Molecular mechanisms and the role of saturated fatty acids in the progression of non-alcoholic fatty liver disease

Association of plasma metabolites and diagnostic imaging findings with hepatic lipidosis in bearded dragons (Pogona vitticeps) and effects of gemfibrozil therapy

OBJECTIVES

To evaluate the association between plasma metabolites, biochemical analytes, diagnostic imaging findings, and the histologic diagnosis of hepatic lipidosis in bearded dragons. To assess the effects of gemfibrozil therapy on hepatic lipid accumulation and associated diagnostic tests.

ANIMALS

Fourteen bearded dragons (Pogona vitticeps) with varying severity of hepatic lipid accumulation (with and without hepatic lipidosis) were included.

PROCEDURES

Animals underwent coelomic ultrasound, computed tomography (CT) scans, and coelioscopic hepatic biopsies. Clinical pathology tests included lipidologic tests, hepatic biomarkers, and mass spectrometry-based metabolomics. Animals were medicated with gemfibrozil 6mg/kg orally once a day for 2 months in a randomized blinded clinical trial prior to repeating previous diagnostic testing.

RESULTS

Hounsfield units on CT were negatively associated with increased hepatic vacuolation, while ultrasound and gross evaluation of the liver were not reliable. Beta-hydroxybutyric-acid (BHBA) concentrations were significantly associated with hepatic lipidosis. Metabolomics and lipidomics data found BHBA and succinic acid to be potential biomarkers for diagnosing hepatic lipidosis in bearded dragons. Succinic acid concentrations were significantly lower in the gemfibrozil treatment group. There was a tendency for improvement in the biomarkers and reduced hepatic fat in bearded dragons with hepatic lipidosis when treated with gemfibrozil, though the improvement was not statistically significant.

CONCLUSIONS

These findings provide information on the antemortem assessment of hepatic lipidosis in bearded dragons and paves the way for further research in diagnosis and treatment of this disease.

Effects of Different Vegetable Oils on the Nonalcoholic Fatty Liver Disease in C57/BL Mice

Background

Nonalcoholic fatty liver disease (NAFLD) is the most common hepatic disorder, affecting 22-28% of the adult population and more than 50% of obese people all over the world. Modulation of the fatty acids in diet as a means of prevention against nonalcoholic fatty liver disease in animal models (NAFLD) remains unclear. The treatment of NAFLD has not been described in specific guidelines so far. Thus, the justification for the study is to check modifications in macronutrients composition, fatty acids, in particular, play a significant role in the treatment of NAFLD regardless of weight loss.

Aim

To investigate different vegetable oils in prevention and progression of NAFLD in animal models.

Methods

For the experiment were used fifty C57BL/6J mice male fed with high fat and fructose diet (HFD) to induce the NAFLD status and they received different commercial vegetable oils for 16 weeks to prevent steatosis. Liver steatosis and oxidative stress parameters were analyzed using biochemical and histological methods. Fatty acids profile in the oils and in the liver samples was obtained.

Results

The high fat and fructose diet led to obesity and the vegetable oils offered were effective in maintaining body weight similar to the control group. At the end of the experiment (16 weeks), the HFHFr group had a greater body weight compared to control and treated groups (HFHFr: 44.20 ± 2.34 g/animal vs. control: 34.80 ± 3.45 g/animal; p < 0.001; HFHFr/OL: 35.40 ± 4.19 g/animal; HFHFr/C: 36.10 ± 3.92 g/animal; HFHFr/S: 36.25 ± 5.70 g/animal; p < 0.01). Furthermore, the HFD diet has caused an increase in total liver fat compared to control (p < 0.01). Among the treated groups, the animals receiving canola oil showed a reduction of hepatic and retroperitoneal fat (p < 0.05). These biochemical levels were positively correlated with the hepatic histology findings. Hepatic levels of omega-3 decreased in the olive oil and high fat diet groups compared to the control group, whereas these levels increased in the groups receiving canola and soybean oil compared to control and the high fat groups.

Conclusion

In conclusion, the commercial vegetable oils either contributed to the prevention or reduction of induced nonalcoholic fatty liver with high fat and fructose diet, especially canola oil.

The effect of acute and chronic exercise on hepatic lipid composition

Exercise is recommended for those with, or at risk of nonalcoholic fatty liver disease (NAFLD), owing to beneficial effects on hepatic steatosis and cardiometabolic risk. Whilst exercise training reduces total intrahepatic lipid in people with NAFLD, accumulating evidence indicates that exercise may also modulate hepatic lipid composition. This metabolic influence is important as the profile of saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) dramatically affect the metabolic consequences of hepatic lipid accumulation; with SFA being especially lipotoxic. Relatedly, obesity and NAFLD are associated with hepatic PUFA depletion and elevated SFA. This review summarizes the acute (single bout) and chronic (exercise training) effects of exercise on hepatic lipid composition in rodents (acute studies: n = 3, chronic studies: n = 13) and humans (acute studies: n = 1, chronic studies: n = 3). An increased proportion of hepatic PUFA after acute and chronic exercise is the most consistent finding of this review. Mechanistically, this may relate to an enhanced uptake of adipose-derived PUFA (reflecting habitual diet), particularly in rodents. A relative decrease in the proportion of hepatic MUFA after chronic exercise is also documented repeatedly, particularly in rodent models with elevated hepatic MUFA. This outcome is related to decreased hepatic stearoyl-CoA desaturase-1 activity in some studies. Findings regarding hepatic SFA are less consistent and limited by the absence of metabolic challenge in rodent models. These findings require confirmation in well-controlled interventions in people with NAFLD. These studies will be facilitated by recently validated magnetic resonance spectroscopy techniques, able to precisely quantify hepatic lipid composition in vivo.

Unsaturated or saturated dietary fat-mediated steatosis impairs hepatic regeneration following partial hepatectomy in mice

BACKGROUND

Partial hepatectomy is a preferred treatment option for many patients with hepatocellular carcinoma however, pre-existing pathological abnormalities originating from hepatic steatosis can alter the decision to perform surgery or postoperative outcomes as a consequence of the impact steatosis has on liver regeneration.

AIM

The aim of this study was to investigate the role of a saturated or unsaturated high fat diet-mediated steatosis on liver regeneration following partial hepatectomy.

METHODS

Mice were fed a low-fat control diet (CD, 13% fat), lard-based unsaturated (LD, 60% fat) or milk-based saturated high fat diet (MD, 60% fat) for 16 weeks at which time partial hepatectomy (approx. 70% resection) was performed. At days-2 and 7 post hepatectomy, one hour prior to euthanization, mice were injected with 5-bromo-2'-deoxyuridine in order to monitor hepatic regeneration. Serum was collected and assessed for levels of ALT and AST. Resected and regenerated liver tissue were examined for inflammation-indicative markers employing RT-PCR, Western blots, and histological methods.

RESULTS

Mice fed LD or MD exhibited higher NAFLD scores, increased expression of inflammatory cytokines, neutrophil infiltration, macrophage accumulation, increased apoptosis, and elevated levels of serum ALT and AST activities, a decrease in the number of BrdU-incorporated-hepatocytes in the regenerated livers compared to the mice fed CD. Mice fed MD showed significantly lower percent of BrdU-incorporated hepatocytes and a higher trend of inflammation compared to the mice fed LD.

CONCLUSION

A diet rich in saturated or unsaturated fat results in NASH with decreased hepatic regeneration however unsaturated fat diet cause lower inflammation and higher regeneration than the saturated fat diet following partial hepatectomy in mice.

A review on the role of fatty acids in colorectal cancer progression

Colorectal cancer (CRC) is the third leading cause of mortality in cancer patients. The role of fatty acids (FA) and their metabolism in cancer, particularly in CRC raises a growing interest. In particular, dysregulation of synthesis, desaturation, elongation, and mitochondrial oxidation of fatty acids are involved. Here we review the current evidence on the link between cancer, in particular CRC, and fatty acids metabolism, not only to provide insight on its pathogenesis, but also on the development of novel biomarkers and innovative pharmacological therapies that are based on FAs dependency of cancer cells.

Adiponectin alleviates non-alcoholic fatty liver injury via regulating oxidative stress in liver cells

BACKGROUND

The aim of the present study was to investigate the role of adiponectin in non-alcoholic fatty liver cell model and its mechanism.

METHODS

The serum were collected from patients with non-alcoholic fatty liver disease and healthy controls. Then the expression of APN in the serum was detected using APN kit. Furthermore, an in vitro model of NAFLD was established using mixed fatty acids treated HepG2 cells, and APN was highly expressed in the culture solution to a concentration of 10 μg/mL. The normal control group (Normal) was normal cells, the model group (NAFLD) was mixed fatty acids treated HepG2 cells, the experimental group (NAFLD+APN) was model cells transfected with high APN expression, and the negative control group (NAFLD+PBS) was model cells transfected with PBS. The expression of NOX2 in each group was detected by Western blot. The corresponding kit was used to detect the level of triglyceride (TG), the activity of superoxide dismutase (SOD), the content of malondialdehyde (MDA), and the ratio of GSH/GSSG in each group of cells.

RESULTS

The expression level of APN was greatly decreased in the serum of NAFLD patients (P<0.01), and the TG content was significantly increased in HepG2 cells treated with fatty acids (P<0.001), indicating successful modeling. The cells had high expression of APN (P<0.001) showed low expression of NOX2 (P<0.001). The kit test results showed that the high expression of APN could reverse the decrease of SOD activity, the increase of MDA level, the decrease of GSH/GSSG ratio and the increase of TG content (P<0.001), all of which were restored to the modeling level after application of NOX2's activator TBCA.

CONCLUSIONS

APN was lowly expressed in the serum of NAFLD patients. Its effect mechanism was to alleviate the injury of NAFLD cells by reducing oxidative stress via regulating NOX2 expression.

Utility of Human Relevant Preclinical Animal Models in Navigating NAFLD to MAFLD Paradigm

Fatty liver disease is an emerging contributor to disease burden worldwide. The past decades of work established the heterogeneous nature of non-alcoholic fatty liver disease (NAFLD) etiology and systemic contributions to the pathogenesis of the disease. This called for the proposal of a redefinition in 2020 to that of metabolic dysfunction-associated fatty liver disease (MAFLD) to better reflect the current understanding of the disease. To date, several clinical cohort studies comparing NAFLD and MAFLD hint at the relevancy of the new nomenclature in enriching for patients with more severe hepatic injury and extrahepatic comorbidities. However, the underlying systemic pathogenesis is still not fully understood. Preclinical animal models have been imperative in elucidating key biological mechanisms in various contexts, including intrahepatic disease progression, interorgan crosstalk and systemic dysregulation. Furthermore, they are integral in developing novel therapeutics against MAFLD. However, substantial contextual variabilities exist across different models due to the lack of standardization in several aspects. As such, it is crucial to understand the strengths and weaknesses of existing models to better align them to the human condition. In this review, we consolidate the implications arising from the change in nomenclature and summarize MAFLD pathogenesis. Subsequently, we provide an updated evaluation of existing MAFLD preclinical models in alignment with the new definitions and perspectives to improve their translational relevance.

Diosgenin Ameliorated Type II Diabetes-Associated Nonalcoholic Fatty Liver Disease through Inhibiting De Novo Lipogenesis and Improving Fatty Acid Oxidation and Mitochondrial Function in Rats

Diosgenin (DIO) is a dietary and phytochemical steroidal saponin representing multiple activities. The present study investigated the protective effect of DIO on type II diabetes-associated nonalcoholic fatty liver disease (D-NAFLD). The rat model was established by high-fat diet and streptozotocin injection and then administered DIO for 8 weeks. The results showed that DIO reduced insulin resistance index, improved dyslipidemia, and relieved pancreatic damage. DIO decreased hepatic injury markers, including aspartate aminotransferase (AST) and alanine aminotransferase (ALT). H&E staining showed that DIO relieved hepatic lipid deposition. Mechanistically, DIO inhibited hepatic de novo lipogenesis (DNL) and increased fatty acid β-oxidation (FAO) through regulation of the AMPK-ACC/SREBP1 pathway. Endoplasmic reticulum (ER) stress was inhibited by DIO through regulation of PERK and IRE1 arms, which may then inhibit DNL. DIO also decreased reactive oxygen species (ROS) and enhanced the antioxidant capacity via an increase in Superoxide dismutase (SOD), Catalase (CAT), and Glutathione peroxidase (GPx) activities. The mitochondria are the site for FAO, and ROS can damage mitochondrial function. DIO relieved mitochondrial fission and fusion disorder by inhibiting DRP1 and increasing MFN1/MFN2 expressions. Mitochondrial apoptosis was then inhibited by DIO. In conclusion, the present study suggests that DIO protects against D-NAFLD by inhibiting DNL and improving FAO and mitochondrial function.

Research Progress on the Therapeutic Effect of Polysaccharides on Non-Alcoholic Fatty Liver Disease through the Regulation of the Gut-Liver Axis

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease affecting global public health at present, which can induce cirrhosis and liver cancer in serious cases. However, NAFLD is a multifactorial disease, and there is still a lack of research on its mechanism and therapeutic strategy. With the development of the gut-liver axis theory, the association between the gut-liver axis and the pathogenesis of NAFLD has been gradually disclosed. Polysaccharides, as a kind of natural product, have the advantages of low toxicity, multi-target and multi-pathway action. It has been reported that polysaccharides can affect the gut-liver axis at multiple interrelated levels, such as maintaining the ecological balance of gut microbiota (GM), regulating the metabolites of GM and improving the intestinal barrier function, which thereby plays a protective role in NAFLD. These studies have great scientific significance in understanding NAFLD based on the gut-liver axis and developing safe and effective medical treatments. Herein, we reviewed the recent progress of polysaccharides in improving nonalcoholic fatty liver disease (NAFLD) through the gut-liver axis.

Dietary carbohydrates: Pathogenesis and potential therapeutic targets to obesity-associated metabolic syndrome

Metabolic syndrome (MetS) is a common feature in obesity, comprising a cluster of abnormalities including abdominal fat accumulation, hyperglycemia, hyperinsulinemia, dyslipidemia, and hypertension, leading to diabetes and cardiovascular diseases (CVD). Intake of carbohydrates (CHO), particularly a sugary diet that rapidly increases blood glucose, triglycerides, and blood pressure levels is the predominant determining factor of MetS. Complex CHO, on the other hand, are a stable source of energy taking a longer time to digest. In particular, resistant starch (RS) or soluble fiber is an excellent source of prebiotics, which alter the gut microbial composition, which in turn improves metabolic control. Altering maternal CHO intake during pregnancy may result in the child developing MetS. Furthermore, lifestyle factors such as physical inactivity in combination with dietary habits may synergistically influence gene expression by modulating genetic and epigenetic regulators transforming childhood obesity into adolescent metabolic disorders. This review summarizes the common pathophysiology of MetS in connection with the nature of CHO, intrauterine nutrition, genetic predisposition, lifestyle factors, and advanced treatment approaches; it also emphasizes how dietary CHO may act as a key element in the pathogenesis and future therapeutic targets of obesity and MetS.

Dietary linoleic acid and the ratio of unsaturated to saturated fatty acids are inversely associated with significant liver fibrosis risk: A nationwide survey

Since no pharmaceuticals have been proven to effectively reduce liver fibrosis, dietary fatty acids may be beneficial as one of the non-pharmaceutical interventions due to their important roles in liver metabolism. In this cross-sectional study, we analyzed the data from the 2017–2018 cycle of National Health and Nutrition Examination Survey to examine the associations between the proportion and composition of dietary fatty acid intakes with significant liver fibrosis among US population. The dietary fatty acid consumptions were calculated based on two 24-h dietary recalls. Significant liver fibrosis was diagnosed based on liver stiffness measurement value derived from the vibration controlled transient elastography. Multivariate logistic regression analysis and sensitivity analysis were performed to assess the association between dietary fatty acid consumption and significant liver fibrosis risk. Finally, restricted cubic spline analysis was carried out to explore the dose–response between polyunsaturated fatty acids (PUFA) or linoleic acid intakes and the risk of significant liver fibrosis. The results showed that the multivariate adjusted odds ratios (95% confidence intervals) of significant liver fibrosis were 0.34 (0.14–0.84), 0.68 (0.50–0.91), and 0.64 (0.47–0.87) for the highest level of unsaturated to saturated fatty acid ratio, dietary PUFA, and linoleic acid intakes compared to the lowest reference, respectively. The sensitivity analysis and restricted cubic spline analysis produced similar results, reinforcing the inverse association of unsaturated to saturated fatty acid ratio, PUFA, and linoleic acid consumptions with significant liver fibrosis risk. However, other dietary fatty acids did not show the statistically significant association with significant liver fibrosis. In conclusion, dietary linoleic acid may play a key role in the inverse association between the unsaturated to saturated fatty acid ratio and the risk of significant liver fibrosis. Further studies are needed to confirm these findings.

Replacement of Fish Oil With Groundnut Oil for Developing Sustainable Feeds for Labeo rohita Fingerling

Groundnut oil (GO) is one of the most widely available vegetable oils (VOs) in India and throughout the world, with a global production of 6.12 million metric tons in the year 2020–2021. GO contains phytochemicals and antioxidants with a longer shelf life. Because of these benefits, GO can produce durable, low-cost, and sustainable aquaculture feeds. To evaluate the nutritional efficacy and possibility of replacing fish oil (FO) with GO, this experiment was carried out to test the effects of partial or total substitution of dietary FO by GO on the growth performance, carcass composition, antioxidant capacity, lysozyme activity, muscle fatty acid composition, and filet nutritional quality in Labeo rohita fingerling. Induced bred healthy rohu fingerlings (4.84 ± 0.13 g) were fed six isonitrogenous (400 g kg−1) and isolipidic (97 g kg−1) casein- and gelatin-containing purified diets, wherein the FO was gradually replaced by 0, 20, 40, 60, 80, and 100% GO. Fishes were stocked randomly in triplicate groups of 30 fish per tank and fed at 08:00, 12:00, and 16:00 h to apparent satiety for 8 weeks. The results showed that FO replacement with GO did not affect the growth but decreased the eicosapentaenoic (EPA), docosahexaenoic acid (DHA) levels, and n-3/n-6 ratio in the muscle of rohu fingerlings. The antioxidant capacity and lysozyme activity improved up to 60% replacement of FO with GO in diet and then declined (P &gt; 0.05) upon further inclusion of GO in diets. Although the atherogenicity, thrombogenicity indices, and hypocholesterolemic/hypercholesterolemic (H/H) ratio did not change significantly among all the muscle samples, the highest filet lipid quality (FLQ) value was found in fish receiving a 100% FO diet. Further inclusion of dietary GO decreased the filet H/H ratio and FLQ value. In summary, replacing FO with GO at a higher level had negative consequences on the filet nutritional quality of rohu fingerlings. Therefore, FO can be replaced by GO in formulated feeds to a level of 60% without hampering the growth, antioxidant capacity, and lysozyme activity and to avoid degrading the nutritional quality of fish filet.

Proteomic analysis reveals USP7 as a novel regulator of palmitic acid-induced hepatocellular carcinoma cell death

Nutrient surplus and consequent free fatty acid accumulation in the liver cause hepatosteatosis. The exposure of free fatty acids to cultured hepatocyte and hepatocellular carcinoma cell lines induces cellular stress, organelle adaptation, and subsequent cell death. Despite many studies, the mechanism associated with lipotoxicity and subsequent cell death still remains poorly understood. Here, we have used the proteomics approach to circumvent the mechanism for lipotoxicity using hepatocellular carcinoma cells as a model. Our quantitative proteomics data revealed that ectopic lipids accumulation in cells severely affects the ubiquitin-proteasomal system. The palmitic acid (PA) partially lowered the expression of deubiquitinating enzyme USP7 which subsequently destabilizes p53 and promotes mitotic entry of cells. Our global phosphoproteomics analysis also provides strong evidence of an altered cell cycle checkpoint proteins' expression that abrogates early G2/M checkpoints recovery with damaged DNA and induced mitotic catastrophe leading to hepatocyte death. We observe that palmitic acid prefers apoptosis-inducing factor (AIF) mediated cell death by depolarizing mitochondria and translocating AIF to the nucleus. In summary, the present study provides evidence of PA-induced hepatocellular death mediated by deubiquitinase USP7 downregulation and subsequent mitotic catastrophe.

Complex FFA1 receptor (in)dependent modulation of calcium signaling by free fatty acids

The expression of free fatty acid 1 receptors (FFA1R), activated by long chain fatty acids in human pancreatic β-cells and enhancing glucose-stimulated insulin secretion are an attractive target to treat type 2 diabetes. Yet several clinical studies with synthetic FFA1R agonists had to be discontinued due to cytotoxicity and/or so-called "liver concerns". It is not clear whether these obstructions are FFA1R dependent. In this context we used CHO-AEQ cells expressing the bioluminescent calcium-sensitive protein aequorin to investigate calcium signaling elicited by FFA1 receptor ligands α-linolenic acid (ALA), oleic acid (OLA) and myristic acid (MYA). This study revealed complex modulation of intracellular calcium signaling by these fatty acids. First these compounds elicited a typical transient increase of intracellular calcium via binding to FFA1 receptors. Secondly slightly higher concentrations of ALA substantially reduced ATP mediated calcium responses in CHO-AEQ cells and Angiotensin II responses in CHO-AEQ cells expressing human AT₁ receptors. This effect was less pronounced with MYA and OLA and was not linked to FFA1 receptor activation nor to acute cytotoxicity as a result of plasma membrane perturbation. Yet it can be hypothesized that, in line with previous studies, unsaturated long chain fatty acids such as ALA and OLA are capable of inactivating the G-proteins involved in purinergic and Angiotensin AT₁ receptor calcium signaling. Alternatively the ability of fatty acids to deplete intracellular calcium stores might underly the observed cross-inhibition of these receptor responses in the same cells.

Deuterium-Reinforced Polyunsaturated Fatty Acids Prevent Diet-Induced Nonalcoholic Steatohepatitis by Reducing Oxidative Stress

Background and Objectives: Oxidative stress is implicated in the progression of nonalcoholic steatohepatitis (NASH) through the triggering of inflammation. Deuterium-reinforced polyunsaturated fatty acids (D-PUFAs) are more resistant to the reactive oxygen species (ROS)-initiated chain reaction of lipid peroxidation than regular hydrogenated (H-) PUFAs. Here, we aimed to investigate the impacts of D-PUFAs on oxidative stress and its protective effect on NASH. Materials and Methods: C57BL/6 mice were randomly divided into three groups and were fed a normal chow diet, a methionine-choline-deficient (MCD) diet, and an MCD with 0.6% D-PUFAs for 5 weeks. The phenotypes of NASH in mice were determined. The levels of oxidative stress were examined both in vivo and in vitro. Results: The treatment with D-PUFAs attenuated the ROS production and enhanced the cell viability in tert-butyl hydroperoxide (TBHP)-loaded hepatocytes. Concurrently, D-PUFAs decreased the TBHP-induced oxidative stress in Raw 264.7 macrophages. Accordingly, D-PUFAs increased the cell viability and attenuated the lipopolysaccharide-stimulated proinflammatory cytokine expression of macrophages. In vivo, the administration of D-PUFAs reduced the phenotypes of NASH in MCD-fed mice. Specifically, D-PUFAs decreased the liver transaminase activity and attenuated the steatosis, inflammation, and fibrosis in the livers of NASH mice. Conclusion: D-PUFAs may be potential therapeutic agents to prevent NASH by broadly reducing oxidative stress.

Hepatic Mitochondrial Dysfunction and Risk of Liver Disease in an Ovine Model of “PCOS Males”

First-degree male relatives of polycystic ovary syndrome (PCOS) sufferers can develop metabolic abnormalities evidenced by elevated circulating cholesterol and triglycerides, suggestive of a male PCOS equivalent. Similarly, male sheep overexposed to excess androgens in fetal life develop dyslipidaemia in adolescence. Dyslipidaemia, altered lipid metabolism, and dysfunctional hepatic mitochondria are associated with the development of non-alcoholic liver disease (NAFLD). We therefore dissected hepatic mitochondrial function and lipid metabolism in adolescent prenatally androgenized (PA) males from an ovine model of PCOS. Testosterone was directly administered to male ovine fetuses to create prenatal androgenic overexposure. Liver RNA sequencing and proteomics occurred at 6 months of age. Hepatic lipids, glycogen, ATP, reactive oxygen species (ROS), DNA damage, and collagen were assessed. Adolescent PA males had an increased accumulation of hepatic cholesterol and glycogen, together with perturbed glucose and fatty acid metabolism, mitochondrial dysfunction, with altered mitochondrial transport, decreased oxidative phosphorylation and ATP synthesis, and impaired mitophagy. Mitochondrial dysfunction in PA males was associated with increased hepatic ROS level and signs of early liver fibrosis, with clinical relevance to NAFLD progression. We conclude that excess in utero androgen exposure in male fetuses leads to a PCOS-like metabolic phenotype with dysregulated mitochondrial function and likely lifelong health sequelae.

Nonalcoholic Steatohepatitis (NASH) and Atherosclerosis: Explaining Their Pathophysiology, Association and the Role of Incretin-Based Drugs

Nonalcoholic steatohepatitis (NASH) is the most severe manifestation of nonalcoholic fatty liver disease (NAFLD), a common complication of type 2 diabetes, and may lead to cirrhosis and hepatocellular carcinoma. Oxidative stress and liver cell damage are the major triggers of the severe hepatic inflammation that characterizes NASH, which is highly correlated with atherosclerosis and coronary artery disease. Regarding drug therapy, research on the role of GLP-1 analogues and DPP4 inhibitors, novel classes of antidiabetic drugs, is growing. In this review, we outline the association between NASH and atherosclerosis, the underlying molecular mechanisms, and the effects of incretin-based drugs, especially GLP-1 RAs, for the therapeutic management of these conditions.

Monkfish Peptides Mitigate High Fat Diet-Induced Hepatic Steatosis in Mice

Non-alcoholic fatty liver disease (NAFLD) is a hepatic metabolic syndrome usually accompanied by fatty degeneration and functional impairment. The aim of the study was to determine whether monkfish peptides (LPs) could ameliorate high-fat diet (HFD)-induced NAFLD and its underlying mechanisms. NAFLD was induced in mice by giving them an HFD for eight weeks, after which LPs were administered in various dosages. In comparison to the HFD control group: body weight in the LP-treated groups decreased by 23–28%; triacylglycerol levels in the blood decreased by 16–35%; and low-density lipoproteins levels in the blood decreased by 23–51%. Additionally, we found that LPs elevated the activity of hepatic antioxidant enzymes and reduced the inflammatory reactions within fatty liver tissue. Investigating the effect on metabolic pathways, we found that in LP-treated mice: the levels of phospho-AMP-activated protein kinase (p-AMPK), and phospho-acetyl CoA carboxylase (p-ACC) in the AMP-activated protein kinase (AMPK) pathway were up-regulated and the levels of downstream sterol regulatory element-binding transcription factor 1 (SREBP-1) were down-regulated; lipid oxidation increased and free fatty acid (FFA) accumulation decreased (revealed by the increased carnitine palmitoyltransferase-1 (CPT-1) and the decreased fatty acid synthase (FASN) expression, respectively); the nuclear factor erythroid-2-related factor 2 (Nrf2) antioxidant pathway was activated; and the levels of heme oxygenase-1 (HO-1) and nicotinamide quinone oxidoreductase 1 (NQO1) were increased. Overall, all these findings demonstrated that LPs can improve the antioxidant capacity of liver to alleviate NAFLD progression mainly through modulating the AMPK and Nrf2 pathways, and thus it could be considered as an effective candidate in the treatment of human NAFLD.

The first study on the effect of crocodile oil from Crocodylus siamensis on hepatic mitochondrial function for energy homeostasis in rats

Background and Aim:

Consumption of fatty acids (FA) can alter hepatic energy metabolism and mitochondrial function in the liver. Crocodile oil (CO) is rich in mono-and polyunsaturated FAs, which have natural anti-inflammatory and healing properties. In rat livers, we investigated the effect of CO on mitochondrial function for energy homeostasis.

Materials and Methods:

Twenty-one male Sprague-Dawley rats were divided into three groups at random. Group 1 rats were given sterile water (RO), Group 2 rats were given CO (3% v/w), and Group 3 rats were given palm oil (PO) (3% v/w). For 7 weeks, rats were given sterile water, CO, and PO orally. The researchers looked at body weight, food intake, liver weight, energy intake, blood lipid profiles, and mitochondria-targeted metabolites in the liver. The liver’s histopathology, mitochondrial architecture, and hydrolase domain containing 3 (HDHD3) protein expression in liver mitochondria were studied.

Results:

Body weight, liver weight, liver index, dietary energy intake, and serum lipid profiles were all unaffected by CO treatment. The CO group consumed significantly less food than the RO group. The CO group also had significantly higher levels of oxaloacetate and malate than the PO group. CO treatment significantly ameliorated hepatic steatosis, as evidenced by a greater decrease in the total surface area of lipid particles than PO treatment. CO administration preserved mitochondrial morphology in the liver by upregulating the energetic maintenance protein HDHD3. Furthermore, chemical-protein interactions revealed that HDHD3 was linked to the energy homeostatic pathway.

Conclusion:

CO may benefit liver function by preserving hepatic mitochondrial architecture and increasing energy metabolic activity.

Peroxisome proliferator-activated receptor gamma is essential for stress adaptation by maintaining lipid homeostasis in female fish

Reduction of lipid synthesis often causes free fatty acid (FFA) overload, resulting consequential oxidative stress and health damage. Environmental stresses also induce cellular oxidative stress in organisms. The functional peroxisome proliferator-activated receptor gamma (pparg) gene is essential for lipid synthesis and homeostatic lipid maintenance. However, the relationship between the pparg-mediated lipid synthesis and environmental stress adaptation awaits full elucidation. Here, we generated a pparg-knockout zebrafish model. The conversion of free fatty acids into triglycerides in the female pparg mutants was hampered by reduced esterification efficiency, thus induced lipotoxicity, as evidenced by high oxidative stress and damaged health in these mutants, which led to reduced resistance to cold, heat and ammonia nitrogen stresses. Activating pparg in the wild-type female fish via dietary supplementation with rosiglitazone (a pparg agonist), or reducing oxidative stress in the female pparg mutants via dietary supplementation with N-acetylcysteine (an antioxidant), or promoting mitochondrial fatty acid β-oxidation in the female pparg mutants via dietary supplementation with l-carnitine, resulted in significantly reduced cellular injury, and improved environmental stress resistance. Collectively, our findings reveal that the regulative function of pparg in FFA esterification is important in stress resistance in female fish, and highlight the tight correlation existing between lipotoxicity and environmental adaptation.

Visceral Adipose Tissue and Non-alcoholic Fatty Liver Disease in Patients with Type 2 Diabetes

AIM

To explore the association of visceral adipose tissue (VAT) area and non-alcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM).

METHODS

This was a cross-sectional study comprising 100 patients with T2DM and 100 non-T2DM individuals, matched for age, sex, and body mass index (BMI). Transient elastography was used to assess hepatic steatosis and liver stiffness measurements (LSM). Controlled attenuation parameter (CAP) was used to quantify hepatic steatosis. To distinguish grades of hepatic steatosis, cutoff values were as follows: S1 ≥ 302, S2 ≥ 331, and S3 ≥ 337 dB/m. Moreover, VAT area was measured by dual-energy X-ray absorptiometry in accordance with validated protocols.

RESULTS

CAP score was significantly higher in participants with T2DM (294.61 ± 3.82 vs. 269.86 ± 3.86 dB/ m; P < 0.001). Furthermore, 42% of participants with T2DM had hepatic steatosis (S > S1: 302 dB/m), while this figure was 26% in non-T2DM group (P < 0.003). The mean liver stiffness measurement was also significantly higher in patients with T2DM (5.53 vs. 4.79 kPa; P < 0.001). VAT area was greater in patients with T2DM compared to non-T2DM individuals: 163.79 ± 47.98 cm² versus 147.49 ± 39.09 cm², P = 0.009. However, total and truncal fat mass were not different between the two groups. Age, BMI, waist circumference, ALT, CAP, and LSM were significantly associated with VAT area. BMI and VAT area were the important determinants of steatosis in both groups of participants with and without T2DM. Moreover, the VAT area was associated with the severity of hepatic steatosis and liver stiffness, independent of anthropometric measures of obesity.

CONCLUSION

VAT area is a major determinant of the severity of hepatic steatosis and liver stiffness in patient with T2DM.

Non-alcoholic Fatty Liver Disease and Steatohepatitis: Risk Factors and Pathophysiology

Non-alcoholic fatty liver disease (NAFLD) and its progressive subtype non-alcoholic steatohepatitis (NASH) are the most prevalent liver diseases, often leading to hepatocellular carcinoma (HCC). This review aims to describe the present knowledge of the risk factors responsible for the development of NAFLD and NASH. I performed a literature review identifying studies focusing on the complex pathogenic pathway and risk factors of NAFLD and steatohepatitis. The relationship between NAFLD and metabolic syndrome is well established and widely recognized. Obesity, dyslipidemia, type 2 diabetes, hypertension, and insulin resistance are the most common risk factors associated with NAFLD. Among the components of metabolic syndrome, current evidence strongly suggests obesity and type 2 diabetes as risk factors of NASH and HCC. However, other elements, namely gender divergences, ethnicity, genetic factors, participation of innate immune system, oxidative stress, apoptotic pathways, and adipocytokines, take a leading role in the onset and promotion of NAFLD. Pathophysiological mechanisms that are responsible for NAFLD development and subsequent progression to NASH are insulin resistance and hyperinsulinemia, oxidative stress, hepatic stellate cell (HSC) activation, cytokine/adipokine signaling pathways, and genetic and environmental factors. Major pathophysiological findings of NAFLD are dysfunction of adipose tissue through the enhanced flow of free fatty acids (FFAs) and release of adipokines, and altered gut microbiome that generate proinflammatory signals and cause NASH progression. Understanding the pathophysiology and risk factors of NAFLD and NASH; this review could provide insight into the development of therapeutic strategies and useful diagnostic tools.

Pelargonidin-3-O-Glucoside Encapsulated Pectin-Chitosan-Nanoliposomes Recovers Palmitic Acid-Induced Hepatocytes Injury

Pelargonidin-3-O-glucoside (Pg) is a well-known anthocyanin derivative possessing potential biological activity. Nonetheless, the bioactivity of Pg is limited due to instability in the physiological environment. Functionalized nanoliposomes using chitosan and/or pectin coating is an excellent carrier system for nanoencapsulation of food bioactive compounds such as Pg. Therefore, this study aimed to investigate the protective effect of Pg-loaded pectin–chitosan coated nanoliposomes against palmitic acid (PA)-induced hepatocytes injury in L02 cells. Firstly, Pg-loaded pectin–chitosan coated nanoliposomes were characterized using the DLS, HPLC, TEM, and cellular uptake study in L02 cells. Thereafter, we assayed the protective effect against PA-induced lipotoxicity, ROS and O₂^•− generation, mitochondrial dysfunction (MMP), and GSH depletion. Results showed that Pg-loaded nanoliposomes significantly reduced the PA-induced L02 cells toxicity via suppressing ROS production, O₂^•− generation, MMP collapse, and GSH reduction, whereas the free-Pg samples were not effective. On the contrary, the chitosan and/or pectin coated nanoliposomes showed higher results compared to coating-free nanoliposomes. Altogether, the results of our study ensured that Pg-loaded pectin–chitosan coated nanoliposomes was capable of reducing PA-induced hepatocytes injury. Thus, pectin–chitosan coated nanoliposomes can be useful for hepatocellular delivery of hydrophilic compounds with greater biological activity.

Psoralen Suppresses Lipid Deposition by Alleviating Insulin Resistance and Promoting Autophagy in Oleate-Induced L02 Cells

Non-alcoholic fatty liver disease (NAFLD) held a high global prevalence in recent decades. Hepatic lipid deposition is the major characteristic of NAFLD. We aim to explore the mechanisms of psoralen on lipid deposition in NAFLD. The effects of psoralen on insulin resistance, lipid deposition, the expression and membrane translocation of glucose transporter type 4 (GLUT4), autophagy, and lipogenesis enzymes were determined on sodium oleate-induced L02 cells. Chloroquine and 3-MA were employed. The AMP-activated protein kinase alpha (AMPKα) was knocked down by siRNA. Psoralen alleviated insulin resistance in sodium oleate-induced L02 hepatocytes by upregulating the expression and membrane translocation of GLUT4. Psoralen inhibited lipid accumulation by decreasing the expression of key lipogenesis enzymes. Psoralen promotes autophagy and the autophagic flux to enhance lipolysis. Psoralen promoted the fusion of the autophagosome with the lysosome. Both chloroquine and 3-MA blocked the effects of psoralen on autophagy and lipid accumulation. The AMPKα deficiency attenuated the effects of psoralen on autophagy and lipid accumulation. Our study demonstrated that as an antioxidant, psoralen attenuates NAFLD by alleviating insulin resistance and promoting autophagy via AMPK, suggesting psoralen to be a promising candidate for NAFLD.

Quantitative proteomics analysis based on tandem mass tag labeling coupled with labeling coupled with liquid chromatography-tandem mass spectrometry discovers the effect of silibinin on non-alcoholic fatty liver disease in mice

In recent years, the beneficial effects of silibinin (SIL) on nonalcoholic fatty liver disease (NAFLD) have attracted widespread attention. We tried to study the intervention effect of SIL on NAFLD, and explore the potential mechanisms and targets of SIL on NAFLD improvement. Thirty-three male C57BL6/J mice were divided into three groups, and, respectively, fed a normal diet (ND), a high-fat diet (HFD) or a HFD given SIL treatment (HFD+SIL). Biochemical indexes and histopathological changes of mice in each group were detected. In addition, quantitative proteomics analysis based on tandem mass tag (TMT) labeling coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and bioinformatics analysis was performed on protein changes in the livers. SIL could reduce the weight of mice, reduce liver lipid deposition, and improve glucose metabolism. Through comparison among the three experimental groups, a total of 30 overlapping proteins were found. These identified proteins were closely linked to liver lipid metabolism and energy homeostasis. Moreover, some drug targets were found, namely perilipin-2, phosphatidate phosphatase LPIN1, farnesyl pyrophosphate synthase, and glutathione S-transferase A1. In conclusions, high-fat diet increases the expressions of proteins implicated in lipid synthesis and transport in the liver, which can result in disorders of liver lipid metabolism. SIL can decrease liver lipid deposition and increase insulin sensitivity by regulating the expressions of these proteins. It not only improves the disorder of lipid metabolism in vivo, but also improves the disorder of glucose metabolism.

PERK prevents hepatic lipotoxicity by activating the p62-ULK1 axis-mediated noncanonical KEAP1-Nrf2 pathway

Hepatic lipotoxicity is a crucial factor in nonalcoholic steatohepatitis resulting from excessive saturated fatty acid-induced reactive oxygen species (ROS)-mediated cell death, which is associated with the accumulation of endoplasmic reticulum (ER) stress in the liver. The unfolded protein response (UPR) alleviates ER stress by restoring ER protein folding homeostasis. However, whether UPR contributes ROS elimination under lipotoxicity remains unclear. The Kelch like ECH-associated protein 1 (KEAP1)-nuclear factor, erythroid 2 like 2 (Nrf2) pathway provides antioxidant defense against lipotoxic stress by eliminating ROS and can be activated by the p62-Unc-51 like autophagy activating kinase 1 (ULK1) axis. However, the upstream molecular regulator of the p62-ULK1 axis-induced KEAP1-Nrf2 pathway in the same context remains unidentified. Here, we demonstrated that PKR-like ER kinase (PERK), a UPR sensor, directly phosphorylates p62 and ULK1, thereby activating the noncanonical KEAP1-Nrf2 pathway. We also elucidated the molecular mechanism underlying the PERK-mediated p62-ULK1 axis-dependent noncanonical KEAP1-Nrf2 pathway, which could represent a promising therapeutic strategy against hepatic lipotoxicity.

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Hepatic lipotoxicity is a crucial factor in the progression of NASH, associated with the increased ER stress.

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PERK, one of UPR sensors, activates noncanonical KEAP1-Nrf2 pathway by phosphorylating p62 at S351.

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PERK also phosphorylates ULK1 at S317, which mediates autophagic KEAP1 degradation and Nrf2 activation.

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PERK protects mouse liver against lipotoxicity via Nrf2 activation.

Emerging pharmacological treatment options for MAFLD

Metabolic dysfunction-associated fatty liver disease (MAFLD) prevalence and incidence is rising globally. It is associated with metabolic comorbidities, obesity, overweight, type 2 diabetes mellitus, and at least two metabolic risk factors, such as hypertension, hypertriglyceridemia, hypercholesterolemia, insulin resistance, and cardiovascular risk, increasing the risk of mortality. The excessive accumulation of fat comprises apoptosis, necrosis, inflammation and ballooning degeneration progressing to fibrosis, cirrhosis, and liver decompensations including hepatocellular carcinoma development. The limitation of approved drugs to prevent MAFLD progression is a paradigm. This review focuses on recent pathways and targets with evidence results in phase II/III clinical trials.

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.

Fatty acid metabolism and acyl-CoA synthetases in the liver-gut axis

Fatty acids are energy substrates and cell components which participate in regulating signal transduction, transcription factor activity and secretion of bioactive lipid mediators. The acyl-CoA synthetases (ACSs) family containing 26 family members exhibits tissue-specific distribution, distinct fatty acid substrate preferences and diverse biological functions. Increasing evidence indicates that dysregulation of fatty acid metabolism in the liver-gut axis, designated as the bidirectional relationship between the gut, microbiome and liver, is closely associated with a range of human diseases including metabolic disorders, inflammatory disease and carcinoma in the gastrointestinal tract and liver. In this review, we depict the role of ACSs in fatty acid metabolism, possible molecular mechanisms through which they exert functions, and their involvement in hepatocellular and colorectal carcinoma, with particular attention paid to long-chain fatty acids and small-chain fatty acids. Additionally, the liver-gut communication and the liver and gut intersection with the microbiome as well as diseases related to microbiota imbalance in the liver-gut axis are addressed. Moreover, the development of potentially therapeutic small molecules, proteins and compounds targeting ACSs in cancer treatment is summarized.

Utility of Metabolomic Biomarkers to Identify Nonalcoholic Fatty Liver Disease in Liver Transplant Recipients

Nonalcoholic fatty liver disease (NAFLD) is a rising indication for liver transplantation (LT). Identification of NAFLD recurrence and those at risk for more progressive disease after LT remains elusive as the diagnosis requires biopsy, which is invasive and impractical for serial monitoring. We therefore aimed to identify metabolites in the blood associated with recurrent NAFLD that could potentially be used for detection and monitoring.

Magnesium intake is inversely associated with risk of non-alcoholic fatty liver disease among American adults

PURPOSE

Human data are limited linking magnesium (Mg) intake to the risk of non-alcoholic fatty liver disease (NAFLD). We aimed to examine the association between Mg intake and the risk of NAFLD among young adults in the US with a 25-year follow-up.

METHODS

This study included 2685 participants from the Coronary Artery Risk Development in Young Adult (CARDIA) study. Diet and dietary supplements were assessed at baseline (1985-1986) and exam years 7 and 20 using an interview-based dietary history. NAFLD, defined as liver attenuation ≤ 51 Hounsfield Units excluding secondary causes of liver fat accumulation, was identified by non-contrast-computed tomography scanning at exam year 25. Multivariable-adjusted logistic regression model was used to examine the associations between cumulative average total intake of Mg (dietary plus supplemental) and NAFLD odds.

RESULTS

A total of 629 NAFLD cases were documented. After adjustment for potential confounders, an inverse association between total Mg intake and NAFLD odds was observed. Compared to participants in the lowest quintile of total Mg intake, the odds of NAFLD was 55% lower among individuals in the highest quintile [multivariable-adjusted odds ratio (OR) = 0.45, 95% confidence interval (CI) (0.23, 0.85), p for trend = 0.03]. Consistently, whole-grain consumption, a major dietary source of Mg, was inversely associated with NAFLD odds (p for trend = 0.02).

CONCLUSIONS

This study suggests that higher cumulative intake of Mg throughout adulthood is associated with lower odds of NAFLD in midlife. Future studies are needed to establish a possible causal relationship.

TLR2 inhibition ameliorates the amplification effect of LPS on lipid accumulation and lipotoxicity in hepatic cells

Background

Gut microbiome dysbiosis is related to the pathogenesis of nonalcoholic fatty liver disease (NAFLD), and the role of toll-like receptor 2 (TLR2) in its molecular mechanism is controversial. Here, we investigated the effects and mechanisms of Escherichia coli-derived lipopolysaccharide (LPS) on lipid accumulation and lipotoxicity in palmitic acid (PA)-treated L02 cell as an NAFLD cell model, and the role of TLR2 in this process.

Methods

Oil red O staining assay and free fatty acid (FFA) content test were performed to determine the effects of LPS on lipid accumulation in a PA-induced NAFLD cell model with or without TLR2 inhibition. The levels of IL-6 and TNF-α were measured to investigate inflammation conditions. Hoechst 33342 staining assay and Caspase-3 activity assay were used to test cell apoptosis, and the expression levels of proteins in the IRS1/PI3K/AKT signaling pathway, TLR2/MyD88/IKKα/NF-κB signaling pathway, and mitochondrion-dependent apoptotic signaling pathway were detected using Western blot.

Results

Lipid accumulation, pro-inflammatory cytokine release, and cell apoptosis with high levels were observed in the PA-induced NAFLD cell model, and LPS aggravated these processes. Whereas TLR2 inhibition could significantly ameliorate PA-induced and LPS-amplified lipid accumulation, inflammatory, and cell apoptosis, it had no significant effect on L02 cells treated with LPS alone.

Conclusions

These results were confirmed by activation or inhibition of the IRS1/PI3K/AKT signaling pathway, TLR2/MyD88/IKKα/NF-κB signaling pathway, and mitochondrion-dependent apoptotic signaling pathway, and were reflected by changes on their proteins expression. TLR2 is involved in PA-induced lipid accumulation and lipotoxicity in L02 cells, which could be aggravated by LPS, although LPS-induced amplification might not be through direct interaction with TLR2.

Cardiac-specific CGI-58 deficiency activates the ER stress pathway to promote heart failure in mice

Excess myocardial triacylglycerol accumulation (i.e., cardiac steatosis) impairs heart function, suggesting that enzymes promoting triacylglycerol metabolism exert essential regulatory effects on heart function. Comparative gene identification 58 (CGI-58) is a key enzyme that promotes the hydrolysis of triglycerides by activating adipose triglyceride lipase and plays a protective role in maintaining heart function. In this study, the effects of CGI-58 on heart function and the underlying mechanism were investigated using cardiac-specific CGI58-knockout mice (CGI-58cko mice). Echocardiography and pathological staining were performed to detect changes in the structure and function of the heart. Proteomic profiling, immunofluorescent staining, western blotting, and real-time PCR were used to evaluate molecular changes. In CGI-58cko mice, we detected cardiac hypertrophic remodeling and heart failure associated with excessive cardiac lipid accumulation, ROS production, and decreased expression of regulators of fatty acid metabolism. These changes were markedly attenuated in CGI-58cko mice injected with rAAV9-CGI58. A quantitative proteomics analysis revealed significant increases in the expression of ER stress-related proteins and decreases in proteins related to fatty acid and amino acid metabolism in the hearts of CGI-58cko mice. Furthermore, the inhibition of ER stress by the inhibitor 4-PBA improved mitochondrial dysfunction, reduced oxidative stress, and reversed cardiac remodeling and dysfunction in cultured cardiomyocytes or in CGI-58cko mice. Our results suggested that CGI-58 is essential for the maintenance of heart function by reducing lipid accumulation and ER stress in cardiomyocytes, providing a new therapeutic target for cardiac steatosis and dysfunction.

Impact of Dietary Fat on the Progression of Liver Fibrosis: Lessons from Animal and Cell Studies

Previous studies have revealed that a high-fat diet is one of the key contributors to the progression of liver fibrosis, and increasing studies are devoted to analyzing the different influences of diverse fat sources on the progression of non-alcoholic steatohepatitis. When we treated three types of isocaloric diets that are rich in cholesterol, saturated fatty acid (SFA) and trans fatty acid (TFA) with hepatitis C virus core gene transgenic mice that spontaneously developed hepatic steatosis without apparent fibrosis, TFA and cholesterol-rich diet, but not SFA-rich diet, displayed distinct hepatic fibrosis. This review summarizes the recent advances in animal and cell studies regarding the effects of these three types of fat on liver fibrogenesis.

Beyond the X Factor: Relevance of Sex Hormones in NAFLD Pathophysiology

Non-alcoholic fatty liver disease (NAFLD) is a major health issue worldwide, being frequently associated with obesity, unbalanced dietary regimens, and reduced physical activity. Despite their greater adiposity and reduced physical activity, women show a lower risk of developing NAFLD in comparison to men, likely a consequence of a sex-specific regulation of liver metabolism. In the liver, sex differences in the uptake, synthesis, oxidation, deposition, and mobilization of lipids, as well as in the regulation of inflammation, are associated with differences in NAFLD prevalence and progression between men and women. Given the major role of sex hormones in driving hepatic sexual dimorphism, this review will focus on the role of sex hormones and their signaling in the regulation of hepatic metabolism and in the molecular mechanisms triggering NAFLD development and progression.

Dietary consumption and serum pattern of bioactive fatty acids in NAFLD patients

INTRODUCTION AND OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome. Some dietary fatty acids have showed different bioactive functions in metabolic syndrome. The aim of this study is to determine the dietary consumption patterns and serum percentage of bioactive fatty acids in NAFLD patients.

PATIENTS AND METHODS

Cross-sectional study with NAFLD patients and non-NAFLD patients. Dietary consumption of bioactive fatty acids was assessed by a food frequency questionnaire. NAFLD and liver fibrosis were diagnosed by transient elastography. The identification of serum bioactive fatty acids was achieved by gas chromatography-mass spectrometry (%). Bioactive fatty acids consumption was correlated with NAFLD clinical characteristics with the Spearman correlation analysis.

RESULTS

A total of 299 patients were included, whose mean of age and body mass index were 44.2±9.9 years and 25.9±3.8kg/m², respectively. The consumption of bioactive fatty acids was no different regarding the presence of NAFLD; however, the consumption of stearic and linoleic fatty acids was higher in relation with NAFLD severity (p≤0.05). The consumption of myristic acid was higher in patients with fibrosis (p=0.02). Serum percentage and dietary consumption did not show correlations.

CONCLUSION

Dietary consumption of bioactive fatty acids is different according to NAFLD severity. Individualized diets according to NAFLD severity could be successful in order to prevent liver injury-related outcomes.

[Parathyroid hormone-related protein aggravates nonalcoholic fatty liver disease induced by methionine choline-deficient diet in mice]

OBJECTIVE

To study the effect of parathyroid hormone-related protein (PTHrP) on nonalcoholic fatty liver disease (NAFLD) induced by methionine choline-deficient diet (MCD) in mice.

METHODS

Twelve male C57BL/6J mice were randomized into blank control group, vehicle group and PTHrP group (n=4). The mice in vehicle group and PTHrP group received injections of a control adeno-associated virus (AAV) vector and an AVV vector carrying PTHrP (AAV-PTHrP) gene, respectively, followed one week later by MCD feeding for 3 weeks; the mice in the blank control were fed a normal diet for 4 weeks. Body weight changes of the mice were monitored during the experiment. At the end of the experiment, liver tissues were harvested from the mice for histological analysis using HE staining, oil red O staining, and Sirius red staining. The levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglyceride, and free fatty acids (FFAs) in the liver and serum were detected to assess hepatic impairment and lipid metabolism of the mice. Cell models of NAFLD were established in mouse and human normal liver cells by treatment with 250 μmol/L FFAs for 24 h, and the effect of AAV-PTHrP on lipid deposition and viability of the cells were tested using Oil Red O and Nile red staining and CCK8 assay.

RESULTS

Treatment with AAV-PTHrP, as compared with the control AVV vector, caused more rapid reduction of body weight in mice with MCD feeding and significantly increased the levels of AST (P < 0.05), ALT (P < 0.05), triglyceride (P < 0.01) and FFA (P < 0.05) in the liver and the scores of NAS (P < 0.01) and SAF (P < 0.05). HE and Oil red O staining of the liver tissue revealed obvious lipid deposition after MCD feeding, which was more serious in PTHrP group. In the cell experiment, FFAs induced steatosis in both mouse and human hepatocytes, and treatment with PTHrP increased the accumulation of lipid droplets and lowered the viability of the cell model of NAFLD (P < 0.01 or 0.05).

CONCLUSION

PTHrP may aggravate MCD-induced NAFLD in mice by promoting the deposition of lipid droplets in the hepatocytes.

A network pharmacology approach: Inhibition of the NF-κB signaling pathway contributes to the NASH preventative effect of an Oroxylum indicum seed extract in oleic acid-stimulated HepG2 cells and high-fat diet-fed rats

BACKGROUND

The incidence of nonalcoholic fatty liver disease (NAFLD), especially nonalcoholic steatohepatitis (NASH), has significantly increased in recent years and has become an important public health issue. However, no U.S. Food and Drug Administration (FDA)-approved first-line drug is currently available for the treatment of NAFLD and NASH; therefore, research on new drugs is currently a hot topic. Oroxylum indicum (Linn.) Kurz is extensively distributed in South China and South Asia and has many biological activities. However, its effects on NAFLD or even NASH and the corresponding mechanisms are still not clear.

PURPOSE

To investigate the effect and mechanism of O. indicum seed extract (OISE) on preventing anti-inflammatory action in the progression from simple nonalcoholic fatty liver (NAFL) to NASH.

METHODS

A network pharmacology method to construct ingredient-target networks and the protein-protein interaction (PPI) network of OISE in NASH were constructed for topological analyses and hub-target screening. Enrichment analyses were performed to identify the critical biological processes and signaling pathways. Simultaneously, in vitro and in vivo experiments investigated the effect and mechanism of OISE, baicalein, and chrysin on inflammation by biochemical indicator detection, luciferase reporters, pathological staining, and immunoblotting in oleic acid-stimulated HepG2 cells or in high-fat diet-fed rats.

RESULTS

The network pharmacology showed that OISE prevented the development and progression of NAFL into NASH through various pathways and targets and that the nuclear factor NF-κB (NF-κB) pathway regulated by baicalein and chrysin played an important role in the treatment of NASH. In in vitro experiments, we further showed that OISE and its ingredients, namely, baicalein and chrysin, all improved the inflammatory status in oleic acid-stimulated HepG2 cells, inhibited the nuclear transcriptional activities of NF-κB, increased the IκB level, and decreased the phosphorylation level of NF-κB. Furthermore, in a high-fat diet-induced NASH model in rats, we also showed that OISE prevented the development and progression of NASH by inhibiting the nuclear transcriptional activity of NF-κB.

CONCLUSION

OISE suppressed inflammatory responses and prevented the development and progression of NAFL into NASH through inhibition of the nuclear transcriptional activity of NF-κB. OISE may be used to treat NAFLD through many functions, including an increase in insulin sensitivity, a decrease in lipid accumulation in the liver, suppression of inflammation, and clearance of free radicals.

Dysregulation of autophagy acts as a pathogenic mechanism of non-alcoholic fatty liver disease (NAFLD) induced by common environmental pollutants

Non-alcoholic fatty liver disease (NAFLD) has been the most common chronic liver disease in the world, including the developing countries. NAFLD is metabolic disease with significant lipid deposition in the hepatocytes of the liver, which is usually associated with oxidative stress, inflammation and fibrogenesis, and insulin resistance. Progressive NAFLD can develop into non-alcoholic steatohepatitis (NASH) or hepatocellular carcinoma. The current evidence proposes that environmental pollutants promote development and progression of NAFLD, and autophagy plays a vital role but is multifactorial affected in NAFLD. In this review, we analyzed on the regulations of common environmental pollutants on autophagy in NAFLD. To clarify the involved roles of autophagy, we discussed the dysregulation of autophagy by environmental pollutants in adipose tissue and gut, and their interactions with liver, as well as epigenetic regulation on autophagy by environmental pollutants. Furthermore, protective roles of potential therapeutic treatments on the multiple-hits of autophagy in NAFLD were descripted.

Suppression of palmitic acid-induced hepatic oxidative injury by neohesperidin-loaded pectin-chitosan decorated nanoliposomes

The biological activity of neohesperidin (NH, a flavanone glycoside) is limited due to instability in the physiological environment. Thus, the current study aimed to explore the protective effect of NH-loaded pectin-chitosan decorated liposomes (P-CH-NH-NL) against palmitic acid (PA)-induced hepatic oxidative injury in L02 cells. The particles were characterized using DLS, TEM, HPLC, DSC, and cellular uptake study. Then, the protective effect of NH-loaded liposomal systems (NH-NLs) against PA-induced oxidative injury was evaluated in terms of cell viability study, intracellular ROS, superoxide ions (O₂^-), MMP, and cellular GSH determination. Our results exhibited that NH-NLs significantly lessened the PA-induced hepatic oxidative injury in L02 cells via decreasing ROS and O₂^- generation, reducing MMP collapse, and attenuating GSH reduction, whereas the free NH samples were ineffective. Furthermore, the coated NH-NLs were more effective than that of uncoated nanoliposome. Overall, our study confirmed that P-CH-NH-NL was capable of reducing PA-induced hepatic oxidative injury. Therefore, the pectin-chitosan decorated nanoliposome can be considered as an efficient delivery system for enhancing cellular uptake of lipophilic compound with controlled release and greater biological activity.

Distinct Dose-Dependent Association of Free Fatty Acids with Diabetes Development in Nonalcoholic Fatty Liver Disease Patients

BACKGROUND

Excessive delivery of free fatty acids (FFAs) to the liver promotes steatosis and insulin resistance (IR), with IR defined as reduced glucose uptake, glycogen synthesis and anti-lipolysis stimulated by normal insulin levels. Whether the associations between FFAs and diabetes development differ between patients with and without nonalcoholic fatty liver disease (NAFLD) remains unclear.

METHODS

Consecutive subjects (2,220 NAFLD subjects and 1,790 non-NAFLD subjects according to ultrasound imaging) were enrolled from the First Affiliated Hospital of Sun Yat-sen University between 2009 and 2019. The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated.

RESULTS

There was an approximate J-shaped relationship between FFA levels and HOMA-IR in the NAFLD group. Higher FFA concentration quartiles were associated with higher risks of IR (odds ratio [OR], 9.24; 95% confidence interval [CI], 6.43 to 13.36), prediabetes (OR, 10.48; 95% CI, 5.66 to 19.39), and type 2 diabetes mellitus (T2DM; OR, 19.43; 95% CI, 12.75 to 29.81) in the NAFLD group but not in the non-NAFLD group. The cut-off points for the FFA levels increased in a stepwise manner in discriminating IR, prediabetes and T2DM (573, 697, and 715 μmol/L) in the NAFLD group but not in non-NAFLD individuals.

CONCLUSION

A distinct dose-dependent relationship of FFA levels was found with IR, prediabetes and T2DM in NAFLD patients. Screening serum FFA levels in NAFLD patients would be valuable in preventing diabetes development.

Non-alcoholic fatty liver disease: An overview of risk factors, pathophysiological mechanisms, diagnostic procedures, and therapeutic interventions

Non-alcoholic fatty liver disease (NAFLD) is a disorder of excessive fat accumulation in the liver, known as steatosis, without alcohol overconsumption. NAFLD can either manifest as simple steatosis or steatohepatitis, known as non-alcoholic steatohepatitis (NASH), which is accompanied by inflammation and possibly fibrosis. Furthermore, NASH might progress to hepatocellular carcinoma. NAFLD and NASH prevalence is in a continuous state of growth, and by 2018, NAFLD became a devastating metabolic disease with a global pandemic prevalence. The pathophysiology of NAFLD and NASH is not fully elucidated, but is known to involve the complex interplay between different metabolic, environmental, and genetic factors. In addition, unhealthy dietary habits and pre-existing metabolic disturbances together with other risk factors predispose NAFLD development and progression from simple steatosis to steatohepatitis, and eventually to fibrosis. Despite their growing worldwide prevalence, to date, there is no FDA-approved treatment for NAFLD and NASH. Several off-label medications are used to target disease risk factors such as obesity and insulin resistance, and some medications are used for their hepatoprotective effects. Unfortunately, currently used medications are not sufficiently effective, and research is ongoing to investigate the beneficial effects of different drugs and phytochemicals in NASH. In this review article, we outline the different risk factors and pathophysiological mechanisms involved in NAFLD, diagnostic procedures, and currently used management techniques.

Role of HO-1 against Saturated Fatty Acid-Induced Oxidative Stress in Hepatocytes

Increased circulating levels of free fatty acids, especially saturated ones, are involved in disease progression in the non-alcoholic fatty liver. Although the mechanism of saturated fatty acid-induced toxicity in the liver is not fully understood, oxidative stress may be deeply involved. We examined the effect of increased palmitic acid, the most common saturated fatty acid in the blood, on the liver of BALB/c mice via tail vein injection with palmitate. After 24 h, among several anti-oxidative stress response genes, only heme oxygenase-1 (HO-1) was significantly upregulated in palmitate-injected mice compared with that in vehicle-injected mice. Elevation of HO-1 mRNA was also observed in the fatty liver of high-fat-diet-fed mice. To further investigate the role of HO-1 on palmitic acid-induced oxidative stress, in vitro experiments were performed to expose palmitate to HepG2 cells. SiRNA-mediated knockdown of HO-1 significantly increased the oxidative stress induced by palmitate, whereas pre-treatment with SnCl₂, a well-known HO-1 inducer, significantly decreased it. Moreover, SB203580, a selective p38 inhibitor, reduced HO-1 mRNA expression and increased palmitate-induced oxidative stress in HepG2 cells. These results suggest that the HO-1-mediated anti-oxidative stress compensatory reaction plays an essential role against saturated fatty acid-induced lipotoxicity in the liver.

Endoplasmic reticulum stress as the basis of obesity and metabolic diseases: focus on adipose tissue, liver, and pancreas

Obesity challenges lipid and carbohydrate metabolism. The resulting glucolipotoxicity  causes endoplasmic reticulum (ER) dysfunction, provoking the accumulation of immature proteins, which triggers the unfolded protein reaction (UPR) as an attempt to reestablish ER homeostasis. When the three branches of UPR fail to correct the unfolded/misfolded proteins, ER stress happens. Excessive dietary saturated fatty acids or fructose exhibit the same impact on the ER stress, induced by excessive ectopic fat accumulation or rising blood glucose levels, and meta-inflammation. These metabolic abnormalities can alleviate through dietary interventions. Many pathways are disrupted in adipose tissue, liver, and pancreas during ER stress, compromising browning and thermogenesis, favoring hepatic lipogenesis, and impairing glucose-stimulated insulin secretion within pancreatic beta cells. As a result, ER stress takes part in obesity, hepatic steatosis, and diabetes pathogenesis, arising as a potential target to treat or even prevent metabolic diseases. The scientific community seeks strategies to alleviate ER stress by avoiding inflammation, apoptosis, lipogenesis suppression, and insulin sensitivity augmentation through pharmacological and non-pharmacological interventions. This comprehensive review aimed to describe the contribution of excessive dietary fat or sugar to ER stress and the impact of this adverse cellular environment on adipose tissue, liver, and pancreas function.

Maternal and Postnatal High Linoleic Acid Diet Impacts Lipid Metabolism in Adult Rat Offspring in a Sex-Specific Manner

Linoleic acid (LA), an n-6 polyunsaturated fatty acid (PUFA), is essential for fetal growth and development. We aimed to investigate the effect of maternal and postnatal high LA (HLA) diet on plasma FA composition, plasma and hepatic lipids and genes involved in lipid metabolism in the liver of adult offspring. Female rats were fed with low LA (LLA; 1.44% LA) or HLA (6.21% LA) diets for 10 weeks before pregnancy, and during gestation/lactation. Offspring were weaned at postnatal day 25 (PN25), fed either LLA or HLA diets and sacrificed at PN180. Postnatal HLA diet decreased circulating total n-3 PUFA and alpha-linolenic acid (ALA), while increased total n-6 PUFA, LA and arachidonic acid (AA) in both male and female offspring. Maternal HLA diet increased circulating leptin in female offspring, but not in males. Maternal HLA diet decreased circulating adiponectin in males. Postnatal HLA diet significantly decreased aspartate transaminase (AST) in females and downregulated total cholesterol, HDL-cholesterol and triglycerides in the plasma of males. Maternal HLA diet downregulated the hepatic mRNA expression of Hmgcr in both male and female offspring and decreased the hepatic mRNA expression of Cpt1a and Acox1 in females. Both maternal and postnatal HLA diet decreased hepatic mRNA expression of Cyp27a1 in females. Postnatal diet significantly altered circulating fatty acid concentrations, with sex-specific differences in genes that control lipid metabolism in the adult offspring following exposure to high LA diet in utero.

Obesity-induced upregulation of microRNA-183-5p promotes hepatic triglyceride accumulation by targeting the B-cell translocation gene 1

AIMS

Obesity is recognized as a risk factor for many metabolic disorders, particularly nonalcoholic fatty liver disease (NAFLD). However, the underlying mechanism is still poorly understood. Several lines of evidence indicate that microRNA (miRNA) is a key regulator of lipid metabolism. In this study, we investigated the role of miR-183-5p in the development of NAFLD.

METHODS

The expression levels of miR-183-5p and B-cell translocation gene 1 (Btg1) were determined by quantitative real-time PCR and histological analysis in livers of obese mice and cell models induced with palmitic acid (PA), respectively. AML12 cells were treated with PA in the presence or absence of miR-183-5p mimics or inhibitor. Moreover, a Luciferase reporter assay was used to determine whether Btg1 is the direct target of miR-183-5p. Protein levels of BTG1 were estimated using western blotting.

KEY FINDINGS

Expression of miR-183-5p was increased in the livers of three murine models and also in the AML12 cell model. Overexpression of miR-183-5p in the cell model and mice led to hepatic triglyceride (TG) accumulation and upregulation of lipogenic genes, whereas inhibition of miR-183-5p in the cell model improved hepatic TG accumulation. Mechanistically, we further identified Btg1 as a direct target gene of miR-183-5p.

SIGNIFICANCE

Our findings revealed that miR-183-5p affected the regulation of hepatic TG homeostasis, which may provide a potential therapeutic target for hepatosteatosis.