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... Chapter 9 Amino Acid Metabolism in Exercise ANTON JM WAGENMAKERS 119 Page 2. ... only two amino acids change substantially in concen-tration in the muscle free amino acid pool, ie glutamate and alanine (Bergström et al. 1985; Sahlin... more
... Chapter 9 Amino Acid Metabolism in Exercise ANTON JM WAGENMAKERS 119 Page 2. ... only two amino acids change substantially in concen-tration in the muscle free amino acid pool, ie glutamate and alanine (Bergström et al. 1985; Sahlin et al. 1990; Van Hall et al. 1995b). ...
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Insulin- and contraction-stimulated increases in glucose uptake into skeletal muscle occur in part as a result of the translocation of glucose transporter 4 (GLUT4) from intracellular stores to the plasma membrane (PM). This study aimed... more
Insulin- and contraction-stimulated increases in glucose uptake into skeletal muscle occur in part as a result of the translocation of glucose transporter 4 (GLUT4) from intracellular stores to the plasma membrane (PM). This study aimed to use immunofluorescence microscopy in human skeletal muscle to quantify GLUT4 redistribution from intracellular stores to the PM in response to glucose feeding and exercise. Percutaneous muscle biopsy samples were taken from the m. vastus lateralis of ten insulin-sensitive men in the basal state and following 30 min of cycling exercise (65% VO2 max). Muscle biopsy samples were also taken from a second cohort of ten age-, BMI- and VO2 max-matched insulin-sensitive men in the basal state and 30 and 60 min following glucose feeding (75 g glucose). GLUT4 and dystrophin colocalization, measured using the Pearson's correlation coefficient, was increased following 30 min of cycling exercise (baseline r = 0.47 ± 0.01; post exercise r = 0.58 ± 0.02; P &...
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This part discusses the complex regulation of fat metabolism. Catecholamines as a stimulator of lipolysis and insulin as a suppressor play very important roles in the regulation of fat oxidation. The interaction of carbohydrate and fat... more
This part discusses the complex regulation of fat metabolism. Catecholamines as a stimulator of lipolysis and insulin as a suppressor play very important roles in the regulation of fat oxidation. The interaction of carbohydrate and fat metabolism has been extensively studied in the past decennia but the understanding of this multifactorial regulation is complex and still incompletely understood. In 1963, Randle et al. proposed the glucose-fatty acid cycle as a possible mechanism, and more recently, regulation through malonyl-CoA has been put forward as a possible way to explain shifts in carbohydrate and fat metabolism at rest and during exercise. The exercise intensity affects fat oxidation mainly by increasing lipolysis and fatty acid availability during exercise of low to moderate intensity. At high exercise intensities, both a reduction in fatty acid availability (decreased RaFa) and intramuscular factors reduce fat oxidation. These intramuscular factors are largely unknown. The...
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Palmitate oxidation was comparatively assayed in various cell-free and cellular systems by 14CO2 production and by the sum of 14CO2 and 14C-labeled acid-soluble products. The 14CO2 production rate was dependent on incubation time and... more
Palmitate oxidation was comparatively assayed in various cell-free and cellular systems by 14CO2 production and by the sum of 14CO2 and 14C-labeled acid-soluble products. The 14CO2 production rate was dependent on incubation time and amount of tissue in contrast to the total oxidation rate. The 14CO2 contribution to the oxidation rate of [1-14C]palmitate varied with homogenates from 1% with rat liver to 28% with rat kidney and amounted to only 2-4% with human muscles. With cellular systems the 14CO2 contribution varied between 20% in human fibroblasts and 70% in rat muscles and myocytes. Addition of cofactors increased the oxidation rate, but decreased the 14CO2 contribution. Various conditions appeared also to influence to a different extent the 14CO2 production and the total oxidation rate with rat tissue homogenates and with rat muscle mitochondria. Incorporation of radioactivity from [1-14C]palmitate into protein was not detectable in cell-free systems and only 2-3% of the sum o...
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Research Interests: Chemistry, Carbon Dioxide, Kinetics, Medicine, Energy Metabolism, and 15 moreBiological Sciences, Humans, Glucose, Blood Glucose, Insulin, Exercise, Applied Physiology, Bioavailability, Adult, Ingestion, Dietary Carbohydrates, Oxidation, Physical Endurance, Anaerobic Threshold, and Medical and Health Sciences
To optimize the postexercise insulin response and to increase plasma amino acid availability, we studied postexercise insulin levels after the ingestion of carbohydrate and wheat protein hydrolysate with and without free leucine and... more
To optimize the postexercise insulin response and to increase plasma amino acid availability, we studied postexercise insulin levels after the ingestion of carbohydrate and wheat protein hydrolysate with and without free leucine and phenylalanine. After an overnight fast, eight male cyclists visited our laboratory on five occasions, during which a control drink and two different beverage compositions in two different
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It is widely believed that glucocorticoids cause insulin resistance in all tissues. We have previously demonstrated that glucocorticoids cause insulin sensitization in human adipose tissue in vitro and induce insulin resistance in... more
It is widely believed that glucocorticoids cause insulin resistance in all tissues. We have previously demonstrated that glucocorticoids cause insulin sensitization in human adipose tissue in vitro and induce insulin resistance in skeletal muscle. Our aim was to determine whether glucocorticoids have tissue-specific effects on insulin sensitivity in vivo. Fifteen healthy volunteers were recruited into a double-blind, randomized, placebo-controlled, crossover study, receiving both an overnight hydrocortisone and saline infusion. The tissue-specific actions of insulin were determined using paired 2-step hyperinsulinemic euglycemic clamps incorporating stable isotopes with concomitant adipose tissue microdialysis. The study was performed in the Wellcome Trust Clinical Research Facility, Queen Elizabeth Hospital, Birmingham, United Kingdom. The sensitivity of sc adipose tissue to insulin action was measured. Hydrocortisone induced systemic insulin resistance but failed to cause sc adipose tissue insulin resistance as measured by suppression of adipose tissue lipolysis and enhanced insulin-stimulated pyruvate generation. In primary cultures of human hepatocytes, glucocorticoids increased insulin-stimulated p-ser473akt/protein kinase B. Similarly, glucocorticoids enhanced insulin-stimulated p-ser473akt/protein kinase B and increased Insulin receptor substrate 2 mRNA expression in sc, but not omental, intact human adipocytes, suggesting a depot-specificity of action. This study represents the first description of sc adipose insulin sensitization by glucocorticoids in vivo and demonstrates tissue-specific actions of glucocorticoids to modify insulin action. It defines an important advance in our understanding of the actions of both endogenous and exogenous glucocorticoids and may have implications for the development and targeting of future glucocorticoid therapies.
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The aim of the present study was to investigate changes in intramuscular triglyceride (IMTG) content and perilipin 2 expression in skeletal muscle tissue following 6 mo of endurance-type exercise training in type 2 diabetes patients. Ten... more
The aim of the present study was to investigate changes in intramuscular triglyceride (IMTG) content and perilipin 2 expression in skeletal muscle tissue following 6 mo of endurance-type exercise training in type 2 diabetes patients. Ten obese male type 2 diabetes patients (age 62 ± 1 yr, body mass index BMI 31 ± 1 kg/m2) completed three exercise sessions/week consisting of 40 min of continuous endurance-type exercise at 75% V̇o2 peak for a period of 6 mo. Muscle biopsies collected at baseline and after 2 and 6 mo of intervention were analyzed for IMTG content and perilipin 2 expression using fiber type-specific immunofluorescence microscopy. Endurance-type exercise training reduced trunk body fat by 6 ± 2% and increased whole body oxygen uptake capacity by 13 ± 7% ( P < 0.05). IMTG content increased twofold in response to the 6 mo of exercise training in both type I and type II muscle fibers ( P < 0.05). A threefold increase in perilipin 2 expression was observed from baselin...
Research Interests: Membrane Proteins, Medicine, Biological Sciences, Insulin Resistance, Overweight, and 15 moreHumans, Male, Exercise, Lipid metabolism, Body Mass Index, Triglycerides, Middle Aged, Time Factors, Abdominal Fat, Type 2 Diabetes Mellitus, Oxygen Consumption, Cohort Studies, Adiposity, Medical and Health Sciences, and Quadriceps Muscle
... Ger J. Van der Vusse PhD 2 ,; Maarten R. Drost PhD 1. Article first published online: 2 MAY 2002. DOI: 10.1002/mus.10125. ... Verbeet MP, Oostra BA, Reuser AJJ, Van der Ploeg AT. Generalized glycogen storage and cardiomegaly in a... more
... Ger J. Van der Vusse PhD 2 ,; Maarten R. Drost PhD 1. Article first published online: 2 MAY 2002. DOI: 10.1002/mus.10125. ... Verbeet MP, Oostra BA, Reuser AJJ, Van der Ploeg AT. Generalized glycogen storage and cardiomegaly in a knockout mouse model of Pompe disease. ...
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Research Interests: Nutrition and Dietetics, Carbon Dioxide, Cardiac Surgery, Heart Failure, Clinical Nutrition, and 14 moreGlutamate, Humans, Carbon Isotopes, Female, Male, High Pressure Liquid Chromatography, Aged, Middle Aged, Glutamine, Myocardium, Glutamic Acid, Blood Plasma, Coronary artery bypass graft, and Coronary Artery Bypass
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Intramuscular triglycerides (IMTG) are assumed to form an important substrate source during prolonged endurance exercise in trained males. This study investigated the effects of endurance exercise and recovery diet on IMTG content in... more
Intramuscular triglycerides (IMTG) are assumed to form an important substrate source during prolonged endurance exercise in trained males. This study investigated the effects of endurance exercise and recovery diet on IMTG content in vastus lateralis muscle. Nine male cyclists were provided with a standardized diet for 3 days, after which they performed a 3-h exercise trial at a 55% maximum workload. Before and immediately after exercise and after 24 and 48 h of recovery, magnetic resonance spectroscopy (MRS) was performed to quantitate IMTG content. Muscle biopsies were taken after 48 h of recovery to determine IMTG content by using quantitative fluorescence microscopy. The entire procedure was performed two times; in one trial, a normal diet containing 39% energy (En%) as fat was provided (NF) and in the other a typical carbohydrate-rich athlete's diet (LF: 24 En% fat) was provided. During exercise, IMTG content decreased by 21.4 +/- 3.1%. During recovery, IMTG content increas...
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The current study investigated the fate of a [U-(13)C]palmitate tracer extracted by forearm muscle in type 2 diabetic and control subjects. We studied seven healthy lean male subjects and seven obese male subjects with type 2 diabetes... more
The current study investigated the fate of a [U-(13)C]palmitate tracer extracted by forearm muscle in type 2 diabetic and control subjects. We studied seven healthy lean male subjects and seven obese male subjects with type 2 diabetes using the forearm muscle balance technique with continuous intravenous infusion of the stable isotope tracer [U-(13)C]palmitate under baseline conditions and during intravenous infusion of the nonselective beta-agonist isoprenaline (ISO; 20 ng *kg(-1) lean body mass* min(-1)). In skeletal muscle of control subjects, there was a significant release of (13)C-labeled oxidation products in the form of (13)CO(2) (15% of (13)C uptake from labeled palmitate) and a significant release of (13)C-labeled glutamine (release of (13)C-labeled atoms from glutamine was 6% of (13)C uptake from labeled palmitate), whereas in type 2 diabetic subjects there was no detectable release of (13)CO(2) and (13)C-glutamine, despite a significant uptake of [U-(13)C]palmitate (60% of control value). There was net uptake of arterial (13)C-labeled glutamate by forearm muscle in both groups. Also, the ISO-induced increase in arterial glutamine enrichment and arterial concentration of (13)C-glutamine was more pronounced in the diabetic group relative to control subjects. In view of the diminished ISO-induced release of (13)C-glutamine from type 2 diabetic muscle, the latter data indicate that more [U-(13)C]palmitate entered the liver in the diabetic group and was incorporated into newly synthesized glutamine and glutamate molecules. Thus, the lack of release of (13)C-labeled oxidation products by type 2 diabetic muscle during beta-adrenergic stimulation, despite significant [U-(13)C]palmitate uptake, indicates differences in the handling of fatty acids between type 2 diabetic subjects and healthy control subjects.
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To examine the motivational process through which increases in aerobic capacity and decreases in total body fat are achieved during high-intensity intermittent training (HIT) and moderate-intensity continuous training (MICT)... more
To examine the motivational process through which increases in aerobic capacity and decreases in total body fat are achieved during high-intensity intermittent training (HIT) and moderate-intensity continuous training (MICT) interventions. Eighty-seven physically inactive adults (65% women, age = 42 ± 12, BMI = 27.67 ± 4.99 kg/m2) took part in a 10-week randomized intervention testing group-based HIT, operationalized as repeated sprints of 15-60 s interspersed with periods of recovery cycling ≤ 25 min/session, 3 sessions/wk-1, or MICT, operationalized as cycling at constant workload of ∼65% maximum aerobic capacity (VO2max, 30-45 min/session-1, 5 sessions/wk-1. Assessments of VO2max and total body fat were made pre- and postintervention. Motivation variables were assessed midintervention and class attendance was monitored throughout. Path analysis was employed, controlling for treatment arm and baseline values of VO2max and total body fat. The 2 groups differed in adherence only, fa...
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The objective of the present study was to develop a combination of fluorescent stains that would allow visualisation of the network of mitochondria and lipid droplets (intramyocellular lipids or IMCL) in human skeletal muscle fibres by... more
The objective of the present study was to develop a combination of fluorescent stains that would allow visualisation of the network of mitochondria and lipid droplets (intramyocellular lipids or IMCL) in human skeletal muscle fibres by means of conventional and confocal microscopy. Muscle biopsies were taken from the vastus lateralis of three lean, healthy and physically active male subjects. Frozen muscle sections were stained for mitochondria using antibodies against three mitochondrial proteins; porin, cytochrome c oxidase (COX) and NADH-ubiquinol oxidoreductase and neutral lipids were stained with oil red O. Anti-COX staining produced images with the strongest fluorescence signal and the highest resolution of the mitochondrial network and this stain was successfully combined with the antibody against type I fibre myosin. A highly organised matrix arrangement of mitochondria within the sarcomeres (in pairs at the I-band) was observed in the oxidative type I fibres. The density of mitochondria was the highest in the subsarcolemmal region. Anti-COX staining was combined with oil red O demonstrating that in type I fibres lipid droplets are mainly located in the space between the mitochondria.
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... Olav E Roovackers, Mieke Faes, Jo W Wierts, Anton JM Wageninakers, and Gerard Hornstra ... Twenty-four hours later, protein-synthesis rates (ks) were measured by using the flooding-dose technique as described by Jepson et al ( 1). The... more
... Olav E Roovackers, Mieke Faes, Jo W Wierts, Anton JM Wageninakers, and Gerard Hornstra ... Twenty-four hours later, protein-synthesis rates (ks) were measured by using the flooding-dose technique as described by Jepson et al ( 1). The gastrocnemius muscle was sampled ...
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Dysfunctional neutrophils with advanced age are a hallmark of immunesenescence. Reduced migration and bactericidal activity increase the risk of infection. It remains unclear why neutrophil dysfunction occurs with age. Physical activity... more
Dysfunctional neutrophils with advanced age are a hallmark of immunesenescence. Reduced migration and bactericidal activity increase the risk of infection. It remains unclear why neutrophil dysfunction occurs with age. Physical activity and structured exercise have been suggested to improve immune function in the elderly. The aim of this study was to assess a comprehensive range of neutrophil functions and determine their association with habitual physical activity. Physical activity levels were determined in 211 elderly (67 ± 5 years) individuals by 7-days of accelerometry wear. Twenty of the most physically active men and women were matched for age and gender to twenty of the least physically active individuals. Groups were compared for neutrophil migration, phagocytosis, oxidative burst, cell surface receptor expression, metabolic health parameters and systemic inflammation. Groups were also compared against ten young participants (23 ± 4 years). The most active group completed o...