X-Message-Number: 27950
Date: Thu, 18 May 2006 11:22:47 -0700 (PDT)
From: Doug Skrecky <>
Subject: telomeres and aging

[The debate regarding the importance of telomeres in human aging goes
on. Some tissues exhibit no decrease in telomere length with age, while
others do. Imatinib mesylate reverses the greying of hair, and increases
telomere length. However this may be merely a side effect of imatinib
killing senescent stem cells, and freeing up room in stem cell niches for
normal melanocyte stem cells to proliferate in. In any case lifespan of
at least least one telomere shortened progeria: dyskeratosis congenita
need not be associated with a reduced lifespan. In addition one study
found no corelation between greying of hair in normal humans, and
mortality. Overall telomeres look to be at best a secondary player in the
human aging process. For the main cause(s) of age associated increases in
human mortality, one will probably have to look elsewhere. One current
focus of study are stem cell niches.]

 J Gerontol A Biol Sci Med Sci. 2005 Jan;60(1):10-20.
Shared phenotypes among segmental progeroid syndromes suggest underlying
pathways of aging.
  Segmental progeroid syndromes are those whose phenotypes resemble
accelerated aging. Here we analyze those phenotypes and hypothesize that
short telomeres produce the same group of symptoms in a variety of
otherwise unrelated progeroid syndromes. Specific findings are the
following: (a) short telomeres in some progeroid syndromes cause an
alopecia/osteoporosis/fingernail-atrophy group of symptoms; (b) fingernail
atrophy in progeroid syndromes resembles the natural slowing of nail
growth that occurs in normal aging and nail growth velocity, and may be a
marker of replicative aging in keratinocyte stem cells; (c) alopecia and
reduced hair diameter parallel the nail results; (d) osteoporosis in
Dyskeratosis Congenita resembles age-related osteoporosis, but the same
is not true of other progerias; and (e) gray hair is associated with
short telomeres, but may also involve reactive oxygen species. On the
basis of these results, we make several predictions and discuss how the
segmental quality of progeroid syndromes may provide insight into
normative aging.

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