TRIM56 protects against nonalcoholic fatty liver disease by promoting the degradation of fatty acid synthase

Metabolism and bioenergetics in the pathophysiology of organ fibrosis

Fibrosis is the tissue scarring characterized by excess deposition of extracellular matrix (ECM) proteins, mainly collagens. A fibrotic response can take place in any tissue of the body and is the result of an imbalanced reaction to inflammation and wound healing. Metabolism has emerged as a major driver of fibrotic diseases. While glycolytic shifts appear to be a key metabolic switch in activated stromal ECM-producing cells, several other cell types such as immune cells, whose functions are intricately connected to their metabolic characteristics, form a complex network of pro-fibrotic cellular crosstalk. This review purports to clarify shared and particular cellular responses and mechanisms across organs and etiologies. We discuss the impact of the cell-type specific metabolic reprogramming in fibrotic diseases in both experimental and human pathology settings, providing a rationale for new therapeutic interventions based on metabolism-targeted antifibrotic agents.

Steatotic liver disease induced by TCPOBOP-activated hepatic constitutive androstane receptor: primary and secondary gene responses with links to disease progression

Constitutive androstane receptor (CAR, Nr1i3), a liver nuclear receptor and xenobiotic sensor, induces drug, steroid, and lipid metabolizing enzymes, stimulates liver hypertrophy and hyperplasia, and ultimately, hepatocellular carcinogenesis. The mechanisms linking early CAR responses to later disease development are poorly understood. Here we show that exposure of CD-1 mice to TCPOBOP (1,4-bis[2-(3,5-dichloropyridyloxy)]benzene), a halogenated xenochemical and selective CAR agonist ligand, induces pericentral steatosis marked by hepatic accumulation of cholesterol and neutral lipid, and elevated circulating alanine aminotransferase, indicating hepatocyte damage. TCPOBOP-induced steatosis was weaker in the pericentral region but stronger in the periportal region in females compared with males. Early (1 day) TCPOBOP transcriptional responses were enriched for CAR-bound primary response genes, and for lipogenesis and xenobiotic metabolism and oxidative stress protection pathways; late (2 weeks) TCPOBOP responses included many CAR binding-independent secondary response genes, with enrichment for macrophage activation, immune response, and cytokine and reactive oxygen species production. Late upstream regulators specific to TCPOBOP-exposed male liver were linked to proinflammatory responses and hepatocellular carcinoma progression. TCPOBOP administered weekly to male mice using a high corn oil vehicle induced carbohydrate-responsive transcription factor (MLXIPL)-regulated target genes, dysregulated mitochondrial respiratory and translation regulatory pathways, and induced more advanced liver pathology. Overall, TCPOBOP exposure recapitulates histological and gene expression changes characteristic of emerging steatotic liver disease, including secondary gene responses in liver nonparenchymal cells indicative of transition to a more advanced disease state. Upstream regulators of both the early and late TCPOBOP response genes include novel biomarkers for foreign chemical-induced metabolic dysfunction-associated steatotic liver disease.

A novel mouse model of familial combined hyperlipidemia and atherosclerosis

Within the context of residual cardiovascular risk in post-statin era, emerging evidence from epidemiologic and human genetic studies have demonstrated that triglyceride (TG)-rich lipoproteins and their remnants are causally related to cardiovascular risk. While, carriers of loss-of-function mutations of ApoC3 have low TG levels and are protected from cardiovascular disease (CVD). Of translational significance, siRNAs/antisense oligonucleotide (ASO) targeting ApoC3 is beneficial for patients with atherosclerotic CVD. Therefore, animal models of atherosclerosis with both hypercholesterolemia and hypertriglyceridemia are important for the discovery of novel therapeutic strategies targeting TG-lowering on top of traditional cholesterol-lowering. In this study, we constructed a novel mouse model of familial combined hyperlipidemia through inserting a human ApoC3 transgene (hApoC3-Tg) into C57BL/6 J mice and injecting a gain-of-function variant of adeno-associated virus-proprotein convertase subtilisin/kexin type 9 (AAV-PCSK9)-D377Y concurrently with high cholesterol diet (HCD) feeding for 16 weeks. In the last 10 weeks, hApoC3-Tg mice were orally treated with a combination of atorvastatin (10 mg·kg-1·d-1) and fenofibrate (100 mg·kg-1·d-1). HCD-treated hApoC3-Tg mice demonstrated elevated levels of serum TG, total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C). Oral administration of atorvastatin and fenofibrate significantly decreased the plaque sizes of en face aorta, aortic sinus and innominate artery accompanied by improved lipid profile and distribution. In summary, this novel mouse model is of considerable clinical relevance for evaluation of anti-atherosclerotic drugs by targeting both hypercholesterolemia and hypertriglyceridemia.

NAFLD and NASH: etiology, targets and emerging therapies

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) pose a significant threat to human health and cause a tremendous socioeconomic burden. Currently, the molecular mechanisms of NAFLD and NASH remain incompletely understood, and no effective pharmacotherapies have been approved. In the past five years, significant advances have been achieved in our understanding of the pathomechanisms and potential pharmacotherapies of NAFLD and NASH. Research advances include the investigation of the effects of the fibroblast growth factor 21 (FGF21) analog pegozafermin and the thyroid hormone receptor-β (THRβ) agonist resmetriom on hepatic fat content, NASH resolution and/or fibrosis regression. Future directions of NAFLD and NASH research (including combination therapy, organoids and humanized mouse models) are also discussed in this state-of-the-art review.