HIF-1a: Hypoxia, Cancer, and Athletic Superpowers

When you think about things that you can’t live without, your iPhone or the internet may top the list :-) But really, oxygen tops all of our ‘can’t live without it’ lists. A minute without it will remind you of just how important it is to every cell in your body.

Have you ever wondered, though, how your cells can survive for a few minutes without oxygen — or how your body manages when oxygen levels are lower than normal? It turns out that we have an innate system that detects when oxygen levels are low and turns on other genes that can help cells survive when precious O₂ is not readily available.

The Nobel Prize in medicine has just been awarded to three scientists who discovered how cells manage oxygen and know when levels are low. This article covers one piece of this O₂ puzzle that they figured out and delves into some of the genetic variants involved in this process.

HIF-1a background information:

The hypoxia-inducible factor-1 alpha (HIF1A) gene codes for a transcription factor, which regulates the rate at which certain other genes get transcribed.

So what is a transcription factor, and why is HIF-1a so important?

Genes code for proteins; your cells need to know which genes need to be translated into the proteins needed at that instance. Basically, a transcription factor is like a switch that can turn on or off the transcription of genes. There are a couple of thousand different transcription factors in the human genome.

HIF-1a (hypoxia-inducible factor-1 alpha) responds to the amount of oxygen available to the cell. Hypoxia refers to a state where there isn’t enough oxygen available.

Thus, when there isn’t enough oxygen available at a cellular level, the HIF-1a transcription factor can change the transcription rate for the genes that code for proteins involved in oxygen and glucose transport. It switches on the genes needed for resolving the problems of low oxygen.

When oxygen levels are low (hypoxia), cells and tissues need to respond quickly. The use of oxygen normally occurs in the cellular process to make energy or ATP. (Yes, your cells have a backup route of anaerobic glycolysis, which works without oxygen, but this isn’t as efficient for making ATP.)

Thus, when oxygen levels drop, HIF-1a levels rise, kicking off a bunch of processes.

One way that HIF-1a helps your body respond to the lack of oxygen is by stimulating the growth of more blood vessels. It also stimulates the production of red blood cells by increasing erythropoietin (EPO) expression.

When are you exposed to low oxygen levels?

The first thing that comes to mind with low oxygen levels may be high altitudes. As you go up a mountain in Colorado – or in the Himalayas – oxygen levels decrease. Anyone who has flown out to Colorado to ski at Breckenridge (or worse, A-basin) knows how bad it feels if you don’t take time to adjust slowly to the altitude. (Spend that first night in Denver. Seriously…)

Another way that oxygen levels can drop in your body is during aerobic exercise. You know… like when it is New Year’s Day, and you decided to join the gym and run on the treadmill — for the first time in a year. Your muscles are suddenly using up oxygen faster than you can suck it in, leaving you gasping and feeling like you’re going to die.

On a cellular or tissue level, hypoxia can occur in a number of situations. First, inflammation can cause hypoxia in a specific area of the body. For example, an inflamed joint due to arthritis will have a low supply of oxygen. Other conditions that cause hypoxia include heart disease, stroke, and kidney disease. HIF-1a levels show increases in all of these chronic inflammatory conditions.[ref][ref][ref]

Hypoxia and HIF-1a are also important in cancer.

Cancer cells grow rapidly and need a lot of oxygen. Thus, they need more blood vessels to bring in the O2, and they need nutrients.

HIF-1a is often upregulated or increased in cancer and helps with the promotion of tumor growth by creating more blood vessels to bring in oxygen. It is sometimes tested as a marker to predict the aggressiveness of the tumor.

Getting more specific, one study showed HIF-1a increased in >90% of colon, lung, and prostate cancers. In addition to causing an increase in blood vessel formation (angiogenesis) to carry oxygen to the tumors, HIF-1a also decreases a cell’s DNA repair mechanism. This increases the rate of mutation in a cell, which is a big problem in tumor cells. Additionally, HIF-1a increases glucose transport, thus providing more energy to cancer cells.[ref][ref]

What does HIF-1a do under normal conditions?

When you have a normal amount of oxygen available, known as normoxia, the production of the HIF1a protein happens in cells while constantly being degraded by prolyl hydroxylases (PHDs). These PHDs are oxygen sensors, altering HIF-1a and degrading it when there is plenty of oxygen present in the cell.[ref]

What happens if you increase HIF-1a under normal oxygen conditions?

Researchers recently developed ways of inhibiting PHDs, thus allowing HIF-1A to be upregulated under normal oxygen conditions. These PHD (prolyl hydroxylase) inhibitors may be used for regenerating damaged tissue (increased blood vessel formation) or for treating specific types of anemia (stimulates red blood cell production).

The flip side of encouraging HIF-1a under normoxia is that you really don’t want to encourage cancer growth. As a result, the use of PHD inhibitors only applies to specific conditions.

What else can activate HIF-1a?

In addition to activation by hypoxia, the activation of HIF-1a also occurs from cytokines, growth factors, hormones, and cancer genes. For example, the growth factor IGF-1 can increase HIF1a. Estrogen can also increase HIF-1a, such as in the thickening of the endometrium each month for premenopausal women.[ref][ref][ref]

Interestingly, tamoxifen, a treatment for estrogen-positive breast cancer, works in part by reducing HIF-1a levels.[ref]

Cytokines are inflammatory molecules that the body produces as part of the immune response. They are signals to increase inflammation. Specifically, the cytokine TNF-alpha causes an increase in HIF-1a. [ref] This is one connection between inflammatory conditions, such as arthritis or atherosclerosis, and higher HIF-1a levels.[ref]

Lifehacks:

There are natural ways to both inhibit HIF1a and increase HIF1a. I’m listing both here – you can decide which way is best for your body right now. Another reason for listing both is that if you are trying to increase HIF1a, you may not want to take an inhibitor of HIF1a at the same time. For example, if you are taking resveratrol (inhibitor) while also trying to increase HIF1a through Wim Hof breathing, you may not get the expected benefits. Space them out :-)

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