March 25, 2013 | 11
It seems that humans have, throughout their life history, suffered from a lot of stress. First there were lions and tigers and bears, then there were other humans with pointy metal objects, and now there are deadlines and traffic jams and bankruptcy. Stress, even the kind of stress many of us deal with nowadays, can be rough on the body. It can produce depression, anxiety, increased sensitivity to illness, and it even can shorten your life expectancy. None of these are good, and many of them are related to cell aging and death.
But our bodies do their best to work around these negative effects. And one new way? Extra telomerase. But there is a way to combat cellular aging, and that’s via something called telomerase. But is it meaningful? That’s a good question.
Beery et al. “Chronic stress elevates telomerase activity in rats” Biology letters, 2013.
(Side note: Nobel Prize winner Elizabeth Blackburn is on this paper! No surprise there, telomeres are right up her alley!)
To know about telomerase you have to know about telomeres. When cells replicate, the DNA within them replicates first (during the S phase). The DNA then forms up into chromatids, which form into X-shaped pairs and get pulled apart during replication, 1/2 of the DNA to each new cell. But during that time, when the DNA is replicating and in chromatids, there are telomeres.
Telomeres are random sequences of DNA at the end of your REAL DNA. They form an incredibly protective cap, and so though they may “say” nonsense, they mean a lot. The enzymes that perform DNA replication can’t go to the very ends of the DNA, they have to stop before they reach the end. If your DNA just ended where it needed to end, with nothing else there, each time replication occurred, you would lose some of your DNA. Some of your important, coding DNA. If you lost a little bit of your genome every time a cell replicated…well none of us would be here at all. So you have telomeres, nonsense DNA strands which get slightly shorter with every replication of the DNA.
(You can see them there on the ends. Source)
Of course, you don’t want to lose your telomeres either, as then you’d start losing regular DNA. And in fact, telomeres getting shorter is a sign of aging. So there are actually enzymes that help to maintain and lengthen your telomeres, called telomerases. Telomerases can save us a lot of grief, lengthening our telomeres and protecting our cells from senescence (when cells get too old to divide). Deficiencies in telomerase can be associated with many problems including premature aging and severe immune deficiency. So high levels of telomerase are protective, promoting long life for a cell.
And this could be meaningful for stress. We know that stress can cause cell death of various types, could telomerase help? And this led the authors of this study to ask about stress. We know that stress increases signs of cell aging and death. And we know that telomerase often increases, to lengthen telomeres and presumably prevent cell aging and death. So what happens to telomerase when you are stressed?
To examine this, the authors of this study took rats and exposed them to chronic stress (what I like to call the rat equivalent of academia). The rats never know what they’re getting on any given day. Sometimes they have to swim, sometimes their cage is tilted. Sometimes they get rock music all night, and sometimes they have to smell the smell of a predator (in this case, fox odor, and I pity ANYONE who has to work with this stuff. It never comes out of anything. Ever). This type of unpredictable stress is hard on rats (not to mention hard on the humans who have to do all the changing, often at very odd hours). The stressed rats didn’t gain as much weight as their relaxed controls, and showed high levels of anxiety in the elevated plus maze, open field, and light dark box.
You can see the measures of open field, elevated plus maze, and light dark box above (left to right). These are all anxiety measures in rats that take advantage of a rat’s natural aversion to bright light and open spaces. The more anxious a rat is, the less time he will spend in the middle of an open field, on the open arms of an elevated maze, or in the light part of a box. You can see that the stressed rats were much more anxious than their related counterparts.
And these behavioral effects were correlated with increased telomerase activity. The more stressed behavior the rats showed, the more telomerase activity they had.
Now, this doesn’t mean that stress directly causes telomerase activity or that telomerase activity causes stress.
But it could mean that increased telomerase activity is one way for cells to deal with the difficulties of stress, increasing telomerase activity to protect the DNA from excessive destruction, and protect cells from senescence. It merely means that when they stressed animals, there was increased telomerase activity. As pointed out in the comments, a lot of things increase telomerase activity, and since stress IS still associated with cell aging signs and cell death, whether or not those increases in telomerase activity are meaningful is unclear. It would be interesting to see if increasing telomerase activity prior to stress could protect animals from the effects of stress (like, say, the effects of stress on neurogenesis, where stress causes major decreases). That would be the way to show that telomerase plays a meaningful role in the effects of stress. But for now, it’s another role for telomeres, and for telomerase. Protecting your telomeres to save you from stress. So, while the two things, stress and increased telomerase, go together, whether they MEAN anything together is less certain.
Beery, A., Lin, J., Biddle, J., Francis, D., Blackburn, E., & Epel, E. (2012). Chronic stress elevates telomerase activity in rats Biology Letters, 8 (6), 1063-1066 DOI: 10.1098/rsbl.2012.0747
EDIT (3/26/13): As people have pointed out in the comments, there is no established LINK between stress and telomerase activitiy. The two are merely shown here to co-occur, and to suggest that the telomerase activity here might be meaningful is too much speculation. I have changed the title and edited parts of the post to reflect this. Corrections throughout the post are in italics.