Oxidative stress and depletion of hepatic long-chain polyunsaturated fatty acids may contribute to nonalcoholic fatty liver disease

Metabolic landscaping of extracellular vesicles from body fluids by phosphatidylserine imprinted polymer enrichment and mass spectrometry analysis

Extracellular vesicles (EVs) are emerging as new source of biomarkers discovery in liquid biopsy due to their stabilization in body fluids, protected by phospholipid bilayers. However, the metabolomics study of EVs is very little reported due to the lack of efficient and high-throughput isolation methods for clinical samples. In this study, phosphatidylserine imprinted polymers were employed for rapid and efficient EVs isolation from five human body fluids, including plasma, urine, amniotic fluid, cerebrospinal fluid, and saliva. The isolated EVs were subsequently analyzed for metabolomic studies by high-resolution mass spectrometry. Metabolic landscaping was conducted between the body fluids and their EVs, indicating EVs contain a large number of metabolites that are completely specific to the body fluid source. Finally, quantitative metabolomic analysis of EVs was carried out with plasma samples of hepatocellular carcinoma. Several differentially expressed exosomal metabolites were revealed including the upregulation of sphingosine (d18:1), taurochenodeoxycholic acid (TCDCA), pipecolic acid (PA), and 4-hydroxynonenal (4-HNE) and down-regulation of piperine, caffeine, and indole. We believe the proposed methodology will provide a deeper understanding of the molecular composition and functions of EVs as an alternative source for biomarker discovery.

Didymin alleviates metabolic dysfunction-associated fatty liver disease (MAFLD) via the stimulation of Sirt1-mediated lipophagy and mitochondrial biogenesis

BACKGROUND

Metabolic dysfunction-associated fatty liver disease (MAFLD) is one of the most prevalent metabolic syndromes worldwide. However, no approved pharmacological treatments are available for MAFLD. Chenpi, one kind of dried peel of citrus fruits, has traditionally been utilized as a medicinal herb for liver diseases. Didymin is a newly identified oral bioactive dietary flavonoid glycoside derived from Chenpi. In this study, we investigated the therapeutic potential of Didymin as an anti-MAFLD drug and elucidated its underlying mechanisms.

METHODS

High-fat diet (HFD)-induced MAFLD mice and alpha mouse liver 12 (AML12) cells were utilized to evaluate the effects and mechanisms of Didymin in the treatment of MAFLD. Liver weight, serum biochemical parameters, and liver morphology were examined to demonstrate the therapeutic efficacy of Didymin in MAFLD treatment. RNA-seq analysis was performed to identify potential pathways that could be affected by Didymin. The impact of Didymin on Sirt1 was corroborated through western blot, molecular docking analysis, microscale thermophoresis (MST), and deacetylase activity assay. Then, a Sirt1 inhibitor (EX-527) was utilized to confirm that Didymin alleviates MAFLD via Sirt1. Western blot and additional assays were used to investigate the underlying mechanisms.

RESULTS

Our results suggested that Didymin may possess therapeutic potential against MAFLD in vitro and in vivo. By promoting Sirt1 expression as well as directly binding to and activating Sirt1, Didymin triggers downstream pathways that enhance mitochondrial biogenesis and function while reducing apoptosis and enhancing lipophagy.

CONCLUSIONS

These suggest that Didymin could be a promising medication for MAFLD treatment. Furthermore, its therapeutic effects are mediated by Sirt1.

Hepatoprotective and Antioxidant Effects of Nanopiperine against Cypermethrin via Mitigation of Oxidative Stress, Inflammations and Gene Expression Using qRT-PCR

Cypermethrin (Cyp) is a pyrethroid that has been associated with the toxicity of various organs. The aim of our study was to evaluate the hepatoprotective and antioxidant activities of nano-piperine (NP) against Cyp toxicity. Cyp (50 mg/kg) was administered orally in all animals of groups III-VI for 15 days. Groups IV-VI each received three doses of NP (125, 250, and 500 µg/kg/day) for 10 days after receiving the Cyp dosage, which was given after 1 h. A rise in serum biomarkers (ALT, AST, ALP, total protein, and albumin), which are indicators of toxicity alongside anomalous oxidative stress indices (lipid peroxidation (LPO), glutathione (GSH), superoxide dismutase (SOD) and catalase), was detected. After Cyp treatment, we observed upregulated cytokines, caspase expression, and histological analysis that the showed distortion of cell shape. However, the administration of NP dramatically reversed all of the Cyp-induced alterations, inducing reductions in serum marker levels, stress level, the production of cytokines, and caspase expression. Additionally, all of the histopathological alterations were minimized to values that were comparable to normal levels. The present findings suggested that NP exhibits potent antioxidant and anti-inflammatory activities that can protect rats' livers against Cyp-induced liver damage through hepatoprotective activities.

Cellular stress in the pathogenesis of nonalcoholic steatohepatitis and liver fibrosis

The burden of chronic liver disease is rising substantially worldwide. Fibrosis, characterized by excessive deposition of extracellular matrix proteins, is the common pathway leading to cirrhosis, and limited treatment options are available. There is increasing evidence suggesting the role of cellular stress responses contributing to fibrogenesis. This Review provides an overview of studies that analyse the role of cellular stress in different cell types involved in fibrogenesis, including hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells and macrophages.

Serum Activities of Paraoxonase 1 (PON1) in Predicting Liver Damage Among Patients Diagnosed With Hepatocellular Carcinoma: A Case-Control Study

Introduction Hepatocellular carcinoma (HCC) is one of the most common cancers in the world and unless diagnosed timely has limited options for treatment. Paraoxonase (PON) is a glycosylated protein that has been implicated in antioxidant and other biochemical functions. Paraoxonase 1 (PON1) is an esterase associated with high-density lipoprotein (HDL) particles. The present study was carried out to assess the PON1 activity and compare it with the standard liver function tests (LFTs) in assessing the predictability of liver damage among patients diagnosed with HCC. Methods This case-control study was carried out in the Department of Biochemistry attached to Great Eastern Medical School and Hospital, Srikakulam, Andhra Pradesh. Serum PON1 activities and LFTs like total bilirubin, direct bilirubin, alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), total protein, and albumin were estimated in 30 patients diagnosed with HCC and 30 healthy persons. All the parameters were estimated using standard biochemical methods. The data was analyzed using GraphPad Prism version 6.0 (GraphPad Software, Inc). A probability (p) value <0.05 was considered to be statistically significant. Receiver operating characteristic curve (ROC) analysis was performed to assess the area under the curve (AUC) for accuracy, sensitivity, specificity, and diagnostic efficiency. Results The serum activities of PON1 had identical sensitivity (70%) to albumin (70%) and were superior to other tested parameters. Additionally, PON1 activities showed lower specificity (86.67%) than the other tested parameters. ROC analysis showed increased diagnostic efficacy (DE) of PON1 (DE=78.3%; p<0.0001) when compared with total bilirubin (DE=76.6%; p=0.0039), direct bilirubin (DE=74.9%; p=0.04), ALT (DE=73.30%; p=0.0006), and total protein (DE=71.6%; p=0.0005). However, the DE of PON1 was comparable with AST (DE=81.60%; p<0.0001), ALP (DE=79.9%; p<0.0001), and albumin (DE=83.30%, p<0.0001). Conclusions Serum activities of PON1 could be used as a diagnostic marker for assessing liver damage among HCC patients.

Role of Oxidative Stress and Carcinoembryonic Antigen-Related Cell Adhesion Molecule 1 in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) has become a widely studied subject due to its increasing prevalence and links to diseases such as type 2 diabetes and obesity. It has severe complications, including nonalcoholic steatohepatitis, cirrhosis, hepatocellular carcinoma, and portal hypertension that can lead to liver transplantation in some cases. To better prevent and treat this pathology, it is important to understand its underlying physiology. Here, we identify two main factors that play a crucial role in the pathophysiology of NAFLD: oxidative stress and the key role of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). We discuss the pathophysiology linking these factors to NAFLD pathophysiology.

miR-27b targets MAIP1 to mediate lipid accumulation in cultured human and mouse hepatic cells

Non-alcoholic liver disease (NAFLD) is a condition caused by excessive fat accumulation in the liver and developed via multiple pathways. miR-27b has been suggested to play crucial roles in the development of NAFLD, assuming via targeting genes involved in lipid catabolism and anabolism. However, other pathways regulated by miR-27b are largely unknown. Here we show that lipid accumulation was induced in miR-27b-transfected human and mouse hepatic cells and that knockdowns of three miR-27b-target genes, β-1,4-galactosyltransferase 3 (B4GALT3), matrix AAA peptidase interacting protein 1 (MAIP1) and PH domain and leucine rich repeat protein phosphatase 2 (PHLPP2), induced lipid accumulation. We also show that B4GALT3 and MAIP1 were direct targets of miR-27b and overexpression of MAIP1 ameliorated miR-27b-induced lipid accumulation. In addition, we show that hepatic Maip1 expression declined in mice fed a high-fat diet, suggesting the involvement of decreased Maip1 expression in the condition of fatty liver. Overall, we identified MAIP1/miR-27b axis as a mediator of hepatic lipid accumulation, a potential therapeutic target for NAFLD.

Chronic hypoxia and hyperoxia alter tissue-specific fatty acid profile and FD6D and elongase gene expression levels in rainbow trout (Oncorhynchus mykiss)

Commercially important trout species, especially rainbow trout, are under great threat due to several negative factors affecting oxygen levels in water such as global warming and eutrophication. In our study, rainbow trout (Oncorhynchus mykiss) was exposed to chronic (for 28 days) hypoxia (4.0 ± 0.5 mg/L) and hyperoxia (12 ± 1.2 mg/L) in order to evaluate the alteration of fatty acid profiles in muscle, liver and gill tissues. In addition, delta-6-desaturase and elongase gene expression profiles were measured in liver, kidney and gill tissues. The amount of saturated fatty acids increased by oxygen applications in the liver, while it decreased in the muscle and gill tissues compared to normoxia (p < 0.05). Monounsaturated fatty acids levels increased in muscle and gill (p < 0.05). Although n-3 polyunsaturated fatty acid (PUFA) decreased in muscle tissue, n-6 PUFA increased (p < 0.05). The n-3/n-6 ratio decreased in muscle tissue in response to the both exposures (p < 0.05) as well as eicosapentaenoic acid/docosahexaenoic acid ratio (p < 0.05). Hypoxia exposure generally increased delta-6-desaturase and elongase mRNA levels in all tissues (p < 0.05). However, gene expression profiles were variable in fish exposed to hyperoxia. As a result of oxygen exposures, the lipid profile of muscle tissue, which stores dense fat, was negatively affected more than that of liver and gill tissues. We determined that the change in expression levels was tissue specific.

Type 2 Diabetes Mellitus, Non-Alcoholic Fatty Liver Disease, and Metabolic Repercussions: The Vicious Cycle and Its Interplay with Inflammation

The prevalence of metabolic-related disorders, such as non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (DM2), has been increasing. Therefore, developing improved methods for the prevention, treatment, and detection of these two conditions is also necessary. In this study, our primary focus was on examining the role of chronic inflammation as a potential link in the pathogenesis of these diseases and their interconnections. A comprehensive search of the PubMed database using keywords such as "non-alcoholic fatty liver disease", "type 2 diabetes mellitus", "chronic inflammation", "pathogenesis", and "progression" yielded 177 relevant papers for our analysis. The findings of our study revealed intricate relationships between the pathogenesis of NAFLD and DM2, emphasizing the crucial role of inflammatory processes. These connections involve various molecular functions, including altered signaling pathways, patterns of gene methylation, the expression of related peptides, and up- and downregulation of several genes. Our study is a foundational platform for future research into the intricate relationship between NAFLD and DM2, allowing for a better understanding of the underlying mechanisms and the potential for introducing new treatment standards.

Cardioprotective Effects of Nano-Piperine Against Cypermethrin Toxicity Through Oxidative Stress, Histopathological and Immunohistochemical Studies in Male Wistar Rats

Background: Cypermethrin (Cyp) is a synthetic derivative of pyrethroids, implicated in various organ toxicity. This study investigated the potential cardio-protective activity of nano-piperine (NP) against Cyp toxicity in adult Wister male rats. Methods: All animals in groups II, III, IV, and V were subjected to Cyp (50 mg/kg) for 15 days. After 1 h of receiving the Cyp dose, 3 doses of NP (125, 250, and 500 µg/kg/day) were administered to groups III, IV, and V, respectively, for 10 days. In Group VI, a dose of 500 µg/kg NP alone was given orally daily for 10 days. Result: The toxic effects were evaluated by an increase in serum cardiac injury biomarkers (lactate dehydrogenase, cardiac troponin I, creatine kinase-myoglobin binding, tissue lipid peroxidation, a decrease in antioxidative activity, such as glutathione, superoxide dismutase [SOD] and catalase, and upregulation of interleukins [interleukin 1β, interleukin 6]). Immunohistochemistry studies of proteins (nuclear factor-κB [NF-kB], apoptotic protease activating factor-1 [Apaf-1], 4-hydroxynonenal [4-HNE] and Bax) showed enhanced expression, and histopathological examination revealed myolysis, loss of striation and hemorrhages indicating heart toxicity in the animals. Administration of NP significantly ameliorated all the changes caused by Cyp, such as a decrease in the levels of serum cardiac injury markers, an increase of antioxidative parameters, decrease in expression of inflammatory cytokines and NF-kB, Apaf-1, 4-HNE, and Bax, as shown by immunohistochemistry studies. Furthermore, all the histopathological changes were reduced to near the values of the control. Conclusion: Collectively our findings indicated that NP could be a potent nutraceutical exhibiting cardioprotective effects against Cyp-induced cardiotoxicity in rats.

Hsp70.1 carbonylation induces lysosomal cell death for lifestyle-related diseases

Alzheimer's disease, type 2 diabetes, and non-alcoholic steatohepatitis (NASH) constitute increasingly prevalent disorders. Individuals with type 2 diabetes are well-known to be susceptible to Alzheimer's disease. Although the pathogenesis of each disorder is multifactorial and the causal relation remains poorly understood, reactive oxygen species (ROS)-induced lipid and protein oxidation conceivably plays a common role. Lipid peroxidation product was recently reported to be a key factor also for non-alcoholic steatohepatitis, because of inducing hepatocyte degeneration/death. Here, we focus on implication of the representative lipid-peroxidation product 'hydroxynonenal' for the cell degeneration/death of brain, pancreas, and liver. Since Hsp70.1 has dual roles as a chaperone and lysosomal membrane stabilizer, hydroxynonenal-mediated oxidative injury (carbonylation) of Hsp70.1 was highlighted. After intake of high-fat diets, oxidation of free fatty acids in mitochondria generates ROS which enhance oxidation of ω-6 polyunsaturated fatty acids (PUFA) involved within biomembranes and generate hydroxynonenal. In addition, hydroxynonenal is generated during cooking deep-fried foods with vegetable oils especially containing linoleic acids. These intrinsic and exogenous hydroxynonenal synergically causes an increase in its serum and organ levels to induce Hsp70.1 oxidation. As it is amphiphilic; being water-soluble but displays strong lipophilic characteristics, hydroxynonenal can diffuse within the cells and react with targets like senile and/or atheromatous plaques outside the cells. Hydroxynonenal can deepen and expand lysosomal injuries by facilitating 'calpain-mediated cleavage of the carbonylated Hsp70.1'. Despite the unique anatomical, physiological, and biochemical characteristics of each organ for its specific disease, there should be a common cascade of the cell degeneration/death which is caused by hydroxynonenal. This review aims to implicate hydroxynonenal-mediated Hsp70.1 carbonylation for lysosomal membrane permeabilization/rupture and the resultant cathepsin leakage for inducing cell degeneration/death. Given the tremendous number of worldwide people suffering various lifestyle-related diseases, it is valuable to consider how ω-6 PUFA-rich vegetable oils is implicated for the organ disorder.

Hepatoprotective Effect of Curcumin Nano-Lipid Carrier against Cypermethrin Toxicity by Countering the Oxidative, Inflammatory, and Apoptotic Changes in Wistar Rats

This study investigated the potential hepatoprotective activity of curcumin-incorporated nano-lipid carrier (Cur-NLC) against cypermethrin (Cyp) toxicity in adult Wistar male rats. All animals in groups III, IV, V, and VI were subjected to Cyp (50 mg/kg) toxicity for 15 days. Three different doses of Cur-NLC (1, 2.5, and 5 mg/kg/day) were administered orally for 10 days. The toxic effects were evaluated considering the increases in serum hepatic biomarkers alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total protein and albumin, and lipid peroxidation (LPO), as well as a decrease in antioxidative activity (reduced glutathione (GSH), superoxide dismutase (SOD), and catalase) and the upregulation of inflammatory cytokines (IL-1β, IL-6, and TNF-α). Immunohistochemistry studies of proteins (NF-κB, Apaf-1, 4-HNE, and Bax) showed enhanced expression, and histopathological examination revealed architectural changes in liver cells, indicating liver toxicity in animals. Toxicity was determined by quantitative and qualitative determinations of DNA fragmentation, which show massive apoptosis with Cyp treatment. The administration of Cur-NLC significantly ameliorates all changes caused by Cyp, such as a decrease in the levels of serum liver markers, an increase in antioxidative parameters, a decrease in expression of inflammatory cytokines (IL-1β, IL-6, TNF-α, and NF-κB), and apoptosis (caspases-3, 9, Apaf-1, 4-HNE, and Bax), according to calorimetric and immunohistochemistry studies. The smear-like pattern of DNA is ameliorated similarly to the control at a high dose of Cur-NLC. Furthermore, all histopathological changes were reduced to a level close to the control. In conclusion, Cur-NLC could be a potent nutraceutical that exhibits a hepatoprotective effect against Cyp-induced hepatotoxicity in rats.

Clinical value of thyroid related hormones combined with neutrophil to lymphocyte ratio in patients with nonalcoholic fatty liver disease

BACKGROUND

In sufferers with nonalcoholic fatty liver disease (NAFLD), the differences of thyroid associated hormones and neutrophil to lymphocyte ratio (NLR) in different liver pathological groups have been compared.

METHODS

Patients with NAFLD diagnosed by liver biopsy in our hospital from July 2012 to February 2019 were selected. All subjects were divided into nonalcoholic steatohepatitis (NASH) team and non-NASH group, no/mild fibrosis group (F0-1) and significant fibrosis group (F2-4). The differences of thyroid related hormones and NLR in these groups were in contrast, respectively. For the TSH, we conducted further evaluation based on gender.

RESULTS

The TSH and NLR in NASH patients were significantly higher than non-NASH patients, but there was no considerable difference in free triiodothyronine (FT3) and free thyroxine (FT4) between the 2 groups. In the gender-based subgroup analysis, the variations of TSH between the 2 groups were nonetheless statistically significant (P < .05). The TSH and NLR in the significant fibrosis group were higher than these in the non/mild liver fibrosis group, and the differences were statistically significant (P < .05), but there was no large difference in FT3 and FT4 between the 2 groups (P > .05). In addition, in the gender-based subgroup analysis and further multivariable analysis, the variations of TSH between the 2 groups were still statistically significant (P < .05).

CONCLUSIONS

In this study, we found that serum thyroid stimulating hormone (TSH) and neutrophil to lymphocyte ratio (NLR) were closely associated to the severity of NAFLD, suggesting that this simple available laboratory index may additionally be incorporated into the future noninvasive diagnostic scoring model to predict the incidence of NASH and the degree of fibrosis.

Antioxidant Intervention against Male Infertility: Time to Design Novel Strategies

Infertility is a highly prevalent condition, affecting 9-20% of couples worldwide. Among the identifiable causes, the male factor stands out in about half of infertile couples, representing a growing problem. Accordingly, there has been a decline in both global fertility rates and sperm counts in recent years. Remarkably, nearly 80% of cases of male infertility (MI) have no clinically identifiable aetiology. Among the mechanisms likely plausible to account for idiopathic cases, oxidative stress (OS) has currently been increasingly recognized as a key factor in MI, through phenomena such as mitochondrial dysfunction, lipid peroxidation, DNA damage and fragmentation and finally, sperm apoptosis. In addition, elevated reactive oxygen species (ROS) levels in semen are associated with worse reproductive outcomes. However, despite an increasing understanding on the role of OS in the pathophysiology of MI, therapeutic interventions based on antioxidants have not yet provided a consistent benefit for MI, and there is currently no clear consensus on the optimal antioxidant constituents or regimen. Therefore, there is currently no applicable antioxidant treatment against this problem. This review presents an approach aimed at designing an antioxidant strategy based on the particular biological properties of sperm and their relationships with OS.

Nonalcoholic Fatty Liver Disease and the Gut-Liver Axis: Exploring an Undernutrition Perspective

Nonalcoholic fatty liver disease (NAFLD) is a chronic condition affecting one quarter of the global population. Although primarily linked to obesity and metabolic syndrome, undernutrition and the altered (dysbiotic) gut microbiome influence NAFLD progression. Both undernutrition and NAFLD prevalence are predicted to considerably increase, but how the undernourished gut microbiome contributes to hepatic pathophysiology remains far less studied. Here, we present undernutrition conditions with fatty liver features, including kwashiorkor and micronutrient deficiency. We then review the gut microbiota-liver axis, highlighting key pathways linked to NAFLD progression within both overnutrition and undernutrition. To conclude, we identify challenges and collaborative possibilities of emerging multiomic research addressing the pathology and treatment of undernourished NAFLD.

Influence of the nutritional status and oxidative stress in the desaturation and elongation of n-3 and n-6 polyunsaturated fatty acids: Impact on non-alcoholic fatty liver disease

Polyunsaturated fatty acids (PUFA) play essential roles in cell membrane structure and physiological processes including signal transduction, cellular metabolism and tissue homeostasis to combat diseases. PUFA are either consumed from food or synthesized by enzymatic desaturation, elongation and peroxisomal β-oxidation. The nutritionally essential precursors α-linolenic acid (C18:3n-3; ALA) and linoleic acid (C18:2n-6; LA) are subjected to desaturation by Δ6D/Δ5D desaturases and elongation by elongases 2/5, enzymes that are induced by insulin and repressed by PUFA. Maintaining an optimally low n-6/n-3 PUFA ratio is linked to prevention of the development of several diseases, including nonalcoholic fatty liver disease (NAFLD) that is characterized by depletion of PUFA promoting hepatic steatosis and inflammation. In this context, supplementation with n-3 PUFA revealed significant lowering of hepatic steatosis in obese patients, whereas prevention of fatty liver by high-fat diet in mice is observed in n-3 PUFA and hydroxytyrosol co-administration. The aim of this work is to review the role of nutritional status and nutrient availability on markers of PUFA biosynthesis. In addition, the impact of oxidative stress developed as a result of NAFLD, a redox imbalance that may alter the expression and activity of the enzymes involved, and diminished n-3 PUFA levels by free-radical dependent peroxidation processes will be discussed.

Olive Oil: Nutritional Applications, Beneficial Health Aspects and its Prospective Application in Poultry Production

Plant polyphenols have promoting health features, including anti-mutagenic, anti-inflammatory, anti-thrombotic, anti-atherogenic, and anti-allergic effects. These polyphenols improve the immune system by affecting the white blood cell proliferation, as well as by the synthesis of cytokines and other factors, which contribute to immunological resistance. Olive trees are one of the most famous trees in the world. Whereas, olive olive oil and derivatives represent a large group of feeding resource for farm animals. In recent years, remarkable studies have been carried out to show the possible use of olive oil and derivatives for improvement of both animal performance and product quality. In vivo application of olive oil and its derived products has shown to maintain oxidative balance owing to its polyphenolic content. Consumption of extra virgin olive oil reduces the inflammation, limits the risk of liver damage, and prevents the progression of steatohepatitis through its potent antioxidant activities. Also, the monounsaturated fatty acids content of olive oil (particularly oleic acid), might have positive impacts on lipid peroxidation and hepatic protection. Therefore, this review article aims to highlight the nutritional applications and beneficial health aspects of olive oil and its effect on poultry production.

Brain-gut-liver interactions across the spectrum of insulin resistance in metabolic fatty liver disease

Metabolic associated fatty liver disease (MAFLD), formerly named "nonalcoholic fatty liver disease" occurs in about one-third of the general population of developed countries worldwide and behaves as a major morbidity and mortality risk factor for major causes of death, such as cardiovascular, digestive, metabolic, neoplastic and neuro-degenerative diseases. However, progression of MAFLD and its associated systemic complications occur almost invariably in patients who experience the additional burden of intrahepatic and/or systemic inflammation, which acts as disease accelerator. Our review is focused on the new knowledge about the brain-gut-liver axis in the context of metabolic dysregulations associated with fatty liver, where insulin resistance has been assumed to play an important role. Special emphasis has been given to digital imaging studies and in particular to positron emission tomography, as it represents a unique opportunity for the noninvasive in vivo study of tissue metabolism. An exhaustive revision of targeted animal models is also provided in order to clarify what the available preclinical evidence suggests for the causal interactions between fatty liver, dysregulated endogenous glucose production and insulin resistance.

Mapping of fatty acid composition with free-breathing MR spectroscopic imaging and compressed sensing

Nonalcoholic fatty liver disease (NAFLD) is a growing health problem, and a major challenge in NAFLD management is identifying which patients are at risk of progression to more serious disease. Simple measurements of liver fat content are not strong predictors of clinical outcome, but biomarkers related to fatty acid composition (ie, saturated vs. unsaturated fat) may be more effective. MR spectroscopic imaging (MRSI) methods allow spatially resolved, whole-liver measurements of chemical composition but are traditionally limited by slow acquisition times. In this work we present an accelerated MRSI acquisition based on spin echo single point imaging (SE-SPI), which, using appropriate sampling and compressed sensing reconstruction, allows free-breathing acquisition in a mouse model of fatty liver disease. After validating the technique's performance in oil/water phantoms, we imaged mice that had received a normal diet or a methionine and choline deficient (MCD) diet, some of which also received supplemental injections of iron to mimic hepatic iron overload. SE-SPI was more resistant to the line-broadening effects of iron than single-voxel spectroscopy measurements, and was consistently able to measure the amplitudes of low-intensity spectral peaks that are important to characterizing fatty acid composition. In particular, in the mice receiving the MCD diet, SE-SPI showed a significant decrease in a metric associated with unsaturated fat, which is consistent with the literature. This or other related metrics may therefore offer more a specific biomarker of liver health than fat content alone. This preclinical study is an important precursor to clinical testing of the proposed method. MR-based quantification of fatty acid composition may allow for improved characterization of non-alcoholic fatty liver disease. A spectroscopic imaging method with appropriate sampling strategy allows whole-liver mapping of fat composition metrics in a free-breathing mouse model. Changes in metrics like the surrogate unsaturation index (UIs) are visible in mice receiving a diet which induces fat accumulation in the liver, as compared to a normal diet; such metrics may prove useful in future clinical studies of liver disease.

Mechanisms underlying the hormetic effect of conjugated linoleic acid: Focus on Nrf2, mitochondria and NADPH oxidases

Nuclear factor erythroid 2-related factor2 (Nrf2) is a redox-sensitive transcription factor. Its activation by low dietary intake of ligands leads to antioxidant effects (eustress), while pro-oxidant effects (oxidative distress) may be associated with high doses. NADPH oxidases (NOXs) and the mitochondrial electron transport chain are the main sources of intracellular ROS, but their involvement in the biphasic/hormetic activity elicited by Nrf2 ligands is not fully understood. In this study, we investigated the involvement of NOX expression and mitochondrial function in the hormetic properties of omega-3 typically present in fish oil (FO) and conjugated linoleic acid (CLA) in the mouse liver. Four-week administration of FO, at both low and high doses (L-FO and H-FO) improves Nrf2-activated cyto-protection (by phase 2 enzymes), while a significant increase in respiration efficiency occurs in the liver mitochondria of H-FO BALB/c mice. Eustress conditions elicited by low dose CLA (L-CLA) are associated with increased activity of phase 2 enzymes, and with higher NOX1-2, mitochondrial defences, mitochondrial uncoupling protein 2 (UCP2), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression, compared with controls. Steatogenic effects (lipid accumulation and alteration of lipid metabolism) elicited by high CLA (H-CLA) elicited that are associated with oxidative distress, increased mitochondrial complex I/III activity and reduced levels of phase 2 enzymes, in comparison with L-CLA-treated mice. Our results confirm the steatogenic activity of H-CLA and first demonstrate the role of NOX1 and NOX2 in the eustress conditions elicited by L-CLA. Notably, the negative association of the Nrf2/PGC-1α axis with the different CLA doses provides new insight into the mechanisms underlying the hormetic effect triggered by this Nrf2 ligand.

alpha-Tocopherol supplementation reduces inflammation and apoptosis in high cholesterol mediated nonalcoholic steatohepatitis

Inflammation and apoptosis signaling are crucial steps in the progression from nonalcoholic fatty liver disease (NAFLD) to nonalcoholic steatohepatitis (NASH). Alpha-tocopherol, the most active form of vitamin E, is an important modulator of signaling mechanisms, but its involvement to cholesterol-induced NASH pathogenesis remains poorly defined. Herein we have reported a novel effect of α-tocopherol in the transition from hepatic steatosis to NASH. High cholesterol diet alone (without α-tocopherol) in rabbits elevated NASH development as indicated by increased inflammatory response, apoptotic activity and liver fibrosis. Such elevation results from induction of signaling mechanisms since the expressions of IL1β, phospho c-Jun/c-Jun ratio, JNK, caspase 9, CHOP and Bax were increased, and recruitment of macrophage, α-smooth muscle actin (α-SMA) and COL1A1 into the liver tissue were induced. Alpha-tocopherol supplementation inhibited inflammatory response, apoptosis and fibrosis development without affecting lipid accumulation in high cholesterol-induced NASH. Specifically, α-tocopherol lowered the inflammatory level as observed by reduced macrophage infiltration and JNK/c-Jun signaling. Lower inflammatory status co-occurred with the reduction of CHOP and Bax expressions as well as fibrosis-related COL1A1 and α-SMA levels. Taken together, α-tocopherol supplementation inhibits cholesterol-induced NASH development by lowering JNK/c-Jun/inflammation axis in addition to JNK/CHOP/apoptosis signaling, which might contribute to resistance against NAFLD/NASH transition.

Eugenol modulates insulin sensitivity by upregulating insulin receptor substrate-2 in non-alcoholic fatty liver disease in rats

OBJECTIVES

The purpose of this study was to estimate the possible modulatory effect of Eugenol (EUG) on insulin resistance (IR) and liver fibrosis in high-fat diet (HFD)-induced experimental non-alcoholic fatty liver disease (NAFLD) in rats. It has been shown that EUG, a natural phenolic compound, has anti-hyperglycaemic, antioxidant and anti-inflammatory actions.

METHODS

For 8 consecutive weeks, standard rat chow diet (control group, EUG only treated group) or HFD (HFD group and HFD+EUG-treated group) were fed to rats daily. HFD+EUG-treated group and EUG only treated group were administered EUG (10 mg/kg) orally three times per week. Various indices of hepatotoxicity, oxidative stress, indicators of inflammation and liver fibrosis were investigated.

KEY FINDINGS

HFD-induced liver transaminases and triglycerides (TGs) were significantly decreased and histopathological lesions were improved with EUG treatment. EUG significantly improved IR evoked by HFD, as demonstrated by Homeostasis model assessment for insulin resistance (HOMA-IR) and increased insulin receptor substrate-2 (IRS-2) sensitivity. In addition, EUG improved oxidative stress damage elicited by HFD as shown by the restoration of reduced glutathione (GSH) level and nuclear factor erythroid-2-related factor 2 (Nrf-2) expression and plummeting lipid peroxidation. Further, EUG lessened pro-inflammatory cytokines surge [tumour necrosis factor-α (TNF-α) and IL-6] via inhibiting nuclear factor-κB (NF-κB) stimulation. As markers of fibrosis, EUG reduced collagen accumulation and smooth muscle alpha actin (SMaA) and TGF-β expression.

CONCLUSIONS

EUG may have protective effect against progression of fibrosis in NAFLD. The antifibrotic effect of EUG is probably due to EUG's antioxidant, anti-inflammatory and anti-hyperglycaemic.

A human liver chimeric mouse model for non-alcoholic fatty liver disease

Background & Aims

The accumulation of neutral lipids within hepatocytes underlies non-alcoholic fatty liver disease (NAFLD), which affects a quarter of the world's population and is associated with hepatitis, cirrhosis, and hepatocellular carcinoma. Despite insights gained from both human and animal studies, our understanding of NAFLD pathogenesis remains limited. To better study the molecular changes driving the condition we aimed to generate a humanised NAFLD mouse model.

Methods

We generated TIRF (transgene-free Il2rg ^-/-/Rag2 ^-/-/Fah ^-/-) mice, populated their livers with human hepatocytes, and fed them a Western-type diet for 12 weeks.

Results

Within the same chimeric liver, human hepatocytes developed pronounced steatosis whereas murine hepatocytes remained normal. Unbiased metabolomics and lipidomics revealed signatures of clinical NAFLD. Transcriptomic analyses showed that molecular responses diverged sharply between murine and human hepatocytes, demonstrating stark species differences in liver function. Regulatory network analysis indicated close agreement between our model and clinical NAFLD with respect to transcriptional control of cholesterol biosynthesis.

Conclusions

These NAFLD xenograft mice reveal an unexpected degree of evolutionary divergence in food metabolism and offer a physiologically relevant, experimentally tractable model for studying the pathogenic changes invoked by steatosis.

Lay summary

Fatty liver disease is an emerging health problem, and as there are no good experimental animal models, our understanding of the condition is poor. We here describe a novel humanised mouse system and compare it with clinical data. The results reveal that the human cells in the mouse liver develop fatty liver disease upon a Western-style fatty diet, whereas the mouse cells appear normal. The molecular signature (expression profiles) of the human cells are distinct from the mouse cells and metabolic analysis of the humanised livers mimic the ones observed in humans with fatty liver. This novel humanised mouse system can be used to study human fatty liver disease.

Serum Metabolomic Profiling to Reveal Potential Biomarkers for the Diagnosis of Fatty Liver Hemorrhagic Syndrome in Laying Hens

Fatty liver hemorrhage syndrome (FLHS), a nutritional and metabolic disease that frequently occurs in laying hens, causes serious losses to the poultry industry. Nowadays, the traditional clinical diagnosis of FLHS still has its limitations. Therefore, searching for some metabolic biomarkers and elucidating the metabolic pathway in vivo are useful for the diagnosis and prevention of FLHS. In the present study, a model of FLHS in laying hens induced by feeding a high-energy, low-protein diet was established. Gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) was used to analyze the metabolites in serum at days 40 and 80. The result showed that, in total, 40 differential metabolites closely related to the occurrence and development of FLHS were screened and identified, which were mainly associated with lipid metabolism, amino acid metabolism, and energy metabolism pathway disorders. Further investigation of differential metabolites showed 10 potential biomarkers such as 3-hydroxybutyric acid, oleic acid, palmitoleic acid, and glutamate were possessed of high diagnostic values by analyzing receiver operating characteristic (ROC) curves. In conclusion, this study showed that the metabolomic method based on GC-TOF-MS can be used in the clinical diagnosis of FLHS in laying hens and provide potential biomarkers for early risk evaluation of FLHS and further insights into FLHS development.

Increase of α-dicarbonyls in liver and receptor for advanced glycation end products on immune cells are linked to nonalcoholic fatty liver disease and liver cancer

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver with a very poor prognosis and constantly growing incidence. Among other primary risks of HCC, metabolic disorders and obesity have been extensively investigated over recent decades. The latter can promote nonalcoholic fatty liver disease (NAFLD) leading to the inflammatory form of nonalcoholic steatohepatitis (NASH), that, in turn, promotes HCC. Molecular determinants of this pathogenic progression, however, remain largely undefined. In this study, we have focussed on the investigation of α-dicarbonyl compounds (α-dC), highly reactive and tightly associated with overweight-induced metabolic disorders, and studied their potential role in NAFLD and progression toward HCC using murine models. NAFLD was induced using high-fat diet (HFD). Autochthonous HCC was induced using transposon-based stable intrahepatic overexpression of oncogenic NRAS^G12V in mice lacking p19^Arf tumor suppressor. Our study demonstrates that the HFD regimen and HCC resulted in strong upregulation of α-dC in the liver, heart, and muscles. In addition, an increase in α-dC was confirmed in sera of NAFLD and NASH patients. Furthermore, higher expression of the receptor for advanced glycation products (RAGE) was detected exclusively on immune cells and not on stroma cells in livers of mice with liver cancer progression. Our work confirms astable interplay of liver inflammation, carbonyl stress mediated by α-dC, and upregulated RAGE expression on CD8⁺ Tand natural killer (NK) cells in situ in NAFLD and HCC, as key factors/determinants in liver disease progression. The obtained findings underline the role of α-dC and RAGE⁺CD8⁺ Tand RAGE⁺ NK cells as biomarkers and candidates for a local therapeutic intervention in NAFLD and malignant liver disease.

Pathophysiological mechanisms underlying MAFLD

BACKGROUND AND AIMS

The pathophysiology underlying metabolic associated fatty liver disease (MAFLD) involves a multitude of interlinked processes, including insulin resistance (IR) underlying the metabolic syndrome, lipotoxicity attributable to the accumulation of toxic lipid species, infiltration of proinflammatory cells causing hepatic injury and ultimately leading to hepatic stellate cell (HSC) activation and fibrogenesis. The proximal processes, such as IR, lipid overload and lipotoxicity are relatively well established, but the downstream molecular mechanisms, such as inflammatory processes, hepatocyte lipoapoptosis, and fibrogenesis are incompletely understood.

METHODS

A literature search was performed with Medline (PubMed), Scopus and Google Scholar electronic databases till June 2020, using relevant keywords (nonalcoholic fatty liver disease; metabolic associated fatty liver disease; nonalcoholic steatohepatitis; NASH pathogenesis) to extract relevant studies describing pathogenesis of MAFLD/MASH.

RESULTS

Several studies have reported new concepts underlying pathophysiology of MAFLD. Activation of HSCs is the common final pathway for diverse signals from damaged hepatocytes and proinflammatory cells. Activated HSCs then secrete excess extracellular matrix (ECM) which accumulates and impairs structure and function of the liver. TAZ (a transcriptional regulator), hedgehog (HH) ligands, transforming growth factor-β (TGF-β), bone morphogenetic protein 8B (BMP8B) and osteopontin play important roles in activating these HSCs. Dysfunctional gut microbiome, dysregulated bile acid metabolism, endogenous alcohol production, and intestinal fructose handling, modify individual susceptibility to MASH.

CONCLUSIONS

Newer concepts of pathophysiology underlying MASH, such as TAZ/Ihh pathway, extracellular vesicles, microRNA, dysfunctional gut microbiome and intestinal fructose handling present promising targets for the development of therapeutic agents.

Targeting n-3 Polyunsaturated Fatty Acids in Non-Alcoholic Fatty Liver Disease

BACKGROUND

Non-Alcoholic Fatty Liver Disease (NAFLD) is characterized by abnormal hepatic accumulation of triacylglycerides in the absence of alcohol consumption, in association with Oxidative Stress (OS), a pro-inflammatory state and Insulin Resistance (IR), which are attenuated by n-3 long-chain polyunsaturated Fatty Acids (FAs) C20-C22 (LCPUFAs) supplementation. Main causes of NAFLD comprise high caloric intake and a sedentary lifestyle, with high intakes of saturated FAs.

METHODS

The review includes several searches considering the effects of n-3 LCPUFAs in NAFLD in vivo and in vitro models, using the PubMed database from the National Library of Medicine- National Institutes of Health.

RESULT

The LCPUFAs eicosapentaenoic acid (C20:5 n-3, EPA) and docosahexaenoic acid (C22:6 n- 3, DHA) have a positive effect in diminishing liver steatosis, OS, and the levels of aspartate aminotransferase, alanine aminotransferase and pro-inflammatory cytokines, with improvement of insulin sensitivity and adiponectin levels. The molecular pathways described for n-3 LCPUFAs in cellular and animal models and humans include peroxisome proliferator-activated receptor-α activation favouring FA oxidation, diminution of lipogenesis due to sterol responsive element binding protein-1c downregulation and inflammation resolution. Besides, nuclear factor erythroid-2-related factor-2 activation is elicited by n-3 LCPUFA-derived oxidation products producing direct and indirect antioxidant responses, with concomitant anti-fibrogenic action.

CONCLUSION

The discussed effects of n-3 LCPUFA supplementation support its use in NAFLD, although having a limited value in NASH, a contention that may involve n-3 LCPUFA oxygenated derivatives. Clinical trials establishing optimal dosages, intervention times, type of patients and possible synergies with other natural products are needed in future studies.

Dietary Intervention Reverses Fatty Liver and Altered Gut Microbiota during Early-Life Undernutrition

Nonalcoholic fatty liver disease (NAFLD), largely studied as a condition of overnutrition, also presents in undernourished populations. Like NAFLD, undernutrition disrupts systemic metabolism and has been linked to gut microbiota dysbiosis. Indeed, chronic exposures to fecal microbes contribute to undernutrition pathology in regions with poor sanitation. Despite a growing prevalence of fatty liver disease, the influence of undernutrition and the gut microbiota remain largely unexplored. Here, we utilize an established murine model (C57BL/6J mice placed on a malnourished diet that received iterative Escherichia coli/Bacteroidales gavage [MBG mice]) that combines a protein/fat-deficient diet and iterative exposure to specific, fecal microbes. Fecal-oral contamination exacerbates triglyceride accumulation in undernourished mice. MBG livers exhibit diffuse lipidosis accompanied by striking shifts in fatty acid, glycerophospholipid, and retinol metabolism. Multiomic analyses revealed metabolomic pathways linked to the undernourished gut microbiome and hepatic steatosis, including phenylacetate metabolism. Intriguingly, fatty liver features were observed only in the early-life, but not adult, MBG model despite similar liver metabolomic profiles. Importantly, we demonstrate that dietary intervention largely mitigates aberrant metabolomic and microbiome features in MBG mice. These findings indicate a crucial window in early-life development that, when disrupted by nutritional deficiency, may significantly influence liver function. Our work provides a multifaceted study of how diet and gut microbes inform fatty liver progression and reversal during undernutrition.IMPORTANCE Nonalcoholic fatty liver disease (NAFLD) remains a global epidemic, but it is often studied in the context of obesity and aging. Nutritional deficits, however, also trigger hepatic steatosis, influencing health trajectories in undernourished pediatric populations. Here, we report that exposure to specific gut microbes impacts fatty liver pathology in mice fed a protein/fat-deficient diet. We utilize a multiomics approach to (i) characterize NAFLD in the context of early undernutrition and (ii) examine the impact of diet and gut microbes in the pathology and reversal of hepatic steatosis. We provide compelling evidence that an early-life, critical development window facilitates undernutrition-induced fatty liver pathology. Moreover, we demonstrate that sustained dietary intervention largely reverses fatty liver features and microbiome shifts observed during early-life malnutrition.

Necroptosis in Hepatosteatotic Ischaemia-Reperfusion Injury

While liver transplantation remains the sole treatment option for patients with end-stage liver disease, there are numerous limitations to liver transplantation including the scarcity of donor livers and a rise in livers that are unsuitable to transplant such as those with excess steatosis. Fatty livers are susceptible to ischaemia-reperfusion (IR) injury during transplantation and IR injury results in primary graft non-function, graft failure and mortality. Recent studies have described new cell death pathways which differ from the traditional apoptotic pathway. Necroptosis, a regulated form of cell death, has been associated with hepatic IR injury. Receptor-interacting protein kinase 3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL) are thought to be instrumental in the execution of necroptosis. The study of hepatic necroptosis and potential therapeutic approaches to attenuate IR injury will be a key factor in improving our knowledge regarding liver transplantation with fatty donor livers. In this review, we focus on the effect of hepatic steatosis during liver transplantation as well as molecular mechanisms of necroptosis and its involvement during liver IR injury. We also discuss the immune responses triggered during necroptosis and examine the utility of necroptosis inhibitors as potential therapeutic approaches to alleviate IR injury.

Oxidative Stress and Pro-Inflammatory Status in Patients with Non-Alcoholic Fatty Liver Disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is characterized by excessive fat accumulation, especially triglycerides, in hepatocytes. If the pathology is not properly treated, it can progress to nonalcoholic steatohepatitis (NASH) and continue to fibrosis, cirrhosis or hepatocarcinoma.

OBJECTIVE

The aim of the current research was to identify the plasma biomarkers of liver damage, oxidative stress and inflammation that facilitate the early diagnosis of the disease and control its progression.

METHODS

Antioxidant and inflammatory biomarkers were measured in the plasma of patients diagnosed with NAFLD (n = 100 adults; 40-60 years old) living in the Balearic Islands, Spain. Patients were classified according to the intrahepatic fat content (IFC) measured by magnetic resonance imaging (MRI).

RESULTS

Circulating glucose, glycosylated haemoglobin, triglycerides, low-density lipoprotein-cholesterol, aspartate aminotransferase and alanine aminotransferase were higher in patients with an IFC ≥ 2 of NAFLD in comparison to patients with an IFC of 0 and 1. The plasma levels of catalase, irisin, interleukin-6, malondialdehyde, and cytokeratin 18 were higher in stage ≥2 subjects, whereas the resolvin D1 levels were lower. No differences were observed in xanthine oxidase, myeloperoxidase, protein carbonyl and fibroblast growth factor 21 depending on liver status.

CONCLUSION

The current available data show that the severity of NAFLD is associated with an increase in oxidative stress and proinflammatory status. It may be also useful as diagnostic purpose in clinical practice.

Attenuation of arsenic induced high fat diet exacerbated oxidative stress mediated hepatic and cardiac injuries in male Wistar rats by piperine involved antioxidative mechanisms

The current study explored the efficacy of piperine in attenuating arsenic induced high fat diet aggravated oxidative stress mediated injury in hepatic and cardiac tissues of male Wistar rats. Oral administration of piperine significantly (p < 0.05) reduced the levels of organ specific and oxidative stress biomarkers in arsenic and high fat diet treated rat hepatic and cardiac tissues in a dose dependant manner with the dose of 60 mg/kg b.w. exhibiting maximum protection. Arsenic induced high fat diet aggravated oxidative stress mediated damages in liver and heart tissues led to decreased activities of antioxidant enzymes, ROS generation, diminished activities of Krebs' cycle and respiratory chain enzymes, collapsed mitochondrial membrane potential, mitochondrial DNA damage along with altered lipid metabolism and inflammatory cytokine levels. Histochemical and histopathological studies supported the above findings. Piperine efficiently counteracted the arsenic induced high fat diet aggravated oxidative stress mediated damages by modulating antioxidant defense mechanism along with free radical quenching ability. These findings indicate that piperine protected the arsenic induced high fat diet aggravated hepatic and cardiac injuries which underline the importance of piperine in providing a possible therapeutic regime for the amelioration of arsenic-induced high fat diet aggravated oxidative stress mediated organ damages.

Review: Lipid biology in the periparturient dairy cow: contemporary perspectives

Coordinated changes in energy metabolism develop to support gestation and lactation in the periparturient dairy cow. Maternal physiology involves the partitioning of nutrients (i.e. glucose, amino acids and fatty acids (FA)) for fetal growth and milk synthesis. However, the inability of the dairy cow to successfully adapt to a productive lactation may trigger metabolic stress characterized by uncontrolled adipose tissue lipolysis and reduced insulin sensitivity. A consequence is lipotoxicity and hepatic triglyceride deposition that favors the development of fatty liver disease (FLD) and ketosis. This review describes contemporary perspectives pertaining to FA surfeit and complex lipid metabolism in the transition dairy cow. The role of saturated and unsaturated FA as bioactive signaling molecules capable of modulating insulin secretion and sensitivity is explored. Moreover, the metabolic fate of FA as influenced by mitochondrial function is considered. This includes the influence of inadequate mitochondrial oxidation on acylcarnitine status and the use of FA for lipid mediator synthesis. Lipid mediators, including the sphingolipid ceramide and diacylglycerol, are evaluated considering their established ability to inhibit insulin signaling and glucose transport in non-ruminant diabetics. The mechanisms of FLD in the transition cow are revisited with attention centered on glycerophospholipid phosphatidylcholine and triglyceride secretion. The relationship between oxidative stress and oxylipids within the context of insulin antagonism, hepatic steatosis and inflammation is also reviewed. Lastly, peripartal hormonal involvement or lack thereof of adipokines (i.e. leptin, adiponectin) and hepatokines (i.e. fibroblast growth factor-21) is described. Similarities and differences in ruminant and non-ruminant physiology are routinely showcased. Unraveling the lipidome of the dairy cow has generated breakthroughs in our understanding of periparturient lipid biology. Therapeutic approaches that target FA and complex lipid metabolism holds promise to enhance cow health, well-being and productive lifespan.

Vitamin E does not prevent Western diet-induced NASH progression and increases metabolic flux dysregulation in mice

Fatty liver involves ectopic lipid accumulation and dysregulated hepatic oxidative metabolism, which can progress to a state of elevated inflammation and fibrosis referred to as nonalcoholic steatohepatitis (NASH). The factors that control progression from simple steatosis to NASH are not fully known. Here, we tested the hypothesis that dietary vitamin E (VitE) supplementation would prevent NASH progression and associated metabolic alterations induced by a Western diet (WD). Hyperphagic melanocortin-4 receptor-deficient (MC4R^-/-) mice were fed chow, chow+VitE, WD, or WD+VitE starting at 8 or 20 weeks of age. All groups exhibited extensive hepatic steatosis by the end of the study (28 weeks of age). WD feeding exacerbated liver disease severity without inducing proportional changes in liver triglycerides. Eight weeks of WD accelerated liver pyruvate cycling, and 20 weeks of WD extensively upregulated liver glucose and oxidative metabolism assessed by ²H/¹³C flux analysis. VitE supplementation failed to reduce the histological features of NASH. Rather, WD+VitE increased the abundance and saturation of liver ceramides and accelerated metabolic flux dysregulation compared with 8 weeks of WD alone. In summary, VitE did not limit NASH pathogenesis in genetically obese mice, but instead increased some indicators of metabolic dysfunction.

Quercetin administration post-weaning attenuates high-fructose, high-cholesterol diet-induced hepatic steatosis in growing, female, Sprague Dawley rat pups

BACKGROUND

Fructose and cholesterol-rich diets have been implicated in the upsurge of metabolic syndrome (MetS). Phytochemicals are being explored as alternatives for the prevention and management of MetS. Thirty-six 21-day-old, female Sprague Dawley rats fed a high-fructose, high-cholesterol diet post-weaning were used to investigate the prophylactic potential of quercetin. Group 1 was given standard rat chow (SRC); Group 2: SRC and quercetin (75 mg kg-1 daily); Group 3: SRC and fenofibrate (100 mg kg-1 daily); Group 4 was given a high cholesterol diet (HCD) (2% added dietary cholesterol in SRC), 20% fructose drinking solution (FS); Group 5 was given HCD, 20% FS and quercetin (75 mg kg-1 daily); Group 6: HCD, 20% FS and fenofibrate (100 mg kg-1 daily). Rats were fed ad libitum for 8 weeks, euthanized, and blood and liver samples were collected.

RESULTS

The HCD and FS significantly increased (P < 0.05) absolute and relative liver masses and serum cholesterol. Fasting blood glucose, serum triglycerides, alanine transaminase, creatinine, and urea were not significantly different (P > 0.05) between groups. The HCD and FS significantly increased liver lipid yield compared to the SRC and rats receiving SRC with fenofibrate (P < 0.05). Quercetin or fenofibrate together with HCD and FS attenuated the diet-induced increase in liver lipids by approximately 50%, although this was not statistically significant. Liver macro- and micro-steatosis scores were significantly increased (P < 0.05) in rats receiving HCD and FS. Quercetin or fenofibrate administration together with HCD and FS significantly decreased (P < 0.05) liver macro-steatosis scores.

CONCLUSION

The prophylactic effect of quercetin on fructose and cholesterol diet-induced liver lipid accumulation may be exploited in the fight against non-alcoholic fatty liver disease (NAFLD). © 2019 Society of Chemical Industry.

Non-invasive assessment of hepatic lipid subspecies matched with non-alcoholic fatty liver disease phenotype

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) is characterized by excessive hepatic fat accumulation. Increased hepatic saturated fats and decreased hepatic polyunsaturated fats may be particularly lipotoxic, contributing to metabolic dysfunction. We compared hepatic lipid subspecies in adults with and without NAFLD, and examined links with hallmark metabolic and clinical characteristics of NAFLD.

METHODS AND RESULTS

Nineteen adults with NAFLD (total hepatic fat:18.8 ± 0.1%) were compared to sixteen adults without NAFLD (total hepatic fat: 2.1 ± 0.01%). ¹H-MRS was used to assess hepatic lipid subspecies. Methyl, allylic, methylene, and diallylic proton peaks were measured. Saturation, unsaturation, and polyunsaturation indices were calculated. Whole-body phenotyping in a subset of participants included insulin sensitivity (40 mU/m² hyperinsulinemic-euglycemic clamps), CT-measured abdominal adipose tissue depots, exercise capacity, and serum lipid profiles. Participants with NAFLD exhibited more saturated and less unsaturated hepatic fat, accompanied by increased insulin resistance, total and visceral adiposity, triglycerides, and reduced exercise capacity compared to controls (all P < 0.05). All proton lipid peaks were related to insulin resistance and hypertriglyceridemia (P < 0.05).

CONCLUSION

Participants with NAFLD preferentially stored excess hepatic lipids as saturated fat, at the expense of unsaturated fat, compared to controls. This hepatic lipid profile was accompanied by an unhealthy metabolic phenotype.

Quercetin improves nonalcoholic fatty liver by ameliorating inflammation, oxidative stress, and lipid metabolism in db/db mice

Multiphase pathological processes involve in Type 2 diabetes (T2DM)-induced nonalcoholic fatty liver disease (NAFLD). However, the therapies are quite limited. In the present study, the hepatoprotective effects and underlying mechanisms of quercetin in T2DM-induced NAFLD were investigated. T2DM-induced NAFLD and quercetin treatment models were established in vivo and in vitro. The results revealed that quercetin alleviated serum transaminase levels and markedly reduced T2DM-induced histological alterations of livers. Additionally, quercetin restored superoxide dismutase, catalase, and glutathione content in livers. Not only that, quercetin markedly attenuated T2DM-induced production of interleukin 1 beta, interleukin 6, and TNF-α. Accompanied by the restoration of the increased serum total bile acid (p = .0001) and the decreased liver total bile acid (p = .0005), quercetin could reduce lipid accumulation in the liver of db/db mice. Further mechanism studies showed that farnesoid X receptor 1/Takeda G-protein-coupled receptor 5 signaling pathways was involved in quercetin regulation of lipid metabolism in T2DM-induced NAFLD. In high D-glucose and free fatty acid cocultured HepG2 cells model, quercetin eliminated lipid droplets and restored the upregulated total cholesterol and triglyceride levels. Similar to the findings in mice, quercetin could also activate farnesoid X receptor 1/Takeda G-protein-coupled receptor 5 signaling pathway. These findings suggested that quercetin might be a potentially effective drug for the treatment of T2DM-induced NAFLD.

Does L-carnitine supplementation affect serum levels of enzymes mainly produced by liver? A systematic review and meta-analysis of randomized controlled clinical trials

BACKGROUND AND AIMS

L-carnitine supplementation is proposed to reduce liver enzymes levels; however, previous findings were equivocal. The current systematic review and meta-analysis of randomized controlled clinical trials (RCTs) were performed to assess the effect of L-carnitine supplementation on serum levels of enzymes mainly produced by liver [alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transpeptidase (GGTP)].

METHODS

Online databases as well as the reference lists of relevant studies were searched from inception up to June 2019. The risk of bias in individual studies was assessed using Cochrane Collaboration's tool. Data were pooled using the random-effects model and expressed as mean differences (MDs) with 95% confidence intervals (CIs).

RESULTS

In total, 18 RCTs (1161 participants) met the eligibility criteria. L-carnitine supplementation dose ranged from 500 to 4000 mg/day. L-carnitine supplementation significantly reduced serum ALT (MD = - 8.65 IU/L, 95% CI - 13.40, - 3.90), AST (MD = - 8.52 IU/L, 95% CI - 12.16, - 4.89), and GGTP (MD = - 8.80 IU/L, 95% CI - 13.67, - 3.92) levels. The subgroup analysis showed that L-carnitine might be more effective in reducing the enzymes when supplemented in higher doses (≥ 2000 mg/day), for longer durations (> 12 weeks), and among patients with liver diseases. The meta-evidence was graded as "moderate" for ALT and AST, and "low" for GGTP according to NutriGrade scoring system.

CONCLUSION

L-carnitine supplementation significantly improves circulating ALT, AST and GGTP levels; therefore, it might positively affect liver function, especially among patients with liver diseases. Further high-quality RCTs are recommended to confirm our results.

Effect of oleic acid on induction of steatosis and cytotoxicity in BRL 3A cells

Recent studies have shown that monounsaturated oleic acid induces steatosis in cultured hepatocyte steatosis in the form of nonalcoholic fatty liver disease models in vitro. However, the underlying mechanism of steatosis development is not completely understood. Therefore, we investigated the molecular mechanism of steatosis and the role of mitogen-activated protein kinase (MAPK)/toll-like receptor 4-related protein (TLR4) expression in this study. Rat hepatocyte cells were subjected to oleic acid in different concentrations (1.2-2.4 mM) for 24 hours. The cell morphological injury index and the changes in the MAPK/TLR4 signaling pathway-related proteins were evaluated. We found that the microstructure of the cells in the oleic acid treatment group was damaged, and higher phosphorylation levels of the MAPK pathway-related proteins were detected than those in the control group. In addition, the protein expression of TLR4, sterol regulatory element-binding protein-1, and fatty acid synthase were increased in the oleic acid treatment group. Our findings demonstrate that oleic acid causes toxic damage to rat hepatocyte cells, and the MAPK/TLR4 signaling pathway plays a significant role in lipid storage.

Ameliorative Effect of Spinach on Non-Alcoholic Fatty Liver Disease Induced in Rats by a High-Fat Diet

The purpose of this work was to evaluate the effect of dietary carotenoids from spinach on the inflammation and oxidative stress biomarkers, liver lipid profile, and liver transcriptomic and metabolomics profiles in Sprague–Dawley rats with steatosis induced by a high-fat diet. Two concentrations of spinach powder (2.5 and 5%) were used in two types of diet: high-fat (H) and standard (N). Although rats fed diet H showed an accumulation of fat in hepatocytes, they did not show differences in the values of adiponectin, tumor necrosis factor alpha (TNF-α), and oxygen radical absorption (ORAC) in plasma or of isoprostanes in urine compared with animals fed diet N. The consumption of spinach and the accumulation of α and β carotenes and lutein in the liver was inversely correlated with serum total cholesterol and glucose and the content of hepatic cholesterol, increasing monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA) and reducing cholesterol in the livers of rats fed diet H and spinach. In addition, changes in the expression of genes related to the fatty liver condition occurred, and the expression of genes involved in the metabolism of fatty acids and cholesterol increased, mainly through the overexpression of peroxisome proliferator activated receptors (PPARs). Related to liver metabolites, animals fed with diet H showed hypoaminoacidemia, mainly for the glucogenic aminoacids. Although no changes were observed in inflammation and oxidative stress biomarkers, the consumption of spinach modulated the lipid metabolism in liver, which must be taken into consideration during the dietary treatment of steatosis.

Metabolomics Characterizes the Effects and Mechanisms of Quercetin in Nonalcoholic Fatty Liver Disease Development

As metabolomics is widely used in the study of disease mechanisms, an increasing number of studies have found that metabolites play an important role in the occurrence of diseases. The aim of this study is to investigate the effects and mechanisms of quercetin in high-fat-sucrose diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) development using nontargeted metabolomics. A rat model of NAFLD was established by feeding with an HFD for 30 and 50 days. The results indicated quercetin exhibited hepatoprotective activity in 30-day HFD-induced NAFLD rats by regulating fatty acid related metabolites (adrenic acid, etc.), inflammation-related metabolites (arachidonic acid, etc.), oxidative stress-related metabolites (2-hydroxybutyric acid) and other differential metabolites (citric acid, etc.). However, quercetin did not improve NAFLD in the 50-day HFD; perhaps quercetin was unable to reverse the inflammation induced by a long-term high-fat diet. These data indicate that dietary quercetin may be beneficial to NAFLD in early stages. Furthermore, combining metabolomics and experimental approaches opens avenues to study the effects and mechanisms of drugs for complex diseases.

Changes induced by non-alcoholic fatty liver disease in liver sinusoidal endothelial cells and hepatocytes: spectroscopic imaging of single live cells at the subcellular level

Non-Alcoholic Fatty Liver Disease (NAFLD) is the most prevalent liver disorder worldwide, involving pathogenic mechanisms of liver sinusoidal endothelial cells (LSECs), hepatocytes and other liver cells. Here, we used a novel approach of label-free Raman confocal imaging to study primary LSECs and hepatocytes freshly isolated from the livers of mice with NAFLD induced by a high fat diet (HFD), in comparison to healthy controls. Our aim was to characterize changes in the biochemical composition in LSECs and hepatocytes that occur in a single cell at the subcellular level. LSECs from NAFLD livers displayed a significant increase in the intensity of marker bands of nuclear DNA that was not associated with changes in LSEC nucleus size. A number of changes in the cytoplasm of hepatocytes were identified. However, the most prominent change in hepatocytes was a substantial increase in the degree of unsaturation of LBs' (lipid bodies) lipids in NAFLD, suggesting an increase in the de novo lipogenesis of unsaturated lipids. The confocal Raman imaging of single live cells isolated from the liver provided a unique tool to better understand disease-induced cell-specific changes in the biochemical phenotype of primary liver cells.

Altered hepatic genes related to retinol metabolism and plasma retinol in patients with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), especially non-alcoholic steatohepatitis (NASH) is a chronic liver disease commonly associated with hepatic fibrosis. NASH patients have an increased risk for hepatocellular carcinoma (HCC). An altered retinol metabolism is one of the pathways involved in the process of hepatic fibrosis, and enzymes involved in retinol metabolism have been associated with HCC. We aimed to determine the association between plasma retinol levels and hepatic expression of genes related to retinol metabolism, as well as to assess the hepatic expression of transcription factors regulated by retinoic acid in patients with NAFLD. Cross-sectional study where hepatic gene expression (Illumina microarray) and plasma retinol levels (HPLC) were measured in 17 patients with simple steatosis (SS), 15 with NASH, and 22 living liver donors (LD) as controls. Plasma retinol levels were higher in SS (1.53 ± 0.44 μmol/L) and NASH (1.51 ± 0.56 μmol/L) compared to LD (1.21 ± 0.38 μmol/L; p<0.05). AKR1B10 was highly overexpressed in NASH compared to SS (+6.2-fold) and LD (+9.9-fold; p = 4.89E-11). Retinaldehyde dehydrogenase 1 family, member A2 (ALDH1A2) and retinaldehyde dehydrogenase 1 family, member A3 (ALDH1A3), key enzymes for retinoic acid synthesis, were underexpressed in SS (-1.48 and -2.3-fold, respectively) and NASH (-1.47 and -2.6-fold, respectively) versus LD. In NASH, hepatic ALDH1A2 and ALDH1A3 were underexpressed and inversely correlated with plasma retinol levels, which may reduce retinoic acid in the liver. This, in addition to changes in expression of other genes involved in retinol metabolism, suggests a role for altered retinol homeostasis in NASH.

Dietary Genistein Alleviates Lipid Metabolism Disorder and Inflammatory Response in Laying Hens With Fatty Liver Syndrome

This study investigated the molecular mechanism underlying the effect of dietary genistein (GEN) on fatty liver syndrome (FLS) in laying hens. Hens in the control group (CG) were fed a high-energy and low-choline (HELC) diet to establish the FLS model. The livers of the FLS hens were friable and swollen from hemorrhage. Hepatic steatosis and inflammatory cell infiltration were present around the liver blood vessels. Hens in the low-genistein (LGE) and high-genistein (he) groups were fed GEN at 40 and 400 mg/kg doses, respectively, as supplements to the HELC diet. GEN at 40 mg/kg significantly increased gonadotropin-releasing hormone (GnRH) mRNA expression in the hypothalamus, the serum estrogen (E2) level, and the laying rate, whereas 400 mg/kg of GEN decreased GnRH expression and the laying rate without significantly affecting E2, suggesting that high-dose GEN adversely affected the reproductive performance. Either high- or low-dose GEN treatment could alleviate metabolic disorders and inflammatory responses in FLS hens. GEN significantly decreased the serum ALT, creatinine, triglyceride (TG), total cholesterol (TC), and free fatty acid (FFA) levels. Accordingly, the TG and long-chain fatty acid (LCFA) levels, including long-chain saturated fatty acids (LSFAs) and monounsaturated fatty acids (MUFAs), and the n-6:n-3 polyunsaturated fatty acid (PUFA) ratio in the liver were reduced after the GEN treatments, whereas the levels of C22:0, n-3 family fatty acids, C20:3n6, and C20:4n6 were increased. These results indicated that dietary GEN downregulated the expression of genes related to fatty acid synthesis [sterol regulatory element-binding protein 1 (SREBP1c), liver X receptor alpha (LXRα), fatty acid synthase (FAS), and acetyl coenzyme A synthetase (ACC)] and the fatty acid transporter (FAT). Furthermore, GEN treatments upregulated the transcription of genes related to fatty acid β-oxidation [peroxisome proliferator-activated receptor (PPAR)α, PPARδ, ACOT8, ACAD8, and ACADs] in the liver and reduced PPARγ and AFABP expression in abdominal fat. Dietary GEN alleviated inflammatory cell infiltration in the livers of FLS hens and downregulated TNF-α, IL-6, and IL-1β expression. Moreover, GEN treatment increased SOD activity and decreased malondialdehyde activity in the liver. In conclusion, GEN supplementation in the feed inhibited fatty acid synthesis and enhanced β-oxidation in the liver through the PPAR-ACAD/ACOT and PPAR-LXRα-SREBP1c-ACC/FAS/FAT pathways. Dietary GEN alleviated metabolic disorder and inflammation in the FLS hens by improving the antioxidant capacity and fatty acid profile.

Oxidative Stress Impairs Fatty Acid Oxidation and Mitochondrial Function in the Term Placenta

Placental fatty acid oxidation (FAO) is impaired and lipid storage is increased in pregnancy states associated with chronic oxidative stress. The effect of acute oxidative stress, as seen in pregnancies complicated with asthma, on placental lipid metabolism is unknown. We hypothesized that induction of acute oxidative stress would decrease FAO and increase esterification. We assessed [³H]-palmitate oxidation and esterification in term placental explants from lean women after exposure to hydrogen peroxide (H₂O₂) for 4 hours. Fatty acid oxidation decreased 16% and 24% in placental explants exposed to 200 (P = .02) and 400 µM H₂O₂ (P = .01), respectively. Esterification was not altered with H₂O₂ exposure. Neither messenger RNA nor protein expression of key genes involved in FAO (eg, peroxisome proliferator-activated receptor α, carnitine palmitoyl transferase 1b) were altered. Adenosine triphosphate (ATP) levels decreased with induction of oxidative stress, without increasing cytotoxicity. Acute oxidative stress decreased FAO and ATP production in the term placenta without altering fatty acid esterification. As decreases in placental FAO and ATP production are associated with impaired fetal growth, pregnancies exposed to acute oxidative stress may be at risk for fetal growth restriction.