IGF gene may play major role in longevity

Have geneticists uncovered one of the master genes for aging? Dr Linda Partridge, a researcher at University College, London, says increasing evidence points to the gene for insulin-like growth factor-1 (IGF-1) playing a major role in longevity.

Partridge, presenting at the XIX International Congress of Genetics, says researchers have long shied away from studying aging because it is a genetically complex phenomenon, affecting many different tissues in ways that vary from individual to individual.

She says it seemed unlikely that natural selection would have favoured a gene that caused tissue damage, pathology and eventual death, and conserved it across the animal kingdom.

The problem, says Partridge, is that aging is an unconditionally deleterious trait, so it's difficult to see how natural selection could have favoured a mechanism that evolved specifically to cause tissue damage, pathology, and eventually, death -- a mechanism that would be shared by all species in the animal kingdom.

But Partridge says evidence is now emerging that the aging mechanism is strongly conserved across animal species as diverse as nematode worms, fruit flies, birds, bats and mammals -- and that IGF-1 is one of the key players.

Mutation studies also implicated the insulin and growth hormone genes -- the latter actually influences the activity of IGF-1, further implicating IGF-1 as the master aging gene.

Partridge says IGF-1 somehow mediates a tradeoff between fertility and longevity.

The emerging story is that animals that delay reproduction, and have fewer offspring, tend to live longer -- humans fit this pattern, as do some species of birds and bats, which defy the general rule that small animals tend to live shorter lives.

These species appear match their reproductive rate to the food supply -- they get by with fewer calories, live lean, have fewer offspring, and live longer.

IFGF-1 may thus be a potential target for anti-aging therapies, or dietary regimes that would prolong the human life span.