DDT and Diseases Generations Later
I heard it on NPR.
Researchers linked DDT exposure to obesity generations later. I was skeptical, with thoughts such as, “correlational data…” and “rats are not humans…” and even, “isn’t this like inheriting an experience? sort of Lamarckian, right?”
I was intrigued. How could an external influence (DDT) result in changes that are inherited?
I was glad to find open access to the original published research.
I’ve learned some stunning things.
An environmental event in one generation could affect the phenotype in subsequent generations!
And in this case, the environmental event is DDT. And 50% of the subsequent generation are obese with a complex suite of diseases.
Their data show that DDT doesn’t change the rat’s DNA sequence; what it does do is change the composition of stuff ‘on top’ of the genes. Scientists call these epigenetic (on top of/in addition to genes) modifications.
I remembered only one thing about epigenetic modification–one type is methylation and that plays a critical role in gene expression.
Methylation turns genes on or off; and this can contribute greatly to the final look/reality of multicellular organisms.
What I didn’t remember was whether or not you could inherit these kinds of modifications.
In some cases, these changes are inheritable.
In general, these modifications are cleared and re-established each generation, but in some organisms, at some places in the genome this clearing is incomplete. And the modifications are inherited along with the actual DNA.
Give a gestating rat a DDT injection, and her offspring, and their offspring, have obesity and associated diseases at a much higher rate.
A huge rate. 50% of the grandrats were obese and also were afflicted with a suite of diseases.
The article extrapolates to humans in my opinion pretty quickly. But they are the experts and it seems obvious the next set of research efforts will look for similar modifications and effects in humans.