Nitric Oxide Increases Insulin Sensitivity in Skeletal Muscle by Improving Mitochondrial Function and Insulin Signaling

Introduction/Aim: Circadian rhythm disruption is emerging as a risk factor for metabolic disorders and particularly, alterations in clock genes circadian expression have been shown to influence insulin sensitivity. Recently, the reciprocal interplay between the circadian clock machinery and HPA axis has been largely demonstrated: the circadian clock may control the physiological circadian endogenous glucocorticoids secretion and action; glucocorticoids, in turn, are potent regulator of the circadian clock and their inappropriate replacement has been associated with metabolic impairment. The aim of the current study was to investigate in vitro the interaction between the timing-of-the-day exposure to different hydrocortisone (HC) concentrations on muscle insulin sensitivity. Methods: Serum-shock synchronized mouse skeletal muscle C2C12 cells were exposed to different HC concentrations recapitulating the circulating daily physiological cortisol profile (standard cortisol profile), the circulating daily cortisol profile that reached in adrenal insufficient (AI) patients treated with once-daily MR-HC (flat cortisol profile) and treated with thrice-daily of conventional IR-HC (steep cortisol profile). The 24 hrs spontaneous oscillation of the clock genes in synchronized C2C12 cells was used to align the timing for in vitro HC exposure (Bmal1 acrophase, midphase and bathyphase) with the reference times of cortisol peaks in AI treated with IR-HC (8 am, 1 pm, 6 pm). A panel of 84 insulin sensitivity related genes and intracellular insulin signaling proteins were analyzed by RT-qPCR and western blot, respectively. Results: Only the steep profile, characterized by a higher HC exposure during Bmal1 bathyphase, produced significant downregulation in 21 insulin sensitivity-related genes. Among these, Insr, Irs1, Irs2, Pi3kca and Adipor2 were downregulated when compared the flat to the standard or steep profile. Reduced intracellular IRS1 Tyr608, AKT Ser473, AMPK Thr172 and ACC Ser79 phosphorylations were also observed. Conclusions: The current study demonstrated that is late-in-the-day cortisol exposure that modulates insulin sensitivity-related genes expression and intracellular insulin signaling in skeletal muscle cells.

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Nicotinamide riboside supplementation alters body composition and skeletal muscle acetylcarnitine concentrations in healthy obese humans

American Journal of Clinical Nutrition ◽

10.1093/ajcn/nqaa072 ◽

2020 ◽

Vol 112 (2) ◽

pp. 413-426 ◽

Cited By ~ 7

Author(s):

Carlijn M E Remie ◽

Kay H M Roumans ◽

Michiel P B Moonen ◽

Niels J Connell ◽

Bas Havekes ◽

...

Keyword(s):

Skeletal Muscle ◽

Body Composition ◽

Insulin Sensitivity ◽

Energy Metabolism ◽

Mitochondrial Function ◽

Dry Weight ◽

Metabolic Health ◽

Men And Women ◽

Nicotinamide Riboside ◽

Wet Weight

ABSTRACT Background Nicotinamide riboside (NR) is an NAD+ precursor that boosts cellular NAD+ concentrations. Preclinical studies have shown profound metabolic health effects after NR supplementation. Objectives We aimed to investigate the effects of 6 wk NR supplementation on insulin sensitivity, mitochondrial function, and other metabolic health parameters in overweight and obese volunteers. Methods A randomized, double-blinded, placebo-controlled, crossover intervention study was conducted in 13 healthy overweight or obese men and women. Participants received 6 wk NR (1000 mg/d) and placebo supplementation, followed by broad metabolic phenotyping, including hyperinsulinemic-euglycemic clamps, magnetic resonance spectroscopy, muscle biopsies, and assessment of ex vivo mitochondrial function and in vivo energy metabolism. Results Markers of increased NAD+ synthesis—nicotinic acid adenine dinucleotide and methyl nicotinamide—were elevated in skeletal muscle after NR compared with placebo. NR increased body fat-free mass (62.65% ± 2.49% compared with 61.32% ± 2.58% in NR and placebo, respectively; change: 1.34% ± 0.50%, P = 0.02) and increased sleeping metabolic rate. Interestingly, acetylcarnitine concentrations in skeletal muscle were increased upon NR (4558 ± 749 compared with 3025 ± 316 pmol/mg dry weight in NR and placebo, respectively; change: 1533 ± 683 pmol/mg dry weight, P = 0.04) and the capacity to form acetylcarnitine upon exercise was higher in NR than in placebo (2.99 ± 0.30 compared with 2.40 ± 0.33 mmol/kg wet weight; change: 0.53 ± 0.21 mmol/kg wet weight, P = 0.01). However, no effects of NR were found on insulin sensitivity, mitochondrial function, hepatic and intramyocellular lipid accumulation, cardiac energy status, cardiac ejection fraction, ambulatory blood pressure, plasma markers of inflammation, or energy metabolism. Conclusions NR supplementation of 1000 mg/d for 6 wk in healthy overweight or obese men and women increased skeletal muscle NAD+ metabolites, affected skeletal muscle acetylcarnitine metabolism, and induced minor changes in body composition and sleeping metabolic rate. However, no other metabolic health effects were observed. This trial was registered at clinicaltrials.gov as NCT02835664

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Eicosapentaenoic Acid-Induced Inhibition of Metabolic Inflammation Is Associated with Preserved Mitochondrial Function and Insulin Sensitivity in Human Primary Myotubes

Current Developments in Nutrition ◽

10.1093/cdn/nzaa045_104 ◽

2020 ◽

Vol 4 (Supplement_2) ◽

pp. 471-471

Author(s):

Domenico Sergi ◽

Natalie Luscombe-Marsh ◽

Leonie Kaye Heilbronn ◽

Mark Birch-Machin ◽

Christopher Proud ◽

...

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Eicosapentaenoic Acid ◽

Mitochondrial Function ◽

Core Protein ◽

Mitochondrial Dynamics ◽

Complex Iii ◽

Nuclear Factor ◽

Metabolic Inflammation ◽

Nuclear Factor Kappa

Abstract Objectives The aim of this study was to investigate whether metabolic inflammation in skeletal muscle may be prevented by eicosapentaenoic acid (EPA) and if this is associated with an improvement in markers of mitochondrial function and insulin sensitivity. Methods Human primary myotubes were treated for 24 hours with palmitic acid (PA, 500 µM) in hyperglycaemic conditions (13 mM glucose), referred to as nutrient overload, in the presence or absence of EPA (100 µM). After the treatments, the expression of peroxisome proliferator-activated receptor-γ coactivator 1-alpha (PGC1α) and interleukin-6 (IL-6) was assessed by q-PCR. Western blot was used to asses the abundance of the inhibitor of nuclear factor kappa-B (IKBα), mitochondrial electron transport chain complex proteins, the phosphorylation of AKT (Ser473) and AKT substrate 160 (AS 160) (Thr642) in response to insulin, the activation of 5'-AMP-activated protein kinase (AMPK) and the inhibition of acetyl-CoA carboxylase (ACC). Mitochondrial dynamics was assessed by immunocytochemistry. Results Nutrient excess activated the proinflammatory nuclear factor kappa-light-chain-enhancer of activated B cells (NFkB) signalling as indicated by the upregulation of IL-6 mRNA (P < 0.001) and a tendency to decrease in IKBα (P = 0.0654), tended to downregulate PGC1α (P = 0.0589) and promoted mitochondrial fragmentation (P < 0.001), all of which were counteracted by EPA. Furthermore, EPA induced complex III-core protein 2 (P < 0.05) relative to control cells, an effect that was absent in the myotubes exposed only to PA and hyperglycaemia. EPA, when administrated in combination with PA and hyperglycaemia, induced the phosphorylation of AMPK (P < 0.05) and its downstream target ACC (P < 0.05) relative to cells exposed to nutrient overload alone. Finally, while fuel surplus impaired insulin-induced phosphorylation of AKT (P < 0.01) and AS160 (P < 0.05), these effects were prevented by EPA. Conclusions EPA inhibited NFkB signalling which was associated with an attenuation of the deleterious effects of PA and hyperglycaemia on markers of mitochondrial function and insulin sensitivity. Thus, EPA may represent a valuable nutritional tool to preserve skeletal muscle mitochondrial function and metabolic health during periods of nutrient overload. Funding Sources CSIRO's Precision Health Future Science Platform (FSP).

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Changes in dietary sodium consumption modulate GLUT4 gene expression and early steps of insulin signaling

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00396.2003 ◽

2004 ◽

Vol 286 (4) ◽

pp. R779-R785 ◽

Cited By ~ 15

Author(s):

Maristela Mitiko Okamoto ◽

Dóris Hissako Sumida ◽

Carla Roberta Oliveira Carvalho ◽

Alessandra Martins Vargas ◽

Joel Cláudio Heimann ◽

...

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Adipose Tissue ◽

Insulin Sensitivity ◽

Insulin Receptor ◽

Tyrosine Phosphorylation ◽

Insulin Signaling ◽

Dietary Sodium ◽

Glut4 Translocation ◽

Glut4 Gene Expression

Previous studies have shown that chronic salt overload increases insulin sensitivity, while chronic salt restriction decreases it. In the present study we investigated the influence of dietary sodium on 1) GLUT4 gene expression, by Northern and Western blotting analysis; 2) in vivo GLUT4 protein translocation, by measuring the GLUT4 protein in plasma membrane and microsome, before and after insulin injection; and 3) insulin signaling, by analyzing basal and insulin-stimulated tyrosine phosphorylation of insulin receptor (IR)-β, insulin receptor substrate (IRS)-1, and IRS-2. Wistar rats were fed normal-sodium (NS-0.5%), low-sodium (LS-0.06%), or high-sodium diets (HS-3.12%) for 9 wk and were killed under pentobarbital anesthesia. Compared with NS rats, HS rats increased ( P < 0.05) the GLUT4 protein in adipose tissue and skeletal muscle, whereas GLUT4 mRNA was increased only in adipose tissue. GLUT4 expression was unchanged in LS rats compared with NS rats. The GLUT4 translocation in HS rats was higher ( P < 0.05) both in basal and insulin-stimulated conditions. On the other hand, LS rats did not increase the GLUT4 translocation after insulin stimulus. Compared with NS rats, LS rats showed reduced ( P < 0.01) basal and insulin-stimulated tyrosine phosphorylation of IRS-1 in skeletal muscle and IRS-2 in liver, whereas HS rats showed enhanced basal tyrosine phosphorylation of IRS-1 in skeletal muscle ( P < 0.05) and of IRS-2 in liver. In summary, increased insulin sensitivity in HS rats is related to increased GLUT4 gene expression, enhanced insulin signaling, and GLUT4 translocation, whereas decreased insulin sensitivity of LS rats does not involve changes in GLUT4 gene expression but is related to impaired insulin signaling.

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Placental Restriction Reduces Insulin Sensitivity and Expression of Insulin Signaling and Glucose Transporter Genes in Skeletal Muscle, But Not Liver, in Young Sheep

Endocrinology ◽

10.1210/en.2011-1955 ◽

2012 ◽

Vol 153 (5) ◽

pp. 2142-2151 ◽

Cited By ~ 34

Author(s):

Miles J. De Blasio ◽

Kathryn L. Gatford ◽

M. Lyn Harland ◽

Jeffrey S. Robinson ◽

Julie A. Owens

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Sensitivity ◽

Insulin Signaling ◽

Glucose Transporter ◽

Postnatal Growth ◽

Whole Body ◽

Poor Growth ◽

Hepatic Expression ◽

Metabolic Genes

Poor growth before birth is associated with impaired insulin sensitivity later in life, increasing the risk of type 2 diabetes. The tissue sites at which insulin resistance first develops after intrauterine growth restriction (IUGR), and its molecular basis, are unclear. We have therefore characterized the effects of placental restriction (PR), a major cause of IUGR, on whole-body insulin sensitivity and expression of molecular determinants of insulin signaling and glucose uptake in skeletal muscle and liver of young lambs. Whole-body insulin sensitivity was measured at 30 d by hyperinsulinaemic euglycaemic clamp and expression of insulin signaling genes (receptors, pathways, and targets) at 43 d in muscle and liver of control (n = 15) and PR (n = 13) lambs. PR reduced size at birth and increased postnatal growth, fasting plasma glucose (+15%, P = 0.004), and insulin (+115%, P = 0.009). PR reduced whole-body insulin sensitivity (−43%, P < 0.001) and skeletal muscle expression of INSR (−36%), IRS1 (−28%), AKT2 (−44%), GLUT4 (−88%), GSK3α (−35%), and GYS1 (−31%) overall (each P < 0.05) and decreased AMPKγ3 expression in females (P = 0.030). PR did not alter hepatic expression of insulin signaling and related genes but increased GLUT2 expression (P = 0.047) in males. Whole-body insulin sensitivity correlated positively with skeletal muscle expression of IRS1, AKT2, HK, AMPKγ2, and AMPKγ3 in PR lambs only (each P < 0.05) but not with hepatic gene expression in control or PR lambs. Onset of insulin resistance after PR and IUGR is accompanied by, and can be accounted for by, reduced expression of insulin signaling and metabolic genes in skeletal muscle but not liver.

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Leptin Enhances Insulin Sensitivity by Direct and Sympathetic Nervous System Regulation of Muscle IGFBP-2 Expression: Evidence From Nonrodent Models

Endocrinology ◽

10.1210/en.2013-2099 ◽

2014 ◽

Vol 155 (6) ◽

pp. 2133-2143 ◽

Cited By ~ 31

Author(s):

Steven W. Yau ◽

Belinda A. Henry ◽

Vincenzo C. Russo ◽

Glenn K. McConell ◽

Iain J. Clarke ◽

...

Keyword(s):

Type 2 Diabetes ◽

Skeletal Muscle ◽

Nervous System ◽

Insulin Sensitivity ◽

Sympathetic Nervous System ◽

Insulin Signaling ◽

In Vivo Experiments ◽

Sympathetic Nervous

Leptin is produced from white adipose tissue and acts primarily to regulate energy balance. Obesity is associated with leptin resistance and increased circulating levels of leptin. Leptin has recently been shown to influence levels of IGF binding protein-2 (IGFBP-2), a protein that is reduced in obesity and type 2 diabetes. Overexpression of IGFBP-2 protects against obesity and type 2 diabetes. As such, IGFBP-2 signaling may represent a novel pathway by which leptin regulates insulin sensitivity. We sought to investigate how leptin regulates skeletal muscle IGFBP-2 levels and to assess the impact of this on insulin signaling and glucose uptake. In vitro experiments were undertaken in cultured human skeletal myotubes, whereas in vivo experiments assessed the effect of intracerebroventricular leptin on peripheral skeletal muscle IGFBP-2 expression and insulin sensitivity in sheep. Leptin directly increased IGFBP-2 mRNA and protein in human skeletal muscle through both signal transducer and activator of transcription-3 and phosphatidylinositol 3-kinase signaling, in parallel with enhanced insulin signaling. Silencing IGFBP-2 lowered leptin- and insulin-stimulated protein kinase B phosphorylation and glucose uptake. In in vivo experiments, intracerebroventricular leptin significantly increased hind-limb skeletal muscle IGFBP-2, an effect completely blocked by concurrent peripheral infusion of a β-adrenergic blocking agent. Sheep receiving central leptin showed improvements in glucose tolerance and circulating insulin levels after an iv glucose load. In summary, leptin regulates skeletal muscle IGFBP-2 by both direct peripheral and central (via the sympathetic nervous system) mechanisms, and these likely impact on peripheral insulin sensitivity and glucose metabolism.

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Modulation of SIRT1-Foxo1 Signaling axis by Resveratrol: Implications in Skeletal Muscle Aging and Insulin Resistance

Cellular Physiology and Biochemistry ◽

10.1159/000369718 ◽

2015 ◽

Vol 35 (2) ◽

pp. 541-552 ◽

Cited By ~ 53

Author(s):

Thomas K. Sin ◽

Benjamin Y. Yung ◽

Parco M. Siu

Keyword(s):

Insulin Resistance ◽

Skeletal Muscle ◽

Insulin Sensitivity ◽

Insulin Signaling ◽

Pyruvate Dehydrogenase ◽

Glycolytic Enzyme ◽

Negative Regulator ◽

Sirtuin 1 ◽

Diabetic Patients ◽

Muscle Aging

Aging individuals and diabetic patients often exhibit concomitant reductions of skeletal muscle mass/strength and insulin sensitivity, suggesting an intimate link between muscle aging and insulin resistance. Foxo1, a member of the FOXO transcription factor family, is an important player in insulin signaling due to its inhibitory role in glucose uptake and utilization in skeletal muscle. Phosphorylation of Foxo1 is thought to mitigate the transactivation of pyruvate dehydrogenase lipoamide kinase 4 (PDK4), which is a negative regulator of the glycolytic enzyme pyruvate dehydrogenase (PDH). In contrast, how aging would regulate acetylation/deacetylation machineries and glucose utilization in skeletal muscle through the Foxo1/PDH axis remains largely undetermined. Accumulating body of evidence have shown that resveratrol, a natural polyphenol in grapes and red wine, activates the longevity-related protein sirtuin 1 (SIRT1) and augments insulin sensitivity in addition to its well-documented effects on mitochondrial energetics. The present review summarizes the role of Foxo1/SIRT1 in insulin signaling in skeletal muscle and proposes the insight that activation of SIRT1 deacetylase activity to deacetylate and suppress the Foxo1-induced transactivation of PDK4 may represent an anti-hyperglycemic mechanism of resveratrol in aging skeletal muscle.

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IUGR with catch-up growth programs impaired insulin sensitivity through LRP6/IRS-1 in male rats

Endocrine Connections ◽

10.1530/ec-21-0203 ◽

2021 ◽

Author(s):

Wenjun Long ◽

Tuo Zhou ◽

Xiuping Xuan ◽

Qiuli Cao ◽

Zuojie Luo ◽

...

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Wnt Signaling ◽

Insulin Signaling ◽

Critical Role ◽

C2c12 Cell ◽

Male Rats ◽

Insulin Resistant ◽

Metabolic Outcomes ◽

Impaired Insulin

Intrauterine growth restriction combined with postnatal accelerated growth (CG-IUGR) could lead to long-term detrimental metabolic outcomes characterized by insulin resistance. As an indispensable co-receptor of Wnt signaling, LRP6 plays a critical role in the susceptibility of metabolic disorders. However, whether LRP6 is involved in the metabolic programing is still unknown. We hypothesized that CG-IUGR programed impaired insulin sensitivity through the impaired LRP6-mediated Wnt signaling in skeletal muscle. A CG-IUGR rat model was employed. The transcriptional and translational alterations of the components of the Wnt and the insulin signaling in the skeletal muscle of the male CG-IUGR rats were determined. The role of LRP6 on the insulin signaling was evaluated by shRNA knockdown or Wnt3a stimulation of LRP6. Compared with controls, the male CG-IUGR rats showed an insulin-resistant phenotype, with impaired insulin signaling and decreased expression of LRP6/β-catenin in skeletal muscle. LRP6 knocked-down lead to reduced expression of the IR-β/IRS-1 in C2C12 cell line, while Wnt3a-mediated LRP6 expression increased the expression of IRS-1 and IGF-1R but not IR-β in the primary muscle cells of male CG-IUGR rats. The impaired LRP6/β-catenin/IGF-1R/IRS-1 signaling is probably one of the critical mechanisms underlying the programed impaired insulin sensitivity in male CG-IUGR.

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PGC-1α-mediated regulation of mitochondrial function and physiological implications

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2020-0005 ◽

2020 ◽

Vol 45 (9) ◽

pp. 927-936

Author(s):

Jens Frey Halling ◽

Henriette Pilegaard

Keyword(s):

Skeletal Muscle ◽

Insulin Sensitivity ◽

Mitochondrial Biogenesis ◽

Mitochondrial Function ◽

Current Evidence ◽

Peroxisome Proliferator ◽

Control Mechanisms ◽

Peroxisome Proliferator Activated Receptor ◽

Age Related ◽

Mitochondrial Functions

The majority of human energy metabolism occurs in skeletal muscle mitochondria emphasizing the importance of understanding the regulation of myocellular mitochondrial function. The transcriptional co-activator peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) has been characterized as a major factor in the transcriptional control of several mitochondrial components. Thus, PGC-1α is often described as a master regulator of mitochondrial biogenesis as well as a central player in regulating the antioxidant defense. However, accumulating evidence suggests that PGC-1α is also involved in the complex regulation of mitochondrial quality beyond biogenesis, which includes mitochondrial network dynamics and autophagic removal of damaged mitochondria. In addition, mitochondrial reactive oxygen species production has been suggested to regulate skeletal muscle insulin sensitivity, which may also be influenced by PGC-1α. This review aims to highlight the current evidence for PGC-1α-mediated regulation of skeletal muscle mitochondrial function beyond the effects on mitochondrial biogenesis as well as the potential PGC-1α-related impact on insulin-stimulated glucose uptake in skeletal muscle. Novelty PGC-1α regulates mitochondrial biogenesis but also has effects on mitochondrial functions beyond biogenesis. Mitochondrial quality control mechanisms, including fission, fusion, and mitophagy, are regulated by PGC-1α. PGC-1α-mediated regulation of mitochondrial quality may affect age-related mitochondrial dysfunction and insulin sensitivity.

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