Characteristics of hepatic fatty acid compositions in patients with nonalcoholic steatohepatitis

Liver Haemorrhagic Syndrome in Broilers: Its Effect on Serum Parameters, Antioxidant Capacity, Liver Enzymes and Fatty Acid Profile of Liver

This study sought to evaluate the occurrence of various degrees of liver haemorrhagic syndrome (LHS) in broilers subjected to commercial rearing conditions. The objective was to investigate the influence of lesion scores on various biochemical parameters. The prevalence of liver lesions graded from 0 to 5 was 12%, 31%, 33%, 15%, 6% and 3%, respectively. The crude protein content decreased, whereas the crude fat content increased in Scores 4 and 5 (p < 0.05). The observed increase in thiobarbituric acid reactive substances (TBARSs), carbonyl and sulphydryl levels in Score 5 (82.8%, 43.3% and 74.8%, respectively) suggests that this score may be more susceptible to oxidation compared to livers with no LHS incidence (p < 0.01). A reduction in total protein in Scores 4 and 5, a decline in albumin in Score 5, an elevation in uric acid and gamma-glutamyl transferase (GGT) in Scores 4 and 5 as well as a rise in cholesterol and alanine transaminase (ALT) in Score 5 were noted (p < 0.05). Furthermore, there was an increase in aspartate transferase (AST) levels in 3, 4 and 5 (p < 0.01). A comparison of the antioxidant data indicated a significant enhancement in the levels of superoxide dismutase (SOD), glutathione peroxidase (GSH PX) and total antioxidants in Scores 1-3, compared to the control group. The lowest levels of SOD, GSH PX and total antioxidants were observed in livers scored 4 and 5 (p < 0.01). Besides, an increase in total saturated fatty acids and a decrease in total monounsaturated fatty acid (MUFA), n-6, n-3 and polyunsaturated fatty acid (PUFA) levels were observed in livers scored 4 and 5 when compared to the other groups (p < 0.05). In conclusion, this study has demonstrated that elevated levels of LHS scores are associated with a detrimental impact on the physicochemical and oxidative quality of livers and blood serum.

The Effect of Chemotherapeutic Agents Used in Breast Cancer Treatment on the Hepatic Lipotoxicity

Breast cancer (BC) is the most common type of cancer in women. Researchers have studied various types of inhibitors of the MAPK/ERK signaling pathway, which plays an important role in the growth of BC cells. PD98059 is a potent and selective inhibitor of MEK, which may have potential application in the combined treatment of BC along with doxorubicin and Taxotere. The aim of this study was to provide a new insight into hepatotoxicity caused by doxorubicin, Taxotere, and PD98059 mono/combination therapy in a hepatoma in vitro model. HepG2 cells were treated with appropriate doses of used drugs. The expression of FASN and SCD1 lipogenic genes was measured by real-time PCR. The fatty acid composition PL and triglyceride fractions were analyzed using gas-liquid chromatography. The indicators of oxidative stress and antioxidant defense systems were measured by the calorimetric method. Doxorubicin and Taxotere significantly decreased FASN expression and increased SCD1 expression. Additionally, the combination of PD98059 alone, in combination with doxorubicin, or doxorubicin and Taxotere significantly increased the expression of SCD1. However, the combination of PD98059 and Taxotere significantly decreased this expression. PD98059 alone also dramatically increased the expression of FASN. In the PL fraction, doxorubicin, Taxotere, or PD98059 increased the percentage of saturated fatty acids and decreased the relative amount of unsaturated fatty acids alone. The doxorubicin + PD98059 combination also enhanced the effect of doxorubicin on PL SFAs and UFAs. Taxotere also reduced the SFAs and increased UFAs in the triglyceride fraction, which was also neutralized by PD98059 addition. Based on these findings, increased expression of SCD1 and elevated levels of SFAs in lipid fractions may indicate the possibility of hepatic lipotoxicity in BC patients, which necessitates the narrow monitoring of steatohepatitis in these patients.

Altered liver lipidome markedly overlaps with human plasma lipids at diabetes risk and reveals adipose-liver interaction

Present study explores the role of liver lipidome in driving T2D-associated metabolic changes. Elevated liver triacylglycerols, reduced PUFAs, and 86 differentially abundant lipid species were identified in diabetes-prone mice. Of these altered lipid species, 82 markedly overlap with human plasma lipids associated with T2D/CVD risk. Pathway enrichment highlighted sphingolipid metabolism, however, only five of all genes involved in the pathway were differentially expressed in the liver. Interestingly, overlap with adipose tissue transcriptome was much higher (57 genes), pointing toward an active adipose-liver interaction. Next, the integration of liver lipidome and transcriptome identified strongly correlated lipid-gene networks highlighting ceramide [Cer(22:0)], dihydroceramide(24:1), and triacylglycerol(58:6) playing a central role in transcriptional regulation. Putative molecular targets of Cer(22:0) were altered (Cyp3a44, Tgf-β1) in primary mouse hepatocytes treated with Cer(22:0). Early alteration of liver lipidome markedly depends on adipose tissue expression pattern and provides substantial evidence linking early liver lipidome alterations and risk of T2D.

Liver magnetic resonance spectroscopy as an alternative for evaluating Niemann-Pick C disease progression

Niemann-Pick disease (NP) is a group of rare genetic disorders that affect normal lipid metabolism and cause an accumulation of lipids in the liver, spleen, brain, and bone marrow. NP patients develop brain alterations and a very fast progression of liver damage. The purpose of this study is to characterize the changes in liver lipid composition during the progression of this disease using ex vivo magnetic resonance spectroscopy (MRS) in mouse models with the aim of identifying potential biomarkers to support a future non-invasive technique to follow-up these patients. NP type C (NPC) and wild-type (WT) mice were fed a chow diet and euthanized at 5 weeks of age (n = 5 per group) and 9 weeks of age (n = 5 per group). We extracted lipids from their livers and analyzed them with Gas Chromatography-Mass Spectrometry (GC-MS) and MRS. With the GC-MS analysis, 7 main fatty acids (FA) and cholesterols were quantified. Using MRS, we identified 5 metabolite peaks that correspond to FA only, 3 peaks that correspond to cholesterol only, and 2 peaks that correspond to FA and cholesterol. Our results show that the increase in liver cholesterol is the key biomarker for liver damage in NPC, which is consistent with a bad liver disease prognosis due to the association of increased cholesterol levels and liver inflammation. Additionally, we identified a difference in the pool of FA stored in the NPC compared to the WT mouse livers. Those different liver spectra could provide potential biomarkers for the non-invasive follow-up of NPC patients.

Emerging insights on the role of Elovl6 in human diseases: Therapeutic challenges and opportunities

ELOVL6, elongation-of-very-long-chain-fatty acids 6, a crucial enzyme in lipid metabolism, primarily responsible for the elongation of carbon chains of C12-C16 saturated fatty acids. It plays a significant role in various human diseases, particularly those associated with metabolic disorders related to fatty acid synthesis, such as insulin resistance, non-alcoholic fatty liver disease, cancer, and cardiovascular diseases. Emerging research also links ELOVL6 to kidney diseases, neurological conditions such as epilepsy, and pulmonary fibrosis. The enzyme's expression is regulated by various factors including diet, oxidative stress, and circadian rhythms. For instance, a high-carbohydrate diet can promote an increase in ELOVL6 expression. This abnormality leads to an accumulation of long-chain fatty acids and lipid deposition, ultimately resulting in pathological consequences across multiple systems in the body. As a biological target, ELOVL6 holds promise for diagnostic and therapeutic applications, with future research expected to uncover its mechanisms and therapeutic potential, paving the way for novel interventions in multiple disease areas. Here, the expression regulation and function of ELOVL6 in various human diseases are reviewed. This review underscores ELOVL6 as a significant therapeutic target for human diseases, with its potential for diagnostic and therapeutic applications anticipated to drive future research and enable innovative interventions in various pathological conditions.

Liver metabolism in human MASLD: A review of recent advancements using human tissue metabolomics

Global incidence of Metabolic dysfunction-Associated Steatotic Liver Disease (MASLD) is on the rise while treatments remain elusive. MASLD is a disease of dysregulated systemic and hepatic metabolism. Current understanding of disease pathophysiology as it relates to metabolome changes largely comes from studies on animal models and human plasma. However, human tissue data are crucial for transitioning from mechanisms to clinical therapies. The close relationship between MASLD and comorbidities like obesity, type 2 diabetes and dyslipidemia make it difficult to determine the contribution from liver disease itself. Here, we review recent metabolomics studies in liver tissue from human MASLD patients, which have predominately focused on lipid metabolism, but also include bile acid, tricarboxylic acid (TCA) cycle, and branched chain amino acid (BCAA) metabolism. Several clinical trials are underway to target various of these lipid-related pathways in MASLD. Although only the β-selective thyroid hormone receptor agonist resmetirom has so far been approved for use, many metabolism-targeting pharmaceuticals show promising results for halting disease progression, if not promoting outright reversal. Ultimately, the scarcity of human tissue data and the variability of confounding factors, like obesity, within and between cohorts are impediments to the pathophysiological understanding required for efficient development of metabolic treatments.

A Comprehensive Analysis of Liver Lipidomics Signature in Adults with Metabolic Dysfunction-Associated Steatohepatitis-A Pilot Study

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) is the most common chronic liver disorder in Western countries, encompassing a range of conditions from steatosis to Metabolic Dysfunction-Associated Steatohepatitis (MASH), which can potentially progress to cirrhosis. Lipidomics approaches have revealed significant alterations in the hepatic lipidome associated with both steatosis and steatohepatitis, with these changes correlating with disease manifestation. While the transition from steatosis to MASH remains poorly understood, recent research indicates that both the quantity and quality of deposited lipids play a pivotal role in MASLD progression. In our study, we utilized untargeted and targeted analyses to identify intact lipids and fatty acids in liver biopsies from healthy controls and MASLD patients, categorized based on their histological findings. In total, 447 lipid species were identified, with 215 subjected to further statistical analysis. Univariate and multivariate analyses revealed alterations in triglyceride species and fatty acids, including FA 16:0, FA 16:1, FA 18:3 n6, the sum of MUFA, and the Δ9-desaturase activity ratio. This research provides insights into the connection between dysregulated lipid metabolism in the progression of MASLD, supporting previous findings. Further studies on lipid metabolism could improve risk assessment methods, particularly given the current limited understanding of the transition from steatosis to MASH.

Dawn of an era of effective treatments for MAFLD

Fatty liver disease is a commonly occurring disease resulting in hepatic and extrahepatic complications. To date, there have been few available treatments beyond conventional lifestyle modification. While lifestyle modifications resulting in weight loss >10% have shown to be beneficial for metabolic dysfunction‐associated steatohepatitis (MASH), for the majority of patients, this is difficult to achieve. The recent approval of resmetirom (a thyroid hormone receptor beta agonist) by the Food and Drug Administration following positive results for histological outcomes in a phase 3 trial has opened the door for new treatments for metabolic (dysfunction)‐associated fatty liver disease (MAFLD) and MASH. There are currently a number of phase 3 trials targeting a variety of signaling pathways involved in the pathogenesis of metabolic steatohepatitis that are also promising. This review focuses on the currently available treatments for MAFLD and MASH, ongoing phase 3 clinical trials, and unresolved controversies in clinical trials in this area.

Sirt1 Mitigates Hepatic Lipotoxic Injury Induced by High-Fat-Diet in Fish Through Ire1α Deacetylation

BACKGROUND

Silent information regulator protein 1 (Sirt1) is crucial in regulating lipid metabolism, but its specific role and mechanism in fish hepatic lipotoxic injury remain undefined.

OBJECTIVES

This study aimed to elucidate the regulatory role of Sirt1 and the underlying mechanisms in dietary lipid-induced hepatic lipotoxic injury in a marine teleost black seabream.

METHODS

Black seabream were fed a control diet (12% lipid level), high-fat diet (HFD) [18% lipid level, oleic acid (OA)-rich], or HFD supplemented with 0.25%, 0.50%, or 1.00% resveratrol (RSV) for 8 wk. The cultured hepatocytes were stimulated by OA (200 μM), OA supplemented with RSV (20 μM), or transfection with sirt1-small interfering RNA (sisirt1). Biochemical indices, gene expression (qPCR), histology, transmission electron microscope, immunofluorescence, Western blot, flow cytometry, and immunoprecipitation assays were conducted to evaluate hepatic lipid deposition, lipid metabolism, endoplasmic reticulum stress, inflammation and apoptosis, and determine protein interactions between Sirt1 and Ire1α.

RESULTS

In vivo, RSV supplementation increased mRNA and protein expression levels of sirt1 (236.2% ± 16.1% and 53.1% ± 14.3%) and downregulated the mRNA and phosphorylated protein expression levels of ire1α/Ire1α (46.0% ± 7.6% and 38.6% ± 7.0%), jnk/Jnk (57.6% ± 7.3% and 122.1%), and nuclear factor κ B (nf-κb/Nf-κb) p65 (41.7% ± 7.1% and 24.6% ± 0.8%) compared with the HFD group. Similar patterns were found in the in vitro experiments; however, after knockdown of sirt1, although the cells were incubated with RSV, the expression levels of ire1α/ Ire1α, jnk/Jnk, and nf-κb/Nf-κb p65 showed no significant differences compared with the OA treatment. Moreover, we found that mutation of K61 to arginine to mimic Ire1α deacetylation confers protection against Ire1α-mediated OA-rich HFD-induced inflammation and apoptosis.

CONCLUSIONS

The findings revealed that Sirt1 protects against OA-rich HFD-induced hepatic lipotoxic injury via the deacetylation of Ire1α on K61, hence reducing Ire1α autophosphorylation level, and suppressing Jnk and Nf-κb p65 activation. This mechanism is elucidated for the first time in fish.

Protective effect of alpha-tocopherol on lipogenesis and oxysterol production in hypercholesterolemia-induced nonalcoholic steatohepatitis

Despite limited number of studies, oxysterols are known to contribute to the progression of nonalcoholic steatohepatitis (NASH) by affecting lipid/cholesterol metabolism and elevating proinflammatory and profibrotic processes. Accordingly, we used a high cholesterol-mediated in vivo NASH model and aimed to determine alterations in fatty acid content and oxysterol levels together with their effects on cholesterol/lipid metabolism during the progression of the disease. We further investigated the beneficial role of α-tocopherol. To this end, in our hypercholesterolemic rabbit model, we determined fatty acid profile by GC-MS while 25-, 27-, 4β-, 7α, and 24(S)-Hydroxycholesterol levels by means of LC-MS/MS. Additionally, lipid (SREBP-1c, PPARα, PPARγ) and cholesterol metabolism-related proteins (LXRα, SREBP2 and ABCA1) were determined by immunoblotting. In conclusion, the present findings provide a complete analysis of the hepatic alterations in lipid and oxysterol profiles mediated by a high-cholesterol diet. In addition, this study explains the protective effect of α-tocopherol on lipogenesis and oxysterol production in hypercholesterolemia-induced NASH. We believe that present study will guide to novel theories in the progression and therapeutic targeting of fatty liver diseases.

Meldonium-induced steatosis is associated with increased delta 6 desaturation and reduced elongation of n-6 polyunsaturated fatty acids

Background and objective

Metabolic associated fatty liver disease (MAFLD) is associated with abnormal lipid metabolism. Mitochondrial dysfunction is considered an important factor in the onset of MAFLD, whereas altered fatty acid composition has been linked to the severity of the disease. Tetradecylthioacetic acid (TTA), shown to induce mitochondrial proliferation and alter the fatty acid composition, was used to delay the accumulation of hepatic triacylglycerol. This study aimed to evaluate how impaired mitochondrial fatty acid beta-oxidation affects fatty acid composition by incorporating meldonium into a high-carbohydrate diet.

Methods

C57BL/6 mice (n = 40) were fed high-carbohydrate diets supplemented with meldonium, TTA, or a combination of meldonium and TTA for 21 days. Lipid levels were determined in liver samples, and fatty acid composition was measured in both liver and plasma samples. Additionally, desaturase and elongase activities were estimated. The hepatic activities and gene expression levels of enzymes involved in fatty acid metabolism were measured in liver samples, whereas carnitines, their precursors, and acylcarnitines were measured in plasma samples.

Results

The meldonium-induced depletion of L-carnitine and mitochondrial fatty acid oxidation was confirmed by reduced plasma levels of L-carnitine and acylcarnitines. Principal component analyses of the hepatic fatty acid composition revealed clustering dependent on meldonium and TTA. The meldonium-induced increase in hepatic triacylglycerol levels correlated negatively with estimated activities of elongases and was associated with higher estimated activities of delta-6 desaturase (D6D; C18:4n-3/C18:3n-3 and C18:3n-6/C18:2n-6), and increased circulating levels of C18:4n-3 and C18:3n-6 (gamma-linolenic acid). TTA mitigated meldonium-induced triacylglycerol levels by 80% and attenuated the estimated D6D activities, and elongation of n-6 polyunsaturated fatty acids (PUFAs). TTA also attenuated the meldonium-mediated reduction of C24:1n-9 (nervonic acid), possibly by stimulating Elovl 5 and increased elongation of erucic acid (C22:1n-9) to nervonic acid. The hepatic levels of nervonic acid and the estimated activity of n-6 PUFA elongation correlated negatively with the hepatic triacylglycerol levels, while the estimated activities of D6D correlated positively.

Conclusion

Circulating levels of gamma-linolenic acid, along with reduced estimated elongation of n-6 PUFAs and D6D desaturation activities, were associated with hepatic triacylglycerol levels.

Alterations of the Fatty Acid Profile and the Expression of Genes Related to FA Metabolism in Cirrhotic Liver Tissue

In addition to direct damage to hepatocytes, long-term ethanol consumption leads to lipid accumulation and hepatic steatosis, as well as to the dysregulation of lipid metabolism. The final step in various liver diseases is cirrhosis. The aim of this study was to compare the FA (fatty acids) profile and expression levels of genes involved in lipid metabolism in cirrhotic liver tissue and normal liver tissue. Exploring the changes in the FA profile and expression of genes related to fatty acid metabolism in cirrhotic liver tissue reveals a molecular landscape that goes beyond the surface of traditional liver function assessments. Understanding the shifts in gene expression and fatty acid composition in liver tissue opens avenues for interventions that may aid in the treatment of cirrhosis in the future.

Hepatocyte programmed cell death: the trigger for inflammation and fibrosis in metabolic dysfunction-associated steatohepatitis

By replacing and removing defective or infected cells, programmed cell death (PCD) contributes to homeostasis maintenance and body development, which is ubiquitously present in mammals and can occur at any time. Besides apoptosis, more novel modalities of PCD have been described recently, such as necroptosis, pyroptosis, ferroptosis, and autophagy-dependent cell death. PCD not only regulates multiple physiological processes, but also participates in the pathogenesis of diverse disorders, including metabolic dysfunction-associated steatotic liver disease (MASLD). MASLD is mainly classified into metabolic dysfunction-associated steatotic liver (MASL) and metabolic dysfunction-associated steatohepatitis (MASH), and the latter putatively progresses to cirrhosis and hepatocellular carcinoma. Owing to increased incidence and obscure etiology of MASH, its management still remains a tremendous challenge. Recently, hepatocyte PCD has been attracted much attention as a potent driver of the pathological progression from MASL to MASH, and some pharmacological agents have been proved to exert their salutary effects on MASH partly via the regulation of the activity of hepatocyte PCD. The current review recapitulates the pathogenesis of different modalities of PCD, clarifies the mechanisms underlying how metabolic disorders in MASLD induce hepatocyte PCD and how hepatocyte PCD contributes to inflammatory and fibrotic progression of MASH, discusses several signaling pathways in hepatocytes governing the execution of PCD, and summarizes some potential pharmacological agents for MASH treatment which exert their therapeutic effects partly via the regulation of hepatocyte PCD. These findings indicate that hepatocyte PCD putatively represents a new therapeutic point of intervention for MASH.

Lipidomic Analysis Reveals Alterations in Hepatic FA Profile Associated With MASLD Stage in Patients With Obesity

CONTEXT

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by the intracellular lipid accumulation in hepatocytes. Excess caloric intake and high-fat diets are considered to significantly contribute to MASLD development.

OBJECTIVE

To evaluate the hepatic and serum fatty acid (FA) composition in patients with different stages of MASLD, and their relationship with FA dietary intake and MASLD-related risk factors.

METHODS

This was a case-control study in patients with obesity undergoing bariatric surgery at a university hospital between January 2020 and December 2021. Participants were distributed in 3 groups: no MASLD (n = 26), steatotic liver disease (n = 33), and metabolic dysfunction-associated steatohepatitis (n = 32). Hepatic and serum FA levels were determined by gas chromatography-mass spectrometry. Nutritional status was evaluated using validated food frequency questionnaires. The hepatic expression of genes involved in FA metabolism was analyzed by reverse transcription quantitative polymerase chain reaction.

RESULTS

The hepatic, but not serum, FA profiles were significantly altered in patients with MASLD compared with those without MASLD. No differences were observed in FA intake between the groups. Levels of C16:0, C18:1, and the C18:1/C18:0 ratio were higher, while C18:0 levels and C18:0/C16:0 ratio were lower in patients with MASLD, being significantly different between the 3 groups. Hepatic FA levels and ratios correlated with histopathological diagnosis and other MASLD-related parameters. The expression of genes involved in the FA metabolism was upregulated in patients with MASLD.

CONCLUSION

Alterations in hepatic FA levels in MASLD patients were due to enhancement of de novo lipogenesis in the liver.

Predicting Non-Alcoholic Steatohepatitis: A Lipidomics-Driven Machine Learning Approach

Nonalcoholic fatty liver disease (NAFLD), nowadays the most prevalent chronic liver disease in Western countries, is characterized by a variable phenotype ranging from steatosis to nonalcoholic steatohepatitis (NASH). Intracellular lipid accumulation is considered the hallmark of NAFLD and is associated with lipotoxicity and inflammation, as well as increased oxidative stress levels. In this study, a lipidomic approach was used to investigate the plasma lipidome of 12 NASH patients, 10 Nonalcoholic Fatty Liver (NAFL) patients, and 15 healthy controls, revealing significant alterations in lipid classes, such as glycerolipids and glycerophospholipids, as well as fatty acid compositions in the context of steatosis and steatohepatitis. A machine learning XGBoost algorithm identified a panel of 15 plasma biomarkers, including HOMA-IR, BMI, platelets count, LDL-c, ferritin, AST, FA 12:0, FA 18:3 ω3, FA 20:4 ω6/FA 20:5 ω3, CAR 4:0, LPC 20:4, LPC O-16:1, LPE 18:0, DG 18:1_18:2, and CE 20:4 for predicting steatohepatitis. This research offers insights into the connection between imbalanced lipid metabolism and the formation and progression of NAFL D, while also supporting previous research findings. Future studies on lipid metabolism could lead to new therapeutic approaches and enhanced risk assessment methods, as the shift from isolated steatosis to NASH is currently poorly understood.

Emerging role of ferroptosis in metabolic dysfunction-associated steatotic liver disease: revisiting hepatic lipid peroxidation

Metabolic dysfunction-associated steatohepatitis (MASH) is characterised by cell death of parenchymal liver cells which interact with their microenvironment to drive disease activity and liver fibrosis. The identification of the major death type could pave the way towards pharmacotherapy for MASH. To date, increasing evidence suggest a type of regulated cell death, named ferroptosis, which occurs through iron-catalysed peroxidation of polyunsaturated fatty acids (PUFA) in membrane phospholipids. Lipid peroxidation enjoys renewed interest in the light of ferroptosis, as druggable target in MASH. This review recapitulates the molecular mechanisms of ferroptosis in liver physiology, evidence for ferroptosis in human MASH and critically appraises the results of ferroptosis targeting in preclinical MASH models. Rewiring of redox, iron and PUFA metabolism in MASH creates a proferroptotic environment involved in MASH-related hepatocellular carcinoma (HCC) development. Ferroptosis induction might be a promising novel approach to eradicate HCC, while its inhibition might ameliorate MASH disease progression.

Liver Metabolomics Analysis Revealing Key Metabolites Associated with Different Stages of Nonalcoholic Fatty Liver Disease in Hamsters

BACKGROUND AND AIM

Nonalcoholic fatty liver disease (NAFLD) is not only the top cause of liver diseases but also a hepatic-correlated metabolic syndrome. This study performed untargeted metabolomics analysis of NAFLD hamsters to identify the key metabolites to discriminate different stages of NAFLD.

METHODS

Hamsters were fed a high-fat diet (HFD) to establish the NAFLD model with different stages (six weeks named as the NAFLD1 group and twelve weeks as the NAFLD2 group, respectively). Those liver samples were analyzed by untargeted metabolomics (UM) analysis to investigate metabolic changes and metabolites to discriminate different stages of NAFLD.

RESULTS

The significant liver weight gain in NAFLD hamsters was observed, accompanied by significantly increased levels of serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Moreover, the levels of TG, LDL-C, ALT, and AST were significantly higher in the NAFLD2 group than in the NAFLD1 group. The UM analysis also revealed the metabolic changes; 27 differently expressed metabolites were detected between the NAFLD2 and NAFLD1 groups. More importantly, the levels of N-methylalanine, allantoin, glucose, and glutamylvaline were found to be significantly different between any two groups (control, NAFLD2 and NAFLD1). Receiver operating characteristic curve (ROC) curve results also showed that these four metabolites are able to distinguish control, NAFLD1 and NAFLD2 groups.

CONCLUSION

This study indicated that the process of NAFLD in hamsters is accompanied by different metabolite changes, and these key differently expressed metabolites may be valuable diagnostic biomarkers and responses to therapeutic interventions.

Echo time optimization for in-vivo measurement of unsaturated lipid resonances using J-difference-edited MRS

PURPOSE

Measuring lipid composition provides more information than just total lipid content. Hence, the non-invasive measurement of unsaturated lipid protons with both high efficiency and precision is of pressing need. This study was to optimize echo time (TE) for the best resolving of J-difference editing of unsaturated lipid resonances.

METHODS

The TE dependence of J-difference-edited (JDE) MRS was verified in the density-matrix simulation, soybean oil phantom, in-vivo experiments of white adipose tissue (WAT), and skeletal muscles using single-voxel MEGA-PRESS sequence at 3T. The peak SNRs and Cramér-Rao lower bounds (CRLBs) acquired at the proposed TE of 45 ms and previously published TE of 70 ms were compared (eight pairs) in WAT, extramyocelluar lipids (EMCLs), and intramyocellular lipids (IMCLs). The lipid composition in skeletal muscles was compared between healthy males (n = 7) and females (n = 7).

RESULTS

The optimal TE was suggested as 45 ms. Compared to 70 ms, the mean signal gains at TE of 45 ms were 151% in WAT, 168% in EMCL, 204% in IMCL for allylic resonance, and 52% in EMCL for diallylic resonance. CRLBs were significantly reduced at TE of 45 ms in WAT, EMCL, IMCL for allylic resonance and in EMCL for diallylic resonance. With TE of 45 ms, significant gender differences were found in the lipid composition in EMCL pools, while no difference in IMCL pools.

CONCLUSION

The JDE-MRS protocol with TE of 45 ms allows improved quantification of unsaturated lipid resonances in vivo and future lipid metabolism investigations.

Differentially Expressed Genes in Response to a Squalene-Supplemented Diet Are Accurate Discriminants of Porcine Non-Alcoholic Steatohepatitis

Squalene is the major unsaponifiable component of virgin olive oil, the fat source of the Mediterranean diet. To evaluate its effect on the hepatic transcriptome, RNA sequencing was carried out in two groups of male Large White x Landrace pigs developing nonalcoholic steatohepatitis by feeding them a high fat/cholesterol/fructose and methionine and choline-deficient steatotic diet or the same diet with 0.5% squalene. Hepatic lipids, squalene content, steatosis, activity (ballooning + inflammation), and SAF (steatosis + activity + fibrosis) scores were analyzed. Pigs receiving the latter diet showed hepatic squalene accumulation and twelve significantly differentially expressed hepatic genes (log2 fold change < 1.5 or <1.5) correlating in a gene network. These pigs also had lower hepatic triglycerides and lipid droplet areas and higher cellular ballooning. Glutamyl aminopeptidase (ENPEP) was correlated with triglyceride content, while alpha-fetoprotein (AFP), neutralized E3 ubiquitin protein ligase 3 (NEURL3), 2'-5'-oligoadenylate synthase-like protein (OASL), and protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B) were correlated with activity reflecting inflammation and ballooning, and NEURL3 with the SAF score. AFP, ENPEP, and PPP1R1B exhibited a remarkably strong discriminant power compared to those pathological parameters in both experimental groups. Moreover, the expression of PPP1R1B, TMEM45B, AFP, and ENPEP followed the same pattern in vitro using human hepatoma (HEPG2) and mouse liver 12 (AML12) cell lines incubated with squalene, indicating a direct effect of squalene on these expressions. These findings suggest that squalene accumulated in the liver is able to modulate gene expression changes that may influence the progression of non-alcoholic steatohepatitis.

Hepatic and serum branched-chain fatty acid profile in patients with nonalcoholic fatty liver disease: A case-control study

OBJECTIVE

Alterations in the hepatic lipidome are a crucial factor involved in the pathophysiology of nonalcoholic fatty liver disease (NAFLD). The aim of this study was to evaluate the serum and hepatic profile of branched-chain fatty acids (BCFAs) in patients with different stages of NAFLD.

METHODS

This was a case-control study performed in 27 patients without NAFLD, 49 patients with nonalcoholic fatty liver, and 17 patients with nonalcoholic steatohepatitis, defined by liver biopsies. Serum and hepatic levels of BCFAs were analyzed by gas chromatography-mass spectrometry. The hepatic expression of genes involved in the endogenous synthesis of BCFAs was analyzed by real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

A significant increase in hepatic BCFAs was found in subjects with NAFLD compared with those without NAFLD; no differences were observed in serum BCFAs between study groups. Trimethyl BCFAs, iso-BCFAs, and anteiso-BCFAs were increased in subjects with NAFLD (either nonalcoholic fatty liver or nonalcoholic steatohepatitis) compared with those without NAFLD. Correlation analysis showed a relationship between hepatic BCFAs and the histopathological diagnosis of NAFLD, as well as other histological and biochemical parameters related to this disease. Gene expression analysis in liver showed that the mRNA levels of BCAT1, BCAT2, and BCKDHA were upregulated in patients with NAFLD.

CONCLUSIONS

These results suggest that the increased production of liver BCFAs might be related to NAFLD development and progression.

Endotoxin Tolerance Acquisition and Altered Hepatic Fatty Acid Profile in Aged Mice

(1) Background: Aging is linked to an altered immune response and metabolism. Inflammatory conditions, such as sepsis, COVID-19, and steatohepatitis are more prevalent in the elderly and steatosis is linked both to severe COVID-19 and sepsis. We hypothesized that aging is linked to a loss of endotoxin tolerance, which normally protects the host from excessive inflammation, and that this is accompanied by elevated levels of hepatic lipids. (2) Methods: An in vivo lipopolysaccharide (LPS) tolerance model in young and old mice was used and the cytokine serum levels were measured by ELISA. Cytokine and toll-like receptor gene expression was determined by qPCR in the lungs and the liver; hepatic fatty acid composition was assessed by GC–MS. (3) Results: The old mice showed a distinct potential for endotoxin tolerance as suggested by the serum cytokine levels and gene expression in the lung tissue. Endotoxin tolerance was less pronounced in the livers of the aged mice. However, the fatty acid composition strongly differed in the liver tissues of the young and old mice with a distinct change in the ratio of C18 to C16 fatty acids. (4) Conclusions: Endotoxin tolerance is maintained in advanced age, but changes in the metabolic tissue homeostasis may lead to an altered immune response in old individuals.

Characterization of hepatic fatty acids using magnetic resonance spectroscopy for the assessment of treatment response to metformin in an eNOS-/- mouse model of metabolic nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease worldwide. Liver biopsy remains the gold standard for diagnosis and staging of disease. There is a clinical need for noninvasive diagnostic tools for risk stratification, follow-up, and monitoring treatment response that are currently lacking, as well as preclinical models that recapitulate the etiology of the human condition. We have characterized the progression of NAFLD in eNOS^-/- mice fed a high fat diet (HFD) using noninvasive Dixon-based magnetic resonance imaging and single voxel STEAM spectroscopy-based protocols to measure liver fat fraction at 3 T. After 8 weeks of diet intervention, eNOS^-/- mice exhibited significant accumulation of intra-abdominal and liver fat compared with control mice. Liver fat fraction measured by ¹ H-MRS in vivo showed a good correlation with the NAFLD activity score measured by histology. Treatment of HFD-fed NOS3^-/- mice with metformin showed significantly reduced liver fat fraction and altered hepatic lipidomic profile compared with untreated mice. Our results show the potential of in vivo liver MRI and ¹ H-MRS to noninvasively diagnose and stage the progression of NAFLD and to monitor treatment response in an eNOS^-/- murine model that represents the classic NAFLD phenotype associated with metabolic syndrome.

Albumin-fused long-acting FGF21 analogue for the treatment of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) currently affects about 25% of the world's population, and the numbers continue to rise as the number of obese patients increases. However, there are currently no approved treatments for NAFLD. This study reports on the evaluation of the therapeutic effect of a recombinant human serum albumin-fibroblast growth factor 21 analogue fusion protein (HSA-FGF21) on the pathology of NAFLD that was induced by using two high-fat diets (HFD), HFD-60 and STHD-01. The HFD-60-induced NAFLD model mice with obesity, insulin resistance, dyslipidemia and hepatic lipid accumulation were treated with HSA-FGF21 three times per week for 4 weeks starting at 12 weeks after the HFD-60 feeding. The administration of HSA-FGF21 suppressed the increased body weight, improved hyperglycemia, hyperinsulinemia, and showed a decreased accumulation of plasma lipid and hepatic lipid levels. The elevation of C16:0, C18:0 and C18:1 fatty acids in the liver that were observed in the HFD-60 group was recovered by the HSA-FGF21 administration. The increased expression levels of the hepatic fatty acid uptake receptor (CD36) and fatty acid synthase (SREBP-1c, FAS, SCD-1, Elovl6) were also suppressed. In adipose tissue, HSA-FGF21 caused an improved adipocyte hypertrophy, a decrease in the levels of inflammatory cytokines and induced the expression of adiponectin and thermogenic factors. The administration of HSA-FGF21 to the STHD-01-induced NAFLD model mice resulted in suppressed plasma ALT and AST levels, oxidative stress, inflammatory cell infiltration and fibrosis. Together, HSA-FGF21 has some potential for use as a therapeutic agent for the treatment of NAFLD.

Plasma Fatty Acid Composition Is Associated with Histological Findings of Nonalcoholic Steatohepatitis

The relationship between advanced nonalcoholic steatohepatitis (NASH) and plasma fatty acid composition remains unknown. We aimed to examine the plasma fatty acid composition in biopsy-confirmed nonalcoholic fatty liver disease (NAFLD) and evaluate the relationship between histological findings and fatty acid composition. Overall, 235 patients (134 women) with NAFLD were enrolled. Comprehensive blood chemistry tests and histological examinations of liver samples were conducted. Multivariate analyses adjusted for age, sex, body mass index, alanine aminotransferase, hemoglobin A1c, creatinine, total cholesterol, triglyceride, and NAFLD Activity Score values showed that lower levels of arachidic, behenic, α-linolenic, eicosatetraenoic, docosapentaenoic, and docosahexaenoic acids and higher levels of mead acid were associated with fibrosis stage 3–4. Furthermore, higher lauric acid, myristic acid, and palmitic acid levels and monounsaturated fatty acids such as palmitoleic acid and oleic acid were significantly associated with high NAS in analyses adjusted for the same factors and fibrosis stage. The plasma fatty acid composition was associated with the histological evidence of NASH. Increased synthesis of fatty acids is associated with NASH; insufficient intake of n-3 essential fatty acids and reduced elongation of fatty acids are associated with fibrosis in NASH. These features may help clinicians to understand and treat advanced NASH cases.

Reduction in gut-derived MUFAs via intestinal stearoyl-CoA desaturase 1 deletion drives susceptibility to NAFLD and hepatocarcinoma

Nonalcoholic fatty liver disease (NAFLD) is defined by a set of hepatic conditions ranging from steatosis to steatohepatitis (NASH), characterized by inflammation and fibrosis, eventually predisposing to hepatocellular carcinoma (HCC). Together with fatty acids (FAs) originated from adipose lipolysis and hepatic lipogenesis, intestinal-derived FAs are major contributors of steatosis. However, the role of mono-unsaturated FAs (MUFAs) in NAFLD development is still debated. We previously established the intestinal capacity to produce MUFAs, but its consequences in hepatic functions are still unknown. Here, we aimed to determine the role of the intestinal MUFA-synthetizing enzyme stearoyl-CoA desaturase 1 (SCD1) in NAFLD. We used intestinal-specific Scd1-KO (iScd1-/- ) mice and studied hepatic dysfunction in different models of steatosis, NASH, and HCC. Intestinal-specific Scd1 deletion decreased hepatic MUFA proportion. Compared with controls, iScd1-/- mice displayed increased hepatic triglyceride accumulation and derangement in cholesterol homeostasis when fed a MUFA-deprived diet. Then, on Western diet feeding, iScd1-/- mice triggered inflammation and fibrosis compared with their wild-type littermates. Finally, intestinal-Scd1 deletion predisposed mice to liver cancer. Conclusions: Collectively, these results highlight the major importance of intestinal MUFA metabolism in maintaining hepatic functions and show that gut-derived MUFAs are protective from NASH and HCC.

Associations of serum n-3 and n-6 polyunsaturated fatty acids with prevalence and incidence of nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major cause of liver diseases worldwide, and lifestyle and diet are significant factors in its development. Recent studies have suggested that dietary fat quality is associated with the development of NAFLD.

OBJECTIVES

Our purpose was to investigate the cross-sectional and longitudinal associations of serum n-3 (ω-3) and n-6 (ω-6) PUFAs with NAFLD among middle-aged and older men and women from eastern Finland. We also investigated the associations of estimated Δ5-desaturase and Δ6-desaturase activities, enzymes involved in PUFA metabolism, with NAFLD.

METHODS

After exclusions, the cross-sectional analyses included 1533 men examined in 1984-1989 and 674 men and 870 women examined in 1998-2001 in the Kuopio Ischaemic Heart Disease Risk Factor Study. The longitudinal analyses included 520 men examined in 1991-1993 and 301 men and 466 women examined in 2005-2008. Fatty liver index (FLI) was used as a surrogate for NAFLD. Hepatic steatosis was defined as FLI >60. ANCOVA and logistic regression were used for analyses.

RESULTS

In the longitudinal analyses, participants with higher serum concentrations of total n-6 PUFA and linoleic acid, the major n-6 PUFA, had markedly lower FLI and lower odds for hepatic steatosis (e.g., odds ratios for incident hepatic steatosis in the highest compared with lowest quartiles were ≤0.41), whereas serum γ-linolenic acid concentration was associated with a higher FLI and higher odds for hepatic steatosis. The associations with the other PUFAs were generally weaker and nonsignificant. In the cross-sectional analyses, also the long-chain n-3 PUFAs had inverse associations. In most analyses, high estimated Δ5-desaturase activity was associated with lower risk and high estimated Δ6-desaturase activity with higher risk for NAFLD.

CONCLUSIONS

In middle-aged and older Finnish adults, higher serum concentrations of total n-6 PUFAs and linoleic acid were associated with lower odds for future NAFLD.

Comprehensive molecular mechanisms and clinical therapy in nonalcoholic steatohepatitis: An overview and current perspectives

Our understanding of nonalcoholic steatohepatitis (NASH) pathophysiology continues to advance rapidly. Given the complexity of the pathogenesis of NASH, the field has moved from describing the single pathogenesis of NASH to deeply phenotyping with a description of the multi-mechanism and multi-target pathogenesis that includes glucose, lipid and cholesterol metabolism, fibrotic progression, inflammation, immune reaction and apoptosis. To make the picture more complex, the pathogenesis of NASH involves pathological connections between the liver and several organs such as the adipose, pancreas, kidney and gut. Numerous pharmacologic candidates have been tested in clinical trials and have generated some positive results. Importantly, PPAR as triglyceride synthesis inhibitor and FXR as bile acids synthesis inhibitor have displayed beneficial effects on candidates for lipid and cholesterol metabolism. Although the efficacy of these drugs has been affirmed, serious side effects hinder their further development. It is a particularly important task to carry out the in-depth long-term research. Additionally, drug combination increases response rate and reduces side effects of a single drug. Mastering the advantages and limitations of clinical candidate drugs and continuous improvement and innovation are necessary to formulate a new strategy for the future treatment of NASH.

Dietary fatty acids and risk of non-alcoholic steatohepatitis: A national study in the United States

Background

Non-alcoholic steatohepatitis (NASH), the early invertible stage of non-alcoholic fatty liver disease, has become a public health challenge due to the great burden and lack of effective treatment. Dietary nutrients are one of the modifiable factors to prevent and slow down disease progression. However, evidence linking dietary fatty acids intake and risk of NASH is lacking.

Objectives

This study aimed to examine the association between dietary total saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), their subtypes, the ratio of unsaturated (UFAs) to SFAs, and the risk of NASH among a nationwide population in the United States.

Methods

This cross-sectional study was conducted among 4,161 adults in the national health and nutrition examination survey in 2017-2018 cycle. Moreover, NASH was defined by transient elastography. Dietary fatty acids were assessed using a validated 24-h food recall method. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs).

Results

A total of 2,089 (50.2%) participants with NASH were identified. Compared with participants in the bottom tercile of dietary intakes of total PUFAs, those in the highest tercile had lower risk of NASH, with an adjusted OR of 0.67 (95% CI: 0.46-0.97). Similar associations were found between the subtype of PUFA 18:3 and NASH, while the fully adjusted OR in the highest tercile was 0.67 (95% CI: 0.47-0.96). Interactions of dietary PUFAs and body mass index (BMI) could be found influencing NASH risk. Stronger associations of dietary total PUFAs intakes with NASH risk were found in obese participants (OR, 95% CI: 0.41, 0.22-0.75) than in the non-obese participants (OR, 95% CI: 1.00, 0.70-1.43; p-interaction = 0.006). Similar effects on risk of NASH were also observed between BMI and dietary intakes of PUFA 18:3. However, no significant associations were observed between NASH risk and dietary total SFAs, MUFAs, their subtypes as well as the ratio of UFAs to SFAs.

Conclusion

Dietary intakes of total PUFAs, as well as its subtype of PUFA 18:3, were inversely associated with risk of NASH. The further large prospective studies need to be conducted to confirm the findings of this study.

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 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 lipidomics. Evolving insights into the pathophysiology of NAFLD will provide the opportunity for drug development.

Hydroxynonenal Causes Hepatocyte Death by Disrupting Lysosomal Integrity in Nonalcoholic Steatohepatitis

BACKGROUND & AIMS

The lipid oxidation is a key factor for damaging hepatocytes and causing cell death. However, the mechanisms underlying hepatocyte death and the role of the most popular lipid peroxidation product 4-hydroxy-2-nonenal (HNE) in nonalcoholic steatohepatitis (NASH) remains unclear.

METHODS

We demonstrated using hepatoma cell lines, a NASH mouse model, HNE-treated monkeys, and biopsy specimens from patients with NASH that HNE induced hepatocyte death by disintegrating the lysosomal limiting membrane.

RESULTS

The degree of HNE deposition in human NASH hepatocytes was more severe in cases with high lobular inflammation, ballooning, and fibrosis scores, and was associated with enlargement of the staining of lysosomes in hepatocytes. In in vitro experiments, HNE activated μ-calpain via G-protein coupled receptor (GPR) 120. The resultant rupture/permeabilization of the lysosomal limiting membrane induced the leakage of cathepsins from lysosomes and hepatocyte death. The blockade of G-protein coupled receptor 120 (GPR120) or μ-calpain expression suppressed lysosomal membrane damage and hepatocyte death by HNE. Alda-1, which activates aldehyde dehydrogenase 2 to degrade HNE, prevented HNE-induced hepatocyte death. Intravenous administration of HNE to monkeys for 6 months resulted in hepatocyte death by a mechanism similar to that of cultured cells. In addition, intraperitoneal administration of Alda-1 to choline-deficient, amino-acid defined treated mice for 8 weeks inhibited HNE deposition, decreased liver inflammation, and disrupted lysosomal membranes in hepatocytes, resulting in improvement of liver fibrosis.

CONCLUSIONS

These results provide novel insights into the mechanism of hepatocyte death in NASH and will contribute to the development of new therapeutic strategies for NASH.

Hepatic Unsaturated Fatty Acids Are Linked to Lower Degree of Fibrosis in Non-alcoholic Fatty Liver Disease

Background: The hepatic lipidome of patients with early stages of non-alcoholic fatty liver disease (NAFLD) has been fairly well-explored. However, studies on more progressive forms of NAFLD, i.e., liver fibrosis, are limited.

Materials and methods: Liver fatty acids were determined in cholesteryl esters (CE), phospholipids (PL), and triacylglycerols (TAG) by gas chromatography. Cross-sectional associations between fatty acids and biopsy-proven NAFLD fibrosis (n = 60) were assessed using multivariable logistic regression models. Stages of fibrosis were dichotomized into none-mild (F0–1) or significant fibrosis (F2–4). Models were adjusted for body-mass index (BMI), age and patatin-like phospholipase domain-containing protein 3 (PNPLA3 rs738409) (I148M) genotype. A secondary analysis examined whether associations from the primary analysis could be confirmed in the corresponding plasma lipid fractions.

Results: PL behenic acid (22:0) was directly associated [OR (95% CI): 1.86 (1.00, 3.45)] whereas PL docosahexaenoic acid (22:6n-3) [OR (95% CI): 0.45 (0.23, 0.89)], TAG oleic acid (18:1n-9) [OR (95% CI): 0.52 (0.28, 0.95)] and 18:1n-9 and vaccenic acid (18:1n-7) (18:1) [OR (95% CI): 0.52 (0.28, 0.96)] were inversely associated with liver fibrosis. In plasma, TAG 18:1n-9 [OR (95% CI): 0.55 (0.31, 0.99)], TAG 18:1 [OR (95% CI): 0.54 (0.30, 0.97)] and PL 22:0 [OR (95% CI): 0.46 (0.25, 0.86)] were inversely associated with liver fibrosis.

Conclusion: Higher TAG 18:1n-9 levels were linked to lower fibrosis in both liver and plasma, possibly reflecting an altered fatty acid metabolism. Whether PL 22:6n-3 has a protective role, together with a potentially adverse effect of hepatic 22:0, on liver fibrosis warrants large-scale studies.

Stearoyl-CoA desaturase 1: A potential target for non-alcoholic fatty liver disease?-perspective on emerging experimental evidence

Non-alcoholic fatty liver disease (NAFLD) is a progressive disease and one of the leading causes of death. An unnamed disease has become a global epidemic disease of public health concern. This spectrum of diseases manifests itself with initial accumulation of excessive triglycerides (due to de novo lipogenesis) in the hepatocytes, leading to simple steatosis. Although its aetiology is multi-factorial, lifestyle changes (diet and physical activity) are considered to be the key thriving factors. In this context, high fructose consumption is associated with an increased risk for developing NAFLD in humans, while high-fructose feeding to experimental animals results in hepatic steatosis and non-alcoholic steatohepatitis, by increasing hepatic lipogenesis. Among several lipogenic genes, the endoplasmic reticulum-bound stearoyl-CoA desaturase 1 (SCD1) is the key determinant of triglycerides biosynthesis pathway, by providing monounsaturated fatty acids, through the incorporation of a double bond at the delta-9 position of saturated fatty acids, specifically, palmitic (C16:0) and stearic (C18:0) acids, yielding palmitoleic (C16:1) and oleic (C18:1) acids, respectively. Various experimental studies involving SCD1 gene knockout and diet-induced rodent models have demonstrated that SCD1 plays a key role in the development of NAFLD, by modulating hepatic lipogenesis and thus triglyceride accumulation in the liver. Several pharmacological and dietary intervention studies have shown the benefits of inhibiting hepatic SCD1 in the pathogenesis of NAFLD. In this review, we give an overview of SCD1 in NAFLD, based on the current experimental evidence and the translational applicability of SCD1 inhibition in human NAFLD conditions, besides discussing the limitations and way-forward.

The role of hepatic lipid composition in obesity-related metabolic disease

Obesity is a primary antecedent to non-alcoholic fatty liver disease whose cardinal feature is excessive hepatic lipid accumulation. Although total hepatic lipid content closely associates with hepatic and systemic metabolic dysfunction, accumulating evidence suggests that the composition of hepatic lipids may be more discriminatory. This review summarises cross-sectional human studies using liver biopsy/lipidomics and proton magnetic resonance spectroscopy to characterise hepatic lipid composition in people with obesity and related metabolic disease. A comprehensive literature search identified 26 relevant studies published up to 31st March 2021 which were included in the review. The available evidence provides a consistent picture showing that people with hepatic steatosis possess elevated saturated and/or monounsaturated hepatic lipids and a reduced proportion of polyunsaturated hepatic lipids. This altered hepatic lipid profile associates more directly with metabolic derangements, such as insulin resistance, and may be exacerbated in non-alcoholic steatohepatitis. Further evidence from lipidomic studies suggests that these deleterious changes may be related to defects in lipid desaturation and elongation, and an augmentation of the de novo lipogenic pathway. These observations are consistent with mechanistic studies implicating saturated fatty acids and associated bioactive lipid intermediates (ceramides, lysophosphatidylcholines and diacylglycerol) in the development of hepatic lipotoxicity and wider metabolic dysfunction, whilst monounsaturated fatty acids and polyunsaturated fatty acids may exhibit a protective role. Future studies are needed to prospectively determine the relevance of hepatic lipid composition for hepatic and non-hepatic morbidity and mortality; and to further evaluate the impact of therapeutic interventions such as pharmacotherapy and lifestyle interventions.

A short report on NGM282/aldafermin for the treatment of nonalcoholic steatohepatitis (NASH)

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming the major cause of liver disease worldwide. Bile acids play a central part in the pathogenesis of NAFLD with agents that target bile acid synthesis and metabolism in development as potential therapies.

AREAS COVERED

The paper presents an overview of NAFLD and its pathogenesis, with focus on bile acid metabolism and regulation through fibroblast growth factor 19 (FGF-19), and the development of aldafermin as a non-tumorigenic FGF-19 analogue. We explore results from preclinical studies on the efficacy and safety of aldafermin.

EXPERT OPINION

Bile acid regulation is a promising therapeutic target in the management of NAFLD. FGF-19 plays key role in this mechanistic pathway, but also exhibits hepatocarcinogenic effect. Aldafermin is an FGF-19 analogue that has shown promising results in nonalcoholic steatohepatitis animal models, with preclinical data supporting its safety profile, specifically, the lack of a tumorigenic effect. The preclinical data presented in this paper support the clinical development of aldafermin, and indeed early data from several phase II clinical trials report promising results in relation to the ability of aldafermin to improve the histological features of NASH particularly in relation to a reduction in liver fat content.

Lipid Profile and Hepatic Fat Content Measured by 1H MR Spectroscopy in Patients before and after Liver Transplantation

Increased hepatic fat content (HFC) is a hallmark of non-alcoholic fatty liver (NAFL) disease, a common condition in liver transplant recipients. Proton MR spectroscopy (¹H MRS) and MR imaging-based proton density fat fraction as the only diagnosis modality enable precise non-invasive measurement of HFC and, also, fatty acid profiles in vivo. Using ¹H MRS at 3T, we examined 47 liver transplantation candidates and 101 liver graft recipients. A point-resolved spectroscopy sequence was used to calculate the steatosis grade along with the saturated, unsaturated and polyunsaturated fractions of fatty acids in the liver. The steatosis grade measured by MRS was compared with the histological steatosis grade. HFC, represented by fat fraction values, is adept at distinguishing non-alcoholic steatohepatitis (NASH), NAFL and non-steatotic liver transplant patients. Relative hepatic lipid saturation increases while unsaturation decreases in response to increased HFC. Additionally, relative hepatic lipid saturation increases while unsaturation and polyunsaturation both decrease in liver recipients with histologically proven post-transplant NASH or NAFL compared to non-steatotic patients. HFC, measured by in vivo ¹H MRS, correlated well with histological results. ¹H MRS is a simple and fast method for in vivo analysis of HFC and its composition. It provides non-invasive support for NAFL and NASH diagnoses.

Hepatic lipidomic remodeling in severe obesity manifests with steatosis and does not evolve with non-alcoholic steatohepatitis

BACKGROUNDS & AIMS

Obesity often leads to non-alcoholic fatty liver disease (NAFLD), which can progress from simple steatosis (non-alcoholic fatty liver (NAFL)) to non-alcoholic steatohepatitis (NASH). The accumulation of certain lipid subtypes is linked with worsening metabolic and liver disease, however, specific changes during progression from No-NAFL to NAFL then NASH are unresolved. Herein, we characterise the liver, adipose tissue and plasma lipidome of worsening NAFLD in obesity, and evaluate the utility of plasma lipids as biomarkers of NAFLD.

METHODS

Venous blood, liver, visceral and subcutaneous adipose tissue samples were obtained from 181 patients undergoing bariatric surgery. NAFLD severity was assessed histologically. Lipidomic analysis was performed using liquid chromatography-tandem mass spectrometry.

RESULTS

The liver lipidome showed substantial changes with increasing steatosis, with increased triacylglycerols, diacylglycerols and sphingolipids including ceramide, dihydroceramide, hexosyl-ceramide and GM3 ganglioside species. These lipid species were also increased in plasma with increasing hepatic steatosis and showed strong correlations with liver lipids. Adipose tissue lipidomes showed no correlation with NAFLD. There were no significant changes in liver lipids with NASH compared to NAFL. The addition of plasma lipid variables to routine markers yielded significant improvements in diagnostic accuracy for NASH (AUROC 0.667 vs. 0.785, p = 0.025).

CONCLUSION

Overall, these data provide a detailed description of the lipidomic changes with worsening NAFLD, showing significant changes with steatosis but no additional changes with NASH. Alterations in the liver lipidome are paralleled by similar changes in plasma. Further investigation is warranted into the potential utility of plasma lipids as non-invasive biomarkers of NAFLD in obesity.

LAY SUMMARY

Non-alcoholic fatty liver disease (NAFLD) is characterised by distinct changes in the liver lipidome with steatosis. The development of non-alcoholic steatohepatitis (NASH) does not result in further changes in the lipidome. Lipids within body fat do not appear to influence the lipid profile of the liver or blood. Changes in liver lipids are paralleled by changes in blood lipids. This has potential to be developed into a non-invasive biomarker for NAFLD.

CLINICAL TRIAL NUMBER

ACTRN12615000875505.

Mediterranean-like mix of fatty acids induces cellular protection on lipid-overloaded hepatocytes from western diet fed mice

INTRODUCTION AND OBJECTIVE

Non-alcoholic fatty liver disease remains as one of the main liver disorders worldwide. It is widely accepted that is the kind of lipid, rather than the amount deposited in the cells that determines cell damage. Cholesterol and saturated free fatty acids are deleterious lipids when accumulated but, in contrast, there are some valuable lipids that could counteract those with harmful properties. Much of this knowledge arises from studies using a single fatty acid, but the effects of a combination of fatty acids, as obtained by diet has been poorly addressed. In the present work, we were focused to figure out the cellular effect of two different mixes of fatty acids, one with high proportion of saturated fatty acids, and another one with high proportion of unsaturated fatty acids (Mediterranean-like) in a cellular model of steatosis.

MATERIAL AND METHODS

Primary mouse hepatocytes from animals fed with a western diet (high fat and carbohydrates diet), were treated with both mixes of fatty acids for 24 h.

RESULTS

Our data clearly show that only the high unsaturated fatty acid mix induced a decrease in triglycerides (47.5%) and cholesterol (59%) content in steatotic hepatocytes mediating cellular protection associated to the decrement of ROS and oxidative damage. The mixture of high saturated fatty acids exhibited no effects, preserving high levels of cholesterol and triglycerides and oxidative damage. In conclusion, our results show that Mediterranean-like mix of fatty acids exerts cellular protection in steatosis by decreasing triglycerides, cholesterol, ROS content and oxidative damage.

The Role of Fatty Acids in Non-Alcoholic Fatty Liver Disease Progression: An Update

Non-alcoholic fatty liver disease (NAFLD) is a major public health problem worldwide. NAFLD (both simple steatosis and steatohepatitis) is characterized by alterations in hepatic lipid metabolism, which may lead to the development of severe liver complications including cirrhosis and hepatocellular carcinoma. Thus, an exhaustive examination of lipid disorders in the liver of NAFLD patients is much needed. Mass spectrometry-based lipidomics platforms allow for in-depth analysis of lipid alterations in a number of human diseases, including NAFLD. This review summarizes the current research on lipid alterations associated with NAFLD and related complications, with special emphasis on the changes in long-chain and short-chain fatty acids levels in both serum and liver tissue, as well as in the hepatic expression of genes encoding the enzymes catalyzing lipid interconversions.

Lipoprotein receptor SR-B1 deficiency enhances adipose tissue inflammation and reduces susceptibility to hepatic steatosis during diet-induced obesity in mice

Scavenger receptor class B type 1 (SR-B1) is a membrane lipoprotein receptor/lipid transporter involved in the pathogenesis of atherosclerosis, but its role in obesity and fatty liver development is unclear. Here, we determined the effects of SR-B1 deficiency on plasma metabolic and inflammatory parameters as well as fat deposition in adipose tissue and liver during obesity. To induce obesity, we performed high-fat diet (HFD) exposure for 12 weeks in male SR-B1 knock-out (SR-B1-/-, n = 14) and wild-type (WT, n = 12) mice. Compared to HFD-fed WT mice, plasma from HFD-fed SR-B1-/- animals exhibited increased total cholesterol, triglycerides (TG) and tumor necrosis factor-α (TNF-α) levels. In addition, hypertrophied adipocytes and macrophage-containing crown-like structures (CLS) were observed in adipose tissue from HFD-fed SR-B1 deficient mice. Remarkably, liver from obese SR-B1-/- mice showed attenuated TG content, dysregulation in hepatic peroxisome proliferator-activated receptors (PPARs) expression, increased hepatic TG secretion, and altered hepatic fatty acid (FA) composition. In conclusion, we show that SR-B1 deficiency alters the metabolic environment of obese mice through modulation of liver and adipose tissue lipid accumulation. Our findings provide the basis for further elucidation of SR-B1's role in obesity and fatty liver, two major public health issues that increase the risk of advanced chronic diseases and overall mortality.

High Choline Intake during Pregnancy Reduces Characteristics of the Metabolic Syndrome in Male Wistar Rat Offspring Fed a High Fat But Not a Normal Fat Post-Weaning Diet

Maternal choline intakes are below recommendations, potentially impairing the child’s later-life metabolic health. This study aims to elucidate the interaction between the choline content of the gestational diet (GD) and fat content of the post-weaning diet (PWD) on metabolic phenotype of male Wistar rats. Pregnant Wistar rats were fed a standard rodent diet (AIN-93G) with either recommended choline (RC, 1 g/kg diet choline bitartrate) or high choline (HC, 2.5-fold). Male pups were weaned to either a normal (16%) fat (NF) or a high (45%) fat (HF) diet for 17 weeks. Body weight, visceral adiposity, food intake, energy expenditure, plasma hormones, triglycerides, and hepatic fatty acids were measured. HC-HF offspring had 7% lower body weight but not food intake, and lower adiposity, plasma triglycerides, and insulin resistance compared to RC-HF. They also had increased hepatic n-3 fatty acids and a reduced n-6/n-3 and C 18:1 n-9/C18:0 ratios. In contrast, HC-NF offspring had 6–8% higher cumulative food intake and body weight, as well as increased leptin and elevated hepatic C16:1 n-7/C16:0 ratio compared to RC-NF. Therefore, gestational choline supplementation associated with improved long-term regulation of several biomarkers of the metabolic syndrome in male Wistar rat offspring fed a HF, but not a NF, PWD.

Therapeutic Effects of Different Animal Bile Powders on Lipid Metabolism Disorders and Their Composition Analysis

OBJECTIVE

To compare the therapeutic effect of different animal bile powders on lipid metabolism disorders induced by high-fat diet in rats, and analyze the bioactive components of each animal bile powder.

METHODS

Sixty Sprague-Dawley rats were randomly divided into 6 groups (n=10): normal diet control group, high-fat diet model group, high-fat diet groups orally treated with bear, pig, cow and chicken bile powders, respectively. Serum biochemical markers from the abdominal aorta in each group were analyzed. Changes in the body weight and liver weight were recorded. Pathohistological changes in the livers were examined. High performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry was used to determine the composition of bioactive components in each animal bile powder.

RESULTS

Treatment with different types of animal bile powders had different inhibitory effects on high-fat diet-induced increase of body weight and/or liver weight in rats, most notably in bear and pig bile powders (P<0.05). High-fat diet induced lipid metabolism disorder in rats, which could be reversed by treatment with all kinds of bile powders. Bear bile and chicken bile showed the most potent therapeutic effect against lipid metabolism disorder. Cow and bear bile effectively alleviated high-fat diet induced liver enlargement and discoloration, hepatocyte swelling, infiltration of inflammatory cells and formation of lipid vacuoles. Bioactive component analysis revealed that there were significant differences in the relative content of taurocholic acid, taurodeoxycholic acid and ursodeoxycholic acid among different types of animal bile. Interestingly, a unique component with molecular weight of 496.2738 Da, whose function has not yet been reported, was identified only in bear bile powder.

CONCLUSIONS

Different animal bile powders had varying therapeutic effect against lipid metabolism disorders induced by high-fat diet, and bear bile powder demonstrated the most effective benefits. Bioactive compositions were different in different types of animal bile with a novel compound identified only in bear bile powder.

Hepatic lipidosis in fattening turkeys: A review

The conditions on turkey fattening farms, including management, housing, and feeding, have been constantly improved recently in favour of animal health. Many studies deal scientifically with poultry health. However, specifically concerning liver health, there are still open questions regarding the influence of dietary factors on the metabolism and function of the liver. Consideration of the factors that could influence and alter liver metabolism is therefore of critical relevance. The liver, as a major metabolic organ, is the main site of fat synthesis in turkeys. Under certain conditions, fat can excessively accumulate in the liver and adversely affect the birds’ health. The so-called hepatic lipidosis (HL) in fattening turkeys has been known for years. This disease has unacceptable economic and animal welfare impacts, with high animal losses up to 15% within only a few days. To date, little is known about the causes and the metabolic changes in fattening turkeys leading to HL despite the increasing focus on health management and animal welfare. To understand what is different in turkeys compared to other species, it is necessary to discuss the metabolism of the liver in more detail, including HL-associated gross and microscopic lesions. In the current review, aspects of liver structure and lipid metabolism with special regard to lipogenesis are explained to discuss all dietary factors attributing to the development and prevention of HL. As part of the prevention of the HL, dietetics measures can be helpful in the future.

Regulation of the cytochrome P450 epoxyeicosanoid pathway is associated with distinct histologic features in pediatric non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a significant health burden in obese children for which there is currently no specific therapy. Preclinical studies indicate that epoxyeicosanoids, a class of bioactive lipid mediators that are generated by cytochrome P450 (CYP) epoxygenases and inactivated by the soluble epoxide hydrolase (sEH), play a protective role in NAFLD. We performed a comprehensive lipidomics analysis using liver tissue and blood samples of 40 children with NAFLD. Proteomics was performed to determine CYP epoxygenase and sEH expressions. Hepatic epoxyeicosanoids significantly increased with higher grades of steatosis, while their precursor PUFAs were unaltered. Concomitantly, total CYP epoxygenase activity increased while protein level and activity of sEH decreased. In contrast, hepatic epoxyeicosanoids showed a strong decreasing trend with higher stages of fibrosis, accompanied by a decrease of CYP epoxygenase activity and protein expression. These findings suggest that the CYP epoxygenase/sEH pathway represents a potential pharmacologic target for the treatment of NAFLD.

A trans fatty acid substitute enhanced development of liver proliferative lesions induced in mice by feeding a choline-deficient, methionine-lowered, L-amino acid-defined, high-fat diet

Background

Nonalcoholic steatohepatitis (NASH) is a form of liver disease characterized by steatosis, necroinflammation, and fibrosis, resulting in cirrhosis and cancer. Efforts have focused on reducing the intake of trans fatty acids (TFAs) because of potential hazards to human health and the increased risk for NASH. However, the health benefits of reducing dietary TFAs have not been fully elucidated. Here, the effects of TFAs vs. a substitute on NASH induced in mice by feeding a choline-deficient, methionine-lowered, L-amino acid-defined, high-fat diet (CDAA-HF) were investigated.

Methods

Mice were fed CDAA-HF containing shortening with TFAs (CDAA-HF-T(+)), CDAA-HF containing shortening without TFAs (CDAA-HF-T(−)), or a control chow for 13 or 26 weeks.

Results

At week 13, NASH was induced in mice by feeding CDAA-HF-T(+) containing TFAs or CDAA-HF-T(−) containing no TFAs, but rather mostly saturated fatty acids (FAs), as evidenced by elevated serum transaminase activity and liver changes, including steatosis, inflammation, and fibrosis. CDAA-HF-T(−) induced a greater extent of hepatocellular apoptosis at week 13. At week 26, proliferative (preneoplastic and non-neoplastic) nodular lesions were more pronounced in mice fed CDAA-HF-T(−) than CDAA-HF-T(+).

Conclusions

Replacement of dietary TFAs with a substitute promoted the development of proliferation lesions in the liver of a mouse NASH model, at least under the present conditions. Attention should be paid regarding use of TFA substitutes in foods for human consumption, and a balance of FAs is likely more important than the particular types of FAs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-020-01423-3.

Effect of pemafibrate on fatty acid levels and liver enzymes in non-alcoholic fatty liver disease patients with dyslipidemia: A single-arm, pilot study

AIM

Dyslipidemia (DL) is commonly associated with non-alcoholic fatty liver disease (NAFLD). Pemafibrate, a selective peroxisome proliferator activated receptor α modulator (SPPARMα), has been shown to improve liver function among patients with DL. The aim of this single-arm prospective study is to evaluate the efficacy of pemafibrate in NAFLD patients with DL.

METHODS

Twenty NAFLD patients with DL who received pemafibrate (0.1 mg) twice a day for 12 weeks were prospectively enrolled in this study. The primary end-point was change in serum alanine aminotransferase (ALT) levels from baseline to week 12.

RESULTS

Serum ALT levels decreased from 75.1 IU/L at baseline to 43.6 IU/L at week 12 (P = 0.001). Significant improvements in triglyceride, high-density lipoprotein cholesterol, total fatty acid, saturated fatty acid (SFA), and unsaturated fatty acid were also noted. The serum level of remnant-like protein cholesterol, SFA, and polyunsaturated / saturated fatty acid ratio (PUFA / SFA ratio) at baseline were correlated with change in ALT level (r = -0.53, r = -0.57, and r = 0.46, respectively). Change in PUFA and change in PUFA / SFA ratio were negatively correlated with change in ALT level (r = -0.49 and r = -0.53). No hepatic or renal adverse events were reported.

CONCLUSIONS

Selective peroxisome proliferator activated receptor α could be a promising novel agent for treatment of NAFLD patients with DL by regulating fatty acid composition. A further long-term large-scale trial is warranted to confirm the efficacy of SPPARMα on NAFLD with DL.

IL-18 but Not IL-1 Signaling Is Pivotal for the Initiation of Liver Injury in Murine Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is rising in prevalence, and a better pathophysiologic understanding of the transition to its inflammatory phenotype (NASH) is key to the development of effective therapies. To evaluate the contribution of the NLRP3 inflammasome and its downstream effectors IL-1 and IL-18 in this process, we applied the true-to-life “American lifestyle-induced obesity syndrome” (ALiOS) diet mouse model. Development of obesity, fatty liver and liver damage was investigated in mice fed for 24 weeks according to the ALiOS protocol. Lipidomic changes in mouse livers were compared to human NAFLD samples. Receptor knockout mice for IL-1 and IL-18 were used to dissect the impact of downstream signals of inflammasome activity on the development of NAFLD. The ALiOS diet induced obesity and liver steatosis. The lipidomic changes closely mimicked changes in human NAFLD. A pro-inflammatory gene expression pattern in liver tissue and increased serum liver transaminases indicated early liver damage in the absence of histological evidence of NASH. Mechanistically, Il-18r^−/−- but not Il-1r^−/− mice were protected from early liver damage, possibly due to silencing of the pro-inflammatory gene expression pattern. Our study identified NLRP3 activation and IL-18R-dependent signaling as potential modulators of early liver damage in NAFLD, preceding development of histologic NASH.

High oleic peanuts improve parameters leading to fatty liver development and change the microbiota in mice intestine

Background

Oleic-acid consumption can possibly prevent or delay metabolic diseases. In Israel, a Virginia-type peanut cultivar with a high content of oleic acid has been developed.

Objective

This study examined the effect of consuming high oleic peanuts (D7) on the development of fatty liver compared to the standard HN strain.

Design

The two peanut cultivars were added to normal diet (ND) and high-fat (HF) mouse diet. Male C57BL/6 mice were fed for 8 and 10 weeks on a 4% D7, 4% HN, or control diet. At the end of the experiments, blood and tissues were collected. Triglyceride, lipid levels, histology, and protein expression were examined. The diets’ effects on intestinal microbiota were also evaluated.

Results

Both D7 and HFD7 led to a reduction in plasma triglycerides. Lipids, triglycerides, and free fatty acids in the liver were low in diets containing D7. Additionally, CD36 expression decreased in the D7 group. Consumption of D7 led to higher Prevotella levels, and consumption of ND that contained HN or D7 led to a lower Firmicutes/Bacteroidetes ratio.

Conclusion

These findings suggest that consumption of peanuts high in oleic acid (D7) may have the potential to delay primary fatty liver symptoms.

Fatty acid-driven modifications in T-cell profiles in non-alcoholic fatty liver disease patients

BACKGROUND

The interaction between T-cells/fatty acids involved in non-alcoholic fatty liver disease (NAFLD) and liver fibrosis progression is poorly understood. In this study, we conducted a comprehensive analysis of T-cell profiles of NAFLD patients to better understand their relationship with fatty acids and relevance to liver fibrosis.

METHODS

We analyzed the differences in T-cell profiles of peripheral blood mononuclear cells (PBMCs) between 40 NAFLD patients and 5 healthy volunteers (HVs), and their relationship with liver fibrosis stage or progression. Moreover, we analyzed the relationship between T-cell profiles and fatty acid compositions in vivo, and changes in T-cell profiles after treatment with fatty acids in vitro.

RESULTS

T-cell profiles of NAFLD patients were different from those of HVs. The CD25⁺CD45⁺CD4⁺ T-cell frequency was increased in NAFLD patients with high liver fibrosis stage and progression, and this indicated immune activation. Despite such a state of immune activation, the PD1⁺CD4⁺ T-cell frequency was decreased in the same patients group. The PD1⁺CD4⁺ T-cell frequency had a significantly negative correlation with the serum fatty acid composition ratio C16:1n7/C16:0. Moreover, the PD1⁺CD4⁺ T-cell frequency was significantly decreased by in vitro treatment with fatty acids. In addition, its rate of frequency change was significantly different between C16:0 and C16:1n7 and decreased by artificially increasing the C16:1n7/C16:0 ratio.

CONCLUSIONS

The analysis of PBMCs in NAFLD patients showed that T-cell profiles were different from those of HVs. And, it suggested that fatty acids modified T-cell profiles and were involved in liver fibrosis in NAFLD patients.

Prevention of Nonalcoholic Hepatic Steatosis by Shenling Baizhu Powder: Involvement of Adiponectin-Induced Inhibition of Hepatic SREBP-1c

Background

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease worldwide, and its incidence is increasing annually, but there is currently no specific drug for treating NAFLD. Shenling Baizhu powder (SL) is a safe herbal compound commonly used in clinical practice. Our previous research has shown that SL has the effect of preventing NAFLD, but its specific mechanism has not been determined. In this study, the potential mechanism of SL on NAFLD was explored by in vivo experiments.

Methods

Wistar rats fed a choline-deficient amino acid-defined diet (CDAA) were treated with SL for 8 weeks. Then, serum samples were collected to obtain biochemical indicators; adipose tissue and liver samples were collected for pathological detection; a moorFLPI-2 blood flow imager was used to measure liver microcirculation blood flow, and a rat cytokine array was used to screen potential target proteins. The expression of liver adiponectin/SREBP-1c pathway-related proteins was determined by Western blotting.

Results

SL effectively reduced the liver wet weight, as well as the levels of total cholesterol (TC) and triglyceride (TG) in the liver, and ameliorated liver injury in CDAA-fed rats. Pathological examinations showed that SL markedly reduced liver lipid droplets and improved liver lipid accumulation. In addition, the detection of liver blood flow showed that SL increased liver microcirculation in CDAA-fed rats. Through the cytokine array, a differentially expressed cytokine, namely, adiponectin, was screened in the liver. Western blotting assays showed that SL increased the expression of adiponectin and phosphoacetyl-CoA Carboxylase (p-ACC) in the liver and decreased the expression of steroid regulatory element-binding protein-1c (SREBP-1c) and fatty acid synthase (FAS).

Conclusion

These results suggest that SL can increase the levels of adiponectin in the liver and serum and can inhibit the expression of SREBP-1c, thereby regulating systemic lipid metabolism and reducing liver lipid accumulation.

Metabolic inflammation as an instigator of fibrosis during non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive storage of fatty acids in the form of triglycerides in hepatocytes. It is most prevalent in western countries and includes a wide range of clinical and histopathological findings, namely from simple steatosis to steatohepatitis and fibrosis, which may lead to cirrhosis and hepatocellular cancer. The key event for the transition from steatosis to fibrosis is the activation of quiescent hepatic stellate cells (qHSC) and their differentiation to myofibroblasts. Pattern recognition receptors (PRRs), expressed by a plethora of immune cells, serve as essential components of the innate immune system whose function is to stimulate phagocytosis and mediate inflammation upon binding to them of various molecules released from damaged, apoptotic and necrotic cells. The activation of PRRs on hepatocytes, Kupffer cells, the resident macrophages of the liver, and other immune cells results in the production of proinflammatory cytokines and chemokines, as well as profibrotic factors in the liver microenvironment leading to qHSC activation and subsequent fibrogenesis. Thus, elucidation of the inflammatory pathways associated with the pathogenesis and progression of NAFLD may lead to a better understanding of its pathophysiology and new therapeutic approaches.