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Nuciferine contained in lotus leaves have been confirmed to have the effect of ameliorating hyperlipemia and hyperglycemia. A laser scanning confocal microscope was used to track the translocation of glucose transporter 4 (GLUT4) in L6 cells and the changes in intracellular Ca2+ levels in real time, and related protease inhibitors combined with western blotting were used to explore the mechanism of nuciferine. Meanwhile, KK-Ay mice, the spontaneous type 2 diabetic mice, were used to evaluate the in vivo activity of nuciferine. In this study, the in vitro studies indicated that nuciferine-induced GLUT4 translocation was regulated by G protein-PLC-PKC and AMPK pathways and nuciferine-enhanced intracellular Ca2+ was mediated by G protein-PLC-IP3-IP3R pathway, the increase in intracellular Ca2+ caused by nuciferine was not directly related to GLUT4 translocation, but both promote glucose uptake. The in vivo results suggested that nuciferine ameliorated weight gain induced by high-fat diet, abnormal lipid metabolism and the symptoms of insulin resistance in KK-Ay diabetic mice. Western blot results suggested that nuciferine increased AMPK and PKC phosphorylation levels in skeletal muscle and liver, and enhanced GLUT4 expression in skeletal muscle. Taken together, this research showed that nuciferine has the non-negligible potential in the treatment of type 2 diabetes mellitus.

This study explores the therapeutic potential of Naringenin, a natural flavonoid, in managing Type 2 Diabetes Mellitus (T2DM) by focusing on Glucose Transporter 4 (GLUT4) and related regulatory proteins that play a role in glucose and lipid metabolism. Through bioinformatics analysis, key proteins such as Carnitine palmitoyltransferase I, mitochondrial carnitine/acylcarnitine carrier protein, and PPARγ were identified, highlighting their importance in insulin sensitivity. Molecular docking results indicated that Naringenin has a strong binding affinity for GLUT4 and PPARγ, with binding energies of -8.18 kcal/mol and -8.21 kcal/mol, respectively. This suggests that Naringenin may modulate these proteins to enhance insulin sensitivity. In contrast, its weaker binding with Enhancer-Binding Protein Alpha points to Naringenin's selective efficacy among various targets. Molecular dynamics (MD) simulations conducted over 100 ns confirmed the stability of the GLUT4-Naringenin complex, showing a reduced RMSD of 1.25 nm and a more compact structure with a Radius of Gyration (Rg) value of 2.14 nm. However, Rho-related GTP exhibited increased instability upon Naringenin binding, indicating a potential inhibitory effect. Additionally, an in silico ADMET profile revealed Naringenin's favorable pharmacokinetics, including low hepatotoxicity, no mutagenic effects, and a high maximum tolerated dose, which supports its safety for drug development. In conclusion, Naringenin shows promising potential in enhancing glucose metabolism and insulin sensitivity, positioning it as a viable candidate for future preclinical and clinical studies in T2DM management. Future research should aim to validate these computational findings through experimental methods and investigate possible synergistic effects with existing antidiabetic medications to improve treatment outcomes.

Copyright of Chinese Journal of Cancer Biotherapy is the property of Editorial Office of Chinese Journal of Cancer Biotherapy and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Morus nigra L. is a traditional ethnomedicinal plants, which is used for the treatment of atherosclerosis, diabetes, hyperlipidemia, and hypertension. The aim of this study was to investigate the antidiabetic activity and potential mechanisms of ethyl acetate extract of Morus nigra L. twigs (MNT-EA). In L6 cells, MNT-EA significantly upregulated glucose uptake, and promoted GLUT4 translocation and expression through AMPK and PKC signaling pathway. In vivo, diabetic mice treated with MNT-EA for 4 weeks improved hyperglycemia, lipid metabolism disorders and insulin resistance. According to histopathological examination, MNT-EA attenuated hepatic steatosis, adipocyte hypertrophy, and islet lesions in diabetic mice. In addition, MNT-EA upregulated p-AMPK, p-PKC, and GLUT4 expression in liver, adipose, and skeletal muscle tissues, thereby enhancing glucose uptake and improving diabetic symptoms. It is the first time to demonstrate that MNT-EA exerted anti-diabetic effects through activation of AMPK/PKC/GLUT4 signaling pathway, providing a basis for the development of new anti-diabetic drugs.

Glucose is vital to embryogenesis, as are glucose transporters. Glucose transporter 4 (Glut4) is one of the glucose transporters, which is involved in rapid uptake of glucose by various cells and promotes glucose homeostasis. Although energy metabolism in insect reproduction is well known, the molecular mechanism of Glut4 in insect reproduction is poorly understood. We suspect that Glut4 is involved in maintaining glucose concentrations in the ovaries and affecting vitellogenesis, which is critical for subsequent oocyte maturation and insect fertility. Harmonia axyridis (Pallas) is a model organism for genetic research and a natural enemy of insect pests. We studied the influence of the Glut4 gene on the reproduction and development of H. axyridis using RNA interference technology. Reverse transcription quantitative polymerase chain reaction analysis revealed that HaGlut4 was most highly expressed in adults. Knockdown of the HaGlut4 gene reduced the transcript levels of HaGlut4, and the weight and number of eggs produced significantly decreased. In addition, the transcript levels of vitellogenin receptor and vitellogenin in the fat bodies and the ovaries of H. axyridis decreased after the interference of Glut4, and decreased the triglyceride, fatty acid, total amino acid and adenosine triphosphate content of H. axyridis. This resulted in severe blockage of ovary development and reduction of yolk formation; there was no development of ovarioles in the developing oocytes. These changes indicate that a lack of HaGlut4 can impair ovarian development and oocyte maturation and result in decreased fecundity. [ABSTRACT FROM AUTHOR]

Abstract Background Trilobatin, a natural compound, has been found to exhibit anti-diabetic properties in high-fat diet (HFD) and streptozotocin (STZ) induced type 2 diabetic mice. But up to now no research has been reported on the effect of trilobatin on insulin resistance in peripheral tissues. Herein, we determined the effects of trilobatin on insulin resistance in palmitate-treated C2C12 myotubes and ob/ob mice. Methods Male ob/ob mice (8-10 weeks) and same background C57BL/6 mice were used to evaluate the role of trilobatin on insulin resistance; protein expression and phosphorylation were measured by western blot; glucose uptake was determined a fluorescent test. Results Treatment with trilobatin prevented palmitate-induced insulin resistance by enhancing glucose uptake and the phosphorylation of insulin resistance substrate 1 (IRS1) and protein Kinase B, (PKB/AKT), recovered the translocation of GLUT4 from cytoplasm to membrane, but preincubation with LY294002, an inhibitor of PI3K, blocked the effects of trilobatin on glucose uptake and the distribution of GLUT4 in C2C12 myotubes. Furthermore, administration with trilobatin for 4 weeks significantly improved insulin resistance by decreasing fasting blood glucose and insulin in serum, enhancing the phosphorylation of IRS1 and AKT, and recovering the expression and translocation of GLUT4 in ob/ob mice. Conclusions IRS-AKT-GLUT4 signaling pathway might be involved in trilobatin ameliorating insulin resistance in skeletal muscle of obese animal models.

14-Deoxy-11,12-didehydroandrographolide (deAND), a bioactive component of Andrographis paniculata, has antidiabetic activity. AMP-activated protein kinase (AMPK) regulates glucose transport and ameliorates insulin resistance. The aim of the present study was to investigate whether activation of AMPK is involved in the mechanism by which deAND ameliorates insulin resistance in muscles. deAND amounts up to 40 μ M dose-dependently activated phosphorylation of AMPK α and TBC1D1 in C2C12 myotubes. In addition, deAND significantly activated phosphorylation of LKB1 at 6 h after treatment, and this activation was maintained up to 48 h. deAND increased glucose uptake at 18 h after treatment, and this increase was time dependent up to 72 h. Compound C, an inhibitor of AMPK, suppressed deAND-induced phosphorylation of AMPK α and TBC1D1 and reversed the effect on glucose uptake. In addition, the expression of GLUT4 mRNA and protein in C2C12 myotubes was up-regulated by deAND in a time-dependent manner. Promotion of GLUT4 gene transcription was verified by a pGL3-GLUT4 (837 bp) reporter assay. deAND also increased the nuclear translocation of MEF-2A and PPAR β. After 16 weeks of feeding, the high-fat diet (HFD) inhibited phosphorylation of AMPK α and TBC1D1 in skeletal muscle of obese C57BL/6JNarl mice, and deactivation of AMPK α and TBC1D1 by the HFD was abolished by deAND supplementation. Supplementation with deAND significantly promoted membrane translocation of GLUT4 compared with the HFD group. Supplementation also significantly increased GLUT4 mRNA and protein expression in skeletal muscle compared with the HFD group. The hypoglycemic effects of deAND are likely associated with activation of the LKB1/AMPK α /TBC1D1/GLUT4 signaling pathway and stimulation of MEF-2A- and PPAR β -dependent GLUT4 gene expression, which account for the glucose uptake into skeletal muscle and lower blood glucose levels. [ABSTRACT FROM AUTHOR]

Proliferation and differentiation of preadipocytes, and other cell types, is accompanied by an increase in glucose uptake. Previous work showed that a pulse of high glucose was required during the first 3 days of differentiation in vitro, but was not required after that. The specific glucose metabolism pathways required for adipocyte differentiation are unknown. Herein, we used 3T3-L1 adipocytes as a model system to study glucose metabolism and expansion of the adipocyte metabolome during the first 3 days of differentiation. Our primary outcome measures were GLUT4 and adiponectin, key proteins associated with healthy adipocytes. Using complete media with 0 or 5 mM glucose, we distinguished between developmental features that were dependent on the differentiation cocktail of dexamethasone, insulin, and isobutylmethylxanthine alone or the cocktail plus glucose. Cocktail alone was sufficient to activate the capacity for 2-deoxglucose uptake and glycolysis, but was unable to support the expression of GLUT4 and adiponectin in mature adipocytes. In contrast, 5 mM glucose in the media promoted a transient increase in glucose uptake and glycolysis as well as a significant expansion of the adipocyte metabolome and proteome. Using genetic and pharmacologic approaches, we found that the positive effects of 5 mM glucose on adipocyte differentiation were specifically due to increased expression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a key regulator of glycolysis and the ancillary glucose metabolic pathways. Our data reveal a critical role for PFKFB3 activity in regulating the cellular metabolic remodeling required for adipocyte differentiation and maturation. [ABSTRACT FROM AUTHOR]

Glucose is an essential energy source for both vertebrates and invertebrates. In mammals, glucose uptake is mediated primarily by glucose transporters (GLUTs), members of the major facilitator superfamily (MFS) of passive transporters. Among the GLUTs, GLUT4 is the main glucose transporter in muscles and adipocytes. In skeletal muscle cells, GLUT4 interacts with the lipid raft protein flotillin to transport glucose upon stimulation by insulin. Although several studies have examined GLUT4 function in mammals, few have been performed in crustaceans, which also use glucose as their main energy source. Crustacean hyperglycemic hormone (CHH) is a multifunctional neurohormone found only in arthropods, and one of its roles is to regulate glucose homeostasis. However, the molecular mechanism that underlies CHH regulation and whether GLUT4 is involved in its regulation in crustaceans remain unclear. In the present study, we identified a full-length GLUT4 cDNA sequence (defined herein as EsGLUT4) from the Chinese mitten crab Eriocheir sinensis and analyzed its tissue distribution and cellular localization. By the ForteBio Octet system, two large hydrophilic regions within EsGLUT4 were found to interact with the CHH binding protein (CHHBP), an E. sinensis flotillin-like protein. Interestingly, live-cell imaging indicated that EsGLUT4 and CHHBP responded simultaneously upon stimulation by CHH, resulting in glucose release. In contrast to insulin-dependent GLUT4, however, EsGLUT4 and CHHBP were present within cytoplasmic vesicles, both translocating to the plasma membrane upon CHH stimulation. In conclusion, our results provide new evidence for the involvement of EsGLUT4 and CHHBP in the regulation of glucose homeostasis in crustacean carbohydrate metabolism.

Objectives: Mouth breathing caused by nasal obstruction (owing to abnormal pressure of masticatory muscles) affects craniofacial growth and development. The influence of unilateral nasal obstruction on jaw-closing muscles was investigated in rats to reveal one of the etiologic mechanisms. Materials and Methods: Forty 8-day-old male Wistar rats were used in this study. Experimental rats were subjected to left-sided nasal obstruction by burning the external nostril tissue at the age of 8 days. Pulse oxygen saturation was recorded each week. Morphologic changes were evaluated by staining with hematoxylin and eosin (to assess the cross-sectional area) and by adenosine triphosphatase activity staining (to assess the myosin heavy chain isoform composition). Immunohistochemical and reverse transcription quantitative real-time polymerase chain reaction analyses of tumor necrosis factor-a and glucose transporter 4 were carried out at 5 and 9 weeks of age. Results: The cross-sectional area of the jaw-closing muscles was lower in the experimental group at 9 weeks of age. The percentage of myosin heavy chain-2a in masseter muscles was increased in the experimental group compared with the control group. An increase in the tumor necrosis factor-a messenger RNA and protein levels and a decrease in the glucose transporter 4 messenger RNA and protein levels at 5 and 9 weeks of age in the jaw-closing muscles in the experimental group were noted. Conclusions: Unilateral nasal obstruction could affect the morphology and contractile characteristics of jaw-closing muscles during growth in rats. [ABSTRACT FROM AUTHOR]

The glucose transporter family (GLUT) consists of fourteen members. It is responsible for glucose homeostasis and glucose transport from the extracellular space to the cell cytoplasm to further cascade catalysis. GLUT proteins are encoded by the solute carrier family 2 (SLC2) genes and are members of the major facilitator superfamily of membrane transporters. Moreover, different GLUTs also have their transporter kinetics and distribution, so each GLUT member has its uniqueness and importance to play essential roles in human physiology. Evidence from many studies in the field of diabetes showed that GLUT4 travels between the plasma membrane and intracellular vesicles (GLUT4-storage vesicles, GSVs) and that the PI3K/Akt pathway regulates this activity in an insulin-dependent manner or by the AMPK pathway in response to muscle contraction. Moreover, some published results also pointed out that GLUT4 mediates insulin-dependent glucose uptake. Thus, dysfunction of GLUT4 can induce insulin resistance, metabolic reprogramming in diverse chronic diseases, inflammation, and cancer. In addition to the relationship between GLUT4 and insulin response, recent studies also referred to the potential upstream transcription factors that can bind to the promoter region of GLUT4 to regulating downstream signals. Combined all of the evidence, we conclude that GLUT4 has shown valuable unknown functions and is of clinical significance in cancers, which deserves our in-depth discussion and design compounds by structure basis to achieve therapeutic effects. Thus, we intend to write up a most updated review manuscript to include the most recent and critical research findings elucidating how and why GLUT4 plays an essential role in carcinogenesis, which may have broad interests and impacts on this field. • GLUT4 is involved in glucose homeostasis, insulin resistance and signaling transduction in the human body. • Dysfunction of GLUT4 is associated with chronic metabolic syndrome and survival curves in several cancer types. • Metabolic reprogramming by GLUT4 further affects fatty acid synthesis and GLUT4 vesicles. • Interacting molecules of GLUT4 reveal a novel insulin-independent mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 21 main chemical components in MNT-EA were identified by UPLC-Q-TOF/MS. • MNT-EA ameliorated a series of diabetes-related indices. • MNT-EA improved the pathological changes in liver, adipose and pancreatic tissues. • MNT-EA up-regulates AMPK and PKC pathways to regulate glucose metabolism in vivo. Morus nigra L. is a traditional ethnomedicinal plants, which is used for the treatment of atherosclerosis, diabetes, hyperlipidemia, and hypertension. The aim of this study was to investigate the antidiabetic activity and potential mechanisms of ethyl acetate extract of Morus nigra L. twigs (MNT-EA). In L6 cells, MNT-EA significantly upregulated glucose uptake, and promoted GLUT4 translocation and expression through AMPK and PKC signaling pathway. In vivo , diabetic mice treated with MNT-EA for 4 weeks improved hyperglycemia, lipid metabolism disorders and insulin resistance. According to histopathological examination, MNT-EA attenuated hepatic steatosis, adipocyte hypertrophy, and islet lesions in diabetic mice. In addition, MNT-EA upregulated p-AMPK, p-PKC, and GLUT4 expression in liver, adipose, and skeletal muscle tissues, thereby enhancing glucose uptake and improving diabetic symptoms. It is the first time to demonstrate that MNT-EA exerted anti-diabetic effects through activation of AMPK/PKC/GLUT4 signaling pathway, providing a basis for the development of new anti-diabetic drugs. [ABSTRACT FROM AUTHOR]

Type 2 diabetes is characterized by insulin resistance and chronic hyperglycemia, and is increasing in incidence and severity. This work explored the effects of trans-cinnamaldehyde (CA) on carbohydrate metabolism, mitochondrial content, and related metabolic gene and protein expression in cultured myotubes treated with various concentrations of CA for up to 24 h. CA treatment increased myotube myocyte enhancer factor 2 (MEF2) along with glucose transporter 4 (GLUT4) content. CA treatment also significantly increased expression of markers of improved oxidative metabolism including 5′ adenosine monophosphate-activated protein kinase (AMPK), peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α), cytochrome c (CytC), as well as peroxisome proliferator-activated receptor α (PPARα) and PPARβ/δ. Despite increased expression of proteins associated with improved oxidative metabolism and glucose uptake, CA-treated myotubes exhibited significantly reduced oxidative metabolism compared with controlled cells. Additionally, CA treatment increased markers of glucose-mediated lipid biosynthesis without elevated PPARγ and sterol receptor element binding protein 1c (SREBP-1c) expression. The ability of CA to stimulate mitochondrial biogenesis and GLUT4 expression suggests CA may offer possible benefits for metabolic disease. However, increases in markers of fatty acid synthesis with simultaneously reduced oxidative metabolism suggest CA may have counterproductive effects for metabolic disease, warranting a need for further investigation. [ABSTRACT FROM AUTHOR]

In this study, lipoic acid and heat shock treatments were applied to C2C12 myotubes and Sprague-Dawley rats to investigate changes in the heat shock protein 70 (HSP70) and glucose transporter 4 (GLUT4) in 4 different skeletal muscle groups. The results of western blotting indicated that treatment of lipoic acid for 24 h, heat-shock and combined lipoic acid and heat-shock which all increased the level of HSP70 substantially in C2C12 myotubes. However, either lipoic acid or heat-shock did not increase the level of GLUT4 in C2C12 myotubes. In an in vitro migration assay, lipoic acid increased wound migration only when it was applied for 3 h. Moreover, our in vivo results revealed that lipoic acid did not increase HSP70 and GLUT4 in all 4 different skeletal muscles. Furthermore, heat-shock increased HSP70 in all 4 different muscle groups, and heat-shock treatment alone increased the GLUT4 in the soleus muscle only, suggesting that the GLUT4 increased by heat-shock was slow-twitch muscle specific. Collectively, our results indicated that heat-shock is critical factor that modulates GLUT4 and HSP70 in the skeletal muscle of rats. [ABSTRACT FROM AUTHOR]

Protein kinase B (Akt) kinases are critical signal transducers mediating insulin action. Genetic studies revealed that Akt1 and Akt2 signalling differentially contribute to sustain lipid and glucose homoeostasis; however Akt isoform-specific effectors remain elusive due to the lack of a suitable model system to mechanistically interrogate Akt isoform-specific signalling. To overcome those technical limitations we developed a novel model system that provides acute and specific control of signalling by Akt isoforms. We generated mutants of Akt1 and Akt2 resistant to the allosteric Akt inhibitor MK-2206. We then developed adipocyte cell lines, in which endogenous Akt1 or Akt2 has been replaced by their corresponding drug-resistant Akt mutant. Treatment of those cells with MK-2206 allowed for acute and specific control of either Akt1 or Akt2 function. Our data showed that Akt1W80A and Akt2W80A mutants are resistant to MK-2206, dynamically regulated by insulin and able to signal to Akt downstream effectors. Analyses of insulin action in this cellular system showed that Akt1 andAkt2 are both able tomediate insulin regulation of the transcription factor forkhead box O1 (FoxO1) and the glucose transporter 4 (GLUT4), revealing a redundant role for these Akt kinases in the control of glucose transport into fat cells. In contrast, Akt1 signalling is uniquely required for adipogenesis, by controlling the mitotic clonal expansion (MCE) of pre-adipocytes that precedes white adipose cell differentiation. Our data provide new insights into the role of Akt kinases in glucose transport and adipogenesis and support our model system as a valuable tool for the biochemical characterization of signalling by specific Akt isoforms. [ABSTRACT FROM AUTHOR]

Copyright of West Indian Medical Journal is the property of West Indian Medical Journal (WIMJ) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Aims: Endothelin (ET) system plays a critical role in the development of insulin resistance and type 2 diabetes. In skeletal muscle, differentiation of myoblasts to myotubes is accompanied by the development of insulin sensitivity. Activation of extracellular signal-regulated kinase (ERK) 1/2 inhibits the differentiation of myoblasts, leading to insulin resistance. Although ET receptor (ETR) stimulation generally activates ERK1/2, the mechanism for ETR-mediated ERK1/2 activation in skeletal muscle is unknown. The purpose of this study was to determine the signal transduction pathway involved in ET-1-stimulated ERK1/2 phosphorylation in L6 myoblasts derived from rat skeletal muscle. Main methods: Changes in phosphorylation levels of ERK1/2 following stimulation with ET-1 were analyzed by Western blot in L6 myoblasts. To inhibit receptor internalization, dominant-negative dynamin (K44A) was overexpressed in L6 myoblasts using adenovirus-mediated gene transfer. Key findings: ET-1 induced phosphorylation of ERK1/2 in L6 myoblasts. The ERK1/2 phosphorylation was abolished by BQ123 (a selective ET type A receptor (ETAR) antagonist), YM-254890 (a Gαq/11 protein inhibitor), and AG370 (a platelet-derived growth factor receptor (PDGFR) kinase inhibitor), while U-73122 (a phospholipase C (PLC) inhibitor) was less potent. The ERK1/2 phosphorylation was inhibited by overexpression of dominant-negative dynamin (K44A). These results suggest that ETAR stimulation induces ERK1/2 phosphorylation in L6 myoblasts through Gq/11 protein-dependent, PLC-independent PDGFR transactivation which requires dynamin-dependent ETAR internalization. Significance: Because activation of ERK1/2 is considered to inhibit differentiation of myoblasts with the development of insulin sensitivity, the ETAR-mediated PDGFR transactivation and subsequent ERK1/2 activation play an important role in ET-1-induced insulin resistance. [Copyright &y& Elsevier]

Abstract: Myosin 1c (Myo1c) plays a key role in supporting motile events that underlie cell migration, vesicle trafficking, insulin-stimulated glucose uptake and hearing. Here, we present the crystal structure of the human Myo1c motor in complex with its light chain calmodulin. Our structure reveals tight interactions of the motor domain with calmodulin bound to the first IQ motif in the neck region. Several of the calmodulin residues contributing to this interaction are also involved in Ca2+ binding. Contact residues in the motor domain are linked to the central β-sheet and the HO helix, suggesting a mechanism for communicating changes in Ca2+ binding in the neck region to the actin and nucleotide binding regions of the motor domain. The structural context and the chemical environment of Myo1c mutations that are involved in sensorineural hearing loss in humans are described and their impact on motor function is discussed. We show that a construct consisting of the motor domain of Myo1c and the first IQ motif is sufficient to establish a tight interaction with 14-3-3β (K D =0.9μM) and present the model of a double-headed Myo1c–14-3-3 complex. This complex has been implicated in the exocytosis of glucose transporter 4 storage vesicles during insulin-stimulated glucose uptake. [Copyright &y& Elsevier]

Abstract: The aim of this study was to test the hypothesis that a combination of corn gluten hydrolysate (CGH) and capsaicin may have an additive or synergistic effect on body weight reduction. For 13 weeks, male Sprague-Dawley rats were provided a diet to induce obesity. Afterward, the rats were randomly divided into 5 dietary groups: the normal control (n = 5), the high-fat control (n = 8), the high-fat diet (HFD) containing 35% CGH (n = 7), the HFD containing 0.02% capsaicin (HF-P) (n = 8), and the HFD containing both CGH and capsaicin (HF-CP) (n = 7) for an additional 4 weeks. Administration of CGH plus capsaicin, along with a HFD, led to significant decreases in body weight, fat mass, lipids in the liver, and plasma leptin as well as increases in plasma adiponectin. The pattern of gene expression was different in each target organ. In the liver, up-regulation of peroxisome proliferator-activated receptor α, carnitine palmitoyltransferase 1α, and acyl-coenzyme A oxidase was found in the HF-CP group. In contrast, down-regulation of peroxisome proliferator-activated receptor γ was found in both the HFD containing 35% CGH and HF-CP groups. In skeletal muscle, up-regulation of insulin receptor and uncoupling protein 3 was found in the HF-P group only, whereas up-regulation of the glucose transporter 4 gene was observed in both the HF-CP and HF-P groups. In adipose tissue, up-regulation of peroxisome proliferator-activated receptor γ and hormone-sensitive lipase was only found in the HF-CP group. In summary, this study suggests that CGH and capsaicin perform complementary actions on food intake, lipid metabolism, and insulin sensitivity by a coordinated control of energy metabolism in the liver, adipose tissue, and skeletal muscle, thus exerting an additive effect on body weight reduction. [Copyright &y& Elsevier]

Abstract: Insulin and insulin-like growth factor 1 (IGF-I) are capable of activating similar intracellular pathways. Insulin acts mainly through its own receptor, but can also activate the IGF-I receptor (IGF-IR). The aim of this study was to investigate the involvement of the IGF-IR in the effects of insulin and IGF-I on the membrane potential of immature Sertoli cells in whole seminiferous tubules, as well as on calcium, amino acid, and glucose uptake in testicular tissue of immature rats. The membrane potential of the Sertoli cells was recorded using a standard single microelectrode technique. In calcium uptake experiments, the testes were pre-incubated with 45Ca2+, with or without JB1 (1μg/mL), and then incubated with insulin (100nM) or IGF-I (15nM). In amino acid and glucose uptake experiments, the gonads were pre-incubated with or without JB1 (1μg/mL) and then incubated with radiolabeled amino acid or glucose analogues in the presence of insulin (100nM) or IGF-I (15nM). The blockade of IGF-IR with JB1 prevented the depolarising effects of both insulin and IGF-I on membrane potential, as well as the effect of insulin on calcium uptake. JB1 also inhibited the effects of insulin and IGF-I on glucose uptake. The effect of IGF-I on amino acid transport was inhibited in the presence of JB1, whereas the effect of insulin was not. We concluded that while IGF-I seems to act mainly through its cognate receptor to induce membrane depolarisation and calcium, amino acid and glucose uptake, insulin appears to be able to elicit its effects through IGF-IR, in seminiferous tubules from immature rats. [Copyright &y& Elsevier]

Highlights: [•] NR5A2 expression in C2C12 is associated with myotube differentiation. [•] DLPC induces an increase in GLUT4 levels and glucose uptake in C2C12 myotubes. [•] In high glucose conditions the activation of NR5A2 inhibits fatty acids oxidation. [ABSTRACT FROM AUTHOR]

Abstract: Skeletal muscle is the largest organ in the body and contributes to innumerable aspects of organismal biology. Muscle dysfunction engenders numerous diseases, including diabetes, cachexia, and sarcopenia. At the same time, skeletal muscle is also the main engine of exercise, one of the most efficacious interventions for prevention and treatment of a wide variety of diseases. The transcriptional coactivator PGC-1α has emerged as a key driver of metabolic programming in skeletal muscle, both in health and in disease. We review here the many aspects of PGC-1α function in skeletal muscle, with a focus on recent developments. [Copyright &y& Elsevier]

Abstract: In heart failure mitochondrial dysfunction is thought to be responsible for energy depletion and contractile dysfunction. The difficulties in procuring fresh left ventricular (LV) myocardium from humans for assessment of mitochondrial function have resulted in the reliance on surrogate markers of mitochondrial function and limited our understanding of cardiac energetics. We isolated mitochondria from fresh LV wall tissue of patients with heart failure and reduced systolic function undergoing heart transplant or left ventricular assist device placement, and compared their function to mitochondria isolated from the non-failing LV (NFLV) wall tissue with normal systolic function from patients with pulmonary hypertension undergoing heart–lung transplant. We performed detailed mitochondrial functional analyses using 4 substrates: glutamate–malate (GM), pyruvate–malate (PM) palmitoyl carnitine–malate (PC) and succinate. NFLV mitochondria showed preserved respiratory control ratios and electron chain integrity with only few differences for the 4 substrates. In contrast, HF mitochondria had greater respiration with GM, PM and PC substrates and higher electron chain capacity for PM than for PC. Surprisingly, HF mitochondria had greater respiratory control ratios and lower ADP-independent state 4 rates than NFLV mitochondria for GM, PM and PC substrates demonstrating that HF mitochondria are capable of coupled respiration ex vivo. Gene expression studies revealed decreased expression of key genes in pathways for oxidation of both fatty acids and glucose. Our results suggest that mitochondria from the failing LV myocardium are capable of tightly coupled respiration when isolated and supplied with ample substrates. Thus energy starvation in the failing heart may be the result of dysregulation of metabolic pathways, impaired substrate supply or reduced mitochondrial number but not the result of reduced mitochondrial electron transport capacity. [Copyright &y& Elsevier]

Abstract: Objective: GLUT4 protein, encoded by the Slc2a4 gene, plays a key role in muscle glucose uptake, and its expression decreases in muscles under insulin resistance. Slc2a4/GLUT4 decreases with fasting and rapidly increases with refeeding and the same occurs to plasma glucose, amino acids, insulin and T3. Thus, they might be potential regulators of the Slc2a4 gene, which makes them promising targets for strategies to improve GLUT4 expression. Herein, we investigate the role of metabolic–hormonal parameters triggered by refeeding upon the Slc2a4 expression. Materials/Methods: Plasma glucose/insulin/T3, and gastrocnemius Slc2a4 mRNA contents were measured in rats studied at the end of 48-h fasting, and subsequently at: i) 2–4h after spontaneous refeeding; ii) 2–4h after T3 injection, without refeeding; and iii) 0.5–2h after intravenous infusion of insulin, insulin+glucose and insulin+amino acids, without refeeding. Results: Refeeding increased plasma glucose/insulin/T3 and muscle Slc2a4 mRNA, reverting insulin resistance. Post-fasting infusions surprisingly induced a further Slc2a4 mRNA decrease (~20%, P <0.05 vs. fasting), but T3 injection induced a ~2-fold increase in Slc2a4 mRNA, 2–4h later (P <0.001). Moreover, T3 increased glycemia and insulinemia to the 2h-refed rats levels, suggesting that T3 elevation is a key factor to the mechanisms of metabolic balance during refeeding. Conclusions: Refeeding induces a rapid increase in muscle Slc2a4 expression, not associated with increased plasma glucose, insulin or amino acids, but highly correlated to increased plasma T3 concentration. This result points out T3 hormone as a powerful Slc2a4 enhancer, an effect that may be acutely explored in situations of insulin resistance. [Copyright &y& Elsevier]

Abstract: Although the underlying mechanism is unclear, β-conglycinin (βCG), the major component of soy proteins, regulates blood glucose levels. Here, we hypothesized that consumption of βCG would normalize blood glucose levels by ameliorating insulin resistance and stimulating glucose uptake in skeletal muscles. To test our hypothesis, we investigated the antidiabetic action of βCG in spontaneously diabetic Goto-Kakizaki (GK) rats. Our results revealed that plasma adiponectin levels and adiponectin receptor 1 messenger RNA expression in skeletal muscle were higher in βCG-fed rats than in casein-fed rats. Phosphorylation of adenosine monophosphate–activated protein kinase (AMP kinase) but not phosphatidylinositol-3 kinase was activated in βCG-fed GK rats. Subsequently, βCG increased translocation of glucose transporter 4 to the plasma membrane. Unlike the results in skeletal muscle, the increase in adiponectin receptor 1 did not lead to AMP kinase activation in the liver of βCG-fed rats. The down-regulation of sterol regulatory element-binding factor 1, which is induced by low insulin levels, promoted the increase in hepatic insulin receptor substrate 2 expression. Based on these findings, we concluded that consumption of soy βCG improves glucose uptake in skeletal muscle via AMP kinase activation and ameliorates hepatic insulin resistance and that these actions may help normalize blood glucose levels in GK rats. [Copyright &y& Elsevier]

Abstract: Dysfunctional regulation of signaling pathways downstream of the insulin receptor plays a pivotal role in the pathogenesis of insulin resistance and type 2 diabetes. In this study we report both in vitro and in vivo experimental evidence for a role of Cullin-RING E3 ubiquitin ligase 7 (CRL7) in the regulation of insulin signaling and glucose homeostasis. We show that Cul7 −/− mouse embryonic fibroblasts displayed enhanced AKT and Erk MAP kinase phosphorylation upon insulin stimulation. Depletion of CUL7 by RNA interference in C2C12 myotubes led to increased activation of insulin signaling pathways and cellular glucose uptake, as well as a reduced capacity of these cells to execute insulin-induced degradation of insulin receptor substrate 1 (IRS1). In vivo, heterozygosity of either Cul7 or Fbxw8, both key components of CRL7, resulted in elevated PI3 kinase/AKT activation in skeletal muscle tissue upon insulin stimulation when compared to wild-type controls. Finally, Cul7 +/− or Fbxw8 +/− mice exhibited enhanced insulin sensitivity and plasma glucose clearance. Collectively, our findings point to a yet unrecognized role of CRL7 in insulin-mediated control of glucose homeostasis by restraining PI3 kinase/AKT activities in skeletal muscle cells. [Copyright &y& Elsevier]

Abstract: Background and Aim: Ceramides are poorly characterized in human adipose tissue. The aim of this study was to investigate concentrations of different ceramide species in human subcutaneous and visceral adipose tissue depots and to determine associations between ceramides and global gene expression profiles. Methods and Results: Concentrations of six ceramide species were determined in plasma and in subcutaneous and mediastinal adipose tissue from 10 overweight subjects (BMI 29.4 ± 4.9 kg/m2). In the adipose tissue biopsies gene expression arrays were performed and relationships between ceramides and gene expression analyzed. Immunostaining of the two adipose tissue depots was performed in an independent group of 10 patients. Mediastinal adipose tissue contained significantly higher concentrations (p < 0.05) of all six ceramide species than the subcutaneous depot. Of the six ceramides in plasma, concentrations of only two (Cer d18:1/18:0 and Cer d18:1/22:0) correlated significantly (p < 0.05) with the corresponding species in mediastinal adipose tissue, but there were no significant correlations between ceramides in plasma and subcutaneous adipose tissue. Multivariate analysis identified significant correlations between the total ceramide concentration and global gene expression within mediastinal, but not subcutaneous adipose tissue, according to cross-validation. Gene ontology analysis of genes related to ceramides in the mediastinal depot revealed that genes positively correlated with ceramides were associated mainly with immune and inflammatory categories, while genes negatively correlated with ceramides were associated mainly with lipid and carbohydrate metabolism. Conclusions: Ceramides in human mediastinal adipose tissue may be involved in inflammation and lipid and carbohydrate metabolism. [Copyright &y& Elsevier]

Abstract: In mammals, excess energy is stored primarily as triglycerides, which are mobilized when energy demands arise. This review mainly focuses on the role of long chain fatty acids (LCFAs) in regulating energy metabolism as ligands of peroxisome proliferator-activated receptors (PPARs). PPAR-alpha expressed primarily in liver is essential for metabolic adaptation to starvation by inducing genes for beta-oxidation and ketogenesis and by downregulating energy expenditure through fibroblast growth factor 21. PPAR-delta is highly expressed in skeletal muscle and induces genes for LCFA oxidation during fasting and endurance exercise. PPAR-delta also regulates glucose metabolism and mitochondrial biogenesis by inducing FOXO1 and PGC1-alpha. Genes targeted by PPAR-gamma in adipocytes suggest that PPAR-gamma senses incoming non-esterified LCFAs and induces the pathways to store LCFAs as triglycerides. Adiponectin, another important target of PPAR-gamma may act as a spacer between adipocytes to maintain their metabolic activity and insulin sensitivity. Another topic of this review is effects of skin LCFAs on energy metabolism. Specific LCFAs are required for the synthesis of skin lipids, which are essential for water barrier and thermal insulation functions of the skin. Disturbance of skin lipid metabolism often causes apparent resistance to developing obesity at the expense of normal skin function. [Copyright &y& Elsevier]

Highlights: [•] MiR-106b gain of function induces mitochondrial dysfunction and insulin resistance in C2C12 myotubes by targeting Mfn2. [•] MiR-106b participates in TNF-α-induced mitochondrial injury and insulin resistance by regulating Mfn2. [•] These results suggest that miR-106b may represent a potential therapeutic target for the treatment of insulin resistance and type 2 diabetes. [Copyright &y& Elsevier]

Abstract: Pancreatic ribonuclease gene (RNASE1) was previously shown to have undergone duplication and adaptive evolution related to digestive efficiency in several mammalian groups that have evolved foregut fermentation, including ruminants and some primates. RNASE1 gene duplications thought to be linked to diet have also been recorded in some carnivores. Of all mammals, bats have evolved the most diverse dietary specializations, mainly including frugivory and insectivory. Here we cloned, sequenced and analyzed RNASE1 gene sequences from a range of bat species to determine whether their dietary adaptation is mirrored by molecular adaptation. We found that seven insect-eating members of the families Vespertilionidae and Molossidae possessed two or more duplicates, and we also detected three pseudogenes. Reconstructed RNASE1 gene trees based on both Bayesian and maximum likelihood methods supported independent duplication events in these two families. Selection tests revealed that RNASE1 gene duplicates have undergone episodes of positive selection indicative of functional modification, and lineage-specific tests revealed strong adaptive evolution in the Tadarida β clade. However, unlike the RNASE1 duplicates that function in digestion in some mammals, the bat RNASE1 sequences were found to be characterized by relatively high isoelectric points, a feature previously suggested to promote defense against viruses via the breakdown of double-stranded RNA. Taken together, our findings point to an adaptive diversification of RNASE1 in these two bat families, although we find no clear evidence that this was driven by diet. Future experimental assays are needed to resolve the functions of these enzymes in bats. [Copyright &y& Elsevier]

Highlights: [•] Both the ER alpha- and the ER beta-selective agonist reduce lipogenesis and adipogenesis in adipocytes. [•] Both ER subtype-selective agonists and genistein reduce lipogenesis and triglyceride accumulation in liver and muscle. [•] The ER beta-selective agonist seems to improve glucose and lipid utilization due to anabolic potency. [•] Untreated OVX rats show impaired insulin sensitivity. [Copyright &y& Elsevier]

Abstract: Objectives: Recently, we have demonstrated that FA transport proteins are located within the t-tubule fraction of rodent muscle, and that insulin stimulation causes their translocation to this membrane fraction. Chronic relocation of the FA transport protein FAT/CD36 to the sarcolemma is observed in obese rodents and humans, and correlates with intramuscular lipid accumulation and insulin resistance. It is not known whether in an obese, insulin resistant state FA transporters also chronically relocate to the t-tubules. Furthermore, it is not known whether the insulin-stimulated translocation of the various FA transport proteins to the t-tubules is impaired in insulin resistance. Methods: Sarcolemmal and t-tubule membrane fractions were isolated via differential centrifugation from muscles of lean and obese female Zucker rats during basal or insulin stimulated conditions. FA transport proteins were measured via western blot on both membrane fractions. Results: Our results demonstrate that in muscle from insulin resistant Zucker rats, FAT/CD36, FABPpm and FATP1 are all increased on the t-tubules in the basal state (+72%, +120%, and +69%, respectively), potentially contributing to the accumulation of intramuscular lipids. Insulin failed to increase the content of the FA transport proteins on either the t-tubule or sarcolemma above the elevated basal levels, analogous to the well characterized impairment of insulin-stimulated GLUT4 translocation to both membrane domains in obesity. Conclusion: FA transport proteins chronically relocate to the t-tubule domain in insulin resistant muscle, potentially contributing to lipid accumulation. Further translocation of the FA transport proteins to this domain during insulin stimulation, however, is impaired. [Copyright &y& Elsevier]

Abstract: Pancreatogenic diabetes (PD) is a potentially fatal disease that occurs secondary to pancreatic disorders. The current anti-diabetic therapy for PD is fraught with adverse effects that can increase morbidity. Here we investigated the efficacy of novel peptide nanomedicine: pancreatic polypeptide (PP) in sterically stabilized micelles (SSM) for management of PD. PP exhibits significant anti-diabetic efficacy but its short plasma half-life curtails its therapeutic application. To prolong and improve activity of PP in vivo, we evaluated the delivery of PP in SSM. PP-SSM administered to rats with PD, significantly improved glucose tolerance, insulin sensitivity and hepatic glycogen content compared to peptide in buffer. The studies established the importance of micellar nanocarriers in protecting enzyme-labile peptides in vivo and delivering them to target site, thereby enhancing their therapeutic efficacy. In summary, this study demonstrated that PP-SSM is a promising novel anti-diabetic nanomedicine and therefore should be further developed for management of PD. From the Clinical Editor: Pancreatic peptide was earlier demonstrated to address pancreatogenic diabetes, but its short half-life represented major difficulties in further development for therapeutic use. PP-SSM (pancreatic polypeptide in sterically stabilized micelles) is a promising novel anti-diabetic nanomedicine that enables prolonged half-life and increased bioactivity of PP, as shown in this novel study, paving the way toward clinical studies in the near future. [Copyright &y& Elsevier]

Abstract: Estrogen receptors are classically known as ligand-activated transcription factors that regulate gene transcription in cells in response to hormone binding. In addition to this “genomic” signaling pathway, a “rapid, non-nuclear” signaling pathway mediated by cell membrane-associated estrogen receptors also has been recognized. Although for many years there was little evidence to support any physiological relevance of rapid-signaling, very recently evidence has been accumulating supporting the importance of the rapid, non-nuclear signaling as potentially critical for the protective effects of estrogen in the cardiovascular system. Better understanding of the rapid, non-nuclear signaling potentially provides an opportunity to design “pathway-specific” selective estrogen receptor modulators capable of differentially regulating non-nuclear vs. genomic effects that may prove useful ultimately as specific therapies for cardiovascular diseases. [Copyright &y& Elsevier]

Abstract: Ethnopharmacological relevance: Panax ginseng is a well-known traditional Chinese medicine and has been used for treatment of various diseases for more than four thousand years in Asia. Ginseng saponins or ginsenosides, the active constituents are reported to possess antidiabetic activity, but their antihyperglycemic mechanisms are not fully elucidated. In the present study, the mechanisms of action of ginsenoside Re were investigated in vitro models. Materials and methods: 3T3-L1 cells were chosen as the model to investigate the molecular mechanisms of action of ginsenoside Re. Influence of ginsenoside Re on the adipogenesis was examined by determining TG levels in 3T3-L1 adipocytes by the method of TG oxidation enzyme. Glucose uptake in 3T3-L1 cells stimulated by insulin in the absence or presence of ginsenoside Re were quantified by measuring 3H-2-deoxy-d-glucose levels. Cytokine proteins released into the medium including adiponectin and TNF-α were tested using respective ELISA kits. In addition, real time RT-PCR was conducted to investigate the expression changes of PPAR-γ and its responsive genes, ap2, adiponectin, IRS-1, GLUT4 and TNF-α. And western blot analysis was performed to determine the translocation of GLUT4. Finally, effects of ginsenoside Re on NO production in 3T3-L1 adipocytes and in macrophages were investigated through measurement of nitrite concentration by Griess reagent. Results: Ginsenoside Re induced adipogenesis of 3T3-L1 adipocytes by accumulating TG, increased glucose uptake and up-regulated PPAR-γ2, IRS-1, ap2 and adiponectin genes expressions. Meanwhile, Re also increased production and release of adiponectin. Although having no effects on GLUT4 gene expression, Re facilitated GLUT4 protein translocation to the membranes. In addition, Re inhibited the expression and release of TNF-α. Finally, Re did not show inhibitory effects on NO production both in 3T3-L1 cells stimulated by LPS, TNF-α and IFN-γ and in LPS-stimulated mouse peritoneal macrophages. Conclusions: Ginsenoside Re exhibited the action of reducing insulin resistance through activation of PPAR-γ pathway by directly increasing the expressions of PPAR-γ2 and its responsive genes, adiponectin, IRS-1, ap2, inhibiting TNF-α production and facilitating the translocation of GLUT4 to promote glucose uptake and disposal in 3T3-L1 adipocytes. [Copyright &y& Elsevier]

Abstract: Efficient storage of dietary and endogenous fatty acids is a prerequisite for a healthy adipose tissue function. Lipoprotein lipase (LPL) is the master regulator of fatty acid uptake from triglyceride-rich lipoproteins. In addition to LPL-mediated fatty acid uptake, adipocytes are able to synthesize fatty acids from non-lipid precursor, a process called de novo lipogenesis (DNL). As the physiological relevance of fatty acid uptake versus DNL for brown and white adipocyte function remains unclear, we studied the role of adipocyte LPL using adipocyte-specific LPL knockout animals (aLKO). ALKO mice displayed a profound increase in DNL-fatty acids, especially palmitoleate and myristoleate in brown adipose tissue (BAT) and white adipose tissue (WAT) depots while essential dietary fatty acids were markedly decreased. Consequently, we found increased expression in adipose tissues of genes encoding DNL enzymes (Fasn, Scd1, and Elovl6) as well as the lipogenic transcription factor carbohydrate response element binding protein-β. In a high-fat diet (HFD) study aLKO mice were characterized by reduced adiposity and improved plasma insulin and adipokines. However, neither glucose tolerance nor inflammatory markers were ameliorated in aLKO mice compared to controls. No signs of increased BAT activation or WAT browning were detected in aLKO mice either on HFD or after 1week of β3-adrenergic stimulation using CL316,243. We conclude that despite a profound increase in DNL-derived fatty acids, proposed to be metabolically favorable, aLKO mice are not protected from metabolic disease per se. In addition, induction of DNL alone is not sufficient to promote browning of WAT. This article is part of a Special Issue entitled Brown and White Fat: From Signaling to Disease. [Copyright &y& Elsevier]

GLUT4 (glucose transporter 4) is responsible for the insulininduced uptake of glucose by muscle and fat cells. In nonstimulated (basal) cells, GLUT4 is retained intracellularly, whereas insulin stimulation leads to its translocation from storage compartments towards the cell surface. How GLUT4 is retained intracellularly is largely unknown. Previously, aberrant GLUT4 N-glycosylation has been linked to increased basal cell-surface levels, while N-glycosylation-deficient GLUT4 was found to be quickly degraded. As recycling and degradation of GLUT4 are positively correlated, we hypothesized that incorrect N-glycosylation of GLUT4 might reduce its intracellular retention, resulting in an increased cell-surface recycling, in increased basal cell-surface levels, and in enhanced GLUT4 degradation. In the present study, we have investigated N-glycosylationdeficient GLUT4 in detail in 3T3-L1 preadipocytes, 3T3-L1 adipocytes and L6 myoblasts. We have found no alterations in retention, insulin response, internalization or glucose transport activity. Degradation of the mutant molecule was increased, although once present at the cell surface, its degradation was identical with that of wild-type GLUT4. Our findings indicate that N-glycosylation is important for efficient trafficking of GLUT4 to its proper compartments, but once the transporter has arrived there, N-glycosylation plays no further major role in its intracellular trafficking, nor in its functional activity. [ABSTRACT FROM AUTHOR]

The article presents a study on the effects of cinnamon also known as Cinnamomum zeylanicum to diabetes. It states that streptozotocin-induced diabetic rats administered with aqueous cinnamon extract (CE) were used in the study while Western blot analysis, histochemical analysis, and cell culture were conducted. Results show that CE up-regulated the rats' mithocondrial uncoupling protein-1 (UCP-1) and improves their muscles' translocation and production of glucose transporter 4 (GLUT).

Abstract: Estrogen receptors (ERs) belong to nuclear hormone receptor superfamily and can be activated by estrogens and regulate many target genes. Two ER isoforms, ERα and ERβ have been discovered to date and ERβ was indicated to involve in anti-inflammatory and anti-diabetogenic effects. Recently, some studies also demonstrated an association between ERβ and GLUT4 expression. The development of selective ERβ ligand has facilitated probing its novel biological functions and clinical benefits. In this work, a new ERβ selective agonist, butyl 4-(butyryloxy)benzoate (DCW234), was discovered as investigated by surface plasmon resonance (SPR) technology, yeast two-hybrid and cell-based transcription-based assays. SPR results demonstrated that DCW234 has a higher binding affinity against ERβ over ERα and induces a strong and selective stimulation on ERβ/SRC1 interaction, which could be efficiently blocked by Tamoxifen. Meanwhile, the yeast two-hybrid technology-based assay indicated that DCW234 exhibits a higher agonistic activity (∼13-fold) in stimulating ERβ ligand-binding domain (LBD) interaction with SRC1 (EC50 =2.5μM) than ERα-LBD/SRC1 interaction (EC50 =32.7μM). The cell-based transcriptional assay further proved the potency and selectivity of DCW234. Moreover, DCW234 was found to be able to induce GLUT4 expression in CHO-K1 cell. The discovered DCW234 might be hopefully developed as a potential lead compound for further research. [Copyright &y& Elsevier]

The article discusses a study to establish a rapid preparation of plasma membrane from adipocytes and muscle cells, to detect translocated glucose transporter (GLUT). A plasma membrane fraction was prepared by sequential centrifugation with buffer containing detergents and its purity was estimated by detecting insulin receptor beta-subunit (IRB). The GLUT translocation was observed in adipocytes and myotubes after insulin stimulus.

Abstract: Previously we identified an unusual potential dual Akt/protein kinase B consensus phosphorylation motif in the protein Synip (RxKxRS97xS99) with serine 99 as a unique Akt2, but not Akt1 or for Akt3, substrate phosphorylation site. Although we have previously reported that serine 99 to phenylalanine (S99F-Synip) resulted in a constitutive inhibition of insulin-stimulated Glut4 translocation, a recent report indicated that Synip serine 99 to alanine mutant (S99A-Synip) failed to inhibit insulin-stimulated Glut4 translocation [H. Sano, S. Kane, E. Sano, G.E. Lienhard, Synip phosphorylation does not regulate insulin-stimulated GLUT4 translocation, Biochem. Biophys. Res. Commun. 332 (2005) 880--884]. To address this apparent discrepancy, we have now examined the S99A-Synip mutant and find that this mutant behaves essentially identical to S99F-Synip in that overexpression inhibits insulin-stimulated Glut4 translocation and is incapable of undergoing insulin-stimulated Syntaxin4 dissociation. These data are consistent with Synip serine 99 phosphorylation required for insulin-stimulated Glut4 translocation. [Copyright &y& Elsevier]

Insulin stimulation of glucose uptake into muscle and fat cells requires movement of GLUT4-containing vesicles from intracellular compartments to the plasma membrane. Accordingly, insulin-derived signals must arrive at and be recognized by the appropriate intracellular GLUT4 pools. We describe the insulin signals participating in GLUT4 translocation, and review evidence that they are recruited to intracellular membranes in conjunction with cytoskeletal elements. Such segregation may facilitate the encounter between signals and target vesicles. In most animal and cellular models of insulin resistance, insulin-stimulated GLUT4 translocation to the plasma membrane is reduced. Insulin resistance caused by oxidative stress does not affect early insulin signals, rather their intracellular localization is altered. In this and several other insulin-resistant states, insulin-induced actin remodelling is concomitantly diminished. We summarize evidence suggesting that spatial localization of signals is critical for efficient insulin action, and that the cytoskeleton may act as a scaffold to promote efficient translocation of GLUT4 to the cell surface. [ABSTRACT FROM AUTHOR]

This study evaluated the efficacy of rosiglitazone in non-obese and obese Korean type 2 diabetic patients of long duration. A total of 125 patients (M:F = 44:81, mean age: 58.4 ± 9.1 years, BMI: 24.2 ± 2.7 kg/m2, duration of diabetes: 11.0 ± 6.4 years) were randomly allocated to 12 weeks of rosiglitazone treatment (4 mg per day) or a control group. Responders were defined as patients who experienced fasting plasma glucose (FPG) reduction of >20% or HbA1c reduction of >1 (%). Rosiglitazone significantly improved glycemic control by reducing FPG and HbA1c (-3.4 mmol/l and -1.1%, P < 0.001, respectively). It also significantly increased HOMAβ-cell function (+9.7, P < 0.01) and QUICKI (+0.029, P < 0.001), and decreased HOMAIR (-1.73, P < 0.001). Females and those with higher waist–hip ratio made up a greater portion of rosiglitazone-responders. Responders (45 patients, 75%) also showed significantly higher FPG, HbA1c, systolic blood pressures, fasting insulin levels and HOMAIR, and lower QUICKI than nonresponders. Among these parameters of responders, waist–hip ratio of non-obese subgroup, initial glycemic control of obese subgroup, and systolic blood pressure of both subgroups lost their significance after subdivision analysis. However, the baseline HOMAIR and QUICKI were significantly correlated with the response rate to rosiglitazone. Moreover, in multiple logistic regression analysis, HOMAIR and QUICKI retained their significance as the independent predictors. Even in Korean type 2 diabetic patients of long duration but with relatively preserved β-cell function, rosiglitazone improved glycemic control, insulin sensitivity, and β-cell function. In this ethnic group, female gender, central obesity, and especially severe insulin resistance were identified as predictive clinical parameters of rosiglitazone-responders. [Copyright &y& Elsevier]

The transport of glucose into cells and tissues is a highly regulated process, mediated by a family of facilitative glucose transporters (GLUTs). Insulin-stimulated glucose uptake is primarily mediated by the transporter isoform GLUT4, which is predominantly expressed in mature skeletal muscle and fat tissues. Our recent work suggests that two separate pathways are initiated in response to insulin: (i) to recruit transporters to the cell surface from intracellular pools and (ii) to increase the intrinsic activity of the transporters. These pathways are differentially inhibited by wortmannin, demonstrating that the two pathways do not operate in series. Conversely, inhibitors of p38 mitogen-activated protein kinase (MAPK) imply that p38 MAPK is involved only in the regulation of the pathway leading to the insulin-stimulated activation of GLUT4. This review discusses the evidence for the divergence of GLUT4 translocation and activity and proposed mechanisms for the regulation of GLUT4.Key words: glucose transporter 4 (GLUT4), glucose uptake, p38 MAPK, GLUT4 activity.Le transport du glucose dans les cellules et les tissus est un processus fortement réglé par l'intermédiaire de transporteurs de glucose facilitant (GLUT). La captation du glucose stimulée par l'insuline est principalement attribuable à l'isoforme GLUT4 du transporteur, qui est surtout exprimée dans les muscles squelettiques matures et le tissu adipeux. Nos travaux récents suggèrent que deux voies séparées sont activées à la suite d'une stimulation par l'insuline : (i) une voie de translocation des transporteurs d'un pool intracellulaire à la surface des cellules et (ii) une autre voie de stimulation de l'activité intrinsèque des transporteurs. Ces voies sont inhibées différemment par la wortmannine, ce qui démontre que les deux voies n'opèrent pas en série. Inversement, des inhibiteurs de la protéine kinase activée par un mitogène (MAPK) p38 indiquent que la MAPK p38 intervient seulement dans la régulation de la voie d'activation de GLUT4 stimulée par l'insuline. Cette revue discute des éléments de preuve concernant la divergence entre la translocation et la stimulation de l'activité de GLUT4 et des mécanismes proposés de régulation de GLUT4.Mots clés : transporteur du glucose 4, GLUT4, captation du glucose, MAPK p38, activité de GLUT4.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

Postprandial insulin-stimulated glucose uptake into target tissue is crucial for the maintenance of normal blood glucose homeostasis. This step is rate-limited by the number of facilitative glucose transporters type 4 (GLUT4) present in the plasma membrane. Since insulin resistance and impaired GLUT4 translocation are associated with the development of metabolic disorders such as type 2 diabetes, this transporter has become an important target of antidiabetic drug research. The application of screening approaches that are based on the analysis of GLUT4 translocation to the plasma membrane to identify substances with insulinomimetic properties has gained global research interest in recent years. Here, we review methods that have been implemented to quantitate the translocation of GLUT4 to the plasma membrane. These methods can be broadly divided into two sections: microscopy-based technologies (e.g., immunoelectron, confocal or total internal reflection fluorescence microscopy) and biochemical and spectrometric approaches (e.g., membrane fractionation, photoaffinity labeling or flow cytometry). In this review, we discuss the most relevant approaches applied to GLUT4 thus far, highlighting the advantages and disadvantages of these approaches, and we provide a critical discussion and outlook into new methodological opportunities., (Creative Commons Attribution license.)