BRAIN S-ADENOSYLMETHIONINE DECARBOXYLASE ACTIVITY IS INCREASED IN ALZHEIMERS-DISEASE

We measured the activity of S-adenosylmethionine decarboxylase (SAMDC) , a key regulatory enzyme of polyamine biosynthesis, in autopsied brai n from 13 patients with Alzheimer's Disease (AD). As compared with the controls, mean enzyme activity was increased by 37-96% in all seven e xamined brain regions with statistically significant increases in temp oral cortex (+96%), frontal cortex (+69%) and hippocampus (+90%). The elevated SAMDC may have occurred as part of a generalized polyamine re sponse to brain injury, which has been previously described in experim ental animal conditions. Above-normal SAMDC activity implies increased levels/metabolism of spermidine and spermine, two polyamines which ar e involved in neuronal regeneration, growth factor production, and act ivation of excitatory N-methyl-D-aspartate preferring glutamate recept ors. Our data suggest the involvement of the polyamine system in the b rain reparative and/or pathogenetic mechanisms of AD.