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YOU ARE WHAT YOUR GRANDPARENTS ATE
Other influential factors
But it was not just food supply that had this epigenetic effect. There have been strange findings in animal experiments for decades which weren't understood until the theory of epigenetics was formulated. Here are some examples:
- If male rats are given a drug called alloxan, which decreases the body's sensitivity to the hormone insulin, their offspring and their offspring's offspring would become progressively more prone to diabetes.
- High doses of morphine given to mice damage their nervous system. This damage was also seen in their descendants.
- It takes only one injection of the thyroid hormone, thyroxin, into a newborn rodent to permanently depress levels of thyroid hormones — not only in the injected mouse but also in its offspring.
- Professor Wolf Reik, at the Babraham Institute in Cambridge, has spent years studying epigenetics. He has found that merely handling mouse embryos is enough to set off 'switches' that turn genes on or off.
- Researchers at Washington State University have shown that exposure to fungicides or pesticides can cause biological changes in rats that persist for at least 4 generations.
Until recently these findings had been regarded as unexplained phenomena and discarded. But Dr Reik's work has gone further, showing that genes switched on or off could be inherited. This means that a 'memory' of a simple environmental event could be passed through generations.
Beckwith-Wiedemann syndrome, Angelmann syndrome, hydatidiform mole,[7] Rett syndrome, facioscapulohumeral muscular dystrophy, immunodeficiency-centromeric instability,[8] and autism spectrum disorders[9] all have epigenetic causes.
In humans, Prader-Willi syndrome and Angelmann syndrome have been shown to be caused by the same faulty gene. This raised the question of how one gene defect could cause two completely different diseases.
Research to answer this question found that it was entirely dependent on whether the faulty gene was passed on by the child's mother or his father. If the father, it was one disease; if the mother it was the other. This indicated that not only did genes have a memory, but also that this memory and the factors that triggered their switching on or off were a lot more complex than anyone had thought possible.
Genes seem able to memorise remarkable things. For example: take in-vitro fertilisation (IVF), which has become commonplace these days. The temperature at which eggs and sperm are stored for in-vitro fertilisation, the way eggs and sperm are handled, the atmosphere in which the procedure takes place, can all, through an epigenetic effect, determine the health and life expectancy of a child conceived in this way. The BBC reported that Stephanie Mullins' first child, her son, Ciaran, who was the result of in-vitro fertilisation was born with Beckwith-Wiedemann Syndrome.[10] It is entirely possible that the IVF procedure was the cause of Ciaran's condition as it has been shown that babies conceived by IVF have a 3- to 4-fold increased chance of developing this condition than babies conceived naturally. If he has children, Ciaran's condition could well be passed on to them as well.
Dr Rachel Yehuda, a psychologist at the Mount Sinai School of Medicine in New York, studied the effects of stress on a group of women who were inside or near the World Trade Center and were pregnant during the tragic events of 11 September 2001. Produced in conjunction with Jonathan Seckl, an Edinburgh doctor, her results suggest that stress effects can pass down generations. As late as December 2006, children of women who witnessed the Twin Towers outrage are still being born smaller than normal. It will be some time until those effects can be measured in the grandchildren of these women, but you can be sure that this will be followed up.
One thing is now certain, however: as Marcus Pembrey says, 'Bizarre things are going on that we are just beginning to get a handle on'.
Poisons may pass down generations
Toxic chemicals that poisoned your great-grandparents may also damage your health according to research published in the journal, Science.[11] A team from Washington State University produced evidence that some inherited diseases may be caused by poisons polluting the womb. The effect could give rise to diseases that pass down at least 4 generations.
The scientists, led by Dr Michael Skinner, exposed pregnant rats to two agricultural chemicals during the period that the sex of their offspring was being determined. The compounds were vinclozolin, a fungicide commonly used in vineyards, and the pesticide methoxychlor. Both are known to be endocrine disruptors — chemicals that interfere with the normal functioning of reproductive hormones.
Rats exposed to the compounds produced male offspring with low sperm counts and poor fertility. They were still able to produce young, however. When these rats were then mated with females that had not been exposed to the poisons, their male offspring had the same low sperm counts.
The researchers found the damage was not caused by alterations in the DNA code, but changes in the way the genes work. They say that 'The ability of an environmental factor (for example, endocrine disruptor) to reprogram the germ line and to promote a transgenerational disease state has significant implications for evolutionary biology and disease etiology.'
Part 4: Cancer Clue | Part 5: Conclusion and References
Last updated 17 November 2009
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