Sunday, 12 February 2012

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.

1 comment:

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