Insulin, and Insulin Like...

Allow me to start this post with some definitions. This will help later on, as you might need to refer back to these to understand what's going on. I know I will.

Insulin: A hormone, produced by the pancreas, that controls levels of glucose in the blood. Insulin controls metabolism of carbohydrates and fats, and triggers the uptake of glucose from the blood to be stored as glycogen in the liver.

Insulin-like growth factor 1: A hormone, produced by the liver, as a result of the effects of growth hormone. Has a molecular structure very similar to insulin, and can therefore bind to the same receptors. IGF-1 stimulates growth in the cell, and triggers growth in many different tissue types (liver, bone, muscle nerves). Can bind to a IGF-1 specific receptor as well as the insulin receptor.

Right, does that clear that up? No? Good.

IGF-1 is a growth hormone. Increased levels of human growth hormone, one of the most prominent growth hormones within the body, increases the produce of IGF-1 from the liver. During our lives, the levels of IGF-1 change. The highest point is during puberty, when a growth spurt in our body takes place, and the lowest levels are recorded in our bodies during infancy and old age. It's clear to see that IGF-1 has an important role in causing the ageing of our bodies.

So how does insulin-like growth factor actually cause the process we see in ageing? Well... it's not exactly very clear. It's currently undecided whether or not the presence or the absence of IGF-1 causes the degenerative ageing process.

WORMS: Very Important

Studies conducted with the model organism Caenorhabditis elegans (or just C. elegans to his friends) show promising results. When the gene responsible for the production of the IGF receptor is mutated, and no longer display the corrected receptor, the lifespan of the worm is doubled. This receptor is present in all life between worms and humans, indicating that the effects of IGF cause ageing in a wide range of life.

However, it's not as clear cut as that. Reduced levels of IGF-1 in the body have been shown to have severe negative effects on the body. Laron's Syndrome, also known as Laron's dwarfism, is the result of a insensitivity to IGF-1 and causes short stature, seizures, hypoglycemia and potentially other undesirable symptoms. Whilst some individuals with Laron's do have a resistance to diabetes and cancer as well as ageing, the other symptoms seem to cancel out the benefits. In studies reviewing the average life span of individuals, it was actually found that those with the lowest levels of IGF had the shortest life spans.

It might seem then that more investigation is needed into quite how IGF-1 works, before we consider pursuing it as an anti-ageing cure. There's no use in having an immortal drug that causes you to suffer from a neurodegenerative disease. That feels like cutting your nose off to spite your face.

And then you have to live forever without a nose.

Why Do We Age?

Our medicines prevent many diseases from killing us. Advances in medical science have allowed us to fix damaged organs, like hearts, or in some cases replace them entirely. The further understanding of nutrition provides us with the knowledge we need to stay healthy throughout our lives. But despite all this, there is still no way to defy death permanently. We can prolong life, almost tripling its natural length, but eventually, the human body can no longer support itself.

So why does this happen? Whilst the precise cause of ageing is as of yet undetermined, there are many theories. One theory indicates that the mitochondria, which are the energy production units in our cells, cause damage to the cells over time via the release of harmful by-products. Mitochondria produce ATP (the energy currency of the cell) through several cycles that split glucose down into various compounds, releasing energy in the form of ATP along the way. This process can release electrons which form reactive oxygen species. You may be more familiar with these under the guise of free radicals. These molecules cause damage to several different components of the cell. Over time, this cell damage builds up, and we see the effects of this in the form of ageing.

Another theory is more centred around DNA as the cause of ageing. As you may know, DNA (or Deoxyribonucleic Acid to be precise) is found in every cell in our body and contains the instructions for each one of the cells. The DNA in our cells produce protein, which activate different functions around the body. When a cell divides, a copy of the DNA is made, after which the cell divides in two. The process of replication is balanced by the rate of cell death. In the first part of our lives, as we grow, the rate of cell division is higher than that of the rate of cell death. However, at about 25 years of age, the rate of cell division begins to decline. It is at this point where our bodies start "ageing" as we know it. This decline in division is the result of the degradation of telomeres. These little caps of DNA are fascinating, and I'll be taking a closer look at them in a future posts.

One final theory around ageing implicates insulin as a contributing factor. You probably already know of insulin through its role in diabetes, but studies have shown that it could also cause ageing when combined with a chemical referred to as insulin-like growth factor 1, or IGF-1. IGF-1 can bind to both specific receptors as well as insulin receptors. Many tests have been conducted on a variety of different species that indicate removal of insulin receptors can lead to incredible prolonging in life. An experiment showed that the lifespan of the roundworm species Caenorhabditis elegans could be doubled by mutating the gene that coded for the insulin-like receptor. Since the insulin/IGF-1 pathway is the same within both worms and mammals, this indicates a possible anti-ageing therapy that could extend life permanently.


It's difficult to say exactly if any of these are the one true cause of ageing. It could be that it is a combination of all the different theories, or it could be that one theory in turn stimulates the others. Whatever the case, each theory offers exciting avenues for potential therapies in anti-ageing.


An excellent review on insulin/IGF-1 ageing theories can be found here; http://www.fly-bay.net/journals/cc/BartkeCC7-21.pdf