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Researchers believe that your longevity, that is, Researchers believe that your longevity, that is, the duration of your life, may rely on your having longevity assurance genes. Genes are the bits of DNA that determine an organism’s physical characteristics and drive a whole range of physiological processes. Longevity assurance genes are variations (called alleles) of certain genes that may allow you to live longer (and perhaps more healthily) than other people who inherit other versions of that gene.
WHY ARE LONGEVITY ASSURANCE GENES IMPORTANT?
If scientists could identify longevity genes in humans, in theory, they might also be able to develop ways to manipulate those genes to enable people to live much longer than they do today. Slowing the
aging process would also likely delay the appearance of agerelated diseases such as cancer, diabetes, and Alzheimer’s disease and therefore make people
healthier as well.
Most longevity assurance genes that have already been identified in lower organisms such as yeast, worms, and fruit flies act to increase lifespan and grant resistance to harmful environmental stress. For example, scientists have identified single gene variantions in roundworms that can extend lifespans by 40 to 100 percent. These genes also allow worms to withstand often fatal temperature extremes, excessive levels of toxic free radicals (cellular waste products), or damage due to ultraviolet light.
Some of the longevity assurance genes in lower organisms have similar counterparts among human or mammalian genes, which scientists are now studying. While researchers have not yet found genes that predispose us to greater longevity, some have identified single human gene variants that seem to have a protective effect against certain age-related diseases and are associated with long life. For example, inheriting one version of a gene for a particular protein called apolipoprotein E (Apo E) may decrease a
person’s risk of developing heart
disease and Alzheimer’s disease.
Identification of genes that prevent or delay crippling diseases at old age may help us find novel strategies for assuring a healthier, longer life, and enhancing the quality of life in the elderly.
Researchers believe that your longevity may rely on your having longevity assurance genes.
Infoaging Guide to Longevity | 3
HOW MUCH OF LONGEVITY IS GENETICALLY DETERMINED?
By some estimates, we humans have about 25,000 genes. But only a small fraction of those affect the length of our lives. It is hard to imagine that so few genes can be responsible for such a complex phenomenon as longevity. In looking at personality, psychologists ask how much is nature, that is, inherited, and how much is nurture, which means resulting from external influences. Similar questions exist about the heritability of lifespan. In other words, just how much of longevity is
genetically determined and how much it is mediated by external influences, such as smoking, diet, lifestyle, stress, and occupational exposures?
Studies do show that long-lived parents have long-lived children. Studies of adoptees confirm that their expected lifespans correlate more strongly to those of their birth parents than those of their adoptive parents. One study of twins reared apart suggests about a 30 percent role for heredity in lifespan, while another says the influence is even smaller.
Some scientists estimate the maximal lifespan of a human to be approximately 120 years, a full 50 years longer than the Biblical three score and ten (Psalms 90:10). The people who have actually achieved that maximum can be counted on one hand—or one finger. Mme. Jeanne Calment of France was 122 years old at her death in 1997. But although few challengers to her record exist, we are seeing more and more members of our society reach 100. In fact, in the United States today, there are more than 60,000 centenarians, and their ranks are projected to grow to nearly 1 million
by 2050. Much of this growth will be due to the convergence of the large aging Boomer demographic and improvements in health and medicine.
Most people who get to 100 do so by avoidance. They shun tobacco and excess alcohol, the sun and pollutants, sloth, bad diets, anger, and isolation. Still, many of us may know at least one smoking, drinking, sunburnt, lazy,
cantankerous recluse who has lived to 100—and wondered how he or she did it.
More and more, scientists are finding that part of the explanation lies in our genes. The siblings of centenarians have a four times greater probability of surviving to age 90 than do siblings of people who have an average life expectancy. When it comes to living 100 years, the probability is 17 times greater in male siblings of centenarians and eight times greater in female siblings of centenarians than the average lifespan of their birth cohort.
On the flip side, we humans carry a number of genes that are deleterious to our health and longevity. These genes increase our risk for heart disease and cancer, as well as age-related but harmless symptoms such as gray hair and wrinkles. Though we cannot change our genetic pedigrees, perhaps if we know what unhelpful genes we carry, we can take steps, such as ridding ourselves of bad health habits and adopting good ones, that can overcome the disadvantages our genes confer and live as long as those people with good genes.
WHAT WE HAVE LEARNED FROM LOWER ORGANISMS
Our understanding of genes and aging has exploded in recent years, due in large part to groundbreaking work done in simpler
organisms. By studying the effect of genetic modification on lifespan in laboratory organisms, researchers now provide fundamental insights into basic mechanisms of aging.
These include:
• Yeast
• Worms
• Fruit Flies
• Mice
Yeast Researchers have identified more than 100 genes in baker’s yeast (Saccharomyces cerevisiae) that are associated with increased longevity, and even more provocatively, have found human versions of many of these genes. Further study is ongoing.
As with all other organisms tested, researchers have reported that restricting the amount of calories available to yeast, either through reducing the sugar or amino acid content of the culture medium, can increase lifespan. Caloric
restriction does not extend lifespan in yeast strains lacking one of the longevity assurance genes, SIR2. This result has been shown in multiple organisms from yeast to flies, and even in mice. The SIR2 protein is the founding member of the sirtuin family involved in
genomic stability, metabolism, stress resistance, and aging. Researchers have found that
overexpression of Sir2 extends lifespan, ... |