Conclusion
The decreased levels of L-Ser are associated with impaired cognitive function in CKD patients. Especially, plasma L-Ser levels may have a potential for novel biomarker of impaired cognitive function in patients with hemodialysis.
Methods
Plasma levels of AAs were compared between 14 patients with CKD, including 8 patients with diabetic kidney disease, and 12 healthy controls to identify the alteration of specific AAs in CKD. Then, these AAs were evaluated in the brains of 42 patients with brain tumor using non-tumor lesion of the resected brain. Cognitive function is analyzed with respect to intra-brain levels of AAs and kidney function. Moreover, plasma AAs were analyzed in 32 hemodialyzed patients with/without dementia.
Results
In patients with CKD, plasma levels of asparagine (Asn), serine (Ser), alanine (Ala), and proline (Pro) were increased as compared to patients without CKD. Among these AAs, L-Ser, L-Ala, and D-Ser show higher levels than the other AAs in the brain. Intra-brain levels of L-Ser was correlated with cognitive function and kidney function. The number of D-amino acid oxidase or serine racemase-positive cells was not correlated with kidney function. Moreover, the plasma levels of L-Ser are also decreased in patients with declined cognitive function who are treated with chronic hemodialysis.