INFLUENCE OF VITAMIN-B-12 ON BRAIN METHIONINE ADENOSYLTRANSFERASE ACTIVITY IN SENILE DEMENTIA OF THE ALZHEIMERS TYPE

The influence of vitamin B-12 On the activity of methionine adenosyltr ansferase (MAT) in postmortem brains of patients with senile dementia of the Alzheimer's type (SDAT) was investigated. In samples of cortex gyrus frontalis from SDAT patients with normal and low levels of serum B-12, MAT V-max was significantly increased by 25% and 19%, respectiv ely. MAT V-max from a SDAT group chronically treated with B-12 was sim ilar to controls. In contrast to cortex gyrus frontalis, no significan t alterations were seen in MAT activity in nucleus caudatus. This stud y provides evidence that SDAT is associated with significant alteratio ns in transmethylation mechanisms in specific regions of the brain. Th e relationship between blood levels of B-12 and the actual status of t his vitamin in the brain influencing the rates of synthesis of both me thionine and SAM may, however, be far more complex and cannot be direc tly clarified on the basis of the present human brain results.