Why do we grow old?
Ageing happens to each and every one of us, but what is really going on and why does it happen? Georgia Mills spoke to Judy Campisi, a professor at the Buck Institute for Research on Aging.
Judy - Of course, we don’t have a clear definition of ageing except to say that it’s a process by which multiple systems within the body are declining in function, and it can be driven by any number of external and internal forces that cause this decline.
Georgia - How does aging affect the different parts of the body?
Judy - It’s interesting that ageing affects different tissues in different ways, but also different people and different animals of different genetic background don’t all age in exactly the same way. So there are some declines in tissue function that we recognise as aging: wrinkles in the skin, eventually loss of muscle mass, and loss of cognitive ability, but not all people and not all genetic backgrounds have the same trajectory for each tissue.
Georgia - What is going on then inside us on a cellular basis to cause this gradual decline?
Judy - The short answer is: we don’t know. The longer answer is: we believe that there probably are a few fundamental processes that we define as a so-called ‘basic ageing process’ that can drive the decline in multiple tissues. One of them is a cellular process - this is what we study - it’s called ‘cellular senescence,’ and what it is a stress response to which cells respond by doing three basic things.
The first thing is they stop dividing. This turns out to be a very important mechanism for preventing cancer. You don’t want stressed or damaged cells to proliferate.
The second thing that the cells do is they begin to secrete molecules that can have rather profound effects on neighbouring cells; that is important for alerting the tissue to the possibility that there is a problem - possible damage or possible injury.
The other thing is they initiate a process called ‘inflammation.’ This is a process in which small molecules attract the immune system, and it turns out that initial attraction is also very important for wound healing and tissue repair, so that’s good - right?
The problem is the third part of what happens to senescent cells. They don’t die very readily, they don’t go away and so now the system becomes chronic. So with age, we slowly accumulate senescent cells and we experience a condition that is been termed ‘inflammaging,’ and what it is is low level chronic inflammation. And virtually every age related disease has as either it’s cause or as a major contributor this process of chronic inflammation.
So we believe now that the process of senescence, which evolved for the good purpose of preventing cancer, and promoting tissue repair can be become what we term ‘maladaptive,’ that is it not longer serves us for good purposes as we age and then begin to drive those aging pathologies.
Georgia - There are a number of other ideas about what could be aging in the body and we’ll look at some of them later in the programme. But what drives the fact that one of us might age faster than another? Some 70 year olds run marathons, others can barely make it up the stairs.
Judith - In our environment everyone knows what they need to do to postpone aging, so don’t smoke, eat a balanced diet, eat your veggies, exercise. Exercise is actually one of the best things you can do to preserve tissue health, and the other thing is choose your grandparents wisely because there is a genetic component. As you know, living to be 100 tends to run in families