Changes in intermediary metabolism in severe surgical illness

Area of Science:

• Biochemistry
• Metabolic Regulation
• Critical Care Medicine

Background:

• Plasma free fatty acids (FFAs) and glucose levels exhibit reciprocal regulation under normal physiological conditions.
• In fasting states, FFAs dominate energy production, while glucose is primary in fed states.
• Glucose availability dictates its oxidation rate, whereas FFAs are often in excess of oxidation capacity.

Purpose of the Study:

• To investigate the metabolic alterations in plasma free fatty acids (FFAs) and glucose during critical illness.
• To understand how substrate availability impacts energy production and storage in critically ill patients.
• To inform nutritional strategies for managing metabolic dysregulation in critical illness.

Main Methods:

• Analysis of plasma free fatty acid (FFA) and glucose concentrations.
• Assessment of substrate oxidation rates and their regulation.
• Evaluation of triglyceride (TG) storage in muscle and liver tissues.
• Monitoring of glucose clearance and lactate levels.

Main Results:

• Critical illness triggers simultaneous mobilization of plasma glucose and FFAs.
• Elevated glucose metabolism limits FFA oxidation, promoting triglyceride (TG) accumulation.
• High FFA levels and increased tissue TG stores impair glucose clearance, contributing to hyperglycemia.
• Excessive glucose metabolism can lead to lacticacidemia and muscle glutamine depletion.

Conclusions:

• Critical illness induces a metabolic state of substrate excess, altering normal FFA and glucose dynamics.
• Impaired FFA oxidation and subsequent TG deposition contribute to hyperglycemia in critical illness.
• Nutritional interventions must address these metabolic derangements to prevent adverse outcomes.