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Altitude babies and epigenetics

December 28th, 2011

Steve Magness has a fascinating post on his blog about a neat new study in the January issue of Journal of Applied Physiology. The researchers took a bunch of rats whose ancestors have been living at the Bolivian Institute for Altitude Biology, which is 3,600 metres above sea level. Half the rats were placed in a room with “enhanced oxygen” to mimic sea level from one day before birth to 15 days after birth; the other half simply grew up normally at 3,600 metres. Then the researchers followed the rats for the rest of their lives to see whether this “postnatal” exposure to low oxygen affected the rats’ development.

This study fits into the recent burst of research into epigenetics — the idea that early environmental influences can produce lasting changes in gene expression. And sure enough, there were significant differences between the rats who grew up at high altitude continuously (HACont) and those who got two weeks of sea-level oxygen (HApNorm):

As you can see, the high-altitude rats had higher hemoglobin and hematocrit long after the two-week exposure period (32 weeks is roughly middle-aged in rats). Among many other differences, the altitude babies also had a bigger heart, and used less oxygen. All of this sounds pretty good for endurance athletes — which is why Steve wrote:

I always joke with my friends that whenever I have kids, I’m going to stick them at altitude during pregnancy and right after just to develop super altitude adapted kids…

But there’s a caveat. Here’s the survival data for the two types of rat:

In fact, the researchers make the overall conclusion that low oxygen levels in the crucial weeks after birth are a bad thing:

We conclude that exposure to ambient hypoxia during postnatal development in [high altitude] rats has deleterious consequences on acclimatization to hypoxia as adults.

So you have to be careful what you wish for your kids. Either way, though, it’s clear that environment alone can produce profound, lifelong changes in physiology — producing group traits that we once might have mistakenly attributed to genetics.

  1. Audrey Giles
    December 28th, 2011 at 21:26 | #1

    That’s really interesting!!! Thanks for sharing such fascinating info! Again, this sort of thing is exactly why I love your blog!

  2. RH
    December 29th, 2011 at 12:05 | #2

    Amazing. Especially the carnage after 500 days in the continuous altitude group.

    Did the authors make the point that further research is needed? If not, I am happy to do it for them.

    Judging from the second graph, every square represents a 5% mortality (with the last square representing the body count after the 600 days of the study). This suggests there were 20 rats in each group, which, at least for a mortality statistic, appears to me a bit shallow. The observed mortality could be a result of housing conditions or a disease if both groups were housed separately.

  3. alex
    December 29th, 2011 at 13:14 | #3

    @RH: Strangely, the authors neglected to explicitly point out the need for further research. I will forward your suggestion to them. :)

    The study started out with 160 rats, but some were sacrificed at each intermediate checkpoint to evaluate heart and lung adaptations. A pre-identified subset was followed for 600 days to evaluate longevity — your estimate of its size looks reasonable, but I don’t see the exact number specified in the paper. And indeed, the result doesn’t reach statistical significance:

    “When data of males and females are pooled, mortality showed a clear tendency to be higher in HACont rats compared with HApNorm (P = 0.07) with a death ratio of 2.8 (95% confidence interval = 0.9 to 7.5) (Fig. 4B).”

    So we definitely shouldn’t conclude that everyone born at high altitude is going to die early! What I found interesting is that this paper doesn’t mention endurance performance at all — the topic isn’t even hinted at. And so the perspective of what’s “good” and “bad” is very different from what I’m used to. I scanned the results, and thought “Oh, higher hematocrit, bigger heart, lower oxygen use — looks like great adaptations!” But they report all these findings as highly negative indicators…

  1. December 29th, 2011 at 02:56 | #1