共查询到20条相似文献,搜索用时 31 毫秒
1.
Mujalin Prasannarong Fernando R. SantosErik J. Henriksen 《Biochemical and biophysical research communications》2012,426(3):369-373
The nonapeptide angiotensin II (ANG II) induces vasoconstriction via the ANG II type I receptor, while its splice product ANG-(1-7) elicits an antihypertensive effect via the Mas receptor. Although a critical role of ANG II in the etiology of skeletal muscle insulin resistance is well documented, the role of the ANG-(1-7)/Mas receptor axis in this context is poorly understood. Therefore, we determined whether ANG-(1-7) is effective in ameliorating the negative effects of ANG II on insulin-stimulated insulin signaling and glucose transport activity in isolated soleus muscle from normotensive lean Zucker rats. ANG II alone (500 nM for 2 h) decreased insulin-stimulated glucose transport activity by 45% (P < 0.05). In the presence of 500-1000 nM ANG-(1-7), insulin-stimulated glucose transport activity in muscle exposed to ANG II improved by ∼30% (P < 0.05). Moreover, ANG-(1-7) treatment increased Akt Ser473 phosphorylation (47%, P < 0.05) without an effect on glycogen synthase kinase-3β Ser9 phosphorylation. The dependence of ANG-(1-7) action on the Mas receptor was assessed using A779 peptide, a selective Mas receptor antagonist. The positive effects of ANG-(1-7) on insulin-stimulated glucose transport activity and Akt Ser473 phosphorylation in soleus muscle were completely prevented in presence of 1000 nM A779. In conclusion, the present study demonstrates that ANG-(1-7), via a Mas receptor-dependent mechanism, can ameliorate the inhibitory effect of ANG II on glucose transport activity in mammalian skeletal muscle, associated with enhanced Akt phosphorylation. These results provide further evidence supporting the targeting of the renin-angiotensin system for interventions designed to reduce insulin resistance in skeletal muscle tissue. 相似文献
2.
Hyperglycaemia has a deferred detrimental effect on glucose metabolism, termed “metabolic memory”. Elevated saturated fatty acids promote insulin resistance, hyperglycaemia and associated atherosclerotic complications, but their effect on “metabolic memory” is unknown. Therefore we investigated whether basal and insulin-stimulated (10−6 M for 12 h) glucose (2-deoxy-d-[3H]-glucose) uptake was affected by palmitate pre-treatment human THP-1 monocytes. Palmitate-induced a time-dependent and concentration-dependent inhibition of insulin-stimulated glucose uptake, showing almost complete abolition of the insulin-stimulatory effect with 300 μM palmitate. Basal glucose uptake was unaffected by palmitate. When palmitate was washed out, the inhibitory effect on insulin-stimulated glucose uptake persisted for at least 60 h. 相似文献
3.
Abdelali Agouni Mirela Delibegovic 《Biochemical and biophysical research communications》2010,401(1):104-111
Background: Components of the insulin receptor signaling pathway are probably some of the best studied ones. Even though methods for studying these components are well established, the in vivo effects of different fasting regimens, and the time course of insulin receptor phosphorylation and that of its downstream components in insulin-sensitive peripheral tissues have not been analyzed in detail. Rationale: When assessing insulin signaling, it may be beneficial to drive insulin levels as low as possible by performing an overnight fast before injecting a supra-physiological dose of insulin. Recent studies have shown however that 5 or 6 h fast in mice is sufficient to assess physiological responses to insulin and/or glucose in glucose tolerance tests [1], insulin tolerance tests [2], [3] and [4] and euglycemic hyperinsulinemic clamp studies [5] and [6]. Moreover, mice are nocturnal feeders, with ∼70% of their daily caloric intake occurring during the dark cycle [5], and their metabolic rate is much higher than humans. Therefore, an overnight fast in mice is closer to starvation than just food withdrawal. Thus our aim was to assess insulin signaling components from the insulin receptor to downstream targets IRS1, Akt/PKB, GSK3, Erk1/2 and ribosomal protein S6 in muscle, liver and adipose tissue in 5 h versus 16 h (overnight) fasted mice, and the time course (0-30 min) of these phosphorylation events. We also assessed whether re-feeding under 5 h and 16 h fasting conditions was a more robust stimulus than insulin alone. Conclusions: Our study determines that a short food withdrawal from mice, for a period of 5 h, results in a similar insulin-stimulated response in phosphorylation events as the long overnight fast, presenting a more physiological experimental set up. We also demonstrate that in vivo, insulin-stimulated phosphorylation of its signaling components is different between different peripheral tissues, and depending on the tissue(s) and protein(s) of interest, an appropriate time course should be chosen. 相似文献
4.
Tara L. Archuleta Andrew M. Lemieux Vitoon Saengsirisuwan Mary K. Teachey Katherine A. Lindborg John S. Kim Erik J. Henriksen 《Free radical biology & medicine》2009,47(10):1486-1493
Oxidative stress is characterized as an imbalance between the cellular production of oxidants and the cellular antioxidant defenses and contributes to the development of numerous cardiovascular and metabolic disorders, including hypertension and insulin resistance. The effects of prolonged oxidant stress in vitro on the insulin-dependent glucose transport system in mammalian skeletal muscle are not well understood. This study examined the in vitro effects of low-level oxidant stress (60–90 μM, H2O2) for 4 h on insulin-stimulated (5 mU/ml) glucose transport activity (2-deoxyglucose uptake) and on protein expression of critical insulin signaling factors (insulin receptor (IR), IR substrates IRS-1 and IRS-2, phosphatidylinositol 3-kinase, Akt, and glycogen synthase kinase-3 (GSK-3)) in isolated soleus muscle of lean Zucker rats. This oxidant stress exposure caused significant (50%, p < 0.05) decreases in insulin-stimulated glucose transport activity that were associated with selective loss of IRS-1 (59%) and IRS-2 (33%) proteins, increased (64%) relative IRS-1 Ser307 phosphorylation, and decreased phosphorylation of Akt Ser473 (50%) and GSK-3β Ser9 (43%). Moreover, enhanced (37%) phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) was observed. Selective inhibition of p38 MAPK (10 μM A304000) prevented a significant portion (29%) of the oxidant stress-induced loss of IRS-1 (but not IRS-2) protein and allowed partial recovery of the impaired insulin-stimulated glucose transport activity. These results indicate that in vitro oxidative stress in mammalian skeletal muscle leads to substantial insulin resistance of distal insulin signaling and glucose transport activity, associated with a selective loss of IRS-1 protein, in part due to a p38 MAPK-dependent mechanism. 相似文献
5.
Malchoff Carl D. Messina Joseph L. Gordon Valery Tamura Shinri Larner Joseph 《Molecular and cellular biochemistry》1985,69(1):83-90
Insulin stimulated phosphorylation of tyrosine residues by the insulin receptor kinase may be part of a signalling mechanism associated with insulin's action. We report that indomethacin inhibited the phosphorylation of the -subunit of the solubilized adipocyte insulin receptor. Indomethacin also inhibited several insulin-sensitive processes in intact rat adipocytes. Indomethacin (1 mM) inhibited basal phosphorylation of the -subunit of the solubilized insulin receptor by 6007o and insulin-stimulated phosphorylation by 30%. In adipocytes, indomethacin inhibited basal 3-0-[methyl-14C]-methyl-D glucose transport by 50070 (P < 0.01), D-[6-14C]-glucose oxidation by 5007o (P < 0.01), D-[6-14C]-glucose conversion to lipid by 30010 (P < 0.01), and D-[1-14C]-glucose conversion to lipid by 6007o (P<0.01). Similarly, indomethacin inhibited insulin-stimulated 3-0-[methyl-14C]-methyl-D-glucose transport by 75070 (P<0.01), D-[6-14C]-glucose oxidation by 20% (P<0.05), D-[1-14C]-glucose oxidation by 35070 (P<0.01), D-[6-14C] glucose conversion to lipid by 25010 (P<0.01), and D-[1-14C] glucose conversion to lipid by 4501o (P<0.01). In contrast, insulin binding to its receptor, basal D-[1-14C]-glucose oxidation and both basal and insulin-stimulated activation of glycogen synthase were unaffected by indomethacin. Thus, indomethacin partially inhibited autophosphorylation of the solubilized insulin receptor on tyrosine and partially inhibited some but not all of insulin's actions. This supports the hypothesis that insulin's metabolic effects are linked to activation of the insulin receptor protein kinase and indicates that there may be heterogeneity in the mechanisms of intracellular metabolic control by insulin. 相似文献
6.
7.
Alvin Ibarra Naisheng BaiKan He Antoine BilyJulien Cases Marc RollerShengmin Sang 《Phytomedicine》2011,18(6):479-485
Purpose
The aim of this study was to determine whether a Fraxinus excelsior L. seed extract, FraxiPure™ (0.5% in the diet), limits weight gain and hyperglycemia in mice. In a previous report, we identified several secoiridoids in FraxiPure™, some of which activated peroxisome proliferator-activated receptor alpha (PPARα) in vitro and inhibited the differentiation of 3T3-L1 preadipocyte cells. In a separate study, FraxiPure™ reduced glycemia in healthy volunteers, following an oral glucose tolerance test. These findings suggest that FraxiPure™ has antiobesity and antihyperglycemia effects.Materials and methods
FraxiPure™ was tested in mice that were fed a high-fat diet over 16 weeks and compared with low-fat and high-fat diet controls. Weight gain, omental and retroperitoneal fat, fasting blood glucose, and fasting blood insulin were measured.Results
FraxiPure™ reduced gains in body weight by 32.30% (p < 0.05), omental fat by 17.92%, and retroperitoneal fat by 17.78%. FraxiPure™ also lowered fasting blood glucose levels by 76.52% (p < 0.001) and plasma insulin levels by 53.43% (p < 0.05) after 16 weeks. Moreover, FraxiPure™ lowered liver weight gains by 63.62% (p < 0.05) and the incidence of fatty livers by 66.67%.Conclusions
Our novel results demonstrate the antiobesity effects of chronic administration of an F. excelsior seed extract and confirm its ability to regulate glycemia and insulinemia. In addition, this extract, which is rich in secoiridoid glucosides, protects against obesity-related liver steatosis. 相似文献8.
Regulation of mRNA translation has been held responsible for effects of diet, age, alcohol, hormones, hibernation, disease and hypoxia on protein synthesis in animal tissues. Dietary effects are due to concentrations of amino acids and insulin in circulation that affect activities of two key translational regulators, eukaryotic initiation factor 2 (F2) and eukaryotic initiation factor 4E binding protein 1 (Bp). To construct a platform for prediction of global protein synthesis to nutritional stimuli, a dynamic, mechanistic model of translational control in whole tissues was developed. The model was composed of a set of differential equations which describe the dynamics of 11 state variables: tRNA and acyl-tRNA for leucine (Leu), limiting (Laa) and other amino acids (Oaa), inactivated F2 with GDP (F2d), activated F2 with GTP (F2t), F4e, Bp and its complex with F4e (4eBp), available mRNA start codons (AUG), and active ribosomes (Arib). Material was assumed to flow from one variable to another according to mass-action kinetics or Michaelis-Menten form. Uncharged tRNA inhibit GTP exchange on eIF2, and free amino acids and insulin inhibit reversible sequestration of F4e by Bp. Initial conditions and parameters were set for a skeletal muscle fractional synthesis rate of 10%/d and ribosome transit time of 80 s. Between amino acid concentrations of 500 and 4000×103 nM, protein synthesis increased from 0.9 to 11.7%/d at 0 μU/mL insulin, and from 5.0 to 12.8%/d at 30 μU/mL insulin. Predicted responses to graded levels of a deficient amino acid were asymptotic. A single parameter accomodated differences between tissues in insulin sensitivity. Seven parameters must be changed to simulate initiation and elongation rates in more active tissues such as liver, or in tissues of older mature animals. An increase in uncharged tRNA during insulin stimulation highlighted the physiological importance of coordinated regulation of amino acid supply by insulin. In conclusion, the regulation of F4e release from Bp by Ins and Leu, and of F2d recycling by uncharged tRNA can be tied together to describe a wide range of FSR values across tissues and physiological states. 相似文献
9.
Shin-ichi Ikeda Yoshifumi Tamura Saori Kakehi Kageumi Takeno Minako Kawaguchi Takahiro Watanabe Fumihiko Sato Takeshi Ogihara Akio Kanazawa Yoshio Fujitani Ryuzo Kawamori Hirotaka Watada 《Biochemical and biophysical research communications》2013
Exercise enhances insulin sensitivity in skeletal muscle, but the underlying mechanism remains obscure. Recent data suggest that alternatively activated M2 macrophages enhance insulin sensitivity in insulin target organs such as adipose tissue and liver. Therefore, the aim of this study was to determine the role of anti-inflammatory M2 macrophages in exercise-induced enhancement of insulin sensitivity in skeletal muscle. C57BL6J mice underwent a single bout of treadmill running (20 m/min, 90 min). Twenty-four hours later, ex vivo insulin-stimulated 2-deoxy glucose uptake was found to be increased in plantaris muscle. This change was associated with increased number of CD163-expressing macrophages (i.e. M2-polarized macrophages) in skeletal muscle. Systemic depletion of macrophages by pretreatment of mice with clodronate-containing liposome abrogated both CD163-positive macrophage accumulation in skeletal muscle as well as the enhancement of insulin sensitivity after exercise, without affecting insulin-induced phosphorylation of Akt and AS160 or exercise-induced GLUT4 expression. These results suggest that accumulation of M2-polarized macrophages is involved in exercise-induced enhancement of insulin sensitivity in mouse skeletal muscle, independently of the phosphorylation of Akt and AS160 and expression of GLUT4. 相似文献
10.
Adrenomedullin (ADM) has been recognized as a multipotent multifunctional peptide. To explore the pathophysiological roles of ADM in insulin resistance (IR), we studied the changes in ADM mRNA level in the myocardium and vessels and the effect of ADM supplementation on rats with IR induced by fructose feeding. Rats were fed 4% fructose in drinking water for 8 weeks, and ADM was administered subcutaneously in pure water through an Alzet Mini-osmotic Pump at 300 ng/kg/h for the last 4 weeks. Compared with controls, rats with IR showed increased levels of fasting blood sugar and serum insulin, by 95% and 67%, respectively (all P < 0.01), and glycogen synthesis and glucose transport activity of the soleus decreased by 54% and 55% (all P < 0.01). mRNA level and content of brain natriuretic peptide (BNP) in myocardial were all increased significantly. Fructose-fed rats showed increased immunoreactive-ADM content in plasma by 110% and in myocardia by 55% and increased mRNA level in myocardia and vessels (all P < 0.01). ADM administration ameliorated the induced IR and myocardial hypertrophy. The glycogen synthesis and glucose transport activity of the soleus muscle increased by 41% (P < 0.01) and 32% (P < 0.05). ADM therapy attenuated myocardial and soleus lipid peroxidation injury and enhanced the antioxidant ability. Our results showed upregulation of endogenous ADM during fructose-induced IR and the protective effect of ADM on fructose-induced IR and concomitant cardiovascular hypertrophy probably by its antioxidant effect, which suggests that ADM could be an endogenous protective factor in IR. 相似文献
11.
Burén J Lai YC Lundgren M Eriksson JW Jensen J 《Archives of biochemistry and biophysics》2008,474(1):91-101
Glucocorticoids initiate whole body insulin resistance and the aim of the present study was to investigate effects of dexamethasone on protein expression and insulin signalling in muscle and fat tissue. Rats were injected with dexamethasone (1 mg/kg/day, i.p.) or placebo for 11 days before insulin sensitivity was evaluated in vitro in soleus and epitrochlearis muscles and in isolated epididymal adipocytes. Dexamethasone treatment reduced insulin-stimulated glucose uptake and glycogen synthesis by 30-70% in epitrochlearis and soleus, and insulin-stimulated glucose uptake by ∼40% in adipocytes. 8-bromo-cAMP-stimulated lipolysis was ∼2-fold higher in adipocytes from dexamethasone-treated rats and insulin was less effective to inhibit cAMP-stimulated lipolysis. A main finding was that dexamethasone decreased expression of PKB and insulin-stimulated Ser473 and Thr308 phosphorylation in both muscles and adipocytes. Expression of GSK-3 was not influenced by dexamethasone treatment in muscles or adipocytes and insulin-stimulated GSK-3β Ser9 phosphorylation was reduced in muscles only. A novel finding was that glycogen synthase (GS) Ser7 phosphorylation was higher in both muscles from dexamethasone-treated rats. GS expression decreased (by 50%) in adipocytes only. Basal and insulin-stimulated GS Ser641 and GS Ser645,649,653,657 phosphorylation was elevated in epitrochlearis and soleus muscles and GS fractional activity was reduced correspondingly. In conclusion, dexamethasone treatment (1) decreases PKB expression and insulin-stimulated phosphorylation in both muscles and adipocytes, and (2) increases GS phosphorylation (reduces GS fractional activity) in muscles and decreases GS expression in adipocytes. We suggest PKB and GS as major targets for dexamethasone-induced insulin resistance. 相似文献
12.
Farah T. van Genderen Frans K. Gorus Ilse Vermeulen Evilien M.F. Vekens Pieter E.M. De Pauw Daniel G. Pipeleers Chris Van Schravendijk 《Analytical biochemistry》2010,404(1):8-13
We present a time-resolved fluorescence immunoassay (TR-FIA) for the measurement of rat insulin in cell extracts and culture media. This assay is based on the binding of two monoclonal antibodies to different parts of the insulin molecule in a 96-well microtiter plate. For the detection, europium-labeled streptavidin that interacts with the second biotinylated antibody is used. Samples of 25 μl could be analyzed in less than 2 days with a measuring range between 5 and 1250 pg (0.2-50 μg/L or 34.4-8600 pM). The inter- and intraassay percentage coefficients of variation were less than 8.3 and 5.1, respectively. Recoveries of 0.48 to 40 μg/L rat insulin, added to culture medium, ranged between 94 and 107%. Results were significantly correlated with those of an in-house radioimmunoassay (RIA) for rodent insulin (P < 0.0001, r2 = 0.99). The TR-FIA method had a similar detection limit (0.16 μg/L), but its working range was at least 5-fold larger. Additional advantages include the lower cost, the applicability to measurements in tissue and serum, and the quantification of insulin from other species. 相似文献
13.
Christine M.A. Martin Nigel IrwinPeter R. Flatt Victor A. Gault 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Rapid enzymatic degradation of the incretin hormone, glucose-dependent insulinotropic polypeptide (GIP), limits therapeutic use of the native peptide for diabetes. However, enzymatically stable analogues of GIP, such as (d-Ala2)GIP, have been generated, but are still susceptible to renal filtration.Methods
The present study examines the in vitro and in vivo biological actions of a novel, acylated GIP analogue, (d-Ala2)GIP[Lys37PAL].Results
In BRIN-BD11 cells, (d-Ala2)GIP[Lys37PAL] concentration-dependently stimulated (p < 0.05 to p < 0.001) insulin secretion at 5.6 and 16.7 mM glucose. Intraperitoneal administration of (d-Ala2)GIP[Lys37PAL] to normal mice 8 h prior to a glucose load significantly reduced (p < 0.05) the overall glycaemic excursion compared to controls, and increased (p < 0.001) the insulinotropic response compared to (d-Ala2)GIP and saline treated high fat control mice. Once daily administration of (d-Ala2)GIP[Lys37PAL] for 21 days in high fat fed mice did not affect energy intake, body weight or fat deposition. However, circulating blood glucose was significantly lower (p < 0.05) accompanied by increased (p < 0.05) insulin concentrations by day 21. In addition, (d-Ala2)GIP[Lys37PAL] treatment significantly (p < 0.01) reduced the overall glycaemic excursion and increased pancreatic insulin content (p < 0.05) and the insulinotropic response (p < 0.01) to an exogenous glucose challenge on day 21. Chronic treatment with (d-Ala2)GIP[Lys37PAL] did not result in resistance to the metabolic effects of a bolus injection of native GIP. Finally, insulin sensitivity was significantly improved (p < 0.001) in (d-Ala2)GIP[Lys37PAL] treated mice compared to high fat controls.Conclusions
These data confirm that (d-Ala2)GIP[Lys37PAL] is a stable, long-acting potent GIP agonist.General significance
(d-Ala2)GIP[Lys37PAL] may be suitable for further evaluation and future clinical development. 相似文献14.
Aims
We evaluated the mechanisms involved in insulin-induced vasodilatation after acute resistance exercise in healthy rats.Main methods
Wistar rats were divided into 3 groups: control (CT), electrically stimulated (ES) and resistance exercise (RE). Immediately after acute RE (15 sets with 10 repetitions at 70% of maximal intensity), the animals were sacrificed and rings of mesenteric artery were mounted in an isometric system. After this, concentration–response curves to insulin were performed in control condition and in the presence of LY294002 (PI3K inhibitor), L-NAME (NOS inhibitor), L-NAME + TEA (K+ channels inhibitor), LY294002 + BQ123 (ET-A antagonist) or ouabain (Na+/K+ ATPase inhibitor).Key findings
Acute RE increased insulin-induced vasorelaxation as compared to control (CT: Rmax = 7.3 ± 0.4% and RE: Rmax = 15.8 ± 0.8%; p < 0.001). NOS inhibition reduced (p < 0.001) this vasorelaxation from both groups (CT: Rmax = 2.0 ± 0.3%, and RE: Rmax = − 1.2 ± 0.1%), while PI3K inhibition abolished the vasorelaxation in CT (Rmax = − 0.1 ± 0.3%, p < 0.001), and caused vasoconstriction in RE (Rmax = − 6.5 ± 0.6%). That insulin-induced vasoconstriction on PI3K inhibition was abolished (p < 0.001) by the ET-A antagonist (Rmax = 2.9 ± 0.4%). Additionally, acute RE enhanced (p < 0.001) the functional activity of the ouabain-sensitive Na+/K+ ATPase activity (Rmax = 10.7 ± 0.4%) and of the K+ channels (Rmax = − 6.1 ± 0.5%; p < 0.001) in the insulin-induced vasorelaxation as compared to CT.Significance
Such results suggest that acute RE promotes enhanced insulin-induced vasodilatation, which could act as a fine tuning to vascular tone. 相似文献15.
M.F.P. Silvestre B. Viollet P.W. Caton J. Leclerc I. Sakakibara M. Foretz M.C. Holness M.C. Sugden 《Life sciences》2014
Aims
SIRT1 and AMP-activated protein kinase (AMPK) share common activators, actions and target molecules. Previous studies have suggested that a putative SIRT1-AMPK regulatory network could act as the prime initial sensor for calorie restriction-induced adaptations in skeletal muscle—the major site of insulin-stimulated glucose disposal. Our study aimed to investigate whether a feedback loop exists between AMPK and SIRT1 in skeletal muscle and how this may be involved glucose tolerance.Main methods
To investigate this, we used skeletal muscle-specific AMPKα1/2 knockout mice (AMPKα1/2−/−) fed ad libitum (AL) or a 30% calorie restricted (CR) diet and L6 rat myoblasts incubated with SIRT1 inhibitor (EX527).Key findings
CR-AMPKα1/2−/− displayed impaired glucose tolerance (*p < 0.05), in association with down-regulated SIRT1 and PGC-1α expression (< 300% vs. CR-WT, ±±p < 0.01). Moreover, AMPK activity was decreased following SIRT1 inhibition in L6 cells (~ 0.5-fold vs. control, *p < 0.05).Significance
This study demonstrates that skeletal muscle-specific AMPK deficiency impairs the beneficial effects of CR on glucose tolerance and that these effects may be dependent on reduced SIRT1 levels. 相似文献16.
Cory M. Dungan David C. Wright David L. Williamson 《Biochemical and biophysical research communications》2014
A lack of the REDD1 promotes dysregulated growth signaling, though little has been established with respect to the metabolic role of REDD1. Therefore, the goal of this study was to determine the role of REDD1 on glucose and insulin tolerance, as well as insulin stimulated growth signaling pathway activation in skeletal muscle. First, intraperitoneal (IP) injection of glucose or insulin were administered to REDD1 wildtype (WT) versus knockout (KO) mice to examine changes in blood glucose over time. Next, alterations in skeletal muscle insulin (IRS-1, Akt, ERK 1/2) and growth (4E-BP1, S6K1, REDD1) signaling intermediates were determined before and after IP insulin treatment (10 min). REDD1 KO mice were both glucose and insulin intolerant when compared to WT mice, evident by higher circulating blood glucose concentrations and a greater area under the curve following IP injections of glucose or insulin. While the REDD1 KO exhibited significant though blunted insulin-stimulated increases (p < 0.05) in Akt S473 and T308 phosphorylation versus the WT mice, acute insulin treatment has no effect (p < 0.05) on REDD1 KO skeletal muscle 4E-BP1 T37/46, S6K1 T389, IRS-1 Y1222, and ERK 1/2 T202/Y204 phosphorylation versus the WT mice. Collectively, these novel data suggest that REDD1 has a more distinct role in whole body and skeletal muscle metabolism and insulin action than previously thought. 相似文献
17.
J.C. Souza E.C Vanzela R.A. Ribeiro L.F. Rezende C.A. de Oliveira E.M. Carneiro H.C.F. Oliveira A.C. Boschero 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2013,1831(4):769-775
Aims/hypothesis
Changes in cellular cholesterol level may contribute to beta cell dysfunction. Islets from low density lipoprotein receptor knockout (LDLR−/−) mice have higher cholesterol content and secrete less insulin than wild-type (WT) mice. Here, we investigated the association between cholesterol content, insulin secretion and Ca2 + handling in these islets.Methods
Isolated islets from both LDLR−/− and WT mice were used for measurements of insulin secretion (radioimmunoassay), cholesterol content (fluorimetric assay), cytosolic Ca2 + level (fura-2AM) and SNARE protein expression (VAMP-2, SNAP-25 and syntaxin-1A). Cholesterol was depleted by incubating the islets with increasing concentrations (0–10 mmol/l) of methyl-beta-cyclodextrin (MβCD).Results
The first and second phases of glucose-stimulated insulin secretion (GSIS) were lower in LDLR−/− than in WT islets, paralleled by an impairment of Ca2 + handling in the former. SNAP-25 and VAMP-2, but not syntaxin-1A, were reduced in LDLR−/− compared with WT islets. Removal of excess cholesterol from LDLR−/− islets normalized glucose- and tolbutamide-induced insulin release. Glucose-stimulated Ca2 + handling was also normalized in cholesterol-depleted LDLR−/− islets. Cholesterol removal from WT islets by 0.1 and 1.0 mmol/l MβCD impaired both GSIS and Ca2 + handling. In addition, at 10 mmol/l MβCD WT islet showed a loss of membrane integrity and higher DNA fragmentation.Conclusion
Abnormally high (LDLR−/− islets) or low cholesterol content (WT islets treated with MβCD) alters both GSIS and Ca2 + handling. Normalization of cholesterol improves Ca2 + handling and insulin secretion in LDLR−/− islets. 相似文献18.
Ognian C. Ikonomov 《Biochemical and biophysical research communications》2009,382(3):566-32114
Silencing of PIKfyve, the sole enzyme for PtdIns(3,5)P2 biosynthesis that controls proper endosome dynamics, inhibits retroviral replication. A novel PIKfyve-specific inhibitor YM201636 disrupts retroviral budding at 800 nM, suggesting its potential use as an antiretroviral therapeutic. Because PIKfyve is also required for optimal insulin activation of GLUT4 surface translocation and glucose influx, we tested the outcome of YM201636 application on insulin responsiveness in 3T3L1 adipocytes. YM201636 almost completely inhibited basal and insulin-activated 2-deoxyglucose uptake at doses as low as 160 nM, with IC50 = 54 ± 4 nM for the net insulin response. Insulin-induced GLUT4 translocation was partially inhibited at substantially higher doses, comparable to those required for inhibition of insulin-induced phosphorylation of Akt/PKB. In addition to PIKfyve, YM201636 also completely inhibited insulin-dependent activation of class IA PI 3-kinase. We suggest that apart from PIKfyve, there are at least two additional targets for YM201636 in the context of insulin signaling to GLUT4 and glucose uptake: the insulin-activated class IA PI 3-kinase and a here-unidentified high-affinity target responsible for the greater inhibition of glucose entry vs. GLUT4 translocation. The profound inhibition of the net insulin effect on glucose influx at YM201636 doses markedly lower than those required for efficient retroviral budding disruption warns of severe perturbations in glucose homeostasis associated with potential YM201636 use in antiretroviral therapy. 相似文献
19.
Maggie K. Diamond-Stanic Elizabeth M. Marchionne Mary K. Teachey David E. Durazo John S. Kim Erik J. Henriksen 《Biochemical and biophysical research communications》2011,(3):2645
Increased cellular exposure to oxidants may contribute to the development of insulin resistance and type 2 diabetes. Skeletal muscle is the primary site of insulin-dependent glucose disposal in the body; however, the effects of oxidative stress on insulin signaling and glucose transport activity in mammalian skeletal muscle are not well understood. We therefore studied the effects of a low-level in vitro oxidant stress (30–40 μM H2O2) on basal and insulin-stimulated (5 mU/ml) glucose transport activity and insulin signaling at 2, 4, and 6 h in isolated rat soleus muscle. H2O2 increased basal glucose transport activity at 2 and 4 h, but not at 6 h. This low-level oxidant stress significantly impaired insulin-stimulated glucose transport activity at all time points, and was associated with inhibition of insulin-stimulated phosphorylation of Akt Ser473 and GSK-3β Ser9. In the presence of insulin, H2O2 decreased total protein expression of IRS-1 at 6 h and IRS-2 at 4 and 6 h. Phosphorylation of p38 MAPK Thr180/Tyr182 was transiently increased by H2O2 in the presence and absence of insulin at 2 and 4 h, but not at 6 h. Selective inhibition of p38 MAPK with A304000 partially rescued the H2O2-induced reduction in insulin-stimulated glucose transport activity. These results indicate that direct in vitro exposure of isolated mammalian skeletal muscle to a low-level oxidant stress impairs distal insulin signaling and insulin-stimulated glucose transport activity, at least in part, due to a p38 MAPK-dependent mechanism. 相似文献
20.
Jacklyn N. Hellwege Nicholette D. Palmer Julie T. Ziegler Carl D. Langefeld Carlos Lorenzo Jill M. Norris Toshinari Takamura Donald W. Bowden 《Gene》2014