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Boon, H., Sjögren, R. J. .., Massart, J., Egan, B., Kostovski, E., Iversen, P. O., . . . Zierath, J. R. (2015). MicroRNA-208b progressively declines after spinal cord injury in humans and is inversely related to myostatin expression. Physiological Reports, 3(11), Article ID e12622.
Open this publication in new window or tab >>MicroRNA-208b progressively declines after spinal cord injury in humans and is inversely related to myostatin expression
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2015 (English)In: Physiological Reports, E-ISSN 2051-817X, Vol. 3, no 11, article id e12622Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Chichester: John Wiley & Sons, 2015
National Category
Physiology
Identifiers
urn:nbn:se:hh:diva-29985 (URN)10.14814/phy2.12622 (DOI)26603456 (PubMedID)2-s2.0-84977662794 (Scopus ID)
Funder
Swedish Research CouncilNovo Nordisk
Note

This work was supported by grants from the Netherlands Organisation for Scientific Research (NWO), the Throne Holst Foundation of the University of Oslo, the Norwegian South-Eastern Health Authority, the Swedish Research Council, the Novo-Nordisk Foundation, and the commission of the European Communities (EUGENEHEARTand EXGENESIS).

Available from: 2015-12-09 Created: 2015-12-09 Last updated: 2018-01-10Bibliographically approved
Kostovski, E., Boon, H., Hjeltnes, N., Lundell, L. S., Ahlsén, M., Chibalin, A. V., . . . Widegren, U. (2013). Altered content of AMP-activated protein kinase isoforms in skeletal muscle from spinal cord injured subjects. American Journal of Physiology. Endocrinology and Metabolism, 305(9), E1071-E1080
Open this publication in new window or tab >>Altered content of AMP-activated protein kinase isoforms in skeletal muscle from spinal cord injured subjects
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2013 (English)In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 305, no 9, p. E1071-E1080Article in journal (Refereed) Published
Abstract [en]

AMP-activated protein kinase (AMPK) is a pivotal regulator of energy homeostasis. Although downstream targets of AMPK are widely characterized, the physiological factors governing isoform expression of this protein kinase are largely unknown. Nerve/contractile activity has a major impact on the metabolic phenotype of skeletal muscle, therefore likely to influence AMPK isoform expression. Spinal cord injury represents an extreme form of physical inactivity, with concomitant changes in skeletal muscle metabolism. We assessed the influence of longstanding and recent spinal cord injury on protein abundance of AMPK isoforms in human skeletal muscle. We also determined muscle fiber type as a marker of glycolytic or oxidative metabolism. In subjects with longstanding complete injury, protein abundance of the AMPKγ3 subunit, as well as myosin heavy chain (MHC) IIa and IIx, were increased, whereas abundance of the AMPKγ1 subunit and MHC I were decreased. Similarly, abundance of AMPKγ3 and MHC IIa proteins were increased, whereas AMPKα2, -β1, and -γ1 subunits and MHC I abundance was decreased during the first year following injury, reflecting a more glycolytic phenotype of the skeletal muscle. However, in incomplete cervical lesions, partial recovery of muscle function attenuated the changes in the isoform profile of AMPK and MHC. Furthermore, exercise training (electrically stimulated leg cycling) partly normalized mRNA expression of AMPK isoforms. Thus, physical activity affects the relative expression of AMPK isoforms. In conclusion, skeletal muscle abundance of AMPK isoforms is related to physical activity and/or muscle fiber type. Thus, physical/neuromuscular activity is an important determinant of isoform abundance of AMPK and MCH. This further underscores the need for physical activity as part of a treatment regimen after spinal cord injury to maintain skeletal muscle metabolism. © 2013 the American Physiological Society.

Place, publisher, year, edition, pages
Bethesda, MD: American Physiological Society, 2013
Keywords
physical inactivity, muscle, metabolism, spinal cord injury
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:hh:diva-26616 (URN)10.1152/ajpendo.00132.2013 (DOI)000326578600003 ()24022865 (PubMedID)2-s2.0-84887013288 (Scopus ID)
Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Jocken, J. W. E., Goossens, G. H., Boon, H., Mason, R. R., Essers, Y., Havekes, B., . . . Blaak, E. E. (2013). Insulin-mediated suppression of lipolysis in adipose tissue and skeletal muscle of obese type 2 diabetic men and men with normal glucose tolerance. Diabetologia, 56(10), 2255-2265
Open this publication in new window or tab >>Insulin-mediated suppression of lipolysis in adipose tissue and skeletal muscle of obese type 2 diabetic men and men with normal glucose tolerance
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2013 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 56, no 10, p. 2255-2265Article in journal (Refereed) Published
Abstract [en]

Aims/hypothesis: Impaired regulation of lipolysis and accumulation of lipid intermediates may contribute to obesity-related insulin resistance and type 2 diabetes mellitus. We investigated insulin-mediated suppression of lipolysis in abdominal subcutaneous adipose tissue (AT) and skeletal muscle (SM) of obese men with normal glucose tolerance (NGT) and obese type 2 diabetic men. Methods: Eleven NGT men and nine long-term diagnosed type 2 diabetic men (7 ± 1 years), matched for age (58 ± 2 vs 62 ± 2 years), BMI (31.4 ± 0.6 vs 30.5 ± 0.6 kg/m2) and V × O 2 max (28.9 ± 1.5 vs 29.5 ± 2.4 ml kg-1 min-1) participated in this study. Interstitial glycerol concentrations in AT and SM were assessed using microdialysis during a 1 h basal period and a 6 h stepwise hyperinsulinaemic-euglycaemic clamp (8, 20 and 40 mU m-2 min -1). AT and SM biopsies were collected to investigate underlying mechanisms. Results: Hyperinsulinaemia suppressed interstitial SM glycerol concentrations less in men with type 2 diabetes (-7 ± 6%, -13 ± 9% and -27 ± 9%) compared with men with NGT (-21 ± 7%, -38 ± 8% and -53 ± 8%) (p = 0.014). This was accompanied by increased circulating fatty acid and glycerol concentrations, a lower glucose infusion rate (21.8 ± 3.1 vs 30.5 ± 2.0 μmol kg body weight-1 min-1; p < 0.05), higher hormone-sensitive lipase (HSL) serine 660 phosphorylation, increased saturated diacylglycerol (DAG) lipid species in the muscle membrane and increased protein kinase C (PKC) activation in type 2 diabetic men vs men with NGT. No significant differences in insulin-mediated reduction in AT interstitial glycerol were observed between groups. Conclusions/interpretation: Our results suggest that a blunted insulin-mediated suppression of SM lipolysis may promote the accumulation of membrane saturated DAG, aggravating insulin resistance, at least partly mediated by PKC. This may represent an important mechanism involved in the progression of insulin resistance towards type 2 diabetes. Trial registration: ClinicalTrials.gov NCT01680133 © 2013 The Author(s).

Place, publisher, year, edition, pages
Heidelberg: Springer Berlin/Heidelberg, 2013
Keywords
Adipose tissue, Diabetes, Insulin resistance, Lipolysis, Skeletal muscle
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:hh:diva-26615 (URN)10.1007/s00125-013-2995-9 (DOI)000324062800020 ()23907381 (PubMedID)2-s2.0-84890120647 (Scopus ID)
Note

This work was supported by a VENI grant (016.116.074) from the Netherlands Organisation for Scientific Research (NWO) to JWEJ and a clinical research grant from the European Foundation for the Study of Diabetes (EFSD) to EEB and JWEJ. MJW is supported by research grants from the National Health and Medical Research Council of Australia.

Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Russell, A. P., Lamon, S., Boon, H., Wada, S., Güller, I., Brown, E. L., . . . Akimoto, T. (2013). Regulation of miRNAs in human skeletal muscle following acute endurance exercise and short-term endurance training. Journal of Physiology, 591(18), 4637-4653
Open this publication in new window or tab >>Regulation of miRNAs in human skeletal muscle following acute endurance exercise and short-term endurance training
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2013 (English)In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 591, no 18, p. 4637-4653Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Chichester: Wiley-Blackwell, 2013
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:hh:diva-26619 (URN)10.1113/jphysiol.2013.255695 (DOI)000324476900029 ()23798494 (PubMedID)2-s2.0-84884286848 (Scopus ID)
Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Boon, H., Kostovski, E., Pirkmajer, S., Song, M., Lubarski, I., Iversen, P. O., . . . Chibalin, A. V. (2012). Influence of chronic and acute spinal cord injury on skeletal muscle Na+-K+-ATPase and phospholemman expression in humans. American Journal of Physiology. Endocrinology and Metabolism, 302(7), E864-E871
Open this publication in new window or tab >>Influence of chronic and acute spinal cord injury on skeletal muscle Na+-K+-ATPase and phospholemman expression in humans
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2012 (English)In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 302, no 7, p. E864-E871Article in journal (Refereed) Published
Abstract [en]

Na +-K +-ATPase is an integral membrane protein crucial for the maintenance of ion homeostasis and skeletal muscle contractibility. Skeletal muscle Na +-K +-ATPase content displays remarkable plasticity in response to long-term increase in physiological demand, such as exercise training. However, the adaptations in Na +-K +-ATPase function in response to a suddenly decreased and/or habitually low level of physical activity, especially after a spinal cord injury (SCI), are incompletely known. We tested the hypothesis that skeletal muscle content of Na +-K +-ATPase and the associated regulatory proteins from the FXYD family is altered in SCI patients in a manner dependent on the severity of the spinal cord lesion and postinjury level of physical activity. Three different groups were studied: 1) six subjects with chronic complete cervical SCI, 2) seven subjects with acute, complete cervical SCI, and 3) six subjects with acute, incomplete cervical SCI. The individuals in groups 2 and 3 were studied at months 1, 3, and 12 postinjury, whereas individuals with chronic SCI were compared with an able-bodied control group. Chronic complete SCI was associated with a marked decrease in [ 3H]ouabain binding site concentration in skeletal muscle as well as reduced protein content of the α 1-, α 1-, and (β1-subunit of the Na +-K +-ATPase. In line with this finding, expression of the Na +-K +-ATPase α 1-, α 1- subunits progressively decreased during the first year after complete but not after incomplete SCI. The expression of the regulatory protein phospholemman (PLM or FXYD1) was attenuated after complete, but not incomplete, cervical SCI. In contrast, FXYD5 was substantially upregulated in patients with complete SCI. In conclusion, the severity of the spinal cord lesion and the level of postinjury physical activity in patients with SCI are important factors controlling the expression of Na +-K +-ATPase and its regulatory proteins PLM and FXYD5. © 2012 the American Physiological Society.

Place, publisher, year, edition, pages
Bethesda, MD: American Physiological Society, 2012
Keywords
FXYD proteins, Paralysis, Physical inactivity, Sodium pump
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:hh:diva-26613 (URN)10.1152/ajpendo.00625.2011 (DOI)000302342100012 ()22275761 (PubMedID)2-s2.0-84859473984 (Scopus ID)
Funder
Swedish Research Council
Note

This work was supported by grants from the Netherlands Organization for Scientific Research, the Throne Holst Foundation of the University of Oslo, the Norwegian South-Eastern Health Authority, the Swedish Research Council, the Novo-Nordisk Foundation, and the Commission of the European Communities (EUGENEHEART and EXGENESIS).

Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Long, Y. C., Kostovski, E., Boon, H., Hjeltnes, N., Krook, A. & Widegren, U. (2011). Differential expression of metabolic genes essential for glucose and lipid metabolism in skeletal muscle from spinal cord injured subjects. Journal of applied physiology, 110(5), 1204-1210
Open this publication in new window or tab >>Differential expression of metabolic genes essential for glucose and lipid metabolism in skeletal muscle from spinal cord injured subjects
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2011 (English)In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 110, no 5, p. 1204-1210Article in journal (Refereed) Published
Abstract [en]

Skeletal muscle plays an important role in the regulation of energy homeostasis; therefore, the ability of skeletal muscle to adapt and alter metabolic gene expression in response to changes in physiological demands is critical for energy balance. Individuals with cervical spinal cord lesions are characterized by tetraplegia, impaired thermoregulation, and altered skeletal muscle morphology. We characterized skeletal muscle metabolic gene expression patterns, as well as protein content, in these individuals to assess the impact of spinal cord injury on critical determinants of skeletal muscle metabolism. Our results demonstrate that mRNA levels and protein expression of skeletal muscle genes essential for glucose storage are reduced, whereas expression of glycolytic genes is reciprocally increased in individuals with spinal cord injury. Furthermore, expression of genes essential for lipid oxidation is coordinately reduced in spinal cord injured subjects, consistent with a marked reduction of mitochondrial proteins. Thus spinal cord injury resulted in a profound and tightly coordinated change in skeletal muscle metabolic gene expression program that is associated with the aberrant metabolic features of the tissue. © 2011 the American Physiological Society.

Place, publisher, year, edition, pages
Bethesda, MD: American Physiological Society, 2011
Keywords
glycogen storage, metabolism, oxidation, physical inactivity, tetraplegia
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:hh:diva-26617 (URN)10.1152/japplphysiol.00686.2010 (DOI)000290472400012 ()21393466 (PubMedID)2-s2.0-79956108795 (Scopus ID)
Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Bosselaar, M., Boon, H., van Loon, L. J. C., van den Broek, P. H. H., Smits, P. & Tack, C. J. (2009). Intra-arterial AICA-riboside administration induces NO-dependent vasodilation in vivo in human skeletal muscle. American Journal of Physiology. Endocrinology and Metabolism, 297(3), E759-E766
Open this publication in new window or tab >>Intra-arterial AICA-riboside administration induces NO-dependent vasodilation in vivo in human skeletal muscle
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2009 (English)In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 297, no 3, p. E759-E766Article in journal (Refereed) Published
Abstract [en]

In animal models, administration of the adenosine analog AICA-riboside has shown beneficial effects on ischemia-reperfusion injury and glucose homeostasis. The vascular and/or metabolic effects of AICA-riboside administration in humans remain to be established. AICA-riboside was infused intra-arterially in four different dosages up to 8 mg·min-1·dl-1 in 24 healthy subjects. Forearm blood flow (FBF) and glucose uptake and plasma glucose, free fatty acid, and AICA-riboside concentrations were assessed. We also combined AICAriboside infusion (2 mg·min-1·dl -1) with the intra-arterial administration of the adenosine receptor antagonist caffeine (90 μg·min-1·dl-1; n = 6) and with the endothelial NO synthase inhibitor L-NMMA (0.4 mg·min-1·dl-1; n = 6). Additional in vitro experiments were performed to explain our in vivo effects of AICA-riboside in humans. AICA-riboside increased FBF dose dependently from 2.0 ± 0.2 to 13.2 ± 1.9 ml·min-1·dl-1 maximally (P < 0.05 for all dosages). The latter was not reduced by caffeine administration but was significantly attenuated by L-NMMA infusion. Despite high plasma AICA-riboside concentrations, forearm glucose uptake did not change. In vitro experiments showed rapid uptake of AICA-riboside by the equilibrative nucleoside transporter in erythrocytes and subsequent phosphorylation to AICA-ribotide. We conclude that AICA-riboside induces a potent vasodilator response in humans that is mediated by NO. Despite high local plasma concentrations, AICA-riboside does not increase skeletal muscle glucose uptake. Copyright © 2009 the American Physiological Society.

Place, publisher, year, edition, pages
Bethesda, MD: American Physiological Society, 2009
Keywords
5-Aminoimidazole-4-carboxamide, Forearm blood flow, Forearm glucose uptake, Nitric oxide
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:hh:diva-26614 (URN)10.1152/ajpendo.00141.2009 (DOI)000269063000021 ()19602584 (PubMedID)2-s2.0-69049120920 (Scopus ID)
Note

This work was supported by a grant from the Dutch Diabetes Foundation.

Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Boon, H., Bosselaar, M., Praet, S. F., Blaak, E. E., Saris, W. H., Wagenmakers, A. J., . . . van Loon, L. J. (2008). Intravenous AICAR administration reduces hepatic glucose output and inhibits whole body lipolysis in type 2 diabetic patients. Diabetologia, 51(10), 1893-1900
Open this publication in new window or tab >>Intravenous AICAR administration reduces hepatic glucose output and inhibits whole body lipolysis in type 2 diabetic patients
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2008 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 51, no 10, p. 1893-1900Article in journal (Refereed) Published
Abstract [en]

AIMS/HYPOTHESIS: The 5'-AMP-activated protein kinase (AMPK) pathway is intact in type 2 diabetic patients and is seen as a target for diabetes treatment. In this study, we aimed to assess the impact of the AMPK activator 5-aminoimidazole-4-carboxamide riboside (AICAR) on both glucose and fatty acid metabolism in vivo in type 2 diabetic patients. METHODS: Stable isotope methodology and blood and muscle biopsy sampling were applied to assess blood glucose and fatty acid kinetics following continuous i.v. infusion of AICAR (0.75 mg kg(-1) min(-1)) and/or NaCl (0.9%) in ten male type 2 diabetic patients (age 64 +/- 2 years; BMI 28 +/- 1 kg/m(2)). RESULTS: Plasma glucose rate of appearance (R (a)) was reduced following AICAR administration, while plasma glucose rate of disappearance (R (d)) was similar in the AICAR and control test. Consequently, blood glucose disposal (R (d) expressed as a percentage of R (a)) was increased following AICAR infusion (p < 0.001). Accordingly, a greater decline in plasma glucose concentration was observed following AICAR infusion (p < 0.001). Plasma NEFA R (a) and R (d) were both significantly reduced in response to AICAR infusion, and were accompanied by a significant decline in plasma NEFA concentration. Although AMPK phosphorylation in skeletal muscle was not increased, we observed a significant increase in acetyl-CoA carboxylase phosphorylation (p < 0.001). CONCLUSIONS/INTERPRETATION: The i.v. administration of AICAR reduces hepatic glucose output, thereby lowering blood glucose concentrations in vivo in type 2 diabetic patients. Furthermore, AICAR administration stimulates hepatic fatty acid oxidation and/or inhibits whole body lipolysis, thereby reducing plasma NEFA concentration. © 2008 The Author(s).

Place, publisher, year, edition, pages
Heidelberg: Springer Berlin/Heidelberg, 2008
Keywords
AICAR, AMPK, Diabetes, Glucose, NEFA, Non-esterified fatty acids
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:hh:diva-26611 (URN)10.1007/s00125-008-1108-7 (DOI)000258958400019 ()18709353 (PubMedID)2-s2.0-51249103805 (Scopus ID)
Note

The study was funded by the Dutch Diabetes Research Foundation.

Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Stellingwerff, T., Boon, H., Gijsen, A. P., Stegen, J. H. C., Kuipers, H. & van Loon, L. J. C. (2007). Carbohydrate supplementation during prolonged cycling exercise spares muscle glycogen but does not affect intramyocellular lipid use. Pflügers Archiv: European Journal of Physiology, 454(4), 635-647
Open this publication in new window or tab >>Carbohydrate supplementation during prolonged cycling exercise spares muscle glycogen but does not affect intramyocellular lipid use
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2007 (English)In: Pflügers Archiv: European Journal of Physiology, ISSN 0031-6768, E-ISSN 1432-2013, Vol. 454, no 4, p. 635-647Article in journal (Refereed) Published
Abstract [en]

Using contemporary stable-isotope methodology and fluorescence microscopy, we assessed the impact of carbohydrate supplementation on whole-body and fiber-type-specific intramyocellular triacylglycerol (IMTG) and glycogen use during prolonged endurance exercise. Ten endurance-trained male subjects were studied twice during 3 h of cycling at 63 ± 4% of maximal O2 uptake with either glucose ingestion (CHO trial; 0.7 g CHO kg−1 h−1) or without (CON placebo trial; water only). Continuous infusions with [U-13C] palmitate and [6,6-2H2] glucose were applied to quantify plasma free fatty acids (FFA) and glucose oxidation rates and to estimate intramyocellular lipid and glycogen use. Before and after exercise, muscle biopsy samples were taken to quantify fiber-type-specific IMTG and glycogen content. Plasma glucose rate of appearance (R a) and carbohydrate oxidation rates were substantially greater in the CHO vs CON trial. Carbohydrate supplementation resulted in a lower muscle glycogen use during the first hour of exercise in the CHO vs CON trial, resulting in a 38 ± 19 and 57 ± 22% decreased utilization in type I and II muscle-fiber glycogen content, respectively. In the CHO trial, both plasma FFA R a and subsequent plasma FFA concentrations were lower, resulting in a 34 ± 12% reduction in plasma FFA oxidation rates during exercise (P  < 0.05). Carbohydrate intake did not augment IMTG utilization, as fluorescence microscopy revealed a 76 ± 21 and 78 ± 22% reduction in type I muscle-fiber lipid content in the CHO and CON trial, respectively. We conclude that carbohydrate supplementation during prolonged cycling exercise does not modulate IMTG use but spares muscle glycogen use during the initial stages of exercise in endurance-trained men. © 2007 Springer-Verlag.

Place, publisher, year, edition, pages
Heidelberg: Springer Berlin/Heidelberg, 2007
Keywords
Fat metabolism, Intramyocellular triacylglycerol, IMTG, Glycogen, Sports drinks, Isotopes, Exercise
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:hh:diva-26620 (URN)10.1007/s00424-007-0236-0 (DOI)000247310800014 ()17333244 (PubMedID)2-s2.0-34249896164 (Scopus ID)
Note

This study was supported by a grant from the Dutch Sugar Foundation.

Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Stellingwerff, T., Boon, H., Jonkers, R. A. M., Senden, J. M., Spriet, L. L., Koopman, R. & van Loon, L. J. C. (2007). Significant intramyocellular lipid use during prolonged cycling in endurance-trained males as assessed by three different methodologies. American Journal of Physiology. Endocrinology and Metabolism, 292(6), E1715-E1723
Open this publication in new window or tab >>Significant intramyocellular lipid use during prolonged cycling in endurance-trained males as assessed by three different methodologies
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2007 (English)In: American Journal of Physiology. Endocrinology and Metabolism, ISSN 0193-1849, E-ISSN 1522-1555, Vol. 292, no 6, p. E1715-E1723Article in journal (Refereed) Published
Abstract [en]

Intramyocellular triacylglycerol (IMTG) has been suggested to represent an important substrate source during exercise. In the present study, IMTG utilization during exercise is assessed through the use of various methodologies. In addition, we identified differences in the use of intramyocellular lipids deposited in the immediate subsarcolemmal (SS) area and those stored in the more central region of the fiber. Contemporary stable isotope technology was applied in combination with muscle tissue sampling before and immediately after 3 h of moderate-intensity cycling exercise (62 ± 2% V̇o2 max) in eight well-trained male cyclists. Continuous infusions with [U-13C]palmitate and [6,6-2H2]glucose were applied to quantify plasma free fatty acid (FFA) and glucose oxidation rates and to estimate whole body IMTG and glycogen use. Both immunohistochemical analyses of oil red O (ORO)-stained muscle cross sections and biochemical triacylglycerol (TG) extraction were performed to assess muscle lipid content. During exercise, plasma FFA, muscle (and/or lipoprotein)-derived TG, plasma glucose, and muscle glycogen oxidation contributed 24 ± 2, 22 ± 3, 11 ± 1, and 43 ± 3% to total energy expenditure, respectively. In accordance, a significant net decline in muscle lipid content was observed following exercise as assessed by ORO staining (67 ± 8%) and biochemical TG extraction (49 ± 8%), and a positive correlation was observed between methods (r = 0.56; P < 0.05). Lipid depots located in the SS area were utilized to a greater extent than the more centrally located depots. This is the first study to show significant use of IMTG as a substrate source during exercise in healthy males via the concurrent implementation of three major methodologies. In addition, this study shows differences in resting subcellular intramyocellular lipid deposit distribution and in the subsequent net use of these deposits during exercise. Copyright © 2007 the American Physiological Society.

Place, publisher, year, edition, pages
Bethesda, MD: American Physiological Society, 2007
Keywords
fat metabolism, intramyocellular triacylglycerol, skeletal muscle, cycling, substrate utilization
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:hh:diva-26621 (URN)10.1152/ajpendo.00678.2006 (DOI)000247939100025 ()17299080 (PubMedID)2-s2.0-34447579088 (Scopus ID)
Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2017-12-05Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4235-0634

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