Reduction of lipid accumulation in HepG2 cells by luteolin is associated with activation of AMPK and mitigation of oxidative stress

Screening of Lipid-Reducing Activity and Cytotoxicity of the Exometabolome from Cyanobacteria

Cyanobacteria are rich producers of secondary metabolites, excreting some of these to the culture media. However, the exometabolome of cyanobacteria has been poorly studied, and few studies have dwelled on its characterization and bioactivity assessment. In this work, exometabolomes of 56 cyanobacterial strains were characterized by HR-ESI-LC-MS/MS. Cytotoxicity was assessed on two carcinoma cell lines, HepG2 and HCT116, while the reduction in lipids was tested in zebrafish larvae and in a steatosis model with fatty acid-overloaded human liver cells. The exometabolome analysis using GNPS revealed many complex clusters of unique compounds in several strains, with no identifications in public databases. Three strains reduced viability in HCT116 cells, namely Tolypotrichaceae BACA0428 (30.45%), Aphanizomenonaceae BACA0025 (40.84%), and Microchaetaceae BACA0110 (46.61%). Lipid reduction in zebrafish larvae was only observed by exposure to Dulcicalothrix sp. BACA0344 (60%). The feature-based molecular network shows that this bioactivity was highly correlated with two flavanones, a compound class described in the literature to have lipid reduction activity. The exometabolome characterization of cyanobacteria strains revealed a high chemodiversity, which supports it as a source for novel bioactive compounds, despite most of the time being overlooked.

Combination of transcriptomic and proteomic approaches helps unravel the mechanisms of luteolin in inducing liver cancer cell death via targeting AKT1 and SRC

Introduction

Luteolin, a natural compound commonly used in traditional Chinese medicine, shows clinical potential as an anti-liver cancer agent. The mechanisms underlying the anti-liver cancer effect of luteolin are limited versus those reported for other cancers. Accordingly, this study was conducted to bridge the existing knowledge gap.

Methods

Transcriptomic and proteomic analyses of the response of the hepatocellular carcinoma cell line HuH-7 to luteolin were conducted, and a possible pathway was elucidated using confocal laser scanning microscopy (CLSM), flow cytometry, western blotting, qRT-PCR and bio-layer interferometry assay to systematically explore the possible mechanisms underlying the inhibition of the proliferation of liver cancer cells by luteolin.

Results and Discussion

Results showed that luteolin significantly inhibited HuH-7 cell proliferation. Transcriptomic and proteomic analyses collectively revealed that luteolin could promote cell cycle arrest and apoptosis in HuH-7 cells through transcription factors p53, nuclear factor kappa B (NF-κB), FOXO, ATF2, and TCF/LEF via AKT1, as well as the KEAP-NRF and SRC-STAT3 pathways. Furthermore, AKT1 and SRC were identified as the 2 targets of luteolin. Nuclear translocation of transcription factors p53 and NF-κB were affected by luteolin administration. Additionally, AKT1 activity affected normal metabolism in HuH-7 cells and resulted in the accumulation of reactive oxygen species, which activated MOMP and further promoted apoptosis. Our results systematically elucidate the mechanism of luteolin in inhibiting the proliferation of liver cancer cells, mainly through cell cycle arrest and apoptosis via targeting AKT1 and SRC.

Sustainable production of multimeric and functional recombinant human adiponectin using genome-edited chickens

BACKGROUND

Adiponectin (ADPN) plays a critical role in endocrine and cardiovascular functions, but traditional production methods, such as Escherichia coli and mammalian systems, have faced challenges in generating sufficiently active middle molecular weight (MMW) and high molecular weight (HMW) forms of recombinant human ADPN (hADPN). In our previous study, we proposed genome-edited chickens as an efficient platform for producing multimeric hADPN. However, the consistency of multimeric hADPN expression in this system across generations had not been further investigated.

RESULTS

In this study, subsequent generations of ovalbumin (OVA) ADPN knock-in chickens showed stable multimeric hADPN production, yielding ~ 26% HMW ADPN (0.59 mg/mL) per hen. Comparative analysis revealed that egg white (EW)-derived hADPN predominantly consisted of hexameric and HMW forms, similar to serum-derived hADPN. In contrast, hADPN obtained from human embryonic kidney (HEK) 293 and High-Five (Hi-5) cells also exhibited the presence of trimers, indicating variability across different production systems. Furthermore, transcriptional expression analysis of ADPN multimerization-associated endoplasmic reticulum chaperone genes (Ero1-Lα, DsbA-L, ERP44, and PDI) indicated upregulation in the oviduct magnum of ADPN KI hens, suggesting the chicken oviduct magnum as the optimal site for HMW ADPN production. Lastly, the functional analysis demonstrated that EW-derived hADPN significantly reduced lipid droplets and downregulated lipid accumulation-related genes (LOX-1, AT1R, FAS, and FABP4) in human umbilical vein endothelial cells (HUVECs).

CONCLUSION

In summary, stable and functional multimeric hADPN can be produced in genome-edited chickens even after generations. This highlights the potential of using chicken bioreactor for producing various high-value proteins.

Hepatic polypeptide nutrient solution improves high-cholesterol diet-induced rats with nonalcoholic fatty liver disease by activating AMP-activated protein kinase signaling pathway

Hepatic polypeptide nutrient solution (HP) is a mixture of hepatoprotective peptides derived from fresh porcine liver with various effects. However, the role and mechanisms of HP in nonalcoholic fatty liver disease (NAFLD) are still not well understood. We investigated the effects of HP NAFLD rats induced by high-cholesterol diet (HCD) and its underlying mechanisms. Rats were provided with HCD for 4 weeks and then received HP or metformin after 2 weeks of HCD feeding. The study found that HP reduced cholesterol and triglyceride levels in rats with NAFLD (all p < .05). Histopathological examination also showed that HP improved the liver lesions induced by the HCD diet. Furthermore, the oxidative stress and inflammatory responses of NAFLD rats treated with HP were also improved. In addition, it was discovered that HP triggered the activation of AMPK and decreased the expression of SREBP-1c and FAS while enhancing the expression of PPAR α and CPT-1 in liver. These findings indicated that HP might have therapeutic potential for NAFLD, possibly via activating AMPK signaling pathway.

Characterization of palmitic acid toxicity induced insulin resistance in HepG2 cells

BACKGROUND

An etiology of palmitic acid (PA) induced insulin resistance (IR) is complex for which two mechanisms are proposed namely ROS induced JNK activation and lipid induced protein kinase-C (PKCε) activation. However, whether these mechanisms act alone or in consortium is not clear.

METHODS AND RESULTS

In this study, we have characterized PA induced IR in liver cells. These cells were treated with different concentrations of PA for either 8 or 16 h. Insulin responsiveness of cells treated with PA for 8 h was found to be same as that of control. However, cells treated with PA for 16 h, showed increased glucose output both in the presence and in absence of insulin only at higher concentrations, indicating development of IR. In these, both JNK and PKCε were activated in response to increased ROS and lipid accumulation, respectively. Activated JNK and PKCε phosphorylated IRS1 at Ser-307 resulting in inhibition of AKT which in turn inactivated GSK3β, leading to reduced glycogen synthase activity. Inhibition of AKT also reduced insulin suppression of hepatic gluconeogenesis by activating Forkhead box protein O1 (FOXO1) and increased expression of the gluconeogenic enzymes and their transcription factors.

CONCLUSION

Thus, our data clearly demonstrate that both these mechanisms work simultaneously and more importantly, identified a threshold of HepG2 cells, which when crossed led to the pathological state of IR in response to PA.

Luteolin prevents TNF-α-induced NF-κB activation and ROS production in cultured human placental explants and endothelial cells

INTRODUCTION

Preeclampsia (PE) is a serious hypertensive pregnancy disorder and a leading cause of maternal and perinatal morbidity and mortality. Despite the prevalence and complications, there are no approved therapeutics to relieve PE symptoms. Inflammation, oxidative stress, and angiogenic imbalance have been shown to contribute to the PE pathophysiology, though there is a lack of understanding in how best to target these pathways in PE. We recently demonstrated that the bioflavonoid luteolin is a potent inhibitor of the anti-angiogenic and pro-hypertensive soluble fms-like tyrosine kinase 1 (sFlt-1), and here we aimed to determine if luteolin was also capable of reducing inflammation and oxidative stress pathways.

METHODS

Tumor necrosis factor (TNF)-α, which is upregulated in PE, was utilized to stimulate these pathways in human placental explants and endothelial cells. Endothelin-1 (ET-1) and interleukin (IL)-6 in the media from explants and cells were measured via ELISA, and NF-κB localization and reactive oxygen species were detected via fluorescence microscopy.

RESULTS

Pretreatment with luteolin demonstrated significant reductions in NF-κB activation, reactive oxygen species, superoxide, and IL-6 and ET-1 expression in endothelial cells. We also saw a significant reduction in phosphorylation of NF-κB in human placental explants.

DISCUSSION

These data demonstrate that luteolin inhibits pathways implicated in the development of PE and should be explored further for its potential as a PE therapeutic.

Targeted Delivery of Celastrol via Chondroitin Sulfate Derived Hybrid Micelles for Alleviating Symptoms in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is caused by an accumulation of excess fat in the liver leading to oxidative stress and liver cell injury, as well as overproduction of inflammatory cytokines. CD44 has been identified as a potential therapeutic target in the development of NAFLD to nonalcoholic steatohepatitis. Here, chondroitin sulfate (CS) is selected to construct a CD44-targeted delivery system for the treatment of NAFLD. Specifically, two CS-derived amphiphilic materials including CS conjugated with either 4-aminophenylboronic acid pinacol ester (CS-PBE) or phenformin (CS-PFM) were synthesized, respectively. The presence of PBE moieties on CS-PBE rendered the vehicle with enhanced loading capacity and scavenging potential against reactive oxygen species, while the presence of guanidine moieties on CS-PFM enhanced the internalization of vehicles in the differentiated hepatocytes. Next, celastrol (CLT) was encapsulated in the hybrid micelle to afford CS-Hybrid/CLT, which demonstrates sufficient stability, enhanced cellular uptake efficiencies in differentiated HepG2 cells, and therapeutic potential to alleviate lipid accumulation in differentiated HepG2 cells. In a high-fat-diet-induced NAFLD rat model, CS-Hybrid/CLT micelles demonstrated the capacity to dramatically decrease hepatic lipid accumulation and free fatty acid levels with greatly improved pathologic liver histology and downregulated hepatic inflammation levels. These results suggest that CS-based amphiphilic micelles may offer a promising strategy to effectively deliver therapeutic cargos to the liver for the treatment of NAFLD.

Modulation of PPAR-γ, SREBP-1c and inflammatory mediators by luteolin ameliorates β-cell dysfunction and renal damage in a rat model of type-2 diabetes mellitus

BACKGROUND

Natural products have been recommended as a complementary therapy for type 2 diabetes mellitus (T2DM) due to constraints of safety and tolerability of existing anti-diabetic agents. Luteolin exhibits anti-diabetic and anti-inflammatory effects. Hence, the impact of luteolin on glucose homoeostasis and organ damage was investigated in high-fat diet (HFD) and streptozotocin (STZ) induced T2DM in rats.

METHODS AND RESULTS

Male Wistar rats were maintained on HFD (provided 55% energy as fat) for 10 days. Subsequently, a single dose of 40 mg/kg STZ was injected intraperitoneally on the 11th day. Seventy-two hours after STZ administration, diabetic rats with established hyperglycemia (fasting serum glucose > 200 mg/dL) were randomized into different groups having six rats each and orally administered either 0.5% hydroxy propyl cellulose or pioglitazone (10 mg/kg) or luteolin (50 mg/kg or 100 mg/kg) once daily for 28 days, while continuing HFD for respective groups. Luteolin significantly reduced hyperglycaemia, homoeostasis model assessment (HOMA) of insulin resistance (HOMA-IR) levels, and improved hypoinsulinemia and HOMA of b-cell function (HOMA-B) in a dose-dependent manner. Increased TNF-α, IL-6 and NFκB levels in diabetic rats were significantly regulated. Additionally, luteolin significantly augmented PPAR-γ expression while attenuating sterol regulatory element binding protein-1c (SREBP-1c) expression. Histopathological scrutiny validated that luteolin effectively attenuated HFD-STZ-induced injury in pancreatic β-cells and kidneys to near normalcy.

CONCLUSION

Our study showed that luteolin ameliorated hyperglycemia and improved hypoinsulinemia, β-cell dysfunction, and renal impairment in HFD-STZ-induced diabetic rats by attenuating inflammation and dysregulated cytokine secretion through modulation of PPAR-γ, TNF-α, IL-6 and NF-kB expression and down-regulation of SREBP-1c.

DNA damage resulting from human endocrine disrupting chemical exposure: Genotoxicity, detection and dietary phytochemical intervention

In recent years, exposure to endocrine disrupting chemicals (EDCs) has posed an increasing threat to human health. EDCs are major risk factors in the occurrence and development of many diseases. Continuous DNA damage triggers severe pathogenic consequences, such as cancer. Beyond their effects on the endocrine system, EDCs genotoxicity is also worthy of attention, owing to the high accessibility and bioavailability of EDCs. This review investigates and summarizes nearly a decade of DNA damage studies on EDC exposure, including DNA damage mechanisms, detection methods, population marker analysis, and the application of dietary phytochemicals. The aims of this review are (1) to systematically summarize the genotoxic effects of environmental EDCs (2) to comprehensively summarize cutting-edge measurement methods, thus providing analytical solutions for studies on EDC exposure; and (3) to highlight critical data on the detoxification and repair effects of dietary phytochemicals. Dietary phytochemicals decrease genotoxicity by playing a major role in the detoxification system, and show potential therapeutic effects on human diseases caused by EDC exposure. This review may support research on environmental toxicology and alternative chemo-prevention for human EDC exposure.

Bioflavonoid luteolin prevents sFlt-1 release via HIF-1α inhibition in cultured human placenta

Preeclampsia (PE) is a serious hypertensive complication of pregnancy and is a leading cause of maternal death and major contributor to maternal and perinatal morbidity, including establishment of long-term complications. The continued prevalence of PE stresses the need for identification of novel treatments which can target prohypertensive factors implicated in the disease pathophysiology, such as soluble fms-like tyrosine kinase 1 (sFlt-1). We set out to identify novel compounds to reduce placental sFlt-1 and determine whether this occurs via hypoxia-inducible factor (HIF)-1α inhibition. We utilized a commercially available library of natural compounds to assess their ability to reduce sFlt-1 release from primary human placental cytotrophoblast cells (CTBs). Human placental explants from normotensive (NT) and preeclamptic (PE) pregnancies were treated with varying concentrations of luteolin. Protein and mRNA expression of sFlt-1 and upstream mediators were evaluated using ELISA, western blot, and real-time PCR. Of the natural compounds examined, luteolin showed the most potent inhibition of sFlt-1 release, with >95% reduction compared to vehicle-treated. Luteolin significantly inhibited sFlt-1 in cultured placental explants compared to vehicle-treated in a dose- and time-dependent manner. Additionally, significant decreases in HIF-1α expression were observed in luteolin-treated explants, suggesting a mechanism for sFlt-1 downregulation. The ability of luteolin to inhibit HIF-1α may be mediated through the Akt pathway, as inhibitors to Akt and its upstream regulator phosphatidylinositol-3 kinase (PI3K) resulted in significant HIF-1α reduction. Luteolin reduces anti-angiogenic sFlt-1 through inhibition of HIF-1α, making it a novel candidate for the treatment of PE.

The great potential of flavonoids as candidate drugs for NAFLD

Non-alcoholic fatty liver disease (NAFLD) has a global prevalence of approximately 25 % and is associated with high morbidity and high mortality. NAFLD is a leading cause of cirrhosis and hepatocellular carcinoma. Its pathophysiology is complex and still poorly understood, and there are no drugs used in the clinic to specifically treat NAFLD. Its pathogenesis involves the accumulation of excess lipids in the liver, leading to lipid metabolism disorders and inflammation. Phytochemicals with the potential to prevent or treat excess lipid accumulation have recently received increasing attention, as they are potentially more suitable for long-term use than are traditional therapeutic compounds. In this review, we summarize the classification, biochemical properties, and biological functions of flavonoids and how they are used in the treatment of NAFLD. Highlighting the roles and pharmacological uses of these compounds will be of importance for enhancing the prevention and treatment of NAFLD.

One new furostane saponin from Allium ramosum and lipid accumulation inhibitory activity

A new furostane saponin, ramosaponin (1), and four known furostane saponins, protodioscin (2), dehydrotomatoside (3), (25 R)-26-O-(β-D-glucopyranosyl)-furost-5-ene-3β,22α,26-triol 3-O-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside (4), and anguivioside A (5) were isolated from the methanol extract of Allium ramosum seeds. Their structures were identified based on spectroscopic evidence and comparison with those reported in the literature. All compounds were evaluated for reduction of lipid accumulation in HepG2 cell line. As a result, compound 1 showed significant lipid accumulation inhibitory activity with an IC₅₀ value of 64.32 ± 3.87 µM.

Furostane Saponins from the Seeds of Allium ramosum and Their Lipid Accumulation Inhibitory Activity

Three new furostane saponins, ramofurosides A-C (1-3), and two known saponins, fistulosaponin B (4) and (25R)-26-O-β-D-glucopyranosyl-1β,3β,26-trihydroxyfurosta-5,20(22)-diene-1-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside (5) were isolated from the methanol extract of Allium ramosum seeds. Their structures were identified based on spectroscopic evidence and comparison with those reported in the literature. All compounds were evaluated for reduction of lipid accumulation in HepG2 cell lines. As a result, compounds 1 and 3 showed a significant reduction in total lipid content by 27.93±3.05 and 27.54±1.68 %, respectively, at a concentration of 100 μM.

The Pathogenesis of HCC Driven by NASH and the Preventive and Therapeutic Effects of Natural Products

Nonalcoholic steatohepatitis (NASH) is a clinical syndrome with pathological changes that are similar to those of alcoholic hepatitis without a history of excessive alcohol consumption. It is a specific form of nonalcoholic fatty liver disease (NAFLD) that is characterized by hepatocyte inflammation based on hepatocellular steatosis. Further exacerbation of NASH can lead to cirrhosis, which may then progress to hepatocellular carcinoma (HCC). There is a lack of specific and effective treatments for NASH and NASH-driven HCC, and the mechanisms of the progression of NASH to HCC are unclear. Therefore, there is a need to understand the pathogenesis and progression of these diseases to identify new therapeutic approaches. Currently, an increasing number of studies are focusing on the utility of natural products in NASH, which is likely to be a promising prospect for NASH. This paper reviews the possible mechanisms of the pathogenesis and progression of NASH and NASH-derived HCC, as well as the potential therapeutic role of natural products in NASH and NASH-derived HCC.

Epigenetic regulations enhance adaptability and valorization efficiency in Eisenia fetida and Eudrilus eugeniae during vermicomposting of textile sludge: Insights on repair mechanisms of metal-induced genetic damage and oxidative stress

Genotoxicity-based assessments of vermitechnology for textile-sludge valorization have rarely been attempted. Therefore, waste sanitization and epigenetic stress-regulation efficiency of Eisenia fetida and Eudrilus eugeniae were evaluated in silk (DSPS) and cotton (CPWS) processing sludge-based vermibeds. Vermicomposting resulted in greater C, N, and P recovery than composting. Earthworm population reduced by 6-50% in DSPS/CPWS, while it significantly increased in cow dung (CD) mixed DSPS/CPWS. The Cr, Cd, Pb, and Zn accumulation efficiency of earthworms was higher in DSPS-based feedstocks than CPWS. However, metal-rich sludge elevated oxidative stress, causing greater inhibition of cell viability and DNA damage in Eudrilus than in Eisenia. Although histo-architecture of chloragogenous tissues was perturbed, earthworms combatted metal-induced lipid peroxidation via the activation of catalase, superoxide-dismutase, and reduced-glutathione. Correlation statistics revealed that genetic integrity in earthworms was restored through DNA-methyltransferase activity, especially in DSPS/CPWS + CD vermibeds. Overall, Eisenia was a healthier choice than Eudrilus for sustainable valorization of textile-sludge.

Modular characteristics and the mechanism of Chinese medicine's treatment of gastric cancer: a data mining and pharmacology-based identification

Background

Traditional Chinese medicine (TCM) is increasingly extensively being applied as a complementary and alternative therapy for gastric cancer (GC); however, there is a lack of large-scale evidence-based deep learning for the guidance of its clinical prescription.

Methods

The combinational search terms of “Gastric cancer and/or gastric malignancy” and “Traditional Chinese Medicine” were used to retrieve clinical study-based herbal prescriptions from public database over the past 3 decades [1990–2020]. Association rules mining (ARM) was used to analyze the prescription patterns of the herbs extracted from the eligible studies. Deep machine learning and computational prediction were conducted to explore candidate prescriptions with general applicability for GC. The action mechanism of the preferred prescription was investigated through network pharmacology, and further validated via in vivo and in vitro experiments.

Results

A total of 194 clinical study-based herbal prescriptions with good efficacy for GC were collected. TCM with focus on invigorating the Spleen and tonifying the vital-Qi is a promising adjuvant therapy for GC. The preferred prescription is composed of Atractylodis Macrocephalae Rhizoma, Astragali Radix, Pinelliae Rhizoma, Citri Reticulatae Pericarpium, Herba Hedyotidis Diffusae, Crataegi Fructus, and so on. We screened 74 bioactive compounds and 2,128 predictive targets of the preferred prescription from public databases. Eventually, 135 GC-related genes were identified as the targets of the preferred prescription. The compound-target network revealed that the crucial substances in the preferred prescription are quercetin, kaempferol, baicalein, and nobiletin. Experimentally, the preferred prescription was validated to modulate GC cell survival and inhibit tumor progression mainly via the hTERT/MDM2-p53 signaling pathway in vivo and in vitro.

Conclusions

TCM aimed at invigorating the Spleen and tonifying the vital-Qi is a promising adjuvant therapy for GC, which offers a guidance for worldwide use of TCM in the treatment of GC.

Exploring the mechanisms underlying the therapeutic effect of Salvia miltiorrhiza in diabetic nephropathy using network pharmacology and molecular docking

The mechanisms underlying the therapeutic effect of Salvia miltiorrhiza (SM) on diabetic nephropathy (DN) were examined using a systematic network pharmacology approach and molecular docking. The Traditional Chinese Medicine Systems Pharmacology (TCMSP) database was used to screen active ingredients of SM. Targets were obtained using the SwissTargetPrediction and TCMSP databases. Proteins related to DN were retrieved from the GeneCards and DisGeNET databases. A protein–protein interaction (PPI) network was constructed using common SM/DN targets in the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database. The Metascape platform was used for Gene Ontology (GO) function analysis, and the Cytoscape plug-in ClueGO was used for Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Molecular docking was performed using iGEMDOCK and AutoDock Vina software. Pymol and LigPlos were used for network mapping. Sixty-six active ingredients and 189 targets of SM were found. Sixty-four targets overlapped with DN-related proteins. The PPI network revealed that AKT serine/threonine kinase 1 (AKT1), VEGFA, interleukin 6 (IL6), TNF, mitogen-activated protein kinase 1 (MAPK1), tumor protein p53 (TP53), epidermal growth factor receptor (EGFR), signal transducer and activator of transcription 3 (STAT3), mitogen-activated protein kinase 14 (MAPK14), and JUN were the ten most relevant targets. GO and KEGG analyses revealed that the common targets of DN and SM were mainly involved in advanced glycation end-products, oxidative stress, inflammatory response, and immune regulation. Molecular docking revealed that potential DN-related targets, including tumor necrosis factor (TNF), NOS2, and AKT1, more stably bound with salvianolic acid B than with tanshinone IIA. In conclusion, the present study revealed the active components and potential molecular therapeutic mechanisms of SM in DN and provides a reference for the wide application of SM in clinically managing DN.

Apigenin and Luteolin Regulate Autophagy by Targeting NRH-Quinone Oxidoreductase 2 in Liver Cells

Dietary flavonoids stimulate autophagy and prevent liver dysfunction, but the upstream signaling pathways triggered by these compounds are not well understood. Certain polyphenols bind directly to NRH-quinone oxidoreductase 2 (NQO2) and inhibit its activity. NQO2 is highly expressed in the liver, where it participates in quinone metabolism, but recent evidence indicates that it may also play a role in the regulation of oxidative stress and autophagy. Here, we addressed a potential role of NQO2 in autophagy induction by flavonoids. The pro-autophagic activity of seven flavonoid aglycons correlated perfectly with their ability to inhibit NQO2 activity, and flavones such as apigenin and luteolin showed the strongest activity in all assays. The silencing of NQO2 strongly reduced flavone-induced autophagic flux, although it increased basal LC3-II levels in HepG2 cells. Both flavones induced AMP kinase (AMPK) activation, while its reduction by AMPK beta (PRKAB1) silencing inhibited flavone-induced autophagy. Interestingly, the depletion of NQO2 levels by siRNA increased the basal AMPK phosphorylation but abrogated its further increase by apigenin. Thus, NQO2 contributes to the negative regulation of AMPK activity and autophagy, while its targeting by flavones releases pro-autophagic signals. These findings imply that NQO2 works as a flavone receptor mediating autophagy and may contribute to other hepatic effects of flavonoids.

Dietary Polyphenols to Combat Nonalcoholic Fatty Liver Disease via the Gut-Brain-Liver Axis: A Review of Possible Mechanisms

Polyphenols are a group of micronutrients widely existing in plant foods including fruits, vegetables, and teas that can improve nonalcoholic fatty liver disease (NAFLD). In this review, the existing knowledge of dietary polyphenols for the development of NAFLD regulated by intestinal microecology is discussed. Polyphenols can influence the vagal afferent pathway in the central and enteric nervous system to control NAFLD via gut-brain-liver cross-talk. The possible mechanisms involve in the alteration of microbial community structure, effects of gut metabolites (short-chain fatty acids (SCFAs), bile acids (BAs), endogenous ethanol (EnEth)), and stimulation of gut-derived hormones (ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and leptin) based on the targets excavated from the gut-brain-liver axis. Consequently, the communication among the intestine, brain, and liver paves the way for new approaches to understand the underlying roles and mechanisms of dietary polyphenols in NAFLD pathology.

D-Mannitol Induces a Brown Fat-like Phenotype via a β3-Adrenergic Receptor-Dependent Mechanism

The presence of brown adipocytes within white adipose tissue is associated with phenotypes that exhibit improved metabolism and proper body weight maintenance. Therefore, a variety of dietary agents that facilitate the browning of white adipocytes have been investigated. In this study, we screened a natural product library comprising 133 compounds with the potential to promote the browning of white adipocytes, and found that D-mannitol induces the browning of 3T3-L1 adipocytes by enhancing the expression of brown fat-specific genes and proteins, and upregulating lipid metabolism markers. D-mannitol also increased the phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase 1 (ACC), suggesting a possible role in lipolysis and fat oxidation. Moreover, an increase in the expression of genes associated with D-mannitol-induced browning was strongly correlated with the activation of the β3-adrenergic receptor as well as AMPK, protein kinase A (PKA), and PPARγ coactivator 1α (PGC1α). D-mannitol effectively reduced the body weight of mice fed a high-fat diet, and increased the expression of β1-oxidation and energy expenditure markers, such as Cidea, carnitine palmityl transferase 1 (CPT1), uncoupling protein 1 (UCP1), PGC1α, and acyl-coenzyme A oxidase (ACOX1) in the inguinal white adipose tissue. Our findings suggest that D-mannitol plays a dual regulatory role by inducing the generation of a brown fat-like phenotype and enhancing lipid metabolism. These results indicate that D-mannitol can function as an anti-obesity supplement.

Dietary Luteolin: A Narrative Review Focusing on Its Pharmacokinetic Properties and Effects on Glycolipid Metabolism

Luteolin, a flavone subclass of flavonoids, is commonly found in food plants and has multiple biological activities. Recently, evidence is growing with regard to the potential of luteolin intake to beneficially affect glycolipid metabolism disorders (GLMDs), particularly insulin resistance, diabetes, and obesity. The aim of this contribution is to provide an overview of recent advances in identifying and understanding the pharmacokinetic properties (absorption, metabolism, and bioavailability) of luteolin, its regulatory effects on glycolipid metabolism, and the underlying mechanisms of action of luteolin in the brain, liver, adipose tissues, and other tissues/organs. Collectively, luteolin or its principal metabolites may contribute to counteracting GLMDs, especially for human obesity and diabetes.

Three Novel Dietary Phenolic Compounds from Pickled Raphanus Sativus L. Inhibit Lipid Accumulation in Obese Mice by Modulating the Gut Microbiota Composition

SCOPE

Although pickled radish is widely consumed worldwide, few studies have investigated the nutritional benefits of bioactive compounds extracted from pickled radish. In this study, the authors investigate the relationship among dietary phenolic compounds, lipid accumulation, and gut microbiota.

METHOD AND RESULTS

Three phenolic compounds 2,6-dihydroxyacetophenone (DHAP), 4-hydroxyphenethyl alcohol (4-HPEA), and 4-hydroxybenzaldehyde (HBA) are extracted from pickled radish. LO2 cells treated with free fatty acid are first used to explore the impact of the above three compounds at different doses on reducing lipid levels. The effects of the three compounds on obesity and the gut microbiota are further investigated in high-fat diet (HFD)-induced KM mice. Results show that three compounds inhibited the lipid accumulation in LO2 cells. The results of animal experiments reveal that three compounds prevented body weight gain and significantly decreased serum lipid levels. Treatment with DHAP, HPEA, and HBA reversed gut microbiome dysbiosis in HFD-induced mice. The three phenolic compounds increase Odoribacter, and decrease Helicobacter and Mucispirillum. Notably, DHAP and HBA reduce the HFD-induced increase in the Firmicutes/Bacteroidetes ratio.

CONCLUSION

These data suggest that phenolic compounds extracted from pickled radish possess excellent lipid-lowering capacity, providing a theoretical basis for further analysis of the nutritional value of pickled radish.

Dietary Polyphenols and Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD), which is emerging as a major public health issue worldwide, is characterized by a wide spectrum of liver disorders, ranging from simple fat accumulation in hepatocytes, also known as steatosis, to non-alcoholic steatohepatitis (NASH) and cirrhosis. At present, the pharmacological treatment of NAFLD is still debated and dietary strategies for the prevention and the treatment of this condition are strongly considered. Polyphenols are a group of plant-derived compounds whose anti-inflammatory and antioxidant properties are associated with a low prevalence of metabolic diseases, including obesity, hypertension, and insulin resistance. Since inflammation and oxidative stress are the main risk factors involved in the pathogenesis of NAFLD, recent studies suggest that the consumption of polyphenol-rich diets is involved in the prevention and treatment of NAFLD. However, few clinical trials are available on human subjects with NAFLD. Here, we reviewed the emerging existing evidence on the potential use of polyphenols to treat NAFLD. After introducing the physiopathology of NAFLD, we focused on the most investigated phenolic compounds in the setting of NAFLD and described their potential benefits, starting from basic science studies to animal models and human trials.

Ugonin J improves metabolic disorder and ameliorates nonalcoholic fatty liver disease by regulating the AMPK/AKT signaling pathway

Closely associated with visceral obesity, hepatic steatosis resulting from non-alcoholic fatty liver disease (NAFLD) exacerbates insulin resistance. Developing effective drugs to treat NAFLD is imperative. Here, we investigated the pharmacological mechanism of ugonin J (UJ) in controlling metabolic disorder and ameliorating NAFLD pathophysiology in diet-induced obese mice. The effects of UJ were assessed in 5-week-old C57BL/6 J mice fed a high-fat diet (HFD) for 12 weeks. UJ treatment averted HFD-induced body weight gain by reducing fat deposition in adipose tissues and reduced HFD-induced hyperlipidemia and hepatic inflammation. UJ also improved HFD-induced glucose tolerance and insulin resistance. Moreover, the mode of action of UJ was analyzed in palmitate (PA)-induced steatotic human HuS-E/2 hepatocytes and in hyperglycemia-simulating rat BRIN-BD11 pancreatic β cells. In PA-induced steatotic human hepatocytes, UJ treatment promoted lipid clearance via pAMPK, pACC and CPT-1 upregulation and SREBP-1c downregulation. Interestingly, UJ upregulated Akt activity in hepatocytes and increased insulin secretion from β cells in acute insulin secretion tests. Taken together, UJ improved adipocyte hypertrophy, hyperinsulinemia, hyperglycemia, hyperlipidemia and fat deposition in livers. UJ also reduced fatty acid accumulation by modulating key metabolic regulators. Our findings demonstrated the therapeutic potential of UJ for the treatment of NAFLD and diet-induced metabolic disorders.

Pathogenesis of NASH and Promising Natural Products

Nonalcoholic steatohepatitis (NASH) is a common clinical condition that can lead to advanced liver diseases. The mechanism of the diaease progression, which is lacking effective therapy, remains obsure. Therefore, there is a need to understand the pathogenic mechanisms responsible for disease development and progression in order to develop innovative therapies. To accomplish this goal, experimental animal models that recapitulate the human disease are necessary. Currently, an increasing number of studies have focused on natural constituents from medicinal plants which have been emerged as a new hope for NASH. This review summarized the pathogenesis of NASH, animal models commonly used, and the promising targets for therapeutics. We also reviewed the natural constituents as potential NASH therapeutic agents.

The selective blockade of metabotropic glutamate receptor-5 attenuates fat accumulation in an <em>in vitro</em> model of benign steatosis

It has been previously found that the blockade of metabotropic glutamate receptor type 5 (mGluR5) protects against hepatic ischemia/reperfusion injury and acetaminophen toxicity. The role of mGluR5 in NAFLD has not yet been elucidated. Here, we evaluated the effects of mGluR5 blockade in an in vitro model of steatosis. HepG2 cells were pre-incubated for 12 h with an mGluR5 agonist, a negative allosteric modulator (DHPG and MPEP, respectively) or vehicle, then treated with 1.5 mM oleate/palmitate (O/P) for another 12 h. Cell viability was evaluated with the MTT assay; fat accumulation was measured using the fluorescent dye nile red; SREBP-1, PPAR-α, iNOS and Caspase-3 protein expression were evaluated by Western blot; NFkB activity was evaluated as pNFkB/NFkB ratio. mGluR5 modulation did not alter cell viability in O/P-incubated cells; MPEP prevented intracellular lipid accumulation in O/P treated cells; MPEP administration was also associated with a reversion of O/P-induced changes in SREBP-1 and PPAR-α expression, involved in free fatty acid (FFA) metabolism and uptake. No changes were observed in iNOS and Caspase-3 expression, or in NFkB activity. In conclusion, mGluR5 pharmacological blockade reduced fat accumulation in HepG2 cells incubated with O/P, probably by modulating the expression of SREBP-1 and PPAR-α.

Strawberry (Fragaria × ananassa cv. Romina) methanolic extract promotes browning in 3T3-L1 cells

In recent years, the conversion of white adipocytes to brown-like adipocytes by pharmacological and dietary compounds has gained attention as an effective strategy to fight obesity. Strawberry bioactive compounds present several biological activities including antioxidant, anti-inflammatory, anti-cancer, anti-atherosclerotic and antiadipogenic properties. However, to the best of our knowledge, the possible role of strawberry bioactive compounds in white adipose tissue (WAT) browning has never been explored. Our results demonstrated that a strawberry methanolic extract (SE) significantly reduced 3T3-L1 pre-adipocytes differentiation, and down-regulated the mRNA expression of the adipogenic transcription factors CCAAT/enhancer-binding protein (C/REB- α) and peroxisome proliferation-activated receptor (PPAR-γ). It also down-regulated the mRNA expression of resistin and angiotensinogen, two genes considered as markers of white adipocytes, while increased the mRNA expression of pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4) and uncoupling protein 1 (UCP1) which, conversely, are brown adipocyte-specific markers. Likewise, SE stimulated AMP-activated protein kinase (AMPKα), sirtuin 1 (Sirt1) and the peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC-1α), suggesting a possible increase in mitochondrial biogenesis. It also stimulated oxygen consumption rate and uncoupled respiration. Taken together, all these results suggest that SE induces brown fat-like phenotype in 3T3-L1 cells and may have potential therapeutic implications for treatment and/or prevention of obesity.

Three-tissue microphysiological system for studying inflammatory responses in gut-liver Axis

The interaction between the gut and the liver, often known as the gut-liver axis, play crucial roles in modulating the body's responses to the xenobiotics as well as progression of diseases. Dysfunction of the axis can cause metabolic disorders as well as obesity, diabetes, and fatty liver disease. During the progression of such diseases, inflammatory responses involving the immune system also play an important part. In this study, we developed a three-tissue microphysiological system (MPS) that can accommodate three different cell types in separated compartments connected via fluidic channels in a microfluidic device. Using computational fluid dynamics, geometry of fluidic channels and flow conditions were optimized for seeding and culturing different cell types in the three-tissue MPS. Caco-2 (gut), RAW264.7 (immune), and HepG2 (liver) cells were seeded and cultured in the chip. Stimulation of the gut cells in the MPS with lipopolysaccharide (LPS) resulted in induction of inflammatory response and production of nitric oxide (NO) in all connected chambers. The anti-inflammatory effect of luteolin was demonstrated. Our study demonstrates that the three-tissue MPS can recapitulate the inflammatory responses involving the gut, liver and immune cells.

Effects of epoxy stearic acid on lipid metabolism in HepG2 cells

In the present study, effects of cis-9,10-epoxystearic acid (ESA) generated by the thermal oxidation of oleic acid on HepG2 cells, including intracellular lipid accumulation, fatty acid composition, and lipid metabolism, were investigated. Our results revealed that ESA increased the number and size of cellular lipid droplets. Intracellular triacylglycerol and total cholesterol content demonstrated that ESA induced lipid accumulation in HepG2 cells in a dose- and time-dependent manner. Results of fatty acid composition further indicated that ESA could lead to intracellular lipid accumulation. Our results also revealed that ESA may suppress the fatty acid oxidation in peroxisomes and mitochondria, including PPARα, Cpt1α, and Acox1, whereas the expression of genes involved in lipid synthesis, including Srebp-1c and Scd1, was enhanced. These findings provide critical information on the effects of ESA on HepG2 cells, particularly lipid accumulation and metabolism, which is important for evaluating the biosafety of the oxidative product of oleic acid. PRACTICAL APPLICATION: The administration of cis-9,10-epoxystearic acid to HepG2 cells could lead to disorder of lipid metabolism of cells by enhancing the intracellular lipid content, as well as suppressing the fatty acid oxidation in peroxisomes and mitochondria. These findings could provide information for the evaluation of the biosafety of the oxidative product of oleic acid.

The Gut Microbiota and Its Metabolites, Novel Targets for Treating and Preventing Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent metabolic disorders worldwide, along with obesity and type 2 diabetes. NAFLD involves a series of liver abnormalities from simple hepatic steatosis to non-alcoholic steatohepatitis, which can ultimately lead to liver cirrhosis and cancer. The gut-liver axis plays an important role in the development of NAFLD, which depends mainly on regulation of the gut microbiota and its bacterial products. These intestinal bacterial species and their metabolites, including bile acids, tryptophan catabolites, and branched-chain amino acids, regulate adipose tissue and intestinal homeostasis and contribute to the pathogenesis of NAFLD/non-alcoholic steatohepatitis. In this review, the current evidence regarding the key role of the gut microbiota and its metabolites in the pathogenesis and development of NAFLD is highlighted, and the advances in the progression and applied prospects of gut microbiota-targeted dietary and exercise therapies is also discussed.

Berbamine induced AMPK activation regulates mTOR/SREBP-1c axis and Nrf2/ARE pathway to allay lipid accumulation and oxidative stress in steatotic HepG2 cells

Non-alcoholic fatty liver disease is emanating as a global cataclysm. This study was designed to investigate the antioxidative, anti-inflammatory and fat metabolism-regulating potential of berbamine (BBM), a natural bis-benzylisoquinoline alkaloid. BBM attenuated intracellular lipid accumulation in oleic-acid exposed HepG2 cells (0.5 mM) by inhibiting fatty acid uptake, lipogenesis, and promoting fatty acid β-oxidation by activating AMP-activated kinase (AMPK) and peroxisome proliferator-activated receptor (PPAR)-α. Berbamine (5 μM) induced AMPK activation (P < 0.001) via LKB1 (Ser-428) and elevated AMP:ATP ratio (P < 0.001). AMPK activation negatively regulated mTOR and also constrained the nuclear translocation of SREBP-1c and inhibited the lipogenic proteins, stearoyl-CoA desaturase-1 (SCD-1) and fatty acid synthase (FAS) (P < 0.001). BBM stimulated nuclear translocation of redox-sensitive nuclear factor erythroid-2-related factor-2 (Nrf2) and increased hepatic expression of Nrf2 responsive enzymes, HO-1 and Nqo-1. BBM treatment reduced the oxidative burst and pro-inflammatory responses by significantly enhancing hepatic antioxidant defenses [SOD (P < 0.001), catalase (P < 0.001) and cellular glutathione (P < 0.01)] and diminishing NF-κB regulated pro-inflammatory cytokines (TNF-α, and IL-6) levels respectively. TEM analysis confirmed the disruption of mitochondrial structure and reduction in mitochondrial size (50.97%, P < 0.001) in steatotic HepG2 cells which was significantly prevented by 5 μM BBM treatment (71.84% as compared to control, P < 0.01). Pre-treatment of Compound C (AMPK inhibitor, 25 μM) greatly repressed the anti-steatotic properties exhibited by BBM confirming the involvement of AMPK signaling pathway. In summary, the results manifest that BBM reduces intracellular lipid accumulation via AMPK/mTOR/SREBP-1c axis mediated regulation of lipid metabolism and upsurged nuclear stability of Nrf2 by promoting AMPK/Nrf2 association to ameliorate oxidative stress/proinflammatory response.

Lemon Balm and Its Constituent, Rosmarinic Acid, Alleviate Liver Damage in an Animal Model of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) ranges in severity from hepatic steatosis to cirrhosis. Lemon balm and its major constituent, rosmarinic acid (RA), effectively improve the liver injury and obesity; however, their therapeutic effects on nonalcoholic steatohepatitis (NASH) are unknown. In this study, we investigated the effects of RA and a lemon balm extract (LBE) on NAFLD and liver fibrosis and elucidated their mechanisms. Palmitic acid (PA)-exposed HepG2 cells and db/db mice fed a methionine- and choline-deficient (MCD) diet were utilized to exhibit symptoms of human NASH. LBE and RA treatments alleviated the oxidative stress by increasing antioxidant enzymes and modulated lipid metabolism-related gene expression by the activation of adenosine monophosphate-activated protein kinase (AMPK) in vitro and in vivo. LBE and RA treatments inhibited the expression of genes involved in hepatic fibrosis and inflammation in vitro and in vivo. Together, LBE and RA could improve liver damage by non-alcoholic lipid accumulation and may be promising medications to treat NASH.

Emerging targets and potential therapeutic agents in non-alcoholic fatty liver disease treatment

Nonalcoholic Fatty Liver Disease (NAFLD) is the most common chronic liver disease in the world, which is characterized by liver fat accumulation unrelated to excessive drinking. Indeed, it attracts growing attention and becomes a global health problem. Due to the complexity of the NAFLD pathogenic mechanism, no related drugs were approved by Food and Drug Administration (FDA) till now. However, it is encouraging that a series of candidate drugs have entered the clinical trial stage with expectation to treat NAFLD. In this review, we summarized the main pathways and pathogenic mechanisms of NAFLD, as well as introduced the main potential therapeutic targets and the corresponding compounds involved in metabolism, inflammation and fibrosis. Furthermore, we also discuss the progress of these compounds, such as drug design and optimization, the choice of pharmacological properties and druglikeness, and the analysis of structure-activity relationship. This review offers a medium on future drug design and development, to be beneficial to relevant studies.

Low dose of luteolin activates Nrf2 in the liver of mice at start of the active phase but not that of the inactive phase

A flavone luteolin has various health-promoting activities. Several studies reported that high dose of luteolin activates the Nrf2/ARE pathway in the liver. However, the effect of the low dose of luteolin that can be taken from a dietary meal on the Nrf2 activation remain unclear. It is expected that the flavonoid metabolism possesses a circadian rhythm, since nutritional metabolism processes daily cycle. In this study we investigated whether an administration affects the Nrf2 activation. ICR mice were orally administered 0.01–10 mg/kg body weight of luteolin once a day for 7 days at two time-points: at the start of active phase (ZT12) or at that of inactive phase (ZT0). Luteolin increased the nuclear translocation of Nrf2, resulting in the increases in its target gene products HO-1 and NQO1 at ZT12 but not at ZT0. The expression level of Nrf2 was lower at ZT12 than at ZT0 in the liver. We also found that the level of luteolin aglycon in the plasma is higher at ZT12 than at ZT0. These results suggest that the low dose of luteolin can activate Nrf2 pathway and the aglycon form of luteolin may mainly contribute to activate the Nrf2 pathway at ZT12 in the liver.

Protective Effect of a Mixture of Astragalus membranaceus and Lithospermum erythrorhizon Extract against Hepatic Steatosis in High Fat Diet-Induced Nonalcoholic Fatty Liver Disease Mice

The present study aimed to evaluate the potential synergistic and protective effects of ALM16, a mixture of Astragalus membranaceus (AM) and Lithospermum erythrorhizon (LE) extract in a ratio of 7 : 3, against hepatic steatosis in high fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) mice. Forty-eight mice were randomly divided into eight groups and orally administered daily for 6 weeks with a normal diet (ND) or high fat diet alone (HFD), HFD with AM (HFD + 100 mg/kg AM extract), HFD with LE (HFD + 100 mg/kg LE extract), HFD with ALM16 (HFD + 50, 100, and 200 mg/kg ALM16), or HFD with MT (HFD + 100 mg/kg Milk thistle extract) as a positive control. ALM16 significantly decreased the body and liver weight, serum and hepatic lipid profiles, including triglyceride (TG), total cholesterol (TC), high-density lipoprotein-cholesterol (HDL), and low-density lipoprotein-cholesterol (LDL), and serum glucose levels, compared to the HFD group. Moreover, ALM16 significantly ameliorated the HFD-induced increased hepatic injury markers, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and gamma-glutamyltransferase (GGT)-1. Furthermore, as compared to the mice fed HFD alone, ALM16 increased the levels of phosphorylated AMP-activated protein kinase (p-AMPK) and acetyl-CoA carboxylase (p-ACC), thereby upregulating the expression of carnitine palmitoyltransferase (CPT)-1 and downregulating the expression of sterol regulatory element-binding protein (SREBP)-1c and fatty acid synthase (FAS). These results demonstrated that ALM16 markedly inhibited HFD-induced hepatic steatosis in NAFLD mice by modulating AMPK and ACC signaling pathways, and may be more effective than the single extracts of AM or LE.

Resveratrol Treatment Enhances the Cellular Response to Leptin by Increasing OBRb Content in Palmitate-Induced Steatotic HepG2 Cells

The interaction of leptin with its hepatic longest receptor (OBRb) promotes the phosphorylation of signal transducer and activator of transcription-3 (STAT3), protecting the liver from lipid accumulation. However, leptin signalling is disrupted in hepatic steatosis, causing leptin resistance. One promising strategy to combat this problem is the use of bioactive compounds such as polyphenols. Since resveratrol (RSV) is a modulator of lipid homeostasis in the liver, we investigated whether treatment with different doses of RSV restores appropriate leptin action and fat accumulation in palmitate-induced steatotic human hepatoma (HepG2) cells. Both RSV metabolism and the expression of molecules implicated in leptin signalling were analysed. RSV at a 10 μM concentration was entirely metabolized to resveratrol-3-sulfate after 24 and counteracted leptin resistance by increasing the protein levels of OBRb. In addition, RSV downregulated the expression of lipogenic genes including fatty acid synthase (Fas) and stearoyl-CoA desaturase-1 (Scd1) without any significant change in Sirtuin-1 (SIRT1) enzymatic activity. These results demonstrate that RSV restored leptin sensitivity in a cellular model of hepatic steatosis in a SIRT1-independent manner.

Hyperglycemia induces key genetic and phenotypic changes in human liver epithelial HepG2 cells which parallel the Leprdb/J mouse model of non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a growing global health concern. With a propensity to progress towards non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma, NAFLD is an important link amongst a multitude of comorbidities including obesity, diabetes, and cardiovascular and kidney disease. As several in vivo models of hyperglycemia and NAFLD are employed to investigate the pathophysiology of this disease process, we aimed to characterize an in vitro model of hyperglycemia that was amenable to address molecular mechanisms and therapeutic targets at the cellular level. Utilizing hyperglycemic cell culturing conditions, we induced steatosis within a human hepatocyte cell line (HepG2 cells), as confirmed by electron microscopy. The deposition and accumulation of lipids within hyperglycemic HepG2 cells is significantly greater than in normoglycemic cells, as visualized and quantified by Nile red staining. Alanine aminotransferase (ALT) and alkaline phosphatase (ALP), diagnostic biomarkers for liver damage and disease, were found to be upregulated in hyperglycemic HepG2 cells as compared with normoglycemic cells. Suppression of CEACAM1, GLUT2, and PON1, and elevation of CD36, PCK1, and G6PK were also found to be characteristic in hyperglycemic HepG2 cells compared with normoglycemic cells, suggesting insulin resistance and NAFLD. These in vitro findings mirror the characteristic genetic and phenotypic profile seen in Lepr^db/J mice, a well-established in vivo model of NAFLD. In conclusion, we characterize an in vitro model displaying several key genetic and phenotypic characteristics in common with NAFLD that may assist future studies in addressing the molecular mechanisms and therapeutic targets to combat this disease.

Inhibition of intestinal glucose transport by polyphenols: a mechanism for indirect attenuation of cholesterol absorption?

Cholesterol uptake and chylomicron synthesis are promoted by increasing glucose concentrations in both healthy and diabetic individuals during the postprandial phase. The goal of this study was to test whether acute inhibition of glucose uptake could impact cholesterol absorption in differentiated human intestinal Caco-2 cells. As expected, high glucose upregulated intestinal cholesterol metabolism promoting its uptake and incorporation in lipoproteins. This was accompanied by an increase in the gene expression of Niemann-Pick C1 Like 1 and proprotein convertase subtillisin/kexin type 9. Cholesterol uptake was attenuated by acute inhibition of glucose absorption by cytochalasin B, by a chamomile extract and by one of its main constituent polyphenols, apigenin 7-O-glucoside; however, chylomicron secretion was only reduced by the chamomile extract. These data support a potential indirect role for bioactives in modulating intestinal lipid pathways through effects on intestinal glucose uptake. This working hypothesis warrants further testing in an in vivo setting such as in hypercholesterolaemic or prediabetic individuals.

Inhibition Effect of Triglyceride Accumulation by Large Yellow Croaker Roe DHA-PC in HepG2 Cells

The phospholipids (PLs) of large yellow croaker (Pseudosciaena crocea, P. crocea) roe contain a high level of polyunsaturated fatty acids, especially docosahexaenoic acid (DHA), which can lower blood lipid levels. In previous research, PLs of P. crocea roe were found able to regulate the accumulation of triglycerides. However, none of these involve the function of DHA-containing phosphatidylcholine (DHA-PC), which is the main component of PLs derived from P. crocea roe. The function by which DHA-PC from P. crocea roe exerts its effects has not yet been clarified. Herein, we used purified DHA-PC and oleic acid (OA) induced HepG2 cells to establish a high-fat model, and the cell activity and intracellular lipid levels were then measured. The mRNA and protein expression of Fatty Acid Synthase (FAS), Carnitine Palmitoyl Transferase 1A (CPT1A) and Peroxisome Proliferator-Activated Receptor α (PPARα) in HepG2 cells were detected via RT-qPCR and western blot as well. It was found that DHA-PC can significantly regulate triglyceride accumulation in HepG2 cells, the effect of which was related to the activation of PPARα receptor activity, upregulation of CPT1A, and downregulation of FAS expression. These results can improve the understanding of the biofunction of hyperlipidemia mediated by DHA-PC from P. crocea roe, as well as provide a theoretical basis for the utilization of DHA-PC from P. crocea roe as a functional food additive.

Peroxiredoxin 6 Confers Protection Against Nonalcoholic Fatty Liver Disease Through Maintaining Mitochondrial Function

Aims: Nonalcoholic fatty liver disease (NAFLD) is accompanied by excessive reactive oxygen species (ROS) production, which has been suggested in several studies to link with mitochondrial function. However, the mechanistic role of ROS-mediated regulation of mitochondrial function in NAFLD has not been elucidated. Since peroxiredoxin 6 (PRDX6) is the only member of the antioxidant PRDX family that translocates to damaged mitochondria, we investigated the PRDX6-mediated antisteatotic mechanism using genetically modified mice and cells. Results: PRDX6 mice were more protective to lipid accumulation, liver injury, and insulin resistance after a high-fat diet. Mechanistically, PRDX6 is required for induction of mitochondrial antioxidant action and beta-oxidation through maintaining mitochondrial integrity and subsequently prevents ROS-induced lipogenesis. Interestingly, oxidative stress-induced Notch signaling was suppressed in PRDX6 mice compared with wild-type mice, and genetic and pharmacological inhibition of Notch signaling improved lipid accumulation. Finally, PRDX knockdown or Notch inhibition reduced induction of mitophagy. PRDX6 antagonizes positive feedback loop between lipid accumulation and ROS production through regulation of mitochondrial function. Innovation: For the first time, we demonstrate that PRDX6 maintains mitochondria integrity under oxidative stress and protects against NAFLD progression by inhibition of Notch signaling. Conclusion: This study describes a novel molecular mechanism underlying the antisteatotic activity of PRDX6, which may be a new therapeutic strategy for the treatment of NAFLD.

Treatment implications of natural compounds targeting lipid metabolism in nonalcoholic fatty liver disease, obesity and cancer

Metabolic disorders can lead to a scarcity or excess of certain metabolites such as glucose, lipids, proteins, purines, and metal ions, which provide the biochemical foundation and directly contribute to the etiology of metabolic diseases. Nonalcoholic fatty liver disease, obesity, and cancer are common metabolic disorders closely associated with abnormal lipid metabolism. In this review, we first describe the regulatory machinery of lipid metabolism and its deregulation in metabolic diseases. Next, we enumerate and integrate the mechanism of action of some natural compounds, including terpenoids and flavonoids, to ameliorate the development of metabolic diseases by targeting lipid metabolism. Medicinal natural products have an established history of use in health care and therapy. Natural compounds might provide a good source of potential therapeutic agents for treating or preventing metabolic diseases with lipid metabolic abnormalities.

Maslinic Acid Inhibits Colon Tumorigenesis by the AMPK-mTOR Signaling Pathway

Maslinic acid (MA), a natural triterpenoid abundant in olives, has a variety of bioactivities. However, its effects and mechanisms on colorectal cancer (CRC) still need to be explored. This research evaluated the effects of MA on CRC progression from the aspect of the adenosine monophosphate (AMP)-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR) pathway. MA inhibited the proliferation and migration of HCT116 and SW480 cells while inducing apoptosis in these cells. Furthermore, it could activate AMPK and negatively regulate the mTOR pathway. Knockdown of AMPK abolished its inhibitory effect on cell proliferation and migration and blocked the MA-induced apoptosis, revealing that AMPK was associated with the anticancer activity of MA. In addition, MA significantly suppressed the tumorigenesis and regulated the AMPK-mTOR pathway in azoxymethane/dextran sulfate sodium mice and xenograft tumor mice. This study demonstrated that the regulation of AMPK-mTOR signaling could potentially contribute to the beneficial effects of MA, including the prevention of CRC.