Longitudinal Analysis of Mitochondrial D-Loop Methylation and Copy Number in Peripheral Blood: Epigenetic Signatures of Alzheimer's Disease Progression and Aging.

Healthy controls showed a progressive increase in mitochondrial D-loop methylation over the eight-year longitudinal follow-up period.

• 75 participants were followed longitudinally over eight years
• Subjects were classified into four groups according to clinical progression from healthy cognition to MCI and AD
• A linear mixed-effects model was used to assess differences in methylation dynamics across groups and time points
• Increased D-loop methylation in healthy controls was interpreted as a possible protective mechanism against mitochondrial dysfunction

Individuals converting to Alzheimer's disease exhibited a marked decrease in mitochondrial D-loop methylation over time.

• The decrease in D-loop methylation was observed longitudinally across the eight-year study period
• Significant differences in methylation dynamics were detected across groups and time points using a linear mixed-effects model
• Reduced D-loop methylation was associated with mitochondrial dysfunction and disease progression
• The trend was opposite to that observed in healthy controls, who showed increasing methylation

mtDNA copy number showed an opposite trend to D-loop methylation across groups, with increased copy number associated with AD progression.

• An opposite trend between D-loop methylation and mtDNA copy number was observed across the study groups
• Increased mtDNA copy number was associated with mitochondrial dysfunction and disease progression
• Significant differences in mtDNA copy number were detected across groups and time points using a linear mixed-effects model
• The relationship between reduced methylation and increased copy number suggests a coordinated epigenetic response during cognitive decline

The study design involved longitudinal classification of 75 participants into four clinical progression groups spanning healthy cognition, MCI, and AD.

• Total sample size was 75 participants followed over eight years
• Subjects were classified into four groups according to clinical progression from healthy cognition to mild cognitive impairment (MCI) and AD
• Blood-derived DNA samples were used for methylation and copy number analyses
• The study built on previous identification of molecular signatures associated with disease progression

Mitochondrial dysfunction and impaired protein homeostasis were identified as playing crucial roles in AD onset and progression beyond amyloid and tau pathologies.

• The study investigated whether epigenetic alterations of mtDNA contribute to cognitive decline
• The D-loop region analyzed is the regulatory region of mtDNA
• AD is described as the leading cause of dementia and is expected to markedly increase in prevalence in coming decades
• The study focused specifically on the methylation status of the mtDNA regulatory D-loop region as a potential contributor to disease progression