Plasma glucose turnover during cold stress in humans

Area of Science:

• Human Physiology
• Metabolic Regulation
• Environmental Stress Response

Background:

• Cold stress significantly elevates metabolic rate and whole-body oxidation of both lipids and carbohydrates.
• The precise contribution of different carbohydrate sources to this increased oxidation during cold exposure remains unclear.

Purpose of the Study:

• To investigate the source of increased carbohydrate oxidation during acute cold stress in humans.
• To quantify the contribution of plasma glucose turnover to carbohydrate oxidation under cold conditions.

Main Methods:

• Six healthy males underwent controlled rest for 3 hours at both 29°C (thermoneutral) and 10°C (cold stress).
• Infusion of [U-13C6]glucose was used to measure plasma glucose rate of appearance (Ra) and turnover.
• Gas chromatography-mass spectrometry analyzed plasma glucose enrichment to determine oxidation rates.

Main Results:

• Cold exposure significantly increased whole-body carbohydrate oxidation (CHOox) and metabolic rate compared to thermoneutral conditions.
• Plasma glucose Ra and glucose clearance were significantly elevated during cold stress.
• Calculations indicated that plasma glucose oxidation accounted for approximately 54% of the increased CHOox, with the remainder (46%) derived from glycogen and lactate oxidation.

Conclusions:

• Cold exposure stimulates carbohydrate oxidation primarily through increased plasma glucose appearance and utilization.
• Both plasma glucose and endogenous sources (glycogen, lactate) contribute substantially to meeting the energy demands during cold stress.
• Understanding these metabolic shifts is crucial for optimizing nutritional and physiological strategies in cold environments.