AIM-deficient mouse fed a high-trans fat, high-cholesterol diet: a new animal model for nonalcoholic fatty liver disease

A novel role of RNase L in the development of nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and affects about 25% of the population globally. NAFLD has the potential to cause significant liver damage in many patients because it can progress to nonalcoholic steatohepatitis (NASH) and cirrhosis, which substantially increases disease morbidity and mortality. Despite the key role of innate immunity in the disease progression, the underlying molecular and pathogenic mechanisms remain to be elucidated. RNase L is a key enzyme in interferon action against viral infection and displays pleiotropic biological functions such as control of cell proliferation, apoptosis, and autophagy. Recent studies have demonstrated that RNase L is involved in innate immunity. In this study, we revealed that RNase L contributed to the development of NAFLD, which further progressed to NASH in a time-dependent fashion after RNase L wild-type (WT) and knockout mice were fed with a high-fat and high-cholesterol diet. RNase L WT mice showed significantly more severe NASH, evidenced by widespread macro-vesicular steatosis, hepatocyte ballooning degeneration, inflammation, and fibrosis, although physiological and biochemical data indicated that both types of mice developed obesity, hyperglycemia, hypercholesterolemia, dysfunction of the liver, and systemic inflammation at different extents. Further investigation demonstrated that RNase L was responsible for the expression of some key genes in lipid metabolism, inflammation, and fibrosis signaling. Taken together, our results suggest that a novel therapeutic intervention for NAFLD may be developed based on regulating the expression and activity of RNase L.

CD5L-associated gene analyses highlight the dysregulations, prognostic effects, immune associations, and drug-sensitivity predicative potentials of LCAT and CDC20 in hepatocellular carcinoma

BACKGROUND

The dysregulation of CD5L has been reported in hepatocellular carcinoma (HCC). However, its functions in HCC were controversial. In this study, we aimed to identify CD5L-associated pathways and markers and explore their values in HCC diagnosis, prognosis and treatment.

METHODS

HCC datasets with gene expression profiles and clinical data in TCGA and ICGC were downloaded. The immune/stroma cell infiltrations were estimated with xCell. CD5L-associated pathways and CD5L-associated genes (CD5L-AGs) were identified with gene expression comparisons and gene set enrichment analysis (GSEA). Cox regression, Kaplan-Meier survival analysis, and least absolute shrinkage and selection operator (LASSO) regression analysis were performed. The correlations of the key genes with immune/stroma infiltrations, immunoregulators, and anti-cancer drug sensitivities in HCC were investigated. At protein level, the key genes dysregulations, their correlations and prognostic values were validated in clinical proteomic tumor analysis consortium (CPTAC) database. Serum CD5L and LCAT activity in 50 HCC and 30 normal samples were evaluated and compared. The correlations of serum LCAT activity with alpha-fetoprotein (AFP), albumin (ALB) and high-density lipoprotein (HDL) in HCC were also investigated.

RESULTS

Through systemic analyses, 14 CD5L-associated biological pathways, 256 CD5L-AGs and 28 CD5L-associated prognostic and diagnostic genes (CD5L-APDGs) were identified. A risk model consisting of LCAT and CDC20 was constructed for HCC overall survival (OS), which could discriminate HCC OS status effectively in both the training and the validation sets. CD5L, LCAT and CDC20 were shown to be significantly correlated with immune/stroma cell infiltrations, immunoregulators and 31 anti-cancer drug sensitivities in HCC. At protein level, the dysregulations of CD5L, LCAT and CDC20 were confirmed. LCAT and CDC20 were shown to be significantly correlated with proliferation marker MKI67. In serum, no significance of CD5L was shown. However, the lower activity of LCAT in HCC serum was obvious, as well as its significant positive correlations ALB and HDL concentrations.

CONCLUSIONS

CD5L, LCAT and CDC20 were dysregulated in HCC both at mRNA and protein levels. The LCAT-CDC20 signature might be new predicator for HCC OS. The associations of the three genes with HCC microenvironment and anti-cancer drug sensitivities would provide new clues for HCC immunotherapy and chemotherapy.

Down-Regulating the High Level of 17-Beta-Hydroxysteroid Dehydrogenase 13 Plays a Therapeutic Role for Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide, and there is no specific drug to treat it. Recent results showed that 17-beta-hydroxysteroid dehydrogenase type 13 (HSD17B13) is associated with liver diseases, but these conclusions are controversial. Here, we showed that HSD17B13 was more highly expressed in the livers of NAFLD patients, and high expression was induced in the livers of murine NAFLD models and cultural hepatocytes treated using various etiologies. The high HSD17B13 expression in the hepatocytes facilitated the progression of NAFLD by directly stabilizing the intracellular lipid drops and by indirectly activating hepatic stellate cells. When HSD17B13 was overexpressed in the liver, it aggravated liver steatosis and fibrosis in mice fed with a high-fat diet, while down-regulated the high expression of HSD17B13 by short hairpin RNAs produced a therapeutic effect in the NAFLD mice. We concluded that high HSD17B13 expression is a good target for the development of drugs to treat NAFLD.

Ruminant fat intake improves gut microbiota, serum inflammatory parameter and fatty acid profile in tissues of Wistar rats

This study tested the hypothesis that naturally and industrially produced trans-fatty acids can exert distinct effects on metabolic parameters and on gut microbiota of rats. Wistar rats were randomized into three groups according to the diet: CONT-control, with 5% soybean oil and normal amount of fat; HVF-20% of hydrogenated vegetable fat (industrial); and RUM-20% of ruminant fat (natural). After 53 days of treatment, serum biochemical markers, fatty acid composition of liver, heart and adipose tissue, histology and hepatic oxidative parameters, as well as gut microbiota composition were evaluated. HVF diet intake reduced triglycerides (≈ 39.39%) and VLDL levels (≈ 39.49%). Trans-fatty acids levels in all tissue were higher in HVF group. However, RUM diet intake elevated amounts of anti-inflammatory cytokine IL-10 (≈ 14.7%) compared to CONT, but not to HVF. Furthermore, RUM intake led to higher concentrations of stearic acid and conjugated linoleic acid in all tissue; this particular diet was associated with a hepatoprotective effect. The microbial gut communities were significantly different among the groups. Our results show that ruminant fat reversed the hepatic steatosis normally caused by high fat diets, which may be related to the remodelling of the gut microbiota and its anti-inflammatory potential.

Diet-Induced Models of Non-Alcoholic Fatty Liver Disease: Food for Thought on Sugar, Fat, and Cholesterol

Non-alcoholic fatty liver disease (NAFLD) affects approximately 1 in 4 people worldwide and is a major burden to health care systems. A major concern in NAFLD research is lack of confidence in pre-clinical animal models, raising questions regarding translation to humans. Recently, there has been renewed interest in creating dietary models of NAFLD with higher similarity to human diets in hopes to better recapitulate disease pathology. This review summarizes recent research comparing individual roles of major dietary components to NAFLD and addresses common misconceptions surrounding frequently used diet-based NAFLD models. We discuss the effects of glucose, fructose, and sucrose on the liver, and how solid vs. liquid sugar differ in promoting disease. We consider studies on dosages of fat and cholesterol needed to promote NAFLD versus NASH, and discuss important considerations when choosing control diets, mouse strains, and diet duration. Lastly, we provide our recommendations on amount and type of sugar, fat, and cholesterol to include when modelling diet-induced NAFLD/NASH in mice.

Animal and Organoid Models of Liver Fibrosis

Liver fibrosis refers to the process underlying the development of chronic liver diseases, wherein liver cells are repeatedly destroyed and regenerated, which leads to an excessive deposition and abnormal distribution of the extracellular matrix such as collagen, glycoprotein and proteoglycan in the liver. Liver fibrosis thus constitutes the pathological repair response of the liver to chronic injury. Hepatic fibrosis is a key step in the progression of chronic liver disease to cirrhosis and an important factor affecting the prognosis of chronic liver disease. Further development of liver fibrosis may lead to structural disorders of the liver, nodular regeneration of hepatocytes and the formation of cirrhosis. Hepatic fibrosis is histologically reversible if treated aggressively during this period, but when fibrosis progresses to the stage of cirrhosis, reversal is very difficult, resulting in a poor prognosis. There are many causes of liver fibrosis, including liver injury caused by drugs, viral hepatitis, alcoholic liver, fatty liver and autoimmune disease. The mechanism underlying hepatic fibrosis differs among etiologies. The establishment of an appropriate animal model of liver fibrosis is not only an important basis for the in-depth study of the pathogenesis of liver fibrosis but also an important means for clinical experts to select drugs for the prevention and treatment of liver fibrosis. The present study focused on the modeling methods and fibrosis characteristics of different animal models of liver fibrosis, such as a chemical-induced liver fibrosis model, autoimmune liver fibrosis model, cholestatic liver fibrosis model, alcoholic liver fibrosis model and non-alcoholic liver fibrosis model. In addition, we also summarize the research and application prospects concerning new organoids in liver fibrosis models proposed in recent years. A suitable animal model of liver fibrosis and organoid fibrosis model that closely resemble the physiological state of the human body will provide bases for the in-depth study of the pathogenesis of liver fibrosis and the development of therapeutic drugs.

Role of Polymeric Immunoglobulin Receptor in IgA and IgM Transcytosis

Transcytosis of polymeric IgA and IgM from the basolateral surface to the apical side of the epithelium and subsequent secretion into mucosal fluids are mediated by the polymeric immunoglobulin receptor (pIgR). Secreted IgA and IgM have vital roles in mucosal immunity in response to pathogenic infections. Binding and recognition of polymeric IgA and IgM by pIgR require the joining chain (J chain), a small protein essential in the formation and stabilization of polymeric Ig structures. Recent studies have identified marginal zone B and B1 cell-specific protein (MZB1) as a novel regulator of polymeric IgA and IgM formation. MZB1 might facilitate IgA and IgM transcytosis by promoting the binding of J chain to Ig. In this review, we discuss the roles of pIgR in transcytosis of IgA and IgM, the roles of J chain in the formation of polymeric IgA and IgM and recognition by pIgR, and focus particularly on recent progress in understanding the roles of MZB1, a molecular chaperone protein.

Inter-organelle Communication in the Pathogenesis of Mitochondrial Dysfunction and Insulin Resistance

PURPOSE OF REVIEW

Impairments in mitochondrial function in patients with insulin resistance and type 2 diabetes have been disputed for decades. This review aims to briefly summarize the current knowledge on mitochondrial dysfunction in metabolic tissues and to particularly focus on addressing a new perspective of mitochondrial dysfunction, the altered capacity of mitochondria to communicate with other organelles within insulin-resistant tissues.

RECENT FINDINGS

Organelle interactions are temporally and spatially formed connections essential for normal cell function. Recent studies have shown that mitochondria interact with various cellular organelles, such as the endoplasmic reticulum, lysosomes and lipid droplets, forming inter-organelle junctions. We will discuss the current knowledge on alterations in these mitochondria-organelle interactions in insulin resistance and diabetes, with a focus on changes in mitochondria-lipid droplet communication as a major player in ectopic lipid accumulation, lipotoxicity and insulin resistance.