oxygen free radicals – molecules that cause dangerous inflammation in the mitochondria themselves as well as in the rest of the cell when they spill over. Think of them as the power plants of our bodily city. Just like an old factory (see Figure B.1), ageing mitochondria spill more industrial waste into the environment. The damage this inflammation causes to your cells and to the mitochondria within your cells is responsible for many ageing-related problems. This oxidation, for example, is what causes a “rusting” of your arteries, which is some of what ages your cardiovascular system. So let’s take a closer look at how mitochondria work.
Mighty Mito: The Body’s Power Plant
If you look at mitochondria from an aerial view (don’t try this at home), you’d see something a bit like a labyrinth or maze. Those jagged little edges you see in Figure B.2 are called cristae. You have hundreds of mitochondrion per cell and dozens of strands of mitochondrial DNA per mitochondrion. That means that every cell contains thousands of strands of mitochondrial DNA.
Now think about your bodily city and picture these mitochondria as your body’s nuclear power plants. They give off a lot of energy but also have the potential to cause a lot of damage. As you’ll see many times throughout the book, most things that are powerful enough to help you are also powerful enough to hurt you.
If something bombs your power plant, it’s not just the physical plant that suffers damage; a whole lot of collateral damage takes place as well. In the case of the power plant, it’s radiation that seeps into surrounding neighbourhoods and towns. In the case of mitochondria, it’s those inflammation-causing oxygen free radicals, which also decrease the ability of your mitochondrial DNA to convert energy. Both forms of damage spin into a cycle of destruction to your body’s cells: inefficiencies in mitochondrial function cause increased production of free radicals. Well, guess what? More free radicals cause more damage to the mitochondrial DNA, which makes them more inefficient, and so on.
Figure B.1 Biological Backbone Mitochondria provide the power to our metaphorical city. Without them, we have no lights, no heat and no fun. But any power plant that is lax on precautions runs the risk of polluting the city. And just like older factories, as the mitochondria age, they tend to put more industrial waste into the environment – so we need more antioxidant regulators to clean up the mess.
Figure B.2 Factory Jobs Mitochondria are our energy factories and continually pump barrels of ATP into the cells as it travels through the circulatory system. They look like a maze with jagged edges called cristae. Mitochondria are especially hardy to withstand the dangers of being near free radicals that can be generated with high-powered energy production.
Figure B.3 Radical Demonstration Oxygen free radicals are created when a pair of electrons is separated while spinning around the nucleus of a cell. The odd man out becomes disruptive as it seeks another partner.
Maybe you’re thinking, So what? So what if my mitochondrial DNA is a little slow on the ol’ energy conversion process? What’s that mean for me?
Well, for a business, inefficiency may mean losing money. For a student, inefficiency may mean pulling all-nighters. But for mitochondria, inefficiency means you’re that much closer to booking a bed at the extended-care facility.
Think about it. If your body can’t produce energy efficiently, it means that mitochondria are not getting the most energy out of the oxygen and sugar that their furnaces are fed. So even if you have good nutrition in what you eat, lower levels of your body’s energy currency, called ATP (adenosine triphosphate), are made.
We know that mitochondrial damage in the heart happens when your body no longer consumes oxygen and glucose efficiently. We also see mitochondrial damage in brain-related disease and in diabetes, where it influences the pancreas’s ability to make insulin. In fact, mitochondrial damage may serve as a contributing factor to certain types of cancer, because the more oxidative damage that takes place, the more DNA is damaged, and that damaged DNA, when it’s replicated over and over again, can evolve into a cancer.
Damage Control
Like a politician who gets bad press, your body can also perform damage control. Over time, those furnaces (the cristae) in your mitochondria swell and become lazy fat cats – they don’t do a whole lot of work. At the same time, young, small but efficient mitochondria that are continually born become the energy work-horses of your body.
In a city model, the big-cristae mitochondria would be the high-salaried bureaucrats who spend all day preventing city government from being reinvigorated by young whippersnappers who could replace them, cut through red tape and do a lot of work for a lower price. In your body, the turf battle happens because the large ones (the bad ones) have the power to survive at the expense of the little ones (the good ones).
It turns out that you can tolerate a lot of damage to your mitochondria because mitochondrial DNA is resilient. This special SAS brand of DNA is used to dealing with the damage that happens when you bombard them with oxidative substances. In a way, they are a little like parents. The mitochondria can tolerate quite a bit, but eventually they blow a gasket. And that’s when the real damage begins.
This all happens as a natural part of the ageing process. In fact, people older than sixty have a 40 percent lower mitochondrial efficiency than people younger than forty. But remember, what’s natural is not necessarily inevitable. As you’ll see in our next chapter on the muscle that uses the most energy, that means this: while these seemingly uncontrollable cellular battles may be taking place deep inside your body, you still have the power of an anatomical puppeteer – to control the ways that your cells function. But when the system starts to spew toxic waste and you can’t keep up with the oxidation in your cells, your arteries begin to rust, which puts heat on quite a few organs, including the heart.
Chapter 2 Take the Heat off Your Heart
YOU Test: Beat Up
During your next intense cardiovascular workout (and with your doctor’s consent), bring your heart rate to 80 percent or more of your maximum heart rate (that’s 220 minus your age). After you stop, how long does it take for your heart rate to drop to 66 beats less than your 80 percent max?
A. Less than 2 minutes
B. Less than 4 minutes
C. Oxygen, NOW!
Results: If you recover quickly enough to have your heart rate drop 66 beats in less than 2 minutes, you’re in prime cardiovascular shape, and your RealAge is at least 8 years younger than your calendar age. Anything longer means you have some work to do.
We all know the things that make our hearts skip a beat (first loves and scoring the winning goal in the cup final). We all know the things that make our hearts pound faster than a military drum (horror flicks and being six minutes away from a train that pulls out in five). And we all like to think that we know the kinds of things that will make our hearts stop forever: cigarettes, sausage links and cyanide.
But when we think about ageing-related heart disease, we have to go beyond the basic assumptions that either we’re born with bad genes that destine us for cardiac troubles, or we create our own by gunking up our arteries with forty-five years of