Effects of hyperinsulinemia and hyperglycemia on insulin receptor function and glycogen synthase activation in skeletal muscle of normal man

Abstract. To examine subcellular mechanisms behind the pathogenesis of peripheral insulin resistance in chronic uremic patients, insulin receptor function and glycogen synthase activity were studied in biopsies of skeletal muscle obtained during renal transplant surgery in 9 non-diabetic uremic patients. The results were compared with values obtained in an age- and sex-matched group of subjects with normal renal function, undergoing surgery for urological or gynecological diseases. The recovery of solubilized, wheat germ agglutinin-purified insulin receptors from skeletal muscle was increased among the uremic patients: 49.3 ± 6.1 vs 31.4 ± 2.8 fmol/100 mg muscle in healthy controls (p < 0.03). Basal as well as insulin-stimulated kinase activities of the insulin receptors, expressed as phosphorylation of the synthetic peptide poly(Glu-Tyr(4:1)) were similar. In addition, the maximal activity of the glycogen synthase was enhanced in uremic muscle: 26.6 ± 2.8 vs 19.5 ± 1.8 nmol · (mg protein)−1 · min−1 (p < 0.05), whereas the half-maximal activation constant for glucose-6-phosphate was identical in the two groups. Likewise, the muscle glycogen concentrations were similar in the uremic patients and the normal controls. In conclusion, our data suggest that neither impaired insulin receptor function nor a reduced maximal glycogen synthase activity of skeletal muscle are involved in the pathogenesis of the insulin resistance of patients with chronic renal failure.

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The regulatory domain of protein kinase C delta positively regulates insulin receptor signaling

Journal of Molecular Endocrinology ◽

10.1677/jme-09-0119 ◽

2009 ◽

Vol 44 (3) ◽

pp. 155-169 ◽

Cited By ~ 9

Author(s):

Avraham I Jacob ◽

Miriam Horovitz-Fried ◽

Shlomit Aga-Mizrachi ◽

Tamar Brutman-Barazani ◽

Hana Okhrimenko ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Kinase C ◽

Protein Kinase ◽

Insulin Receptor ◽

Glycogen Synthase ◽

Regulatory Domain ◽

Protein Kinase C Delta ◽

Kinase C ◽

Regulatory Effects ◽

In Cells

Protein kinase C delta (PKCδ) is induced by insulin to rapidly associate with insulin receptor (IR) and upregulates insulin signaling. We utilized specific JM and CT receptor domains and chimeras of PKCα and PKCδ regulatory and catalytic domains to elucidate which components of PKCδ are responsible for positive regulatory effects of PKCδ on IR signaling. Studies were performed on L6 and L8 skeletal muscle myoblasts and myotubes. PKCδ was preferentially bound to the JM domain of IR, and insulin stimulation increased this binding. Both PKCδ/α and PKCα/δ chimeras (regulatory/catalytic) were bound preferentially to the JM but not to the CT domain of IR. Although IR–PKCδ binding was higher in cells expressing either the PKCδ/α or PKCα/δ chimera than in control cells, upregulation of IR signaling was observed only in PKCδ/α cells. Thus, in response to insulin increases in tyrosine phosphorylation of IR and insulin receptor substrate-1, downstream signaling to protein kinase B and glycogen synthase kinase 3 (GSK3) and glucose uptake were greater in cells overexpressing PKCδ/α and the PKCδ/δ domains than in cells expressing the PKCα/δ domains. Basal binding of Src to PKCδ was higher in both PKCδ/α- and PKCα/δ-expressing cells compared to control. Binding of Src to IR was decreased in PKCα/δ cells but remained elevated in the PKCδ/α cells in response to insulin. Finally, insulin increased Src activity in PKCδ/α-expressing cells but decreased it in PKCα/δ-expressing cells. Thus, the regulatory domain of PKCδ via interaction with Src appears to determine the role of PKCδ as a positive regulator of IR signaling in skeletal muscle.

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Insulin Receptor Function and Glycogen Synthase Activity in Skeletal Muscle Biopsies from Patients with Insulin-Dependent Diabetes Mellitus: Effects of Physical Training*

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jcem-69-1-158 ◽

1989 ◽

Vol 69 (1) ◽

pp. 158-164 ◽

Cited By ~ 34

Author(s):

JENS FRIIS BAK ◽

UFFE KJELDBERG JACOBSEN ◽

FRITZ SCHONAU JORGENSEN ◽

OLUF PEDERSEN

Keyword(s):

Diabetes Mellitus ◽

Skeletal Muscle ◽

Physical Training ◽

Glycogen Synthase ◽

Insulin Dependent Diabetes Mellitus ◽

Dependent Diabetes Mellitus ◽

Receptor Function ◽

Insulin Dependent ◽

Glycogen Synthase Activity ◽

Muscle Biopsies

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Caffeine modulates phosphorylation of insulin receptor substrate-1 and impairs insulin signal transduction in rat skeletal muscle

Journal of Applied Physiology ◽

10.1152/japplphysiol.00249.2011 ◽

2011 ◽

Vol 111 (6) ◽

pp. 1629-1636 ◽

Cited By ~ 24

Author(s):

Tatsuro Egawa ◽

Satoshi Tsuda ◽

Xiao Ma ◽

Taku Hamada ◽

Tatsuya Hayashi

Keyword(s):

Skeletal Muscle ◽

Insulin Receptor ◽

Insulin Signaling ◽

Kinase Inhibitor ◽

Glycogen Synthase ◽

Mammalian Target Of Rapamycin ◽

Insulin Receptor Substrate ◽

Dependent Manner ◽

Insulin Signal Transduction ◽

Physiological Dose

Caffeine decreases insulin sensitivity and insulin-stimulated glucose transport in skeletal muscle; however, the precise mechanism responsible for this deleterious effect is not understood fully. We investigated the effects of incubation with caffeine on insulin signaling in rat epitrochlearis muscle. Caffeine (≥1 mM, ≥15 min) suppressed insulin-stimulated insulin receptor substrate (IRS)-1 Tyr612 phosphorylation in a dose- and time-dependent manner. These responses were associated with inhibition of the insulin-stimulated phosphorylation of phosphatidylinositol 3-kinase (PI3K) Tyr458, Akt Ser473, and glycogen synthase kinase-3β Ser9 and with inhibition of insulin-stimulated 3- O-methyl-d-glucose (3MG) transport but not with inhibition of the phosphorylation of insulin receptor-β Tyr1158/62/63. Furthermore, caffeine enhanced phosphorylation of IRS-1 Ser307 and an IRS-1 Ser307 kinase, inhibitor-κB kinase (IKK)-α/β Ser176/180. Blockade of IKK/IRS-1 Ser307 by caffeic acid ameliorated the caffeine-induced downregulation of IRS-1 Tyr612 phosphorylation and 3MG transport. Caffeine also increased the phosphorylation of IRS-1 Ser789 and an IRS-1 Ser789 kinase, 5′-AMP-activated protein kinase (AMPK). However, inhibition of IRS-1 Ser789 and AMPK phosphorylation by dantrolene did not rescue the caffeine-induced downregulation of IRS-1 Tyr612 phosphorylation or 3MG transport. In addition, caffeine suppressed the phosphorylation of insulin-stimulated IRS-1 Ser636/639 and upstream kinases, including the mammalian target of rapamycin and p70S6 kinase. Intravenous injection of caffeine at a physiological dose (5 mg/kg) in rats inhibited the phosphorylation of insulin-stimulated IRS-1 Tyr612 and Akt Ser473 in epitrochlearis muscle. Our results indicate that caffeine inhibits insulin signaling partly through the IKK/IRS-1 Ser307 pathway, via a Ca2+- and AMPK-independent mechanism in skeletal muscle.

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Cellular depletion of atypical PKCλ is associated with enhanced insulin sensitivity and glucose uptake in L6 rat skeletal muscle cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00171.2010 ◽

2010 ◽

Vol 299 (3) ◽

pp. E402-E412 ◽

Cited By ~ 19

Author(s):

Clare Stretton ◽

Ashleigh Evans ◽

Harinder S. Hundal

Keyword(s):

Skeletal Muscle ◽

Protein Kinase ◽

Insulin Receptor ◽

Glucose Uptake ◽

Glucose Transport ◽

Insulin Signaling ◽

Glycogen Synthase ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Dominant Negative Mutant

Atypical protein kinase C (aPKC) isoforms (λ and ζ) have been implicated in the control of insulin-stimulated glucose uptake in adipose and skeletal muscle, but their precise role in this process remains unclear, especially in light of accumulating evidence showing that, in response to numerous stimuli, including insulin and lipids such as ceramide, activation of aPKCs acts to negatively regulate key insulin-signaling molecules, such as insulin receptor substrate-1 (IRS-1) and protein kinase B (PKB)/cAMP-dependent PKC (Akt). In this study, we have depleted PKCλ in L6 skeletal muscle cells using RNA interference and assessed the effect this has upon insulin action. Muscle cells did not express detectable amounts of PKCζ. Depletion of PKCλ (>95%) had no significant effect on the expression of proteins participating in insulin signaling [i.e., insulin receptor, IRS-1, phosphatidylinositol 3-kinase (PI 3-kinase), PKB, or phosphate and tensin homolog deleted on chromosome 10] or those involved in glucose transport [Akt substrate of 160 kDa, glucose transporter (GLUT)1, or GLUT4]. However, PKCλ-depleted muscle cells exhibited greater activation of PKB/Akt and phosphorylation of its downstream target glycogen synthase kinase 3, in the basal state and displayed greater responsiveness to submaximal doses of insulin with respect to p85-PI 3-kinase/IRS-1 association and PKB activation. The increase in basal and insulin-induced signaling resulted in an associated enhancement of basal and insulin-stimulated glucose transport, both of which were inhibited by the PI 3-kinase inhibitor wortmannin. Additionally, like RNAi-mediated depletion of PKCλ, overexpression of a dominant-negative mutant of PKCζ induced a similar insulin-sensitizing effect on PKB activation. Our findings indicate that aPKCs are likely to play an important role in restraining proximal insulin signaling events but appear dispensable with respect to insulin-stimulated glucose uptake in cultured L6 muscle cells.

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Functional Studies of Akt Isoform Specificity in Skeletal Muscle in Vivo; Maintained Insulin Sensitivity Despite Reduced Insulin Receptor Substrate-1 Expression

Molecular Endocrinology ◽

10.1210/me.2006-0154 ◽

2007 ◽

Vol 21 (1) ◽

pp. 215-228 ◽

Cited By ~ 70

Author(s):

Mark E. Cleasby ◽

Tracie A. Reinten ◽

Gregory J. Cooney ◽

David E. James ◽

Edward W. Kraegen

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Glucose Metabolism ◽

Insulin Receptor ◽

Glucose Uptake ◽

Glycogen Synthase ◽

Insulin Receptor Substrate ◽

Insulin Receptor Substrate 1 ◽

Short Hairpin

Abstract The phosphoinositide 3-kinase/Akt pathway is thought to be essential for normal insulin action and glucose metabolism in skeletal muscle and has been shown to be dysregulated in insulin resistance. However, the specific roles of and signaling pathways triggered by Akt isoforms have not been fully assessed in muscle in vivo. We overexpressed constitutively active (ca-) Akt-1 or Akt-2 constructs in muscle using in vivo electrotransfer and, after 1 wk, assessed the roles of each isoform on glucose metabolism and fiber growth. We achieved greater than 2.5-fold increases in total Ser473 phosphorylation in muscles expressing ca-Akt-1 and ca-Akt-2, respectively. Both isoforms caused hypertrophy of muscle fibers, consistent with increases in p70S6kinase phosphorylation, and a 60% increase in glycogen accumulation, although only Akt-1 increased glycogen synthase kinase-3β phosphorylation. Akt-2, but not Akt-1, increased basal glucose uptake (by 33%, P = 0.004) and incorporation into glycogen and lipids, suggesting a specific effect on glucose transport. Consistent with this, short hairpin RNA-mediated silencing of Akt-2 caused reductions in glycogen storage and glucose uptake. Consistent with Akt-mediated insulin receptor substrate 1 (IRS-1) degradation, we observed approximately 30% reductions in IRS-1 protein in muscle overexpressing ca-Akt-1 or ca-Akt-2. Despite this, we observed no decrease in insulin-stimulated glucose uptake. Furthermore, a 68% reduction in IRS-1 levels induced using short hairpin RNAs targeting IRS-1 also did not affect glucose disposal after a glucose load. These data indicate distinct roles for Akt-1 and Akt-2 in muscle glucose metabolism and that moderate reductions in IRS-1 expression do not result in the development of insulin resistance in skeletal muscle in vivo.

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Voluntary exercise training enhances glucose transport but not insulin signaling capacity in muscle of hypertensive TG(mREN2)27 rats

Journal of Applied Physiology ◽

10.1152/japplphysiol.00100.2005 ◽

2005 ◽

Vol 99 (1) ◽

pp. 357-362 ◽

Cited By ~ 5

Author(s):

Andrew M. Lemieux ◽

Cody J. Diehl ◽

Julie A. Sloniger ◽

Erik J. Henriksen

Keyword(s):

Skeletal Muscle ◽

Exercise Training ◽

Insulin Receptor ◽

Glucose Transport ◽

Insulin Signaling ◽

Glycogen Synthase ◽

Abdominal Fat ◽

Voluntary Exercise ◽

Phosphatidylinositol 3 Kinase ◽

Muscle Glucose Transport

Male heterozygous TG(mREN2)27 rats (TGR) overexpress a murine renin transgene, display marked hypertension, and have insulin resistance of skeletal muscle glucose transport and insulin signaling. We have shown previously that voluntary exercise training by TGR improves insulin-mediated skeletal muscle glucose transport (Kinnick TR, Youngblood EB, O’Keefe MP, Saengsirisuwan V, Teachey MK, and Henriksen EJ. J Appl Physiol 93: 805–812, 2002). The present study evaluated whether this training-induced enhancement of muscle glucose transport is associated with upregulation of critical insulin signaling elements, including insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3-kinase, Akt, and glycogen synthase kinase-3. TGR remained sedentary or ran spontaneously in activity wheels for 6 wk, averaging 7.1 ± 0.8 km/day by the end of week 3 and 4.3 ± 0.5 km/day over the final week of training. Exercise training reduced total abdominal fat by 20% ( P < 0.05) in TGR runners (2.64 ± 0.01% of body weight) compared with sedentary TGR controls (3.28 ± 0.01%). Insulin-stimulated (2 mU/ml) glucose transport activity in soleus muscle was 36% greater in TGR runners compared with sedentary TGR controls. However, the protein expression and functionality of tyrosine phosphorylation of insulin receptor and IRS-1, IRS-1 associated with the p85 regulatory subunit of phosphatidylinositol 3-kinase, and Ser473 phosphorylation of Akt were not altered by exercise training. Only insulin-stimulated glycogen synthase kinase-3β Ser9 phosphorylation was increased (22%) by exercise training. These results indicate that voluntary exercise training in TGR can enhance insulin-mediated glucose transport in skeletal muscle, as well as reduce total abdominal fat mass. However, this adaptive response in muscle occurs independently of modifications in the proximal elements of the insulin signaling cascade.

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Defective insulin signaling in skeletal muscle of the hypertensive TG(mREN2)27 rat

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00396.2004 ◽

2005 ◽

Vol 288 (6) ◽

pp. E1074-E1081 ◽

Cited By ~ 40

Author(s):

Julie A. Sloniger ◽

Vitoon Saengsirisuwan ◽

Cody J. Diehl ◽

Betsy B. Dokken ◽

Narissara Lailerd ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Angiotensin Ii ◽

Insulin Receptor ◽

Signaling Pathway ◽

Glucose Transport ◽

Insulin Signaling ◽

Glycogen Synthase ◽

Insulin Signaling Pathway ◽

Whole Body

Essential hypertension is frequently associated with insulin resistance of skeletal muscle glucose transport, with a potential role of angiotensin II in the pathogenesis of both conditions. The male heterozygous TG(mREN2)27 rat harbors the mouse transgene for renin, exhibits local elevations in angiotensin II, and is an excellent model of both hypertension and insulin resistance. The present study was designed to investigate the potential cellular mechanisms for insulin resistance in this hypertensive animal model, including an assessment of elements of the insulin-signaling pathway. Compared with nontransgenic, normotensive Sprague-Dawley control rats, male heterozygous TG(mREN2)27 rats displayed elevated ( P < 0.05) fasting plasma insulin (74%), an exaggerated insulin response (108%) during an oral glucose tolerance test, and reduced whole body insulin sensitivity. TG(mREN2)27 rats also exhibited decreased insulin-mediated glucose transport and glycogen synthase activation in both the type IIb epitrochlearis (30 and 46%) and type I soleus (22 and 64%) muscles. Importantly, there were significant reductions (∼30–50%) in insulin stimulation of tyrosine phosphorylation of the insulin receptor β-subunit and insulin receptor substrate-1 (IRS-1), IRS-1 associated with the p85 subunit of phosphatidylinositol 3-kinase, Akt Ser473 phosphorylation, and Ser9 phosphorylation of glycogen synthase kinase-3β in epitrochlearis and soleus muscles of TG(mREN2)27 rats. Soleus muscle triglyceride concentration was 25% greater in the transgenic group compared with nontransgenic animals. Collectively, these data provide the first evidence that the insulin resistance of the hypertensive male heterozygous TG(mREN2)27 rat can be attributed to specific defects in the insulin-signaling pathway in skeletal muscle.

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Effects of growth hormone on fuel utilization and muscle glycogen synthase activity in normal humans

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1991.260.5.e736 ◽

1991 ◽

Vol 260 (5) ◽

pp. E736-E742 ◽

Cited By ~ 11

Author(s):

J. F. Bak ◽

N. Moller ◽

O. Schmitz

Keyword(s):

Skeletal Muscle ◽

Growth Hormone ◽

Lipid Oxidation ◽

Insulin Receptor ◽

Kinase Activity ◽

Glycogen Synthase ◽

Random Order ◽

Glucose Disposal ◽

Energy Expenditures ◽

Muscle Biopsies

To examine the insulin antagonistic effects of growth hormone (GH), seven healthy subjects underwent, in random order, two 5-h euglycemic clamp studies with moderate hyperinsulinemia. A GH infusion (45 ng.kg-1.min-1) was given throughout one of the studies. GH inhibited the insulin-stimulated glucose disposal by 27% from 4.4 +/- 0.7 to 3.3 +/- 0.4 mg.kg-1.min-1 (P less than 0.02) and raised the nonprotein energy expenditures (NPEE) from 18.7 +/- 0.5 to 20.5 +/- 0.3 kcal.kg-1.24 h-1 (P less than 0.03). Lipid oxidation contributed 71.7 +/- 5.6% of NPEE during the GH infusion as compared with 48.7 +/- 5.2% during the control clamp (P less than 0.02). In skeletal muscle biopsies, insulin binding to wheat germ agglutinin-purified insulin receptors and insulin receptor kinase activity were unaffected by GH infusion. Glycogen synthase activation by insulin was inhibited by 41% during the GH clamp (fractional velocity 14.1 +/- 2.5 vs. 8.3 +/- 1.4%, P less than 0.03). In conclusion, GH 1) increases energy expenditures and inhibits glucose oxidation in favor of an increased lipid oxidation, and 2) inhibits insulin-mediated activation of the glycogen synthase in skeletal muscle biopsies by a mechanism distal to insulin receptor binding and kinase activity.

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