| 1. |
- Barnes, Brian R, et al.
(författare)
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5'-AMP-activated protein kinase regulates skeletal muscle glycogen content and ergogenics
- 2005
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 19:7, s. 773-779
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Tidskriftsartikel (refereegranskat)abstract
- 5'-AMP-activated protein kinase (AMPK) activity is increased during exercise in an intensity- and glycogen-dependent manner. We previously reported that a mutation in the AMPK3 subunit (Prkag3225Q) increases AMPK activity and skeletal muscle glycogen content. Transfection experiments revealed the R225Q mutation is associated with high basal AMPK activity and diminished AMP dependence. Thus, the R225Q mutation can be considered a loss-of-function mutation that abolished allosteric regulation by AMP/ATP, causing increased basal AMPK activity. We used AMPK3 transgenic (Tg-Prkag3225Q) and knockout (Prkag3-/-) mice to determine the relationship between AMPK activity, glycogen content, and ergogenics (ability to perform work) in isolated extensor digitorum longus skeletal muscle after contractions induced by electrical stimulation. Contraction-induced AMPK activity was inversely coupled to glycogen content in wild-type and Tg-Prkag3225Q mice, but not in Prkag3-/- mice, highlighting a partial feedback control of glycogen on contraction-induced AMPK activity in the presence of a functional AMPK3 isoform. Skeletal muscle glycogen content was positively correlated to work performance, regardless of genotype. Thus, chronic activation of AMPK by the Prkag3225Q mutation directly influences skeletal muscle ergogenics by enhancing glycogen content. In conclusion, functional studies of the AMPK3 isoform further support the close connection between glycogen content and exercise performance in skeletal muscle.
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| 2. |
- Barnes, Brian R, et al.
(författare)
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The 5'-AMP-activated protein kinase gamma3 isoform has a key role in carbohydrate and lipid metabolism in glycolytic skeletal muscle
- 2004
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 279:37, s. 38441-38447
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Tidskriftsartikel (refereegranskat)abstract
- 5'-AMP-activated protein kinase (AMPK) is a metabolic stress sensor present in all eukaryotes. A dominant missense mutation (R225Q) in pig PRKAG3, encoding the muscle-specific gamma3 isoform, causes a marked increase in glycogen content. To determine the functional role of the AMPK gamma3 isoform, we generated transgenic mice with skeletal muscle-specific expression of wild type or mutant (225Q) mouse gamma3 as well as Prkag3 knockout mice. Glycogen resynthesis after exercise was impaired in AMPK gamma3 knock-out mice and markedly enhanced in transgenic mutant mice. An AMPK activator failed to increase skeletal muscle glucose uptake in AMPK gamma3 knock-out mice, whereas contraction effects were preserved. When placed on a high fat diet, transgenic mutant mice but not knock-out mice were protected against excessive triglyceride accumulation and insulin resistance in skeletal muscle. Transfection experiments reveal the R225Q mutation is associated with higher basal AMPK activity and diminished AMP dependence. Our results validate the muscle-specific AMPK gamma3 isoform as a therapeutic target for prevention and treatment of insulin resistance.
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| 3. |
- Fritz, Tomas, et al.
(författare)
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Low-intensity exercise increases skeletal muscle protein expression of PPARdelta and UCP3 in type 2 diabetic patients
- 2006
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Ingår i: Diabetes/Metabolism Research Reviews. - : Wiley. - 1520-7552 .- 1520-7560. ; 22:6, s. 492-498
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Physical exercise provides health benefits for people with type 2 diabetes mellitus, partly by enhancing skeletal muscle insulin action. We tested the hypothesis that changes in expression of key genes in skeletal muscles relate to exercise-induced improvements in type 2 diabetic patients. METHODS: We determined mRNA expression of 20 selected genes following a self-supervised program of walking (> 150 min per week) over a 4-month period. RESULTS: This level of physical activity improved clinical parameters in approximately half the participants, as determined by reduced hypertension and enhanced insulin sensitivity (defined by reduced plasma-insulin levels and improved homeostasis model assessment (HOMA)). Skeletal muscle mRNA expression of Cbl-associated protein (CAP), diacylglycerol kinase (DGK)delta, uncoupling protein (UCP) 3, nuclear respiratory factor (NRF)-1, and peroxisome proliferator-activated receptor (PPAR)delta tended to increase in type 2 diabetic patients with an improved clinical profile. Skeletal muscle protein expression of PPARdelta and UCP3 was increased significantly after physical exercise in patients with an improved clinical profile, but were unchanged in patients who did not show exercise-mediated improvements in clinical parameters. CONCLUSIONS: This study provides clinical evidence that improvements in insulin sensitivity can be achieved in type 2 diabetic patients after individually executed low-intensity exercise training. Moreover, the positive clinical response to exercise is correlated with changes in skeletal muscle proteins involved in the regulation of mitochondrial biogenesis and metabolism. These changes in skeletal muscle gene expression offer a possible molecular explanation for the improvements in clinical outcomes.
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| 4. |
- Gonzalez-Franquesa, Alba, et al.
(författare)
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Discovery of thymosin β4 as a human exerkine and growth factor
- 2021
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Ingår i: American Journal of Physiology - Cell Physiology. - : American Physiological Society. - 0363-6143 .- 1522-1563. ; 321:5, s. 770-778
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Tidskriftsartikel (refereegranskat)abstract
- Skeletal muscle is an endocrine organ secreting exercise-induced factors (exerkines), which play a pivotal role in interorgan cross talk. Using mass spectrometry (MS)-based proteomics, we characterized the secretome and identified thymosin b4 (TMSB4X) as the most upregulated secreted protein in the media of contracting C2C12 myotubes. TMSB4X was also acutely increased in the plasma of exercising humans irrespective of the insulin resistance condition or exercise mode. Treatment of mice with TMSB4X did not ameliorate the metabolic disruptions associated with diet induced-obesity, nor did it enhance muscle regeneration in vivo. However, TMSB4X increased osteoblast proliferation and neurite outgrowth, consistent with its WADA classification as a prohibited growth factor. Therefore, we report TMSB4X as a human exerkine with a potential role in cellular cross talk.
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| 5. |
- Karlsson, Håkan K R, et al.
(författare)
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Branched-chain amino acids increase p70S6k phosphorylation in human skeletal muscle after resistance exercise.
- 2004
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 287:1, s. E1-7
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to investigate the effect of resistance exercise alone or in combination with oral intake of branched-chain amino acids (BCAA) on phosphorylation of the 70-kDa S6 protein kinase (p70(S6k)) and mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK1/2), and p38 MAPK in skeletal muscle. Seven male subjects performed one session of quadriceps muscle resistance training (4 x 10 repetitions at 80% of one repetition maximum) on two occasions. In a randomized order, double-blind, crossover test, subjects ingested a solution of BCAA or placebo during and after exercise. Ingestion of BCAA increased plasma concentrations of isoleucine, leucine, and valine during exercise and throughout recovery after exercise (2 h postexercise), whereas no change was noted after the placebo trial. Resistance exercise led to a robust increase in p70(S6k) phosphorylation at Ser(424) and/or Thr(421), which persisted 1 and 2 h after exercise. BCAA ingestion further enhanced p70(S6k) phosphorylation 3.5-fold during recovery. p70(S6k) phosphorylation at Thr(389) was unaltered directly after resistance exercise. However, during recovery, Thr(389) phosphorylation was profoundly increased, but only during the BCAA trial. Furthermore, phosphorylation of the ribosomal protein S6 was also increased in the recovery period only during the BCAA trial. Exercise led to a marked increase in ERK1/2 and p38 MAPK phosphorylation, which was completely suppressed upon recovery and unaltered by BCAA. In conclusion, BCAA, ingested during and after resistance exercise, mediate signal transduction through p70(S6k) in skeletal muscle.
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| 6. |
- Kulkarni, Sameer S., et al.
(författare)
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Suppression of 5 '-Nucleotidase Enzymes Promotes AMP-activated Protein Kinase (AMPK) Phosphorylation and Metabolism in Human and Mouse Skeletal Muscle
- 2011
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology, Inc.. - 0021-9258 .- 1083-351X. ; 286:40, s. 34567-34574
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Tidskriftsartikel (refereegranskat)abstract
- The 5'-nucleotidase (NT5) family of enzyme dephosphorylates non-cyclic nucleoside monophosphates to produce nucleosides and inorganic phosphates. We hypothesized that gene silencing of NT5 enzymes to increase the intracellular availability of AMP would increase AMP-activated protein kinase (AMPK) activity and metabolism. We determined the role of cytosolic NT5 in metabolic responses linked to the development of insulin resistance in obesity and type 2 diabetes. Using siRNA to silence NT5C2 expression in cultured human myotubes, we observed a 2-fold increase in the AMP/ATP ratio, a 2.4-fold increase in AMPK phosphorylation (Thr(172)), and a 2.8-fold increase in acetyl-CoA carboxylase phosphorylation (Ser(79)) (p<0.05). siRNA silencing of NT5C2 expression increased palmitate oxidation by 2-fold in the absence and by 8-fold in the presence of 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside. This was paralleled by an increase in glucose transport and a decrease in glucose oxidation, incorporation into glycogen, and lactate release from NT5C2-depleted myotubes. Gene silencing of NT5C1A by shRNA injection and electroporation in mouse tibialis anterior muscle reduced protein content (60%; p<0.05) and increased phosphorylation of AMPK (60%; p<0.05) and acetyl-CoA carboxylase (50%; p<0.05) and glucose uptake (20%; p<0.05). Endogenous expression of NT5C enzymes inhibited basal lipid oxidation and glucose transport in skeletal muscle. Reduction of 5'-nucleotidase expression or activity may promote metabolic flexibility in type 2 diabetes.
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| 7. |
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| 8. |
- Sjögren, Rasmus J. O., et al.
(författare)
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Branched-chain amino acid metabolism is regulated by ERRα in primary human myotubes and is further impaired by glucose loading in type 2 diabetes
- 2021
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Ingår i: Diabetologia. - : Springer. - 0012-186X .- 1432-0428. ; 64:9, s. 2077-2091
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis: Increased levels of branched-chain amino acids (BCAAs) are associated with type 2 diabetes pathogenesis. However, most metabolomic studies are limited to an analysis of plasma metabolites under fasting conditions, rather than the dynamic shift in response to a metabolic challenge. Moreover, metabolomic profiles of peripheral tissues involved in glucose homeostasis are scarce and the transcriptomic regulation of genes involved in BCAA catabolism is partially unknown. This study aimed to identify differences in circulating and skeletal muscle BCAA levels in response to an OGTT in individuals with normal glucose tolerance (NGT) or type 2 diabetes. Additionally, transcription factors involved in the regulation of the BCAA gene set were identified.Methods: Plasma and vastus lateralis muscle biopsies were obtained from individuals with NGT or type 2 diabetes before and after an OGTT. Plasma and quadriceps muscles were harvested from skeletal muscle-specific Ppargc1a knockout and transgenic mice. BCAA-related metabolites and genes were assessed by LC-MS/MS and quantitative RT-PCR, respectively. Small interfering RNA and adenovirus-mediated overexpression techniques were used in primary human skeletal muscle cells to study the role of PPARGC1A and ESRRA in the expression of the BCAA gene set. Radiolabelled leucine was used to analyse the impact of oestrogen-related receptor α (ERRα) knockdown on leucine oxidation.Results: Impairments in BCAA catabolism in people with type 2 diabetes under fasting conditions were exacerbated after a glucose load. Branched-chain keto acids were reduced 37–56% after an OGTT in the NGT group, whereas no changes were detected in individuals with type 2 diabetes. These changes were concomitant with a stronger correlation with glucose homeostasis biomarkers and downregulated expression of branched-chain amino acid transaminase 2, branched-chain keto acid dehydrogenase complex subunits and 69% of downstream BCAA-related genes in skeletal muscle. In primary human myotubes overexpressing peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α, encoded by PPARGC1A), 61% of the analysed BCAA genes were upregulated, while 67% were downregulated in the quadriceps of skeletal muscle-specific Ppargc1a knockout mice. ESRRA (encoding ERRα) silencing completely abrogated the PGC-1α-induced upregulation of BCAA-related genes in primary human myotubes. Conclusions/interpretation: Metabolic inflexibility in type 2 diabetes impacts BCAA homeostasis and attenuates the decrease in circulating and skeletal muscle BCAA-related metabolites after a glucose challenge. Transcriptional regulation of BCAA genes in primary human myotubes via PGC-1α is ERRα-dependent. Graphical abstract: [Figure not available: see fulltext.]
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| 9. |
- Sögård, Peter, et al.
(författare)
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Validation of the in vitro incubation of extensor digitorum longus muscle from mice with a mathematical model
- 2010
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Ingår i: Journal of biological systems. - : World Scientific. - 0218-3390. ; 18:3, s. 687-707
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Tidskriftsartikel (refereegranskat)abstract
- In vitro incubation of tissues; in particular, skeletal muscles from rodents, is a widely-used experimental method in diabetes research. This experimental method has previously been validated, both experimentally and theoretically. However, much of the method's experimental data remains unclear, including the high-rate of lactate production and the lack of an observable increase in glycogen content, within a given time. The predominant hypothesis explaining the high-rate of lactate production is that this phenomenon is dependent on a mechanism in glycolysis that works as a safety valve, producing lactate when glucose uptake is super-physiological. Another hypothesis is that existing anoxia forces more ATP to be produced from glycolysis, leading to an increased lactate concentration. The lack of an observable increase in glycogen content is assumed to be dependent on limitations in sensitivity of the measuring method used. We derived a mathematical model to investigate which of these hypotheses is most likely to be correct. Using our model, data analysis indicates that the in vitro incubated muscle specimens, most likely are sensing the presence of existing anoxia, rather than an overflow in glycolysis. The anoxic milieu causes the high lactate production. The model also predicts an increased glycogenolysis. After mathematical analyses, an estimation of the glycogen concentration could be made with a reduced model. In conclusion, central anoxia is likely to cause spatial differences in glycogen concentrations throughout the entire muscle. Thus, data regarding total glycogen levels in the incubated muscle do not accurately represent the entire organ. The presented model allows for an estimation of total glycogen, despite spatial differences present in the muscle specimen.
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| 10. |
- Boon, Hanneke, 1981-, et al.
(författare)
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MicroRNA-208b progressively declines after spinal cord injury in humans and is inversely related to myostatin expression
- 2015
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Ingår i: Physiological Reports. - Chichester : John Wiley & Sons. - 2051-817X. ; 3:11
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Tidskriftsartikel (refereegranskat)abstract
- The effects of long‐term physical inactivity on the expression of microRNAs involved in the regulation of skeletal muscle mass in humans are largely unknown. MicroRNAs are short, noncoding RNAs that fine‐tune target expression through mRNA degradation or by inhibiting protein translation. Intronic to the slow, type I, muscle fiber type genes MYH7 and MYH7b, microRNA‐208b and microRNA‐499‐5p are thought to fine‐tune the expression of genes important for muscle growth, such as myostatin. Spinal cord injured humans are characterized by both skeletal muscle atrophy and transformation toward fast‐twitch, type II fibers. We determined the expression of microRNA‐208b, microRNA‐499‐5p, and myostatin in human skeletal muscle after complete cervical spinal cord injury. We also determined whether these microRNAs altered myostatin expression in rodent skeletal muscle. A progressive decline in skeletal muscle microRNA‐208b and microRNA‐499‐5p expression occurred in humans during the first year after spinal cord injury and with long‐standing spinal cord injury. Expression of myostatin was inversely correlated with microRNA‐208b and microRNA‐499‐5p in human skeletal muscle after spinal cord injury. Overexpression of microRNA‐208b in intact mouse skeletal muscle decreased myostatin expression, whereas microRNA‐499‐5p was without effect. In conclusion, we provide evidence for an inverse relationship between expression of microRNA‐208b and its previously validated target myostatin in humans with severe skeletal muscle atrophy. Moreover, we provide direct evidence that microRNA‐208b overexpression decreases myostatin gene expression in intact rodent muscle. Our results implicate that microRNA‐208b modulates myostatin expression and this may play a role in the regulation of skeletal muscle mass following spinal cord injury. © 2015 The Authors
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| 11. |
- Cansby, Emmelie, 1984, et al.
(författare)
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Increased expression of STK25 leads to impaired glucose utilization and insulin sensitivity in mice challenged with a high-fat diet.
- 2013
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Ingår i: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - : Wiley. - 1530-6860. ; 27:9, s. 3660-3671
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Tidskriftsartikel (refereegranskat)abstract
- Partial depletion of serine/threonine protein kinase 25 (STK25), a member of the Ste20 superfamily of kinases, increases lipid oxidation and glucose uptake in rodent myoblasts. Here we show that transgenic mice overexpressing STK25, when challenged with a high-fat diet, develop reduced glucose tolerance and insulin sensitivity compared to wild-type siblings, as evidenced by impairment in glucose and insulin tolerance tests as well as in euglycemic-hyperinsulinemic clamp studies. The fasting plasma insulin concentration was elevated in Stk25 transgenic mice compared to wild-type littermates (4.9±0.8 vs. 2.6±0.4 ng/ml after 17 wk on high-fat diet, P<0.05). Overexpression of STK25 decreased energy expenditure during the dark phase of observation (P<0.05), despite increased spontaneous activity. The oxidative capacity of skeletal muscle of transgenic carriers was reduced, as evidenced by altered expression of Cpt1, Acox1, and ACC. Hepatic triglycerides and glycogen were elevated (1.6- and 1.4-fold, respectively; P<0.05) and expression of key enzymes regulating lipogenesis (Fasn), glycogen synthesis (Gck), and gluconeogenesis (G6pc, Fbp1) was increased in the liver of the transgenic mice. Our findings suggest that overexpression of STK25 in conditions of excess dietary fuels associates with a shift in the metabolic balance in peripheral tissues from lipid oxidation to storage, leading to a systemic insulin resistance.-Cansby, E., Amrutkar, M., Mannerås Holm, L., Nerstedt, A., Reyahi, A., Stenfeldt, E., Borén, J., Carlsson, P., Smith, U., Zierath, J.R., Mahlapuu, M. Increased expression of STK25 leads to impaired glucose utilization and insulin sensitivity in mice challenged with a high-fat diet.
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| 12. |
- Cedernaes, Jonathan, et al.
(författare)
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Acute sleep loss results in tissue-specific alterations in genome-wide DNA methylation state and metabolic fuel utilization in humans
- 2018
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 4:8
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Tidskriftsartikel (refereegranskat)abstract
- Curtailed sleep promotes weight gain and loss of lean mass in humans, although the underlying molecular mechanisms are poorly understood. We investigated the genomic and physiological impact of acute sleep loss in peripheral tissues by obtaining adipose tissue and skeletal muscle after one night of sleep loss and after one full night of sleep. We find that acute sleep loss alters genome-wide DNA methylation in adipose tissue, and unbiased transcriptome-, protein-, and metabolite-level analyses also reveal highly tissue-specific changes that are partially reflected by altered metabolite levels in blood. We observe transcriptomic signatures of inflammation in both tissues following acute sleep loss, but changes involving the circadian clock are evident only in skeletal muscle, and we uncover molecular signatures suggestive of muscle breakdown that contrast with an anabolic adipose tissue signature. Our findings provide insight into how disruption of sleep and circadian rhythms may promote weight gain and sarcopenia.
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| 13. |
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| 14. |
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| 15. |
- Ka, Sojeong, et al.
(författare)
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The expression of carnitine palmitoyl-CoA transferase-1B is influenced by a cis-acting eQTL in two chicken lines selected for high and low body weight
- 2013
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Ingår i: Physiological Genomics. - : American Physiological Society. - 1094-8341 .- 1531-2267. ; 45:9, s. 367-376
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Tidskriftsartikel (refereegranskat)abstract
- Carnitine palmitoyl-CoA transferase-1B is a mitochondrial enzyme in the fatty acid oxidation pathway. In a previous study, CPT1B was identified as differentially expressed in the hypothalamus of two lines of chickens established by long-term selection for high (HWS) or low (LWS) body weight. Mammals have three paralogs (CPT1a, b and c) while non-mammalian vertebrates only have two (CPT1A, B). CPT1A is expressed in liver and CPT1B in muscle. CPT1c is expressed in hypothalamus, where it regulates feeding and energy expenditure. We identified an intronic length polymorphism, fixed for different alleles in the two populations and mapped the hitherto missing CPT1B locus in the chicken genome assembly, to the distal tip of chromosome 1p. Based on molecular phylogeny and gene synteny we suggest that chicken CPT1B is pro-orthologous of the mammalian CPT1c. Chicken CPT1B was differentially expressed in both muscle and hypothalamus but in opposite directions: higher levels in hypothalamus but lower levels in muscle in the HWS than in the LWS line. Using an advanced inter-cross population of the lines, CPT1B expression was found to be influenced by a cis-acting expression quantitative trait locus in muscle. The increased expression in hypothalamus and reduced expression in muscle is consistent with an increased food intake in the HWS line and at the same time reduced fatty acid oxidation in muscle yielding a net accumulation of energy intake and storage. The altered expression of CPT1B in hypothalamus and peripheral tissue is likely to be a mechanism contributing to the remarkable difference between lines.
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| 16. |
- Katayama, Mutsumi, et al.
(författare)
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Circulating Exosomal miR-20b-5p is Elevated in Type 2 Diabetes and Could Impair Insulin Action in Human Skeletal Muscle.
- 2019
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 68:3, s. 515-526
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Tidskriftsartikel (refereegranskat)abstract
- MicroRNAs (miRNAs) are noncoding RNAs representing an important class of gene expression modulators. Extracellular circulating miRNAs are both candidate biomarkers for disease pathogenesis and mediators of cell-to-cell communication. We examined the miRNA expression profile of total serum and serum derived exosome-enriched extracellular vesicles in people with normal glucose tolerance or type 2 diabetes. In contrast to total serum miRNA, which did not reveal any differences in miRNA expression, we identified differentially abundant miRNAs in type 2 diabetes patients using miRNA expression profiles of exosome RNA (exoRNA). To validate the role of these differentially abundant miRNAs on glucose metabolism, we transfected miR-20b-5p, a highly abundant exoRNA in type 2 diabetic patients, into primary human skeletal muscle cells. miR-20b-5p overexpression increased basal glycogen synthesis in human skeletal muscle cells. We identified AKTIP and STAT3 as miR-20b-5p targets. miR-20b-5p overexpression reduced AKTIP abundance and insulin-stimulated glycogen accumulation. In conclusion, exosome derived extracellular miR-20b-5p is a circulating biomarker associated with type 2 diabetes, which plays an intracellular role in modulating insulin-stimulated glucose metabolism via AKT signaling.
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| 17. |
- Krämer, David Kitz, et al.
(författare)
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Direct activation of glucose transport in primary human myotubes after activation of peroxisome proliferator-activated receptor delta
- 2005
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Ingår i: Diabetes. - Alexandria, USA : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 54:4, s. 1157-1163
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Tidskriftsartikel (refereegranskat)abstract
- Activators of peroxisome proliferator-activated receptor (PPAR)gamma have been studied intensively for their insulin-sensitizing properties and antidiabetic effects. Recently, a specific PPARdelta activator (GW501516) was reported to attenuate plasma glucose and insulin levels when administered to genetically obese ob/ob mice. This study was performed to determine whether specific activation of PPARdelta has direct effects on insulin action in skeletal muscle. Specific activation of PPARdelta using two pharmacological agonists (GW501516 and GW0742) increased glucose uptake independently of insulin in differentiated C2C12 myotubes. In cultured primary human skeletal myotubes, GW501516 increased glucose uptake independently of insulin and enhanced subsequent insulin stimulation. PPARdelta agonists increased the respective phosphorylation and expression of AMP-activated protein kinase 1.9-fold (P < 0.05) and 1.8-fold (P < 0.05), of extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase (MAPK) 2.2-fold (P < 0.05) and 1.7-fold (P < 0.05), and of p38 MAPK 1.2-fold (P < 0.05) and 1.4-fold (P < 0.05). Basal and insulin-stimulated protein kinase B/Akt was unaltered in cells preexposed to PPARdelta agonists. Preincubation of myotubes with the p38 MAPK inhibitor SB203580 reduced insulin- and PPARdelta-mediated increase in glucose uptake, whereas the mitogen-activated protein kinase kinase inhibitor PD98059 was without effect. PPARdelta agonists reduced mRNA expression of PPARdelta, sterol regulatory element binding protein (SREBP)-1a, and SREBP-1c (P < 0.05). In contrast, mRNA expression of PPARgamma, PPARgamma coactivator 1, GLUT1, and GLUT4 was unaltered. Our results provide evidence to suggest that PPARdelta agonists increase glucose metabolism and promote gene regulatory responses in cultured human skeletal muscle. Moreover, we provide biological validation of PPARdelta as a potential target for antidiabetic therapy.
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| 18. |
- Markljung, Ellen, et al.
(författare)
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ZBED6, a novel transcription factor derived from a domesticated DNA transposon regulates IGF2 expression and muscle growth
- 2009
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Ingår i: PLoS biology. - : Public Library of Science (PLoS). - 1544-9173 .- 1545-7885. ; 7:12, s. e1000256-
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Tidskriftsartikel (refereegranskat)abstract
- A single nucleotide substitution in intron 3 of IGF2 in pigs abrogates a binding site for a repressor and leads to a 3-fold up-regulation of IGF2 in skeletal muscle. The mutation has major effects on muscle growth, size of the heart, and fat deposition. Here, we have identified the repressor and find that the protein, named ZBED6, is previously unknown, specific for placental mammals, and derived from an exapted DNA transposon. Silencing of Zbed6 in mouse C2C12 myoblasts affected Igf2 expression, cell proliferation, wound healing, and myotube formation. Chromatin immunoprecipitation (ChIP) sequencing using C2C12 cells identified about 2,500 ZBED6 binding sites in the genome, and the deduced consensus motif gave a perfect match with the established binding site in Igf2. Genes associated with ZBED6 binding sites showed a highly significant enrichment for certain Gene Ontology classifications, including development and transcriptional regulation. The phenotypic effects in mutant pigs and ZBED6-silenced C2C12 myoblasts, the extreme sequence conservation, its nucleolar localization, the broad tissue distribution, and the many target genes with essential biological functions suggest that ZBED6 is an important transcription factor in placental mammals, affecting development, cell proliferation, and growth.
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| 19. |
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| 20. |
- Parikh, Hemang, et al.
(författare)
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TXNIP regulates peripheral glucose metabolism in humans
- 2007
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Ingår i: PLoS Medicine. - : Public Library of Science (PLoS). - 1549-1676. ; 4:5, s. 868-879
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Tidskriftsartikel (refereegranskat)abstract
- Background Type 2 diabetes mellitus ( T2DM) is characterized by defects in insulin secretion and action. Impaired glucose uptake in skeletal muscle is believed to be one of the earliest features in the natural history of T2DM, although underlying mechanisms remain obscure. Methods and Findings We combined human insulin/glucose clamp physiological studies with genome-wide expression profiling to identify thioredoxin interacting protein ( TXNIP) as a gene whose expression is powerfully suppressed by insulin yet stimulated by glucose. In healthy individuals, its expression was inversely correlated to total body measures of glucose uptake. Forced expression of TXNIP in cultured adipocytes significantly reduced glucose uptake, while silencing with RNA interference in adipocytes and in skeletal muscle enhanced glucose uptake, confirming that the gene product is also a regulator of glucose uptake. TXNIP expression is consistently elevated in the muscle of prediabetics and diabetics, although in a panel of 4,450 Scandinavian individuals, we found no evidence for association between common genetic variation in the TXNIP gene and T2DM. Conclusions TXNIP regulates both insulin-dependent and insulin- independent pathways of glucose uptake in human skeletal muscle. Combined with recent studies that have implicated TXNIP in pancreatic beta-cell glucose toxicity, our data suggest that TXNIP might play a key role in defective glucose homeostasis preceding overt T2DM.
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| 21. |
- Pillon, Nicolas J., et al.
(författare)
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Distinctive exercise-induced inflammatory response and exerkine induction in skeletal muscle of people with type 2 diabetes
- 2022
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Ingår i: Science Advances. - : NLM (Medline). - 2375-2548. ; 8:36
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Tidskriftsartikel (refereegranskat)abstract
- Mechanistic insights into the molecular events by which exercise enhances the skeletal muscle phenotype are lacking, particularly in the context of type 2 diabetes. Here, we unravel a fundamental role for exercise-responsive cytokines (exerkines) on skeletal muscle development and growth in individuals with normal glucose tolerance or type 2 diabetes. Acute exercise triggered an inflammatory response in skeletal muscle, concomitant with an infiltration of immune cells. These exercise effects were potentiated in type 2 diabetes. In response to contraction or hypoxia, cytokines were mainly produced by endothelial cells and macrophages. The chemokine CXCL12 was induced by hypoxia in endothelial cells, as well as by conditioned medium from contracted myotubes in macrophages. We found that CXCL12 was associated with skeletal muscle remodeling after exercise and differentiation of cultured muscle. Collectively, acute aerobic exercise mounts a noncanonical inflammatory response, with an atypical production of exerkines, which is potentiated in type 2 diabetes.
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| 22. |
- Russell, Aaron P., et al.
(författare)
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Regulation of miRNAs in human skeletal muscle following acute endurance exercise and short-term endurance training
- 2013
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Ingår i: Journal of Physiology. - Chichester : Wiley-Blackwell. - 0022-3751 .- 1469-7793. ; 591:18, s. 4637-4653
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Tidskriftsartikel (refereegranskat)abstract
- The identification of microRNAs (miRNAs) has established new mechanisms that control skeletal muscle adaptation to exercise. The present study investigated the mRNA regulation of components of the miRNA biogenesis pathway (Drosha, Dicer and Exportin-5), muscle enriched miRNAs, (miR-1, -133a, -133b and -206), and several miRNAs dysregulated in muscle myopathies (miR-9, -23, -29, -31 and -181). Measurements were made in muscle biopsies from nine healthy untrained males at rest, 3 h following an acute bout of moderate-intensity endurance cycling and following 10 days of endurance training. Bioinformatics analysis was used to predict potential miRNA targets. In the 3 h period following the acute exercise bout, Drosha, Dicer and Exportin-5, as well as miR-1, -133a, -133-b and -181a were all increased. In contrast miR-9, -23a, -23b and -31 were decreased. Short-term training increased miR-1 and -29b, while miR-31 remained decreased. Negative correlations were observed between miR-9 and HDAC4 protein (r=-0.71; P= 0.04), miR-31 and HDAC4 protein (r =-0.87; P= 0.026) and miR-31 and NRF1 protein (r =-0.77; P= 0.01) 3 h following exercise. miR-31 binding to the HDAC4 and NRF1 3′ untranslated region (UTR) reduced luciferase reporter activity. Exercise rapidly and transiently regulates several miRNA species in muscle. Several of these miRNAs may be involved in the regulation of skeletal muscle regeneration, gene transcription and mitochondrial biogenesis. Identifying endurance exercise-mediated stress signals regulating skeletal muscle miRNAs, as well as validating their targets and regulatory pathways post exercise, will advance our understanding of their potential role/s in human health. © 2013 The Authors. The Journal of Physiology © 2013 The Physiological Society.
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| 23. |
- Sogaard, Peter, et al.
(författare)
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Spatial Insulin Signalling in Isolated Skeletal Muscle Preparations
- 2010
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Ingår i: Journal of Cellular Biochemistry. - : Wiley-Liss, Inc.. - 0730-2312 .- 1097-4644. ; 109:5, s. 943-949
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Tidskriftsartikel (refereegranskat)abstract
- During in vitro incubation in the absence or presence of insulin, glycogen depletion occurs in the inner core of the muscle specimen, concomitant with increased staining of hypoxia-induced-factor-1-alpha and caspase-3, markers of hypoxia and apoptosis, respectively. The aim of this study was to determine whether insulin is able to diffuse across the entire muscle specimen in sufficient amounts to activate signalling cascades to promote glucose uptake and glycogenesis within isolated mouse skeletal muscle. Phosphoprotein multiplex assay on lysates from muscle preparation was performed to detect phosphorylation of insulin-receptor on Tyr1146, Akt on Ser473 and glycogen-synthases-kinase-3 on Ser21/Ser9. To address the spatial resolution of insulin signalling, immunohistochemistry studies on cryosections were performed. Our results provide evidence to suggest that during the in vitro incubation, insulin sufficiently diffuses into the centre of tubular mouse muscles to promote phosphorylation of these signalling events. Interestingly, increased insulin signalling was observed in the core of the incubated muscle specimens, correlating with the location of oxidative fibres. In conclusion, insulin action was not restricted due to insufficient diffusion of the hormone during in vitro incubation in either extensor digitorum longus or soleus muscles from mouse under the specific experimental settings employed in this study. Hence, we suggest that the glycogen depleted core as earlier observed is not due to insufficient insulin action.
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| 24. |
- Treebak, Jonas T, et al.
(författare)
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AMPK-mediated AS160 phosphorylation in skeletal muscle is dependent on AMPK catalytic and regulatory subunits.
- 2006
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 55:7, s. 2051-2058
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Tidskriftsartikel (refereegranskat)abstract
- AMP-activated protein kinase (AMPK) is a heterotrimeric protein that regulates glucose transport mediated by cellular stress or pharmacological agonists such as 5-aminoimidazole-4-carboxamide 1 beta-D-ribonucleoside (AICAR). AS160, a Rab GTPase-activating protein, provides a mechanism linking AMPK signaling to glucose uptake. We show that AICAR increases AMPK, acetyl-CoA carboxylase, and AS160 phosphorylation by insulin-independent mechanisms in isolated skeletal muscle. Recombinant AMPK heterotrimeric complexes (alpha 1 beta 1 gamma l and alpha 2 beta 2 gamma 1) phosphorylate AS160 in a cell-free assay. In mice deficient in AMPK signaling (alpha 2 AMPK knockout [KO], alpha 2 AMPK kinase dead [KD], and gamma 3 AMPK KO), AICAR effects on AS160 phosphorylation were severely blunted, highlighting that complexes containing alpha 2 and gamma 3 are necessary for AICAR-stimulated AS160 phosphorylation in intact skeletal muscle. Contraction-mediated AS160 phosphorylation was also impaired in alpha 2 AMPK KO and KD but not gamma 3 AMPK KO mice. Our results implicate AS160 as a downstream target of AMPK.
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| 25. |
- Tsuchida, Hiroki, et al.
(författare)
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Gene expression of the p85alpha regulatory subunit of phosphatidylinositol 3-kinase in skeletal muscle from type 2 diabetic subjects.
- 2002
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Ingår i: Pflügers Archiv. - : Springer Science and Business Media LLC. - 0031-6768 .- 1432-2013. ; 445:1, s. 25-31
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Tidskriftsartikel (refereegranskat)abstract
- The gene of the p85alpha regulatory subunit of phosphatidylinositol (PI) 3-kinase gives rise to several splice variants. We hypothesized that the expression of p85alpha splice variants may be altered in skeletal muscle from subjects with type 2 diabetes mellitus. Skeletal muscle biopsies were obtained from nine type 2 diabetic and eight healthy men, matched for age, body mass index (BMI) and physical fitness. PI 3-kinase activity in skeletal muscle following in vitro insulin stimulation was reduced in subjects with type 2 diabetes. p85alpha mRNA was elevated fourfold in type 2 diabetic as compared to healthy control subjects ( P<0.05). p85alpha mRNA abundance was positively correlated with plasma insulin concentration ( P<0.01) and serum glucose concentration ( P<0.01). Despite this, protein levels of p85alpha, p55alpha, and the novel human p50alpha were not altered in type 2 diabetic subjects. Thus, although gene expression of full-length p85alpha is increased in skeletal muscle from type 2 diabetics, this is not reflected by increased protein levels. Therefore, defects in PI 3-kinase activity are likely due to impaired activation of the enzyme rather than changes in protein expression of the isoforms of the regulatory subunit.
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| 26. |
- Vieira, Elaine, et al.
(författare)
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Relationship between AMPK and the transcriptional balance of clock-related genes in skeletal muscle
- 2008
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Ingår i: American Journal of Physiology-Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 295:5
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Tidskriftsartikel (refereegranskat)abstract
- Circadian clocks coordinate physiological, behavioral, and biochemical events with predictable daily environmental changes by a self-sustained transcriptional feedback loop. CLOCK and ARNTL are transcriptional activators that regulate Per and Cry gene expression. PER and CRY inhibit their own transcription, and their turnover allows this cycle to restart. The transcription factors BHLHB2 and BHLHB3 repress Per activation, whereas orphan nuclear receptors of the NR1D and ROR families control Arntl expression. Here we show the AMP-activated protein kinase (AMPK)γ3 subunit is involved in the regulation of peripheral circadian clock function. AMPKγ3 knockout ( Prkag3−/−) mice or wild-type littermates were injected with saline or an AMPK activator, 5-amino-4-imidazole-carboxamide riboside (AICAR), and white glycolytic gastrocnemius muscle was removed for gene expression analysis. Genes involved in the regulation of circadian rhythms ( Cry2, Nr1d1, and Bhlhb2) were differentially regulated in response to AICAR in wild-type mice but remained unaltered in Prkag3−/− mice. Basal expression of Per1 was higher in Prkag3−/− mice compared with wild-type mice. Distinct diurnal changes in the respiratory exchange ratio (RER) between the light and dark phase of the day were observed in wild-type mice but not Prkag3−/− mice. In summary, the expression profile of clock-related genes in skeletal muscle in response to AICAR, as well as the diurnal shift in energy utilization, is impaired in AMPKγ3 subunit knockout mice. Our results indicate AMPK heterotrimeric complexes containing the AMPKγ3 subunit may play a specific role in linking circadian oscillators and energy metabolism in skeletal muscle.
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