Innate immune regulatory networks in hepatic lipid metabolism. J Mol Med (Berl). 2019;97:593-604. [PMID: 30891617 DOI: 10.1007/s00109-019-01765-1]

Sustainable Fish Meal-Free Diets for Gilthead Sea Bream (Sparus aurata): Integrated Biomarker Response to Assess the Effects on Growth Performance, Lipid Metabolism, Antioxidant Defense and Immunological Status

The growth of the aquaculture industry requires more sustainable and circular economy-driven aquafeed formulas. Thus, the goal of the present study was to assess in farmed gilthead sea bream (Sparus aurata L.) how different combinations of novel and conventional fish feed ingredients supported proper animal performance in terms of growth and physiological biomarkers of blood/liver/head kidney. A 77-day feeding trial was conducted with three experimental diets (PAP, with terrestrial processed animal protein from animal by-products; NOPAP, without processed animal protein from terrestrial animal by-products; MIX, a combination of alternative ingredients of PAP and NOPAP diets) and a commercial-type formulation (CTRL), and their effects on growth performance and markers of endocrine growth regulation, lipid metabolism, antioxidant defense and inflammatory condition were assessed at circulatory and tissue level (liver, head kidney). Growth performance was similar among all dietary treatments. However, fish fed the PAP diet displayed a lower feed conversion and protein efficiency, with intermediate values in MIX-fed fish. Such gradual variation in growth performance was supported by different biomarker signatures that delineated a lower risk of oxidation and inflammatory condition in NOPAP fish, in concurrence with an enhanced hepatic lipogenesis that did not represent a risk of lipoid liver degeneration.

USP13 ameliorates nonalcoholic fatty liver disease through inhibiting the activation of TAK1

BACKGROUND

The molecular mechanisms underlying nonalcoholic fatty liver disease (NAFLD) remain to be fully elucidated. Ubiquitin specific protease 13 (USP13) is a critical participant in inflammation-related signaling pathways, which are linked to NAFLD. Herein, the roles of USP13 in NAFLD and the underlying mechanisms were investigated.

METHODS

L02 cells and mouse primary hepatocytes were subjected to free fatty acid (FFA) to establish an in vitro model reflective of NAFLD. To prepare in vivo model of NAFLD, mice fed a high-fat diet (HFD) for 16 weeks and leptin-deficient (ob/ob) mice were used. USP13 overexpression and knockout (KO) strategies were employed to study the function of USP13 in NAFLD in mice.

RESULTS

The expression of USP13 was markedly decreased in both in vitro and in vivo models of NAFLD. USP13 overexpression evidently inhibited lipid accumulation and inflammation in FFA-treated L02 cells in vitro. Consistently, the in vivo experiments showed that USP13 overexpression ameliorated hepatic steatosis and metabolic disorders in HFD-fed mice, while its deficiency led to contrary outcomes. Additionally, inflammation was similarly attenuated by USP13 overexpression and aggravated by its deficiency in HFD-fed mice. Notably, overexpressing of USP13 also markedly alleviated hepatic steatosis and inflammation in ob/ob mice. Mechanistically, USP13 bound to transforming growth factor β-activated kinase 1 (TAK1) and inhibited K63 ubiquitination and phosphorylation of TAK1, thereby dampening downstream inflammatory pathways and promoting insulin signaling pathways. Inhibition of TAK1 activation reversed the exacerbation of NAFLD caused by USP13 deficiency in mice.

CONCLUSIONS

Our findings indicate the protective role of USP13 in NAFLD progression through its interaction with TAK1 and inhibition the ubiquitination and phosphorylation of TAK1. Targeting the USP13-TAK1 axis emerges as a promising therapeutic strategy for NAFLD treatment.

Intestinal microbiota and gene expression alterations in leopard coral grouper (Plectropomus leopardus) under enteritis

Enteritis poses a significant threat to fish farming, characterized by symptoms of intestinal and hepatic inflammation, physiological dysfunction, and dysbiosis. Focused on the leopard coral grouper (Plectropomus leopardus) with an enteritis outbreak on a South China Sea farm, our prior scrutiny did not find any abnormalities in feeding or conventional water quality factors, nor were any specific pathogen infections related to enteritis identified. This study further elucidates their intestinal flora alterations, host responses, and their interactions to uncover the underlying pathogenetic mechanisms and facilitate effective prevention and management strategies. Enteritis-affected fish exhibited substantial differences in intestinal flora compared to control fish (P = 0.001). Notably, norank_f_Alcaligenaceae, which has a negative impact on fish health, predominated in enteritis-affected fish (91.76 %), while the probiotic genus Lactococcus dominated in controls (93.90 %). Additionally, certain genera with pathogenesis potentials like Achromobacter, Sphingomonas, and Streptococcus were more abundant in diseased fish, whereas Enterococcus and Clostridium_sensu_stricto with probiotic potentials were enriched in control fish. At the transcriptomic level, strong inflammatory responses, accompanied by impaired metabolic functions, tissue damage, and iron death signaling activation were observed in the intestines and liver during enteritis. Furthermore, correlation analysis highlighted that potential pathogen groups were positively associated with inflammation and tissue damage genes while presenting negatively correlated with metabolic function-related genes. In conclusion, dysbiosis in the intestinal microbiome, particularly an aberrantly high abundance of Alcaligenaceae with pathogenic potential may be the main trigger for this enteritis outbreak. Alcaligenaceae alongside Achromobacter, Sphingomonas, and Streptococcus emerged as biomarkers for enteritis, whereas some species of Lactococcus, Clostridium_sensu_stricto, and Enterococcus showed promise as probiotics to alleviate enteritis symptoms. These findings enhance our understanding of enteritis pathogenesis, highlight intestinal microbiota shifts in leopard coral grouper, and propose biomarkers for monitoring, probiotic selection, and enteritis management.

Current remarks and future directions on the interactions between metabolic dysfunction-associated fatty liver disease and COVID-19

During the outbreak of the coronavirus disease 2019 (COVID-19) pandemic, particular interest rose regarding the interaction between metabolic dysfunction-associated fatty liver disease (MAFLD) and the COVID-19 infection. Several studies highlighted the fact that individuals with MAFLD had higher probability of severe acute respiratory syndrome coronavirus 2 infection and more severe adverse clinical outcomes. One of the proposed mechanisms is the inflammatory response pathway, especially the one involving cytokines, such as interleukin 6, which appeared particularly elevated in those patients and was deemed responsible for additional insult to the already damaged liver. This should increase our vigilance in terms of early detection, close follow up and early treatment for individuals with MAFLD and COVID-19 infection. In the direction of early diagnosis, biomarkers such as cytokeratin-18 and scoring systems such as Fibrosis-4 index score are proposed. COVID-19 is a newly described entity, expected to be of concern for the years to come, and MAFLD is a condition with an ever-increasing impact. Delineating the interaction between these two entities should be brought into the focus of research. Reducing morbidity and mortality of patients with COVID-19 and MAFLD should be the ultimate objective, and the optimal way to achieve this is by designing evidence-based prevention and treatment policies.

Recent advances in age-related metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects approximately 25% of the world's population and has become a leading cause of chronic liver disease. In recent years, an increasing amount of data suggests that MASLD is associated with aging. As the population ages, age-related MASLD will become a major global health problem. Targeting an aging will become a new approach to the treatment of MASLD. This paper reviews the current studies on the role of aging-related factors and therapeutic targets in MASLD, including: Oxidative stress, autophagy, mitochondrial homeostasis, bile acid metabolism homeostasis, and dysbiosis. The aim is to identify effective therapeutic targets for age-related MASLD and its progression.

Attenuated AKT signaling by miR-146a-5p interferes with chicken granulosa cell proliferation, lipid deposition and progesterone biosynthesis

Steroid hormones play a crucial role in the growth and maturation of poultry ovarian follicles, with progesterone secretion by granulosa cells (GC) being essential. According to our previous transcriptome analysis, it apparented that miR-146a-5p expressions were upregulated in the follicles undergoing atresia. In this study, we delved the depth to explore the underlying mechanisms by miR-146a-5p in the regulation of follicle functions in chicken. The study demonstrated that miR-146a-5p suppressed cell growth, lipids accumulation, and progesterone biosynthesis in chicken GC. Through targeting association validations, we identified delta 4-desaturase, sphingolipid 1 (DEGS1) as capable of interacting with miR-146a-5p. Co-transfection experiments further confirmed that DEGS1 reversed the impairment of GC functions by miR-146a-5p. Moreover, we discovered that miR-146a-5p suppressed AKT phosphorylation, while DEGS1 enhanced AKT phosphorylation. Phosphatidylinositol-3 kinase (PI3K) inhibitor (LY294002) studies showed that miR-146a-5p would inhibit AKT phosphorylation by governing the DEGS1/AKT pathway, which in turn regulates GC function. In summary, the findings revealed that miR-146a-5p suppressed cell growth, lipid deposition, and progesterone biosynthesis via the DEGS1/AKT pathway. These results may further enrich our understandings of how non-coding RNA regulates productive performance in chickens.

Association between dietary inflammation index and hypertension in participants with different degrees of liver steatosis

BACKGROUND

The prevalence of hypertension (HTN) is higher in patients with non-alcoholic fatty liver disease (NAFLD). Inflammation is the key link between HTN and NAFLD. Systemic inflammation can be dramatically increased by inflammatory diet intake. However, whether controlling the inflammatory diet intake in NAFLD patients could affect the occurrence of HTN still remains unknown. Our aim here is to evaluate the effect of the dietary inflammatory index (DII) on blood pressure in patients with different grades of hepatic steatosis.

MATERIALS AND METHODS

The data were collected from the National Health and Nutrition Examination Survey (NHANES) (2017-2018). DII was calculated based on the data of 24-h dietary recall interviews. The severity of liver steatosis was assessed by a controlled attenuation parameter. Multivariable logistic regression, multivariable linear regression and subgroup analyses were conducted to determine the association between DII and blood pressure in patients with different degrees of hepatic steatosis.

RESULTS

A total of 5449 participants were included in this analysis. In male participants with severe liver steatosis (S3), the highest DII tertile group was more likely to have higher systolic blood pressure (SBP) compared with the lowest tertile group (Tertile1: 128.31(125.31,131.31), Tertile3: 133.12(129.40,136.85), P for trend =0.03551). DII was positively correlated with SBP and the prevalence of HTN in males with hepatic steatosis grade S3 (≥ 67% steatosis) (SBP: P for trend = 0.011, HTN: P for trend = 0.039). Regarding the association of DII with SBP and HTN, the tests for interaction were significant for hepatic steatosis (SBP: interaction for p = 0.0015, HTN: interaction for p = 0.0202).

CONCLUSIONS

In the present study, we demonstrated that DII was a risk factor for increased SBP and the prevalence of HTN in males with severe hepatic steatosis S3, indicating that anti-inflammatory dietary management should be considered in these individuals to reduce the risk of developing HTN.

MiR-484 promotes nonalcoholic fatty liver disease progression in mice via downregulation of Sorbs2

OBJECTIVE

MicroRNA 484 (miR-484) plays a pivotal role in the development and progression of different diseases and is typically described as a mitochondrial regulator. Whether miR-484 is involved in lipid metabolism or exerts a role in nonalcoholic fatty liver disease remains unclear.

METHODS

miR-484 levels were examined in the livers of male mice fed a high-fat diet and in hepatocytes treated with free fatty acids. Sorbin and SH3 structural domain-containing protein 2 (Sorbs2) were identified as a novel target of miR-484 by sequencing mRNA in the livers of miR-484 knockout mice. Sorbs2 liver-specific knockdown mice were constructed by tail vein injection of adeno-associated virus vector to miR-484 knockout mice. In addition, genetic manipulation of SORBS2 was performed in human hepatocyte lines, mouse primary hepatocytes, and the liver.

RESULTS

Serum and hepatic miR-484 levels are upregulated in nonalcoholic fatty liver disease mice. miR-484 knockdown ameliorated hepatocyte steatosis, whereas miR-484 overexpression increased hepatocyte lipid load. miR-484 knockdown-mediated alleviation of hepatic steatosis, liver injury, inflammation, and apoptosis was compromised after high-fat diet-induced knockdown of Sorbs2 in mouse liver and free fatty acid-induced primary mouse hepatocytes.

CONCLUSIONS

These results identify Sorbs2-mediated mitochondrial β-oxidation and apoptosis that promote miR-484 knockdown-mediated remission of hepatic steatosis.

Metabolomic Insights into the Mechanisms of Ganoderic Acid: Protection against α-Amanitin-Induced Liver Injury

α-Amanitin is a representative toxin found in the Amanita genus of mushrooms, and the consumption of mushrooms containing α-Amanitin can lead to severe liver damage. In this study, we conduct toxicological experiments to validate the protective effects of Ganoderic acid A against α-amanitin-induced liver damage. By establishing animal models with different durations of Ganoderic acid A treatment and conducting a metabolomic analysis of the serum samples, we further confirmed the differences in serum metabolites between the AMA+GA and AMA groups. The analysis of differential serum metabolites after the Ganoderic acid A intervention suggests that Ganoderic acid A may intervene in α-amanitin-induced liver damage by participating in the regulation of retinol metabolism, tyrosine and tryptophan biosynthesis, fatty acid biosynthesis, sphingosine biosynthesis, spermidine and spermine biosynthesis, and branched-chain amino acid metabolism. This provides initial insights into the protective intervention mechanisms of GA against α-amanitin-induced liver damage and offers new avenues for the development of therapeutic drugs for α-Amanitin poisoning.

Comparative Analysis of Different Proteins and Metabolites in the Liver and Ovary of Local Breeds of Chicken and Commercial Chickens in the Later Laying Period

The liver and ovary perform a vital role in egg production in hens. In the later laying period, the egg-laying capacity of female hens, particularly that of local breeds, declines significantly. Hence, it is essential to study the features and conditions of the ovary and liver during this period. In this research, we characterized the proteins and metabolites in the liver and ovary of 55-week-old Guangyuan gray chickens (Group G) and Hy-Line gray chickens (Group H) by using liquid chromatography chip/electrospray ionization quadruple time-of-flight/mass spectroscopy (LC-MS/MS). In total, 139 differentially expressed proteins (DEPs) and 186 differential metabolites (DMs) were identified in the liver, and 139 DEPs and 36 DMs were identified in the ovary. The upregulated DEPs and DMs in both the liver and ovary of Group G were primarily enriched in pathways involved in amino acid and carbohydrate metabolism. This suggests that energy metabolism was highly active in the Guangyuan gray chickens. In contrast, the upregulated DEPs and DMs in Group H were mainly enriched in pathways associated with lipid metabolism, which may explain the higher egg production and the higher fatty liver rate in Hy-Line gray hens in the later laying period. Additionally, it was found that the unique protein s-(hydroxymethyl) glutathione dehydrogenase (ADH4) in Group G was implicated in functions such as fatty acid degradation, glycolysis, and pyruvate metabolism, whereas the unique proteins, steroid sulfatase (STS), glucosylceramidase (LOC107050229), and phospholipase A2 Group XV (PLA2G15), in Group H were involved in the metabolism of steroid hormones and glycerol phosphate. In conclusion, variations in how carbohydrates, lipids, and amino acids are processed in the liver and ovary of local breeds of chicken and commercial hens towards the end of their laying period could explain the disparities in their egg production abilities.

Asprosin contributes to nonalcoholic fatty liver disease through regulating lipid accumulation and inflammatory response via AMPK signaling

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a primary contributor to liver-related morbidity and mortality. Asprosin has been reported to be implicated in NAFLD.

AIMS

This work is to illuminate the effects of Asprosin on NAFLD and the possible downstream mechanism.

MATERIALS & METHODS

The weight of NAFLD mice induced by a high-fat diet was detected. Quantitative reverse-transcription polymerase chain reaction (RT-qPCR) examined serum Asprosin expression. RT-qPCR and western blot analysis examined Asprosin expression in mice liver tissues. Intraperitoneal glucose tolerance test (IPGTT) and intraperitoneal insulin tolerance test (IPITT) were implemented. Biochemical kits tested liver enzyme levels in mice serum and liver tissues. Hematoxylin and eosin staining evaluated liver histology. Liver weight was also tested and oil red O staining estimated lipid accumulation. RT-qPCR and western blot analysis analyzed the expression of gluconeogenesis-, fatty acid biosynthesis-, fatty acid oxidation-, and inflammation-associated factors. Besides, western blot analysis examined the expression of AMP-activated protein kinase (AMPK)/p38 signaling-associated factors. In palmitic acid (PA)-treated mice hepatocytes, RT-qPCR and western blot analysis examined Asprosin expression. Lipid accumulation, gluconeogenesis, fatty acid biosynthesis, fatty acid oxidation, and inflammation were appraised again.

RESULTS

Asprosin was overexpressed in the serum and liver tissues of NAFLD mice and PA-treated mice hepatocytes. Asprosin interference reduced mice body and liver weight, improved glucose tolerance and diminished liver injury in vivo. Asprosin knockdown alleviated lipid accumulation and inflammatory infiltration both in vitro and in vivo. Additionally, Asprosin absence activated AMPK/p38 signaling and AMPK inhibitor Compound C reversed the impacts of Asprosin on lipid accumulation and inflammatory response.

CONCLUSION

Collectively, Asprosin inhibition suppressed lipid accumulation and inflammation to obstruct NAFLD through AMPK/p38 signaling.

Higher pNRF2, SOCS3, IRF3, and RIG1 Tissue Protein Expression in NASH Patients versus NAFL Patients: pNRF2 Expression Is Concomitantly Associated with Elevated Fasting Glucose Levels

Non-alcoholic fatty liver disease (NAFLD) embraces simple steatosis in non-alcoholic fatty liver (NAFL) to advanced non-alcoholic steatohepatitis (NASH) associated with inflammation, fibrosis, and cirrhosis. NAFLD patients often have metabolic syndrome and high risks of cardiovascular and liver-related mortality. Our aim was to clarify which proteins play a role in the progression of NAFL to NASH. The study investigates paraffin-embedded samples of 22 NAFL and 33 NASH patients. To detect potential candidates, samples were analyzed by immunohistochemistry for the proteins involved in innate immune regulation, autophagy, apoptosis, and antioxidant defense: IRF3, RIG-1, SOCS3, pSTAT3, STX17, SGLT2, Ki67, M30, Caspase 3, and pNRF2. The expression of pNRF2 immunopositive nuclei and SOCS3 cytoplasmic staining were higher in NASH than in NAFL (p = 0.001); pNRF2 was associated with elevated fasting glucose levels. SOCS3 immunopositivity correlated positively with RIG1 (r = 0.765; p = 0.001). Further, in NASH bile ducts showed stronger IRF3 immunostaining than in NAFL (p = 0.002); immunopositive RIG1 tissue was higher in NASH than in NAFL (p = 0.01). Our results indicate that pNRF2, SOCS3, IRF3, and RIG1 are involved in hepatic lipid metabolism. We suggest that they may be suitable for further studies to assess their potential as therapeutics.

Genome wide transcriptome analysis provides bases on hepatic lipid metabolism disorder affected by increased dietary grain ratio in fattening lambs

BACKGROUND

The liver is a principal metabolic organ and has a major role in regulating lipid metabolism. With the development of rapidly fattening livestock in the modern breeding industry, the incidence of hepatic steatosis and accumulation in animals was significantly increased. However, the molecular mechanisms responsible for hepatic lipid metabolic disturbances in a high concentrate diet remain unclear. The objective of this study was to evaluate the effects of increasing concentrate level in a fattening lamb diet on biochemical indices, hepatic triglycerides (TG) concentration, and hepatic transcriptomic profiles. In the present study, 42 weaned lambs (about 3 ± 0.3 months old) were randomly assigned to the GN60 group (60% concentrate of dry matter, GN60, n = 21) or GN70 group (70% concentrate of dry matter, n = 21) for a 3-months feeding trial.

RESULTS

No difference was observed in the growth performance or plasma biochemical parameters between the GN60 group and the GN70 group. The hepatic TG concentration was higher in the GN70 group than GN60 group (P < 0.05). Hepatic transcriptomic analysis showed that there were 290 differentially expressed genes identified between GN60 and GN70 groups, with 125 genes up-regulated and 165 genes down-regulated in the GN70 group. The enriched Gene Ontology (GO) items and KEGG pathways and protein-protein interaction (PPI) network of differentially expressed genes (DEGs) revealed that the majority of enriched pathways were related to lipid metabolism. Further analysis revealed that the fatty acid synthesis was up-regulated, while fatty acid transport, oxidation, and TG degradation were down-regulated in the GN70 group when compared with the GN60 group.

CONCLUSIONS

These results indicated that GN70 induced excess lipid deposition in the liver of lambs during the fattening period, with high synthesis rates and low degradation rates of TG. The identified mechanisms may help understand hepatic metabolism in lambs with a high concentrate diet and provide insight into decreasing the risk of liver metabolism disorder in animals.

Correlation between the triglyceride-glucose index and the onset of atrial fibrillation in patients with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is associated with atrial fibrillation (AF). Insulin resistance (IR) is the main cause of the high prevalence of AF in NAFLD patients. The triglyceride-glucose index (TyG) is a novel IR-related indicator implicated in the incidence and severity of NAFLD. However, the role of TyG in determining the risk for AF in patients with NAFLD remains unclear.

METHODS

A retrospective study was conducted on 912 patients diagnosed with NAFLD via ultrasonography. These patients were divided into two groups: (1) NAFLD+ AF and (2) NAFLD+ non-AF. Least Absolute Shrinkage and Selection Operator (LASSO) regression was used to assess the correlation between the TyG index and the high risk for AF. A receiver operating characteristic (ROC) curve was constructed to evaluate the predictive value for the TyG index for AF. Restricted cubic splines (RCS) were used to test the linear correlation between TyG and the risk for AF.

RESULTS

A total of 204 patients with AF and 708 patients without AF were included in this study. The LASSO logistic regression analysis showed that TyG was an independent risk factor for AF (odds ratio [OR] = 4.84, 95% confidence interval [CI] 2.98-7.88, P < 0.001). The RCS showed that the risk for AF increased linearly with TyG over the entire TyG range; this risk was also evident when the patients were analyzed based on sex (P for nonlinear > 0.05). In addition, the correlation between TyG and AF was a consistent finding in subgroup analysis. Furthermore, ROC curve analysis showed that TyG levels combined with traditional risk factors improved the predictive value for atrial fibrillation.

CONCLUSION

The TyG index is useful in assessing the risk for atrial fibrillation in patients with NAFLD. Patients with NAFLD and increased TyG indices have higher risks for atrial fibrillation. Therefore, TyG indices should be assessed when managing patients with NAFLD.

Transcriptome analysis of liver, gill and intestine in rainbow trout (Oncorhynchus mykiss) symptomatically or asymptomatically infected with Vibrio anguillarum

Rainbow trout (Oncorhynchus mykiss), an important economic cold-water fish worldwide, is severely threatened by viruses and bacteria in the farming industry. The vibriosis outbreak has caused a significant setback to aquaculture. Vibrio anguillarum, one of the common disease-causing vibriosis associated with severe lethal vibriosis in aquaculture, infects fish mainly by adsorption and invasion of the skin, gills, lateral line and intestine. To investigate the defense mechanism of rainbow trout against the pathogen after infection with Vibrio anguillarum, trout were intraperitoneally injected by Vibrio anguillarum and divided into symptomatic group (SG) and asymptomatic group (AG) according to the phenotype. RNA-Seq technology was used to evaluate the transcriptional signatures of liver, gill and intestine of trout injected with Vibrio anguillarum (SG and AG) and corresponding control groups (CG(A) and CG(B)). The GO and KEGG enrichment analyses were used to investigate the mechanisms underlying the differences in susceptibility to Vibrio anguillarum. Results showed that in SG, immunomodulatory genes in the cytokine network were activated and tissue function-related genes were down-regulated, while apoptosis mechanisms were activated. However, AG responded to Vibrio anguillarum infection by activating complement related immune defenses, while metabolism and function related genes were up-regulated. Conclusively, a rapid and effective immune and inflammatory response can successfully defend Vibrio anguillarum infection. However, a sustained inflammatory response can lead to tissue and organ damage and cause death. Our results may provide a theoretical basis for breeding rainbow trout for disease resistance.

Severity of non-alcoholic fatty liver disease is a risk factor for developing hypertension from prehypertension

BACKGROUND

There is little published evidence about the role of non-alcoholic fatty liver disease (NAFLD) in the progression from prehypertension to hypertension. This study was conducted to investigate the association of NAFLD and its severity with the risk of hypertension developing from prehypertension.

METHODS

The study cohort comprised 25, 433 participants from the Kailuan study with prehypertension at baseline; those with excessive alcohol consumption and other liver diseases were excluded. NAFLD was diagnosed by ultrasonography and stratified as mild, moderate, or severe. Univariable and multivariable Cox proportional hazard regression was used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs) of incident hypertension according to the presence and 3 categories of severity of NAFLD.

RESULTS

During a median of 12.6 years of follow-up, 10,638 participants progressed to hypertension from prehypertension. After adjusting for multiple risk factors, patients with prehypertension and NAFLD had a 15% higher risk of incident hypertension than those without NAFLD (HR = 1.15, 95% CI 1.10-1.21). Moreover, the severity of NAFLD was associated with the incidence of hypertension, which was higher in patients with more severe NAFLD (HR = 1.15 [95% CI 1.10-1.21] in the mild NAFLD group; HR = 1.15 [95% CI 1.07-1.24] in the moderate NAFLD group; and HR = 1.20 [95% CI 1.03-1.41] in the severe NAFLD group). Subgroup analysis indicated that age and baseline systolic blood pressure may modify this association.

CONCLUSIONS

NAFLD is an independent risk factor for hypertension in patients with prehypertension. The risk of incident hypertension increases with the severity of NAFLD.

NOD1 activation in 3T3-L1 adipocytes confers lipid accumulation in HepG2 cells

AIMS

Activation of specific innate immune receptors has been characterized to modulate nutrient metabolism in individual metabolic tissue directly or indirectly via secretory molecules. Activation of the nucleotide-binding oligomerization domain-containing protein 1 (NOD1) in adipocytes has been reported to induce lipolysis linked with insulin resistance and inflammatory response. These cues are positioned to modulate metabolic action in distal organs through paracrine/endocrine signaling. Here, we assessed the role of NOD1-mediated lipolysis and inflammatory response in adipocytes to affect lipid metabolism in hepatocytes.

MAIN METHODS

Human hepatoma cells (HepG2) were exposed to conditioned medium obtained from 3 T3-L1 adipocytes pretreated with NOD1 ligand (iE-DAP) and the effects on lipid accumulation, inflammation and insulin response were assessed. Activation of mechanisms leading to hepatic lipid accumulation was investigated by gene expression analysis.

KEY FINDINGS

The conditioned medium from NOD1-activated 3 T3-L1 adipocytes (CM-DAP) induced lipid accumulation in HepG2 cells, driven by both lipolysis and inflammatory responses. The CM-DAP-induced lipid accumulation was independent to de novo lipogenesis and resulted from the enhanced transport of fatty acids inside and consequent increase in rate of triglycerides synthesis in hepatocytes. Moreover, CM-DAP-induced lipid accumulation instigated the expression of the markers of fatty acid oxidation and VLDL assembly for the export of triglycerides from hepatocyte. Furthermore, CM-DAP-induced lipid accumulation was associated with induction of inflammatory response and impairment of insulin signaling in HepG2 cells.

SIGNIFICANCE

Beyond showing liver-specific mechanisms to adipocytes-derived factors, our findings support the involvement of adipose tissue as a mediator in NOD1-mediated biological responses to modulate hepatic metabolism.

Recent updates on targeting the molecular mediators of NAFLD

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

Metabolic dysfunction-associated fatty liver disease is associated with an increase in systolic blood pressure over time: linear mixed-effects model analyses

Metabolic dysfunction-associated fatty liver disease (MAFLD), a new feature of fatty liver (FL) disease that is defined as FL with overweight/obesity, type 2 diabetes mellitus or metabolic dysregulation, has been reported to be associated with the development of diabetes mellitus, chronic kidney disease and cardiovascular disease. However, the association between MAFLD and hypertension remains unclear. We investigated the association between MAFLD and systolic blood pressure (SBP) over a 10-year period in 28,990 Japanese subjects who received annual health examinations. After exclusion of subjects without data for SBP and abdominal ultrasonography at baseline, a total of 17,021 subjects (men/women: 10,973/6048; mean age: 49 years) were recruited. Linear mixed-effects model analyses using diagnoses of FL, nonalcoholic fatty liver disease (NAFLD) or MAFLD and age, sex, SBP, use of anti-hypertensive drugs, levels of uric acid and estimated glomerular filtration rate, family history of hypertension and habits of current smoking and alcohol drinking at baseline as well as the duration of the observation period and the interaction between each covariate and the duration of the observation period showed that the significant association of change in SBP over time with diagnosis of MAFLD (estimate: 0.223 mmHg/year, P < 0.001) was greater than that with diagnoses of FL (estimate: 0.196 mmHg/year, P < 0.001) and NAFLD (estimate: 0.203 mmHg/year, P < 0.001). Furthermore, the rate of increase in SBP over time was higher in subjects with MAFLD than in subjects without FL and subjects with FL who had no MAFLD. In conclusion, MAFLD is significantly associated with an increase in SBP over time. The presence of metabolic dysfunction-associated fatty liver disease (MAFLD) is significantly associated with an increase in systolic blood pressure over time.

Clinical implications of COVID-19 in patients with metabolic-associated fatty liver disease

People across the world are affected by the "coronavirus disease 2019 (COVID-19)", brought on by the "SARS-CoV type-2 coronavirus". Due to its high incidence in individuals with diabetes, metabolic syndrome, and metabolic-associated fatty liver disease (MAFLD), COVID-19 has gained much attention. The metabolic syndrome's hepatic manifestation, MAFLD, carries a significant risk of type-2-diabetes. The link between the above two conditions has also drawn increasing consideration since MAFLD is intricately linked to the obesity epidemic. Independent of the metabolic syndrome, MAFLD may impact the severity of the viral infections, including COVID-19 or may even be a risk factor. An important question is whether the present COVID-19 pandemic has been fueled by the obesity and MAFLD epidemics. Many liver markers are seen elevated in COVID-19. MAFLD patients with associated comorbid conditions like obesity, cardiovascular disease, renal disease, malignancy, hypertension, and old age are prone to develop severe disease. There is an urgent need for more studies to determine the link between the two conditions and whether it might account for racial differences in the mortality and morbidity rates linked to COVID-19. The role of innate and adaptive immunity alterations in MAFLD patients may influence the severity of COVID-19. This review investigates the implications of COVID-19 on liver injury and disease severity and vice-versa. We also addressed the severity of COVID-19 in patients with prior MAFLD and its potential implications and therapeutic administration in the clinical setting.

Dysregulated hepatic lipid metabolism and gut microbiota associated with early-stage NAFLD in ASPP2-deficiency mice

BACKGROUND

Growing evidence indicates that lipid metabolism disorders and gut microbiota dysbiosis were related to the progression of non-alcoholic fatty liver disease (NAFLD). Apoptosis-stimulating p53 protein 2 (ASPP2) has been reported to protect against hepatocyte injury by regulating the lipid metabolism, but the mechanisms remain largely unknown. In this study, we investigate the effect of ASPP2 deficiency on NAFLD, lipid metabolism and gut microbiota using ASPP2 globally heterozygous knockout (ASPP2+/-) mice.

METHODS

ASPP2+/- Balb/c mice were fed with methionine and choline deficient diet for 3, 10 and 40 day to induce an early and later-stage of NAFLD, respectively. Fresh fecal samples were collected and followed by 16S rRNA sequencing. HPLC-MRM relative quantification analysis was used to identify changes in hepatic lipid profiles. The expression level of innate immunity-, lipid metabolism- and intestinal permeability-related genes were determined. A spearman's rank correlation analysis was performed to identify possible correlation between hepatic medium and long-chain fatty acid and gut microbiota in ASPP2-deficiency mice.

RESULTS

Compared with the WT control, ASPP2-deficiency mice developed moderate steatosis at day 10 and severe steatosis at day 40. The levels of hepatic long chain omega-3 fatty acid, eicosapentaenoic (EPA, 20:5 n-3) and docosahexaenoic (DHA, 22:6 n-3), were decreased at day 10 and increased at day 40 in ASPP+/- mice. Fecal microbiota analysis showed significantly increased alpha and beta diversity, as well as the composition of gut microbiota at the phylum, class, order, family, genus, species levels in ASPP2+/- mice. Moreover, ASPP-deficiency mice exhibited impaired intestinal barrier function, reduced expression of genes associated with chemical barrier (REG3B, REG3G, Lysozyme and IAP), and increased expression of innate immune components (TLR4 and TLR2). Furthermore, correlation analysis between gut microbiota and fatty acids revealed that EPA was significantly negatively correlated with Bifidobacterium family.

CONCLUSION

Our findings suggested that ASPP2-deficiency promotes the progression of NAFLD, alterations in fatty acid metabolism and gut microbiota dysbiosis. The long chain fatty acid EPA was significantly negatively correlated with Bifidobacterial abundance, which is a specific feature of NAFLD in ASPP2-deficiency mice. Totally, the results provide evidence for a mechanism of ASPP2 on dysregulation of fatty acid metabolism and gut microbiota dysbiosis.

Progress in understanding of association between metabolic associated fatty liver disease and viral infectious diseases

Metabolic associated fatty liver disease (MAFLD) is a chronic liver disease with the highest incidence in the world, which affects 1/4-1/3 of the world population and has a serious effect on people's health. As is a multi-systemic disease, MAFLD is closely related to the occurrence and prognosis of many diseases. Studies have shown that MAFLD is associated with viral infectious diseases, and their interaction affects the prognosis of the disease. This paper reviews the research progress in this field in recent years.

COVID-19 metabolism: Mechanisms and therapeutic targets

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) dysregulates antiviral signaling, immune response, and cell metabolism in human body. Viral genome and proteins hijack host metabolic network to support viral biogenesis and propagation. However, the regulatory mechanism of SARS-CoV-2-induced metabolic dysfunction has not been elucidated until recently. Multiomic studies of coronavirus disease 2019 (COVID-19) revealed an intensive interaction between host metabolic regulators and viral proteins. SARS-CoV-2 deregulated cellular metabolism in blood, intestine, liver, pancreas, fat, and immune cells. Host metabolism supported almost every stage of viral lifecycle. Strikingly, viral proteins were found to interact with metabolic enzymes in different cellular compartments. Biochemical and genetic assays also identified key regulatory nodes and metabolic dependencies of viral replication. Of note, cholesterol metabolism, lipid metabolism, and glucose metabolism are broadly involved in viral lifecycle. Here, we summarized the current understanding of the hallmarks of COVID-19 metabolism. SARS-CoV-2 infection remodels host cell metabolism, which in turn modulates viral biogenesis and replication. Remodeling of host metabolism creates metabolic vulnerability of SARS-CoV-2 replication, which could be explored to uncover new therapeutic targets. The efficacy of metabolic inhibitors against COVID-19 is under investigation in several clinical trials. Ultimately, the knowledge of SARS-CoV-2-induced metabolic reprogramming would accelerate drug repurposing or screening to combat the COVID-19 pandemic.

COVID-19 Pandemic: Insights into Interactions between SARS-CoV-2 Infection and MAFLD

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become an ongoing global health pandemic. Since 2019, the pandemic continues to cast a long shadow on all aspects of our lives, bringing huge health and economic burdens to all societies. With our in-depth understanding of COVID-19, from the initial respiratory tract to the later gastrointestinal tract and cardiovascular systems, the multiorgan involvement of this infectious disease has been discovered. Metabolic dysfunction-associated fatty liver disease (MAFLD), formerly named nonalcoholic fatty liver disease (NAFLD), is a major health issue closely related to metabolic dysfunctions, affecting a quarter of the world's adult population. The association of COVID-19 with MAFLD has received increasing attention, as MAFLD is a potential risk factor for SARS-CoV-2 infection and severe COVID-19 symptoms. In this review, we provide an update on the interactions between COVID-19 and MAFLD and its underlying mechanisms.

Role of hepatic lipid species in the progression of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease due to the global pandemic of metabolic diseases. Dysregulation of hepatic lipid metabolism plays a central role in the initiation and progression of NAFLD. With the advancement of lipidomics, an increasing number of lipid species and underlying mechanisms associating hepatic lipid components have been revealed. Therefore, the focus of this mini-review is to highlight the links between hepatic lipid species and their mechanisms mediating the pathogenesis of NAFLD. We first summarized the interplay between NAFLD and hepatic lipid disturbances. Next, we focused on reviewing the role of saturated fatty acids, cholesterol, oxidized phospholipids, and their respective intermediates in the pathogenesis of NAFLD. The mechanisms by which monounsaturated fatty acids and other pro-resolving mediators exert protective effects are also addressed. Finally, we further discussed the implication of different analysis approaches in lipidomic. Evolving insights into the pathophysiology of NAFLD will provide the opportunity for drug development.

Inhibition of MAP4K4 Signaling Initiaties Metabolic Reprogramming to Protect Hepatocytes from Lipotoxic Damage

The primary hepatic consequence of obesity is non-alcoholic fatty liver disease (NAFLD), affecting about 25% of the global adult population. Non-alcoholic steatohepatitis (NASH) is a severe form of NAFLD characterized by liver lipid accumulation, inflammation, and hepatocyte ballooning, with a different degree of hepatic fibrosis. In the light of rapidly increasing prevalence of NAFLD and NASH, there is an urgent need for improved understanding of the molecular pathogenesis of these diseases. The aim of this study was to decipher the possible role of STE20-type kinase MAP4K4 in the regulation of hepatocellular lipotoxicity and susceptibility to NAFLD. We found that MAP4K4 mRNA expression in human liver biopsies was positively correlated with key hallmarks of NAFLD (i.e., liver steatosis, lobular inflammation, hepatocellular ballooning, and fibrosis). We also found that the silencing of MAP4K4 suppressed lipid deposition in human hepatocytes by stimulating β-oxidation and triacylglycerol secretion, while attenuating fatty acid influx and lipid synthesis. Furthermore, downregulation of MAP4K4 markedly reduced the glycolysis rate and lowered incidences of oxidative/endoplasmic reticulum stress. In parallel, we observed suppressed JNK and ERK and increased AKT phosphorylation in MAP4K4-deficient hepatocytes. Together, these results provide the first experimental evidence supporting the potential involvement of STE20-type kinase MAP4K4 as a component of the hepatocellular lipotoxic milieu promoting NAFLD susceptibility.

Liver Steatosis: A Marker of Metabolic Risk in Children

Obesity is one of the greatest health challenges affecting children of all ages and ethnicities. Almost 19% of children and adolescents worldwide are overweight or obese, with an upward trend in the last decades. These reports imply an increased risk of fat accumulation in hepatic cells leading to a series of histological hepatic damages gathered under the acronym NAFLD (Non-Alcoholic Fatty Liver Disease). Due to the complex dynamics underlying this condition, it has been recently renamed as 'Metabolic Dysfunction Associated Fatty Liver Disease (MAFLD)', supporting the hypothesis that hepatic steatosis is a key component of the large group of clinical and laboratory abnormalities of Metabolic Syndrome (MetS). This review aims to share the latest scientific knowledge on MAFLD in children in an attempt to offer novel insights into the complex dynamics underlying this condition, focusing on the novel molecular aspects. Although there is still no treatment with a proven efficacy for this condition, starting from the molecular basis of the disease, MAFLD's therapeutic landscape is rapidly expanding, and different medications seem to act as modifiers of liver steatosis, inflammation, and fibrosis.

Metabolomics analysis of the effects of quercetin on Cd-induced hepatotoxicityin rats

Cadmium(Cd) is known to cause damage to the liver. In this study, metabolomics technology was used to investigate the effect of quercetin(QE) on Cd-induced hepatotoxicity. A total of 60 male SD rats were randomly divided into the following 6 groups: control group (C), low and high dose QE group (Q1: 10 mg/kg·bw, Q2: 50 mg/kg·bw), Cd group (D), low and high dose QE and Cd combined intervention group (DQ1, DQ2). The rats were given Cd chloride (CdCl₂) at a concentration of 40 mg/L through free drinking water. After 12 weeks of treatment, liver samples of rats were collected for metabonomic analysis. A total of 12 metabolites were identified, the intensities of PC(18:0/14:1(9Z)) and Arachidonate acid were decreased in the Cd-treated group (p < 0.01), whereas the intensities of Chenodeoxyglycocholic acid, Cholic acid, Taurochenodesoxycholic acid, Glycocholic acid, Prostaglandin D2, 15-Deoxy-d-12,14-PGJ2, Oxidized glutathione, Cholesterol, Protoporphyrin IX, Bilirubinwere increased significantly in the Cd-treated group compared with group C(p < 0.01). When rats were given high doses of QE and Cd at the same time, the intensity of the above metabolites was significantly restored in group DQ2. Results suggest that The protective effect of QE on Cd-induced liver injury is associated with antioxidant activity of QE, as well as QE can regulates hepatic bile acid metabolism by affecting FXR and BSEP, and regulates AA metabolism by inhibiting Cd-induced activities of COX-2 and PLA2.

Adipose tissue dysfunction and MAFLD in obesity on the scene of COVID-19

Obesity is a known risk factor for respiratory infection and many other chronic diseases, including metabolic dysfunction-associated fatty liver disease (MAFLD), previously known as nonalcoholic fatty liver disease (NAFLD). Recently, it has been considered an important and independent predictor for coronavirus disease 2019 (COVID-19) complications in adults, especially cardiopulmonary, presenting in a great number of individuals in critical care. In obesity, adipose tissue (AT) undergoes expansion via several processes: expansion of adipocytes and insufficient vascularization lead to hypoxia; adipocyte apoptosis/necrosis; irregular fatty acid flux; and enhanced secretion of inflammatory adipokines, cytokines, and chemokines. In individuals with obesity the liver can also become a target of COVID-19 infection, although major liver damage is uncommon. COVID-19 acute pandemic often develops in patients with major metabolic abnormalities, including fatty liver disease, which is part of a chronic pandemic together with body fat accumulation. During metabolic abnormalities, the expansion of metabolically active fat parallels chronic inflammatory changes, the development of Insulin Resistance (IR), and in the liver, the accumulation of fat, possibly, an underlying fibrosis. SARS-Cov-2 virus might affect the liver by direct or indirect mechanisms. The current epidemic of obesity and related metabolic diseases has extensively contributed to increase the number of severe cases and deaths from COVID-19, resulting in a health, political and economic crisis with long-lasting consequences. In this review, the authors explore the relationship between AT dysfunction and MAFLD in obesity on the scene of COVID-19.

High Remnant Cholesterol Level Potentiates the Development of Hypertension

BACKGROUND

Emerging evidence suggests an association between remnant cholesterol (RC) and vascular damage and hypertension. However, this association has not been explored in a large-scale population in China, and a temporal relationship between RC and hypertension also needs to be investigated.

METHODS

We conducted a retrospective cross-sectional study in 2,199,366 individuals and a longitudinal study in 24,252 individuals with repeated measurements of lipid profile and blood pressure in at least a 3-year follow-up. The logistic model was used to explore the association between lipid components and hypertension in the cross-sectional analysis. The Cox model was used to analyze the association between high RC (HRC) at baseline and the subsequent incidence of hypertension or the association between hypertension at baseline and incidence of HRC. The cross-lagged panel model was applied to analyze the temporal relationship between RC and hypertension.

RESULTS

RC level as a continuous variable had the highest correlation with hypertension among lipid profiles, including RC, low-density lipoprotein cholesterol, total cholesterol, non-high-density lipoprotein cholesterol, and triglycerides, with an odds ratio of 1.59 (95% confidence interval: 1.58-1.59). In the longitudinal cohort, HRC at baseline was associated with incident hypertension. We further explored the temporal relationship between RC and hypertension using the cross-lagged analysis, and the results showed that RC increase preceded the development of hypertension, rather than vice versa.

CONCLUSIONS

RC had an unexpected high correlation with the prevalence and incidence of hypertension. Moreover, RC increase might precede the development of hypertension, suggesting the potential role of RC in the development of hypertension.

High-fat-induced nonalcoholic fatty liver potentiates vulnerability to and the severity of viral hepatitis in a C3H/HeN mouse model

Although the concomitance of nonalcoholic fatty liver disease (NAFLD) and viral hepatitis is soaring, there is not much knowledge about the impact of NAFLD on viral hepatitis. Here, we aimed to investigate how NAFLD influences the pathogenesis of viral hepatitis. Wild-type C3H/HeN mice with NAFLD induced by high-fat diet were infected with murine hepatitis virus 3 (MHV-3) and sacrificed at Days 4, 8, 12, and 16 post infection. Although there was no difference in the survival rate between mice with and without NAFLD, individuals with steatosis suffered more severe and prolonged liver injury demonstrated by transaminases and histology examination. The intrahepatic viral load was higher in NAFLD group during early infection, although it declined ultimately. On the contrary, the serum antiviral antibody titer remained in a lower level in mice with NAFLD throughout the investigation. In NAFLD group, the production of proinflammatory cytokines (tumor necrosis factor α, interleukin 1β, interleukin 6, and interleukin 17A) and the frequencies of antiviral immune cells (NKG2D⁺ NK cells and CD69⁺ cytotoxic T lymphocytes [CTLs]) were profoundly increased. Parallelly, the production of anti-inflammatory cytokine (interleukin 10) and inhibitory checkpoint expression (NKG2A on NK cells and programmed cell death-1 on CTLs) were also significantly elevated to maintain homeostasis. However, the upregulation of interleukin 22, a protective cytokine was deficient in NAFLD group post MHV-3 infection. Conclusively, hepatic lipid metabolic abnormalities disturb antiviral immunity and increase the vulnerability to and severity of viral hepatitis.

Overexpression of PDE4D in mouse liver is sufficient to trigger NAFLD and hypertension in a CD36-TGF-β1 pathway: therapeutic role of roflumilast

Emerging evidence has shown that nonalcoholic fatty liver disease (NAFLD) may be both a consequence and a cause of hypertension. Recent studies have demonstrated that phosphodiesterase 4 (PDE4)-cAMP signaling represents a pathway relevant to the pathophysiology of metabolic disorders. This study aims to investigate the impact and the underlying mechanism of PDE4 in the pathogenesis of NAFLD and its associated hypertension. Here we demonstrated that high-fat-diet (HFD) fed mice developed NAFLD and hypertension, with an associated increase in hepatic PDE4D expression, which can be prevented and even reversed by PDE4 inhibitor roflumilast. Furthermore, we demonstrated that hepatic overexpression of PDE4D drove significant hepatic steatosis and elevation of blood pressure. Mechanistically, PDE4D activated fatty acid translocase CD36 signaling which facilitates hepatic lipid deposition, resulting in TGF-β1 production by hepatocytes and excessive TGF-β1 signaling in vessels and consequent hypertension. Specific silencing of TGF-β1 in hepatocytes by siRNA using poly (β-amino ester) nanoparticles significantly normalized hepatic PDE4D overexpression-activated TGF-β1 signaling in vessels and hypertension. Together, the conclusions indicated that PDE4D plays an important role in the pathogenesis of NAFLD and associated hypertension via activation of CD36-TGF-β1 signaling in the liver. PDE4 inhibitor such as roflumilast, which is clinically approved for chronic obstructive pulmonary disease (COPD) treatment, has the potential to be used as a preventive or therapeutic drug against NAFLD and associated hypertension in the future.

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

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

Hepatocyte SH3RF2 Deficiency Is a Key Aggravator for NAFLD

BACKGROUND AND AIMS

NAFLD has become the most common liver disease worldwide but lacks a well-established pharmacological therapy. Here, we aimed to investigate the role of an E3 ligase SH3 domain-containing ring finger 2 (SH3RF2) in NAFLD and to further explore the underlying mechanisms.

METHODS AND RESULTS

In this study, we found that SH3RF2 was suppressed in the setting of NAFLD across mice, monkeys, and clinical individuals. Based on a genetic interruption model, we further demonstrated that hepatocyte SH3RF2 deficiency markedly deteriorates lipid accumulation in cultured hepatocytes and diet-induced NAFLD mice. Mechanistically, SH3RF2 directly binds to ATP citrate lyase, the primary enzyme promoting cytosolic acetyl-coenzyme A production, and promotes its K48-linked ubiquitination-dependent degradation. Consistently, acetyl-coenzyme A was significantly accumulated in Sh3rf2-knockout hepatocytes and livers compared with wild-type controls, leading to enhanced de novo lipogenesis, cholesterol production, and resultant lipid deposition.

CONCLUSION

SH3RF2 depletion in hepatocytes is a critical aggravator for NAFLD progression and therefore represents a promising therapeutic target for related liver diseases.

Association of non-alcoholic fatty liver disease and COVID-19: A literature review of current evidence

The coronavirus disease 2019 (COVID-19) pandemic has swept through nations, crippled economies and caused millions of deaths worldwide. Many people diagnosed with COVID-19 infections are often found to develop liver injury, which, in a small portion of patients, progresses to severe liver disease. Liver injury in the form of elevated transaminases, hyperbilirubinemia and alterations in serum albumin has been observed to be higher in patients with severe forms of the disease. Those who already have insult to the liver from chronic disease, such as nonalcoholic fatty liver disease (NAFLD) may be at the greatest disadvantage. The severity of COVID-19 also seems to be driven by the presence of NAFLD and other co-morbidities. About 25% of the global population has NAFLD. With such a widespread prevalence of NAFLD, understanding the disease progression of COVID-19 and the occurrence of liver injury in this vulnerable population assumes great significance. In this review, we present an overview of COVID-19 infection in patients with NAFLD.

The COP9 Signalosome Variant CSNCSN7A Stabilizes the Deubiquitylating Enzyme CYLD Impeding Hepatic Steatosis

Hepatic steatosis is a consequence of distorted lipid storage and plays a vital role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). This study aimed to explore the role of the COP9 signalosome (CSN) in the development of hepatic steatosis and its interplay with the deubiquitylating enzyme (DUB) cylindromatosis (CYLD). CSN occurs as CSNCSN7A and CSNCSN7B variants regulating the ubiquitin proteasome system. It is a deneddylating complex and associates with other DUBs. CYLD cleaves Lys63-ubiquitin chains, regulating a signal cascade that mitigates hepatic steatosis. CSN subunits CSN1 and CSN7B, as well as CYLD, were downregulated with specific siRNA in HepG2 cells and human primary hepatocytes. The same cells were transfected with Flag-CSN7A or Flag-CSN7B for pulldowns. Hepatic steatosis in cell culture was induced by palmitic acid (PA). Downregulation of CSN subunits led to reduced PPAR-γ expression. Flag-pulldowns in both LiSa-2 and HepG2 cells and human primary hepatocytes revealed binding of CYLD preferentially to CSNCSN7A. This was influenced by PA treatment. Silencing of CSNCSN7B blocked lipid droplet formation caused a compensatory increase of CSNCSN7A stabilizing CYLD. Our results demonstrate that CSNCSN7A-mediated CYLD stabilization impedes hepatic steatosis. Therefore, stabilizing CSNCSN7A-CYLD interaction might be a strategy to retard hepatic steatosis.

Mitochondria Matter: Systemic Aspects of Nonalcoholic Fatty Liver Disease (NAFLD) and Diagnostic Assessment of Liver Function by Stable Isotope Dynamic Breath Tests

The liver plays a key role in systemic metabolic processes, which include detoxification, synthesis, storage, and export of carbohydrates, lipids, and proteins. The raising trends of obesity and metabolic disorders worldwide is often associated with the nonalcoholic fatty liver disease (NAFLD), which has become the most frequent type of chronic liver disorder with risk of progression to cirrhosis and hepatocellular carcinoma. Liver mitochondria play a key role in degrading the pathways of carbohydrates, proteins, lipids, and xenobiotics, and to provide energy for the body cells. The morphological and functional integrity of mitochondria guarantee the proper functioning of β-oxidation of free fatty acids and of the tricarboxylic acid cycle. Evaluation of the liver in clinical medicine needs to be accurate in NAFLD patients and includes history, physical exam, imaging, and laboratory assays. Evaluation of mitochondrial function in chronic liver disease and NAFLD is now possible by novel diagnostic tools. "Dynamic" liver function tests include the breath test (BT) based on the use of substrates marked with the non-radioactive, naturally occurring stable isotope 13C. Hepatocellular metabolization of the substrate will generate 13CO2, which is excreted in breath and measured by mass spectrometry or infrared spectroscopy. Breath levels of 13CO2 are biomarkers of specific metabolic processes occurring in the hepatocyte cytosol, microsomes, and mitochondria. 13C-BTs explore distinct chronic liver diseases including simple liver steatosis, non-alcoholic steatohepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug, and alcohol effects. In NAFLD, 13C-BT use substrates such as α-ketoisocaproic acid, methionine, and octanoic acid to assess mitochondrial oxidation capacity which can be impaired at an early stage of disease. 13C-BTs represent an indirect, cost-effective, and easy method to evaluate dynamic liver function. Further applications are expected in clinical medicine. In this review, we discuss the involvement of liver mitochondria in the progression of NAFLD, together with the role of 13C-BT in assessing mitochondrial function and its potential use in the prevention and management of NAFLD.

Nonalcoholic fatty liver disease and COVID-19: An epidemic that begets pandemic

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic, affecting all the individuals across the planet. COVID-19 has gained significant attention due to its high prevalence among individuals with diabetes, nonalcoholic fatty liver disease (NAFLD), and metabolic syndrome. NAFLD is the hepatic manifestation of metabolic syndrome and can be associated with a high risk of developing type 2 diabetes. The association of COVID-19 and NAFLD has also gained more attention because NAFLD is highly associated with the epidemic of obesity. NAFLD is a potential risk factor for SARS-CoV-2 infection and severe COVID-19, independent of metabolic syndrome. Importantly, it is not yet clear whether the epidemics of obesity and NAFLD have perpetuated the current pandemic of COVID-19. Further research is urgently needed to assess the following: (1) Whether NAFLD is a high risk factor for SARS-CoV-2 infection; (2) Whether NAFLD is associated with the severe form of COVID-19; and (3) Whether the presence of NAFLD can explain the racial variation in the morbidity and mortality associated with COVID-19. This review summarizes the interactions between COVID-19 and NAFLD, mechanism of liver injury by COVID-19, and effect of lockdown due to COVID- 19 on patients with NAFLD.

Nonalcoholic Fatty Liver Disease: An Emerging Driver of Cardiac Arrhythmia

Cardiac arrhythmias and the resulting sudden cardiac death are significant cardiovascular complications that continue to impose a heavy burden on patients and society. An emerging body of evidence indicates that nonalcoholic fatty liver disease (NAFLD) is closely associated with the risk of cardiac arrhythmias, independent of other conventional cardiometabolic comorbidities. Although most studies focus on the relationship between NAFLD and atrial fibrillation, associations with ventricular arrhythmias and cardiac conduction defects have also been reported. Mechanistic investigations suggest that a number of NAFLD-related pathophysiological alterations may potentially elicit structural, electrical, and autonomic remodeling in the heart, contributing to arrhythmogenic substrates in the heart. NAFLD is now the most common liver and metabolic disease in the world. However, the upsurge in the prevalence of NAFLD as an emerging risk factor for cardiac arrhythmias has received little attention. In this review, we summarize the clinical evidence and putative pathophysiological mechanisms for the emerging roles of NAFLD in cardiac arrhythmias, with the purpose of highlighting the notion that NAFLD may serve as an independent risk factor and a potential driving force in the development and progression of cardiac arrhythmias.

Nonalcoholic Fatty Liver Disease (NAFLD). Mitochondria as Players and Targets of Therapies?

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and represents the hepatic expression of several metabolic abnormalities of high epidemiologic relevance. Fat accumulation in the hepatocytes results in cellular fragility and risk of progression toward necroinflammation, i.e., nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Several pathways contribute to fat accumulation and damage in the liver and can also involve the mitochondria, whose functional integrity is essential to maintain liver bioenergetics. In NAFLD/NASH, both structural and functional mitochondrial abnormalities occur and can involve mitochondrial electron transport chain, decreased mitochondrial β-oxidation of free fatty acids, excessive generation of reactive oxygen species, and lipid peroxidation. NASH is a major target of therapy, but there is no established single or combined treatment so far. Notably, translational and clinical studies point to mitochondria as future therapeutic targets in NAFLD since the prevention of mitochondrial damage could improve liver bioenergetics.

Inclusion of Salvia hispanica L. and Chenopodium quinoa into bread formulations improves metabolic imbalances derived from a high-fat intake in hyperglycaemic mice

High-energy intake causes imbalances in nutrient homeostasis contributing to a high prevalence of metabolic chronic diseases. The extent to what metabolic imbalances can be ameliorated by the inclusion of immunonutritional ingredients obtained from flours favouring nutrient and calorie management remains poorly understood. Herein, it is demonstrated that partial replacement of wheat flour (WB) with that from Chenopodium quinoa varieties [red (RQ, 25% w/w) and white (WQ, 25% w/w)] as well as from Salvia hispanica L., [whole (Ch, 20% w/w) and semi-defatted (Ch_D, 20% w/w)] in bread formulations ameliorates the metabolic and inflammation consequences of high-fat diet consumption in hyperglycaemic animals. Feeding animals with bread formulations replacing wheat flour effectively reduced insulin resistance (by 2-fold, HOMAir). The reduction in starch content did not appear as a determinant of controlling HOMAir. Only animals fed with RQ and Ch diet displayed increased plasma levels of triglycerides, which significantly contributed to mitigate HFD-induced hepatic lipid peroxidation. The latter was increased in animals receiving Ch_D diet, where PUFAs were eliminated from chia's flour. Feeding with WQ and Ch samples caused an upward trend in hepatic TNF-α and IL-6 levels. Despite similarities between immunonutritional agonists in animals fed with RQ and WQ, IL-17 levels were quantified higher for animals fed with WQ. All bread formulations except Ch_D samples significantly increased the hepatic granulocyte-monocyte colony stimulation factor levels. These results indicated that replacement of wheat flour with that from quinoa and chia improved the metabolic imbalances in hyperglycaemic animals.

Non-Alcoholic Fatty Liver Disease and Cardiovascular Comorbidities: Pathophysiological Links, Diagnosis, and Therapeutic Management

Non-alcoholic fatty liver disease (NAFLD) has a growing prevalence in recent years. Its association with cardiovascular disease has been intensively studied, and certain correlations have been identified. The connection between these two entities has lately aroused interest regarding therapeutic management. In order to find the best therapeutic options, a detailed understanding of the pathophysiology that links (NAFLD) to cardiovascular comorbidities is needed. This review focuses on the pathogenic mechanisms that are behind these two diseases and on the therapeutic management available at this time.

Immunity as Cornerstone of Non-Alcoholic Fatty Liver Disease: The Contribution of Oxidative Stress in the Disease Progression

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of metabolic syndrome and has become the major cause of chronic liver disease, especially in western countries. NAFLD encompasses a wide spectrum of hepatic histological alterations, from simple steatosis to steatohepatitis and cirrhosis with a potential development of hepatocellular carcinoma. Non-alcoholic steatohepatitis (NASH) is characterized by lobular inflammation and fibrosis. Several studies reported that insulin resistance, redox unbalance, inflammation, and lipid metabolism dysregulation are involved in NAFLD progression. However, the mechanisms beyond the evolution of simple steatosis to NASH are not clearly understood yet. Recent findings suggest that different oxidized products, such as lipids, cholesterol, aldehydes and other macromolecules could drive the inflammation onset. On the other hand, new evidence indicates innate and adaptive immunity activation as the driving force in establishing liver inflammation and fibrosis. In this review, we discuss how immunity, triggered by oxidative products and promoting in turn oxidative stress in a vicious cycle, fuels NAFLD progression. Furthermore, we explored the emerging importance of immune cell metabolism in determining inflammation, describing the potential application of trained immune discoveries in the NASH pathological context.

Biochanin A Regulates Cholesterol Metabolism Further Delays the Progression of Nonalcoholic Fatty Liver Disease

PURPOSE

To discover the possible target of biochanin A (BCA) in the lipid metabolism pathway and further explore its mechanism to nonalcoholic fatty liver disease (NAFLD).

METHODS

We adopted a high-fat and high-glucose diet for 12 weeks to build the NAFLD rat model, which was then treated with different proportions of BCA for 4 weeks. General condition, body weight, Lee index, and liver index were then evaluated. Furthermore, blood lipid level and insulin resistance (IR) were detected. Moreover, hematoxylin and eosin and oil red O staining were used to observe the pathological changes in the liver. Finally, Western blotting was used to detect the protein expression levels of CYP7A1, HMGCR, LDLR, PPAR-α, PPAR-γ, and SREBP-1c in the liver.

RESULTS

The vital signs of rats in each group were stable. The treatment with BCA effectively reduced Lee index and liver index (F = 104.781, P < 0.05); however, the weight was not effected in each group. Additionally, BCA effectively reduced the related lipid metabolism indexes of NAFLD, such as total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), blood glucose, insulin, IR (F =12.463 (TC), 6.909 [TG], and 15.3 effected 75 [LDL], P < 0.05), and increased HDL (F = 11.580, P < 0.05). We observed that BCA could significantly improve steatosis and inflammatory cell infiltration in liver slices. Furthermore, BCA significantly increased the CYP7A1, LDLR, and PPAR-α protein expression in the liver and downregulated the HMGCR, SREBP-1c, and PPAR-γ protein expression.

CONCLUSION

BCA could delay the liver damage of NAFLD induced by a high-fat diet, regulate the blood lipid level, and improve the expression of lipid metabolism-related genes in rats.

Protocols for Mitochondria as the Target of Pharmacological Therapy in the Context of Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent metabolic chronic liver diseases in developed countries and puts the populations at risk of progression to liver necro-inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma. Mitochondrial dysfunction is involved in the onset of NAFLD and contributes to the progression from NAFLD to nonalcoholic steatohepatitis (NASH). Thus, liver mitochondria could become the target for treatments for improving liver function in NAFLD patients. This chapter describes the most important steps used for potential therapeutic interventions in NAFLD patients, discusses current options gathered from both experimental and clinical evidence, and presents some novel options for potentially improving mitochondrial function in NAFLD.

COVID-19 and non-alcoholic fatty liver disease: Two intersecting pandemics

BACKGROUND

Initial evidence from China suggests that most vulnerable subjects to COVID-19 infection suffer from pre-existing illness, including metabolic abnormalities. The pandemic characteristics and high-lethality rate of COVID-19 infection have raised concerns about interactions between virus pathobiology and components of the metabolic syndrome.

METHODS

We harmonized the information from the recent existing literature on COVID-19 acute pandemic and mechanisms of damage in non-alcoholic fatty liver disease (NAFLD), as an example of chronic (non-communicable) metabolic pandemic.

RESULTS

COVID-19-infected patients are more fragile with underlying metabolic illness, including hypertension, cardiovascular disease, type 2 diabetes, chronic lung diseases (e.g. asthma, chronic obstructive pulmonary disease and emphysema) and metabolic syndrome. During metabolic abnormalities, expansion of metabolically active fat ('overfat condition') parallels chronic inflammatory changes, development of insulin resistance and accumulation of fat in configuring NAFLD. The deleterious interplay of inflammatory pathways chronically active in NAFLD and acutely in COVID-19-infected patients, can explain liver damage in a subgroup of patients and might condition a worse outcome in metabolically compromised NAFLD patients. In a subgroup of patients with NAFLD, the underlying liver fibrosis might represent an additional and independent risk factor for severe COVID-19 illness, irrespective of metabolic comorbidities.

CONCLUSIONS

NAFLD can play a role in the outcome of COVID-19 illness due to frequent association with comorbidities. Initial evidences suggest that increased liver fibrosis in NAFLD might affect COVID-19 outcome. In addition, long-term monitoring of post-COVID-19 NAFLD patients is advisable, to document further deterioration of liver damage. Further studies are required in this field.

Liver Steatosis, Gut-Liver Axis, Microbiome and Environmental Factors. A Never-Ending Bidirectional Cross-Talk

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide and parallels comorbidities such as obesity, metabolic syndrome, dyslipidemia, and diabetes. Recent studies describe the presence of NAFLD in non-obese individuals, with mechanisms partially independent from excessive caloric intake. Increasing evidences, in particular, point towards a close interaction between dietary and environmental factors (including food contaminants), gut, blood flow, and liver metabolism, with pathways involving intestinal permeability, the composition of gut microbiota, bacterial products, immunity, local, and systemic inflammation. These factors play a critical role in the maintenance of intestinal, liver, and metabolic homeostasis. An anomalous or imbalanced gut microbial composition may favor an increased intestinal permeability, predisposing to portal translocation of microorganisms, microbial products, and cell wall components. These components form microbial-associated molecular patterns (MAMPs) or pathogen-associated molecular patterns (PAMPs), with potentials to interact in the intestine lamina propria enriched in immune cells, and in the liver at the level of the immune cells, i.e., Kupffer cells and stellate cells. The resulting inflammatory environment ultimately leads to liver fibrosis with potentials to progression towards necrotic and fibrotic changes, cirrhosis. and hepatocellular carcinoma. By contrast, measures able to modulate the composition of gut microbiota and to preserve gut vascular barrier might prevent or reverse NAFLD.

Role of oxidative stress in the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common chronic liver disease worldwide and is strongly associated with the presence of oxidative stress. Disturbances in lipid metabolism lead to hepatic lipid accumulation, which affects different reactive oxygen species (ROS) generators, including mitochondria, endoplasmic reticulum, and NADPH oxidase. Mitochondrial function adapts to NAFLD mainly through the downregulation of the electron transport chain (ETC) and the preserved or enhanced capacity of mitochondrial fatty acid oxidation, which stimulates ROS overproduction within different ETC components upstream of cytochrome c oxidase. However, non-ETC sources of ROS, in particular, fatty acid β-oxidation, appear to produce more ROS in hepatic metabolic diseases. Endoplasmic reticulum stress and NADPH oxidase alterations are also associated with NAFLD, but the degree of their contribution to oxidative stress in NAFLD remains unclear. Increased ROS generation induces changes in insulin sensitivity and in the expression and activity of key enzymes involved in lipid metabolism. Moreover, the interaction between redox signaling and innate immune signaling forms a complex network that regulates inflammatory responses. Based on the mechanistic view described above, this review summarizes the mechanisms that may account for the excessive production of ROS, the potential mechanistic roles of ROS that drive NAFLD progression, and therapeutic interventions that are related to oxidative stress.

Herbal formulation MIT ameliorates high-fat diet-induced non-alcoholic fatty liver disease

Background

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases and is caused by obesity, diabetes, high blood pressure, and insulin resistance. Many studies have explored novel candidates to treat NAFLD using herbal medicines owing to their fewer side effects. In this study, we examined the effect of MIT, an herbal formula comprising Ephedra sinica, Panax ginseng, and Alisma orientale, on the murine model of NAFLD.

Methods

To evaluate the effect of MIT on NAFLD, we used the high-fat diet (HFD)-induced NAFLD mice model. The mice were divided into four groups: control, HFD, HFD with metformin administration, and HFD with MIT administration. Freeze-dried MIT was dissolved in phosphate buffered saline and orally administered for 8 weeks to MIT-treated mice (60 mg/kg) after feeding them with HFD for 16 weeks.

Results

MIT treatment significantly attenuated fat accumulation, serum glucose levels, and excessive cholesterol. It also reduced the activation of NF-κB, JNK, ERK, mammalian target of rapamycin, and peroxisome proliferator-activated receptor γ in the HFD-induced NAFLD mice. The expression level of enzymes involved in the synthesis and oxidation of fatty acids, acetyl-coA carboxylase and CYP2E1, were clearly reduced by MIT treatment. Reactive oxygen species (ROS) production and subsequent liver damage were effectively reduced by MIT treatment.

Conclusion

We suggest that MIT is a potent herbal formula that can be used for the prevention and treatment of obesity-related NAFLD via regulating the levels of serum glucose and free fatty acids, inflammation, lipid accumulation, and ROS-mediated liver damage.