HD is beneficial for enzymatic conversion of some amino-acids in the elderly

ABSTRACT

Many different causes of abnormal amino acid profile in uremic patients including inadequate nutritional intake, uremic disturbances in amino acid metabolism, loss or fibrosis of renal tissues, metabolic acidosis and hormonal derangement. Some of these factors; such as metabolic acidosis are particularly corrected with dialytic therapy; but others such as decreased intake or hormonal disturbances may persist or worsen after initiation of dialysis. This study was done to investigate the plasma amino acids profile in uremic elderly patients. The present study was carried out on three matched groups [G1] on HD, [G2] CRF and a control. A significant uniform decrease of Threonine, Valine and Leucine in both HD and CRF. However, a peculiar situation of significant increase in phenylalanine in HD in comparison to CRF and to control. This is similar to the significant increase of Arginine in HD group in comparison to the others. In contrast, phenylalanine was significantly decreased in CRF in comparison to both HD group and the control. The latter was similar to the decrease of Leucine in CRF in comparison to the other two groups. Hence, Phenylalanine was the only AA that was found to be significantly increased in HD and significantly decreased in CRF in comparison to control. Moreover, only Phenylalanine and Arginine were significantly increased in HD group in contrast to the rest of the essential amino-acids, which showed either decrease or no change. Tyrosine and lysine were significantly lower in pre -dialysis CRF group in comparison to patients on HD and the control. This may imply that HD can correct the deficiency of tyrosine and lysine in uremic patients probably due to less inhibition of phenylalanine hydrorxylase. Inter-conversion of phenylalanine to tyrosine was reported to be impaired in CRF; whereas tyrosine metabolism per se does not seem to be grossly affected by uremia. However; Serine was significantly lower in both groups of uremic patients in the current study compared with the control group, with no significant difference in-between pre -dialysis patients and patients on HD. In conclusion, our study showed that HD may be beneficial in restoring the enzymatic turnover of certain amino-acids including Phenylalanine hydroxylase to normalize tyrosine plasma level, Arginine synthetase to convert citrulline to Arginine. On the other hand, HD may be injurious to the production of other amino-acids like serine due to complete lost of the renal tissue that is responsible of its production from glycine