Mechanisms of insulin resistance by simvastatin in C2C12 myotubes and in mouse skeletal muscle

Circadian misalignment induces insulin resistance in both human and animal models, and skeletal muscle is the largest organ response to insulin. However, how circadian clock regulates muscle insulin sensitivity and the underlying molecular mechanisms are still largely unknown. Here we show circadian locomotor output cycles kaput (CLOCK) and brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein (BMAL)-1, two core circadian transcription factors, are down-regulated in insulin-resistant C2C12 myotubes and mouse skeletal muscle. Furthermore, insulin signaling is attenuated in the skeletal muscle of ClockΔ19/Δ19 mice, and knockdown of CLOCK or BMAL1 by small interfering RNAs induces insulin resistance in C2C12 myotubes. Consistently, ectopic expression of CLOCK and BMAL1 improves insulin sensitivity in C2C12 myotubes. Moreover, CLOCK and BMAL1 regulate the expression of sirtuin 1 (SIRT1), an important regulator of insulin sensitivity, in C2C12 myotubes and mouse skeletal muscle, and two E-box elements in Sirt1 promoter are responsible for its CLOCK- and BMAL1-dependent transcription in muscle cells. Further studies show that CLOCK and BMAL1 regulate muscle insulin sensitivity through SIRT1. In addition, we find that BMAL1 and SIRT1 are decreased in the muscle of mice maintained in constant darkness, and resveratrol supplementation activates SIRT1 and improves insulin sensitivity. All these data demonstrate that CLOCK and BMAL1 regulate muscle insulin sensitivity via SIRT1, and activation of SIRT1 might be a potential valuable strategy to attenuate muscle insulin resistance related to circadian misalignment.

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14-Deoxy-11,12-Didehydroandrographolide Ameliorates Glucose Intolerance Enhancing the LKB1/AMPKα/TBC1D1/GLUT4 Signaling Pathway and Inducing GLUT4 Expression in Myotubes and Skeletal Muscle of Obese Mice

The American Journal of Chinese Medicine ◽

10.1142/s0192415x21500695 ◽

2021 ◽

pp. 1-19

Author(s):

Chih-Chieh Chen ◽

Chong-Kuei Lii ◽

Chia-Wen Lo ◽

Yi-Hsueh Lin ◽

Ya-Chen Yang ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Glucose Uptake ◽

Signaling Pathway ◽

Nuclear Translocation ◽

Time Dependent ◽

Antidiabetic Activity ◽

C2c12 Myotubes ◽

Dependent Manner ◽

Compound C

14-Deoxy-11,12-didehydroandrographolide (deAND), a bioactive component of Andrographis paniculata, has antidiabetic activity. AMP-activated protein kinase (AMPK) regulates glucose transport and ameliorates insulin resistance. The aim of the present study was to investigate whether activation of AMPK is involved in the mechanism by which deAND ameliorates insulin resistance in muscles. deAND amounts up to 40 [Formula: see text]M dose-dependently activated phosphorylation of AMPK[Formula: see text] and TBC1D1 in C2C12 myotubes. In addition, deAND significantly activated phosphorylation of LKB1 at 6 h after treatment, and this activation was maintained up to 48 h. deAND increased glucose uptake at 18 h after treatment, and this increase was time dependent up to 72 h. Compound C, an inhibitor of AMPK, suppressed deAND-induced phosphorylation of AMPK[Formula: see text] and TBC1D1 and reversed the effect on glucose uptake. In addition, the expression of GLUT4 mRNA and protein in C2C12 myotubes was up-regulated by deAND in a time-dependent manner. Promotion of GLUT4 gene transcription was verified by a pGL3-GLUT4 (837 bp) reporter assay. deAND also increased the nuclear translocation of MEF-2A and PPAR[Formula: see text]. After 16 weeks of feeding, the high-fat diet (HFD) inhibited phosphorylation of AMPK[Formula: see text] and TBC1D1 in skeletal muscle of obese C57BL/6JNarl mice, and deactivation of AMPK[Formula: see text] and TBC1D1 by the HFD was abolished by deAND supplementation. Supplementation with deAND significantly promoted membrane translocation of GLUT4 compared with the HFD group. Supplementation also significantly increased GLUT4 mRNA and protein expression in skeletal muscle compared with the HFD group. The hypoglycemic effects of deAND are likely associated with activation of the LKB1/AMPK[Formula: see text]/TBC1D1/GLUT4 signaling pathway and stimulation of MEF-2A- and PPAR[Formula: see text]-dependent GLUT4 gene expression, which account for the glucose uptake into skeletal muscle and lower blood glucose levels.

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Hepatokine ERAP1 impairs skeletal muscle insulin sensitivity via ADRB2/PKA pathway

10.21203/rs.3.rs-37586/v1 ◽

2020 ◽

Author(s):

Feifan Guo ◽

Yuguo Niu ◽

Haizhou Jiang ◽

Hanrui Yin ◽

Fenfen Wang ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Sensitivity ◽

Neutralizing Antibodies ◽

Leptin Receptor ◽

Whole Body ◽

C2c12 Myotubes ◽

Insulin Resistant ◽

Skeletal Muscle Insulin Sensitivity ◽

Pka Pathway

Abstract The current study aimed to investigate the role of endoplasmic reticulum aminopeptidase 1 (ERAP1), a novel hepatokine, in whole-body glucose metabolism. Here, we found that hepatic ERAP1 levels were increased in insulin-resistant leptin-receptor-mutated (db/db) and high-fat diet (HFD)-fed mice. Consistently, hepatic ERAP1 overexpression attenuated skeletal muscle (SM) insulin sensitivity, whereas knockdown ameliorated SM insulin resistance. Furthermore, serum and hepatic ERAP1 levels were positively correlated, and recombinant mouse ERAP1 or conditioned medium with high ERAP1 content (CM-ERAP1) attenuated insulin signaling in C2C12 myotubes, and CM-ERAP1 or HFD-induced insulin resistance was blocked by ERAP1 neutralizing antibodies. Mechanistically, ERAP1 reduced ADRB2 expression and interrupted ADRB2-dependent signaling in C2C12 myotubes. Finally, ERAP1 inhibition via global knockout or the inhibitor thimerosal improved insulin sensitivity. Together, ERAP1 is a hepatokine that impairs SM and whole-body insulin sensitivity, and its inhibition might provide a therapeutic strategy for diabetes, particularly for those with SM insulin resistance.

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In vivo analysis of insulin signaling pathway in the mouse skeletal muscle, and influence of insulin resistance induced by TNF-α and glucosamine

Diabetes Research and Clinical Practice ◽

10.1016/s0168-8227(00)81987-7 ◽

2000 ◽

Vol 50 ◽

pp. 156

Author(s):

Motoyoshi Sakaue ◽

Takeshi Miki ◽

Masato Kasuga

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Signaling Pathway ◽

Insulin Signaling ◽

Insulin Signaling Pathway ◽

Mouse Skeletal Muscle ◽

Tnf Α ◽

In Vivo Analysis

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RNA-sequencing analysis reveals the potential contribution of lncRNAs in palmitic acid-induced insulin resistance of skeletal muscle cells

Bioscience Reports ◽

10.1042/bsr20192523 ◽

2020 ◽

Vol 40 (1) ◽

Cited By ~ 1

Author(s):

Mei Han ◽

Lianghui You ◽

Yanting Wu ◽

Nan Gu ◽

Yan Wang ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Palmitic Acid ◽

Signaling Pathway ◽

Rna Sequencing ◽

Metabolic Diseases ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

C2c12 Myotubes ◽

Insulin Resistant

Abstract Insulin resistance (IR) has been considered as the common pathological basis and developmental driving force for most metabolic diseases. Long noncoding RNAs (lncRNAs) have emerged as pivotal regulators in modulation of glucose and lipid metabolism. However, the comprehensive profile of lncRNAs in skeletal muscle cells under the insulin resistant status and the possible biological effects of them were not fully studied. In this research, using C2C12 myotubes as cell models in vitro, deep RNA-sequencing was performed to profile lncRNAs and mRNAs between palmitic acid-induced IR C2C12 myotubes and control ones. The results revealed that a total of 144 lncRNAs including 70 up-regulated and 74 down-regulated (|fold change| > 2, q < 0.05) were significantly differentially expressed in palmitic acid-induced insulin resistant cells. In addition, functional annotation analysis based on the Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) databases revealed that the target genes of the differentially expressed lncRNAs were significantly enriched in fatty acid oxidation, lipid oxidation, PPAR signaling pathway, and insulin signaling pathway. Moreover, Via qPCR, most of selected lncRNAs in myotubes and db/db mice skeletal muscle showed the consistent expression trends with RNA-sequencing. Co-expression analysis also explicated the key lncRNA–mRNA interactions and pointed out a potential regulatory network of candidate lncRNA ENSMUST00000160839. In conclusion, the present study extended the skeletal muscle lncRNA database and provided novel potential regulators for future genetic and molecular studies on insulin resistance, which is helpful for prevention and treatment of the related metabolic diseases.

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MBNL1-Associated Mitochondrial Dysfunction and Apoptosis in C2C12 Myotubes and Mouse Skeletal Muscle

International Journal of Molecular Sciences ◽

10.3390/ijms21176376 ◽

2020 ◽

Vol 21 (17) ◽

pp. 6376

Author(s):

Shingo Yokoyama ◽

Yoshitaka Ohno ◽

Tatsuro Egawa ◽

Kazuya Ohashi ◽

Rika Ito ◽

...

Keyword(s):

Skeletal Muscle ◽

Mitochondrial Dysfunction ◽

Physiological Role ◽

B Cell Lymphoma ◽

Expression Level ◽

C2c12 Myotubes ◽

Peroxisome Proliferator ◽

Plantaris Muscle ◽

Mouse Skeletal Muscle ◽

Old Mice

We explored the interrelationship between a tissue-specific alternative splicing factor muscleblind-like 1 (MBNL1) and peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC-1α), B-cell lymphoma 2 (Bcl-2) or Bcl-2-associated X protein (Bax) in C2C12 myotubes and mouse skeletal muscle to investigate a possible physiological role of MBNL1 in mitochondrial-associated apoptosis of skeletal muscle. Expression level of PGC-1α and mitochondrial membrane potential evaluated by the fluorescence ratio of JC-1 aggregate to monomer in C2C12 myotubes were suppressed by knockdown of MBNL1. Conversely, the ratio of Bax to Bcl-2 as well as the apoptotic index in C2C12 myotubes was increased by MBNL1 knockdown. In plantaris muscle, on the other hand, not only the minimum muscle fiber diameter but also the expression level of MBNL1 and PGC-1α in of 100-week-old mice were significantly lower than that of 10-week-old mice. Furthermore, the ratio of Bax to Bcl-2 in mouse plantaris muscle was increased by aging. These results suggest that MBNL1 may play a key role in aging-associated muscle atrophy accompanied with mitochondrial dysfunction and apoptosis via mediating PGC-1α expression in skeletal muscle.

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A Class I Histone Deacetylase Inhibitor Attenuates Insulin Resistance and Inflammation in Palmitate-Treated C2C12 Myotubes and Muscle of HF/HFr Diet Mice

Frontiers in Pharmacology ◽

10.3389/fphar.2020.601448 ◽

2020 ◽

Vol 11 ◽

Author(s):

Soo Jin Lee ◽

Sung-E Choi ◽

Han Byeol Lee ◽

Min-Woo Song ◽

Young Ha Kim ◽

...

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Histone Deacetylase ◽

Muscle Tissue ◽

Inflammatory Cytokine ◽

Skeletal Muscle Tissue ◽

Class I ◽

C2c12 Myotubes ◽

Peroxisome Proliferator ◽

Hdac Inhibition

Histone deacetylase (HDAC) inhibitors, which regulate gene expression by inhibiting the deacetylation of histones and nonhistone proteins, have been shown to exert a wide array of biological effects; these include anti-cancer, anti-obesity, and anti-diabetes effects, as well as cardiovascular-protective activity. However, the effects of class I HDAC inhibition on lipotoxicity in C2C12 myotubes and skeletal muscle tissue remain poorly understood. In this study, we investigated the molecular mechanism underlying the protective effect of class I HDAC inhibition under lipotoxic conditions, i.e., in palmitate (PA)-treated C2C12 myotubes and skeletal muscle tissue in high fat (HF)/high fructose (HFr) diet mice. PA treatment of C2C12 myotubes increased HDAC3 protein expression and impaired mitochondrial oxidation, resulting in increased mitochondrial ROS generation and an accumulation of intracellular triglycerides (TG). Prolonged exposure led to increased inflammatory cytokine expression and insulin resistance. In contrast, MS-275, a class I HDAC inhibitor, dramatically attenuated lipotoxicity, preventing PA-induced insulin resistance and inflammatory cytokine expression. Similar beneficial effects were also seen following HDAC3 knockdown. In addition, MS-275 increased the mRNA expression of peroxisome proliferator activator receptor γ-coactivator 1α (PGC1α) and mitochondrial transcription factor A (TFAM), which serve as transcriptional coactivators in the context of mitochondrial metabolism and biogenesis, and restored expression of peroxisome proliferator-activated receptor alpha (PPARα), medium-chain acyl-coenzyme A dehydrogenase (MCAD), enoyl-CoA hydratase, and 3-hydroxyacyl CoA dehydrogenase (EHHADH). In vivo, treatment of HF/HFr-fed mice with MS-275 ameliorated hyperglycemia, insulin resistance, stress signals, and TNF-α expression in skeletal muscle. Taken together, these results suggest that HDAC3 inhibition rather than HDAC1/2 inhibition by MS-275 protects against lipotoxicity in C2C12 myotubes and skeletal muscle, and may be effective for the treatment of obesity and insulin resistance.

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