Telomeres in the Brain Cortex of Patients with Major Depressive Disorder

Telomeres are complex structures formed by the end of the DNA molecule at the tip of each chromosomal arm. The repeated (TTAGGG) telomeric sequence progressively shortens during lifespan because it cannot be replicated as somatic cells divide, and is highly susceptible to breakage by free radicals. Critically shortened telomeres activate the genetic program of cell senescence and/or apoptosis. The telomere length measured in peripheral blood leucocytes is considered a reliable marker of biological age, mortality risk and exposure to various pathological conditions, including cardiovascular disease, dementia, and metabolic syndrome. Telomere erosion has been observed in psychiatric disorders including schizophrenia and mood disorders, suggesting an accelerated aging of 10 to 20 years. Whether this peripheral dynamic is reflected by a similar pattern in the brain remains unknown. To address this issue we have measured the telomere length in the occipital DNA cortex of 24 patients with major depressive disorder and 12 controls (donated by the Stanley Research Institute) by a real time quantitative PCR technique. The mean telomere lengths were identical in the depressed and control groups. Thus, although there is consistent evidence for the role of systemic inflammation and oxidative stress in depression, it must be concluded that the cerebral status of telomeres is not affected. This observation raises the issue of the relation between the psychiatric pathological process, and peripheral and central biomarkers.