In <941220234350.17bb0 at wnmeds.ac.nz> BEVANMCW at wnmeds.ac.nz (Bevan McWilliam Tel No 64 4 385 9755) writes:
>Rattan,
>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.
Quite so. AGEs are a manifestation of a biochemical process with long term
degenerative effects. To my mind, glycosyslation qualifies as a genuine aging
process. Several interventions (most notably calorie restriction) reduce its
effects and also extend lifespan.
Further study of glycosylation in biological systems, along with other
more recognised aging processes (eg free radical damage) can only help our
understanding of aging.
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(I_lurk,_therefore_I_am!_\ ,,, Steve Chambers
(o o) steve at chambers.ak.planet.co.nz
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