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The Biological basis of the aging process
El proc茅s biol貌gic b脿sic subjacent de l'envelliment va 茅sser
avan莽at per la teoria de l'envelliment basada en els radicals lliures
l'any 1954: la reacci贸 dels radicals lliures actius, produ茂ts fisiol貌gicament
en l'organisme, amb els constituents cel路lulars
inicia els canvis associats a l'envelliment. La implicaci贸 dels radicals
lliures en l'envelliment est脿 relacionada amb el seu paper
clau en l'origen i l'evoluci贸 de la vida. La informaci贸 disponible
avui en dia ens mostra que la composici贸 espec铆fica de les macromol猫cules
cel路lulars (prote茂nes, 脿cids nucleics, l铆pids i carbohidrats)
en les esp猫cies animals longeves tenen intr铆nsicament
una resist猫ncia elevada a la modificaci贸 oxidativa, la qual cosa
probablement contribueix a la longevitat superior d'aquestes
esp猫cies. Les esp猫cies longeves tamb茅 mostren unes taxes redu茂des
de producci贸 de radicals lliures i de lesi贸 oxidativa. D'altra
banda, la restricci贸 diet脿ria disminueix la producci贸 de radicals
lliures i la lesi贸 molecular oxidativa. Aquests canvis estan
directament associats a la reducci贸 de la ingesta de prote茂nes
dels animals sotmesos a restricci贸, que alhora sembla que s贸n
deguts espec铆ficament a la reducci贸 de la ingesta de metionina.
En aquesta revisi贸 s'emfatitza que una taxa baixa de generaci贸
de lesi贸 end貌gena i una resist猫ncia intr铆nsecament elevada a la
modificaci贸 de les macromol猫cules cel路lulars s贸n trets clau de la
longevitat de les esp猫cies animals.The basic chemical process underlying aging was first put forward
by the free radical theory of aging in 1956; the reaction of
active free radicals (normally produced within an organism itself)
with cellular constituents initiates the changes associated
with aging. The involvement of free radicals in aging is related
to their key role in the origin and evolution of life. The specific
composition of tissue macromolecules (proteins, nucleic acids,
lipids and carbohydrates) in long-lived animal species gives
them an intrinsically high resistance to modification that probably
contributes to the superior longevity of these species.
Long-lived species also show low rates of reactive oxygen
species (ROS) generation and oxidative damage to their mitochondria.
Dietary restriction further decreases mitochondrial
ROS production and oxidative molecular damage due to the
decreased intake of dietary proteins. These effects of protein
restriction seem to be specifically due to the lowered methionine
intake of protein and dietary restricted animals. Both a low
rate of generation of endogenous damage and an intrinsically
high resistance to the modification of tissue macromolecules
are key traits of animal longevity