Mitochondrial abnormalities in Alzheimer brain: mechanistic implications

Area of Science:

• Neuroscience
• Biochemistry
• Metabolic Disorders

Background:

• Alzheimer's disease (AD) is characterized by reduced cerebral metabolism, correlating with cognitive decline.
• The role of specific mitochondrial metabolic pathways, like the tricarboxylic acid (TCA) cycle, in AD pathogenesis requires further elucidation.

Purpose of the Study:

• To investigate the correlation between the activity of key tricarboxylic acid (TCA) cycle enzymes in the brain and the clinical disability in patients with Alzheimer's disease (AD).

Main Methods:

• Enzyme activity assays were performed on post-mortem brain samples from individuals with autopsy-confirmed AD.
• Enzyme activities were quantified for multiple tricarboxylic acid (TCA) cycle enzymes.
• Enzyme activity levels were statistically correlated with pre-mortem clinical dementia ratings (CDRs).

Main Results:

• Significant reductions in pyruvate dehydrogenase complex (-41%), isocitrate dehydrogenase (-27%), and alpha-ketoglutarate dehydrogenase complex (-57%) activities were observed in AD brains (p < 0.01).
• Conversely, succinate dehydrogenase (+44%) and malate dehydrogenase (+54%) activities were significantly increased (p < 0.01).
• All observed TCA cycle enzyme activity alterations correlated significantly with the clinical severity of AD (p < 0.01), with pyruvate dehydrogenase complex showing the highest correlation (r = 0.77).

Conclusions:

• Mitochondrial tricarboxylic acid (TCA) cycle enzymes exhibit coordinated alterations in Alzheimer's disease (AD) brains.
• These metabolic changes are closely linked to the clinical disability experienced by AD patients.
• Targeting TCA cycle metabolism presents a potential therapeutic strategy for Alzheimer's disease (AD).