An interventional study of Sea Level and High Altitude in Glucose Metabolism and High Altitude, sponsored by United States Army Research Institute of Environmental Medicine. Completed at 1 site in United States. Open to male participants aged 18 Years to 39 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2021-09-02.
Sponsored by United States Army Research Institute of Environmental Medicine · Not applicable, Interventional, and Basic science
Recent studies have reported that oxidation of exogenous carbohydrate is reduced under acute hypobaric hypoxic (high altitude; HA) conditions compared to normoxia (sea level; SL) in native lowlanders. However, the mechanisms by which HA suppresses exogenous carbohydrate oxidation are not known. This study will seek to confirm that acute HA exposure decreases exogenous carbohydrate oxidation during steady-state aerobic exercise compared to SL, and explore if the mechanism inhibiting plasma glucose uptake is insulin dependent or independent.
This randomized crossover study will examine substrate metabolic responses to ingesting supplemental carbohydrate during steady-state aerobic-type exercise at sea level (SL) and following acute (\~5 h) exposure to HA (4,300 m) conditions in 10 healthy, recreationally active adults between the ages of 18-39 yrs. Following a 48-hr muscle glycogen normalization period, volunteers will complete 80-min of metabolically-matched, steady-state aerobic exercise on a treadmill, and consume 145 g of glucose (1.8 g·min-1) at SL and HA. Treadmill exercise will be performed at the same absolute workload, with speed and grade being the same at SL and HA to induce the same absolute workload between phases. SL and HA trials will occur in the US Army Research Institute of Environmental Medicine (USARIEM) hypobaric chamber and will be separated by a minimum 7-d washout period between each protocol day. 6-6-[2H2] glucose will be used as a tracer to assess glucose turnover. Indirect calorimetry, breath sampling for 13C/12C expired in CO2, and urine collections will be used to determine carbohydrate, fat, and protein oxidation during exercise at SL and HA. Serial blood draws will be collected during each trial to assess endocrine and circulating substrate responses to exercise, carbohydrate, and hypoxia. Muscle biopsies will be collected before and after steady-state exercise to examine intramuscular glucose transport expression and translocation, glycogen status, and activity enzyme intermediates in aerobic and anaerobic energy metabolism.
189 studies on the registry are indexed under Altitude Sickness; 44 are open to participants now.
This study's enrollment of 10 is below the median of 33 across 157 interventional studies indexed under Altitude Sickness.
Browse Altitude Sickness studies →United States Army Research Institute of Environmental Medicine is the lead sponsor of 67 studies on the registry; 9 are open to participants now.
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Exclusion Criteria:
Carbohydrate metabolism measured at SL
Other: Sea Level
Carbohydrate metabolism measured at HA
Other: High Altitude
Carbohydrate consumed at 1.8 g/min during treadmill exercise at SL
Carbohydrate consumed at 1.8 g/min during treadmill exercise at HA
Rate of Exogenous Carbohydrate Oxidation
Use indirect calorimetry and stable isotope methodologies to measure if acute HA exposure changes the rate of exogenous carbohydrate oxidation during steady-state aerobic exercise compared to SL
Time frame: 7 hours
Rate of Glucose Turnover
Use stable isotope methodologies to measure if acute HA exposure changes the rate of glucose turnover during steady-state aerobic exercise compared to SL
Time frame: 7 hours
| Milestone | Sea Level First, Then High Altitude | High Altitude First, Then Sea Level |
|---|---|---|
| Started | 4 | 6 |
| Completed | 4 | 4 |
| Not completed | 0 | 2 |
Use indirect calorimetry and stable isotope methodologies to measure if acute HA exposure changes the rate of exogenous carbohydrate oxidation during steady-state aerobic exercise compared to SL
| g/min | Sea Level | High Altitude |
|---|---|---|
| Rate of Exogenous Carbohydrate Oxidation | 0.44 ± 0.05 | 0.35 ± 0.07 |
Use stable isotope methodologies to measure if acute HA exposure changes the rate of glucose turnover during steady-state aerobic exercise compared to SL
| mg/kg/min | Sea Level | High Altitude |
|---|---|---|
| Glucose Rate of Disappearance | 14.3 ± 2.0 | 12.7 ± 1.7 |
| Metabolic Clearance Rate | 12.1 ± 2.3 | 8.9 ± 1.8 |
Collected over 3 weeks. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Sea Level | 0/8 (0%) | 0/8 (0%) | 0/8 (0%) |
| High Altitude | 0/10 (0%) | 0/10 (0%) | 0/10 (0%) |
| Age, Categorical(Participants) | Sea Level First, Then High Altitude | High Altitude, Then Sea Level | Total |
|---|---|---|---|
| <=18 years | 0 | 0 | 0 |
| Between 18 and 65 years | 4 | 6 | 10 |
| >=65 years | 0 | 0 | 0 |
| Sex: Female, Male(Participants) | Sea Level First, Then High Altitude | High Altitude, Then Sea Level | Total |
|---|---|---|---|
| Female | 0 | 0 | 0 |
| Male | 4 | 6 | 10 |
| Race (NIH/OMB)(Participants) | Sea Level First, Then High Altitude | High Altitude, Then Sea Level | Total |
|---|---|---|---|
| American Indian or Alaska Native | 0 | 0 | 0 |
| Asian | 0 | 0 | 0 |
| Native Hawaiian or Other Pacific Islander | 0 | 0 | 0 |
| Black or African American | 0 | 0 | 0 |
| White | 4 | 6 | 10 |
| More than one race | 0 | 0 | 0 |
| Unknown or Not Reported | 0 | 0 | 0 |
| Region of Enrollment(participants) | Sea Level First, Then High Altitude | High Altitude, Then Sea Level | Total |
|---|---|---|---|
| United States | 4 | 6 | 10 |
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United States Army Research Institute of Environmental Medicine