The current status of protein sparing

Area of Science:

• Nutritional Science
• Metabolism
• Clinical Nutrition

Background:

• Nitrogen balance is a critical indicator of nutritional status.
• Protein sparing therapy is used for short-term nutritional support.
• The role of insulin in protein metabolism is debated.

Purpose of the Study:

• To evaluate the impact of amino acid infusion levels on nitrogen balance.
• To determine the effect of dextrose addition on nitrogen balance during amino acid infusion.
• To assess the utility of protein sparing therapy in specific clinical scenarios.

Main Methods:

• Infusion of crystalline amino acids at varying levels (1.0-1.7 g/kg) without dextrose.
• Comparison of nitrogen balance with and without dextrose co-infusion.
• Assessment of body fat mobilization and fatty acid deficiency during protein sparing.

Main Results:

• Amino acid solutions significantly improved nitrogen balance.
• Increasing amino acid infusion levels further enhanced nitrogen balance.
• Dextrose addition did not affect nitrogen balance and suggests an overemphasis on insulin's role in protein sparing.
• Nonprotein dextrose calories showed a slight, non-significant advantage in nitrogen balance.
• Amino acid solutions are isotonic for peripheral infusion, unlike dextrose-added solutions.
• Protein sparing mobilizes endogenous fat and prevents fatty acid deficiency.
• Protein sparing provides suboptimal caloric replacement.

Conclusions:

• Protein sparing with amino acids is effective for short-term nutritional support, especially when risks of total parenteral hyperalimentation are high.
• It aids in preventing fatty acid deficiency and treating fatty liver infiltration.
• It should be used temporarily until oral feeding resumes or intravenous hyperalimentation is indicated.
• Routine use as a substitute for dextrose therapy post-operatively is not recommended due to cost and patient outcomes.