High blood sugar makes Alzheimer’s plaque more toxic to brain, study
High blood-sugar levels, such as those linked with type 2 diabetes, make beta amyloid protein associated with Alzheimer’s disease dramatically more toxic to cells lining blood vessels in the brain, according to a new study from Tulane University in New Orleans.
The study, published in the Journal of Alzheimer’s Disease in October 2013, 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 Dr David Busijua, senior investigator, Regents Professor and Chair of Pharmacology at Tulane University School of Medicine.
“While neuron involvement is a major factor in Alzheimer’s development, recent evidence indicates damaged cerebral blood vessels compromised by high blood sugar play a role,” Dr Busijua said. “Even though the links among type 2 diabetes, brain blood vessels and Alzheimer’s progression are unclear, hyperglycemia appears to play a role,” he said.
Researchers studied cell cultures taken from the lining of cerebral 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, later measuring their viability. Cells exposed to high glucose of beta amyloid alone showed no changes in viability. However, when exposed to hyperglycemic conditions and beta amyloid, viability decreased by 40 per cent. Researchers said they suspected the damage was due to oxidative stress from the mitochondria of 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.
Researchers said the findings underscore the need to “aggressively” control blood sugar levels in diabetic individuals.
Drs Cristina Carvalho and Paula Moreira from the University of Coimbra in Portugal were co-investigators in the study.