What you can pass down extends beyond your genes

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Our children and grandchildren are what we eat.

They are also the genetic recipients of our traumatic experiences, high stress levels, and exposure to toxic chemicals (including alcohol and other drugs).

When we pass down our genes to the next generations, we also pass along something else — our epigenes, molecular “tags” that attach themselves to genes and switch them on or off.

Think of the genome as the hardware of a computer, suggests Duke University geneticist Randy Jirtle, and the epigenome as “the software that tells the computer when to work, how to work and how much.”

The epigenetic “software” is extraordinarily powerful and the implications are mind-boggling. Scientists, who normally are not prone to hyperbole, use words like “amazing,” “exciting,” “marvelous,” and “fantastic” to describe the epigenetic research.

Experiments with mice tell part of the story. When researchers fed pregnant fat yellow mice a diet rich in methyl groups (found in “human” foods such as soybeans, red grapes, and green tea), the mice gave birth to skinny brown mice.

The methyl “tags” of carbon and hydrogen attached to the rodents’ agouti gene, which causes obesity, and flipped the switch to the “off” position.

When researchers fed pregnant brown mice environmental toxins such as Bisphenol A — a compound found in water bottles and tin cans — the mice gave birth to (you guessed it) fat, yellow mice prone to obesity (and more likely to develop diabetes and cancer).

Most intriguing of all, the next generation of mice inherited the epigenetic changes, with thin brown mice giving birth to thin brown mice and fat yellow mice bearing fat yellow mice.

In another study, researchers compared rats born to mothers who lovingly licked and groomed them after birth to mothers who took a more “paws off” approach. When stressed, the offspring of the low-licking mothers had higher blood pressure and stress hormone levels. These physiological changes had obvious behavioral consequences — when researchers walked into their cages, the rats would “scream” and try to bite them. Researchers subsequently discovered that the low-licked rats had multiple epigenetic tags that switched off a stress-lowering gene, causing the rats’ stress levels to soar.

But — and what a “but” this is — when researchers injected the rats with a drug capable of removing epigenetic markers, the rodents became less anxious.

Now to humans. In a study with women who reported experiencing stress during pregnancy — marital conflict, depression, parenting difficulties, financial problems — researchers discovered higher levels of the stress hormone cortisol in their daughters at age 4. (For some mysterious reason, higher levels were not found in boys.)

At age 14, the daughters were more likely to have problems with anxiety. Maternal stress during pregnancy apparently weakened the connections between the daughters’ prefrontal cortex and amygdala, two brain areas that normally work together in sync to shut down negative emotions.

Psychoactive drugs such as cocaine and marijuana can reprogram our brain cells’ epigenetic code, ultimately leading to addiction. Certain genes are switched on by infrequent cocaine use while other genes are switched on by frequent use. Chronic (frequent) use can turn on a number of genes that remain “on” long after a person stops using the drug.

Drug use — and, in fact, any exposure to toxic chemicals — can actually change the way our brains work, rewriting our epigenetic code for generations to come.

Nuclear bombs and millions of years of evolutionary adaptations are capable of altering our genes.

But our epigenes can be manipulated in one generation by diet, lifestyle, and chemical exposure.

“You live your life as a sort of guardian of your genome,” geneticist Marcus Pembrey said. “You’ve got to be careful of it because it’s not just you. You can’t be selfish because you can’t say, ‘Well, I’ll smoke,’ or ‘I’ll do whatever it is because I’m prepared to die early.’ You’re also looking after it for your children and grandchildren.”

“Responsibility” and “hope” are two words often used by epigenetic researchers who are busy designing drugs that target the epigene to reduce the risk of cancer, obesity, autism and addiction.

But the word I like best is “Wow!” A sense of awe and wonder may be the most reverential, if not the most scientific, response to Hamlet’s question: “What is this quintessence of dust?”

What an astonishing piece of work we are.

Kathy Ketcham is the co-author of 14 books and executive director of Trilogy Recovery Community. For more information, go to www.trilogyrecovery.org.

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