Markers of Aging

Bevan McWilliam Tel No 64 4 385 9755 BEVANMCW at
Tue Dec 20 05:45:10 EST 1994


You claim that there are *no* biological markers of aging that can be used 
as a general measure of age. Surely it is far more important to find the 
substances that accumulate as a function of time and *cause* the symptoms 
of aging, rather than simply reflect an individuals age. Those products 
that you have listed may all be possible candidates for these and if so, 
are much more important than a mere age marker. 

There are many such substances.  You have listed some. A group of such are 
those formed by the reaction of a reducing sugar with any protein. The 
resultant "Amadori" product may then undergo a series of rearrangements and 
dehydration (and possibly oxidative) reactions and form a heterogenous 
group of compounds, termed Advanced Glycation End products (AGE products). 
These products have been shown to accumulate in vivo with normal aging and 
at an accelerated rate with diabetes (I can't remember the references of 
the top of my head, but if you're interested, I could find and email them 
to you). These AGE products have been linked to the pathology of the 
diabetic condition (renal failure, atherosclerosis, retinopathy). These 
same disease states reflect many found in the elderly, and in many ways 
those patients with diabetes seem to be suffering a form of "advanced 
aging". If these AGE products are responsible for many of the symptoms of 
aging (this hasn't been shown yet, only the correlation between AGE product 
accumulation and pathology), then AGE products would be a perfect measure 
of "biological" aging.

It is true that different individuals will have different levels of sugar 
present in the circulation as evidenced by the diabetic patients, and so 
AGE products will accumulate at different rates. The age of an individual 
may not be accurately reflected in the amount of AGE products formed.

But it is the aging *symptoms* and the causes of these symptoms that are 
important. An accurate estimation of the amount of time that an individual 
has been around from a biological marker may be irrelevant.

Tell me what you (and any other members of the list) think. 

Bevan McWilliam,
Wellington School of Medicine
New Zealand.

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