointestinal and cardiovascular signs of CESD. Three family members who were LIPA heterozygous had a lysosomal acid lipase activity below the reference value. One of these carriers, a seven-year-old boy, was found to have severe dyslipidemia and was subsequently treated with statins.

CONCLUSION

Our study underlines that CESD is a multi-organ disease, the progression of which may occur post-liver transplantation. Our findings underline the need for monitoring of complications and assessment of possible further treatment.

AISF update on the diagnosis and management of adult-onset lysosomal storage diseases with hepatic involvement

Lysosomal storage diseases (LSDs) are a heterogeneous group of inherited disorders caused by loss-of-function mutations in genes encoding for lysosomal enzymes/proteins. The consequence is a progressive accumulation of substrates in these intracellular organelles, resulting in cellular and tissue damage. The overall incidence is about 1/8000 live births, but is likely underestimated. LSDs are chronic progressive multi-systemic disorders, generally presenting with visceromegaly, and involvement of the central nervous system, eyes, the skeleton, and the respiratory and cardiovascular systems. The age at onset and phenotypic expression are highly variable, according to the specific enzymatic defect and tissues involved, the residual activity, and the disease-causing genotype. Enzyme-replacement therapies and substrate-reduction therapies have recently become available, leading to the improvement in symptoms, disease progression and quality of life of affected individuals. Liver involvement and hepatosplenomegaly are frequent features of LSDs and a hallmark of adult-onset forms, frequently leading to medical attention. LSDs should therefore be considered in the differential diagnosis of liver disease with organomegaly. The present document will provide a short overview of adult-onset LSDs with hepatic involvement, highlighting the specificities and systemic manifestations of the ones most frequently encountered in clinical practice, which may hint at the correct diagnosis and the appropriate treatment.

Cholesterol Handling in Lysosomes and Beyond

Lysosomes are of major importance for the regulation of cellular cholesterol homeostasis. Food-derived cholesterol and cholesterol esters contained within lipoproteins are delivered to lysosomes by endocytosis. From the lysosomal lumen, cholesterol is transported to the inner surface of the lysosomal membrane through the glycocalyx; this shuttling requires Niemann-Pick C (NPC) 1 and NPC2 proteins. The lysosomal membrane proteins lysosomal-associated membrane protein (LAMP)-2 and lysosomal integral membrane protein (LIMP)-2/SCARB2 also bind cholesterol. LAMP-2 may serve as a cholesterol reservoir, whereas LIMP-2, like NPC1, is able to transport cholesterol through a transglycocalyx tunnel. Contact sites and fusion events between lysosomes and other organelles mediate the distribution of cholesterol. Lysosomal cholesterol content is sensed thereby regulating mammalian target of rapamycin complex (mTORC)-dependent signaling. This review summarizes our understanding of the major steps in cholesterol handling from the moment it enters the lysosome until it leaves this compartment.

Inborn errors of metabolism in the differential diagnosis of fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease across all age groups. Obesity, diabetes, and metabolic syndrome, are the primary causes that are closely linked with the development of NAFLD. However, in young children, rare inborn errors of metabolism are predominant secondary causes of NAFLD. Furthermore, inborn errors of metabolism causing hepatosteatosis are often misdiagnosed as NAFLD in adolescents and adults. Many inborn errors of metabolism are treatable disorders and therefore require special consideration. This review aims to summarize the basic characteristics and diagnostic clues of inborn errors of metabolism associated with fatty liver disease. A suggested clinical and laboratory diagnostic approach is also discussed.

Lysosomal Acid Lipase Deficiency: Therapeutic Options

Lysosomal acid lipase (LAL) deficiency is a metabolic (storage) disorder, encompassing a severe (Wolman disease) and attenuated (Cholesterol ester storage disease) subtype; both inherited as autosomal recessive traits. Cardinal clinical features include the combination of hepatic dysfunction and dyslipidemia, as a consequence of cholesteryl esters and triglyceride accumulation, predominately in the liver and vascular and reticuloendothelial system. Significant morbidity can arise, due to liver failure and/or atherosclerosis; in part related to the severity of the underlying gene defect and corresponding enzyme deficiency. Diagnosis is based on demonstration of decreased LAL enzyme activity, complemented by analysis of the cognate gene defects. Therapeutic options include dietary manipulation and the use of lipid-lowering drugs. Sebelipase alfa, a recombinant enzyme replacement therapy, has garnered regulatory approval, following demonstration of improvements in disease-relevant markers and clinical benefit in clinical trials, which included increased survival in the most severe cases.

Liver gene regulatory networks: Contributing factors to nonalcoholic fatty liver disease

Metabolic diseases such as nonalcoholic fatty liver disease (NAFLD) result from complex interactions between intrinsic and extrinsic factors, including genetics and exposure to obesogenic environments. These risk factors converge in aberrant gene expression patterns in the liver, which are underlined by altered cis-regulatory networks. In homeostasis and in disease states, liver cis-regulatory networks are established by coordinated action of liver-enriched transcription factors (TFs), which define enhancer landscapes, activating broad gene programs with spatiotemporal resolution. Recent advances in DNA sequencing have dramatically expanded our ability to map active transcripts, enhancers and TF cistromes, and to define the 3D chromatin topology that contains these elements. Deployment of these technologies has allowed investigation of the molecular processes that regulate liver development and metabolic homeostasis. Moreover, genomic studies of NAFLD patients and NAFLD models have demonstrated that the liver undergoes pervasive regulatory rewiring in NAFLD, which is reflected by aberrant gene expression profiles. We have therefore achieved an unprecedented level of detail in the understanding of liver cis-regulatory networks, particularly in physiological conditions. Future studies should aim to map active regulatory elements with added levels of resolution, addressing how the chromatin landscapes of different cell lineages contribute to and are altered in NAFLD and NAFLD-associated metabolic states. Such efforts would provide additional clues into the molecular factors that trigger this disease. This article is categorized under: Biological Mechanisms > Metabolism Biological Mechanisms > Regulatory Biology Laboratory Methods and Technologies > Genetic/Genomic Methods.

The Puzzling Conservation and Diversification of Lipid Droplets from Bacteria to Eukaryotes

Membrane compartments are amongst the most fascinating markers of cell evolution from prokaryotes to eukaryotes, some being conserved and the others having emerged via a series of primary and secondary endosymbiosis events. Membrane compartments comprise the system limiting cells (one or two membranes in bacteria, a unique plasma membrane in eukaryotes) and a variety of internal vesicular, subspherical, tubular, or reticulated organelles. In eukaryotes, the internal membranes comprise on the one hand the general endomembrane system, a dynamic network including organelles like the endoplasmic reticulum, the Golgi apparatus, the nuclear envelope, etc. and also the plasma membrane, which are linked via direct lateral connectivity (e.g. between the endoplasmic reticulum and the nuclear outer envelope membrane) or indirectly via vesicular trafficking. On the other hand, semi-autonomous organelles, i.e. mitochondria and chloroplasts, are disconnected from the endomembrane system and request vertical transmission following cell division. Membranes are organized as lipid bilayers in which proteins are embedded. The budding of some of these membranes, leading to the formation of the so-called lipid droplets (LDs) loaded with hydrophobic molecules, most notably triacylglycerol, is conserved in all clades. The evolution of eukaryotes is marked by the acquisition of mitochondria and simple plastids from Gram-positive bacteria by primary endosymbiosis events and the emergence of extremely complex plastids, collectively called secondary plastids, bounded by three to four membranes, following multiple and independent secondary endosymbiosis events. There is currently no consensus view of the evolution of LDs in the Tree of Life. Some features are conserved; others show a striking level of diversification. Here, we summarize the current knowledge on the architecture, dynamics, and multitude of functions of the lipid droplets in prokaryotes and in eukaryotes deriving from primary and secondary endosymbiosis events.

Inherited metabolic disorders and dyslipidaemia

Monogenic dyslipidaemia is a diverse group of multisystem disorders. Patients may present to various specialities from early childhood to late in adult life, and it usually takes longer before the diagnosis is established. Increased awareness of these disorders among clinicians is imperative for early diagnosis. This best practice review provides an overview of primary dyslipidaemias, highlighting their clinical presentation, relevant biochemical and molecular tests. It also addresses the emerging role of genetics in the early diagnosis and prevention of these disorders.

SNARE proteins rescue impaired autophagic flux in Down syndrome

Down syndrome (DS) is a chromosomal disorder caused by trisomy of chromosome 21 (Ts21). Unbalanced karyotypes can lead to dysfunction of the proteostasis network (PN) and disrupted proteostasis is mechanistically associated with multiple DS comorbidities. Autophagy is a critical component of the PN that has not previously been investigated in DS. Based on our previous observations of PN disruption in DS, we investigated possible dysfunction of the autophagic machinery in human DS fibroblasts and other DS cell models. Following induction of autophagy by serum starvation, DS fibroblasts displayed impaired autophagic flux indicated by autophagolysosome accumulation and elevated p62, NBR1, and LC3-II abundance, compared to age- and sex-matched, euploid (CTL) fibroblasts. While lysosomal physiology was unaffected in both groups after serum starvation, we observed decreased basal abundance of the Soluble N-ethylmaleimide-sensitive-factor Attachment protein Receptor (SNARE) family members syntaxin 17 (STX17) and Vesicle Associated Membrane Protein 8 (VAMP8) indicating that decreased autophagic flux in DS is due at least in part to a possible impairment of autophagosome-lysosome fusion. This conclusion was further supported by the observation that over-expression of either STX17 or VAMP8 in DS fibroblasts restored autophagic degradation and reversed p62 accumulation. Collectively, our results indicate that impaired autophagic clearance is a characteristic of DS cells that can be reversed by enhancement of SNARE protein expression and provides further evidence that PN disruption represents a candidate mechanism for multiple aspects of pathogenesis in DS and a possible future target for therapeutic intervention.

Clinical outcome of a patient with lysosomal acid lipase deficiency and first results after initiation of treatment with Sebelipase alfa: A case report

We report on a case of very rare autosomal recessive cholesteryl ester storage disease due to lysosomal acid lipase deficiency (LALD). LALD is caused by mutations in the lysosomal acid lipase A (LIPA) gene resulting in cholesteryl ester accumulation in liver, spleen, and macrophages. It can lead to liver failure, accelerated atherosclerosis and premature death. Until recently, treatment options were limited to lipid-lowering medications to control dyslipidemia. Presently, a long-term enzyme replacement therapy with Sebelipase alfa, a recombinant human lysosomal acid lipase, is available for patients with LALD. Our patient's condition became conspicuous at the age of two due to a xanthogranuloma of the chin together with increased lipid levels, elevated liver enzymes and hepatomegaly. It took another five years until our patient was diagnosed with LALD after genetic testing. A bi-weekly therapy with intravenous Sebelipase alfa was started at the age of 26 years. It led to normalization of lipid levels, reduction of liver enzymes and beginning regression of hepatomegaly in the absence of adverse drug reactions after 46 infusions. Since LALD can take a fatal course even in patients with a long-term stable condition, it is essential to identify affected patients early and to treat them appropriately by enzyme replacement therapy. LALD should be suspected in patients with low high-density lipoprotein cholesterol (HDL-C) and high low-density lipoprotein cholesterol (LDL-C) in conjunction with elevated liver enzymes or hepatomegaly. A registry for LALD patients shall help to advance our understanding of the disease as well as improve patient care (NCT01633489).

Lysosomal acid lipase deficiency in Brazilian children: a case series

OBJECTIVE

To describe the demographic, clinical, laboratory and molecular characteristics of patients with lysosomal acid lipase deficiency.

METHODS

A retrospective review of the medical records of children with the disease.

RESULTS

Seven children with lysosomal acid lipase deficiency (5 male; 2 female); 6 were mixed race, and 1 was black. The mean ages at the first onset of symptoms and at diagnosis were 5.0 years (4 months to 9 years) and 6.9 years (3-10 years), respectively. Symptom manifestations at onset were: 3 patients had abdominal pain, one had bone/joint pain due to rickets, and 1 had chronic diarrhea and respiratory insufficiency due to interstitial pneumonitis. One was asymptomatic, and clinical suspicion arose due to hepatomegaly. Six patients had hepatomegaly, and none had splenomegaly. Two patients were siblings. Enzymatic assay and molecular analysis confirmed the diagnoses. Genetic analysis revealed a rare pathogenic variant (p.L89P) in three patients, described only once in medical literature and never described in Brazil. None of those patients were related to each other. Lysosomal acid lipase deficiency was previously described as an autosomal recessive disease, but three patients were heterozygous and undoubtedly had the disease (low enzyme activity, suggestive lab findings and clinical symptoms).

CONCLUSION

This case series supports that lysosomal acid lipase deficiency can present with highly heterogeneous signs and symptoms among patients, but it should be considered in children presenting with gastrointestinal symptoms associated with dyslipidemia. We describe a rare variant in three non-related patients that may suggest a Brazilian genotype for lysosomal acid lipase deficiency.

NAFLD in children: new genes, new diagnostic modalities and new drugs

Nonalcoholic fatty liver disease (NAFLD) has rapidly become the most common form of chronic liver disease in children and adolescents. Over the past 5 years, developments have revolutionized our understanding of the genetic factors, natural history, diagnostic modalities and therapeutic targets for this disease. New polymorphisms, such as those in PNPLA3, TM6SF2, MBOAT7 and GCKR, have been identified and used to predict the development and severity of NAFLD in both adults and children, and their interaction with environmental factors has been elucidated. Studies have demonstrated the true burden of paediatric NAFLD and its progression to end-stage liver disease in adulthood. In particular, nonalcoholic steatohepatitis can progress to advanced fibrosis and cirrhosis, emphasizing the importance of early diagnosis. Non-invasive imaging tests, such as transient elastography, will probably replace liver biopsy for the diagnosis of nonalcoholic steatohepatitis and the assessment of fibrosis severity in the near future. The therapeutic landscape is also expanding rapidly with the development of drugs that can modify liver steatosis, inflammation and fibrosis, indicating that pharmacotherapy for NAFLD will become available in the future. In this Review, we summarize current knowledge and new advances related to the pathogenesis and management of paediatric NAFLD.

Early diagnosis of infantile-onset lysosomal acid lipase deficiency in the advent of available enzyme replacement therapy

BACKGROUND

Lysosomal acid lipase deficiency (LAL-D) is an autosomal recessive disorder that can present as a severe, infantile form also known as Wolman disease. We sought to determine the outcomes and clinical needs of infants diagnosed with LAL-D, treated with enzyme replacement therapy (ERT).

METHODS

A chart review was conducted on two infantile-onset LAL-D patients to determine clinical outcomes based on laboratory results, abdominal imaging, growth and dietary records, cardiology, endocrinology, ophthalmology, hematology, and neurocognitive evaluations.

RESULTS

Two patients, both diagnosed and treated before 6 months old, demonstrated clinical improvement following weekly ERT. They required dosage increases to optimize growth and symptomatology. Both received a formula low in long chain triglycerides and high in medium chain triglycerides, an intervention that allowed significant catch-up growth. Patient 1 required treatment for partial adrenal insufficiency and hypothyroidism. Both patients demonstrated reduction in liver and spleen size and varying degrees of improved liver function. Neither experienced serious adverse reactions to ERT.

CONCLUSION

ERT has led to longer and healthier survival of affected infants. It is imperative that dietary interventions and systemic clinical care become integral to the management. Continued evidence of survival and clinical improvement in this population, coupled with available mass spectrometry enzyme assay from dried blood spots, raises the question of this rare and possibly underdiagnosed disorder's candidacy for newborn screening.

Novel Insights into the Genetic Landscape of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), the most common liver disorder worldwide, is epidemiologically associated with overweight, insulin resistance features and type 2 diabetes, and can progress to advanced liver fibrosis and hepatocellular carcinoma. Genetic factors play an important role in the development of NAFLD, which is a multifactorial disease. Several common naturally occurring variants modulating lipid and retinol metabolism in hepatocytes predispose to NAFLD development and progression, in particular those in PNPLA3, TM6SF2, MBOAT7, and HSD17B13. In addition, genetic variants that protect hepatic cells from oxidative stress modulate the susceptibility to progressive NAFLD. Although the molecular mechanisms linking these genetic variants with liver disease are not yet fully understood, hepatic fat has emerged as a major driver of the disease, while altered retinol metabolism and mitochondrial oxidative stress play a role in determining the development of advanced NAFLD.

Association between Lysosomal Dysfunction and Obesity-Related Pathology: A Key Knowledge to Prevent Metabolic Syndrome

Obesity causes various health problems, such as type 2 diabetes, non-alcoholic fatty liver disease, and cardio- and cerebrovascular diseases. Metabolic organs, particularly white adipose tissue (WAT) and liver, are deeply involved in obesity. WAT contains many adipocytes with energy storage capacity and secretes adipokines depending on the obesity state, while liver plays pivotal roles in glucose and lipid metabolism. This review outlines and underscores the relationship between obesity and lysosomal functions, including lysosome biogenesis, maturation and activity of lysosomal proteases in WAT and liver. It has been revealed that obesity-induced abnormalities of lysosomal proteases contribute to inflammation and cellular senescence in adipocytes. Previous reports have demonstrated obesity-induced ectopic lipid accumulation in liver is associated with abnormality of lysosomal proteases as well as other lysosomal enzymes. These studies demonstrate that lysosomal dysfunction in WAT and liver underlies part of the obesity-related pathology, raising the possibility that strategies to modulate lysosomal function may be effective in preventing or treating the metabolic syndrome.

Treatment with fibrates is associated with higher LAL activity in dyslipidemic patients

Lysosomal acid lipase (LAL) is responsible for the hydrolysis of cholesteryl esters (CE) and triglycerides (TG) within the lysosomes; generated cholesterol and free fatty acids (FFA) are released in the cytosol where they can regulate their own synthesis and metabolism. When LAL is not active, as in case of genetic mutations, CE and TG accumulate in the lysosomal compartment, while the lack of release of cholesterol and FFA in the cytosol leads to an upregulation of their synthesis. Thus, LAL plays a central role in the intracellular homeostasis of lipids. Since there are no indications about the effect of different lipid-lowering agents on LAL activity, aim of the study was to address the relationship between LAL activity and the type of lipid-lowering therapy in a cohort of dyslipidemic patients. LAL activity was measured on dried blood spot from 120 patients with hypercholesterolemia or mixed dyslipidemia and was negatively correlated to LDL-cholesterol levels. Among enrolled patients, ninety-one were taking one or more lipid-lowering drugs, as statins, fibrates, ezetimibe and omega-3 polyunsaturated fatty acids. When patients were stratified according to the type of lipid-lowering treatment, i.e. untreated, taking statins or taking fibrates, LAL activity was significantly higher in those with fibrates, even after adjustment for sex, age, BMI, lipid parameters, liver function, metabolic syndrome, diabetes and statin use. In a subset of patients tested after 3 months of treatment with micronized fenofibrate, LAL activity raised by 21%; the increase was negatively correlated with baseline LAL activity. Thus, the use of fibrates is independently associated with higher LAL activity in dyslipidemic patients, suggesting that the positive effects of PPAR-α activation on cellular and systemic lipid homeostasis can also include an improved LAL activity.

Mutations identified in a cohort of Mexican patients with lysosomal acid lipase deficiency

INTRODUCTION AND OBJECTIVES

Lysosomal acid lipase deficiency (LAL-D) is an autosomal recessive disease caused by mutations in the LIPA gene, located on the long arm of chromosome 10 (10q23.31). Up until now, more than 59 mutations have been described and which are the cause of a very wide clinical spectrum. The goal of this study was to identify the mutations present in Mexican pediatric patients with a diagnosis of LAL-D.

MATERIALS AND METHODS

A cross-sectional study was carried out which included all the pediatric patients with LAL-D treated in a tertiary hospital in Mexico from January 2000 to June 2017.

RESULTS

Sixteen patients with LAL-D were identified with a disease phenotype marked by the accumulation of cholesteryl esters. Eight distinct variants in the LIPA gene sequence were found, four pathogenic variants and four probably pathogenic. In six individuals, the variants were found in the homozygous state and ten were compound heterozygous. The eight variants were inverted, with five found on exon 4 and the others on exons 2, 8 and 10. The variant c.386A>G;p.His129Arg was the most common, being found in six of the 16 individuals (37.5%), making it much more frequent than what had previously been reported in the literature in proportion to the rest of the variants. The mutation known as E8SJM, which has been the mostly frequently found at the international level, was not the most common among this group of Mexican patients. In conclusion, Mexican patients present a different frequency of mutations associated with LAL-D in comparison to European populations.

A kinetic assay of total lipase activity for detecting lysosomal acid lipase deficiency (LAL-D) and the molecular characterization of 18 LAL-D patients from Russia

Laboratory diagnostics of lysosomal acid lipase deficiency (LAL-D), a rare disorder associated with LIPA alterations, are based on the evaluation of LAL activity. In dry blood spots (DBS) submitted for LAL-D diagnostics (the screening cohort) over a two-year period or obtained from a cohort of retrospective LAL-D patients, we measured: (1) LAL activity using a two-reaction assay with 4-methylumbelliferone palmitate (4-MU-Palm) and Lalistat-2, a specific LAL inactivator; (2) total lipase (TL) activity by a 1-hour kinetic 4-MU-Palm cleavage reaction (no Lalistat-2). The TL activity was expressed as the area under the kinetic curve after 1 hour (TL-AUC1h) of the reaction and presented as the median (min-max). LAL activity was reduced in 30/537 individuals from the screening cohort, among which LIPA sequencing revealed six patients and one carrier. Overall, 16 (89%) individuals among six novel and 12 retrospective LAL-D patients carried at least one c.894G>A mutation (six were homozygous). The TL-AUC1h in nonLAL-D specimens with normal LAL activity (n = 90) was unambiguously higher (9471 [4015-23 585] RFU*h/punch) compared to LAL-D patients, including six new and nine retrospective patients (1810 [357-2608] RFU*h/punch). Importantly, in 13/15 examined nonLAL-D specimens with reduced LAL activity the TL-AUC1h was above a threshold of 2652 RFU*h/punch. Applying this threshold, the TL-AUC1h index discriminated all LAL-D patients (100% sensitivity) and 103/105 nonLAL-D specimens (98% specificity). Given that there is no need for Lalistat-2 and two parallel enzymatic reactions in conjunction with high sensitivity and specificity, the kinetic assay seems to be practical for LAL-D screening.

SYNOPSIS

Lysosomal acid lipase deficiency responsible for Wolman disease and cholesterol ester storage disease could be reliably detected using a kinetic assay of total lipase activity with a fluorogenic substrate.

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.

Current status, problems, and perspectives of non-alcoholic fatty liver disease research

Non-alcoholic fatty liver disease (NAFLD) is a major chronic liver disease that can lead to liver cirrhosis, liver cancer, and ultimately death. NAFLD is pathologically classified as non-alcoholic fatty liver (NAFL) or non-alcoholic steatohepatitis (NASH) based on the existence of ballooned hepatocytes, although the states have been known to transform into each other. Moreover, since the detection of ballooned hepatocytes may be difficult with limited biopsied specimens, its clinical significance needs reconsideration. Repeated liver biopsy to assess histological NAFLD activity for therapeutic response is also impractical, creating the need for body fluid biomarkers and less invasive imaging modalities. Recent longitudinal observational studies have emphasized the importance of advanced fibrosis as a determinant of NAFLD outcome. Thus, identifying predictors of fibrosis progression and developing better screening methods will enable clinicians to isolate high-risk NAFLD patients requiring early intensive intervention. Despite the considerable heterogeneity of NAFLD with regard to underlying disease, patient age, and fibrosis stage, several clinical trials are underway to develop a first-in-class drug. In this review, we summarize the present status and future direction of NAFLD/NASH research towards solving unmet medical needs.

Glycoprotein Non-Metastatic Protein B: An Emerging Biomarker for Lysosomal Dysfunction in Macrophages

Several diseases are caused by inherited defects in lysosomes, the so-called lysosomal storage disorders (LSDs). In some of these LSDs, tissue macrophages transform into prominent storage cells, as is the case in Gaucher disease. Here, macrophages become the characteristic Gaucher cells filled with lysosomes laden with glucosylceramide, because of their impaired enzymatic degradation. Biomarkers of Gaucher cells were actively searched, particularly after the development of costly therapies based on enzyme supplementation and substrate reduction. Proteins selectively expressed by storage macrophages and secreted into the circulation were identified, among which glycoprotein non-metastatic protein B (GPNMB). This review focusses on the emerging potential of GPNMB as a biomarker of stressed macrophages in LSDs as well as in acquired pathologies accompanied by an excessive lysosomal substrate load in macrophages.

Lipometabolism and Glycometabolism in Liver Diseases

The liver is the main metabolic organ in the body especially in lipometabolism and glycometabolism. Carbohydrates and fats disorders can result in insulin resistance in the liver. Metabolic imbalance can even lead to life-threatening conditions. Therefore, it is essential to maintain the normal metabolic function of the liver. When the liver is in a pathological state, liver metabolism homeostasis is damaged, and metabolic disorders will further aggravate liver disease. Consequently, it is essential to determine the relationship between liver diseases and metabolic disorders. Here we review a lot of evidence that liver diseases are closely related to lipometabolism and glycometabolism. Although the disorder of the liver metabolism is caused by different liver diseases, the break of metabolic balance is determined by changes in the state of the liver. We discuss the relationship between liver disease and metabolic changes, outline the process of how metabolic changes are regulated by liver diseases, and describe the role which metabolic changes play in the process and prognosis of liver disease.

The role of the chronic care model in promoting the management of the patient with rare liver disease

INTRODUCTION

The chronic care model (CCM) provides a holistic approach for managing chronic illnesses. Patients with rare liver diseases (RLD) have complex needs, impaired quality of life and often life-threatening complications. Most RLD meet the criteria for a long-term chronic condition and should be viewed through the prism of CCM. We aimed to ascertain whether the CCM has been considered for the frequently-encountered RLD.

METHODS

MEDLINE®/PubMed®/Cochrane/EMBASE were searched to identify publications relating to the use of the CCM for the management of six RLD. We identified 33 articles eligible for inclusion.

RESULTS

Six, eleven, one, thirteen, two and zero studies, discussed individual components of the CCM for autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), primary sclerosing cirrhosis (PSC), Wilsons disease (WD), alpha-1 antitrypsin deficiency (A1AD) and lysosomal acid lipase deficiency (LALd) respectively. We have not identified studies using the full CCM for any of the aforementioned RLD.

DISCUSSION

Unlike in common chronic conditions e.g. diabetes, there has been limited consideration of the use of CCM (or its components) for the management of RLD. This may reflect a reluctance of the clinical community to view these diseases as chronic or lack of healthcare policy investment in rare diseases in general.

Access to care in rare liver diseases: New challenges and new opportunities

Patients with rare diseases are often disadvantaged, particularly those with rare liver diseases. Reasons for disadvantage include delayed or overlooked diagnosis, lack of local expertise and high-quality care, poor scientific understanding of the disease process and limited therapeutic options. In adult liver disease this can be compounded by prejudices towards patients with liver disease in general, because of a perception (incorrect for all rare liver diseases) that liver disease is lifestyle related and thus "self-inflicted". In paediatric rare liver diseases, such as biliary atresia, optimising outcomes requires a particularly timely diagnosis. Irrespective of patient age, the scientific and medical community must rise to the challenge of advancing our understanding of rare liver disease, searching for more effective and specific therapies, and providing the infrastructure to provide the best care for all patients, infants, children, young and older adults. The European Reference Network for Rare Liver Diseases is an important step in this direction.

Lysosomal Acid Lipase Deficiency: Report of Five Cases across the Age Spectrum

Lysosomal acid lipase (LAL) deficiency is an autosomal recessive lysosomal storage disorder caused by mutations in the LIPA gene that leads to premature organ damage and mortality. We present retrospective data from medical records of 5 Brazilian patients, showing the broad clinical spectrum of the disease.