Kimchi attenuates endoplasmic reticulum stress-induced hepatic steatosis in HepG2 cells and C57BL/6N mice

Kimchi is a traditional fermented food that contains abundant nutrients and functional ingredients with various health benefits. We previously reported that kimchi active components suppress hepatic steatosis caused by endoplasmic reticulum (ER) stress in vitro and in vivo. Therefore, we assessed the effect of kimchi on the inhibition of hepatic steatosis caused by ER stress in HepG2 cells and C57BL/6N mice to verify the hypothesis that kimchi may potentially inhibit nonalcoholic fatty liver disease. We investigated the effect of kimchi on cell viability and triglyceride concentrations in cells and on lipid profile, lipid accumulation, and expression of related genes in cells and mice with hepatic steatosis. A mechanistic study was also performed using the liver X receptor α agonist T0901317 and the AMP-activated protein kinase agonist AICAR. Kimchi was noncytotoxic and effectively reduced triglyceride concentrations and suppressed hepatic steatosis-related gene expression in cells and mice. Additionally, kimchi recovered weight loss, lowered the serum and liver tissue lipid profiles, suppressed lipid accumulation, and reduced the effects of T0901317 and AICAR on lipogenic gene expression in tunicamycin-treated mice. Our results highlight that kimchi could prevent hepatic steatosis caused by ER stress in cells and mice.

Association between kimchi consumption and obesity based on BMI and abdominal obesity in Korean adults: a cross-sectional analysis of the Health Examinees study

OBJECTIVE

Previous animal studies have shown the anti-obesity effect of kimchi-derived probiotic lactic acid bacteria. However, only a few epidemiological studies have investigated the association between kimchi consumption and obesity. Therefore, we aim to assess this relationship in Korean adults.

DESIGN

Cross-sectional study.

SETTING

The Health Examinees study was conducted from 2004 to 2013.

PARTICIPANTS

This study analysed 115 726 participants aged 40-69 years enrolled in the Health Examinees study in Korea.

PRIMARY AND SECONDARY OUTCOME MEASURES

Obesity was defined as body mass index ≥25 kg/m2, and abdominal obesity was defined as waist circumference ≥90 cm in men and ≥85 cm in women. Kimchi consumption was assessed by the validated food frequency questionnaire.

RESULTS

In men, total kimchi consumption of 1-3 servings/day was related to a lower prevalence of obesity (OR: 0.875 in 1-2 servings/day and OR: 0.893 in 2-3 servings/day) compared with total kimchi consumption of <1 serving/day. Also, men with the highest baechu kimchi (cabbage kimchi) consumption had 10% lower odds of obesity and abdominal obesity. Participants who consumed kkakdugi (radish kimchi) ≥median were inversely associated with 8% in men and 11% in women with lower odds of abdominal obesity compared with non-consumers, respectively.

CONCLUSIONS AND RELEVANCE

Consumption of 1-3 servings/day of total kimchi was associated with a lower risk of obesity in men. Baechu kimchi was associated with a lower prevalence of obesity in men, and kkakdugi was associated with a lower prevalence of abdominal obesity in both men and women. However, since all results showed a 'J-shaped' association, it is recommended to limit excessive kimchi intake.

Metabolic shift during fermentation in kimchi according to capsaicinoid concentration

The cultivar of red pepper used in kimchi contributes to spiciness, red color, and fermentation characteristics. Capsaicinoids are the main components of red pepper. Therefore, understanding changes in metabolites during kimchi fermentation according to capsaicinoid concentration is necessary to control the quality of kimchi. The purpose of this study was to investigate the effect of capsaicinoids on metabolites during kimchi fermentation. To profile the effect of capsaicinoid concentrations on kimchi fermentation, five kimchi samples were prepared using different concentrations of capsaicinoids (4, 12, 30.7, 40.9, and 50.3 mg/kg) and stored at 4 °C for 28 days. During kimchi fermentation, pH, titratable acidity, capsaicinoid concentration, total viable and lactic acid bacteria, free sugars, amino acids, and microbial community were evaluated. Each result was statistically analyzed for changes in capsaicin concentration and fermentation time. The capsaicinoid concentration did not change during kimchi fermentation but the growth of lactic acid bacteria changed. According to the growth of lactic acid bacteria, free sugar, amino acids, and microbial community changed with the capsaicinoid concentration. Overall, the results of this study provide preliminary information on the use of red pepper and capsaicinoids in the kimchi industry.

Anti-Obesity Effect of Kimchi with Starter Cultures in 3T3-L1 Cells

Lactic acid bacteria (LAB) isolated from kimchi have various functions, including antioxidant, anti-inflammation, and anti-obesity activities, and are therefore widely used in the food, pharmaceutical, and medical fields. To date, the health functionalities of LAB have been widely reported; however, those of kimchi fermented with LAB as a starter have rarely been reported. Therefore, research on the selection of LAB with anti-obesity activity and the health functionality of kimchi fermented with LAB is needed. In the present study, LAB with anti-obesity activity were initially selected by measuring the Oil-Red O intensity. Among the four LAB strains, anti-obesity activity was confirmed by measuring cell viability, lipid levels, and lipid accumulation. Then, starter kimchi (SK) was prepared by inoculating selected LABs, and its pH, total acidity, and salinity were compared with those of naturally fermented kimchi (NK). Lastly, anti-obesity activity was also investigated in 3T3-L1 cells. Selected LAB showed no cytotoxicity up to 107 CFU/ml, with Lactobacillus brevis JC7 and Leuconostoc mesenteroides KCKM0828 having higher inhibitory effects on TG, TC content and lipid accumulation. Most SKs showed fermentation properties similar to those of the NK. SKs showed no cytotoxicity at concentrations of up to 1,000 μg/ml. SKs showed strong inhibitory effects on TG content, lipid accumulation, and obesity-related gene and protein expressions. Taken together, the utilization of LAB as a starter could improve the health benefits of kimchi.

A Novel Interaction between MFN2/Marf and MARK4/PAR-1 Is Implicated in Synaptic Defects and Mitochondrial Dysfunction

As cellular energy powerhouses, mitochondria undergo constant fission and fusion to maintain functional homeostasis. The conserved dynamin-like GTPase, Mitofusin2 (MFN2)/mitochondrial assembly regulatory factor (Marf), plays a role in mitochondrial fusion, mutations of which are implicated in age-related human diseases, including several neurodegenerative disorders. However, the regulation of MFN2/Marf-mediated mitochondrial fusion, as well as the pathologic mechanism of neurodegeneration, is not clearly understood. Here, we identified a novel interaction between MFN2/Marf and microtubule affinity-regulating kinase 4 (MARK4)/PAR-1. In the Drosophila larval neuromuscular junction, muscle-specific overexpression of MFN2/Marf decreased the number of synaptic boutons, and the loss of MARK4/PAR-1 alleviated the synaptic defects of MFN2/Marf overexpression. Downregulation of MARK4/PAR-1 rescued the mitochondrial hyperfusion phenotype caused by MFN2/Marf overexpression in the Drosophila muscles as well as in the cultured cells. In addition, knockdown of MARK4/PAR-1 rescued the respiratory dysfunction of mitochondria induced by MFN2/Marf overexpression in mammalian cells. Together, our results indicate that the interaction between MFN2/Marf and MARK4/PAR-1 is fine-tuned to maintain synaptic integrity and mitochondrial homeostasis, and its dysregulation may be implicated in neurologic pathogenesis.

Optimization of extraction and nanoencapsulation of kimchi cabbage by-products to enhance the simulated in vitro digestion of glucosinolates

Kimchi cabbage is a well-known glucosinolate (GLS)-containing vegetable, but its by-products are discarded despite the presence of GLS. The aim of this study was the optimization of the extraction and nanoencapsulation of GLS from kimchi cabbage by-products to enhance the intestinal absorption of GLS. The optimal GLS extraction conditions included steaming thrice as pretreatment, utilizing 70% methanol, and ultrasonication at 20% amplitude for 15 min. Under these conditions, 80.11 ± 4.40 mg/100 g of GLS extraction was obtained and the extraction yield was 81.70 ± 4.73%. The optimized kimchi cabbage by-product extract (KCE) was coated with chitosan-lipid nanoparticles (KCE-NPs) and their stability and release under simulated in vitro gastrointestinal conditions were evaluated. KCE-NPs protected the encapsulated GLS under acidic gastric conditions and released 91.63 ± 0.76% of GLS in the simulated intestinal medium. Therefore, the proposed KCE-NPs are a promising delivery system for increasing GLS absorption.

Antioxidant and anti-inflammatory effects of solar salt brined kimchi

Salt is an essential ingredient in the kimchi fermentation process. Solar salt has antioxidant, anti-cancer, and anti-obesity properties. The aim of this study was to determine the antioxidant and anti-inflammatory effects of solar salt brined kimchi. Purified salt (PS), dehydrated solar salt (DSS), 1-year aged solar salt (SS1), and 3-years aged solar salt (SS3) were investigated. Anti-inflammatory effects were determined by analyzing cytotoxicity, nitric oxide (NO) production, and inflammation-related gene expression in lipopolysaccharide-treated RAW264.7 cells. Antioxidant activities of DSS, SS1, and SS3 were higher than that of PS. Solar salt significantly inhibited NO production with low cytotoxicity and decreased inflammation-related gene expression. Kimchi containing solar salt (DSSK, SS1K, and SS3K) showed higher antioxidant activity than PSK. Additionally, DSSK, SS1K, and SS3K significantly inhibited NO production and decreased the expression of inflammation-related genes. Owing to the antioxidant and anti-inflammatory effects, using solar salt in kimchi preparation could have potential health benefits.

Effect of kimchi intake on body weight of general community dwellers: a prospective cohort study

The impact of kimchi intake on weight management has been a topic of interest. We aimed to conduct an epidemiological study to investigate the association between kimchi intake and weight loss. Participants were selected from the Health Examinees cohort study. Kimchi intake was assessed by a 106-item semi-quantitative food frequency questionnaire, including four types of kimchi. Obesity was defined according to the Korean Society for the Study of Obesity guidelines. We performed a correlation analysis among all participants (N = 58 290) and conducted a prospective risk assessment analysis among participants with a baseline BMI value ≥25 kg m^-2 (N = 20 066). In the correlation analysis, higher kimchi consumption was found to be associated with a lower increment in BMI change (men, β 0.169, 95% CI (0.025, 0.313); women, β 0.140, 95% CI (0.046, 0.236)) compared with the lower group. The risk assessment analysis indicated that moderate kimchi consumption is associated with normal weight development in men (Q3, hazard ratio, 1.28, 95% CI (1.06, 1.54)). Baechu [cabbage] kimchi intake also showed a significant association among men participants (all p for trend <0.05). In conclusion, moderate kimchi intake was associated with weight loss among middle-aged and older Koreans, especially in men.

Anti-obesity effect of vegetable juice fermented with lactic acid bacteria isolated from kimchi in C57BL/6J mice and human mesenchymal stem cells

This study aimed to investigate the effect of fermented vegetable juice (VJ) obtained from a blend of four crops (Brassica oleracea var. capitata, B. oleracea var. italica, Daucus carota L., and Beta vulgaris) on adipogenesis along with the identification of active compounds. Two lactic acid bacteria (LAB) (Companilactobacillus allii WiKim39 and Lactococcus lactis WiKim0124), isolated from kimchi, were used to ferment the VJ and their effectiveness was evaluated in differentiated human mesenchymal stem cells and obese mice. In vitro antibody array analysis was done to understand signaling proteins in adipogenesis. Gene Ontology enrichment analysis showed that differentially expressed proteins are related to biological processes including immunological processes. These were effectively regulated by LAB and fermented VJ. Supplementation of fermented VJ reduced the weight gain, blood biochemical indicators, and liver fat accumulation in mice. Oil Red O staining indicated that the fermentation metabolites of VJ (indole-3-lactic acid, leucic acid, and phenyllactic acid) had an inhibitory effect on lipid accumulation in vitro. Therefore, it can be concluded that LAB-fermented VJ and its metabolites have the potential to counter obesity, and thus can be therapeutically effective.

UPLC-QTOF-MS/MS and GC-MS Characterization of Phytochemicals in Vegetable Juice Fermented Using Lactic Acid Bacteria from Kimchi and Their Antioxidant Potential

This study aims to investigate fermentative metabolites in probiotic vegetable juice from four crop varieties (Brassica oleracea var. capitata, B. oleracea var. italica, Daucus carota L., and Beta vulgaris) and their antioxidant properties. Vegetable juice was inoculated with two lactic acid bacteria (LAB) (Companilactobacillus allii WiKim39 and Lactococcus lactis WiKim0124) isolated from kimchi and their properties were evaluated using untargeted UPLC-QTOF-MS/MS and GC-MS. The samples were also evaluated for radical (DPPH^• and OH^•) scavenging activities, lipid peroxidation, and ferric-reducing antioxidant power. The fermented vegetable juices exhibited high antioxidant activities and increased amounts of total phenolic compounds. Fifteen compounds and thirty-two volatiles were identified using UPLC-QTOF-MS/MS and GC-MS, respectively. LAB fermentation significantly increased the contents of d-leucic acid, indole-3-lactic acid, 3-phenyllactic acid, pyroglutamic acid, γ-aminobutyric acid, and gluconic acid. These six metabolites showed a positive correlation with antioxidant properties. Thus, vegetable juices fermented with WiKim39 and WiKim0124 can be considered as novel bioactive health-promoting sources.

Antioxidant, Anti-Obesity, and Anti-Aging Activities of Jeju Citrus Blended Vinegar

Various types of vinegars have been developed as interest in their health benefits has increased. In this study, we prepared Jeju citrus blended vinegars (CBVs) by mixing premature mandarin vinegar and mandarin vinegar, with mandarin vinegar used as a control. The physicochemical properties of the vinegars, including pH, total acidity, and sugar content was determined. Moreover, antioxidant, anti-obesity, and anti-aging activities of the vinegars were investigated. Physicochemical analysis revealed that the CBVs had a pH similar to that of mandarin vinegar, whereas CBVs with relatively high premature mandarin vinegar content showed higher acidity and lower sugar content (p < 0.05). Moreover, the antioxidant activities and phenol contents of CBVs were significantly higher than those of mandarin vinegar (p < 0.05). Meanwhile, CBVs showed significantly decreased intracellular triglyceride, lipid accumulation, and anti-obesity related gene levels (p < 0.05), thereby highlighting their anti-obesity activity. In addition, CBVs showed anti-aging activity by increasing cell viability and cell lifespan, while decreasing the expression of senescence-related genes under H₂O₂-induced oxidative stress. Therefore, CBVs may be useful as a functional food with antioxidant, anti-obesity, and anti-aging effects in various food fields.

Free Amino Acid and Volatile Compound Profiles of Jeotgal Alternatives and Its Application to Kimchi

Jeotgal containing abundant free amino acids plays an important role in the unique savory taste (umami) and flavor in kimchi. However, it is also responsible for the unpleasant fishy smell and high salt content of kimchi. Therefore, the present study aimed to identify alternative jeotgal sources and investigate the fermentation properties of jeotgal alternatives added to kimchi. The tomato hot-water extract (TH2) and dry-aged beef hot-water extract (DBH) were selected as jeotgal alternatives for kimchi preparation based on their glutamic acid contents. Characteristics of kimchi with TH2 alone (JA1) and TH2 and DBH in combination (1:1, JA2) were compared with kimchi prepared using commercially available anchovy fish sauce (CON). The pH of JA1 and JA2 was slightly decreased during fermentation, whereas the salinity was significantly lower than CON (p < 0.05). Notably, the most effective factor of the savory taste of kimchi, glutamic acid contents of JA1 and JA2 were significantly higher than that of CON (p < 0.05). In conclusion, JA1 showed slower fermentation with lower salinity and higher glutamic acid content than CON. Overall, this study showed that JA1 derived from TH2 could improve the taste and quality of kimchi by increasing glutamic acid content and decreasing the unpleasant flavor.

Recombinant stromal cell‑derived factor‑1 protein promotes neurite outgrowth in PC‑12 cells

Stromal cell‑derived factor‑1 (SDF‑1) is a chemokine involved in neuronal differentiation, as well as proliferation and migration. In the present study, the effects of recombinant SDF‑1 on neurite outgrowth for nerve regeneration and engineering were evaluated in PC‑12 cells. The effects of purified SDF‑1 protein on cell toxicity, proliferation and migration were also assessed. SDF‑1 significantly augmented cell proliferation in a dose‑dependent manner, with low cytotoxicity in PC‑12 cells. Cell migration also increased in the presence of SDF‑1. SDF‑1 significantly increased neurite number and length, compared with the control (untreated cells). Neurofilament mRNA levels, which are involved in neuronal differentiation, were also significantly upregulated in the presence of SDF‑1. These results suggested that SDF‑1 might prove useful for tissue engineering through induction of neuronal differentiation.

Antioxidant activity and calcium bioaccessibility of Moringa oleifera leaf hydrolysate, as a potential calcium supplement in food

Moringa oleifera leaf (ML) is rich in vitamins and minerals, specially abundant calcium, therefore it is widely used as a calcium supplement for food. This study aimed to investigate the antioxidant activity and calcium bioaccessibility of M. oleifera leaf hydrolysate (MLH) as a calcium supplement for kimchi. MLH was prepared under three different proteases, two different protease contents, and three different incubation times. Total phenol content (TPC), total flavonoid content (TFC), and antioxidant activities were investigated. Cellular activity and calcium bioaccessibility were also investigated. The highest calcium level of MLH was observed in 3% Protamex treatment for 4 h. TPC, TFC, and antioxidant activities of MLH in Protamex and Alcalase treatments were higher than those in Flavourzyme treatment (p < 0.05). Moreover, high cell viability and alkaline phosphatase activity were also observed in C2C12 cells. Kimchi containing MLH showed high calcium accessibility compared to kimchi alone. Taken together, the application of MLH could have potential as a calcium supplement for kimchi production.

Evaluation of onion juices quality following heat-treatment and their application as a sugar substitute in Kimchi

This study was conducted to evaluate the quality of onion juices that had been heat-treated for different times as well as their use as a table sugar substitute in Kimchi. The onions were steamed at 100 ∘C for 30 min and boiled at 90 ∘C for 30, 60, and 120 min. The highest cycloalliin (0.76 mM), free-sugar (sucrose 1.66 g/L, glucose 8.62 g/L, and fructose 7.64 g/L), and malic acid (0.82 g/L) contents were observed in onion boiled at 90 ∘C for 120 min. The possibility of using heat-treated onion juices as an alternative to table sugar in Kimchi was evaluated by comparing the lactic acid bacteria count, pH, acidity, organic acid, and free-sugar in these juices with those in Kimchi prepared using table sugar (control). The total viable bacteria and lactic acid bacteria showed similar growth patterns as in the control. The average pH reduction and increase in titratable acidity (%) in all treated Kimchi samples during fermentation for 4 weeks were 1.18 ± 0.05 and 0.81 ± 0.06, respectively. Kimchi with onion juice heat-treated for 120 min (K120) had the most similar lactic acid and acetic acid contents to that in the control after fermentation for 4 weeks. The highest mannitol level after fermentation for 4 weeks was detected in K120, which showed better sensory qualities compared to the control.

Allium hookeri root extract exerts anti-inflammatory effects by nuclear factor-κB down-regulation in lipopolysaccharide-induced RAW264.7 cells

Background

Allium hookeri (AH) is widely consumed as a vegetable and herbal medicine in southeastern Asia. AH has been reported antioxidant, antimicrobial, improvement of bone health and antidiabetic effects. In the present study, we investigated the inhibitory effect of a methanol extract of AH root (AHE) on inflammatory response in lipopolysaccharide (LPS)-induced RAW264.7 cells.

Methods

Initially, characterization of organic sulfur compounds in AHE was determined using high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS). Cells were incubated with LPS and AHE for 24 h. The productions of nitric oxide (NO), reactive oxygen species (ROS), and inflammation-related cytokines were examined. Gene and protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were assessed by polymerase chain reaction and Western blotting. Key factor, nuclear factor kappa B (NF-κB) was also determined.

Results

AHE contained organosulfur compounds such as alliin and S-allylcysteine by HPLC-ESI-MS. AHE significantly inhibited NO, ROS, and cytokines production in LPS-induced RAW264.7 cells. In addition, AHE treatment inhibited iNOS and COX-2 mRNA and protein levels, leading to a decrease in iNOS-derived NO level. Furthermore, NF-κB activation was, at least in part, suppressed by AHE treatment.

Conclusion

Our data suggest that AHE treatment inhibits the inflammation condition through suppression of iNOS and COX-2 expression via NF-κB down-regulation.

Gomisin N inhibits adipogenesis and prevents high-fat diet-induced obesity

Gomisin N (GN) is a physiological lignan derived from Schisandra chinensis. In the present study, we investigated the inhibitory effects of GN on differentiation of 3T3-L1 preadipocytes and the anti-obesity effects of GN in high-fat diet (HFD)-induced obese mice. Incubation with GN significantly inhibited the differentiation of 3T3-L1 preadipocytes in a dose-dependent manner. This inhibitory effect primarily occurred at an early adipogenic stage through impairment of mitotic clonal expansion (MCE) caused by cell cycle arrest at the G1/S phase transition. GN inhibited the extracellular signal-regulated kinase and phosphoinositide 3-kinase/protein kinase B signaling in the MCE process and activated AMP-activated protein kinase. Furthermore, GN downregulated CCAT/enhancer-binding protein β (C/EBPβ) and histone H3K9 demethylase JMJD2B during early stages of adipogenesis, and therefore repressed the expression of C/EBPβ-targeted cell cycle genes. In addition, GN also repressed the expression of histone H3K4 methyltransferase MLL4 and reduced PPARγ expression. Moreover, GN effectively lowered the final body weight, adipose tissue mass, and reduced the serum levels of glucose, total triglyceride, and cholesterol in the HFD-induced obese mice. GN also markedly reduced hepatic triglyceride level induced by HFD. Collectively, these findings suggest that GN has potential as a novel agent for the prevention and treatment of obesity.

Protective effects of gomisin N against hepatic steatosis through AMPK activation

Gomisin N (GN) is a phytochemical derived from Schisandra chinensis. It has been reported to exert a protective effect against hepatic steatosis by attenuating endoplasmic reticulum (ER) stress. However, the detailed mechanism by which GN inhibits hepatic steatosis remains to be elucidated. In this study, we examined whether GN activates AMP-activated protein kinase (AMPK) and exerts therapeutic effects on liver X receptor (LXR)- or palmitic acid (PA)-induced triglyceride (TG) accumulation in HepG2 cells. Furthermore, in vivo protective effects of GN against hepatic steatosis were assessed in high-fat diet (HFD)-induced obese mice. GN stimulated the phosphorylation of AMPK, acetyl-CoA carboxylase (ACC), and sterol regulatory element-binding protein 1c (SREBP1c) in HepG2 cells. It decreased the expression of lipogenesis genes, but increased the expression of fatty acid oxidation genes. Additionally, GN decreased the expression of lipogenesis genes induced by the LXR agonist T0901317 or PA in HepG2 cells, resulting in reduced intracellular TG content. However, preincubation with compound C, an AMPK inhibitor, prevented GN-mediated effects. Administration of GN to HFD-induced obese mice decreased HFD-induced liver weight, hepatic TG accumulation, and cytoplasmic lipid droplet. These findings demonstrate that GN activates the AMPK pathway and ameliorates HFD-induced hepatic steatosis.

Schisandra chinensis extract ameliorates nonalcoholic fatty liver via inhibition of endoplasmic reticulum stress

ETHNOPHARMACOLOGICAL RELEVANCE

Schisandra chinensis (Turcz.) Baill. (SC) is a traditional Chinese herbal medicine with diverse pharmacological activities for treatment of various human diseases. Endoplasmic reticulum (ER) stress is associated with the pathogenesis of nonalcoholic fatty liver disease (NAFLD). In this study, we investigated the protective effects of methanol extract of Schisandra chinensis (SC extract) against ER stress-induced NAFLD in vitro and in vivo.

MATERIAL AND METHODS

The protective effects of SC extract were examined in tunicamycin- or palmitate-treated HepG2 cells in vitro, and in tunicamycin-injected mice or high fed diet (HFD) obese mice in vivo. Expression of ER stress markers including glucose regulated protein 78 (GRP78), C/EBP homolog protein (CHOP), and X-box-binding protein-1 (XBP-1), and triglyceride accumulation were measured in HepG2 cells and in the liver of mice.

RESULTS

SC extract significantly inhibited expression of tunicamycin-induced ER stress markers in tunicamycin-treated HepG2 cells and in the liver of tunicamycin-injected mice, and it also inhibited tunicamycin-induced triglyceride accumulation. Similar observations were made under physiological ER stress conditions such as in palmitate-treated HepG2 cells and in the liver of HFD obese mice. In addition, SC extract repressed the expression of inflammatory genes and lipogenic genes in palmitate-treated HepG2 cells. Schisandrin, an abundant bioactive lignan in SC extract, inhibited the expression of ER stress markers in tunicamycin-or palmitate-treated HepG2 cells, whereas Gomisin J did not affect ER stress markers.

CONCLUSIONS

SC attenuates ER stress and prevents development of NAFLD. SC may be useful as a pharmacological agent for protection against ER stress-induced human diseases.

Protective Effect of Gomisin N against Endoplasmic Reticulum Stress-Induced Hepatic Steatosis

Gomisin N is a physiological substance derived from Schisandra chinensis. In the present study, the in vitro and in vivo effects of gomisin N on endoplasmic reticulum (ER) stress and hepatic steatosis were investigated. We quantified the expression of markers of ER stress, including glucose regulated protein 78 (GRP78), CCAAT/enhancer binding protein (C/EBP) homolog protein (CHOP), and X-box-binding protein-1 (XBP-1), and triglyceride (TG) accumulation, in HepG2 cells treated with tunicamycin or palmitate. Tunicamycin treatment in HepG2 cells induced expression of markers of ER stress and increased TG levels; Gomisin N reversed these effects, reducing the expression of markers of ER stress and TG levels. Similar effects were seen following palmitate pretreatment of HepG2 cells. The inhibitory effects of gomisin N were further confirmed in mice injected with tunicamycin. Gomisin N reduced expression of markers of ER stress and decreased TG levels in mouse liver after tunicamycin injection. Furthermore, gomisin N decreased expression of inflammatory and lipogenic genes in palmitate-incubated HepG2 cells. These results suggest that gomisin N inhibits ER stress and ameliorates hepatic steatosis induced by ER stress.

Engineering of Self-Assembled Fibronectin Matrix Protein and Its Effects on Mesenchymal Stem Cells

Fibronectin (FN) contributes to cell adhesion, proliferation, and differentiation in various cell types. To enhance the activity of fibronectin at the sites of focal adhesion, we engineered a novel recombinant fibronectin (FNIII10) fragment connected to the peptide amphiphile sequence (PA), LLLLLLCCCGGDS. In this study, the effects of FNIII10-PA on rat mesenchymal stem cells (rMSCs) were compared with those of FNIII10. FNIII10-PA showed the prominent protein adhesion activity. In addition, FNIII10-PA showed a significantly higher effect on adhesion, proliferation, and differentiation of rMSCs than FNIII10. Taken together, the FNIII10-containing self-assembled sequence enhanced rMSCs adhesion, proliferation, and differentiation.

Kimchi methanol extract and the kimchi active compound, 3'-(4'-hydroxyl-3',5'-dimethoxyphenyl)propionic acid, downregulate CD36 in THP-1 macrophages stimulated by oxLDL

Macrophage foam cell formation by oxidized low-density lipoprotein (oxLDL) is a key step in the progression of atherosclerosis, which is involved in cholesterol influx and efflux in macrophages mediated by related proteins such as peroxisome proliferator-activated receptor γ (PPARγ), CD36, PPARα, liver-X receptor α (LXRα), and ATP-binding cassette transporter A1 (ABCA1). The aim of this study was to investigate the beneficial effects of kimchi methanol extract (KME) and a kimchi active compound, 3-(4'-hydroxyl-3',5'-dimethoxyphenyl)propionic acid (HDMPPA) on cholesterol flux in THP-1-derived macrophages treated with oxLDL. The effects of KME and HDMPPA on cell viability and lipid peroxidation were determined. Furthermore, the protein expression of PPARγ, CD36, PPARα, LXRα, and ABCA1 was examined. OxLDL strongly induced cell death and lipid peroxidation in THP-1-derived macrophages. However, KME and HDMPPA significantly improved cell viability and inhibited lipid peroxidation induced by oxLDL in THP-1-derived macrophages (P<.05). Moreover, KME and HDMPPA suppressed CD36 and PPARγ expressions, both of which participate in cholesterol influx. In contrast, KME and HDMPPA augmented LXRα, PPARα, and ABCA1 expression, which are associated with cholesterol efflux. Consequently, KME and HDMPPA suppressed lipid accumulation. These results indicate that KME and HDMPPA may inhibit lipid accumulation, in part, by regulating cholesterol influx- and efflux-related proteins. These findings will thus be useful for future prevention strategies against atherosclerosis.

Biointerface control of electrospun fiber scaffolds for bone regeneration: engineered protein link to mineralized surface

Control over the interface of biomaterials that favors the initial adhesion and subsequent differentiation of stem cells is one of the key strategies in bone tissue engineering. Here we engineer the interface of biopolymer electrospun fiber matrices with a fusion protein of fibronectin 9-10 domain (FNIII9-10) and osteocalcin (OCN), aiming to stimulate mesenchymal stem cell (MSC) functions, including initial adhesion, growth and osteogenic differentiation. In particular, a specific tethering of FNIII9-10-OCN protein was facilitated by the hydroxyapatite (HA) mineralization of the biopolymer surface through a molecular recognition of OCN to the HA crystal lattice. The FNIII9-10-OCN anchorage to the HA-mineralized fiber was observed to be highly specific and tightly bound to preserve stability over a long period. Initial cell adhesion levels, as well as the spreading shape and process, of MSCs within 24h were strikingly different between the fibers linked with and without fusion protein. Significant up-regulations in the mRNA expression of adhesion signaling molecules occurred with the fusion protein link, as analyzed by the reverse transcriptase polymerase chain reaction. The expression of a series of osteogenic-related genes at later stages, over 2-3weeks, was significantly improved in the fusion protein-tailored fiber, and the osteogenic protein levels were highly stimulated, as confirmed by immunofluorescence imaging and fluorescence-activated cell sorting analyses. In vivo study in a rat calvarium model confirmed a higher quantity of new bone formation in the fiber linked with fusion protein, and a further increase was noticed when the MSCs were tissue-engineered with the fusion protein-linked fiber. Collectively, these results indicate that FN-OCN fusion protein links via HA mineralization is a facile tool to generate a biointerface with cell-attractive and osteogenic potential, and that the engineered fibrous matrix is a potential bone regenerative scaffold.

Efficacy of mesoporous silica nanoparticles in delivering BMP-2 plasmid DNA for in vitro osteogenic stimulation of mesenchymal stem cells

We report the ability of aminated mesoporous silica nanoparticles (MSN-NH2) with large mesopore space and positive-charged surface to deliver genes within rat mesenchymal stem cells (MSCs). The amine functionalized inorganic nanoparticles were complexed with bone morphogenetic protein-2 (BMP2) plasmid DNA (pDNA) to study their transfection efficiency in MSCs. Intracellular uptake of the complex BMP2 pDNA/MSN-NH2 occurred significantly, with a transfection efficiency of approximately 68%. Furthermore, over 66% of the transfected cells produced BMP2 protein. The osteogenic differentiation of the transfected MSCs was demonstrated by the expression of bone-related genes and proteins including bone sialoprotein, osteopontin, and osteocalcin. The MSN-NH2 delivery vehicle for BMP2 pDNA developed in this study may be a potential gene delivery system for bone tissue regeneration.

Mineralized poly(lactic acid) scaffolds loading vascular endothelial growth factor and the in vivo performance in rat subcutaneous model

The functionalization of degradable polymeric scaffolds with therapeutic molecules such as vascular endothelial growth factor (VEGF) is a key strategy to gain better regenerative ability of damaged bone tissue by stimulating vascularization and tissue perfusion. Here, we combined VEGF with poly(lactic acid) (PLA) porous scaffold, after modifying the PLA surface with calcium phosphate (CaP) mineral. The mineralized PLA scaffold (mPLA) showed more effective loading capacity of VEGF than the PLA without mineralization as well as profiled sustainable release of VEGF for up to a couple of weeks. The VEGF-loaded mPLA scaffold presented significantly improved proliferation of primary endothelial cells for up to 7 days, with respect to the scaffold without the VEGF loading. The performance of the engineered scaffold was assessed after subcutaneous implantation in rats for 4 weeks. Histological results showed favorable tissue compatibility of both the mPLA scaffolds (with and without VEGF loading), as characterized by infiltration of inflammatory cells, formation of fibrous capsule, and ingrowth of fibroblasts into the matrices. Immunohistochemical staining of the von Willebrand Factor revealed significantly improved formation of neo-capillaries in the VEGF-loaded mPLA. Based on this study, the strategy of VEGF loading onto mineralized PLA scaffold is considered beneficial for gaining improved vascularization of the polymeric scaffolds, suggesting potential applications for bone tissue engineering.

Characterization and optimization of vascular endothelial growth factor(165) (rhVEGF(165)) expression in Escherichia coli

Vascular endothelial growth factors(165) (VEGF(165)) is the most potent and widely used pro-angiogenic factor. Here we determined optimal culture condition of recombinant human VEGF(165) (rhVEGF(165)) in Escherichia coli (E. coli). rhVEGF(165) expression was the highest in 0.25% of L-arabinose induction concentration, at 20 °C induction temperature, and for 5 h induction time under the control of araBAD promoter using pBADHisA vector. In biological activity test, rhVEGF(165) significantly increased the proliferative activity of CPAE cells (p<0.001) and upregulated the expressions of endothelial cell growth-related genes, such as platelet endothelial cell adhesion molecule (PECAM-1), endothelial-specific receptor tyrosine kinase (TEK), kinase insert domain protein receptor (KDR), and tyrosine kinase with immunoglobulin-like and EGF-like domains 1 (TIE1) in calf pulmonary artery endothelial (CPAE) cells.

Investigating the role of FGF18 in the cultivation and osteogenic differentiation of mesenchymal stem cells

Fibroblast growth factor18 (FGF18) belongs to the FGF family and is a pleiotropic protein that stimulates proliferation in several tissues. Bone marrow mesenchymal stem cells (BMSCs) participate in the normal replacement of damaged cells and in disease healing processes within bone and the haematopoietic system. In this study, we constructed FGF18 and investigated its effects on rat BMSCs (rBMSCs). The proliferative effects of FGF18 on rBMSCs were examined using an MTS assay. To validate the osteogenic differentiation effects of FGF18, ALP and mineralization activity were examined as well as osteogenic differentiation-related gene levels. FGF18 significantly enhanced rBMSCs proliferation (p<0.001) and induced the osteogenic differentiation by elevating ALP and mineralization activity of rBMSCs (p<0.001). Furthermore, these osteogenic differentiation effects of FGF18 were confirmed via increasing the mRNA levels of collagen type I (Col I), bone morphogenetic protein 4 (BMP4), and Runt-related transcription factor 2 (Runx2) at 3 and 7 days. These results suggest that FGF18 could be used to improve bone repair and regeneration.

Administration of growth factors for bone regeneration

Growth factors (GFs) such as BMPs, FGFs, VEGFs and IGFs have significant impacts on osteoblast behavior, and thus have been widely utilized for bone tissue regeneration. Recently, securing biological stability for a sustainable and controllable release to the target tissue has been a challenge to practical applications. This challenge has been addressed to some degree with the development of appropriate carrier materials and delivery systems. This review highlights the importance and roles of those GFs, as well as their proper administration for targeting bone regeneration. Additionally, the in vitro and in vivo performance of those GFs with or without the use of carrier systems in the repair and regeneration of bone tissue is systematically addressed. Moreover, some recent advances in the utility of the GFs, such as using fusion technology, are also reviewed.

Expression and purification recombinant human dentin sialoprotein in Escherichia coli and its effects on human dental pulp cells

Dentin sialoprotein (DSP) is cleaved from dentin sialophosphoprotein (DSPP) and most abundant dentinal non-collagenous proteins in dentin. DSP is believed to participate in differentiation and mineralization of cells. In this study, we first constructed recombinant human DSP (rhDSP) in Escherichia coli (E. coli) and investigated its odontoblastic differentiation effects on human dental pulp cells (hDPCs). Cell adhesion activity was measured by crystal violet assay and cell proliferation activity was measured by MTT assay. To assess mineralization activity of rhDSP, Alizarin Red S staining was performed. In addition, the mRNA levels of collagen type І (Col І), alkaline phosphatase (ALP), and osteocalcin (OCN) were measured due to their use as mineralization markers for odontoblast-/osteoblast-like differentiation of hDPCs. The obtained rhDSP in E. coli was approximately identified by SDS-PAGE and Western blot. Initially, rhDSP significantly enhanced hDPCs adhesion activity and proliferation (p<0.05). In Alizarin Red S staining, stained hDPCs increased in a time-dependent manner. This odontoblastic differentiation activity was also verified through mRNA levels of odontoblast-related markers. Here, we first demonstrated that rhDSP may be an important regulatory ECM in determining the hDPCs fate including cell adhesion, proliferation, and odontoblastic differentiation activity. These findings indicate that rhDSP can induce growth and differentiation on hDPCs, leading to improve tooth repair and regeneration.

Emerging role of vitamin D in colorectal cancer

Colorectal cancer is a common cancer and the fourth leading cause of death in Korea. The incidence and mortality of colorectal cancer varies according to risk factors, such as age, family history, genetic history, food habits, and physical activities. Some studies have focused on the association between vitamin D and colorectal cancer. Today, there is growing evidence that high vitamin D intake and a plasma level of 25(OH)D₃ reduce the incidence of colorectal cancer by modifying cancer angiogenesis, cell apoptosis, differentiation, and proliferation. Taken together, these results suggest that vitamin D supplementation alone, or in combination with anti-cancer agents, might reduce the incidence of colorectal cancer. In this review, we discuss the function and mechanism of vitamin D including the effect of vitamin D on colorectal cancer.

Fibroblast growth factors: biology, function, and application for tissue regeneration

Fibroblast growth factors (FGFs) that signal through FGF receptors (FGFRs) regulate a broad spectrum of biological functions, including cellular proliferation, survival, migration, and differentiation. The FGF signal pathways are the RAS/MAP kinase pathway, PI3 kinase/AKT pathway, and PLCγ pathway, among which the RAS/MAP kinase pathway is known to be predominant. Several studies have recently implicated the in vitro biological functions of FGFs for tissue regeneration. However, to obtain optimal outcomes in vivo, it is important to enhance the half-life of FGFs and their biological stability. Future applications of FGFs are expected when the biological functions of FGFs are potentiated through the appropriate use of delivery systems and scaffolds. This review will introduce the biology and cellular functions of FGFs and deal with the biomaterials based delivery systems and their current applications for the regeneration of tissues, including skin, blood vessel, muscle, adipose, tendon/ligament, cartilage, bone, tooth, and nerve tissues.