Aging: A Biological Perspective

A variety of techniques extend the lives of model organisms, and similar approaches might help human beings stay healthy longer

Robert Arking

Science and Society

Although the genetic manipulations explored in the lab do not make likely therapeutic tools so far, the results encouraged many scientists to explore pharmaceutical attacks on aging. A variety of such experiments recorded significant increases in an animal's health span or a significant extension of an animal's functional abilities. For example, Semour Benzer and his team at the California Institute of Technology fed fruit flies a drug called 4-phenylbutyrate, which inhibits enzymes used by the cell to repress its stress-resistance genes, and it delayed the onset of senescence. Nonetheless, different strains of flies needed different drug doses in order to yield the same result. This implies the existence of genetically based individual differences in response to drug-based interventions to increase longevity.

Other types of pharmaceutical interventions are also being pursued. For instance, Simon Melov of the Buck Institute for Age Research and his colleagues gave worms drugs which that functioned as synthetic superoxide dismutase/catalase enzymes, or mimetics, and scavenge excess ROS within cells. The worms lived 44 percent longer, on average. So pharmaceutical interventions against aging seem feasible.

Nonetheless, people should mistrust the nonscientific claims and blarney put out by the present antiaging industry. For example, at least 250,000 Web sites sell human growth hormone, and many tout it as a cure for aging. It is not. In the original study behind antiaging claims for growth hormone, a dozen men showed positive effects at first, but then suffered deleterious side effects that cancelled the study. Now, scientific data suggest that taking growth hormone advances aging—quite the opposite from what the ads purport.

The future of aging research faces three significant questions. First, can science increase the health span of a laboratory primate? Second, will similar interventions extend human life in a safe way? Third, will public debate on this matter encourage or inhibit using this knowledge? Given the success of pharmaceuticals extending the health span of invertebrates, a similar outcome seems biologically reasonable in mammals, but proving that will take some time—definitely years, although no one knows how many. In monkeys, perhaps another decade will provide good data on whether interventions can slow the rate of aging, but it could take longer for a complete assessment of lifetime effects. The pace of discovery in this field, however, increases rapidly, so these time lines might be too conservative.

If someone finds a pharmaceutical that mimics the effects of caloric restriction or of IGF-1 reduction or of releasing the repression of stress-resistance genes, it might be possible to add about 25 years to a person's lifespan. Humans might then be healthy adults from the age of 20 to 80 years, instead of the current 20 to 55 or so. That sounds great to most people, but some critics see only increased despair and financial costs. This criticism, however, overlooks the fact that the senescent phase will stay the same in absolute terms, and the associated costs will not change. In fact, an increased health span will not cost more. Instead, it would give us longer, healthier and more productive lives.

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