• Korean Journal of Veterinary Research
• /
• v.37 no.2
• /
• pp.301-310
• /
• 1997

Diabetes mellitus is associated with a wide range of pathophysiological in the kidney. This study was designed to examine the effects of high glucose concentration on IGF-I binding and glucose transporters in renal proximal tubule cells. The results were as follows : The binding of $^{125}I-IGF-I$ reached the peak at the 30 minutes and gradually decreased by the time dependent manner. The binding of $^{125}I-IGF-I$ was inhibited by the unlabelled IGF-I($10^{-14}{\sim}10^{-8}M$) in a concentration dependent manner. The relative affinity of IGF-I receptor for IGF-I, IGF-II and insulin exhibited typical type 1 binding(IGF-I > insulin > IGF-II). However IGF-II did not compete for the cultured cell membrane $^{125}I-IGF-I$ binding site at $10^{-14}{\sim}10^{-8}M$. Under optimal conditions, IGF-I binding to the membranes from 5mM and 20mM glucose treated cells was analyzed. It was found that 20mM glucose treated cells exhibited higher binding activity for IGF-I. In order to further substantiate this increase in IGF-I binding sites, we performed affinity-labelling studies. The cross-linked cell membrane subjected to SDS-PAGE; labelled material was detected by autoradiography. 20mM glucose treated cells exhibited higher levels. The initial rate of $methyl-{\alpha}-D-glucopyranoside({\alpha}-MG)$ uptake was significantly lower($74.41{\pm}6.71%$) in monolayers treated with 20mM glucose than those of 5mM glucose. However, 3-O-methyl-D-glucose(3-O-MG) uptake was not affected by glucose concentration in culture media. IGF-I significantly increased ${\alpha}-MG$ uptake in both 5mM and 20mM glucose treated cells. However, 3-O-MG uptake was not affected by IGF-I in both conditions. In conclusion, 20mM glucose increased binding sites of $^{125}I-IGF-I$, inhibited Na/glucose cotransporter activity. But 20mM glucose did not change facilitated glucose transporter.

• Nutrition Research and Practice
• /
• v.11 no.3
• /
• pp.198-205
• /
• 2017

BACKGROUND/OBJECTIVES: The anti-diabetic activity of pear through inhibition of ${\alpha}-glucosidase$ has been demonstrated. However, little has been reported about the effect of pear on insulin signaling pathway in obesity. The aims of this study are to establish pear pomace 50% ethanol extract (PPE)-induced improvement of insulin sensitivity and characterize its action mechanism in 3T3-L1 cells and high-fat diet (HFD)-fed C57BL/6 mice. MATERIALS/METHODS: Lipid accumulation, monocyte chemoattractant protein-1 (MCP-1) secretion and glucose uptake were measure in 3T3-L1 cells. Mice were fed HFD (60% kcal from fat) and orally ingested PPE once daily for 8 weeks and body weight, homeostasis model assessment of insulin resistance (HOMA-IR), and serum lipids were measured. The expression of proteins involved in insulin signaling pathway was evaluated by western blot assay in 3T3-L1 cells and adipose tissue of mice. RESULTS: In 3T3-L1 cells, without affecting cell viability and lipid accumulation, PPE inhibited MCP-1 secretion, improved glucose uptake, and increased protein expression of phosphorylated insulin receptor substrate 1 [p-IRS-1, ($Tyr^{632})$)], p-Akt, and glucose transporter type 4 (GLUT4). Additionally, in HFD-fed mice, PPE reduced body weight, HOMA-IR, and serum lipids including triglyceride and LDL-cholesterol. Furthermore, in adipose tissue, PPE up-regulated GLUT4 expression and expression ratio of p-IRS-1 ($Tyr^{632})/IRS$, whereas, down-regulated p-IRS-1 ($Ser^{307})/IRS$. CONCLUSIONS: Our results collectively show that PPE improves glucose uptake in 3T3-L1 cells and insulin sensitivity in mice fed a HFD through stimulation of the insulin signaling pathway. Furthermore, PPE-induced improvement of insulin sensitivity was not accompanied with lipid accumulation.

• YAKHAK HOEJI
• /
• v.48 no.4
• /
• pp.247-253
• /
• 2004

We investigated the hypoglycemic effect of formula containing Euonymus alatus (EA) and Mori Folium (MF) in multiple low dose (MLD) streptozotocin (STZ)-induced diabetic rats. In order to iduce hyperglycemic state 25 mg/kg of STZ was injected intraperitoneally for 5 consecutive days. SD rats were randomly divided into diabetic control and treatment groups. Treatment groups were administered with either 250 mg/kg of EA and 250 mg/kg of MF (E1Ml), or 500 mg/kg of EA mixed with same dose of MF (E2M2) for 3 weeks. Blood glucose levels and body weights were measured every 5th or 6th day. E1Ml and E2M2 both significantly reduced food intake, water intake, and fasting blood and urine glucose levels as compared to those in diabetic control group in a dose dependent manner. Body weight in diabetic control group was increased slightly after 3 weeks. Treatment group, however, showed gradual increase in body weights during 3 week-period. While plasma insulin levels of the diabetic control group were decreased to the level of 387$\pm$14 pg/ml from 534$\pm$36 pg/ml, those levels in E1Ml and E2M2-treated groups were both markedly increased by 13% and 26%, respectively. Urine glucose levels in E1Ml and E2M2-treated groups were also remarkably reduced by 17 and 26% compared to the levels of diabetic control group. While expression of membrane-bound glucose transporter-4 (GLUT-4) protein in skeletal muscle was reduced by 45% in diabetic control compared to the normal control, GLUT-4 protein expressions in E1Ml and E2M2-treated groups were augmented by 2 and 3.5 times compared to the diabetic control, respectively. Pancreatic HE staining experiments showed that E2M2-treated group revealed much less infiltrated mononuclear cells, indicating that E2M2 efficiently blocked insulitis induced by multiple low dose streptozotocin. Taken together, we conclude that formula containing EA and MF may prevent or delay the development of hyperglycemia through overexpression of GLUT-4 protein in skeletal muscle and prevention of insulitis.

• Korean Journal of Pharmacognosy
• /
• v.38 no.1
• /
• pp.10-14
• /
• 2007

Type 2 diabetes mellitus relavant to insulin resistance is a chronic and hard to control. In order to develop an antidiabetic agent from natural products, anti-hyperglycemic effect of herbal formula containing Mori Follium, Euonymi Lignum Suberalatum and Ginseng Radix(MEG) was investigated in db/db mice. Treatment group was administered orally with MEG formula at a dose of 300 mg/kg for 5 weeks, and blood glucose, insulin and lipid levels were determined. MEG treatment group showed a marked decrease in fasting blood glucose level and insulin resistance index(IRI) compared to those in diabetic control. Improvement of insulin resistance(60.6%) was indicative of reducing lipid levels in plasma and triglyceride contents in muscle and adipose tissue. In addition, expressions of an insulin responsive gene, glucose transporter 4(Glut4), in muscle and adipose tissue were upregulated in MEG treatment group. Compared islet morphology between groups, MEG formula prevented the ${\beta}$-cell destruction caused by high blood glucose. Taken together, MEG formula can act as an anti-hyperglycemic agent with insulin sensitizing effect, and thus deserves a clinical trial in the future.

• Korean Journal of Microbiology
• /
• v.47 no.4
• /
• pp.281-288
• /
• 2011

To screen downstream genes of Aspergillus nidulans MsnA showing amino acid sequence similarity to the zinc finger region of Msn2/4 stress response transcription factors in Saccharomyces cerevisiae, differentially expressed genes (DEG) in MsnA overexpressed or msnA null mutant strains compared to wild type have been isolated. The cognate gene IDs were identified by DNA sequencing of the selected DEGs. Among those, DEG6 was known as mstB encoding a putative monosaccharide transporter. Expression level of mstB mRNA was increased in MsnA overproducing strains and MsnA bound directly to the promoter region of mstB in vitro. MstB containing twelve transmembrane domains exhibited 80% of amino acid sequence identities to A. niger MstA a high-affinity monosaccharide transporter. A null mutant of mstB was phenotypically undistinguishable to wild type. On the other hand, forced overexpression of MstB caused the increased formation of sexual structure cleistothecia in 0.1% glucose condition where wild type showed almost no cleistothecia. This result implies that mstB is involved in transport of monosaccharide required for sexual differentiation.

• The Korean Journal of Physiology and Pharmacology
• /
• v.5 no.2
• /
• pp.183-188
• /
• 2001

To elucidate antidiabetic effect and mechanism(s) of acarbose in a polygenic spontaneous hyperglycemic and hyperinsulinemic diabetic animal model, $KKA^y$ mice, acarbose was administered orally for 4 weeks and effects on body weight, plasma glucose and insulin levels, genetic expressions of intestinal sucrase-isomaltase (SI), sodium-glucose cotransporter (sGLT1) and glucose transporter in quadriceps muscle (GLUT4) were examined in this study. Although no differences in body weight were detected between control and acarbose-treated groups, plasma glucose level in acarbose-treated group was markedly reduced as compared to the control. In the mechanism study, acarbose downregulated the SI and SGLT1 gene expressions, and upregulated the GLUT4 mRNA and protein expressions when compared to the control group. In conclusion, the data obtained strongly implicate that acarbose can prevent the hyperglycemia in $KKA^y$ mice possibly through blocking intestinal glucose absorption by downregulations of SI and sGLT1 mRNA expressions, and upregulation of skeletal muscle GLUT4 mRNA and protein expressions.

• Journal of Nutrition and Health
• /
• v.47 no.3
• /
• pp.167-175
• /
• 2014

Purpose: Previous studies have shown that treatment with Smilax china L. leaf extract (SCLE) produces antidiabetic effects due to ${\alpha}$-glucosidase inhibition. In this study, we examined the mechanism underlying these antidiabetic effects by examining glucose uptake in HepG2 cells cultured with SCLE. Methods: Glucose uptake and glucokinase activity were examined using an assay kit. Expression of glucose transporter (GLUT)-2, GLUT-4, and HNF-$1{\alpha}$ was measured by RT-PCR or western blot. Results: Treatment with SCLE resulted in enhanced glucose uptake in HepG2 cells, and this effect was especially pronounced when cells were cultured in an insulin-free medium. SCLE induced an increase in expression of GLUT-2 but not GLUT-4. The increase in the levels of HNF-$1{\alpha}$, a GLUT-2 transcription factor, in total protein extract and nuclear fraction suggest that the effects of SCLE may occur at the level of GLUT-2 transcription. In addition, by measuring the change in glucokinase activity following SCLE treatment, we confirmed that SCLE stimulates glucose utilization by direct activation of this enzyme. Conclusion: These results demonstrate that the potential antidiabetic activity of SCLE is due at least in part to stimulation of glucose uptake and an increase in glucokinase activity, and that SCLE-stimulated glucose uptake is mediated through enhancement of GLUT-2 expression by inducing expression of its transcription factor, HNF-$1{\alpha}$.

• 대한두경부종양학회:학술대회논문집
• /
• 2006.11a
• /
• pp.203-203
• /
• 2006

• Biomedical Science Letters
• /
• v.15 no.1
• /
• pp.55-60
• /
• 2009

Insect cells such as Spodoptera frugiperda Clone 9 (Sf9) cells are widely chosen as the host for heterologous expression of a mammalian sugar transport protein using the baculovirus expression system. Characterization of the expressed protein is expected to include assay of its function, including its ability to transport sugars and to bind inhibitory ligands such as cytochalasin B. It is therefore very important first to establish the transport characteristics and other properties of the endogenous sugar transport proteins of the host insect cells. However, very little is known of the transport characteristics of Sf9 cells, although their ability to grow on TC-100 medium strongly suggested the presence of endogenous glucose transport system. In order to investigate the substrate and inhibitor recognition properties of the Sf9 cell transporter, the ability of pentoses to inhibit 2-deoxy-D-glucose (2dGlc) transport was investigated by measuring inhibition constants $(K_i)$. To determine the time period over which of sugar into the Sf cells was linear, the uptake of 2dGlc 0.1mM extracellular concentration was measured over periods ranging from 30 seconds to 30 minutes. The uptake was linear for at least 2 minutes at the concentration, implying that uptake made over a 1 minute time course would reflect initial rates of the sugar uptake. The data have also revealed the existence of a saturable transport system for pentose uptake by the insect cells. The transport was inhibited by D-xylose and D-ribose, although not as effective as hexoses. However, L-xylose had a little effect on 2dGlc transport in the Sf9 cells, indicating that the transport is stereoselective. Unlike the human erythrocyte-type glucose transport system, D-ribose had a somewhat greater apparent affinity for the Sf9 cell transporter than D-xylose. It is therefore concluded that Sf9 cells contain an endogenous sugar transport activity that in some aspects resembled the human erythrocyte-type counterpart, although the Sf9 and human transport systems do differ in their affinity for cytochalasin B.

• Food Science and Biotechnology
• /
• v.17 no.6
• /
• pp.1228-1234
• /
• 2008

Having idea to develop more effective anti-diabetic agent from ginseng root, we comprehensively assessed the anti-diabetic activity and mechanisms of ginsam in C57BL/KsJ db/db mice. The db/db mice were divided into 4 groups; diabetic control (DC), ginsam at a dose of 300 or 500 mg/kg (GS300 or GS500) and metformin at a dose of 300 mg/kg (MT300). Ginsam was orally administered for 8 weeks. GS500 reduced the blood glucose concentration and significantly decreased an insulin resistance index. In addition, GS500 reduced the plasma non-esterified fatty acid, triglyceride, and increased high density lipoprotein-cholesterol as well as decreased the hepatic cholesterol and triglyceride. More interestingly, ginsam increased the plasma adiponectin level by 17% compared to diabetic control group. Microarray, quantitative-polymerase chain reaction and enzyme activity results showed that gene and protein expressions associated with glycolysis, gluconeogenesis, and fatty acid oxidation were changed to the way of reducing hepatic glucose production, insulin resistance and enhancing fatty acid $\beta$-oxidation. Ginsam also increased the phosphorylation of AMP-activated protein kinase and glucose transporter expressions in the liver and skeletal muscle, respectively. These changes in gene expression were considered to be the mechanism by which the ginsam exerted the anti-diabetic and anti-dyslipidemic activities in C57BL/KsJ db/db mice.