Hajin Nam

Silk fibroin hydrolysate exerts an anti-diabetic effect by increasing pancreatic β cell mass in C57BL/KsJ-db/db mice.

Components of silk including silk fibroin have long been used as anti-diabetic remedies in oriental medicine. However, detailed mechanisms underlying these anti-diabetic effects remain unclear. In this study, we examined the anti-diabetic activity of silk fibroin hydrolysate (SFH) in C57BL/KsJ-db/db (db/db) mice, a well-known animal model of non-insulin dependent diabetes mellitus. When the db/db mice were administered SFH in drinking water for 6 weeks, hyperglycemia in the animals gradually disappeared and the level of glycosylated hemoglobin decreased, indicating that SFH plays important role in reducing the symptoms of diabetes. In addition, SFH-treated db/db mice exhibited improved glucose tolerance with increased plasma insulin levels. Immunohistochemical and morphological analyses showed that SFH up-regulated insulin production by increasing pancreatic β cell mass in the mice. In summary, our results suggest that SFH exerts anti-diabetic effects by increasing pancreatic β cell mass in a non-insulin dependent diabetes mellitus mouse model.

Anti-diabetic Effect of the Soybean Extract Fermented by Bacillus subtilis MORI in db/db Mice

This study investigated the effects of soy bean extract fermented by Bacillus subtilis MORI (BTD-1) on blood glucose, hemoglobin A1c (HbA1c), plasma insulin, and pancreatic β islets in db/db mice. The BTD-1 (500 mg/kg) group showed significantly lower fasting blood glucose level (p<0.01) and postprandial 2 h blood glucose level (p<0.01) compared with the db control group. The BTD-1 (500 mg/kg) group showed significantly lower HbA1c level compared with the db control group (p<0.01). After 8 weeks of BTD-1 administration, the pancreatic islet architecture was preserved and the immunofluorescent intensities of insulin in BTD-1 (500mg/kg) group apparently increased compared to in the db control group. Plasma insulin levels were found to be significantly higher in the BTD-1 (500 mg/kg) group than in the db control group (p<0.05). In summary, our results suggest that BTD-1 has an anti-diabetes effect in a non-insulin dependent diabetes mellitus mouse model.

Comparison of N-Methyl-d-aspartate Receptor Subunit 1 and 4-Hydroxynonenal in the Hippocampus of Natural and Chemical-Induced Aging Accelerated Mice

Abstract In this study, we compared N-methyl-d-aspartate receptor type 1 (NMDAR1) and 4-hydroxynonenal (4-HNE) in the hippocampus of d-galactose (d-gal)-induced and naturally aging models of mice. These markers represent general phenotypes in aging, and they allowed us to examine the possibility of d-gal as a chemical model agent for aging. We observed an age-dependent reduction of NMDAR1 and an increase in 4-HNE in the dentate gyrus, CA1, and CA3 regions of the hippocampus via immunohistochemistry and western blot analyses. In the d-gal-induced chemical aging model, we observed similar changes in NMDAR1 and 4-HNE although the degree of reduction/increase in NMDAR1/4-HNE was not as severe as that in the naturally aged mice. These results suggest that the d-gal-induced aging model is comparable to naturally aged mice and may be useful for studies of the aging hippocampus.

Rapid and efficient identification of the mouse leptin receptor mutation (C57BL/KsJ-db/db) by tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) analysis

The C57BLKS/J-Leprdb mouse has a point mutation in the leptin receptor gene and is one of the most useful animal model for non-insulin dependent diabetes mellitus in human. Since the homozygote of C57BLKS/J-Leprdb mouse is infertile, detection of point mutation in the leptin receptor gene is important for efficient maintaining strains as well as mass production of homozygotes. To develop a rapid and efficient genotyping method for C57BLKS/J-Leprdb mouse, the tetra-primer amplification-refractory mutation system polymerase chain reaction (ARMS-PCR) was used. The 407 and 199 bp PCR products were amplified from normal (+/+) mice; while the 407 and 268 bp PCR products were amplified from homozygotes (db/db) mice; and the 407, 268, and 199 bp PCR products were amplified from heterozygotes (db/+) mice. This result showed that the tetra-primer ARMS-PCR analysis by us is suitable to detect point mutation of the leptin receptor gene. Taken together, our method will dramatically reduce animal use for maintenance of strains as well as production of homozygote in the C57BLKS/J-Leprdb strains.

Anti-obesity Effects of the Stem Bark of Japanese Horse Chestnut (Aesculus turbinate) in 3T3-L1 Preadipocytes

The inhibitory effects of lipid accumulation on ethanol extract from stem bark of Japanese horse chestnut (JHC) were evaluated. Exposure to JHC extract (10–100 μg/mL) for a 72 h incubation period did not alter cell viability compared to the untreated control. JHC extract, with concentrations of 25, 50, and 100 μg/mL, inhibited lipid accumulation in 3T3-L1 adipocytes in a dose dependent manner. The expression of PPARγ and C/EBPα, important adpogenic key markers was significantly reduced when JHC extract was added to cells for 8 days compared with the untreated control group. These results suggest that JHC extract might be a potential therapeutic agent as a natural anti-obesity material.

Anti-adipogenic effects in 3T3-L1 cells of acetone extracts and fractions from Styrax japonica fruit

Reduction in reactive oxygen species (ROS) production facilitated by Styrax japonica (SJ) extracts and fractions for inhibition of obesity development through inhibition of adipogenesis was investigated. Treatment of cells with SJ extracts and fractions did not result in changes in cell viability. SJ extracts and fractions inhibited lipid accumulation in a dose-dependent manner during adipogenesis. Expressions of PPARγ and C/EBPα, key adipogenic markers, were decreased in cells treated with SJ extracts and fractions. Inhibitory effects of SJ extracts and fractions were the most powerful in the early stages of differentiation (days 0-2). Intracellular ROS production was decreased in cells treated with SJ extracts and fractions. SJ extracts and fractions can inhibit adipogenesis via reduced ROS levels, which involves down-regulation of adipogenic transcription factors.

Anti-apoptotic effects of silk fibroin hydrolysate in RIN5F cell on high glucose condition

Hyperglycemia-induced pancreatic β-cell apoptosis causes serious health complications in diabetic patients. Recently, studies demonstrated that silk and silk-related materials have anti-diabetic effects. We previously reported that silk fibroin hydrolysate (SFH) has anti-diabetic effects through increased pancreatic β-cell mass in type 2 diabetic animals (C57BL/KsJdb/db). However, it is not known whether SFH has anti-apoptotic effects in hyperglycemic conditions. The present study investigates the anti-apoptotic effects of SFH on high glucose-induced apoptosis using RIN5F cells, a rat pancreatic β-cell line. Hyperglycemic conditions decreased RIN5F cell viability in a concentration-dependent manner. High glucose treatment of 33 mM or higher caused a significant decrease in RIN5F cell viability. However, addition of SFH significantly recovered cell viability in the presence of high glucose. Flow cytometry analysis showed that high glucose treatment significantly increased early stage apoptosis in RIN5F cells. This was inhibited by SFH treatment, which significantly decreased not only early stage apoptosis but also decreased the production of nitrite. Additionally, SFH protected RIN5F cells from oxidative stress-induced apoptosis. These results suggest that SFH has anti-apoptotic effects by protecting pancreatic β-cell from high glucose and/or oxidative stress. Our results support in vivo anti-diabetic effects of SFH and validation of the traditional use of silkworm and silkworm materials in the treatment of diabetes.

A high resolution genetic mapping of the faded (fe) gene to a region between D10mit156 and D10mit193 on mouse chromosome 10

The C57BL/6J-fe/fe mouse is a coat color mutant. The coat color of the homozygote mouse becomes progressively lighter with advancing age. The faded gene (fe) of C57BL/6J-fe/fe was mapped in a 2.0 cM distal to D10mit191 by our group. To make a high-resolution map, we used the Korean wild mouse (KWHM) for a backcross panel, which was captured in 1995 and has been maintained as an inbred line by our laboratory. In the inter-specific backcross panel (N=400), the fe gene was mapped to 1.0 cM distal to D10mit156. The gene order was defined: centromere -D10mit3/85 (1.3±0.6 cM)-D10mit155 (1.3±0.6 cM)-D10mit191 (2.0±0.7 cM)-D10mit156 (1.0±0.5 cM)-fe-D10mit193 (1.3±0.6 cM)-D10mit54 (1.0±0.5 cM)-D10mit44 (8.5±1.4 cM)-D10mit42 (10.0±1.5 cM). The measured distance between D10mit191 and D10mit 44 differed in both inter-specific (DBA/2) and intra-specific (KWHM) backcross panels (14.2 vs 13.8 cM). Taken together, our high-resolution linkage map of the fe locus from an intra-specific backcross panel will provide a good entry point to isolate the fe gene.

Fagopyritol, a Derivative of D-chiro-inositol, Induces GLUT4 Translocation via Actin Filament Remodeling in L6-GLUT4myc Skeletal Muscle Cells

Insulin induces glucose transporter 4 (GLUT4) translocation to the muscle cell surface. As fagopyritol has insulin-like effects, the effects of fagopyritol on GLUT4 translocation and filamentous (F) actin remodeling in L6-GLUT4myc skeletal muscle cells were investigated. Fagopyritol significantly increased plasma membrane GLUT4 levels compared with the basal control in L6-GLUT4myc myoblast cells. Phosphatidylinositol (PI) 3-kinase inhibitor (LY294002) treatment prevented GLUT4 translocation to the plasma membrane in the myoblasts. Fagopyritol treatment apparently stimulates F-actin remodeling in myoblasts. In addition, fagopyritol treatment induced GLUT4 translocation and F-actin remodeling in myotubes. Taken together, these results suggest that fagopyritol promotes GLUT4 translocation and F-actin remodeling by activating the PI 3-kinase-dependent signaling pathway.

Silk fibroin hydrolysate ameliorates diabetic dyslipidemia in type 2 diabetic model mice

The antidiabetic properties in silk materials, such as silkworm and silk fibroin, have been described in traditional folk medicine. In a previous study, we reported that the silk fibroin hydrolysate (SFH) had a protective effect against glucotoxicity in HIT-15 cells and an antidiabetic effect in a noninsulin-dependent diabetes mellitus (type 2 diabetes, T2DM) mouse model. This study aimed to determine whether SFH ameliorates diabetic dyslipidemia and promotes pancreatic β-cell function in a T2DM animal model (C57BL/KsJdb/db). SFH significantly improved blood glucose levels after 4 weeks of treatment. T2DM animals had a normal serum blood glucose level after 6 weeks of SFH treatment. Hemoglobin A1c (HbA1c) levels were significantly lower in T2DM animals that were treated with SFH for 6 weeks. Glucose tolerance in T2DM animals also significantly improved after 6 weeks of SFH treatment. Furthermore, plasma total cholesterol, high-density lipoprotein cholesterol, nonesterified fatty acid, and triglyceride concentrations significantly decreased in SFH-treated T2DM animals compared to T2DM animals. This result showed that SFH ameliorated diabetic dyslipidemia in the T2DM model mice. Taken together, our results suggest that SFH could be used as a potential agent to treat dyslipidemia in patients who have type 2 diabetes mellitus.