Any athlete and coach who has ever taken a biology class will find themselves immediately drawn to the mitochondria. This little dynamo inside your cells is responsible for aerobic energy production, which dominates every activity you do that lasts longer than a few seconds. Mitochondria are also responsible for your unconscious processes like the beating of your heart and digestion.
A recent editorial by Extreme Physiology and Medicine reviewed the role of the mitochondria in extreme situations.
History of Mitochondria
The author began by outlining the extreme origins of the mitochondria. The founding of complex life (even on the level of single cell organisms) had a shot in the dark when the first phospholipids (a kind of fat) came together to create the first membranes. Numerous organisms took advantage of this biological technology because it separated the internal environment of the organism from the outside.
Initially, there were two different cells – one large cell and the smaller mitochondria. No one is sure which was the predator, but one of them was out to get the other. The large one either swallowed up the mitochondria, or the mitochondria was an invader. Either way, the two different cells lived together for so long that they became one and are now found in most eukaryotic cells, the type of cell that every multicellular organism (like humans) is made from.
The little organisms that became organelles now fuel everything you do, and it’s a tall order they have to meet. Mitochondria can live in situations of extremes, such as high acidity, high temperatures, and low light. Today’s study shed light on how mitochondria behave in three extreme conditions: hot and cold temperatures, high altitude, and fasting.
According to the author, more complex organisms have to work harder to maintain stable conditions inside the body. This is especially true for endotherms, or warm-blooded animals like birds and mammals. Exercising, or even surviving, in both cold and hot environments requires constant energy output. When you’re out on a run in freezing temperatures, your mitochondria don’t just make energy to move. They also act as a literal furnace to expend energy and generate heat.
Mitochondria also provide protection during changes in altitude. During altitude training, the mitochondria undergo several changes to maintain the level of oxygen in your blood. They burn less fuel (and thus need less oxygen), use different fuel, and even go away entirely. These changes help maintain oxygen levels in the face of thinning air.
Speaking of fuel choice, many factors can influence what fuels mitochondria use. For example, the author of the study points out that in times of nutritional plenty, mitochondria prefer pyruvate. During short-term fasting, fat becomes the preferred energy source. During long-term hunger, the mitochondria switch to ketogenesis for fuel.
This research supports the idea that food choices and timing should reflect which fuels you want to use. Generally, consuming fat regularly and practicing short-term fasting will, in time, increase your ability to use fat as fuel, right down to the mitochondrial level.
The review also reiterated that exercise helps determine the number of mitochondria in your cell. The less frequently you exercise, the fewer mitochondria you’ll have, and energy, coordination, and overall fitness will suffer as a result. But it works the other way, too. Your body will actually grow more mitochondria in response to exercise, which means a greater ability to produce energy. So get out there and move!
1. Andrew Murray, “Mitochondria at the extremes: pioneers, protectorates, protagonists,” Extreme Physiology & Medicine 2014, 3:10
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