Brain amino acid abnormalities in kidney disease and diabetes mellitus

The present postmortem study examines whether specific amino acid abnormalities associated with renal diseases or diabetes mellitus in animal experiments and on clinical examination may also be found in human brain samples obtained at clinical autopsies. The material includes 12 deceased with renal insufficiency, 23 deceased with diabetes mellitus and 26 control cases with lethal cardiovascular diseases (without a history of hepatic, renal or metabolic disturbances). The autopsy and clinical records were retrospectively analyzed for age, sex, postmortem delay, cause of death, substantial preexisting diseases and histological findings. The analysis of free amino acid concentrations in human brain specimens was performed applying a Beckman amino acid analyzer. The results were evaluated using the U-test according to Mann, Willcox and Whitney. A P-value less than 0.05 was considered to be significantly different. Differences of amino acid concentrations attributable to sex, age and postmortem delay were not significant. The comparison of postmortem amino acid concentrations in the brains of patients with diabetes mellitus and controls did not reveal relevant changes. However, the patients with renal diseases, as compared to controls, showed a significant cerebral increase of urea, phenylethanolamine and gamma-aminobutyric acid. Thus, the postmortem amino acid analysis may contribute to the understanding of pathophysiological mechanisms of uremic encephalopathy and may supplement the conventional postmortem morphological diagnosis in kidney diseases by indication of functional impairment.