Epigallocatechin gallate (EGCG) binds to low-density lipoproteins (LDL) and protects them from oxidation and glycation under high-glucose conditions mimicking diabetes

The aim of this study was to determine whether low-density lipoprotein (LDL)-bound epigallocatechin gallate (EGCG) attenuates LDL oxidation and glycation under high-glucose (HG) conditions mimicking diabetes. Pooled plasma was preincubated with EGCG for three hours, followed by sequential ultracentrifugation and extensive dialysis to isolate LDL. The kinetics of α-tocopherol and EGCG consumption in LDL were measured by a solid-phase extraction system with HPLC-diode array detection (HPLC-DAD) upon oxidation. EGCG enrichment effectively increased the resistance of LDL to oxidation caused by HG/Cu²⁺. A dose-dependent inhibition of HG-mediated long-term glycation of LDL was also observed by LDL-bound EGCG. Data from HPLC-DAD demonstrated that EGCG was able to bind lipoproteins and to facilitate the antioxidant and antiglycation properties of LDL. This study suggests that loading plasma with EGCG is an efficient way to increase the content of this phytochemical in LDL, which may imply favourable in vivo activity of EGCG in diabetes.     

表没食子儿茶素没食子酸酯的抗癌机制的研究进展

表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)是茶叶中主要的活性成分之一,具有抗氧化、抗炎症、抗癌等生理功效.在癌症的治疗和预防研究中,研究者将EGCG作为一种高效的天然化学预防剂,并期望将EGCG开发为保健食品和药品.本文就近年来国内外对EGCG抗癌活性、抗癌机理(抗氧化、抑制血管生成、诱导癌细胞周期阻滞、诱导癌细胞凋亡、抗炎症)方面的研究工作进行概述;并就当前EGCG在抗癌方面存在的缺陷提出解决方案和可实行的改进技术措施.     

Effects of Epigallocatechin gallate glucoside on antitumor activities in human laryngeal epidermoid carcinoma Hep2

(−)-Epigallocatechin-3-gallate (EGCG) has been reported to inhibit cellular proliferation and induce apoptosis in a range of cancer cells. This study examined the cytotoxicity of EGCG glucoside on human laryngeal epidermoid carcinoma Hep2 cells. The EGCG glucoside treatment decreased the cell viability in Hep2 cells. Furthermore, EGCG glucoside caused apoptotic morphological changes with chromatin condensation and nuclear fragmentation, as observed by a terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and activated caspase-3 immunohistochemisty. However, the EGCG glucoside did not induce the production of reactive oxygen species (ROS), suggesting that oxidative stress is not involved in the apoptotic response. EGCG glucoside induces apoptosis in Hep2 cells through not the generation of ROS, but the activation of caspase-3.     

Protective effects of epigallocatechin gallate (EGCG) derivatives on azoxymethane-induced colonic carcinogenesis in mice

Epigallocatechin gallate (EGCG), the major polyphenol in green tea and a functional food ingredient/nutraceutical with health-promoting properties, was structurally modified by esterification with butyric and docosahexaenoic (DHA) acid in order to improve its lipophilicity and hence bioefficacy in vivo. The lipophilic derivatives of EGCG so-prepared were evaluated for their anticancer activity against azoxymethane (AOM)-induced colon carcinogenesis in mice. Formation of colonic aberrant crypt foci (ACF) was monitored as the biomarker of colorectal cancer (CRC). It was found that oral administration of EGCG derivatives led to reduced size of ACF in the mouse colon. EGCG–DHA esters were more effective than EGCG-butyrate in inhibiting the formation of ACF. The total number of large colonic ACF was remarkably decreased by treatment with EGCG derivatives, especially by the EGCG–DHA esters, which showed a 100% inhibition of large ACF formation. Two tumor-promoting enzymes, iNOS and COX-2 were also inhibited by EGCG derivatives to various extents at the expression level. The results suggest that the lipophilic ester derivatives of EGCG are effective in inhibiting colon carcinogenesis and may be good candidates for colon cancer prevention/treatment.     

Lipophilised epigallocatechin gallate (EGCG) derivatives and their antioxidant potential in food and biological systems

Epigallocatechin gallate (EGCG) was structurally modified for enhanced lipophilicity and hence expanded applications, as well as improved cellular absorption in vivo. Ester derivatives of EGCG with stearic acid, eicosapentaenoic acid and docosahexaenoic acid were prepared. All EGCG derivatives inhibited oxidation of bulk oil, and their potency was superior or similar to that of the parent EGCG molecule. The derivatives were more efficient than EGCG in inhibiting oxidation in a β-carotene/linoleic acid emulsion and pork model systems, and their efficiency correlated well with their lipophilicity. In biological systems, the ester derivatives showed higher cell membrane affinity and therefore better cellular absorption than EGCG. The derivatives were more effective than EGCG against Cu²⁺-induced LDL-cholesterol oxidation and also effectively inhibited hydroxyl and peroxyl radical-induced DNA scission and UV-induced liposome oxidation. These results suggest that EGCG esters may be used in food as lipophilic alternatives to EGCG, without compromising functional and physiological properties. Moreover, EGCG-polyunsaturated fatty acid esters may render additional advantages to human health.     

Korean red ginseng attenuates hepatic lipid accumulation via AMPK activation in human hepatoma cells

In this study, we examined Korean red ginseng (KRG) extract affects on the lipid metabolism in HepG2 cells. Increase in AMP-activated protein kinase (AMPK) phosphorylation was observed when the cells were treated with KRG. Activation of AMPK was also demonstrated by measuring the phosphorylation of acetyl-CoA caboxylase (ACC), a substrate of AMPK. KRG down-regulated gene expressions of sterol regulatory element binding protein 1c (SREBP1c) and its target proteins, such as fatty acid synthase (FAS) and stearoyl-CoA desaturase (SCD1) in time- and dose-dependent fashions. In contrast, gene expressions of peroxisome proliferator-activated receptor α (PPARα) and CD36 were increased. These effects were reversed in the presence of compound C, an AMPK inhibitor. However, there were no differences in gene expressions of SREBP2, 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, and low-density-lipoprotein receptor (LDLR). Taken together, KRG induced supression of SREBP1c and activation of PPARα via AMPK and these effects seem to be one of anti-hyperlipidemic mechanism of KRG in HepG2 cells.     

Phillyrin attenuates high glucose-induced lipid accumulation in human HepG2 hepatocytes through the activation of LKB1/AMP-activated protein kinase-dependent signalling

Phillyrin, an active constituent found in many medicinal plants and certain functional foods, has anti-obesity activity in vivo. The aim of our study was to provide new data on the molecular mechanism(s) underlying the role of phillyrin in the prevention of high glucose-induced lipid accumulation in human HepG2 hepatocytes. We found that phillyrin suppressed high glucose-induced lipid accumulation in HepG2 cells. Phillyrin strongly inhibited high glucose-induced fatty acid synthase (FAS) expression by modulating sterol regulatory element-binding protein-1c (SREBP-1c) activation. Moreover, use of the pharmacological AMP-activated protein kinase (AMPK) inhibitor compound C revealed that AMPK is essential for suppressing SREBP-1c expression in phillyrin-treated cells. Finally, we found that liver kinase B1 (LKB1) phosphorylation is required for the phillyrin-enhanced activation of AMPK in HepG2 hepatocytes. These results indicate that phillyrin prevents lipid accumulation in HepG2 cells by blocking the expression of SREBP-1c and FAS through LKB1/AMPK activation, suggesting that phillyrin is a novel AMPK activator with a role in the prevention and treatment of obesity.     

Anti-cancer activity of the ethylacetate fraction from Orostachys japonicus for modulation of the signaling pathway in HepG2 human hepatoma cells

The molecular mechanisms of the ethylacetate (EtOAc) fraction from Orostachys japonicus (OJE) (including gallic acid, kaempferol, and quercetin) for anti-cancer activities in HepG2 cells were investigated. Apoptosis was detected using morphological observation of nuclear changes and investigation of phosphatidylserine exposure at the cytoplasmic membrane using FITC-Annexin V/PI staining. Activities of the apoptotic factors bcl-2, bax, cytochrome c, pro-caspase-3, 8, and 9, as well as MAPKs levels, were measured using western blotting. Some morphologic features of apoptosis were identified using confocal microscopy. OJE caused the expression of apoptotic proteins to change, as evidenced by an increased bax/bcl-2 ratio and increased expression of cytochrome c, and decreased expressions of pro-caspase-3, 8, and 9. After HepG2 cells were exposed to OJE, expressions of p-JNK and p-ERK1/2 increased in a dose dependent manner. OJE exhibits anti-cancer activity via apoptosis induction through a mitochondria dependent signaling pathway in HepG2 cells.     

Protective effect of Cordyceps militaris against high glucose-induced oxidative stress in human umbilical vein endothelial cells

The protective effect of Cordyceps militaris against high glucose-induced oxidative stress in human umbilical vein endothelial cells (HUVECs), as compared with Cordyceps sinensis, was examined. The cytotoxicity of HUVECs induced by 40 mM glucose was ameliorated by water extracts of C. militaris (CME) and water extracts of C. sinensis (CSE). CME and CSE inhibited the increase in ROS and NO in HUVECs induced by 40 mM high glucose. Moreover, CME increased the Bcl-2/Bax ratio, modulated the mitochondrial membrane potential and reduced the caspase-3 activity in high glucose-induced HUVECs. In addition, cordycepin, a component of CME and CSE, displayed protective effects against oxidative stress, which was partly responsible for the cytoprotective effects of CME and CSE against high glucose-induced oxidative stress in HUVECs. Overall, the obtained results show C. militaris helps preventing diabetic endothelial dysfunction and related complications.     

TiO2 particles induce ER stress and apoptosis in human hepatoma cells,HepG2, in a particle size-dependent manner

Food Science and Biotechnology - The cytotoxicity of TiO2 nanoparticles are well-known, but the particle size-dependent induction of ER stress and apoptosis by TiO2 in hepatocytes has not been...     

苦丁茶叶制虫茶粗多酚对HepG2人肝癌细胞的凋亡诱导效果

茶多酚是茶叶中的功能性成分。虫茶作为传统饮品也含有这些化合物,这些多酚类物质的抗癌效果有待科学的研究。本研究对苦丁茶叶制虫茶粗多酚(CPKMI)的癌细胞凋亡诱导作用进行了测定。采用MTT法对CPKMI对癌细胞的体外生长抑制作用进行了分析,然后进一步采用RT-PCR检测对CPKMI的癌细胞凋亡诱导效果进行了实验。经过25、50和100μg/m L的CPKMI处理癌细胞48h,Hep G2人肝癌细胞的增殖被抑制,其中100μg/m L的CPKMI表现出最高的抑制率(72.8%)。CPKMI也可以通过上调caspase-3、caspase-9、p53、p21、E2F1、p73和下调HIAP-1,HIAP-2基因的mRNA的表达对Hep G2癌细胞起到显著的凋亡诱导效果(p0.05)。由此可见,CPKMI表现出强的体外癌细胞凋亡诱导效果。     

Anti-invasion and apoptosis induction of chlorella (Chlorella sorokiniana) in Hep G2 human hepatocellular carcinoma cells

The effects of 80% ethanolic extract derived from commercial granule chlorella (GPE) on cell viability, invasion capacity and apoptosis in human hepatoma cell line (Hep G2 cells) were investigated. The results demonstrated that GPE decreased cell viability, induced apoptosis and showed invasion inhibitory effects in the Hep G2 cells. GPE-triggered apoptosis was confirmed by 4′-6-diamidino-2-phenyindole (DAPI) staining and comet assay. GPE promoted an increase of reactive oxygen species (ROS) and Ca²⁺, and loss of mitochondrial membrane potential (ΔΨm) accompanied by cytochrome c release that was due to the decrease of Bcl-2 in the Hep G2 cells. GPE also induced the protein levels of apoptosis-inducing factor (AIF), increased the levels of caspase-3, -8 and -9, and stimulated the levels of fatty acid synthase (Fas) and Fas ligand (FasL) in the Hep G2 cells. Additionally GPE inhibited invasion of Hep G2 cells by down-regulation of the expression of matrix metalloproteinase (MMP)-2 and -9. Furthermore, cellular glutathione content and superoxide dismutases (SOD) activities were significantly reduced and thiobarbituric acid-reactive substances (TBARS) levels were significantly increased after GPE treatment. These results suggest that GPE can induce cytotoxicity on Hep G2 cells and inhibit the invasive capacity of malignant cells.     

Effects of AMP-activated protein kinase (AMPK) signaling and essential amino acids on mammalian target of rapamycin (mTOR) signaling and protein synthesis rates in mammary cells

Regulation of mammary protein synthesis potentially changes the relationships between AA supply and milk protein output represented in current nutrient requirement models. Glucose and AA regulate muscle protein synthesis via cellular signaling pathways involving mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK). The objective of this study was to investigate the effects of essential AA (EAA) and acetate or glucose on mTOR and AMPK signaling pathways and milk protein synthesis rates. A bovine mammary epithelial cell line, MAC-T, was subjected to different media containing 0 or 3.5 mmol/L EAA concentrations with 0 or 5 mmol/L acetate or 0 or 17.5 mmol/L glucose in 2 separate 2 × 2 factorial studies. In a separate set of experiments, lactogenic bovine mammary tissue slices were subjected to the same treatments except that the low EAA treatment contained a low level of EAA (0.18 mmol/L). Supplementation of EAA enhanced phosphorylation of mTOR (Ser2448) and eukaryotic initiation factor 4E binding protein 1 (4EBP1, Thr37/46), and reduced phosphorylation of eukaryotic elongation factor 2 (eEF2, Thr56) in MAC-T cells. Concentration of ATP and phosphorylation of AMPK increased and decreased, respectively, in the presence of EAA in MAC-T cells. Acetate, EAA, or glucose numerically reduced AMPK phosphorylation by about 16% in mammary tissue slices. Provision of EAA increased phosphorylation of mTOR and 4EBP1, intracellular total EAA concentration, and casein synthesis rates in mammary tissue slices, irrespective of the presence of acetate or glucose in the medium. Phosphorylation of mTOR had a marginally negative association with AMPK phosphorylation, which was positively related to eEF2 phosphorylation. Casein synthesis rates were positively and more strongly linked to mTOR phosphorylation than the negative link between eEF2 phosphorylation and casein synthesis rates. A 100% increase in mTOR phosphorylation was associated with an increase in the casein synthesis rate of 0.74%·h⁻¹, whereas a 100% increase in eEF2 phosphorylation was related to a decline in the casein synthesis rate of 0.33%·h⁻¹. Although AMPK phosphorylation was responsive to cellular energy status and had a negative effect on mTOR-mediated signals in bovine mammary epithelial cells, its effect on milk protein synthesis rates appeared to be marginal compared with the mTOR-mediated regulation of milk protein synthesis by EAA.     

Beef shelf life in low O(2) and high CO(2) atmospheres containing different low CO concentrations

The use of atmospheres with low concentrations of CO (0.1 to 1%), in combination with O₂ (24%), high CO₂ (50%) and N₂ (25 to 25.9%), for preserving chilled beef steaks was investigated. The atmosphere used as reference contained 70% O₂+20% CO₂+10% N₂. Bacterial counts showed that all atmospheres containing CO greatly reduced total aerobic population numbers, including Brochothrix thermosphacta. Lactic acid bacteria, however, were not affected. CO concentrations of 0.5–0.75% were able to extend shelf life by 5–10 days at 1±1°C, as demonstrated by delayed metmyoglobin formation (less than 40% of total myoglobin after 29 days of storage), stabilisation of red colour (no change of CIE a* and hue angle after 23 days), maintenance of fresh meat odour (no variation of sensory score after 24 days) and significant (P<0.01) slowing of oxidative reactions (TBARS).     

Kiwifruit (Actinidia chinensis) extract annuls chronic insulininduced insulin resistance in l6 skeletal muscle cells

Kiwi fruit has long been believed to be beneficial to human health due to its numerous biological actions; however the pharmacological mechanisms associated with these benefits are incompletely understood. In the present study, the effects of ‘Halla Gold’ (Actinidia chinensis var.), a new kiwifruit cultivar bred by the Jeju Rural Development Administration (RDA), on chronic insulin-induced insulin resistance in L6 skeletal muscle cells was investigated. Chronic insulin reduced phosphorylation of Akt and GSK-3α/β, and increased phosphorylation of glycogen synthase (GS). Furthermore, glucose consumption and glucose transporter 4 (Glut4) translocation to the plasma membrane were inhibited. However, ‘Halla Gold’ extract (HGE) increased phosphorylation of Akt and GSK-3α/β concomitantly with decreased phosphorylation of GS. Moreover, HGE improved insulin-stimulated glucose consumption by facilitating Glut4 translocation and this stimulation was suppressed by inhibition of PI3 kinase. Together, our data suggest that ‘Halla Gold’ extract abolishes chronic insulin-induced insulin resistance through the PI3K/Akt pathway.     

Cytokine responses of human intestinal epithelial-like Caco-2 cells to the nonpathogenic bacterium Bacillus subtilis (natto)

Intestinal epithelial cells produce cytokines in response to pathogenic bacteria. However, cellular responses of these cells to nonpathogenic strains, such as Bacillus subtilis, are yet to be determined. In this study, we investigate whether epithelial-like human colon carcinoma Caco-2 cells produce cytokines in response to B. subtilis or B. subtilis (natto). The latter strain is utilized for manufacturing the fermented soy food "natto". Live cells of nonpathogenic B. subtilis JCM 1465(T), B. subtilis (natto) and E. coli JCM 1649(T), as well as pathogenic S. enteritidis JCM 1652 and P. aeruginosa JCM 5516 strains, induced secretion of interleukin-6 (IL-6) and/or IL-8, but not IL-7, IL-15 or tumor necrosis factor alpha (TNF-alpha). Transepithelial electrical resistance (TER) of Caco-2 cell monolayers cultured with E. coli, S. enteritidis or P. aeruginosa decreased more rapidly than that of cells cultured with B. subtilis or B. subtilis (natto). The amounts of cytokine induced by B. subtilis (natto) cells were strain-dependent. Moreover, B. subtilis (natto) cells subjected to hydrochloric acid treatment, but not autoclaving, induced a higher secretion of IL-6 and IL-8 than intact cells. Tyrosine kinase inhibitors, including AG126 and genistein, suppressed cytokine secretion. Our results suggest that the nonpathogenic B. subtilis (natto) bacterium induces cytokine responses in intestinal epithelial cells via activation of an intracellular signaling pathway, such as that of nuclear factor-kappa B (NF-kappaB).     

Zinc in human nutrition: actual consumption and bioavailability requirements (communication 2)

This revue discusses data concerning essential trace element zinc (Zn) dietary consumption levels in Russian Federation and some foreign countries. There are discussed biochemical criteria of Zn security in humans. It's concluded that zinc insufficiency is widely distributed among adult and children population in many districts of Russia.     

Purification of naringin and neohesperidin from Huyou (Citrus changshanensis) fruit and their effects on glucose consumption in human HepG2 cells

Huyou (Citrus changshanensis) is rich in naringin and neohesperidin, which are natural flavanone glycosides with a range of biological activities. Among the different fruit parts, i.e. flavedo, albedo, segment membrane (SM), and juice sacs (JS), albedo showed the highest contents of both compounds, with 27.00 and 19.09mg/g DW for naringin and neohesperidin, respectively. Efficient simultaneous purification of naringin and neohesperidin from Huyou albedo was established by the combination of macroporous D101 resin chromatography and high-speed counter-current chromatography (HSCCC). Purified naringin and neohesperidin were identified by both HPLC and LC-MS, and their effects on glucose consumption were investigated in HepG2 cells. Cells treated with naringin and neohesperidin showed increased consumption of glucose, and this was associated with increased phosphorylation of AMP-activated protein kinase (AMPK). Therefore, naringin and neohesperidin from Huyou may act as potential hypoglycaemic agents through regulation of glucose metabolism.