RESUMO
Omega-3 polyunsaturated fatty acids (PUFAs) have unique properties purported to influence several aspects of metabolism, including energy expenditure and protein function. Supplementing with n-3 PUFAs may increase whole-body resting metabolic rate (RMR), by enhancing Na+ /K+ ATPase (NKA) activity and reducing the efficiency of sarcoplasmic reticulum (SR) Ca2+ ATPase (SERCA) activity by inducing a Ca2+ leak-pump cycle. The purpose of this study was to examine the effects of fish oil (FO) on RMR, substrate oxidation, and skeletal muscle SERCA and NKA pump function in healthy older individuals. Subjects (n = 16 females; n = 8 males; 65 ± 1 years) were randomly assigned into groups supplemented with either olive oil (OO) (5 g/day) or FO (5 g/day) containing 2 g/day eicosapentaenoic acid and 1 g/day docosahexaenoic acid for 12 weeks. Participants visited the laboratory for RMR and substrate oxidation measurements after an overnight fast at weeks 0 and 12. Skeletal muscle biopsies were taken during weeks 0 and 12 for analysis of NKA and SERCA function and protein content. There was a main effect of time with decrease in RMR (5%) and fat oxidation (18%) in both the supplementation groups. The kinetic parameters of SERCA and NKA maximal activity, as well as the expression of SR and NKA proteins, were not affected after OO and FO supplementation. In conclusion, these results suggest that FO supplementation is not effective in altering RMR, substrate oxidation, and skeletal muscle SERCA and NKA protein levels and activities, in healthy older men and women.
Assuntos
Suplementos Nutricionais , Ácidos Graxos Ômega-3/administração & dosagem , Óleos de Peixe/administração & dosagem , Músculo Esquelético/fisiologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Fatores Etários , Idoso , Metabolismo Basal , Metabolismo Energético , Feminino , Humanos , Masculino , Músculo Esquelético/efeitos dos fármacos , Azeite de Oliva/administração & dosagem , OxirreduçãoRESUMO
INTRODUCTION: In skeletal muscle, the Na/K ATPase (NKA) plays essential roles in processes linked to muscle contraction, fatigue, and energy metabolism; however, very little information exists regarding the regulation of NKA activity. The scarcity of information regarding NKA function in skeletal muscle likely stems from methodological constraints, as NKA contributes minimally to total cellular ATP utilization, and therefore contamination from other ATPases prevents the assessment of NKA activity in muscle homogenates. Here we introduce a method that improves accuracy and feasibility for the determination of NKA activity in small rodent muscle samples (5-10 mg) and in human skeletal muscle. METHODS: Skeletal muscle homogenates from mice (n = 6) and humans (n = 3) were used to measure NKA and sarcoplasmic reticulum Ca ATPase (SERCA) activities with the addition of specific ATPase inhibitors to minimize "background noise." RESULTS: We observed that myosin ATPase activity was the major interfering factor for estimation of NKA activity in skeletal muscle homogenates, as the addition of 25 µM of blebbistatin, a specific myosin ATPase inhibitor, considerably minimized "background noise" (threefold) and enabled the determination of NKA maximal activity with values three times higher than previously reported. The specificity of the assay was demonstrated after the addition of 2 mM ouabain, which completely inhibited NKA. On the other hand, the addition of blebbistatin did not affect the ability to measure SERCA function. The coefficient of variation for NKA and SERCA assays were 6.2% and 4.4%, respectively. CONCLUSION: The present study has improved the methodology to determine NKA activity. We further show the feasibility of measuring NKA and SERCA activities from a common muscle homogenate. This methodology is expected to aid in our long-term understanding of how NKA affects skeletal muscle metabolic homeostasis and contractile function in diverse situations.
Assuntos
Fluorometria/métodos , Músculo Esquelético/química , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/análise , ATPase Trocadora de Sódio-Potássio/análise , Idoso , Animais , Metabolismo Energético , Acoplamento Excitação-Contração , Estudos de Viabilidade , Feminino , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Humanos , Masculino , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Músculo Esquelético/metabolismo , Miosinas/metabolismo , Ouabaína/farmacologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/efeitos dos fármacos , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , ATPase Trocadora de Sódio-Potássio/antagonistas & inibidores , ATPase Trocadora de Sódio-Potássio/metabolismoRESUMO
Fish oil (FO) supplementation in humans results in the incorporation of omega-3 fatty acids (FAs) eicosapentaenoic acid (EPA; C20:5) and docosahexaenoic acid (DHA; C20:6) into skeletal muscle membranes. However, despite the importance of membrane composition in structure-function relationships, a paucity of information exists regarding how different muscle membranes/organelles respond to FO supplementation. Therefore, the purpose of the present study was to determine the effects 12 weeks of FO supplementation (3g EPA/2g DHA daily) on the phospholipid composition of sarcolemmal and mitochondrial fractions, as well as whole muscle responses, in healthy young males. FO supplementation increased the total phospholipid content in whole muscle (57%; p < 0.05) and the sarcolemma (38%; p = 0.05), but did not alter the content in mitochondria. The content of omega-3 FAs, EPA and DHA, were increased (+3-fold) in whole muscle, and mitochondrial membranes, and as a result the omega-6/omega-3 ratios were dramatically decreased (-3-fold), while conversely the unsaturation indexes were increased. Intriguingly, before supplementation the unsaturation index (UI) of sarcolemmal membranes was â¼3 times lower (p < 0.001) than either whole muscle or mitochondrial membranes. While supplementation also increased DHA within sarcolemmal membranes, EPA was not altered, and as a result the omega-6/omega-3 ratio and UI of these membranes were not altered. All together, these data revealed that mitochondrial and sarcolemmal membranes display unique phospholipid compositions and responses to FO supplementation.
RESUMO
This study investigated the effects of acute and chronic beetroot juice (BRJ) supplementation on submaximal exercise oxygen uptake (VO2 ), time trial (TT) performance, and contractile properties of the plantar flexors in females. Study 1: Using a double blind, randomized, crossover design, 12 recreationally active females using hormonal contraceptives supplemented acutely (2.5 h) and chronically (8 days) with 280 mL BRJ/d (~26 mmoles nitrate [ NO3- ]) or a NO3- -free placebo (PLA). On days 1 and 8, participants cycled for 10 min at 50% and 70% VO2peak and completed a 4 kJ/kg body mass TT. Plasma [ NO3- ] and nitrite ([NO2- ]) increased significantly following BRJ supplementation versus PLA. There was no effect of BRJ supplementation on VO2 at 50% or 70% VO2peak , or TT performance. Study 2: 12 recreationally active females (n = 7 from Study 1) using hormonal contraceptives participated in a baseline visit and were supplemented acutely (2.5 h) and chronically (8 days) with 280 mL BRJ/d. Maximum voluntary strength (MVC) of the plantar flexors was assessed and a torque-frequency curve performed. BRJ had no effect on MVC, voluntary activation, peak twitch torque, time to peak torque, or half relaxation time. Following both acute (46.6 ± 4.9% of 100 Hz torque) and chronic (47.2 ± 4.4%) supplementation, 10 Hz torque was significantly greater compared to baseline (32.9 ± 2.6%). In summary, BRJ may not be an effective ergogenic aid in recreationally active females as it did not reduce submaximal exercise VO2 or improve aerobic TT performance despite increasing low frequency torque production.
Assuntos
Antioxidantes/farmacologia , Desempenho Atlético/fisiologia , Beta vulgaris/química , Exercício Físico/fisiologia , Sucos de Frutas e Vegetais , Músculo Esquelético/efeitos dos fármacos , Consumo de Oxigênio/efeitos dos fármacos , Adulto , Estudos Cross-Over , Suplementos Nutricionais , Método Duplo-Cego , Feminino , Humanos , Adulto JovemRESUMO
During exercise, the supply of adenosine triphosphate (ATP) is essential for the energy-dependent processes that underpin ongoing contractile activity. These pathways involve both substrate-level phosphorylation, without any need for oxygen, and oxidative phosphorylation that is critically dependent on oxygen delivery to contracting skeletal muscle by the respiratory and cardiovascular systems and on the supply of reducing equivalents from the degradation of carbohydrate, fat, and, to a limited extent, protein fuel stores. The relative contribution of these pathways is primarily determined by exercise intensity, but also modulated by training status, preceding diet, age, gender, and environmental conditions. Optimal substrate availability and utilization before, during, and after exercise is critical for maintaining exercise performance. This review provides a brief overview of exercise metabolism, with expanded discussion of the regulation of muscle glucose uptake and fatty acid uptake and oxidation.
Assuntos
Metabolismo Energético/fisiologia , Exercício Físico/fisiologia , Músculo Esquelético/metabolismo , Fosforilação Oxidativa , Trifosfato de Adenosina/metabolismo , Metabolismo dos Carboidratos , Ácidos Graxos/metabolismo , Proteínas Facilitadoras de Transporte de Glucose/metabolismo , HumanosRESUMO
Fish oil (FO) has been shown to have beneficial effects in the body via incorporation into the membranes of many tissues. It has been proposed that omega-3 fatty acids in FO may increase whole body resting metabolic rate (RMR) and fatty acid (FA) oxidation in human subjects, but the results to date are equivocal. The purpose of this study was to investigate the effects of a 12 week FO supplementation period on RMR and substrate oxidation, in comparison to an olive oil (OO) control group, in young healthy males (n = 26; 22.8 ± 2.6 yr). Subjects were matched for age, RMR, physical activity, VO2max and body mass, and were randomly separated into a group supplemented with either OO (3 g/d) or FO containing 2 g/d eicosapentaenoic acid (EPA) and 1 g/d docosahexaenoic acid (DHA). Participants visited the lab for RMR and substrate oxidation measurements after an overnight fast (10-12 hr) at weeks 0, 6 and 12. Fasted blood samples were taken at baseline and after 12 weeks of supplementation. There were significant increases in the EPA (413%) and DHA (59%) levels in red blood cells after FO supplementation, with no change of these fatty acids in the OO group. RMR and substrate oxidation did not change after supplementation with OO or FO after 6 and 12 weeks. Since there was no effect of supplementation on metabolic measures, we pooled the two treatment groups to determine whether there was a seasonal effect on RMR and substrate oxidation. During the winter season, there was an increase in FA oxidation (36%) with a concomitant decrease (34%) in carbohydrate (CHO) oxidation (p < 0.01), with no change in RMR. These measures were unaffected during the summer season. In conclusion, FO supplementation had no effect on RMR and substrate oxidation in healthy young males. Resting FA oxidation was increased and CHO oxidation reduced over a 12 week period in the winter, with no change in RMR. TRIAL REGISTRATION: ClinicalTrials.gov NCT02092649.
Assuntos
Metabolismo Basal/efeitos dos fármacos , Óleos de Peixe/farmacologia , Adulto , Metabolismo dos Carboidratos/efeitos dos fármacos , Suplementos Nutricionais , Ácidos Docosa-Hexaenoicos/sangue , Ácidos Docosa-Hexaenoicos/farmacologia , Ácido Eicosapentaenoico/sangue , Ácido Eicosapentaenoico/farmacologia , Eritrócitos/efeitos dos fármacos , Eritrócitos/metabolismo , Ácidos Graxos/sangue , Voluntários Saudáveis , Humanos , Masculino , Azeite de Oliva/farmacologia , Oxirredução , Estações do AnoRESUMO
This study determined whether mild dehydration influenced skeletal muscle glycogen use, core temperature or performance during high-intensity, intermittent cycle-based exercise in ice hockey players vs. staying hydrated with water. Eight males (21.6 ± 0.4 yr, 183.5 ± 1.6 cm, 83.9 ± 3.7 kg, 50.2 ± 1.9 ml·kg-1·min-1) performed two trials separated by 7 days. The protocol consisted of 3 periods (P) containing 10 × 45-s cycling bouts at ~133% VO2max, followed by 135 s of passive rest. Subjects drank no fluid and dehydrated during the protocol (NF), or maintained body mass by drinking WATER. Muscle biopsies were taken at rest, immediately before and after P3. Subjects were mildly dehydrated (-1.8% BM) at the end of P3 in the NF trial. There were no differences between the NF and WATER trials for glycogen use (P1+P2; 350.1 ± 31.9 vs. 413.2 ± 33.2, P3; 103.5 ± 16.2 vs. 131.5 ± 18.9 mmol·kg dm-1), core temperature (P1; 37.8 ± 0.1 vs. 37.7 ± 0.1, P2; 38.2 ± 0.1 vs. 38.1 ± 0.1, P3; 38.3 ± 0.1 vs. 38.2 ± 0.1 °C) or performance (P1; 156.3 ± 7.8 vs. 154.4 ± 8.2, P2; 150.5 ± 7.8 vs. 152.4 ± 8.3, P3; 144.1 ± 8.7 vs. 148.4 ± 8.7 kJ). This study demonstrated that typical dehydration experienced by ice hockey players (~1.8% BM loss), did not affect glycogen use, core temperature, or voluntary performance vs. staying hydrated by ingesting water during a cycle-based simulation of ice hockey exercise in a laboratory environment.
Assuntos
Atletas , Desempenho Atlético , Desidratação/metabolismo , Glicogenólise , Treinamento Intervalado de Alta Intensidade , Hóquei , Músculo Esquelético/metabolismo , Adulto , Ciclismo , Biópsia , Temperatura Corporal , Temperatura Baixa/efeitos adversos , Estudos Cross-Over , Desidratação/patologia , Desidratação/fisiopatologia , Desidratação/prevenção & controle , Ingestão de Líquidos , Humanos , Masculino , Músculo Esquelético/patologia , Músculo Esquelético/fisiologia , Músculo Esquelético/fisiopatologia , Consumo de Oxigênio , Índice de Gravidade de Doença , Redução de Peso , Adulto JovemRESUMO
SCOPE: Increased consumption of fish oils rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is associated with improved cardiometabolic health and inflammatory status; however, age-related responses remain poorly described. METHODS AND RESULTS: In a placebo-controlled study, healthy young and older men consumed five fish oil capsules daily, providing 2.0 g/d EPA and 1.0g/d DHA, for three months. Both young and older men experienced a â¼30% reduction in blood triglycerides with fish oil supplementation. A significant group × time interaction was observed for DHA, with young men experiencing a â¼twofold increase in DHA in serum and RBCs, while older men showed negligible increases. Other fatty acids were differentially regulated between young and older men, most notably osbond acid and several saturates. Small changes were observed in serum oxylipins, with both groups of men responding similarly: 5-HETE was reduced, while PGF2α and 17-HDoHE were increased. Changes in oxylipins occurred independent of changes in whole blood expression of key genes regulating oxylipin production. CONCLUSION: Our study suggests that both young and older men experience the triglyceride-lowering benefits associated with fish oil supplements, but show differential responses in blood fatty acids. Additionally, fish oil promotes an improved oxylipin profile in both groups of men.
Assuntos
Ácidos Graxos/sangue , Óleos de Peixe/farmacologia , Oxilipinas/sangue , Adolescente , Adulto , Fatores Etários , Idoso , Suplementos Nutricionais , Ácidos Docosa-Hexaenoicos/farmacologia , Ácido Eicosapentaenoico/farmacologia , Expressão Gênica , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Skeletal muscle is extremely adaptable to a variety of metabolic challenges, as both traditional moderate-intensity endurance (ET) and high-intensity interval training (HIIT) increases oxidative potential in a coordinated manner. Although these responses have been clearly demonstrated in healthy individuals, it remains to be determined whether both produce similar responses in the context of hypertension, one of the most prevalent and costly diseases worldwide. Therefore, in the current study, we used the Dahl sodium-sensitive rat, a model of hypertension, to determine the molecular responses to 4 wk of either ET or HIIT in the red (RG) and white gastrocnemius (WG) muscles. In the RG, both ET and HIIT increased the content of electron transport chain proteins and increased succinate dehydrogenase (SDH) content in type I fibers. Although both intensities of exercise shifted fiber type in RG (increased IIA, decreased IIX), only HIIT was associated with a reduction in endothelial nitric oxide synthase and an increase in HIF-1α proteins. In the WG, both ET and HIIT increased markers of the electron transport chain; however, HIIT decreased SDH content in a fiber-specific manner. ET increased type IIA, decreased IIB fibers, and increased capillarization, while, in contrast, HIIT increased the percentage of IIB fibers, decreased capillary-to-fiber ratios, decreased endothelial nitric oxide synthase, and increased hypoxia inducible factor-1α (HIF-1α) protein. Altogether, these data show that unlike in healthy animals, ET and HIIT have divergent effects in the skeletal muscle of hypertensive rats. This suggests ET may be optimal at improving the oxidative capacity of skeletal muscle in animals with hypertension.
Assuntos
Hipertensão/fisiopatologia , Contração Muscular , Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/fisiopatologia , Resistência Física , Esforço Físico , Adaptação Fisiológica , Animais , Pressão Sanguínea , Capilares/metabolismo , Capilares/fisiopatologia , Modelos Animais de Doenças , Complexo de Proteínas da Cadeia de Transporte de Elétrons/metabolismo , Hipertensão/etiologia , Hipertensão/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Masculino , Mitocôndrias Musculares/metabolismo , Fibras Musculares de Contração Rápida/metabolismo , Fibras Musculares de Contração Lenta/metabolismo , Músculo Esquelético/metabolismo , Neovascularização Fisiológica , Óxido Nítrico Sintase Tipo III/metabolismo , Ratos Endogâmicos Dahl , Cloreto de Sódio na Dieta , Succinato Desidrogenase/metabolismo , Fatores de TempoRESUMO
There has been re-emerging interest and significant work dedicated to investigating the metabolic effects of high intensity interval training (HIIT) in recent years. HIIT is considered to be a time efficient alternative to classic endurance training (ET) that elicits similar metabolic responses in skeletal muscle. However, there is a lack of information on the impact of HIIT on cardiac muscle in disease. Therefore, we determined the efficacy of ET and HIIT to alter cardiac muscle characteristics involved in the development of diastolic dysfunction, such as ventricular hypertrophy, fibrosis and angiogenesis, in a well-established rodent model of hypertension-induced heart failure before the development of overt heart failure. ET decreased left ventricle fibrosis by ~40% (P < 0.05), and promoted a 20% (P<0.05) increase in the left ventricular capillary/fibre ratio, an increase in endothelial nitric oxide synthase protein (P<0.05), and a decrease in hypoxia inducible factor 1 alpha protein content (P<0.05). In contrast, HIIT did not decrease existing fibrosis, and HIIT animals displayed a 20% increase in left ventricular mass (P<0.05) and a 20% decrease in cross sectional area (P<0.05). HIIT also increased brain natriuretic peptide by 50% (P<0.05), in the absence of concomitant angiogenesis, strongly suggesting pathological cardiac remodeling. The current data support the longstanding belief in the effectiveness of ET in hypertension. However, HIIT promoted a pathological adaptation in the left ventricle in the presence of hypertension, highlighting the need for further research on the widespread effects of HIIT in the presence of disease.
Assuntos
Insuficiência Cardíaca/fisiopatologia , Hipertensão/fisiopatologia , Condicionamento Físico Animal/fisiologia , Remodelação Ventricular , Animais , Biomarcadores/sangue , Insuficiência Cardíaca/metabolismo , Hipertensão/metabolismo , Hipertrofia Ventricular Esquerda/metabolismo , Hipertrofia Ventricular Esquerda/fisiopatologia , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Masculino , Óxido Nítrico Sintase Tipo III/metabolismo , Resistência Física , Distribuição Aleatória , Ratos , Ratos Endogâmicos Dahl , Sódio na Dieta/administração & dosagemRESUMO
Caffeine can improve exercise performance when it is ingested at moderate doses (3-6 mg/kg body mass). Caffeine also has an effect on the central nervous system (CNS), and it is now recognized that most of the performance-enhancing effect of caffeine is accomplished through the antagonism of the adenosine receptors, influencing the dopaminergic and other neurotransmitter systems. Adenosine and dopamine interact in the brain, and this might be one mechanism to explain how the important components of motivation (i.e. vigor, persistence and work output) and higher-order brain processes are involved in motor control. Caffeine maintains a higher dopamine concentration especially in those brain areas linked with 'attention'. Through this neurochemical interaction, caffeine improves sustained attention, vigilance, and reduces symptoms of fatigue. Other aspects that are localized in the CNS are a reduction in skeletal muscle pain and force sensation, leading to a reduction in perception of effort during exercise and therefore influencing the motivational factors to sustain effort during exercise. Because not all CNS aspects have been examined in detail, one should consider that a placebo effect may also be present. Overall, it appears that the performance-enhancing effects of caffeine reside in the brain, although more research is necessary to reveal the exact mechanisms through which the CNS effect is established.
Assuntos
Adenosina/metabolismo , Encéfalo/efeitos dos fármacos , Cafeína/farmacologia , Estimulantes do Sistema Nervoso Central/farmacologia , Dopamina/metabolismo , Exercício Físico/fisiologia , Resistência Física/fisiologia , Atenção/efeitos dos fármacos , Encéfalo/metabolismo , Cafeína/uso terapêutico , Exercício Físico/psicologia , Fadiga/prevenção & controle , Humanos , Motivação/efeitos dos fármacos , Músculo Esquelético , Dor Musculoesquelética/prevenção & controle , Extratos Vegetais/farmacologia , Antagonistas de Receptores Purinérgicos P1/farmacologiaRESUMO
OBJECTIVE: Increasing omega-3 fatty acid (FA) intake, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), is associated with numerous health benefits; however, the benefits on inflammation appear to vary depending on the study population examined. While improvements in inflammatory status have been reported in the elderly, there is less evidence regarding the effects of fish oil supplementation on inflammation in young adults. The goal of the present study was to examine the influence of fish oil supplementation on lipid metabolites and the inflammatory status of young healthy men. MATERIALS/METHODS: Fasted serum samples were collected from 10 young healthy males (23.4 ± 1.7 years) before and after a 3-month supplementation of fish-oil containing 2.0g EPA and 1.0g DHA. Samples were analyzed to investigate changes in FA profiles, bioclinical parameters (e.g. triglyceride and hs-CRP), and a panel of 26 eicosanoids. Paired t-tests were used to evaluate changes between the time points. RESULTS: Serum triglycerides decreased (P=0.0006) while the proportion of HDL-c (relative to total cholesterol) increased significantly (P=0.0495) after fish oil supplementation. Specific monounsaturated and polyunsaturated FA levels were changed following supplementation, including reductions in palmitoleic and oleic acid, and, as expected, increases in EPA and DHA. We also observed increases in eicosanoids, namely prostaglandin-F2α (P<0.0001) and thromboxane-B2 (P=0.0296), after fish oil supplementation. CONCLUSIONS: A 3-month fish oil supplementation in young healthy men improved circulating triglyceride levels and the HDL-c ratio while, concomitantly, increasing the concentrations of two eicosanoids (prostaglandin-F2α and thromboxane-B2). This suggests that fish oil supplementation does have significant benefits in young healthy adults and that specific omega-6-derived eicosanoids can help to further our understanding regarding the beneficial link between omega-3 FA and inflammation.
Assuntos
Suplementos Nutricionais , Eicosanoides/sangue , Óleos de Peixe/farmacologia , Adolescente , Adulto , Dinoprosta/sangue , Ácidos Docosa-Hexaenoicos/sangue , Ácido Eicosapentaenoico/sangue , Ácidos Graxos/sangue , Ácidos Graxos Monoinsaturados/sangue , Ácidos Graxos Insaturados/sangue , Humanos , Inflamação/sangue , Lipídeos/sangue , Masculino , Tromboxano B2/sangue , Adulto JovemRESUMO
Energy transfer between mitochondrial and cytosolic compartments is predominantly achieved by creatine-dependent phosphate shuttling (PCr/Cr) involving mitochondrial creatine kinase (miCK). However, ADP/ATP diffusion through adenine nucleotide translocase (ANT) and voltage-dependent anion carriers (VDACs) is also involved in this process. To determine if exercise alters the regulation of this system, ADP-stimulated mitochondrial respiratory kinetics were assessed in permeabilized muscle fibre bundles (PmFBs) taken from biopsies before and after 2 h of cycling exercise (60% ) in nine lean males. Concentrations of creatine (Cr) and phosphocreatine (PCr) as well as the contractile state of PmFBs were manipulated in situ. In the absence of contractile signals (relaxed PmFBs) and miCK activity (no Cr), post-exercise respiratory sensitivity to ADP was reduced in situ (up to 126% higher apparent K(m) to ADP) suggesting inhibition of ADP/ATP diffusion between matrix and cytosolic compartments (possibly ANT and VDACs). However this effect was masked in the presence of saturating Cr (no effect of exercise on ADP sensitivity). Given that the role of ANT is thought to be independent of Cr, these findings suggest ADP/ATP, but not PCr/Cr, cycling through the outer mitochondrial membrane (VDACs) may be attenuated in resting muscle after exercise. In contrast, in contracted PmFBs, post-exercise respiratory sensitivity to ADP increased with miCK activation (saturating Cr; 33% lower apparent K(m) to ADP), suggesting prior exercise increases miCK sensitivity in situ. These observations demonstrate that exercise increases miCK-dependent respiratory sensitivity to ADP, promoting mitochondrial-cytosolic energy exchange via PCr/Cr cycling, possibly through VDACs. This effect may mask an underlying inhibition of Cr-independent ADP/ATP diffusion. This enhanced regulation of miCK-dependent phosphate shuttling may improve energy homeostasis through more efficient coupling of oxidative phosphorylation to perturbations in cellular energy charge during subsequent bouts of contraction.
Assuntos
Difosfato de Adenosina/fisiologia , Creatina Quinase Mitocondrial/fisiologia , Exercício Físico/fisiologia , Músculo Esquelético/fisiologia , Animais , Humanos , Masculino , Contração Muscular , Ratos , Ratos Sprague-DawleyRESUMO
Fatty acid oxidation is highly regulated in skeletal muscle and involves several sites of regulation, including the transport of fatty acids across both the plasma and mitochondrial membranes. Transport across these membranes is recognized to be primarily protein mediated, limited by the abundance of fatty acid transport proteins on the respective membranes. In recent years, evidence has shown that fatty acid transport proteins move in response to acute and chronic perturbations; however, in human skeletal muscle the localization of fatty acid transport proteins in response to training has not been examined. Therefore, we determined whether high-intensity interval training (HIIT) increased total skeletal muscle, sarcolemmal, and mitochondrial membrane fatty acid transport protein contents. Ten untrained females (22 +/- 1 yr, 65 +/- 2 kg; .VO(2peak): 2.8 +/- 0.1 l/min) completed 6 wk of HIIT, and biopsies from the vastus lateralis muscle were taken before training, and following 2 and 6 wk of HIIT. Training significantly increased maximal oxygen uptake at 2 and 6 wk (3.1 +/- 0.1, 3.3 +/- 0.1 l/min). Training for 6 wk increased FAT/CD36 at the whole muscle (10%) and mitochondrial levels (51%) without alterations in sarcolemmal content. Whole muscle plasma membrane fatty acid binding protein (FABPpm) also increased (48%) after 6 wk of training, but in contrast to FAT/CD36, sarcolemmal FABPpm increased (23%), whereas mitochondrial FABPpm was unaltered. The changes on sarcolemmal and mitochondrial membranes occurred rapidly, since differences (< or =2 wk) were not observed between 2 and 6 wk. This is the first study to demonstrate that exercise training increases fatty acid transport protein content in whole muscle (FAT/CD36 and FABPpm) and sarcolemmal (FABPpm) and mitochondrial (FAT/CD36) membranes in human skeletal muscle of females. These results suggest that increases in skeletal muscle fatty acid oxidation following training are related in part to changes in fatty acid transport protein content and localization.
Assuntos
Proteínas de Transporte de Ácido Graxo/metabolismo , Mitocôndrias Musculares/metabolismo , Músculo Esquelético/metabolismo , Aptidão Física/fisiologia , Sarcolema/metabolismo , Limiar Anaeróbio , Ciclismo/fisiologia , Biópsia , Western Blotting , Metabolismo Energético/fisiologia , Exercício Físico/fisiologia , Feminino , Humanos , Ácido Láctico/sangue , Mitocôndrias Musculares/enzimologia , Consumo de Oxigênio/fisiologia , Sarcolema/enzimologia , Adulto JovemRESUMO
High-intensity aerobic interval training (HIIT) is a compromise between time-consuming moderate-intensity training and sprint-interval training requiring all-out efforts. However, there are few data regarding the ability of HIIT to increase the capacities of fat and carbohydrate oxidation in skeletal muscle. Using untrained recreationally active individuals, we investigated skeletal muscle and whole-body metabolic adaptations that occurred following 6 weeks of HIIT (~1 h of 10 x 4 min intervals at ~90% of peak oxygen consumption (VO2 peak), separated by 2 min rest, 3 d.week-1). A VO2 peak test, a test to exhaustion (TE) at 90% of pre-training VO2 peak, and a 1 h cycle at 60% of pre-training VO2 peak were performed pre- and post-HIIT. Muscle biopsies were sampled during the TE at rest, after 5 min, and at exhaustion. Training power output increased by 21%, and VO2 peak increased by 9% following HIIT. Muscle adaptations at rest included the following: (i) increased cytochrome c oxidase IV content (18%) and maximal activities of the mitochondrial enzymes citrate synthase (26%), beta-hydroxyacyl-CoA dehydrogenase (29%), aspartate-amino transferase (26%), and pyruvate dehydrogenase (PDH; 21%); (ii) increased FAT/CD36, FABPpm, GLUT 4, and MCT 1 and 4 transport proteins (14%-30%); and (iii) increased glycogen content (59%). Major adaptations during exercise included the following: (i) reduced glycogenolysis, lactate accumulation, and substrate phosphorylation (0-5 min of TE); (ii) unchanged PDH activation (carbohydrate oxidation; 0-5 min of TE); (iii) ~2-fold greater time during the TE; and (iv) increased fat oxidation at 60% of pre-training VO2 peak. This study demonstrated that 18 h of repeated high-intensity exercise sessions over 6 weeks (3 d.week-1) is a powerful method to increase whole-body and skeletal muscle capacities to oxidize fat and carbohydrate in previously untrained individuals.
Assuntos
Metabolismo dos Carboidratos/fisiologia , Exercício Físico/fisiologia , Gorduras/metabolismo , Músculo Esquelético/metabolismo , Esforço Físico/fisiologia , Adulto , Aspartato Aminotransferase Mitocondrial/metabolismo , Biomarcadores/sangue , Biomarcadores/metabolismo , Biópsia , Glicemia/análise , Western Blotting , Citrato (si)-Sintase/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Glicerol/sangue , Glicogênio/metabolismo , Humanos , Ácido Láctico/sangue , Masculino , Resistência Física/fisiologia , Complexo Piruvato Desidrogenase/metabolismo , Adulto JovemRESUMO
This study examined 1) the plasma taurine response to acute oral taurine supplementation (T), and 2) the effects of 7 days of T on muscle amino acid content and substrate metabolism during 2 h of cycling at approximately 60% peak oxygen consumption (VO2peak). In the first part of the study, after an overnight fast, 7 volunteers (28+/-3 yr, 184+/-2 cm, 88.0+/-6.6 kg) ingested 1.66 g oral taurine doses with breakfast (8 AM) and lunch (12 noon), and blood samples were taken throughout the day. In the second part of the study, eight men (22+/-1 yr, 181+/-1 cm, 80.9+/-3.8 kg, 4.21+/-0.16 l/min VO2peak) cycled for 2 h after 7 days of placebo (P) ingestion (6 g glucose/day) and again following 7 days of T (5 g/day). In the first part of the study, plasma taurine was 64+/-4 microM before T and rose rapidly to 778+/-139 microM by 10 AM and remained elevated at noon (359+/-56 microM). Plasma taurine reached 973+/-181 microM at 1 PM and was 161+/-31 microM at 4 PM. In the second part of the study, seven days of T had no effect on muscle taurine content (mmol/kg dry muscle) at rest (P, 44+/-15 vs. T, 42+/-15) or after exercise (P, 43+/-12 vs. T, 43+/-11). There was no difference in muscle glycogen or other muscle metabolites between conditions, but there were notable interaction effects for muscle valine, isoleucine, leucine, cystine, glutamate, alanine, and arginine amino acid content following exercise after T. These data indicate that 1) acute T produces a 13-fold increase in plasma taurine concentration; 2) despite the ability to significantly elevate plasma taurine for extended periods throughout the day, 7 days of T does not alter skeletal muscle taurine content or carbohydrate and fat oxidation during exercise; and 3) T appears to have some impact on muscle amino acid response to exercise.
Assuntos
Exercício Físico/fisiologia , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Taurina/metabolismo , Taurina/farmacologia , Difosfato de Adenosina/metabolismo , Monofosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Adulto , Aminoácidos/metabolismo , Limiar Anaeróbio/efeitos dos fármacos , Limiar Anaeróbio/fisiologia , Glicemia/metabolismo , Creatina/metabolismo , Suplementos Nutricionais , Ácidos Graxos não Esterificados/sangue , Feminino , Glicogênio/metabolismo , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Humanos , Ácido Láctico/sangue , Masculino , Consumo de Oxigênio/efeitos dos fármacos , Consumo de Oxigênio/fisiologia , Fosfocreatina/metabolismo , Troca Gasosa Pulmonar/efeitos dos fármacos , Taurina/sangueRESUMO
We examined the controversial notion of whether lactate is directly oxidized by subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria obtained from red and white rat skeletal muscle. Respiratory control ratios were normal in SS and IMF mitochondria. At all concentrations (0.18-10 mm), and in all mitochondria, pyruvate oxidation greatly exceeded lactate oxidation, by 31- to 186-fold. Pyruvate and lactate oxidation were inhibited by alpha-cyano-4-hydroxycinnamate, while lactate oxidation was inhibited by oxamate. Excess pyruvate (10 mm) inhibited the oxidation of palmitate (1.8 mm) as well as lactate (1.8 mm). In contrast, excess lactate (10 mm) failed to inhibit the oxidation of either palmitate (1.8 mm) or pyruvate (1.8 mm). The cell-permeant adenosine analogue, AICAR, increased pyruvate oxidation; in contrast, lactate oxidation was not altered. The monocarboxylate transporters MCT1 and 4 were present on SS mitochondria, but not on IMF mitochondria, whereas, MCT2, a high-affinity pyruvate transporter, was present in both SS and IMF mitochondria. The lactate dehydrogenase (LDH) activity associated with SS and IMF mitochondria was 200- to 240-fold lower than in whole muscle. Addition of LDH increased the rate of lactate oxidation, but not pyruvate oxidation, in a dose-dependent manner, such that lactate oxidation approached the rates of pyruvate oxidation. Collectively, these studies indicate that direct mitochondrial oxidation of lactate (i.e. an intracellular lactate shuttle) does not occur within the matrix in either IMF or SS mitochondria obtained from red or white rat skeletal muscle, because of the very limited quantity of LDH within mitochondria.
Assuntos
L-Lactato Desidrogenase/metabolismo , Lactatos/metabolismo , Mitocôndrias Musculares/metabolismo , Fibras Musculares de Contração Rápida/fisiologia , Sarcolema/metabolismo , Aminoimidazol Carboxamida/análogos & derivados , Aminoimidazol Carboxamida/farmacologia , Animais , Isoenzimas/metabolismo , Cinética , Masculino , Mitocôndrias Musculares/efeitos dos fármacos , Fibras Musculares de Contração Rápida/efeitos dos fármacos , Miofibrilas/efeitos dos fármacos , Miofibrilas/fisiologia , Oxirredução , Consumo de Oxigênio , Ratos , Ratos Sprague-Dawley , Ribonucleotídeos/farmacologiaRESUMO
The energy required to run a marathon is mainly provided through oxidative phosphorylation in the mitochondria of the active muscles. Small amounts of energy from substrate phosphorylation are also required during transitions and short periods when running speed is increased. The three inputs for adenosine triphosphate production in the mitochondria include oxygen, free adenosine diphosphate and inorganic phosphate, and reducing equivalents. The reducing equivalents are derived from the metabolism of fat and carbohydrate (CHO), which are mobilised from intramuscular stores and also delivered from adipose tissue and liver, respectively. The metabolism of fat and CHO is tightly controlled at several regulatory sites during marathon running. Slower, recreational runners run at 60-65% maximal oxygen uptake (VO(2max)) for approximately 3:45:00 and faster athletes run at 70-75% for approximately 2:45:00. Both groups rely heavily on fat and CHO fuels. However, elite athletes run marathons at speeds requiring between 80% and 90% VO(2max), and finish in times between 2:05:00 and 2:20:00. They are highly adapted to oxidise fat and must do so during training. However, they compete at such high running speeds, that CHO oxidation (also highly adapted) may be the exclusive source of energy while racing. Further work with elite athletes is needed to examine this possibility.
Assuntos
Mitocôndrias Musculares/metabolismo , Fosforilação Oxidativa , Esforço Físico/fisiologia , Corrida/fisiologia , Humanos , OntárioRESUMO
Skeletal muscle hormone-sensitive lipase (HSL) activity is increased by contractions and increases in blood epinephrine (EPI) concentrations and cyclic AMP activation of the adrenergic pathway during prolonged exercise. To determine the importance of hormonal stimulation of HSL activity during the onset of moderate- and high-intensity exercise, nine men [age 24.3 +/- 1.2 yr, 80.8 +/- 5.0 kg, peak oxygen consumption (VO2 peak) 43.9 +/- 3.6 ml x kg(-1) x min(-1)] cycled for 1 min at approximately 65% VO2 peak, rested for 60 min, and cycled at approximately 90% VO2 peak for 1 min. Skeletal muscle biopsies were taken pre- and postexercise, and arterial blood was sampled throughout exercise. Arterial EPI increased (P < 0.05) postexercise at 65% (0.45 +/- 0.10 to 0.78 +/- 0.27 nM) and 90% VO2 peak (0.57 +/- 0.34 to 1.09 +/- 0.50 nM). HSL activity increased (P < 0.05) following 1 min of exercise at 65% VO2 peak [1.05 +/- 0.39 to 1.78 +/- 0.54 mmol x min(-1) x kg dry muscle (dm)(-1)] and 90% VO2 peak (1.07 +/- 0.24 to 1.91 +/- 0.62 mmol x min(-1) x kg dm(-1)). Cyclic AMP content also increased (P < 0.05) at both exercise intensities (65%: 1.52 +/- 0.67 to 2.75 +/- 1.12, 90%: 1.85 +/- 0.65 to 2.64 +/- 0.93 micromol/kg dm). HSL Ser660 phosphorylation (approximately 55% increase) and ERK1/2 phosphorylation ( approximately 33% increase) were augmented following exercise at both intensities, whereas HSL Ser563 and Ser565 phosphorylation were not different from rest. The results indicate that increases in arterial EPI concentration during the onset of moderate- and high-intensity exercise increase cyclic AMP content, which results in the phosphorylation of HSL Ser660. This adrenergic stimulation contributes to the increase in HSL activity that occurs in human skeletal muscle in the first minute of exercise at 65% and 90% VO2 peak.