In my last blog entry, I talked about why aging made good biological sense. It doesn’t seem quite so attractive to the individual. We would like to live longer and not age.

One contributory factor is that we lead unhealthy lifestyles. We are sedentary and we eat too much salt, fat and sugar. Again, this is the result of the conditions that we lived in before we developed a civilisation. Sugar and fat are good energy sources. They were in short supply when we were plains hunter gatherers. If you found some fat or sugar, you ate it in order to improve your chances of making it to the next mealtime. They were not any better for you then than they are now but thy were not something that individuals encountered often enough for it to be a major problem. This is especially true when you consider how short the lifespan of the hunter gathers was – 30 years was a good age. 50 was ancient. A disease that might kill you at 60 was no threat at all. As for salt, it was good for protection against sun since we lose salt when we sweat. That was handy when we lived under the baking African sun but less so when we live in air-conditioned homes.

Interesting, the life expectancy of a male newborn in 1900s America was 49 years. Maybe we are closer to the hunter gatherers than we like to think. In evolutionary terms, they are the same species. Give one a shave and a sharp suit and you would pass him on a street without a second glance.

We also ingest all manner of toxins for their psychotropic effects. We are not alone in this as some other mammals will eat spoiled fruit for the alcohol.

So, as we get older, we tend to gain fat that we don’t need and fur up our arteries with fatty deposits. We are fighting back against this with gyms and drugs called Statins that reduce cholesterol but prevention is better than cure – and I speak as someone who eats too much fat and doesn’t spend enough time in the gym.

Not all species show aging. The common factor seems to be that creatures that never stop growing (such as lobsters) do not show aging and don’t generally die of old age unlike creatures that reach a final growth such as humans.

So, why do we stop growing? Well, there is a regulatory mechanism. Our DNA has tags on the end, called Telomeres. When a cell divides, so does the DNA. I am sure that you will have seen the ball and stick DNA models. In division, one side of the strand goes to each of the cells. The other half of the DNA is then reconstructed so that each cell gets a full strand of DNA – and this is a pretty complex thing with all manner of clever error checking. Now, telomeres are on the end of DNA and DNA division knocks off one of a chain of telomeres. If this can’t happen then the replication fails and the cells die. This limits the number of divisions. The length of the telomere chain is a key factor in cell aging. Old cells have short chains. Young cells have long chains.

So, those pesky telomeres deserve the blame? Can something be done? Well, no, they don’t deserve any blame and yes, something can be done. Unlimited cell division is not a good thing. We need and have mechanisms for regulating this. When it fails, you get uncontrolled replication and that is called cancer. They are cells where something has gone very wrong with the growth regulation. So, to the question of whether anything can be done about the shortening of telomere chains. Something is done – we have a repair mechanism that uses an enzyme called Telomerase which tacks new telomeres on the end of the chain. Some forms of cancer are associated with cells producing their own telomerase.

Could we use telomerase to rejuvenate cells without causing cancer? The answer is yes and no. We can fix up the telomere chains and that will help a lot. However, DNA does get damaged, both in the normal life of the cell and in cell division. Ionising radiation and free radicals all damage DNA. We have mechanisms to detect damaged DNA and even to repair it but they all rely on the mechanism of detection and repair working properly. However, we know that the DNA is damaged in cases where repair is necessary and accordingly, the cell is in an abnormal state. The detection and repair mechanisms may fail and let errors through. How dangerous these errors are will vary a great deal. Some DNA appears to be redundant and errors here probably don’t matter at all. An error to the replication control mechanisms could be fatal not just to the cell but to the organism. This is a place where we must tread very softly indeed. Let us assume that the chance of a dangerous error was 1 in 10 million. 10 million cell divisions really isn’t that long in biological terms.

There are also other factors – not all cells reproduce but they still age. That is because the cells have complex mechanisms that rely on complex chemicals song as lipids. They get damaged just as much as the DNA. When the cell is damaged, it works less well, If it is damaged enough then it dies.

So, what would we need to do at a cellular level to reduce aging? There are a few things that are possible with current technology and a few more which may be possible relatively soon:

- reduce the amount of free radicals. This is actually not that hard to do. Anti-oxidants are good at mopping up free radicals and can be absorbed by humans without trouble. Beta-carotene is just such a compound and it is found in fresh vegetables, especially carrots. So, eat up your greens everyone.

- avoid ionising radiation. Alpha particles are not that bad because they don’t penetrate far in to the body. Beta radiation such as that given out by a conventional television and monitors is a bit worse but manufacturers are increasing keeping radiation levels low. Gamma radiation will go where it wants and there is not much that you can do about it.

- Maybe we can use telomerase to extend cell life and therefore life of the individual

- Maybe we can use Nanotechnology to ungunk blocked arteries and repair damaged structures. If you are unfamiliar with the idea of nanotechnology, it is the production of tiny structures and machines with molecular parts. At present, we only have some very simple building blocks such as a ball (Buckminsterfullerene), tubes (carbon nanotubes) and a design for a toothed gear wheel. It is safe to say that it will be a while before this technology will blossom but it shows great promise.

- Recombinant DNA. It is just becoming possible to patch up DNA using a virus to replace a damaged section of human DNA with a fixed segment. Again, this technology is in it infancy but it is possible that it could be used to repair errors in DNA , bit by bit and so reduce aging.

A child born today can reasonably expect to see his or her 80th birthday.
Maybe their grandchildren will see their 200th.

Next: Something completely different.