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The purpose of this study is to examine the effect of 4 weeks of Citrulline supplementation on macro- and microvascular function during acute hyperglycemia in middle-aged and older adults with type 2 diabetes.
Using a double-blind, randomized, placebo-controlled, and cross-over design, middle-aged and older adults with type 2 diabetes will be randomized to receive either CIT supplementation (6g/day) or placebo (Microcrystalline Cellulose, 6g/day) for 4 weeks.
There will be a total of 5 laboratory visits. Visit 1 (screening visit) will take approximately 1 hour and 30 minutes, visit 2 will take approximately 2 hours and 30 minutes, and visits 3-5 will be approximately 3 hours each.
Visit 1 will measure blood pressure, blood glucose and lipid levels, anthropometry, body composition, and muscle strengths. Visits 2-5 will assess vascular function and glucose control during fasted and acute hyperglycemia conditions induced by 75g of glucose ingestion.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| L-citrulline | Experimental | 6 grams/day |
|
| Placebo | Placebo Comparator | Microcrystalline cellulose |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| L-citrulline | Dietary Supplement | 4 weeks of L-citrulline (6 g/day) in 8 capsules. Supplementation will be ingested daily, half of the doses in the morning and half at night. |
|
| Measure | Description | Time Frame |
|---|---|---|
| Change in macrovascular endothelial function in the fasted condition | Macrovascular endothelial function will be measured using brachial artery flow mediated dilation (ultrasonography) during reactive hyperemia at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in macrovascular endothelial function during acute hyperglycemia | Macrovascular endothelial function will be measured using brachial artery flow mediated dilation (ultrasonography) during reactive hyperemia at 60 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in microvascular endothelial function in the fasted condition | Microvascular endothelial function will be assessed using peripheral arterial tonometry (EndoPAT device) during reactive hyperemia at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in microvascular endothelial function in the fasted condition | Microvascular endothelial function will be assessed using forearm muscle oxygenation (near-infrared spectroscopy) during reactive hyperemia at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in microvascular endothelial function during acute hyperglycemia | Microvascular endothelial function will be assessed using forearm muscle oxygenation (near-infrared spectroscopy) during reactive hyperemia at 60 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in blood glucose levels in the fasted condition |
| Measure | Description | Time Frame |
|---|---|---|
| Change in body composition | Body composition (fat and lean mass) will be measured at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in muscle strength | Maximal handgrip strength will be measured using handgrip dynamometer. Leg extension and plantar flexion strength will be measured using the 10RM test at baseline and after 4 weeks of supplementation. |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Arturo Figueroa, Ph.D, MD | Texas Tech University | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| TTU Kinesiology and Sport Management Building | Lubbock | Texas | 79409 | United States |
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| ID | Term |
|---|---|
| D003924 | Diabetes Mellitus, Type 2 |
| D006943 | Hyperglycemia |
| ID | Term |
|---|---|
| D003920 | Diabetes Mellitus |
| D044882 | Glucose Metabolism Disorders |
| D008659 | Metabolic Diseases |
| D009750 | Nutritional and Metabolic Diseases |
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| ID | Term |
|---|---|
| D002956 | Citrulline |
| ID | Term |
|---|---|
| D000599 | Amino Acids, Diamino |
| D000596 | Amino Acids |
| D000602 | Amino Acids, Peptides, and Proteins |
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Double-blind (subject, investigator), randomized, cross-over, placebo-controlled
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Double-blind (subject, investigator), randomized, cross-over, placebo-controlled
| Placebo | Dietary Supplement | 4 weeks of microcrystalline cellulose in 8 capsules. Supplementation will be ingested daily, half of the doses in the morning and half at night. |
|
Blood glucose levels will be measured by finger prick at baseline and after 4 weeks of supplementation.
| 4 weeks |
| Change in blood glucose levels during acute hyperglycemia | Blood glucose levels will be measured by finger prick at 60 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in central and peripheral arterial stiffness in the fasted condition | Arterial stiffness will be assessed using the central (carotid-femoral) and peripheral (femoral-ankle) pulse wave velocity at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in central and peripheral arterial stiffness during acute hyperglycemia | Arterial stiffness will be assessed using the central (carotid-femoral) and peripheral (femoral-ankle) pulse wave velocity at 60 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in blood pressure in the fasted condition | Brachial and aortic blood pressure will be measured using an automated sphygmomanometry arm cuff (SphygmoCor XCEL). Beat-to-beat blood pressure will be measured using an automated photoplethysmography finger cuff (Finometer). Blood pressure will be measured at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in blood pressure during acute hyperglycemia | Brachial and aortic blood pressure will be measured using an automated sphygmomanometry arm cuff (SphygmoCor XCEL). Beat-to-beat blood pressure will be measured using an automated photoplethysmography finger cuff (Finometer). Blood pressure will be measured at 60 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in stroke volume in the fasted condition | Stroke volume will be measured using impedance cardiography (PhysioFlow) at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in stroke volume during acute hyperglycemia | Stroke volume will be measured using impedance cardiography (PhysioFlow) at 60 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in total peripheral resistance in the fasted condition | Total peripheral resistance will be measured using impedance cardiography (PhysioFlow) at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in total peripheral resistance during acute hyperglycemia | Total peripheral resistance will be measured using impedance cardiography (PhysioFlow) at 60 minutes after oral glucose ingestion at baseline and after 4 weeks of supplementation. | 4 weeks |
| 4 weeks |
| Change in insulin levels | Serum insulin levels will be tested at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in serum arginine levels | Serum arginine levels will tested at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in serum arginase activity levels | Serum arginase activity levels will tested at baseline and after 4 weeks of supplementation. | 4 weeks |
| Change in 24-hour ambulatory blood pressure monitoring | Ambulatory blood pressure will be obtained using a monitor during daytime and nighttime on two separate days at baseline and after 4 weeks of supplementation. | 4 weeks |
| D004700 | Endocrine System Diseases |