Calorie restriction prevents the development of insulin resistance and impaired insulin signaling in skeletal muscle of ovariectomized rats

The mammalian target of rapamycin (mTOR) pathway integrates insulin and nutrient signaling in numerous cell types. Recent studies also suggest that this pathway negatively modulates insulin signaling to phosphatidylinositol 3-kinase/Akt in adipose and muscle cells. However, it is still unclear whether activation of the mTOR pathway is increased in obesity and if it could be involved in the promotion of insulin resistance. In this paper we show that basal (fasting state) activation of mTOR and its downstream target S6K1 is markedly elevated in liver and skeletal muscle of obese rats fed a high fat diet compared with chow-fed, lean controls. Time-course studies also revealed that mTOR and S6K1 activation by insulin was accelerated in tissues of obese rats, in association with increased inhibitory phosphorylation of insulin receptor substrate-1 (IRS-1) on Ser636/Ser639 and impaired Akt activation. The relationship between mTOR/S6K1 overactivation and impaired insulin signaling to Akt was also examined in hepatic cells in vitro. Insulin caused a time-dependent activation of mTOR and S6K1 in HepG2 cells. This was associated with increased IRS-1 phosphorylation on Ser636/Ser639. Inhibition of mTOR/S6K1 by rapamycin blunted insulininduced Ser636/Ser639 phosphorylation of IRS-1, leading to a rapid (∼5 min) and persistent increase in IRS-1-associated phosphatidylinositol 3-kinase activity and Akt phosphorylation. These results show that activation of the mTOR pathway is increased in liver and muscle of high fat-fed obese rats. In vitro studies with rapamycin suggest that mTOR/S6K1 overactivation contributes to elevated serine phosphorylation of IRS-1, leading to impaired insulin signaling to Akt in liver and muscle of this dietary model of obesity.

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Mouse models of insulin resistance

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00561.2001 ◽

2002 ◽

Vol 282 (5) ◽

pp. E977-E981 ◽

Cited By ~ 40

Author(s):

Marta Letizia Hribal ◽

Francesco Oriente ◽

Domenico Accili

Keyword(s):

Insulin Resistance ◽

Type 2 Diabetes ◽

Skeletal Muscle ◽

Insulin Signaling ◽

Insulin Action ◽

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Impaired Insulin

The hallmarks of type 2 diabetes are impaired insulin action in peripheral tissues and decreased pancreatic β-cell function. Classically, the two defects have been viewed as separate entities, with insulin resistance arising primarily from impaired insulin-dependent glucose uptake in skeletal muscle, and β-cell dysfunction arising from impaired coupling of glucose sensing to insulin secretion. Targeted mutagenesis and transgenesis involving components of the insulin action pathway have changed our understanding of these phenomena. It appears that the role of insulin signaling in the pathogenesis of type 2 diabetes has been overestimated in classic insulin target tissues, such as skeletal muscle, whereas it has been overlooked in liver, pancreatic β-cells, and brain, which had been thought not to be primary insulin targets. We review recent progress and try to reconcile areas of apparent controversy surrounding insulin signaling in skeletal muscle and pancreatic β-cells.

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MG53 is not a critical regulator of insulin signaling pathway in skeletal muscle

10.1101/2020.12.24.424288 ◽

2020 ◽

Author(s):

Clothilde Philouze ◽

Sophie Turban ◽

Béatrice Cremers ◽

Audrey Caliez ◽

Gwladys Lamarche ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Receptor ◽

Signaling Pathway ◽

Insulin Signaling ◽

Insulin Response ◽

Muscle Cells ◽

Insulin Signaling Pathway ◽

Akt Phosphorylation ◽

Impaired Insulin

AbstractIn type 2 diabetes (T2D), both muscle and liver are severely resistant to insulin action. Muscle insulin resistance accounts for more than 80% of the impairment in total body glucose disposal in T2D patients and is often characterized by an impaired insulin signaling. Mitsugumin 53 (MG53), a muscle-specific TRIM family protein initially identified as a key regulator of cell membrane repair machinery has been suggested to be a critical regulator of muscle insulin signaling pathway by acting as ubiquitin E3 ligase targeting both the insulin receptor and insulin receptor substrate 1 (IRS1). Here, we show using in vitro and in vivo approaches that MG53 is not a critical regulator of insulin signaling and glucose homeostasis. First, MG53 expression is not consistently regulated in skeletal muscle from various preclinical models of insulin resistance. Second, MG53 gene knock-down in muscle cells does not lead to impaired insulin response as measured by Akt phosphorylation on Serine 473 and glucose uptake. Third, recombinant human MG53 does not alter insulin response in both differentiated C2C12 and human skeletal muscle cells. Fourth, ectopic expression of MG53 in HEK293 cells lacking endogenous MG53 expression fails to alter insulin response as measured by Akt phosphorylation. Finally, both male and female mg53 −/− mice were not resistant to high fat induced obesity and glucose intolerance compared to wild-type mice. Taken together, these results strongly suggest that MG53 is not a critical regulator of insulin signaling pathway in skeletal muscle.

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MG53 is not a critical regulator of insulin signaling pathway in skeletal muscle

PLoS ONE ◽

10.1371/journal.pone.0245179 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0245179

Author(s):

Clothilde Philouze ◽

Sophie Turban ◽

Beatrice Cremers ◽

Audrey Caliez ◽

Gwladys Lamarche ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Receptor ◽

Signaling Pathway ◽

Insulin Signaling ◽

Insulin Response ◽

Muscle Cells ◽

Insulin Signaling Pathway ◽

Akt Phosphorylation ◽

Impaired Insulin

In type 2 diabetes (T2D), both muscle and liver are severely resistant to insulin action. Muscle insulin resistance accounts for more than 80% of the impairment in total body glucose disposal in T2D patients and is often characterized by an impaired insulin signaling. Mitsugumin 53 (MG53), a muscle-specific TRIM family protein initially identified as a key regulator of cell membrane repair machinery has been suggested to be a critical regulator of muscle insulin signaling pathway by acting as ubiquitin E3 ligase targeting both the insulin receptor and insulin receptor substrate 1 (IRS1). Here, we show using in vitro and in vivo approaches that MG53 is not a critical regulator of insulin signaling and glucose homeostasis. First, MG53 expression is not consistently regulated in skeletal muscle from various preclinical models of insulin resistance. Second, MG53 gene knock-down in muscle cells does not lead to impaired insulin response as measured by Akt phosphorylation on Serine 473 and glucose uptake. Third, recombinant human MG53 does not alter insulin response in both differentiated C2C12 and human skeletal muscle cells. Fourth, ectopic expression of MG53 in HEK293 cells lacking endogenous MG53 expression fails to alter insulin response as measured by Akt phosphorylation. Finally, both male and female mg53 -/- mice were not resistant to high fat induced obesity and glucose intolerance compared to wild-type mice. Taken together, these results strongly suggest that MG53 is not a critical regulator of insulin signaling pathway in skeletal muscle.

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TNF-α impairs insulin signaling and insulin stimulation of glucose uptake in C2C12muscle cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1999.276.5.e849 ◽

1999 ◽

Vol 276 (5) ◽

pp. E849-E855 ◽

Cited By ~ 47

Author(s):

Luis F. del Aguila ◽

Kevin P. Claffey ◽

John P. Kirwan

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Glucose Uptake ◽

Tyrosine Phosphorylation ◽

Insulin Signaling ◽

Insulin Stimulation ◽

Kinase Activation ◽

Tnf Α ◽

Impaired Insulin ◽

Stimulation Of

Physiological stressors such as sepsis and tissue damage initiate an acute immune response and cause transient systemic insulin resistance. This study was conducted to determine whether tumor necrosis factor-α (TNF-α), a cytokine produced by immune cells during skeletal muscle damage, decreases insulin responsiveness at the cellular level. To examine the molecular mechanisms associated with TNF-α and insulin action, we measured insulin receptor substrate (IRS)-1- and IRS-2-mediated phosphatidylinositol 3-kinase (PI 3-kinase) activation, IRS-1-PI 3-kinase binding, IRS-1 tyrosine phosphorylation, and the phosphorylation of two mitogen-activated protein kinases (MAPK, known as p42MAPK and p44MAPK) in cultured C2C12myotubes. Furthermore, we determined the effects of TNF-α on insulin-stimulated 2-deoxyglucose (2-DG) uptake. We observed that TNF-α impaired insulin stimulation of IRS-1- and IRS-2-mediated PI 3-kinase activation by 54 and 55% ( P< 0.05), respectively. In addition, TNF-α decreased insulin-stimulated IRS-1 tyrosine phosphorylation by 40% ( P < 0.05). Furthermore, TNF-α repressed insulin-induced p42MAPKand p44MAPK tyrosine phosphorylation by 81% ( P < 0.01). TNF-α impairment of insulin signaling activation was accompanied by a decrease ( P < 0.05) in 2-DG uptake in the muscle cells (60 ± 4 vs. 44 ± 6 pmol ⋅ min−1 ⋅ mg−1). These data suggest that increases in TNF-α may cause insulin resistance in skeletal muscle by inhibiting IRS-1- and IRS-2-mediated PI 3-kinase activation as well as p42MAPK and p44MAPK tyrosine phosphorylation, leading to impaired insulin-stimulated glucose uptake.

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Protection from Palmitate-Induced Mitochondrial DNA Damage Prevents from Mitochondrial Oxidative Stress, Mitochondrial Dysfunction, Apoptosis, and Impaired Insulin Signaling in Rat L6 Skeletal Muscle Cells

Endocrinology ◽

10.1210/en.2011-1442 ◽

2012 ◽

Vol 153 (1) ◽

pp. 92-100 ◽

Cited By ~ 49

Author(s):

Larysa V. Yuzefovych ◽

Viktoriya A. Solodushko ◽

Glenn L. Wilson ◽

Lyudmila I. Rachek

Keyword(s):

Oxidative Stress ◽

Insulin Resistance ◽

Skeletal Muscle ◽

Dna Repair ◽

Mitochondrial Dna ◽

Mitochondrial Dysfunction ◽

Insulin Signaling ◽

Mtdna Damage ◽

L6 Myotubes ◽

Impaired Insulin

Saturated free fatty acids have been implicated in the increase of oxidative stress, mitochondrial dysfunction, apoptosis, and insulin resistance seen in type 2 diabetes. The purpose of this study was to determine whether palmitate-induced mitochondrial DNA (mtDNA) damage contributed to increased oxidative stress, mitochondrial dysfunction, apoptosis, impaired insulin signaling, and reduced glucose uptake in skeletal muscle cells. Adenoviral vectors were used to deliver the DNA repair enzyme human 8-oxoguanine DNA glycosylase/(apurinic/apyrimidinic) lyase (hOGG1) to mitochondria in L6 myotubes. After palmitate exposure, we evaluated mtDNA damage, mitochondrial function, production of mitochondrial reactive oxygen species, apoptosis, insulin signaling pathways, and glucose uptake. Protection of mtDNA from palmitate-induced damage by overexpression of hOGG1 targeted to mitochondria significantly diminished palmitate-induced mitochondrial superoxide production, restored the decline in ATP levels, reduced activation of c-Jun N-terminal kinase (JNK) kinase, prevented cells from entering apoptosis, increased insulin-stimulated phosphorylation of serine-threonine kinase (Akt) (Ser473) and tyrosine phosphorylation of insulin receptor substrate-1, and thereby enhanced glucose transporter 4 translocation to plasma membrane, and restored insulin signaling. Addition of a specific inhibitor of JNK mimicked the effect of mitochondrial overexpression of hOGG1 and partially restored insulin sensitivity, thus confirming the involvement of mtDNA damage and subsequent increase of oxidative stress and JNK activation in insulin signaling in L6 myotubes. Our results are the first to report that mtDNA damage is the proximal cause in palmitate-induced mitochondrial dysfunction and impaired insulin signaling and provide strong evidence that targeting DNA repair enzymes into mitochondria in skeletal muscles could be a potential therapeutic treatment for insulin resistance.

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Age and tissue specific differences in the development of acute insulin resistance following injury

Journal of Endocrinology ◽

10.1677/joe-09-0269 ◽

2009 ◽

Vol 203 (3) ◽

pp. 365-374 ◽

Cited By ~ 10

Author(s):

Lidong Zhai ◽

Joseph L Messina

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Signaling ◽

Intracellular Signaling ◽

Male Rats ◽

Hepatic Insulin Resistance ◽

Surgical Trauma ◽

Induce Insulin Resistance ◽

Old Rats ◽

Effect Of Age

Injuries, hemorrhage, sepsis, burn, and critical illnesses all induce insulin resistance, and insulin resistance is strongly associated with advancing age. However, the effect of age on injury induced insulin resistance is not well studied. We performed surgical trauma in male rats of three different ages (3-, 6-, and 10-weeks old). Rats were either hemorrhaged to a mean arterial pressure of 35–40 mmHg and subsequently maintained at that pressure for up to 90 min, or maintained without hemorrhage as controls. Results indicate that insulin-induced intracellular signaling was diminished in liver and skeletal muscle of 6- and 10-week old rats following trauma and hemorrhage. In even younger rats, immediately post-weaning (∼3 weeks of age), insulin signaling was lost in liver, but not in skeletal muscle. Glucocorticoids can play a role in the chronic development of insulin resistance. Our results demonstrate that corticosterone levels were increased in 6- and 10-week old animals following hemorrhage, but little change was measured in 3-week old animals. Blockade of glucocorticoid synthesis prevented the development of insulin resistance in skeletal muscle, but not in liver of 6- and 10-week old rats. Moreover, skeletal muscle glucocorticoid receptor levels increased dramatically between 3 and 6 weeks of age. These results indicate that trauma and hemorrhage-induced hepatic insulin resistance occurs at all ages tested. However, there is no development of insulin resistance following trauma and hemorrhage in skeletal muscle of post-weaning rats. In skeletal muscle of 6- and 10-week old rats, inhibition of glucocorticoid levels prevents the development of insulin resistance.

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