21 results on '"Mitchell, W. Kyle"'
Search Results
2. Muscle responses to transcranial stimulation in man depend on background oscillatory activity
- Author
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Mitchell, W. Kyle, Baker, Mark R., and Baker, Stuart N.
- Published
- 2007
3. A novel D2O tracer method to quantify RNA turnover as a biomarker of de novo ribosomal biogenesis, in vitro, in animal models, and in human skeletal muscle
- Author
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Brook, Matthew S., Wilkinson, D.J., Mitchell, W. Kyle, Lund, Jonathan N., Phillips, Bethan E., Szewczyk, Nathaniel J., Kainulainen, H., Lensu, S., Koch, L.G., Britton, S.L., Greenhaff, Paul L., Smith, K., and Atherton, Philip J.
- Subjects
Ribosomal biogenesis ,Muscle ,RNA synthesis ,D2O - Abstract
Current methods to quantify in vivo RNA dynamics are limited. Here, we developed a novel stable isotope (D2O) methodology to quantify RNA synthesis (i.e., ribosomal biogenesis) in cells, animal models, and humans. First, proliferating C2C12 cells were incubated in D2O-enriched media and myotubes ±50 ng/ml IGF-I. Second, rat quadriceps (untrained, n = 9; 7-wk interval-“like” training, n = 13) were collected after ~3-wk D2O (70 atom %) administration, with body-water enrichment monitored via blood sampling. Finally, 10 (23 ± 1 yr) men consumed 150-ml D2O followed by 50 ml/wk and undertook 6-wk resistance exercise (6 × 8 repetitions, 75% 1-repetition maximum 3/wk) with body-water enrichment monitored by saliva sampling and muscle biopsies (for determination of RNA synthesis) at 0, 3, and 6 wk. Ribose mole percent excess (r-MPE) from purine nucleotides was analyzed via GC-MS/MS. Proliferating C2C12 cell r-MPE exhibited a rise to plateau, whereas IGF-I increased myotube RNA from 76 ± 3 to 123 ± 3 ng/μl and r-MPE by 0.39 ± 0.1% (both P < 0.01). After 3 wk, rat quadriceps r-MPE had increased to 0.25 ± 0.01% (P < 0.01) and was greater with running exercise (0.36 ± 0.02%; P < 0.01). Human muscle r-MPE increased to 0.06 ± 0.01 and 0.13 ± 0.02% at 3/6 wk, respectively, equating to synthesis rates of ~0.8%/day, increasing with resistance exercise to 1.7 ± 0.3%/day (P < 0.01) and 1.2 ± 0.1%/day (P < 0.05) at 3/6 wk, respectively. Therefore, we have developed and physiologically validated a novel technique to explore ribosomal biogenesis in a multimodal fashion.
- Published
- 2017
4. Eccentric Exercise and the Critically Ill Patient
- Author
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Mitchell, W. Kyle, primary, Taivassalo, Tanja, additional, Narici, Marco V., additional, and Franchi, Martino V., additional
- Published
- 2017
- Full Text
- View/download PDF
5. Pancreas preserving distal duodenectomy: A versatile operation for a range of infra-papillary pathologies
- Author
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Mitchell, W Kyle, primary, Thomas, Pradeep F, additional, Zaitoun, Abed M, additional, Brooks, Adam J, additional, and Lobo, Dileep N, additional
- Published
- 2017
- Full Text
- View/download PDF
6. Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle size and strength; a quantitative review
- Author
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Mitchell, W Kyle, Williams, John, Atherton, Philip J., Larvin, Michael, Lund, Jonathan N., Narici, Marco, Mitchell, W Kyle, Williams, John, Atherton, Philip J., Larvin, Michael, Lund, Jonathan N., and Narici, Marco
- Abstract
peer-reviewed, Changing demographics make it ever more important to understand the modifiable risk factors for disability and loss of independence with advancing age. For more than two decades there has been increasing interest in the role of sarcopenia, the age-related loss of muscle or lean mass, in curtailing active and healthy aging. There is now evidence to suggest that lack of strength, or dynapenia, is a more constant factor in compromised wellbeing in old age and it is apparent that the decline in muscle mass and the decline in strength can take quite different trajectories. This demands recognition of the concept of muscle quality; that is the force generating per capacity per unit cross-sectional area (CSA). An understanding of the impact of aging on skeletal muscle will require attention to both the changes in muscle size and the changes in muscle quality. The aim of this review is to present current knowledge of the decline in human muscle mass and strength with advancing age and the associated risk to health and survival and to review the underlying changes in muscle characteristics and the etiology of sarcopenia. Cross-sectional studies comparing young (18-45â years) and old (>65â years) samples show dramatic variation based on the technique used and population studied. The median of values of rate of loss reported across studies is 0.47% per year in men and 0.37% per year in women. Longitudinal studies show that in people aged 75â years, muscle mass is lost at a rate of 0.64-0.70% per year in women and 0.80-00.98% per year in men. Strength is lost more rapidly. Longitudinal studies show that at age 75â years, strength is lost at a rate of 3-4% per year in men and 2.5-3% per year in women. Studies that assessed changes in mass and strength in the same sample report a loss of strength 2-5 times faster than loss of mass. Loss of strength is a more consistent risk for disability and death than is loss of muscle mass., PUBLISHED, peer-reviewed
- Published
- 2016
7. The impact of delivery profile of essential amino acids upon skeletal muscle protein synthesis in older men: clinical efficacy of pulse vs. bolus supply
- Author
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Mitchell, W. Kyle, primary, Phillips, Bethan E., additional, Williams, John P., additional, Rankin, Debbie, additional, Lund, Jonathan N., additional, Wilkinson, Daniel J., additional, Smith, Kenneth, additional, and Atherton, Philip J., additional
- Published
- 2015
- Full Text
- View/download PDF
8. Sarcopenia, Dynapenia, and the Impact of Advancing Age on Human Skeletal Muscle Size and Strength; a Quantitative Review
- Author
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Mitchell, W. Kyle, primary, Williams, John, additional, Atherton, Philip, additional, Larvin, Mike, additional, Lund, John, additional, and Narici, Marco, additional
- Published
- 2012
- Full Text
- View/download PDF
9. Pancreas preserving distal duodenectomy: a versatile operation for a range of infra-papillary pathologies
- Author
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Mitchell, W. Kyle, Thomas, Pradeep F., Zaitoun, Abed M., Brooks, Adam J., Lobo, Dileep N., Mitchell, W. Kyle, Thomas, Pradeep F., Zaitoun, Abed M., Brooks, Adam J., and Lobo, Dileep N.
- Abstract
AIM To investigate the range of pathologies treated by pancreas preserving distal duodenectomy (PPDD) and present the outcome of follow-up. METHODS Neoplastic lesions of the duodenum are treated conventionally by pancreaticoduodenectomy. Lesions distal to the major papilla may be suitable for a pancreas-preserving distal duodenectomy, potentially reducing morbidity and mortality. We present our experience with this procedure. Selective intraoperative duodenoscopy assessed the relationship of the papilla to the lesion. After duodenal mobilisation and confirmation of the site of the lesion, the duodenum was transected distal to the papilla and beyond the duodenojejunal flexure and a side-to-side duodenojejunal anastomosis was formed. Patients were identified from a prospectively maintained database and outcomes determined from digital health records with a dataset including demographics, co-morbidities, mode of presentation, preoperative imaging and assessment, nutritional support needs, technical operative details, blood transfusion requirements, length of stay, pathology including lymph node yield and lymph node involvement, length of follow-up, complications and outcomes. Related published literature was also reviewed. RESULTS Twenty-four patients had surgery with the intent of performing PPDD from 2003 to 2016. Nineteen underwent PPDD successfully. Two patients planned for PPDD proceeded to formal pancreaticoduodenectomy (PD) while three had unresectable disease. Median post-operative follow-up was 32 mo. Pathologies resected included duodenal adenocarcinoma (n = 6), adenomas (n = 5), gastrointestinal stromal tumours (n = 4) and lipoma, bleeding duodenal diverticulum, locally advanced colonic adenocarcinoma and extrinsic compression (n = 1 each). Median postoperative length of stay (LOS) was 8 d and morbidity was low [pain and nausea/vomiting (n = 2), anastomotic stricture (n = 1), pneumonia (n = 1), and overwhelming postsplenectomy sepsis (n = 1, asplenic patient
- Full Text
- View/download PDF
10. Supplementing essential amino acids with the nitric oxide precursor, l-arginine, enhances skeletal muscle perfusion without impacting anabolism in older men
- Author
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Mitchell, W. Kyle, Phillips, Bethan E., Wilkinson, Daniel J., Williams, John P., Rankin, Debbie, Lund, Jonathan N., Smith, Kenneth, Atherton, Philip J., Mitchell, W. Kyle, Phillips, Bethan E., Wilkinson, Daniel J., Williams, John P., Rankin, Debbie, Lund, Jonathan N., Smith, Kenneth, and Atherton, Philip J.
- Abstract
Postprandial limb blood flow and skeletal muscle microvascular perfusion reduce with aging. Here we tested the impact of providing bolus essential amino acids (EAA) in the presence and absence of the nitric oxide precursor, l-Arginine (ARG), upon skeletal muscle blood flow and anabolism in older men. Healthy young (YOUNG: 19.7 ± 0.5 y, N = 8) and older men (OLD, 70 ± 0.8 y, N = 8) received 15 g EAA or (older only) 15 g EAA +3 g ARG (OLD-ARG, 69.2 ± 1.2 y, N = 8). We quantified responses in muscle protein synthesis (MPS; incorporation of 13C phenylalanine into myofibrillar proteins), leg and muscle microvascular blood flow (Doppler/contrast enhanced ultrasound (CEUS)) and insulin/EAA in response to EEA ± ARG. Plasma EAA increased similarly across groups but argininemia was evident solely in OLD-ARG (∼320 mmol, 65 min post feed); increases in plasma insulin (to ∼13 IU ml−1) were similar across groups. Increases in femoral flow were evident in YOUNG >2 h after feeding; these effects were blunted in OLD and OLD-ARG. Increases in microvascular blood volume (MBV) occurred only in YOUNG and these effects were isolated to the early postprandial phase (+45% at ∼45 min after feeding) coinciding with detectable arterio-venous differences in EAA reflecting net uptake by muscle. Increases in microvascular flow velocity (MFV) and tissue perfusion (MBV × MFV) occurred (∼2 h) in YOUNG and OLD-ARG, but not OLD. Postprandial protein accretion was greater in YOUNG than OLD or OLD-ARG; the latter two groups being indistinguishable. Therefore, ARG rescues aspects of muscle perfusion in OLD without impacting anabolic blunting, perhaps due to the “rescue” being beyond the period of active EAA-uptake.
- Full Text
- View/download PDF
11. Eccentric exercise and the critically ill patient
- Author
-
Mitchell, W. Kyle, Taivassalo, Tanja, Narici, Marco V., Franchi, Martino V., Mitchell, W. Kyle, Taivassalo, Tanja, Narici, Marco V., and Franchi, Martino V.
- Full Text
- View/download PDF
12. Pancreas preserving distal duodenectomy: a versatile operation for a range of infra-papillary pathologies
- Author
-
Mitchell, W. Kyle, Thomas, Pradeep F., Zaitoun, Abed M., Brooks, Adam J., Lobo, Dileep N., Mitchell, W. Kyle, Thomas, Pradeep F., Zaitoun, Abed M., Brooks, Adam J., and Lobo, Dileep N.
- Abstract
AIM To investigate the range of pathologies treated by pancreas preserving distal duodenectomy (PPDD) and present the outcome of follow-up. METHODS Neoplastic lesions of the duodenum are treated conventionally by pancreaticoduodenectomy. Lesions distal to the major papilla may be suitable for a pancreas-preserving distal duodenectomy, potentially reducing morbidity and mortality. We present our experience with this procedure. Selective intraoperative duodenoscopy assessed the relationship of the papilla to the lesion. After duodenal mobilisation and confirmation of the site of the lesion, the duodenum was transected distal to the papilla and beyond the duodenojejunal flexure and a side-to-side duodenojejunal anastomosis was formed. Patients were identified from a prospectively maintained database and outcomes determined from digital health records with a dataset including demographics, co-morbidities, mode of presentation, preoperative imaging and assessment, nutritional support needs, technical operative details, blood transfusion requirements, length of stay, pathology including lymph node yield and lymph node involvement, length of follow-up, complications and outcomes. Related published literature was also reviewed. RESULTS Twenty-four patients had surgery with the intent of performing PPDD from 2003 to 2016. Nineteen underwent PPDD successfully. Two patients planned for PPDD proceeded to formal pancreaticoduodenectomy (PD) while three had unresectable disease. Median post-operative follow-up was 32 mo. Pathologies resected included duodenal adenocarcinoma (n = 6), adenomas (n = 5), gastrointestinal stromal tumours (n = 4) and lipoma, bleeding duodenal diverticulum, locally advanced colonic adenocarcinoma and extrinsic compression (n = 1 each). Median postoperative length of stay (LOS) was 8 d and morbidity was low [pain and nausea/vomiting (n = 2), anastomotic stricture (n = 1), pneumonia (n = 1), and overwhelming postsplenectomy sepsis (n = 1, asplenic patient
- Full Text
- View/download PDF
13. Supplementing essential amino acids with the nitric oxide precursor, l-arginine, enhances skeletal muscle perfusion without impacting anabolism in older men
- Author
-
Mitchell, W. Kyle, Phillips, Bethan E., Wilkinson, Daniel J., Williams, John P., Rankin, Debbie, Lund, Jonathan N., Smith, Kenneth, Atherton, Philip J., Mitchell, W. Kyle, Phillips, Bethan E., Wilkinson, Daniel J., Williams, John P., Rankin, Debbie, Lund, Jonathan N., Smith, Kenneth, and Atherton, Philip J.
- Abstract
Postprandial limb blood flow and skeletal muscle microvascular perfusion reduce with aging. Here we tested the impact of providing bolus essential amino acids (EAA) in the presence and absence of the nitric oxide precursor, l-Arginine (ARG), upon skeletal muscle blood flow and anabolism in older men. Healthy young (YOUNG: 19.7 ± 0.5 y, N = 8) and older men (OLD, 70 ± 0.8 y, N = 8) received 15 g EAA or (older only) 15 g EAA +3 g ARG (OLD-ARG, 69.2 ± 1.2 y, N = 8). We quantified responses in muscle protein synthesis (MPS; incorporation of 13C phenylalanine into myofibrillar proteins), leg and muscle microvascular blood flow (Doppler/contrast enhanced ultrasound (CEUS)) and insulin/EAA in response to EEA ± ARG. Plasma EAA increased similarly across groups but argininemia was evident solely in OLD-ARG (∼320 mmol, 65 min post feed); increases in plasma insulin (to ∼13 IU ml−1) were similar across groups. Increases in femoral flow were evident in YOUNG >2 h after feeding; these effects were blunted in OLD and OLD-ARG. Increases in microvascular blood volume (MBV) occurred only in YOUNG and these effects were isolated to the early postprandial phase (+45% at ∼45 min after feeding) coinciding with detectable arterio-venous differences in EAA reflecting net uptake by muscle. Increases in microvascular flow velocity (MFV) and tissue perfusion (MBV × MFV) occurred (∼2 h) in YOUNG and OLD-ARG, but not OLD. Postprandial protein accretion was greater in YOUNG than OLD or OLD-ARG; the latter two groups being indistinguishable. Therefore, ARG rescues aspects of muscle perfusion in OLD without impacting anabolic blunting, perhaps due to the “rescue” being beyond the period of active EAA-uptake.
- Full Text
- View/download PDF
14. Eccentric exercise and the critically ill patient
- Author
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Mitchell, W. Kyle, Taivassalo, Tanja, Narici, Marco V., Franchi, Martino V., Mitchell, W. Kyle, Taivassalo, Tanja, Narici, Marco V., and Franchi, Martino V.
- Full Text
- View/download PDF
15. Pancreas preserving distal duodenectomy: a versatile operation for a range of infra-papillary pathologies
- Author
-
Mitchell, W. Kyle, Thomas, Pradeep F., Zaitoun, Abed M., Brooks, Adam J., Lobo, Dileep N., Mitchell, W. Kyle, Thomas, Pradeep F., Zaitoun, Abed M., Brooks, Adam J., and Lobo, Dileep N.
- Abstract
AIM To investigate the range of pathologies treated by pancreas preserving distal duodenectomy (PPDD) and present the outcome of follow-up. METHODS Neoplastic lesions of the duodenum are treated conventionally by pancreaticoduodenectomy. Lesions distal to the major papilla may be suitable for a pancreas-preserving distal duodenectomy, potentially reducing morbidity and mortality. We present our experience with this procedure. Selective intraoperative duodenoscopy assessed the relationship of the papilla to the lesion. After duodenal mobilisation and confirmation of the site of the lesion, the duodenum was transected distal to the papilla and beyond the duodenojejunal flexure and a side-to-side duodenojejunal anastomosis was formed. Patients were identified from a prospectively maintained database and outcomes determined from digital health records with a dataset including demographics, co-morbidities, mode of presentation, preoperative imaging and assessment, nutritional support needs, technical operative details, blood transfusion requirements, length of stay, pathology including lymph node yield and lymph node involvement, length of follow-up, complications and outcomes. Related published literature was also reviewed. RESULTS Twenty-four patients had surgery with the intent of performing PPDD from 2003 to 2016. Nineteen underwent PPDD successfully. Two patients planned for PPDD proceeded to formal pancreaticoduodenectomy (PD) while three had unresectable disease. Median post-operative follow-up was 32 mo. Pathologies resected included duodenal adenocarcinoma (n = 6), adenomas (n = 5), gastrointestinal stromal tumours (n = 4) and lipoma, bleeding duodenal diverticulum, locally advanced colonic adenocarcinoma and extrinsic compression (n = 1 each). Median postoperative length of stay (LOS) was 8 d and morbidity was low [pain and nausea/vomiting (n = 2), anastomotic stricture (n = 1), pneumonia (n = 1), and overwhelming postsplenectomy sepsis (n = 1, asplenic patient
- Full Text
- View/download PDF
16. Supplementing essential amino acids with the nitric oxide precursor, l-arginine, enhances skeletal muscle perfusion without impacting anabolism in older men
- Author
-
Mitchell, W. Kyle, Phillips, Bethan E., Wilkinson, Daniel J., Williams, John P., Rankin, Debbie, Lund, Jonathan N., Smith, Kenneth, Atherton, Philip J., Mitchell, W. Kyle, Phillips, Bethan E., Wilkinson, Daniel J., Williams, John P., Rankin, Debbie, Lund, Jonathan N., Smith, Kenneth, and Atherton, Philip J.
- Abstract
Postprandial limb blood flow and skeletal muscle microvascular perfusion reduce with aging. Here we tested the impact of providing bolus essential amino acids (EAA) in the presence and absence of the nitric oxide precursor, l-Arginine (ARG), upon skeletal muscle blood flow and anabolism in older men. Healthy young (YOUNG: 19.7 ± 0.5 y, N = 8) and older men (OLD, 70 ± 0.8 y, N = 8) received 15 g EAA or (older only) 15 g EAA +3 g ARG (OLD-ARG, 69.2 ± 1.2 y, N = 8). We quantified responses in muscle protein synthesis (MPS; incorporation of 13C phenylalanine into myofibrillar proteins), leg and muscle microvascular blood flow (Doppler/contrast enhanced ultrasound (CEUS)) and insulin/EAA in response to EEA ± ARG. Plasma EAA increased similarly across groups but argininemia was evident solely in OLD-ARG (∼320 mmol, 65 min post feed); increases in plasma insulin (to ∼13 IU ml−1) were similar across groups. Increases in femoral flow were evident in YOUNG >2 h after feeding; these effects were blunted in OLD and OLD-ARG. Increases in microvascular blood volume (MBV) occurred only in YOUNG and these effects were isolated to the early postprandial phase (+45% at ∼45 min after feeding) coinciding with detectable arterio-venous differences in EAA reflecting net uptake by muscle. Increases in microvascular flow velocity (MFV) and tissue perfusion (MBV × MFV) occurred (∼2 h) in YOUNG and OLD-ARG, but not OLD. Postprandial protein accretion was greater in YOUNG than OLD or OLD-ARG; the latter two groups being indistinguishable. Therefore, ARG rescues aspects of muscle perfusion in OLD without impacting anabolic blunting, perhaps due to the “rescue” being beyond the period of active EAA-uptake.
- Full Text
- View/download PDF
17. Eccentric exercise and the critically ill patient
- Author
-
Mitchell, W. Kyle, Taivassalo, Tanja, Narici, Marco V., Franchi, Martino V., Mitchell, W. Kyle, Taivassalo, Tanja, Narici, Marco V., and Franchi, Martino V.
- Full Text
- View/download PDF
18. Pancreas preserving distal duodenectomy: a versatile operation for a range of infra-papillary pathologies
- Author
-
Mitchell, W. Kyle, Thomas, Pradeep F., Zaitoun, Abed M., Brooks, Adam J., Lobo, Dileep N., Mitchell, W. Kyle, Thomas, Pradeep F., Zaitoun, Abed M., Brooks, Adam J., and Lobo, Dileep N.
- Abstract
AIM To investigate the range of pathologies treated by pancreas preserving distal duodenectomy (PPDD) and present the outcome of follow-up. METHODS Neoplastic lesions of the duodenum are treated conventionally by pancreaticoduodenectomy. Lesions distal to the major papilla may be suitable for a pancreas-preserving distal duodenectomy, potentially reducing morbidity and mortality. We present our experience with this procedure. Selective intraoperative duodenoscopy assessed the relationship of the papilla to the lesion. After duodenal mobilisation and confirmation of the site of the lesion, the duodenum was transected distal to the papilla and beyond the duodenojejunal flexure and a side-to-side duodenojejunal anastomosis was formed. Patients were identified from a prospectively maintained database and outcomes determined from digital health records with a dataset including demographics, co-morbidities, mode of presentation, preoperative imaging and assessment, nutritional support needs, technical operative details, blood transfusion requirements, length of stay, pathology including lymph node yield and lymph node involvement, length of follow-up, complications and outcomes. Related published literature was also reviewed. RESULTS Twenty-four patients had surgery with the intent of performing PPDD from 2003 to 2016. Nineteen underwent PPDD successfully. Two patients planned for PPDD proceeded to formal pancreaticoduodenectomy (PD) while three had unresectable disease. Median post-operative follow-up was 32 mo. Pathologies resected included duodenal adenocarcinoma (n = 6), adenomas (n = 5), gastrointestinal stromal tumours (n = 4) and lipoma, bleeding duodenal diverticulum, locally advanced colonic adenocarcinoma and extrinsic compression (n = 1 each). Median postoperative length of stay (LOS) was 8 d and morbidity was low [pain and nausea/vomiting (n = 2), anastomotic stricture (n = 1), pneumonia (n = 1), and overwhelming postsplenectomy sepsis (n = 1, asplenic patient
- Full Text
- View/download PDF
19. Supplementing essential amino acids with the nitric oxide precursor, l-arginine, enhances skeletal muscle perfusion without impacting anabolism in older men
- Author
-
Mitchell, W. Kyle, Phillips, Bethan E., Wilkinson, Daniel J., Williams, John P., Rankin, Debbie, Lund, Jonathan N., Smith, Kenneth, Atherton, Philip J., Mitchell, W. Kyle, Phillips, Bethan E., Wilkinson, Daniel J., Williams, John P., Rankin, Debbie, Lund, Jonathan N., Smith, Kenneth, and Atherton, Philip J.
- Abstract
Postprandial limb blood flow and skeletal muscle microvascular perfusion reduce with aging. Here we tested the impact of providing bolus essential amino acids (EAA) in the presence and absence of the nitric oxide precursor, l-Arginine (ARG), upon skeletal muscle blood flow and anabolism in older men. Healthy young (YOUNG: 19.7 ± 0.5 y, N = 8) and older men (OLD, 70 ± 0.8 y, N = 8) received 15 g EAA or (older only) 15 g EAA +3 g ARG (OLD-ARG, 69.2 ± 1.2 y, N = 8). We quantified responses in muscle protein synthesis (MPS; incorporation of 13C phenylalanine into myofibrillar proteins), leg and muscle microvascular blood flow (Doppler/contrast enhanced ultrasound (CEUS)) and insulin/EAA in response to EEA ± ARG. Plasma EAA increased similarly across groups but argininemia was evident solely in OLD-ARG (∼320 mmol, 65 min post feed); increases in plasma insulin (to ∼13 IU ml−1) were similar across groups. Increases in femoral flow were evident in YOUNG >2 h after feeding; these effects were blunted in OLD and OLD-ARG. Increases in microvascular blood volume (MBV) occurred only in YOUNG and these effects were isolated to the early postprandial phase (+45% at ∼45 min after feeding) coinciding with detectable arterio-venous differences in EAA reflecting net uptake by muscle. Increases in microvascular flow velocity (MFV) and tissue perfusion (MBV × MFV) occurred (∼2 h) in YOUNG and OLD-ARG, but not OLD. Postprandial protein accretion was greater in YOUNG than OLD or OLD-ARG; the latter two groups being indistinguishable. Therefore, ARG rescues aspects of muscle perfusion in OLD without impacting anabolic blunting, perhaps due to the “rescue” being beyond the period of active EAA-uptake.
- Full Text
- View/download PDF
20. Eccentric exercise and the critically ill patient
- Author
-
Mitchell, W. Kyle, Taivassalo, Tanja, Narici, Marco V., Franchi, Martino V., Mitchell, W. Kyle, Taivassalo, Tanja, Narici, Marco V., and Franchi, Martino V.
- Full Text
- View/download PDF
21. The impact of delivery profile of essential amino acids upon skeletal muscle protein synthesis in older men: clinical efficacy of pulse vs. bolus supply.
- Author
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Mitchell WK, Phillips BE, Williams JP, Rankin D, Lund JN, Wilkinson DJ, Smith K, and Atherton PJ
- Subjects
- Aged, Amino Acids, Essential metabolism, Carbon Isotopes administration & dosage, Carbon Isotopes metabolism, Humans, Insulin metabolism, Male, Mechanistic Target of Rapamycin Complex 1, Multiprotein Complexes metabolism, Muscle, Skeletal blood supply, Muscle, Skeletal diagnostic imaging, Muscle, Skeletal metabolism, Phenylalanine metabolism, Protein Biosynthesis, Quadriceps Muscle blood supply, Quadriceps Muscle diagnostic imaging, Regional Blood Flow, Signal Transduction, TOR Serine-Threonine Kinases metabolism, Ultrasonography, Amino Acids, Essential administration & dosage, Muscle Proteins biosynthesis, Phenylalanine administration & dosage, Quadriceps Muscle metabolism
- Abstract
Essential amino acids (EAA) are responsible for skeletal muscle anabolic effects after nutrient intake. The pattern of appearance of EAA in blood, e.g., after intake of "slow" or "fast" protein sources or in response to grazing vs. bolus feeding patterns, may impact anabolism. However, the influence of this on muscle anabolism is poorly understood, particularly in older individuals. We determined the effects of divergent feeding profiles of EAA on blood flow, anabolic signaling, and muscle protein synthesis (MPS) in older men. Sixteen men (∼70 yr) consumed EAA either as a single dose (bolus, 15 g; n = 8) or as small repeated fractions (pulse, 4 × 3.75 g every 45 min; n = 8) during (13)C6 phenylalanine infusion. Repeated blood samples and muscle biopsies permitted measurement of fasting and postprandial plasma EAA, insulin, anabolic signaling, and MPS. Muscle blood flow was assessed by contrast-enhanced ultrasound (Sonovue). Bolus achieved rapid insulinemia (12.7 μiU/ml 25-min postfeed), essential aminoacidemia (∼3,000 μM, 45-65 min postfeed), and mTORC1 activity; pulse achieved attenuated insulin responses, gradual low-amplitude aminoacidemia (∼1,800 μM 80-195 min after feeding), and undetectable mTORC1 signaling. Despite this, equivalent anabolic responses were observed: fasting FSRs of 0.051 and 0.047%/h (bolus and pulse, respectively) increased to 0.084 and 0.073%/h, respectively. Moreover, pulse led to sustainment of MPS beyond 180 min, when bolus MPS had returned to basal rates. We detected no benefit of rapid aminoacidemia in this older population despite enhanced anabolic signaling and greater overall EAA exposure. Rather, apparent delayed onset of the "muscle-full" effect permitted identical MPS following low-amplitude-sustained EAA exposure., (Copyright © 2015 the American Physiological Society.)
- Published
- 2015
- Full Text
- View/download PDF
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