Thrombospondin-I is a critical modulator in non-alcoholic steatohepatitis (NASH)

Pathophysiological underpinnings of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is emerging as the leading cause of chronic liver disease worldwide, reflecting the global epidemics of obesity, metabolic syndrome, and type 2 diabetes. Beyond its strong association with excess adiposity, MASLD encompasses a heterogeneous population that includes individuals with normal body weight ("lean MASLD") highlighting the complexity of its pathogenesis. This disease results from a complex interplay between genetic susceptibility, epigenetic modifications, and environmental factors, which converge to disrupt metabolic homeostasis. Adipose tissue dysfunction and insulin resistance trigger an overflow of lipids to the liver, leading to mitochondrial dysfunction, oxidative stress, and hepatocellular injury. These processes promote hepatic inflammation and fibrogenesis, driven by cross talk among hepatocytes, immune cells, and hepatic stellate cells, with key contributions from gut-liver axis perturbations. Recent advances have unraveled pivotal molecular pathways, such as transforming growth factor-β signaling, Notch-induced osteopontin, and sphingosine kinase 1-mediated responses, that orchestrate fibrogenic activation. Understanding these interconnected mechanisms is crucial for developing targeted therapies. This review integrates current knowledge on the pathophysiology of MASLD, emphasizing emerging concepts such as lean metabolic dysfunction-associated steatohepatitis (MASH), epigenetic alterations, hepatic extracellular vesicles, and the relevance of extrahepatic signals. It also discusses novel therapeutic strategies under investigation, aiming to provide a comprehensive and structured overview of the evolving MASLD landscape for both basic scientists and clinicians.

Liver lipid droplet cholesterol content is a key determinant of metabolic dysfunction-associated steatohepatitis

Metabolic dysfunction-associated steatohepatitis (MASH) represents a progressive form of steatotic liver disease which increases the risk for fibrosis and advanced liver disease. The accumulation of discrete species of bioactive lipids has been postulated to activate signaling pathways that promote inflammation and fibrosis. However, the key pathogenic lipid species is a matter of debate. We explored candidates using various dietary, molecular, and genetic models. Mice fed a choline-deficient L-amino acid-defined high-fat diet (CDAHFD) developed steatohepatitis and manifested early markers of liver fibrosis associated with increased cholesterol content in liver lipid droplets within 5 days without any changes in total liver cholesterol content. Treating mice with antisense oligonucleotides (ASOs) against Coenzyme A synthase (Cosay) or treatment with bempedoic acid or atorvastatin decreased liver lipid droplet cholesterol content and prevented CDAHFD-induced MASH and the fibrotic response. All these salutary effects were abrogated with dietary cholesterol supplementation. Analysis of human liver samples demonstrated that cholesterol in liver lipid droplets was increased in humans with MASH and liver fibrosis and was higher in PNPLA3 I148M (variants rs738409) than in HSD17B13 variants (rs72613567). Together, these data identify cholesterol in liver lipid droplets as a critical mediator of MASH and demonstrate that COASY knockdown and bempedoic acid are novel therapeutic approaches to reduce liver lipid droplet cholesterol content and thereby prevent the development of MASH and liver fibrosis.

Significance Statement

Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive liver disease linked to fibrosis. The role of specific lipid species in its pathogenesis remains debated. Using dietary, molecular, and genetic models, we found that mice on a choline-deficient, high-fat diet (CDAHFD) developed steatohepatitis and early fibrosis, marked by increased cholesterol in liver lipid droplets within five days. Targeting COASY with antisense oligonucleotides or treating with bempedoic acid or atorvastatin reduced lipid droplet cholesterol and prevented MASH. However, dietary cholesterol supplementation negated these effects. Human liver samples confirmed elevated lipid droplet cholesterol in MASH and fibrosis, especially in PNPLA3 I148M carriers. These findings highlight cholesterol reduction as a potential MASH therapy.

Targeting AhR suppresses hepatocyte ferroptosis in MASH by regulating the Pten/Akt/β catenin axis

Aryl hydrocarbon Receptor (AhR), an essential host regulator, has been observed to be significantly upregulated in patients with Metabolic dysfunction-associated steatohepatitis (MASH). However, the underlying mechanism remains unclear. The specific AhR antagonist CH223191 and siRNAs were employed to investigated the role of AhR and its potential as a therapeutic target for MASH in mice and hepatocytes model. Significant upregulation of hepatic AhR was found in our MASH model and across three public datasets. CH223191 (5 mg/kg) treatment effectively ameliorated lipid deposition, serum ALT/AST level, inflammatory cytokines and hepatocyte senescence. Moreover, inhibiting AhR reduced aberrant iron overload, MDA and ROS levels, and suppressed iron transporter DMT1 and iron storage protein ferritin. Furthermore, CH223191 treatment resulted in the restoration of β-catenin and Pten while reducing the phosphorylation of Akt. Suppression of Pten or β-catenin by specific antagonists significantly abolished the hepatoprotective effects of CH223191, leading to increased DMT1 and ferritin and subsequent hepatic ferroptosis in mice. In conclusions, these findings suggested a novel regulatory role of AhR plays in ferroptosis and iron overload through the Pten/Akt/βcatenin pathway, which makes AhR a promising therapeutic target for the treatment of MASH.

Expression of Vascular Adhesion Protein-1 and Thrombospondin-1 in Gingival Crevicular Fluid of Patients with Periodontitis and Non-Alcoholic Fatty Liver Disease

PURPOSE

Non-alcoholic fatty liver disease (NAFLD) represents a heterogeneous spectrum of liver diseases that encompass simple steatosis, non-alcoholic steatohepatitis (NASH), and advanced fibrosis or cirrhosis. Periodontitis is a chronic infectious disease with multiple causal factors that presents a complex interaction between the microbial biofilm and the host's immune response. The aim of this study was to investigate the concentrations of Vascular Adhesion Protein-1 (VAP-1) and Thrombospondin-1 (TSP-1) in patients with coexisting periodontitis and NAFLD.

PATIENTS AND METHODS

This study included 48 patients, who were dental and periodontal assessed. Of these patients, 25 were diagnosed with NAFLD. After performing the periodontal clinical examination, gingival crevicular fluid (GCF) samples were collected. Enzyme-linked immunosorbent assay (ELISA) dedicated kits tests were used for the detection and quantitative determination of VAP-1 and TSP-1 in GCF samples. Statistical methods were applied for the comparison and correlation of data.

RESULTS

VAP-1 and TSP-1 levels showed significant differences between all test and control groups (p<0.0001). Statistically significant correlations (p<0.05) between VAP-1 and periodontal and liver parameters were found in patients with NAFLD and periodontitis.

CONCLUSION

Periodontal inflammation is more marked in patients with periodontitis-NAFLD association. Vascular adhesion and angiogenesis could be affected in patients with periodontitis and NAFLD. These findings could suggest that addressing periodontal inflammation in individuals with the periodontitis-NAFLD association may have a broader impact on vascular adhesion and angiogenesis, highlighting the interplay between oral health and liver conditions for comprehensive patient care.

Evaluating the impact of type 2 diabetes mellitus on pulmonary vascular function and the development of pulmonary fibrosis

The increasing prevalence of type 2 diabetes mellitus (T2DM) is a significant worldwide health concern caused by sedentary lifestyles and unhealthy diets. Beyond glycemic control, T2DM impacts multiple organ systems, leading to various complications. While traditionally associated with cardiovascular and microvascular complications, emerging evidence indicates significant effects on pulmonary health. Pulmonary vascular dysfunction and fibrosis, characterized by alterations in vascular tone and excessive extracellular matrix deposition, are increasingly recognized in individuals with T2DM. The onset of T2DM is often preceded by prediabetes, an intermediate hyperglycemic state that is associated with increased diabetes and cardiovascular disease risk. This review explores the relationship between T2DM, pulmonary vascular dysfunction and pulmonary fibrosis, with a focus on potential links with prediabetes. Pulmonary vascular function, including the roles of nitric oxide (NO), prostacyclin (PGI2), endothelin-1 (ET-1), thromboxane A2 (TxA2) and thrombospondin-1 (THBS1), is discussed in the context of T2DM and prediabetes. Mechanisms linking T2DM to pulmonary fibrosis, such as oxidative stress, dysregulated fibrotic signaling, and chronic inflammation, are explained. The impact of prediabetes on pulmonary health, including endothelial dysfunction, oxidative stress, and dysregulated vasoactive mediators, is highlighted. Early detection and intervention during the prediabetic stage may reduce respiratory complications associated with T2DM, emphasizing the importance of management strategies targeting blood glucose regulation and vascular health. More research that looks into the mechanisms underlying pulmonary complications in T2DM and prediabetes is needed.

CD47, a novel YAP target gene, contributes to hepatic stellate cell activation and liver fibrosis induced by high-fat diet

Activated hepatic stellate cells (HSCs) have been widely recognized as a primary source of pathological myofibroblasts, leading to the accumulation of extracellular matrix and liver fibrosis. CD47, a transmembrane glycoprotein expressed on the surface of various cell types, has been implicated in non-alcoholic fatty liver disease. However, the precise role of CD47 in HSC activation and the underlying regulatory mechanisms governing CD47 expression remain poorly understood. In this study, we employed single-cell RNA sequencing analysis to investigate CD47 expression in HSCs from mice subjected to a high-fat diet. CD47 silencing in HSCs markedly inhibited the expression of fibrotic genes and promoted apoptosis. Mechanistically, we found that Yes-associated protein (YAP) collaborates with TEAD4 to augment the transcriptional activation of CD47 by binding to its promoter region. Notably, disruption of the interaction between YAP and TEAD4 caused a substantial decrease in CD47 expression in HSCs and reduced the development of high-fat diet-induced liver fibrosis. Our findings highlight CD47 as a critical transcriptional target of YAP in promoting HSC activation in response to a high-fat diet. Targeting the YAP/TEAD4/CD47 signaling axis may hold promise as a therapeutic strategy for liver fibrosis.

Shared and Compartment-Specific Processes in Nucleus Pulposus and Annulus Fibrosus During Intervertebral Disc Degeneration

Elucidating how cell populations promote onset and progression of intervertebral disc degeneration (IDD) has the potential to enable more precise therapeutic targeting of cells and mechanisms. Single-cell RNA-sequencing (scRNA-seq) is performed on surgically separated annulus fibrosus (AF) (19,978; 26,983 cells) and nucleus pulposus (NP) (20,884; 24,489 cells) from healthy and diseased human intervertebral discs (IVD). In both tissue types, depletion of cell subsets involved in maintenance of healthy IVD is observed, specifically the immature cell subsets - fibroblast progenitors and stem cells - indicative of an impairment of normal tissue self-renewal. Tissue-specific changes are also identified. In NP, several fibrotic populations are increased in degenerated IVD, indicating tissue-remodeling. In degenerated AF, a novel disease-associated subset is identified, which expresses disease-promoting genes. It is associated with pathogenic biological processes and the main gene regulatory networks include thrombospondin signaling and FOXO1 transcription factor. In NP and AF cells thrombospondin protein promoted expression of genes associated with TGFβ/fibrosis signaling, angiogenesis, and nervous system development. The data reveal new insights of both shared and tissue-specific changes in specific cell populations in AF and NP during IVD degeneration. These identified mechanisms and molecules are novel and more precise targets for IDD prevention and treatment.

The Contributions of Thrombospondin-1 to Epilepsy Formation

Epilepsy is a neural network disorder caused by uncontrolled neuronal hyperexcitability induced by an imbalance between excitatory and inhibitory networks. Abnormal synaptogenesis plays a vital role in the formation of overexcited networks. Recent evidence has confirmed that thrombospondin-1 (TSP-1), mainly secreted by astrocytes, is a critical cytokine that regulates synaptogenesis during epileptogenesis. Furthermore, numerous studies have reported that TSP-1 is also involved in other processes, such as angiogenesis, neuroinflammation, and regulation of Ca2+ homeostasis, which are closely associated with the occurrence and development of epilepsy. In this review, we summarize the potential contributions of TSP-1 to epilepsy development.

Platelet-derived thrombospondin 1 promotes immune cell liver infiltration and exacerbates diet-induced steatohepatitis

Background & Aims

Recent studies have implicated platelets, particularly α-granules, in the development of non-alcoholic steatohepatitis (NASH). However, the specific mechanisms involved have yet to be determined. Notably, thrombospondin 1 (TSP1) is a major component of the platelet α-granules released during platelet activation. Hence, we aimed to determine the role of platelet-derived TSP1 in NASH.

Methods

Platelet-specific Tsp1 knockout mice (TSP1Δpf4) and their wild-type littermates (TSP1F/F) were used. NASH was induced by feeding the mice with a diet enriched in fat, sucrose, fructose, and cholesterol (AMLN diet). A human liver NASH organoid model was also employed.

Results

Although TSP1 deletion in platelets did not affect diet-induced steatosis, TSP1Δpf4 mice exhibited attenuated NASH and liver fibrosis, accompanied by improvements in plasma glucose and lipid homeostasis. Furthermore, TSP1Δpf4 mice showed reduced intrahepatic platelet accumulation, activation, and chemokine production, correlating with decreased immune cell infiltration into the liver. Consequently, this diminished proinflammatory signaling in the liver, thereby mitigating the progression of NAFLD. Moreover, in vitro data revealed that co-culturing TSP1-deficient platelets in a human liver NASH organoid model attenuated hepatic stellate cell activation and NASH progression. Additionally, TSP1-deficient platelets play a role in regulating brown fat endocrine function, specifically affecting Nrg4 (neuregulin 4) production. Crosstalk between brown fat and the liver may also influence the progression of NAFLD.

Conclusions

These data suggest that platelet α-granule-derived TSP1 is a significant contributor to diet-induced NASH and fibrosis, potentially serving as a new therapeutic target for this severe liver disease.

Impact and implications

Recent studies have implicated platelets, specifically α-granules, in the development of non-alcoholic steatohepatitis, yet the precise mechanisms remain unknown. In this study, through the utilization of a tissue-specific knockout mouse model and human 3D liver organoid, we demonstrated that platelet α-granule-derived TSP1 significantly contributes to diet-induced non-alcoholic steatohepatitis and fibrosis. This contribution is, in part, attributed to the regulation of intrahepatic immune cell infiltration and potential crosstalk between fat and the liver. These findings suggest that platelet-derived TSP1 may represent a novel therapeutic target in non-alcoholic fatty liver disease.

Approaching Thrombospondin-1 as a Potential Target for Mesenchymal Stromal Cells to Support Liver Regeneration after Partial Hepatectomy in Mouse and Humans

Extended liver resection carries the risk of post-surgery liver failure involving thrombospondin-1-mediated aggravation of hepatic epithelial plasticity and function. Mesenchymal stromal cells (MSCs), by interfering with thrombospondin-1 (THBS1), counteract hepatic dysfunction, though the mechanisms involved remain unknown. Herein, two-thirds partial hepatectomy in mice increased hepatic THBS1, downstream transforming growth factor-β3, and perturbation of liver tissue homeostasis. All these events were ameliorated by hepatic transfusion of human bone marrow-derived MSCs. Treatment attenuated platelet and macrophage recruitment to the liver, both major sources of THBS1. By mitigating THBS1, MSCs muted surgery-induced tissue deterioration and dysfunction, and thus supported post-hepatectomy regeneration. After liver surgery, patients displayed increased tissue THBS1, which is associated with functional impairment and may indicate a higher risk of post-surgery complications. Since liver dysfunction involving THBS1 improves with MSC treatment in various animal models, it seems feasible to also modulate THBS1 in humans to impede post-surgery acute liver failure.

Thrombospondin 1 enhances systemic inflammation and disease severity in acute-on-chronic liver failure

BACKGROUND

The key role of thrombospondin 1 (THBS1) in the pathogenesis of acute-on-chronic liver failure (ACLF) is unclear. Here, we present a transcriptome approach to evaluate THBS1 as a potential biomarker in ACLF disease pathogenesis.

METHODS

Biobanked peripheral blood mononuclear cells (PBMCs) from 330 subjects with hepatitis B virus (HBV)-related etiologies, including HBV-ACLF, liver cirrhosis (LC), and chronic hepatitis B (CHB), and normal controls (NC) randomly selected from the Chinese Group on the Study of Severe Hepatitis B (COSSH) prospective multicenter cohort underwent transcriptome analyses (ACLF = 20; LC = 10; CHB = 10; NC = 15); the findings were externally validated in participants from COSSH cohort, an ACLF rat model and hepatocyte-specific THBS1 knockout mice.

RESULTS

THBS1 was the top significantly differentially expressed gene in the PBMC transcriptome, with the most significant upregulation in ACLF, and quantitative polymerase chain reaction (ACLF = 110; LC = 60; CHB = 60; NC = 45) was used to verify that THBS1 expression corresponded to ACLF disease severity outcome, including inflammation and hepatocellular apoptosis. THBS1 showed good predictive ability for ACLF short-term mortality, with an area under the receiver operating characteristic curve (AUROC) of 0.8438 and 0.7778 at 28 and 90 days, respectively. Enzyme-linked immunosorbent assay validation of the plasma THBS1 using an expanded COSSH cohort subjects (ACLF = 198; LC = 50; CHB = 50; NC = 50) showed significant correlation between THBS1 with ALT and γ-GT (P = 0.01), and offered a similarly good prognostication predictive ability (AUROC = 0.7445 and 0.7175) at 28 and 90 days, respectively. ACLF patients with high-risk short-term mortality were identified based on plasma THBS1 optimal cut-off value (< 28 µg/ml). External validation in ACLF rat serum and livers confirmed the functional association between THBS1, the immune response and hepatocellular apoptosis. Hepatocyte-specific THBS1 knockout improved mouse survival, significantly repressed major inflammatory cytokines, enhanced the expression of several anti-inflammatory mediators and impeded hepatocellular apoptosis.

CONCLUSIONS

THBS1 might be an ACLF disease development-related biomarker, promoting inflammatory responses and hepatocellular apoptosis, that could provide clinicians with a new molecular target for improving diagnostic and therapeutic strategies.

Effects of laparoscopic sleeve gastrectomy on nonalcoholic fatty liver disease and TGF-β signaling pathway

Nonalcoholic fatty liver disease (NAFLD) develops as a result of unhealthy lifestyle but improves with laparoscopic sleeve gastrectomy (LSG). The transforming growth factor (TGF)-β signaling pathway reportedly contributes to liver fibrosis, mainly in animal experiments. The aim of the present study was to evaluate changes in serum proteins before and after LSG by proteomic analysis and to investigate their association with NAFLD. This study enrolled 36 severely obese patients who underwent LSG at our hospital from January 2020 to April 2022. As a pilot study, proteomic analysis was conducted on six patients using serum collected before and at 6 months after LSG, and significantly fluctuating proteins were extracted. Subsequently, verification by enzyme-linked immunosorbent assay (ELISA) using collected serum was performed on the remaining 30 patients. The mean weight of enrolled patients was 118.5 kg. Proteomic analysis identified 1,912 proteins, many of which were related to the TGF-β signaling pathway. Among these proteins, we focused on five TGF-β-related proteins: asporin, EMILIN-1, platelet factor-4, serglycin, and thrombospondin-1. Verification by ELISA revealed that asporin (p = 0.006) and thrombospondin-1 (p = 0.043) levels significantly fluctuated before and after LSG. Univariate analysis with a linear regression model showed that aspartate aminotransferase (p = 0.045), asporin (p = 0.011), and thrombospondin-1 (p = 0.022) levels were significantly associated with postoperative liver fibrosis. On multivariate analysis, asporin was an independent prognostic factor for postoperative liver fibrosis (95% confidence interval: 0.114-1.291, p = 0.002). TGF-β-related proteins dramatically fluctuated before and after LSG and were correlated with NAFLD pathogenesis. Asporin may be a useful prognostic marker of liver fibrosis in NAFLD after LSG.

Targeting Thbs1 reduces bladder remodeling caused by partial bladder outlet obstruction via the FGFR3/p-FGFR3 pathway

BACKGROUND

Partial bladder outlet obstruction (pBOO) may lead to bladder remodeling, including fibrosis and extracellular matrix (ECM) deposition. Despite the extensive research on the mechanisms underlying pBOO, potential therapeutic targets for the treatment of pBOO require further research. Dysregulated expression of thrombospondin-1 (Thbs1) has been reported in various human fibrotic diseases; however, its relationship with pBOO remains unclear.

AIMS

Investigate the effects of Thbs1 on bladder remodeling caused by pBOO.

METHODS

We established a pBOO model in Sprague-Dawley rats and performed urodynamic analyses to estimate functional changes in the bladder, validated the histopathological changes in the bladder by using haematoxylin-eosin and Masson's trichrome staining, identified key target genes by integrating RNA sequencing (RNA-seq) and bioinformatics analyses, validated the expression of related factors using Western blot analysis and RT-qPCR, and used immunofluorescence staining to probe the potential interaction factors of Thbs1.

RESULTS

Urodynamic results showed that pressure-related parameters were significantly increased in rats with pBOO. Compared with the sham group, the pBOO group demonstrated significant increases in bladder morphology, bladder weight, and collagen deposition. Thbs1 was significantly upregulated in the bladder tissues of rats with pBOO, consistent with the RNA-seq data. Thbs1 upregulation led to increased expression of matrix metalloproteinase (MMP) 2, MMP9, and fibronectin (Fn) in normal human urinary tract epithelial cells (SV-HUC-1), whereas anti-Thbs1 treatment inhibited the production of these cytokines in TGF-β1-treated SV-HUC-1. Further experiments indicated that Thbs1 affected bladder remodeling in pBOO via the fibroblast growth factor receptor 3 (FGFR3) pathway.

CONCLUSIONS

Thbs1 plays a crucial role in bladder remodeling caused by pBOO. Targeting Thbs1 might alleviate ECM damage. Mechanistically, Thbs1 may function via the FGFR signaling pathway by regulating the FGFR3 receptor, identified as the most relevant disease target of pBOO, and FGF2 may be a mediator. These findings suggest that Thbs1 plays a role in BOO development and is a therapeutic target for this condition.

Myeloid-specific ablation of Basp1 ameliorates diet-induced NASH in mice by attenuating pro-inflammatory signaling

BACKGROUND AND AIMS

NASH represents a severe stage of fatty liver disease characterized by hepatocyte injury, inflammation, and liver fibrosis. Myeloid-derived innate immune cells, such as macrophages and dendritic cells, play an important role in host defense and disease pathogenesis. Despite this, the nature of transcriptomic reprogramming of myeloid cells in NASH liver and its contribution to disease progression remain incompletely defined.

APPROACH AND RESULTS

In this study, we performed bulk and single-cell RNA sequencing (sc-RNA seq) analysis to delineate the landscape of macrophage and dendritic cell transcriptomes in healthy and NASH livers. Our analysis uncovered cell type-specific patterns of transcriptomic reprogramming on diet-induced NASH. We identified brain-abundant membrane-attached signal protein 1 (Basp1) as a myeloid-enriched gene that is markedly induced in mouse and human NASH liver. Myeloid-specific inactivation of Basp1 attenuates the severity of diet-induced NASH pathologies, as shown by reduced hepatocyte injury and liver fibrosis in mice. Mechanistically, cultured macrophages lacking Basp1 exhibited a diminished response to pro-inflammatory stimuli, impaired NLRP3 inflammasome activation, and reduced cytokine secretion.

CONCLUSIONS

Together, these findings uncover Basp1 as a critical regulator of myeloid inflammatory signaling that underlies NASH pathogenesis.

Thrombospondin-1 promotes liver fibrosis by enhancing TGF-β action in hepatic stellate cells

Insulin resistance in adipose tissue is thought to be a key contributor to the pathogenesis of various metabolic disorders including metabolic dysfunction-associated steatotic liver disease/metabolic dysfunction-associated steatohepatitis (MASLD/MASH), but the mechanism underlying this contribution to MASLD/MASH has remained unknown. We previously showed that dysregulation of the PDK1-FoxO1 signaling axis in adipocytes plays a role in the development of MASLD/MASH by analysis of adipocyte-specific PDK1 knockout (A-PDK1KO) and adipocyte-specific PDK1/FoxO1 double-knockout (A-PDK1/FoxO1DKO) mice. We here focused on the role of the extracellular matrix protein thrombospondin-1 (TSP-1) as a secreted factor whose expression in adipose tissue is increased in A-PDK1KO mice and normalized in A-PDK1/FoxO1DKO mice. Genetic ablation of TSP-1 markedly ameliorated liver fibrosis in A-PDK1KO mice fed a high-fat diet. With regard to the potential mechanism of this effect, TSP-1 augmented the expression of fibrosis-related genes induced by TGF-β in LX-2 human hepatic stellate cells. We also showed that TSP-1 expression and secretion were negatively regulated by insulin signaling via the PDK1-FoxO1 axis in cultured adipocytes. Our results thus indicate that TSP-1 plays a key role in the pathogenesis of liver fibrosis in MASH. Regulation of TSP-1 expression by PDK1-FoxO1 axis in adipocytes may provide a basis for targeted therapy of hepatic fibrosis in individuals with MASH.

Nrf2 Pathway and Oxidative Stress as a Common Target for Treatment of Diabetes and Its Comorbidities

Diabetes is a chronic disease that induces many comorbidities, including cardiovascular disease, nephropathy, and liver damage. Many mechanisms have been suggested as to how diabetes leads to these comorbidities, of which increased oxidative stress in diabetic patients has been strongly implicated. Limited knowledge of antioxidative antidiabetic drugs and substances that can address diabetic comorbidities through the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway calls for detailed investigation. This review will describe how diabetes increases oxidative stress, the general impact of that oxidative stress, and how oxidative stress primarily contributes to diabetic comorbidities. It will also address how treatments for diabetes, especially focusing on their effects on the Nrf2 antioxidative pathway, have been shown to similarly affect the Nrf2 pathway of the heart, kidney, and liver systems. This review demonstrates that the Nrf2 pathway is a common pathogenic component of diabetes and its associated comorbidities, potentially identifying this pathway as a target to guide future treatments.

Microarray-based Detection of Critical Overexpressed Genes in the Progression of Hepatic Fibrosis in Non-alcoholic Fatty Liver Disease: A Protein-protein Interaction Network Analysis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a prevalent cause of chronic liver disease and encompasses a broad spectrum of disorders, including simple steatosis, steatohepatitis, fibrosis, cirrhosis, and liver cancer. However, due to the global epidemic of NAFLD, where invasive liver biopsy is the gold standard for diagnosis, it is necessary to identify a more practical method for early NAFLD diagnosis with useful therapeutic targets; as such, molecular biomarkers could most readily serve these aims. To this end, we explored the hub genes and biological pathways in fibrosis progression in NAFLD patients.

METHODS

Raw data from microarray chips with GEO accession GSE49541 were downloaded from the Gene Expression Omnibus database, and the R package (Affy and Limma) was applied to investigate differentially expressed genes (DEGs) involved in the progress of low- (mild 0-1 fibrosis score) to high- (severe 3-4 fibrosis score) fibrosis stage NAFLD patients. Subsequently, significant DEGs with pathway enrichment were analyzed, including gene ontology (GO), KEGG and Wikipathway. In order to then explore critical genes, the protein-protein interaction network (PPI) was established and visualized using the STRING database, with further analysis undertaken using Cytoscape and Gephi software. Survival analysis was undertaken to determine the overall survival of the hub genes in the progression of NAFLD to hepatocellular carcinoma.

RESULTS

A total of 311 significant genes were identified, with an expression of 278 being upregulated and 33 downregulated in the high vs. low group. Gene functional enrichment analysis of these significant genes demonstrated major involvement in extracellular matrix (ECM)-receptor interaction, protein digestion and absorption, and the AGE-RAGE signaling pathway. The PPI network was constructed with 196 nodes and 572 edges with PPI enrichment using a p-value < 1.0 e-16. Based on this cut-off, we identified 12 genes with the highest score in four centralities: Degree, Betweenness, Closeness, and Eigenvector. Those twelve hub genes were CD34, THY1, CFTR, COL3A1, COL1A1, COL1A2, SPP1, THBS1, THBS2, LUM, VCAN, and VWF. Four of these hub genes, namely CD34, VWF, SPP1, and VCAN, showed significant association with the development of hepatocellular carcinoma.

CONCLUSION

This PPI network analysis of DEGs identified critical hub genes involved in the progression of fibrosis and the biological pathways through which they exert their effects in NAFLD patients. Those 12 genes offer an excellent opportunity for further focused research to determine potential targets for therapeutic applications.

Recent Insights into the Biomarkers, Molecular Targets and Mechanisms of Non-Alcoholic Steatohepatitis-Driven Hepatocarcinogenesis

Non-alcoholic fatty liver disease (NAFLD) or metabolic dysfunction-associated steatotic liver disease (MASLD) and steatohepatitis (NASH) are chronic hepatic conditions leading to hepatocellular carcinoma (HCC) development. According to the recent "multiple-parallel-hits hypothesis", NASH could be caused by abnormal metabolism, accumulation of lipids, mitochondrial dysfunction, and oxidative and endoplasmic reticulum stresses and is found in obese and non-obese patients. Recent translational research studies have discovered new proteins and signaling pathways that are involved not only in the development of NAFLD but also in its progression to NASH, cirrhosis, and HCC. Nevertheless, the mechanisms of HCC developing from precancerous lesions have not yet been fully elucidated. Now, it is of particular importance to start research focusing on the discovery of novel molecular pathways that mediate alterations in glucose and lipid metabolism, which leads to the development of liver steatosis. The role of mTOR signaling in NASH progression to HCC has recently attracted attention. The goals of this review are (1) to highlight recent research on novel genetic and protein contributions to NAFLD/NASH; (2) to investigate how recent scientific findings might outline the process that causes NASH-associated HCC; and (3) to explore the reliable biomarkers/targets of NAFLD/NASH-associated hepatocarcinogenesis.

Integrative network-based analysis on multiple Gene Expression Omnibus datasets identifies novel immune molecular markers implicated in non-alcoholic steatohepatitis

Introduction

Non-alcoholic steatohepatitis (NASH), an advanced subtype of non-alcoholic fatty liver disease (NAFLD), has becoming the most important aetiology for end-stage liver disease, such as cirrhosis and hepatocellular carcinoma. This study were designed to explore novel genes associated with NASH.

Methods

Here, five independent Gene Expression Omnibus (GEO) datasets were combined into a single cohort and analyzed using network biology approaches.

Results

11 modules identified by weighted gene co-expression network analysis (WGCNA) showed significant association with the status of NASH. Further characterization of four gene modules of interest demonstrated that molecular pathology of NASH involves the upregulation of hub genes related to immune response, cholesterol and lipid metabolic process, extracellular matrix organization, and the downregulation of hub genes related to cellular amino acid catabolic, respectively. After DEGs enrichment analysis and module preservation analysis, the Turquoise module associated with immune response displayed a remarkably correlation with NASH status. Hub genes with high degree of connectivity in the module, including CD53, LCP1, LAPTM5, NCKAP1L, C3AR1, PLEK, FCER1G, HLA-DRA and SRGN were further verified in clinical samples and mouse model of NASH. Moreover, single-cell RNA-seq analysis showed that those key genes were expressed by distinct immune cells such as microphages, natural killer, dendritic, T and B cells. Finally, the potential transcription factors of Turquoise module were characterized, including NFKB1, STAT3, RFX5, ILF3, ELF1, SPI1, ETS1 and CEBPA, the expression of which increased with NASH progression.

Discussion

In conclusion, our integrative analysis will contribute to the understanding of NASH and may enable the development of potential biomarkers for NASH therapy.

Fibrosis-Related Gene Profiling in Liver Biopsies of PiZZ α1-Antitrypsin Children with Different Clinical Courses

PiZZ (Glu342Lys) α1-antitrypsin deficiency (AATD) is characterized by intrahepatic AAT polymerization and is a risk factor for liver disease development in children. The majority of PiZZ children are disease free, hence this mutation alone is not sufficient to cause the disease. We investigated Z-AAT polymers and the expression of fibrosis-related genes in liver tissues of PiZZ children with different clinical courses. Liver biopsies obtained during 1979-2010 at the Department of Paediatrics, Karolinska University Hospital, Sweden, were subjected to histological re-evaluation, immunohistochemistry and NanoString-based transcriptome profiling using a panel of 760 fibrosis plus 8 bile acid-related genes. Subjects were divided into three groups based on clinical outcomes: NCH (neonatal cholestasis, favourable outcome, n = 5), NCC (neonatal cholestasis, early cirrhosis and liver transplantation, n = 4), and NNCH (no neonatal cholestasis, favourable outcome, n = 5, six biopsies). Hepatocytes containing Z-AAT polymers were abundant in all groups whereas NCC showed higher expression of genes related to liver fibrosis/cirrhosis and lower expression of genes related to lipid, aldehyde/ketone, and bile acid metabolism. Z-AAT accumulation per se cannot explain the clinical outcomes of PiZZ children; however, changes in the expression of specific genes and pathways involved in lipid, fatty acid, and steroid metabolism appear to reflect the degree of liver injury.

Advances in Anti-metabolic Disease Treatments Targeting CD47

Metabolic disorders include a cluster of conditions that result from hyperglycemia, hyperlipidemia, insulin resistance, obesity, and hepatic steatosis, which cause the dysfunction of immune cells and innate cells, such as macrophages, natural killer cells, vascular endothelial cells, hepatocytes, and human kidney tubular epithelial cells. Besides targeting the derangements in lipid metabolism, therapeutic modulations to regulate abnormal responses in the immune system and innate cell dysfunctions may prove to be promising strategies in the management of metabolic diseases. In recent years, several targets have been explored for the CD47 molecule (CD47), a glycosylated protein, which was originally reported to transmit an anti-phagocytic signal known as "don't eat me" in the atherosclerotic environment, hindering the efferocytosis of immune cells and promoting arterial plaque accumulation. Subsequently, the role of CD47 has been explored in obesity, fatty liver, and lipotoxic nephropathy, and its utility as a therapeutic target has been investigated using anti-CD47 antibodies or inhibitors of the THBS1/CD47 axis and the CD47/SIRPα signaling pathway. This review summarizes the mechanisms of action of CD47 in different cell types during metabolic diseases and the clinical research progress to date, providing a reference for the comprehensive targeting of CD47 to treat metabolic diseases and the devising of potential improvements to possible side effects.

Discrete Correlation Summation Clustering Reveals Differential Regulation of Liver Metabolism by Thrombospondin-1 in Low-Fat and High-Fat Diet-Fed Mice

Thrombospondin-1 (TSP1) is a matricellular protein with many important roles in mediating carcinogenesis, fibrosis, leukocyte recruitment, and metabolism. We have previously shown a role of diet in the absence of TSP1 in liver metabolism in the context of a colorectal cancer model. However, the metabolic implications of TSP1 regulation by diet in the liver metabolism are currently understudied. Therefore Discrete correlation summation (DCS) was used to re-interrogate data and determine the metabolic alterations of TSP1 deficiency in the liver, providing new insights into the role of TSP1 in liver injury and the progression of liver pathologies such as nonalcoholic fatty liver disease (NAFLD). DCS analysis provides a straightforward approach to rank covariance and data clustering when analyzing complex data sets. Using this approach, our previous liver metabolite data was re-analyzed by comparing wild-type (WT) and Thrombospondin-1 null (Thbs1-/-) mice, identifying changes driven by genotype and diet. Principal component analysis showed clustering of animals by genotype regardless of diet, indicating that TSP1 deficiency alters metabolite handling in the liver. High-fat diet consumption significantly altered over 150 metabolites in the Thbs1-/- livers versus approximately 90 in the wild-type livers, most involved in amino acid metabolism. The absence of Thbs1 differentially regulated tryptophan and tricarboxylic acid cycle metabolites implicated in the progression of NAFLD. Overall, the lack of Thbs1 caused a significant shift in liver metabolism with potential implications for liver injury and the progression of NAFLD.

TSP1 promotes fibroblast proliferation and extracellular matrix deposition via the IL6/JAK2/STAT3 signalling pathway in keloids

Keloids are benign fibroproliferative diseases with abnormally proliferated bulges beyond the edge of the skin lesions, and they are characterized by uncontrolled fibroblast proliferation and excessive extracellular matrix deposition in the dermis. However, the definite mechanisms that increase fibroblast proliferation and collagen deposition in keloids remain unclear. Thrombospondin 1 (TSP1) has been suggested to play an important role in wound healing and fibrotic disorders, but its role in keloids is unknown. In this study, we aimed to clarify the specific role of TSP1 in keloids and explore the potential mechanism. Our results demonstrated that TSP1 was highly expressed in keloid lesions compared to normal skin. Knockdown of TSP1 in keloid fibroblasts decreased cell proliferation and collagen I deposition. Exogenous TSP1 treatment increased cell proliferation and collagen I deposition in normal fibroblasts. We further investigated the underlying mechanism and found that TSP1 promoted fibroblast proliferation and extracellular matrix deposition by upregulating the IL6/JAK2/STAT3 pathway. Moreover, we verified that TSP1 expression was positively correlated with IL6/STAT3 signalling activity in keloids. Taken together, our findings indicate that TSP1 promotes keloid development via the IL6/JAK2/STAT3 signalling pathway and blocking TSP1 may represent a potential strategy for keloid therapy.

Human Mesenchymal Stromal Cells Resolve Lipid Load in High Fat Diet-Induced Non-Alcoholic Steatohepatitis in Mice by Mitochondria Donation

Mesenchymal stromal cells (MSC) increasingly emerge as an option to ameliorate non-alcoholic steatohepatitis (NASH), a serious disease, which untreated may progress to liver cirrhosis and cancer. Before clinical translation, the mode of action of MSC needs to be established. Here, we established NASH in an immune-deficient mouse model by feeding a high fat diet. Human bone-marrow-derived MSC were delivered to the liver via intrasplenic transplantation. As verified by biochemical and image analyses, human mesenchymal stromal cells improved high-fat-diet-induced NASH in the mouse liver by decreasing hepatic lipid content and inflammation, as well as by restoring tissue homeostasis. MSC-mediated changes in gene expression indicated the switch from lipid storage to lipid utilization. It was obvious that host mouse hepatocytes harbored human mitochondria. Thus, it is feasible that resolution of NASH in mouse livers involved the donation of human mitochondria to the mouse hepatocytes. Therefore, human MSC might provide oxidative capacity for lipid breakdown followed by restoration of metabolic and tissue homeostasis.

Naltrexone protects against BDL-induced cirrhosis in Wistar rats by attenuating thrombospondin-1 and enhancing antioxidant defense system via Nrf-2

AIMS

It is well-established that thrombospondin-1 (THBS-1), vascular endothelial growth factor-A (VEGF-A), nuclear factor-erythroid 2-related factor 2 (Nrf-2), Kelch-like ECH-associated protein 1 (Keap-1), and transforming growth factor-beta 1 (TGF-β1) are the pivotal players of liver fibrosis. Recent studies have shown that endogenous opioid levels increase during liver cirrhosis. Therefore, the present study aimed to clarify the effect of naltrexone (NTX), an opioid antagonist, on the alteration of these factors following bile duct ligation (BDL)-induced liver cirrhosis.

MAIN METHODS

Wistar male rats (n = 50) were categorized equally into 5 groups (baseline, sham+saline, BDL + saline, sham+NTX (10 mg/kg of body weight (BW)), and BDL + NTX (10 mg/kg of BW)). At the end of the experiment, H&E staining was used to assess necrosis and lobular damage of hepatic tissue. The gene expression of THBS-1 and NADPH oxidase 1 (NOX-1) was measured by real time-PCR and VEGF-A, Nrf-2, Keap-1, and TGF-β1 protein levels were assessed by western blot. The antioxidant enzymes activity, total oxidant status (TOS) and MDA level were measured by commercial kits.

KEY FINDINGS

Hepatic necrosis and lobular damage increased substantially and NTX reduced them markedly in the BDL group. Gene expression of hepatic THBS-1 and NOX-1, TOS and MDA levels increased markedly in the BDL + saline group, and Nrf-2 and VEGF-A values decreased significantly in the BDL + NTX group. NTX recovered THBS-1, NOX-1 and Nrf-2 in the BDL + NTX group, substantially (p-value ≤ 0.05).

SIGNIFICANCE

Data showed that NTX treatment attenuates liver fibrosis mainly by lowering THBS-1 and NOX-1 and increasing Nrf-2 protein level and antioxidant enzymes.

Key hepatic signatures of human and mouse nonalcoholic steatohepatitis: A transcriptome-proteome data meta-analysis

BACKGROUND

Despite the global prevalence of nonalcoholic fatty liver disease (NAFLD), its pathophysiology remains unclear. In this study, we established highly confident nonalcoholic steatohepatitis (NASH) gene signatures and evaluated the pathological mechanisms underlying NASH through a systematic meta-analysis of transcriptome and proteome datasets obtained from NASH patients and mouse models.

METHODS

We analyzed NASH transcriptome datasets from 539 patients and 99 mice. A whole-liver tissue proteome dataset was used to confirm the protein level dysregulation of NASH signatures significant in both humans and mice.

RESULTS

In total, 254 human and 1,917 mouse NASH gene signatures were established. Up-regulated genes of 254 human signatures were associated with inflammation, steatosis, apoptosis, and extracellular matrix organization, whereas down-regulated genes were associated with response to metal ions and lipid and amino acid metabolism. When different mouse models were compared against humans, models with high fat and high fructose diet most closely resembled the genetic features of human NAFLD. Cross-species analysis revealed 66 genes that were concordantly dysregulated between human and mouse NASH. Among these, 14 genes were further validated to be dysregulated at the protein level. The resulting 14 genes included some of the well-established NASH associated genes and a promising NASH drug target. Functional enrichment analysis revealed that dysregulation of amino acid metabolism was the most significant hepatic perturbation in both human and mouse NASH.

CONCLUSIONS

We established the most comprehensive hepatic gene signatures for NASH in humans and mice to date. To the best of our knowledge, this is the first study to collectively analyze the common signatures between human and mouse NASH on a transcriptome-proteome scale.

Identification of a 17-gene-signature in Non-alcoholic Steatohepatitis and Its Relationship with Immune Cell Infiltration

Background: Non-alcoholic steatohepatitis (NASH) is a risk factor for hepatocellular carcinoma, but the understanding of the regulatory mechanisms driving NASH is not comprehensive. Objectives: We aimed to identify the potential markers of NASH and explore their relationship with immune cell populations. Methods: Five gene expression datasets for NASH were downloaded from the Gene Expression Omnibus and European Bioinformatics Institute Array Express databases. Differentially expressed genes (DEGs) between NASH and controls were screened. Gene Ontology-Biological Process (GO-BP) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed for functional enrichment analysis of DEGs. Among the candidate genes selected from the protein-protein interaction (PPI) network and module analysis, DEG signatures were further identified using least absolute shrinkage and selection operator regression analysis. The Spearman correlation coefficient was calculated to assess the correlation between DEG signatures and immune cell abundance based on the CIBERSORT algorithm. Results: We screened 403 upregulated, and 158 downregulated DEGs for NASH, and they were mainly enriched in GO-BP, including the inflammatory response, innate immune response, signal transduction, and KEGG pathways, such as the pathways involved in cancer (e.g., the PI3K-Akt signaling pathway), and focal adhesion. We then screened 73 candidate genes from the PPI network and module analysis and finally identified 17 DEG signatures. By evaluating their relationship with immune cell populations, 12 DEG signatures were found to correlate with activated dendritic cells, resting dendritic cells, M2 macrophages, monocytes, neutrophils, and resting memory CD4 T cells, which were significantly different between the NASH and control tissues. Conclusions: We identified a 17-DEG-signature as a candidate biomarker for NASH and analyzed its relationship with immune infiltration in NASH.

Antiangiogenic Drugs in NASH: Evidence of a Possible New Therapeutic Approach

Non-alcoholic fatty liver disease is the most common liver disorder worldwide, and its progressive form non-alcoholic steatohepatitis (NASH) is a growing cause of liver cirrhosis and hepatocellular carcinoma (HCC). Lifestyle changes, which are capable of improving the prognosis, are hard to achieve, whereas a pharmacologic therapy able to combine efficacy and safety is still lacking. Looking at the pathophysiology of various liver diseases, such as NASH, fibrosis, cirrhosis, and HCC, the process of angiogenesis is a key mechanism influencing the disease progression. The relationship between the worsening of chronic liver disease and angiogenesis may suggest a possible use of drugs with antiangiogenic activity as a tool to stop or slow the progression of the disorder. In this review, we highlight the available preclinical data supporting a role of known antiangiogenic drugs (e.g., sorafenib), or phytotherapeutic compounds with multiple mechanism of actions, including also antiangiogenic activities (e.g., berberine), in the treatment of NASH.

Circulating Thrombospondin-2 as a Novel Fibrosis Biomarker of Nonalcoholic Fatty Liver Disease in Type 2 Diabetes

OBJECTIVE

Preclinical studies have suggested that thrombospondin-2 (TSP2) is implicated in liver fibrosis. However, the clinical relevance of TSP2 in nonalcoholic fatty liver disease (NAFLD) remains undefined. Here, we investigated the cross-sectional and longitudinal associations of circulating TSP2 levels with advanced fibrosis (F3 or greater [≥FE] fibrosis) in NAFLD.

RESEARCH DESIGN AND METHODS

Serum TSP2 levels were measured in 820 patients with type 2 diabetes and NAFLD. All participants received vibration-controlled transient elastography (VCTE) at baseline to evaluate their hepatic steatosis and fibrosis using controlled attenuation parameter (CAP) and liver stiffness (LS) measurements, respectively. Among those without advanced fibrosis at baseline, reassessment VCTE was performed to determine whether ≥F3 fibrosis had developed over time. Multivariable logistic regression analysis was used to evaluate the cross-sectional and longitudinal associations of serum TSP2 level with ≥F3 fibrosis.

RESULTS

Baseline serum TSP2 level was independently associated with the presence of ≥F3 fibrosis (odds ratio [OR] 5.13, P < 0.001). The inclusion of serum TSP2 level significantly improved the identification of ≥F3 fibrosis by clinical risk factors. Over a median follow-up of 1.5 years, 8.8% developed ≥F3 fibrosis. Baseline serum TSP2 level was significantly associated with incident ≥F3 fibrosis (OR 2.82, P = 0.005), independent of other significant clinical risk factors of fibrosis progression, including BMI, platelet count, and CAP at baseline.

CONCLUSIONS

Circulating TSP2 level was associated with both the presence and the development of advanced fibrosis and might be a potentially useful prognostic biomarker for the development and progression of liver fibrosis in patients with type 2 diabetes and NAFLD.

A unique esophageal extracellular matrix proteome alters normal fibroblast function in severe eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is a chronic TH2 disorder complicated by tissue fibrosis and loss of esophageal luminal patency. The fibrostenotic esophagus does not respond well to therapy, but profibrotic therapeutic targets are largely unclear.

OBJECTIVE

Our aim was to utilize proteomics and primary cells as a novel approach to determine relevant profibrotic factors.

METHODS

We utilized primary esophageal EoE and normal fibroblasts, their derivative extracellular matrixes (ECMs), an approach of fibroblast culture on autologous versus nonautologous ECM, and proteomics to elucidate EoE ECM proteins that dysregulate cellular function.

RESULTS

We cultured esophageal fibroblasts from normal esophagi and esophagi from patients with severe EoE on autologous versus nonautologous ECM. The EoE ECM proteome shifted normal esophageal fibroblast protein expression. Proteomic analysis demonstrated that thrombospondin-1 is detected only in the EoE ECM, is central in the EoE ECM protein-protein interactome, is found at significantly elevated levels in biopsy specimens from patients with active EoE, and induces fibroblast collagen I production.

CONCLUSION

Fibroblasts from patients with EoE secrete a unique ECM proteome that reflects their in vivo state and induces collagen I and α-smooth muscle actin protein expression from normal fibroblasts. Thrombospondin-1 is a previously unappreciated profibrotic molecule in EoE.

MicroRNA Sequences Modulated by Beta Cell Lipid Metabolism: Implications for Type 2 Diabetes Mellitus

Alterations in lipid metabolism within beta cells and islets contributes to dysfunction and apoptosis of beta cells, leading to loss of insulin secretion and the onset of type 2 diabetes. Over the last decade, there has been an explosion of interest in understanding the landscape of gene expression which influences beta cell function, including the importance of small non-coding microRNA sequences in this context. This review sought to identify the microRNA sequences regulated by metabolic challenges in beta cells and islets, their targets, highlight their function and assess their possible relevance as biomarkers of disease progression in diabetic individuals. Predictive analysis was used to explore networks of genes targeted by these microRNA sequences, which may offer new therapeutic strategies to protect beta cell function and delay the onset of type 2 diabetes.

CD47 and thrombospondin-1 regulation of mitochondria, metabolism, and diabetes

Thrombospondin-1 (TSP1) is the prototypical member of a family of secreted proteins that modulate cell behavior by engaging with molecules in the extracellular matrix and with receptors on the cell surface. CD47 is widely displayed on many, if not all, cell types and is a high-affinity TSP1 receptor. CD47 is a marker of self that limits innate immune cell activities, a feature recently exploited to enhance cancer immunotherapy. Another major role for CD47 in health and disease is to mediate TSP1 signaling. TSP1 acting through CD47 contributes to mitochondrial, metabolic, and endocrine dysfunction. Studies in animal models found that elevated TSP1 expression, acting in part through CD47, causes mitochondrial and metabolic dysfunction. Clinical studies established that abnormal TSP1 expression positively correlates with obesity, fatty liver disease, and diabetes. The unabated increase in these conditions worldwide and the availability of CD47 targeting drugs justify a closer look into how TSP1 and CD47 disrupt metabolic balance and the potential for therapeutic intervention.

Serum thrombospondin 2 is a novel predictor for the severity in the patients with NAFLD

AIM

Thrombospondins are a family of multidomain and secretory glycoproteins. Among them, thrombospondin 2 (TSP2) encoded by TSP2 gene has been reported to be involved in various functions such as collagen/fibrin formation, maintenance of normal blood vessel density and cell adhesion properties. Microarray analyses ranked TSP2 as one of the most highly up-regulated genes in the fibrotic liver in patients with non-alcoholic fatty liver disease (NAFLD). Since TSP2 possesses unique properties as a secretory protein, we hypothesized that hepatic TSP2 gene expression levels would be reflected in serum TSP2 levels. In this study, we examined the relationship between serum TSP2 concentrations and clinicopathological findings in NAFLD patients.

METHODS

One hundred and thirty NAFLD patients who had undergone liver biopsy between 2009 and 2015 were retrospectively enrolled. Serum samples were collected at the time of biopsy, and TSP2 was measured by enzyme immunoassays.

RESULTS

Serum TSP2 levels moderately correlated with ballooning (r = 0.56, P < .001) and fibrosis stage (r = 0.53, P < .001). The AUC values of TSP2 for predicting mild fibrosis (≧F1), moderate fibrosis (≧F2) and severe fibrosis (≧F3) were 0.73, 0.76 and 0.82 respectively. Additionally, NAFLD activity score (NAS) correlated best with TSP2 (r = 0.52, P < .001) compared to conventional NAFLD-related biomarkers, such as cytokeratin 18 M30, hyaluronic acid, type IV collagen 7S, APRI and FIB-4 index.

CONCLUSION

Serum TSP2 levels reflected hepatocyte ballooning, fibrosis and NAS in NAFLD patients. For clinical application of serum TSP2 as a predictor of NAFLD histological activity, additional validation and mechanistic investigations are required.

Comparative Transcriptomics Analyses in Livers of Mice, Humans, and Humanized Mice Define Human-Specific Gene Networks

Mouse is the most widely used animal model in biomedical research, but it remains unknown what causes the large number of differentially regulated genes between human and mouse livers identified in recent years. In this report, we aim to determine whether these divergent gene regulations are primarily caused by environmental factors or some of them are the result of cell-autonomous differences in gene regulation in human and mouse liver cells. The latter scenario would suggest that many human genes are subject to human-specific regulation and can only be adequately studied in a human or humanized system. To understand the similarity and divergence of gene regulation between human and mouse livers, we performed stepwise comparative analyses in human, mouse, and humanized livers with increased stringency to gradually remove the impact of factors external to liver cells, and used bioinformatics approaches to retrieve gene networks to ascertain the regulated biological processes. We first compared liver gene regulation by fatty liver disease in human and mouse under the condition where the impact of genetic and gender biases was minimized, and identified over 50% of all commonly regulated genes, that exhibit opposite regulation by fatty liver disease in human and mouse. We subsequently performed more stringent comparisons when a single specific transcriptional or post-transcriptional event was modulated in vitro or vivo or in liver-specific humanized mice in which human and mouse hepatocytes colocalize and share a common circulation. Intriguingly and strikingly, the pattern of a high percentage of oppositely regulated genes persists under well-matched conditions, even in the liver of the humanized mouse model, which represents the most closely matched in vivo condition for human and mouse liver cells that is experimentally achievable. Gene network analyses further corroborated the results of oppositely regulated genes and revealed substantial differences in regulated biological processes in human and mouse cells. We also identified a list of regulated lncRNAs that exhibit very limited conservation and could contribute to these differential gene regulations. Our data support that cell-autonomous differences in gene regulation might contribute substantially to the divergent gene regulation between human and mouse livers and there are a significant number of biological processes that are subject to human-specific regulation and need to be carefully considered in the process of mouse to human translation.

Macrophage-derived thrombospondin 1 promotes obesity-associated non-alcoholic fatty liver disease

Background & Aims

Thrombospondin 1 (TSP1) is a multifunctional matricellular protein. We previously showed that TSP1 has an important role in obesity-associated metabolic complications, including inflammation, insulin resistance, cardiovascular, and renal disease. However, its contribution to obesity-associated non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD or NASH) remains largely unknown; thus, we aimed to determine its role.

Methods

High-fat diet or AMLN (amylin liver NASH) diet-induced obese and insulin-resistant NAFLD/NASH mouse models were utilised, in addition to tissue-specific Tsp1-knockout mice, to determine the contribution of different cellular sources of obesity-induced TSP1 to NAFLD/NASH development.

Results

Liver TSP1 levels were increased in experimental obese and insulin-resistant NAFLD/NASH mouse models as well as in obese patients with NASH. Moreover, TSP1 deletion in adipocytes did not protect mice from diet-induced NAFLD/NASH. However, myeloid/macrophage-specific TSP1 deletion protected mice against obesity-associated liver injury, accompanied by reduced liver inflammation and fibrosis. Importantly, this protection was independent of the levels of obesity and hepatic steatosis. Mechanistically, through an autocrine effect, macrophage-derived TSP1 suppressed Smpdl3b expression in liver, which amplified liver proinflammatory signalling (Toll-like receptor 4 signal pathway) and promoted NAFLD progression.

Conclusions

Macrophage-derived TSP1 is a significant contributor to obesity-associated NAFLD/NASH development and progression and could serve as a therapeutic target for this disease.

Lay summary

Obesity-associated non-alcoholic fatty liver disease is a most common chronic liver disease in the Western world and can progress to liver cirrhosis and cancer. No treatment is currently available for this disease. The present study reveals an important factor (macrophage-derived TSP1) that drives macrophage activation and non-alcoholic fatty liver disease development and progression and that could serve as a therapeutic target for non-alcoholic fatty liver disease/steatohepatitis.

Animal Models of Fibrosis in Nonalcoholic Steatohepatitis: Do They Reflect Human Disease?

Nonalcoholic steatohepatitis (NASH) is one of the most common chronic liver diseases in the world, yet no pharmacotherapies are available. The lack of translational animal models is a major barrier impeding elucidation of disease mechanisms and drug development. Multiple preclinical models of NASH have been proposed and can broadly be characterized as diet-induced, deficiency-induced, toxin-induced, genetically induced, or a combination of these. However, very few models develop advanced fibrosis while still reflecting human disease etiology or pathology, which is problematic since fibrosis stage is considered the best prognostic marker in patients and an important endpoint in clinical trials of NASH. While mice and rats predominate the NASH research, several other species have emerged as promising models. This review critically evaluates animal models of NASH, focusing on their ability to develop advanced fibrosis while maintaining their relevance to the human condition.