Translocation Of Glucose Transporter Research Articles

Identification of adenine modulating AMPK activation in NIH/3T3 cells by proteomic approach.

AMPK is a fuel sensing enzyme that responds to a central role of energy homeostasis and contributes to the acceleration of insulin signaling. Recently, we have shown that exogenous adenine exerted anti-inflammatory effects through activation of AMPK, suggesting the treatment is a potent therapeutic strategy against hyperglycemia. Adenine had similar effects with 5-amino-4-imidazole-carboxamide riboside (AICAR, an AMPK activator) in modulating glucose uptake via AMPK-mediated signaling. In this study, we performed a 2DE-DIGE/MS-based approach to investigate the mechanism of exogenous adenine in NIH/3T3 cells. Our results provide evidence of a novel role for adenine in AMPK-mediated signaling and glucose metabolism and suggest potential therapeutic perspectives in insulin resistance and metabolic dysfunctions.

N-hydroxycinnamide derivatives of osthole ameliorate hyperglycemia through activation of AMPK and p38 MAPK.

Our previous studies found that osthole markedly reduced blood glucose levels in both db/db and ob/ob mice. To improve the antidiabetic activity of osthole, a series of N-hydroxycinnamide derivatives of osthole were synthesized, and their hypoglycemia activities were examined in vitro and in vivo. Both N-hydroxycinnamide derivatives of osthole, OHC-4p and OHC-2m, had the greatest potential for activating AMPK and increasing glucose uptake by L6 skeletal muscle cells. In addition, OHC-4p and OHC-2m time- and dose-dependently increased phosphorylation levels of AMPK and p38 MAPK. The AMPK inhibitor, compound C, and the p38 MAPK inhibitor, SB203580, significantly reversed activation of AMPK and p38 MAPK, respectively, in OHC-4p- and OHC-2m-treated cells. Compound C and SB203580 also inhibited glucose uptake induced by OHC-4p and OHC-2m. Next, we found that OHC-4p and OHC-2m significantly increased glucose transporter 4 (GLUT4) translocation to plasma membranes and counteracted hyperglycemia in mice with streptozotocin-induced diabetes. These results suggest that activation of AMPK and p38 MAPK by OHC-4p and OHC-2m is associated with increased glucose uptake and GLUT4 translocation and subsequently led to amelioration of hyperglycemia. Therefore, OHC-4p and OHC-2m might have potential as antidiabetic agents for treating type 2 diabetes.

General aspects of muscle glucose uptake.

Glucose uptake in peripheral tissues is dependent on the translocation of GLUT4 glucose transporters to the plasma membrane. Studies have shown the existence of two major signaling pathways that lead to the translocation of GLUT4. The first, and widely investigated, is the insulin activated signaling pathway through insulin receptor substrate-1 and phosphatidylinositol 3-kinase. The second is the insulin-independent signaling pathway, which is activated by contractions. Individuals with type 2 diabetes mellitus have reduced insulin-stimulated glucose uptake in skeletal muscle due to the phenomenon of insulin resistance. However, those individuals have normal glucose uptake during exercise. In this context, physical exercise is one of the most important interventions that stimulates glucose uptake by insulin-independent pathways, and the main molecules involved are adenosine monophosphate-activated protein kinase, nitric oxide, bradykinin, AKT, reactive oxygen species and calcium. In this review, our main aims were to highlight the different glucose uptake pathways and to report the effects of physical exercise, diet and drugs on their functioning. Lastly, with the better understanding of these pathways, it would be possible to assess, exactly and molecularly, the importance of physical exercise and diet on glucose homeostasis. Furthermore, it would be possible to assess the action of drugs that might optimize glucose uptake and consequently be an important step in controlling the blood glucose levels in diabetic patients, in addition to being important to clarify some pathways that justify the development of drugs capable of mimicking the contraction pathway.

Chikusetsu saponin IVa regulates glucose uptake and fatty acid oxidation: implications in antihyperglycemic and hypolipidemic effects.

The aim of this study is to investigate antidiabetic effects and molecular mechanisms of the chemical Chikusetsu saponin IVa (CHS) that isolated from root bark of Aralia taibaiensis, which has multiple pharmacological activity, such as relieving rheumatism, promoting blood circulation to arrest pain and antidiabetic action. Rats with streptozotocin/nicotinamide-induced type 2 diabetes mellitus (T2DM) and insulin-resistant myocytes were used. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) and acetyl-CoA carboxylase were quantified by immunoblotting. Assays of glucose uptake, fatty acid oxidation, glucose transporter 4 (GLUT4) translocation and carnitine palmitoyl transferase-1 (CPT-1) activity were performed. Chronic oral administration of CHS effectively decreases blood glucose, triglyceride, free fatty acid (FFA) and low density lipoprotein-cholesterol levels in T2DM rats. In both normal and insulin-resistant C2C12 myocytes, CHS activates AMPK, and increases glucose uptake or fatty acid oxidation through enhancing membrane translocation of GLUT4 or CPT-1 activity respectively. Knockdown of AMPK significantly diminishes the effects of CHS on glucose uptake and fatty acid oxidation. CHS is a novel AMPK activator that is capable of bypassing defective insulin signalling and could be useful for the treatment of T2DM or other metabolic disorders.

The beneficial effects of tetracosanol on insulin-resistance by insulin receptor kinase sensibilisation

In this study, we investigated whether tetracosanol, an aliphatic alcohol isolated from Saccharum sinense, enhances insulin receptor kinase activity to exhibit an insulin synergistic effect in vitro and in vivo. The insulin plus tetracosanol enhanced insulin receptor kinase showed that AKT activity was down-regulated by S961 in differentiated L6 myotubes. Meanwhile, insulin plus tetracosanol restored the ability of glucose transporter translocation and glucose uptake in differentiated myotubes with S961-induced insulin resistance in vitro. The modification of carbon chain lengths and the hydroxyl group of tetracosanol showed that it served as a critical chemical structure for the glucostasis effect in vivo. This study provides new evidence to show that tetracosanol can improve glycaemic control via insulin receptor kinase activity induced and leads to the enhancement of glucose transporter translocation to improve glucose uptake. The hydroxyl group of tetracosanol plays a critical role for insulin receptor kinase activity.

A receptor state space model of the insulin signalling system in glucose transport.

Insulin is a potent peptide hormone that regulates glucose levels in the blood. Insulin-sensitive cells respond to insulin stimulation with the translocation of glucose transporter 4 (GLUT4) to the plasma membrane (PM), enabling the clearance of glucose from the blood. Defects in this process can give rise to insulin resistance and ultimately diabetes. One widely cited model of insulin signalling leading to glucose transport is that of Sedaghat et al. (2002) Am. J. Physiol. Endocrinol. Metab. 283, E1084-E1101. Consisting of 20 deterministic ordinary differential equations (ODEs), it is the most comprehensive model of insulin signalling to date. However, the model possesses some major limitations, including the non-conservation of key components. In the current work, we detail mathematical and sensitivity analyses of the Sedaghat model. Based on the results of these analyses, we propose a reduced state space model of the insulin receptor subsystem. This reduced model maintains the input-output relation of the original model but is computationally more efficient, analytically tractable and resolves some of the limitations of the Sedaghat model.

Acetylation of TUG Protein Promotes the Accumulation of GLUT4 Glucose Transporters in an Insulin-responsive Intracellular Compartment

Insulin causes the exocytic translocation of GLUT4 glucose transporters to stimulate glucose uptake in fat and muscle. Previous results support a model in which TUG traps GLUT4 in intracellular, insulin-responsive vesicles termed GLUT4 storage vesicles (GSVs). Insulin triggers TUG cleavage to release the GSVs; GLUT4 then recycles through endosomes during ongoing insulin exposure. The TUG C terminus binds a GSV anchoring site comprising Golgin-160 and possibly other proteins. Here, we report that the TUG C terminus is acetylated. The TUG C-terminal peptide bound the Golgin-160-associated protein, ACBD3 (acyl-CoA-binding domain-containing 3), and acetylation reduced binding of TUG to ACBD3 but not to Golgin-160. Mutation of the acetylated residues impaired insulin-responsive GLUT4 trafficking in 3T3-L1 adipocytes. ACBD3 overexpression enhanced the translocation of GSV cargos, GLUT4 and insulin-regulated aminopeptidase (IRAP), and ACBD3 was required for intracellular retention of these cargos in unstimulated cells. Sirtuin 2 (SIRT2), a NAD(+)-dependent deacetylase, bound TUG and deacetylated the TUG peptide. SIRT2 overexpression reduced TUG acetylation and redistributed GLUT4 and IRAP to the plasma membrane in 3T3-L1 adipocytes. Mutation of the acetylated residues in TUG abrogated these effects. In mice, SIRT2 deletion increased TUG acetylation and proteolytic processing. During glucose tolerance tests, glucose disposal was enhanced in SIRT2 knock-out mice, compared with wild type controls, without any effect on insulin concentrations. Together, these data support a model in which TUG acetylation modulates its interaction with Golgi matrix proteins and is regulated by SIRT2. Moreover, acetylation of TUG enhances its function to trap GSVs within unstimulated cells and enhances insulin-stimulated glucose uptake.

β-Conglycinin Peptides Improve Glucose Uptake through the AMPK Signaling Pathway in L6 Myotubes

Soy β-conglycinin (βCG) consumption has been shown to improve insulin resistance and suppress diet-induced obesity. These physiological effects seem to be mediated by the normalization of adiponectin and insulin sensitivity. Here, we show that artificial enzyme-hydrolyzed βCG peptides promote uptake of 2-deoxyglucose, a glucose analogue, accompanied by translocation of glucose transporter 4 in skeletal L6 myotubes. Inhibition of AMP-activated protein kinase (AMPK) attenuated βCG peptides-induced glucose uptake activity, while inhibition of both insulin and nitrogen monoxide signaling did not affect the glucose uptake activity. Taken together, these results indicate that βCG peptides directly induced glucose uptake through the AMPK signaling pathway in muscle cells and might function to prevent insulin resistance.

Exercise Causes Muscle GLUT4 Translocation in an Insulin-Independent Manner

Glucose uptake in skeletal is dependent on the translocation of GLUT4 glucose transporters to the plasma membrane. The most important stimulators of glucose transport in skeletal are and exercise. Glucose uptake in skeletal during exercise induces acceleration of many processes compared to the resting state. The scientific literature does not underline the role played by to increase glucose uptake with insulin-independent mechanisms. Search on Pub Med (May 05, 2015) using the key words contraction and glucose uptake and muscle gives 717 reports, while a search using the key words insulin and glucose uptake and muscle cites 5676 publications. The present paper describes the role of exercise in the glucose uptake. Contraction of induces GLUT4 translocation in the absence of insulin. There are different intracellular pools of GLUT4, one stimulated by and another one stimulated by exercise. The roles exerted by AMPK, AICAR, calcium, NO, glycogen and hypoxia in the glucose uptake during exercise are emphasized. The effects of these phenomena on human wellness are reported

Black Tea Polyphenols Promotes GLUT4 Translocation through Both PI3K-and AMPK-dependent Pathways in Skeletal Muscle Cells

We previously reported that the intake of black tea promotes translocation of the insulin-sensitive glucose transporter (GLUT) 4 in skeletal muscle. In this study, we investigated whether black tea polyphenols (BTP) promote GLUT4 translocation in L6 myotubes. BTP promoted glucose uptake accompanied by GLUT4 translocation in L6 myotubes. As the molecular mechanism, BTP induced the phosphorylation of insulin receptor substrate-1, atypical protein kinase C, Akt Thr308, Akt substrate 160, and AMP-activated protein kinase (AMPK), but did not affect that of Akt Ser473. BTP increased glycogen accumulation through inactivation of glycogen synthase kinase 3β (GSK-3β). Theaflavin, one of the major components in black tea, also promoted the glucose uptake accompanied by GLUT4 translocation observed with BTP in L6 myotubes. These results indicate that BTP activates both PI3K- and AMPK-dependent pathways to promote GLUT4 translocation and glycogen accumulation in skeletal muscle cells. Moreover, theaflavin is one of the active components in BTP.

Human Adipose Cell Response to Insulin: Analysis of Cellular Switch-Like Transformations and Distributions

Insulin resistance is associated with decreased glucose transporter-4 (GLUT4) translocation in adipose cells and muscles in response to insulin. Here we quantified, per cell, insulin's effects on GLUT4 storage vesicle (GSV) tethering and fusion in adipose cells from human subjects with varying insulin sensitivity index (SI). Basal GSV tethering and fusion rates were distributed unimodally and did not vary significantly with SI. In contrast, after a maximal insulin challenge, both tethering and fusion rates were bimodally distributed, with two distinct subpopulations; the first subpopulation was indistinguishable from the basal distribution, while the second corresponded to a normal insulin response. Importantly, the fraction of cells in the two-subpopulations were strongly correlated with donor subject SI. These data suggest that the loss of systemic SI is not due to a gradual decrease in the insulin response of all cells, but rather an increase in the fraction of cells that switch off their insulin response. This observed heterogeneity may be an important consideration in modeling the cellular transitions and systemic changes associated with the onset of Type II diabetes. Thus, isolated human adipose cells, when treated with high concentrations of insulin, exist in either the basal or fully insulin-stimulated state, and population dose response curves reflect the proportion of adipose cells in these two distinct states.

Interaction of glucose transporters SGLT1 and GLUT2 with cytoskeleton in enterocytes and Caco2 cells during hexose absorption

The distribution of cytoskeleton elements (microtubules and actin filaments) and glucose transporters SGLT1 or GLUT2 in enterocyte of rat intestine and Caco2 cells during hexose absorption was studied. Confocal microscopy revealed that the distribution of SGLT1 and GLUT2 transporters in absorptive cells of the intestinal villus was altered depending on maltose concentration. The transporters were colocalized with actin. An increased number of vesicles close to microtubules in the apical cell part during absorption of high hexoze concentration was observed with electron microscopy. This observation, as well as uncovered colocalization of the transporters and actin, as well as actin and α-tubulin, suggests that elements of the cytoskeleton participate in the translocation of glucose transporters to the apical cell membrane.

霊芝菌糸体培養培地抽出物のラット骨格筋培養細胞における GLUT4 膜移行促進作用

霊芝菌糸体培養培地抽出物のラット骨格筋培養細胞における GLUT4 膜移行促進作用

Increased skeletal muscle glucose uptake by rosemary extract through AMPK activation.

Stimulation of the energy sensor AMP-activated kinase (AMPK) has been viewed as a targeted approach to increase glucose uptake by skeletal muscle and control blood glucose homeostasis. Rosemary extract (RE) has been reported to activate AMPK in hepatocytes and reduce blood glucose levels in vivo but its effects on skeletal muscle are not known. In the present study, we examined the effects of RE and the mechanism of regulation of glucose uptake in muscle cells. RE stimulated glucose uptake in L6 myotubes in a dose- and time-dependent manner. Maximum stimulation was seen with 5 μg/mL of RE for 4 h (184% ± 5.07% of control, p < 0.001), a response comparable to maximum insulin (207% ± 5.26%, p < 0.001) and metformin (216% ± 8.77%, p < 0.001) stimulation. RE did not affect insulin receptor substrate 1 and Akt phosphorylation but significantly increased AMPK and acetyl-CoA carboxylase phosphorylation. Furthermore, the RE-stimulated glucose uptake was significantly reduced by the AMPK inhibitor compound C, but remained unchanged by the PI3K inhibitor, wortmannin. RE did not affect GLUT4 or GLUT1 glucose transporter translocation in contrast with a significant translocation of both transporters seen with insulin or metformin treatment. Our study is the first to show a direct effect of RE on muscle cell glucose uptake by a mechanism that involves AMPK activation.

The cholesterol-lowering agent methyl-β-cyclodextrin promotes glucose uptake via GLUT4 in adult muscle fibers and reduces insulin resistance in obese mice.

Insulin stimulates glucose uptake in adult skeletal muscle by promoting the translocation of GLUT4 glucose transporters to the transverse tubule (T-tubule) membranes, which have particularly high cholesterol levels. We investigated whether T-tubule cholesterol content affects insulin-induced glucose transport. Feeding mice a high-fat diet (HFD) for 8 wk increased by 30% the T-tubule cholesterol content of triad-enriched vesicular fractions from muscle tissue compared with triads from control mice. Additionally, isolated muscle fibers (flexor digitorum brevis) from HFD-fed mice showed a 40% decrease in insulin-stimulated glucose uptake rates compared with fibers from control mice. In HFD-fed mice, four subcutaneous injections of MβCD, an agent reported to extract membrane cholesterol, improved their defective glucose tolerance test and normalized their high fasting glucose levels. The preincubation of isolated muscle fibers with relatively low concentrations of MβCD increased both basal and insulin-induced glucose uptake in fibers from controls or HFD-fed mice and decreased Akt phosphorylation without altering AMPK-mediated signaling. In fibers from HFD-fed mice, MβCD improved insulin sensitivity even after Akt or CaMK II inhibition and increased membrane GLUT4 content. Indinavir, a GLUT4 antagonist, prevented the stimulatory effects of MβCD on glucose uptake. Addition of MβCD elicited ryanodine receptor-mediated calcium signals in isolated fibers, which were essential for glucose uptake. Our findings suggest that T-tubule cholesterol content exerts a critical regulatory role on insulin-stimulated GLUT4 translocation and glucose transport and that partial cholesterol removal from muscle fibers may represent a useful strategy to counteract insulin resistance.

Novel regulatory mechanisms in muscle metabolism during exercise.

Novel regulatory mechanisms in muscle metabolism during exercise.

Novel intracellular mediator of adiponectin secretion from adipocytes.

Mature white fat cells (adipocytes) are unusual terminally differentiated cells because of their large spherical shape, the fact that their presence is not fixed at a particular location in the body, the fact that they can proliferate in various ways and the weird intracellular structures that permit a unilocular lipid droplet to occupy a large part of the intracellular space, allowing only a small crescent-shaped cytoplasmic space in which all cellular events occur (Sugihara et al. 1987). Since the verification of the hypothesis that insulin stimulates the translocation of glucose transporter (GLUT4) vesicles from intracellular storage to the plasma membrane in isolated rat adipocytes, thus increasing the cellular uptake of glucose (Cushman & Wardzala, 1980; Suzuki & Kono, 1980), the mechanism(s) of vesicular trafficking in fat cells have been the subject of many research studies. Over 10 years later, the discoveries of a number of biologically active cytokines derived from adipocytes, generally named adipokines, have changed the viewpoint, with adipocytes now being considered an endocrine organ rather than a simple energy storage organ. Of the various adipokines, adiponectin has attracted the most studies because of its protective roles against obesity-related diseases, including type-2 diabetes and cardiovascular diseases, and the reports that the reduction in the plasma level of adiponectin in obese subjects precedes the reduction in insulin sensitivity and onset of diabetes (Trujillo & Scherer, 2005; Smith & Minson, 2012; Yamauchi & Kadowaki, 2013). Most of the studies concerning adiponectin secretion have therefore been focused on the long-term chronic regulation, whereas the short-term (≤30 min) regulation of adipocyte exocytosis by intracellular mediators is not well understood. In this issue of The Journal of Physiology, Komai et al. (2014) describe a novel mechanism underlying the short-term regulation of adiponectin secretion, in 3T3-L1 adipocytes derived from mice, using a combination of membrane capacitance patch-clamp recordings and measurements of secreted adiponectin. The mechanism regulating adiponectin secretion is fundamentally different from that occurring in other endocrine cells. The authors demonstrate that the final step of adiponectin secretion in mature adipocytes, the release of adipokines from vesicles fused with the plasma membrane, is stimulated by cAMP and an exchange protein activated by cAMP (Epac), without depending on Ca2+ or protein kinase A (PKA). Biochemical measurements showed that adiponectin is the dominant adipokine secreted in a cAMP/Epac-dependent manner, whereas the amounts of other secreted adipokines, such as leptin, resistin and apelin, are very low. Interestingly, Ca2+ was shown to have no apparent effect on the final step of adipokine release, although most neurotransmitter release is considered to be Ca2+ dependent. However, the role of Ca2+ is important in the early steps of exocytosis when the secretion vesicles are recruited and refilled with adiponectin to form ready-to-release vesicles. The regulation of the entire process of adiponectin secretion in adipocytes is thus proposed to be a sequential regulation by Ca2+ and cAMP, and ATP may provide energy and substrates for the phosphorylation of proteins that play a role in exocytosis. The findings thus indicate that all three intracellular mediators, Ca2+, ATP and cAMP, are required to accomplish the short-term secretion of adiponectin, through Ca2+ and ATP, and cAMP regulates different steps of the exocytosis. In human subcutaneous adipocytes, the adiponectin secretion was also shown to be cAMP-dependent, similar to that observed in 3T3-L1 adipocytes. There is increasing evidence that obesity is associated with not only metabolic syndrome and atherosclerosis, but also non-alcoholic steatohepatitis (NASH), cancer and Alzheimer's disease, and adiponectin plays a pleiotropic role in protecting against such diseases (Smith & Minson, 2012; Yamauchi & Kadowaki, 2013). Adiponectin is thus expected to be a valuable target molecule for therapeutics supporting a healthy, long life in humans. The key findings that each step of the short-term regulation of adiponectin secretion and the packaging of vesicles is individually regulated by cAMP, Ca2+ and ATP would provide a pin-point therapeutic approach for obesity-related diseases. In white adipocytes, the binding of insulin to the receptor located on the plasma membrane is a trigger for a number of dynamic cellular events, including translocation of GLUT4 vesicles, the secretion of adiponectin and other adipokines, which are controlled in different ways. It is amazing that these complex mechanisms are well organized in the small crescent-shaped cytoplasmic space of the fat cells.

Methanolic extract of Momordica cymbalaria enhances glucose uptake in L6 myotubes in vitro by up-regulating PPAR-γ and GLUT-4

The present study was undertaken to evaluate the influence of the methanolic fruit extract of Momordica cymbalaria (MFMC) on PPARγ (Peroxisome Proliferator Activated Receptor gamma) and GLUT-4 (Glucose transporter-4) with respect to glucose transport. Various concentrations of MFMC ranging from 62.5 to 500 μg·mL−1 were evaluated for glucose uptake activity in vitro using L6 myotubes, rosiglitazone was used as a reference standard. The MFMC showed significant and dose-dependent increase in glucose uptake at the tested concentrations, further, the glucose uptake activity of MFMC (500 μg·mL−1) was comparable with rosigilitazone. Furthermore, MFMC has shown up-regulation of GLUT-4 and PPARγ gene expressions in L6 myotubes. In addition, the MFMC when incubated along with cycloheximide (CHX), which is a protein synthesis inhibitor, has shown complete blockade of glucose uptake. This indicates that new protein synthesis is required for increased GLUT-4 translocation. In conclusion, these findings suggest that MFMC is enhancing the glucose uptake significantly and dose dependently through the enhanced expression of PPARγ and GLUT-4 in vitro.

Identification of novel insulin mimetic drugs by quantitative total internal reflection fluorescence (TIRF) microscopy.

Background and PurposeInsulin stimulates the transport of glucose in target tissues by triggering the translocation of glucose transporter 4 (GLUT4) to the plasma membrane. Resistance to insulin, the major abnormality in type 2 diabetes, results in a decreased GLUT4 translocation efficiency. Thus, special attention is being paid to search for compounds that are able to enhance this translocation process in the absence of insulin.Experimental ApproachTotal internal reflection fluorescence (TIRF) microscopy was applied to quantify GLUT4 translocation in highly insulin-sensitive CHO-K1 cells expressing a GLUT4-myc-GFP fusion protein.Key ResultsUsing our approach, we demonstrated GLUT4 translocation modulatory properties of selected substances and identified novel potential insulin mimetics. An increase in the TIRF signal was found to correlate with an elevated glucose uptake. Variations in the expression level of the human insulin receptor (hInsR) showed that the insulin mimetics identified stimulate GLUT4 translocation by a mechanism that is independent of the presence of the hInsR.Conclusions and ImplicationsTaken together, the results indicate that TIRF microscopy is an excellent tool for the quantification of GLUT4 translocation and for identifying insulin mimetic drugs.

Antidiabetic effect of green rooibos (Aspalathus linearis) extract in cultured cells and type 2 diabetic model KK-A(y) mice.

Previous studies have demonstrated antidiabetic effects for rooibos (Aspalathus linearis) and aspalathin (ASP), one of its main polyphenols. Rooibos, an endemic plant of South Africa, is well-known for its use as herbal tea. Green ('unfermented') rooibos has been shown to contain more ASP than 'fermented' rooibos tea, currently the major product. In the present study, we investigated the antidiabetic effect of green rooibos extract (GRE) through studies on glucose uptake in L6 myotubes and on pancreatic β-cell protective ability from reactive oxygen species (ROS) in RIN-5F cells. Its in vivo effect was also examined using obese diabetic KK-A(y) mice. GRE increased glucose uptake under insulin absent condition and induced phosphorylation of 5'-adenosine monophosphate-activated protein kinase (AMPK) in L6 myotubes as previously demonstrated for ASP. In addition to AMPK, GRE also promoted phosphorylation of Akt, another promoter of glucose transporter 4 (GLUT4) translocation, in L6 myotubes unlike ASP, suggesting an involvement of GRE component(s) other than ASP in Akt phosphorylation. Promotion of GLUT4 translocation to the plasma membrane by GRE in L6 myotubes was demonstrated by Western blotting analysis. GRE suppressed the advanced glycation end products (AGEs)-induced increase in ROS levels in RIN-5F pancreatic β-cells. Subchronic feeding with GRE suppressed the increase in fasting blood glucose levels in type 2 diabetic model KK-A(y) mice. These in vitro and in vivo results strongly suggest that GRE has antidiabetic potential through multiple modes of action.