Nobiletin Inhibits Hepatic Lipogenesis via Activation of AMP-Activated Protein Kinase

Unsaponifiable Matter from Wheat Bran Cultivated in Korea Inhibits Hepatic Lipogenesis by Activating AMPK Pathway

Unsaponifiable matter (USM) from wheat bran, a by-product obtained from wheat milling, is abundant in health-promoting compounds such as phytosterols, tocopherols, policosanols, and alkylresorcinols. This study aimed to examine the effects of USM from the wheat bran of normal and waxy type wheat, Saekeumkang (SKK) and Shinmichal (SMC), on hepatic lipid accumulation in free fatty acid (FFA)-induced hepatocytes and to investigate the cellular mechanism. The total phytochemical contents were 46.562 g/100 g USM and 38.130 g/100 g USM from SKK and SMC, respectively. FFA treatment increased intracellular lipid accumulation by approximately 260% compared to the control group; however, treatment with USM from SKK and SMC significantly attenuated lipid accumulation in the hepatocytes in a dose-dependent manner. Moreover, USM downregulated the expression of lipogenic factors such as fatty acid synthase and sterol regulatory-element-binding protein 1c by approximately 40% compared to the FFA treatment group. Treatment with USM promoted lipolysis and positively regulated the expression of the proteins involved in β-oxidation, including peroxisome proliferator-activated receptor α and its downstream protein, carnitine palmitoyltransferase 1A. Moreover, the blockade of AMPK activation significantly abolished the inhibitory effects of USM on hepatic lipid accumulation. These results indicated that the USM from both SKK and SMC can alleviate lipid accumulation in hepatocytes in an AMPK-dependent manner. Therefore, USM from wheat bran may be useful as a therapeutic intervention for treating metabolic-dysfunction-associated fatty liver disease.

Si-Ni-San reduces lipid droplet deposition associated with decreased YAP1 in metabolic dysfunction-associated fatty liver disease

ETHNOPHARMACOLOGICAL RELEVANCE

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common chronic liver disease worldwide. However, its complex pathogenesis and lack of effective drugs for treating it present significant challenges. Si-Ni-San (SNS) is one of the representative formulas for treating patients with MAFLD in traditional Chinese medicine (TCM) clinics. According to our previous work, SNS reduces lipid droplet (LD) deposition in livers of mice with MAFLD.

AIM OF THE STUDY

To elucidate the mechanism of SNS in reducing LD deposition in MAFLD.

MATERIALS AND METHODS

First, LD areas were detected with Oil red O staining in HepG2 cells induced by oleic acid (OA). Cell Counting Kit-8 (CCK-8) assay was used to test cell viability after treatment with different concentrations of SNS serum. The expression of Yes-associated protein 1 (YAP1) was monitored by Western blot. Second, C57BL/6 mice were fed a high-fat diet (HFD) for 12 weeks and gavaged with SNS decoction during the 11th and 12th weeks. Then, the weight of the body and the liver was examined. LD numbers and their locations in the liver were detected by triglyceride (TG) assay and hematoxylin and eosin staining (H&E). The expression levels of YAP1 and perilipin2 (PLIN2) were detected using Western blot and immunohistochemistry (IHC) in liver tissues. Finally, active ingredients of SNS decoction and SNS serum were identified by liquid chromatography-mass spectrometry (LC-MS). Finally, molecular docking was performed between the compounds in SNS and YAP1 to analyze their active interaction.

RESULTS

Cellular experiments showed that SNS serum reduced LD vacuoles and YAP1 expression in OA-induced HepG2 cells. Animal experiments confirmed that LD vacuoles, PLIN2 expression (3.16-fold), and YAP1 expression (2.50-fold) were increased in the HFD group compared with the normal diet (ND) group. SNS reduced LD vacuoles, TG content (0.84-fold), PLIN2 expression (0.33-fold), and YAP1 expression (0.27-fold) compared with the normal saline (NS) group in Yap1^Flox mice with MAFLD. In SNS, baicalein-6-glucuronide, desoxylimonin, galangin-7-glucoside, glycyrrhizic-acid, licoricesaponin-K2, and nobiletin showed a high binding effect with YAP1. Knockout of hepatocyte YAP1 reduced LD vacuoles, TG content (0.40-fold), and PLIN2 expression (0.62-fold) in mice. Meanwhile, SNS reduced LD vacuoles, TG content (0.70-fold), and PLIN2 expression (0.19-fold) in Yap1^LKO mice with MAFLD. The effect of SNS in reducing TG and PLIN2 was diminished in Yap1^LKO mice compared with Yap1^Flox mice.

CONCLUSION

SNS reduced LD deposition and YAP1 expression in MAFLD liver cells both in vivo and in vitro. YAP1 was highly expressed in livers with MAFLD, and knockout of hepatocellular YAP1 reduced LD deposition in mice. SNS reduced LD deposition associated with decreased YAP1 in MAFLD liver cells.

Therapeutic potential of bioactive phytoconstituents found in fruits in the treatment of non-alcoholic fatty liver disease: A comprehensive review

Nonalcoholic fatty liver disease (NAFLD), a chronic liver condition affects a large number of people around the world with a frequency of 25% of all the chronic liver disease worldwide. Several targets viz. anti-inflammatory, anti-apoptotic and, anti-fibrotic factors, anti-oxidant and insulin-sensitizing pathways, metabolic regulators as well as repurposing traditional medications have been studied for the pharmacologic therapy of NAFLD. Newer pharmacotherapies like caspases blockade, agonists of PPAR and farnesoid X receptor agonists are currently being investigated in treating human NAFLD. However, NAFLD has no FDA-approved pharmacological therapy, therefore there is a considerable unmet therapy need. Apart from the conventional treatment regime, the current approaches to treating NAFLD include lifestyle interventions including healthy diet with adequate nutrition and physical activity. Fruits are known to play a key role in the well-being of human health. Fruits are loaded with a repertoire of bioactive phytoconstituents like catechins, phytosterols, proanthocyanidin, genestin, daidzen, resveratrol, magiferin found in fruits like pear, apricot, strawberries, oranges, apples, bananas, grapes, kiwi, pineapple, watermelon, peach, grape seed and skin, mango, currants, raisins, dried dates, passion fruit and many more. These bioactive phytoconstituents are reported to demonstrate promising pharmacological efficacy like reduction in fatty acid deposition, increased lipid metabolism, modulation of insulin signaling pathway, gut microbiota and hepatic inflammation, inhibition of histone acetyltransferase enzymatic activity to name a few. Not only fruits, but their derivatives like oils, pulp, peel, or their preparations are also found to be equally beneficial in various liver diseases like NAFLD, NASH. Although most of the fruits contains potent bioactive phytoconstituents, however, the presence of sugar in fruits put a question mark on the ameliorative property of the fruits and there has been contrasting reports on the glycemic control post fruit consumption in type 2 diabetic patients. This review is an attempt to summarize the beneficial effects of fruit phytoconstituents on NAFLD based on epidemiological, clinical and experimental evidence, focusing especially on their mechanisms of action.

Nobiletin Intake Attenuates Hepatic Lipid Profiling and Oxidative Stress in HFD-Induced Nonalcoholic-Fatty-Liver-Disease Mice

Nobiletin (NOB) is a naturally occurring compound, commonly found in citrus peel, that shows hepatoprotective and lipid-reducing effects. However, the lipid biomarkers and the potential improvement mechanisms have not been adequately explored. Therefore, we investigated the ameliorative effect and the molecular mechanism of NOB on NAFLD induced by a high-fat diet in mice. The results showed that supplementation with NOB over 12 weeks markedly improved glucose tolerance, serum lipid profiles, inflammatory factors, hepatic steatosis, and oxidative stress. These beneficial effects were mainly related to reduced levels of potential lipid biomarkers including free fatty acids, diacylglycerols, triacylglycerols, and cholesteryl esters according to hepatic lipidomic analysis. Twenty lipids, including DGs and phosphatidylcholines, were identified as potential lipid biomarkers. Furthermore, RT-qPCR and Western blot analysis indicated that NOB inhibited the expression of lipogenesis-related factors such as SREBP-1c, SCD-1, and FAS, and upregulated the expression of lipid oxidation (PPARα) and cholesterol conversion (LXRα, CYP7A1, and CYP27A1) genes as well as antioxidation-related factors (Nucl-Nrf2, NQO1, HO-1, and GCLC), indicating that NOB intake may reduce lipid biosynthesis and increase lipid consumption to improve hepatic steatosis and oxidative stress. This study is beneficial for understanding the ameliorative effects of NOB on NAFLD.

Plants-based medicine implication in the evolution of chronic liver diseases

Hepatic disorders are considered major health problems, due to their high incidence, increased risk of chronicling or death and the costs involved in therapies. A large number of patients with chronic liver diseases use herbal medicines and dietary supplements in parallel with allopathic treatment. The current review provides a thorough analysis of the studies conducted on the most important species of medicinal plants used in this disease, bioactive compounds and on the activity of herbal medicines in the evolution of chronic liver diseases. However, a negative aspect is that there is frequently a lack of comprehensive data on the progression of the illness and the living standards of patients who are affected when evaluating the effects of these phytocomponents on the evolution of chronic liver disease, the patients' health, and their quality of life. It is essential to take this impairment into account when evaluating the long-term effects of herbal treatments on the health of individuals who suffer from liver illness. Bioactive phytocomponents may be a suitable source for the development of novel medications due to the correlation between traditional uses and medical advances. Additional high-quality preclinical examinations utilizing cutting-edge approaches are needed to assess safety and effectiveness and to detect, categorize, and standardize the active substances and their formulations for the most suitable therapeutic management of liver illnesses.

Evaluation and Optimization of Quality Based on the Physicochemical Characteristics and Metabolites Changes of Qingpi during Storage

Qingpi, the dried immature pericarp of Citrus reticulata Blanco, is a commonly used medicinal food with some health-promoting benefits. In general, it is essential that Qingpi be stored for a period of time, but there are no reports about the number of storage years needed to obtain the best quality of Qingpi. Our aim was to determine the best storage time of Qingpi by studying the physicochemical properties and metabolite changes in product stored from 1 to 5 years. As a result, the color of Qingpi became darker during storage. Both the levels of three flavonoids (hesperidin, nobiletin, and tangeretin) and total flavonoids (TFs) and the antioxidant activity decreased during storage and the total phenolics (TPs) content fluctuated during storage. Cluster analysis was performed on the color parameters measured using a color difference meter, revealing that the color of Qingpi differed before and after 3 years of storage. A total of 9 special differential metabolites were identified that could be used to distinguish the storage years of Qingpi. This is the first study to report the quality changes of Qingpi during storage. The optimized results of the quality evaluation indicated that Qingpi should be stored for no more than 3 years.

Pharmaceutical Food Science: Search for Bio-Functional Molecules Obtained from Natural Resources to Prevent and Ameliorate Lifestyle Diseases

In this review, our resent pharmaceutical food science research for bio-functional molecules obtained from natural resources that contribute to i) suppression of postprandial blood glucose elevation and/or improvement of glucose tolerance and ii) reduction of visceral fat accumulation and improvement of lipid metabolism were summarized. Based on studies using MONOTORI science, salacinol (1), neokotalanol (4), and trans-tiliroside (20) have been approved or notified by the Consumer Affairs Agency in Japan as functional substances in food with health claims, Food for Specified Health Use and Food with Functional Claims.

The Citrus Flavonoid Nobiletin Downregulates Angiopoietin-like Protein 3 (ANGPTL3) Expression and Exhibits Lipid-Modulating Effects in Hepatic Cells and Adult Zebrafish Models

Nobiletin, a dietary citrus flavonoid, exerts biological activities against hyperlipidemia, obesity, and atherosclerotic cardiovascular diseases (ASCVDs). The aim of this study was to explore the lipid-lowering effects of nobiletin and the underlying molecular mechanisms in vitro in hepatic cells and in vivo in zebrafish models. Transcriptome and gene ontology (GO) analyses of differentially expressed genes (DEGs) by gene set enrichment analysis (GSEA) showed that a set of twenty-eight core enrichment DEGs associated with “GO BP regulation of lipid metabolic process” (GO: 0019216) were significantly downregulated in nobiletin-treated cells. Among these genes, angiopoietin-like 3 (ANGPTL3), an inhibitor of lipoprotein lipase (LPL) activity that regulates TG-rich lipoprotein (TGRL) metabolism in circulation, was the protein most markedly downregulated by nobiletin. Nobiletin (20 and 40 μM) significantly reduced the levels of ANGPTL3 mRNA and intracellular and secreted ANGPTL3 proteins in hepatic cell lines. Furthermore, alleviation of secreted ANGPTL3 production by nobiletin was found to reinstate LPL catalytic activity. Nobiletin significantly inhibited ANGPTL3 promoter activity and attenuated the transcription factor liver X receptor-α (LXRα)-mediated ANGPTL3 transcription. Molecular docking analysis predicted that nobiletin could bind to the ligand-binding domain of LXRα, thereby counteracting LXRα activation. In animal studies, orally administered nobiletin significantly alleviated the levels of plasma triglycerides (TGs) and cholesterol in zebrafish fed a high-fat diet. Moreover, nobiletin significantly reduced the amounts of hepatic ANGPTL3 protein in zebrafish. Our findings suggest that nobiletin may regulate the LXRα-ANGPTL3-LPL axis and exhibit lipid-modulating effects in vitro and in vivo. Thus, nobiletin is a potential ANGPTL3 inhibitor for the regulation of lipid metabolism to ameliorate dyslipidemia and ASCVDs.

The biological clock enhancer nobiletin ameliorates steatosis in genetically obese mice by restoring aberrant hepatic circadian rhythm

Nonalcoholic fatty liver disease (NAFLD) is associated with disruption of homeostatic lipid metabolism, but underlying processes are poorly understood. One possible mechanism is impairment in hepatic circadian rhythm, which regulates key lipogenic mediators in the liver and whose circadian oscillation is diminished in obesity. Nobiletin enhances biological rhythms by activating RAR-related orphan receptor nuclear receptor, protecting against metabolic syndrome in a clock-dependent manner. The effect of nobiletin in NAFLD is unclear. In this study, we investigate the clock-enhancing effects of nobiletin in genetically obese (db/db) PER2::LUCIFERASE reporter mice with fatty liver. We report microarray expression data suggesting hepatic circadian signaling is impaired in db/db mice with profound hepatic steatosis. Circadian PER2 activity, as assessed by mRNA and luciferase assay, was significantly diminished in liver of db/db PER2::LUCIFERASE reporter mice. Continuous animal monitoring systems and constant dark studies suggest the primary circadian defect in db/db mice lies within peripheral hepatic oscillators and not behavioral rhythms or the master clock. In vitro, nobiletin restored PER2 amplitude in lipid-laden PER2::LUCIFERASE reporter macrophages. In vivo, nobiletin dramatically upregulated core clock gene expression, hepatic PER2 activity, and ameliorated steatosis in db/db PER2::LUCIFERASE reporter mice. Mechanistically, nobiletin reduced serum insulin levels, decreased hepatic Srebp1c, Acaca1, Tnfα, and Fgf21 expression, but did not improve Plin2, Plin5, or Cpt1, suggesting nobiletin attenuates steatosis in db/db mice via downregulation of hepatic lipid accumulation. These data suggest restoring endogenous rhythm with nobiletin resolves steatosis in obesity, proposing that hypothesis that targeting the biological clock may be an attractive therapeutic strategy for NAFLD.NEW & NOTEWORTHY NAFLD is the most common chronic liver disease, but underlying mechanisms are unclear. We show here that genetically obese (db/db) mice with fatty liver have impaired hepatic circadian rhythm. Hepatic Per2 expression and PER2 reporter activity are diminished in db/db PER2::LUCIFERASE mice. The biological clock-enhancer nobiletin restores hepatic PER2 in db/db PER2::LUCIFERASE mice, resolving steatosis via downregulation of Srebp1c. These studies suggest targeting the circadian clock may be beneficial strategy in NAFLD.

Anti-adipogenic effect of the flavonoids through the activation of AMPK in palmitate (PA)-treated HepG2 cells

BACKGROUND

Flavonoids are natural polyphenols found widely in citrus fruit and peel that possess anti-adipogenic effects. On the other hand, the detailed mechanisms for the anti-adipogenic effects of flavonoids are unclear.

OBJECTIVES

The present study observed the anti-adipogenic effects of five major citrus flavonoids, including hesperidin (HES), narirutin (NAR), nobiletin (NOB), sinensetin (SIN), and tangeretin (TAN), on AMP-activated protein kinase (AMPK) activation in palmitate (PA)-treated HepG2 cells.

METHODS

The intracellular lipid accumulation and triglyceride (TG) contents were quantified by Oil-red O staining and TG assay, respectively. The glucose uptake was assessed using 2-[N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-d-glucose (2-NBDG) assay. The levels of AMPK, acetyl-CoA carboxylase (ACC), and glycogen synthase kinase 3 beta (GSK3β) phosphorylation, and levels of sterol regulatory element-binding protein 2 (SREBP-2) and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) expression were analyzed by Western blot analysis. The potential interaction between the flavonoids and the γ-subunit of AMPK was investigated by molecular docking analysis.

RESULTS

The flavonoid treatment reduced both intracellular lipid accumulation and TG content in PA-treated HepG2 cells significantly. In addition, the flavonoids showed increased 2-NBDG uptake in an insulin-independent manner in PA-treated HepG2 cells. The flavonoids increased the AMPK, ACC, and GSK3β phosphorylation levels and decreased the SREBP-2 and HMGCR expression levels in PA-treated HepG2 cells. Molecular docking analysis showed that the flavonoids bind to the CBS domains in the regulatory γ-subunit of AMPK with high binding affinities and could serve as potential AMPK activators.

CONCLUSION

The overall results suggest that the anti-adipogenic effect of flavonoids on PA-treated HepG2 cells results from the activation of AMPK by flavonoids.

Efficacy of nobiletin in improving hypercholesterolemia and nonalcoholic fatty liver disease in high-cholesterol diet-fed mice

BACKGROUND/OBJECTIVES

Nobiletin (NOB), a citrus flavonoid, is reported to have beneficial effects on cardiovascular and metabolic health. However, there is limited research investigating the effect of long-term supplementation with low-dose NOB on high-cholesterol diet (HCD)-induced hypercholesterolemia and non-obese nonalcoholic fatty liver disease (NAFLD). Therefore, we investigated the influence of NOB on hypercholesterolemia and NAFLD in HCD-fed mice.

SUBJECTS/METHODS

C57BL/6J mice were fed a normal diet (ND) or HCD (35 kcal% fat, 1.25% cholesterol, 0.5% cholic acid) with or without NOB (0.02%) for 20 weeks.

RESULTS

HCD feeding markedly reduced the final body weight compared to ND feeding, with no apparent energy intake differences. NOB supplementation suppressed HCD-induced weight loss without altering energy intake. Moreover, NOB significantly decreased the total cholesterol (TC) levels and the low-density lipoprotein (LDL)/very-LDL-cholesterol to TC ratio, and increased the high-density lipoprotein-cholesterol/TC ratio in plasma, compared to those for HCD feeding alone. The plasma levels of inflammatory and atherosclerosis markers (C-reactive protein, oxidized LDL, interleukin [IL]-1β, IL-6, and plasminogen activator inhibitor-1) were significantly lower, whereas those of anti-atherogenic adiponectin and paraoxonase were higher in the NOB-supplemented group than in the HCD control group. Furthermore, NOB significantly decreased liver weight, hepatic cholesterol and triglyceride contents, and lipid droplet accumulation by inhibiting messenger RNA expression of hepatic genes and activity levels of cholesterol synthesis-, esterification-, and fatty acid synthesis-associated enzymes, concomitantly enhancing fatty acid oxidation-related gene expression and enzyme activities. Dietary NOB supplementation may protect against hypercholesterolemia and NAFLD via regulation of hepatic lipid metabolism in HCD-fed mice; these effects are associated with the amelioration of inflammation and reductions in the levels of atherosclerosis-associated cardiovascular markers.

CONCLUSIONS

The present study suggests that NOB may serve as a potential therapeutic agent for the treatment of HCD-induced hypercholesterolemia and NAFLD.

Current innovations in nutraceuticals and functional foods for intervention of non-alcoholic fatty liver disease

As innovations in global agricultural production and food trading systems lead to major dietary shifts, high morbidity rates from non-alcoholic fatty liver disease (NAFLD), accompanied by elevated risk of lipid metabolism-related complications, has emerged as a growing problem worldwide. Treatment and prevention of NAFLD and chronic liver disease depends on the availability of safe, effective, and diverse therapeutic agents, the development of which is urgently needed. Supported by a growing body of evidence, considerable attention is now focused on interventional approaches that combines nutraceuticals and functional foods. In this review, we summarize the pathological progression of NAFLD and discuss the beneficial effects of nutraceuticals and the active ingredients in functional foods. We also describe the underlying mechanisms of these compounds in the intervention of NAFLD, including their effects on regulation of lipid homeostasis, activation of signaling pathways, and their role in gut microbial community dynamics and the gut-liver axis. In order to identify novel targets for treatment of lipid metabolism-related diseases, this work broadly explores the molecular mechanism linking nutraceuticals and functional foods, host physiology, and gut microbiota. Additionally, the limitations in existing knowledge and promising research areas for development of active interventions and treatments against NAFLD are discussed.

Effects of Coenzyme Q10 Supplementation on Anthropometric Indices in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background:

Obesity is related to increase in the incidence of morbidity and mortality. Previous studies have led to conflicting results regarding the effect of coenzyme Q10 (CoQ10) supplementation on anthropometric indices. This study aimed to evaluate the efficacy of CoQ10 supplementation on body weight, body mass index (BMI), and waist circumference (WC) through a systematic review and meta-analysis of randomized controlled trials (RCTs).

Methods:

PubMed, Scopus, Web of Science, and Cochrane Library as well as the reference lists of the identified relevant RCTs were searched up to March 2019, and weighted mean differences (WMDs) were pooled by using the random-effects model.

Results:

Twenty RCTs (976 participants) were eligible to be included in the systematic review. The meta-analysis revealed that CoQ10 supplementation had no effect on body weight (WMD = −0.04 kg; 95% confidence interval [CI]: −1.96, 1.6; I² = 0.0%), BMI (WMD = −0.06 kg/m²; 95% CI: −0.54, 0.42; I² = 0.0%), and WC (WMD = 0.79 cm; 95% CI: −2.83, 0.04; I² = 0.0%).

Conclusions:

CoQ10 supplementation might not improve anthropometric indices. Future well-designed trials are still needed to confirm these results.

Nobiletin Protects from Renal Ischemia-Reperfusion Injury in Rats by Suppressing Inflammatory Cytokines and Regulating iNOS-eNOS Expressions

Ischemia-reperfusion injury is an organ failure caused by hypoxia and reperfusion, which is closely associated with oxidative stress and inflammation. In this study, we investigated whether nobiletin had protective effects on inflammatory parameters, oxidative damage, iNOS-eNOS expressions, and histopathological structure of renal tissue in rats with renal ischemia-reperfusion injury. For this purpose, 24 rats were divided into 4 groups: group 1 (Control), group 2 (Ischemia-Reperfusion-IR), group 3 (Nobiletin-10 mg/kg p.o.), group 4 (Nobiletin + IR). The study was continued for 7 days. At the end of the study, urea (p < 0.05), creatine (p < 0.05), MDA (p < 0.001), TNF-alpha (p < 0.001), IL-1 beta (p < 0.05), and IL-6 (p < 0.001) levels increased in the IR group; however, a significant decrease occurred in group 4 (Nobiletin + IR) and it reached the control group levels. In the IR group, GSH (p < 0.01) levels, and GSH.Px (p < 0.01) and CAT (p < 0.05) activities decreased whereas they increased significantly in group 4 (Nobiletin + IR) and reached the same levels as the control group. In histopathological analyses, destruction and increased iNOS-eNOS expressions in the IR group showed a significant decrease in group 4 (Nobiletin + IR). As a result, the application of nobiletin has shown that it has protective effects by reducing kidney damage caused by IR injury.

Tri-Herbal Medicine Divya Sarva-Kalp-Kwath (Livogrit) Regulates Fatty Acid-Induced Steatosis in Human HepG2 Cells through Inhibition of Intracellular Triglycerides and Extracellular Glycerol Levels

Steatosis is characterized by excessive triglycerides accumulation in liver cells. Recently, application of herbal formulations has gained importance in treating complex diseases. Therefore, this study explores the efficacy of tri-herbal medicine Divya Sarva-Kalp-Kwath (SKK; brand name, Livogrit) in treating free fatty acid (FFA)-induced steatosis in human liver (HepG2) cells and rat primary hepatocytes. Previously, we demonstrated that cytosafe SKK ameliorated CCl₄-induced hepatotoxicity. In this study, we evaluated the role of SKK in reducing FFA-induced cell-death, and steatosis in HepG2 through analysis of cell viability, intracellular lipid and triglyceride accumulation, extracellular free glycerol levels, and mRNA expression changes. Plant metabolic components fingerprinting in SKK was performed via High Performance Thin Layer Chromatography (HPTLC). Treatment with SKK significantly reduced the loss of cell viability induced by 2 mM-FFA in a dose-dependent manner. SKK also reduced intracellular lipid, triglyceride accumulation, secreted AST levels, and increased extracellular free glycerol presence in the FFA-exposed cells. SKK normalized the FFA-stimulated overexpression of SREBP1c, FAS, C/EBPα, and CPT1A genes associated with the induction of steatosis. In addition, treatment of rat primary hepatocytes with FFA and SKK concurrently, reduced intracellular lipid accumulation. Thus, SKK showed efficacy in reducing intracellular triglyceride accumulation and increasing extracellular glycerol release, along with downregulation of related key genetic factors for FFA-associated steatosis.

Flavonoids from Aurantii Fructus Immaturus and Aurantii Fructus: promising phytomedicines for the treatment of liver diseases

Background

Liver diseases and related complications are major sources of morbidity and mortality, which places a huge financial burden on patients and lead to nonnegligible social problems. Therefore, the discovery of novel therapeutic drugs for the treatment of liver diseases is urgently required. Aurantii Fructus Immaturus (AFI) and Aurantii Fructus (AF) are frequently used herbal medicines in traditional Chinese medicine (TCM) formulas for the treatment of diverse ailments. A variety of bioactive ingredients have been isolated and identified from AFI and AF, including alkaloids, flavonoids, coumarins and volatile oils.

Main body

Emerging evidence suggests that flavonoids, especially hesperidin (HD), naringenin (NIN), nobiletin (NOB), naringin (NRG), tangeretin (TN), hesperetin (HT) and eriodictyol (ED) are major representative bioactive ingredients that alleviate diseases through multi-targeting mechanisms, including anti-oxidative stress, anti-cytotoxicity, anti-inflammation, anti-fibrosis and anti-tumor mechanisms. In the current review, we summarize the recent progress in the research of hepatoprotective effects of HD, NIN, NOB, NRG, TN, HT and ED and highlight the potential underlying molecular mechanisms. We also point out the limitations of the current studies and shed light on further in-depth pharmacological and pharmacokinetic studies of these bioactive flavonoids.

Conclusion

This review outlines the recent advances in the literature and highlights the potential of these flavonoids isolated from AFI and AF as therapeutic agents for the treatment of liver diseases. Further pharmacological studies will accelerate the development of natural products in AFI and AF and their derivatives as medicines with tantalizing prospects in the clinical application.

Nobiletin Ameliorates NLRP3 Inflammasome-Mediated Inflammation Through Promoting Autophagy via the AMPK Pathway

Multiple lines of evidence have shown that neuroinflammation and autophagy are highly involved in the process of depression. Nobiletin (NOB) displays neuroprotective effects and anti-depressant-like effects. Given the evidence that NOB exerts anti-inflammatory effects and regulates autophagy, we investigate the anti-neuroinflammatory properties and the effect of regulating the autophagy of NOB and subsequently uncover the potential anti-depressant mechanisms of NOB. The behavioral changes of rats were observed after prolonged lipopolysaccharide (LPS) treatment and NOB administration. Rat hippocampus and BV2 cells treated by LPS and NOB were evaluated. The methods of real-time PCR analysis, Western blot, immunostaining, and adenovirus transfection were employed to determine neuroinflammation, autophagic markers, and nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) activation. Our study showed LPS enhanced the expression of pro-inflammatory cytokines and NLRP3 inflammasome activation but inhibited autophagy in both rat hippocampus and BV2 cells. NOB significantly improved the behavioral deficits and ameliorated the neuroinflammation induced by LPS in rats. Furthermore, NOB promoted autophagy and attenuated NLRP3 inflammasome activation induced by LPS, involving in the process the adenosine monophosphate-activated protein kinase (AMPK) pathway. Neuroprotective and anti-depressant actions of NOB relied on its effects of promoting autophagy and suppressing the activation of NLRP3, in which process of AMPK pathway may be involved.

Nobiletin affects circadian rhythms and oncogenic characteristics in a cell-dependent manner

The natural product nobiletin is a small molecule, widely studied with regard to its therapeutic effects, including in cancer cell lines and tumors. Recently, nobiletin has also been shown to affect circadian rhythms via their enhancement, resulting in protection against metabolic syndrome. We hypothesized that nobiletin's anti-oncogenic effects, such as prevention of cell migration and formation of anchorage independent colonies, are correspondingly accompanied by modulation of circadian rhythms. Concurrently, we wished to determine whether the circadian and anti-oncogenic effects of nobiletin differed across cancer cell lines. In this study, we assessed nobiletin's circadian and therapeutic characteristics to ascertain whether these effects depend on cell line, which here also varied in terms of baseline circadian rhythmicity. Three cell culture models where nobiletin's effects on cell proliferation and migration have been studied previously were evaluated: U2OS (bone osteosarcoma), which possesses robust circadian rhythms; MCF7 (breast adenocarcinoma), which has weak circadian rhythms; and MDA-MB-231 (breast adenocarcinoma), which is arrhythmic. We found that circadian, migration, and proliferative effects following nobiletin treatment were subtle in the U2OS and MCF7 cells. On the other hand, changes were clear in MDA-MB-231s, where nobiletin rescued rhythmicity and substantially reduced oncogenic features, specifically two-dimensional cell motility and anchorage-independent growth. Based on these results and those previously described, we posit that the effects of nobiletin are indeed cell-type dependent, and that a positive correlation may exist between nobiletin's circadian and therapeutic effects.

Herbal Medicine in the Treatment of Non-Alcoholic Fatty Liver Diseases-Efficacy, Action Mechanism, and Clinical Application

Non-alcoholic fatty liver disease (NAFLD) is a common chronic liver disease with high prevalence in the developed countries. NAFLD has been considered as one of the leading causes of cryptogenic cirrhosis and chronic liver disease. The individuals with obesity, insulin resistance and diabetes mellitus, hyperlipidaemia, and hypertension cardiovascular disease have a high risk to develop NAFLD. The related critical pathological events are associated with the development of NAFLD including insulin resistance, lipid metabolism dysfunction, oxidative stress, inflammation, apoptosis, and fibrosis. The development of NAFLD range from simple steatosis to non-alcoholic steatohepatitis (NASH). Hepatic steatosis is characterized by fat accumulation, which represents the early stage of NAFLD. Then, inflammation triggered by steatosis drives early NAFLD progression into NASH. Therefore, the amelioration of steatosis and inflammation is essential for NAFLD therapy. The herbal medicine have taken great effects on the improvement of steatosis and inflammation for treating NAFLD. It has been found out that these effects involved the multiple mechanisms underlying lipid metabolism and inflammation. In this review, we pay particular attention on herbal medicine treatment and make summary about the research of herbal medicine, including herb formula, herb extract and naturals compound on NAFLD. We make details about their protective effects, the mechanism of action involved in the amelioration steatosis and inflammation for NAFLD therapy as well as the clinical application.

Nobiletin in Cancer Therapy: How This Plant Derived-Natural Compound Targets Various Oncogene and Onco-Suppressor Pathways

Cancer therapy is a growing field, and annually, a high number of research is performed to develop novel antitumor drugs. Attempts to find new antitumor drugs continue, since cancer cells are able to acquire resistance to conventional drugs. Natural chemicals can be considered as promising candidates in the field of cancer therapy due to their multiple-targeting capability. The nobiletin (NOB) is a ubiquitous flavone isolated from Citrus fruits. The NOB has a variety of pharmacological activities, such as antidiabetes, antioxidant, anti-inflammatory, hepatoprotective, and neuroprotective. Among them, the antitumor activity of NOB has been under attention over recent years. In this review, we comprehensively describe the efficacy of NOB in cancer therapy. NOB induces apoptosis and cell cycle arrest in cancer cells. It can suppress migration and invasion of cancer cells via the inhibition of epithelial-to-mesenchymal transition (EMT) and EMT-related factors such as TGF-β, ZEB, Slug, and Snail. Besides, NOB inhibits oncogene factors such as STAT3, NF-κB, Akt, PI3K, Wnt, and so on. Noteworthy, onco-suppressor factors such as microRNA-7 and -200b undergo upregulation by NOB in cancer therapy. These onco-suppressor and oncogene pathways and mechanisms are discussed in this review.

Nobiletin suppresses IL-21/IL-21 receptor-mediated inflammatory response in MH7A fibroblast-like synoviocytes (FLS): An implication in rheumatoid arthritis

The mechanisms driving the development and progression of Rheumatoid arthritis (RA) are complex, novel targeted therapies are gaining traction as potential methods to prevent or slow the progression of RA. Nobiletin is a derivative of citrus fruit that has been shown to attenuate the development of osteoarthritis and inhibit the expression of proinflammatory cytokines. However, the exact mechanisms by which nobiletin exerts these chondroprotective effects remain poorly understood. In the present study, we investigated the impact of nobiletin in mediating the effects of interleukin-21 (IL-21) in MH7A fibroblast-like synoviocytes (FLS), the main cell type found in the articular synovium. Firstly, we demonstrate that nobiletin (25 μM and 50 μM) reduced the expression of the IL-21 receptor by 29% and 51%, respectively, in FLS. Additionally, our findings demonstrate that nobiletin potently ameliorated IL-21-induced increased production of reactive oxygen species and 4-hydroxynonenal, increased expression of interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α), and high-mobility group box 1 (HMGB1), and decreased mitochondrial membrane potential. We also demonstrate the ability of nobiletin to attenuate IL-21-induced expression of matrix metalloproteinases 3 and 13 (MMP-3, MMP-13), key degradative enzymes involved in RA-associated cartilage destruction. Finally, we show that the effects of nobiletin are mediated through the JAK1/STAT3 pathway, as nobiletin significantly reduced the phosphorylation of both JAK1 and STAT3. Taken together, our findings indicate that nobiletin may offer a safe and effective treatment against the development and progression of RA induced by the expression of IL-21 and its receptor.

The citrus flavonoid nobiletin confers protection from metabolic dysregulation in high-fat-fed mice independent of AMPK

Obesity, dyslipidemia, and insulin resistance, the increasingly common metabolic syndrome, are risk factors for CVD and type 2 diabetes that warrant novel therapeutic interventions. The flavonoid nobiletin displays potent lipid-lowering and insulin-sensitizing properties in mice with metabolic dysfunction. However, the mechanisms by which nobiletin mediates metabolic protection are not clearly established. The central role of AMP-activated protein kinase (AMPK) as an energy sensor suggests that AMPK is a target of nobiletin. We tested the hypothesis that metabolic protection by nobiletin required phosphorylation of AMPK and acetyl-CoA carboxylase (ACC) in mouse hepatocytes, in mice deficient in hepatic AMPK (Ampkβ1 ^-/-), in mice incapable of inhibitory phosphorylation of ACC (AccDKI), and in mice with adipocyte-specific AMPK deficiency (iβ1β2AKO). We fed mice a high-fat/high-cholesterol diet with or without nobiletin. Nobiletin increased phosphorylation of AMPK and ACC in primary mouse hepatocytes, which was associated with increased FA oxidation and attenuated FA synthesis. Despite loss of ACC phosphorylation in Ampkβ1 ^-/- hepatocytes, nobiletin suppressed FA synthesis and enhanced FA oxidation. Acute injection of nobiletin into mice did not increase phosphorylation of either AMPK or ACC in liver. In mice fed a high-fat diet, nobiletin robustly prevented obesity, hepatic steatosis, dyslipidemia, and insulin resistance, and it improved energy expenditure in Ampkβ1 ^-/-, AccDKI, and iβ1β2AKO mice to the same extent as in WT controls. Thus, the beneficial metabolic effects of nobiletin in vivo are conferred independently of hepatic or adipocyte AMPK activation. These studies further underscore the therapeutic potential of nobiletin and begin to clarify possible mechanisms.

Nobiletin, a novel inhibitor, inhibits HBsAg production and hepatitis B virus replication

Chronic hepatitis B virus (HBV) infection is a serious problem due to its extensive worldwide distribution and poor prognosis including cirrhosis and/or hepatocellular carcinoma. The hepatitis B surface antigen(HBsAg) is a vital serum marker in HBV infection and a major obstacle for effective and subsequently virus clearance. However, Current anti-HBV drugs, such as nucleos(t)ide analogs (NA) and PegIFN, do not meet ideal result of sustained HBsAg loss (defined as functional cure). Therefore, there is an urgent need to identify a new compound targeting HBsAg. In this study, nobiletin was screened out from 1500 compounds due to its low cytotoxicity and high antiviral activity. The effect of nobiletin on HBV was determined in HepG2.2.15 and HepG2-NTCP cells. Furthermore, the antiviral capability of nobiletin was also verified in vivo. Unlike entecavir (ETV) therapy, which reduced HBV DNA but do not lead to an effective reduction in HBsAg, nobiletin significantly reduced the level of HBsAg as well as lowered HBV DNA in vivo and in vitro. Meanwhile, combination of nobiletin and ETV led to broad reductions of both HBV DNA and HBsAg level. This study may shed light on the development of a novel class of anti-HBV agents.

Glucose Tolerance-Improving Activity of Helichrysoside in Mice and Its Structural Requirements for Promoting Glucose and Lipid Metabolism

An acylated flavonol glycoside, helichrysoside, at a dose of 10 mg/kg/day per os for 14 days, improved the glucose tolerance in mice without affecting the food intake, visceral fat weight, liver weight, and other plasma parameters. In this study, using hepatoblastoma-derived HepG2 cells, helichrysoside, trans-tiliroside, and kaempferol 3-O-β-d-glucopyranoside enhanced glucose consumption from the medium, but their aglycones and p-coumaric acid did not show this activity. In addition, several acylated flavonol glycosides were synthesized to clarify the structural requirements for lipid metabolism using HepG2 cells. The results showed that helichrysoside and related analogs significantly inhibited triglyceride (TG) accumulation in these cells. The inhibition by helichrysoside was more potent than that by other acylated flavonol glycosides, related flavonol glycosides, and organic acids. As for the TG metabolism-promoting activity in high glucose-pretreated HepG2 cells, helichrysoside, related analogs, and their aglycones were found to significantly reduce the TG contents in HepG2 cells. However, the desacyl flavonol glycosides and organic acids derived from the acyl groups did not exhibit an inhibitory impact on the TG contents in HepG2 cells. These results suggest that the existence of the acyl moiety at the 6′′ position in the D-glucopyranosyl part is essential for glucose and lipid metabolism-promoting activities.

Influence of Olive Extracts on the Expression of Genes Involved in Lipid Metabolism in Medaka Fish

Aims. To assess the possible effect of polyphenol-rich olive extracts on lipid metabolism in medaka fish by quantifying the expression of lipogenic and lipolytic genes. Materials and methods. Adult medaka fish were maintained in tanks for five days with five extracts at 0.01% in water, causing obesity through a diet rich in carbohydrates, with a control group maintained in water with a normal diet. The extracts contained polyphenols ranging between 7 and 116 mg/g (oleuropein, hydroxytyrosol) with an antioxidant power of 2-13 mmol of 2,4,6-tri(2-pyridyl)-1,3,5-triazine/100 g. After five days, the fish were sacrificed and the hepatic mRNA and its complementary DNA were extracted by reverse transcription. Complementary DNAs were quantified for three lipolytic and three lipogenic genes by real-time PCR. The relative gene expression was calculated from the amplification curves in reference to the control group. Results. The expression of genes involved in lipolysis, including peroxisome proliferator-activated receptor-±, acyl-CoA oxidase 1, and carnitine palmitoyltransferase 1, were clearly decreased in fish subjected to an obesogenic diet, and this situation could not be reversed in fish maintained with polyphenol-rich extracts. In contrast, lipogenic fatty acid synthase, acetyl-CoA carboxylase 1, and sterol regulatory element-binding protein 1 genes increased considerably with the obesogenic diet and reverted to the normal state with the olive extracts. The effect was not dependent on the total polyphenol content, the specific oleuropein or hydroxytyrosol concentration, or the antioxidant power, suggesting a synergistic effect. Conclusion. Olive polyphenols, acting as anti-lipogenic agents, have a positive effect on lipid metabolism, but their mechanism in each gene is different according to the extract, which supports synergistic mechanisms with the different proportions of polyphenols and accompanying phytochemicals in each extract.

Nobiletin and Derivatives: Functional Compounds from Citrus Fruit Peel for Colon Cancer Chemoprevention

The search for effective methods of cancer treatment and prevention has been a continuous effort since the disease was discovered. Recently, there has been increasing interest in exploring plants and fruits for molecules that may have potential as either adjuvants or as chemopreventive agents against cancer. One of the promising compounds under extensive research is nobiletin (NOB), a polymethoxyflavone (PMF) extracted exclusively from citrus peel. Not only does nobiletin itself exhibit anti-cancer properties, but its derivatives are also promising chemopreventive agents; examples of derivatives with anti-cancer activity include 3'-demethylnobiletin (3'-DMN), 4'-demethylnobiletin (4'-DMN), 3',4'-didemethylnobiletin (3',4'-DMN) and 5-demethylnobiletin (5-DMN). In vitro studies have demonstrated differential efficacies and mechanisms of NOB and its derivatives in inhibiting and killing of colon cancer cells. The chemopreventive potential of NOB has also been well demonstrated in several in vivo colon carcinogenesis animal models. NOB and its derivatives target multiple pathways in cancer progression and inhibit several of the hallmark features of colorectal cancer (CRC) pathophysiology, including arresting the cell cycle, inhibiting cell proliferation, inducing apoptosis, preventing tumour formation, reducing inflammatory effects and limiting angiogenesis. However, these substances have low oral bioavailability that limits their clinical utility, hence there have been numerous efforts exploring better drug delivery strategies for NOB and these are part of this review. We also reviewed data related to patents involving NOB to illustrate the extensiveness of each research area and its direction of commercialisation. Furthermore, this review also provides suggested directions for future research to advance NOB as the next promising candidate in CRC chemoprevention.

Genome-wide analysis of DNA methylation identifies novel differentially methylated regions associated with lipid accumulation improved by ethanol extracts of Allium tubersosum and Capsella bursa-pastoris in a cell model

Hepatic steatosis is the most common chronic liver disease in Western countries. Both genetic and environmental factors are known as causes of the disease although their underlying mechanisms have not been fully understood. This study investigated the association of DNA methylation with oleic acid-induced hepatic steatosis. It also examined effects of food components on DNA methylation in hepatic steatosis. Genome-wide DNA methylation of oleic acid (OA)-induced lipid accumulation in vitro cell model was investigated using reduced representation bisulfite sequencing. Changes of DNA methylation were also analyzed after treatment with food components decreasing OA-induced lipid accumulation in the model. We identified total 81 regions that were hypermethylated by OA but hypomethylated by food components or vice versa. We determined the expression of seven genes proximally located at the selected differentially methylated regions. Expression levels of WDR27, GNAS, DOK7, MCF2L, PRKG1, and CMYA5 were significantly different between control vs OA and OA vs treatment with food components. We demonstrated that DNA methylation was associated with expression of genes in the model of hepatic steatosis. We also found that food components reversely changed DNA methylation induced by OA and alleviated lipid accumulation. These results suggest that DNA methylation is one of the mechanisms causing the hepatic steatosis and its regulation by food components provides insights that may prevent or alleviate lipid accumulation.

Role of Natural Phenolics in Hepatoprotection: A Mechanistic Review and Analysis of Regulatory Network of Associated Genes

The liver is not only involved in metabolism and detoxification, but also participate in innate immune function and thus exposed to frequent target Thus, they are the frequent target of physical injury. Interestingly, liver has the unique ability to regenerate and completely recoup from most acute, non-iterative situation. However, multiple conditions, including viral hepatitis, non-alcoholic fatty liver disease, long term alcohol abuse and chronic use of medications can cause persistent injury in which regenerative capacity eventually becomes dysfunctional resulting in hepatic scaring and cirrhosis. Despite the recent therapeutic advances and significant development of modern medicine, hepatic diseases remain a health problem worldwide. Thus, the search for the new therapeutic agents to treat liver disease is still in demand. Many synthetic drugs have been demonstrated to be strong radical scavengers, but they are also carcinogenic and cause liver damage. Present day various hepatic problems are encountered with number of synthetic and plant based drugs. Nexavar (sorafenib) is a chemotherapeutic medication used to treat advanced renal cell carcinoma associated with several side effects. There are a few effective varieties of herbal preparation like Liv-52, silymarin and Stronger neomin phages (SNMC) against hepatic complications. Plants are the huge repository of bioactive secondary metabolites viz; phenol, flavonoid, alkaloid etc. In this review we will try to present exclusive study on phenolics with its mode of action mitigating liver associated complications. And also its future prospects as new drug lead.