Renal Transplant Patient Protein Oxidation Study

Generally, there are two major fates for the amino acids derived from protein ingestion: 1) uptake into amino acid pool thereby being available for protein synthesis and 2) oxidation of excess amino acids. All amino acids that are oxidized, are not incorporated.

For the healthy adult population, a protein intake of 0.8 g/kg bw/day is recommended. However, stable renal transplant patients benefit from a higher protein intake of ¡Ý1.1 g protein/kg bw/day, suggesting higher protein requirements. Possible reasons for higher protein requirement could be the chronic use of corticosteroids in renal transplant patients, a low grade inflammatory state, or other. Corticosteroids are used to prevent graft failure, but also have side effects, such as muscle wasting/protein catabolism. Whether protein catabolism is altered in renal transplant recipients however, is unknown.

The question is whether in stable renal transplant patients higher levels of protein catabolism (oxidation) can be measured with the 13C-milk protein breath test, as compared to age-controlled healthy subjects.

Ingested protein derived amino acids are used for the synthesis of new proteins. After the protein synthesis requirements are met, all surplus amino acids are oxidized as their is no storage for amino acids. Stable renal transplant patients benefit from a higher protein intake (>1,1 g/kg/day). One of the likely causes is the use of corticosteroids to prevent graft rejection. Corticosteroids lead to loss of lean body mass, which suggests disturbed protein metabolism. We suspect that stable renal transplant patients oxidize more of their ingested proteins compared to healthy controls. To test this hypothesis we will apply a 13C-milk protein breath test to measure whole body protein oxidation by measuring exhaled 13CO2:12CO2.

3 baseline breath samples before the breath test

t=0 consumption of test drink (30 g milkprotein dissolved in 500 ml water)

33 timepoints: a breath sample is given every 10 minutes, from t=10 to t=330 minutes

No intervention is given prior to the breath test