Mitochondrial dysfunction results from oxidative stress in the skeletal muscle of diet-induced insulin-resistant mice.
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ABSTRACT:
SUBMITTER: Bonnard C
PROVIDER: S-EPMC2176186 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:High-fat diet (HFD) is an environmental factor that contributes to the pathogenesis of obesity and type 2 diabetes. A number of genes influencing oxidative phosphorylation (OXPHOS) were found to be downregulated in skeletal muscle of humans and rats treated with HFD and have been implicated in mitochondrial dysfunction, insulin resistance, and consequent type 2 diabetes. In this study, we hypothesized that DNA methylation plays a crucial role in the regulation of OXPHOS genes in skeletal muscle of rats exposed to HFD. Using whole genome promoter methylation analysis of skeletal muscle followed by qPCR and bisulfite sequencing analysis, we identified hypermethylation of Cox5a in HFD rats. Furthermore, we found that Cox5a hypermethylation was associated with downregulation of Cox5a expression at the mRNA and protein level, and a reduction in mitochondrial complex IV activity and ATP content in HFD-induced insulin resistant rats compared to controls. Moreover, we found that while exposure to palmitate resulted in hypermethylation of the Cox5a promoter in rat myotubes, demethylation with 5-aza-2'-deoxycytidine was associated with preserved Cox5a expression, as well as restoration of complex IV activity and cellular ATP content. These novel observations indicate that Cox5a hypermethylation is associated with mitochondrial dysfunction in skeletal muscle of HFD-induced insulin resistant rats.
| S-EPMC4249960 | biostudies-literature
Project description:Protein synthesis and autophagy are regulated by cellular ATP content. We tested the hypothesis that mitochondrial dysfunction, including generation of reactive oxygen species (ROS), contributes to impaired protein synthesis and increased proteolysis resulting in tissue atrophy in a comprehensive array of models. In myotubes treated with ethanol, using unbiased approaches, we identified defects in mitochondrial electron transport chain components, endogenous antioxidants, and enzymes regulating the tricarboxylic acid (TCA) cycle. Using high sensitivity respirometry, we observed impaired cellular respiration, decreased function of complexes I, II, and IV, and a reduction in oxidative phosphorylation in ethanol-treated myotubes and muscle from ethanol-fed mice. These perturbations resulted in lower skeletal muscle ATP content and redox ratio (NAD+/NADH). Ethanol also caused a leak of electrons, primarily from complex III, with generation of mitochondrial ROS and reverse electron transport. Oxidant stress with lipid peroxidation (thiobarbituric acid reactive substances) and protein oxidation (carbonylated proteins) were increased in myotubes and skeletal muscle from mice and humans with alcoholic liver disease. Ethanol also impaired succinate oxidation in the TCA cycle with decreased metabolic intermediates. MitoTEMPO, a mitochondrial specific antioxidant, reversed ethanol-induced mitochondrial perturbations (including reduced oxygen consumption, generation of ROS and oxidative stress), increased TCA cycle intermediates, and reversed impaired protein synthesis and the sarcopenic phenotype. We show that ethanol causes skeletal muscle mitochondrial dysfunction, decreased protein synthesis, and increased autophagy, and that these perturbations are reversed by targeting mitochondrial ROS.
| S-EPMC6910229 | biostudies-literature
Project description:Mitochondrial dysfunction in skeletal muscle has been implicated in the development of insulin resistance and type 2 diabetes. Considering the importance of mitochondrial dynamics in mitochondrial and cellular functions, we hypothesized that obesity and excess energy intake shift the balance of mitochondrial dynamics, further contributing to mitochondrial dysfunction and metabolic deterioration in skeletal muscle. First, we revealed that excess palmitate (PA), but not hyperglycemia, hyperinsulinemia, or elevated tumor necrosis factor alpha, induced mitochondrial fragmentation and increased mitochondrion-associated Drp1 and Fis1 in differentiated C2C12 muscle cells. This fragmentation was associated with increased oxidative stress, mitochondrial depolarization, loss of ATP production, and reduced insulin-stimulated glucose uptake. Both genetic and pharmacological inhibition of Drp1 attenuated PA-induced mitochondrial fragmentation, mitochondrial depolarization, and insulin resistance in C2C12 cells. Furthermore, we found smaller and shorter mitochondria and increased mitochondrial fission machinery in the skeletal muscle of mice with genetic obesity and those with diet-induced obesity. Inhibition of mitochondrial fission improved the muscle insulin signaling and systemic insulin sensitivity of obese mice. Our findings indicated that aberrant mitochondrial fission is causally associated with mitochondrial dysfunction and insulin resistance in skeletal muscle. Thus, disruption of mitochondrial dynamics may underlie the pathogenesis of muscle insulin resistance in obesity and type 2 diabetes.
| S-EPMC3255771 | biostudies-literature
Project description:UnlabelledCentral to bioenergetics and reactive oxygen species (ROS) signaling, the mitochondrion plays pivotal roles in the pathogenesis of metabolic diseases. Recent advances have shown that mitochondrial flash ("mitoflash") visualized by the biosensor mt-cpYFP affords a frequency-coded, optical readout linked to mitochondrial ROS production and energy metabolism, at the resolution of a single mitochondrion. To investigate possible mitoflash responses to metabolic stress in insulin resistance (IR), we generated an mt-cpYFP-expressing db/db mouse model with the obesity and IR phenotypes unaltered. In conjunction with in vivo imaging of skeletal muscles, we uncovered a progressive increase of mitoflash frequency along with its morphological changes. Interestingly, enhanced mitochondrial networking occurred at 12 weeks of age, and this was followed by mitochondrial fragmentation at 34 weeks. Pioglitazone treatment normalized mitoflash frequency and morphology while restored mitochondrial respiratory function and insulin sensitivity in 12 weeks mt-cpYFP db/db mice. Mechanistic study revealed that the mitoflash remodeling was associated with altered expression of proteins involved in mitochondrial dynamics and quality control. These findings indicate that mitoflash activity may serve as an optical functional readout of the mitochondria, a robust and sensitive biomarker to gauge IR stresses and their amelioration by therapeutic interventions.Key message• In vivo detection of mitochondrial flashes in mt-cpYFP-expressing db/db mouse. • Mitoflash frequency increased progressively with disease development. • Mitoflash morphology revealed a biphasic change in mitochondrial networking. • Mitoflash abnormalities and mitochondrial defects are restored by pioglitazone. • Mitoflash may serve as a unique biomarker to gauge metabolic stress in insulin resistance.
| S-EPMC4589561 | biostudies-literature
Project description:BackgroundThe skeletal muscle of pigs is vulnerable to oxidative damage, resulting in growth retardation. Selenoproteins are important components of antioxidant systems for animals, which are generally regulated by dietary selenium (Se) level. Here, we developed the dietary oxidative stress (DOS)-inducing pig model to investigate the protective effects of selenoproteins on DOS-induced skeletal muscle growth retardation.ResultsDietary oxidative stress caused porcine skeletal muscle oxidative damage and growth retardation, which is accompanied by mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and protein and lipid metabolism disorders. Supplementation with Se (0.3, 0.6 or 0.9 mg Se/kg) in form of hydroxy selenomethionine (OH-SeMet) linearly increased muscular Se deposition and exhibited protective effects via regulating the expression of selenotranscriptome and key selenoproteins, which was mainly reflected in lower ROS levels and higher antioxidant capacity in skeletal muscle, and the mitigation of mitochondrial dysfunction and ER stress. What's more, selenoproteins inhibited DOS induced protein and lipid degradation and improved protein and lipid biosynthesis via regulating AKT/mTOR/S6K1 and AMPK/SREBP-1 signalling pathways in skeletal muscle. However, several parameters such as the activity of GSH-Px and T-SOD, the protein abundance of JNK2, CLPP, SELENOS and SELENOF did not show dose-dependent changes. Notably, several key selenoproteins such as MSRB1, SELENOW, SELENOM, SELENON and SELENOS play the unique roles during this protection.ConclusionsIncreased expression of selenoproteins by dietary OH-SeMet could synergistically alleviate mitochondrial dysfunction and ER stress, recover protein and lipid biosynthesis, thus alleviate skeletal muscle growth retardation. Our study provides preventive measure for OS-dependent skeletal muscle retardation in livestock husbandry.
| S-EPMC10239589 | biostudies-literature
Project description:This study sought to elucidate the relationship between skeletal muscle mitochondrial dysfunction, oxidative stress, and insulin resistance in two mouse models with differential susceptibility to diet-induced obesity. We examined the time course of mitochondrial dysfunction and insulin resistance in obesity-prone C57B and obesity-resistant FVB mouse strains in response to high-fat feeding. After 5 wk, impaired insulin-mediated glucose uptake in skeletal muscle developed in both strains in the absence of any impairment in proximal insulin signaling. Impaired mitochondrial oxidative capacity preceded the development of insulin resistant glucose uptake in C57B mice in concert with increased oxidative stress in skeletal muscle. By contrast, mitochondrial uncoupling in FVB mice, which prevented oxidative stress and increased energy expenditure, did not prevent insulin resistant glucose uptake in skeletal muscle. Preventing oxidative stress in C57B mice treated systemically with an antioxidant normalized skeletal muscle mitochondrial function but failed to normalize glucose tolerance and insulin sensitivity. Furthermore, high fat-fed uncoupling protein 3 knockout mice developed increased oxidative stress that did not worsen glucose tolerance. In the evolution of diet-induced obesity and insulin resistance, initial but divergent strain-dependent mitochondrial adaptations modulate oxidative stress and energy expenditure without influencing the onset of impaired insulin-mediated glucose uptake.
| S-EPMC3359615 | biostudies-literature
Project description:Clinical use of the chemotherapeutic doxorubicin (DOX) promotes skeletal muscle atrophy and weakness, adversely affecting patient mobility and strength. Although the mechanisms responsible for DOX-induced skeletal muscle dysfunction remain unclear, studies implicate the significant production of reactive oxygen species (ROS) in this pathology. Supraphysiological ROS levels can enhance protein degradation via autophagy, and it is established that DOX upregulates autophagic signaling in skeletal muscle. To determine the precise contribution of accelerated autophagy to DOX-induced skeletal muscle dysfunction, we inhibited autophagy in the soleus via transduction of a dominant negative mutation of the autophagy related 5 (ATG5) protein. Targeted inhibition of autophagy prevented soleus muscle atrophy and contractile dysfunction acutely following DOX administration, which was associated with a reduction in mitochondrial ROS and maintenance of mitochondrial respiratory capacity. These beneficial modifications were potentially the result of enhanced transcription of antioxidant response element-related genes and increased antioxidant capacity. Specifically, our results showed significant upregulation of peroxisome proliferator-activated receptor gamma co-activator 1-alpha, nuclear respiratory factor-1, nuclear factor erythroid-2-related factor-2, nicotinamide-adenine dinucleotide phosphate quinone dehydrogenase-1, and catalase in the soleus with DOX treatment when autophagy was inhibited. These findings establish a significant role of autophagy in the development of oxidative stress and skeletal muscle weakness following DOX administration.
| S-EPMC7139604 | biostudies-literature
Project description:Aims/hypothesisMitochondria operate in networks, adapting to external stresses and changes in cellular metabolic demand and are subject to various quality control mechanisms. On the basis of these traits, we here hypothesise that the regulation of mitochondrial networks in skeletal muscle is hampered in humans with compromised oxidative capacity and insulin sensitivity.MethodsIn a cross-sectional design, we compared four groups of participants (selected from previous studies) ranging in aerobic capacity and insulin sensitivity, i.e. participants with type 2 diabetes (n = 11), obese participants without diabetes (n = 12), lean individuals (n = 10) and endurance-trained athletes (n = 12); basal, overnight fasted muscle biopsies were newly analysed for the current study and we compared the levels of essential mitochondrial dynamics and quality control regulatory proteins in skeletal muscle tissue.ResultsType 2 diabetes patients and obese participants were older than lean participants and athletes (58.6 ± 4.0 and 56.7 ± 7.2 vs 21.8 ± 2.5 and 25.1 ± 4.3 years, p < 0.001, respectively) and displayed a higher BMI (32.4 ± 3.7 and 31.0 ± 3.7 vs 22.1 ± 1.8 and 21.0 ± 1.5 kg/m2, p < 0.001, respectively) than lean individuals and endurance-trained athletes. Fission protein 1 (FIS1) and optic atrophy protein 1 (OPA1) protein content was highest in muscle from athletes and lowest in participants with type 2 diabetes and obesity, respectively (FIS1: 1.86 ± 0.79 vs 0.79 ± 0.51 AU, p = 0.002; and OPA1: 1.55 ± 0.64 vs 0.76 ± 0.52 AU, p = 0.014), which coincided with mitochondrial network fragmentation in individuals with type 2 diabetes, as assessed by confocal microscopy in a subset of type 2 diabetes patients vs endurance-trained athletes (n = 6). Furthermore, lean individuals and athletes displayed a mitonuclear protein balance that was different from obese participants and those with type 2 diabetes. Mitonuclear protein balance also associated with heat shock protein 60 (HSP60) protein levels, which were higher in athletes when compared with participants with obesity (p = 0.048) and type 2 diabetes (p = 0.002), indicative for activation of the mitochondrial unfolded protein response. Finally, OPA1, FIS1 and HSP60 correlated positively with aerobic capacity (r = 0.48, p = 0.0001; r = 0.55, p < 0.001 and r = 0.61, p < 0.0001, respectively) and insulin sensitivity (r = 0.40, p = 0.008; r = 0.44, p = 0.003 and r = 0.48, p = 0.001, respectively).Conclusions/interpretationCollectively, our data suggest that mitochondrial dynamics and quality control in skeletal muscle are linked to oxidative capacity in humans, which may play a role in the maintenance of muscle insulin sensitivity. CLINICAL TRIAL REGISTRY: numbers NCT00943059, NCT01298375 and NL1888 Graphical abstract.
| S-EPMC7801361 | biostudies-literature
Project description:Ad libitum high-fat diet (HFD) induces obesity and skeletal muscle metabolic dysfunction. Liver kinase B1 (LKB1) regulates skeletal muscle metabolism by controlling the AMP-activated protein kinase family, but its importance in regulating muscle gene expression and glucose tolerance in obese mice has not been established. The purpose of this study was to determine how the lack of LKB1 in skeletal muscle (KO) affects gene expression and glucose tolerance in HFD-fed, obese mice. KO and littermate control wild-type (WT) mice were fed a standard diet or HFD for 14 weeks. RNA sequencing, and subsequent analysis were performed to assess mitochondrial content and respiration, inflammatory status, glucose and insulin tolerance, and muscle anabolic signaling. KO did not affect body weight gain on HFD, but heavily impacted mitochondria-, oxidative stress-, and inflammation-related gene expression. Accordingly, mitochondrial protein content and respiration were suppressed while inflammatory signaling and markers of oxidative stress were elevated in obese KO muscles. KO did not affect glucose or insulin tolerance. However, fasting serum insulin and skeletal muscle insulin signaling were higher in the KO mice. Furthermore, decreased muscle fiber size in skmLKB1-KO mice was associated with increased general protein ubiquitination and increased expression of several ubiquitin ligases, but not muscle ring finger 1 or atrogin-1. Taken together, these data suggest that the lack of LKB1 in skeletal muscle does not exacerbate obesity or insulin resistance in mice on a HFD, despite impaired mitochondrial content and function and elevated inflammatory signaling and oxidative stress.
| S-EPMC8432303 | biostudies-literature
Project description:Insulin resistance is associated with mitochondrial dysfunction, but the mechanism by which mitochondria inhibit insulin-stimulated glucose uptake into the cytoplasm is unclear. The mitochondrial permeability transition pore (mPTP) is a protein complex that facilitates the exchange of molecules between the mitochondrial matrix and cytoplasm, and opening of the mPTP occurs in response to physiological stressors that are associated with insulin resistance. In this study, we investigated whether mPTP opening provides a link between mitochondrial dysfunction and insulin resistance by inhibiting the mPTP gatekeeper protein cyclophilin D (CypD) in vivo and in vitro. Mice lacking CypD were protected from high fat diet-induced glucose intolerance due to increased glucose uptake in skeletal muscle. The mitochondria in CypD knockout muscle were resistant to diet-induced swelling and had improved calcium retention capacity compared to controls; however, no changes were observed in muscle oxidative damage, insulin signaling, lipotoxic lipid accumulation or mitochondrial bioenergetics. In vitro, we tested 4 models of insulin resistance that are linked to mitochondrial dysfunction in cultured skeletal muscle cells including antimycin A, C2-ceramide, ferutinin, and palmitate. In all models, we observed that pharmacological inhibition of mPTP opening with the CypD inhibitor cyclosporin A was sufficient to prevent insulin resistance at the level of insulin-stimulated GLUT4 translocation to the plasma membrane. The protective effects of mPTP inhibition on insulin sensitivity were associated with improved mitochondrial calcium retention capacity but did not involve changes in insulin signaling both in vitro and in vivo. In sum, these data place the mPTP at a critical intersection between alterations in mitochondrial function and insulin resistance in skeletal muscle.
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