Mitochondrial dysfunction and oxidative stress are involved in
Alzheimer disease (AD) pathogenesis. In human AD brains, the activity of the
alpha-ketoglutarate dehydrogenase enzyme complex (alpha-KGDHC) is reduced. KGDHC is mostly involved in
NADH production. It can also participate in oxidative stress and
reactive oxygen species (ROS) production. The mitochondrial dihydrolipoyl succinyltransferase
enzyme (DLST) is a key subunit specific to the alpha-KGDHC. In cultured cells, reduction of DLST increased H(2)O(2)-induced ROS generation and cell death. Thus, we asked whether partial genetic deletion of DLST could accelerate the onset of AD pathogenesis, using a transgenic mouse model of
amyloid deposition crossed with DLST(+/-) mice. Tg19959 mice, which carry the human
amyloid precursor
protein with two mutations, develop
amyloid deposits and progressive behavioral abnormalities. We compared Tg19959 mice to Tg19959-DLST(+/-) littermates at 2-3 months of age and studied the effects of DLST deficiency on
amyloid deposition, spatial learning and memory, and oxidative stress. We found that alpha-KGDHC activity was reduced in DLST(+/-) mice. We also found that DLST deficiency increased
amyloid plaque burden, Abeta oligomers, and
nitrotyrosine levels and accelerated the occurrence of spatial learning and
memory deficits in female Tg19959 mice. Our data suggest that alpha-KGDHC may be involved in AD pathogenesis through increased mitochondrial oxidative stress.