FROM THE EDITORS

Understanding epigenetics

By Robert D. Sheeler, M.D.
Medical Editor, Mayo Clinic Health Letter

In Mayo Clinic Health Letter, we try to write about a spectrum of topics, from cutting edge advances in science to the most common medical maladies you are likely to encounter on a day-to-day basis.

This month, we bring you a leading edge article on "Epigenetics" — the science of how our genes are influenced by environmental factors in ways that turn them on and off to determine what characteristics and programs within the genetic code are activated. We explain some of the basics of how this works —how different mechanisms that are now coming to light activate and deactivate parts of our genetic program. This is a very optimistic and important area of new development. It represents the interface between what our genetic code tells us to do and how it can be influenced by factors in the environment — not only on a day-to-day basis, but actually over generations.

As we learn about factors that activate and deactivate our genetic program, we will be able to find more subtle and elegant ways to influence the behavior of cells. This will change everything from how we age to how we treat cancer. Many of the oncologists I know here at Mayo Clinic say that advances in medicine have already made curable some kinds of cancers that were always fatal just a few years ago. They look forward to a time when more and more cancers will be treatable because of advances in understanding of how cells and our genetic programs are affected. As we come to understand the sophistication of the cellular machinery, we will be able to have more finely tuned therapies that aren't as devastating as many of the modern chemotherapies that are available today.

A fascinating example of how expression of the genetic code can be influenced is the agouti mouse. Certain genetic traits of these mice can lead them to be obese, diabetic and have an increased susceptibility to tumors. These mice even have shorter life spans. When pregnant agouti mice are fed a diet supplemented with methyl group donors — foods that promote a process called methylation, as described in an article in this month's Health Letter — the genetic program in the next generation is not expressed. The resulting offspring of the mice fed this diet while pregnant are thinner, healthier, and live longer. They are also a different color. This is all due to the effect that this diet has on whether certain genes in the offspring are turned on or off. Not only do the mice look dramatically different, their overall health and susceptibility to disease is dramatically altered.

We are just at the beginning phases of understanding how such delicate details of the cellular machinery affect the ways our genetic code gets turned on and off — and hence how environmental factors and diet in particular can play a huge role in our health, well-being and longevity.

An area that especially excites me is how our emotional health and psychosocial networks come into play in regulating our health outcomes. For a long time we have known that social and emotional health are related to physical health and life span. But we didn't have the level of understanding to see how this could come into play. As is often the case when something is beyond our understanding, we tend to downplay it or think that it is less important. But these new developments show that over time, we will be able to learn about and then control the expression of our genetic heritage to influence our health over the course of our lives. For me, that is wonderful news and truly exciting.