Tag Archives: Hormones

A mitochondrial hormone that’s apparently a critical regulator of metabolism has been discovered

A new paper just came out in Cell Metabolism that is really cool for a couple reasons.

Lee et al. (2015) found that a hormone produced by mitochondria, parts of our cells that are important in metabolism and have their own DNA. They called the hormone MOTS-c.

Hormones, remember from earlier posts, are just signaling molecules that circulate in our cells and bodies and have important biological effects.

This discovery is especially cool for a couple reasons.

The first is that although we know that mitochondria are really important in metabolism, we don’t really know much about signaling molecules that are actually produced by our mitochondria.

The second is that the hormone appears to be really conserved among all mammals. This is often seen for hormones whose purpose is so specific, important, and widespread that its difficult for the hormone to even evolve. Insulin is another example of a hormone that is very conserved among mammals.

A final reason why this discovery is so cool is that MOTS-c seems to have really important effects on metabolism. It’s action activates AMPK. AMPK is another really important signaling molecule that we understand much more about. For now, its just important to know that AMPK regulates fat metabolism, and it looks like treatment with MOTS-c actually prevents obesity and insulin resistance in mice.

Maybe this represents a future treatment for obesity and diabetes? It’s actually quite strange to think that someday we might understand endocrinology well enough to regulate weight and even to some extent processes like aging by simply hormone injections without the current negative consequences that generally accompany these approaches.

That day is not yet here, so I’m gonna go hit the gym.

Lee, C., Zeng, J., Brew, B.G., Sallam, T., Martin-Montalvo, A., Wan, J., Kim, S., Mehta, H., Hevener, A.L., de Cabo, R., Cohen, P. (2015) The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance. Cell Metabolism 21, 443-454.


What are hormones and how do they work: some basics

We hear a lot about hormones these days. Estrogen is good for women; estrogen is bad for women. Growth hormone will help you stay young; growth hormone will give you cancer. Hormones make cows get big and tasty; hormones that we give cows are bad for our kids when they drink milk. But what IS a hormone? Why are they important? How do they work?

To start with, there are three major types of hormones – peptides, catecholamines, and steroids. Each one is different. But all three are released in response to a signal from the brain (or another hormone), and travel throughout your body in your blood, affecting cells and tissues along the way. Hormones are important before you are born, and until you die. They control how your body develops, and influence your behavior.

Peptides are proteins – they are produced within cells, and are represented by one gene. Insulin is a well-known example of a peptide hormone. Peptide hormones bind to receptors on the outside of cells, which results in complex signalling cascades (like a waterfall of biology inside the cell). These cascades eventually influence how DNA is turned into new proteins that will have different effects.

Catecholamines are kind of like amino acids, and function a little like peptides – binding to the outside of a cell. Epinephrine and dopamine are examples of catecholamines. Catecholamines can also be important in the brain.

Steroid hormones are the third major type of hormone, and perhaps the best known. Testosterone and estrogen are both examples of steroid hormones. Steroid hormones are similar in structure to cholesterol molecules, and in fact cholesterol is a kind of non-hormone steroid. Steroids differ from catecholamines and peptides in that they are able to enter cells. Instead of binding at cell surfaces, steroids can actually go straight to the DNA and have direct effects.

There are several more generally important things to recognize. First, the systems within cells that respond to hormones are very complex. Second, individuals vary genetically in how we produce hormones – your genes DO affect your life in many ways. Nevertheless, production of hormones from genes occurs in response to the environment – for example, insulin is produced in response to eating sugar. So what you do in life, what you think, and what you experience influences your hormones, which then influences your physical body. Hormonal systems are complicated and can affect each other. If you have a disorder that is characterized by low levels of a hormone, it can be difficult to figure out exactly what’s wrong – do you produce too little, does your body break it down extra fast, or is something else going on? Finally, there are other types of signals in our bodies – for example, ‘neurotransmitters’ work somewhat like hormones, but are in our brains. ‘Cytokines’ are another important signaling molecule that is especially common in immune function.

How hormones influence our outward traits, or ‘phenotypes’ is a complicated question, but hopefully this is enough of a background allowing readers without a background in biology to understand mention of hormones in future posts.