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Experimental hyperglycemia (5 hours) will be induced via a constant- or fluctuating-rate glucose infusion to establish different patterns of glycemia in healthy individuals. The effects of these acute models of hyperglycemia on the adaptations to a single aerobic exercise bout will be tested. Changes in pancreatic endocrine function, insulin sensitivity, endothelial function, and oxidative stress will be measured.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Normoglycemia + exercise | Experimental | At T = 0 h participants will undergo an intravenous glucose tolerance test (IVGTT, 0.33 g/kg glucose) immediately followed by a 4-hour rest period. At T = 5 h, participants will undertake 45 minutes of moderate-intensity (70% VO2max) bicycle ergometry. Immediately following (T = 6 h) and 1- (T = 7 h), 3- (T = 9 h), and 18- hours (T = 24 h) after exercise, participants will undergo additional IVGTTs. |
|
| Steady-State Hyperglycemia + exercise | Experimental | At T = 0 h participants will undergo an intravenous glucose tolerance test (IVGTT, 0.33 g/kg glucose) immediately followed by a 4-hour rest period. During this time, steady-state hyperglycemia (~10 mM) will be induced experimentally via a variable-rate intravenous infusion of 20% dextrose. At T = 5 h, participants will undertake 45 minutes of moderate-intensity (70% VO2max) bicycle ergometry. Immediately following (T = 6 h) and 1- (T = 7 h), 3- (T = 9 h), and 18- hours (T = 24 h) after exercise, participants will undergo additional IVGTTs. |
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| Fluctuating Hyperglycemia + exercise | Experimental | At T = 0 h participants will undergo an intravenous glucose tolerance test (IVGTT, 0.33 g/kg glucose) immediately followed by a 4-hour rest period. During this time, fluctuating hyperglycemia (~8-15 mM) will be induced by intravenously injecting 0.15 g/kg boluses of 20% dextrose every 30 minutes. At T = 5 h, participants will undertake 45 minutes of moderate-intensity (70% VO2max) bicycle ergometry. Immediately following (T = 6 h) and 1- (T = 7 h), 3- (T = 9 h), and 18- hours (T = 24 h) after exercise, participants will undergo additional IVGTTs. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Exercise | Behavioral |
| ||
| Measure | Description | Time Frame |
|---|---|---|
| Pancreatic endocrine function | The plasma insulin, C-peptide, and glucagon responses to a 0.33 g/kg intravenous glucose tolerance test (IVGTT) will be measured. In each trial, the IVGTT will be performed at T = 0, 6, 7, 9, and 24 hours. | 0, 6, 7, 9, and 24 hours |
| Measure | Description | Time Frame |
|---|---|---|
| Glucose tolerance | Glucose tolerance will be measured during an IVGTT in each trial at T = 0, 6, 7, 9, and 24 hours. | 0, 6, 7, 9, and 24 hours |
| Endothelial function | Blood flow and flow-mediated dilation by Doppler ultrasound will be measured in each trial at T = 0, 6, 7, 9, and 24 hours. |
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Inclusion criteria for participation:
Exclusion criteria for participation:
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| Name | Affiliation | Role |
|---|---|---|
| Thomas P Solomon, PhD | University of Birmingham | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| University of Birmingham | Birmingham | West Midlands | B15 2TT | United Kingdom |
| ID | Term |
|---|---|
| D003922 | Diabetes Mellitus, Type 1 |
| D003924 | Diabetes Mellitus, Type 2 |
| D009043 | Motor Activity |
| ID | Term |
|---|---|
| D003920 | Diabetes Mellitus |
| D044882 | Glucose Metabolism Disorders |
| D008659 | Metabolic Diseases |
| D009750 | Nutritional and Metabolic Diseases |
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| ID | Term |
|---|---|
| D015444 | Exercise |
| ID | Term |
|---|---|
| D009043 | Motor Activity |
| D009068 | Movement |
| D009142 | Musculoskeletal Physiological Phenomena |
| D055687 | Musculoskeletal and Neural Physiological Phenomena |
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| Hyperglycemia |
| Procedure |
|
| 0, 6, 7, 9, and 24 hours |
| Oxidative stress | Urine will be collected over the whole 24-hour period of each trial and 8-iso Prostaglandin F3α will be measured. | 24 hours |
| D004700 | Endocrine System Diseases |
| D001327 | Autoimmune Diseases |
| D007154 | Immune System Diseases |
| D001519 | Behavior |