Reactivation of PPARαalleviates myocardial lipid accumulation and cardiac dysfunction by improving fatty acidβ-oxidation in Dsg2-deficient arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy(ACM),a fatal heart disease characterized by fibroadipocytic replacement of cardiac myocytes,accounts for 20%of sudden cardiac death and lacks effective treatment.It is often caused by mutations in desmosome proteins,with Desmoglein-2(DSG2)mutations as a common etiology.However,the mechanism underlying the accumulation of fibrofatty in ACM remains unknown,which impedes the development of curative treatment.Here we investigated the fat accumulation and the underlying mechanism in a mouse model of ACM induced by cardiac-specific knockout of Dsg2(CS-Dsg2^(-/-)).Heart failure and cardiac lipid accumulation were observed in CSDsg2^(-/-)mice.We demonstrated that these phenotypes were caused by decline of fatty acid(FA)β-oxidation resulted from impaired mammalian target of rapamycin(m TOR)signaling.Rapamycin worsened while overexpression of m TOR and 4EBP1 rescued the FAβ-oxidation pathway in CS-Dsg2^(-/-)mice.Reactivation of PPARa by fenofibrate or AAV9-Ppara significantly alleviated the lipid accumulation and restored cardiac function.Our results suggest that impaired m TOR-4EBP1-PPARa-dependent FAβ-oxidation contributes to myocardial lipid accumulation in ACM and PPARa may be a potential target for curative treatment of ACM.

Integrative analysis of bulk and single-cell RNA sequencing data reveals distinct subtypes of MAFLD based on N1-methyladenosine regulator expression

Background:Metabolic dysfunction-associated fatty liver disease(MAFLD)is now the most prevalent chronic liver disease worldwide,with an increasing incidence rate.MAFLD is a heterogeneous disease that can have a low or high-risk profile for developing severe liver disease in its natural course.Recent evidence has highlighted the critical role of RNA methylation modification in the pathogenesis of various liver diseases.However,it remains unclear whether the RNA N1-methyladenosine(m1A)modification of immune cells could potentially contribute to the pathogenesis and heterogeneity of MAFLD.Materials and methods:To address this issue,we conducted an integrated bioinformatics analysis of MAFLD bulk and single-cell RNA sequencing(scRNA-seq)data to pinpoint m1A regulators in the network.This was followed by a description of the immune landscape,pathway enrichment analysis,and molecular subtyping.Results:The expression patterns of m1A regulatory genes stratify MAFLD into two molecular subtypes,Cluster 1 and Cluster 2.These subtypes demonstrate different immune cell infiltration with distinct inflammation characteristics,which suggest different immune-inflammatory responses in the liver.Notably,Cluster 2 is associated with pro-inflammation and may be more likely to lead to progressive stages of MAFLD.Through intersection analysis of weighted gene co-expression network analysis(WGCNA)and m1A regulatory genes,three true hub genes(ALKBH1,YTHDC1,and YTHDF3)were identified,all of which were strongly correlated with infiltrating immune cells.The specific signaling pathways involved in the three core genes were derived from genomic variation analysis.Furthermore,scRNA-seq data from 33,168 cells from six liver samples identified 26 cell clusters and eight cell types,with endothelial cells,macrophages,and monocytes showing the most significant differences between MAFLD and normal controls.The cell-cell communication network between immune cells and nonparenchymal cells was extremely sophisticated and changed significantly in MAFLD.Conclusions:In summary,these findings demonstrate the involvement of m1A in MAFLD heterogeneity and emphasize the crucial role of m1A modulation of immune cells in regulating inflammation in MAFLD.These results may suggest potential therapeutic strategies for MAFLD.

Hepatocyte nuclear factor 1A suppresses innate immune response by inducing degradation of TBK1 to inhibit steatohepatitis

Non-alcoholic steatohepatitis(NASH),a progressive form of non-alcoholic fatty liver disease(NAFLD),is characterised by chronic liver inflammation,which can further prog-ress into complications such as liver cirrhosis and NASH-associated hepatocellular carcinoma(HCC)and therefore has become a growing health problem worldwide.The type I interferon(IFN)signaling pathway plays a pivotal role in chronic inflammation;however,the molecular mechanisms underlying NAFLD/NASH from the perspective of innate immune response has not yet been fully explored.In this study,we elucidated the mechanisms of how innate im-mune response modulates NAFLD/NASH pathogenesis,and demonstrated that hepatocyte nu-clear factor-1alpha(HNF1A)was suppressed and the typeⅠIFN production pathway was activated in liver tissues of patients with NAFLD/NASH.Further experiments suggested that HNF1A negatively regulates the TBK1-IRF3 signaling pathway by promoting autophagic degra-dation of phosphorylated-TBK1,which constrains IFN production,thereby inhibiting the activa-tion of type I IFN signaling.Mechanistically,HNF1A interacts with the phagophore membrane protein LC3 through its LIR-docking sites,and mutations of LIRs(LIR2,LIR3,LIR4,and LIRs)block the HNF1A-LC3 interaction.In addition,HNF1A was identified not only as a novel autop-hagic cargo receptor but also to specifically induce K33-linked ubiquitin chains on TBK1 at Lys670,thereby resulting in autophagic degradation of TBK1.Collectively,our study illustrates the crucial function of the HNF1A-TBK1 signaling axis in NAFLD/NASH pathogenesis via cross-talk between autophagy and innate immunity.

Human mesenchymal stromal cells enhance the immunomodulatory function of CD8＋CD28- regulatory T cells

One important aspect of mesenchymal stromal cells （MSCs）-mediated immunomodulation is the recruitment and induction of regulatory T （Treg） cells. However, we do not yet know whether MSCs have similar effects on the other subsets of Treg cells. Herein, we studied the effects of MSCs on CD8＋CD28- Treg cells and found that the MSCs could not only increase the proportion of CD8＋CD28- T cells, but also enhance CD8＋CD28-T cells＇ ability of hampering naive CD4＋ T-cell proliferation and activation, decreasing the production of IFN-γ by activated CD4＋ T cells and inducing the apoptosis of activated CD4＋ T cells. Mechanistically, the MSCs affected the functions of the CD8＋CD28- T cells partially through moderate upregulating the expression of IL-10 and FasL. The MSCs had no distinct effect on the shift from CD8＋CD28＋ T cells to CD8＋CD28- T cells, but did increase the proportion of CD8＋CD28- T cells by reducing their rate of apoptosis. In summary, this study shows that MSCs can enhance the regulatory function of CD8＋CD28- Treg cells, shedding new light on MSCs-mediated immune regulation.

The mechanisms of nucleotide actions in insulin resistance

Insulin resistance contributes to metabolic disorders in obesity and type 2 diabetes.In mechanisms of insulin resistance,the roles of glucose,fatty acids,and amino acids have been extensively documented in literature.However,the activities of nucleotides remain to be reviewed comprehensively in the regulation of insulin sensitivity.Nucleotides are well known for their activities in biosynthesis of DNA and RNA as well as their signaling activities in the form of c AMP and c GAMP.Their activities in insulin resistance are dependent on the derivatives and corresponding receptors.ATP and NADH,derivatives of adenosine,inhibit insulin signaling inside cells by downregulation of activities of AMPK and SIRT1,respectively.ATP,ADP and AMP,the well-known energy carriers,regulate cellular responses to insulin outside cells through the purinergic receptors in cell surface.Current evidence suggests that ATP,NADH,c GAMP,and uridine are potential biomarkers of insulin resistance.However,GTP and c GMP are likely the markers of insulin sensitization.Here,studies crossing the biomedical fields are reviewed to characterize nucleotide activities in the regulation of insulin sensitivity.The knowledge brings new insights into the mechanisms of insulin resistance.

The functional analysis of transiently upregulated miR-101 suggests a “braking” regulatory mechanism during myogenesis

Skeletal muscle differentiation is a highly coordinated process that involves many cellular signaling pathways and microRNAs(miRNAs).A group of muscle-specific miRNAs has been reported to promote myogenesis by suppressing key signaling pathways for cell growth.However,the functional role and regulatory mechanism of most non-muscle-specific miRNAs with stage-specific changes during differentiation are largely unclear.Here,we describe the functional characterization of miR-101a/b,a pair of non-muscle-specific miRNAs that show the largest change among a group of transiently upregulated miRNAs during myogenesis in C2C12 cells.The overexpression of miR-101a/b inhibits myoblast differentiation by suppressing the p38/MAPK,Interferon Gamma,and Wnt pathways and enhancing the C/EBP pathway.Mef2a,a key protein in the p38/MAPK pathway,was identified as a direct target of miR-101a/b.Interestingly,we found that the long non-coding RNA(lncRNA)Malat1,which promotes muscle differentiation,interacts with miR-101a/b,and this interaction competes with Mef2a mRNA to relieve the inhibition of the p38/MAPK pathway during myogenesis.These results uncovered a“braking”role in differentiation of transiently upregulated miRNAs and provided new insights into the competing endogenous RNA(ceRNA)regulatory mechanism in myoblast differentiation and myogenesis.

The clinical implication of gamma-glutamyl transpeptidase in COVID-19

Background and aim:Coronavirus disease 2019(COVID-19)is a life-threatening disease that predomi-nantly causes respiratory failure.The impact of COVID-19 on other organs remains elusive.Herein,we aimed to investigate the effects of COVID-19 on the hepatobiliary system.Methods:In the current study,we obtained the clinical records and laboratory results from 66 laboratory-confirmed patients with COVID-19 at the Wuhan Tongji Hospital between 10 February 2020 and 28 February 2020.The detailed clinical features and laboratory findings were collected for analysis.Bioinformatics analysis was conducted to evaluate the correlation between gamma-glutamyl transferase(GGT)and severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)entry receptor angiotensin-converting enzyme 2(ACE2).Results:In this cohort,30(51.7%)patients had abnormal liver function on admission,which was asso-ciated with disease severity and enriched in the male and diabetic patients.The elevated levels of direct bilirubin(P¼0.029)and GGT(P¼0.004)were common in patients with severe pneumonia when compared with those with mild pneumonia.In addition,elevated levels of GGT(P¼0.003)and aspartate aminotransferase(AST)(P¼0.007)were positively associated with longer hospital stay.The expression of ACE2 was closely associated with GGT in various human tissues because they shared the common transcriptional regulator hepatic nuclear factor-1 b(HNF1B).Conclusions:Increased GGT levels were common in severe cases and elevated GGT levels were positively associated with prolonged hospital stay and disease severity.Due to the consistent expression with ACE2,GGT is a potent biomarker indicating the susceptibility of SARS-CoV-2 infection.

MUTYH is a potential prognostic biomarker and correlates with immune infiltrates in hepatocellular carcinoma

Background:Hepatocellular carcinoma(HCC)is a leading cause of cancer-related death worldwide.The development of biomarkers for early detection and monitoring of HCC has not shown significant prog-ress.Meanwhile,the second adenomatous polyposis-related gene,MUTYH,which encodes a DNA gly-cosylase,has been observed in its contribution to oxidative DNA damage repair.Abnormal expression of MUTYH can reduce cell survival rate.Therefore,this study investigated the usefulness of MUTYH in diagnosing and prognosis HCC.Materials and methods:Using The Cancer Genome Atlas(TCGA)data,we analyzed the prognostic value of MUTYH in HCC.We used logistic regression,Wilcoxon signed-rank test,and KruskaleWallis test to examine MUTYH expression concerning clinical-pathologic characteristics.Univariate and multivariate Cox regression methods and Kaplan-Meier analysis were applied to determine the related prognostic factors of HCC.The enrichment analysis(GSEA)was used to determine the critical pathways associated with MUTYH.The single-sample gene set enrichment analysis(ssGSEA)was conducted to examine the correlation between MUTYH expression and cancer immune infiltration.Results:The higher expression of MUTYH in HCC patients was associated with a poorer overall survival rate and a shorter disease-specific survival rate.The Kyoto Encyclopedia of Genes and Genomes(KEGG)analysis showed that all differentially expressed genes(DEGs)between the high and low expression levels of MUTYH significantly enriched in the trace ligand-receptor interaction,cell cycle,oocyte meiosis,gap junction,and DNA replication.Group analysis revealed the signals of their open access.The neuron system,M phase,DNA repair,Rho GTPase effector,and cell cycle checkpoints were significantly enriched.ssGSEA showed a positive correlation between MUTYH expression and the infiltration levels of Th2 cells,NK cells,and T helper cells.Moreover,a negative correlation was found between MUTYH expression and the infiltration levels of dendritic cells(DCs)and cytotoxic cells.Conclusions:MUTYH expression levels were positively correlated with immune checkpoint gene expression levels in HCC tissues.The expression level of MUTYH was related to the prognosis of HCC and the immune infiltration of HCC.

Glycogen accumulation drives hepatocarcinogenesis by targeting the Hippo signaling pathway

Recent advances highlight accelerated glucose metabolism as one of the hallmarks of cancer cells.Normal differentiated cells usually utilize the process of mitochondrial oxidative phosphorylation to metabolize glucose into carbon dioxide(CO_(2))and adenosine triphosphate(ATP).However,the cancer cell preferentially takes advantage of aerobic glycolysis to generate lactate and ATP to support the high energy demand for rapid cancer cell proliferation even in the presence of sufficient oxygen.1 This intriguing observation was first reported by the German physiologist Otto Warburg,and thus,this process is termed“the Warburg effect”.

Mesenchymal stem cells for treatment of steroid-resistant acute rejection after liver transplantation

A patient with steroid-resistant acute rejection 50 days after ABO-compatible orthotopic liver transplantation(LT)received regular infusion of allogeneic mesenchymal stem cells(MSCs)after three sessions of steroid pulse therapy which failed to control the pathogenetic condition as shown by biopsy.Liver function improved gradually after intravenous injection of MSCs once weekly for 10 weeks(as confirmed by biopsy)and remained stable under administration of conventional immunosuppressive agents.There was no evidence of neoplasms 5 years after treatment.MSCs infusion appears to successfully reverse resistance to immunosuppressive agents and may be a useful treatment for post-liver transplant steroid-resistant rejection.

Mechanical regulation of lipid and sugar absorption by Piezo1 in enterocytes

Obesity is primarily caused by excessive intake as well as absorption of sugar and lipid.Postprandial surge in distention pressure and intestinal motility accelerates the absorption of nutrients.The response of intestinal epithelial cells to mechanical stimulation is not fully understood.Piezo1,a mechanosensitive ion channel,is widely expressed throughout the digestive tract.However,its function in intestinal nutrient absorption is not yet clear.In our study,excessive lipid deposition was observed in the duodenum of obese patients,while duodenal Piezo1-CaMKK2-AMPKa was decreased when compared to normal-weight individuals.Under high-fat diet condition,the Piezo1iKO mice exhibited abnormally elevated sugar and lipid absorption as well as severe lipid deposition in the duodenum and liver.These phenotypes were mainly caused by the inhibition of duodenal CaMKK2-AMPKa and the upregulation of SGLT1 and DGAT2.In contrast,Yoda1,a Piezo1 agonist,was found to reduce intestinal lipid absorption in diet induced obese mice.Overexpression of Piezo1,stretch and Yoda1 inhibited lipid accumulation and the expression of DGAT2 and SGLT1,whereas knockdown of Piezo1 stimulated lipid accumulation and DGAT2 in Caco-2 cells.Our study reveals a previously unexplored mechanical regulation of nutrient absorption in intestinal epithelial cells,which may shed new light on the therapy of obesity.