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WHEN RESEARCH subjects pedaled their bikes for three months using only one leg — 45 minutes, four times a week — the most surprising effect on the pedaling leg was altered DNA.
Well, not exactly DNA, but the epigenome, described as packaging material for DNA. The epigenome is compared to software, determining how the hardware DNA functions by acting on genes to prompt physiological responses.
The epigenome can turn some genes permanently on or off, and it plays a role in the specialization of cells, turning cells into liver cells that will produce more liver cells, etc. The face is a good example: skin, eyes, teeth and hair all contain the same DNA but the genes in each are expressed — turned on or off – differently.
It turns out that the epigenome can be altered — by the environment, stress, diet, behavior, toxins and the environment.
The bad news is that bad epigenomic modifications or “marks” can be passed along to create vulnerabilities in future generations. But the good news is that these propensities are potentially reversible: once the causes of epigenomic marks – for example, those creating a vulnerability to cancer — have been determined, the risk could be lowered by changing behavioral or environmental factors.
“Epigenetic changes represent a biological response to an environmental stressor,” writes John Cloud in TIME magazine. “But if you remove the environmental pressure, the epigenetic marks will eventually fade, and the DNA code will – over time—begin to revert to its original programming.”
Operating changes to the epigenomic software have been observed — along with the potential for altering them — in an array of instances:
Diet — the best human example comes from the remote north of Sweden where boys who lived through rare winters of abundant food, i.e. “who went from normal eating to gluttony in a single season,” produced sons who lived shorter lives, and subsequently grandsons with decreased life expectancies of “an astonishing 32 years,” according to the TIME article.
When the females of a breed of mice that are yellow, fat and prone to diabetes and cancer are fed with a cocktail of vitamins prior to and during pregnancy, their babies are brown, slim and healthy – and these offspring have babies similar to themselves. Researchers quip: you are what you eat, and now your grandchildren are what you eat.
“Nutritional epigenetics,” using diet to prevent or delay diseases, has been considered an “attractive tool” for use with type 2 diabetes, obesity, inflammation and neurocognitive disorders — including “to delay aging-associated processes.”
Cancer — epigenetic changes could silence a tumor suppressor gene, thereby allowing the uncontrolled growth of tumors, or could turn off genes that help repair DNA. The hope is that treatments less toxic than chemotherapy could reverse these changes to treat the cancer.
Memory — mice with inherited memory limitations problems, when exposed to a rich environment with toys, exercise and extra attention, showed significant improvement in one neural activity key to memory formation. Even without the extra attention, their offspring showed the same improvement.
Allergic reactions – a British university study recruited some 14,000 pregnant mothers in the early 1990s and then followed their children, finding: high maternal anxiety during pregnancy may cause a child’s asthma; baby lotions containing peanut oil may help cause peanut allergies; and kids kept too clean are at a higher risk for eczema. These epigenetic marks have been suspected to make future generations more susceptible to allergies – but the marks could also be altered or reversed, for example in the latter case, by increasing exposure to bacteria.
Twins – epigenetics could explain why only one twin can develop asthma or bipolar disorder, despite having exactly the same DNA as the other.
While the Human Genome project, completed in 2000, located some 25,000 genes at a cost of about $3 billion, a project now underway in the U.S. and Europe to map the human epigenome will need to investigate millions of patterns of epigenetic marks, requiring untold billions of dollars as well as “major advances in computing power.”
The TIME article concludes: “Now we can imagine a world in which we can tinker with DNA, bend it to our will…Be assured: the age of epigenetics has arrived.”
–Mary Carpenter