Abstract-Text (inkl. Referenzen und Bildunterschriften)

Objective: Chronic kidney disease (CKD) affects >10% of the population wordwide. In CKD patients the plasma concentration of uremic mediators is increased due to reduced kidney function. These increased concentrations cause numerous post-translational modifications (PTMs) like carbamylation, guanidinylation or oxidation of proteins, which can lead to an alteration of conformation, activity or function. Specifically PTMs of proteins like albumin are undesired, since their high mass prevents them to be cleared by the kidney or hemofiltration. Therefore, preventing PTMs beforehand is of high interest. Here we analyse the effect of amino acid supplementation and their capability to protect peptides from PTMs.

Methods: Three peptides were analyzed for PTMs (carbamylation, guanidinylation, oxidation) after incubation with molecules like urea, o-methylisourea and hydrogen peroxide by mass spectrometry. After reliably inducing PTMs, lysine, serin, or cysteine were added before the incubation.

Results: After incubation with urea, the peptides showed an additional signal in mass spectrometry caused by carbamylation, which was prevented by amino acid supplementation. Incubation with o-methylisourea led to guanidinylation of the peptides. Lysine and serine supplementation prevented most of the guanidinylation, but cysteine could fully protect all three peptides. Lastly, incubation with hydrogen peroxide caused oxidation. Depending on the peptide, low or high amount of oxidation was detected. Low amount of oxidation could be prevented by all three amino acids, but high amount of oxidation was only reduced by cysteine.

Conclusion: Here we were able to induce uremic toxin specific PTMs. The presence of free amino acids showed an amino acid depending protection from PTMs, with cysteine being the most effective. The underlying mechanism will be further elucidated, as amino acid supplementation might be a promising therapy option to prevent PTMs in CKD to improve patient outcome.