Ecuadorean Villagers May Hold Secret to Longevity

People living in remote villages in Ecuador have a mutation that some biologists say may throw light on human longevity and ways to increase it.


The villagers are very small, generally less than three and a half feet tall, and have a rare condition known as Laron syndrome or Laron-type dwarfism. They are probably the descendants of conversos, Sephardic Jews from Spain and Portugal who were forced to convert to Christianity in the 1490s but were nonetheless persecuted in the Inquisition. They are also almost completely free of two age-related diseases, cancer anddiabetes.
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The Laron patients’ mutation means that their growth hormone receptor lacks the last eight units of its exterior region, so it cannot react to growth hormone. In normal children, growth hormone makes the cells of the liver churn out another hormone, called insulinlike growth factor, or IGF-1, and this hormone makes the children grow. If the Laron patients are given doses of IGF-1 before puberty, they can grow to fairly normal height.

This is where the physiology of the Laron patients links up with the longevity studies that researchers have been pursuing with laboratory animals. IGF-1 is part of an ancient signaling pathway that exists in the laboratory roundworm as well as in people. The gene that makes the receptor for IGF-1 in the roundworm is called DAF-2. And worms in which this gene is knocked out live twice as long as normal.

The Laron patients have the equivalent defect — their cells make very little IGF-1, so very little IGF-1 signaling takes place, just as in the DAF-2-ablated worms. So the Laron patients might be expected to live much longer.

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Dr. Longo said that some level of IGF-1 was necessary to protect against heart disease, but that lowering the level might be beneficial. A drug that does this is already on the market for treatment of acromegaly, a thickening of the bones caused by excessive growth hormone. “Our underlying hypothesis is that this drug would prolong life span,” Dr. Longo said. He said he was not taking the drug, called pegvisomant or Somavert, which is very hard to obtain.

A strain of mice bred by John Kopchick of Ohio University has a defect in the growth hormone receptor gene, just as do the Laron patients, and lives 40 percent longer than usual.