Issue 22 – Epigenetics

Issue 22, January 2010 (scroll down for this month’s articles): Lamarckianism and the epigenetic revolution in environmental health; 75 new chemicals in US biomonitoring survey; and a UN bisphenol-A safety summit – plus our update on news and science from December.

Lamarck lives! The epigenetic revolution in environmental health

Chromatin

Chromatin: Change to the 3D stucture of DNA is just one epigenetic mechanism for turning genes on and off. (Picture: Zephyris, Wikimedia Commons.)

by Jade Johnston

The idea that evolutionary change occurs by the inheritance of acquired traits, as expounded by 18th-Century biologist Jean-Baptiste Lamarck, is long-thought to have been consigned to the bin of scientific oddities.

However, in a new twist on old science, faint echoes of Lamarck’s ideas can once again be heard in biologists’ laboratories – those at the cutting edge of genetic research, in the field of epigenetics.

“We now have evidence that our cells detect their environment and tag the DNA in ways that can be understood by the cells of subsequent offspring. It allows cells to adapt very rapidly to their environment and pass that adaptation on to future generations,” says Dr. Thea Edwards, a research associate at the US University of Florida’s Department of Zoology.

Epigenetics research has flourished in the last twenty years and studies how, through biochemical process, genes become switched on and off in response to changes in the environment. Organisms, in a way analagous to that originally proposed by Lamarck, pick up throughout their lives subtle changes to the way in which their genes are expressed.

This is significant for health because some of these changes can cause harm. “There are data showing that environmental contaminants can alter DNA tagging patterns. This can affect things like fertility – [and] we don’t know what it would take to get the tags back to their original form,” explains Edwards.

Research into a number of chemicals including vinclozolin, methoxychlor, and BPA are showing potential to cause epigenetic effects related to various diseases including cancer, diabetes and obesity, infertility, respiratory diseases, allergies, and neurodegenerative disorders such as Parkinson’s and Alzheimer’s disease. [EHP 115, No.9 Edwards at al.]

These effects stack up over a lifetime. Studies involving monozygotic twins have shown that although the twins begin life epigenetically identical, they accrue differences in methylation patterns as they age, with the greatest differences found between older twins living farther apart. [PNAS July 26, 2005 vol. 102 no. 30, Fraga et al.]

Given that twins who begin life genetically and epigenitally identical, something is modifying the supra-genetic mechanisms which control when their genes are turned on and off, which may result in one twin developing a disease such as cancer while the other twin does not.

“To me what’s so exciting about the field is that once we start defining these genes that are being altered genetically, you really do have the potential to prevent it and maybe even be able to go in and treat it,” says Dr. Randy Jirtle, Director of the Epigenetics and Imprinting Laboratory at Duke University, USA.

Currently, several new pharmaceuticals are coming onto the market which use epigenetic means to reactivate tumor supressor genes in cancer patients.

However, both Jirtle and Edwards insist it is much easier to use epigenetic knowledge to prevent disease rather than try to cure it. One possible application of epigenetic research in the future could be in risk assessment for chemical agents.

“In my opinion, public policy that protects us from exposure in the first place will make better medical and economic sense,” says Edwards.

75 chemicals measured in US population for first time

Perchlorate, connected with thyroid disorders and used in rocket propellant, is ubiquitous in the US population. (Picture: shildey, stock.xchng)

A new report examining US citizens’ exposure to environmental contaminants has revealed levels of 75 chemicals never before studied for their concentration in human populations.

Carried out by the Centers for Disease Control and Prevention (CDC), the research is intended to help doctors and health officials prevent health impacts from environmental chemicals, by determining what chemicals are in US citizens’ bodies and at what concentrations.

Significant findings included the discovery that one type of brominated fire retardant was found in almost every single research subject, while bisphenol-A, the common plastic additive, was found in just over 90% of the urine samples taken in the study.

PFOA, a byproduct of processes used to create non-stick coatings for pans, was also found in almost every single participant in the study. Perchlorate, a chemical used in the manufacture of rocket propellant, was similarly ubiquitous.

EU begins its own biomonitoring project: In December 2009, the European Commission gave the geen light to funding a pilot project to examine the feasibility of harmonised standards for human biomitoring in Europe.

Currently no systems exist which allow comparisons to be drawn for environmental exposure to chemicals in different countries, seen as an important data gap for guiding chemicals regulation in Europe.

24 countries are included in the project. One key player in the UK is the Health Protection Agency. Using new laboratories and state-of the art equipment, the Agency says it hopes to be able to publish its first biomonitoring data by the end of 2010.

  • For the CDC biomonitoring report, click here.
  • For more information about the EU biomonitoring project, please click here.

United Nations orders expert meeting on BPA safety

Many polycarbonate consumer products, such as those pictured, are a potential source of BPA exposure. (Picture: cjp24, Wikimedia Commons)

Recent concern about the safety of bisphenol-A (BPA), a plastic additive common in food packaging, has resulted in the UN World Health Organisation (WHO) and Food and Agriculture Organisation (FAO) to call for experts to meet in Canada in October 2010.

The WHO has voiced concern about “considerable discrepancies” in outcome among studies into the health effects of BPA, both with respect to the nature of the effects observed and, where reported, the levels at which they occur.

Evidence suggests consumers are almost ubiquitously exposed to BPA, with 90% of US adults exposed [see p3 of the Executive Summary downloadable here] and a new umbilical cord blood study suggesting the same proportion of children may be exposed even before birth.

Research has shown that, among other health effects, BPA may cause obesity, affect thyroid function, cause behavioural changes and increase the risk of developing cardiovascular problems and cancer.

A recent French animal study became the first to show that low doses of BPA reduce the permeability of the gut and increase the chances of test animals developing severe intestinal inflammation in adulthood.

The WHO has also observed that health effects are being observed at “doses several orders of magnitude lower” than those on which regulatory initiatives have been based.

The WHO has issued a plea for submission of data on BPA in food and its possible effects and called for experts to attend the ad hoc assembly, in order to “outline a risk assessment strategy and identify any current knowledge gaps”.

News and science from December

Pressure to ban endocrine disruptors in Denmark: The Danish Consumer Council has compiled a list of cosmetic products which contain chemicals on an EU list of suspected endocrine disruptors and wants them banned in Denmark.

The myth of the BPA-free diet: A journalist attempts to avoid BPA for a week, finding out how hard it is to do and how poorly regulated the substance is.

Unrelated endocrine disruptors synergise anyway: In a surprise outcome, researchers have found that four antiandrogens have a synergistic effect – in spite of each acting by different biological mechanisms.

Common plastics chemicals linked to ADHD symptoms: More evidence that accidental environmental exposure to phthalates may be contributing to behavioral and cognitive problems in children.

15 new substances to be prioritised under REACH: [pdf] The EU is expecting in January to add another 15 chemicals to its priority list, bringing the grand total up to 30.

3 Comments »

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  1. […] You can also see the H&E epigenetics edition here. […]

  2. […] Epigenetics, a discipline which has emerged only recently, is a further example of how onset of disease may be much more complex than simply a matter of what genes themselves are coding for, because it responds to evidence that the environment itself affects gene expression by switching genes on and off. […]

  3. […] How might exogenous stressors have almost invisible physiological effects, yet affect long-term health? In this regard, of particular interest to the DoHAD hypothesis is epigenetics (see H&E #22). […]


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