Search

Approaches to manage nonalcoholic fatty liver disease (NAFLD) are limited by an incomplete understanding of disease pathogenesis. The aim of this study was to identify hepatic gene-expression patterns associated with different patterns of liver injury in a high-risk cohort of adults with obesity. Using the NanoString Technologies (Seattle, WA) nCounter assay, we quantified expression of 795 genes, hypothesized to be involved in hepatic fibrosis, inflammation, and steatosis, in liver tissue from 318 adults with obesity. Liver specimens were categorized into four distinct NAFLD phenotypes: normal liver histology (NLH), steatosis only (steatosis), nonalcoholic steatohepatitis without fibrosis (NASH F0), and NASH with fibrosis stage 1-4 (NASH F1-F4). One hundred twenty-five genes were significantly increasing or decreasing as NAFLD pathology progressed. Compared with NLH, NASH F0 was characterized by increased inflammatory gene expression, such as gamma-interferon-inducible lysosomal thiol reductase (IFI30) and chemokine (C-X-C motif) ligand 9 (CXCL9), while complement and coagulation related genes, such as C9 and complement component 4 binding protein beta (C4BPB), were reduced. In the presence of NASH F1-F4, extracellular matrix degrading proteinases and profibrotic/scar deposition genes, such as collagens and transforming growth factor beta 1 (TGFB1), were simultaneously increased, suggesting a dynamic state of tissue remodeling. Conclusion: In adults with obesity, distinct states of NAFLD are associated with intrahepatic perturbations in genes related to inflammation, complement and coagulation pathways, and tissue remodeling. These data provide insights into the dynamic pathogenesis of NAFLD in high-risk individuals.

T cell exhaustion is associated with failure to clear chronic infections and malignant cells. Defining the molecular mechanisms of T cell exhaustion and reinvigoration is essential to improving immunotherapeutic modalities. Here we confirmed pervasive phenotypic, functional and transcriptional differences between memory and exhausted antigen-specific CD8+ T cells in human hepatitis C virus (HCV) infection before and after treatment. After viral cure, phenotypic changes in clonally stable exhausted T cell populations suggested differentiation toward a memory-like profile. However, functionally, the cells showed little improvement, and critical transcriptional regulators remained in the exhaustion state. Notably, T cells from chronic HCV infection that were exposed to antigen for less time because of viral escape mutations were functionally and transcriptionally more similar to memory T cells from spontaneously resolved HCV infection. Thus, the duration of T cell stimulation impacts exhaustion recovery, with antigen removal after long-term exhaustion being insufficient for the development of functional T cell memory. Lauer and colleagues examine CD8+ T cells following cure of human hepatitis C virus (HCV) infection. CD8+ T cells exposed to chronic HCV-specific activation show durable functional, phenotypic and transcriptional exhaustion that is maintained even after antigen stimulus is removed.

T cells play an important role to build up an effective immune response and are essential in the eradication of pathogens. To establish a long-lasting protection even after a re-challenge with the same pathogen, some T cells differentiate into memory T cells. Recently, a certain subpopulation of memory T cells at different tissue-sites of infection was detected—tissue-resident memory T cells (TRM cells). These cells can patrol in the tissue in order to encounter their cognate antigen to establish an effective protection against secondary infection. The liver as an immunogenic organ is exposed to a variety of pathogens entering the liver through the systemic blood circulation or via the portal vein from the gut. It could be shown that intrahepatic TRM cells can reside within the liver tissue for several years. Interestingly, hepatic TRM cell differentiation requires a distinct cytokine milieu. In addition, TRM cells express specific surface markers and transcription factors, which allow their identification delimited from their circulating counterparts. It could be demonstrated that liver TRM cells play a particular role in many liver diseases such as hepatitis B and C infection, non-alcoholic fatty liver disease and even play a role in the development of hepatocellular carcinoma and in building long-lasting immune responses after vaccination. A better understanding of intrahepatic TRM cells is critical to understand the pathophysiology of many liver diseases and to identify new potential drug targets for the development of novel treatment strategies.

Both acute and chronic hepatic inflammation likely result from an imbalance in the TH1/TH2 cell response and can lead to liver fibrosis and end-stage liver disease. More recently, a novel CD4+ T helper cell subset was described, characterized by the production of IL-17 and IL-22. These TH17 cells 50were predominantly implicated in host defense against infections and in autoimmune diseases. Interestingly, studies over the last 10 years revealed that the development of TH17 cells favors pro-inflammatory responses in almost all tissues and there is a reciprocal relationship between TH17 and TReg cells. The balance between TH17and TReg cells is critical for immune reactions, especially in injured liver tissue and the return to immune homeostasis. The pathogenic contribution of TH17 and TReg cells in autoimmunity, acute infection, and chronic liver injury is diverse and varies among disease etiologies. Understanding the mechanisms underlying TH17 cell development, recruitment, and maintenance, along with the suppression of TReg cells, will inform the development of new therapeutic strategies in liver diseases. Active manipulation of the balance between pathogenic and regulatory processes in the liver may assist in the restoration of homeostasis, especially in hepatic inflammation.

Background: Obesity is a state of relative growth hormone (GH) and insulin-like growth factor-1 (IGF-1) deficiency, and the GH/IGF-1 axis has been implicated in the pathophysiology of nonalcoholic fatty liver disease (NAFLD) and the progression to steatohepatitis (NASH) in preclinical models and human studies. GH has both lipolytic and anti-inflammatory properties while IGF-1 has been implicated in reducing hepatic fibrosis and promoting hepatic regeneration. The GH/IGF-1 axis may be a therapeutic target in NAFLD/NASH, however, IGF-1, IGF-1 receptor (IGF-1R) and GH receptor (GHR) expression in adult human hepatic tissue has not been studied across the spectrum of disease severity. Methods: We quantified IGF-1, IGF-1R, and GHR gene expression in hepatic tissue from 318 adults with obesity using the Nanostring nCounter assay. Subjects were classified into four categories of disease severity based on histopathology: normal liver histology (NLH) (n=76, 24%), steatosis only (Steatosis) (n=88, 28%), NASH without fibrosis (NASH F0) (n=72, 23%), and NASH with fibrosis (NASH F1-F4) (n=82, 26%). Gene expression analysis is presented as normalized gene counts by group with p-value of the generalized linear model controlled for age, sex and BMI. Results: Mean (±SD) age (whole cohort 44.0±12 years) and BMI (whole cohort 46.8±7.2 kg/m2) did not differ across groups (p=0.2 for both). ALT was higher with increasing disease severity (NLH 30.1±26.7, Steatosis 31.9±15.7, NASH F0 35.7±16.5, NASH F1-4 48.4±34.9, p0.05 between any disease state; GHR NLH 6382±2366, Steatosis 6544±2699, NASH F0 7220±2542 and NASH F1-4 5997±2352, p>0.05 between any disease state). Conclusion: We demonstrated that IGF-1 gene expression was lower in liver tissue from patients with NAFLD and NASH than healthy controls. This is consistent with our prior finding that histologic NASH and fibrosis are associated with lower serum IGF-1 levels. Moreover, we demonstrated that hepatic IGF-1R and GHR gene expression is not lower in liver tissue from patients with NAFLD and does not decline across disease severity. This reinforces our prior finding that GHR staining intensity and zonality by immunohistochemistry does not change with increasing disease severity in NAFLD/NASH. These data demonstrate that the GH axis is relatively suppressed but that expression of GHR and IGF-1R receptors is stable with worsening disease severity in NAFLD/NASH, suggesting that GH augmentation may be a viable therapeutic target in NAFLD.