[dohboi]

Ancestors’ exposure to DDT may contribute to obesity, study says

http://articles.latimes.com/2013/oct/23 ... s-20131023

Exposure to the pesticide DDT could be playing a role in high rates of obesity three generations later, a new study says.

Scientists injected pregnant rats with DDT and found no change in their levels of obesity or their offspring. But by the third generation, more than half of the rats (think of them as the great-grandchildren) showed dramatically higher levels of fat and weight gain, even though they were never exposed to the pesticide themselves.

"Here is an ancestral exposure in your great-grandmother, which is passed on to you and you’re going to pass on to your grandchildren," said Michael Skinner, a professor of biological sciences at Washington State University who led the research published in the journal BMC Medicine.

At work is a disease inheritance phenomenon discovered more than 15 years ago, Skinner said.

A series of experiments on lab rats found that chemicals known as endocrine disruptors, including fungicides, dioxin and bisphenol-A, or BPA, can alter the molecular processes around their DNA without changing its sequence, Skinner said.

The contaminants can turn genes on or off and be passed on to descendants generations down the line, leading them to develop conditions like kidney disease, ovarian disease or obesity.

"We’ve all been taught that the primary way for us to inherit things from our parents is genetics," Skinner said. "This is a totally new concept for how we inherit things from our ancestors."

Though the study makes no conclusions about the risk to humans, Skinner said it should give pause to those advocating the use of DDT to combat malaria more than 50 years after Rachel Carson’s book Silent Spring brought attention to the pesticide’s lasting damage to the environment...

[Subjectivist]

Epigenetics is an exciting new field of research. They have discovered all sorts of hings influence which genes are expressed and which are not. For a basic overview try this vid http://youtu.be/Y4XgMWSJ3zk the presentation is entertaining and short.

Some of the research supports the idea that your own environmental exposure at key hormonal transitions in your life have a huge epigenetic impact. For example children who are about to enter puberty who have a low starch diet are much less likely to become obese later in life than those who are on a high starch diet. Something about the way high blood insulin influences their epignetic expression is set during the transition from childhood high growth rate hormone state to adult body mass maintenance state. You have a growth spurt at onset of puberty, but then your body starts taking on its final adult characteristics as you enter your late teen years. What you eat seems to determine what those long term charecteristics will be set to become.

[dohboi]

Interesting. The weird thing about the effect in the main post is that it doesn't effect the generation exposed, nor the next gen, but the third generation out. This seems very odd to me.

[jedrider]

Interesting. The weird thing about the effect in the main post is that it doesn't effect the generation exposed, nor the next gen, but the third generation out. This seems very odd to me.

I am always fascinated by stories of epigenetics. It is clear that we are not the product of purely random changes to DNA. Yes, the source changes are random, but thereafter there is a mechanism of amplification of desired/necessary changes.

My guess is all that 'junk' DNA that we haven't discovered a purpose for could be where this lies. So, by my calculation:

0th gen - exposure - DNA changing
1st gen - inherit new epi changes
2nd gen - primary DNA change
3rd gen - new DNA w. new traits

Why would nature want changes to wait to propagate for three generations? Maybe, the junk DNA is the 'lab' for future evolution?

My field is software, not biology, though.

[dohboi]

Good question. But I think it has more to do with chemistry than with 'intentions.'

The other place that I've heard of this phenomenon is effects of starvation on genes, but I can't remember when they were expressed.

[Surf]

I am always fascinated by stories of epigenetics. It is clear that we are not the product of purely random changes to DNA. Yes, the source changes are random, but thereafter there is a mechanism of amplification of desired/necessary changes.

My guess is all that 'junk' DNA that we haven't discovered a purpose for could be where this lies.

When scientist first discovered DNA they discovered two classes of DNA.
1. DNA that makes proteins Scientists called these DNA sequences Genes
2. DNA that didn't produce proteins. Since it didn't appear to do anything it has been called junk DNA.

Scientist focused most of there study of DNA on genes. To answer many of the questions they had they focused on mapping the entire human genome as well as the Genome of other animals. Once the Genome maps were completed many people were surprised. The Genes in humans were essentially identical to the genes in apes and other animals. So the human DNA that makes proteins doesn't have any information that make use human.

Therefore about 15 years ago people started studding the junk DNA. They found the following:
1. The junk DNA can turn genes on and off. The junk DNA was not junk but actually controls the expression of genes.
2. In the junk DNA they found numerous differences between humans and other apes. Including DNA that controls the development of the unique human thumb. Other DNA difference appear to e related to development of the human brain as well as DNA that controller the growth of the human skull.
3. Many of the big differences between between humans and apes is in the junk DNA but not in the genes that make proteins.
4. SMall changes in the junk can rapidly be passed onto our descendants.


Scientist now call junk DNA the epigenome. The study of epigenetics is increasingly be tied into the study of the Epigenome. There never was any junk DNA in the human genome.

[dohboi]

Thanks, Surf. I'm still surprised that these effects wait three generations to express themselves in this case.

It makes one wonder, with the toxic stew of other persistent chemicals and radioactive material that we have introduced into the environment and into our bodies, what effects are going to show up down the road in our kids kids (if there are any). It also makes me wonder if something like autism may be another effect from exposure of grandparents to something or other.

[Cid_Yama]

I missed this thread when it was first posted. How interesting. Things previous generations were exposed to can express themselves in generations that far down the road.

I remember the DDT trucks fogging us a couple times a night at the drive-in to suppress mosquitoes back in my prime. Guess it's a good thing I didn't have kids.