Systematic evaluation of phenolic compounds and protective capacity of a new mulberry cultivar J33 against palmitic acid-induced lipotoxicity using a simulated digestion method

Encapsulated Mulberry Fruit Extract Alleviates Changes in an Animal Model of Menopause with Metabolic Syndrome

Currently, the therapeutic strategy against metabolic syndrome and its complications is required due to the increasing prevalence and its impact. Due to the benefits of both mulberry fruit extract and encapsulation technology, we hypothesized that encapsulated mulberry fruit extract (MME) could improve metabolic parameters and its complication risk in postmenopausal metabolic syndrome. To test this hypothesis, female Wistar rats were induced experimental menopause with metabolic syndrome by bilateral ovariectomy (OVX) and high-carbohydrate high-fat (HCHF) diet. Then, they were orally given MME at doses of 10, 50, and 250 mg/kg BW for 8 weeks and the parameters, such as percentage of body weight gain, total cholesterol, triglycerides, HDL-C, LDL-C, atherogenic index, fasting blood glucose, plasma glucose area under the curve, serum angiotensin-converting enzyme (ACE), oxidative stress status, histology, and protein expression of PPAR-γ, TNF-α, and NF-κB in adipose tissues were determined. MME improved body weight gain, adiposity index, glucose intolerance, lipid profiles, atherogenic index, ACE, oxidative stress status, and protein expression of TNF-α and NF-κB. Moreover, MME attenuated adipocyte hypertrophy and enhanced PPAR-γ expression. Taken altogether, MME decreased metabolic syndrome and its complication via the increased PPAR-γ expression. Therefore, MME is the potential candidate for improving metabolic syndrome and its related complications. However, further research in clinical trial is still necessary.

Green extraction of mulberry anthocyanin with improved stability using β-cyclodextrin

BACKGROUND

Mulberry anthocyanin is reported to possess various biological activities and it is unstable during extraction or food production. The use of organic solvents for extraction of mulberry anthocyanins may cause environmental pollution and safety concerns. Therefore, the aim of this study was to investigate the effect of a green extraction solvent (cyclodextrin) on the recovery of anthocyanin from mulberry fruits, as well as the thermal stability of anthocyanin.

RESULTS

β-Cyclodextrin (β-CD) or hydroxypropyl-β-cyclodextrin showed better anthocyanin extraction efficiency than water and ethanol aqueous solution for all tested mulberry cultivars. A molecular docking study indicated that anthocyanin (cyanidin-3-O-glucoside) was encapsulated in the cavity of β-CD, thus enhancing the solubility of anthocyanin. The extraction process was subsequently optimized using a Box-Behnken design. The optimal extraction conditions for anthocyanin and antioxidant activity were found at extraction temperature of 20 °C, extraction time of 44.95 min and β-CD concentration of 45 g L^-1 . Furthermore, a degradation kinetic study demonstrated that addition of β-CD could significantly improve the thermal stability of anthocyanin during extraction, with the activation energy of anthocyanin degradation increasing from 63.06 to 76.77 kJ mol^-1 .

CONCLUSIONS

Overall, our study suggests that β-CD is an alternative green extraction solvent for the recovery of anthocyanins, and addition of β-CD may potentially increase the thermal stability of anthocyanin during the extraction, which may give guidance for functional beverage production. © 2018 Society of Chemical Industry.

Transcription factor EB (TFEB)-mediated autophagy protects against ethyl carbamate-induced cytotoxicity

Ethyl carbamate (EC) is thought to be a toxicant that widely exists in cigarette smoke and polluted air, as well as fermented food and alcoholic beverages. However, the mechanism and approach to treat hepatic damage after EC exposure remain unclear. Here, we first found that EC caused decreased cell viability, reactive oxygen species (ROS) overproduction and glutathione (GSH) depletion in normal human hepatocytes L02 cells. Excessive ROS generation was found to be one of the major reasons for cell cytotoxicity of EC treatment. Furthermore, increased ROS levels also promoted autophagy, a lysosomal degradation process, which was confirmed by detection of LC3-II expression and puncta in GFP-RFP-LC3 transfection assay. Autophagy inhibitor chloroquine (CQ) pretreatment led to decreased cell viability and higher ROS levels compared with EC group, suggesting that autophagy protected EC-treated cells against oxidative stress and cytotoxicity. Notably, we observed increased lysosomal biogenesis and activation of transcription factor EB (TFEB), a master regulator of lysosomal generation, in the process of autophagy. Taken together, we unveiled a novel mechanism of hepatotoxicity and endogenous potent protection of TFEB-mediated autophagy against decreased cell viability and redox disturbance under EC exposure in normal human hepatocytes.

Activation of Nrf2 by Phloretin Attenuates Palmitic Acid-Induced Endothelial Cell Oxidative Stress via AMPK-Dependent Signaling

Phloretin, a dihydrochalcone structural flavonoid compound, possesses antioxidant activity. In this study, we conducted studies to explore the function of phloretin on high palmitic acid-induced oxidative stress in human umbilical vein endothelial cells and investigated the potential mechanism using ribonucleic acid sequencing (RNA-Seq). Our findings reveal that phloretin significantly decreased the levels of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA), increased superoxide dismutase (SOD) and glutathione peroxidase-1 (Gpx-1) activity, and restored the loss of mitochondrial membrane potential (MMP). Next, whole transcriptome analysis was performed using RNA-Seq The results indicated more than 3000 differentially expressed genes (DEGs). Gene Ontology analysis revealed that the DEGs were categorized functionally, mainly by the biological processes, cell metabolism, and cellular response to chemical stimulus. The Kyoto Encyclopedia of Genes and Genomes indicated that they were mainly enriched in cAMP, apoptosis, and cytoskeletal regulation signaling pathways. Furthermore, on the basis of the results of RNA-Seq and Western blotting, our study verified that phloretin upregulated the expression of p-Nrf2 and HO-1 by promoting the phosphorylation of AMPK at Thr¹⁷² through activation of liver kinase B1. In conclusion, phloretin attenuates PA-induced oxidative stress in HUVECs via the AMPK/Nrf2 antioxidative pathway.

UPLC-DAD-QTOF/MS Analysis of Flavonoids from 12 Varieties of Korean Mulberry Fruit

Mulberry (Morus alba L.) has been used in East Asia (Korea, China, and Japan) as a medicine because of its various pharmacological effects including the excellent antioxidant properties of its fruit. This study analyzed extracts from 12 varieties of Korean mulberry fruit for flavonoids using ultrahigh-performance liquid chromatography coupled with diode array detection and quadrupole time-of-flight mass spectrometry (UPLC-DAD-QTOF/MS). Six quercetin derivatives were identified by mass spectrometry (MS) based on the [quercetin + H]+ ion (m/z 303), while four kaempferol derivatives were identified based on the [kaempferol + H]+ ion (m/z 287). Two new compounds (morkotin A and morkotin C, quercetin derivatives) were identified for the first time in mulberry fruit. The total flavonoid contents of the mulberry fruits ranged from 35.0 ± 2.3 mg/100 g DW in the Baek Ok Wang variety (white mulberry) to 119.9 ± 7.0 mg/100 g DW in the Dae Shim variety. This study has, for the first time, evaluated the flavonoid chromatographic profiles of 12 varieties of Korean mulberry fruits in a following quali-quantitative approach, which will contribute to improved utilization of these fruits as health foods.

Mulberry Fruit Extract Ameliorates Nonalcoholic Fatty Liver Disease (NAFLD) through Inhibition of Mitochondrial Oxidative Stress in Rats

Mulberry is known to have pharmacological effects against cholesterol, obesity, and dyslipidemia. Many studies have revealed that mulberry leaf possesses hepatoprotective properties against nonalcoholic fatty liver disease (NAFLD); however, mulberry fruit is less studied in this context. Therefore, this study aimed to investigate the preventive effects of mulberry fruit against high fat diet- (HFD-) induced NAFLD. To evaluate the effects of mulberry fruit on NAFLD, two doses of mulberry fruit ethanol extracts [MB, 100, and 200 mg/kg BW (body weight)] were given to HFD-fed rats for 10 weeks. MB dramatically prevented liver damage as shown by biochemical analysis of the liver injury markers, alanine transaminase, and aspartate transaminase. MB treatment significantly inhibited the increased levels of total cholesterol, triacylglycerol, and low-density lipoprotein-cholesterol but restored the level of high-density lipoprotein-cholesterol in HFD-fed rats. Notably, histological analysis of liver tissues demonstrated that MB substantially ameliorated lipid accumulation. Expression of cholesterol-regulating genes was also suppressed by MB treatment. For its underlying mechanisms, MB suppressed hepatic reactive oxygen species (ROS) overproduction and mitochondrial oxidative stress in HFD-fed rats. MB potentially protects liver tissue against NAFLD by inhibition of mitochondrial oxidative stress, suggesting its possible use as a therapeutic agent for treatment of NAFLD.

Soy genistein administered in soluble chitosan microcapsules maintains antioxidant activity and limits intestinal inflammation

We used water-soluble Chitosan obtained by Maillard reaction with glucosamine to microencapsulate soy genistein (Ge) and preserve its biological activity for oral administration. Release of Ge was pH dependent with a super Case II mechanism at pH 1.2 and an anomalous transport with non-Fickian kinetics at pH 6.8. Microencapsulated Ge retained its antioxidant properties in vitro and its daily administration to mice attenuated clinical signs of acute colitis, limited inflammatory reaction and reduced oxidative stress and tissue injury as well. Remarkably, after feeding microencapsulated Ge the production of IL-10 in colonic tissue was restored to levels of untreated controls. According to statistical multivariate analysis, this cytokine was the parameter with the highest influence on the inflammatory/oxidative status. Microencapsulation of Ge with derivatized Chitosan becomes an interesting alternative to develop therapeutic approaches for oxidative inflammatory diseases; our findings suggest that the soy isoflavone could be incorporated into any functional food for application in intestinal inflammation.

Chlorogenic acid against palmitic acid in endoplasmic reticulum stress-mediated apoptosis resulting in protective effect of primary rat hepatocytes

Background

We demonstrated growing evidence supports a protective role of chlorogenic acid of rat hepatocytes elicited by two compounds, i.e. thapsigargin and palmitic acid. Nevertheless, little is known about the mechanisms of palmitic acid induced endoplasmic reticulum (ER) stress and cell death.

Methods

The proliferation of primary rat hepatocytes was detected by MTT assay. The expression of GRP78, CHOP and GRP94 was detected by Western blot analyses.

Caspase-3 activity was detected by a Caspase-3 substrate kit. Cell apoptosis was detected by Hoechst 33342 staining.

Results

We demonstrated that incubation of hepatocytes for 16 h with palmitic acid elevated cell death. Moreover, Western blot analyses demonstrated increased levels of the endoplasmic reticulum stress markers — glucose regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), and glucose regulated protein 94 (GRP94). Chlorogenic acid could inhibit ER stress induced cell death and levels of indicators of ER stress caused by palmitic acid. The effect of thapsigargin, which evokes ER stress were reversed by chlorogenic acid.

Conclusions

Altogether, our data indicate that in primary rat hepatocytes, chlorogenic acid prevents ER stress-mediated apoptosis of palmitic acid.

Protocatechuic Acid Ameliorated Palmitic-Acid-Induced Oxidative Damage in Endothelial Cells through Activating Endogenous Antioxidant Enzymes via an Adenosine-Monophosphate-Activated-Protein-Kinase-Dependent Pathway

Protocatechuic acid (PCA, 3,4-dihydroxybenzoic acid), the main metabolite of anthocyanins, is widely distributed in fruits and vegetables and has been reported to possess a strong antioxidant activity. Herein, we aimed to investigate the protective effect of PCA against high palmitic-acid (PA)-induced oxidative damage and the underling molecular mechanisms in human umbilical vein endothelial cells (HUVECs). PCA reduced the levels of intracellular reactive oxygen species and malondialdehyde and increased the activities of endogenous antioxidant enzymes, including superoxide dismutase, glutathione peroxidase 1, and heme oxygenase 1 (HO-1). Metabolomic analysis showed that PCA affected numerous metabolites, especially some of which were related with energy metabolism. PCA also upregulated the phosphorylation of adenosine-monophosphate-activated protein kinase (AMPK) at Thr¹⁷² through activating liver kinase B1 and then promoted the expression of p-Nrf2 and HO-1. Moreover, PCA reversed the decreased expression of peroxisome proliferator-activated receptor γ coactivator 1α and significantly increased the mitochondrial density. Collectively, these results demonstrated that PCA attenuated PA-induced oxidative damage in HUVECs via an AMPK-dependent pathway.

Procyanidin B2 ameliorates free fatty acids-induced hepatic steatosis through regulating TFEB-mediated lysosomal pathway and redox state

Procyanidin B2, a naturally occurring phenolic compound, has been reported to exert multiple beneficial functions. However, the effect of procyanidin B2 on free fatty acids (FFAs)-induced hepatic steatosis remains obscure. The present study is therefore aimed to elucidate the protective effect of procyanidin B2 against hepatic steatosis and its underlying mechanism. Herein, we reported that procyanidin B2 attenuated FFAs-induced lipid accumulation and its associated oxidative stress by scavenging excessive ROS and superoxide anion radicals, blocking loss of mitochondrial membrane potential, restoring glutathione content, and increasing activity of antioxidant enzymes (GPx, SOD and CAT) in hepatocytes. Procyanidin B2 mechanistically promoted lipid degradation via modulation of transcription factor EB (TFEB), a master regulator of lysosomal pathway. Molecular docking analysis indicated a possible ligand-binding position of procyanidin B2 with TFEB. In addition, administration of procyanidin B2 resulted in a significant reduction of hepatic fat accumulation in high-fat diet (HFD)-induced obese mice, and also ameliorated HFD-induced metabolic abnormalities, including hyperlipidemia and hyperglycemia. It was confirmed that procyanidin B2 prevented HFD-induced hepatic fat accumulation through down-regulating lipogenesis-related gene expressions (PPARγ, C/EBPα and SREBP-1c), inhibiting pro-inflammatory cytokines production (IL-6 and TNF-α) and increasing antioxidant enzymes activity (GPx, SOD and CAT). Moreover, hepatic fatty acids analysis indicated that procyanidin B2 caused a significant increase in the levels of palmitic acid, oleic acid and linoleic acid. Intriguingly, procyanidin B2 restored the decreased nuclear TFEB expression in HFD-induced liver steatosis and up-regulated its target genes involved in lysosomal pathway (Lamp1, Mcoln, Uvrag), which suggested a previously unrecognized mechanism of procyanidin B2 on ameliorating HFD-induced hepatic steatosis. Taken together, our results demonstrated that procyanidin B2 attenuated FFAs-induced hepatic steatosis through regulating TFEB-mediated lysosomal pathway and redox state, which had important implications that modulation of TFEB might be a potential therapeutic strategy for hepatic steatosis and procyanidin B2 could represent a promising novel agent in the prevention and treatment of non-alcoholic fatty liver disease (NAFLD).

Hexanoic, Octanoic and Decanoic Acids Promote Basal and Insulin-Induced Phosphorylation of the Akt-mTOR Axis and a Balanced Lipid Metabolism in the HepG2 Hepatoma Cell Line

Metabolic illnesses such as non-alcoholic fatty liver disease (NAFLD) are in constant increase worldwide. Highly consumed long chain fatty acids (LCFA) are among the most obesogenic and steatogenic nutrients. Hepatic steatosis is associated with several complications such as insulin resistance. Growing evidence points to medium chain fatty acids (MCFA), more efficiently oxidized than LCFA, as a promising dietary alternative against NAFLD. However, reports on the hepatic effects of MCFA are sometimes conflicting. In this study we exposed HepG2 cells, a human hepatocellular model, to 0.25 mM of hexanoic (C6), or octanoic (C8), and decanoic (C10) acids separately or in a C8 + C10 equimolar mix reflecting commercially available MCFA-rich oils. We found that C6, a poorly studied MCFA, as well as C8 and C10 did not provoke the deleterious lipid anabolism runaway typically induced by LCFA palmitate. MCFA tended, instead, to promote a balanced metabolic profile and were generally non-cytotoxic. Accordingly, mitochondrial integrity was mostly preserved following MCFA treatment. However, treatments with C8 induced a mitochondrial membrane potential decrease, suggesting prolonged exposure to this lipid could be problematic. Finally, MCFA treatments maintained optimal insulin sensitivity and even fostered basal and insulin-dependent phosphorylation of the Akt-mTOR pathway. Overall, MCFA could constitute an effective nutritional tool to manage liver steatosis and hepatic insulin resistance.