Dietary nucleotides and gut mucosal defence

Area of Science:

• Biochemistry
• Cell Biology
• Nutritional Science

Background:

• Nucleic acid synthesis, particularly for DNA, rRNA, and tRNA, is crucial for cellular function.
• Energy expenditure for synthesizing cellular machinery (ribosomes, tRNA) is estimated at 5-10% of protein synthesis energy.
• Nucleotides are sourced via salvage pathways or de novo synthesis from amino acids and glucose.

Purpose of the Study:

• To highlight the quantitative significance of nucleotide synthesis beyond informational aspects.
• To explore the roles of salvage and de novo pathways in nucleotide supply.
• To investigate the implications of nucleotide availability in critically ill patients receiving artificial nutrition.

Main Methods:

• Review of animal and human studies on nucleotide metabolism and synthesis.
• Analysis of energy costs associated with synthesizing cellular machinery.
• Examination of nucleotide sources (salvage vs. de novo) and their regulation.

Main Results:

• RRNA production necessitates significant de novo nucleotide synthesis, especially in rapidly dividing cells.
• The gut uniquely relies on hepatic de novo nucleotide synthesis.
• Animal studies demonstrate benefits of exogenous nucleotides (salvage) for liver, immunity, and gut health.
• Human adaptation involves downregulating de novo pathways in response to dietary nucleotide intake.

Conclusions:

• Current artificial nutrition regimens (parenteral and enteral) often lack nucleotides, potentially leading to inadequate supply for gut and immune cells in critically ill patients.
• Further clinical studies are needed to confirm the impact of nucleotide supplementation in artificially fed, critically ill individuals.