High blood sugar combined with Alzheimer's causes brain damage
31 October 2013
High blood-sugar levels damage blood vessels in the brain of
Alzheimer's sufferers according to a study at Tulane University
published in the Journal of Alzheimer's Disease.
The study found that high blood-sugar levels, such as those that
occur with Type 2 diabetes, make beta amyloid protein associated
with Alzheimer’s disease dramatically more toxic to cells lining
blood vessels in the brain. This supports growing evidence pointing
to glucose levels and vascular damage as contributors to dementia.
“Previously, it was believed that Alzheimer’s disease was due to
the accumulation of ‘tangles’ in neurons in the brain from
overproduction and reduced removal of beta amyloid protein,” said
senior investigator Dr. David Busija, regents professor and chair of
pharmacology at Tulane University School of Medicine. “While
neuronal involvement is a major factor in Alzheimer’s development,
recent evidence indicates damaged cerebral blood vessels compromised
by high blood sugar play a role. Even though the links among Type 2
diabetes, brain blood vessels and Alzheimer’s progression are
unclear, hyperglycemia appears to play a role.”
Researchers studied cell cultures taken from the lining of brain
blood vessels, one from normal rats and another from mice with
uncontrolled chronic diabetes. They exposed the cells to beta
amyloid and different levels of glucose and later measured their
viability. Cells exposed to high glucose or beta amyloid alone
showed no changes in viability.
However, when exposed to hyperglycemic conditions and beta
amyloid, viability decreased by 40%. Researchers suspect the damage
is due to oxidative stress from the mitochondria — components of
cells that produce the chemical used to supply energy in the cell.
The cells from diabetic mice were more susceptible to damage and
death to beta amyloid protein − even at normal glucose levels. The
increased toxicity of beta amyloid may damage the blood-brain
barrier, disrupt normal blood flow to the brain and decrease
clearance of beta amyloid protein.
The study’s findings underscore the need to aggressively control
blood sugar levels in diabetic individuals, Busija said.