scholarly journals Impaired insulin-stimulated glucose transport in ATM-deficient mouse skeletal muscle

2013 ◽  
Vol 38 (6) ◽  
pp. 589-596 ◽  
Author(s):  
James Kain Ching ◽  
Larry D. Spears ◽  
Jennifer L. Armon ◽  
Allyson L. Renth ◽  
Stanley Andrisse ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Cell Types ◽  
Glucose Disposal ◽  
Wild Type ◽  
Phosphatidylinositol 3 Kinase ◽  
Ataxia Telangiectasia Mutated ◽  
Akt Phosphorylation ◽  
Atm Protein

There are reports that ataxia telangiectasia mutated (ATM) plays a role in insulin-stimulated Akt phosphorylation, although this is not the case in some cell types. Because Akt plays a key role in insulin signaling, which leads to glucose transport in skeletal muscle, the predominant tissue in insulin-stimulated glucose disposal, we examined whether insulin-stimulated Akt phosphorylation and (or) glucose transport would be decreased in skeletal muscle of mice lacking functional ATM, compared with muscle from wild-type mice. We found that in vitro insulin-stimulated Akt phosphorylation was normal in soleus muscle from mice with 1 nonfunctional allele of ATM (ATM+/−) and from mice with 2 nonfunctional alleles (ATM−/−). However, insulin did not stimulate glucose transport or the phosphorylation of AS160 in ATM−/− soleus. ATM protein level was markedly higher in wild-type extensor digitorum longus (EDL) than in wild-type soleus. In EDL from ATM−/− mice, insulin did not stimulate glucose transport. However, in contrast to findings for soleus, insulin-stimulated Akt phosphorylation was blunted in ATM−/− EDL, concomitant with a tendency for insulin-stimulated phosphatidylinositol 3-kinase activity to be decreased. Together, the findings suggest that ATM plays a role in insulin-stimulated glucose transport at the level of AS160 in muscle comprised of slow and fast oxidative-glycolytic fibers (soleus) and at the level of Akt in muscle containing fast glycolytic fibers (EDL).

scholarly journals Furosemide decreases the sensitivity of glucose transport to insulin in skeletal muscle in vitro

1998 ◽  
Vol 139 (1) ◽  
pp. 118-122 ◽  
Author(s):  
G Dimitriadis ◽  
B Leighton ◽  
M Parry-Billings ◽  
C Tountas ◽  
S Raptis ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Soleus Muscle ◽  
Transport Process ◽  
Glucose Utilization ◽  
Glucose Disposal ◽  
Rat Soleus Muscle ◽  
Lactate Formation

The effects of the diuretic furosemide on the sensitivity of glucose disposal to insulin were investigated in rat soleus muscle in vitro. At basal levels of insulin, the rates of 3-O-methylglucose transport, 2-deoxyglucose phosphorylation and lactate formation were not affected significantly by furosemide (0.5 mmol/l). However, furosemide significantly decreased these rates at physiological and maximal levels of insulin. The contents of 2-deoxyglucose and glucose 6-phosphate in the presence of furosemide were not significantly different from those in control muscles at all levels of insulin studied. It is concluded that furosemide decreases the sensitivity of glucose utilization to insulin in skeletal muscle by directly inhibiting the glucose transport process.

Elevated L-PGDS activity contributes to PMA-induced apoptosis concomitant with downregulation of PI3-K

2003 ◽  
Vol 284 (1) ◽  
pp. C119-C126 ◽  
Author(s):  
Louis Ragolia ◽  
Thomas Palaia ◽  
Enesa Paric ◽  
John K. Maesaka
Keyword(s):  
Protein Kinase ◽  
Phorbol Ester ◽  
Cell Types ◽  
Phosphatidylinositol 3 Kinase ◽  
Akt Phosphorylation ◽  
Enzymatic Activation ◽  
Induced Apoptosis ◽  
In Vitro Treatment

Recently we demonstrated the induction of apoptosis by the addition of recombinant lipocalin-type prostaglandin D2 synthase (L-PGDS) to the culture medium of LLC-PK1 cells. Because protein kinase C (PKC) has been shown to be involved in the apoptotic process of various cell types, we examined the potential role of L-PGDS in phorbol 12-myristate 13-acetate (PMA)-induced apoptosis. We report here the enzymatic activation and phosphorylation of L-PGDS in response to phorbol ester in cell culture and the direct phosphorylation of recombinant L-PGDS by PKC in vitro. Treatment of cells with PMA or L-PGDS decreased phosphatidylinositol 3-kinase (PI3-K) activity and concomitantly inhibited protein kinase B (PKB/Akt) phosphorylation, which led to the hypophosphorylation and activation of Bad. In addition, hypophosphorylation of retinoblastoma protein was also observed in response to L-PGDS-induced apoptosis. Cellular depletion of L-PGDS levels by using an antisense RNA strategy prevented PI3-K inactivation by phorbol ester and inhibited caspase-3 activation and apoptosis. We conclude that phorbol ester-induced apoptosis is mediated by L-PGDS phosphorylation and activation by PKC and is accompanied by inhibition of the PI3-K/PKB anti-apoptotic signaling pathways.

scholarly journals Rapid Reversal of Insulin-Stimulated AS160 Phosphorylation in Rat Skeletal Muscle after Insulin Exposure

2010 ◽  
pp. 71-78
Author(s):  
N Sharma ◽  
E B Arias ◽  
G D Cartee
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Time Course ◽  
Half Time ◽  
Rat Skeletal Muscle ◽  
Akt Phosphorylation ◽  
Rapid Reversal ◽  
Time Courses

Increased phosphorylation of Akt substrate of 160 kDa (AS160) is essential to trigger the full increase in insulin-stimulated glucose transport in skeletal muscle. The primary aim of this study was to characterize the time course for reversal of insulin-stimulated AS160 phosphorylation in rat skeletal muscle after insulin removal. The time courses for reversal of insulin effects both upstream (Akt phosphorylation) and downstream (glucose uptake) of AS160 were also determined. Epitrochlearis muscles were incubated in vitro using three protocols which differed with regard to insulin exposure: No Insulin (never exposed to insulin), Transient Insulin (30 min with 1.8 nmol/l insulin, then incubation without insulin for 10, 20 or 40 min), or Sustained Insulin (continuously incubated with 1.8 nmol/l insulin). After removal of muscles from insulin, Akt and AS160 phosphorylation reversed rapidly, each with a half-time of <10 min and essentially full reversal by 20 min. Glucose uptake reversed more slowly (half time between 10 and 20 min with essentially full reversal by 40 min). Removal of muscles from insulin resulted in a rapid reversal of the increase in AS160 phosphorylation which preceded the reversal of the increase in glucose uptake, consistent with AS160 phosphorylation being essential for maintenance of insulin-stimulated glucose uptake.

Calorie restriction increases the ratio of phosphatidylinositol 3-kinase catalytic to regulatory subunits in rat skeletal muscle

2005 ◽  
Vol 288 (5) ◽  
pp. E996-E1001 ◽  
Author(s):  
Carrie E. McCurdy ◽  
Robert T. Davidson ◽  
Gregory D. Cartee
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Calorie Restriction ◽  
Insulin Signaling ◽  
Serine Phosphorylation ◽  
Phosphatidylinositol 3 Kinase ◽  
Rat Skeletal Muscle ◽  
Regulatory Subunits ◽  
Akt Phosphorylation ◽  
Ad Libitum

Calorie restriction [CR; 60% of ad libitum (AL) intake] improves insulin-stimulated glucose transport, concomitant with enhanced phosphorylation of Akt. The mechanism(s) for the CR-induced increase in Akt phosphorylation of insulin-stimulated muscle is unknown. The purpose of this study was to determine whether CR increased the ratio of catalytic to regulatory subunits favoring enhanced phosphatidylinositol (PI) 3-kinase signaling, which may contribute to increases in Akt phosphorylation and glucose transport in insulin-stimulated muscles. We measured the PI 3-kinase regulatory (p85α/β, p50α, and p55α) and catalytic (p110) subunits abundance in skeletal muscle from male F344B/N rats after 8 wk of AL or CR treatment. In CR compared with AL muscles, regulatory isoforms, p50α and p55α abundance were ∼40% lower ( P < 0.01) with unchanged p85α/β levels. There was no diet-related change in catalytic subunit abundance. Despite lower IRS-1 levels (∼35%) for CR vs. AL, IRS-1-p110 association in insulin-stimulated muscles was significantly ( P < 0.05) enhanced by ∼50%. Downstream of PI 3-kinase, CR compared with AL significantly enhanced Akt serine phosphorylation by 1.5-fold higher ( P = 0.01) and 3- O-methylglucose transport by ∼20% in muscles incubated with insulin. The increased ratio of PI 3-kinase catalytic to regulatory subunits favors enhanced insulin signaling, which likely contributes to greater Akt phosphorylation and improved insulin sensitivity associated with CR in skeletal muscle.

Measuring GLUT4 translocation in mature muscle fibers

2010 ◽  
Vol 299 (2) ◽  
pp. E169-E179 ◽  
Author(s):  
Hans P. M. M. Lauritzen ◽  
Jonathan D. Schertzer
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Cell Biology ◽  
Glucose Transporter ◽  
Surface Membrane ◽  
Muscle Fibers ◽  
Postprandial Glucose ◽  
Glucose Disposal ◽  
Glut4 Translocation

Skeletal muscle is the major tissue for postprandial glucose disposal. Facilitated glucose uptake into muscle fibers is mediated by increases in surface membrane levels of the glucose transporter GLUT4 via insulin- and/or muscle contraction-mediated GLUT4 translocation. However, the regulatory mechanisms controlling GLUT4 translocation in skeletal muscle have been difficult to characterize at the cell biology level due to muscle tissue complexity. Muscle cell culture models have improved our understanding of GLUT4 translocation and glucose transport regulation, but in vitro muscle models lack many of the characteristics of mature muscle fibers. Thus, the molecular and cellular details of GLUT4 translocation in mature skeletal muscle are deficient. The objective of this review is to highlight how advances in recent experimental approaches translate into an enhanced understanding of the regulation of GLUT4 translocation and glucose transport in mature skeletal muscle.

scholarly journals Toll-Like Receptor 2 Controls the Gamma Interferon Response to Francisella tularensis by Mouse Liver Lymphocytes

2007 ◽  
Vol 75 (11) ◽  
pp. 5338-5345 ◽  
Author(s):  
Kee-Jong Hong ◽  
Jason R. Wickstrum ◽  
Hung-Wen Yeh ◽  
Michael J. Parmely
Keyword(s):  
Francisella Tularensis ◽  
Cell Types ◽  
Gamma Interferon ◽  
Interferon Response ◽  
Interleukin 12 ◽  
Toll Like Receptor ◽  
Wild Type ◽  
Ifn Γ ◽  
Deficient Mice

ABSTRACT The production of gamma interferon (IFN-γ) is a key step in the protective innate immune response to Francisella tularensis. Natural killer cells and T cells in the liver are important sources of this cytokine during primary F. tularensis infections, and interleukin-12 (IL-12) appears to be an essential coactivating cytokine for hepatic IFN-γ expression. The present study was undertaken to determine whether or not macrophages (Mφ) or dendritic cells (DC) provide coactivating signals for the liver IFN-γ response in vitro, whether IL-12 mediates these effects, and whether Toll-like receptor (TLR) signaling is essential to induce this costimulatory activity. Both bone marrow-derived Mφ and DC significantly augmented the IFN-γ response of F. tularensis-challenged liver lymphocytes in vitro. While both cell types produced IL-12p40 in response to F. tularensis challenge, only DC secreted large quantities of IL-12p70. DC from both IL-12p35-deficient and TLR2-deficient mice failed to produce IL-12p70 and did not costimulate liver lymphocytes for IFN-γ production in response to viable F. tularensis organisms. Conversely, liver lymphocytes from TLR2-deficient mice cocultured with wild-type accessory cells produced IFN-γ at levels comparable to those for wild-type hepatic lymphocytes. These findings indicate that TLR2 controls hepatic lymphocyte IFN-γ responses to F. tularensis by regulating DC IL-12 production. While Mφ also coinduced hepatic IFN-γ production in response to F. tularensis, they did so in a fashion less dependent on TLR2.

scholarly journals Absence of the Macrophage Mannose Receptor in Mice Does Not Increase Susceptibility to Pneumocystis carinii Infection In Vivo

2003 ◽  
Vol 71 (11) ◽  
pp. 6213-6221 ◽  
Author(s):  
Steve D. Swain ◽  
Sena J. Lee ◽  
Michel C. Nussenzweig ◽  
Allen G. Harmsen
Keyword(s):  
Pneumocystis Carinii ◽  
Hydrolytic Enzymes ◽  
Mannose Receptor ◽  
Opportunistic Pathogen ◽  
Cell Types ◽  
Surface Expression ◽  
Wild Type ◽  
Macrophage Mannose Receptor

ABSTRACT Host defense against the opportunistic pathogen Pneumocystis carinii requires functional interactions of many cell types. Alveolar macrophages are presumed to be a vital host cell in the clearance of P. carinii, and the mechanisms of this interaction have come under scrutiny. The macrophage mannose receptor is believed to play an important role as a receptor involved in the binding and phagocytosis of P. carinii. Although there is in vitro evidence for this interaction, the in vivo role of this receptor in P. carinii clearance in unclear. Using a mouse model in which the mannose receptor has been deleted, we found that the absence of this receptor is not sufficient to allow infection by P. carinii in otherwise immunocompetent mice. Furthermore, when mice were rendered susceptible to P. carinii by CD4+ depletion, mannose receptor knockout mice (MR-KO) had pathogen loads equal to those of wild-type mice. However, the MR-KO mice exhibited a greater influx of phagocytes into the alveoli during infection. This was accompanied by increased pulmonary pathology in the MR-KO mice, as well as greater accumulation of glycoproteins in the alveoli (glycoproteins, including harmful hydrolytic enzymes, are normally cleared by the mannose receptor). We also found that the surface expression of the mannose receptor is not downregulated during P. carinii infection in wild-type mice. Our findings suggest that while the macrophage mannose receptor may be important in the recognition of P. carinii, in vivo, this mechanism may be redundant, and the absence of this receptor may be compensated for.

Metabolic control analysis of insulin-stimulated glucose disposal in rat skeletal muscle

1999 ◽  
Vol 277 (3) ◽  
pp. E505-E512 ◽  
Author(s):  
Beat M. Jucker ◽  
Nicole Barucci ◽  
Gerald I. Shulman
Keyword(s):  
Skeletal Muscle ◽  
Metabolic Control ◽  
Glucose Transport ◽  
Distributed Control ◽  
Metabolic Flux ◽  
Glycogen Synthesis ◽  
Metabolic Control Analysis ◽  
Glucose Disposal ◽  
Control Analysis ◽  
Awake Rats

Metabolic control analysis was used to calculate the distributed control of insulin-stimulated skeletal muscle glucose disposal in awake rats. Three separate hyperinsulinemic infusion protocols were performed: 1) protocol I was a euglycemic (∼6 mM)-hyperinsulinemic (10 mU ⋅ kg−1 ⋅ min−1) clamp, 2) protocol II was a hyperglycemic (∼11 mM)-hyperinsulinemic (10 mU ⋅ kg−1 ⋅ min−1) clamp, and 3) protocol III was a euglycemic (∼6 mM)-hyperinsulinemic (10 mU ⋅ kg−1 ⋅ min−1)-lipid/heparin (increased plasma free fatty acid) clamp. [1-13C]glucose was administered in all three protocols for a 3-h period, during which time [1-13C]glucose label incorporation into [1-13C]glycogen, [3-13C]lactate, and [3-13C]alanine was detected in the hindlimb of awake rats via13C-NMR. Combined steady-state and kinetic data were used to calculate rates of glycogen synthesis and glycolysis. Additionally, glucose 6-phosphate (G-6- P) was measured in the hindlimb muscles with the use of in vivo31P-NMR during the three infusion protocols. The clamped glucose infusion rates were 31.6 ± 2.9, 49.7 ± 1.0, and 24.0 ± 1.5 mg ⋅ kg−1 ⋅ min−1at 120 min in protocols I– III, respectively. Rates of glycolysis were 62.1 ± 10.3, 71.6 ± 11.8, and 19.5 ± 3.6 nmol ⋅ g−1 ⋅ min−1and rates of glycogen synthesis were 125 ± 15, 224 ± 23, and 104 ± 17 nmol ⋅ g−1 ⋅ min−1in protocols I– III, respectively. Insulin-stimulated G-6- Pconcentrations were 217 ± 8, 265 ± 12, and 251 ± 9 nmol/g in protocols I– III, respectively. A top-down approach to metabolic control analysis was used to calculate the distributed control among glucose transport/phosphorylation [GLUT-4/hexokinase (HK)], glycogen synthesis, and glycolysis from the metabolic flux and G-6- P data. The calculated values for the control coefficients ( C) of these three metabolic steps ([Formula: see text]= 0.55 ± 0.10,[Formula: see text]= 0.30 ± 0.06, and[Formula: see text] = 0.15 ± 0.02; where J is glucose disposal flux, and glycogen syn is glycogen synthesis) indicate that there is shared control of glucose disposal and that glucose transport/phosphorylation is responsible for the majority of control of insulin-stimulated glucose disposal in skeletal muscle.

Selective in vitro reversal of the insulin resistance of glucose transport in denervated rat skeletal muscle

1989 ◽  
Vol 257 (3) ◽  
pp. E418-E425 ◽  
Author(s):  
M. O. Sowell ◽  
S. L. Dutton ◽  
M. G. Buse
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Insulin Receptor ◽  
Glucose Transport ◽  
Glycogen Synthesis ◽  
Insulin Response ◽  
Medium Composition ◽  
Insulin Resistant ◽  
Denervated Muscles

Denervation (24 h) of skeletal muscle causes severe postreceptor insulin resistance of glucose transport and glycogen synthesis that is demonstrable in isolated muscles after short (30 min) preincubations. After longer preincubations (2-4 h), the insulin response of glucose transport increased to normal, whereas glycogen synthesis remained insulin resistant. Basal and insulin-stimulated amino acid transport were significantly lower in denervated muscles than in controls after short or long incubations, although the percentage stimulation of transport by insulin was not significantly different. The development of glucose transport insulin resistance after denervation was not attributable to increased sensitivity to glucocorticoids or adenosine. The selective in vitro reversal of glucose transport insulin resistance was not dependent on medium composition, did not require protein or prostaglandin synthesis, and could not be attributed to release of a positive regulator into the medium. The data suggest 1) the insulin receptor in muscle stimulates glucose transport by a signaling pathway that is not shared by other insulin-sensitive effector systems, and 2) denervation may affect insulin receptor signal transduction at more than one site.

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