Inverse changes in telomere length between the blood and brain in depressive-like mice.

Background: Telomeres are nucleoprotein complexes located at the end of chromosomes. Previous studies have confirmed that telomere length is reduced in the peripheral blood of depression patients. However, studies regarding whether telomere length is altered in brain regions associated with depression are limited. It remains unclear whether the peripheral blood telomere length indicates telomere variation in the brain.

Methods: Using quantitative PCR, we measured telomere length in five brain regions (prefrontal cortex, amygdala, nucleus accumbens, paraventricular nucleus, and hippocampus) from depressive-like mice and in peripheral blood from depressive-like mice and major depressive disorder (MDD) patients. We also examined the expression of telomerase- and alternative lengthening of telomere (ALT)-related genes in the prefrontal cortex and amygdala of depressive-like mice.

Results: Telomeres were shortened in the peripheral blood of depressive-like mice and MDD patients, but were elongated in the prefrontal cortex and amygdala compared with healthy controls. We also observed that the expression of ALT-related genes increased in the prefrontal cortex and amygdala.

Limitations: The amount of human sample was limited. The mechanism of telomere lengthening in the brain of depressive-like mice was not well explained. Mice and humans have inherently different telomere and telomere maintenance systems.

Conclusion: These findings illustrate that the telomere length in the peripheral blood may not indicate the dynamics of telomere length in the brain. They offer a new perspective on variable telomere length in different brain regions affected in depression and provide a new basis for understanding the relationship between variable telomere length and MDD.