Cholesteryl Ester Hydrolysis Research Articles

Elucidating the impact of bacterial lipases, human serum albumin, and FASII inhibition on the utilization of exogenous fatty acids by Staphylococcus aureus.

Incorporation of host-derived exogenous fatty acids (eFAs), particularly unsaturated fatty acids (UFAs), by Staphylococcus aureus could affect the bacterial membrane fluidity and susceptibility to antimicrobials. In this work, we found that glycerol ester hydrolase (Geh) is the primary lipase hydrolyzing cholesteryl esters and, to a lesser extent, triglycerides and that human serum albumin (HSA) could serve as a buffer of eFAs, where low levels of HSA facilitate the utilization of eFAs but high levels of HSA inhibit it. The fact that the type II fatty acid synthesis (FASII) inhibitor, AFN-1252, leads to an increase in UFA content even in the absence of eFA suggests that membrane property modulation is part of its mechanism of action. Thus, Geh and/or the FASII system look to be promising targets to enhance S. aureus killing in a host environment by restricting eFA utilization or modulating membrane properties, respectively.

TMET-05. LIPOPHAGY CONTROLS CHOLESTEROL HOMEOSTASIS AND BRAIN TUMOR GROWTH

Abstract Cholesterol is an essential structural component of cell membranes. How rapidly growing tumor cells maintain membrane cholesterol homeostasis is poorly understood. Here, we found that glioblastoma (GBM), the most lethal brain tumor, maintains normal levels of membrane cholesterol, but with an abundant presence of cholesteryl esters (CEs) in their lipid droplets (LDs). Mechanistically, we found that SREBP-1, a master transcription factor that is activated upon cholesterol depletion, upregulates critical autophagic genes, including ATG9B, ATG4A and LC3B, as well as lysosome cholesterol transporter NPC2. This upregulation promotes LD lipophagy, resulting in the hydrolysis of CEs and the liberation of cholesterol from the lysosomes, thus maintaining plasma membrane cholesterol homeostasis. When this pathway is blocked GBM cells became quite sensitive to cholesterol deficiency with poor growth. Our study unravels a previously unrecognized SREBP-1-autophagy-LD-CE hydrolysis pathway that plays an important role in maintaining membrane cholesterol homeostasis, while providing a potential new therapeutic avenue for GBM

The potential role and mechanism of circRNAs in foam cell formation.

Atherosclerosis is a significant risk factor for coronary heart disease (CHD) and myocardial infarction (MI). Atherosclerosis develops during foam cell generation, which is caused by an imbalance in cholesterol uptake, esterification, and efflux. LOX-1, SR-A1, and CD36 all increased cholesterol uptake. ACAT1 and ACAT2 promote free cholesterol (FC) esterification to cholesteryl esters (CE). The hydrolysis of CE to FC was aided by nCEH. FC efflux was promoted by ABCA1, ABCG1, ADAM10, and apoA-I. SR-BI promotes not only cholesterol uptake but also FC efflux. Circular RNAs (circRNAs), which are single-stranded RNAs with a closed covalent circular structure, have emerged as promising biomarkers and therapeutic targets for atherosclerosis due to their highly tissue, cell, and disease state-specific expression profiles. Numerous studies have shown that circRNAs regulate foam cell formation, acting as miRNA sponges to influence atherosclerosis development by regulating the expression of SR-A1, CD36, ACAT2, ABCA1, ABCG1, ADAM10, apoA-I, SR-B1. Several circRNAs, including circ-Wdr91, circ 0004104, circRNA0044073, circRNA_0001805, circDENND1B, circRSF1, circ 0001445, and circRNA 102682, are potential biomarkers for atherosclerosis to better evaluate cardiovascular risk. It is difficult to deliver synthetic therapeutic circRNAs to the desired target tissues. Nanotechnology, such as GA-RM/GZ/PL, may be an important solution to this problem. In this review, we focus on the potential role and mechanism of circRNA/miRNA axis in foam cell formation in the hopes of discovering new targets for the diagnosis, prevention, and treatment of atherosclerosis.

First LIPA Mutational Analysis in Egyptian Patients Reveals One Novel Variant: Wolman Disease

Lysosomal acid lipase (LAL) is a necessary enzyme for the hydrolysis of both triglycerides (TGs) and cholesteryl esters (CEs) in the lysosome. Deficiency of this enzyme encoded by the lipase A (LIPA) gene leads to LAL deficiency (LAL-D). A severe disease subtype of LAL-D is known as Wolman disease (WD), present with diarrhea, hepatosplenomegaly, and adrenal calcification. Untreated patients do not survive more than a year. The aim of this study was to assess the clinical and molecular characterizations of WD patients in Egypt. A total of seven patients (from five unrelated Egyptian families) were screened by targeted next-generation sequencing (NGS), and the co-segregation of causative variants was analyzed using Sanger sequencing. Furthermore, multiple in silico analyses were performed to assess the pathogenicity of the candidate variants. Overall, we identified three diseases causing variants harbored in the LIPA gene. One of these variants is a novel missense variant (NM_000235.4: c.1122 T > G; p. His374Gln), which was classified as a likely pathogenic variant. All variants were predicted to be disease causing using in silico analyses. Our findings expand the spectrum of variants involved in WD which may help to investigate phenotype-genotype correlation and assist genetic counseling. To the best of our knowledge, this is the first clinico-genetic study carried out on Egyptian patients affected with WD.

SREBP-1 upregulates lipophagy to maintain cholesterol homeostasis in brain tumor cells

Cholesterol is a structural component of cell membranes. How rapidly growing tumor cells maintain membrane cholesterol homeostasis is poorly understood. Here, we found that glioblastoma (GBM), the most lethal brain tumor, maintains normal levels of membrane cholesterol but with an abundant presence of cholesteryl esters (CEs) in its lipid droplets (LDs). Mechanistically, SREBP-1 (sterol regulatory element-binding protein 1), a master transcription factor that is activated upon cholesterol depletion, upregulates critical autophagic genes, including ATG9B, ATG4A, and LC3B, as well as lysosome cholesterol transporter NPC2. This upregulation promotes LD lipophagy, resulting in the hydrolysis of CEs and the liberation of cholesterol from the lysosomes, thus maintaining plasma membrane cholesterol homeostasis. When this pathway is blocked, GBM cells become quite sensitive to cholesterol deficiency with poor growth invitro. Our study unravels an SREBP-1-autophagy-LD-CE hydrolysis pathway that plays an important role in maintaining membrane cholesterol homeostasis while providing a potential therapeutic avenue for GBM.

Impact of (intestinal) LAL deficiency on lipid metabolism and macrophage infiltration

ObjectiveTo date, the only enzyme known to be responsible for the hydrolysis of cholesteryl esters and triacylglycerols in the lysosome at acidic pH is lysosomal acid lipase (LAL). Lipid malabsorption in the small intestine (SI), accompanied by macrophage infiltration, is one of the most common pathological features of LAL deficiency. However, the exact role of LAL in intestinal lipid metabolism is still unknown. MethodsWe collected three parts of the SI (duodenum, jejunum, ileum) from mice with a global (LAL KO) or intestine-specific deletion of LAL (iLAL KO) and corresponding controls. ResultsWe observed infiltration of lipid-associated macrophages into the lamina propria, where neutral lipids accumulate massively in the SI of LAL KO mice. In addition, LAL KO mice absorb less dietary lipids but have accelerated basolateral lipid uptake, secrete fewer chylomicrons, and have increased fecal lipid loss. Inflammatory markers and genes involved in lipid metabolism were overexpressed in the duodenum of old but not in younger LAL KO mice. Despite the significant reduction of LAL activity in enterocytes of enterocyte-specific (iLAL) KO mice, villous morphology, intestinal lipid concentrations, expression of lipid transporters and inflammatory genes, as well as lipoprotein secretion were comparable to control mice. ConclusionsWe conclude that loss of LAL only in enterocytes is insufficient to cause lipid deposition in the SI, suggesting that infiltrating macrophages are the key players in this process.

The formation and consequences of cholesterol-rich deposits in atherosclerotic lesions.

Cardiovascular diseases remain the leading cause of death throughout the world. Accumulation of lipoprotein-associated lipids and their interaction with macrophages are early steps in the development of atherosclerotic lesions. For decades, it has been known that aggregates of lipoproteins in the subendothelial space are found in early plaques, and these aggregates are tightly associated with extracellular matrix fibers. Additionally, most of the cholesterol in these subendothelial aggregates is unesterified, in contrast to the core of low-density lipoproteins (LDL), in which cholesteryl esters predominate. This suggests that the hydrolysis of cholesteryl esters occurs extracellularly. At the cellular level, macrophages in early plaques engage with the LDL and ingest large amounts of cholesterol, which is esterified and stored in lipid droplets. When excessive lipid droplets have accumulated, endoplasmic reticulum stress responses are activated, leading to cell death. The cholesterol-laden dead cells must be cleared by other macrophages. For many years, it was unclear how unesterified (free) cholesterol could be formed extracellularly in early lesions. Papers in the past decade have shown that macrophages form tightly sealed extracellular attachments to aggregates of LDL. These sealed regions become acidified, and lysosomal contents are secreted into these compartments. Lysosomal acid lipase hydrolyzes the cholesteryl esters, and the free cholesterol is transported into the macrophages. High concentrations of cholesterol can also lead to formation of crystals of cholesterol hydrate, and these crystals have been observed in atherosclerotic blood vessels. Characterization of this process may lead to novel therapies for the prevention and treatment of atherosclerosis.

Bromelain Ameliorates Atherosclerosis by Activating the TFEB-Mediated Autophagy and Antioxidant Pathways.

Bromelain, a cysteine protease found in pineapple, has beneficial effects in the treatment of inflammatory diseases; however, its effects in cardiovascular pathophysiology are not fully understood. We investigated the effect of bromelain on atherosclerosis and its regulatory mechanisms in hyperlipidemia and atheroprone apolipoprotein E-null (apoe-/-) mice. Bromelain was orally administered to 16-week-old male apoe-/- mice for four weeks. Daily bromelain administration decreased hyperlipidemia and aortic inflammation, leading to atherosclerosis retardation in apoe-/- mice. Moreover, hepatic lipid accumulation was decreased by the promotion of cholesteryl ester hydrolysis and autophagy through the AMP-activated protein kinase (AMPK)/transcription factor EB (TFEB)-mediated upregulation of autophagy- and antioxidant-related proteins. Moreover, bromelain decreased oxidative stress by increasing the antioxidant capacity and protein expression of antioxidant proteins while downregulating the protein expression of NADPH oxidases and decreasing the production of reactive oxygen species. Therefore, AMPK/TFEB signaling may be crucial in bromelain-mediated anti-hyperlipidemia, antioxidant, and anti-inflammatory effects, effecting the amelioration of atherosclerosis.

Role of lysosomal acid lipase in PPAR-mediated reduction of lipid accumulation in hepatocytes

Background and Aims : Lysosomal acid lipase (LAL) catalyzes the hydrolysis of cholesteryl esters and triglycerides in the lysosomal compartment. Recently, it was shown that NAFLD patients can develop an acquired LAL deficiency which is rescued by PPAR-alpha activation. Aim of the study was to investigate the role of other isoform-specific and dual PPAR agonists on lipid accumulation and LAL activity using an in vitro model of steatosis.

Apple polyphenol extract targets circadian rhythms to improve liver biological clock and lipid homeostasis in C57BL/6 male mice with mistimed high-fat diet feeding

To the best of our knowledge, this is the first study to explore the novel ability of apple polyphenol extract to target circadian rhythms in the regulation of hepatic biological clock and lipid homeostasis. • Mice were fed according to four different feeding patterns and the interactive effects of feeding time and food composition were studied. • This was the first study of the capacity of one of the polyphenolic compounds, apple polyphenol extract (APE), to target circadian rhythms to improve hepatic biological clock and lipid homeostasis in C57BL/6 male mice with mistimed HFD feeding. • APE treatment significantly improved the increase in body weight, liver weight and fat accumulation mediated by daytime HFD feeding in the short term. • APE treatment regulated the rhythmic expressions of hepatic circadian clock genes, and genes related to lipid and bile acid metabolism. To investigate the potential role of apple polyphenol extract (APE) in the prevention and alleviation of circadian rhythm disturbances, eighty male C57BL/6 mice fed a high-fat diet (HFD) were randomized into four groups: 24 h ad libitum feeding (AL), 12 h restricted nighttime feeding (NF) or daytime feeding (DF), and daytime feeding with APE intragastric administration (DF-APE). Five weeks later, the mice were sacrificed at 6 h intervals over 24 h. Disrupted fluctuations in serum lipid profiles and hormones, along with desynchronization of circadian clock genes and metabolic genes were observed after daytime HFD feeding. However, APE treatment improved hepatic steatosis and recovered circadian rhythms of Cry1/2 , and genes Acc and Hsl related to lipid synthesis and hydrolysis of cholesteryl esters, and Cyp7a1 in bile acid synthesis. In conclusion, the present study provides new evidence revealing that the circadian clock might be a novel target for APE to regulate metabolic homeostasis.

Correlation of cholesteryl ester metabolism to pathogenesis, progression and disparities in colorectal Cancer

BackgroundColorectal cancer (CRC) is one of the most common cancers worldwide characterized by disparities in age, gender, race and anatomic sites. The mechanism underlying pathogenesis, progression and disparities of CRC remains unclear. This study aims to reveal the association of expression levels of enzymes related to cholesteryl ester (CE) metabolism with pathogenesis, progression and disparities of CRC.MethodsThe differences in gene expression levels were analyzed for enzymes in CE synthesis (acyl CoA: cholesterol acyltransferase 1 and 2, ACAT1, and ACAT2), and in CE hydrolysis (neutral cholesterol ester hydrolase, NCEH1 and lysosomal acid lipase, LAL) on TNMplot platform between CRC and normal colorectal tissues (NCT) in a large cohort. The differences in protein expression levels for these enzymes were determined by Immunochemistry (IHC) performed on tissue microarray containing 96 pairs of CRC and benign colorectal tissues (BCT) from different patient populations. The expression level represented as IHC score of each enzyme was compared between CRC and BCT in entire population and populations stratified by race, gender and anatomic sites. Student’s t-test, Fisher exact test and ANOVA were used for data analysis. Significant p value was set at P<0.05.ResultsThe gene expression level of ACAT1 was significantly lower in CRC than in NCT (P = 2.15e-119). The gene expression level of ACAT2 was not statistically different between CRC and NCT. The gene expression level of LIPA (encoding LAL) was significantly higher in CRC than in NCT (P = 2.01e-14). No data was found for the gene expression level of NCEH1. The IHC score of ACAT1was significantly lower in CRC than in BCT in all studied populations and in sub site of colon, but not in that of rectum. The IHC score of ACAT2 was not statistically different between CRC and BCT. IHC score of NCEH1 was significantly higher in CRC than in BCT only in African American (AA) population. The IHC score of LAL was significantly higher in CRC than in BCT in all studied populations and in all sub sites. In addition, decreased ACAT1 in CRC significantly correlated to progression of CRC: the lower IHC score of ACAT1, the more advanced clinical stage of CRC will be.ConclusionsThis study revealed that altered expression levels in enzymes related to CE metabolism highly correlate to the pathogenesis, clinical progression and disparities of CRC. The results will add revenue in elucidating mechanisms underlying progression of CRC, and shed light on seeking biomarkers and exploring therapeutic targets for CRC in a new direction.

Prostate cancer cell proliferation is influenced by LDL-cholesterol availability and cholesteryl ester turnover

BackgroundProstate cancer growth is driven by androgen receptor signaling, and advanced disease is initially treatable by depleting circulating androgens. However, prostate cancer cells inevitably adapt, resulting in disease relapse with incurable castrate-resistant prostate cancer. Androgen deprivation therapy has many side effects, including hypercholesterolemia, and more aggressive and castrate-resistant prostate cancers typically feature cellular accumulation of cholesterol stored in the form of cholesteryl esters. As cholesterol is a key substrate for de novo steroidogenesis in prostate cells, this study hypothesized that castrate-resistant/advanced prostate cancer cell growth is influenced by the availability of extracellular, low-density lipoprotein (LDL)-derived, cholesterol, which is coupled to intracellular cholesteryl ester homeostasis.MethodsC4-2B and PC3 prostate cancer cells were cultured in media supplemented with fetal calf serum (FCS), charcoal-stripped FCS (CS-FCS), lipoprotein-deficient FCS (LPDS), or charcoal-stripped LPDS (CS-LPDS) and analyzed by a variety of biochemical techniques. Cell viability and proliferation were measured by MTT assay and Incucyte, respectively.ResultsReducing lipoprotein availability led to a reduction in cholesteryl ester levels and cell growth in C4-2B and PC3 cells, with concomitant reductions in PI3K/mTOR and p38MAPK signaling. This reduced growth in LPDS-containing media was fully recovered by supplementation of exogenous low-density lipoprotein (LDL), but LDL only partially rescued growth of cells cultured with CS-LPDS. This growth pattern was not associated with changes in androgen receptor signaling but rather increased p38MAPK and MEK1/ERK/MSK1 activation. The ability of LDL supplementation to rescue cell growth required cholesterol esterification as well as cholesteryl ester hydrolysis activity. Further, growth of cells cultured in low androgen levels (CS-FCS) was suppressed when cholesteryl ester hydrolysis was inhibited.ConclusionsOverall, these studies demonstrate that androgen-independent prostate cancer cell growth can be influenced by extracellular lipid levels and LDL-cholesterol availability and that uptake of extracellular cholesterol, through endocytosis of LDL-derived cholesterol and subsequent delivery and storage in the lipid droplet as cholesteryl esters, is required to support prostate cancer cell growth. This provides new insights into the relationship between extracellular cholesterol, intracellular cholesterol metabolism, and prostate cancer cell growth and the potential mechanisms linking hypercholesterolemia and more aggressive prostate cancer.

Molecular markers of brain cholesterol homeostasis are unchanged despite a smaller brain mass in a mouse model of cholesteryl ester storage disease.

Lysosomal acid lipase (LAL), encoded by the gene LIPA, facilitates the intracellular processing of lipids by hydrolyzing cholesteryl esters and triacylglycerols present in newly internalized lipoproteins. Loss-of-function mutations in LIPA result in cholesteryl ester storage disease (CESD) or Wolman disease when mutations cause complete loss of LAL activity. Although the phenotype of a mouse CESD model has been extensively characterized, there has not been a focus on the brain at different stages of disease progression. In the current studies, whole-brain mass and the concentrations of cholesterol in both the esterified (EC) and unesterified (UC) fractions were measured in Lal-/- and matching Lal+/+ mice (FVB-N strain) at ages ranging from 14 up to 280 days after birth. Compared to Lal+/+ controls at 50, 68-76, 140-142, and 230-280 days of age, Lal-/- mice had brain weights that averaged approximately 6%, 7%, 18%, and 20% less, respectively. Brain EC levels were higher in the Lal-/- mice at every age, being elevated 27-fold at 230-280 days. Brain UC concentrations did not show a genotypic difference at any age. The elevated brain EC levels in the Lal-/- mice did not reflect EC in residual blood. An mRNA expression analysis for an array of genes involved in the synthesis, catabolism, storage, and transport of cholesterol in the brains of 141-day old mice did not detect any genotypic differences although the relative mRNA levels for several markers of inflammation were moderately elevated in the Lal-/- mice. The possible sites of EC accretion in the central nervous system are discussed.

Impaired Bile Acid Metabolism and Gut Dysbiosis in Mice Lacking Lysosomal Acid Lipase.

Lysosomal acid lipase (LAL) is the sole enzyme known to be responsible for the hydrolysis of cholesteryl esters and triglycerides at an acidic pH in lysosomes, resulting in the release of unesterified cholesterol and free fatty acids. However, the role of LAL in diet-induced adaptations is largely unexplored. In this study, we demonstrate that feeding a Western-type diet to Lal-deficient (LAL-KO) mice triggers metabolic reprogramming that modulates gut-liver cholesterol homeostasis. Induction of ileal fibroblast growth factor 15 (three-fold), absence of hepatic cholesterol 7α-hydroxylase expression, and activation of the ERK phosphorylation cascade results in altered bile acid composition, substantial changes in the gut microbiome, reduced nutrient absorption by 40%, and two-fold increased fecal lipid excretion in LAL-KO mice. These metabolic adaptations lead to impaired bile acid synthesis, lipoprotein uptake, and cholesterol absorption and ultimately to the resistance of LAL-KO mice to diet-induced obesity. Our results indicate that LAL-derived lipolytic products might be important metabolic effectors in the maintenance of whole-body lipid homeostasis.

Disturbance of lipid homeostasis in lysosomal lipase deficiency – pathomechanism, diagnosis and treatment

Lysosomal acid lipase (LAL) plays a key role in lipid metabolism through the hydrolysis of cholesteryl esters and triglycerides in lysosomes. LAL deficiency is a rare autosomal recessive lysosomal storage disease caused by deleterious mutations in the LIPA gene. In the case of LAL deficiency, cholesteryl esters and triglycerides accumulate within the lysosomes. The up-regulation of endogenous cholesterol production, increased synthesis of apolipoprotein B (ApoB) and increased production of very-low-density lipoprotein cholesterol (VLDL-C) is observed. The diagnosis is easy due to the currently available method of testing the enzyme activity in a dry blood spot. Molecular analysis is necessary to verify the clinical and biochemical diagnosis and to analyze the genotype-phenotype correlation. Sebelipase alfa is a recombinant human lysosomal lipase intended for use in enzyme replacement therapy in patients with LAL deficiency.

Loss of function of lysosomal acid lipase (LAL) profoundly impacts osteoblastogenesis and increases fracture risk in humans.

Lysosomal acid lipase (LAL) is essential for cholesteryl ester (CE) and triacylglycerol (TAG) hydrolysis in the lysosome. Clinically, an autosomal recessive LIPA mutation causes LAL deficiency (LALD), previously described as Wolman Disease or Cholesteryl Ester Storage Disease (CESD). LAL-D is associated with ectopic lipid accumulation in the liver, small intestine, spleen, adrenal glands, and blood. Considering the importance of unesterified cholesterol and fatty acids in bone metabolism, we hypothesized that LAL is essential for bone formation, and ultimately, skeletal health. To investigate the role of LAL in skeletal homeostasis, we used LAL-deficient (-/-) mice, in vitro osteoblast cultures, and novel clinical data from LAL-D patients. Both male and female LAL-/- mice demonstarted lower trabecular and cortical bone parameters , which translated to reduced biomechanical properties. Further histological analyses revealed that LAL-/- mice had fewer osteoblasts, with no change in osteoclast or marrow adipocyte numbers. In studying the cell-autonomous role of LAL, we observed impaired differentiation of LAL-/- calvarial osteoblasts and in bone marrow stromal cells treated with the LAL inhibitor lalistat. Consistent with LAL's role in other tissues, lalistat resulted in profound lipid puncta accumulation and an altered intracellular lipid profile. Finally, we analyzed a large de-identified national insurance database (i.e. 2016/2017 Optum Clinformatics®) which revealed that adults (≥18years) with CESD (n=3076) had a higher odds ratio (OR=1.21; 95% CI=1.03-1.41) of all-cause fracture at any location compared to adults without CESD (n=13.7M) after adjusting for demographic variables and osteoporosis. These data demonstrate that alterations in LAL have significant clinical implications related to fracture risk and that LAL's modulation of lipid metabolism is a critical for osteoblast function.

Carboxylesterase 1d (Ces1d) does not contribute to cholesteryl ester hydrolysis in the liver

The liver is the central organ regulating cholesterol synthesis, storage, transport, and elimination. Mouse carboxylesterase 1d (Ces1d) and its human ortholog CES1 have been described to possess lipase activity and play roles in hepatic triacylglycerol metabolism and VLDL assembly. It has been proposed that Ces1d/CES1 might also catalyze cholesteryl ester (CE) hydrolysis in the liver and thus be responsible for the hydrolysis of HDL-derived CE; this could contribute to the final step in the reverse cholesterol transport (RCT) pathway, wherein cholesterol is secreted from the liver into bile and feces, either directly or after conversion to water-soluble bile salts. However, the proposed function of Ces1d/CES1 as a CE hydrolase is controversial. In this study, we interrogated the role hepatic Ces1d plays in cholesterol homeostasis using liver-specific Ces1d-deficient mice. We rationalized that if Ces1d is a major hepatic CE hydrolase, its absence would (1) reduce in vivo RCT flux and (2) provoke liver CE accumulation after a high-cholesterol diet challenge. We found that liver-specific Ces1d-deficient mice did not show any difference in the flux of in vivo HDL-to-feces RCT nor did it cause additional liver CE accumulation after high-fat, high-cholesterol Western-type diet feeding. These findings challenge the importance of Ces1d as a major hepatic CE hydrolase.

S1158 Is Lysosomal Acid Lipase Activity a Reliable Marker of Non-Alcoholic Fatty Liver Disease? A Systematic Review

INTRODUCTION: NAFLD encompasses a spectrum of liver damage varying from non-alcoholic fatty liver (NAFL) on the most clinically benign end of the spectrum to cirrhosis on the opposite extreme, where most liver-related morbidity and mortality occurs. Lysosomal acid lipase (LAL) is an enzyme that hydrolyzes cholesteryl esters and triglycerides (TG) into cholesterol, free fatty acids and glycerol. A deficiency of LAL causes build-up of TG and cholesteryl esters in the liver, spleen, intestinal mucosa, adrenal glands, lymph nodes, vascular endothelium and macrophages of the body, leading to elevation of transaminases, fatty acid infiltration of the hepatocytes and hepatomegaly, all of which are the characteristic features of NAFLD. METHODS: We comprehensively searched the databases of MEDLINE and EMBASE from inception to June 2020. Included studies were cohort, cross sectional and review studies that investigated the correlation of the lysosomal acid lipase (LAL) activity with the severity of non-alcoholic fatty liver disease (NAFLD). End note was used to screen the articles. RESULTS: We identified 12 studies that commented upon the correlation of LAL activity with NAFLD. The total sample size was 2850 subjects. LAL activity is significantly reduced in NAFLD when compared to healthy subjects and subjects with HCV. In addition, cryptogenic cirrhosis has marked reduction in LAL activity when compared to known etiology cirrhosis. Moreover, splenomegaly was significantly associated with reduced LAL activity. Furthermore, low LAL activity was associated with increased in levels of various serological marks of liver disease (GGT, INR, Cr). We also noticed inverse correlation between the platelets and WBC count with LAL activity. Table 1 summarizes our findings. CONCLUSION: We conclude that LAL activity is inversely related to the severity of NAFLD. Further prospective multicenter studies are warranted to establish the correlation.Table 1.: Lysosomal Acid Lipase activity in patients with Non-Alcoholic Fatty Liver Disease

Persistent dyslipidemia in treatment of lysosomal acid lipase deficiency

BackgroundLysosomal acid lipase deficiency (LALD) is an autosomal recessive inborn error of lipid metabolism characterized by impaired lysosomal hydrolysis and consequent accumulation of cholesteryl esters and triglycerides. The phenotypic spectrum is diverse, ranging from severe, neonatal onset failure to thrive, hepatomegaly, hepatic fibrosis, malabsorption and adrenal insufficiency to childhood-onset hyperlipidemia, hepatomegaly, and hepatic fibrosis. Sebelipase alfa enzyme replacement has been approved by the Food and Drug Administration for use in LALD after demonstrating dramatic improvement in transaminitis and dyslipidemia with initiation of enzyme replacement therapy.MethodsA chart review was performed on 2 patients with childhood-onset, symptomatic LALD with persistent dyslipidemia despite appropriate enzyme replacement therapy to identify biological pathways and risk factors for incomplete response to therapy.ResultsTwo patients with attenuated, symptomatic LALD had resolution of transaminitis on enzyme replacement therapy without concomitant effect on dyslipidemia despite dose escalation and no evidence of antibody response to enzyme.ConclusionEnzyme replacement therapy does not universally resolve all complications of LALD. Persistent dyslipidemia remains a clinically significant issue, likely related to the complex metabolic pathways implicated in LALD pathogenesis. We discuss the possible mechanistic basis for this unexpected finding and the implications for curative LALD therapy.

SREBP2-STARD4 is involved in synthesis of cholesteryl ester stimulated by mono-butyl phthalate in MLTC-1 cells.

Sterol is synthesized from cholesterol which is from the hydrolysis of stored cholesteryl esters. The process of maintaining cholesterol homeostasis is regulated by SREBP2-STARD4. Lots of researches demonstrated that male steroidogenesis could be interfered by di-n-butyl phthalate (DBP) or monobutyl phthalate (MBP). However, mechanisms of MBP exposure in this process have not been uncovered clearly. The objectiveof this study was to explore roles of SREBP2 and STARD4 in cholesteryl estersynthesis stimulated by MBP in mouse Leydig tumor cells (MLTC-1). MLTC-1 exposedto 10-8, 10-7, 10-6, 10-5 M MBP showed that levels of cholestery ester were increased significantly at 10-7 M MBP. Besides, cholesteryl ester synthesis stimulated by MBP was down-regulate when STARD4 or SREBP2 were inhibited. Activity of SREBP2 binding to the promoter of STARD4 was increased after MBP exposure. This study suggests that MBP can increase cholesteryl ester synthesis through SREBP2-STARD4 signal pathway in MLTC-1 cells.