NCT03851744

High Altitude and Exogenous Carbohydrate Oxidation

The Mechanistic Effects of Acute Hypobaric Hypoxia on Exogenous Carbohydrate Utilization During Steady-state Aerobic Exercise

• Status: Completed
• Phase: N/A
• Study type: Interventional
• Enrollment: 10 (actual)
• Sponsor: United States Army Research Institute of Environmental Medicine · Federal
• Sex: Male
• Age: 18 Years – 39 Years
• Healthy volunteers: Accepted

Summary

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.

Detailed description

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.

Conditions

• Glucose Metabolism
• High Altitude

Interventions

Type	Name	Description
OTHER	Sea Level	Carbohydrate consumed at 1.8 g/min during treadmill exercise at SL
OTHER	High Altitude	Carbohydrate consumed at 1.8 g/min during treadmill exercise at HA

Timeline

• Start date: 2018-11-28
• Primary completion: 2019-11-01
• Completion: 2020-09-01
• First posted: 2019-02-22
• Last updated: 2021-09-02
• Results posted: 2021-09-02

Locations

1 site across 1 country: United States