Genetics of sport- Are we searching in the wrong places?
The topic of genetics of endurance sport is a fascinating one. For as long as I’ve been a competitive runner, the question of whether nature or nurture gave rise to the pocket of dominating distance runners in East Africa has been around.
Researcher Yannis Ptisliadis exemplifies this search. In an article last year, he was quoted as saying that, 10 years ago he would have said that East Africans were better because of genetics, but now he’s not convinced. His change of heart was the result of his group, and others, trying hard to find some genetic difference that some of the best Kenyans and Ethiopians had but finding only minor associations that didn’t fully explain the phenomenon.
So, is it right to conclude that there are no or very little genetic reasons for success in elite East African runners?
I’m not a geneticist, or anything close to it, but a few years ago the field of epigenetics really caught my eye. Epigenetics can be best summed up by the analogy by Dolinoy et al. (2007) that “if the genome is compared to the hardware in a computer, the epigenome is the software that directs the computer’s operation.” It’s best to think of epigenetics as a mechanism to up-regulate or down-regulate gene expression.
The fact that a variety of stressors could actually affect gene expression was fascinating. I’ve delved into the topic a bit elsewhere, and even threw out some rough hypothesis on whether maybe that East Africans due to living at altitude, high activity levels, a different nutrition, etc. could affect things on an epigenetic level to create a perfect storm that results in being predisposed to distance running success.
A fascinating review article by Ehlert et al. (2013) entitled “Epigenetics in Sports” helps clear up the picture on genetics and elite sport, and how epigentics may play a role. I highly recommend you read it for those interested (and at least some knowledge of genetics, as it can get kind of confusing), but I thought I’d highlight some of the more interesting parts and talk about it’s implications.
The problem with association studies:
The review starts by laying the foundation that researchers are working on a broken premise. The idea that we can search for single or multiple genes that influence performance is too simplistic. The way most studies work, is they look at a wide variety of gene candidates in both an elite grouping and a control grouping and see if they can find any standouts. So it’s essentially a comparison, where we take elites and a control group and see what is different.
The general consensus on single gene and multiple polymorphisms is inconclusive at best. When I was in school, the big thing initially was the ACE gene for endurance. The problem is after the initial study, duplicate studies failed to collaborate the finding (rankinen et al. 2000). The same goes with multiple gene association studies. Ehlert et al. make a pretty thorough case for the multiple limitations association studies have, which I suggest you read, but the easiest and simplest is to look at the search for the genetic component of Diabetes mellitus. They point out that research has been extensive and there have been many large scale genome-wide association studies. They’re not saying it’s not valuable research, but rather that using a similar design in smaller scale to a complex problem might not be the best route.
So are genetics not the answer?
Ehlert et al. outline the premise that genes play a role but it’s not that simple. Instead epigenetic processes cloud the picture.
I’ve outline epigenetics before here if you want a refresher:
The epigenome essentially modulates gene activity, acting as a semi-permanent up or down regulator for genetic activity. I look at epigenetic modifications as a way for your body to make subtle changes for the environment. A large number of these changes happen during fetal development.
So, the classic studies I remember from grad school were when a mother went through a traumatic/high stress experience during pregnancy (such as 9/11 if you were in NY) then the baby has a hyperstress response and chronically high cortisol levels throughout their life. Another quick classic example would be if a mother goes through famine during pregnancy, then there was an increase risk for obesity and food related diseases. The theory is that when these stressors are applied to the mother/child the developing baby gets epigenetic changes to prepare for its environment essentially. So, if there’s famine, certain genes are up/down regulated, which might make the baby more susceptible to obesity or diabetes when food is plentiful.
What’s really interesting though is that, epigenetic changes are present throughout life. Fraza et al. (2005) compared sets of twins and found that twins epigeneomes were different based on their lifestyles.
Researchers have started using rat studies to see how nutrition during development or early childhood and/or behavior affects the epigenome. So far there have been studies showing protein restriction, high fiber diets, high folic acid diets, and a slew of others all cause epigenetic changes that can affect life expectancy, disease risk, etc.
Taking it a step further, there is some preliminary evidence that performance is a partial result of an altered epigenome. According to Ehlert et al. Terruzzi et al. found that in a group of elite athletes several epigenetic changes were significant. Similarly, short term studies have shown that training effects DNA methylation. In fact, a recent journal article on the famous ACE gene claimed that “Epigenetic regulation of the ACE gene might be more relevant to endurance physiology than the I/D polymorphism”
Based on these findings, Ehlert et al. make the case that training, diet, and lifestyle should have large impacts on the epigenome.
Implications for performance and athletics:
Lifestyle, diet, and training may play a bigger role in causing changes on the epigenetic level than previously thought. While, researchers are still at the beginning stages of figuring this puzzle out, and it is entirely possible that there is another layer of complexity beyond this, it’s still exciting to think about.
The fact that animal studies have shown that manipulating certain vitamins effects methylation of DNA is intriguing. It adds a whole new level of complexity to diet and nutrition. So far, research has shown that diet plays a large role during development stages. For example, research by Pemrey (2006) shows that overeating during developmental years (8-12yrs old roughly) might impact type 2 diabetes likelihood epigenetically. How much a role it plays epigenetically beyond that is anyones guess at this point. The question arises whether your mom eating a certain diet or taking certain vitamins impacts how well you process carbohydrates or fats could be huge for performance.
Thinking in terms of east Africans, does a diet very high in sugar generally give some sort of advantage for running?
A very interesting topic was raised in Ehlert’s paper on the use of performance enhancing drugs and epigenetics. In the review, they mentioned several studies that showed that giving animals various hormones effected the epigenome. The most studied so far have been Growth Hormone, IGF-1, and anabolic steroid administration in rats. What is crazy, is that the studies found that administration of these hormones caused epigenetic changes that could potentially last for a long duration.
The implication in humans is that if you are doping, the acute effects might be gone after your 2yr ban, but the changes at the genetic level still persist. Meaning even off the juice, an athlete might be benefiting from his prior use. (After all, other rat studies have found an epigenetic impact on fiber type development).
It’s pretty scary to think about that hormones not only used for their acute benefits of recovery, repair, or muscle growth, might cause permanent genetic changes.
While it’s more of scientific than practical interest, it seems like training should cause epigenetic changes. So instead of simply breaking down the training adaptation process into signaling pathways and the like, it might be possible to look at DNA methylation for instance to see what effect different training regimes have on the epigenome.
We know that there are several different blood response patterns to altitude (various groups show different adaptations in terms of hemoglobin and hematocrit to altitude), so is it possible that some of this is partly epigenetic? What role does being born at altitude have over a life time. Or better yet, does exercise at altitude during the developmental years cause some epigenetic change. No one has the answer yet in terms of athletic performance.
Researchers are beginning to look at epigenetic changes to low altitude (http://www.xtreme-everest.co.uk/article.php?article=847) so it’s a matter of time before more research comes out in terms of endurance performance.
It’s an interesting new realm. The take away is that genetic studies aren’t the be all end all and once again it’s a very complex process. It’s not an either/or question.
So if you are asking if the East Africans are genetically superior, the answer is perhaps partly. It’s not the simple answer that researchers set out to find a decade or so ago. Instead, like everything, it seems to be a combination of genetics, epigenetics, lifestyle, and training.
It also means that genetic testing for athletic performance, which a lot of companies are starting to jump on, is probably useless.