Lysosomal Acid Lipase: Can it be a New Non-Invasive Serum Biomarker of Cryptogenic Liver Fibrosis and Cirrhosis?

From LAL-D to MASLD: Insights into the role of LAL and Kupffer cells in liver inflammation and lipid metabolism

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent liver pathology worldwide, closely associated with obesity and metabolic disorders. Increasing evidence suggests that macrophages play a crucial role in the development of MASLD. Several human studies have shown an inverse correlation between circulating lysosomal acid lipase (LAL) activity and MASLD. LAL is the sole enzyme known to degrade cholesteryl esters (CE) and triacylglycerols in lysosomes. Consequently, these substrates accumulate when their enzymatic degradation is impaired due to LAL deficiency (LALD). This study aimed to investigate the role of hepatic LAL activity and liver-resident macrophages (i.e., Kupffer cells (KC)) in MASLD. To this end, we analyzed lipid metabolism in hepatocyte-specific (hep)Lal-/- mice and depleted KC with clodronate treatment. When fed a high-fat/high-cholesterol diet (HF/HCD), hepLal-/- mice exhibited CE accumulation and an increased number of macrophages in the liver and significant hepatic inflammation. KC were depleted upon clodronate administration, whereas infiltrating/proliferating CD68-expressing macrophages were less affected. This led to exacerbated hepatic CE accumulation and dyslipidemia, as evidenced by increased LDL-cholesterol concentrations. Along with proteomic analysis of liver tissue, these findings indicate that hepatic LAL-D in HF/HCD-fed mice leads to macrophage infiltration into the liver and that KC depletion further exacerbates hepatic CE concentrations and dyslipidemia.

Lanifibranor Reduces Inflammation and Improves Dyslipidemia in Lysosomal Acid Lipase-Deficient Mice

Background and Aims

Recent studies showed that patients suffering from lysosomal acid lipase deficiency (LAL-D) benefit from enzyme replacement therapy; however, liver histopathology improved in some but not all patients. We hypothesized that the pan-peroxisome proliferator-activated receptor agonist lanifibranor may have beneficial effects on liver inflammation in LAL knockout (Lal-/-) mice based on its promising results in alleviating liver inflammation in patients with metabolic dysfunction-associated steatohepatitis.

Methods

Female Lal-/- mice were daily gavaged with lanifibranor or vehicle for 21 days. The effects of the treatment were assessed by measuring body and organ weights, plasma lipids and lipoproteins, as well as hematological parameters, followed by liver proteomics and metabolomics.

Results

Lanifibranor treatment slightly altered organ weights without affecting the total body weight of Lal-/- mice. We observed major changes in the proteome, with multiple proteins related to lipid metabolism, peroxisomal, and mitochondrial activities being upregulated and inflammation-related proteins being downregulated in the livers of treated mice. Hepatic lipid levels and histology remained unaltered, whereas plasma triacylglycerol and total cholesterol levels were decreased and the lipoprotein profile of lanifibranor-treated Lal-/- mice improved.

Conclusion

Lanifibranor treatment positively affected liver inflammation and dyslipidemia in Lal-/- mice. These findings suggest the necessity of a further combined study of lanifibranor with enzyme replacement therapy in Lal-/- mice to improve the phenotype. Moreover, there is a compelling rationale for conducting clinical trials to assess the efficacy of lanifibranor as a potential treatment option for LAL-D in humans.

Transcriptomic screening of novel targets of sericin in human hepatocellular carcinoma cells

Sericin, a natural protein derived from Bombyx mori, is known to ameliorate liver tissue damage; however, its molecular mechanism remains unclear. Herein, we aimed to identify the possible novel targets of sericin in hepatocytes and related cellular pathways. RNA sequencing analysis indicated that a low dose of sericin resulted in 18 differentially expressed genes (DEGs) being upregulated and 68 DEGs being downregulated, while 61 DEGs were upregulated and 265 DEGs were downregulated in response to a high dose of sericin (FDR ≤ 0.05, fold change > 1.50). Functional analysis revealed that a low dose of sericin regulated pathways associated with the complement and coagulation cascade, metallothionine, and histone demethylate (HDMs), whereas a high dose of sericin was associated with pathways involved in lipid metabolism, mitogen-activated protein kinase (MAPK) signaling and autophagy. The gene network analysis highlighted twelve genes, A2M, SERPINA5, MT2A, MT1G, MT1E, ARID5B, POU2F1, APOB, TRAF6, HSPA8, FGFR1, and OGT, as novel targets of sericin. Network analysis of transcription factor activity revealed that sericin affects NFE2L2, TFAP2C, STAT1, GATA3, CREB1 and CEBPA. Additionally, the protective effects of sericin depended on the counterregulation of APOB, POU2F1, OGT, TRAF6, and HSPA5. These findings suggest that sericin exerts hepatoprotective effects through diverse pathways at different doses, providing novel potential targets for the treatment of liver diseases.

Recent insights into lysosomal acid lipase deficiency

Lysosomal acid lipase (LAL) is the sole enzyme known to degrade neutral lipids in the lysosome. Mutations in the LAL-encoding LIPA gene lead to rare lysosomal lipid storage disorders with complete or partial absence of LAL activity. This review discusses the consequences of defective LAL-mediated lipid hydrolysis on cellular lipid homeostasis, epidemiology, and clinical presentation. Early detection of LAL deficiency (LAL-D) is essential for disease management and survival. LAL-D must be considered in patients with dyslipidemia and elevated aminotransferase concentrations of unknown etiology. Enzyme replacement therapy, sometimes in combination with hematopoietic stem cell transplantation (HSCT), is currently the only therapy for LAL-D. New technologies based on mRNA and viral vector gene transfer are recent efforts to provide other effective therapeutic strategies.

A Form of Metabolic-Associated Fatty Liver Disease Associated with a Novel LIPA Variant

BACKGROUND

The LIPA gene on chromosome 10q23.31 contains 10 exons and encodes lipase A, the lysosomal acid lipase (LAL) containing 399 amino acids. Pathogenic variants in the LIPA result in autosomal recessive Wolman disease and cholesteryl ester storage disease (CESD). Here, we report a novel missense variant (NM_001127605.3:c.928T>A, p.Trp310Arg) of LIPA in an Iranian family with fatty liver disease identified by whole-exome sequencing and confirmed by Sanger sequencing.

METHODS

A 28-year-old woman referred with lean NASH cirrhosis and extremely high cholesterol levels. Fatty liver disease was found in six of her family members using vibration-controlled transient elastography (VCTE). Baseline routine laboratory tests were performed and whole-exome sequencing and confirmation by Sanger sequencing were done.

RESULTS

The index case had severe dyslipidemia and cirrhosis despite a body mass index of 21.09 kg/m2 . Six other family members had dyslipidemia and fatty liver or cirrhosis. A homozygous missense variant (NM_001127605.3:c.928T>A, p.Trp310Arg) of LIPA which caused LAL-D was found to be associated with fatty liver disease and/or cirrhosis.

CONCLUSION

A homozygous missense variant (NM_001127605.3:c.928T>A, p.Trp310Arg) of the LIPA gene which caused LAL-D was found to be associated with dyslipidemia, fatty liver disease and/or cirrhosis in six members of an Iranian family. These results should be confirmed by functional studies and extending the study to at least three families.

Lysosomal acid lipase deficiency: A rare inherited dyslipidemia but potential ubiquitous factor in the development of atherosclerosis and fatty liver disease

Lysosomal acid lipase (LAL), encoded by the gene LIPA, is the sole neutral lipid hydrolase in lysosomes, responsible for cleavage of cholesteryl esters and triglycerides into their component parts. Inherited forms of complete (Wolman Disease, WD) or partial LAL deficiency (cholesteryl ester storage disease, CESD) are fortunately rare. Recently, LAL has been identified as a cardiovascular risk gene in genome-wide association studies, though the directionality of risk conferred remains controversial. It has also been proposed that the low expression and activity of LAL in arterial smooth muscle cells (SMCs) that occurs inherently in nature is a likely determinant of the propensity of SMCs to form the majority of foam cells in atherosclerotic plaque. LAL also likely plays a potential role in fatty liver disease. This review highlights the nature of LAL gene mutations in WD and CESD, the association of LAL with prediction of cardiovascular risk from genome-wide association studies, the importance of relative LAL deficiency in SMC foam cells, and the need to further interrogate the pathophysiological impact and cell type-specific role of enhancing LAL activity as a novel treatment strategy to reduce the development and induce the regression of ischemic cardiovascular disease and fatty liver.

Morroniside, a novel GATA3 binding molecule, inhibits hepatic stellate cells activation by enhancing lysosomal acid lipase expression

BACKGROUND

Liver fibrosis can be easily developed into irreversible liver cirrhosis or even liver cancer. Lysosomal acid lipase (LAL), encoded by the lipase A (Lipa) gene, is a critical enzyme involved in liver fibrosis development. Morroniside, an iridoid glycoside isolated from Cornus officinalis Sieb. et Zucc., exerts hepatic protective effects. However, the mechanism of action underling the anti-liver fibrosis effects of morroniside have not been fully elucidated.

PURPOSE

To explore whether Lipa served as a biomarker for liver fibrosis and investigate the anti-liver fibrosis effects of morroniside and the underlying action mechanism in liver fibrosis cell models.

METHODS

LAL expression was examined in the liver tissues of CCl₄ and high-fat diet (HFD)-induced liver fibrosis animal models. α-smooth muscle actin (α-SMA) level, collagen and GATA family expressions were analyzed by Real-time PCR and Western blot. Putative transcription factor binding sites in the DNA sequences of Lipa was identified by PROMO-ALGGEN v8.3 online software and ENCODE ChIP-Seq Significance Tool. MD simulation was performed to explore the protein-ligand interaction.

RESULTS

We found that the expression of hepatic LAL is lower in the liver fibrosis animal models than the control models. The reduced LAL expression is associated with HSCs activation, suggesting LAL is novel liver fibrosis biomarker. More importantly, our data showed that morroniside exerts anti-liver fibrosis effects in vitro. Mechanistic studies reveal that it binds to the hydrophobic sites of GATA3 and also reduces GATA3 expression, which increases LAL expression.

CONCLUSIONS

This study, for the first time, suggests LAL is a novel biomarker for liver fibrosis. Besides, morroniside exerts its anti-liver fibrosis effects by targeting GATA3 and LAL and hence inhibits HSC activation. These findings provide strong scientific evidence to support the development of morroniside as novel alternative or complementary therapeutics for liver injury prevention and treatment.

MiR-34a promotes fibrosis of hepatic stellate cells via the TGF-β pathway

Background

Previous studies have confirmed that MicroRNA (miRNA) is a key regulator exhibiting different effects in human liver fibrosis. However, the function of miR-34a in liver fibrosis has not been reported. Hence, this study aimed to investigate the regulatory mechanism of miR-34a in liver fibrosis.

Methods

The expression of miR-34a was measured in fibrosis tissues via the quantitative real-time PCR (qRT-PCR) assay. Subsequently, 30 male C57BL/6J mice were divided into control and treatment groups and used to establish animal models of liver fibrosis to explore the expression level of miR-34a. Moreover, Cell Counting Kit 8 (CCK-8) and transwell assays were preformed to identify the regulatory mechanism of miR-34a in cells. The effect of miR-34a on the activity of transforming growth factor-β (TGF-β) pathway was observed by western blot.

Results

Up-regulation of miR-34a was detected in fibrosis cells. Moreover, the cellular phenotype was suppressed by miR-34a down-regulation in a primary culture of hepatic stellate cells (HSCs). Besides, it was found that increased miR-34a could significantly promote the invasion and migration of HSCs. Moreover, miR-34a activates HSCs through transforming TGF-β, α-smooth muscle actin (α-SMA), and Monocyte chemoattractant protein-1 (MCP-1), which further affects liver fibrosis.

Conclusions

MiR-34a promotes the fibrosis of HSCs as well as cell proliferation, migration, and invasion.

Mitochondrial Mutations and Genetic Factors Determining NAFLD Risk

NAFLD (non-alcoholic fatty liver disease) is a widespread liver disease that is often linked with other life-threatening ailments (metabolic syndrome, insulin resistance, diabetes, cardiovascular disease, atherosclerosis, obesity, and others) and canprogress to more severe forms, such as NASH (non-alcoholic steatohepatitis), cirrhosis, and HCC (hepatocellular carcinoma). In this review, we summarized and analyzed data about single nucleotide polymorphism sites, identified in genes related to NAFLD development and progression. Additionally, the causative role of mitochondrial mutations and mitophagy malfunctions in NAFLD is discussed. The role of mitochondria-related metabolites of the urea cycle as a new non-invasive NAFLD biomarker is discussed. While mitochondria DNA mutations and SNPs (single nucleotide polymorphisms) canbe used as effective diagnostic markers and target for treatments, age and ethnic specificity should be taken into account.