Characterization of the CDAA Diet-Induced Non-alcoholic Steatohepatitis Model: Sex-Specific Differences in Inflammation, Fibrosis, and Cholesterol Metabolism in Middle-Aged Mice

S-Adenosylmethionine: A Multifaceted Regulator in Cancer Pathogenesis and Therapy

S-adenosylmethionine (SAMe) is a key methyl donor that plays a critical role in a variety of cellular processes, such as DNA, RNA and protein methylation, essential for maintaining genomic stability, regulating gene expression and maintaining cellular homeostasis. The involvement of SAMe in cancer pathogenesis is multifaceted, as through its multiple cellular functions, it can influence tumor initiation, progression and therapeutic resistance. In addition, the connection of SAMe with polyamine synthesis and oxidative stress management further underscores its importance in cancer biology. Recent studies have highlighted the potential of SAMe as a biomarker for cancer diagnosis and prognosis. Furthermore, the therapeutic implications of SAMe are promising, with evidence suggesting that SAMe supplementation or modulation could improve the efficacy of existing cancer treatments by restoring proper methylation patterns and mitigating oxidative damage and protect against damage induced by chemotherapeutic drugs. Moreover, targeting methionine cycle enzymes to both regulate SAMe availability and SAMe-independent regulatory effects, particularly in methionine-dependent cancers such as colorectal and lung cancer, presents a promising therapeutic approach. Additionally, exploring epitranscriptomic regulations, such as m6A modifications, and their interaction with non-coding RNAs could enhance our understanding of tumor progression and resistance mechanisms. Precision medicine approaches integrating patient subtyping and combination therapies with chemotherapeutics, such as decitabine or doxorubicin, together with SAMe, can enhance chemosensitivity and modulate epigenomics, showing promising results that may improve treatment outcomes. This review comprehensively examines the various roles of SAMe in cancer pathogenesis, its potential as a diagnostic and prognostic marker, and its emerging therapeutic applications. While SAMe modulation holds significant promise, challenges such as bioavailability, patient stratification and context-dependent effects must be addressed before clinical implementation. In addition, better validation of the obtained results into specific cancer animal models would also help to bridge the gap between research and clinical practice.

Protein restriction associated with high fat induces metabolic dysregulation without obesity in juvenile mice

Dysregulation of energy metabolism, including hyperglycemia, insulin resistance and fatty liver have been reported in a substantial proportion of lean children. However, non-obese murine models recapitulating these features are lacking to study the mechanisms underlying the development of metabolic dysregulations in lean children. Here, we develop a model of diet-induced metabolic dysfunction without obesity in juvenile mice by feeding male and female mice a diet reflecting Western nutritional intake combined with protein restriction (mWD) during 5 weeks after weaning. mWD-fed mice (35% fat, 8% protein) do not exhibit significant weight gain and have moderate increase in adiposity compared to control mice (16% fat, 20% protein). After 3 weeks of mWD, juvenile mice have impaired glucose metabolism including hyperglycemia, insulin resistance and glucose intolerance. mWD also triggers hepatic metabolism alterations, as shown by the development of simple liver steatosis. Both male and female mice fed with mWD displayed metabolic dysregulation, which a probiotic treatment with Lactiplantibacillus plantarum WJL failed to improve. Overall, mWD-fed mice appear to be a good preclinical model to study the development of diet-induced metabolic dysfunction without obesity in juveniles.

NASH triggers cardiometabolic HFpEF in aging mice

Both heart failure with preserved ejection fraction (HFpEF) and non-alcoholic fatty liver disease (NAFLD) develop due to metabolic dysregulation, has similar risk factors (e.g., insulin resistance, systemic inflammation) and are unresolved clinical challenges. Therefore, the potential link between the two disease is important to study. We aimed to evaluate whether NASH is an independent factor of cardiac dysfunction and to investigate the age dependent effects of NASH on cardiac function. C57Bl/6 J middle aged (10 months old) and aged mice (24 months old) were fed either control or choline deficient (CDAA) diet for 8 weeks. Before termination, echocardiography was performed. Upon termination, organ samples were isolated for histological and molecular analysis. CDAA diet led to the development of NASH in both age groups, without inducing weight gain, allowing to study the direct effect of NASH on cardiac function. Mice with NASH developed hepatomegaly, fibrosis, and inflammation. Aged animals had increased heart weight. Conventional echocardiography revealed normal systolic function in all cohorts, while increased left ventricular volumes in aged mice. Two-dimensional speckle tracking echocardiography showed subtle systolic and diastolic deterioration in aged mice with NASH. Histologic analyses of cardiac samples showed increased cross-sectional area, pronounced fibrosis and Col1a1 gene expression, and elevated intracardiac CD68+ macrophage count with increased Il1b expression. Conventional echocardiography failed to reveal subtle change in myocardial function; however, 2D speckle tracking echocardiography was able to identify diastolic deterioration. NASH had greater impact on aged animals resulting in cardiac hypertrophy, fibrosis, and inflammation.

Exploring Fibrosis Pathophysiology in Lean and Obese Metabolic-Associated Fatty Liver Disease: An In-Depth Comparison

While obesity-related nonalcoholic fatty liver disease (NAFLD) is linked with metabolic dysfunctions such as insulin resistance and adipose tissue inflammation, lean NAFLD more often progresses to liver fibrosis even in the absence of metabolic syndrome. This review aims to summarize the current knowledge regarding the mechanisms of liver fibrosis in lean NAFLD. The most commonly used lean NAFLD models include a methionine/choline-deficient (MCD) diet, a high-fat diet with carbon tetrachloride (CCl4), and a high-fructose and high-cholesterol diet. The major pro-fibrogenic mechanisms in lean NAFLD models include increased activation of the extracellular signal-regulated kinase (ERK) pathway, elevated expression of α-smooth muscle actin (α-SMA), collagen type I, and TGF-β, and modulation of fibrogenic markers such as tenascin-X and metalloproteinase inhibitors. Additionally, activation of macrophage signaling pathways promoting hepatic stellate cell (HSC) activation further contributes to fibrosis development. Animal models cannot cover all clinical features that are evident in patients with lean or obese NAFLD, implicating the need for novel models, as well as for deeper comparisons of clinical and experimental studies. Having in mind the prevalence of fibrosis in lean NAFLD patients, by addressing specific pathways, clinical studies can reveal new targeted therapies along with novel biomarkers for early detection and enhancement of clinical management for lean NAFLD patients.

IL-1β neutralization prevents diastolic dysfunction development, but lacks hepatoprotective effect in an aged mouse model of NASH

Interleukin-1β (IL-1β) is a key mediator of non-alcoholic steatohepatitis (NASH), a chronic liver disease, and of systemic inflammation-driven aging. IL-1β contributes to cardio-metabolic decline, and may promote hepatic oncogenic transformation. Therefore, IL-1β is a potential therapeutic target in these pathologies. We aimed to investigate the hepatic and cardiac effects of an IL-1β targeting monoclonal antibody in an aged mouse model of NASH. 24 months old male C57Bl/6J mice were fed with control or choline deficient (CDAA) diet and were treated with isotype control or anti-IL-1β Mab for 8 weeks. Cardiac functions were assessed by conventional-and 2D speckle tracking echocardiography. Liver samples were analyzed by immunohistochemistry and qRT-PCR. Echocardiography revealed improved cardiac diastolic function in anti-IL-1β treated mice with NASH. Marked hepatic fibrosis developed in CDAA-fed group, but IL-1β inhibition affected fibrosis only at transcriptomic level. Hepatic inflammation was not affected by the IL-1β inhibitor. PCNA staining revealed intensive hepatocyte proliferation in CDAA-fed animals, which was not influenced by neutralization of IL-1β. IL-1β inhibition increased hepatic expression of Pd-1 and Ctla4, while Pd-l1 expression increased in NASH. In conclusion, IL-1β inhibition improved cardiac diastolic function, but did not ameliorate features of NASH; moreover, even promoted hepatic immune checkpoint expression, with concomitant NASH-related hepatocellular proliferation.

Treatment with Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitors (PCSK9i): Current Evidence for Expanding the Paradigm?

Background: Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) are low-density lipoprotein cholesterol (LDL-C)-lowering drugs that play a critical role in lipoprotein clearance and metabolism. PCSK9i are used in patients with familial hypercholesterolemia and for the secondary prevention of acute cardiovascular events in patients with atherosclerotic cardiovascular disease (CVD). Methods: We focused on the literature from 2015, the year of approval of the PCSK9 monoclonal antibodies, to the present on the use of PCSK9i not only in the lipid field but also by evaluating their effects on metabolic factors. Results: PCSK9 inhibits cholesterol efflux from macrophages and contributes to the formation of macrophage foam cells. PCSK9 has the ability to bind to Toll-like receptors, thus mediating the inflammatory response and binding to scavenger receptor B/cluster of differentiation 36. PCSK9i lower the entire spectrum of apolipoprotein B-100 containing lipoproteins (LDL, very LDLs, intermediate-density lipoproteins, and lipoprotein[a]) in high CVD-risk patients. Moreover, PCSK9 inhibitors are neutral on risk for new-onset diabetes mellitus and might have a beneficial impact on the development of nonalcoholic fatty liver disease by improving lipid and inflammatory biomarker profiles, steatosis biomarkers such as the triglyceride-glucose index, and hepatic steatosis index, although there are no comprehensive studies with long-term follow-up studies. Conclusion: The discovery of PCSK9i has opened a new era in therapeutic management in patients with hypercholesterolemia and high cardiovascular risk. Increasingly, there has been mounting scientific and clinical evidence supporting the safety and tolerability of PCSK9i.

Utility of Human Relevant Preclinical Animal Models in Navigating NAFLD to MAFLD Paradigm

Fatty liver disease is an emerging contributor to disease burden worldwide. The past decades of work established the heterogeneous nature of non-alcoholic fatty liver disease (NAFLD) etiology and systemic contributions to the pathogenesis of the disease. This called for the proposal of a redefinition in 2020 to that of metabolic dysfunction-associated fatty liver disease (MAFLD) to better reflect the current understanding of the disease. To date, several clinical cohort studies comparing NAFLD and MAFLD hint at the relevancy of the new nomenclature in enriching for patients with more severe hepatic injury and extrahepatic comorbidities. However, the underlying systemic pathogenesis is still not fully understood. Preclinical animal models have been imperative in elucidating key biological mechanisms in various contexts, including intrahepatic disease progression, interorgan crosstalk and systemic dysregulation. Furthermore, they are integral in developing novel therapeutics against MAFLD. However, substantial contextual variabilities exist across different models due to the lack of standardization in several aspects. As such, it is crucial to understand the strengths and weaknesses of existing models to better align them to the human condition. In this review, we consolidate the implications arising from the change in nomenclature and summarize MAFLD pathogenesis. Subsequently, we provide an updated evaluation of existing MAFLD preclinical models in alignment with the new definitions and perspectives to improve their translational relevance.

The role of PCSK9 in NAFLD/NASH and therapeutic implications of PCSK9 inhibition

INTRODUCTION

There are inconsistent findings regarding the effect of lipid-lowering agents on nonalcoholic fatty liver disease (NAFLD). Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) is an important player in cholesterol homeostasis and intracellular lipogenesis, and PCSK9 inhibitors (PCSK9-i) have been found to be efficient for pharmacological management of hyperlipidemia.

AREAS COVERED

Whether PCSK9 (itself) or PCSK9-i affects NAFLD is still disputed. To address this question, we review published preclinical and clinical studies providing evidence for the role of PCSK9 in and the effect of PCSK9-I on the development and pathogenesis of NAFLD.

EXPERT OPINION

The current evidence from a landscape of preclinical and clinical studies examining the role of PCSK9 in NAFLD shows controversial results. Preclinical studies indicate that PCSK9 associates with NAFLD and nonalcoholic steatohepatitis (NASH) progression in opposite directions. In humans, it has been concluded that the severity of hepatic steatosis affects the correlation between circulating PCSK9 and liver fat content in humans, with a possible impact of circulating PCSK9 in the early stages of NAFLD, but not in the late stages. However, data from clinical trials with PCSK9-i reassure to the safety of these agents, although real-life long-term evidence is needed.

Dehydromevalonolactone ameliorates liver fibrosis and inflammation by repressing activation of NLRP3 inflammasome

Liver fibrosis is an important process in chronic liver disease and is strongly related to poor prognosis. Dehydromevalonolactone (C8) is a natural product isolated from a fungus of Fusarium sp. CPCC 401218, and its pharmacological activity has never been reported before. In this study, the potential of C8 as an anti-hepatic fibrosis agent was investigated. In human hepatic stellate cell (HSC) line LX-2, C8 suppressed the increased expression of COL1A1 and α-SMA induced by TGFβ1, which indicated that C8 could repress the activation of HSCs. In bile duct ligated rats, C8 administration (100 mg/kg, i.p.) markedly attenuated liver injury, fibrosis, and inflammation, and suppressed the expression of the macrophage surface marker F4/80. In terms of mechanism, C8 treatment blocked the activation of the NLRP3 inflammasome, which was stimulated by LPS and nigericin in bone marrow-derived macrophages (BMDMs) and companied by the release of active IL-1β. In addition, the activation of LX-2 cells induced by IL-1β released from BMDMs was also inhibited after C8 administration, which indicated that C8 repressed HSCs activation by inhibiting the activation of NLRP3 inflammasome in macrophages. Furthermore, C8 exhibited the effects of anti-fibrosis and inhibiting the expression of NLRP3 inflammasome in non-alcoholic steatohepatitis (NASH) mice. Finally, C8 can be commendably absorbed in vivo and was safe for mice at the concentration of 1000 mg/kg (p.o.). In summary, our study reveals that C8 ameliorates HSCs activation and liver fibrosis in cholestasis rats and NASH mice by inhibiting NLRP3 inflammasome in macrophages, and C8 might be a safe and effective candidate for the treatment of liver fibrosis.

Pathophysiological Mechanisms in Non-Alcoholic Fatty Liver Disease: From Drivers to Targets

Non-alcoholic fatty liver disease (NAFLD) is characterized by the excessive and detrimental accumulation of liver fat as a result of high-caloric intake and/or cellular and molecular abnormalities. The prevalence of this pathological event is increasing worldwide, and is intimately associated with obesity and type 2 diabetes mellitus, among other comorbidities. To date, only therapeutic strategies based on lifestyle changes have exhibited a beneficial impact on patients with NAFLD, but unfortunately this approach is often difficult to implement, and shows poor long-term adherence. For this reason, great efforts are being made to elucidate and integrate the underlying pathological molecular mechanism, and to identify novel and promising druggable targets for therapy. In this regard, a large number of clinical trials testing different potential compounds have been performed, albeit with no conclusive results yet. Importantly, many other clinical trials are currently underway with results expected in the near future. Here, we summarize the key aspects of NAFLD pathogenesis and therapeutic targets in this frequent disorder, highlighting the most recent advances in the field and future research directions.