The “On/Off Switch�?for Genes and Susceptibility for Disease

Along with our genes, we inherit certain "marks" that sit on our genes. Because these marks don’t alter the sequence of the gene, they are called “epigenetic.�?Epigenetic marks hold information such as which parent the gene came from. The marks also turn genes on or off. When working well, epigenetic marks help “bad�?genes stay silent, while encouraging “good�?genes to activate. When the marks improperly turn genes on or off, they may trigger later development of diseases such as diabetes, heart disease, and obesity.

But here’s the good news: unlike genes, scientists believe that epigenetic marks can be modified in the womb.

Research suggests that it might be as simple as common nutrients—such as vitamins—that change epigenetic marks in a developing fetus, and affect which genes turn on and off. This research could eventually explain why some individuals who inherit genes for certain diseases (such as diabetes, heart disease, obesity, and certain cancers) may not develop those conditions as adults, while others do. It could also provide a better understanding of how to prevent “bad�?genes from activating later in life—and how to increase the chances of passing that protection on to future generations.

Pregnancy and Nutrition: An Epigenetic Link?

Scientists have long known that poor prenatal nutrition can influence the likelihood of diabetes, heart disease, obesity, breast cancer, and other cancers. Studies have shown that children born to mothers during periods of famine have higher rates of these chronic diseases when they become adults. Also, these children seem to pass on an inherited susceptibility to these diseases to their children, and so on.

Epigenetic marks could be the link. While the relationship between nutrition and epigenetics isn’t yet clear, early evidence points to the possibility that a pregnant woman’s diet can affect the epigenetic marks on her baby’s genes in such a way that not only her children but also her grandchildren—and possibly her great-grandchildren—inherit the same health problems.

If a poor diet during pregnancy can damage the health of future generations through epigenetic factors, can this process be reversed to protect children from developing diseases they may have inherited? Human studies addressing this question do not yet exist. But a recent animal study offered evidence that researchers could stop the expression of cancer genes in mice by altering epigenetic factors—not the genes themselves, but whether they were turned on or off.

The study of autism and genes also lends support to the possibility that the environment in the womb can lead to certain outcomes for the child later in life. Identical twins, who have the same DNA, are much more likely to share the diagnosis of autism than fraternal twins. But sometimes one identical twin is diagnosed with autism while the other remains healthy. Experts have not yet identified the specific genetic components related to autism. But in a new study, experts proposed that multiple factors—some of them related to whether genes turn on or off in the womb—are involved.

Best Bet for a Healthy Baby

What can a pregnant woman do to increase the chances of having a baby who expresses healthy genes? Research is still needed to investigate this question. Until we know more about the relationship between nutrition, epigenetic marks, and long-term protection against chronic diseases, pregnant women should continue to follow the advice of health care professionals, including these basic guidelines:

• Get good health care—before, during, and after your pregnancy.
• Eat adequately during pregnancy to avoid having an undernourished baby who fails to grow properly.
• If you eat a mix of foods and eat enough servings of foods from the revised Food Guide Pyramid, you will be eating a satisfactory diet. If you follow the Mediterranean Food Pyramid, you will be eating a very good diet.
• Folic acid is key vitamin to the growth of your baby, especially during the first months of pregnancy. Take 0.4 milligrams of folic acid daily before and during pregnancy.
• Avoid alcohol, tobacco, all drugs, and other harmful substances while you’re pregnant.
• Keep caffeine intake below two items per day.
• If you’re pregnant and you have diabetes, keep your blood sugar levels in good control, stay healthy, and try to plan your pregnancy for a time when your diabetes is under good control.

RESOURCES:

American Dietetic Association
http://www.eatright.org/

Care Before and During Pregnancy—Prenatal Care
National Institutes of Health
http://www.nichd.nih.gov/

The Genomic Imprinting Website
http://www.geneimprint.com

Sources:

G. Kaati et al., “Cardiovascular and diabetes mortality determined by nutrition during parents�?and grandparents�?slow growth period,�?Eur J Hum Genet, 10:682-8, 2002.

Hochedlinger K, Blelloch R, Brennan C, Yamada Y, Kim M, Chin L, Jaenisch R. “Reprogramming of a melanoma genome by nuclear transplantation.�?Genes Dev. 2004 Aug 1;18(15):1875-85.

Jiang YH, Sahoo T, Michaelis RC, Bercovich D, Bressler J, Kashork CD, Liu Q, Shaffer LG, Schroer RJ, Stockton DW, Spielman RS, Stevenson RE, Beaudet AL. “A mixed epigenetic/genetic model for oligogenic inheritance of autism with a limited role for UBE3A.�?Am J Med Genet. 30 August 2004

L.H. Lumey, “Decreased birthweights in infants after maternal in utero exposure to the Dutch famine of 1944-45,�?Paediatr Perinat Ep, 6:240-53, 1992.

R.A. Waterland, R.A. Jirtle, “Transposable elements targets for early nutritional effects on epigenetic gene regulation,�?Mol Cell Biol, 23:5293-300, 2003

Last reviewed September 2004 by Jeff Andrews, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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