What are the 'seven deadly causes of human aging'?
Since aging is the accumulation of damage, the ongoing accumulation of side effects, of metabolism, we can go a bit further and say, well, what are those side effects? And we can classify them. And I've discovered that it's possible to classify them into just seven major categories in a rather useful way. Because within each of these categories, the sort of thing that we need to do to actually repair the damage, to actually reverse the problem, is actually more or less the same thing within all of the examples within the category. So what are the categories? Well, the first one is loss of cells. When a cell dies and it is not naturally replaced by the division of another cell. In most of our tissues, it is naturally replaced by cell division, but it some tissues it isn't. So that's one type of problem. As cells progressively die, then the organ may get less functional. Parkinson's disease, for example, is caused by the loss of a particular type of cell in a particular area of the brain. The second one is really the opposite of the first one. It is the accumulation of cells. I'm not talking about cancer here. I'll come to cancer in a moment. I'm talking about cells that are not necessarily dividing, but they're also not dying when they should, and they're getting in the way, and for various reasons they may be toxic. So we need to get rid of those cells. Number three is mutations in our chromosomes. And of course, this is cancer I'm talking about. Cancer is definitely a consequence of that. And there is good reason to believe that cancer is actually the only consequence of mutations that we really need to worry about. But cancer is a big problem, so we need to fix that. Number four is also mutations, but this time not in our chromosomes. Mutations in a special part of the cell called the mitochondria, which has its own DNA. It's the only part of the cell that has its own DNA apart from the nucleus. And mitochondrial mutations accumulate during aging, just like mutations in our chromosomes. And we are actually still at this point not entirely clear what the bad consequences of mitochondrial mutations are, but there are lots of circumstantial reasons to believe that there are such consequences. So we'd like to fix that. And in this case actually, and also in the case of chromosomal mutations, we are not really talking about repairing the mutations, but rather about making them harmless, obviating them by essentially disrupting the mechanisms whereby they can be harmful. OK, so that's four. Number five is the accumulation of garbage. The accumulation of indigestible molecules of one sort or another inside the cell. And this is a really important one for a number of the most important age-related diseases, such as Alzheimer's and atherosclerosis, and macular degeneration. Essentially, stuff accumulates in the cell because we don't have the enzymes to get rid of it, and it just gets in the way eventually, just like not taking out your garbage for a month. Number six is very similar to number five, but here we're talking about garbage outside the cell, in the spaces between cells. And again, that can cause a bunch of problems. It can disrupt the communication between cells. Things like that. So we need to get rid of that garbage. And finally, number seven is again outside the cell in extracellular structures, but this time it's not garbage. It's not stuff that we just want to eliminate. It's loss of elasticity. Stiffening of tissues that are made of proteins and that need to be elastic in order to do their job. Like, for example, the walls of our major arteries or the lens of our eyes. These things get stiffer with age, and we know why that is. It's because of additional, spontaneous chemical bonds forming between the proteins that are making up these tissues, and we need to get rid of those spontaneous chemical bonds. So those are the seven things.
