The Science Behind Longevity
By Nicole Wang
Jeanne Calment was born in 1875, a time period in which the average life expectancy for females ranged from 44.6- 47.2 years old. Clament defied against the odds and instead lived for a total of 122 years and 164 days, adopting the title as the longest living person in the world. In comparison to Calment, the current average life expectancy for Americans is about 78.6 years (81.1 years for women vs. 76.1 years for men). While death is inevitable, many individuals continue to turn towards anti-aging products, such as supplements and hormone replacements, to maintain their youthful nature and to live longer. While the environment plays a role in life expectancy, genetics factors can also enhance one’s longevity. Such has been demonstrated by various studies.
Over the last few decades, Caenorhabditis elegans has been the subject of many published studies due to its fairly short lifespan of 2-3 weeks, simple physiology, and easily manipulated genes. Perhaps the most famous study involving longevity occurred in 1993 when Cynthia Kenyon demonstrated that mutations in the daf-2 gene can cause fertile, active, adult C. elegans to live more than twice as long as wild type. This finding is significant because it disproved the idea that aging, age-related illnesses, and death were consequences of multiple cellular and physiological processes and thus is under the regulation of a wide and diverse set of genes. After a group of scientist solved daf-2’s DNA sequence in 1997, they noticed that the protein encoded by daf-2 is similar to the human receptor protein that responds to the hormone insulin. Hence, the question becomes: How does daf-2 mutations lead to longevity? Normally, daf-2 phosphorylates daf-16 to dampen daf-16’s effect. However, when daf-2 is mutated, daf-16 is not phosphorylated. This activation of daf-16 (caused by the absence of a phosphate group) is a necessary step toward life span extension.
While there are implications that insulin-like signalling plays a role in aging and lifespan, there are still many gaps within our understanding of the mechanism of longevity. Furthermore, most research regarding the insulin-like pathways are focused on C. elegans rather than humans.