• BMB Reports
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• v.32 no.5
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• pp.429-435
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• 1999

Unlike the mammalian glucose transporter GLUT1, little is known about the nature of the endogenous sugar transporter(s) in insect cells. In order to establish the transport characteristics and other properties of the sugar transport proteins of Sf9 cells, a series of kinetic analyses was performed. A saturable transport system for hexose uptake has been revealed in the insect cells. The apparent affinity of this transport system(s) for 2-deoxy-D-glucose was relatively high, the $K_m$ for uptake being <0.5 mM. To further investigate the substrate and inhibitor recognition properties of the insect cell transporter, the ability of other sugars or drugs to inhibit 2-deoxy-D-glucose transport was examined by measuring inhibition constants ($K_j$). Transport was inhibited by D-mannose, D-glucose, and D-fructose. However, the apparent affinity of the C-4 epimer, D-galactose, for the Spodoptera transporter was relatively low, implying that the hydroxyl group at the C-4 position may play a role in the strong binding of glucose and mannose to the transporter. The results also showed that transport was stereoselective, being inhibited by D-glucose but not by L-glucose. It is therefore concluded that insect cells contain an endogenous glucose transport activity that in several aspects resembles the human erythrocyte glucose transporter. However, the mammalian and insect transporters were different in some of their kinetic properties, namely, their affinities for fructose and for cytochalasin B.

• Journal of Life Science
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• v.27 no.3
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• pp.289-294
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• 2017

Diabetes mellitus is associated with insulin resistance, which leads to down-regulation of insulin signaling and the decreased glucose uptake. Adipocytes are sensitive to insulin, and closely implicated in insulin resistance and diabetes. Insulin stimulates differentiation of preadipocytes to adipocytes, and increases glucose transport. Allium species have been used as traditional medicine and health-promoting foods. Allium hookeri (A. hookeri) is reported to improve the pancreatic ${\beta}-cell$ damage and exhibit pancreatic anti-inflammatory activity in streptozotocin-induced diabetic rats. We investigated whether A. hookeri extract (AHE) may stimulate glucose uptake in adipocytes through increasing insulin sensitivity. AHE enhanced fat accumulation, a differentiation biomarker, under the partial induction of differentiation by insulin. $PPAR{\gamma}$, a transcription factor highly expressed in adipocytes, promotes adipocyte differentiation and insulin sensitivity. AHE increased the differentiation of preadipocytes through up-regulation of $PPAR{\gamma}$. The activation of $PPAR{\gamma}$ increases the GLUT4 expression during adipocyte differentiation. GLUT4 is responsible for glucose uptake into the adipocytes. AHE increased the expression of GLUT4 in adipocytes, and subsequently enhanced the insulin-stimulated glucose uptake. These results suggest that AHE promotes adipocyte differentiation through activation of $PPAR{\gamma}$, and leads to enhance glucose uptake in adipocytes along with GLUT4 up-regulation. Thus, AHE may be effective for the insulin-sensitizing and anti-diabetic activities.

• Journal of Life Science
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• v.32 no.2
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• pp.86-93
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• 2022

Lupeol is a type of pentacyclic triterpene and has been reported to have pharmacological activities against various diseases; however, the effect of lupeol on glucose absorption has not been elucidated yet. This study aimed to investigate the effect of lupeol on glucose uptake in 3T3-L1 adipocytes. Lupeol significantly facilitated glucose uptake by translocating glucose transporter type 4 (GLUT4) to the plasma membrane of the 3T3-L1 adipocytes, which was related to activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) and 5 'adenosine monophosphate-activated protein kinase (AMPK) pathways. In the PI3K/AKT pathway, lupeol stimulates the phosphorylation of insulin receptor substrate 1 (IRS-1), which activates PI3K. Its activation by lupeol promotes the phosphorylation of AKT, but not the atypical protein kinase C isoforms ζ and λ. Lupeol also promoted the phosphorylation of AMPK. The activation of AMPK increased the expressions of the plasma membrane GLUT4 and the intracellular glucose uptake. The increase in the glucose uptake by lupeol was suppressed by wortmannin (PI3K inhibitor) and compound C (AMPK inhibitor) in the 3T3-L1 adipocytes. The results indicate that lupeol can facilitate glucose uptake by increasing insulin sensitivity through the stimulation of the expression of plasma membrane glucose transporter type 4 via the PI3K/AKT and AMPK pathways in the 3T3-L1 adipocytes.

• Molecular & Cellular Toxicology
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• v.4 no.3
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• pp.224-229
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• 2008

Eucommia ulmoides (Duchung) is commonly used for treatment of diabetes in Korean traditional medicine. However, the exact mechanism of its anti-diabetic effect has not yet been fully elucidated. In this study, the effect of E. ulmoides extract on glucose uptake was investigated in L6 rat skeletal muscle cells. E. ulmoides extract stimulated the activity of phosphatidylinositol (PI) 3-kinase that is a major regulatory molecule in glucose uptake pathway. Protein kinase B (PKB) and protein kinase C-${\xi}$ (PKC-${\xi}$), downstream mediators of PI 3-kinase, were also activated by E. ulmoides extract. We assessed the activity of AMP-activated protein kinase (AMPK), another regulatory molecule in glucose uptake pathway. Phosphorylation level of AMPK did not change with treatment of E. ulmoides extract. Phosphorylations of p38 mitogen activated protein kinase (p38 MAPK) and acetyl-CoA carboxylase (ACC), downstream mediators of AMPK, were not significantly different. Taken together, our results suggest that E. ulmoides may stimulate glucose uptake through PI 3-kinase but not AMPK in L6 skeletal muscle cells.

• Journal of Ginseng Research
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• v.34 no.3
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• pp.192-197
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• 2010

Recent studies have indicated that $\beta$-cell dysfunction and insulin resistance are important factors in the development of type 2 diabetes. The present study investigated the effect of extracts from different parts of white, Taegeuk, and red ginseng root on insulin-stimulated glucose uptake in muscle cells and proliferation of $\beta$-cells. Extracts of the fine roots of Taegeuk ginseng significantly enhanced glucose uptake compared with the control. White ginseng lateral root extracts enhanced insulin-induced glucose uptake. Proliferation of $\beta$-cells was significantly increased by Taegeuk ginseng main and lateral root extracts and by red ginseng lateral and fine root extracts. In conclusion, different root parts of white, Taegeuk, and red ginseng differentially affect glucose uptake and pancreatic $\beta$-cell proliferation.

• Nutrition Research and Practice
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• v.11 no.3
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• pp.180-189
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• 2017

BACKGROUND/OBJECTIVES: Recent living condition improvements, changes in dietary habits, and reductions in physical activity are contributing to an increase in metabolic syndrome symptoms including diabetes and obesity. Through such societal developments, humankind is continuously exposed to metabolic diseases such as diabetes, and the number of the victims is increasing. This study investigated Cordyceps militaris water extract (CMW)-induced glucose uptake in HepG2 cells and the effect of CMW treatment on glucose metabolism. MATERIALS/METHODS: Colorimetric assay kits were used to determine the glucokinase (GK) and pyruvate dehydrogenase (PDH) activities, glucose uptake, and glycogen content. Either RT-PCR or western blot analysis was performed for quantitation of glucose transporter 2 (GLUT2), hepatocyte nuclear factor 1 alpha ($HNF-1{\alpha}$), phosphatidylinositol 3-kinase (PI3k), protein kinase B (Akt), phosphorylated AMP-activated protein kinase (pAMPK), phosphoenolpyruvate carboxykinase, GK, PDH, and glycogen synthase kinase 3 beta ($GSK-3{\beta}$) expression levels. The ${\alpha}-glucosidase$ inhibitory activities of acarbose and CMW were evaluated by absorbance measurement. RESULTS: CMW induced glucose uptake in HepG2 cells by increasing GLUT2 through $HNF-1{\alpha}$ expression stimulation. Glucose in the cells increased the CMW-induced phosphorylation of AMPK. In turn, glycolysis was stimulated, and glyconeogenesis was inhibited. Furthermore, by studying the mechanism of action of PI3k, Akt, and $GSK-3{\beta}$, and measuring glycogen content, the study confirmed that the glucose was stored in the liver as glycogen. Finally, CMW resulted in a higher level of ${\alpha}-glucosidase$ inhibitory activity than that from acarbose. CONCLUSION: CMW induced the uptake of glucose into HepG2 cells, as well, it induced metabolism of the absorbed glucose. It is concluded that CMW is a candidate or potential use in diabetes prevention and treatment.

• Environmental Analysis Health and Toxicology
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• v.20 no.1
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• pp.87-95
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• 2005

Cadmium is well known as a toxic metal and has insulin mimicking effects in rat adipose tissue. This study was undertaken to investigate the effect of CdCl₂ on glucose transport and its mechanism in 3T3 - L1 adipocytes. CdCl₂ exhibits respectively 2.2 and 2.8 fold increases in the 2-deoxyglucose uptake when exposed to 10 and 25 μM of CdCl₂ for 12 hr. To investigate the stimulating mechanism of glucose transport induced by CdCl₂. Wortmannin and PD98059 were used respectively as PI3K inhibitor and MAPK inhibitor, which did not affect 2-DOG uptake. This results suggest that induced 2-deoxy-(l-3H)-D-glucose (2-DOG) uptake by CdCl₂ may not be concerned with the insulin signalling pathway. Whereas nifedipine, a calcium channel blocker inhibited the 2- DOG uptake stimulated by CdCl₂. In addition, we also measured the increased production of Reactive oxygen substances (ROS) and glutathione (GSH) level in 3T3-L1 adipocytes to investigate correlation between the glucose uptake and increased production of ROS with H2DCFDA. CdCl₂ increased production of ROS. Induced 2-DOG uptake and increased production of ROS by CdCl₂ were decreased by N-acetylcystein (NAC). And L-buthionine sulfoximine (BSO) a potent inhibitor of γ-GCS, decreased of 2-DOG uptake. Also NAC and BSO changed the cellular GSH level, but GSH/GSSG ratio remained unchanged at 10, 25 μM of CdCl₂.

• Korean Journal of Microbiology
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• v.29 no.5
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• pp.329-338
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• 1991

From July 1985 to December 1986, 28 variables of phycal-chemical factors, bacteria and heterotrophic activity were investigated 17 times at 3 stations in the estuary of Naktong River and the influences of environmental factors to bacterial population and heterotrophic activity were analyzed through multiple regression. The results of multiple regression were as follows. At station 1, total bacteria and heterotrophic bacteria(Z-25) could explain 57% of the variation of maximum uptake velocity for glucose and 54% of turnover time for glucose was explained by total coliform bacteria and MBOD, Sixty four percent of the variation of Kt+SN was accounted for salinity, MBOD-N and inorganic phosphate. Turnover rate for acetate was also accounted for the change of MBOD-P by 56%. At station 2 maximum uptake velocity for glucose depends on MBOD-N by 81%; turnover time on bacteria by 50%; Kt+Sn on avilable nutrient by 61%. More than 50% of maximum uptake velocity and turnover time for glucose were influenced by bacteria and that of Kt+Sn by the change of nutrient in the surface water of station 3. In the bottom water of station 3, the change of maximumuptake velocity, turnover time and Kt+Sn for glucose was controlled by total bacteria and available nutrient, bacteria, the change of nutrient salts respectively. On the whole, more than 50% of maximum uptake velocity and turnover time for glucose could be due to the change in the number of bacetria and the value of Kt+Sn was affected by the change of nutrient salts. Turnover rate for acetate was controlled by available phosphate at station 1 and by bacteria at station 2 and 3, which showed a distinct difference between the environmental factors which govern the rate of glucose and acetate uptake in the Naktong esturine ecosystem. And bacterial communities were controlled by available nutrients at station 1, by nutrient salts and salinity at station 2 and in the surface water of station 3 and by salinity in the bottom water of station 3.

• Proceedings of the Korean Society of Toxicology Conference
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• 2002.11b
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• pp.147-147
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• 2002

In this study, a mechanism by which glucose level modulates glucose transport in Jurkat cells was investigated. Glucose uptake was more efficient in the cells cultivated in low glucose (2.5 mM) medium than that grown in high glucose (20 $\mu$M) medium. Vmax (0.74 n㏖/10$^6$ cells$\cdot$min) of glucose uptake measured with the cells grown in the low glucose medium was higher than the one (1.06 n㏖/10$^6$ cells$\cdot$min) in the high glucose medium while Km was almost consistent through the change of glucose levels, indicating the increase of glucose transporter number.

• Molecules and Cells
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• v.23 no.3
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• pp.272-279
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• 2007

The maintenance of normal blood glucose levels at rest and during exercise is critical. The maintenance of blood glucose homeostasis depends on the coordination and integration of several physiological systems, including the sympathetic nervous system and the endocrine system. During prolonged exercise increased demand for glucose by contracting muscle causes to increase glucose uptake to working skeletal muscle. Increase in glucose uptake by working skeletal muscle during prolonged exercise is due to an increase in the translocation of insulin and contraction sensitive glucose transporter-4 (GLUT4) proteins to the plasma membrane. However, normal blood glucose level can be maintained by the augmentation of glucose production and release through the stimulation of liver glycogen breakdown, and the stimulation of the synthesis of glucose from other substances, and by the mobilization of other fuels that may serve as alternatives. Both feedback and feedforward mechanisms allow glycemia to be controlled during exercise. This review focuses on factors that control blood glucose homeostasis during prolonged exercise.