Continuous Oral Stable Isotope Ingestion to Measure Whole-Body Protein Turnover

Hirsch, K.R.; Church, D.D.; Wolfe, R.R.; et al.

Stable isotope tracer technologies are routinely implemented to study human protein metabolism, physiology, and disease. To overcome the limitations of tracer infusion approaches, Hirsch and Church et al., developed an oral “sip-feeding” method to quantify acute changes in whole-body protein kinetics. Using sip doses of stable isotope-labeled amino acids (e.g., D₅ L-phenylalanine, D₂ L-tyrosine), rates of protein synthesis and breakdown were determined in human plasma over a time course period. This preliminary study demonstrated the reliable measurement of whole-body protein metabolism and its feasibility as a potential alternative to traditional infusion tracer techniques.