• Journal of Life Science
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• v.28 no.10
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• pp.1140-1146
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• 2018

Dual-specificity phosphatases (DUSPs) play a role in cell growth and differentiation by modulating mitogen-activated protein kinases. DUSPs are considered targets for drugs against cancers, diabetes, immune diseases, and neuronal diseases. Part of the DUSP family, DUSP19 modulates c-Jun N-terminal kinase activity and is involved in osteoarthritis pathogenesis. Here, we report screening of cavity-creating mutants and the crystal structure of a cavity-creating L75A mutant of DUSP19 which has significantly enhanced enzyme activity in comparison to the wild-type protein. The crystal structure reveals a well-formed cavity due to the absent Leu75 side chain and a rotation of the active site-bound sulfate ion. Despite the cavity creation, residues surrounding the cavity did not rearrange significantly. Instead, a tightened hydrophobic interaction by a remote tryptophan residue was observed, indicating that the protein folding of the L75A mutant is stabilized by global folding energy minimization, not by local rearrangements in the cavity region. Conformation of the rotated active site sulfate ion resembles that of the phosphor-tyrosine substrate, indicating that cavity creation induces an optimal active site conformation. The activity enhancement by an internal cavity and its structural information provide insight on allosteric modulation of DUSP19 activity and development of therapeutics.

• Journal of Life Science
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• v.28 no.10
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• pp.1233-1243
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• 2018

Sterol regulatory-element binding proteins (SREBPs) are a family of transcription factors that regulate lipid homeostasis and metabolism by controlling the expression of enzymes required for endogenous cholesterol, fatty acid (FA), triacylglycerol, and phospholipid synthesis. The three SREBPs are encoded by two different genes. The SREBP1 gene gives rise to SREBP-1a and SREBP-1c, which are derived from utilization of alternate promoters that yield transcripts in which distinct first exons are spliced to a common second exon. SREBP-2 is derived from a separate gene. Additionally, SREBPs are implicated in numerous pathogenic processes, such as endoplasmic reticulum stress, inflammation, autophagy, and apoptosis. They also contribute to obesity, dyslipidemia, diabetes mellitus, and nonalcoholic fatty liver diseases. Genome-wide analyses have revealed that these versatile transcription factors act as important nodes of biological signaling networks. Changes in cell metabolism and growth are reciprocally linked through SREBPs. Anabolic and growth signaling pathways branch off and connect to multiple steps of SREBP activation and form complex regulatory networks. SREBPs are activated through the PI3K-Akt-mTOR pathway in these processes, but the molecular mechanism remains to be understood. This review aims to provide a comprehensive understanding of the role of SREBPs in physiology and pathophysiology at the cell, organ, and organism levels.

• Molecules and Cells
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• v.38 no.4
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• pp.356-361
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• 2015

Mitochondrial dysfunction is associated with insulin resistance and diabetes. We previously showed that retinoid X receptor ${\alpha}$ ($RXR{\alpha}$) played an important role in transcriptional regulation of oxidative phosphorylation (OXPHOS) genes in cells with mitochondrial dysfunction caused by mitochondrial DNA mutation. In this study, we investigated whether mitochondrial dysfunction induced by incubation with OXPHOS inhibitors affects insulin receptor substrate 1 (IRS1) mRNA and protein levels and whether $RXR{\alpha}$ activation or overexpression can restore IRS1 expression. Both IRS1 and $RXR{\alpha}$ protein levels were significantly reduced when C2C12 myotubes were treated with the OXPHOS complex inhibitors, rotenone and antimycin A. The addition of $RXR{\alpha}$ agonists, 9-cis retinoic acid (9cRA) and LG1506, increased IRS1 transcription and protein levels and restored mitochondrial function, which ultimately improved insulin signaling. $RXR{\alpha}$ overexpression also increased IRS1 transcription and mitochondrial function. Because $RXR{\alpha}$ overexpression, knock-down, or activation by LG1506 regulated IRS1 transcription mostly independently of mitochondrial function, it is likely that $RXR{\alpha}$ directly regulates IRS1 transcription. Consistent with the hypothesis, we showed that $RXR{\alpha}$ bound to the IRS1 promoter as a heterodimer with peroxisome proliferator-activated receptor ${\delta}$ ($PPAR{\delta}$). These results suggest that $RXR{\alpha}$ overexpression or activation alleviates insulin resistance by increasing IRS1 expression.

• Korean Journal of Plant Resources
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• v.22 no.5
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• pp.454-460
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• 2009

Phyllanthus urinaria was an important species in Korea and distributed in all around of Korea. The roots and stems of this plant have been used for natural medicine for the treatment of diabetes, the hepatitis B virus and disturbances of the kidney and urinary bladder. Production of adventitious roots in P. urinaria by in vitro cultures could be used as alternatives materials. Shoot and root segments from P. urinaria seedling were cultured on Murashige and Skoog (MS) medium supplemented with 3.0 mg/L IBA and 30 g/L sucrose. After 4 weeks of culture, the highest induction of adventitious roots was obtained from the shoot part. Frequency of adventitious root formation on medium with various kinds of auxins (IAA, NAA, 2,4-D, and IBA) and various concentrations of IBA (0, 0.1, 0.5, 1.0, 3.0, and 5.0 mg/L) was tested. The maximun induction of adventitious root was obtained on medium with 0.5 mg/L IBA. In liquid culture, growth of root was best on medium supplemented with 30 g/L sucrose. Adventitious roots were cultured in 5 L bioreactor containing 1/2 MS medium supplemented with 0.5 mg/L IBA and 30 g/L sucrose and mass-production of adventitious roots was successfully achieved. These results revealed the first attempt for the production of adventitious roots in P. urinaria.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.108-109
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• 2013

Mitochondria play key roles in the production of cell's energy. Their dominant function is the synthesis of adenosine 5'-triphosphate (ATP) from adenosine diphosphate (ADP) and phosphate (Pi) through the oxidative phosphorylation. Evaluation of drug-induced mitochondrial toxicity has become increasingly important since mitochondrial dysfunction has recently been implicated in numerous diseases including cancer and diabetes mellitus. Mitochondrial functions have been monitored via oxygen consumption, mitochondrial membrane potential, and more importantly via ATP synthesis since ATP synthesis is the most essential function of mitochondria. Various analytical methods have been employed to investigate ATP synthesis in mitochondria, including high performance liquid chromatography (HPLC), bioluminescence technique, and pH measurement. However, most of these methods are based on destructive analysis or indirect monitoring through the enzymatic reaction. Infrared absorption spectroscopy (IRAS) is one of the useful techniques for real-time, label-free, and direct monitoring of biological reactions [1,2]. However, the strong water absorption requires very short path length in the order of several micrometers. Transmission measurements with thin path length are not suitable for mitochondrial assays because solution handlings necessary for evaluating mitochondrial toxicity, such as rapid mixing of drugs and oxygen supply, are difficult in such a narrow space. On the other hand, IRAS in the multiple internal reflection (MIR) geometry provides an ideal optical configuration to combine solution handling and aqueous-phase measurement. We have recently reportedon a real-time monitoring of drug-induced necrotic and apoptotic cell death using MIR-IRAS [3,4]. Clear discrimination between viable and damaged cells has been demonstrated, showing a promise as a label-free and real-time detection for cell-based assays. In the present study, we have applied our MIR-IRAS system to mitochondria-based assays by monitoring ATP synthesis in isolated mitochondria from rat livers. Mitochondrial ATP synthesis and hydrolysis were in situ monitored with MIR-IRAS, while dissolved oxygen level and solution pH were simultaneously monitored with O2 and pH electrodes, respectively. It is demonstrated that ATP synthesis and hydrolysis can be monitored by the IR spectral changes in phosphate groups in adenine nucleotides and MIR-IRAS is useful for evaluating time-dependent drug effects of mitochondrial toxicants.

• Food Science of Animal Resources
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• v.33 no.2
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• pp.276-280
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• 2013

Obesity, the leading metabolic disease, is a prevalent health problem in industrialized countries and is closely associated with coronary heart disease, hypertension, diabetes, and even cancer. In this study, we investigated the effects of dip-sauce for meat containing Garcinia cambogia extract (GC) on the lipid accumulation and body weight reduction in rats fed high-fat diet for three months. Eighteen Sprague Dawley male rats of five-week-old were randomly assigned to one of three groups; normal chew diet (NCD) group, high-fat diet plus GC-noncontaining dip-sauce (HFD) group, and HFD plus GC-containing dip-sauce (HFD+GC) group. Co-administration of GC-containing dip-sauce (5 g/kg body weight/day) with HFD significantly attenuated cumulative body weight gain, compared with NCD or HFD groups. Both epididymal and perirenal fat pad weights in the HFD plus GC group were significantly lower than those of HFD or NCD groups. Administration of GC-containing dip-sauce also resulted in significant reduction in the serum levels of total cholesterol, total lipid, and triglyceride, compared with NCD or HFD groups. Thus, GC-containing dip-sauce confers beneficial effects to pathological states associated with metabolic disorder via its anti-obesity and lipid lowering properties.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.122-127
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• 2006

The effects of fermented chaga mushroom (Inonotus obliquus) powder on the lipid concentrations and the activities of liver marker enzymes of serum in genetically diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats were investigated. Rats were fed a semisynthetic diet supplemented with 50 g/kg chaga mushroom powder (CM) or 50 g/kg fermented chaga mushroom powder (FCM) for 8 weeks (26 to 34 weeks of age). Nondiabetic Long-Evans Toknshima Otsuka (LETO) rats were used as age-matched nondiabetic control animals. Water consumption was significantly higher in the OLETF control than the LETO rats. Water consumption in the FCM-fed OLETF rats tended to be less than in both the OLETF control and CM-fed OLETF rats. Serum concentrations of triglycerides and total cholesterol were significantly higher in the OLETF control rats than in the LETO rats while within the OLETF rat groups, the consumption of FCM resulted in a significantly lower serum triglyceride concentration and slightly lowered serum total cholesterol concentration when compared to the OLETF control and CM-fed rats. The alanine aminotransferase (ALT) activity was significantly higher in the OLETF control than in the LETO rats, but this difference was significantly reduced compared to the CM-fed rats and essentially no difference in the ALT levels was observed between the LETO and OLETF-FCM rats. This observation suggests an adaptive effect of the fermented chaga mushroom in liver function. Livers of the LETO rats showed no histopathological changes, whereas those of the OLETF control rats were characterized by many fat depositions in the central zone of the hepatocytes. The livers of the OLETF CM-fed rats showed less fatty changes compared to the OLETF control rats and fat deposition in the hepatocytes was nearly absent. These results suggest that orally ingested fermented chaga mushroom has a potential beneficial effect on the complications known to occur in the obesity-related non-insulin dependent diabetes mellitus (NlDDM) OLETF rat.

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.795-801
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• 2001

Effects of Mucilage fraction from Yam (Dioscorea batatas DECENE), which has long been used as a wild vegetable and folk medicine, on blood glucose and lipid composition in alloxan-induced diabetic mice were investigated. Diabetes mellitus was induced in male ICR mice by the injection of alloxan into the tail vein at a dose of 75 mg/kgBW. Alloxan-induced diabetic mice were administered the yam mucilage fraction1 orally ; y500F1 group (500 mg/kgBW/day fraction1) and y750F1 group (750 mg/kgBW/day fraction1); and the normal and alloxan-control group were orally administered with saline for 10 days. The body weight gain and food intake were monitored every day. The concentrations of glucose, triglyceride, total cholesterol, and LDL-cholesterol of serum and liver levels of glucose, triglyceride, and cholesterol were determined. Also weight of liver, heart, spleen and kidney were measured. The fraction 1 of yam mucilage lowered body weight gain significantly (p<0.05) and decreased serum glucose levels in alloxan-induced diatetic mice compared to that of alloxan-control group. In alloxan induced diabetic mice serum triglyceride level was lowered and liver HDL-cholesterol level increased significantly (p<0.05). In conclusion, it was assumed that yam mucilage fraction 1 has anti-hyperglycemic and anti-obesitic effects by reducing body weight gain and decreasing serum glucose and triglyceride level.

• Korean Journal of Food Science and Technology
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• v.33 no.6
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• pp.802-807
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• 2001

Effects of ${\beta}-glucan$ from Lentinus edodes and hordeum vulgare on blood glucose and lipid composition were investigated. Diabetes mellitus was induced in male ICR mice by the injection of alloxan into the tail vein at a dose of 75 mg/kg. The ${\beta}-glucan$ were administered orally for 10 days and the normal and alloxan-control group were orally administered with saline. The body weight gain and food intake were monitored every day and plasma levels of glucose, triglyceride, total cholesterol, LDL-cholesterol were determined at last day. Also the weight of liver, heart, spleen and kidney were determined. The ${\beta}-glucan$ from Lentinus edodes and hordeum vulgure lowered significantly body weight gain in alloxan-induced diatetic mice (p<0.05) and plasma glucose levels compared to that of alloxan-control group. Plasma triglyceride level in B500 was lowered in alloxan-induced diabetic mice. The ${\beta}-glucan$ of hordeum vulgare lowered weight of liver significantly (p<0.05). In conclusion, it was assumed that ${\beta}-glucan$ from hordeum vulgare have anti-hyperglycemic and anti-obese effects by reducing body weight gain and decreasing serum glucose and triglyceride level.

• Korean Journal of Medicinal Crop Science
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• v.4 no.4
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• pp.333-339
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• 1996

The root and stem bark of Eleutherococcus spp. is used for the treatment of paralysis, rheumatism, arthritis, diabetes, stamina failure, high blood pressure, etc. This study was con­ducted to identify botanical origins and to select standard variety of Eleutherococcus spp. with analyzing eleutheroside E content(%) of root bark and that of Eleutherococcus senticosus at different collected area, time, part and grown area. The content of eleutheroside E in the root bark was determined by HPLC, and it was 0.1925% in Eleutherococcus senticosus, 0.1103% in E. chiisanensis, 0.0348% in E. koreanum and 0.0236% in E. sieboldianum. In seasonal change of eleutheroside E content, it was higher in autumn product than summer product in Eleutherococcus senticosus. It also was higher in root bark than stem bark in different part. To investigate eleutheroside E content of root bark among different collected local area in E. sen­ticosus, it was high order to Mt. Deokyu, Hokkaido and Mt. Seolak as a 0.1625%. 0.0493% and 0.027 %, respectively. The growth of Eleutherococcus senticosus was good at grown Unbong (altitude 10m), but eleu­theroside E content was high at grown Nogodan (altitude 1, 450m).