RESUMO
Our recent studies have shown that glucose-dependent insulinotropic polypeptide (GIP), but not glucagon-like peptide 1 (GLP-1), augments Na-glucose transporter 1- (SGLT1-) mediated glucose absorption in mouse jejunum. Na-dependent glucose absorption sharply rose and peaked in 3 months of high-fat (i.e., obese) compared to normal (i.e., normal weight) diet fed animals. Previous studies have shown that GIP-augmented SGLT1 and PEPT1 (peptide transporter 1) are regulated by protein kinase A (PKA) signaling in mouse jejunum. Additional studies have indicated that cAMP and PI3 kinase signaling augment PEPT1 through EPAC and AKT activation pathways, respectively, through increased apical PEPT1 trafficking in intestinal epithelial cells. However, little is known about how the signaling glucose transport paradigm is altered over a long period. Early on, increased glucose absorption occurs through SGLT1, but as the obesity and diabetes progress, there is a dramatic shift towards a Na-independent mechanism. Surprisingly, at the peak of glucose absorption during the fifth month of the progression of obesity, the SGLT1 activity was severely depressed, while a Na-independent glucose absorptive process begins to appear. Since glucose transporter 2 (GLUT2) is expressed on the apical membrane of the small intestine in obese patients and animal models of obesity, it was hypothesized to be the new more efficient route. Western blot analyses and biotinylation of the apical membrane revealed that the GIP expression increases in the obese animals and its trafficking to the apical membrane increases with the GIP treatment.
Assuntos
Polipeptídeo Inibidor Gástrico/efeitos dos fármacos , Transportador de Glucose Tipo 4/efeitos dos fármacos , Jejuno/metabolismo , Fragmentos de Peptídeos/efeitos dos fármacos , Animais , Modelos Animais de Doenças , Polipeptídeo Inibidor Gástrico/metabolismo , Transportador de Glucose Tipo 4/metabolismo , Jejuno/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL/metabolismo , Camundongos Obesos/metabolismo , Fragmentos de Peptídeos/metabolismoRESUMO
Type 2 diabetes is a major factor contributing to cognitive decline and Alzheimer's disease (AD). Treadmill running is considered to be a critical approach for mice and rats to lower blood sugar and improve learning and memory capacity. The growth factor receptor-bound protein 10 (Grb10) has been proposed to inhibit insulin signaling and defective brain insulin signaling resulted in the cognitive deficits in patients with AD. However, the positive roles of treadmill training on diabetic- related impaired cognitive function and their molecular mechanisms remain unclear. Here, to investigate whether there was neuroprotective effects of treadmill training on impaired cognitive function caused by diabetes, the rats were injected intraperitoneally with streptozotocin at a dose of 30 mg/kg to establish diabetic model (DM). We found that higher Grb10, BACE1 and PHF10 protein levels in the hippocampus of DM rats, lower phosphorylation IGF-1Rß and IRS-1(ser307). However, 8 weeks treadmill training effectively reduced abnormal Grb10, enhanced postsynaptic density protein PSD-93, PSD-95, SYN expressions of hippocampus, restored PI3K/Akt/ERK and mTOR/AMPK signaling, thus alleviated spatial learning and memory deficit, compared with DM group. Additionally, treadmill training also increased GLUT4 transportation. Overall, our findings suggest that treadmill intervention improved cognitive impairments caused by diabetes disease partly through modulating Grb10/ PI3K/Akt/ERK as well as mTOR/AMPK signaling.
Assuntos
Disfunção Cognitiva/terapia , Complicações do Diabetes/terapia , Diabetes Mellitus Experimental/complicações , Diabetes Mellitus Tipo 2/complicações , Terapia por Exercício , Proteína Adaptadora GRB10/metabolismo , Transportador de Glucose Tipo 4/efeitos dos fármacos , Condicionamento Físico Animal , Corrida , Animais , Antibióticos Antineoplásicos/administração & dosagem , Disfunção Cognitiva/induzido quimicamente , Disfunção Cognitiva/metabolismo , Complicações do Diabetes/induzido quimicamente , Complicações do Diabetes/metabolismo , Diabetes Mellitus Experimental/induzido quimicamente , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/induzido quimicamente , Diabetes Mellitus Tipo 2/metabolismo , Condicionamento Físico Animal/fisiologia , Ratos , Corrida/fisiologia , Estreptozocina/administração & dosagemRESUMO
Coumarins have been shown to reduce blood glucose levels and improve insulin sensitivity in other studies. The purpose of this study was to investigate the effects of scopoletin, which is a type of coumarin family, on glucose uptake in 3T3-L1 cells to test the hypothesis that scopoletin exerts an antidiabetic function on adipocytes. Scopoletin significantly increased glucose uptake, which was associated with increased expression of the plasma membrane glucose transporter type 4 (PM-GLUT4) in 3T3-L1 adipocytes. This increase in PM-GLUT4 expression was promoted by phosphorylation of protein kinase B, activation of phosphatidylinositol-3-kinase (PI3K), and enhanced intracellular glucose uptake. Scopoletin also promoted phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and enhanced PM-GLUT4 expression. Scopoletin-induced glucose uptake in 3T3-L1 adipocytes was inhibited by treatment with the PI3K inhibitor wortmannin and the AMPK inhibitor compound C. These results suggest that scopoletin has an antidiabetic effect by stimulating GLUT4 translocation to the PM through activation of the PI3K and AMPK pathways in 3T3-L1 adipocytes, thereby upregulating glucose uptake.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Adipócitos/metabolismo , Desoxiglucose/metabolismo , Resistência à Insulina , Fosfatidilinositol 3-Quinase/metabolismo , Escopoletina/farmacologia , Células 3T3-L1 , Proteínas Quinases Ativadas por AMP/antagonistas & inibidores , Adipócitos/efeitos dos fármacos , Animais , Ativação Enzimática/efeitos dos fármacos , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Camundongos , Inibidores de Fosfoinositídeo-3 Quinase/farmacologia , Transdução de Sinais/efeitos dos fármacosRESUMO
ErbB4, a member of the EGF receptor family, plays a variety of roles in physiological and pathological states. Genetic studies have indicated a link between ErbB4 and type 2 diabetes and obesity, but its role in metabolic syndrome (MetS) has not been reported. In the current study we found that mice with ErbB4 deletion developed MetS after 24 wk on a medium-fat diet (MFD), as indicated by development of obesity, dyslipidemia, hepatic steatosis, hyperglycemia, hyperinsulinemia, and insulin resistance, compared with wild-type mice. ErbB4 deletion mice also exhibited increased amounts of subcutaneous and visceral fat, with increased serum leptin levels, compared with wild-type mice, whereas levels of adiponectin were not significantly different. Histologically, severe inflammation, indicated by F4/80 immunostaining and M1 macrophage polarization, was detected in inguinal and epididymal white adipose tissue in ErbB4 deletion mice. ErbB4 expression decreased during 3T3-L1 preadipocyte differentiation. Administration of neuroregulin 4, a specific ligand for ErbB4, to 3T3-L1 adipocytes had no effect on adipogenesis and lipolysis but significantly inhibited lipogenesis, promoted browning, induced GLUT4 redistribution to the cell membrane, and increased glucose uptake. Neuroregulin 4 also significantly increased glucose uptake in adipocytes isolated from wild-type mice, while these effects were significantly decreased in adipocytes isolated from ErbB4 deletion mice. In conclusion, our results indicate that ErbB4 may play an important role in glucose homeostasis and lipogenesis. ErbB4 deficiency-related obesity and adipose tissue inflammation may contribute to the development of MetS.
Assuntos
Gorduras na Dieta , Dislipidemias/genética , Fígado Gorduroso/genética , Hiperglicemia/genética , Resistência à Insulina/genética , Síndrome Metabólica/genética , Obesidade/genética , Receptor ErbB-4/genética , Células 3T3-L1 , Adipogenia/efeitos dos fármacos , Adiponectina/metabolismo , Tecido Adiposo Branco/imunologia , Animais , Deleção de Genes , Predisposição Genética para Doença , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Hiperinsulinismo/genética , Inflamação , Gordura Intra-Abdominal , Leptina/metabolismo , Lipogênese/efeitos dos fármacos , Macrófagos , Masculino , Camundongos , Neurregulinas/farmacologia , Gordura SubcutâneaRESUMO
Ulomoides dermestoides is a beetle traditionally consumed to treat diabetes. In this study, we performed a composition analysis of U. dermestoides to obtain the principal fractions, which were used to assess the effect on glycemia, liver and pancreatic architecture, and PPARγ and GLUT4 expression. Normal mice and alloxan-induced diabetic mice were administered fractions of chitin, protein or fat, and the acute hypoglycemic effect was evaluated. A subacute study involving daily administration of these fractions to diabetic mice was also performed over 30 days, after which the liver and pancreas were processed by conventional histological techniques and stained with hematoxylin and eosin to evaluate morphological changes. The most active fraction, the fat fraction, was analyzed by gas chromatography-mass spectrometry (GC-MS), and PPARγ and GLUT4 mRNA expressions were determined in 3T3-L1 adipocytes. The protein and fat fractions exhibited hypoglycemic effects in the acute as well as in the 30-day study. Only the fat fraction led to elevated insulin levels and reduced glycemia, as well as lower intake of water and food. In the liver, we observed recovery of close hepatic cords in the central lobule vein following treatment with the fat fraction, while in the pancreas there was an increased density and percentage of islets and number of cells per islet, suggesting cellular regeneration. The GC-MS analysis of fat revealed three fatty acids as the major components. Finally, increased expression of PPARγ and GLUT4 was observed in 3T3-L1 adipocytes, indicating an antidiabetic effect.
Assuntos
Animais , Masculino , Pâncreas/efeitos dos fármacos , Extratos de Tecidos/uso terapêutico , Besouros/química , Corpo Adiposo/química , Hipoglicemiantes/uso terapêutico , Fígado/efeitos dos fármacos , Pâncreas/metabolismo , Pâncreas/patologia , Extratos de Tecidos/isolamento & purificação , RNA Mensageiro/efeitos dos fármacos , RNA Mensageiro/metabolismo , Regulação da Expressão Gênica , PPAR gama/efeitos dos fármacos , PPAR gama/metabolismo , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Experimental/tratamento farmacológico , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Hipoglicemiantes/isolamento & purificação , Fígado/metabolismo , Fígado/patologia , Cromatografia Gasosa-Espectrometria de MassasRESUMO
Insulin resistance participates in the glycaemic control disruption in type 2 diabetes mellitus (T2DM), by reducing muscle glucose influx and increasing liver glucose efflux. GLUT4 (Slc2a4 gene) and GLUT2 (Slc2a2 gene) proteins play a fundamental role in the muscle and liver glucose fluxes, respectively. Resveratrol is a polyphenol suggested to have an insulin sensitizer effect; however, this effect, and related mechanisms, have not been clearly demonstrated in T2DM. We hypothesized that resveratrol can improve glycaemic control by restoring GLUT4 and GLUT2 expression in muscle and liver. Mice were rendered obese T2DM in adult life by neonatal injection of monosodium glutamate. Then, T2DM mice were treated with resveratrol for 60 days or not. Glycaemic homeostasis, GLUT4, GLUT2, and SIRT1 (sirtuin 1) proteins (Western blotting); Slc2a4, Slc2a2, and Pck1 (key gluconeogenic enzyme codifier) mRNAs (RT-qPCR); and hepatic glucose efflux were analysed. T2DM mice revealed: high plasma concentration of glucose, fructosamine, and insulin; insulin resistance (insulin tolerance test); decreased Slc2a4/GLUT4 content in gastrocnemius and increased Slc2a2/GLUT2 content in liver; and increased Pck1 mRNA and gluconeogenic activity (pyruvate tolerance test) in liver. All alterations were restored by resveratrol treatment. Additionally, in both muscle and liver, resveratrol increased SIRT1 nuclear content, which must participate in gene expression regulations. In sum, the results indisputably reveals that resveratrol improves glycaemic control in T2DM, and that involves an increase in muscle Slc2a4/GLUT4 and a decrease in liver Slc2a2/GLUT2 expression. This study contributes to our understanding how resveratrol might be prescribed for T2DM according to the principles of evidence-based medicine.
Assuntos
Glicemia/efeitos dos fármacos , Diabetes Mellitus Tipo 2/tratamento farmacológico , Regulação da Expressão Gênica/efeitos dos fármacos , Estilbenos/metabolismo , Estilbenos/farmacologia , Animais , Glucose/metabolismo , Transportador de Glucose Tipo 2/efeitos dos fármacos , Transportador de Glucose Tipo 2/genética , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/genética , Humanos , Insulina/metabolismo , Resistência à Insulina , Fígado/metabolismo , Masculino , Camundongos , Camundongos Obesos , Músculo Esquelético/metabolismo , RNA Mensageiro/efeitos dos fármacos , Resveratrol , Sirtuína 1RESUMO
BACKGROUND: From ancient times, marine algae have emerged as alternative medicine and foods, contains the rich source of natural products like proteins, vitamins, and secondary metabolites, especially Chlorella vulgaris (C. vulgaris) contains numerous anti-inflammatory, antioxidants and wound healing substances. Type 2 diabetes mellitus is closely associated with adipogenesis and their factors. Hence, we aimed to investigate the chemical constituents and adipo-genic modulatory properties of C. vulgaris in 3T3-L1 pre-adipocytes. RESULTS: We analysed chemical constituents in ethanolic extract of C. vulgaris (EECV) by LC-MS. Results revealed that the EECV contains few triterpenoids and saponin compounds. Further, the effect of EECV on lipid accumulation along with genes and proteins expressions which are associated with adipogenesis and lipogenesis were evaluated using oil red O staining, qPCR and western blot techniques. The data indicated that that EECV treatment increased differentiation and lipid accumulation in 3T3-L1 cells, which indicates positive regulation of adipogenic and lipogenic activity. These increases were associated with up-regulation of PPAR-γ2, C/EBP-α, adiponectin, FAS, and leptin mRNA and protein expressions. Also, EECV treatments increased the concentration of glycerol releases as compared with control cells. Troglitazone is a PPAR-γ agonist that stimulates the PPAR-y2, adiponectin, and GLUT-4 expressions. Similarly, EECV treatments significantly upregulated PPAR-γ, adiponectin, GLUT-4 expressions and glucose utilization. Further, EECV treatment decreased AMPK-α expression as compared with control and metformin treated cells. CONCLUSION: The present research findings confirmed that the EECV effectively modulates the lipid accumulation and differentiation in 3T3-L1 cells through AMPK-α mediated signalling pathway.
Assuntos
Animais , Camundongos , Alga Marinha/química , Extratos Vegetais/farmacologia , Células 3T3-L1/efeitos dos fármacos , Chlorella vulgaris/química , Fatores de Tempo , Regulação para Baixo , Expressão Gênica , Diferenciação Celular/efeitos dos fármacos , Regulação para Cima , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Adipócitos/citologia , Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células 3T3-L1/fisiologia , PPAR gama/análise , PPAR gama/efeitos dos fármacos , PPAR gama/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Adiponectina/análise , Adiponectina/metabolismo , Transportador de Glucose Tipo 4/análise , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Proteínas Quinases Ativadas por AMP/análise , Proteínas Quinases Ativadas por AMP/efeitos dos fármacos , Proteínas Quinases Ativadas por AMP/metabolismo , Glucose/metabolismoRESUMO
Diabetes mellitus (DM) is currently ranked among leading causes of death worldwide in which type 2 DM is reaching an epidemic proportion. Hypoglycemic medications for type 2 DM have either proven inadequate or posed adverse effects; therefore, the Chinese herbal products are under investigation as an alternative treatment. In this study, a novel combination of fruiting body and mycelia powder of herbal Cordyceps militaris number 1 (CmNo1) was administered to evaluate their potential hypoglycemic effects in high-fat diet- (HFD-) induced type 2 DM in C57BL/6J mice. Body weight, fasting blood glucose (FBG), oral glucose tolerance test (OGTT), and blood biochemistry indexes were measured. Results indicated that CmNo1 lowered the blood glucose level by increasing insulin sensitivity, while no change in body weight was observed. Increased protein expression of IRS-1, pIRS-1, AKT, pAKT, and GLUT-4 in skeletal muscle and adipose tissue was found indicating restoration of insulin signaling. Additionally, PPAR-γ expression in adipose tissue restored the triglyceride and cholesterol levels. Finally, our results suggest that CmNo1 possesses strong hypoglycemic, anticholesterolemic, and antihypertriglyceridemic actions and is more economical alternate for DM treatment.
Assuntos
Glicemia/efeitos dos fármacos , Cordyceps , Diabetes Mellitus Tipo 2/metabolismo , Carpóforos , Hipoglicemiantes/farmacologia , Micélio , Preparações de Plantas/farmacologia , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/metabolismo , Animais , Glicemia/metabolismo , Western Blotting , Colesterol/metabolismo , Dieta Hiperlipídica , Modelos Animais de Doenças , Teste de Tolerância a Glucose , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Insulina/metabolismo , Proteínas Substratos do Receptor de Insulina/efeitos dos fármacos , Proteínas Substratos do Receptor de Insulina/metabolismo , Resistência à Insulina , Camundongos , Camundongos Endogâmicos C57BL , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , PPAR gama/efeitos dos fármacos , PPAR gama/metabolismo , Fosforilação/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/metabolismo , Triglicerídeos/metabolismoRESUMO
In this study, we examined the in vivo effect and the mechanism of asiatic acid (AA) on glucose uptake in an insulin target skeletal muscle. Diabetic rats showed significantly increased levels of plasma glucose, thiobarbituric acid reactive substances, and lipid hydroperoxides, decreased levels of insulin and antioxidants, and impairment in insulin-signaling proteins such as insulin receptor (IR), insulin receptor substrate (IRS)-1/2, phosphoinositide 3-kinase (PI3K), Akt, and glucose transporter 4 (GLUT4) proteins. Oral treatment with AA (20 mg/kg body weight) showed near-normalized levels of plasma glucose, lipid peroxidation products, and antioxidants and improved insulin, IR, IRS-1/2, PI3K, Akt, and GLUT4 proteins. These findings suggest that AA improves glucose response by increasing GLUT4 in skeletal muscle through Akt and antioxidant defense in plasma and it also improves glucose homeostasis.
Assuntos
Diabetes Mellitus Experimental/metabolismo , Transportador de Glucose Tipo 4/metabolismo , Glucose/metabolismo , Proteína Oncogênica v-akt/metabolismo , Triterpenos Pentacíclicos/farmacologia , Fosfatidilinositol 3-Quinases/metabolismo , Transdução de Sinais/efeitos dos fármacos , Animais , Antioxidantes/metabolismo , Diabetes Mellitus Experimental/sangue , Transportador de Glucose Tipo 4/efeitos dos fármacos , Insulina/sangue , Peroxidação de Lipídeos/efeitos dos fármacos , Masculino , Proteína Oncogênica v-akt/efeitos dos fármacos , Fosfatidilinositol 3-Quinases/efeitos dos fármacos , Ratos , Ratos Wistar , Receptor de Insulina/biossíntese , Substâncias Reativas com Ácido Tiobarbitúrico/metabolismoRESUMO
Menopause leads to a decrease in estrogen production that increases central insulin resistance, contributing to the development of neurodegenerative diseases. We have evaluated the influence of aging and estradiol or genistein treatments on some key stages of the insulin signaling pathway in the cerebral cortex. Young and aged female Wistar rats were ovariectomized and treated acutely with 17ß-estradiol (1.4µg/kg body weight), two doses of genistein (10 or 40mg/kg body weight), or vehicle. The cortical expression of several key insulin signaling pathway components was analyzed by western blotting. Our results showed an age-related deterioration in the interactions between the regulatory subunit of phosphatidylinositol 3-kinase (p85α) and the activated form of insulin receptor substrate 1 (p-IRS1tyr612), as well as between p85α and the 46kDa isoform of the estrogen receptor α (ERα46). Moreover, aging also decreased the translocation of glucose transporter-4 (GLUT4) to the plasma membrane. 17ß-Estradiol but not genistein reduced the negative impact of aging on central insulin sensitivity by favoring this GLUT4 translocation, and therefore could be neuroprotective against the associated neurodegenerative diseases. However, protein kinase B (Akt) activation by genistein suggests that other possible mechanisms are involved in the neuroprotective effects of this phytoestrogen during the aging process.
Assuntos
Córtex Cerebral/efeitos dos fármacos , Estradiol/farmacologia , Genisteína/farmacologia , Terapia de Reposição Hormonal , Insulina/metabolismo , Fitoestrógenos/farmacologia , Transdução de Sinais/efeitos dos fármacos , Fatores Etários , Envelhecimento , Animais , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Córtex Cerebral/metabolismo , Classe Ia de Fosfatidilinositol 3-Quinase/metabolismo , Ativação Enzimática , Receptor alfa de Estrogênio/agonistas , Receptor alfa de Estrogênio/metabolismo , Feminino , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Proteínas Substratos do Receptor de Insulina/metabolismo , Ovariectomia , Fosforilação , Transporte Proteico , Proteínas Proto-Oncogênicas c-akt/metabolismo , Ratos WistarRESUMO
Methylglyoxal (MG) is a highly reactive dicarbonyl compound derived mainly from glucose degradation pathways, but also from protein and fatty acid metabolism. MG modifies structure and function of different biomolecules and thus plays an important role in the pathogenesis of diabetic complications. Hyperglycemia-associated accumulation of MG might be associated with generation of oxidative stress and subsequently insulin resistance. Therefore, the effects of MG on insulin signaling and on translocation of glucose transporter 4 (GLUT4) were investigated in the rat skeletal muscle cell line L6-GLUT4myc stably expressing myc-tagged GLUT4. Twenty four-hour MG treatment resulted in elevated GLUT4 presentation on the surface of L6 myoblasts and in an increased uptake of glucose even without insulin stimulation. Exogenously added MG neither effected IRS-1 expression nor IRS-1 phosphorylation. A decreased expression of Akt1 but not Akt2 and concomitantly increased apoptosis were detected following MG treatment. To exclude that oxidative stress caused by MG treatment leads to increased GLUT4 translocation, effects of pretreatment with 2 antioxidants were investigated. The antioxidant and MG scavenger NAC prevented the MG-induced GLUT4 translocation. In contrast, tiron, a well-known antioxidant that does not exert MG-scavenger function, had no impact on MG-induced GLUT4 translocation supporting the hypothesis of a direct effect of MG on GLUT4 trafficking. In conclusion, prolonged treatment with MG augments GLUT4 level on the surface of L6 myoblasts, at least in part through a higher translocation of GLUT4 from the intracellular compartment as well as a reduction of GLUT4 internalization, resulting in increased glucose uptake.
Assuntos
Transportador de Glucose Tipo 4/metabolismo , Glucose/metabolismo , Músculo Esquelético/metabolismo , Mioblastos/efeitos dos fármacos , Mioblastos/metabolismo , Aldeído Pirúvico/farmacologia , 4-Cloro-7-nitrobenzofurazano/análogos & derivados , 4-Cloro-7-nitrobenzofurazano/metabolismo , Animais , Apoptose , Transporte Biológico/efeitos dos fármacos , Linhagem Celular , Membrana Celular/química , Desoxiglucose/análogos & derivados , Desoxiglucose/metabolismo , Transportador de Glucose Tipo 4/análise , Transportador de Glucose Tipo 4/efeitos dos fármacos , Insulina/metabolismo , Músculo Esquelético/citologia , Mioblastos/química , Estresse Oxidativo/efeitos dos fármacos , Fosforilação/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/análise , Proteínas Proto-Oncogênicas c-akt/metabolismo , Aldeído Pirúvico/metabolismo , Ratos , Transdução de Sinais/efeitos dos fármacosRESUMO
BACKGROUND AND PURPOSE: Genistein is an isoflavone phytoestrogen found in a number of plants such as soybeans and there is accumulating evidence that it has beneficial effects on the regulation of glucose homeostasis. In this study we evaluated the effect of genistein on glucose homeostasis and its underlying mechanisms in normal and insulin-resistant conditions. EXPERIMENTAL APPROACH: To induce insulin resistance, mice or differentiated 3T3-L1 adipocytes were treated with macrophage-derived conditioned medium. A glucose tolerance test was used to investigate the effect of genistein. Insulin signalling activation, glucose transporter-4 (GLUT4) translocation and AMP-activated PK (AMPK) activation were detected by Western blot analysis or elisa. KEY RESULTS: Genistein impaired glucose tolerance and attenuated insulin sensitivity in normal mice by inhibiting the insulin-induced phosphorylation of insulin receptor substrate-1 (IRS1) at tyrosine residues, leading to inhibition of insulin-mediated GLUT4 translocation in adipocytes. Mac-CM, an inflammatory stimulus induced glucose intolerance accompanied by impaired insulin sensitivity; genistein reversed these changes by restoring the disturbed IRS1 function, leading to an improvement in GLUT4 translocation. In addition, genistein increased AMPK activity under both normal and inflammatory conditions; this was shown to contribute to the anti-inflammatory effect of genistein, which leads to an improvement in insulin signalling and the amelioration of insulin resistance. CONCLUSION AND IMPLICATIONS: Genistein showed opposite effects on insulin sensitivity under normal and inflammatory conditions in adipose tissue and this action was derived from its negative or positive regulation of IRS1 function. Its up-regulation of AMPK activity contributes to the inhibition of inflammation implicated in insulin resistance.
Assuntos
Tecido Adiposo/efeitos dos fármacos , Genisteína/farmacologia , Glucose/metabolismo , Insulina/metabolismo , Células 3T3-L1 , Proteínas Quinases Ativadas por AMP/efeitos dos fármacos , Proteínas Quinases Ativadas por AMP/metabolismo , Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Tecido Adiposo/patologia , Animais , Anti-Inflamatórios/farmacologia , Teste de Tolerância a Glucose , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Homeostase/efeitos dos fármacos , Inflamação/tratamento farmacológico , Inflamação/fisiopatologia , Resistência à Insulina , Masculino , Camundongos , Camundongos Endogâmicos ICR , Fosforilação/efeitos dos fármacos , Fitoestrógenos/farmacologia , Regulação para Cima/efeitos dos fármacosRESUMO
Glucose homeostasis depends on insulin-regulated glucose uptake in the skeletal muscles and fat tissues via glucose transporter (GLUT) 4 translocation into cellular plasma membranes. The present study sought to elucidate GLUT4 expression, GLUT1 and GLUT4 translocation and glucose uptake in the skeletal muscles of Shetland ponies. Semitendinosus muscle explants were removed by open muscle biopsy from six Shetland pony geldings under general anaesthesia. The expression of GLUT4 was analysed by measuring muscle crude membrane (CM) GLUT4 protein contents. To determine the insulin-stimulated GLUT translocation, GLUT1 and GLUT4 concentrations were measured in partially purified plasma membranes (PM) and cytoplasmic vesicles (CV). GLUT contents were determined semi-quantitatively by Western blotting. Insulin-stimulated glucose uptake was analysed using 3-O-d-methyl[(3)H]glucose uptake. Incubation of semitendinosus muscle strips with 0.1 and 20mIU/mL insulin significantly increased GLUT4 translocation (PM GLUT4 contents), but had no significant effect on GLUT4 expression (CM GLUT4 concentrations) or PM GLUT1. The uptake of myocyte 3-O-Methylglucose was not significantly increased following insulin stimulation. The sub-cellular fractionation technique proved to be an appropriate tool for determining insulin-stimulated GLUT4 translocation in equine skeletal muscle. GLUT4 translocation in equines is insulin-dependent, as has been described in rodents and farm animals, but insulin-stimulated GLUT4 activation in ponies is lower than reported for pigs and cows under the same experimental conditions. Poor insulin-activated GLUT4 translocation may account for insulin resistance in ponies in previous euglycaemic, hyperinsulinaemic clamp tests.
Assuntos
Transportador de Glucose Tipo 4/metabolismo , Insulina/farmacologia , Músculo Esquelético/metabolismo , 3-O-Metilglucose/metabolismo , Animais , Transporte Biológico/efeitos dos fármacos , Transportador de Glucose Tipo 1/efeitos dos fármacos , Transportador de Glucose Tipo 1/metabolismo , Transportador de Glucose Tipo 4/efeitos dos fármacos , Cavalos , Masculino , Músculo Esquelético/efeitos dos fármacosRESUMO
AIM: Addition of dehydroepiandrosterone (DHEA) to a cultured skeletal muscle locally synthesizes 5alpha-dihydrotestosterone (DHT). It induced activation of glucose metabolism-related signalling pathway via protein kinase B (Akt) and protein kinase C zeta/lambda (PKC zeta/lambda)-glucose transporter-4 (GLUT4) proteins. However, such an effect of DHEA in vivo remains unclear. METHODS: Using streptozotocin (STZ)-induced rats with type 1 diabetes mellitus, we tested the hypothesis that a single bout of DHEA injection in the rats improves hyperglycaemia and muscle GLUT4-regulated signalling pathway. After 1 week of STZ injection (55 mg kg(-1)) with male Wistar rats, fasting glucose concentrations were determined in a blood sample taken from the tail vein. Blood glucose levels were then monitored for 180 min after DHEA or sesame oil (control) was injected (n = 10 for each group). RESULTS: Blood glucose levels decreased significantly for 30-150 min after 2 mg DHEA injection in the STZ rats. In the skeletal muscle, expression and translocation of GLUT4 protein, phosphorylation of Akt and PKC zeta/lambda, and phosphofructokinase and hexokinase enzyme activities increased significantly by DHEA injection. However, DHEA-induced improvements in Akt and PKC zeta/lambda-GLUT4 pathways were blocked by a DHT inhibitor. CONCLUSION: These results suggest that a single bout of DHEA injection can improve hyperglycaemia and activate the glucose metabolism-related signalling pathway via Akt and PKC zeta/lambda-GLUT4 proteins of skeletal muscles in rats. Moreover, these results show that a DHEA-induced increase in muscle glucose uptake and utilization might contribute to improvement in hyperglycaemia in type 1 diabetes mellitus.
Assuntos
Desidroepiandrosterona/farmacologia , Diabetes Mellitus Experimental/metabolismo , Transportador de Glucose Tipo 4/efeitos dos fármacos , Hiperglicemia/metabolismo , Músculo Esquelético/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/efeitos dos fármacos , Adjuvantes Imunológicos , Animais , Glicemia/efeitos dos fármacos , Diabetes Mellitus Experimental/tratamento farmacológico , Ativação Enzimática/efeitos dos fármacos , Ensaio de Imunoadsorção Enzimática , Transportador de Glucose Tipo 4/metabolismo , Immunoblotting , Masculino , Músculo Esquelético/metabolismo , Proteína Quinase C/efeitos dos fármacos , Proteína Quinase C/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Ratos , Ratos Wistar , Transdução de Sinais/efeitos dos fármacosRESUMO
Ginseng has been reported to ameliorate hyperglycemia in experimental and clinical studies; however, its mechanism of action remains unclear. In this study, we investigated the metabolic effects and putative molecular mechanisms of Korean red ginseng (KRG, Panax ginseng) in animal models for type 2 diabetes mellitus (T2DM) and peripheral insulin-responsive cell lines. Korean red ginseng was administered orally at a dose of 200 mg/(kg d) to Otsuka Long-Evans Tokushima fatty rats for 40 weeks. Initially, chronic administration of KRG reduced weight gain and visceral fat mass in the early period without altering food intake. The KRG-treated Otsuka Long-Evans Tokushima fatty rats showed improved insulin sensitivity and significantly preserved glucose tolerance compared with untreated control animals up to 50 weeks of age, implying that KRG attenuated the development of overt diabetes. KRG promoted fatty acid oxidation by the activation of adenosine monophosphate-activated protein kinase (AMPK) and phosphorylation of acetyl-coenzyme A carboxylase in skeletal muscle and cultured C2C12 muscle cells. Increased expression of peroxisome proliferator-activated receptor-gamma coactivator-1alpha, nuclear respiratory factor-1, cytochrome c, cytochrome c oxidase-4, and glucose transporter 4 by KRG treatment indicates that activated AMPK also enhanced mitochondrial biogenesis and glucose utilization in skeletal muscle. Although these findings suggest that KRG is likely to have beneficial effects on the amelioration of insulin resistance and the prevention of T2DM through the activation of AMPK, further clinical studies are required to evaluate the use of KRG as a supplementary agent for T2DM.
Assuntos
Diabetes Mellitus Tipo 2/prevenção & controle , Hipoglicemiantes/farmacologia , Resistência à Insulina , Insulina/metabolismo , Gordura Intra-Abdominal/efeitos dos fármacos , Obesidade/metabolismo , Panax , Preparações de Plantas/farmacologia , Animais , Western Blotting , Teste de Tolerância a Glucose , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Hipoglicemiantes/administração & dosagem , Masculino , Obesidade/complicações , Obesidade/fisiopatologia , Preparações de Plantas/administração & dosagem , Ratos , Ratos Endogâmicos OLETFRESUMO
OBJECTIVE: Cytokines are elevated in various insulin-resistant states, including type 2 diabetes and obesity, although the contribution of interleukin-6 (IL-6) in the induction of these diseases is controversial. RESEARCH DESIGN AND METHODS: We analyzed the impact of IL-6 on insulin action in murine primary myocytes, skeletal muscle cell lines, and mice (wild type and protein-tyrosine phosphatase 1B [PTP1B] deficient). RESULTS: IL-6 per se increased glucose uptake by activating serine/threonine protein kinase 11 (LKB1)/AMP-activated protein kinase/protein kinase B substrate of 160 kDa (AS160) pathway. A dual effect on insulin action was observed when myotubes and mice were exposed to this cytokine: additive with short-term insulin (increased glucose uptake and systemic insulin sensitivity) but chronic exposure produced insulin resistance (impaired GLUT4 translocation to plasma membrane and defects in insulin signaling at the insulin receptor substrate 1 [IRS-1] level). Three mechanisms seem to operate in IL-6-induced insulin resistance: activation of c-Jun NH(2)-terminal kinase 1/2 (JNK1/2), accumulation of suppressor of cytokine signaling 3 (socs3) mRNA, and an increase in PTP1B activity. Accordingly, silencing JNK1/2 with either small interfering RNA or chemical inhibitors impaired phosphorylation of IRS-1 (Ser307), restored insulin signaling, and normalized insulin-induced glucose uptake in myotubes. When using a pharmacological approach, liver X receptor agonists overcome IL-6-induced insulin resistance by producing downregulation of socs3 and ptp1b gene expression. Finally, the lack of PTP1B confers protection against IL-6-induced insulin resistance in skeletal muscle in vitro and in vivo, in agreement with the protection against the IL-6 hyperglycemic effect observed on glucose and insulin tolerance tests in adult male mice. CONCLUSIONS: These findings indicate the important role of IL-6 in the pathogenesis of insulin resistance and further implicate PTP1B as a potential therapeutic target in the treatment of type 2 diabetes.
Assuntos
Insulina/farmacologia , Interleucina-6/fisiologia , Células Musculares/fisiologia , Músculo Esquelético/fisiologia , Adenilato Quinase/efeitos dos fármacos , Adenilato Quinase/metabolismo , Animais , Animais Recém-Nascidos , Transporte Biológico/efeitos dos fármacos , Extremidades , Glucose/metabolismo , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/metabolismo , Camundongos , Células Musculares/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Mioblastos/citologia , Mioblastos/efeitos dos fármacos , Mioblastos/fisiologia , Reação em Cadeia da Polimerase , Transporte Proteico/efeitos dos fármacos , Transporte Proteico/fisiologia , Proteínas Proto-Oncogênicas c-akt/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/metabolismo , RNA Interferente Pequeno/genéticaRESUMO
Corosolic acid, a triterpenoid compound widely existing in many traditional Chinese medicinal herbs, has been proved to have antidiabetic effects on animal experiments and clinical trials. However, the underlying mechanisms remain unknown. Here, we investigate its cellular effects and related signaling pathway. We demonstrate that it enhances glucose uptake in L6 myotubes and facilitates glucose transporter isoform 4 translocation in CHO/hIR cells. These actions are mediated by insulin pathway activation and can be blocked by phosphatidylinositol 3-kinase (PI(3) Kinase) inhibitor wortmannin. Furthermore, Corosolic acid inhibits the enzymatic activities of several diabetes-related non-receptor protein tyrosine phosphatases (PTPs) in vitro, such as PTP1B, T-cell-PTP, src homology phosphatase-1 and src homology phosphatase-2.
Assuntos
Inibidores Enzimáticos/farmacologia , Glucose/metabolismo , Hipoglicemiantes/farmacologia , Receptor de Insulina/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Triterpenos/farmacologia , Proteínas Quinases Ativadas por AMP , Androstadienos/farmacologia , Animais , Transporte Biológico , Células CHO , Cricetinae , Cricetulus , Relação Dose-Resposta a Droga , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/genética , Transportador de Glucose Tipo 4/metabolismo , Humanos , Insulina/metabolismo , Complexos Multienzimáticos/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Inibidores de Fosfoinositídeo-3 Quinase , Fosforilação , Inibidores de Proteínas Quinases/farmacologia , Proteínas Serina-Treonina Quinases/metabolismo , Transporte Proteico , Proteínas Tirosina Fosfatases não Receptoras/antagonistas & inibidores , Proteínas Tirosina Fosfatases não Receptoras/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptor de Insulina/genética , Receptor de Insulina/metabolismo , WortmaninaRESUMO
Administration of the PPARgamma agonist GW1929 (10 mg/kg body weight) results in amelioration of muscle loss in tumour-bearing mice experimental cachexia. The effect of the agonist, which seems to be specific for white muscle extensor digitorum longus (EDL), is accompanied by an increase in the levels of the transcription factor MyoD and also the GLUT-4 glucose transporter. In addition, the effects of GW1929 on skeletal muscle are direct since incubation of isolated rat skeletal muscles in its presence results in a decreased rate of protein degradation. Collectively, the results presented suggest a potential clinical application - possibly in combination with other anabolic strategies - of GW1929 in restoring muscle waste during cancer cachexia.
Assuntos
Benzofenonas/farmacologia , Caquexia/etiologia , Caquexia/fisiopatologia , Carcinoma Pulmonar de Lewis/complicações , Músculo Esquelético/efeitos dos fármacos , PPAR gama/antagonistas & inibidores , Tirosina/análogos & derivados , Animais , Western Blotting , Transportador de Glucose Tipo 4/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Músculo Esquelético/patologia , Músculo Esquelético/fisiopatologia , Tirosina/farmacologiaRESUMO
Temporary defects in the plasma lipid and glucose homeostasis are frequent complication accompanying chronic treatment with 13-cis-retinoic acid (13cRA). White adipose tissue acts as an endocrine organ producing a variety of hormones (adipocytokines) including leptin, adiponectin, tumor-necrosis factor alpha (TNFalpha) and angiotensin II (Ang II), which influence lipid metabolism, systemic insulin sensitivity and inflammation. To study the effect of a short-term 13cRA administration on metabolism of epididymal fat tissue, we treated Wistar rats with five identical therapeutic doses of 13cRA (0.8 mg/kg b.w.) by gavage during a period of 10 days. Expression of adiponectin, leptin, TNFalpha and selected proteins such as adipocyte fatty acid binding protein (aP2), insulin-dependent glucose transporter GLUT4, peroxisome proliferator-activated receptor gamma (PPARgamma) and retinoid X receptors (RXRs) was investigated using RT-PCR. Short-term treatment with therapeutic doses of 13cRA caused significant increase of the aP2, PPARgamma and moderately RXRalpha gene expression. Similarly, the relative amount of mRNA for leptin and GLUT4 was increased, while the TNFa transcript was decreased after treatment with 13cRA. The gene expression and plasma concentration of adiponectin were without any significant changes. Since local adipose renin-angiotensin system (RAS) has been presumed to be involved in the regulation of fat tissue metabolism, we also investigated the gene expression of RAS components in epididymal fat depot. Our data has shown that 13cRA elevated Ang II receptor type 1 (AT(1) receptor)--at both, mRNA and protein level. Thus, our results demonstrate that short-term 13cRA treatment is inducing alterations in fat tissue metabolism in relation to stimulated adipogenesis.
Assuntos
Fármacos Dermatológicos/toxicidade , Regulação da Expressão Gênica/efeitos dos fármacos , Isotretinoína/toxicidade , Tecido Adiposo Branco/efeitos dos fármacos , Tecido Adiposo Branco/metabolismo , Animais , Proteínas de Ligação a Ácido Graxo/efeitos dos fármacos , Proteínas de Ligação a Ácido Graxo/genética , Transportador de Glucose Tipo 4/efeitos dos fármacos , Transportador de Glucose Tipo 4/genética , Leptina/genética , Leptina/metabolismo , Masculino , PPAR gama/deficiência , PPAR gama/efeitos dos fármacos , PPAR gama/genética , RNA Mensageiro/efeitos dos fármacos , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Receptor Tipo 1 de Angiotensina/efeitos dos fármacos , Receptor Tipo 1 de Angiotensina/genética , Receptores X de Retinoides/efeitos dos fármacos , Receptores X de Retinoides/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Necrose Tumoral alfa/efeitos dos fármacos , Fator de Necrose Tumoral alfa/genéticaRESUMO
In muscle cells, insulin elicits recruitment of the glucose transporter GLUT4 to the plasma membrane. This process engages sequential signaling from insulin receptor substrate (IRS)-1 to phosphatidylinositol (PI) 3-kinase and the serine/threonine kinase Akt. GLUT4 translocation also requires an Akt-independent but PI 3-kinase-and Rac-dependent remodeling of filamentous actin. Although IRS-1 phosphorylation is often reduced in insulin-resistant states in vivo, several conditions eliciting insulin resistance in cell culture spare this early step. Here, we show that insulin-dependent Rac activation and its consequent actin remodeling were abolished upon exposure of L6 myotubes beginning at doses of C2-ceramide or oxidant-producing glucose oxidase as low as 12.5 micromol/l and 12.5 mU/ml, respectively. At 25 micromol/l and 25 mU/ml, glucose oxidase and C2-ceramide markedly reduced GLUT4 translocation and glucose uptake and lowered Akt phosphorylation on Ser473 and Thr308, yet they affected neither IRS-1 tyrosine phosphorylation nor its association with p85 and PI 3-kinase activity. Small interfering RNA-dependent Rac1 knockdown prevented actin remodeling and GLUT4 translocation but spared Akt phosphorylation, suggesting that Rac and actin remodeling do not contribute to overall Akt activation. We propose that ceramide and oxidative stress can each affect two independent arms of insulin signaling to GLUT4 at distinct steps, Rac-GTP loading and Akt phosphorylation.