Reduced steady-state levels of mitochondrial RNA and increased mitochondrial DNA amount in human brain with aging.
The contribution of the mitochondrial genetic system in the degenerative processes of senescence remains unclear. This study deals with age-related changes in brain mtDNA expression in humans. Brain tissue from the frontal lobe cortex was obtained from autopsy of 13 humans aged between 21 and 84 years. No structural changes were detected in mtDNA, increased mtDNA content and reduced steady-state level of mitochondrial transcripts and transcription ratio (mtRNA/mtDNA) were associated with aging. These findings suggest that the increase of the mtDNA levels could be considered as an inefficient compensatory mechanism to maintain the normal levels of mtRNA transcripts. This unbalanced mitochondrial condition could play a role in the process of senescence in human brain.