Death By A Thousand Cuts - The Seven Deadly Sins of Ageing
We have moved beyond mysticism in our understanding of the human body.
We now view living organisms as biological machines.
''I would like you to consider that these functions [...] follow every bit as naturally as the movements of a clock follow from the arrangement of its counterweights and wheels.''
- René Descartes on higher functions such as imagination, Treatise of Man
Much like a machine, a single event is not required to destroy us.
Most machines break down from the slow accumulation of unrepaired damage over time.
This gives us hope that our understanding of the ageing process is close to completion.
No new forms of age-related damage have been discovered since the 1980s
Gerontologist Dr Aubrey de Grey had nicknamed these ''the seven deadly sins'' of ageing.
Age related damage falls into 7 categories.
However, certain molecules cannot be fully broken down.
1. Cellular Junk
Organelles called lysosomes break down waste molecules within the cell.
1. Cellular Junk
This junk accumulates over time and disrupts the cellular machinery, contributing to diseases like Parkinson's.
One example of this is the development of amyloid plaques seen in Alzheimer's disease.
2. Extracellular Junk
Just as junk accumulates inside cells, it also builds up in spaces in between cells.
Senescent cells no longer divide, and the tissues they are part of weaken as dying cells aren't replaced fast enough.
3. Too Few Healthy Cells
After dividing a certain number of times, cells enter a state called senescence.
They can also release harmful signalling molecules that contribute to diseases like cancer.
4. Too Many Senescent Cells
Senescent cells are 'dead weight' to the tissue that they are part of, which makes it harder for surrounding cells to do their jobs.
These mutations can cause cellular dysfunction, senescence or, at worst, cancer.
5. Nuclear DNA Damage
Mutations in our DNA accumulate throughout life due to random error and damage from a variety of sources.
They were separate organisms millions of years ago, and still have their own DNA.
6. Mitochondrial DNA Damage
Mitochondria are are the organelles responsible for producing ATP, the energy source of the cell.
These dysfunctional mitochondria also produce and leak more waste products that cause further damage.
6. Mitochondrial DNA Damage
Mutations in this DNA make mitochondria 'leaky', which reduces their efficiency in producing energy.
These proteins hold cells together and are responsible for the elasticity of certain tissues.
7. Protein Crosslinks
The space between cells is occupied by a network of long protein chains called the extracellular matrix.
This stiffening causes wrinkle formation, as well as contributing to high blood pressure and far-sightedness.
7. Protein Crosslinks
Over time, sugar molecules bind and link neighbouring proteins together, causing them to stiffen.
In a future post, we will explore how science is aiming to achieve this goal.
If these 7 types of age-related damage can be addressed, we should be able to greatly extend human lifespan.