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El
concepto
darwiniano
de
la
allostasis…

ABSTRACT

The
Darwinian
concept
of
allostasis.
Epigenetic
programming

At
the
end
of
last
Century
the
concept
of
allostasis
was
proposed
as
the
group
of

responses
from
live
beings,
regulated
by
the
brain,
leading
to
maintain
the

organism
balance
and,
therefore,
to
survival.

But
this
concept
has
clear
Darwinian

significance.

Questions
established
in
the
XX
Century.
The
HPA
(hypothalamus-­-pituitary-­-
adrenal
gland)
axis
is
the
most
important
among
all
regulatory
systems
triggered

by
allostasis,
and
it
is
programmed
during
the
gestational
period
in
mammals.

Under
a
stressful
situation
the
mother
HPA
axis
operates
secreting
high
amounts

of
glucocorticoids
(GC)
that
get
into
the
foetus
affecting
to
the
normal
HPA

programming;
this
abnormal
development
is
irreversible
in
adulthood
and
will

also
reduce
birth
weight.
Besides,
it
is
a
risk
factor
for
possible
adult
pathologies

such
as
diabetes
mellitus
type
2,
cardiovascular
disease
or
chronic
hypertension.

The
reason
is
the
decrease
of
glucocorticoid
receptors
(GR)
in
hippocampus,
since

they
are
crucial
for
the
negative
feedback
of
HPA
axis.
However,
the
mechanism

by
which
GC
reduce
GR
expression
in
hippocampus
was
unknown
in
the
XX

Century.

Questions
established
in
the
XXI
Century.
A
number
of
research
articles

published
in
the
XXI
Century
reporting
information
about
the
epigenetic

mechanism
involved
in
the
hippocampal
reduction
of
GR
are
selected
and

presented.
The
main
epigenetic
mechanisms
known
up
to
date
are
also

mentioned.

Finally,
the
great
therapeutic
possibilities
of
the
epigenetic
mechanisms
in
the

near
future
are
enunciated
as
well
as
the
possible
explanation
of
evolutional

processes.

Keywords:
Allostasis;
gestational
period;
HPA
axis;
epigenetic
programming;

Darwin.

1.
INTRODUCCIÓN

El
concepto
de
allostasis,
establecido
a
finales
del
siglo
XX,
recoge
el

conjunto
de
sistemas
que
se
activan
en
los
organismos
vivos,
regidos
por
el

cerebro,
para
conservar
el
equilibrio
interno
y,
por
tanto,
la
supervivencia.
Todo

ello
cuando
factores
externos
al
organismo,
o
internos
a
él,
alteran
su
homeostasis

provocando
un
estado
de
emergencia.
Los
factores
internos
que
producen
el

desequilibrio
pueden
ser
un
aumento
de
pH,
de
temperatura,
una
infección,
etc.,
y

los
externos
pueden
ser
una
alteración
climática,
falta
de
comida,
o
un
depredador

que
nos
ataca.
Y
todas
las
respuestas
que
los
organismos
habilitan,
con
fines
de

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