While most of us have to worry about limiting our intake of fried foods, bacon, eggs, or anything that we’re told is on the “cholesterol-raising list” of the moment, a few people can eat all these things and more without fear. In fact, no matter what they consume, their “bad cholesterol” (blood levels of low-density lipoprotein, associated with heart disease) remains virtually non-existent.
These people were born with a genetic mutation. More specifically, they lack working copies of a gene known as PCSK9, and while it’s usually unlucky to be born with a missing gene, in this case, it seems to have some positive side effects.
After scientists discovered the relationship between this gene (or lack thereof) and cholesterol about 10 years ago, drug companies have worked frantically to create a pill that would block PCSK9 in other individuals. The drug is close to getting FDA approval. In early trials, patients who have taken it have experienced as much as a 75-percent reduction in their cholesterol levels.
So far, scientists have only found the mutation in a handful of African Americans, and those with it have the benefit of a 90-percent reduced risk of heart disease.
Resistance To HIV
All sorts of things could wipe out the human race—asteroid strikes, nuclear annihilation, and extreme climate change, just to name a few. Perhaps the scariest threat is some type of super-virulent virus. If a disease ravages the population, only the rare few who are immune would have a chance of survival. Fortunately, we know that certain people are indeed resistant to particular diseases.
Take HIV, for example. Some people have a genetic mutation that disables their copy of the CCR5 protein. HIV uses that protein as a doorway into human cells. So, if a person lacks CCR5, HIV can’t enter their cells, and they’re extremely unlikely to become infected with the disease.
That being said, scientists say that people with this mutation are resistant rather than immune to HIV. A few individuals without this protein have contracted and even died from AIDS. Apparently, some unusual types of HIV have figured out how to use proteins other than CCR5 to invade cells. This type of resourcefulness is why viruses are so scary.
Folks with two copies of the defective gene are most resistant to HIV. Currently, that includes only about 1 percent of Caucasians and is even more rare in other ethnicities.
Those who have an especially high resistance to malaria are carriers of another deadly disease: sickle cell anemia. Of course, no one wants the ability to dodge malaria only to die prematurely from malformed blood cells, but there is one situation where having the sickle cell gene pays off. To understand how that works, we have to explore the basics of both diseases.
Malaria is a type of parasite carried by mosquitoes that can lead to death (about 660,000 people per year) or at the very least make someone feel at death’s door. Malaria does its dirty work by invading red blood cells and reproducing. After a couple days, new malaria parasites burst out of the inhabited blood cell, destroying it. They then invade other red blood cells. This cycle continues until the parasites are stopped through treatment, the body’s defense mechanisms, or death. This process causes a loss of blood and weakens the lungs and liver. It also increases blood clotting, which can spark a coma or seizure.
Sickle cell anemia causes changes in the shape and makeup of red blood cells, which makes it difficult for them to flow through the blood stream and deliver adequate levels of oxygen. However, because the blood cells are mutated, they confuse the malaria parasite, making it difficult for it to attach and infiltrate the blood cells. Consequently, those who have sickle cells are naturally protected against malaria.
You can get the anti-malaria benefits without actually having sickle cells, so long as you’re a carrier of the sickle cell gene. To get sickle cell anemia, a person has to inherit two copies of the mutated gene, one from each parent. If they only get one, they have enough abnormal hemoglobin to resist malaria yet will never develop full-fledged anemia.
Because of its strong protection against malaria, the sickle cell trait has become highly naturally selected in areas of the world where malaria is widespread, with as much 10–40 percent of people carrying the mutation.
7Tolerance For Coldness