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Every cell in our body will age. With
wrinkles and age spots, the skin is the first human organ to
show signs of ageing. It would be wrong to suggest that we have
found a way to beat ageing. The truth is we have not. We do know
enough about the ageing process, however, to formulate strategies
that target processes implicated in the ageing process.
Two popular theories on ageing can form
the basis of an age defying strategy:
- The free radical or anti-oxidant theory
- The hormonal theory
 Photo courtesy
of Michael Bonkowski |
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Animal models such as Drosphila
(fruitfly), Caenorrhabditis elegans (roundworm) and mice are
providing important insights into the biology of ageing. |
Theories on ageing
- Free radical theory
Free radicals (reactive oxygen species or ROS) are unstable molecules
with an extra electron that go around stealing electrons from
wherever they can, causing oxidative damage to cell membranes,
DNA (deoxyribonucliec acid) and other proteins. Our body's metabolic
processes, tobacco smoke, pollution and ultraviolet light generates
free radicals.
- Advanced glysolated end-products
(AGEs)
AGEs are formed when glucose and other reducing sugars form cross-linkages
with amino acids (proteins). This process is called glycosylation
or glycation and once formed, AGEs cannot be broken down and
accumulate in tissues, impairing function. AGEs may act together
with oxidative damage caused by free radicals in a process known
as glyco-oxidation.
- Telomere theory
Telomeres are repeat sequences of DNA that cap the end of chromosomes.
When a cells divides, it replicates all its chromosomes except
for some of the DNA sequences for the telomere. The telomere
therefore gets shorter and shorter with each cell division until
the cell stops dividing altogether. Telomeres therefore act as
a molecular clock that signals the end of cell division and the
start of ageing.
- Hormone theory
Hormone levels fall with age and this is particularly the case
HGH (human growth hormone), testosterone, DHEA and estrogen.
The hormone theory argues that ageing is a consequence of declining
levels of hormones. It forms the basis for the use of hormone
replacement therapy to delay the ageing process.
- Accumulation of chemical
garbage theory
According to this theory, cells stop functioning because they
become cluttered up with toxic by-products of cellular metabolism.
Interestingly, lipofuscin, the yellowish-brown garbage that accumulates
in lysosomes (our cell's trash cans) has also been found in age
spots (senile lentigines or liver spots) that are often the first
sign of skin ageing.
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