Fatty Acid Synthase Inhibitor TVB-2640 Reduces Hepatic de Novo Lipogenesis in Males With Metabolic Abnormalities

Role of liver FGF21-KLB signaling in ketogenic diet-induced amelioration of hepatic steatosis

BACKGROUND

The effectiveness of ketogenic diet (KD) in ameliorating fatty liver has been established, although its mechanism is under investigation. Fibroblast growth factor 21 (FGF21) positively regulates obesity-associated metabolic disorders and is elevated by KD. FGF21 conventionally initiates its intracellular signaling via receptor β-klotho (KLB). However, the mechanistic role of FGF21-KLB signaling for KD-ameliorated fatty liver remains unknown. This study aimed to delineate the critical role of FGF21 signaling in the ameliorative effects of KD on hepatic steatosis.

METHODS

Eight-week-old C57BL/6 J mice were fed a chow diet (CD), a high-fat diet (HFD), or a KD for 16 weeks. Adeno-associated virus-mediated liver-specific KLB knockdown mice and control mice were fed a KD for 16 weeks. Phenotypic assessments were conducted during and after the intervention. We investigated the mechanism underlying KD-alleviated hepatic steatosis using multi-omics and validated the expression of key genes.

RESULTS

KD improved hepatic steatosis by upregulating fatty acid oxidation and downregulating lipogenesis. Transcriptional analysis revealed that KD dramatically activated FGF21 pathway, including KLB and fibroblast growth factor receptor 1 (FGFR1). Impairing liver FGF21 signaling via KLB knockdown diminished the beneficial effects of KD on ameliorating fatty liver, insulin resistance, and regulating lipid metabolism.

CONCLUSION

KD demonstrates beneficial effects on diet-induced metabolic disorders, particularly on hepatic steatosis. Liver FGF21-KLB signaling plays a critical role in the KD-induced amelioration of hepatic steatosis.

Advances in management of metabolic dysfunction-associated steatotic liver disease: from mechanisms to therapeutics

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the leading cause of chronic liver disease that affects over 30% of the world's population. For decades, the heterogeneity of non-alcoholic fatty liver disease (NAFLD) has impeded our understanding of the disease mechanism and the development of effective medications. However, a recent change in the nomenclature from NAFLD to MASLD emphasizes the critical role of systemic metabolic dysfunction in the pathophysiology of this disease and therefore promotes the progress in the pharmaceutical treatment of MASLD. In this review, we focus on the mechanism underlying the abnormality of hepatic lipid metabolism in patients with MASLD, and summarize the latest progress in the therapeutic medications of MASLD that target metabolic disorders.

Metabolic effects of an essential amino acid supplement in adolescents with PCOS and obesity

OBJECTIVE

Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenism, insulin resistance, and hepatic steatosis (HS). Because dietary essential amino acid (EAA) supplementation has been shown to decrease HS in various populations, this study's objective was to determine whether supplementation would decrease HS in PCOS.

METHODS

A randomized, double-blind, crossover, placebo-controlled trial was conducted in 21 adolescents with PCOS (BMI 37.3 ± 6.5 kg/m2, age 15.6 ± 1.3 years). Liver fat, very low-density lipoprotein (VLDL) lipogenesis, and triacylglycerol (TG) metabolism were measured following each 28-day phase of placebo or EAA.

RESULTS

Compared to placebo, EAA was associated with no difference in body weight (p = 0.673). Two markers of liver health improved: HS was lower (-0.8% absolute, -7.5% relative reduction, p = 0.013), as was plasma aspartate aminotransferase (AST) (-8%, p = 0.004). Plasma TG (-9%, p = 0.015) and VLDL-TG (-21%, p = 0.031) were reduced as well. VLDL-TG palmitate derived from lipogenesis was not different between the phases, nor was insulin sensitivity (p > 0.400 for both). Surprisingly, during the EAA phase, participants reported consuming fewer carbohydrates (p = 0.038) and total sugars (p = 0.046).

CONCLUSIONS

Similar to studies in older adults, short-term EAA supplementation in adolescents resulted in significantly lower liver fat, AST, and plasma lipids and thus may prove to be an effective treatment in this population. Additional research is needed to elucidate the mechanisms for these effects.

A revisit of drugs and potential therapeutic targets against non-alcoholic fatty liver disease: learning from clinical trials

PURPOSE

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease, with a worldwide prevalence of 25%. Although numerous clinical trials have been conducted over the last few decades, an effective treatment has not been approved yet. Extensive research has accumulated a large amount of data and experience; however, the vast number of clinical trials and new therapeutic targets for NAFLD make it impossible to keep abreast of the relevant information. Therefore, a systematic analysis of the existing trials is necessary.

METHODS

Here, we reviewed clinical trials on NAFLD registered in the mandated federal database, ClinicalTrials.gov, to generate a detailed overview of the trials related to drugs and therapeutic targets for NAFLD treatment. Following screening for pertinence to therapy, a total of 440 entries were identified that included active trials as well as those that have already been completed, suspended, terminated, or withdrawn.

RESULTS

We summarize and systematically analyze the state, drug development pipeline, and discovery of treatment targets for NAFLD. We consider possible factors that may affect clinical outcomes. Furthermore, we discussed these results to explore the mechanisms responsible for clinical outcomes.

CONCLUSION

We summarised the landscape of current clinical trials and suggested the directions for future NAFLD therapy to assist internal medicine specialists in treating the whole clinical spectrum of this highly prevalent liver disease.

Exploring the Multifaceted Landscape of MASLD: A Comprehensive Synthesis of Recent Studies, from Pathophysiology to Organoids and Beyond

Non-alcoholic fatty liver disease (NAFLD) is a widespread contributor to chronic liver disease globally. A recent consensus on renaming liver disease was established, and metabolic dysfunction-associated steatotic liver disease, MASLD, was chosen as the replacement for NAFLD. The disease's range extends from the less severe MASLD, previously known as non-alcoholic fatty liver (NAFL), to the more intense metabolic dysfunction-associated steatohepatitis (MASH), previously known as non-alcoholic steatohepatitis (NASH), characterized by inflammation and apoptosis. This research project endeavors to comprehensively synthesize the most recent studies on MASLD, encompassing a wide spectrum of topics such as pathophysiology, risk factors, dietary influences, lifestyle management, genetics, epigenetics, therapeutic approaches, and the prospective trajectory of MASLD, particularly exploring its connection with organoids.

Pharmacologic inhibition of lipogenesis for the treatment of NAFLD

The hepatic accumulation of excess triglycerides is a seminal event in the initiation and progression of non-alcoholic fatty liver disease (NAFLD). Hepatic steatosis occurs when the hepatic accrual of fatty acids from the plasma and de novo lipogenesis (DNL) is no longer balanced by rates of fatty acid oxidation and secretion of very low-density lipoprotein-triglycerides. Accumulating data indicate that increased rates of DNL are central to the development of hepatic steatosis in NAFLD. Whereas the main drivers in NAFLD are transcriptional, owing to both hyperinsulinemia and hyperglycaemia, the effectors of DNL are a series of well-characterised enzymes. Several have proven amenable to pharmacologic inhibition or oligonucleotide-mediated knockdown, with lead compounds showing liver fat-lowering efficacy in phase II clinical trials. In humans with NAFLD, percent reductions in liver fat have closely mirrored percent inhibition of DNL, thereby affirming the critical contributions of DNL to NAFLD pathogenesis. The safety profiles of these compounds have so far been encouraging. It is anticipated that inhibitors of DNL, when administered alone or in combination with other therapeutic agents, will become important agents in the management of human NAFLD.

MiR-192-5p Ameliorates Hepatic Lipid Metabolism in Non-Alcoholic Fatty Liver Disease by Targeting Yy1

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation in the liver. Clarifying the molecular mechanism of lipid metabolism is crucial for the treatment of NAFLD. We examined miR-192-5p levels in the livers of mice in which NAFLD was induced via a high-fat diet (HFD), as well as in mouse primary hepatocytes and human HepG2 cells treated with free fatty acids (FFAs). MiR-192-5p inhibitor was administered to NAFLD mice and hepatocytes to verify the specific function of miR-192-5p in NAFLD. We validated the target gene of miR-192-5p and further illustrated the effects of this miRNA on the regulation of triglyceride (TG) metabolism. We found that miR-192-5p was significantly increased in the livers of NAFLD mice and FFA-treated hepatocytes. Inhibition of miR-192-5p increased the accumulation of hepatic TGs and aggravated hepatic steatosis in NAFLD mice. In FFA-treated hepatocytes, miR-192-5p inhibitors markedly increased TG content, whereas overexpression of miR-192-5p reduced TG levels. Yin Yang 1 (Yy1) was identified as the target gene of miR-192-5p, which regulates TG synthesis via the YY1/fatty-acid synthase (FASN) pathway. Our results demonstrated that miR-192-5p should be considered a protective regulator in NAFLD that can inhibit hepatic TG synthesis by targeting Yy1.

Lipid Metabolism in Metabolic-Associated Steatotic Liver Disease (MASLD)

Metabolic-associated steatotic liver disease (MASLD) is a cluster of pathological conditions primarily developed due to the accumulation of ectopic fat in the hepatocytes. During the severe form of the disease, i.e., metabolic-associated steatohepatitis (MASH), accumulated lipids promote lipotoxicity, resulting in cellular inflammation, oxidative stress, and hepatocellular ballooning. If left untreated, the advanced form of the disease progresses to fibrosis of the tissue, resulting in irreversible hepatic cirrhosis or the development of hepatocellular carcinoma. Although numerous mechanisms have been identified as significant contributors to the development and advancement of MASLD, altered lipid metabolism continues to stand out as a major factor contributing to the disease. This paper briefly discusses the dysregulation in lipid metabolism during various stages of MASLD.

Isotope Labeling and Biochemical Assessment of Liver-Triacylglycerol in Patients with Different Levels of Histologically-Graded Liver Disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) prevalence is rapidly growing, and fatty liver has been found in a quarter of the US population. Increased liver lipids, particularly those derived from the pathway of de novo lipogenesis (DNL), have been identified as a hallmark feature in individuals with high liver fat. This has led to much activity in basic science and drug development in this area. No studies to date have investigated the contribution of DNL across a spectrum of disease, although it is clear that inhibition of DNL has been shown to reduce liver fat.

OBJECTIVES

The purpose of this study was to determine whether liver lipid synthesis increases across the continuum of liver injury.

METHODS

Individuals (n = 49) consumed deuterated water for 10 d before their scheduled bariatric surgeries to label DNL; blood and liver tissue samples were obtained on the day of the surgery. Liver lipid concentrations were quantitated, and levels of protein and gene expression assessed.

RESULTS

Increased liver DNL, measured isotopically, was significantly associated with liver fatty acid synthase protein content (R = 0.470, P = 0.003), total steatosis assessed by histology (R = 0.526, P = 0.0008), and the fraction of DNL fatty acids in plasma very low-density lipoprotein-triacylglycerol (R = 0.747, P < 0.001). Regression analysis revealed a parabolic relationship between fractional liver DNL (percent) and NAFLD activity score (R = 0.538, P = 0.0004).

CONCLUSION

These data demonstrate that higher DNL is associated with early to mid stages of liver disease, and this pathway may be an effective target for the treatment of NAFLD and nonalcoholic steatohepatitis. This study was registered at clinicaltrials.gov as NCT03683589.

Inflammation-induced TRIM21 represses hepatic steatosis by promoting the ubiquitination of lipogenic regulators

Nonalcoholic steatohepatitis (NASH) is a leading cause for chronic liver diseases. Current therapeutic options are limited due to an incomplete mechanistic understanding of how steatosis transitions to NASH. Here we show that the TRIM21 E3 ubiquitin ligase is induced by the synergistic actions of proinflammatory TNF-α and fatty acids in livers of humans and mice with NASH. TRIM21 ubiquitinates and degrades ChREBP, SREBP1, ACC1, and FASN, key regulators of de novo lipogenesis, and A1CF, an alternative splicing regulator of the high-activity ketohexokinase-C (KHK-C) isoform and rate-limiting enzyme of fructose metabolism. TRIM21-mediated degradation of these lipogenic activators improved steatosis and hyperglycemia as well as fructose and glucose tolerance. Our study identifies TRIM21 as a negative regulator of liver steatosis in NASH and provides mechanistic insights into an immunometabolic crosstalk that limits fatty acid synthesis and fructose metabolism during metabolic stress. Thus, enhancing this natural counteracting force of steatosis through inhibition of key lipogenic activators via TRIM21-mediated ubiquitination may provide a therapeutic opportunity to treat NASH.

Targeting cellular metabolism in head and neck cancer precision medicine era: A promising strategy to overcome therapy resistance

Head and neck squamous cell carcinoma (HNSCC) is among the most prevalent cancer worldwide, with the most severe impact on quality of life of patients. Despite the development of multimodal therapeutic approaches, the clinical outcomes of HNSCC are still unsatisfactory, mainly caused by relatively low responsiveness to treatment and severe drug resistance. Metabolic reprogramming is currently considered to play a pivotal role in anticancer therapeutic resistance. This review aimed to define the specific metabolic programs and adaptations in HNSCC therapy resistance. An extensive literature review of HNSCC was conducted via the PubMed including metabolic reprogramming, chemo- or immune-therapy resistance. Glucose metabolism, fatty acid metabolism, and amino acid metabolism are closely related to the malignant biological characteristics of cancer, anti-tumor drug resistance, and adverse clinical results. For HNSCC, pyruvate, lactate and almost all lipid categories are related to the occurrence and maintenance of drug resistance, and targeting amino acid metabolism can prevent tumor development and enhance the response of drug-resistant tumors to anticancer therapy. This review will provide a better understanding of the altered metabolism in therapy resistance of HNSCC and promote the development of new therapeutic strategies against HNSCC, thereby contribute to a more efficacious precision medicine.

Human skin stem cell-derived hepatic cells as in vitro drug discovery model for insulin-driven de novo lipogenesis

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), is characterized by intrahepatic triglyceride accumulation and can progress to metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. Hepatic de novo lipogenesis (DNL), activated by glucose and insulin, is a central pathway contributing to early-stage development of MASLD. The emerging global prevalence of MASLD highlights the urgent need for pharmaceutical intervention to combat this health threat. However, the identification of novel drugs that could inhibit hepatic DNL is hampered by a lack of reliable, insulin-sensitive, human, in vitro, hepatic models. Here, we report human skin stem cell-derived hepatic cells (hSKP-HPC) as a unique in vitro model to study insulin-driven DNL (iDNL), evidenced by both gene expression and lipid accumulation readouts. Insulin-sensitive hSKP-HPC showed increased sterol regulatory element-binding protein 1c (SREBP-1c) expression, a key transcription factor for DNL. Furthermore, this physiologically relevant in vitro human steatosis model allowed both inhibition and activation of the iDNL pathway using reference inhibitors and activators, respectively. Optimisation of the lipid accumulation assay to a high-throughput, 384-well format enabled the screening of a library of annotated compounds, delivering new insights on key players in the iDNL pathway and MASLD pathophysiology. Together, these results establish the value of the hSKP-HPC model in preclinical development of antisteatotic drugs to combat MASLD.

Potential Therapeutic Strategies in the Treatment of Metabolic-Associated Fatty Liver Disease

Metabolic-associated Fatty Liver Disease is one of the outstanding challenges in gastroenterology. The increasing incidence of the disease is undoubtedly connected with the ongoing obesity pandemic. The lack of specific symptoms in the early phases and the grave complications of the disease require an active approach to prompt diagnosis and treatment. Therapeutic lifestyle changes should be introduced in a great majority of patients; but, in many cases, the adherence is not satisfactory. There is a great need for an effective pharmacological therapy for Metabolic-Associated Fatty Liver Disease, especially before the onset of steatohepatitis. Currently, there are no specific recommendations on the selection of drugs to treat liver steatosis and prevent patients from progression toward more advanced stages (steatohepatitis, cirrhosis, and cancer). Therefore, in this Review, we provide data on the clinical efficacy of therapeutic interventions that might improve the course of Metabolic-Associated Fatty Liver Disease. These include the drugs used in the treatment of obesity and hyperlipidemias, as well as affecting the gut microbiota and endocrine system, and other experimental approaches, including functional foods. Finally, we provide advice on the selection of drugs for patients with concomitant Metabolic-Associated Fatty Liver Disease.

Hepatic FASN deficiency differentially affects nonalcoholic fatty liver disease and diabetes in mouse obesity models

Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes are interacting comorbidities of obesity, and increased hepatic de novo lipogenesis (DNL), driven by hyperinsulinemia and carbohydrate overload, contributes to their pathogenesis. Fatty acid synthase (FASN), a key enzyme of hepatic DNL, is upregulated in association with insulin resistance. However, the therapeutic potential of targeting FASN in hepatocytes for obesity-associated metabolic diseases is unknown. Here, we show that hepatic FASN deficiency differentially affects NAFLD and diabetes depending on the etiology of obesity. Hepatocyte-specific ablation of FASN ameliorated NAFLD and diabetes in melanocortin 4 receptor-deficient mice but not in mice with diet-induced obesity. In leptin-deficient mice, FASN ablation alleviated hepatic steatosis and improved glucose tolerance but exacerbated fed hyperglycemia and liver dysfunction. The beneficial effects of hepatic FASN deficiency on NAFLD and glucose metabolism were associated with suppression of DNL and attenuation of gluconeogenesis and fatty acid oxidation, respectively. The exacerbation of fed hyperglycemia by FASN ablation in leptin-deficient mice appeared attributable to impairment of hepatic glucose uptake triggered by glycogen accumulation and citrate-mediated inhibition of glycolysis. Further investigation of the therapeutic potential of hepatic FASN inhibition for NAFLD and diabetes in humans should thus consider the etiology of obesity.

Small molecule inhibitors for cancer metabolism: promising prospects to be explored

BACKGROUND

Abnormal metabolism is the main hallmark of cancer, and cancer metabolism plays an important role in tumorigenesis, metastasis, and drug resistance. Therefore, studying the changes of tumor metabolic pathways is beneficial to find targets for the treatment of cancer diseases. The success of metabolism-targeted chemotherapy suggests that cancer metabolism research will provide potential new targets for the treatment of malignant tumors.

PURPOSE

The aim of this study was to systemically review recent research findings on targeted inhibitors of tumor metabolism. In addition, we summarized new insights into tumor metabolic reprogramming and discussed how to guide the exploration of new strategies for cancer-targeted therapy.

CONCLUSION

Cancer cells have shown various altered metabolic pathways, providing sufficient fuel for their survival. The combination of these pathways is considered to be a more useful method for screening multilateral pathways. Better understanding of the clinical research progress of small molecule inhibitors of potential targets of tumor metabolism will help to explore more effective cancer treatment strategies.

Dual targeting of hepatocyte DGAT2 and stellate cell FASN alleviates nonalcoholic steatohepatitis in mice

Nonalcoholic steatohepatitis (NASH) is a malady of multiple cell types associated with hepatocyte triglyceride (TG) accumulation, macrophage inflammation, and stellate cell-induced fibrosis, with no approved therapeutics yet available. Here, we report that stellate cell fatty acid synthase (FASN) in de novo lipogenesis drives the autophagic flux that is required for stellate cell activation and fibrotic collagen production. Further, we employ a dual targeting approach to NASH that selectively depletes collagen through selective stellate cell knockout of FASN (using AAV9-LRAT Cre in FASNfl/fl mice), while lowering hepatocyte triglyceride by depleting DGAT2 with a GalNac-conjugated, fully chemically modified siRNA. DGAT2 silencing in hepatocytes alone or in combination with stellate cell FASNKO reduced liver TG accumulation in a choline-deficient NASH mouse model, while FASNKO in hepatocytes alone (using AAV8-TBG Cre in FASNfl/fl mice) did not. Neither hepatocyte DGAT2 silencing alone nor FASNKO in stellate cells alone decreased fibrosis (total collagen), while loss of both DGAT2 plus FASN caused a highly significant attenuation of NASH. These data establish proof of concept that dual targeting of DGAT2 plus FASN alleviates NASH progression in mice far greater than targeting either gene product alone.

Lipidomics in pathogenesis, progression and treatment of nonalcoholic steatohepatitis (NASH): Recent advances

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease affecting up to 30% of the general adult population. NAFLD encompasses a histological spectrum ranging from pure steatosis to non-alcoholic steatohepatitis (NASH). NASH can progress to cirrhosis and is becoming the most common indication for liver transplantation, as a result of increasing disease prevalence and of the absence of approved treatments. Lipidomic readouts of liver blood and urine samples from experimental models and from NASH patients disclosed an abnormal lipid composition and metabolism. Collectively, these changes impair organelle function and promote cell damage, necro-inflammation and fibrosis, a condition termed lipotoxicity. We will discuss the lipid species and metabolic pathways leading to NASH development and progression to cirrhosis, as well as and those species that can contribute to inflammation resolution and fibrosis regression. We will also focus on emerging lipid-based therapeutic opportunities, including specialized proresolving lipid molecules and macrovesicles contributing to cell-to-cell communication and NASH pathophysiology.

Insulin Regulation of Hepatic Lipid Homeostasis

The incidence of obesity, insulin resistance, and type II diabetes (T2DM) continues to rise worldwide. The liver is a central insulin-responsive metabolic organ that governs whole-body metabolic homeostasis. Therefore, defining the mechanisms underlying insulin action in the liver is essential to our understanding of the pathogenesis of insulin resistance. During periods of fasting, the liver catabolizes fatty acids and stored glycogen to meet the metabolic demands of the body. In postprandial conditions, insulin signals to the liver to store excess nutrients into triglycerides, cholesterol, and glycogen. In insulin-resistant states, such as T2DM, hepatic insulin signaling continues to promote lipid synthesis but fails to suppress glucose production, leading to hypertriglyceridemia and hyperglycemia. Insulin resistance is associated with the development of metabolic disorders such as cardiovascular and kidney disease, atherosclerosis, stroke, and cancer. Of note, nonalcoholic fatty liver disease (NAFLD), a spectrum of diseases encompassing fatty liver, inflammation, fibrosis, and cirrhosis, is linked to abnormalities in insulin-mediated lipid metabolism. Therefore, understanding the role of insulin signaling under normal and pathologic states may provide insights into preventative and therapeutic opportunities for the treatment of metabolic diseases. Here, we provide a review of the field of hepatic insulin signaling and lipid regulation, including providing historical context, detailed molecular mechanisms, and address gaps in our understanding of hepatic lipid regulation and the derangements under insulin-resistant conditions. © 2023 American Physiological Society. Compr Physiol 13:4785-4809, 2023.

The Interplay between Dysregulated Metabolism and Epigenetics in Cancer

Cellular metabolism (or energetics) and epigenetics are tightly coupled cellular processes. It is arguable that of all the described cancer hallmarks, dysregulated cellular energetics and epigenetics are the most tightly coregulated. Cellular metabolic states regulate and drive epigenetic changes while also being capable of influencing, if not driving, epigenetic reprogramming. Conversely, epigenetic changes can drive altered and compensatory metabolic states. Cancer cells meticulously modify and control each of these two linked cellular processes in order to maintain their tumorigenic potential and capacity. This review aims to explore the interplay between these two processes and discuss how each affects the other, driving and enhancing tumorigenic states in certain contexts.

TRIM21 ameliorates hepatic glucose and lipid metabolic disorders in type 2 diabetes mellitus by ubiquitination of PEPCK1 and FASN

Hepatic glucose and lipid metabolism disorders promote the development and progression of type 2 diabetes mellitus (T2DM), yet the underlying mechanisms are not fully understood. Here, we identify tripartite motif-containing protein 21 (TRIM21), a class IV TRIM family member, as a pivotal regulator of hepatic metabolism in T2DM for the first time. Bioinformatic analysis suggests that TRIM21 expression is significantly reduced in T2DM patients. Intriguingly, in a mouse model of obese diabetes, TRIM21 expression is predominantly reduced in the liver rather than in other metabolic organs. It is further demonstrated that hepatic overexpression of TRIM21 significantly ameliorates glucose intolerance, insulin resistance, hepatic steatosis, and dyslipidemia in obese diabetic mice. In contrast, the knockdown of TRIM21 promotes glucose intolerance, insulin resistance, and triglyceride accumulation. Mechanistically, both phosphoenolpyruvate carboxykinase 1 (PEPCK1) and fatty acid synthase (FASN) are the hepatic targets of TRIM21. We revealed that TRIM21 promotes the degradation of PEPCK1 and FASN through a direct protein-protein interaction mediated K48-linked ubiquitination. Notably, overexpression of PEPCK1 and FASN essentially abolished the beneficial effects achieved by TRIM21 overexpression in obese diabetic mice. Overall, our data demonstrate that TRIM21 is a novel regulator of hepatic metabolic disorder, and suggest TRIM21 as a promising therapeutic target for T2DM.

Physiological and pathological roles of lipogenesis

Lipids are essential metabolites, which function as energy sources, structural components and signalling mediators. Most cells are able to convert carbohydrates into fatty acids, which are often converted into neutral lipids for storage in the form of lipid droplets. Accumulating evidence suggests that lipogenesis plays a crucial role not only in metabolic tissues for systemic energy homoeostasis but also in immune and nervous systems for their proliferation, differentiation and even pathophysiological roles. Thus, excessive or insufficient lipogenesis is closely associated with aberrations in lipid homoeostasis, potentially leading to pathological consequences, such as dyslipidaemia, diabetes, fatty liver, autoimmune diseases, neurodegenerative diseases and cancers. For systemic energy homoeostasis, multiple enzymes involved in lipogenesis are tightly controlled by transcriptional and post-translational modifications. In this Review, we discuss recent findings regarding the regulatory mechanisms, physiological roles and pathological importance of lipogenesis in multiple tissues such as adipose tissue and the liver, as well as the immune and nervous systems. Furthermore, we briefly introduce the therapeutic implications of lipogenesis modulation.

What's New in the Treatment of Non-Alcoholic Fatty Liver Disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a serious health problem due to its high incidence and consequences. In view of the existing controversies, new therapeutic options for NAFLD are still being sought. Therefore, the aim of our review was to evaluate the recently published studies on the treatment of NAFLD patients. We searched for articles in the PubMed database using appropriate terms, including "non-alcoholic fatty liver disease", "nonalcoholic fatty liver disease", "NAFLD", "diet", "treatment", "physical activity", "supplementation", "surgery", "overture" and "guidelines". One hundred forty-eight randomized clinical trials published from January 2020 to November 2022 were used for the final analysis. The results show significant benefits of NAFLD therapy associated with the use of not only the Mediterranean but also other types of diet (including low-calorie ketogenic, high-protein, anti-inflammatory and whole-grain diets), as well as enrichment with selected food products or supplements. Significant benefits in this group of patients are also associated with moderate aerobic physical training. The available therapeutic options indicate, above all, the usefulness of drugs related to weight reduction, as well as the reduction in insulin resistance or lipids level and drugs with anti-inflammatory or antioxidant properties. The usefulness of therapy with dulaglutide and the combination of tofogliflozin with pioglitazone should be emphasized. Based on the results of the latest research, the authors of this article suggest a revision of the therapeutic recommendations for NAFLD patients.

Recent updates on targeting the molecular mediators of NAFLD

Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming the most common disease worldwide in an era of rapid economic growth. NAFLD is a multifactorial disease, involving multiple genetic, metabolic, and environmental factors, and is closely associated with metabolic syndrome, obesity, and cardiovascular disease. NAFLD can be classified into nonalcoholic fatty liver disease (NAFL) and nonalcoholic steatohepatitis (NASH), which can both progress to cirrhosis and even hepatocellular carcinoma (HCC). Due to the enormous burden of NAFLD and its complications, no FDA-approved drugs for the treatment of NAFLD are on the market, and therapeutic targets and drug therapies are being actively investigated. In view of the various pathological mechanisms of NAFLD, numbers of preclinical studies and clinical trials have made rapid progress. This review mainly summarizes the most recently characterized mechanisms and therapeutic targets in each mechanism of NAFLD, focusing on the mechanism and application potential.

Fatty Acid Synthase (FASN): A Patent Review Since 2016-Present

INTRODUCTION

Fatty acid synthase (FASN), is a key metabolic enzyme involved in fatty acid biosynthesis and is an essential target for multiple disease progressions like cancer, obesity, NAFLD, etc. Aberrant expression of FASN is associated with deregulated energy metabolism of cells in these diseases.

AREA COVERED

This article provides a summary of the most recent developments in the discovery of novel FASN inhibitors with potential therapeutic uses in cancer, obesity, and other metabolic disorders such as nonalcoholic fatty liver disease from 2016 to the present. The recently published patent applications and forthcoming clinical data of FASN inhibitors from both academia and the pharma industries are also highlighted in this study.

EXPERT OPINION

The implication of FASN in multiple diseases has provided an impetus for developing novel inhibitors by both pharma companies and academia. Critical analysis of the patent literature reveals the exploration of diverse molecular scaffolds to identify potential FASN inhibitors that target the different catalytic domains of the enzyme. In spite of these multifaceted efforts, only one molecule, TVB-2640, has reached phase II trials for nonalcoholic steatohepatitis (NASH) and many malignancies. However, thecombined efforts of pharma companies to produce several FASN inhibitors might facilitate the clinical translation of this unique class of inhibitors. Nevertheless, concerted efforts towards developing multiple FASN inhibitors by pharma companies might facilitate the clinical translation of this novel class of inhibitors.

Progress of potential drugs targeted in lipid metabolism research

Lipids are a class of complex hydrophobic molecules derived from fatty acids that not only form the structural basis of biological membranes but also regulate metabolism and maintain energy balance. The role of lipids in obesity and other metabolic diseases has recently received much attention, making lipid metabolism one of the attractive research areas. Several metabolic diseases are linked to lipid metabolism, including diabetes, obesity, and atherosclerosis. Additionally, lipid metabolism contributes to the rapid growth of cancer cells as abnormal lipid synthesis or uptake enhances the growth of cancer cells. This review introduces the potential drug targets in lipid metabolism and summarizes the important potential drug targets with recent research progress on the corresponding small molecule inhibitor drugs. The significance of this review is to provide a reference for the clinical treatment of metabolic diseases related to lipid metabolism and the treatment of tumors, hoping to deepen the understanding of lipid metabolism and health.

FASN inhibition targets multiple drivers of NASH by reducing steatosis, inflammation and fibrosis in preclinical models

Fatty acid synthase (FASN) is an attractive therapeutic target in non-alcoholic steatohepatitis (NASH) because it drives de novo lipogenesis and mediates pro-inflammatory and fibrogenic signaling. We therefore tested pharmacological inhibition of FASN in human cell culture and in three diet induced mouse models of NASH. Three related FASN inhibitors were used; TVB-3664, TVB-3166 and clinical stage TVB-2640 (denifanstat). In human primary liver microtissues, FASN inhibiton (FASNi) decreased triglyceride (TG) content, consistent with direct anti-steatotic activity. In human hepatic stellate cells, FASNi reduced markers of fibrosis including collagen1α (COL1α1) and α-smooth muscle actin (αSMA). In CD4+ T cells exposed to NASH-related cytokines, FASNi decreased production of Th17 cells, and reduced IL-1β release in LPS-stimulated PBMCs. In mice with diet induced NASH l, FASNi prevented development of hepatic steatosis and fibrosis, and reduced circulating IL-1β. In mice with established diet-induced NASH, FASNi reduced NAFLD activity score, fibrosis score, ALT and TG levels. In the CCl4-induced FAT-NASH mouse model, FASN inhibition decreased hepatic fibrosis and fibrosis markers, and development of hepatocellular carcinoma (HCC) tumors by 85%. These results demonstrate that FASN inhibition attenuates inflammatory and fibrotic drivers of NASH by direct inhibition of immune and stellate cells, beyond decreasing fat accumulation in hepatocytes. FASN inhibition therefore provides an opportunity to target three key hallmarks of NASH.

Progress in research of lipogenesis inhibitors for treatment of nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the main cause of chronic liver disease. At present, the main clinical treatment for NAFLD is diet adjustment, exercise, and weight loss, but the effect is poor, and there is still a lack of recognized drugs with significant efficacy in NAFLD. In recent years, with the in-depth study of the pathogenesis of NAFLD, it has been found that the core enzymes that inhibit intrahepatic de novo lipogenesis (DNL), including citrate/isocitrate carrier (CIC), ATP-citrate lyase (ACLY), acetyl-CoA carboxylase (ACC), fatty acid synthase (FASN), and stearoyl-CoA desaturase 1 (SCD1), can improve hepatic steatosis and provide a new method for the treatment of NAFLD. This article reviews the research progress of five different types of lipogenesis inhibitors for treatment of NAFLD.

Signaling pathways in obesity: mechanisms and therapeutic interventions

Obesity is a complex, chronic disease and global public health challenge. Characterized by excessive fat accumulation in the body, obesity sharply increases the risk of several diseases, such as type 2 diabetes, cardiovascular disease, and nonalcoholic fatty liver disease, and is linked to lower life expectancy. Although lifestyle intervention (diet and exercise) has remarkable effects on weight management, achieving long-term success at weight loss is extremely challenging, and the prevalence of obesity continues to rise worldwide. Over the past decades, the pathophysiology of obesity has been extensively investigated, and an increasing number of signal transduction pathways have been implicated in obesity, making it possible to fight obesity in a more effective and precise way. In this review, we summarize recent advances in the pathogenesis of obesity from both experimental and clinical studies, focusing on signaling pathways and their roles in the regulation of food intake, glucose homeostasis, adipogenesis, thermogenesis, and chronic inflammation. We also discuss the current anti-obesity drugs, as well as weight loss compounds in clinical trials, that target these signals. The evolving knowledge of signaling transduction may shed light on the future direction of obesity research, as we move into a new era of precision medicine.

Impact of NAFLD and its pharmacotherapy on lipid profile and CVD

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death worldwide. Increasing evidence suggests that, in addition to traditional metabolic risk factors such as obesity, hypercholesterolemia, hypertension, diabetes mellitus, and insulin resistance (IR), nonalcoholic fatty liver disease (NAFLD) is an emerging driver of ASCVD via multiple mechanisms, mainly by disrupting lipid metabolism. The lack of pharmaceutical treatment has spurred substantial investment in the research and development of NAFLD drugs. However, many reagents with promising therapeutic potential for NAFLD also have considerable impacts on the circulating lipid profile. In this review, we first summarize the mechanisms linking lipid dysregulation in NAFLD to the progression of ASCVD. Importantly, we highlight the potential risks of/benefits to ASCVD conferred by NAFLD pharmaceutical treatments and discuss potential strategies and next-generation drugs for treating NAFLD without the unwanted side effects.

Pathogenesis and Therapeutic Strategies Related to Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD), one of the most common types of chronic liver disease, is strongly correlated with obesity, insulin resistance, metabolic syndrome, and genetic components. The pathological progression of NAFLD, consisting of non-alcoholic fatty liver (NAFL), non-alcoholic steatohepatitis (NASH), and liver cirrhosis, is characterized by a broad spectrum of clinical phenotypes. Although patients with mild NAFL are considered to show no obvious clinical symptoms, patients with long-term NAFL may culminate in NASH and further liver fibrosis. Even though various drugs are able to improve NAFLD, there are no FDA-approved medications that directly treat NAFLD. In this paper, the pathogenesis of NAFLD, the potential therapeutic targets, and their underlying mechanisms of action were reviewed.

The Deubiquitinase USP13 Maintains Cancer Cell Stemness by Promoting FASN Stability in Small Cell Lung Cancer

USP13 is significantly amplified in over 20% of lung cancer patients and critical for tumor progression. However, the functional role of USP13 in small cell lung cancer (SCLC) remains largely unclear. In this study, we found that the deubiquitinase USP13 is highly expressed in SCLC tumor samples and positively associated with poor prognosis in multiple cohorts. In vitro and in vivo depletion of USP13 inhibited SCLC cancer stem cells (CSCs) properties and tumorigenesis, and this inhibitory effect was rescued by reconstituted expression of wide type (WT) USP13 but not the enzyme-inactive USP13 mutant. Mechanistically, USP13 interacts with fatty acid synthase (FASN) and enhances FASN protein stability. FASN downregulation suppresses USP13-enhanced cell renewal regulator expression, sphere formation ability, and de novo fatty acids biogenesis. Accordingly, we found FASN expression is upregulated in surgical resected SCLC specimens, positively correlated with USP13, and associated with poor prognosis of SCLC patients. More importantly, the small molecule inhibitor of FASN, TVB-2640, significantly inhibits lipogenic phenotype and attenuates self-renewal ability, chemotherapy resistance and USP13-mediated tumorigenesis in SCLC. Thus, our study highlights a critical role of the USP13-FASN-lipogenesis axis in SCLC cancer stemness maintenance and tumor growth, and reveals a potential combination therapy for SCLC patients.

Fatty Acid Synthase inhibitor TVB-3166 prevents S-acylation of the Spike protein of human coronaviruses

The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other coronaviruses mediates host cell entry and is S-acylated on multiple phylogenetically conserved cysteine residues. Multiple protein acyltransferase enzymes have been reported to post-translationally modify spike proteins; however, strategies to exploit this modification are lacking. Using resin-assisted capture MS, we demonstrate that the spike protein is S-acylated in SARS-CoV-2-infected human and monkey epithelial cells. We further show that increased abundance of the acyltransferase ZDHHC5 associates with increased S-acylation of the spike protein, whereas ZDHHC5 knockout cells had a 40% reduction in the incorporation of an alkynyl-palmitate using click chemistry detection. We also found that the S-acylation of the spike protein is not limited to palmitate, as clickable versions of myristate and stearate were also labelled the protein. Yet, we observed that ZDHHC5 was only modified when incubated with alkyne-palmitate, suggesting it has specificity for this acyl-CoA, and that other ZDHHC enzymes may use additional fatty acids to modify the spike protein. Since multiple ZDHHC isoforms may modify the spike protein, we also examined the ability of the FASN inhibitor TVB-3166 to prevent S-acylation of the spike proteins of SARS-CoV-2 and human CoV-229E. We show that treating cells with TVB-3166 inhibited S-acylation of expressed spike proteins and attenuated the ability of SARS-CoV-2 and human CoV-229E to spread in vitro. Our findings further substantiate the necessity of CoV spike protein S-acylation and demonstrate that de novo fatty acid synthesis is critical for the proper S-acylation of the spike protein.

Overexpression of NAG-1/GDF15 prevents hepatic steatosis through inhibiting oxidative stress-mediated dsDNA release and AIM2 inflammasome activation

Mitochondrial dysfunction and oxidative stress-mediated inflammasome activation play critical roles in the pathogenesis of the non-alcoholic fatty liver disease (NAFLD). Non-steroidal anti-inflammatory drug (NSAID)-activated gene-1 (NAG-1), or growth differentiation factor-15 (GDF15), is associated with many biological processes and diseases, including NAFLD. However, the role of NAG-1/GDF15 in regulating oxidative stress and whether this process is associated with absent in melanoma 2 (AIM2) inflammasome activation in NAFLD are unknown. In this study, we revealed that NAG-1/GDF15 is significantly downregulated in liver tissues of patients with steatosis compared to normal livers using the Gene Expression Omnibus (GEO) database, and in free fatty acids (FFA, oleic acid/palmitic acid, 2:1)-induced HepG2 and Huh-7 cellular steatosis models. Overexpression of NAG-1/GDF15 in transgenic (Tg) mice significantly alleviated HFD-induced obesity and hepatic steatosis, improved lipid homeostasis, enhanced fatty acid β-oxidation and lipolysis, inhibited fatty acid synthesis and uptake, and inhibited AIM2 inflammasome activation and the secretion of IL-18 and IL-1β, as compared to their wild-type (WT) littermates without reducing food intake. Furthermore, NAG-1/GDF15 overexpression attenuated FFA-induced triglyceride (TG) accumulation, lipid metabolism deregulation, and AIM2 inflammasome activation in hepatic steatotic cells, while knockdown of NAG-1/GDF15 demonstrated opposite effects. Moreover, NAG-1/GDF15 overexpression inhibited HFD- and FFA-induced oxidative stress and mitochondrial damage which in turn reduced double-strand DNA (dsDNA) release into the cytosol, while NAG-1/GDF15 siRNA showed opposite effects. The reduced ROS production and dsDNA release may be responsible for attenuated AIM2 activation by NAG-1/GDF15 upon fatty acid overload. In conclusion, our results provide evidence that other than regulating lipid homeostasis, NAG-1/GDF15 protects against hepatic steatosis through a novel mechanism via suppressing oxidative stress, mitochondrial damage, dsDNA release, and AIM2 inflammasome activation.

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NAG-1/GDF15 is downregulated in human steatotic liver and FFA-induced liver cells.

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NAG-1/GDF15 inhibits hepatic steatosis and improves lipid homeostasis.

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AIM2 inflammasome is activated in steatosis models and is inhibited by NAG-1/GDF15.

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NAG-1/GDF15 reduces oxidative stress and mitochondrial damage in steatosis models.

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NAG-1/GDF15 inhibits mitochondrial dsDNA release and thus inhibits AIM2 activation.

Reprogramming of Fatty Acid Metabolism in Gynaecological Cancers: Is There a Role for Oestradiol?

Gynaecological cancers are among the leading causes of cancer-related death among women worldwide. Cancer cells undergo metabolic reprogramming to sustain the production of energy and macromolecules required for cell growth, division and survival. Emerging evidence has provided significant insights into the integral role of fatty acids on tumourigenesis, but the metabolic role of high endogenous oestrogen levels and increased gynaecological cancer risks, notably in obesity, is less understood. This is becoming a renewed research interest, given the recently established association between obesity and incidence of many gynaecological cancers, including breast, ovarian, cervical and endometrial cancers. This review article, hence, comprehensively discusses how FA metabolism is altered in these gynaecological cancers, highlighting the emerging role of oestradiol on the actions of key regulatory enzymes of lipid metabolism, either directly through its classical ER pathways, or indirectly via the IGIFR pathway. Given the dramatic rise in obesity and parallel increase in the prevalence of gynaecological cancers among premenopausal women, further clarifications of the complex mechanisms underpinning gynaecological cancers are needed to inform future prevention efforts. Hence, in our review, we also highlight opportunities where metabolic dependencies can be exploited as viable therapeutic targets for these hormone-responsive cancers.

Combined Use of Bicyclol and Berberine Alleviates Mouse Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), is a liver disease worldwide without approved therapeutic drugs. Anti-inflammatory and hepatoprotective drug bicyclol and multi-pharmacological active drug berberine, respectively, have shown beneficial effects on NAFLD in murine nutritional models and patients, though the therapeutic mechanisms remain to be illustrated. Here, we investigated the combined effects of bicyclol and berberine on mouse steatosis induced by Western diet (WD), and NASH induced by WD/CCl₄. The combined use of these was rather safe and better reduced the levels of transaminase in serum and triglycerides and cholesterol in the liver than their respective monotherapy, accompanied with more significantly attenuating hepatic inflammation, steatosis, and ballooning in mice with steatosis and NASH. The combined therapy also significantly inhibited fibrogenesis, characterized by the decreased hepatic collagen deposition and fibrotic surface. As per mechanism, bicyclol enhanced lipolysis and β-oxidation through restoring the p62-Nrf2-CES2 signaling axis and p62-Nrf2-PPARα signaling axis, respectively, while berberine suppressed de novo lipogenesis through downregulating the expression of acetyl-CoA carboxylase and fatty acid synthetase, along with enrichment of lipid metabolism-related Bacteroidaceae (family) and Bacteroides (genus). Of note, the combined use of bicyclol and berberine did not influence each other but enhanced the overall therapeutic role in the amelioration of NAFLD. Conclusion: Combined use of bicyclol and berberine might be a new available strategy to treat NAFLD.

Lipid alterations in chronic liver disease and liver cancer

Lipids are a complex and diverse group of molecules with crucial roles in many physiological processes, as well as in the onset, progression, and maintenance of cancers. Fatty acids and cholesterol are the building blocks of lipids, orchestrating these crucial metabolic processes. In the liver, lipid alterations are prevalent as a cause and consequence of chronic hepatitis B and C virus infections, alcoholic hepatitis, and non-alcoholic fatty liver disease and steatohepatitis. Recent developments in lipidomics have also revealed that dynamic changes in triacylglycerols, phospholipids, sphingolipids, ceramides, fatty acids, and cholesterol are involved in the development and progression of primary liver cancer. Accordingly, the transcriptional landscape of lipid metabolism suggests a carcinogenic role of increasing fatty acids and sterol synthesis. However, limited mechanistic insights into the complex nature of the hepatic lipidome have so far hindered the development of effective therapies.

Druggability of lipid metabolism modulation against renal fibrosis

Renal fibrosis contributes to progressive damage to renal structure and function. It is a common pathological process as chronic kidney disease develops into kidney failure, irrespective of diverse etiologies, and eventually leads to death. However, there are no effective drugs for renal fibrosis treatment at present. Lipid aggregation in the kidney and consequent lipotoxicity always accompany chronic kidney disease and fibrosis. Numerous studies have revealed that restoring the defective fatty acid oxidation in the kidney cells can mitigate renal fibrosis. Thus, it is an important strategy to reverse the dysfunctional lipid metabolism in the kidney, by targeting critical regulators of lipid metabolism. In this review, we highlight the potential "druggability" of lipid metabolism to ameliorate renal fibrosis and provide current pre-clinical evidence, exemplified by some representative druggable targets and several other metabolic regulators with anti-renal fibrosis roles. Then, we introduce the preliminary progress of noncoding RNAs as promising anti-renal fibrosis drug targets from the perspective of lipid metabolism. Finally, we discuss the prospects and deficiencies of drug targeting lipid reprogramming in the kidney.

Activation of Liver mTORC1 Protects Against NASH via Dual Regulation of VLDL-TAG Secretion and De Novo Lipogenesis

BACKGROUND & AIMS

Dysregulation of liver lipid metabolism is associated with the development and progression of nonalcoholic fatty liver disease, a spectrum of liver diseases including nonalcoholic steatohepatitis (NASH). In the liver, insulin controls lipid homeostasis by increasing triglyceride (TAG) synthesis, suppressing fatty acid oxidation, and enhancing TAG export via very low-density lipoproteins. Downstream of insulin signaling, the mechanistic target of rapamycin complex 1 (mTORC1), is a key regulator of lipid metabolism. Here, we define the role of hepatic mTORC1 activity in mouse models of NASH and investigate the mTORC1-dependent mechanisms responsible for protection against liver damage in NASH.

METHODS

Utilizing 2 rodent NASH-promoting diets, we demonstrate that hepatic mTORC1 activity was reduced in mice with NASH, whereas under conditions of insulin resistance and benign fatty liver, mTORC1 activity was elevated. To test the beneficial effects of hepatic mTORC1 activation in mouse models of NASH, we employed an acute, liver-specific knockout model of TSC1 (L-TSC-KO), a negative regulator of mTORC1.

RESULTS

L-TSC-KO mice are protected from and have improved markers of NASH including reduced steatosis, decreased circulating transaminases, and reduced expression of inflammation and fibrosis genes. Mechanistically, protection from hepatic inflammation and fibrosis by constitutive mTORC1 activity occurred via promotion of the phosphatidylcholine synthesizing enzyme, CCTα, and enhanced very low-density lipoprotein-triglyceride export. Additionally, activation of mTORC1 protected from hepatic steatosis via negative feedback of the mTORC2-AKT-FOXO-SREBP1c lipogenesis axis.

CONCLUSIONS

Collectively, this study identifies a protective role for liver mTORC1 signaling in the initiation and progression of NASH in mice via dual control of lipid export and synthesis.

Role of Lipogenesis Rewiring in Hepatocellular Carcinoma

Metabolic rewiring is one of the hallmarks of cancer. Altered de novo lipogenesis is one of the pivotal metabolic events deregulated in cancers. Sterol regulatory element-binding transcription factor 1 (SREBP1) controls the transcription of major enzymes involved in de novo lipogenesis, including ACLY, ACACA, FASN, and SCD. Studies have shown the increased de novo lipogenesis in human hepatocellular carcinoma (HCC) samples. Multiple mechanisms, such as activation of the AKT/mechanistic target of rapamycin (mTOR) pathway, lead to high SREBP1 induction and the coordinated enhanced expression of ACLY, ACACA, FASN, and SCD genes. Subsequent functional analyses have unraveled these enzymes' critical role(s) and the related de novo lipogenesis in hepatocarcinogenesis. Importantly, targeting these molecules might be a promising strategy for HCC treatment. This paper comprehensively summarizes de novo lipogenesis rewiring in HCC and how this pathway might be therapeutically targeted.

Pharmacotherapy for Non-Alcoholic Fatty Liver Disease: Emerging Targets and Drug Candidates

Non-alcoholic fatty liver disease (NAFLD), or metabolic (dysfunction)-associated fatty liver disease (MAFLD), is characterized by high global incidence and prevalence, a tight association with common metabolic comorbidities, and a substantial risk of progression and associated mortality. Despite the increasingly high medical and socioeconomic burden of NAFLD, the lack of approved pharmacotherapy regimens remains an unsolved issue. In this paper, we aimed to provide an update on the rapidly changing therapeutic landscape and highlight the major novel approaches to the treatment of this disease. In addition to describing the biomolecules and pathways identified as upcoming pharmacological targets for NAFLD, we reviewed the current status of drug discovery and development pipeline with a special focus on recent evidence from clinical trials.

Lipogenesis inhibitors: therapeutic opportunities and challenges

Fatty acids are essential for survival, acting as bioenergetic substrates, structural components and signalling molecules. Given their vital role, cells have evolved mechanisms to generate fatty acids from alternative carbon sources, through a process known as de novo lipogenesis (DNL). Despite the importance of DNL, aberrant upregulation is associated with a wide variety of pathologies. Inhibiting core enzymes of DNL, including citrate/isocitrate carrier (CIC), ATP-citrate lyase (ACLY), acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), represents an attractive therapeutic strategy. Despite challenges related to efficacy, selectivity and safety, several new classes of synthetic DNL inhibitors have entered clinical-stage development and may become the foundation for a new class of therapeutics.

De novo lipogenesis (DNL) is vital for the maintenance of whole-body and cellular homeostasis, but aberrant upregulation of the pathway is associated with a broad range of conditions, including cardiovascular disease, metabolic disorders and cancers. Here, Steinberg and colleagues provide an overview of the physiological and pathological roles of the core DNL enzymes and assess strategies and agents currently in development to therapeutically target them.

Emerging pharmacological treatment options for MAFLD

Metabolic dysfunction-associated fatty liver disease (MAFLD) prevalence and incidence is rising globally. It is associated with metabolic comorbidities, obesity, overweight, type 2 diabetes mellitus, and at least two metabolic risk factors, such as hypertension, hypertriglyceridemia, hypercholesterolemia, insulin resistance, and cardiovascular risk, increasing the risk of mortality. The excessive accumulation of fat comprises apoptosis, necrosis, inflammation and ballooning degeneration progressing to fibrosis, cirrhosis, and liver decompensations including hepatocellular carcinoma development. The limitation of approved drugs to prevent MAFLD progression is a paradigm. This review focuses on recent pathways and targets with evidence results in phase II/III clinical trials.

Advancements in the treatment of non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a series of diseases, involving excessive lipid deposition in the liver and is often accompanied by obesity, diabetes, dyslipidemia, abnormal blood pressure, and other metabolic disorders. In order to more accurately reflect its pathogenesis, an international consensus renamed NAFLD in 2020 as metabolic (dysfunction) associated with fatty liver disease (MAFLD). The changes in diet and lifestyle are recognized the non-drug treatment strategies; however, due to the complex pathogenesis of NAFLD, the current drug therapies are mainly focused on its pathogenic factors, key links of pathogenesis, and related metabolic disorders as targets. There is still a lack of specific drugs. In clinical studies, the common NAFLD treatments include the regulation of glucose and lipid metabolism to protect the liver and anti-inflammation. The NAFLD treatments based on the enterohepatic axis, targeting gut microbiota, are gradually emerging, and various new metabolism-regulating drugs are also under clinical development. Therefore, this review article has comprehensively discussed the research advancements in NAFLD treatment in recent years.

Insights into the molecular targets and emerging pharmacotherapeutic interventions for nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease worldwide. With no Food and Drug Administration approved drugs, current treatment options include dietary restrictions and lifestyle modification. NAFLD is closely associated with metabolic disorders such as obesity, type 2 diabetes, and dyslipidemia. Hence, clinically various pharmacological approaches using existing drugs such as antidiabetic, anti-obesity, antioxidants, and cytoprotective agents have been considered in the management of NAFLD and nonalcoholic steatohepatitis (NASH). However, several pharmacological therapies aiming to alleviate NAFLD-NASH are currently being examined at various phases of clinical trials. Emerging data from these studies with drugs targeting diverse molecular mechanisms show promising outcomes. This review summarizes the current understanding of the pathogenic mechanisms of NAFLD and provides an insight into the pharmacological targets and emerging therapeutics with specific interventional mechanisms. In addition, we also discuss the importance and utility of new approach methodologies and regulatory perspectives for NAFLD-NASH drug development.

Fatty Acid Synthase Inhibitor Platensimycin Intervenes the Development of Nonalcoholic Fatty Liver Disease in a Mouse Model

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease affecting about 25% of world population, while there are still no approved targeted therapies. Although platensimycin (PTM) was first discovered to be a broad-spectrum antibiotic, it was also effective against type II diabetes in animal models due to its ability to inhibit both bacterial and mammalian fatty acid synthases (FASN). Herein, we report the pharmacological effect and potential mode of action of PTM against NAFLD in a Western diet/CCI₄-induced mouse model and a free fatty acids (FFAs)-induced HepG2 cell model. The proper dose of PTM and its liposome-based nano-formulations not only significantly attenuated the Western diet-induced weight gain and the levels of plasma total triglycerides and glucose, but reduced liver steatosis in mice according to histological analyses. Western blotting analysis showed a reduced protein level of FASN in the mouse liver, suggesting that PTM intervened in the development of NAFLD through FASN inhibition. PTM reduced both the protein and mRNA levels of FASN in FFAs-induced HepG2 cells, as well as the expression of several key proteins in lipogenesis, including sterol regulatory element binding protein-1, acetyl-CoA carboxylase, and stearoyl-CoA desaturase. The expression of lipid oxidation-related genes, including peroxisome proliferator activated receptor α and acyl-CoA oxidase 1, was significantly elevated. In conclusion, our study supports the reposition of PTM to intervene in NAFLD progression, since it could effectively inhibit de novo lipogenesis.

MicroRNA Cues from Nature: A Roadmap to Decipher and Combat Challenges in Human Health and Disease?

MicroRNAs are small non-coding RNA (18–24 nt long) that fine-tune gene expression at the post-transcriptional level. With the advent of “multi-omics” analysis and sequencing approaches, they have now been implicated in every facet of basic molecular networks, including metabolism, homeostasis, and cell survival to aid cellular machinery in adapting to changing environmental cues. Many animals must endure harsh environmental conditions in nature, including cold/freezing temperatures, oxygen limitation (anoxia/hypoxia), and food or water scarcity, often requiring them to revamp their metabolic organization, frequently on a seasonal or life stage basis. MicroRNAs are important regulatory molecules in such processes, just as they are now well-known to be involved in many human responses to stress or disease. The present review outlines the role of miRNAs in natural animal models of environmental stress and adaptation including torpor/hibernation, anoxia/hypoxia tolerance, and freeze tolerance. We also discuss putative medical applications of advances in miRNA biology including organ preservation for transplant, inflammation, ageing, metabolic disorders (e.g., obesity), mitochondrial dysfunction (mitoMirs) as well as specialized miRNA subgroups respective to low temperature (CryomiRs) and low oxygen (OxymiRs). The review also covers differential regulation of conserved and novel miRNAs involved at cell, tissue, and stress specific levels across multiple species and their roles in survival. Ultimately, the species-specific comparison and conserved miRNA responses seen in evolutionarily disparate animal species can help us to understand the complex miRNA network involved in regulating and reorganizing metabolism to achieve diverse outcomes, not just in nature, but in human health and disease.

Roles of IκB kinases and TANK-binding kinase 1 in hepatic lipid metabolism and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and is strongly associated with obesity-related ectopic fat accumulation in the liver. Hepatic lipid accumulation encompasses a histological spectrum ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), which can progress to cirrhosis and hepatocellular carcinoma. Given that dysregulated hepatic lipid metabolism may be an onset factor in NAFLD, understanding how hepatic lipid metabolism is modulated in healthy subjects and which steps are dysregulated in NAFLD subjects is crucial to identify effective therapeutic targets. Additionally, hepatic inflammation is involved in chronic hepatocyte damage during NAFLD progression. As a key immune signaling hub that mediates NF-κB activation, the IκB kinase (IKK) complex, including IKKα, IKKβ, and IKKγ (NEMO), has been studied as a crucial regulator of the hepatic inflammatory response and hepatocyte survival. Notably, TANK-binding kinase 1 (TBK1), an IKK-related kinase, has recently been revealed as a potential link between hepatic inflammation and energy metabolism. Here, we review (1) the biochemical steps of hepatic lipid metabolism; (2) dysregulated lipid metabolism in obesity and NAFLD; and (3) the roles of IKKs and TBK1 in obesity and NAFLD.

Liver Fibrosis and MAFLD: From Molecular Aspects to Novel Pharmacological Strategies

Metabolic-associated fatty liver disease (MAFLD) is a new disease definition, and this nomenclature MAFLD was proposed to renovate its former name, non-alcoholic fatty liver disease (NAFLD). MAFLD/NAFLD have shared and predominate causes from nutrition overload to persistent liver damage and eventually lead to the development of liver fibrosis and cirrhosis. Unfortunately, there is an absence of effective treatments to reverse MAFLD/NAFLD-associated fibrosis. Due to the significant burden of MAFLD/NAFLD and its complications, there are active investigations on the development of novel targets and pharmacotherapeutics for treating this disease. In this review, we cover recent discoveries in new targets and molecules for antifibrotic treatment, which target pathways intertwined with the fibrogenesis process, including lipid metabolism, inflammation, cell apoptosis, oxidative stress, and extracellular matrix formation. Although marked advances have been made in the development of antifibrotic therapeutics, none of the treatments have achieved the endpoints evaluated by liver biopsy or without significant side effects in a large-scale trial. In addition to the discovery of new druggable targets and pharmacotherapeutics, personalized medication, and combinatorial therapies targeting multiple profibrotic pathways could be promising in achieving successful antifibrotic interventions in patients with MAFLD/NAFLD.

Contradictory roles of lipid metabolism in immune response within the tumor microenvironment

Complex interactions between the immune system and tumor cells exist throughout the initiation and development of cancer. Although the immune system eliminates malignantly transformed cells in the early stage, surviving tumor cells evade host immune defense through various methods and even reprogram the anti-tumor immune response to a pro-tumor phenotype to obtain unlimited growth and metastasis. The high proliferation rate of tumor cells increases the demand for local nutrients and oxygen. Poorly organized vessels can barely satisfy this requirement, which results in an acidic, hypoxic, and glucose-deficient tumor microenvironment. As a result, lipids in the tumor microenvironment are activated and utilized as a primary source of energy and critical regulators in both tumor cells and related immune cells. However, the exact role of lipid metabolism reprogramming in tumor immune response remains unclear. A comprehensive understanding of lipid metabolism dysfunction in the tumor microenvironment and its dual effects on the immune response is critical for mapping the detailed landscape of tumor immunology and developing specific treatments for cancer patients. In this review, we have focused on the dysregulation of lipid metabolism in the tumor microenvironment and have discussed its contradictory roles in the tumor immune response. In addition, we have summarized the current therapeutic strategies targeting lipid metabolism in tumor immunotherapy. This review provides a comprehensive summary of lipid metabolism in the tumor immune response.

TVB-2640 (FASN Inhibitor) for the Treatment of Nonalcoholic Steatohepatitis: FASCINATE-1, a Randomized, Placebo-Controlled Phase 2a Trial

BACKGROUND & AIMS

Increased de novo lipogenesis creates excess intrahepatic fat and lipotoxins, propagating liver damage in nonalcoholic steatohepatitis. TVB-2640, a fatty acid synthase inhibitor, was designed to reduce excess liver fat and directly inhibit inflammatory and fibrogenic pathways. We assessed the safety and efficacy of TVB-2640 in patients with nonalcoholic steatohepatitis in the United States.

METHODS

3V2640-CLIN-005 (FASCINATE-1) was a randomized, placebo-controlled, single-blind study at 10 US sites. Adults with ≥8% liver fat, assessed by magnetic resonance imaging proton density fat fraction, and evidence of liver fibrosis by magnetic resonance elastography ≥2.5 kPa or liver biopsy were eligible. Ninety-nine patients were randomized to receive placebo or 25 mg or 50 mg of TVB-2640 (orally, once-daily for 12 weeks). The primary end points of this study were safety and relative change in liver fat after treatment.

RESULTS

Liver fat increased in the placebo cohort by 4.5% relative to baseline; in contrast TVB-2640 reduced liver fat by 9.6% in the 25-mg cohort (n = 30; least squares mean: -15.5%; 95% confidence interval, -31.3 to -0.23; P = .053), and 28.1% in the 50-mg cohort (n = 28; least squares mean: -28.0%; 95% confidence interval, -44.5 to -11.6; P = .001). Eleven percent of patients in the placebo group achieved a ≥30% relative reduction of liver fat compared to 23% in the 25-mg group, and 61% in the 50-mg group (P < .001). Secondary analyses showed improvements of metabolic, pro-inflammatory and fibrotic markers. TVB-2640 was well tolerated; adverse events were mostly mild and balanced among the groups.

CONCLUSIONS

TVB-2640 significantly reduced liver fat and improved biochemical, inflammatory, and fibrotic biomarkers after 12 weeks, in a dose-dependent manner in patients with nonalcoholic steatohepatitis. ClinicalTrials.gov, Number NCT03938246.