Aging enzyme: MRI reveals depressing link

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  • Published: Jun 1, 2013
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Aging enzyme: MRI reveals depressing link

Protection in depression

Magnetic resonance imaging has revealed a possible protective role for the enzyme telomerase in processes associated with the development of depression in aging patients. The study investigated untreated, depressed participants and found that 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.

Magnetic resonance imaging has revealed a possible protective role for the enzyme telomerase in processes associated with the development of depression in aging patients. The study investigated untreated, depressed participants and found that 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. A direct cause and effect has not been found but the work perhaps offers new pointers to understanding the activity of this enzyme in depression and aging.

Although clinical depression is commonly seen as nothing more than a chronically bad mood, it is certainly much more than that in terms of its physical and psychological symptoms. Moreover, although it is a mental illness its biology is not confined to the brain. Indeed, major, long-term depression has been correlated with various life-threatening illnesses and a risk of premature death in research carried out during the last few years, this seems to be true even when lifestyle risk factors are factored out of the equation.

Depression and immunity

Now a research team led by Owen Wolkowitz, professor of psychiatry at the University of California San Francisco has found a possible link between the apparently psychological effects of depression and activity within the cells of the immune system. Specifically, they have focused on the enzyme, telomerase, which is involved in extending the protective ends - the telomeres - of DNA as it replicates with each successive generation of cell division. Newer data (largely in rodents) suggest that it also has neurotrophic (brain cell growth promotion) and antidepressant-like effects. Reduced enzyme activity is linked to the aging process and the development of multiple serious illnesses, including cancer as DNA with shorter telomeres is more susceptible to damage.

The work by Wolkowitz and colleagues shows that this enzyme is more active on average in untreated individuals with major depression than in controls. The research does not prove a cause and effect link. However, one might hypothesise that greater telomerase activity is a response to the body detecting susceptibility to biological damage associated with the clinical effects of depression. The researchers offered details of their preliminary findings at the annual meeting of the American Psychiatric Association in San Francisco in May 2013-05-30.

Telomeric effects

The team has also demonstrated the possible protective effect of 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 to learning and memory, correlated with the level of telomerase activity measured in the white blood cells of the immune system. Wolkowitz emphasises that this, again, is not necessarily a cause and effect relationship, but perhaps great telomerase activity in depression is a response to protecting the cells of the hippocampus from damage.

“Our results are consistent with the beneficial effect of telomerase when it is boosted in animal studies, where it has been associated with the growth of new nerve cells in the hippocampus and with antidepressant-like effects, evidenced by increased exploratory behaviour,” Wolkowitz explains. The researchers also showed that enzyme activity rose in patients prescribed antidepressants, but only in those who experienced an antidepressant effect. . “The longer people had been depressed, the shorter their telomeres were,” he said. “Shortened telomere length has been previously demonstrated in major depression in most, but not all, studies that have examined it. The duration of depression may be a critical factor.”

“New insights into the mechanisms of these processes may well lead to new treatments — both pharmacological and behavioural - that will be distinctly different from the current generation of drugs prescribed to treat depression,” adds Wolkowitz. “Additional studies might lead to simple blood tests that can measure accelerated immune-cell aging."

Related Links

APA Scientific Program 2013

Mol Psychiat, vol 17, 164-172, "Resting leukocyte telomerase activity is elevated in major depression and predicts treatment response"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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