ER Stress Drives Lipogenesis and Steatohepatitis via Caspase-2 Activation of S1P.

Nonalcoholic fatty liver disease (NAFLD) progresses to nonalcoholic steatohepatitis (NASH) in response to elevated endoplasmic reticulum (ER) stress. Whereas the onset of simple steatosis requires elevated de novo lipogenesis, progression to NASH is triggered by accumulation of hepatocyte-free cholesterol. We now show that caspase-2, whose expression is ER-stress inducible and elevated in human and mouse NASH, controls the buildup of hepatic-free cholesterol and triglycerides by activating sterol regulatory element-binding proteins (SREBP) in a manner refractory to feedback inhibition. Caspase-2 colocalizes with site 1 protease (S1P) and cleaves it to generate a soluble active fragment that initiates SCAP-independent SREBP1/2 activation in the ER. Caspase-2 ablation or pharmacological inhibition prevents diet-induced steatosis and NASH progression in ER-stress-prone mice. Caspase-2 inhibition offers a specific and effective strategy for preventing or treating stress-driven fatty liver diseases, whereas caspase-2-generated S1P proteolytic fragments, which enter the secretory pathway, are potential NASH biomarkers.

SREBP-1c impairs ULK1 sulfhydration-mediated autophagic flux to promote hepatic steatosis in high-fat-diet-fed mice.

A metabolic imbalance between lipid synthesis and degradation can lead to hepatic lipid accumulation, a characteristic of patients with non-alcoholic fatty liver disease (NAFLD). Here, we report that high-fat-diet-induced sterol regulatory element-binding protein (SREBP)-1c, a key transcription factor that regulates lipid biosynthesis, impairs autophagic lipid catabolism via altered H2S signaling. SREBP-1c reduced cystathionine gamma-lyase (CSE) via miR-216a, which in turn decreased hepatic H2S levels and sulfhydration-dependent activation of Unc-51-like autophagy-activating kinase 1 (ULK1). Furthermore, Cys951Ser mutation of ULK1 decreased autolysosome formation and promoted hepatic lipid accumulation in mice, suggesting that the loss of ULK1 sulfhydration was directly associated with the pathogenesis of NAFLD. Moreover, silencing of CSE in SREBP-1c knockout mice increased liver triglycerides, confirming the connection between CSE, autophagy, and SREBP-1c. Overall, our results uncover a 2-fold mechanism for SREBP-1c-driven hepatic lipid accumulation through reciprocal activation and inhibition of hepatic lipid biosynthesis and degradation, respectively.

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.

Histological improvements following energy restriction and exercise: The role of insulin resistance in resolution of MASH.

BACKGROUND & AIMS: Metabolic dysfunction-associated steatohepatitis (MASH) is one of the most common liver diseases worldwide and is characterized by multi-tissue insulin resistance. The effects of a 10-month energy restriction and exercise intervention on liver histology, anthropometrics, plasma biochemistries, and insulin sensitivity were compared to standard of care (control) to understand mechanisms that support liver health improvements. METHODS: Following medical diagnosis of MASH, individuals were randomized to treatment (n = 16) or control (n = 8). Liver fat (magnetic resonance spectroscopy), 18-hour plasma biochemical measurements, and isotopically labeled hyperinsulinemic-euglycemic clamps were completed pre- and post-intervention. Body composition and cardiorespiratory fitness (VO2peak) were also measured mid-intervention. Those in the treatment group were counseled to reduce energy intake and completed supervised, high-intensity interval training (3x/week) for 10 months. Controls continued physician-directed care. RESULTS: Treatment induced significant (p <0.05) reductions in body weight, fat mass, and liver injury, while VO2peak (p <0.05) and non-esterified fatty acid suppression (p = 0.06) were improved. Both groups exhibited reductions in total energy intake, hemoglobin A1c, hepatic insulin resistance, and liver fat (p <0.05). Compared to control, treatment induced a two-fold increase in peripheral insulin sensitivity which was significantly related to higher VO2peak and resolution of liver disease. CONCLUSIONS: Exercise and energy restriction elicited significant and clinically meaningful treatment effects on liver health, potentially driven by a redistribution of excess nutrients to skeletal muscle, thereby reducing hepatic nutrient toxicity. Clinical guidelines should emphasize the addition of aerobic exercise in lifestyle treatments for the greatest histologic benefit in individuals with advanced MASH. IMPACT AND IMPLICATIONS: The mechanisms that underpin histologic improvement in individuals with metabolic dysfunction-associated steatohepatitis (MASH) are not well understood. This study evaluated the relationship between liver and metabolic health, testing how changes in one may affect the other. We investigated the effects of energy restriction and exercise on the association between multi-tissue insulin sensitivity and histologic improvements in participants with biopsy-proven MASH. For the first time, these results show that an improvement in peripheral (but not hepatic) insulin sensitivity and systemic markers of muscle function (i.e. cardiorespiratory fitness) were strongly related to resolution of liver disease. Extrahepatic disposal of substrates and improved fitness levels supported histologic improvement, confirming the addition of exercise as crucial to lifestyle interventions in MASH. CLINICAL TRIAL NUMBER: NCT03151798.

Hepatic venous pressure gradient predicts risk of hepatic decompensation and liver-related mortality in patients with MASLD.

BACKGROUND & AIMS: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a leading cause of advanced chronic liver disease (ACLD). Portal hypertension drives hepatic decompensation and is best diagnosed by hepatic venous pressure gradient (HVPG) measurement. Here, we investigate the prognostic value of HVPG in MASLD-related compensated ACLD (MASLD-cACLD). METHODS: This European multicentre study included patients with MASLD-cACLD characterised by HVPG at baseline. Hepatic decompensation (variceal bleeding/ascites/hepatic encephalopathy) and liver-related mortality were considered the primary events of interest. RESULTS: A total of 340 patients with MASLD-cACLD (56.2% male; median age 62 [55-68] years, median MELD 8 [7-9], 71.2% with diabetes) were included. Clinically significant portal hypertension (CSPH: i.e., HVPG ≥10 mmHg) was found in 209 patients (61.5%). During a median follow-up of 41.5 (27.5-65.8) months, 65 patients developed hepatic decompensation with a cumulative incidence of 10.0% after 2 years (2Y) and 30.7% after 5 years (5Y) in those with MASLD-cACLD with CSPH, compared to 2.4% after 2Y and 9.4% after 5Y in patients without CSPH. Variceal bleeding did not occur without CSPH. CSPH (subdistribution hazard ratio [SHR] 5.13; p <0.001) was associated with an increased decompensation risk and a higher HVPG remained an independent risk factor in the multivariable model (adjusted SHR per mmHg: 1.12, p <0.001). Liver-related mortality occurred in 37 patients at a cumulative incidence of 3.3% after 2Y and 21.4% after 5Y in CSPH. Without CSPH, the incidence after 5Y was 0.8%. Accordingly, a higher HVPG was also independently associated with a higher risk of liver-related death (adjusted SHR per mmHg: 1.20, p <0.001). CONCLUSION: HVPG measurement is of high prognostic value in MASLD-cACLD. In patients with MASLD-cACLD without CSPH, the short-term risk of decompensation is very low and liver-related mortality is rare, while the presence of CSPH substantially increases the risk of both. IMPACT AND IMPLICATIONS: While the incidence of compensated advanced chronic liver disease (cACLD) due to metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing worldwide, insights into the impact of clinically significant portal hypertension (CSPH) on the risk of liver-related events in MASLD-cACLD remain limited. Based on the findings of this European multicentre study including 340 MASLD-cACLD patients, we could show that increasing HVPG values and the presence of CSPH in particular were associated with a significantly higher risk of first hepatic decompensation and liver-related mortality. In contrast, the short-term incidence of decompensation in patients with MASLD-cACLD without CSPH was low and the risk of liver-mortality remained negligible. Thus, HVPG measurements can provide important prognostic information for individualised risk stratification in MASLD-cACLD and may help facilitate the study of novel and promising treatment possibilities for MASLD.

Association of disproportionate liver fat with markers of heart failure: The multi-ethnic study of atherosclerosis.

BACKGROUND: Metabolic dysfunction associated steatotic liver disease (MASLD) has been linked to heart failure with preserved ejection fraction (HFpEF). We sought to understand association between individuals with amounts of liver adiposity greater than would be predicted by their body mass index (BMI) in order to understand whether this disproportionate liver fat (DLF) represents a proxy of metabolic risk shared between liver and heart disease. METHODS: We studied 2,932 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) who received computed tomography (CT) measurements of hepatic attenuation. Quartiles of DLF were compared and multivariable linear regression was performed to evaluate the association of DLF with clinical, echocardiographic, and quality of life metrics. RESULTS: Compared to the lowest quartile of DLF, individuals in the highest quartile of DLF were more likely to be male (52.0% vs 47.1%, P < .001), less likely to be Black or African American (14.8 % vs 38.1% P < .001), have higher rates of dysglycemia (31.9% vs 16.6%, P < .001) and triglycerides (140 [98.0, 199.0] vs 99.0 [72.0, 144.0] mg/dL, P > .001). These individuals had lower global longitudinal strain (-0.13 [-0.25, -0.02], P = .02), stroke volumes (-1.05 [-1.76, -0.33], P < .01), lateral e' velocity (-0.10 [-0.18, -0.02], P = .02), and 6-minute walk distances (-4.25 [-7.62 to -0.88], P = .01). CONCLUSION: DLF is associated with abnormal metabolic profiles and ventricular functional changes known to be associated with HFpEF and may serve as an early metric to assess for those that may progress to clinical HFpEF.

Six-month supplementation with high dose coenzyme Q10 improves liver steatosis, endothelial, vascular and myocardial function in patients with metabolic-dysfunction associated steatotic liver disease: a randomized double-blind, placebo-controlled trial.

BACKROUND: Metabolic-dysfunction Associated Steatotic Liver Disease (MASLD) has been associated with increased cardiovascular risk. The aim of this Randomized Double-blind clinical Trial was to evaluate the effects of coenzyme-Q10 supplementation in patients with MASLD in terms of endothelial, vascular and myocardial function. METHODS: Sixty patients with MASLD were randomized to receive daily 240 mg of coenzyme-Q10 or placebo. At baseline and at 6-months, the a)Perfused boundary region of sublingual vessels using the Sideview Darkfield imaging technique, b)pulse-wave-velocity, c)flow-mediated dilation of the brachial artery, d)left ventricular global longitudinal strain, e)coronary flow reserve of the left anterior descending coronary artery and f)controlled attenuation parameter for the quantification of liver steatosis were evaluated. RESULTS: Six months post-treatment, patients under coenzyme-Q10 showed reduced Perfused boundary region (2.18 ± 0.23vs.2.29 ± 0.18 µm), pulse-wave-velocity (9.5 ± 2vs.10.2 ± 2.3 m/s), controlled attenuation parameter (280.9 ± 33.4vs.304.8 ± 37.4dB/m), and increased flow-mediated dilation (6.1 ± 3.8vs.4.3 ± 2.8%), global longitudinal strain (-19.6 ± 1.6vs.-18.8 ± 1.9%) and coronary flow reserve (3.1 ± 0.4vs.2.8 ± 0.4) compared to baseline (p < 0.05). The placebo group exhibited no improvement during the 6-month follow-up period (p > 0.05). In patients under coenzyme-Q10, the reduction in controlled attenuation parameter score was positively related to the reduction in Perfused boundary region and pulse wave velocity and reversely related to the increase in coronary flow reserve and flow-mediated dilation (p < 0.05 for all relations). CONCLUSIONS: Six-month treatment with high-dose coenzyme-Q10 reduces liver steatosis and improves endothelial, vascular and left ventricle myocardial function in patients with MASLD, demonstrating significant improvements in micro- and macro-vasculature function. TRIAL REGISTRATION: NCT05941910.

Epicardial and liver fat implications in albuminuria: a retrospective study.

BACKGROUND: Albuminuria is considered an early and sensitive marker of kidney dysfunction, but also an independent cardiovascular risk factor. Considering the possible relationship among metabolic liver disease, cardiovascular disease and chronic kidney disease, we aimed to evaluate the risk of developing albuminuria regarding the presence of epicardial adipose tissue and the steatotic liver disease status. METHODS: A retrospective long-term longitudinal study including 181 patients was carried out. Epicardial adipose tissue and steatotic liver disease were assessed by computed tomography. The presence of albuminuria at follow-up was defined as the outcome. RESULTS: After a median follow up of 11.2 years, steatotic liver disease (HR 3.15; 95% CI, 1.20-8.26; p = 0.02) and excess amount of epicardial adipose tissue (HR 6.12; 95% CI, 1.69-22.19; p = 0.006) were associated with an increased risk of albuminuria after adjustment for visceral adipose tissue, sex, age, weight status, type 2 diabetes, prediabetes, hypertriglyceridemia, hypercholesterolemia, arterial hypertension, and cardiovascular prevention treatment at baseline. The presence of both conditions was associated with a higher risk of developing albuminuria compared to having steatotic liver disease alone (HR 5.91; 95% CI 1.15-30.41, p = 0.033). Compared with the first tertile of visceral adipose tissue, the proportion of subjects with liver steatosis and abnormal epicardial adipose tissue was significantly higher in the second and third tertile. We found a significant correlation between epicardial fat and steatotic liver disease (rho = 0.43 [p < 0.001]). CONCLUSIONS: Identification and management/decrease of excess adiposity must be a target in the primary and secondary prevention of chronic kidney disease development and progression. Visceral adiposity assessment may be an adequate target in the daily clinical setting. Moreover, epicardial adipose tissue and steatotic liver disease assessment may aid in the primary prevention of renal dysfunction.

When the liver is in poor condition, so is the heart - cardiac remodelling in MASH mouse models.

Metabolic dysfunction-associated steatohepatitis (MASH) confers a risk for cardiovascular diseases in patients. Animal models may help exploring the mechanisms linking liver and heart diseases. Hence, we explored the cardiac phenotype in two MASH mouse models: foz/foz mice fed a high-fat diet (HFD) for 24 or 60 weeks and C57BL/6J mice fed a high-fat-, high-cholesterol-, and high-fructose diet for 60 weeks. Angiotensin II (AngII) was used as an additional cardiovascular stressor for 4 weeks in 10 weeks HFD-fed foz/foz mice. Foz/foz mice with fibrosing MASH developed cardiac hypertrophy with adverse cardiac remodelling not seen in WT similarly fed the HFD. AngII caused hypertension and up-regulated the expression of genes contributing to pathological cardiac hypertrophy (Nppa, Myh7) more severely so in foz/foz mice than in controls. After 60 weeks of HFD, while liver disease had progressed to burn-out non steatotic MASH with hepatocellular carcinoma in 50% of the animals, the cardiomyopathy did not. In an independent model (C57BL/6J mice fed a fat-, cholesterol- and fructose-rich diet), moderate fibrosing MASH is associated with cardiac fibrosis and dysregulation of genes involved in pathological remodelling (Col1a1, Col3a1, Vim, Myh6, Slc2a1). Thus, animals with MASH present consistent adverse structural changes in the heart with no patent alteration of cardiac function even when stressed with exogenous AngII. Liver disease, and likely not overfeeding or aging alone, is associated with this cardiac phenotype. Our findings support foz/foz mice as suitable for studying links between MASH and heart structural changes ahead of heart failure.

Independent and joint relationships of cardiorespiratory fitness and body mass index with liver fat content.

AIMS: To investigate the relationship between cardiorespiratory fitness (CRF) and liver fat content (LFC) in community-based participants and highlight their relationship in people with different body mass indices (BMIs). MATERIALS AND METHODS: Using UK Biobank data, CRF was estimated with bicycle ergometer fitness testing and was evaluated based on physical work capacity at 75% maximum heart rate (PWC75%). LFC was quantified through liver proton density fat fraction (PDFF) on magnetic resonance imaging. Multivariate linear regression models were used to analyse the associations of CRF and BMI with absolute reduction and percentage change in PDFF (%). RESULTS: In total, 5765 participants with a mean age of 55.57 years and a median (range) follow-up of 10.7 (4.0-17.7) years were included. Compared with the lowest PWC75% tertile, the absolute reduction and percentage change in PDFF in the highest PWC75% tertile were -0.450 (95% confidence interval [CI] -0.699 to -0.192) and -4.152 (95% CI -6.044 to -2.104), respectively. These associations were independent of BMI, and individuals with obesity and normal weight had the largest absolute reduction and percentage change in LFC, respectively (p for interaction <0.001). Joint analysis showed that PWC75% and BMI had a negative dose-response relationship with PDFF. These associations were consistent in different sex and age subgroups (p for interaction >0.05). CONCLUSIONS: There was a significant negative association between CRF and LFC, and this association was independent of BMI. The results of this study strongly recommend improving CRF to mitigate LFC.

Joint effects of sleep disturbance and renal function impairment on incident new-onset severe metabolic dysfunction-associated steatotic liver disease.

AIM: To elucidate the effects of sleep parameters and renal function on the risk of developing new-onset severe metabolic dysfunction-associated steatotic liver disease (MASLD). MATERIALS AND METHODS: The primary analysis involved a cohort of 305 257 participants. Multivariable Cox models were employed to calculate hazard ratios and 95% confidence intervals. Traditional mediation and two-step Mendelian randomization (MR) analyses were conducted to assess the associations and mediating roles of renal function indicators between sleep and new-onset severe MASLD. RESULTS: Poor sleep score and renal function biomarker score (RFS) were associated with an increased risk of new-onset severe MASLD (all ptrend <0.001). Participants with poor sleep patterns and the highest RFS had a 5.45-fold higher risk of new-onset severe MASLD, compared to those with healthy sleep patterns and the lowest RFS (p < 0.001). The RFS could explain 10.08% of the correlations between poor sleep score and risk of new-onset severe MASLD. Additionally, MR analyses supported a causal link between insomnia and new-onset severe MASLD and revealed a mediating role of chronic kidney disease in the connection between insomnia and new-onset severe MASLD risk. CONCLUSIONS: This study highlights the independent and combined associations of sleep parameters and renal function indicators with new-onset severe MASLD, underscoring the bidirectional communication of the liver-kidney axis and providing modifiable strategies for preventing MASLD.

Estimated pulse wave velocity in metabolic dysfunction-associated steatotic liver disease and all-cause/cause-specific mortality.

BACKGROUND AND AIM: Several reports show a significant association between metabolic dysfunction-associated steatotic liver disease (MASLD) and arterial stiffness (estimated pulse wave velocity [ePWV]) as a surrogate marker of vascular age. We investigate whether ePWV as arterial stiffness in MASLD is associated with all-cause/cause-specific mortality. METHODS: This cohort study was based on the third National Health and Nutrition Examination Survey (NHANES, 1988-1994) and NHANES 2007-2014 and linked mortality datasets through 2019. Cox regression models assessed the association between ePWV categorized by quartile and all-cause/cause-specific mortality among individuals with MASLD. RESULTS: During the follow-up of a median of 26.3 years (interquartile range: 19.9-27.9), higher levels of ePWV among individuals with MASLD were associated with increased all-cause mortality, which remained significant after adjusting for demographic, lifestyle, clinical, and metabolic risk factors. Furthermore, higher ePWV in MASLD was associated with higher cardiovascular mortality. There was a 44% (hazard ratio: 1.44, 95% confidence interval: 1.32-1.58) increase in all-cause mortality and a 53% (hazard ratio: 1.53, 95% confidence interval: 1.32-1.77) increase in cardiovascular mortality for every 1 m/s increase in ePWV in MASLD. However, there was no significant association between ePWV and cancer-related mortality. Sensitivity analyses using the NHANES 2007-2014 dataset showed results identical to the original analysis. CONCLUSION: Higher ePWV in MASLD was associated with a higher risk of all-cause and cardiovascular mortality beyond traditional cardiovascular risk factors. Screening for ePWV in individuals with MASLD may be an effective and beneficial approach to reducing all-cause and cardiovascular mortality.

Associations between allostatic load and hepatic steatosis and liver fibrosis: evidence from NHANES 2017-2020.

BACKGROUND: Allostatic load, the cumulative strain resulting from chronic stress responses, has been linked to disease occurrence and progression, yet research quantifying this relationship is limited. This study aimed to explore the relationship between allostatic load score (ALS) levels and the degree of hepatic steatosis and fibrosis. METHODS: Data from the National Health and Nutrition Examination Survey 2017-2020 were analyzed. The ALS was based on the statistical distribution, assigning one point for each biomarker if it was in the highest risk quartile, and then summing them to generate the ALS score (range, 0-8). The multivariate linear regression was employed to analyze the association between the controlled attenuation parameter (CAP) and liver stiffness measurement (LSM) with ALS. Additionally, multinomial logistic regression was used to investigate the association between ALS and the degree of hepatic steatosis and fibrosis. RESULTS: Participants had a weighted mean age of 52.69 years and 56.14% were female. In the multivariate linear regression analysis, ALS showed a significant positive correlation with CAP (ß = 15.56, 95% CI: 14.50-16.62) and LSM (ß = 0.58, 95% CI: 0.48-0.67). Age, healthy dietary level, and PIR had significant interactions with this positive correlation. In the multinomial logistic regression analysis, ALS exhibited a significant positive correlation with different degrees of hepatic steatosis and fibrosis. Consistency of the results was observed in sensitivity analyses using clinical thresholds of ALS. CONCLUSIONS: Comprehensive clinical assessment targeting load adaptation may enhance the effectiveness of risk assessment in patients with hepatic steatosis and fibrosis.

Association between metabolic dysfunction-associated steatotic liver disease and pulmonary function: a population-based and two-sample mendelian randomization study.

BACKGROUND: Hepatic steatosis and its related complications are risk factors for multiple respiratory diseases; however, the causal relationship between metabolic dysfunction-associated steatotic liver disease (MASLD) and pulmonary function remains controversial. We aimed to identify it using a national cohort and Mendelian randomization (MR). METHODS: We enrolled 30,442 participants from the 2007 to 2012 National Health and Nutrition Examination Survey. Demographics, pulmonary function indices (forced expiratory volume in 1 s [FEV1], forced vital capacity [FVC]), and variables used to calculate the liver fat score (LFS) were collected. A two-sample MR analysis employing the summary data of genome-wide association studies on MASLD and FEV1/FVC, chronic obstructive pulmonary disease (COPD), and asthma from the Finngen Biobank and Medical Research Council Integrative Epidemiology Unit was performed. RESULTS: A total of 3,462 participants, 1,335 of whom had MASLD (LFS > -0.640), were finally included in the study. The FEV1 (3,204.7 vs. 3,262.5 ml, P = 0.061), FVC (4,089.1 vs. 4,143.8 ml, P = 0.146), FEV1/FVC ratio (78.5% vs. 78.8%, P = 0.233), and FEV1/predicted FEV1 ratio (146.5% vs. 141.7%, P = 0.366) were not significantly different between people with MASLD and those without. Additionally, the MR analysis suggested no causal correlation between MASLD and FEV1/FVC (P = 0.817), MASLD and COPD (P = 0.407), and MASLD and asthma (P = 0.808). Reverse MR studies showed no causal relationships yet (all P > 0.05). CONCLUSION: Our study provides convincing evidence that there is no causal association between MASLD and pulmonary function.

Inhibition of ATG3 ameliorates liver steatosis by increasing mitochondrial function.

BACKGROUND & AIMS: Autophagy-related gene 3 (ATG3) is an enzyme mainly known for its actions in the LC3 lipidation process, which is essential for autophagy. Whether ATG3 plays a role in lipid metabolism or contributes to non-alcoholic fatty liver disease (NAFLD) remains unknown. METHODS: By performing proteomic analysis on livers from mice with genetic manipulation of hepatic p63, a regulator of fatty acid metabolism, we identified ATG3 as a new target downstream of p63. ATG3 was evaluated in liver samples from patients with NAFLD. Further, genetic manipulation of ATG3 was performed in human hepatocyte cell lines, primary hepatocytes and in the livers of mice. RESULTS: ATG3 expression is induced in the liver of animal models and patients with NAFLD (both steatosis and non-alcoholic steatohepatitis) compared with those without liver disease. Moreover, genetic knockdown of ATG3 in mice and human hepatocytes ameliorates p63- and diet-induced steatosis, while its overexpression increases the lipid load in hepatocytes. The inhibition of hepatic ATG3 improves fatty acid metabolism by reducing c-Jun N-terminal protein kinase 1 (JNK1), which increases sirtuin 1 (SIRT1), carnitine palmitoyltransferase 1a (CPT1a), and mitochondrial function. Hepatic knockdown of SIRT1 and CPT1a blunts the effects of ATG3 on mitochondrial activity. Unexpectedly, these effects are independent of an autophagic action. CONCLUSIONS: Collectively, these findings indicate that ATG3 is a novel protein implicated in the development of steatosis. LAY SUMMARY: We show that autophagy-related gene 3 (ATG3) contributes to the progression of non-alcoholic fatty liver disease in humans and mice. Hepatic knockdown of ATG3 ameliorates the development of NAFLD by stimulating mitochondrial function. Thus, ATG3 is an important factor implicated in steatosis.

iRhom2 Promotes Hepatic Steatosis by Activating MAP3K7-Dependent Pathway.

BACKGROUND AND AIMS: Nonalcoholic fatty liver disease (NAFLD) has been widely recognized as a precursor to metabolic complications. Elevated inflammation levels are predictive of NAFLD-associated metabolic disorder. Inactive rhomboid-like protein 2 (iRhom2) is regarded as a key regulator in inflammation. However, the precise mechanisms by which iRhom2-regulated inflammation promotes NAFLD progression remain to be elucidated. APPROACH AND RESULTS: Here, we report that insulin resistance, hepatic steatosis, and specific macrophage inflammatory activation are significantly alleviated in iRhom2-deficient (knockout [KO]) mice, but aggravated in iRhom2 overexpressing mice. We further show that, mechanistically, in response to a high-fat diet (HFD), iRhom2 KO mice and mice with iRhom2 deficiency in myeloid cells only showed less severe hepatic steatosis and insulin resistance than controls. Inversely, transplantation of bone marrow cells from healthy mice to iRhom2 KO mice expedited the severity of insulin resistance and hepatic dyslipidemia. Of note, in response to HFD, hepatic iRhom2 binds to mitogen-activated protein kinase kinase kinase 7 (MAP3K7) to facilitate MAP3K7 phosphorylation and nuclear factor kappa B cascade activation, thereby promoting the activation of c-Jun N-terminal kinase/insulin receptor substrate 1 signaling, but disturbing AKT/glycogen synthase kinase 3ß-associated insulin signaling. The iRhom2/MAP3K7 axis is essential for iRhom2-regulated liver steatosis. CONCLUSIONS: iRhom2 may represent a therapeutic target for the treatment of HFD-induced hepatic steatosis and insulin resistance.

Liver X Receptor Alpha Activation Inhibits Autophagy and Lipophagy in Hepatocytes by Dysregulating Autophagy-Related 4B Cysteine Peptidase and Rab-8B, Reducing Mitochondrial Fuel Oxidation.

BACKGROUND AND AIMS: Fat accumulation results from increased fat absorption and/or defective fat metabolism. Currently, the lipid-sensing nuclear receptor that controls fat utilization in hepatocytes is elusive. Liver X receptor alpha (LXRα) promotes accumulation of lipids through the induction of several lipogenic genes. However, its effect on lipid degradation is open for study. Here, we investigated the inhibitory role of LXRα in autophagy/lipophagy in hepatocytes and the underlying basis. APPROACH AND RESULTS: In LXRα knockout mice fed a high-fat diet, or cell models, LXRα activation suppressed the function of mitochondria by inhibiting autophagy/lipophagy and induced hepatic steatosis. Gene sets associated with "autophagy" were enriched in hepatic transcriptome data. Autophagy flux was markedly augmented in the LXRα knockout mouse liver and primary hepatocytes. Mechanistically, LXRα suppressed autophagy-related 4B cysteine peptidase (ATG4B) and Rab-8B, responsible for autophagosome and -lysosome formation, by inducing let-7a and microRNA (miR)-34a. Chromatin immunoprecipitation assay enabled us to find LXRα as a transcription factor of let-7a and miR-34a. Moreover, 3' untranslated region luciferase assay substantiated the direct inhibitory effects of let-7a and miR-34a on ATG4B and Rab-8B. Consistently, either LXRα activation or the let-7a/miR-34a transfection lowered mitochondrial oxygen consumption rate and mitochondrial transmembrane potential and increased fat levels. In obese animals or nonalcoholic fatty liver disease (NAFLD) patients, let-7a and miR-34a levels were elevated with simultaneous decreases in ATG4B and Rab-8B levels. CONCLUSIONS: LXRα inhibits autophagy in hepatocytes through down-regulating ATG4B and Rab-8B by transcriptionally activating microRNA let-7a-2 and microRNA 34a genes and suppresses mitochondrial biogenesis and fuel consumption. This highlights a function of LXRα that culminates in the progression of liver steatosis and steatohepatitis, and the identified targets may be applied for a therapeutic strategy in the treatment of NAFLD.

Mechanism of subchronic vinyl chloride exposure combined with a high-fat diet on hepatic steatosis.

Vinyl chloride (VC) is a common industrial organic chlorine and environmental pollutant. In recent years, the dietary structure of residents especially Chinese has gradually shifted to western dietary patterns. VC aggravates dietary fatty acid-induced hepatic steatosis, but its mechanism is still unclear. And if the risk factors for steatosis persist, more severe diseases such as fibrosis and cirrhosis will occur. Therefore, we studied the effects and mechanisms of VC (160 and 800 mg/m3 ) and its metabolite (chloroacetaldehyde, 2.25, 4.5, and 9 µM) on hepatic steatosis of high-fat diet (HFD)-fed mice and palmitic acid (PA, 100 µM) treated HepG2 cells. Liver and serum biochemical indicators and pathological staining of the liver showed that the hepatic steatosis of VC combined with HFD groups was more severe than that of single-exposure groups (HFD group, low-dose VC group, and high-dose VC group). Moreover, VC enhanced HFD-induced oxidative stress (OS) and endoplasmic reticulum stress (ERS) and further upregulated the expression of sterol regulatory element-binding protein 1 (SREBP-1) and FAS. Besides, antioxidants and ERS inhibitors reduced the steatosis of HepG2 cells induced by VC metabolites and PA. These results suggest that VC exposure can enhance the degree of hepatic steatosis in HFD-fed mice. VC combined with HFD led to OS and ERS and upregulated the expression of de novo lipogenesis-related proteins, which may be related to the occurrence of hepatic steatosis. And the increased expression of CYP2E1 induced by VC combined with HFD may be the cause of OS.

Estradiol treatment or modest exercise improves hepatic health and mitochondrial outcomes in female mice following ovariectomy.

We recently reported that compared with males, female mice have increased hepatic mitochondrial respiratory capacity and are protected against high-fat diet-induced steatosis. Here, we sought to determine the role of estrogen in hepatic mitochondrial function, steatosis, and bile acid metabolism in female mice and investigate potential benefits of exercise in the absence or presence of estrogen via ovariectomy (OVX). Female C57BL mice (n = 6 per group) were randomly assigned to sham surgery (sham), ovariectomy (OVX), or OVX plus estradiol replacement therapy (OVX + Est). Half of the mice in each treatment group were sedentary (SED) or had access to voluntary wheel running (VWR). All mice were fed a high-fat diet (HFD) and were housed at thermoneutral temperatures. We assessed isolated hepatic mitochondrial respiratory capacity using the Oroboros O2k with both pyruvate and palmitoylcarnitine as substrates. As expected, OVX mice presented with greater hepatic steatosis, weight gain, and fat mass gain compared with sham and OVX + Est animals. Hepatic mitochondrial coupling (basal/state 3 respiration) with pyruvate was impaired following OVX, but both VWR and estradiol treatment rescued coupling to levels greater than or equal to sham animals. Estradiol and exercise also had different effects on liver electron transport chain protein expression depending on OVX status. Markers of bile acid metabolism and excretion were also impaired by ovariectomy but rescued with estradiol add-back. Together our data suggest that estrogen depletion impairs hepatic mitochondrial function and liver health, and that estradiol replacement and modest exercise can aid in rescuing this phenotype.NEW & NOTEWORTHY OVX induces hepatic steatosis in sedentary mice which can be prevented by modest physical activity (VWR) and/or estradiol treatment. Estrogen impacts hepatic mitochondrial coupling in a substrate-specific manner. OVX mice have impaired fecal bile acid excretion, which was rescued with estradiol treatment.

The Chinese Society of Hepatology position statement on the redefinition of fatty liver disease.

Fatty liver disease associated with metabolic dysfunction is of increasing concern in mainland China, the world's most populous country. The incidence of fatty liver disease is highest in China, surpassing the incidence in European countries and the USA. An international consensus panel recently published an influential report recommending a novel definition of fatty liver disease associated with metabolic dysfunction. This recommendation includes a switch in name from non-alcoholic fatty liver disease (NAFLD) to metabolic (dysfunction)-associated fatty liver disease (MAFLD) and adoption of a set of positive criteria for disease diagnosis that are independent of alcohol intake or other liver diseases. Given the unique importance of this proposal, the Chinese Society of Hepatology (CSH) invited leading hepatologists and gastroenterologists representing their respective provinces and cities to reach consensus on alternative definitions for fatty liver disease from a national perspective. The CSH endorses the proposed change from NAFLD to MAFLD (supported by 95.45% of participants). We expect that the new definition will result in substantial improvements in health care for patients and advance disease awareness, public health policy, and political, scientific and funding outcomes for MAFLD in China.