Heightened telomerase activity in patients with untreated major depression may represent the body’s attempt to fight back against the progression of disease, according to a new study.
Researchers led by Owen Wolkowitz, professor of psychiatry at University of California San Francisco, in an ongoing study found that within cells of the immune system, activity of an enzyme called telomerase is greater, on average, in untreated individuals with major depression.
Telomerase is an enzyme that lengthens protective end caps on the chromosomes’ DNA, called telomeres. Shortened telomeres have been associated with earlier death and with chronic diseases in population studies.
The heightened telomerase activity in untreated major depression might represent the body’s attempt to fight back against the progression of disease, in order to prevent biological damage in long-depressed individuals, Wolkowitz said.
The researchers made another discovery that may suggest a protective role for telomerase. Using magnetic resonance imaging (MRI), they found that, in untreated, depressed study participants, the size of the hippocampus, a brain structure that is critical for learning and memory, was associated with the amount of telomerase activity measured in the white blood cells.
Such an association at a single point in time cannot be used to conclude that there is a cause-and-effect relationship with telomerase helping to protect the hippocampus, but it is plausible, Wolkowitz said.
The researchers also found that the enzyme’s activity went up when some patients began taking an antidepressant. In fact, depressed participants with lower telomerase activity at baseline – as well as those in whom enzyme activity increased the most with treatment – were the most likely to become less depressed with treatment.
The researchers also measured telomere length in the same immune cells. Only very chronically depressed individuals showed telomere shortening, Wolkowitz said.
The 20 depressed participants enrolled in the study had been untreated for at least six weeks and had an average lifetime duration of depression of about 13 years.
After baseline evaluation and laboratory measures, 16 of the depressed participants were treated with sertraline, a member of the most popular class of antidepressants, the serotonin-selective-reuptake-inhibitors (SSRIs), and then evaluated again after eight weeks. There were 20 healthy participants who served as controls.
The preliminary findings from the study were presented at the annual meeting of the American Psychiatric Association in San Francisco.