The Blame Game of Epigenetics

Epigenetics, Public Health, and Social Responsibility

The lines between our body and the outside world are becoming fuzzy. A revolution in genetics — termed epigenetics — is revealing the complicated ways our genes and biology are influenced by the world around us. But what do we do with this information? And who is to blame when things go wrong?

Since the work of Gregor Mendel and his discovery of the gene, scientists have viewed our DNA as fixed from conception, arranged as tiles of information mixed and matched between a child’s parents to produce an infinite variety of biological mosaics. These mosaics were thought to be permanent, cemented in our cells and indifferent to our environment or events in our lives. While we might damage our liver with excessive drinking or tone our muscles through a daily regimen of exercise, our DNA would remain unchanged, and our children and grandchildren would be no better or worse off for it.

Our bodies were the secure vessels for our DNA, for the most part doing a good job shielding it from the outside world. But over the last 50 years, views of a stable genome have been shifting. While the actual code of our DNA does remain pretty much the same throughout our life — the A’s, C’s, G’s and T’s that make up our genes and chromosomes — how those genes are expressed, turned on and off, is a much more dynamic process.

We’re realizing are bodies are not quite so insulating — our genetic material, the stuff that makes us who we are, is much more vulnerable than we thought.

Above it all

The ‘epi’ in epigenetics comes from the Latin for ‘above’ — that is, the molecular processes that work on top of our genetic code to regulate the transformation of DNA to RNA and proteins. These epigenetic processes turn on, speed up, slow down, or stop altogether the expression of genes. By suppressing certain genes and activating others, cells containing the same DNA can specialize into our liver, bones, or brain. Some of these epigenetic processes are controlled by our own internal molecular signals. But external signals from the environment — air pollution, chemical exposures, nutrition, stress, and even class — also manifest themselves as epigenetic changes to our DNA. In this way, epigenetics can be thought of us our “molecular memory of past stimuli.” [1]

Cigarette smoke, alcohol, famine, high-fat diets, and the infamous chemical BPA have all been shown to affect the epigenome. The harmful effects of these agents on human health have in some cases been known for decades, but scientists are just now discovering that their effects may last for generations, even after the initial exposure is gone. For example, in a study at UCLA Medical Center, scientists exposed female rats to nicotine during their pregnancy. These mothers bore offspring (Generation 2) with an increased risk for asthma — a risk that Generation 2 in turn passed on to a third generation, even though neither Generation 2 nor 3 had ever been directly exposed to nicotine themselves. [2]

Most incredibly, though, are the non-physical triggers for epigenetic change. Dr. Weaver at the Douglas Hospital Research Center in Quebec found that rat mothers who licked and groomed their pups compared to more neglectful mothers changed the epigenome of the pups, who grew up to handle stress better than their less-licked counterparts. [3]

In humans, researchers have observed epigenetic differences in Italian shift workers compared to their day-working counterparts, and between people of different socioeconomic status. [4] [5] And like rats exposed to nicotine, epigenetic effects in humans can persist over generations. Take for example the epigenetic effects of childhood abuse, which could be a contributing factor to the high numbers of abusive parents who were themselves abused as children. [6] [7]

What to do?

The discovery of epigenetic risk factors, particularly from nutritional and chemical agents, have triggered a wave of public health recommendations from doctors, researchers and officials who are eager to translate these findings into actionable information for parents and would-be parents. Popular magazines and blogs are abound with recommendations for making the best of a child’s 9 months in utero. But epigenetics is still an infant science, and much of this work — highly controlled laboratory experiments, animal models, or observational studies — begin only to trace the outlines of epigenetics’ potential impact on human health.

For example, while BPA has been associated with an increased risk for obesity in humans, a lab at The University of Michigan found the opposite to be true in mice, who were generally leaner and more active than their non-exposed counterparts. [8] So what we observe in animal models may not be as easily translated to humans as we’d like to hope.

Science is often granted funding based on its applicability to human health, because we value the quick translation of biological research into medical and healthcare applications. In the meantime, science journalists have the difficult task of communicating complicated work performed by a whole team of PhDs in a way that is interesting and accessible to the public. Often, much is lost in translation. So we can get a bit carried away with ourselves, jumping to conclusions and making health recommendations that we don’t actually have the evidence from rigorous human trials to back up. (The current controversy between wellness advice publisher Goop and Twitter’s doctors is over this exact issue).

An epigenetic society

Making epigenetic public health recommendations is problematic for another reason. As environmental conditions, epigenetic risk factors are by definition external. They are complex and often come from sources we have no control over. Having patients avoid these risks is not as simple as having them eat healthier or find cleaner air. Without a living wage, no amount of willpower or health literacy will bring fresh food to a working mother living in the middle of a food desert. Understanding the importance of nutrition during pregnancy does not necessarily arm people with the tools to do something about it. Food deserts, air pollution, poverty, and crime are systemic issues that no single person or family can do much about. Short of picking up and relocating to a more ideal environment (an option few can afford), one must play with the cards they’ve been dealt.

In the United States, these factors disproportionately affect immigrants, people of color, trans people, and those with low income. Without the ability to do anything about it, recommendations to avoid epigenetic risk factors are meaningless at best. At worst, they chip away at a patient’s sense of control over their health and the health of their children. Epigenetic discussion has been called out as too often placing the blame directly on mothers, who ‘should have known better’ or who should have done something to lay a better foundation for their child. But are mothers to blame for traffic pollution from the highway just beyond the back yard? Or for an income that only provides room in the budget for fast food?

Instead, future recommendations based off epigenetic findings need to move beyond the fields of biology and medicine, and engage sociology, politics, and economics. As Hannah Landecker and Aaron Panofsky point out, life scientists with their rat models and cell cultures “do not possess the tools to understand the social, cultural, economic, and political structuring of these exposures.”[9] This is where social scientists can lend their expertise. Economists, sociologists, and policymakers must work together with life scientists to synthesize social and economic models of epigenetic disease and to create social and political interventions to address them.

Epigenetics is a fascinating new science that sits squarely between the biological and social, between the medical and political. Translating our understanding of it into healthier, happier, and longer lives can’t rely on life scientists or doctors alone. It requires health literacy of the patient, to be sure, but more importantly, the health literacy and empathy of urban planners, politicians, school administrators, and economists. It is a public problem that deserves public attention and effort. Success matters not only for the health of those living now, but for the health of our children, grandchildren, and generations to come.

[1] Bonasio R, Tu S, Reinberg D. 2010. “Molecular signals of epigenetic states.” Science 330:612–16.

[2] Rehan V, Liu J, Naeem E, Tian J, Sakurai R, et al. 2012. “Perinatal nicotine exposure induces asthma in second generation offspring.” BMC Med. 10:129.

[3] Weaver ICG, Cervoni N, Champagne FA, D’Alessio AC, Sharma S, et al. 2004. “Epigenetic programming by maternal behavior.” Nat. Neurosci. 7(8):847–54.

[4] Bollati V, Baccarelli A, Sartori S, Tarantini L, Motta V, et al. 2010. “Epigenetic effects of shiftwork on blood DNA methylation.” Chronobiol. Int. 27:1093–104.

[5] McGuinness D, McGlynn LM, Johnson PCD, MacIntyre A, Batty DG, et al. 2012. “Socio-economic status is associated with epigenetic differences in the pSoBid cohort.” Int. J. Epidemiol. 41:151–60.

[6] Chapman D, Scott K. “The impact of maternal intergenerational risk factors on adverse developmental outcomes.” Developmental Review. 2001;21:305–325.

[7] McGowan PO, Sasaki A, D’Alessio AC, Dymov S, Labonté B, Szyf M, Turecki G, Meaney MJ. 2009. “Epigenetic regulation of the glucocorticoid receptor in human brain associates with childhood abuse.” Nature Neuroscience. 12(3):342–8.

[8] Anderson OS, Peterson KE, Sanchez BN, Zhang Z,Mancuso P, Dolinoy DC. 2013. “Perinatal bisphenol A exposure promotes hyperactivity, lean body composition, and hormonal responses across the murine life course.” FASEB J. 27:1784–92

[9] Landecker H, Panofsky A. 2013. “From social structure to gene regulation, and back: A critical introduction to environmental epigenetics for sociology.” Annu. Rev. Sociol. 39:333–357.

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