Distinct contributions of metabolic dysfunction and genetic risk factors in the pathogenesis of non-alcoholic fatty liver disease

The association of metabolic dysfunction-associated steatotic liver disease (MASLD) with the risk of myocardial infarction: a systematic review and meta-analysis

Objective While studies have documented how metabolic dysfunction-associated steatotic liver disease (MASLD) can contribute to cardiovascular disease (CVD), whether MASLD is associated with myocardial infarction (MI) remains debateable. Herein, we systematically reviewed published articles and performed a meta-analysis to determine the relationship between MASLD and MI risk.Methods PubMed, MEDLINE, Embase, Web of Science, CNKI, CBM, VIP, and WanFang databases were searched, and the DerSimonian Laird method was used to obtain hazard ratios (HRs) for binary variables to assess the correlation between MASLD and MI risk. Subgroup analyses for the study region, MASLD diagnosis, quality score, study design, and follow-up time were conducted simultaneously for the selected studies retrieved from the time of database establishment to March 2022. All study procedures were independently conducted by two investigators.Results The final analysis included seven articles, including eight prospective and two retrospective cohort studies. The MI risk was higher among MASLD patients than among non-MASLD patients (HR = 1.26; 95% CI: 1.08-1.47, p = 0.003). The results of the subgroup analysis of the study region revealed an association of MASLD with MI risk among Americans and Asians, but not in Europeans. Subgroup analyses of MASLD diagnosis showed that ultrasonography and other (fatty liver index[FLI] and computed tomography [CT)]) diagnostic methods, but not international classification of disease (ICD), increased the risk of MI. Subgroup analysis of the study design demonstrated a stronger relationship between MASLD and MI in retrospective studies but not in prospective studies. Subgroup analysis based on the follow-up duration revealed the association of MASLD with MI risk in cases with < 3 years of follow-up but not with ≥3 years of follow-up.Conclusion MASLD increases the risk of MI, independent of traditional risk factors.

Natural history and progression of metabolic dysfunction-associated steatotic liver disease

The natural history of metabolic dysfunction-associated steatotic liver disease (MASLD), previously referred to as non-alcoholic fatty liver disease (NAFLD), is complex and long. A minority of patients develop inflammation and risk progressive fibrosis that can result in cirrhosis. Progression to cirrhosis occurs in 3-5% of patients and often takes more than 20 years. This narrative review presents an update on the natural history of MASLD, discussing studies and risk estimates for progression to severe outcomes, such as decompensated cirrhosis or hepatocellular carcinoma. We highlight the dynamic progression of liver damage, how to identify patients whose disease progresses over time, and how risk factors might be mitigated to reduce the risk for disease progression.

Greater hepatic lipid saturation is associated with impaired glycaemic regulation in men with metabolic dysfunction-associated steatotic liver disease but is not altered by 6 weeks of exercise training

AIMS

To examine the impact of impaired glycaemic regulation (IGR) and exercise training on hepatic lipid composition in men with metabolic dysfunction-associated steatotic liver disease (MASLD).

MATERIALS AND METHODS

In Part A (cross-sectional design), 40 men with MASLD (liver proton density fat fraction [PDFF] ≥5.56%) were recruited to one of two groups: (1) normal glycaemic regulation (NGR) group (glycated haemoglobin [HbA1c] < 42 mmol∙mol-1 [<6.0%]; n = 14) or (2) IGR group (HbA1c ≥ 42 mmol∙mol-1 [≥6.0%]; n = 26). In Part B (randomized controlled trial design), participants in the IGR group were randomized to one of two 6-week interventions: (1) exercise training (EX; 70%-75% maximum heart rate; four sessions/week; n = 13) or (2) non-exercise control (CON; n = 13). Saturated (SI; primary outcome), unsaturated (UI) and polyunsaturated (PUI) hepatic lipid indices were determined using proton magnetic resonance spectroscopy. Additional secondary outcomes included liver PDFF, HbA1c, fasting plasma glucose (FPG), homeostatic model assessment of insulin resistance (HOMA-IR), peak oxygen uptake (VO2 peak), and plasma cytokeratin-18 (CK18) M65, among others.

RESULTS

In Part A, hepatic SI was higher and hepatic UI was lower in the IGR versus the NGR group (p = 0.038), and this hepatic lipid profile was associated with higher HbA1c levels, FPG levels, HOMA-IR and plasma CK18 M65 levels (rs ≥0.320). In Part B, hepatic lipid composition and liver PDFF were unchanged after EX versus CON (p ≥ 0.257), while FPG was reduced and VO2 peak was increased (p ≤ 0.030). ΔVO2 peak was inversely associated with Δhepatic SI (r = -0.433) and positively associated with Δhepatic UI and Δhepatic PUI (r ≥ 0.433).

CONCLUSIONS

Impaired glycaemic regulation in MASLD is characterized by greater hepatic lipid saturation; however, this composition is not altered by 6 weeks of moderate-intensity exercise training.

Association between remnant cholesterol and metabolic dysfunction-associated steatotic liver disease in the elderly

BACKGROUND & AIMS

Whether maintaining optimal remnant cholesterol (RC) levels later in life may improve metabolic dysfunction-associated steatotic liver disease (MASLD) outcomes remained ambiguous. This study aimed to investigate the relationship between RC and MASLD in the elderly Chinese population.

METHODS

A total of 131,868 subjects aged ≥ 65 years were included in this study. The association of RC with MASLD, and severity of MASLD was analyzed by logistic regression. In addition, stratified analysis was conducted to test the potential interaction.

RESULTS

MASLD prevalence and RC concentration decreased with age. After adjustment for possible confounders, the odds ratio of MASLD at the highest quartile of RC compared to the lowest quartile was 1.587(95% CI: 1.524-1.652), and this effect remained in MASLD with liver fibrosis. Stratified analysis showed a more prominent effect on the MASLD in males, those aged 65-69 years, those without central obesity, those with diabetes, and normal level of total cholesterol, low-density lipoprotein cholesterol (Pfor interaction<0.05).

CONCLUSIONS

In the elderly subset of the Chinese population, higher RC levels achieved a significant risk effect against MASLD. More RC monitoring should be given to older for the prevention and intervention of MASLD.

Nano-drug delivery systems (NDDS) in metabolic dysfunction-associated steatotic liver disease (MASLD): current status, prospects and challenges

About one-third of the global population suffers from metabolic dysfunction-associated steatotic liver disease (MASLD), but specific treatments for MASLD have long been lacking, primarily due to the unclear etiology of the disease. In addition to lifestyle modifications and weight loss surgery, pharmacotherapy is the most common treatment among MASLD patients, and these drugs typically target the pathogenic factors of MASLD. However, bioavailability, efficacy, and side effects all limit the maximum therapeutic potential of the drugs. With the development of nanomedicine, recent years have seen attempts to combine MASLD pharmacotherapy with nanomaterials, such as liposomes, polymer nanoparticles, micelles, and cocrystals, which effectively improves the water solubility and targeting of the drugs, thereby enhancing therapeutic efficacy and reducing toxic side effects, offering new perspectives and futures for the treatment of MASLD.

METS-IR/HOMA-IR and MAFLD in U.S. adults: dose-response correlation and the effect mediated by physical activity

OBJECTIVES

Metabolic dysfunction-associated fatty liver disease (MAFLD), a globally prevalent disease, is closely linked to insulin resistance (IR). Physical activity (PA) is closely linked to both MAFLD and IR. We aim to explore the dose-response relationship between metabolic score for IR (METS-IR)/homeostasis model assessment of IR (HOMA-IR) and MAFLD, and investigate the relationship between PA, IR and MAFLD.

METHODS

Participants from the NHANES study were included in this cross-section study. Logistic regression and the receiver operating characteristic were used to assess the predictive performance of METS-IR/HOMA-IR for MAFLD. Restrictive cubic splines were performed to visualize their dose-response relationship. Decision tree analysis was used to identify high-risk populations of MAFLD. PA's mediating effect in the association between METS-IR/HOMA-IR and MAFLD was also examined.

RESULTS

Of all 1,313 participants, 693 had MAFLD (52.78%). There were a positive association between METS-IR (OR = 1.162, 95% CI = 1.126-1.199) and HOMA-IR (OR = 1.630, 95% CI = 1.431-1.856) and MAFLD risk. The AUCs of the METS-IR and HOMA-IR were 0.831 (0.809, 0.853) and 0.767 (0.741, 0.791), respectively, with significantly different predictive performance (P < 0.001). Adding METS-IR/HOMA-IR to the basic model greatly improved the statistical significance for MAFLD. Five high-risk subgroups were identified for MAFLD. PA mediated about 0.81% and 0.78% (indirect effect/total effect) in the association between METS-IR/HOMA-IR and MAFLD.

CONCLUSIONS

MAFLD risk might be predicted by METS-IR/HOMA-IR, among which METS-IR performed better. And PA mediated the association between them. More attention should be paid to the therapeutic effect of lifestyle changes on MAFLD.

HIGHLIGHTS

1. Positive associations were found between METS-IR and HOMA-IR and MAFLD risk. 2. METS-IR has better predictive performance for MAFLD risk than HOMA-IR. 3.Two high-risk subgroups were identified for MAFLD by METS-IR: individuals with METS-IR ≥ 40; Hispanic black individuals with 34 ≤ METS-IR < 40 and aged ≥ 46. 4. In the significant association between METS-IR/HOMA-IR and MAFLD, about 0.81% and 0.78% (indirect effect/total effect), respectively, were mediated by physical activity.

Mechanism of cytochrome P450s mediated interference with glutathione and amino acid metabolisms from halogenated PAHs exposure

Epidemiological evidence indicates that exposure to halogenated polycyclic aromatic hydrocarbons (HPAHs) is associated with many adverse effects. However, the mechanisms of metabolic disorder of HPAHs remains limited. Herein, effects of pyrene (Pyr), and its halogenated derivatives (1-chloropyrene (1-Cl-Pyr), 1-bromopyrene (1-Br-Pyr)) on endogenous metabolic pathways were investigated, in human hepatoma (HepG2) and HepG2-derived cell lines expressing various human cytochrome P450s (CYPs). Non-targeted metabolomics results suggested that 1-Br-Pyr and Pyr exposure (625 nM) induced disruption in glutathione and riboflavin metabolism which associated with redox imbalance, through abnormal accumulation of oxidized glutathione, mediated by bioactivation of CYP2E1. Conversely, CYP2C9-mediated 1-Cl-Pyr significantly interfered with glutathione metabolism intermediates, including glycine, L-glutamic acid and pyroglutamic acid. Notably, CYP1A1-mediated Pyr-induced perturbation of amino acid metabolism which associated with nutrition and glycolipid metabolism, resulting in significant upregulation of most amino acids, whereas halogenated derivatives mediated by CYP1A2 substantially downregulated amino acids. In conclusion, this study suggested that Pyr and its halogenated derivatives exert potent effects on endogenous metabolism disruption under the action of various exogenous metabolic enzymes (CYPs). Thus, new evidence was provided to toxicological mechanisms of HPAHs, and reveals potential health risks of HPAHs in inducing diseases caused by redox and amino acid imbalances.

The Effects of Long-Term High Fat and/or High Sugar Feeding on Sources of Postprandial Hepatic Glycogen and Triglyceride Synthesis in Mice

BACKGROUND

In MASLD (formerly called NAFLD) mouse models, oversupply of dietary fat and sugar is more lipogenic than either nutrient alone. Fatty acids suppress de novo lipogenesis (DNL) from sugars, while DNL inhibits fatty acid oxidation. How such factors interact to impact hepatic triglyceride levels are incompletely understood.

METHODS

Using deuterated water, we measured DNL in mice fed 18-weeks with standard chow (SC), SC supplemented with 55/45-fructose/glucose in the drinking water at 30% (w/v) (HS), high-fat chow (HF), and HF with HS supplementation (HFHS). Liver glycogen levels and its sources were also measured. For HS and HFHS mice, pentose phosphate (PP) fluxes and fructose contributions to DNL and glycogen were measured using [U-13C]fructose.

RESULTS

The lipogenic diets caused significantly higher liver triglyceride levels compared to SC. DNL rates were suppressed in HF compared to SC and were partially restored in HFHS but supplied a minority of the additional triglyceride in HFHS compared to HF. Fructose contributed a significantly greater fraction of newly synthesized saturated fatty acids compared to oleic acid in both HS and HFHS. Glycogen levels were not different between diets, but significant differences in Direct and Indirect pathway contributions to glycogen synthesis were found. PP fluxes were similar in HS and HFHS mice and were insufficient to account for DNL reducing equivalents.

CONCLUSIONS

Despite amplifying the lipogenic effects of fat, the fact that sugar-activated DNL per se barely contributes suggests that its role is likely more relevant in the inhibition of fatty acid oxidation. Fructose promotes lipogenesis of saturated over unsaturated fatty acids and contributes to maintenance of glycogen levels. PP fluxes associated with sugar conversion to fat account for a minor fraction of DNL reducing equivalents.

Association of Obstructive Sleep Apnea with Nonalcoholic Fatty Liver Disease: Evidence, Mechanism, and Treatment

Obstructive sleep apnea (OSA), a common sleep-disordered breathing condition, is characterized by intermittent hypoxia (IH) and sleep fragmentation and has been implicated in the pathogenesis and severity of nonalcoholic fatty liver disease (NAFLD). Abnormal molecular changes mediated by IH, such as high expression of hypoxia-inducible factors, are reportedly involved in abnormal pathophysiological states, including insulin resistance, abnormal lipid metabolism, cell death, and inflammation, which mediate the development of NAFLD. However, the relationship between IH and NAFLD remains to be fully elucidated. In this review, we discuss the clinical correlation between OSA and NAFLD, focusing on the molecular mechanisms of IH in NAFLD progression. We meticulously summarize clinical studies evaluating the therapeutic efficacy of continuous positive airway pressure treatment for NAFLD in OSA. Additionally, we compile potential molecular biomarkers for the co-occurrence of OSA and NAFLD. Finally, we discuss the current research progress and challenges in the field of OSA and NAFLD and propose future directions and prospects.

Insulin resistance is an integral feature of MASLD even in the presence of PNPLA3 variants

Background & Aims

It has been postulated that carriers of PNPLA3 I148M (CG [Ile/Met] or GG [Met/Met]) develop metabolic dysfunction-associated steatotic liver disease (MASLD) in the absence of insulin resistance or metabolic syndrome. However, the relationship between insulin resistance and MASLD according to the PNPLA3 allele has not been carefully assessed.

Methods

A total of 204 participants were recruited and underwent PNPLA3 genotyping, an oral glucose tolerance test, liver proton magnetic resonance spectroscopy and percutaneous liver biopsy if diagnosed with MASLD. A subgroup of patients (n = 55) had an euglycemic hyperinsulinemic clamp with glucose tracer infusion.

Results

As expected, patients with the CG/GG genotype had worse intrahepatic triglyceride content and worse liver histology. However, regardless of PNPLA3 genotype, patients with a diagnosis of MASLD had severe whole-body insulin resistance (Matsuda index, an estimation of insulin resistance in glucose metabolic pathways) and fasting and postprandial adipose tissue insulin resistance (Adipo-IR index and free fatty acid suppression during the oral glucose tolerance test, respectively, as measures of insulin resistance in lipolytic metabolic pathways) compared to patients without MASLD. Moreover, for the same amount of liver fat accumulation, insulin resistance was similar in patients with genotypes CC vs. CG/GG. In multiple regression analyses, A1c and Adipo-IR were associated with the presence of MASLD and advanced liver fibrosis, independently of PNPLA3 genotype.

Conclusions

PNPLA3 variant carriers with MASLD are equally insulin resistant as non-carriers with MASLD at the level of the liver, muscle, and adipose tissue. This calls for reframing "PNPLA3 MASLD" as an insulin-resistant condition associated with increased hepatic susceptibility to metabolic insults, such as obesity or diabetes, wherein early identification and aggressive intervention are warranted to reverse metabolic dysfunction and prevent disease progression.

Impact and implications

It has been proposed that the PNPLA3 G allele is associated with the presence of metabolic dysfunction-associated steatotic liver disease (MASLD) in the absence of insulin resistance. However, our results suggest that regardless of PNPLA3 alleles, the presence of insulin resistance is necessary for the development of MASLD. This calls for reframing patients with "PNPLA3 MASLD" not as insulin sensitive, but on the contrary, as an insulin-resistant population with increased hepatic susceptibility to metabolic insults, such as obesity or diabetes.

Surveillance of the liver in type 2 diabetes: important but unfeasible?

Fatty liver plays a pivotal role in the pathogenesis of the metabolic syndrome and type 2 diabetes. According to an updated classification, any individual with liver steatosis and one or more features of the metabolic syndrome, without excess alcohol consumption or other known causes of steatosis, has metabolic dysfunction-associated steatotic liver disease (MASLD). Up to 60-70% of all individuals with type 2 diabetes have MASLD. However, the prevalence of advanced liver fibrosis in type 2 diabetes remains uncertain, with reported estimates of 10-20% relying on imaging tests and likely overestimating the true prevalence. All stages of MASLD impact prognosis but fibrosis is the best predictor of all-cause and liver-related mortality risk. People with type 2 diabetes face a two- to threefold increase in the risk of liver-related death and hepatocellular carcinoma, with 1.3% progressing to severe liver disease over 7.7 years. Because reliable methods for detecting steatosis are lacking, MASLD mostly remains an incidental finding on imaging. Regardless, several medical societies advocate for universal screening of individuals with type 2 diabetes for advanced fibrosis. Proposed screening pathways involve annual calculation of the Fibrosis-4 (FIB-4) index, followed by a secondary test such as transient elastography (TE) for intermediate-to-high-risk individuals. However, owing to unsatisfactory biomarker specificity, these pathways are expected to channel approximately 40% of all individuals with type 2 diabetes to TE and 20% to tertiary care, with a false discovery rate of up to 80%, raising concerns about feasibility. There is thus an urgent need to develop more effective strategies for surveying the liver in type 2 diabetes. Nonetheless, weight loss through lifestyle changes, pharmacotherapy or bariatric surgery remains the cornerstone of management, proving highly effective not only for metabolic comorbidities but also for MASLD. Emerging evidence suggests that fibrosis biomarkers may serve as tools for risk-based targeting of weight-loss interventions and potentially for monitoring response to therapy.

MASLD/MASH and type 2 diabetes: Two sides of the same coin? From single PPAR to pan-PPAR agonists

Type 2 diabetes (T2D) and metabolic dysfunction-associated steatotic liver disease (MASLD), mainly related to nutrition and lack of physical activity, are both very common conditions, share several disease pathways and clinical manifestations, and increasingly co-occur with disease progression. Insulin resistance is an upstream node in the biology of both conditions and triggers liver parenchymal injury, inflammation and fibrosis. Peroxisome proliferator-activated receptor (PPAR) nuclear transcription factors are master regulators of energy homeostasis - insulin signaling in liver, adipose and skeletal muscle tissue - and affect immune and fibrogenesis pathways. Among distinct yet overlapping effects, PPARα regulates lipid metabolism and energy expenditure, PPARβ/δ has anti-inflammatory effects and increases glucose uptake by skeletal muscle, while PPARγ improves insulin sensitivity and exerts direct antifibrotic effects on hepatic stellate cells. Together PPARs thus represent pharmacological targets across the entire biology of MASH. Single PPAR agonists are approved for hypertriglyceridemia (PPARα) and T2D (PPARγ), but these, as well as dual PPAR agonists, have shown mixed results as anti-MASH treatments in clinical trials. Agonists of all three PPAR isoforms have the potential to improve the full disease spectrum from insulin resistance to fibrosis, and correspondingly to improve cardiometabolic and hepatic health, as has been shown (phase II data) with the pan-PPAR agonist lanifibranor.

Impaired Hepatic Very Low-Density Lipoprotein Secretion Promotes Tumorigenesis and Is Accelerated with Fabp1 Deletion

Genetic polymorphisms that impair very low-density lipoprotein (VLDL) secretion are linked to hepatic steatosis, fibrosis, and hepatocellular cancer. Liver-specific deletion of microsomal triglyceride transfer protein (Mttp-LKO) impairs VLDL assembly, promoting hepatic steatosis and fibrosis, which are attenuated in Mttp-LKO X Fabp1-null [Fabp1/Mttp double knockout (DKO)] mice. The current study examined the impact of impaired VLDL secretion in Mttp-LKO mice on hepatocellular cancer incidence and progression in comparison to Fabp1/Mttp DKO mice. Diethylnitrosamine-treated Mttp-LKO mice exhibited steatosis with increased tumor burden compared with flox controls, whereas diethylnitrosamine-treated Fabp1/Mttp DKO mice exhibited a paradoxical increase in tumor burden and >50% mortality by 50 weeks. Serum high-density lipoprotein cholesterol was elevated in both Mttp-LKO and Fabp1/Mttp DKO mice, with increased intratumoral expression of apolipoprotein A1 and apolipoprotein E. Lipidomic surveys revealed progressive enrichment in distinct triglyceride species in livers from Mttp-LKO mice with further enrichment in Fabp1/Mttp DKO mice. RNA sequencing revealed mRNA changes suggesting altered monocarboxylic acid use and increased aerobic glycolysis, whereas hepatocytes from Fabp1/Mttp DKO mice exhibited increased capacity to use glucose and glutamine. These metabolic shifts were accompanied by reduced expression of HNF1 homeobox A (HNF1a), which correlated with tumor burden. Taken together, these findings demonstrate that hepatic tumorigenesis is increased in mice with impaired VLDL secretion and further accelerated via pathways including altered fatty acid compartmentalization and shifts in hepatic energy use.

Steatotic Liver Disease: Pathophysiology and Emerging Pharmacotherapies

Steatotic liver disease (SLD) displays a dynamic and complex disease phenotype. Consequently, the metabolic dysfunction-associated steatotic liver disease (MASLD)/metabolic dysfunction-associated steatohepatitis (MASH) therapeutic pipeline is expanding rapidly and in multiple directions. In parallel, noninvasive tools for diagnosing and monitoring responses to therapeutic interventions are being studied, and clinically feasible findings are being explored as primary outcomes in interventional trials. The realization that distinct subgroups exist under the umbrella of SLD should guide more precise and personalized treatment recommendations and facilitate advancements in pharmacotherapeutics. This review summarizes recent updates of pathophysiology-based nomenclature and outlines both effective pharmacotherapeutics and those in the pipeline for MASLD/MASH, detailing their mode of action and the current status of phase 2 and 3 clinical trials. Of the extensive arsenal of pharmacotherapeutics in the MASLD/MASH pipeline, several have been rejected, whereas other, mainly monotherapy options, have shown only marginal benefits and are now being tested as part of combination therapies, yet others are still in development as monotherapies. Although the Food and Drug Administration (FDA) has recently approved resmetirom, additional therapeutic approaches in development will ideally target MASH and fibrosis while improving cardiometabolic risk factors. Due to the urgent need for the development of novel therapeutic strategies and the potential availability of safety and tolerability data, repurposing existing and approved drugs is an appealing option. Finally, it is essential to highlight that SLD and, by extension, MASLD should be recognized and approached as a systemic disease affecting multiple organs, with the vigorous implementation of interdisciplinary and coordinated action plans. SIGNIFICANCE STATEMENT: Steatotic liver disease (SLD), including metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis, is the most prevalent chronic liver condition, affecting more than one-fourth of the global population. This review aims to provide the most recent information regarding SLD pathophysiology, diagnosis, and management according to the latest advancements in the guidelines and clinical trials. Collectively, it is hoped that the information provided furthers the understanding of the current state of SLD with direct clinical implications and stimulates research initiatives.

mARC1 in MASLD: Modulation of lipid accumulation in human hepatocytes and adipocytes

BACKGROUND

Mutations in the gene MTARC1 (mitochondrial amidoxime-reducing component 1) protect carriers from metabolic dysfunction-associated steatohepatitis (MASH) and cirrhosis. MTARC1 encodes the mARC1 enzyme, which is localized to the mitochondria and has no known MASH-relevant molecular function. Our studies aimed to expand on the published human genetic mARC1 data and to observe the molecular effects of mARC1 modulation in preclinical MASH models.

METHODS AND RESULTS

We identified a novel human structural variant deletion in MTARC1, which is associated with various biomarkers of liver health, including alanine aminotransferase levels. Phenome-wide Mendelian Randomization analyses additionally identified novel putatively causal associations between MTARC1 expression, and esophageal varices and cardiorespiratory traits. We observed that protective MTARC1 variants decreased protein accumulation in in vitro overexpression systems and used genetic tools to study mARC1 depletion in relevant human and mouse systems. Hepatocyte mARC1 knockdown in murine MASH models reduced body weight, liver steatosis, oxidative stress, cell death, and fibrogenesis markers. mARC1 siRNA treatment and overexpression modulated lipid accumulation and cell death consistently in primary human hepatocytes, hepatocyte cell lines, and primary human adipocytes. mARC1 depletion affected the accumulation of distinct lipid species and the expression of inflammatory and mitochondrial pathway genes/proteins in both in vitro and in vivo models.

CONCLUSIONS

Depleting hepatocyte mARC1 improved metabolic dysfunction-associated steatotic liver disease-related outcomes. Given the functional role of mARC1 in human adipocyte lipid accumulation, systemic targeting of mARC1 should be considered when designing mARC1 therapies. Our data point to plasma lipid biomarkers predictive of mARC1 abundance, such as Ceramide 22:1. We propose future areas of study to describe the precise molecular function of mARC1, including lipid trafficking and subcellular location within or around the mitochondria and endoplasmic reticulum.

Hepatic glucose metabolism in the steatotic liver

The liver is central in regulating glucose homeostasis, being the major contributor to endogenous glucose production and the greatest reserve of glucose as glycogen. It is both a target and regulator of the action of glucoregulatory hormones. Hepatic metabolic functions are altered in and contribute to the highly prevalent steatotic liver disease (SLD), including metabolic dysfunction-associated SLD (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). In this Review, we describe the dysregulation of hepatic glucose metabolism in MASLD and MASH and associated metabolic comorbidities, and how advances in techniques and models for the assessment of hepatic glucose fluxes in vivo have led to the identification of the mechanisms related to the alterations in glucose metabolism in MASLD and comorbidities. These fluxes can ultimately increase hepatic glucose production concomitantly with fat accumulation and alterations in the secretion and action of glucoregulatory hormones. No pharmacological treatment has yet been approved for MASLD or MASH, but some antihyperglycaemic drugs approved for treating type 2 diabetes have shown positive effects on hepatic glucose metabolism and hepatosteatosis. A deep understanding of how MASLD affects glucose metabolic fluxes and glucoregulatory hormones might assist in the early identification of at-risk individuals and the use or development of targeted therapies.

PPARα is one of the key targets for dendrobine to improve hepatic steatosis in NAFLD

ETHNOPHARMACOLOGICAL RELEVANCE

Dendrobium nobile Lindl. (DNL) is a traditional Chinese ethnobotanical herb. Dendrobine (DNE) has been designated as a quality indicator for DNL in the Chinese Pharmacopoeia. DNE exhibits various pharmacological activities, including the reduction of blood lipids, regulation of blood sugar levels, as well as anti-inflammatory and antioxidant properties.

AIM OF THE STUDY

The objective of this study is to explore the impact of DNE on lipid degeneration in nonalcoholic fatty liver disease (NAFLD) liver cells and elucidate its specific mechanism. The findings aim to offer theoretical support for the development of drugs related to DNL.

MATERIALS AND METHODS

We utilized male C57BL/6J mice, aged 6 weeks old, to establish a NAFLD model. This model allowed us to assess the impact of DNE on liver pathology and lipid levels in NAFLD mice. We investigated the mechanism of DNE's regulation of lipid metabolism through RNA-seq analysis. Furthermore, a NAFLD model was established using HepG2 cells to further evaluate the impact of DNE on the pathological changes of NAFLD liver cells. The potential mechanism of DNE's improvement was rapidly elucidated using HT-qPCR technology. These results were subsequently validated using mouse liver samples. Following the in vitro activation or inhibition of PPARα function, we observed changes in DNE's ability to ameliorate pathological changes in NAFLD hepatocytes. This mechanism was further verified through RT-qPCR and Western blot analysis.

RESULTS

DNE demonstrated a capacity to enhance serum TC, TG, and liver TG levels in mice, concurrently mitigating liver lipid degeneration. RNA-seq analysis unveiled that DNE primarily modulates the expression of genes related to metabolic pathways in mouse liver. Utilizing HT-qPCR technology, it was observed that DNE markedly regulates the expression of genes associated with the PPAR signaling pathway in liver cells. Consistency was observed in the in vivo data, where DNE significantly up-regulated the expression of PPARα mRNA and its protein level in mouse liver. Additionally, the expression of fatty acid metabolism-related genes (ACOX1, CPT2, HMGCS2, LPL), regulated by PPARα, was significantly elevated following DNE treatment. In vitro experiments further demonstrated that DNE notably ameliorated lipid deposition, peroxidation, and inflammation levels in NAFLD hepatocytes, particularly when administered in conjunction with fenofibrate. Notably, the PPARα inhibitor GW6471 attenuated these effects of DNE.

CONCLUSIONS

In summary, DNE exerts its influence on the expression of genes associated with downstream fat metabolism by regulating PPARα. This regulatory mechanism enhances liver lipid metabolism, mitigates lipid degeneration in hepatocytes, and ultimately ameliorates the pathological changes in NAFLD hepatocytes.

Hepatic mitochondrial reductive stress in the pathogenesis and treatment of steatotic liver disease

Steatotic liver diseases (SLDs) affect one-third of the population, but the pathogenesis underlying these diseases is not well understood, limiting the available treatments. A common factor in SLDs is increased hepatic mitochondrial reductive stress, which occurs as a result of excessive lipid and alcohol metabolism. Recent research has also shown that genetic risk factors contribute to this stress. This review aims to explore how these risk factors increase hepatic mitochondrial reductive stress and how it disrupts hepatic metabolism, leading to SLDs. Additionally, the review will discuss the latest clinical studies on pharmaceutical treatments for SLDs, specifically peroxisome proliferator-activated receptor gamma (PPAR-γ) agonists, thyroid hormone receptor (THR) agonists, acetyl-CoA carboxylase (ACC) inhibitors, and mitochondrial uncouplers. These treatments have a common effect of decreasing hepatic mitochondrial reductive stress, which has been largely overlooked.

Underlying Mechanisms behind the Brain-Gut-Liver Axis and Metabolic-Associated Fatty Liver Disease (MAFLD): An Update

Metabolic-associated fatty liver disease (MAFLD) includes several metabolic dysfunctions caused by dysregulation in the brain-gut-liver axis and, consequently, increases cardiovascular risks and fatty liver dysfunction. In MAFLD, type 2 diabetes mellitus, obesity, and metabolic syndrome are frequently present; these conditions are related to liver lipogenesis and systemic inflammation. This study aimed to review the connection between the brain-gut-liver axis and MAFLD. The inflammatory process, cellular alterations in hepatocytes and stellate cells, hypercaloric diet, and sedentarism aggravate the prognosis of patients with MAFLD. Thus, to understand the modulation of the physiopathology of MAFLD, it is necessary to include the organokines involved in this process (adipokines, myokines, osteokines, and hepatokines) and their clinical relevance to project future perspectives of this condition and bring to light new possibilities in therapeutic approaches. Adipokines are responsible for the activation of distinct cellular signaling in different tissues, such as insulin and pro-inflammatory cytokines, which is important for balancing substances to avoid MAFLD and its progression. Myokines improve the quantity and quality of adipose tissues, contributing to avoiding the development of MAFLD. Finally, hepatokines are decisive in improving or not improving the progression of this disease through the regulation of pro-inflammatory and anti-inflammatory organokines.

Whole-Exome Sequencing (WES) Reveals Novel Sex-Specific Gene Variants in Non-Alcoholic Steatohepatitis (MASH)

Non-alcoholic steatohepatitis (NASH, also known as MASH) is a severe form of non-alcoholic fatty liver disease (NAFLD, also known as MASLD). Emerging data indicate that the progression of the disease to MASH is higher in postmenopausal women and that genetic susceptibility increases the risk of MASH-related cirrhosis. This study aimed to investigate the association between genetic polymorphisms in MASH and sexual dimorphism. We applied whole-exome sequencing (WES) to identify gene variants in 8 age-adjusted matched pairs of livers from both male and female patients. Sequencing alignment, variant calling, and annotation were performed using standard methods. Polymerase chain reaction (PCR) coupled with Sanger sequencing and immunoblot analysis were used to validate specific gene variants. cBioPortal and Gene Set Enrichment Analysis (GSEA) were used for actionable target analysis. We identified 148,881 gene variants, representing 57,121 and 50,150 variants in the female and male cohorts, respectively, of which 251 were highly significant and MASH sex-specific (p < 0.0286). Polymorphisms in CAPN14, SLC37A3, BAZ1A, SRP54, MYH11, ABCC1, and RNFT1 were highly expressed in male liver samples. In female samples, Polymorphisms in RGSL1, SLC17A2, HFE, NLRC5, ACTN4, SBF1, and ALPK2 were identified. A heterozygous variant 1151G>T located on 18q21.32 for ALPK2 (rs3809983) was validated by Sanger sequencing and expressed only in female samples. Immunoblot analysis confirmed that the protein level of β-catenin in female samples was 2-fold higher than normal, whereas ALPK2 expression was 0.5-fold lower than normal. No changes in the protein levels of either ALPK2 or β-catenin were observed in male samples. Our study suggests that the perturbation of canonical Wnt/β-catenin signaling observed in postmenopausal women with MASH could be the result of polymorphisms in ALPK2.

Decoding active compounds and molecular targets of herbal medicine by high-throughput metabolomics technology: A systematic review

Clinical experiences of herbal medicine (HM) have been used to treat a variety of human intractable diseases. As the treatment of diseases using HM is characterized by multi-components and multi-targets, it is difficult to determine the bio-active components, explore the molecular targets and reveal the mechanisms of action. Metabolomics is frequently used to characterize the effect of external disturbances on organisms because of its unique advantages on detecting changes in endogenous small-molecule metabolites. Its systematicity and integrity are consistent with the effective characteristics of HM. After HM intervention, metabolomics can accurately capture and describe the behavior of endogenous metabolites under the disturbance of functional compounds, which will be used to decode the bioactive ingredients of HM and expound the molecular targets. Metabolomics can provide an approach for explaining HM, addressing unclear clinical efficacy and undefined mechanisms of action. In this review, the metabolomics strategy and its applications in HM are systematically introduced, which offers valuable insights for metabolomics methods to characterizing the pharmacological effects and molecular targets of HM.

Hepatic Fibrosis and Cancer: The Silent Threats of Metabolic Syndrome

Metabolic dysfunction-associated steatotic (fatty) liver disease (MASLD), previously termed non-alcoholic fatty liver disease, is a worldwide epidemic that can lead to hepatic inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). The disease is typically a component of the metabolic syndrome that accompanies obesity, and is often overlooked because the liver manifestations are clinically silent until late-stage disease is present (i.e., cirrhosis). Moreover, Asian populations, including Koreans, have a higher fraction of patients who are lean, yet their illness has the same prognosis or worse than those who are obese. Nonetheless, ongoing injury can lead to hepatic inflammation and ballooning of hepatocytes as classic features. Over time, fibrosis develops following activation of hepatic stellate cells, the liver's main fibrogenic cell type. The disease is usually more advanced in patients with type 2 diabetes mellitus, indicating that all diabetic patients should be screened for liver disease. Although there has been substantial progress in clarifying pathways of injury and fibrosis, there no approved therapies yet, but current research seeks to uncover the pathways driving hepatic inflammation and fibrosis, in hopes of identifying new therapeutic targets. Emerging molecular methods, especially single cell sequencing technologies, are revolutionizing our ability to clarify mechanisms underlying MASLD-associated fibrosis and HCC.

Role of Insulin Resistance in the Development of Nonalcoholic Fatty Liver Disease in People With Type 2 Diabetes: From Bench to Patient Care

Insulin resistance is implicated in both the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and its progression from steatosis to steatohepatitis, cirrhosis, and even hepatocellular carcinoma, which is known to be more common in people with type 2 diabetes. This article reviews the role of insulin resistance in the metabolic dysfunction observed in obesity, type 2 diabetes, atherogenic dyslipidemia, and hypertension and how it is a driver of the natural history of NAFLD by promoting glucotoxicity and lipotoxicity. The authors also review the genetic and environmental factors that stimulate steatohepatitis and fibrosis progression and their relationship with cardiovascular disease and summarize guidelines supporting the treatment of NAFLD with diabetes medications that reduce insulin resistance, such as pioglitazone or glucagon-like peptide 1 receptor agonists.

Association between updated cardiovascular health construct and risks of non-alcoholic fatty liver disease

BACKGROUND AND AIMS

The American Heart Association (AHA) updated the construct and algorithm of cardiovascular health (CVH) recently. We aimed to explore the relationship between the new CVH score and the development of non-alcoholic fatty liver disease (NAFLD).

METHODS AND RESULTS

3266 adults free of NAFLD identified via ultrasound were recruited in this prospective study. A modified AHA "Life's Essential 8" (mLE8, i.e., physical activity, nicotine exposure, sleep health, body mass index, blood lipids, blood glucose, and blood pressure) were collected to evaluate the CVH score. Then participants were categorized into low, moderate, and high CVH subgroups based on overall mLE8 CVH score. According to modified Life's Simple 7 (mLS7) CVH construct, participants were also subdivided into poor, intermediate, and ideal CVH subgroups. During a median 4.3 years follow-up, 623 incident cases of NAFLD were recorded. Compared to those with high CVH, participants with low CVH (adjusted OR = 2.56, 95% CI 1.55-4.24) and moderate CVH (adjusted OR = 1.83, 95% CI 1.17-2.85) had a significantly increased risk of incident NAFLD. Participants with poor CVH (mLS7) but without low CVH (mLE8) did not show a significant elevated risk of incident NAFLD (P = 0.1053). A significant trend was found between increased changes in mLE8 score and a lower risk of NAFLD occurrence.

CONCLUSION

Our findings suggested high mLE8 CVH score was associated with a lower risk of NAFLD incidence. The new CVH construct showed a more reasonable classification of CVH status and was more robust in association with NAFLD risks compared with the original one.

Unique Genetic Features of Lean NAFLD: A Review of Mechanisms and Clinical Implications

Non-alcoholic fatty liver disease (NAFLD) affects 25% of the global population. About 20% have a normal body mass index (BMI) and a variant known as lean NAFLD. Unlike typical NAFLD cases associated with obesity and diabetes, lean NAFLD causes liver disease by mechanisms not related to excess weight or insulin resistance. Genetic disorders are among the major factors in developing lean NAFLD, and genome-wide association studies have identified several genes associated with the condition. This review aims to increase awareness by describing the genetic markers linked to NAFLD and the defects involved in developing lean NAFLD.

Intact ketogenesis predicted reduced risk of moderate-severe metabolic-associated fatty liver disease assessed by liver transient elastography in newly diagnosed type 2 diabetes

Aim

Hepatic ketogenesis is a key metabolic pathway that regulates energy homeostasis. Some related controversies exist regarding the pathogenesis of metabolic-associated fatty liver disease (MAFLD). We aimed to investigate whether intact ketogenic capacity could reduce the risk of MAFLD based on transient electrography (TE) in patients with newly diagnosed type 2 diabetes (T2D).

Methods

A total of 361 subjects with newly diagnosed T2D were recruited and classified into two groups based on the median serum β-hydroxybutyrate (βHB) level, referred to as the intact and impaired ketogenesis groups. The glucometabolic relevance of ketogenic capacity and associations of the baseline serum β-HB and MAFLD assessed with TE were investigated.

Results

Compared to the impaired ketogenesis group, the intact ketogenesis group showed better insulin sensitivity, lower serum triglyceride levels, and higher glycated hemoglobin levels. The controlled attenuation parameter (CAP) was lower in the intact ketogenesis group without statistical significance (289.7 ± 52.1 vs. 294.5 ± 43.6; p=0.342) but the prevalence of moderate-severe steatosis defined by CAP ≥260 dB/m was significantly lower in the intact group. Moreover, intact ketogenesis was significantly associated with a lower risk of moderate-severe MAFLD after adjusting for potential confounders (adjusted odds ratio 0.55, 95% confidence interval 0.30-0.98; p=0.044).

Conclusion

In drug-naïve, newly diagnosed T2D patients, intact ketogenesis predicted a lower risk of moderate-severe MAFLD assessed by TE.

Fatty acid synthesis suppresses dietary polyunsaturated fatty acid use

Dietary polyunsaturated fatty acids (PUFA) are increasingly recognized for their health benefits, whereas a high production of endogenous fatty acids - a process called de novo lipogenesis (DNL) - is closely linked to metabolic diseases. Determinants of PUFA incorporation into complex lipids are insufficiently understood and may influence the onset and progression of metabolic diseases. Here we show that fatty acid synthase (FASN), the key enzyme of DNL, critically determines the use of dietary PUFA in mice and humans. Moreover, the combination of FASN inhibition and PUFA-supplementation decreases liver triacylglycerols (TAG) in mice fed with high-fat diet. Mechanistically, FASN inhibition causes higher PUFA uptake via the lysophosphatidylcholine transporter MFSD2A, and a diacylglycerol O-acyltransferase 2 (DGAT2)-dependent incorporation of PUFA into TAG. Overall, the outcome of PUFA supplementation may depend on the degree of endogenous DNL and combining PUFA supplementation and FASN inhibition might be a promising approach to target metabolic disease.

Time-restricted feeding ameliorates non-alcoholic fatty liver disease through modulating hepatic nicotinamide metabolism via gut microbiota remodeling

Non-alcoholic fatty liver disease (NAFLD) has emerged as a global health concern, lacking specific therapeutic strategies. Time-restricted feeding (TRF) regimen demonstrated beneficial effects in NAFLD; however, the underlying mechanisms remain unclear. In this study, we established a NAFLD mouse model through a high-fat diet (HFD) and implemented the 16:8 TRF regimen for a duration of 6 weeks. We demonstrated that TRF remarkably alleviated hepatic steatosis in HFD mice. Of note, aldehyde oxidase 1 (AOX1), a key enzyme in hepatic nicotinamide (NAM) catabolism, exhibited apparent upregulation in response to HFD, leading to abnormal accumulation of N-Methyl-6-pyridone-3-carboxamide (N-Me-6-PY, also known as 2PY) and N-Methyl-4-pyridone-5-carboxamide (N-Me-4-PY, also known as 4PY), whereas it was almost restored by TRF. Both N-Me-6-PY and N-Me-4-PY promoted de novo lipogenesis and fatty acid uptake capacities in hepatocyte, and aggravated hepatic steatosis in mice either fed chow diet or HFD. In contrast, pharmacological inhibition of AOX1 was sufficient to ameliorate the hepatic steatosis and lipid metabolic dysregulation induced by HFD. Moreover, transplantation of fecal microbiota efficiently mimicked the modulatory effect of TRF on NAM metabolism, thus mitigating hepatic steatosis and lipid metabolic disturbance, suggesting a gut microbiota-dependent manner. In conclusion, our study reveals the intricate relationship between host NAM metabolic modification and gut microbiota remodeling during the amelioration of NAFLD by TRF, providing promising insights into the prevention and treatment of NAFLD.

Adiponectin-leptin ratio for the early detection of lean non-alcoholic fatty liver disease independent of insulin resistance

BACKGROUND

Lean Non-alcoholic Fatty Liver Disease (NAFLD) shares a similar disease burden to those of their overweight counterparts and should be detected early. We hypothesized that the adiponectin-leptin ratio (AL ratio) could be a good marker for early detection of lean NAFLD independent of insulin resistance.

MATERIALS AND METHODS

A total of 575 adults without diabetes were enrolled in a community-based study. The subjects were stratified into the lean controls, lean NAFLD, simple overweight/obesity and overweight/obesity NAFLD groups according to body mass index (BMI) and ultrasonographic fatty liver indicators. Serum adiponectin and leptin levels were measured by enzyme-linked immunosorbent assay. Multivariate logistic regression analyses were performed to estimate the odds ratio of having NAFLD in relation to the tertiles of serum AL concentration after adjustment. Receiver operating characteristic (ROC) analyses were applied to evaluate the diagnostic performance of the AL ratio for NAFLD.

RESULTS

The mean age of the participants was 42.8 ± 11.5 years. Comparing with the lean controls, the odds of having lean NAFLD for the highest versus the lowest tertile of AL ratio was 0.28(95%CI: 0.12-0.69) after adjustment. Putting AL ratio, BMI, triglyceride, AST/ALT ratio to the diagnosis performance of NAFLD, the ROC was 0.85 (95% CI: 0.82-0.88), 0.83 (95% CI 0.78-0.87) and 0.86 (95% CI 081-0.91) for all NAFLD, NAFLD in women and NAFLD in men, respectively. (p < .001).

CONCLUSIONS

The study revealed that the AL ratio could be a good biomarker to early distinguish lean NAFLD patients from lean controls independent of insulin resistance. [AQ3]Key messagesThe prevalence of non-alcoholic fatty liver disease (NAFLD) increases globally and is related to liver diseases and metabolic dysfunctions. Lean subset of NAFLD shares a similar disease burden to those of their overweight counterparts and should be detected early.Adiponectin-leptin ratio were associated with the severity of steatosis and was a predictor of obese NAFLD better than each single adipokine. To date, there is no investigation that explores specifically for the relationship between lean NAFLD and AL ratio.Our study found that adiponectin-leptin ratio is a sole independent marker regardless of insulin resistance in lean NAFLD. Having lean NAFLD for the highest versus the lowest tertile of adiponectin-leptin ratio was 0.28(95%CI: 0.12-0.69) after adjustment of age, sex, current smoking, exercise habits, HOMA-IR and AST/ALT. ROC for the NAFLD performance is good for the early detection (0.85; 95% CI: 0.82-0.88). Further rigorous investigation is necessary and should be promptly performed.

The association between metabolic dysfunction-associated steatotic liver disease, cardiovascular and cerebrovascular diseases and the thickness of carotid plaque

BACKGROUND

The relationship between metabolic dysfunction-associated steatotic liver disease (MASLD) and atherosclerosis has been controversial, which has become a hit of recent research. The study aimed to explore the association between MASLD, cardiovascular and cerebrovascular diseases (CCVD), and the thickness of carotid plaque which was assessed by ultrasound.

METHODS

From September 2018 to June 2019, 3543 patients were enrolled. We asked participants to complete questionnaires to obtain information. All patients underwent liver ultrasound and bilateral carotid ultrasound to obtain carotid intima-media thickness (IMT) and maximum carotid plaque thickness (CPT). Hepatic steatosis was quantified during examination according to Hamaguchi's ultrasonographic score, from 0 to 6 points. A score < 2 was defined as without fatty liver, and a score ≥ 2 was defined as fatty liver. Information about blood lipids was collected based on the medical records.

RESULTS

We found common risk factors for CCVD events, MASLD, and atherosclerosis. There was a significant correlation between MASLD and carotid plaque, but not with CPT. No association was found between MASLD and CCVD events. CPT and IMT were thicker in CCVD patients than in non-CCVD patients. No significant difference was found between IMT and CPT in MASLD patients and non-MASLD patients. CCVD was independently and consistently associated with higher IMT, and free fatty acid (FFA).

CONCLUSIONS

According to our results, we recommend carotid ultrasound examination of the patients when FFA is increased, regardless of the presence of risk factors and MASLD. Due to the distribution of CPT of both CCVD and MASLD patients in the CPT 2-4 mm group, contrast-enhanced ultrasound is necessary to assess the vulnerability of the plaque when CPT ≥ 2 mm. Timely treatment of vulnerable plaques may reduce the incidence of future CCVD events.

The PNPLA3 I148M variant increases ketogenesis and decreases hepatic de novo lipogenesis and mitochondrial function in humans

The PNPLA3 I148M variant is the major genetic risk factor for all stages of fatty liver disease, but the underlying pathophysiology remains unclear. We studied the effect of this variant on hepatic metabolism in homozygous carriers and non-carriers under multiple physiological conditions with state-of-the-art stable isotope techniques. After an overnight fast, carriers had higher plasma β-hydroxybutyrate concentrations and lower hepatic de novo lipogenesis (DNL) compared to non-carriers. After a mixed meal, fatty acids were channeled toward ketogenesis in carriers, which was associated with an increase in hepatic mitochondrial redox state. During a ketogenic diet, carriers manifested increased rates of intrahepatic lipolysis, increased plasma β-hydroxybutyrate concentrations, and decreased rates of hepatic mitochondrial citrate synthase flux. These studies demonstrate that homozygous PNPLA3 I148M carriers have hepatic mitochondrial dysfunction leading to reduced DNL and channeling of carbons to ketogenesis. These findings have implications for understanding why the PNPLA3 variant predisposes to progressive liver disease.

A review of the occurrence, metabolites and health risks of butylated hydroxyanisole (BHA)

Butylated hydroxyanisole (BHA) is mainly used as a food additive due to its antioxidant properties, which prevent or delay oxidation reactions and extend the storage life of products. The widespread use of BHA has led to its extensive presence in various environmental matrices and human tissues. Food intake is the main route of human exposure to BHA. Under different conditions, BHA can produce different metabolites, with tert-butyl hydroquinone (TBHQ) being one of the major products. Several studies have shown that BHA could cause thyroid system damage, metabolic and growth disorders, neurotoxicity, and carcinogenesis. Mechanisms such as endocrine disruption, genotoxicity, disturbances of energy metabolism, reactive oxygen species (ROS) production, signaling pathways, and imbalances in calcium homeostasis appear to be associated with the toxic effects of BHA. Avoiding the toxic effects of BHA to the maximum extent possible is a top priority. Finding safe, non-toxic and environmentally friendly alternatives to BHA should be the focus of subsequent research. In all, this review summarized the current situation related to BHA and might make recommendations for future research directions. © 2023 Society of Chemical Industry.

Insulin resistance and central obesity determine hepatic steatosis and explain cardiovascular risk in steatotic liver disease

Background

Metabolic dysfunction-associated steatotic liver disease (MASLD) has recently been proposed to replace non-alcoholic fatty liver disease and focus on patients with progressive disease due to the presence of metabolic dysfunction. However, it is unclear whether the new definition actually identifies patients with hepatic steatosis at increased cardiovascular risk.

Methods

A total of 4,286 asymptomatic subjects from the SAKKOPI study aged 45-80 years undergoing screening colonoscopy were analyzed. Steatosis was diagnosed by abdominal ultrasound. MASLD was diagnosed according to the recent expert consensus. Insulin resistance was assessed by homeostasis model assessment-insulin resistance score (HOMA-IR) (cutoff: ≥2.5), subclinical inflammation was estimated by ferritin/CRP/uric acid, and cardiovascular risk was assessed using SCORE2/ASCVD.

Results

Mean age was 59.4 ± 8.5 years, 51.6% were male; mean BMI was 27.0 ± 4.5 kg/m², 9.2% had type 2 diabetes mellitus. In total, 1,903 (44.4%) were diagnosed with hepatic steatosis and were characterized by more severe metabolic dysfunction including insulin resistance (47.1% vs. 12.2%, p < 0.001) and central obesity (waist circumference ≥102/88 cm, 71.8% vs. 37.1%, p < 0.001). This translated into higher (subclinical) inflammation (ferritin 153 vs. 95 mg/dL, p < 0.001, uric acid 6.3 mg/dL vs. 5.2 mg/dL, p < 0.001) and 10-year cardiovascular risk (SCORE2 7.8 points vs. 5.1 points, p < 0.001, ASCVD 17.9 points vs. 10.8 points, p < 0.001). 99.0% of subjects with steatosis met the MASLD definition, 95.4% met the MAFLD definition, and 53.6% met the definition of metabolic syndrome, while 95.4% of subjects without steatosis also met the MASLD criteria for metabolic dysfunction compared to 69.0% and 17.4% who met the MAFLD and metabolic syndrome criteria, respectively. Forward stepwise regression indicated that waist circumference, HOMA-IR, and triglycerides were most relevant in explaining the presence of hepatic steatosis across all subgroups of increasing metabolic dysfunction. At the same time, hepatic steatosis was not associated with cardiovascular risk in the overall cohort (SCORE2: B = 0.060, 95% CI: -0.193-0.314, and p = 0.642) and in patients with metabolic dysfunction after adjusting for age, sex, and these three metabolic dysfunction components.

Conclusion

Although hepatic steatosis is associated with increased central obesity and insulin resistance, metabolic dysfunction per se rather than hepatic steatosis explains cardiovascular risk in these patients.

High-density lipoproteins and non-alcoholic fatty liver disease

Background and aims

Non-alcoholic fatty liver disease (NAFLD), a high incidence liver pathology, is associated with a ∼1.5-fold higher cardiovascular disease risk. This phenomenon is generally attributed to the NAFLD-associated increase in circulating levels of pro-atherogenic apolipoprotein B100-containing small dense low-density lipoprotein and plasma hypertriglyceridemia. However, also a significant reduction in cholesterol transported by anti-atherogenic high-density lipoproteins (HDL) is frequently observed in subjects suffering from NAFLD as compared to unaffected people. In this review, we summarize data regarding the relationship between NAFLD and plasma HDL-cholesterol levels, with a special focus on highlighting potential causality between the NAFLD pathology and changes in HDL metabolism.

Methods and results

Publications in PUBMED describing the relationship between HDL levels and NAFLD susceptibility and/or disease severity, either in human clinical settings or genetically-modified mouse models, were critically reviewed for subsequent inclusion in this manuscript. Furthermore, relevant literature describing effects on lipid loading in cultured hepatocytes of models with genetic alterations related to HDL metabolism have been summarized.

Conclusions

Although in vitro observations suggest causality between HDL formation by hepatocytes and protection against NAFLD-like lipid accumulation, current literature remains inconclusive on whether relative HDL deficiency is actually driving the development of fatty liver disease in humans. In light of the current obesity pandemic and the associated marked rise in NAFLD incidence, it is of clear scientific and societal interest to gain further insight into the relationship between HDL-cholesterol levels and fatty liver development to potentially uncover the therapeutic potential of pharmacological HDL level and/or function modulation.

Clinical trials reimagined

Clinical trials have been a central driver of change and have provided the evidence base necessary to advance new therapies for liver diseases. This review provides a perspective on the status of trials in hepatology and a vantage point into the emerging capabilities and external forces that will shape the conduct of clinical trials in the future. The adaptations to clinical trial operations in response to the disruptions by the COVID-19 pandemic and opportunities for innovation in hepatology trials are emphasized. Future trials in hepatology will be driven by unmet therapeutic needs and fueled by technological advances incorporating digital capabilities with expanded participant-derived data collection, computing, and analytics. Their design will embrace innovative trial designs adapted to these advances and that emphasize broader and more inclusive participant engagement. Their conduct will be further shaped by evolving regulatory needs and the emergence of new stakeholders in the clinical trials ecosystem. The evolution of clinical trials will offer unique opportunities to advance new therapeutics that will ultimately improve the lives of patients with liver diseases.

Inulin ameliorates metabolic syndrome in high-fat diet-fed mice by regulating gut microbiota and bile acid excretion

Background: Inulin is a natural plant extract that improves metabolic syndrome by modulating the gut microbiota. Changes in the gut microbiota may affect intestinal bile acids. We suggest that inulin may improve metabolism by inducing bile acid excretion by gut microbes. Methods: Male C57/BL mice were fed either a high-fat diet (60% calories) or a regular diet for 16 weeks, with oral inulin (10% w/w). At the end of the experiment, the gene expression levels (FGF15, CD36, Srebp-1c, FASN, and ACC) in the liver and intestines, as well as the serum levels of triglycerides (TGs), low-density lipoprotein (LDL) cholesterol, total cholesterol, and free fatty acids, were collected. The expression of FGF15 was examined using Western blot analysis. The fat distribution in the liver and groin was detected by oil red and hematoxylin and eosin staining. Simultaneously, the levels of serum inflammatory factors (alanine aminotransferase and aspartate aminotransferase) were detected to explore the side effects of inulin. Results: Inulin significantly improved glucose tolerance and insulin sensitivity, and decreased body weight and serum TG and LDL levels, in mice fed normal diet. Furthermore, inulin increased the α-diversity of the gut microbiota and increased the fecal bile acid and TG excretion in inulin-treated mice. In addition, inulin significantly reduced lipid accumulation in liver and inguinal fat, white fat weight, and hepatic steatosis. Western blot analysis showed that inulin reduced the expression of FGF15, a bile acid reabsorption protein. Conclusion: Inulin ameliorates the glucose and lipid metabolic phenotypes of mice fed a normal diet, including decreased intestinal lipid absorption, increased glucose tolerance, increased insulin sensitivity, and decreased body weight. These changes may be caused by an increase in bile acid excretion resulting from changes in the gut microbiota that affect intestinal lipid absorption.

Cell Self-Destruction (Programmed Cell Death), Immunonutrition and Metabolism

The main purpose of this Special Issue is to provide readers with current understandings of the interactions and causal relations among injury stimuli (including microorganism infections), immune response and overnutrition/lipotoxicity in disease pathogenesis [...].

Efruxifermin, an investigational treatment for fibrotic or cirrhotic non-alcoholic steatohepatitis (NASH)

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease and strongly associated with metabolic disorders: obesity, type 2 diabetes (T2D), cardiovascular disease. Persistent metabolic injury results in inflammatory processes leading to nonalcoholic steatohepatitis (NASH), liver fibrosis and ultimately cirrhosis. To date, no pharmacologic agent is approved for the treatment of NASH. Fibroblast growth factor 21 (FGF21) agonism has been linked to beneficial metabolic effects ameliorating obesity, steatosis and insulin resistance, supporting its potential as a therapeutic target in NAFLD.

AREAS COVERED

Efruxifermin (EFX, also AKR-001 or AMG876) is an engineered Fc-FGF21 fusion protein with an optimized pharmacokinetic and pharmacodynamic profile, which is currently tested in several phase 2 clinical trials for the treatment of NASH, fibrosis and compensated liver cirrhosis. EFX improved metabolic disturbances including glycemic control, showed favorable safety and tolerability, and demonstrated antifibrotic efficacy according to FDA requirements for phase 3 trials.

EXPERT OPINION

While some other FGF-21 agonists (e.g. pegbelfermin) are currently not further investigated, available evidence supports the development of EFX as a promising anti-NASH drug in fibrotic and cirrhotic populations. However, antifibrotic efficacy, long-term safety and benefits (i.e. cardiovascular risk, decompensation events, disease progression, liver transplantation, mortality) remain to be determined.

Sulfosuccinimidyl oleate ameliorates the high-fat diet-induced obesity syndrome by reducing intestinal and hepatic absorption

Background: A high-fat Western diet is a risk factor for obesity and steatosis. Reducing intestinal absorption of a high-fat diet (HFD) is a feasible strategy to control obesity. Sulfosuccinimidyl oleate (SSO) inhibits intestinal fatty acid transport. Therefore, the aim of this study was to investigate the effects of SSO on HFD-induced glucose and lipid metabolism in mice and its possible underlying mechanisms. Methods: Male C57/BL were fed a HFD (60% calories) for 12 weeks and were administered an oral dose of SSO (50 mg/kg/day). The expression of lipid absorption genes (CD36, MTTP, and DGAT1) and the serum levels of triglycerides (TGs), total cholesterol (TC), and free fatty acids (FFAs) were detected. Lipid distribution in the liver was detected by oil red and hematoxylin and eosin staining. In addition, serum levels of inflammatory factors, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were measured to detect side effects. Results: SSO was effective in the treatment of obesity and metabolic syndrome induced by HFD in mice. It attenuated the assembly of intestinal epithelial chylomicrons by inhibiting intestinal epithelial transport and absorption of fatty acids, thereby reducing the gene expression levels of MTTP and DGAT1, resulting in decreased plasma TG and FFA levels. At the same time, it inhibited the transport of fatty acids in the liver and improved the steatosis induced by a HFD. The results of oil red staining showed that SSO treatment can reduce lipid accumulation in the liver by 70%, with no drug-induced liver injury detected on the basis of interleukin-6, C-reactive protein, ALT, and AST levels. In addition, SSO treatment significantly improved insulin resistance, decreased fasting blood glucose levels, and improved glucose tolerance in HFD-fed mice. Conclusion: SSO is effective in the treatment of obesity and metabolic syndrome induced by a HFD in mice. SSO reduces intestinal fatty acid absorption by reducing the inhibition of intestinal CD36 expression, followed by decreased TG and FFA levels, which attenuates HFD-induced fatty liver.

Research Priorities for Precision Medicine in NAFLD

NAFLD is a multisystem condition and the leading cause of chronic liver disease globally. There are no approved NAFLD-specific dugs. To advance in the prevention and treatment of NAFLD, there is a clear need to better understand the pathophysiology and genetic and environmental risk factors, identify subphenotypes, and develop personalized and precision medicine. In this review, we discuss the main NAFLD research priorities, with a particular focus on socioeconomic factors, interindividual variations, limitations of current NAFLD clinical trials, multidisciplinary models of care, and novel approaches in the management of patients with NAFLD.

An integrated view of anti-inflammatory and antifibrotic targets for the treatment of NASH

Successful development of treatments for non-alcoholic fatty liver disease (NAFLD) and its progressive form, non-alcoholic steatohepatitis (NASH) has been challenging. Because NASH and fibrosis lead to NAFLD progression towards cirrhosis and to clinical outcomes, approaches have either sought to attenuate metabolic dysregulation and cell injury, or directly target the inflammation and fibrosis that ensue. Targets for reducing the activation of inflammatory cascades include nuclear receptor agonists (thyroid hormone receptor-beta, e.g. resmetirom, peroxisome proliferator-activated receptor [PPAR], e.g. lanifibranor, farnesoid X receptor [FXR], e.g. obeticholic acid), modulators of lipotoxicity (e.g. aramchol, acetyl-CoA carboxylase inhibitors) or modification of genetic variants (e.g. PNPLA3 gene silencing). Extrahepatic inflammatory signals from circulation, adipose tissue or gut are targets of hormonal agonists (e.g. glucagon-like peptide-1 [GLP-1] like semaglutide, fibroblast growth factor [FGF]-19 or FGF21), microbiota or lifestyle (weight loss, diet, exercise) interventions. Stress signals and hepatocyte death activate immune responses engaging innate (macrophages, lymphocytes) and adaptive (auto-aggressive T-cells) mechanisms. Therapies seek to blunt immune cell activation, recruitment (chemokine receptor inhibitors) and responses (e.g. galectin 3 inhibition, anti-platelet drugs). The disease-driving pathways of NASH converge to elicit fibrosis, which is reversible. The activation of hepatic stellate cells (HSC) into matrix-producing myofibroblasts can be inhibited by antagonizing soluble factors (e.g. integrins, cytokines), cellular crosstalk (e.g. with macrophages), and agonizing nuclear receptor signaling (e.g. FXR or PPAR agonists). In advanced fibrosis, cell therapy with restorative macrophages or reprogrammed T-cells (e.g., CAR T) may accelerate repair through HSC deactivation or killing, or by enhancing matrix degradation. Heterogeneity of disease - either due to genetics or divergent disease drivers - is an obstacle to defining effective drugs for all patients with NASH that will be incrementally overcome.

A phase I/II study of ARO-HSD, an RNA interference therapeutic, for the treatment of non-alcoholic steatohepatitis

BACKGROUND & AIMS

Loss-of-function HSD17β13 mutations protect against the development of chronic liver disease. HSD17β13 inhibition represents a potential approach to treat liver diseases, such as non-alcoholic steatohepatitis (NASH). ARO-HSD is an RNA interference (RNAi) therapeutic designed to selectively reduce expression of HSD17β13 mRNA in hepatocytes. In this study, we evaluated the effects of ARO-HSD in normal healthy volunteers (NHVs) and patients with confirmed or clinically suspected NASH.

METHODS

The safety, tolerability, and pharmacodynamics of ARO-HSD were evaluated in 32 NHVs and 18 patients with confirmed/clinically suspected NASH. Double-blind NHV cohorts received single escalating doses of ARO-HSD (25, 50, 100, or 200 mg) or placebo subcutaneously on Day 1. Open-label patient cohorts received ARO-HSD (25, 100, or 200 mg) subcutaneously on Days 1 and 29. Liver biopsy was performed pre-dose and on Day 71 to evaluate expression levels of HSD17β13 mRNA and protein.

RESULTS

ARO-HSD treatment was well tolerated with no treatment-related serious adverse events or drug discontinuations. The most frequently reported treatment-emergent adverse events were mild injection site reactions, which were short in duration. Mean changes in hepatic HSD17β13 mRNA from baseline to Day 71 were: -56.9% (25 mg), -85.5% (100 mg), and -93.4% (200 mg). The mean HSD17β13 mRNA reduction was 78.6% (p <0.0001) across pooled cohorts. Hepatic HSD17β13 protein levels were similarly reduced across doses. In patients, mean changes in alanine aminotransferase from baseline to Day 71 were -7.7% (25 mg), -39.3% (100 mg), and -42.3% (200 mg) (p <0.001 for pooled cohorts).

CONCLUSIONS

ARO-HSD was well tolerated at doses ≤200 mg. This proof-of-concept study demonstrated that short-term treatment with ARO-HSD reduces hepatic HSD17β13 mRNA and protein expression, which is accompanied by reductions in alanine aminotransferase.

CLINICALTRIALS

GOV NUMBER

NCT04202354.

IMPACTS AND IMPLICATIONS

There is an unmet medical need for new therapies to treat alcohol-related and non-alcoholic liver disease. ARO-HSD is a small-interfering RNA designed to silence HSD17β13 expression and hence to phenocopy the protective effect seen in individuals with HSD17β13 loss-of-function. The reductions in HSD17β13 expression and in transaminases seen with ARO-HSD administration represent an initial step towards clinical validation of HSD17β13, a drug target with substantial genetic validation, as an important modulator of human liver disease.

Insulin resistance in adipose tissue and metabolic diseases

Adipose tissue regulates systemic energy metabolism through adipokine production as well as energy storage and energy supply to other organs in response to changes in energy status. Adipose tissue dysfunction is therefore thought to be a key contributor to the pathogenesis of a variety of metabolic disorders including nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Given that insulin plays a central role in the regulation of many aspects of adipocyte function, insulin resistance in adipose tissue is implicated in the pathogenesis of metabolic disorders as a cause of adipose tissue dysfunction. The concept of metabolic dysfunction-associated fatty liver disease (MAFLD) has recently been proposed for liver disease associated with metabolic disorders in both obese and nonobese individuals, with insulin resistance in adipose tissue likely being an important factor in its pathogenesis. This review outlines the relation between insulin resistance in adipose tissue and metabolic disorders, with a focus on the physiological relevance and mechanism of action of 3'-phosphoinositide-dependent kinase 1 (PDK1), a key kinase in insulin signaling, and its downstream transcription factor FoxO1 in adipocytes.

LCN2 contributes to the improvement of nonalcoholic steatohepatitis by 8-Cetylberberine

AIMS

Nonalcoholic steatohepatitis (NASH) is becoming one of the most common causes of liver transplantation and hepatocellular carcinoma, but no specific drugs are FDA-approved to treat it. 8-cetylberberine (CBBR), which is a long-chain alkane derivative of berberine, exhibits potent pharmacological activities and improves metabolism performance. The aim of this study is to explore the function and mechanism of CBBR against NASH.

MATERIALS AND METHODS

L02 and HepG2 hepatocytes were treated with the medium containing palmitic acids and oleic acids (PO) and incubated with CBBR for 12 h, then the levels of lipid accumulation were tested by kits or western blots. C57BL/6 J mice were fed with a high-fat diet or a high-fat/high-cholesterol diet. CBBR (15 mg/kg or 30 mg/kg) was orally administered for 8 weeks. Liver weight, steatosis, inflammation, and fibrosis were evaluated. Transcriptomic indicated the target of CBBR in NASH.

KEY FINDINGS

CBBR significantly reduced lipid accumulation, inflammation, liver injury, and fibrosis in NASH mice. CBBR also decreased lipid accumulation and inflammation in PO-induced L02 and HepG2 cells. RNA sequencing and bioinformatics analysis indicated that CBBR inhibited the pathways and key regulators associated with lipid accumulation, inflammation, and fibrosis in the pathogenesis of NASH. Mechanically, CBBR may prevent NASH via inhibiting LCN2, as proved by the finding that the anti-NASH effect of CBBR was more obvious in PO-stimulated HepG2 cells treated with LCN2 overexpression.

SIGNIFICANCE

Our work provides an insight into the effectiveness of CBBR in improving metabolic-stress-caused NASH as well as the mechanism by regulating LCN2.